28 - operator training

MORGAN CONSTRUCTIONCOMPANY

for

JSWRod Mill

OPERATOR TRAINING FORROD & BAR MILLS

OPERATOR TRAINING FOR ROD & BAR MILLS

2

INTRODUCTION

AUDIENCE

This training manual is written for Rolling Mill Operators and Maintenance personnel.

PURPOSE OF THE MANUAL

The manual provides a guide to the operating procedures required to achieve a consistentperformance from a Wire Rod/Bar Rolling Mill.

TRAINING MANUAL USAGE

The manual has been written as a training tool, to be used in a class room environment. Itprovides a general understand of rolling techniques.

WARNING

This manual is intended to be used in a class room and is not intended as a substitute forgood common sense and time proven mill operating procedures. Morgan ConstructionCompany, expressly disclaim any suggestion that this manual is written for any otherpurpose than a teaching aid.

PROPERTY OF MORGAN CONSTRUCTION COMPANY

The manual is being provided to the audience as part of the training program. Acceptance ofthe manual constitutes agreement that:

1. It and any copies thereof shall not be transmitted or exhibited to others.

2. This Training Manual has been developed by Morgan Construction Company and isto be used only in conjunction with a Morgan sponsored training program.


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TABLE OF CONTENTS

SECTION 1

ROLLING TECHNIQUES....................................................... .7

Correctly Positioning The Rolls In The Roll Housing................................. . 9

Rest Bar Elevation................................................................................... .11

Setting And Checking Roll Elevation. ....................................................... .13

Rest Bar Alignment.................................................................................. .15

Correct Stand Alignment. ........................................................................ .17

Guide Alignment. ..................................................................................... .18

Roller Guide Lubrication and Cooling. ...................................................... .20

Roll Cooling. ............................................................................................ .22

Tension Control ....................................................................................... 24

Crop & Cobble Shear Speed, And Crop Length.......................................... 26

SECTION 2

STOCK CONTROL TECHNIQUES ........................................ 28

Stock Control Techniques........................................................................ 29

Standard Stock Settings .......................................................................... 29

Establishing Stock Control Techniques .................................................... 29

Measuring The Stock............................................................................... 29

Controlling Stock By Tonnage Through The Mill....................................... 30

Control Stock By The Weight And Area Method....................................... 31

Stock Control At The NTM / V Mill ........................................................... 31


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SECTION 3

TABLE OF CONTENTS (CONT)

PRINCIPLES OF N.T.M. ROLLING ................................... ...33

Tungsten Carbide Rolls ........................................................................... 34

Roll Mounting And Removal..................................................................... 36

Mounting Procedure ................................................................................ 38

Procedure For Roll Removal .................................................................... 39

Roll Alignment ......................................................................................... 41

Roll Partings............................................................................................ 43

Guide Alignment ..................................................................................... 45

Guide Brackets........................................................................................ 49

Stock Adjustments................................................................................... 51

Flutter, The Causes And The Solutions.................................................... 53

Grouping Of Rolls ................................................................................... 57

SECTION 4

QUALITY ASPECTS .............................................................. 61

Rod Defect Trouble Shooting................................................................... 62

Cracks..................................................................................................... 62

Laps ........................................................................................................ 64

Fins (Overfill) ........................................................................................... 65

Underfill ................................................................................................... 66

Scratches (Occurring During The Rolling Process)................................... 67

Cracks And Chips In The Carbide Rolls ................................................... 68

Roughness Of The Rod Surface .............................................................. 69

Mechanical Damage ................................................................................ 70


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Shell Or Slivers........................................................................................ 72

Tolerance And Quality Checks................................................................. 73

SECTION 5

STANDARD OPERATING PROCEDURES ........................... 75

What Are Standard Operating Procedures ............................................... 76

Examples Of Standard Operating Procedures, Roughing And Intermediate Mill

Inspection Procedures To Be Done During Periods WhenThe Mill Is Not Rolling.............................................................................. 79

Inspection Procedure To Be Done When The Mill Is Rolling..................... 81

Inspection Procedure At The Start Of Each Shift......................................83

Example Of Standard Operating Procedure For The NTM

Inspection Procedures To Be Done During Periods WhenThe Mill Is Not Rolling.............. ................................................................ 85

SECTION 6

ROD AND BAR MILL YIELD CONTROL............................... 87

Yield ........................................................................................................ 88

The Reheat Furnace................................................................................ 88

Crop Losses ............................................................................................ 88

Cobble Losses......................................................................................... 89

Scale Losses ........................................................................................... 89

Trimming Losses ..................................................................................... 90


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SECTION 7

ROLLING MILL EFFICIENCY MANAGEMENT..................... .91

Development Of Reports ......................................................................... ..92

Report Analysis ....................................................................................... ..92

Response To Report Analysis.................................................................. ..93

Production Scheduling ............................................................................. ..94

Yield Awareness And Maximization.......................................................... ..95

Quality Control And Customer Satisfaction Philosophy............................. ..96

Developing And Implementing Standard Working Procedures.................. ..97

Billet Reheating, Furnace Management ................................................... ..98

Roll And Guide Shop Management .......................................................... ..99

Maintenance Management Systems ........................................................ .100

Spare Parts Strategy ............................................................................... .101

Management Of The Finishing And The Coil Handling Area ..................... .102

Safety...................................................................................................... .102

MORGAN CONSTRUCTION COMPANY

7

SECTION 1

ROLLING TECHNIQUES


8

INTRODUCTION

To effectively and efficiently operate a rolling mill, modern thinking and correct rolling techniquesmust be implemented and practiced. To accomplish this, the following areas must be givenattention:

Correctly Positioning The Rolls In The Roll Housing.

Rest Bar Elevation.

Setting And Checking Roll Elevation.

Rest Bar Alignment.

Correct Stand Alignment.

Guide Alignment.

Roller Guide Lubrication and Cooling.

Roll Cooling.

Tension Control.

Crop & Cobble Shear Speed, And Crop Length.


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CORRECTLY POSITIONING THE ROLLS IN THE ROLL HOUSING.

It is important that the roll and housing assemblies are mounted in the correct position within themill stand cradle assembly. Failure to achieve this, will result in the roll grooves (passes) notbeing correctly aligned to each other and possibly the grooves not being aligned with the guidepositions . Which in turn could result in :

Poor front end delivery from the stands.

Possible surface damage to the stock if the alignment is very poor.

Premature failure or rapid wear of the guides, due to constant stock interference.

Many rolling mill stands have a method of axially adjusting the roll and housing assemblies inorder to enable perfect adjustment of the roll pass. Once this is achieved, the complete rollhousing assembly can be clamped into a fixed position in the stand. See Roll Shop mountingand dismounting instructions.

It is extremely important to have the roll houing assembly of the fixed roll in the correct position.Should there be an error in the roll position, the roll passes will not be aligned correctly to thefixed rest bar positions.

REASONS FOR ROLL MISALIGNMENT.

Rolls incorrectly mounted into the housing halfs.

The lugs on the chock cover becoming bent, the main cause of this is due extreme axialthrust when rolls break in the mill.

The hard faced pads on the cradle, or clamps become worn.

The clamps are not fitted correctly.

KEY POINTS.

1. The roll and housing assembly must be installed correctly.

2. The clamp assembly on the cradle must not be damaged.

3. Hard wear pads on the stands and clamps must be in good condition and securedcorrectly.

4. The threads on the clamp securing studs and the nuts must be in good condition.


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BAR GUIDE ELEVATION.

Refer to Roll Pass Drawings

The correct elevation of the bar guide is extremely important, this is fixed by design and onceset, the elevation should not change unless there is a change of guide with different overalldimensions.

Incorrect elevation is one of the causes of a poor front end delivery from a roll stand. Examplesof poor front end delivery, is when the front end moves off the pass line, or when there is aknuckle formed on the front end of the bar or rod.

The bar guide (trumpet) are usually supported on shoulders on the housings, properly installedblocks are then used to gain the correct elevation to suit each guide type. The blocks should befixed permanently to the housing and welded in place.

In order to achieve the correct elevation it is necessary to establish the following :

The elevation of all the stands is correct, poor installation, wear to the feet of the standsor to the sole plates (the mounting on which the stand is fitted), are the normal reasonsfor elevation errors.

The rest bar mounting shoulders on the stands are at the correct elevation.

The rest bars are manufactured correctly.

It is important that the securing nuts, bolts and washers are maintained in a good condition.

On a regular basis, a "bubble" level should be used to check that the bar guide is levelhorizontally and that the mounting surface is parallel to the pass line.

If the rest bars are not level horizontally on a multi-strand mill, the guide on at least one strandwill be at an incorrect elevation, which will result in a poor entry or delivery from the rolling stand.

If the mounting surface is not parallel to the pass line, the guides will be either pointingdownwards or upwards, either of these conditions will cause a poor entry and delivery from theroll stand.

Note: Optical Alignment must be completed before start up.


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KEY POINTS.

1. The correct elevation of the rest bars is critically important.

2. Incorrect elevation is one of the causes of a poor front end delivery from the rollingstands.

3. Special optical equipment or a surveyors optical level should be used to establish thecorrect elevations of the guide on the stands.

4. On a routine basis, rest bars should be checked to ensure they remain level.

5. Only one packing block should be used under each side of the rest bar, they should bespecially machined for each mill position.

6. After a cobble the trumpet bar guide should be checked to ensure it is level and notbent.


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SETTING AND CHECKING THE ROLL ELEVATION.

This section deals with setting and checking the roll elevation on the conventional mill stands.

The mill pass center line remains at a constant elevation, despite the fact that the roll diametersslightly decrease as they are machined after each visit to the mill. In order to maintain the correctmill center line as the roll diameter reduces, it is necessary to raise the bottom roll.

On many mill stands, this is achieved by attaching pre-machined spacers (shims) to theunderside of the bottom chocks, as the diameter of the rolls decreases the spacer thicknessincreases by 50% of the amount removed from the rolls during the machining process.

Many older mill stands have a bottom adjustment screw which incorporates a sliding wedgearrangement that lowers or raises the bottom roll and chock assembly in order to achieve thecorrect roll elevation.

Human nature being as it is, makes it possible for mistakes to be made when measuring thediameter of the rolls and when calculating or selecting the spacers required to be placed on thebottom chock for any given roll diameter.

Once the roll parting has been set, preferably by the methods described in the Section entitledStandard Mill Settings, the rolls should then be checked to ensure that the elevation is correct.This should be done every time any rolls are installed in the mill.

In order to check the roll elevation, it is necessary to have a jig that is located on the rest bar. Inthe previous sub-section of this manual, the fact that the rest bars should be in a permanent, itis therefore a datum against which the roll elevation can be checked.

If, when checked, the elevation of any of the rolls are found to be incorrect, the reason for theerror should be investigated and rectified. Possible reasons for such an error are :

The wear pads at the base of the stand windows are not positioned correctly, or aredamaged, broken, or possibly badly worn.

The spacers that are located on the bottom chocks, which compensate for the changesin the roll diameter, are not the correct thickness.

The checking jig set-up is not correct.

To run the mill with roll elevation errors, is to invite problems such as:

Front ends of the stock being knuckled (bent).

Guide equipment being continually stressed by the knuckled front ends, whicheventually leads to premature failure of the guide equipment.

Cobbles.


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Knuckling of the front end usually causes a bad entry into the next stand, this is one ofthe main causes for an extended length of defectivness of the front end on the stock.

As a result of this, the length of cuts at the mill shears would have to be extended, inorder to remove the defective end. This can result in a large yield loss.

KEY POINTS.

1. The roll elevation should be checked each time rolls are installed in the mill.

2. Care must be used to ensure the correct spacers are used for each diameter of roll.

3. The stand, and all the wear pads on the stand, must be maintained in good condition.

4. Scale and debris must be cleaned off the mill stand, chock location pads and wedgeassemblies, before the rolls are mounted.

5. Incorrect roll elevation is the possible cause of cobbles and premature guide failure.

6. Incorrect roll elevation can result in excessive yield losses.


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REST BAR ALIGNMENT.

On a multi-strand mill the strand centers of all rest bars should be checked, prior to them beingfitted to the mill, as should the condition of the rest bar dove tail and guide alignment key ways. Itis also important that rest bars are not bent or twisted in any way.

As a general rule, the rest bars being fitted by Morgan Construction Company to modern mills,are of a robust, prefabricated structure. With this type of construction the likelihood of the restbar flexing, bending or twisting is greatly reduced.

On many multi-strand mills, the early stands in the roughing mill will have the same number ofpasses in the rolls as there are strands, therefore the rest bars would not be adjustablehorizontally. One reason for this is that the roll passes are large, and there is not enough roomon the roll to fit more passes. Another reason could be that the mill stands were installed in afixed position and it would be difficult to achieve good alignment from stand to stand.

On the stands which have more than one set of passes, it is necessary to move the rest barwhenever the passes are changed. These stands normally have some form of lateral hydraulicadjustment which enables a good alignment to be achieved from stand to stand.

It is necessary to have at least one of the guides correctly mounted and clamped securely ontothe rest bar in order to achieve the most accurate alignment. On a multi-strand mill, only when allthe guides are mounted, will it be possible to ensure that the alignment is correct and that thestrand centers are also correct.

Should any misalignment exist, the reason should be investigated. The following are items to bechecked :

Are the rolls mounted correctly ?

The strand centers of the rest bars must be correct (multi-strand mills only).

Roll pass strand centers must be correct.

Roller guides must be set symmetrically (roller holder evenly spaced from the guidecenter line)

Static guides must be fitted correctly into the guide holders, and there must be no wearin the guides.

The total dimension of the buttons on the chock front plate (ears) lugs, are theybent?

Dimensions and condition of the hard faced pads (chock location) on the stand.

A flashlight should also be used to illuminate the roll pass and the relationship of the guide to thepass, failure to follow this basic procedure usually leads to an incorrect alignment of the rest barand guides.


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KEY POINTS.

1. Rest bar strand centers should be checked prior to them being fitted to the mill.

2. Rest bars should be routinely checked to ensure they are not bent.

3. The keys fitted to the rest bar strand centers should always be maintained in goodcondition.

4. Before fitting guides, the debris and scale should be removed, paying particular attentionto the dove tails and guide mounting surfaces.

5. Spacers (shims or packing) should not be used behind the rest bars.

6. Care should be taken to ensure there is no dirt or scale behind the rest bars.

7. The bolts and nuts securing the rest bars should be in good condition. Flat washersshould be used between the rest bar and the nut.


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CORRECT STAND ALIGNMENT

Smooth flow of the front end of each billet through the mill is essential. Correct stand alignmentis one of the important procedures that will enable this to occur.

One method of achieving the correct alignment is to have a tabulation showing the position ofthe stand from the end of the sole plate, and the tabulation would show a dimension for eachpass on the roll barrel.

It is essential that once the stands are correctly positioned, they are firmly secured in order toensure the integrity of the alignment. Some mills use hydraulic clamping systems, older millstend to use cap and wedge assemblies to hold the stands in position. Whichever method is usedit is important that the equipment is well maintained.

Failure to secure the stands firmly will also result in rapid wear and damage occurring to the soleplate and the wear pads on the feet of the stand, eventually the stand will "rock and roll"everytime a bar enters or leaves, and it will become impossible to secure the stand firmly.

KEY POINTS

1. Correct stand alignment is essential in order to achieve a smooth flow of the front endsthrough the mill.

2. Use a tabulation sheet to achieve correct stand position.

3. Stand clamping equipment must be well maintained.

4. Failure to secure the stand firmly will result in rapid wear to the sole plate and stand feet.


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GUIDE ALIGNMENT.

To achieve the best rolling condition it is important that all the guides in the mill are alignedcorrectly.

Failure to carry out this basic step will certainly result in a poor entry and delivery of the stock ateach mill stand. Knuckling of the front ends and front ends lifting or diving as they exit thedelivery guides will occur. This is also one of the main reasons for premature failure and damageto guide equipment. The probability of cobbles is greatly increased.

There is also a possibility that quality problems will occur due to the stock interfering with guides.Sparking from guides indicates what there is a problem, the cause of the sparking should alwaysbe investigated and rectified.

Where multi-strand guides are used, it is important to ensure that the guides on all the strandsalign correctly to the roll grooves. If they do not, the rest bar or multiple guide assembly shouldbe changed.

A build up of mill scale is often the cause of many misalignment problems, care should be takento remove scale and other debris when the guides are changed. This condition can be preventedby regularly washing away the scale during each shift.

Damage to the dove tails on rest bars, on guide holders and on the guide bases is also acommon occurrence that will result in poor guide alignment. This condition can easily beeliminated if basic inspection of equipment is carried out prior to fitting any guides.

Entry guides must be aligned in the center of the roll pass. The collars of the roll pass shouldnot be seen when looking through the guide. If the pass collars can be seen, there is a problemwith the guide. This could be :

The wrong guide has been fitted.

The guide is set incorrectly.

In the case of a static guide, it could be that the guide is badly worn.

Static delivery guides are wider than the pass but still should be set accurately to the passcenter line, there should be an even amount of the roll collar showing on either side of the pass.

Roller twist delivery guides should be set so that the centerline of the twister is in the center ofthe pass. This is very difficult to determine by eye, it is therefore important that the rest baralignment is correct. Morgan RTD guides can be aligned with the aid of an alignment gaugewhich is mounted in a key way on the top of the guide body.

Secure clamping of the guide equipment and of the rest bar is important. The condition of theclamps and of the securing bolts, nuts and washers should be checked regularly.


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KEY POINTS.

1. Ensure scale is removed from the rest bar before introducing the guides.

2. Use a flash light to illuminate the inside of the guide and the roll pass when aligningguides.

3. Ensure the guide is the correct item for the running size. If there is any doubt , the guideshould be checked by guide preparation personnel, before it is fitted.

4. Entry guide must be set in the center of the roll pass.

5. Static delivery guides should be set accurately.

6. Accurate alignment of roller twist delivery guides can only be achieved through accuraterest bar alignment.

7. The rest bar and guide dove tails must be in a good condition.

8. Clamps and clamp bolts, etc. should be checked regularly.


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ROLLER GUIDE LUBRICATION AND COOLING.

ROUGHING AND INTERMEDIATE MILLS

It is essential that the rollers in ROLLER ENTRY and ROLLER TWIST DELIVERY guides, areadequately cooled and lubricated. The heat of the stock passing through the guides, will causethe rollers to crack or break if there is no water spraying on them. Also if the rollers are notcooled the bearings will overheat and quickly become seized. Premature bearing failures due tothe grease lubrication melting and running out of the bearing, rather than lubricating the bearingwill also occur.

As the water pipes are normally a small diameter there is a tendency for scale sludge in thewater to block them. It is important to ensure the water is flowing freely, so as to adequately coolthe guide rolls and bearings.

Lubrication is essential, if the guide is to have a long life in the mill. Should an automatic air/oil orgrease lubrication system be used it is essential that it is maintained correctly. Any leaking pipesshould be changed immediately a problem is observed.

When a guide is installed in the mill it is important that the cooling and lubrication pipes arechecked for holes before they are fitted. During the normal course of each shift, it should be partof the rollers (worker in each area) procedure to check both these systems on all the guides, ona regular basis.

Loose lubrication pipes or fittings on the guide itself will enable some of the air pressure and oilor grease to leak, which could well result in the bearings being starved of lubrication, perhapsresulting in premature bearing and therefore guide failure.

After a cobble, the lubrication pipes to the guides and those fixed to the housings should bechecked. Leaking pipes should be changed, as should those which are squashed or bentenough to cause the flow of lubrication to be reduced.

For Guides On A Air/Oil Lubrication System:

On completion of the guide assembly, after the guide roller holders have been aligned, it is agood policy to feed some oil into the lubrication lines. In addition, air from a clean supply (onewith a filter) can be blown into the lubrication lines, distributing the oil into the bearings. Thisprocedure ensures that the guide has sufficient lubrication once in the mill, should the mill air oilsystem not cycle prior to the first bar passing through the guide.

During mill delays it is important that there is a procedure for checking the condition of theguides in each area of the rolling mill.


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KEY POINTS.

1. Ensure that the water and lubrication pipes are always reconnected after a guide ischanged.

2. Ensure there are no holes in the pipes.

3. Ensure that the cooling water is flowing freely, when the Mill is stopped for maintenanceor a major change, do a water check.

4. The Roller should constantly monitor the guide cooling and lubrication.

5. Ensure the lubrication fittings are clean and are damage free before reconnecting after aguide change.


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ROLL COOLING.

Maintaining an adequate flow of cooling water onto the working passes of each roll is essential.To achieve the most efficient cooling of the rolls, the water should be introduced as near aspossible to the point where the rod or bar exits the rolls.

Experience would indicate that Banana type water headers or manifolds generally give the bestresults.

On the top roll it is important that the water header should not extend past the "five past twelve"position, as a carry over of water onto the entry side of the rolls is not desirable. Such carryoveronto the entry side will result in the front of the stock becoming chilled as it passes through thecascade of water which in turn could have the following results :

The front end of the stock tends to lift as it exits the delivery guides.

If the front end becomes extremely chilled, it can cause a miss feed (slipping in rolls), oreven cobble.

Bent front ends due to chilling can dislodge delivery guides. Also, the constant barinterference with the guide tends to cause premature failure of the guide.

Because the material is cold, it tends to spread more rather than elongate. This spreadcauses extended front end defects due to overfilling and in some cases this can result inthe defective part of the bar splitting open due to the constant rolling in of the overfilledend.

The length of the front end cut on the crop and cobble shears has to be lengthened toensure that the chilled and defective section is removed.

Water cascading out of the entry and delivery guides will also contribute to the front end chillingproblem. This condition can occur if the water cooling sprays for the guides or the bottom roll areincorrectly positioned.

Full coverage of the roll pass is also essential. It is therefore necessary to have different typesof cooling manifolds which will suit the various pass widths used in the mill.

The benefits to be gained from efficient roll cooling are ;

Greatly reduced pass wear.

Improved product quality due to the passes being smoother.

Increased tonnage before pass or roll changes are required.

Reductions in mill downtime for unscheduled pass or roll changes.

Reductions in operating cost, achieved through longer roll life.


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Greater ability to plan work in the roll preparation work shop.

Overall mill productivity will be increased.

The application of cooling water should be controlled. It is necessary for the production workersto be able to see all the guide equipment; therefore, it is necessary to ensure there is not a largevolume of excess water spraying over the equipment.

To achieve the required control it may be necessary to have different flows to individual stands,this will depend upon the size of the roll pass and the type of cooling manifold. This type ofcontrol is normally made possible by having individual control valves on each mill stand.

During the normal course of each shift it should be part of the production workers (in each area)normal working procedure to check the water cooling on all the mill stands. This should be doneon a regular basis throughout the shift.

Inspection of the rolls during mill delays could well reveal if there are water related problemsdeveloping. It is important that the bottom roll as well as the top roll be inspected. Water pipesshould also be inspected. Those which are damaged should be changed. Wrapping cloth orsimilar material around pipes with holes should be discouraged.

KEY POINTS.

1. Constant monitoring of the water cooling at each stand is required.

2. It is essential that the flow of water cover the full face of the roll pass.

3. There must be enough pressure to wash off any scale that may be sticking to thesurface of the roll.

4. Excessive water on the entry side of the stand is detrimental as it will chill the front endof the bar.

5. The application of the water onto the roll passes must be controlled.

6. Substantial benefits for the mill can be achieved through improving the cooling to the rollgrooves.


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TENSION CONTROL.

In order to achieve consistent rod tolerance along the full length of each coil, it is necessary tostrictly control the amount of tension in the mill. The ideal condition is to achieve minimumtension between each stand.

In the roughing stands where the stock speed is relatively slow, the main pulpit operator shouldideally be able to remove most of the tension with the aid of the motor ammeters. The Roller inthat area should assist by monitoring the stock flow and section shape.

On a multi-strand mill, compression or tension in any of the strands will cause problems in theprocess at the down stream stands.

Should there be any stands having tied gear boxes, it is extremely important that the stock sizesat these stands remain in the correct ratio. On a multi-strand mill, the stock in such stands needsto be correctly balanced in order to achieve a "minimum tension condition" on all strands.

An accurate check of the tension condition in a roughing mill is to send two billets through themill on the same strand, with the head of the second billet fed very close to the tail of the first. Agap will have to be created at the crop and cobble shear in order to ensure that the billet iscorrect for feeding to the finishing mill. Ideally on multi-strand mills this should be done on all thestrands to ensure that the stock drafting is the same on all strands. Otherwise It would bepossible to have one strand with tension, whilst other strands have a minimum tension condition,or vice versa. In tension free rolling this gap should remain relatively cinstant. Should the gapincrease, tension or “pull” is evident.

At the intermediate mill where the speed is greater, the responsibility for achieving the minimumtension condition must be a joint effort by the speed pulpit operator and the Roller on the millfloor. On the fast stands it is extremely difficult to achieve a "minimum tension condition" by onlychecking with the ammeters, as they will not have time to become stable before the bar entersthe next stand. The Roller can assist by checking the tension condition by striking the materialbetween the stands with a heavy object such as a bar. The true tension condition is thencommunicated to the pulpit operator who can make any necessary speed changes.

Tension should be checked every time a material grade change occurs. As a general rule, thestock spreads more and elongates less, as the carbon content (carbon equivalent) increases.This means that tension is created between stands as the material gets harder and thatcompression (speed loops) are created. . The same is generally true when the temperaturechanges. The colder the material the greater the spread.

It should also be the standard procedure to check the tension condition when the mill stock isadjusted.

Modern mills will normally have a "minimum tension control" function built into the electricalcontrol system for the mill. When selected "on", this will ensure that the most favorable tensioncondition is maintained at all times. As rolling temperatures change, or after steel gradechanges, the control system will automatically monitor the feedback from the ammeters andmake any adjustments that are required.


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KEY POINTS.

1. Stock must remain balanced by stand and by strand (multi-strand mills).

2. The roll partings must be set correctly.

3. There is a need to constantly monitor tension condition, particularly as steel gradeschange and when the mill is adjusted.

4. Feed two billets close together to check tension in the roughing mill.

5. Tension in the intermediate should be checked by striking the stock with a heavy bar.

6. Ensure the stock at the tied stands is correct.


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CROP AND COBBLE SHEAR, SPEED CONTROL AND CROPLENGTH.

In order to cut the front end of the bar without buckling, the crop and cobble shear should be setwith some lead speed. This will ensure that the peripheral speed of the shear blades is slightlyfaster than the stock passing through the shear.

For cutting the tail end, the shears should have a control system which will reduce the shearspeed prior to it cutting, this will eliminate the possibility of the tail end buckling. Unfortunately,very few shears actually have this system and so, if the shear is used for tail cutting. the leadspeed must be reduced to the minimum over speed, in order that the ideal condition of havingthe minimum amount of tail end buckling as the shear makes a cut is achieved. Excessivebuckling of the tail end will result in:

Tend to loosen the shear knife bolts.

Tend to cause misalignment of the shear troughs or guides at the entry of the nextstand.

Damage to the surface of the bar. This could cause quality problems as the buckledmaterial is dragged through the shear troughs and the entry guides.

Because of guide misalignment, the tail end of the material will have defects which couldwell cause it to split open in a "fish tail" effect. It is then possible for the tail end to breakoff in the NTM guides, the water boxes, or in the pinch roll guides.

The crop length should be closely monitored, excessive crop length means a considerable lossof yield. The following conditions must be maintained if the crop length is to be minimized :

The guide arrangement in the roughing mill must be correct.

Correct guide alignment must be maintained.

The correct elevation of the rest bars and rolls must be maintained.

Correct heating of the front and tail ends in the furnace.

Front end chilling of the bar in the roughing mill must be eliminated.

Failure to maintain these conditions will mean that there will be an extensive front end defect oneach bar through the mill. Taking short crop cuts under those conditions could result in the frontend of the bars opening up (splitting) and causing a cobble in the intermediate or pre-finishing orNTM's.

It is not unrealistic to have a consistent front end crop of 100 to 150 mm. This is being achievedin mills around the world.


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Should the shear not be cutting consistent lengths, it will be necessary to have the mechanicaland electrical systems checked.

KEY POINTS.

1. Lead speed should be closely controlled.

2. Monitor crop length to minimize yield loss..

3. The guide arrangement and guide setting must be good.

4. The elevation of the rest bars and rolls must be correct.

5. Correct heating of the front and tail ends in the furnace.

6. Eliminate the excessive chilling of the front ends at the roughing mill.

7. The shear mechanical and electrical systems must be well maintained.


27

SECTION 2

STOCK CONTROL TECHNIQUES


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STOCK CONTROL TECHNIQUES.

INTRODUCTION.

To achieve any sort of continuity it is essential that the mill stock is monitored and closelycontrolled . Making a number of small adjustments has a far less disruptive effect on the millthan making large adjustments only when problems occur. Making small adjustments on aregular basis is also more favorable for maintaining the correct stock balance throughout themill.

STANDARD STOCK SETTINGS.

The prerequisite to checking actual mill stock against the standard is to ensure that there is infact only one standard. A common occurrence in many mills is that each Roller or shift have theirown ideas as to what the correct stock should be. Usually none of these actually agree with therolling diagram or to the standard being used to assemble the mill guides.

As a first step in establishing just one common standard, the rolling diagram should be used. Ifduring the actual rolling it becomes evident that the standard needs some small alterations,these can then be made in a controlled manner, ensuring that all the necessary people anddepartments (guide assembly) are informed.

This procedure should ensure that all alterations to the standards are documented andcontrolled. Perhaps most importantly, the reason why the change was required can beinvestigated.

ESTABLISHING THE TOLERANCE STANDARDS

Each mill should establish tolerance standards for stock sizes in each area of the mill.

Example

Roughing mill - 1.00 mm or 0.040 inch.Intermediate mill - 0.50 mm or 0.020 inch.NTM entry section - + or - 1 to 1.5% of actually section size.

MEASURING THE STOCK.

Once the mill is restarted after a shutdown or a major size change it is necessary to check thesection dimensions. In the roughing mill, checking with calipers is quite accurate enough, as asmall deviation from the standard can be tolerated. If there is a large deviation from thestandard, adjustments should be made to rectify this immediately.


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Many operations use the practice of checking the stock size with calipers, and measuring thecaliper gap with a steel scale (steel measure). It is considered that this procedure is not accurateenough. Roller calipers are now being used at many plants where Morgan have been involved ingiving technical assistance. These have been proven to give a more accurate measurement ofthe stock. A vernier caliper should be used to measure the setting (gap) of the roller calipers. Ifcontrol of the stock is ever to reach a high degree of accuracy, this procedure should beintroduced.

Taking samples from all shear positions at a regular, predetermined period is one of theessentials of a stock control program. The samples should be measured, the size recorded onthe procedure sheet and most importantly, adjustments made to compensate for the pass wearwhich would have taken place since the previous samples had been taken.

Measuring cobbles is another step of the stock control technique. When a deviation from thestandard stock settings is found, steps should be taken to reset to the standard.

As the stock speed increases, it becomes difficult to take accurate measurements with handheld calipers. It becomes increasingly necessary to rely on the measuring and weighing of thesamples taken from the shears and those created by cobbles. Once again, if large deviationsfrom the standard are found, adjustments to the mill must be made to rectify the problemimmediately.

When adjustments are made to the rolling mill to compensate for wear in the roll grooves, it isimportant that the mill be kept in balance. On no account should one or two stands be adjustedmore than the others in the group. This will cause excessive wearing of those few stands andwill result in increased roll groove changing.

EXAMPLE - if the roughing mill is being adjusted, all the stands in the roughing mill should beclosed. The amount they are closed should vary as round or square sections will need to beadjusted more than the oval or diamond sections.

CONTROLLING STOCK BY TONNAGE THROUGH THE MILL.

Another philosophy for stock control in the roughing and intermediate mills is to make regularadjustments based on the tonnage through the mill. A correlation can be made between passwear and tons rolled through each pass. As the results appear to be linear, it therefore followsthat quite accurate control of the stocks can be maintained by this method.

It must be mentioned that to implement such a system requires a considerable amount of dataand analysis of performance over a long period before the necessary accurate stock controlresults can be achieved.

Recognition of differences created by various steel grades and rolling temperatures is important.

It is normal when using this system to record the roll partings for each stand when adjustmentsare made. This is an important cross check of the stock control activity against the actualrunning stock. Also, it will be used as a reference when checking against the standardprocedure for stock control in that area.


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CONTROLLING STOCK BY THE WEIGHT AND AREA METHOD.

At some operations, which incidentally are those operating at "best world practice", they go onestep further than just measuring the stock. Samples from the mill shear cuts are taken. Theseare then cut accurately to a predetermined short length. After being weighed, the cross-sectionarea is then calculated. Adjustments are then made to achieve the correct section area ratherthan just using the measured size.

EXAMPLE - To Check The Area Of A Section Into A NTM.

PROCEDURE

1. The weight of each of the theoretical sections to be weighed would be inserted onto atabulation sheet.

2. The sample section would be weighed and the actual weight compared to the theoreticalweight.

3. The mill stock size would be adjusted based on the difference between the actual weight andthe theoretical weight.

The main advantages of this method is that the amount of stock passing through the mill can bemore easily determined and controlled, despite the wear taking place in the roll grooves.

STOCK CONTROL AT THE NTM.

Verifying the stocks in the NTM is a virtually impossible task when the mill is running. The onlyopportunity to check the actual section arises when a cobble occurs.

The correct method to operate these mills is to maintain the correct stock size into the mills.

The stock control function at the NTM is virtually nil, as there should be few occasions when theoperator need adjust any stands other than the first or last stand. Adjusting the stands in thecenter of the mill should be discouraged, as alterations to the stock sizes means that in theorythe roller guide at the stand following the adjusted stand (if it was an oval section) should bealtered to match the new stock size.

The entry sections into the NTM is critical, for best results they must be maintained to within + or- 1 to 1.5% of the standard.

If the following conditions are met, the likelyhood of having cobbles is greatly reduced:

Correct roll partings.

The correct guide settings.


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The correct entry stock section.

The correct roll diameters are used.

Should a cobble occur, the Roller must take a front end sample off the cobble, this will beinspected to find the e cause of the cobble.The roll parting at the last stand before the cobbleshould also be checked and recorded. This process will enable a comparison to bemade ofthe standard roll parting to the actual stock obtained during rolling. As a result of thesefindings, it may be necessary to make some small adjustments to the partings in

order to actually achieve the correct running stock measurements.

KEY POINTS.

Using standard stock for the complete product range.

Check shear samples on a regular predetermined schedule.

Where possible, measure stock with hand calipers.

Measure cobbles whenever they occur.

Inspect the front end of cobbles to determine the cause.

Adjustments made to keep the stock balanced, stand to stand.

Correct entry stock size is required for the NTM.

Make small adjustments at regular intervals.

Ensure the correct roll gap partings are used, particularly for the NTM.

Do not make arbitrary adjustments to the center stands of the NTM.

Checking stock areas by weight is far more accurate than checking by measurement.


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SECTION 3

PRINCIPLES OF N.T.M. ROLLING


33

TUNGSTEN CARBIDE ROLLS.

INTRODUCTION.

Tungsten carbide rolls are produced using powder metallurgy and are not related to steel or ironrolls in any way. In a sophisticated process, fine tungsten carbide particles are blended with abinder which acts as a cement. The binder is normally cobalt, although in certain applicationsnickel and chromium are used. The powder mixture is heated while it is pressed into shapebefore being sintered and finished machining takes place.

Because of their extremely hard nature, carbide rolls are much more wear resistant than iron orsteel rolls. Wear is caused by two main factors, abrasion and corrosion.

Abrasion is due to tonnage, grade and temperature of the material that is rolled.

Corrosion is more to do with the quality of the cooling water and the type of binder beingused. It is essential to chemically control the cooling water in order to reduce itscorrosive effect. The pH should be approximately 7.5 to 8.5 which is slightly alkaline.Particles of scale should be kept to the minimum. This is achieved by using an effectivewater treatment and filtering process.

Because of the resistance to wear the rolling process becomes much easier to control. Correctsection size can be maintained for longer periods which results in improved quality and lessdowntime required for adjustments and pass or roll changes.

HANDLING CARBIDE ROLLS.

Carbide rolls are extremely expensive and they need to be handled with care. They are resistantto wear but they are extremely brittle. This means that they must be handled with great care ordamage such as chipping of the corners is likely to occur.

In the machining area the rolls should be stored on specially prepared racks and all workstations should have rubber or wooden surfaces.

The same applies to the area where the rolls and sleeves will be prepared for the mill. Everyeffort should be made to ensure that rolls do not contact each other as accidental contact couldeasily chip the edges of the rolls.

Transporting the rolls to the mill should be done in a specially prepared basket or bin. The insideof which should be constructed of wood, or lined with rubber and divided in such a way as toensure the rolls are kept separate.

An alternative to this is to use an "A frame" type of transport, which has rubber coated tubesattached at 90 degrees to the frame, on which to mount the rolls and tapered sleeve assemblies

Handling the rolls on the mill is historically where most of the damage takes place. This is partlydue to the fact that the rolls are extremely heavy, particularly those used on the NTM 8"housings and on Morgan pre-finishing mills.


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Work surfaces where the rolls may be placed on the mill should be covered with rubber or wood.The floor should never be used as a storage place, however temporary it may be.

When the rolls are removed from the mill they should be placed immediately into the transportingbin, or onto the "A frame". For roll installation and removal it is an advantage to use 2 man workteams. This will ensure that there is always a person available to handle the rolls, so eliminatingthe need for them to be put down between the transport and the mill pinion shaft.

KEY POINTS.

Carbide rolls are extremely expensive.

They are extremely resistant to wear.

The rolls are very brittle, handle with care.

Rolls should not be allowed to contact each other.

Work surfaces should be covered with rubber or wood.

The rolls are extremely heavy.

Rolls should never be placed on the floor.

Stock size and section are maintained for long periods, ensuring an improved productquality.


35

ROLL MOUNTING AND REMOVAL

V-MILLS

PRE-FINISHING MILLS

LAYING HEAD PINCH ROLLS

PINCH ROLLS USED PRIOR TO A V MILL

NOTE - This Section Is For Equipment Using The "TWO CYLINDER ROLL MOUNTINGSYSTEM"

INTRODUCTION.

The roll mounting on the above equipment can only be done using the special hydraulicequipment provided.

The tungsten carbide rolls have a tapered sleeve mounted in the bore before they are fitted ontothe pinion shafts. The roll shafts of the equipment are tapered to except the tapered sleeves.

The pinch rolls which can be scrap diameter 8" rolls from the N.T.M. or V Mill, have a steel insertshrunk into the bore. The tapered sleeves which are for 6" rolls are then mounted into the boreof the steel insert.

Once the rolls are mounted on the roll shafts the tapered sleeves are hydraulically pushed intoplace. A hydraulic tool is also used to remove the rolls.

THE HYDRAULIC EQUIPMENT.

There are two different size sets of tools for this process, they are :

8" mounting and removal tools - which is typically used in the NTM, housings 1 to 5.

6" mounting and removal tools - which are typically used in the NTM, housings 6 to 10,also the laying head pinch rolls and the pre-V Mill pinch rolls.

Roll Mounting Tools.


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The tool screws onto the end of the roll shaft and applies an axial force to the tapered sleevewhich locks the roll onto the shaft.

It is a two piston system :

No 1 piston applies an axial force to the roll face to hold it against the flinger .

No 2 piston applies an axial force to the tapered sleeve, pressing it to lock the roll inposition.

Roll Removal Tools.

The tool is locked onto the flange of the tapered sleeve. An axial force is applied to the end ofthe roll shaft, which in turn releases the sleeve. We are not pulling the roll, we are pulling thesleeve.

The Electro-Hydraulic Pump.

The pump unit supplies the force to mount and remove the rolls.

CLEANLINESS.

Cleanliness is the highest priority when mounting the rolls on the mill, this also applies whenassembling the sleeves into the rolls, wherever this operation takes place.

If dirt is present in the roll sleeve and shaft assembly, the wear process on the tapered sleeveand the roll pinion shaft is rapidly accelerated.

Once the support contact area of the roll shaft is lost, the likelihood of roll breakages increases.The useful life of the tapered sleeve is also greatly reduced when the wear process isaccelerated.

To achieve the best results it is necessary to clean the roll shaft tapers every time a roll ischanged. This should be done using SCOTCH-BRITE or CROCUS CLOTH.

Any oil residue should be removed by using a non- petroleum based cleaning fluid and cleaningcloths should be of a lint free type.

Should a roll be remounted on the mill without going to the roll shop, the bore of the roll and thetapered sleeve should be cleaned before they are reassembled. The roll shaft taper must also becleaned. So should both faces of the roll as it is important that the roll is contacting the flinger orthe spacers squarely and dirt on the face of the roll would damage the neck seals on the oldertype of NTM.


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USING SPACERS.

Carbide rolls can have between 1 and 4 grooves cut in the barrel. The size of groove and thelocation of the roll in the mill is the governing factor to the actual number of grooves on each roll.

In order to maintain the working groove on the mill pass line it is necessary to mount spacersunder the rolls when using the outside grooves on multi-groove rolls. When not using spacersunder the rolls it will be necessary to mount spacers on the open side face of the rolls.

Reference must be made to the relevant drawing for each piece of equipment and for each millin order that the correct assembly can be made.

PROCEDURE FOR ROLL MOUNTING.

1. Ensure the roll shafts are at operating temperature prior to mounting any rolls.

2. Release the entry and delivery side guides if they are mounted on the housing and removethem.

3. Clean the roll shafts thoroughly using Scotch-Brite and a non-petroleum based solvent toeliminate the possibility of an oil film remaining on the shafts. Ensure the cleaning cloth usedis lint free.

4. Ensure that the flinger is seated correctly.

5. Carefully place the roll and sleeve assembly onto the shaft taking care that no dirt isintroduced (if gloves are worn by the operator they should be clean), as should the operatorshands if gloves are not worn.

6. Check that the roll is correctly positioned against the flinger.

7. Screw the mounting tool onto the roll shaft until it is hand tight against the face of the roll.

8. Connect the two hoses to the correct nipples, once again check that the tool is fully handtight against the face of the roll.

9. Switch on the pump unit at the front mounted on\off switch.

10. On the pump unit manual control box, turn the switch to " MOUNT ", release the red pushbutton marked "pull to start"

11. Press the mount push button on the control box. The sequence of events is :

A. Piston No 1 is pressurized and the roll is held in position at approximately 200 Bar(approx. 2980 P.S.I.)

B. Piston No 2 is also pressurized and the tapered sleeve is pressed in until thepressure reaches approximately 400 Bar (approx. 5960 P.S.I.) on both pistons.

12. Before releasing the pressure check that both lines have reached the pressure set position(400 Bar, 5960 P.S.I.).


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13. Release the push button on the control box. The sequence of events is :

A. Piston No 2 is released immediately and is pushed back to its home position.

B. Piston No 1 is released only after a time preset (approximately 30 seconds) hastimed out. It is then pushed back to its home position by the force of the springs inthe tool.

14. It is recommended that the steps 7,10, 11, and 12, are repeated to ensure that the rolls aresecurely locked onto the roll shaft.

15. Depress the red push button on the manual control box "push to stop", this will eliminate thepossibility that the pump could be operated accidentally.

16. Disconnect the hoses and remove the tool.

17. Place the running cover over the shaft, check that it is positioned against the face of the roll.

18. Fit the running cover retaining bolt and tighten.

PROCEDURE FOR ROLL REMOVAL.

1. Release the entry and delivery guides and move them back from the rolls.

2. Release the running cover retaining bolt and remove the cover.

3. Fit the removal tool onto the flange of the tapered sleeve, ensure that it is correctly locatedon the flange. The spring pin located in the side of the removal tool must be located againstone of the protruding tabs on the flange of the tapered sleeve.

4. Connect the hose to the nipple on the tool, ensure the correct hose is used.

5. Switch on the pump unit, at the front mounted on\off switch.

6. Release the red push button marked (pull to start) on the pump unit manual control box Turnthe switch to " DISMOUNT ".

7. Press the dismount button on the control box. The piston is pressurized and the taperedsleeve is pulled off the shaft.

8. RELEASE the button as soon as the tapered sleeve is loose, this will allow the spring in thetool to push the piston back to its home position.

Normally the operator will hear a slight cracking noise as the taper between the roll shaftand the sleeve is broken. At the same moment the needle on the pressure gauge willfall. It is at this point that the button is released.

If the operator continues to press the button the pressure in the tool will push the pistonbeyond its designed stroke, damaging the seals in the tool.


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9. Depress the red push button on the hand control unit marked "push to stop" to disable theunit.

10. Remove the hose and disengage the removal tool.

11. Remove the roll and sleeve assembly together, place on a protected surface or directly on tothe roll transport.

12. Remove any spacers which may have been used.

KEY POINTS.

All the hydraulic tools must be well maintained, the hose connector nipples must be keptclean.

Hydraulic fluid level in the pump unit must be checked regularly.

Cleanliness is the highest priority when mounting rolls.

If spacers are being used, ensure they are the correct items for that particular position.

Ensure the procedure for roll mounting is carried out in the correct sequence.

ensure the procedure for roll removal is carried out in the correct sequence.

Hydraulic pressure should never be put to the tools until they are locked in position on theroll shaft or on the tapered sleeve.

The pump unit should always be switched off and the red push button on the hand controlshould always be depressed when the pump is not being used.

Take care when handling the carbide rolls, they are heavy and are easily damaged.


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ROLL ALIGNMENT.

INTRODUCTION.

It is possible to get roll groove misalignment (roll crossing), if the roll mounting procedure is notcarried out correctly. Should a roll not be pushed firmly against the flinger, it is probable that theflinger will rotate freely, causing the flinger and possibly the shoulder of the roll pinion shaft towear.

If the mill rolled with a crossed roll condition, the quality of the product would be jeopardized.

If the wrong thickness spacers are mounted under a pair of rolls, the rolls will not be on the passline. The guides would not line up correctly to the roll passes which could result in a cobble orpoor quality product.

It should become the practice to check for roll misalignment each time the rolls are changed.

CHECKING THE ROLL ALIGNMENT.

For the purpose of this training manual, only checking with the PORTABLE OPTICALEQUIPMENT is covered. This is the only positive method of achieving the required accuracy toproduce a quality product.

Prior to mounting either the light source or the portable optic on the mill stand, all the mountingsurfaces must be cleaned and checked to ensure there is no mechanical damage.

Ensure the correct adapter plates are being used to mount the optic and the light source.

NOTE - The newer portable optical equipment provided by Morgan does not require an adaptorplate when used in a Pre-finishing or NTM.

With the light source switched on, the operator views the resultant shadow image of the roll passthrough the optic projection screen. The shadow image should be exactly in the center of theprojection screen, this assumes the guide holder has already been set to the pass line. Thereare target type lines engraved on the projector lens to assist in the alignment of the image.

It may be necessary to adjust the position of the optic or light source to create the sharpestimage on the projection screen.

When looking at the image of the roll pass against the projection screen target lines, it ispossible to check if the rolls are mounted correctly.


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If roll crossing can be seen, it will be necessary to dismount the incorrect roll, clean all thecomponents and mount the roll again. Should roll crossing still be present it will be necessary toremove both rolls. The following should be checked :

if spacers are being used, they should be checked to ensure they are the same thickness. Ifthe error is in the spacers, they should be replaced and the rolls re-mounted.

if the spacers are correct, the outside flingers should be removed and checked to ensurethey are the same thickness. If the error is in the flingers, they should be replaced and therolls remounted.

if the flingers are correct, the rolls should be sent to the machine shop to check that thegrooves are correctly machined. Should these be found to be correct, an investigation willneed to be done on a whole series of other components, such as the inner flinger and rollshaft shoulder . These checks are outside the scope of this training manual.

Should the image show that the rolls are not on pass line, it will be necessary to remove both therolls and check that the flingers are the same thickness. Before remounting the rolls all thecomponents should be cleaned.

KEY POINTS.

Before mounting the optical equipment, clean the mounting surfaces.

Check for roll misalignment each time rolls are changed.

Ensure the correct adapter plates are used for the optical equipment.

It may be necessary to adjust the position of the light to get the sharpest image.

If roll crossing is found, it must be rectified.

Ensure components are cleaned correctly before re-mounting rolls

If the rolls are not on pass line, the problem must be rectified.


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ROLL PARTINGS.

INTRODUCTION.

The initial roll partings used in the NTM are taken from the rolling diagram. These figures aretheoretical and are produced using the following formula :

Stock Height - ( Roll Pass Depth x 2 )

In practice it is sometimes necessary to make some small adjustments to the theoretical figures,as they take no account of the deflection of the roll pinion shafts which takes place during therolling process.

In order to find what the actual parting should be it is necessary to pass trial pieces of hot steelthrough the rolls.

This is a procedure which need only be done once for each "family" of sizes. It is normally doneprior to the first hot run of the V Mill or N.T.M.

It is not always possible to use this procedure, as most mills do not have the necessaryequipment or time available to carry out such trials.

The alternative method is to measure samples taken from cobbles and from the finished productand gradually build up a file of information that will enable the correct settings to be established.When measuring cobbles it is important to also measure the roll parting of the last stand to rollthe material. This will enable the Roller to see immediately if there is an error in the standard rollparting information sheet.

Accurately setting the roll partings is an essential aspect for obtaining the correct section andhaving a trouble free start-up after a section change. Time spent to achieve an accurate set-upis time well spent.

SETTING THE ROLL PARTINGS.

To obtain the best results it is necessary to run the mill in jog, the speed should be atapproximately 5 - 10% of normal operating speed. Aluminum, copper or low carbon steel wire ispassed between the roll collars at each stand, the deformed section is then measured with amicrometer. This is the roll parting. If it is not correct, it will be necessary to adjust the stand andrepeat the process until the correct parting is obtained.

The material used to pass through the roll collars must be the same each time the process iscarried out. If different materials are used it will never be possible to obtain accurate partingfigures that will enable a trouble free start-up to be achieved each time the product size ischanged.

SAFETY - The normal plant safety rules must be considered when carrying out this process.


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The above method is the nearest simulation to the actual rolling condition that can practically beobtained. Being repeatable on every occasion, the roll partings require checking.

KEY POINTS.

Be aware of the safety aspect.

Using the correct settings is essential.

An accurate set-up is essential.

Measure the aluminum sample accurately, if there is an error, repeat the process.

Measure all cobbles and check the parting in order to check the accuracy of the set-up.

The material used to take the roll partings must be the same each time.


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GUIDES & GUIDE ALIGNMENT.

INTRODUCTION.

The basic function of the guides is to direct the section through the mill stands in such a mannerthat ensures that the front end does not deviate from the pass line.

The type of guide used at each stand will differ due to the size and shape of the section. Inmany cases it is necessary to change the guides or the guide components, as the size of thesection changes.

It is normal in many mills that the guides are prepared in a work area away from the mill floor.Once the guides are set it is then the responsibility of the mill operators to install them. It is theinstallation into the mill that is covered in this section of the manual.

It is essential that the correct components are used in the guides for each position and for eachsize of product being rolled. Reference to the guide tabulation sheets for each mill will identifywhich items are required.

THE TYPES OF GUIDES USED IN A STANDARD NTM OR V MILL.

Roller Entry Guides:

These are used at the entry side of the stand with the round profile in the rolls, also it is oftenused as the entry guide for the 1st stand in the NTM or V Mill. This guide can have either 2 or 4guide rollers.

Static Delivery Guides:

On a standard NTM, this type of guide is normally located at the delivery of every stand. Thereare many different designs, the better of which incorporate a breakout feature. On high speedmills, cooling guides are used on some stands. The use of the static delivery guide is thenrestricted to the stands that are producing an oval section.

Receiving Cooling Guide

Used on high speed mills for the entry side of stands with an oval profile in the rolls, only a roundsection is passed through a cooling guide.

Delivery Cooling Guides:

Used on high speed mills for the delivery side of a stand producing a round section.

Anti-Flutter Guide:

This guide is used only with an oval section, it is positioned between the delivery guide of onestand and the entry guide of the next stand. Over the years many different designs have beentried, the current Morgan anti-flutter guide is actually attached to the entry end of a RE 35 AS/4SP guide (4 roller entry guide)


45

Dummy Pipes:

Used where stands are dummied.

Breakout Troughs:

These are located between the NTM or V Mill and the water boxes.

MOUNTING AND ALIGNING THE GUIDES.

Roller Entry Guide:

These guides are normally clamped onto an adjustable saddle, which is attached to a bracket(base), located by means of a key and keyway to the housing face plate and held in position bybolts

Function: receives the section from the previous stand and provides support for the

section, directing the rod into the next stand. The section is usually an oval, but it isused for a round section when used at the entry of stand # 1.

Alignment is carried out as described in the section dealing with the portable optic.

There is an optional nose piece available which should certainly be used, particularly at the fastend of the NTM. It guides the front end of the rod into the center of the pass. It eliminate thepossibility of the front end striking the collar of the roll pass, which will cause a front endturndown or a cobble.

Static Delivery Guides:

Once again these guides are located on a bracket which is aligned on the pass center line by akey and keyway. The latest Morgan design is a split type guide. The bottom guide is held inposition on the bracket by a clamp, the top guide is located onto the bottom guide by 4 lugs andheld in position by a spring plate. This guide has particularly good breakout function.

Function: directs the stock in a straight line into the next stand. Should a cobble occur,the spring plate will be released by the pressure and the cobbling section will break free.This will reduce the likelihood of the rolls being damaged by a build-up of the cobblingsection.

Static Delivery Guide For Rebar And Finishing Positions Other Than Stand # 10:

These guides are a tube type guide, which has a separate nose piece. The guide tube fits into aholder which is mounted onto the same bracket as the cooling guide. For rebar, a spring is alsofitted behind the nose piece in order to ensure the nose is always fitting snugly into the roll pass

Function: the fitted nose ensure that the guide strips the stock from the roll pass. Theguide tube directs the bar in a straight line into the next stand entry guide. There is also


46

a breakout function which will reduce the likelihood of the rolls being damaged by abuild-up of cobble material.

Delivery Cooling Guides:

These guides are fixed in a holder, which is mounted on a bracket located on the pass centerline by a key on the housing. There is no adjustment for either the guide or the holder.

The mounting incorporates a breakout feature in the form of a spring located in the holding downscrew assembly. The tension on the spring must be preset by the Roller at the time of the initialguide installation.

Function: is to cool the round process section in-between the rolling stands, to obtaincertain metallurgical properties in the finished product.

Receiving Cooling Guide:

These guides differ from the delivery guides in that there is no breakout feature. Mounting of theguide is very similar to that of the delivery cooling guide.

Function: is the same as for the delivery cooling guides.

Anti-Flutter Guide:

Many of these guides are mounted in the position of the delivery guide bracket, a delivery guideis then fitted onto the guide in front of the roller holders.

With the latest design of Morgan anti-flutter guide, once it is mounted on to the RE-35 AS/4 SProller guide, the anti-flutter guide is automatically aligned to the same center line as the rollerguide.

Function: of this guide is to give extra support to the rod. It is used to restrict the fluttertendency of the oval section.

Dummy Pipes:

The dummy pipes are used when stands are not used for rolling. They replace the mill rolls,roller entry guide and the delivery guides.

Function : is to guide the rod to the next stand, or to the breakout box.

The pipes are mounted into holders, which are fitted directly onto the existing guide brackets andare therefore correctly aligned to the pass line.

The Breakout Box:


47

Over the years many designs of breakout box have been used, most of which proved to bedifficult to maintain on the pass center line.

Morgan has now introduced a design where one end of the assembly is attached onto the lastNTM housing. It is aligned by means of a key on the housing face plate. The delivery end isattached to the first water box, alignment is done at the mill installation or when the newassembly is installed in a mill. There are a number of sections of inserts, one of which willincorporate air wipe. this ensures that no water will flow out of the mill in front of the deliveryside H.M.D.

Function: the breakout box is designed to guide the rod from the NTM to the waterboxes. In the event of a problem down stream, it enables the rod to have a controlledcobble in an enclosed compartment. It gives the stock space to breakout, rather thancobble between the delivery guide and the rolls.


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GUIDE BRACKETS.

INTRODUCTION

The guide brackets are located on the face plates of the housings. In all cases, they are locatedat the correct elevation to the pass line by a key. These can either be attached in a keyway onthe housing face plate, attached in a key way in the base of the bracket, or are an integral part ofthe bracket.

In all cases, the guide brackets are held in position by bolts screwed into the housing face plate,or by "Tee" bolts located into slots in the housing face plate. These pass through the guidebracket and are secured in position by nuts screwed onto the protruding bolt.

FUNCTION.

They provide a means for location of the guides at the correct pass line elevation. In the case ofthe brackets for the roller guides they also provide a means of adjusting the guides axially acrossthe pass line (adjusting the guides correctly to the pass).

MAINTENANCE.

Correct guide location will only be achieved if the guide brackets are maintained in goodcondition. Before mounting a guide the bracket should be thoroughly cleaned, particularly at thelocation face for the guide.

Clamps and clamp bolts should be in a good condition and free to move with ease.

A procedure should be devised where every bracket is removed from the mill at a regular intervaland replaced with an item that has been refurbished in the guide preparation area.

Particular care should be taken to ensure that there are no burrs or raised surfaces on themounting surface of the brackets. Also, that the saddles of the roller guide brackets move freely.

It is essential that the key or keyway is also in good condition. Any damage or deterioration ofthese can be the cause of cobbles, as the bracket and the guide may not be located at thecorrect pass elevation or possibly not even parallel to the pass line.


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KEY POINTS.

The brackets must be located correctly and secured firmly in position.

When guides are changed, the location surfaces of both the guide and the base should becleaned.

A procedure for changing each bracket on a regular basis should be devised.

Ensure all mounting surfaces are damage free.

All keys and keyways must be in a good condition. Severely damaged or worn items shouldbe scrapped.

The saddles of the roller guide brackets must slide freely, without being free to twist.


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STOCK ADJUSTMENTS.

INTRODUCTION.

Accurately setting the roll partings is an essential requirement for obtaining the correct sectionand having a trouble free start-up after a size, pass or roll change. Time spent to achieve anaccurate set-up, is time well spent.

As the mill has a fixed gear ratio between the stands, it is important to maintain the correctstocks at each of the stand in order to minimize problems.

NOTE WELL - SPEED X AREA = MILL CONSTANT

The guides for the mills are preset to the standard stock. Arbitrary adjustments at the mills willcause the stock to change, which could mean that the guides will not perform correctly. Thiscould well cause premature guide failure or a serious quality problems

It is important that the entry section into the N.T.M. is maintained at the correct size. If this isachieved, there should be few adjustments required, once the correct stock sizes have beenestablished.

The last stand prior to the N.T.M. should be adjusted in order to make the delivery section round.It is important that a round section is maintained as this will ensure a smooth and constant entryinto the first NTM stand. Also, it will ensure a smooth passage through the trough sections andthrough the Crop & Divide Shear into the NTM.

ADJUSTMENTS TO THE NTM OR V MILL.

The function of the NTM is to reduce the stock size in order to produce an accurately sizedproduct. The size range of rod that can be produced from a standard Morgan NTM or V Mill isfrom 5.0 mm to 25.4 mm ( 0.197" to 1.00" ).

It is important that the entry section into the mill is kept to the correct size. If this is achieved,there should be few adjustments required, once the correct stock sizes have been established.

If the correct roll diameter ratio is maintained throughout the Mill and the correct roll gap settingsare used, there should be few occasions when the operator need adjust any stand other than thefirst or last stand.

Adjusting stands in the center of the NTM should be discouraged as alterations to the stockshould in theory make it necessary to adjust the roller guides.

This is particularly so with the oval sections, where stock adjustments could well cause a qualityproblem due to the roller entry guide at the following stand being unable to hold the sectioncorrectly.


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KEY POINTS.

The stands have fixed gear ratio's, and the correct roll diameter ratio must be maintained.

The roll gap partings must be correct.

Entry section to the NTM or V Mill must be the correct stock size.

Only make small adjustments or the guides will not function correctly.

The entry section into the NTM or V Mill should ideally be good and round.

The center stands of the NTM or V Mill should not be adjusted.


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FLUTTER, THE CAUSES AND THE SOLUTIONS.

INTRODUCTION

Flutter is a phenomenon that sometimes occurs in the NTM's. The rod vibrates at a highfrequency between two rolling stands, it is in fact a slight compression condition of the stockbetween the rolling stands. Normally it is the oval section that flutters.

It can sometimes be seen on the finished product as an overfill, which occurs repetitively onalternate sides of the rod. It is sometimes termed as an "in and out" defect. The amount ofoverfill and its repetitive frequency will depend upon the conditions which are actually causingthe flutter.

POSSIBLE CAUSES.

Area of the entry section into the NTM, is to large.

The correct diameters for the rolls within the NTM, are not being maintained.

The stock sections (roll partings) in the NTM are not correct.

The combination of guide equipment and accurate setting of the guide is incorrect.

Stable temperature conditions along the length of the billets is not being maintained.

Bearing problems in the NTM housings. This is a very rare source of a flutter condition.

THE SOLUTIONS.

The area of the entry section must be strictly controlled to the established standards. Anyincrease in the volume of the entry stock will increase the volume of stock flowing through theNTM. Section shape and size will not be correct, this increases the likelihood of a fluttercondition occurring between rolling stands.

Using the front end sample from the crop and divide shear is likely to give a false reflection ofthe actual section size of the majority of the bar length. The very front end is chilled andoverfilled, some short length further back it is possible that there will be a slight tensioncondition. This slight tension condition occurs when there are loopers in the mill, an example ofthis is in a pre-finishing mill where the front end is in a slight tension condition as it passesthrough the pre-finishing stands before the up loopers raise and the loop control releases thetension.

In order to obtain a truer picture, it will be necessary to take samples from the tail end of the bar,perhaps 2-3 meters from the tail end would be ideal.Reductions in area of the entry section will decrease the tendency for a flutter condition to occur.


53

Maintaining the correct roll diameters between stands is important. Various mills haveestablished policies for roll diameters which suit that particular mills requirement. Such policiesas :

NEVER make the roll diameter on a stand, less than that of the preceding stand.

Make the rolls of the finishing stand, larger by 1 or 2 mm, than those of the oval leaderstand.

Should it be necessary to have incorrect roll diameters, it is important that the difference indiameter is communicated to the rolling mill as it will be necessary to adjust the roll gaps tocompensate. Failure to do this could result in :

Increased tendency to flutter.

Cobbles due to excessive flutter/speed loop.

Tension between rolling stands.

The correct section size of the stock between each of the rolling stands within the NTM must bemaintained. This is only possible if standard procedures for setting the roll gaps and operatingthe NTM are established.

An incorrect stock balance between the stands where excessive flutter is occurring, or at thestands prior to the flutter is often the source of that excessive flutter.

One of the problems when operating a NTM is that the actual stock size between the stands israrely known. Operators need to gain more information as to what is actually passing through themill.

Having a procedure for measuring and recording the dimensions of cobbles and at the sametime measuring and recording the roll parting from the stand where the cobble occurred, willhigh-light any deviations from standards. These deviations generally occur because the roll pshaft deflections are greater than those which were anticipated, and which were possible builtinto the standard partings.

Constant monitoring of the actual running conditions and maintaining standards. will reduce thelikelihood of heavy disruptive flutter from occurring.

The correct guide equipment must be supplied to the mill. The equipment must also be setcorrectly, both in the assembly area and in the mill.

Roller guides which are set tight and so are in fact rolling the stock, can create a conditionsimilar to flutter, as the previous stand has to drive the stock through the roller guide. Theeventual outcome of this condition is normally a cobble.

An uneven temperature along the length of the billet changes the conditions under which thematerial is rolled. Should there be a large deviation along the length, it is possible that whenrolling a particularly cold section, the material will start to flutter , due to incorrect material flowratio's between the stands.


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The condition when mechanical problems with the bearings causes the material dimensions tovary to an extent that flutter results are extremely rare. Operators should be aware that it canoccur. If it does, the housing causing the problem should be changed immediately as the fluttercondition indicates that there is a major problem that will quickly result in a housing "burn up".

SETTING THE ANTI-FLUTTER GUIDE ON THE MILL.

This section refers to anti-flutter guides with adjustable roller holders.

The anti-flutter guide is designed to minimize the effect of any flutter that occurs in the NTM. Inmany cases, flutter is not completely eliminated. The guide will minimize the flutter to a pointwhere it is not a problem on the finished product.

The success of the guide depends upon the setting of the guide in the mill. The philosophy isthat the guide will restrict the amount of movement of the section. This increases the frequencyof the vibration, but the amplitude (amount of movement) is decreased. On the finished product,the result is that the tendency to show "in and out" overfill is greatly reduced.

Once the anti-flutter guide has been installed onto the roll housing, it is necessary to set theroller holder symmetrically to the pass center line of the rolling mill. Also, the rollers must be setto the correct position to minimize the flutter.

NOTE - THE MORGAN ANTI-FLUTTER GUIDE USED IN CONJUNCTION WITH THE RE-35AS/4 SP GUIDE IS SET SYMMETRICALLY AT THE TIME OF ASSEMBLY.

It is necessary to use a setting jig and a combination of setbars to achieve the correct setting foreach rod size. The jig is located on the saddle for the roller entry guide, on the stand followingthat fitted with an anti-flutter guide.

A set bar is placed on the jig, the end of which extends between the rolls of the anti-flutter guide.The guide is adjusted until the roller holders are in the correct position, normally the roller wouldjust be touching the setbar, which is slightly larger than the section passing through the guide .

The actual setting used by mills varies, some like the roller set to the stock, at others the rollersare set slightly open. Setting the rollers tight onto the section will not reduce flutter, it will onlyresult in premature failure of the guides due to bearing failure or roll wear.

In some mills, only one arm and roller are used in the guide, this works quite successfully. Thethinking behind this is, as the guide controls the amplitude of the flutter rather than actuallystopping the flutter, one roller arm will work as well as two.

It is important that this type of guide is set in the same manner as described for the two armguide. The roller must not protrude into the pass line or front ends will be deflected off line,possibly resulting in a cobble.

KEY POINTS.


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Correct feed stock into the NTM is likely to minimize the possibility of flutter occurring.

Back end samples from the C&D shear will give a more accurate picture of the truestock size.

The roll diameters within the NTM must be correct.

The stock sizes in the NTM must be correct.

Minimize adjustments to the center stands of the NTM

If an anti-flutter guide is used, the final symmetrical setting should be made with theguide mounted in the mill.


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GROUPING OF ROLLS.

From each set of rolls installed onto a NTM or V Mill it is possible to roll a number of differentsize rod products, by either:

Removing or installing two or more pair of rolls in the V Mill, while maintaining the sameor very similar entry stock size and similar roll gap settings in the mill.

Changing the rolls on the last stand and

- changing the area of the entry section.

- changing the roll partings in the N.T.M. or V Mill (stock sizes).

- changing the roller guides.

It is normal to have 5 or 6 different groups of rolls used in a NTM or V Mill. From these groupsthe full rod product range can be produced.

The groups of rolls are frequently known as "FAMILIES" or "SEQUENCES" of rolls. Reference tothe rolling diagram will clearly show the groups and the stock entry size required for each group.

It is very important that the correct diameter ratio's are maintained between each stand andacross the complete group of rolls. There are many mills who will never install a roll that has asmaller diameter than the roll on the preceding stand.

In order to be able to achieve the requirement of maintaining the correct diameter ratio, manymills keep the rolls in groups which correspond to the sequences mentioned above. Rolls fromeach sequence are kept together and would not be used when another sequence was in themill. With careful planning it is possible to ensure that each sequence has the correct number ofrolls that will enable the planned production to be rolled without being forced to deviate to rollsoutside the correct diameter range.

When machining of the rolls in any sequence takes place, the same amount would be removedfrom each and every roll in the group. It is therefore very important to control the wear whichoccurs on each roll pass. This is achieved be having a predetermined plan as to how many tonswill be rolled over each stand before the rolls are changed. Obviously this will differ from mill tomill, according to the product mix of the mills. An example of typical tons per pass is shownbelow.

NOTE. In the example below the tons per pass are low as the mill concerned was producingmaterial for the top end of the rod market. The tons are "short tons" add 10% for metric tonnes.It should also be noted that this mill had old style water headers on the NTM at the time.

In this example, no finished product is rolled from the 1st two stands.

The designation "Process Pass" is given to passes other than the "leader" or "finishing pass",They can be the same size and shape as when a product is being rolled from that particularstand.


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TYPICAL EXAMPLE OF PLANNED TONS PER PASS FOR A ROLLING SEQUENCE

NTM STAND WHEN USED AS A WHEN USED AS ANo FINISHING PASS PROCESS PASS

1 NOT APPLICABLE 2000 TONS2 " 2000 "3 800 TONS 1600 "4 800 " 1600 "5 600 " 1200 "6 600 " 1200 "7 600 " 800 "8 600 " 800 "9 400 " NOT APPLICABLE10 400 " "

PROCEDURE FOR ASSEMBLING A FAMILY GROUP OF ROLLS

The basic requirement is to know the average tons to be rolled in each sequence, historic data,perhaps the last 6 months rolling schedule should be used.

In this example alphabetical letters are used to identify the different sequences (A, B , C, D &E),

EXAMPLE, For B Sequence

Average Tons from the last 6 months rolling cycles:

Rod Size Tons Finishing Stand29/64 500 3 & 423/64 900 5 & 69/32 2000 7 & 87/32 7000 9 & 10

The next step is to set the standards for the tons to be rolled over each pass at each stand. It isnecessary to differentiate between finishing passes and process passes. The oval prior to theround pass should be changed each time the round is changed. Data from the example givenabove will be used.

TYPICAL EXAMPLE OF PLANNED TONS PER PASS FOR A ROLLING SEQUENCE

NTM STAND WHEN USED AS A WHEN USED AS A


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No FINISHING PASS PROCESS PASS

1 NOT APPLICABLE 2000 TONS2 " 2000 "3 800 TONS 1600 "4 800 " 1600 "5 600 " 1200 "6 600 " 1200 "7 600 " 800 "8 600 " 800 "9 400 " NOT APPLICABLE10 400 " "

From the information above in the two charts, "Planned Tons To Be Rolled" and "Planned TonsPer Pass", it is now possible to calculate the total number of rolls required for B Sequence.

THE FAMILY GROUP WOULD CONSIST OF THE FOLLOWING NUMBER OF ROLLS

It must be remembered that there are two different figures used for tons per pass. ons over a"finishing pass" and tons over a "process pass"

Stand Pass No. Passes Total Tons Finishing Process Total RollsNo. Design In Roll Per Stand Passes Passes Required

1 P 1 10,400 0 6 62 Q 1 10,400 0 6 63 R1 2 10,400 1 6 44 29\64 2 10,400 1 6 45 T1 2 9,900 2 8 56 23\64 2 9,900 2 8 57 V 2 9,000 4 9 78 9\32 4 9,000 4 9 49 X 4 7,000 18 0 5

10 7\32 4 7,000 18 0 5

KEY POINTS.

The correct roll diameter ratio must be maintained between the rolls in each group.


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Always ensure that the correct pass profiles are being used.

In order to achieve the best rolling condition for each group, the correct entry stock size isrequired.


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SECTION 4.

QUALITY ASPECTS.


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ROD DEFECT TROUBLESHOOTING

There are many similarities between the defects found in both bars and rod, this is specially truewhere steel making defects are concerned.

One major problem is that the small size of rod products makes it more difficult to detect thedefect in the first place. Also, the fact that the product is in a coil means that it is difficult todetect small defects.

Another difference is that the rolling process in a standard NTM or V Mill cannot be seen due tothe Cobble Guard Door enclosing the mill. The mill must be stopped and the door opened inorder to hunt the cause of quality problems, this is very time consuming. It is therefore of greatbenefit to be aware of the likely source of many of the defects that can be found in the finishedrod product.

TROUBLE SHOOTING.

Continuous monitoring of the rolling process is the key to trouble shooting any defect. TheRollers in each area should be aware of the condition of the mill, the guides and the stockpassing through their area.

CRACKS.

Cracks are breaks in the rod surface which penetrate the rod vertically or at an angle. They varyin length and depth and can usually be found running along the length of the rod.

The Causes.

There can be many reasons for cracks in a billet. These can be created during the steel makingand subsequent rolling to billet or continuous casting operations. Also, poor conditioning of thebillets can create problems.

Causes of cracks created during the Rod Rolling process:

Improper roll groove shape (sharp corners, wrong size groove).

Excessive roughness or damaged groove surface.

Guide scratches from early roughing mill stands.

Course scale rolled into the surface of the bar. Again, this normally occurs in the earlyroughing mill stands.

Using incorrect size of guide (too large).


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Trouble Shooting.

Should cracking occur the following should be checked :

Billet descaler must be working efficiently. Has any of the mill stand roll cooling becomeblocked or moved off the groove?

Guides, check to see if any have moved out of line, possibly there is scrap lodged in one ofthe guides.

Excessively worn roll grooves. Have any of the grooves been damaged by a cobble or whileremoving a cobble?

Check to see if there are any crossed rolls in the NTM. Are the guides correctly aligned andare the guides the correct size for the section being rolled?


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LAPS.

Laps are breaks in the rod surface, they can penetrate the rod surface at any angle. Normallythey are quite long, but occurrences of intermittent short laps can be troublesome and usually tobe seen running longitudinally in the rod.

The Causes.

Defects in the billet such as pipe, segregation, inclusions, poor billet preparation etc. can be thecause of laps in the finished product.

Causes of laps created during the Rod Rolling process:

Pass overfilling is the most common cause.

Pass under filling can also be a cause where the empty part of the section falls over in theroll pass.

Heavy tension in the mill has the same effect as pass under filling.

Poor guide alignment can result in a lap on one side of the rod.

A poor standard of mill set-up, incorrect stocks poor guide alignment and incorrect or badlyworn guides can be associated with intermittent laps.

Fluctuations in billet temperature.

Trouble Shooting.

Billet descaler must be working efficiently. Check roll cooling. Heavy deposits of scalerolled in during at the roughing mill can be the source of intermittent laps.

Has a guide moved out of line causing an overfill ?

Guides must be in a good condition. Check for material build-up on static guides andinspect the condition of rollers in the roller guides.

Is the stock throughout the mill correct ? Check for overfill or under fill.

Check the tension condition.

The billet discharge temperature should be checked. Fluctuations along the length of a billetcan result in an intermittent overfilling of the section.


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FINS (OVERFILL).

Fins are narrow lines running longitudinally on the rod.

The Causes.

Defects in the billet such as pipe, segregation and inclusions can result in overfill on the rod.

Causes of fins created during the Rod Rolling process:

Incorrect stock or incorrect roll adjustment.

Excessive tension resulting in heavy front and tail end overfilling.

Incorrect guide alignment or guide setting on the finishing stand.

Fluctuations in the billet temperature.

Flutter, causing intermittent fins first on one side then on the other side of the rod.

Trouble Shooting.

Correct stock size into the NTM is extremely important.

Correct roll diameter matching and roll gap settings are essential.

Check the tension condition in the mill. If the settings, roll diameters and entry stock into themill are correct, there will be a minimum tension condition in the NTM.

If the fin is on only one side of the rod, check the finishing stand entry guide alignment.

Intermittent fins on either side of the rod is caused by a condition in the NTM known as"flutter". The following list of items must be correct if the "flutter" condition is to beeliminated.

Roll diameters in the NTM or V Mill must be correct.

The entry stock into the NTM or V Mill must be correct.

The roll gap settings must be correct.

The guide settings must be correct. That is, they must match the stock size being rolled.

The anti-flutter guides should be used if flutter occurs. If conventional anti-flutter guides areused, It is important to ensure that the anti-flutter guide is set correctly.

Check to see if the steel grade has changed. As the carbon equivalent increase, so thetendency for the material to spread increases.


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UNDER FILL.

Under fill leaves the open sides of the rod empty at the scale-break.

The Causes.

Incorrect roll gap settings.

Excessive tension in the mill.

Roller guides set too tight.

Loop control regulation is incorrect.

Trouble Shooting.

The mill must be set correctly. Check the stock sizes with calipers and take samples at theshear positions.

The tension condition in the mill should always be at the minimum. Changes of steel gradewill necessitate the operator to make adjustments to the speeds. As the carbon equivalentincrease, elongation decreases. Therefore, speed changes are necessary.

Check the loop heights to ensure the best possible shape is maintained. Loop regulationmust be checked on a regular basis. The "Auto reset" function should always be selectedexcept for the first few bars after a change.

Excessively tight roller guides can create a tension condition and also cause the front andtail ends to be under filled.


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SCRATCHES (OCCURRING DURING THE ROLLING PROCESS).

Scratches are longitudinal furrow like depressions. The form and size can vary from a minutesharp crack like indentations, to large furrows with partial projecting or overlapped edges.

The Causes.

Pick-up in the guides (material adhering to the guide surface).

Guides in a bad condition or broken guides.

Debris caught in a guide.

Bad mill stand alignment or poor guide alignment.

Loose guides.

Trouble Shooting.

The mill should always be checked during stoppages. Guides at every stand would normallybe inspected. It is necessary to use a flash light in order to see into the guides properly.

Incorrect stand pass or guide alignment is unfortunately quite a common error, that shouldbe checked regularly.


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CRACKS AND CHIPS IN THE CARBIDE ROLLS

Cracks in the carbide rolls normally appear on the rod surface as longitudinal lines. In extremecircumstances they can also appear as a crazing effect on the rod surface.

Chips in the rolls will appear as embossed elevations on the rod surface.

The Causes.

Because of the nature of carbide rolls, they are susceptible to cracking if the roll cooling isnot correct.

Chipping of the roll groove can be caused through :

- poor cooling.

- mishandling of the rolls.

- poor machining techniques.

Incorrect pH of the cooling water.

Trouble Shooting.

The condition of the rolls on the mill should be checked during mill delays. The reasons forpremature deterioration of the groove surface should be investigated.

Carbide rolls should always be handled with care. Proper methods of transporting andstorage must be deviced

Marks or elevations in the rod surface should be measured from one elevation to the next. Itis then quite obvious if the working roll is chipped, or a guide roller is chipped.

Poor machining techniques can severely overheat the roll. The roll surface will appear as apurple-blue color. Rolls in this condition should not be mounted on the mill.

The quality of the mill cooling water should be checked regularly. Suspended solids(scale) must be controlled, as should the pH. This should be approximately 7.5 to 8.5which is slightly alkaline.


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ROUGHNESS OF THE ROD SURFACE.

Continuously occurring irregular depressions and elevations on the rod surface can be bestdetected under magnification.

The Causes.

Severe roll groove wear, due to over rolling the grooves or poor groove cooling.

Roll cooling water pH too low (acidity too high). If the pH becomes too low, the acid contentattacks the bonding of the carbide rolls, resulting in small particles of carbide to pull out ofthe surface during the rolling process.

Trouble Shooting.

There should be a strict schedule for changing grooves for all the stands in the mill.

Inspection of the roll cooling and groove surface should be done throughout each of therolling shifts.

Checking water quality regularly.

Check the water roll cooling headers (nozzles) for blockage.


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MECHANICAL DAMAGE.

Abrasions, gouging of the surface, bruising of the cross section and distortion of the rings areknown as mechanical damage. All these occur after the rod has left the finishing stand.

The Causes.

Sharp corners or equipment damage :

- in the breakout box.

- cooling and recovery zones inserts.

- pinch roll entry or delivery guides.

- laying head pipe.

Incorrect tension control on the pinch rolls causing the rod to flop about in the water boxesand recovery zones.

Damaged or badly adjusted laying head tripper plates or side deflectors.

Seized rollers in the Stelmor side deflectors.

Damaged or badly worn components in the reform tub, coil chamber, transfer car,downender or hooks.

Damaged or worn components at the compactor stations.

Incorrect handling of the coils at the takeoff and in the stock area.

Incorrect loading on the transport to the customer.

Trouble Shooting.

Care should always be taken when assembling all the equipment on the rod path. Alignmentand cleanliness should always be paramount in an operators thoughts.

Inspection of the rod as it passes through the water boxes with the pinch rolls closed willshow if there is enough tension control and lead speed set in the process control system.The rod should be stable, not flopping about (vibrating).

Close inspection of the damage can give some indication of where the likely problem occurs:

Continuous or semi continuous longitudinal scratches would normally occur in theequipment from the delivery guide (including the delivery guide) of the last stand tothe beginning of the laying head pipe.


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Small elevations or depressions, appearing at a regular frequency in the rod surfacecould well be caused by a pitted or damaged pinch roll, or a damaged pinch rolldelivery guide.

Helical scratches are likely to be caused by a badly worn laying head pipe.

Bruising of the cross section on the outside of the coil could come from :

Laying head tripper plates or side deflectors.

Damaged surfaces inside the reform tub and coil chamber.

The transfer car, or downender ,surface damage or incorrect elevation.

Compactor station and take off station.

Bruising of the inside cross section of the coils :

Damaged surface of the sail/mandrel, or it is not aligned correctly.

Damaged surface of the nose cone.

The compactor mandrel.

The surface condition of the hooks.

Handling of the coils at and after the takeoff station is an area which is quite oftenneglected. Severe damage often occurs due to handling. Correct well maintainedequipment combined with training is required.


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SHELL OR SLIVERS.

Shell (slivers) is overlapping material varying in shape and size. It is distributed irregular on therod surface and adheres to the rod base material only in small places.

The Causes.

Poor quality billets are the root cause of many of the instances of shell.

Other reasons created in the rolling mill:

Overheating of the billets.

Poor quality of billet preparation.

Excessively worn roll grooves.

Debris laying in the mill guides.

Trouble Shooting.

Excessive heating of the billets will cause segregation and excessive scale which may wellnot be removed by the descaler. Heavy particles of rolled in scale will normally fall out of thesurface during the rolling process, leaving small indentations which can be rolled over.These will eventually break open, forming a shell defect.

Segregation forms an uneven billet surface. Indentations get rolled over and break open ata later stage of the rolling process.

As previously mentioned, the condition of the rolls should be continuously monitored.

Continuously checking the mill during delays should reduce the likelihood of debris laying inthe guides.


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TOLERANCE AND QUALITY CHECKS

TOLERANCE.

Dependent on the operation and the requirements of the finished product, the pass design of theNTM or V Mill can differ. It is becoming more common for customers to demand half toleranceproduct. This is only possible if the correct stock is maintained at all times. And the minimumtension conditions are maintained, and if the correct settings are used in the NTM or V Mill.

BASIC AIDS REQUIRED FOR CHECKING SAMPLES ON LINE.

At the rod finishers station there should be a work bench on which is mounted a "magnifyingglass mounted in a lamp". Micrometers are necessary to ensure accurate measurements.

TOLERANCE CHECKS BY OPERATORS.

When starting a new size it is essential that rod samples are brought to the rod finisher at theNTM. If long delays are to be eliminated, it is necessary to cut the samples on the Stelmor line.Adequate means for cutting samples should be provided.

Throughout the rolling, samples should be cut for the rod finisher. This is particularly important atgrade changes where the open side measurement of the rod is likely to change.

The rolling program should be closely monitored by the rod finisher. And he should be aware ofall grade changes that take place.

The section can be constantly monitored by the rod finisher, at the exit end of the NTM. With theaid of a high intensity light he will be able to see if the rod is over filled or under filled.

The final solution to constantly monitoring the section is to install an "automatic laser gauge"which will scan the rod section as it passes through the gauge. The actual size and variation inthe size can then be displayed in many forms.

At some point after the coil is on the hook conveyor there will be an inspection station. It isimportant that there are not too many coils between the reform and the inspection station, so asto reduce the likelihood of a large number of rejects should a problem occur in the mill.

QUALITY CHECKS BY THE OPERATORS.

As well as checking the samples for size, the rod finisher should be checking the followingquality checks :

Ovality due to roll crossing.

Ovality due to incorrect stock size or roller guide setting.


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Surface defects due to :

Roll or guide problems as listed in the previous pages.

Rolled in debris or scale.

Laps and cracks, these can only be detected if they are severe.

Scratches and mechanical damage occurring between the mill and the point wherethe sample is taken.

At the coil inspection station the following additional quality checks should be made :

Check the coil for tension.

Check for scratches and mechanical damage.

Assess the coil package from the reform area and inform the mill if it is unsatisfactory.

The mechanical testing of the rod is out of the scope of this manual.


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SECTION 5.

STANDARD OPERATING PROCEDURES.


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STANDARD OPERATING PROCEDURES.

WHAT ARE STANDARD OPERATING PROCEDURES ?

Documented working methods, devised to show the most efficient and effective method ofperforming an operation. With the expressed aim of obtaining continuity in performance betweeneach operating shift.

Considerations are given to the use of correct maintenance procedures, the necessity ofproducing a high quality product and following current safety practices.

The following are some suggestions for areas where the introduction of standard procedureswould immediately assist in improving mill performance:

1. STANDARD STOCK SETTINGS.

2. STOCK CONTROL PROCEDURES.

Making regular small adjustments to the stock.

Taking samples from shears and recording stock size.

Checking stock sizes at grade changes.

Continually checking the tension condition.

Using wood burning sticks to monitor stock.

3. WORKING METHODS.

OPERATORS MUST ACTUALLY BE AT THEIR WORK STATIONS.

The roughing and intermediate mills need constant checking during the rolling operation.

Examples of items to be checked are as follows :

Monitor the stock entry into the guides and roll passes.

Monitor the stock at the delivery side of the stand.

Examine the twist, (in an all horizontal stand mill).

Verify the stock temperature.


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Check the roll cooling water on the roll passes.

Ensure the guides are secured firmly and that they are functioning correctly.

Watch for surface defects on the stock and trace the source to any defects thatoccur.

Check tension.

Study the effect of steel grade changes on the stock.

The Finishing Roller should constantly check the finished rod section and also the entry sectioninto the N.T.M.

Downtime should be used effectively (delays and cobble related stoppages).

Operators not directly effected by the delay should check all the guides for wearand ensure they are working correctly.

Check to ensure there is no debris deposited in the guides.

Ensure that all auxiliary rollers at loopers etc. are free to rotate and are free ofpickup.

Check for deterioration and cracking of the carbide N.T.M. rolls.

Check for excessive wear of the mill rolls.

Check that the process water jets, sprays and headers are not blocked by scale,debris, etc.

4. GUIDE PREPARATION AND SETTING PROCEDURES.

Guide checking gauges which are the same as the standard stock sizes.

Use standard setting devices.

Make up tabulation charts for all the guide components and guide parts.

Develop and maintain cleanliness standards.

Develop component wear standards (time in use).

5. ROLL AND PASS CHANGES.

These should ideally be based on mill throughput and some consideration should be given to thesteel grades being rolled.

Working methods for changing rolls and passes (grooves) should be developed.


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6. SETTING THE ROLL GAPS (PARTINGS).

Develop working procedures for setting the roll gaps throughout the mill. Where the roll gap ismeasured by passing material through the roll collars, a sufficiently tough material must be usedso as to simulate the separating force of the rolling process.

7. OPERATING THE NTM or V Mill.

If due to poor setting techniques and to operators making numerous, random adjustments to thestand settings in the V Mill, or the stock is incorrect, it is unlikely that a consistently good qualityand toleranced product will be produced

This procedure of random changes is not recommended as the stocks will not be the same asthe guide settings. This is the likely cause of guide failures, turndowns add quality problems.

The correct procedure is to accurately set the stock and accurately set the guides. Choose thecorrect roll diameters and ensure the entry stock is the correct size (+ or - 1 to 1.5% of therequired area).

Develop a standard for operating the NTM or V Mill.

8. FURNACE CONTROL.

Develop a procedure to control the furnace combustion rate during full rolling for all mill rollingrates and steel grades. Identifying furnace priorities for different steel grades is a vital step in thisprocess.

Procedures for reduced combustion rates during changes and delay periods should also bedeveloped.


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STANDARD WORKING PROCEDURES

The following are EXAMPLES of standard working procedures. Each mill must make their ownprocedures, this is best done in collaboration with the people who have to carry out theprocedures. It is important that the workers feel that they have had some input into what is ineffect, part of their job description.

Also the format and the amount of detail written into the procedures should be made to suit theculture and educational standard of the work force.

STANDARD WORKING PROCEDURE

WORK AREA: ROUGHING AND INTERMEDIATE MILLS

PEOPLE INVOLVED: ROLLERS

TITLE: INSPECTION PROCEDURES TO BE DONE DURING PERIODS WHEN THE MILL ISNOT ROLLING

Items in this procedure should be done every time a mill delay occurs, for example: when waiting for billets during delays on the Stelmor conveyors or delays on the NTM’s during times when there is a cobble on the roughing or intermediate mills, one Roller

can inspect the mill while other Rollers or helpers remove the cobble

ITEMS TO CHECK

Check through all the mill guides using aflashlight to illuminate the guide interior.

Check the condition of the rollers in theroller entry and roller twist delivery guides(twisting type mill)

Check the roll cooling water at every millstand.

JOB DESCRIPTION

Ensure there is no scrap or debris inside theguides.Ensure that the alignment of theguides is correct.Ensure the guides are not excessively worn.

Ensure the rollers are free to rotate.Ensure there is no "pick up" on the rollers.Ensure the rollers are not excessively worn.

Ensure the water headers (pipes) arecorrectly aligned to the roll passes.Check the spray holes in the headers arenot blocked.Ensure there are no holes in the rubberhoses.Ensure that all the rubber hoses aresecurely attached to the main water pipesand to the headers.


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Check the lubrication and cooling to the millguides.

Check the condition of the roll passes ateach mill stand.

Check the inter-stand troughs.

Check the removable entry trumpets.

Check the alignment of the mill stands.

Ensure there are no holes in either thelubrication or the cooling water pipes.Ensure that the lubrication and coolingwater pipes are attached to the guides.Check the surface condition of the roll passesfor excessive wear or cracks, problems shouldbe noted on the rollers, shift report sheet.

Check to see if the pass wear is in thecenter of the passes, this will indicate if theentry guide alignment is correct.

Ensure the alignment is correct.Remove any scrap or debris from inside thetroughs. Remove any scale build-up.Ensure the water is connected to thosetroughs that are water cooled.

Ensure the alignment is correct. Ensurethey are firmly located in the mountingbrackets.Remove any scrap or scale. Ensure there isno build-up of material on the delivery end(caused by bars rubbing against thetrumpet).

Ensure


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TITLE: INSPECTION PROCEDURE TO BE DONE WHEN THE MILL IS ROLLING

Items in this procedure should be done during the periods when the mill is rolling, the checksshould be done as a matter of routine throughout ever shift.

ITEMS TO CHECK

Check the section sizes at every millstand, use roller calipers to measure thesection and vernier calipers to measurethe gap between the rollers of the rollercalipers.

Continually check the bars passingthrough the mill, walking the front ends of

some bars through the complete millshould be done on a regular basis.

JOB DESCRIPTION

This should be done every 2 hoursthroughout each shift.The size of each section must be enteredonto the stock size record report.If the section size is outside the permittedtolerance for any stand, the roller MUSTmake an adjustment

Ensure there is no sparking from anyguides (this is a potential quality problem).Check that the twist condition of the frontends is correct.Check front end delivery from the stands,it should be straight, no hooks or raisingup or diving down.Rectify any alignment problems which are

creating bad front ends, as these are apotential cobble problem.Check the front end entry into the stands,it should be smooth.Rectify any problem that are causing thefront end to hesitate. Indicates alignmentproblems.Check for scrap or debris in the guides,inter-stand troughs and entry trumpets.Check that roll pass cooling on all stands

is in the correct position.Ensure all guides are secure.Ensure that all the R.E and R.T.D rollersare turning freely.Check guide lubrication and water coolingpipes are connected


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ITEMS TO CHECK

Use wood burning technique to check theprofile of the sections at each stand.

Should a cobble occur the front end mustbe closely inspected, or cut off forinspection.

Measure the size of every cobble.

JOB DESCRIPTION

Check the condition of the bars passingthrough the mill, defects can indicate thatthere is a rolling problem.

Wood burns should be taken after the millstands are adjusted.The practice of burning the section onboth sides should be used.

The mill should not be restarted after acobble until the front end has beeninspected and where possible the cause ofthe cobble identified and rectified.The cause of many cobbles can beidentified by inspecting the front end.

This should be accurately done, thedimensions should be recorded on thestock control sheet and compared to themeasurement made with the calipers.Should the size section be outside thepermitted tolerance, the stand must beadjusted.


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STANDARD WORKING PROCEDURES



TITLE: INSPECTION PROCEDURE AT THE START OF EACH SHIFT

The mill SHOULD NOT be stopped at the start of each shift, the following are the checks thatthe roller must make as soon as he takes over at the start of each shift. Should the mil not berunning, the rollers should carry out the procedure entitled "Inspection Procedures To Be DoneDuring Periods When The Mill Is Not Running".

ITEMS TO CHECK

Walk the front end of some bars throughthe mill, this should be done on each line.

Check the roll pass cooling water iscorrectly aligned on all the mill stands.

Take samples from the shears at stand #7& 13.

Check the section size report sheet fromthe previous shift.

JOB DESCRIPTION

Check that the twist condition of the frontends is correct.Ensure there is no sparking from anyguides.Check front end delivery from the stands, itshould be straight.Check the front end entry into the stands, itshould be smooth.Check for large pieces of scrap or debris inthe guides, inter-stand troughs and entrytrumpets.Check the condition of the bars passingthrough the mill, defects can indicate thatthere is a rolling problem.

This should be done as soon as the 1stchecks (walking the bars through the mill)has been completed.

Check the section dimensions, this will giveearly warning of potential stock problems.Record the dimensions on the stock sizerecord reportIf the stock sizes off stands # 7 & 13 areout of tolerance, immediately start theprocedure of measuring and rectifyingstock at each stand.

The report sheet will indicate the conditionof the sections passing through the mill.It will show potential stock deviations fromthe standards.


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ITEMS TO CHECK

Check the cobble report sheet from thepervious shift

JOB DESCRIPTION

The cobble report will show areas wherethe previous shift had problems.The roller should check those mill stands toensure the problems have been rectified.


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WORK AREA: NTM's

PERSONS INVOLVED: ROLLERS

PROCEDURE TITLE: INSPECTION PROCEDURES TO BE DONE WHEN THE MILL IS NOTROLLING

Items in this procedure should be done every time a mill delay occurs, for example: when waiting for billets during delays on the Stelmor conveyors or delays on the NTM’s during times when there is a cobble on the roughing or intermediate mills.

ITEMS TO CHECK

Check the roll partings for all the NTMstands.

Check through the mill for scrap anddebris.

Check all the NTM guides.

JOB DESCRIPTION

This should be done at the firstopportunity after the start of each shift.The NTM MUST be running in "jog".If the motor cannot be run in "jog", theprocedure should not be carried out.There can be deviations of up to 0.2mm inthe dimension of the aluminum rodbetween turning the mill by hand and themill run in "jog".

A flashlight and mirror MUST be used forthis procedure.Pay particular attention to the nose of thestatic delivery guides and the inserts androllers of the roller entry guides.

Ensure there is no scrap or debris in theguides.Ensure all the guides are correctly andsecurely positioned.Ensure the roller entry guide rollers arerotating freely.Check the wear on the roller entry guiderollers. If there is a groove in the portionof the roll where the section is supported,the guide should be changed.Check for severe wear patterns in thestatic guides, change any that are worn.Ensure all the guide brackets (supports)are firmly mounted to the housing faceplate.


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ITEMS TO CHECK

Check lubrication to the roller entry guide.

Inspect the carbide rolls (NTM rolls).

Check the breakout box.

Check the fish line.

JOB DESCRIPTION

If dummy pipes are being used, check thealignment and ensure they are securelymounted.

Ensure all lubrication pipes are connectedto the guides and that they are notdamaged.

Check roll pass surface, should there besigns of sever roughness or cracking, itindicates a possible cooling problem.Change the rolls and check the waterheaders for blockages.

Ensure there is no scrap or debris in thebreakout box, also ensure that it is closedcorrectly.Check that it has not been knocked out ofalignment by a cobble.

Ensure the fish line is tight and that theweight is off the limit switch.


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SECTION 6

ROD AND BAR MILL YIELD CONTROL


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YIELD

INTRODUCTION

Yield is defined as the percentage of quality product that results from the billet tons charged intothe reheat furnace. The higher the yield percentage, the more efficient the rolling operation. Theareas where yield losses occur are:

THE REHEAT FURNACE

The higher the temperature in the furnace, the greater the amount of scale formation on thebillets. Scale losses account for a large percentage of losses in yield, it is therefor important thatheating practices be developed so that:

The billet temperature remains below 700 degrees C (1300 deg F) for as long as possibleprior to the commencement of rolling, since scale starts to form when the temperature raisesabove this point.

The billet rolling temperature should be closely controlled in order to achieve the bestthermomechanical properties for each specific grade of steel. In older mills the criteria willnormally be the power available at the roughing and intermediate drives. Temperatureshould be held as low as this equipment will allow.

In addition to decreasing scale loss, lower rolling temperatures result in lower fuel consumptionand this will result in significant financial savings. There are many mills around the world that usea furnace discharge temperature as low as 975 degrees C (1790 degrees F). To further enhancethe success of the rolling operation and the quality of the final product, the billet temperaturemust be uniform along its length. Attention to this will permit uniform dimensional tolerancethroughout the length of the product.

CROP LOSSES

Much of the yield losses occur at the various mill shears. These losses are the result of:

the length of the crop

cobbles, which will be discussed in the following section

The correct conditions must be set-up for each of the shears in the mill, crop length should bekept to the minimum. Steel grade, the condition of the billets and the setting of the mill equipmenthas a significant effect on the minimum length of cut that can be achieved. The following criteriashould be followed:

The length of the crop should be maintained to the minimum so that unnecessary yield lossesdo not occur. The length of the crop will vary depending on the type of shear, but typicallengths from a roughing mill Crop & Cobble shear would be 75 mm to 150 mm (3" to 6"), froma modern Crop & Divide shear, the typical crop length should be 500 mm to 700 mm (20" to28").


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Regular checks should be made of all crop lengths, pieces should be visually checked andmeasured, also weighing of the crops can be introduced, all the relevant information shouldbe recorded.

It is important that the correct lead speed is used for each shear and should be standardized.On some shears, changes of the shear speeds will have an effect on the length of the cropcut.

COBBLE LOSSES

The major source of yield loss in the majority of mills is due to cobbles. Cobbles are a result offailures in the mill operation and can be caused by mechanical, electrical or operational problems.Many of the Worlds best rod and bar mills are able to run for periods in excess of a monthwithout having any cobbles.

Mill operating personnel must make precise set-ups of rolls, passes, elevations, alignments,guides and stock settings. These standards must be maintained throughout the rollingprocess.

Stock measurements and adjustments must be routinely made and documented.

Regular checking of samples from the various mill shears, including snap shears must occur.Measurement of samples from cobbles and rectifying deviations in stock sizes to thestandard is also an important procedure.

Small stock adjustments at regular intervals are far less disruptive to the operation thanmaking major stock adjustments infrequently.

Constant visual checks of stock, guides and rolling equipment must be undertaken. Visualinspection of covered mills (pre-finishing and NTM's), should be made whenever a rollinginterruption allows time for the covers to be raised.

Uniform billet temperature must be maintained.

Mill speeds must be monitored and tension avoided.

Mechanical and electrical equipment must be properly maintained. This will include visualinspection of all the equipment and reporting the condition through check list documentationfor each shift.

Adhering to these practices will result in a consistent quality operation which will ensure minimumlikelihood of cobbles

SCALE LOSSES

Scale losses occur throughout the mill as the steel temperature is above 700 degrees C (1300degrees F). Many mills have water boxes positioned prior to the pre-finishing mills, the NTM's andafter the NTM's. These are used to control the temperature of the bar prior to it entering thefollowing mill equipment, thereby marginally reducing scale loss. It is however sometimesdesirable for metallurgical reasons and when mechanical de-scaling of rod is required, for aheavy scale during the Stelmor process.

TRIMMING LOSSES


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Since rebar undergoes minimum trimming, the yield is inherently high. Most rod productshowever, require that the overfill on the front and tail ends of each coil is removed. When a mill isoperated under strictly controlled conditions these losses will be small, 0.10% to 0.2%. The actualamount removed from each end of the coil will be dependent on the size of the finished rodproduct.


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SECTION 7

ROLLING MILL EFFICIENCYMANAGEMENT


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ROLLING MILL EFFICIENCY MANAGEMENT

In order to obtain the optimal results from a high speed Morgan Rod Mill, an effectivemanagement system must be implemented that enables the rolling operation to be constantlyassessed. To accomplish this , a comprehensive reporting system should be developed, wherebyevery aspect of the operation is monitored. After detailed information is gathered, it must beanalyzed and the resultant information utilized to improve the operation.

DEVELOPMENT OF REPORTS

Each segment of the operation beginning with the receiving of billets through the storage, rollingprocess and shipping of the finished product must be covered by a reporting system that detailsthe process in each area. In some areas such as billet storage, reporting may be as simple as aninventory record. In other areas such as the rolling process, reporting must be more complex. Anexample of this would typically be a cobble report, where accurate information of the reason forthe cobble, where the cobble occurred and steps made to rectify the problem, are required.

REPORT ANALYSIS

A system for reviewing the information gathered through the reporting systems must bedeveloped so that the operation is closely monitored. Because of the diverse nature of the rollingmill operation, the frequency of the review procedures will vary, depending on each area of thereport. In addition, a strategy must also be developed to automatically implement correctiveaction when the process deviates from accepted standards.

Examples of areas needing frequent analysis are:

1. Mill delays and the reasons for them occurring.

2. Mill utilization - percentage of time steel is actually being rolled.

3. Mechanical and electrical interruptions to the operation and the nature of these interruptions.

4. Frequency and location of cobbles.

5. Rejections and their origins.

6. Yield.

7. Furnace fuel and electricity consumption.

8. Effectiveness of maintenance.

Dependent on the local environment and operational problems, other areas may have highpriority for management.


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RESPONSE TO REPORT ANALYSIS

Once the process of reporting and analysis is in place, adequate and timely response isnecessary to eliminate problem areas. Often, it is desirable to place the response in quantitativeterms, as long as the results remain within defined levels only monitoring is warranted. However,when the deviation is greater than that permitted, an adjustment to the process may be required.This system of response levels (response triggering mechanisms), as well as those responsiblefor its implementation must be determined by management. As the operation progresses andexperience is gathered, the quantitative levels must be adjusted and modified. As one goal isachieved, a new goal should be set.

Since the efficiency of the mill operation is largely governed by the performance of the work force,much consideration must be given to the work force as an important ingredient in the formula forsuccess. In addition to excellent mill equipment selected by the management team. a properlytrained work force is essential.

A company's philosophy dictates the level of staffing as well as the employee selection system.Where possible, a concerted effort should be made to place the most qualified people in thoseareas demanding above average intelligence. Whatever the selection process, it is imperative toimplement a comprehensive training program. Initially this should be done with the help ofMorgan. Eventually, the training responsibility should be taken over by the line managementteam.

Job skills should be the primary target for the initial training. However, these basic skillsnecessary to be a productive rolling operation must also be understood. It is necessary to identifythese operative skills and implement an ongoing program to develop an above average workforce.


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PRODUCTION SCHEDULING

Efforts must be made to maximize the quality and productivity of the mill by effectively schedulingthe operation. Obviously, the rolling plan must be formulated well enough in advance in order thatbillet acquisition and storage can be planned in order to maximize the mills performance. Mostmills develop a monthly rolling cycle within which all customer requirements can be met. Therolling strategy can then be refined so that the following criteria can be met:

Utilizing NTM Production Sequences/Family Groupings

The mill passes, particularly the NTM or V Mill, have been designed so that groups ofsizes fall into sequences or families. To maximize quality and productivity and to minimizeunnecessary size change times, every effort must be made to change sizes in theirnatural order within their sequence groups. Random changes of sizes will result in majordelays as numerous rolls will require changing on the NTM.

Scheduling To Maximize Quality

Naturally, it is desirable to roll a quality product at all times. Due to the nature of theprocess, the probability of success is greater early in the rolling cycle before the rollpasses in the mill become worn. Conversely, later in the rolling week the probability ofsuccessfully rolling high quality products diminishes. With this in mind , the highest qualityproducts should be scheduled as early as possible after changing to each new size, withthe lesser qualities following.

Scheduling To Maximize Furnace Efficiency

Scheduling similar grades with the same furnace priorities should be a managementpriority, the planning for this must be done while also maximizing the quality aspect fromthe mill. Furnace performance and efficiency will also be maximized.

Scheduling For Customers Requirements

Satisfying the customers requirements is the ultimate key to successful scheduling. Everyeffort must be made to achieve this while also scheduling to maximize the quality of theproduct and to achieve maximum productivity from the mill.


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YIELD AWARENESS AND MAXIMIZATION

Of great significance to the efficiency of the mill operation is the level of yield performance. Yieldis the quantitative measurement in percentage of the amount of finished rod produced for eachbillet ton charged into the furnace. Efficient mills consistently have a yield performance of 96% to98% of billets tons charged. Attention to the following areas enhances mill yield:

1. Reheat furnace operation and its effect on scale formation (see section on Reheat FurnaceManagement).

2. Cobbles - fewer cobbles result in higher yield.

3. Trimming losses - correct mill and Stelmor operation (water boxes) will minimize the numberof rings requiring removal from the front and tail end of each coil.

4. Rejections - quality billets and proper mill set-up and operation will minimize losses to nonprime production.

Attention to these four areas will result in the probability of achieving the expected yield results.


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QUALITY CONTROL AND CUSTOMER SATISFACTIONPHILOSOPHY

A strong relationship between the mill and the customer is necessary in order to fulfill the mill'srole as a quality supplier. This is particularly true when a mill has aspirations to be a producer ofhigh quality rod or bar. Constant feedback concerning product performance enables the mill tomake “change procedures” when they become necessary to ensure that high product standardsare achieved.

An effective "in-house" quality control mechanism is needed to insure that only high qualitymaterial is dispatched to customers. This quality control mechanism must be integrated within theplant production quality control system, in order that only prime billets are processed by the milland that mill operation is maintained within the prescribed quality standards. This will ensure thatcustomers will receive only quality product. Should there be a failure at any point during theproduction process, the process control system of reporting deviations should give a warning ofthe problem and the process should be stopped until the problem is corrected


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DEVELOPING AND IMPLEMENTING STANDARD WORKINGPROCEDURES

In a "World Class" rolling operation, management has assured a posture that the process is to beperformed the correct way. This philosophy has to be developed into one that relies on "StandardWorking Procedures". In doing so, the process is controlled by following set steps as laid down inwritten procedures, this will result in a consistent and repeatable process day after day.

Management's Role

The management of every rolling mill must come to realize that the philosophy of utilizing the"Standard Working Procedures" is needed for the smooth operation of the process and then trainand direct its work force in these procedures.

System Design

Individuals in the management team should formulate step by step working procedures for eachjob in the operation, ideally there should also be worker involvement which will make theprocedures more acceptable to the work force.

Implementation

The management team, in particular the first line supervisors should teach, direct, check andassist the employees in the implementation of the procedures. Each level of management shouldhave a similar role with their subordinates.

System Feedback

Constant monitoring of the procedures will provide information as to when there are deviationsfrom the specified standards, this constant monitoring will also expose areas where permanentadjustments or changes are required. The system must be dynamic, there will always be validreasons for changing the procedures.


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BILLET REHEATING FURNACE MANAGEMENT

The billet reheating furnace fuel consumption constitutes a major part of the operating cost of amodern rolling mill. Management needs a philosophy that will enable quality and productivitygoals to be met as well as to efficiently control the operation of the reheating furnace.

Effect On Quality

Producers of high carbon, alloy and special steel qualities must develop a heating concept thatmaximizes mill utilization while enhancing finishing product quality. This is accomplished by usinglow furnace discharge temperatures 950 to 980 degrees C (1742 to 1796 degrees F),conservative heating practices and closely controlling furnace atmosphere. Fortunately, thisapproach is complementary to the strategy of efficiently operating the reheating furnace.

Yield

A considerable amount of the yield loss is directly related to the billet reheating furnace operation.To maximize yield, thus limiting reheating furnace scale losses, the billet temperatures mustremain low for as long as possible. Should a mill delay occur, the furnace temperature should bereduced based on the expected duration of the delay. Simply stated, the furnace should beoperated at as low a temperature as is possible, without jeopardizing the mill equipment, productquality or productivity.

Fuel Consumption

As with mill yield, fuel consumption is directly related with the performance of the mill and thefurnace temperature. Generally speaking, the higher the furnace temperature, the greater the fuelconsumption. Therefore, the strategy developed to maximize yield and ensure product integrityalso results in the efficient use of fuel.

At some point, a comparison should be made to weigh savings in the reheating furnace fuelconsumption against the additional electricity required to power the mill at the lower rollingtemperatures. Some mills utilize this comparison to "fine tune" the efficiency equation.


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ROLL AND GUIDE SHOP MANAGEMENT

Due to its integral nature to the rolling process, a great deal of importance is placed on themanagement and performance of the roll and guide shop. Good record keeping is essential.Detailed scheduling of the work in the shop is mandatory. It is therefore necessary for acomprehensive strategy to be formulated for this area, preferably well in advance of the millcommencing operation.

Scheduling Roll And Guide Shop Functions

The management of the roll and guide shop must be in the communication chain that areconstantly informed of the current progress of the rolling mill schedule. Changes to the millschedule will almost certainly necessitate changes to equipment line-ups already prepared in thisarea. Equipment should always be prepared ahead of the requirements of the mill.

Roll Selection & Inventory Management - Development Of Roll Performance Data

For most mills, collecting data and utilizing this effectively in the roll inventory and selectionprocedures is a tedious task. Fortunately, Morgan is marketing a recently developed P.C.program that greatly simplifies this task. Whether a manual or a P.C. approach is taken, muchimportance must be given to accurate inventory and selection procedures being maintained, asthey can have a significant impact on the mill performance and the overhead costs of theoperation.

Guide Use & Care And Performance Data

Often the importance of the mill guide system is not given the necessary level of attention. As aresult of this, many mills fail to achieve the expected level of productivity or quality. It is thereforerecommended that a great deal of emphasis be placed on the importance of detail in guideassembly and preparation. This is a highly specialized area which requires a great deal ofattention and good levels of skill and understanding.

Work Roll And Guide Roll Materials

It is important that mills do not "penny pinch" on material for work and guide rolls. Inferiorproducts are likely give poor performance in the mill and will result in performance and qualitylevels falling. Mills should keep abreast with constantly changing technology being introduced toRod Mills. New material development can enhance mill performance and quality of the finishedproduct.


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MAINTENANCE MANAGEMENT SYSTEMS

The modern high speed Rod and Bar Mills require exceptional maintenance practices andprocedures. It is therefore necessary to utilize the latest ideas in planning and maintenancetechnology, in order to achieve the designed productivity of the mills.

Predictive Maintenance

Predictive maintenance utilizes techniques that enable you to determine, with a great deal ofcertainty, at what interval maintenance should be performed on a particular piece of equipment.This requires extensive record keeping of equipment performance and service intervals.Predictive maintenance, if done properly, will ensure a high level of performance.

Some typical procedures used for predictive maintenance:

Vibration Monitoring And Analysis.

Lubrication And Hydraulic Oil Analysis

Thermographic Monitoring And Analysis

Gear Inspections

Pro-Active Maintenance

Once again, this procedure requires need for extensive and accurate records. Analysis ofequipment failures and problems is the basis of this procedure. The reason for each failure isfound and analyzed in order to eliminate the possibility of the failure occurring again.

Preventative Maintenance

Preventative maintenance uses the principle of periodic service of equipment, performed atregular intervals. Initially, service periods should be based on the manufacturesrecommendations, and as experience is gained with the equipment, service periods can be basedon actual historic data collected on equipment performance. Once experience is gained withPredictive Maintenance Techniques it should be possible for much of the equipment to be takenoff the Preventative Maintenance Program. Preventative maintenance programs are normallybased on a P.C. program which will on a weekly basis, print a list of the equipment requiringmaintenance.

Cost Management

Whatever maintenance procedures are used, the extensive record keeping necessary to monitorand control the systems will make it possible to determine the cost effectiveness of the system.The actual cost efficiency of maintenance can be determined by comparing the cost against thecost of mill down time.


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SPARE PART STRATEGY

In order to achieve the continuous operation of a rolling mill, there must be a well managed andwell planned spare parts strategy. Levels of spare parts, sources for spare parts as well as sparepart quality, are important considerations.

Operational Spares

Generally, operational spares are consumed in the rolling process. Many of the operationalspares are influenced by the product mix and tonnage levels per product size. This makes itnecessary to closely correlate the operating plan versus the operational spares. As with all otheraspects of management, extensive record keeping is essential.

Mechanical Spares

Unlike operational spares, consumption of mechanical spares is not directly related to the rollingprocess. Therefore, spare part quantities are usually lower. In addition, consumption ofmaintenance spares have little or no correlation to the product mix and therefore are simpler tomanage. However, extensive and accurate record keeping is just as important to the successfulperformance of the maintenance program.

Note: It is very important to understand that the source and quality of spare parts is essential tothe anticipated performance of a rolling mill. Spare parts must be manufactured to the same highstandard as the original mill equipment.

Electrical Spares

Special attention must be given to the electrical spares as many of them are quite often unique toa particular mill and local availability is often non-existent. Good inventory levels and accuraterecords of usage are essential in this area.


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MANAGEMENT OF THE FINISHING AND THE COILHANDLING AREA

The coil handling and storage area is important to the maintenance of high productivity andquality levels. Its management must incorporate quality handling and storage principles thatfacilitate high levels of dispatching of the finished product.

Product Inspection

Ideally, initial inspection of the product must occur as close to the reform area as possible. Thiswill ensure that a minimum amount of out of specification material is produced in the event of aquality problem.

Product Handling

Coil handling must be accomplished in such a way as to minimize the possibility of damaging theproduct. Great care must be utilized so that not even minor scratches occur. In order to facilitatethis, coil movement should be kept to a minimum.

Storage Techniques

The storage area should be arranged to facilitate ease for ontime dispatch of product to thecustomers, and to ensure no damage occurs to the finished product. The storage and shippingdepartments must work closely with each other so that the optimum storage area selection canbe made for each order.

SAFETY

Safety should be a major concern in the operation of high speed automated equipment in rodmills. Basic safety principles must be followed to ensure the well being of the mill team. A safetyprogram that educates the work force on these safety principles should be formulated.

28 - operator training

Documents

control stock

stock control techniques

training tool

manualthe manual

warningthis manual

rolling techniques

bar alignment

controlling stock