ACKNOWLEDGEMENT

We began our internship with the name of Most Beneficent and Merciful Allah, Almighty who provided us the power to complete this report. We are very thankful from core of our heart to chairman Pakistan steel for providing us the opportunity for training whose intelligent wise & sound leadership converting the man pier into a wining combination by converting this industry into Gold mine.

We wish express our deep gratefulness to Mr. Qaiser Saleem PEO (HRD) for his consideration & supervision. It was memorable time in Pakistan Steel. We are also thankful to Nisar khowaja Incharge (HRD) (Training Wing) & Mr. Yusuf Ayub Dy.Manager (HRD) for their precious advices & for great amount of encouragement & co-operation, so that we successfully completed our internship at Pakistan Steel Mill and leaned a lot.

Over all we are thankful to head of the departments, officers & workers of Pakistan steel and we wish all the workers to do jobs with the same sense of responsibility, commitment and carefulness in future.

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IndexS.No Department Pages

1 History of Pakistan Steel Mill 3-4

2 Coke Oven & By Product Plant 5-23

3 Sintering Plant 24-29

4 Process Laboratory 30-45

5 S.M.D 46-54

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History Of Pakistan Steel Mill:-In 1968 besides other factors, it was considered by the Government of Pakistan that a basic steel industry should be established in the public sector, as public sponsorship of the project would enable intergrated development of the steel industry in the country. In light of this, the government decided that the Karachi Steel Project should be sponsored in the public sector for which a separate Corporation under the Companies Act be formed. As a result on the 2nd of July, 1968 Pakistan Steel Mills Corporation was setup as a private limited company

In January, 1969, Pakistan Steel concluded an agreement with V/O Tiajproexport of the then USSR for the preparation of a feasibility report into the establishment of a steel mill at Karachi. Subsequently in January, 1971 Pakistan and the USSR signed an agreement under which the latter agreed to provide techno-financial assistance for the construction of a coastal based intergrated steel mill at Karachi.The foundation stone for this gigantic project was laid on the 30th of December, 1973 by the then prime minister Mr. Zulfiqar Ali Bhutto. The mammoth construction and erection work of the intergrated steel mill, never experienced before in the country, was carried out by a consortium of Pakistani construction companies under the supervision of Soviet experts.

Component units of the steel mill numbering over twenty and each a big enough factory in its own right were commisioned as they were completed between April, 1981 to August, 1985 with the Coke Ovens and By Products Plant coming online first and the Galvanising Unit last. Commissioning of Blast Furnace Number 1on the 14th of August, 1981 marked Pakistan's entry into the elite club of iron and steel producing nations. The project was completed at a capital cost of Rs. 24,700 million. The completion of the steel mill was formally launched by General Zia-Ul-Haq the then President of Pakistan on the 15th of January 1985.

Today Pakistan Steel is the country's largest industrial undertaking having a production capacity of 1.1 million tonnes of steel. The enormous dimensions of the project can be visualised from the construction inputs which involved the use of 1.29 million cubic meters of concrete, 5.70 million cubic meters of earth work (second to Tarbela Dam), 330,000 tonnes of machinery, steel structures and electrical equipment. Its unloading and conveyor system at Port Qasim isthethirdlargest in the world and its industrial water reservior with a capacity of 110 million gallons per day is the largest in Asia.

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Coke Oven &

By-Product Plant

Coke Oven & By-Product Plant:-Coke Oven & By-Product Department is one of the most important departments of Pakistan Still Mill it is designed for the production of metallurgical coke, with facilities for processing of coke oven gas (C.O.G) for recovery of various by product e .g ammonia, benzol, naphthalene, tar etc. After treatment C.O.G suitable for use at coke oven batteries, thermal power plant, sintering plant, refractory & lime production unit.

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The annual demand of coke & coke breeze is estimated as 9, 10,000 tons. The existing coke oven batteries are designed to produce 9, 70,000 tons coke per annum at coking period of 15.3 hrs. Sulphur coke may be consumed in the home market. The annual production of C.O.B.P complex may be summarized as follows.

Main Products Annual Production

Coke 9,70,000 tons

C.O.G 490 M .cu .m

Dehydrated Tar 46,500M.tons

Ammonium Sulphate 17,200 M .tons

Production Units:-Coke Oven Plant is mainly composed of following production units.

1. Coal Handling & Processing Plant .2. Coke Oven Plant .3. Coke Dry Quenching Plant.4. Coke Wet Quenching Plant .5. Coke Screening .6. By-Product Plant .

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Coal Handling & Processing Plant

(C.H.P)

Coal Handling & Processing Plant:-

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Coal handling & processing department involve the operations of storing & transporting the coal . Different varieties of coal are imported mainly from Canada, Australia & India coal available in Pakistan is not use due to high sulphur & moisture content . From Port Qasim these varieties of coal are conveyed to the yard of still mill where it is stored in the from of pills. The coal handling process involve the following main steps :-

Coal storage yard of open type . Foreign object removal unit . Proportionating Bins . Crushing section . Mixing section . Coal tower .

Coal Storage yard:-Coal which is stored as 12 pills in open area of yard through two Universal machine are transported by conveyer belts to the storage bins. In storage yard a network of conveyer belt is available which are interlink with each other . Conveyer which are use to transport coal from yard to storage bins are named as C-1 to C-5 and the conveyer after bins to the coal tower are named as Y-1 to Y-20 .

Foreign object removal unit :-Coal from storage yard than passes through Electo-magnetic Drums to remove any metal particles present in the coal before sending it for storage & crushing Metal particles are removed to increase the purity of coal .Now coal is transported to storage bin by conveyers .

Proportionating Bins (Silos) :-Proportionating bins section consists of 12 bins . Each coal variety is stored in allocated rows of bins . Bins are provided with Batch Meter of continues action . Each bin having effective capacity of 750 tons/hr . Coal is delivered to the crushing section by two conveyer of 350 tons/hrs capacity each .

Crushing Section :-

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Crushing section is equipped with 03 Hammer Crushers , each crusher has a capacity of 300 tons/hrs and the movement of bar screen to or from crusher rotor does size adjusment. After coal blend is delivered by a conveyer of 500 tons/hr capacity into the mixing section .

Mixing Section :-Mixing section is equipped with 02 Electro-Mechanical type mixer having 2% blending accuracy with a total capacity of 1000 tons/hr in two mixer. Used solar oil is sprinkled here & mixed with coal blend which is then fed into coal tower . The mixture composition of different varieties of coal is give in table below along with ash & sulphur percentage .

Coals

Vol % A

sh % Sul

ph %

Gleenies Creek 38.40 9.00 0.60

Moura Dawson 34.0 9.00 0.60

Eagle 26.50 8.20 0.60

Curragh 21.80 7.50 0.60

German Creek 20.0 8.90 0.69

Coal Tower :-Coal blend after mixing is transported by conveyer belt & stored in coal tower .Coal tower have a capacity of 3200 tons and is sufficient for approximately 28 hrs of coke production It has four compartment equipped with devices pneumatic elimination of blend bridging .

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CokeOven Plant

(C.O.P)

Coke Oven Plant :-Production of Coke :-

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There are three basic ingredients to make iron and iron, in turn, is used to make steel .The three basic ingredients are iron ore, limestone, and coke.  The first two are natural raw materials, but coke is a by product of coal.

Coke is a solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. Coke from coal is gray, hard, and porous. coal must meet a set of criteria for use as coking coal, determined by particular coal assay techniques. These include moisture content, ash content, sulfur content, volatile content, tar, and plasticity. Coke have high calorific value about 13 ,800 B TH /KG .

Structure of Coke Batteries:-Pakistan Still mill coke oven plant consist of two Coke Oven Batteries , each having 49 ovens . First battery was commissioned on 18 August 1981 & second battery went into coke production on 6 May 1985 . Batteris are basically beehive ovens lined up side by side and supported by stone retaining walls.  The inside still has the beehive shape. Coke oven are Under Jet design and control of coke ovens as and air with twin heating flues and recirculation of waste heat gases.

22.4 ton of coal blend is charged per oven from the top of the batteries by Coke Charging Car according to a fixed sequence & pre determined coking period .The sequence of charging is as under :-

38 % Coal blend from machine side . 22 % Coal blend from Centre .

40 % Coal blend from Coke side.

Temperature and heating regimes are adjusted according to the cooking period adopted .Tentative temperature of the machine side and coke side of the oven according to the cooking period is given below:-

Cooking Period

Temp machine/side

Temp coke/side

No of Ovens Per day both batters

15.3 1280 1320 187 18.0 1250 1290 131

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20.0 1230 1270 117

22.0 1215 1255 107

Reaction occurring inside the ovens is carbonization of coal in the result of which 92 % carbon containing red hot coke is formed .After production of coke it is discharge by coke pushing car in to a bucket , which is transported to the Coke Wet or Dry Quenching Plant with an Electric Locomotive for cooling it down .Coke oven gas is collected at the top of the batteries at very high temperature are showered by ammonium water to cool down its temperature & send to the by product plant Coke oven gas which is the by product of carbonization is used as burning fuel in coke ovens . Coke Oven gas have moisture upto 3 % it is pre heated upto 50C before using in oven . Exaust gases are discharge into the air by chimney of the batteries . Following machines are employed in coke oven plant :-

Machine Name Working Stand By

Coke Pusher 2 1

Coke Charging Car 2 1

Door Extractor 2 1

Electric Locomotive 1 1

Quenching Car (Wet) 1 1

Quenching Cars (Dry) 2 1

Now a days one battery of still mill is renovating due to which coking period is 21 hrs and temperature adjusment is b/w 1200 to 1250 Celcius and natural gas is used as burning fuel b/c of low production of coke oven gas .

Products of Coke Oven Plant :-Following chart shows the quantity of products which are produce after the destructive distillation of per ton of coal blend :-

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Products Quantity

Coke 750 to 800 kg

Coke Oven Gas 300 to 350 cu. M

Tar 30 to 40 kg

Benzene 10 kg

Ammonia Gas 2.5 to 4.5 kg

Steam 80 to 120 kg

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Coke Dry

Quenching Plant

(C.D.Q.P)

Coke Dry Quenching Plant :-Coke dry quenching plant consists of three separate blocks, each includes a quenching chamber with hoist and a waste boiler. Through put of one block

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is 56 tons / hour. Hot coke pushed from coke oven is received into a bucket , which is transported to the Coke Dry Quenching Plant with an Electric Locomotive . Hot coke at about 1050 Celcius is lifted up through a hoist assembly ad fed into the quenching chamber. Red hot coke is cooled down with the counter flow of nitrogen gas. The heated Nitrogen gas is used in the waste heat boiler to generate steam at a pressure of 39 kg / sq .cm and temperature 430Celcius . Steam produce in the boiler is transported to Thermal Power Plant Unit (T.P.P ) .

The transported coke from CDQP is then transported to coke screening for its sizing onward to blast furnace , sintering plant and coke stockyard .

Quenching Plant Conditions :-Operational conditions of dry quenching plant are characterized by following :-

Temperature of coke supplied to the chamber = 950 - 1050 `C Temperature of quenched coke = 250 `C Temperature of circulating gases (before boiler) = 750 - 800 `C Temperature of circulating gases (after boiler ) = 150 – 200 `C Maximum number of discharging from chamber = 35 per hour Volume of each discharged portion of the coke = 1.7 tons

Wet Quenching Plant :-As a reserve for coke quenching section , a wet quenching unit is provided consisting of pump house , settling tanks spray chamber and a clarified water collecting tank . In wet quenching heat energy of hot coke is not utilized b/c water is directly shawered on hot coke & steam is evaporated in the air . Mostly dry quenching of cooke is done in which energy of coke is utilized to produce steam .

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By – Product

Plant (B.P.P)

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By-Product Recovery Plant:-In a by-product coke oven the evolved coke oven gas leaves the coke oven chambers at high temperatures approaching 1200 C. This hot gas is immediately quenched by direct contact with a spray of aqueous liquor (Ammonia water). The resulting cooled gas is water saturated and has a temperature of 80 C. After cooling By-products are began to recovered .The By-Product Recovery Plant is consist of Sections and facilities:-

Separator. Mechanized Decanter. Primary Gas Cooler. Exhausters. Ammonia Sulphate Section (Saturator). Final Gas Coolers. Scrubber. Coal tar Pitch Plant Tar & Solar oil storage Sulphuric Acid storage.

Separator:-The mixture of coke oven gas & ammonia water is introduced into the separator where raw coke oven gas & water are separated due to gravity difference. Coke oven gas from the top of separator pumped to the primary gas cooler & bottom water which contain coal tar moves to the mechanized decanter.

Mechanized Decanter:-In decanter the ammonia water & coal tar are separated by the difference of gravity. In decanter the upper layer is of water, second layer of coal tar & last layer of tar sludge. The ammonia water is pumped back into the ammonia tank where it is condensed and again send to batteries for cooling of coke oven gas. The coal tar is send to the coal tar storage tank. The coal tar is used as a fuel at the Thermal Power Plant & sulphur quantity is marketed.

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Primary Gas Cooler:-The first step in the treatment of raw coke oven gas is to cool it to remove water vapors and so greatly reduce its volume this is done in primary cooler. The Primary Gas Cooler is tubular type, the coke oven gas is cooled indirectly by flowing across horizontally mounted tubes through which cooling water is pumped. In this case, the cooling water does not come into contact with the coke oven gas and so it can be cooled As the coke oven gas is cooled is send to the exhauster and water, tar, naphthalene condense out . The condensate collects in the primary cooler system and it is discharged to the tar & liquor plant.

Exhauster:-The exhauster is a large blower that provides the motive force to induce the coke oven gas to flow from the coke oven battery and through the by-product plant. The exhauster is of prime importance to the operation of the coke oven battery. It allows the close control of the gas pressure in the collecting main, which in turn affects the degree of emissions, for example door emissions, from the battery. A failure of the exhauster will immediately result in venting to atmosphere, through the battery flares, of all of the raw coke oven gas produced.

Ammonia Sulphate Section (Saturator) :-Due to the corrosive nature of ammonia, its removal is a priority in coke oven by-product plant. The removal of ammonia from coke oven gas has yielded one of the more profitable by-products that of ammonium sulfate. The ammonium sulfate process can take various forms but all basically involve contacting the coke oven gas with a solution of sulfuric acid (mother liquid).The use of a saturator in which the gas is bubbled through a bath of sulfuric acid solution. The sulfuric acid reacts readily with the ammonia in the coke oven gas to form ammonium sulfate. This is than crystallized which is centrifuged ,dried , and bagged or marketed in lose form.

Chemical Reaction in Saturator:-

Following reactions of ammonia of coke oven gas is occurring with mother liquid to form ammonia sulphate .NH3 + H2SO4 ================NH4HSO4 NH4HSO4 + NH3 =============== (NH4)2SO4

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Final Gas Cooler:-Coke Oven Gas from saturators enters into Final Gas Coolers of shelf type which are continuously sprayed with circulating service water. Final coolers typically cool the coke oven gas by direct contact with a cooling water. An important aspect of final cooler operation is that when the coke oven gas is cooled below the outlet temperature of the primary cooler, naphthalene will condense from the gas.

Scrubber:-After final gas cooler coke oven gas is send to the scrubber for removal of naphthalene. In scrubber solar oil is showered from the top & gas is entered from the bottom. Content of naphthalene in the spent solar oil is 7-8%. Solar oil is stored which is then marketed. The purified & scrubber coke oven gas is sent to coke oven plant & other Units of Pakistan Steel to used as fuel.

Composition of Coke Oven Gas:-

Gas Name Wt % H2 59 CO 7.2

CO2 2.6 CnHn 2.3 Ethylene 25 N2 3.5 O2 0.7

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Sintering plantSintering Department is one of the most important departments of Pakistan Steel Mill it is designed for the production of sinter, with facilities for supply to the blast furnace for production of pig iron. The annual demand of sinter is estimated as 56, 000, 0 tons per annum.

Sinter Plant:-The function of the Sinter Plant is to supply the blast furnaces with sinter, a combination of blended ores, fluxes and coke which is partially ‘cooked’ or sintered. In this form, the materials combine efficiently in the blast furnace and allow for more consistent and controllable iron manufacture. Figure 1 shows a simplified diagram of a sinter plant.

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Materials enter the sinter plant from storage bins. They are mixed in the correct proportions using weigh hoppers, one per storage bin, except for the return fines for which an impact meter is used instead. Weighing is continuous, as is the whole sintering process. The weighed materials pass along a conveyor to the mixing drum where water is added either manually or as a calculated percentage of the weight of material entering the drum. The moisture content of the coke is measured in the strand roll feed hopper and used to trim the secondary water flow rate. The mix permeability is also measured and used to modify the amount of water required. The mix material is fed onto the strand from the hopper by a roll feeder. The bed depth is set and kept constant by adjusting the cut-off plate which is fitted with probes to sense the depth of material and automatically vary the roll feeder speed. The quantity of material in the feed hopper itself is held constant by automatic adjustment of the feed rates from the individual raw material bins.  

Figure 1 Simplified diagram of a sinter plant of Pakistan steel  

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Production unit:-Sintering plant is mainly composed of following production unit.

Charge preparation Primary mixing Secondary mixing Sintering section

Charge Preparation:-The various substances are first mixed like calcium carbonate, manganese ore, dolomite, raw silica sand and if desired granulated.These raw materials in obtained from 12 bunkers which are sided in 2 rows. Each bunker contain different materials for charge preparation The required size for flux and dolomite is about 0-50mm which is screened form used for charge preparation. The required size for fuel grinding is about 0-25mm for sintering of charge preparation. The iron ore required for charge preparation is about 0-6mm size and these same conditions is also for manganese ore for charge preparation. Iron ores are agglomerated on the conveyor belts consist of a large number of wagons. These wagons that have been linked up as an endless conveyor belt which can be as big as 4 m in width and 100 m in length. The fine ore to be sintered is moistened and fed on to the circulating grid together with coke slack and additions such as limestone, quick lime, olivine or dolomite.

Primary Mixing:-

 The amount of primary water added is about 4-5% proportional to the weight of raw mix entering the mixing drum. This can be easily achieved as shown in Figure 2.

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Secondary Mixing:-The secondary water addition is about 2-3% setpoint is frequently taken as a proportion of the raw mix belt weighed PV. For greater accuracy, the moisture meter reading is used to trim the material/water ratio. This corrects the water flow rate according to the measured moisture content of the raw mix. Cascade control is not always used but since the water flow loop responds faster than the moisture loop it does produce better results. Then it is passes through the shuttle conveyors into the hopper. Then after the hopper it drops into the balling drum for frequent mixing is allowed for 1-2 hours.

Sintering Section:-

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The materials from the baling drum are passed through in to sintering

section. Burners above a heat-resistant grate belt heat the material to the required temperature (1100-1200 °C). In the sintering machine 92 pellet car are used. In Pakistan steel 2 sintering machine are available but nowadays only one sintering machine is working This causes the fuel in the mixture to be ignited. The carbon burns with the aid of the air sucked through the grid into the mixture by means of 8 blower fans at the bottom of sintering machine. Resulting in the flame front being moved through the sintering bed. The sintering processes are completed once the flame front has passed through the entire mixed layer and all fuel has been burnt.Chlorine compounds can enter into the sinter installation by means of the additive cokes The raw mix is ignited by the ignition hood, which is fuelled by a mixture of coke oven gas, blast furnace gas and sometimes natural gas. The calorific value of the mixture and the set hood temperature are controlled. A separate control system is provided to maintain a fixed hood pressure by adjusting the wind box dampers immediately under the ignition hood. The sinter strand is a moving conveyor of hot sinter, which continues to ‘cook’ after leaving the hood, where air is pulled from the sinter by a strand draught fan. An important part of the sintering process is burn-through. This is where the sinter layer has completely burned through its section and is detected by temperature probes under the sinter bed. Burn through should be achieved but must not occur too soon after the ignition hood. The draught on the strand is maintained at a preset value by controlling the main fan louvers

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from pressure measurements in the wind main. This governs the point at which burn through occurs.

Sinter handling:-After the end of the strand, the sinter passes through a spiked roll crusher and the hot screens to the rotating circular cooler. A number of fans are usually used for cooling, and the speed of the cooler is determined by:

Strand speed Bed depth

 The fines removed by the hot screens of -8mm size are conveyed to the return fines bin. After cooling, the sinter is passed into the discharge bunker. At this stage, the level is controlled by varying the outlet feed rate (usually vibros). The sinter then passes to the cold screening area, where it is passed through crushers and screens to produce particles in a specific size range. Sinter below the required size passes over a belt weigher and returns with the hot fines to the return fines bin. The difference between the weight of the cold fines, and the weight of the total fines produced, gives a measure of the hot fines.  The following factors can affect the rate at which fines are produced: 

Mix control Particle size Chemistry Weight Moisture content Bed depth Ignition hood temperature and pressure Warm screens

 Two important properties of sinter are basicity, which is controlled by the amount of limestone, and strength, which is controlled by coke content. The sinter is passes through conveyor belt which is then screened up to +20mm size which is used suitable for use in the blast furnace. Conveyors transport the material to the blast furnace stock house, where it is added to other materials to form the blast furnace burden. The sinter which is screened up to -20mm size is return to the sinter plant.

  

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Process LaboratoryProcess laboratory is one of the most important departments of Pakistan Steel Mill it is designed for built-in reproducibility of the product turned out by the process. Such a determination is made using statistical data, not wishful thinking. Statistically determined limits are compared to specification limits to decide if a process can consistently produce acceptable product. Process capability is best established through closely monitored testing and recording of data over a set period of actually production.

Process Lab:-In the war of modern inventions, the needs of good quality material going to be maximize. Any component performs well in application when it is properly examined after manufacturing. Its ability of resistance to corrosion and some other mechanical properties may enhance its workability. From a needle to air craft components, most of these are designed by a defect free material. It means all the risks of component’s life depend on the manufacturer. Foundry is a place where casting of components is to be done. Production of foundry depends on the pattern designing which provides the basic structural model or design of component by keeping different allowances. Pakistan steel makes the product more desirable for the

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customers. The best performance of component can be obtained by making its defect free micro structure. A good product needs perfect pattern designing, proper melting of metal and its micro structure.

We have visited the following departments in process lab:- Mechanical testing lab Spectrometry lab Metallographic lab

Mechanical Testing Lab:-In mechanical testing lab different test were performed which are as follows.

Tensile test Hardness test Impact test Vickers test Rockwell hardness test Bend test

Tensile test: - Flat specimen geometry is preferred when the end product is a thin plate or sheet. Round – cross section specimen are preferred for products such as extruded bars, forging, and castings. As shown in the figure below, one end of the specimen is gripped in a fixture that is attached to the stationary end of the testing machine; the other end is gripped in a fixture attached to an actuator (moving portion) of the testing machine. The actuator usually moves at a fixed rate of displacement and thus applies load to the specimen. The test usually continues until the specimen fractures.During the test, the load on the specimen is measured by an extensometer (a device for measuring the change in length of the specimen) attached directly to the specimen gage length. Loads and elongations are recorded directly.

The main product of a tensile test is a load versus elongation curve which is then converted into a stress versus strain curve. Since both the engineering stress and the engineering strain are obtained by dividing the load and elongation by constant values (specimen geometry information), the load-

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elongation curve will have the same shape as the engineering stress-strain curve. The stress-strain curve relates the applied stress to the resulting strain and each material has its own unique stress-strain curve. A typical engineering stress-strain curve is shown below. If the true stress, based on the actual cross-sectional area of the specimen, is used, it is found that the stress-strain curve increases continuously up to fracture.

Tensile Testing Machine

HARDNESS TEST:-

In mineralogy, hardness is defined as the resistance of the smooth surface of a mineral to scratching. A soft surface is scratched more easily than a hard surface; thus a hard mineral, such as diamond, will scratch a soft mineral, such as graphite, and the hard mineral will not be scratched by the soft. The Brinell hardness test method consists of indenting the test material with a hardened steel or carbide ball. This ball is regarded as being infinitely hard compared with any of the materials, whose hardness is to be tested, thereby eliminating any consideration of permanent deformation of the

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indenter. In this test a 10 mm dia steel ball is subjected to a load of 3000 kg. For softer materials the load can be reduced to 1500 kg or 500 kg to avoid excessive indentation. The full load is normally applied for 10 to 15 seconds in the case of iron and steel and for at least 30 seconds in the case of other metals. The diameter of the indentation left in the test material is measured with a low powered microscope. The diameter of the impression is measured instead of the depth of penetration because lip is formed around the indentor.

The depth ‘h’ can only be measured with difficulty and, therefore, the diameter is measured. The Brinell hardness number is calculated by dividing the load applied by the surface area of the indentation.

The diameter of the impression is the average of two readings at right angles and the use of a Brinell

Hardness number table can simplify the determination of the Brinell hardness.Originally the indenting was confined to a load of 3000 kg on a 10 mm dia steel ball. When balls of smaller diameter than 10 mm are used, the following relationship should be obeyed in order that the two impressions may be geometrically similar:

F / D2 = constant Where F = load in kg and D = ball diameter in mmThe constant depends upon the hardness of the materials to be tested and the values specified by the British Standards are as follows:

Steel and cast iron = 30

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Brinell hardness Testing Machine

IMPACT TEST:-Charpy v notch test, is a standardized high strain-

Rate test which determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's toughness and acts as a tool to study temperature-dependent brittle-ductile transition. It is widely applied in industry, since it is easy to prepare and conduct and results can be obtained quickly and cheaply. But a major disadvantage is that all results are only comparative.

The test was developed in 1905 by the French scientist Georges Charpy. It was pivotal in understanding the fracture problems of ships during the

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Second World War Today it is used in many industries for testing building and construction materials used in the construction of pressure vessels, bridges and to see how storms will affect materials used in building.

The apparatus consists of a pendulum axe swinging at a notched sample of material. The energy transferred to the material can be inferred by comparing the difference in the height of the hammer before and after a big fracture.

The notch in the sample affects the results of the impact test, thus it is necessary for the notch to be of a regular dimensions and geometry. The size of the sample can also affect results, since the dimensions determine whether or not the material is in plane strain. This difference can greatly affect conclusions made. The quantitative result of the impact test—the energy needed to fracture a material—can be used to measure the toughness of the material and the yield strength. Also, the strain rate may be studied and analyzed for its effect on fracture.

The ductile-brittle transition temperature (DBTT) may be derived from the temperature where the energy needed to fracture the material drastically changes. However, in practice there is no sharp transition and so it is difficult to obtain a precise transition temperature. An exact DBTT may be empirically derived in many ways: a specific absorbed energy, change in aspect of fracture (such as 50% of the area is cleavage), etc.

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Impact Testing Machine

Vickers Test:-

The Vickers hardness test was developed in 1924 by Smith and Sand land as an alternative to the brinell method to measure the hardness of materials.] The Vickers test is often easier to use than other hardness tests since the required calculations are independent of the size of the indenter, and the indenter can be used for all materials irrespective of hardness. The basic principle, as with all common measures of hardness, is to observe the questioned material's ability to resist plastic deformation from a standard source. The Vickers test can be used for all metals and has one of the widest scales among hardness tests. The unit of hardness given by the test is known as the Vickers Pyramid Number (HV). The hardness number can be converted into units of PASCAL’s, but should not be confused with a pressure, which also has units of PASCAL’s. The hardness number is determined by the load over the surface area of the indentation and not the area normal to the force, and is therefore not a pressure.

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The hardness number is not really a true property of the material and is an empirical value that should be seen in conjunction with the experimental methods and hardness scale used. When doing the hardness tests the distance between indentations must be more than 2.5 indentation diameters apart to avoid interaction between the work-hardened regions.

The yield strength of the material can be approximated as:

.

Where c is a constant determined by geometrical factors usually ranging between 2 and 4.

Vickers hardness test

Implementation:-

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Vickers’s test scheme

An indentation left in case-hardened steel after a Vickers hardness test.

It was decided that the indenter shape should be capable of producing geometrically similar impressions, irrespective of size; the impression should have well-defined points of measurement; and the indenter should have high resistance to self-deformation. A diamond in the form of a square-based pyramid satisfied these conditions. It had been established that the ideal size of a brinell impression was 3/8 of the ball diameter. As two tangents to the circle at the ends of a chord 3d/8 long, intersect at 136°, it was decided to use this as the included angle of the indenter. The angle was varied experimentally and it was found that the hardness value obtained on a homogeneous piece of material remained constant, irrespective of load accordingly; loads of various magnitudes are applied to a flat surface, depending on the hardness of the material to be measured. The HV number is then determined by the ratio F/A where F is the force applied to the diamond and A is the surface area of the resulting indentation. A can be determined by the formula

This can be approximated by evaluating the sine term to give

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Where d is the average length of the diagonal left by the indenter. Hence,

The corresponding units of HV are then kilogram-force per square millimeter (kgf/mm²). To convert a Vickers hardness number to SI units (MPa or GPa) one needs to convert the force applied from kilograms-force to Newton’s and the area from mm2 to m2 to give results in PASCAL’s (1 kgf/mm² = 9.80665×106 Pa).

Vickers hardness numbers are reported as xxxHVyy, e.g. 440HV30, where:

440 is the hardness number, HV gives the hardness scale (Vickers), 30 indicates the load used in kg.

Rockwell Hardness Test:-It differs from the Brinell test in that the indenter and the loads are smaller, and the Rockwell hardness number is read directly. The Rockwell hardness test method consists of indenting the test material with a diamond cone or hardened steel ball indenter. The indenter is forced into the test material under a preliminary minor load F0 (Fig. 1A) usually 10 kgf. When equilibrium has been reached, an indicating device, which follows the movements of the indenter and so responds to changes in depth of penetration of the indenter, is set to a datum position. While the preliminary minor load is still applied an additional major load is applied with resulting increase in penetration (Fig. 1B). When equilibrium has again been reached, the additional major load is removed but the preliminary minor load is still maintained. Removal of the additional major load allows a partial recovery, so reducing the depth of penetration (Fig. 1C). The permanent increase in depth of penetration, resulting from the application and removal of the additional major load is used to calculate the Rockwell hardness number.

HR = E - e

F0 = preliminary minor load in kgfF1 = additional major load in kgf

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F = total load in kgfe = permanent increase in depth of penetration due to major load F1 measured in units of 0.002 mmE = a constant depending on form of indenter: 100 units for diamond indenter, 130 units for steel ball indenterHR = Rockwell hardness numberD = diameter of steel ball

Fig. 1.Rockwell Principle

Typical Application of Rockwell Hardness ScalesHRA. Cemented carbides, thin steel and shallow case hardened steelHRB. Copper alloys, soft steels, aluminum alloys, malleable irons, etc.HRC . . . . Steel, hard cast irons, case hardened steel and other materials harder than 100 HRBHRD. . Thin steel and medium case hardened steel and pearlitic malleable ironHRE. Cast iron, aluminum and magnesium alloys, bearing metalsHRF . . . . Annealed copper alloys, thin soft sheet metalsHRG . . . . Phosphor bronze, beryllium copper, malleable irons HRH . . . . Aluminum, zinc, leadsHRK . . . . } HRL . . . . } HRM . . . .} . . . . Soft bearing metals, plastics and other very soft materialsHRP . . . . }

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HRR . . . . } HRS . . . . } HRV . . . . }

Advantages of the Rockwell hardness method include the direct Rockwell hardness number readout and rapid testing time. Disadvantages include many arbitrary non-related scales and possible effects from the specimen support anvil (try putting a cigarette paper under a test block and take note of the effect on the hardness reading! Vickers and Brinell methods don't suffer from this effect)

Rockwell hardness machine

Bend test:-Bending tests are carried out to ensure that a metal has sufficient ductility to stand bending without fracturing. A standard specimen is bent through a specified arc and in the case of strip, the direction of grain flow is noted and whether the bend is with or across the grain.

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Bend testing measures the ductility of materials. Terms associated with bend testing apply to specific forms or types of materials. For example, materials specifications sometimes require that a specimen be bent to a specified inside diameter (ASTM A-360, steel products).

Bend testing provides a convenient method for characterizing the strength of the miniature components and specimens that are typical of those found in microelectronics applications. Instron has bend and flexure fixtures available for both three and four point loading.

Spectrometer Lab:-It is one of the most important departments of steel mill. Analytical technique for the determination of the elemental composition of a sample or molecule. It is also used for elucidating the chemical structures of molecules, such as peptides and other chemical compounds. The MS principle consists of ionizing chemical compounds to generate charged molecules or molecule fragments and measurement of their mass-to-charge ratios. In a typical MS procedure:

1. a sample is loaded onto the MS instrument, and2. the components of the sample are ionized by one of a variety of

methods (e.g., by impacting them with an electron beam), which results in the formation of charged particles (ions)

3. directing the ions into an electric and/or magnetic field4. computation of the mass-to-charge ratio of the particles based on the

details of motion of the ions as they transit through electromagnetic fields, and

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5. Detection of the ions, which in step 4 were sorted according to m/z.

Spectrometer:-A spectrometer (spectrograph or spectroscope) is an optical instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization state. The independent variable is usually the wavelength of the light, normally expressed in nanometers, but sometimes expressed as a unit directly proportional to the photon energy, such as wave number or electron volts, which has a reciprocal relationship to wavelength. A spectrometer is used in spectroscopy for producing spectral lines and measuring their wavelengths and intensities. Spectrometer is a term that is applied to instruments that operate over a very wide range of wavelengths, from gamma rays and X-rays into the far infrared. If the region of interest is restricted to near the visible spectrum, the study is called spectrophotometer.

In general, any particular instrument will operate over a small portion of this total range because of the different techniques used to measure different portions of the spectrum. Below optical frequencies (that is, at microwave and radio frequencies), the spectrum analyzer is a closely related electronic device.

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Metallographic Lab:-It is one of the important department of steel mill in which the Study of the crystalline structure of metals and alloys and the relationship of this structure to the physical properties of metals.

Metallographic consist of the microscopic study of the structural characteristics of a metal or an alloy.

Preparation of specimen:-Specimen is polish and cleaned surface to study of its microstructure, because the microscope makes the use of the principle of reflection of light to obtain the final image of the metal structure.

A properly prepared metal specimen

Is flat, Does not contain scratches,

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Is nicely polished and, and

Is suitably etched.

The most important tools of the metallographic are the microscope and the X-ray machine. Microscopic examination of suitably prepared specimens makes possible the determination of size, structure, and orientation of the metal crystals. By means of such examinations, metallurgists can frequently identify a metal or alloy, discover possible impurities, and check on the effectiveness of heat treatments for hardening or annealing. Metal specimens for metallographic examination are usually highly polished and then etched with dilute acids; this treatment brings out the grain structure by attacking the boundaries between the grains or by attacking one of the constituents of an alloy. When metals are to be examined under the high magnification of an electron microscope a thin, electron-transparent replica or cast of the etched surface can be made, because bulk metals do not transmit an electron beam. Alternatively, an extremely thin specimen can be made; the microstructure that is observed is a projection of that contained within the thin specimen.

Metallurgical Microscope for inspection of microstructure

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Steel making departmentSteel making department is one of the most important departments of Pakistan steel mill. In these department can produce 1.1 million tons steel in form of cast slab, bloom and cast billet.

Basic operation of steel making department is to convert hot metal into liquid steel by oxygen blowing and continuous casting of liquid steel in the form of slab, bloom and billets.

Hot metal mixer:-Molten pig iron coming from the iron making department is received by hot metal mixer. The mixer has a capacity of 1300 tons with inner volume approximately 285 m³.The temperature of hot metal is near about 1320 ºC with the chemical composition as

Carbon not less than 4% S : 0.04% max Si : 0.4 – 0.8% P : 0.2% max Mn : 0.5 – 1.0%

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Safety lining of mixer vessel is of fireclay and working lining is made of magnesite. The lining life of mixer vessel is about 0.8 million ton hot metal cycling.

LD converter:-

LD converter is used to convert the pig iron into steel. There are two LD converts in steel making department. Each has metal charging capacity about 130 tons. The converter has height to diameter ration approximately 1:37. The tap to tap time is 55 minutes. The LD converter is top oxygen blown converter. Oxygen is delivered by the oxygen lance. Oxygen reacts with unwanted materials and oxides form the top of the vessel. The oxygen flow rate is 300 – 45 M³/min. the safety lining of LD vessel is chrome magnesite whereas tar bonded dolomite is used as a working lining refractory. Production rate of each converter is about 27heats per day. In these figure below showing oxygen lacing

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When iron is produced from the ore in a blast furnace, it is rich in carbon and also contains many impurities. It then has to be converted into steel which has controlled quantities of carbon and much reduced concentrations of impurities.

Bessemer realized that forcing air through molten steel would oxidize impurities in the pig iron and raise the metal temperature without the need for additional fuel, i.e., `The manufacture of malleable iron and steel without fuel'.

His invention nearly failed in that some of the iron ores used by those who applied the idea found the iron to contain larger quantities of sulphur and phosphorus, leading to very poor properties. However, this was solved by adding ferromanganese to the melt.

The nitrogen concentration of steel produced using the Bessemer process tended to be greater than desirable because of the use of air (which is mostly nitrogen).

This problem was solved in the Linz-Donawitz process (Lenz and Donowitz are both parts of Austria). In this, high-pressure oxygen is blown at the molten pig iron using a water-cooled lance. A slag of lime and dolomite is used. The process is fast because of the use of commercially pure oxygen, and generates large quantities of heat which can be exploited to add scrap steel to the melt. The basic nature of the flux helps remove phosphorus so there is a greater tolerance to the raw materials used in the process.

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Charging materials:- LD converter has capacity of charge 130tons. Detail of input material description given as under.

Hot metal Basic raw materialSteel scrap CoolantIron ore CoolantOxygen gas for blowingLime Fluxing materialCalcium fluoride Slag forming materialAluminum DeoxidizerFe – Alloys alloying of steel

Charging of LD vessel

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Operation of LD process:-1. Molten iron from a blast furnace is poured into a large refractory-lined

container called a ladle;2. The metal in the ladle is sent directly for basic oxygen steelmaking or

to a pretreatment stage. Pretreatment of the blast furnace metal is used to reduce the refining load of sulfur, silicon, and phosphorus. In desulfurising pre treatment, a lance is lowered into the molten iron in the ladle and several hundred kilograms of powdered magnesium are added. Sulfur impurities are reduced to magnesium sulfide in a violent exothermic reaction. The sulfide is then raked off. Similar pretreatment is possible for desiliconisation and dephosphorisation using mill scale (iron oxide) and lime as reagents. The decision to pretreat depends on the quality of the blast furnace metal and the required final quality of the BOS steel.

3. Filling the furnace with the ingredients is called charging. The BOS process is autogenously: the required thermal energy is produced during the process. Maintaining the proper charge balance, the ratio of hot metal to scrap, is therefore very important. The BOS vessel is one-fifth filled with steel scrap. Molten iron from the ladle is added as required by the charge balance. A typical chemistry of hot metal charged into the BOS vessel is: 4% C, 0.2-0.8% Si, 0.08%-0.18% P, and 0.01-0.04% S.

4. The vessel is then set upright and a water-cooled lance is lowered down into it. The lance blows 99% pure oxygen onto the steel and iron, igniting the carbon dissolved in the steel and burning it to form carbon monoxide and carbon dioxide, causing the temperature to rise to about 1700°C. This melts the scrap, lowers the carbon content of the molten iron and helps remove unwanted chemical elements. It is this use of oxygen instead of air that improves upon the Bessemer process, for the nitrogen (and other gases) in air do not react with the charge as oxygen does. High purity oxygen is blown into the furnace or BOS vessel through a vertically oriented water-cooled lance with velocities faster than Mach 1.[1]

5. Fluxes (burnt lime or dolomite) are fed into the vessel to form slag which absorbs impurities of the steelmaking process. During blowing the metal in the vessel forms an emulsion with the slag, facilitating the refining process. Near the end of the blowing cycle, which takes about 20 minutes, the temperature is measured and samples are taken. The samples are tested and a computer analysis of the steel given within

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six minutes. A typical chemistry of the blown metal is 0.3-0.6% C, 0.05-0.1% Mn, 0.01-0.03% Si, 0.01-0.03% S and P.

6. The BOS vessel is tilted again and the steel is poured into a giant ladle. This process is called tapping the steel. The steel is further refined in the ladle furnace, by adding alloying materials to give the steel special properties required by the customer. Sometimes argon or nitrogen gas is bubbled into the ladle to make sure the alloys mix correctly. The steel now contains 0.1-1% carbon. The more carbon in the steel, the harder it is, but it is also more brittle and less flexible.

7. After the steel is removed from the BOS vessel, the slag, filled with impurities, is poured off and cooled.

Process in Pakistan steel:-The charging material is charged into the vessel by tilting the vessel. After charging, vessel is located it position. Lancing is started. The oxygen blowing is continued for 18 minutes. The blowing has three phases; each phase consists of 6 minutes. In the first phase of six minutes pig iron deoxidizes and removes the silicon impurity.

In the second phase of six minute other impurities are oxidizes such as sulphur, phosphorous, manganese etc. In the last phase of blowing the temperature is maintained according to the requirement. After completion of this conversion process from pig iron to steel, the vessel is tilted and molten steel is tilted into the steel ladle. In ladle some alloying elements are added according to demand and mixed by the nitrogen purging.

This purged molten metal is ready to send directly to the mold for casting. A sketch of LD process is given below.

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The molten steel is pored into the mold in order to produce slab, billets and bloom. Some technical parameters so these casting machines are given a under. Low %C 0.35 – 0.65 Medium % 0.65 – 0.75 High %C 0.75 – 1.25

No. of machines ONE TWO ONEType of machine Radial Radial/ curvilinear RadialNo. of strands Four Two SixProfile size 260 × 260 W= 1000 - 1550Metallurgical length

22meter 24meter 15.8meter

Casting speed 0.7 M/min 0.7 M/min 1.5 M/minSteel Ladle 130 ton

dolomite lining Life AVG30 Heats

Tundish capacity 15 ton 5 ton 12 ton

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Continuous Casting:-

Molten steel is poured into the mold cavity of continuous casting. The walls of mold are made of copper. Water cooling system is provided inner side to the walls of mold. Continuous water circulation system helps to solidify soon and cools the copper walls which are heated by the poured molten steel. The flow of molten metal is controlled and flow of circulating water as well. The solidified product travels by the rotating rollers. The speed of rollers is controlled. the final product thus obtained in the form of billets, blooms and slab. In continuous casting process in Pakistan steel for casting 6 billets can cast at a time,4 bloom and 2 slab in casting process in Pakistan steel

Final product:-

Billets Blooms Slabs

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A metallurgical flow diagram at steel making department is available.

For further for further Rolling to rolling to,Billet mill HSM, CRM for Steel and coil

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BF hot metal

Calcined limeThrough conveyer From refractory

iron ore lump coke lump calcium

flroide

SCRAP

Ferro alloys Aluminum

99% Coke breeze

Slag in slag dirt

Bloom caster

Hot Metal

Slag skimming

Mixer Capacity: 1300 tons

Weighing device

Converter

Weighing devicefgvf

Steel Ladle

Purging unit

Billet Caster

Billet stock Yard

Slab caster

Bloom/Slab handling and conditioning lines and cart slap/bloom stock yard

BLOOM SLAB

PSPS for marker Billet mill for re rolling

Gas cleaning

exhauster

Steam

Net work

Total 2 Nos.Design capacity 130 tonTotal Production1100, 000/year

Natural gas for pre heating

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