foundry hand tools

7/31/2019 Foundry Hand Tools

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Mr. D.A.Ghatge


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INTRODUCTION

Foundry Engineering deals with the process ofmaking casting in moulds prepared by patterns

Stages:

1. Pattern making

2. Moulding and core making3. Melting and casting

4. Fettling

5. Testing and inspection


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FOUNDRY HAND TOOLS


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FOUNDRY HAND TOOLS


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FOUNDRY HAND TOOLS


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FOUNDRY HAND TOOLS


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FOUNDRY HAND TOOLS - LADLES


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FOUNDRY HAND TOOLS- CRUCIBLES


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MELTING EQUIPMENTS In order to obtain the proper pouring and melting

temperature of the metal several furnaces are used: For ferrous metals:

Cupola furnaces

Open heart furnaces

Electric furnaces For non-ferrous metals:

Pit Type

Stationary type

Tilting Type


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CUPOLA

Used for melting for

cast iron. Low cost.

Better control of tempand chemical

composition. Easy tapping.

Consumes easilyavailable fuels.


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ELECTRIC FURNACE

High Temp.

Fast Melting.

Controlled atm.

For largequantities.

High cost andmaintenance.

Fumes, smokeand noise.


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OIL / GASFIRED ROTARY FURNACE


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MOULDING

Mould is a void or cavity created in a compactsand mass with the help of pattern.

Core is a sand shape exactly similar to thecavities to be produced in casting. Generally

made differently in a core box.Permanent moulds are made up of ferrous

metals and alloys, normally used for casting oflow melting point material, costly

Temporary refractory moulds are made ofrefractory sands and resin, for high meltingpoints and bigger objects, Cheap.


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PATTERNSANDCORES


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Mould

Pattern MouldCore

Casted Job

Casted JobHole in Job

by Core

AIN CONSTITUENTS OF OULDING


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AINCONSTITUENTSOF OULDINGSAND

Principle Constituents:Silica Sand

Major Portion, 80-82 % High Softening Temperature and thermal

Stability, chemical resistively and permeability. Found in banks and bottom of rivers.

Binders Imparts sufficient strength and cohesiveness,

but decreases permeability of sand. Organic, in-organic and Clay are used.

AdditivesWater


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ADDITIVESOF MOULDINGSAND


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ADDITIVESOF MOULDINGSAND


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SAND GRAINS


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PROPERTIESOF MOULDING SAND

Porosity or Permeability Flowability or PlasticityRefractorinessAdhesiveness

CohesivenessCollapsibilityDurability Fitness

Bench lifeCo-efficient of expansionChemically NeutralReusable, Cheap and Easily available


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CLASSIFICATIONOF MOULDING SAND


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SPECIAL SAND


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SPECIAL SAND


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SPECIAL SAND


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PREPARATION MOULDING SAND


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SAND TESTING


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MOULDING PROCESS

According to the method Used:

1. Floor Moulding

Foundry floor acts as drag and may be coveredwith cope or may be casted open.

Used for all medium and large casting

2. Bench Moulding For small and light moulds Done in cope and drag

3. Pit Moulding

Moulding for extremely large casting is done in pit Pit acts as drag and separate cope can be used to

make gates and runners


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MOULDING PROCESS

4. Machine Moulding

All the jobs of ramming, moulding and gate making,drawing of pattern is done by machines.

Produces identical and consistent castings

Preferred for the mass production


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MOULDING PROCESS


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MOULDING PROCESS


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MOULDING PROCESS


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MOULDING PROCESS


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GATING SYSTEM

Gating System means all

the passages throughwhich the molten metalenters the mould cavity.

Includes: Pouring basin Runner

Gate

Riser

It has great impact uponthe quality of the castingproduced.


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REQUIREMENTOF GATING SYSTEM

Low flow velocity of molten metal. Insure complete filling of cavity.

Prevent absorption of moisture while flow.

Prevent formation of oxides.

Prevent entry of slag, dross etc.

Assist directional solidification.

Should be practical and economical.


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TYPESOF GATES

1. Top Gate

2. Bottom Gate

3. Parting Gate

4. Step Gate


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TYPESOF GATES


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SPECIAL CASTING PROCESSES

G D P M


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GRAVITY DIEOR PERMANENT MOULDCASTING

Molten metal is poured undergravity only.

Uses permanent moulds; canbe reused many times

Made of grey cast iron; innersurface coated with refractories.

Made in two halves with built-ingating system.


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CENTRIFUGAL CASTING

Mould is rotated rapidly about its central axisas the metal is pored into it.

Centrifugal force plays major role in shapingand feeding of the casting.

C.F. helps to distribute the molten metalevenly to all surfaces and separates the slagfrom out flowing molten metal.

Three types:1. True Centrifugal 2. Semi Centrifugal 3.

Centrifuge


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TRUE CENTRIFUGAL CASTING


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TRUE CENTRIFUGAL CASTING

SEMI CENTRIFUGAL AND CENTRIFUGE


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SEMI CENTRIFUGALAND CENTRIFUGECASTING


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CARBONDIOXIDE MOULDING

This process is basically a hardening process forthe moulds and cores.

As Co2 gas is passed through a sand mixturecontaining sodium silicate, the sand immediatelybecomes extremely strong bonded as sodiumsilicate becomes a stiff gel giving the necessarystrength to the mould.

Pure dry silica is mixed with 3-5% sodium silicateand water; and is rammed in the moulding box.

Co2 is forced into mould at high pressure.

Additional hardening may be done by baking.


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SHELL MOULDING

The sand mixed with thermosetting resign is allowedto come into contact with heated metallic patternplate.

A thin and strong shell of mould is formed around thepattern.

The shell is removed from the pattern and paced incope and drag with backing material and molten metalis poured for casting.


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SHELL MOLDING PROCESS

It is a process in which, the sand mixed witha thermosetting resin is allowed to come incontact with a heated pattern plate (200 oC),

this causes a skin (Shell) of about 3.5 mm ofsand/plastic mixture to adhere to thepattern.. Then the shell is removed from thepattern. The cope and drag shells are kept

in a flask with necessary backup materialand the molten metal is poured into themold.


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This process can produce complex partswith good surface finish 1.25 m to 3.75 m,and dimensional tolerance of 0.5 %.

A good surface finish and good sizetolerance reduce the need for machining.

The process overall is quite cost effectivedue to reduced machining and cleanupcosts.

The materials that can be used with thisprocess are cast irons, and aluminum andcopper alloys.


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MOLDING SANDIN SHELL

MOLDING PROCESS The molding sand is a mixture of fine grained

quartz sand and powdered Bakelite. There are twomethods of coating the sand grains with Bakelite.

First method is Cold coating method

and another one is the hot method of coating.


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COLDCOATING,

In the method of cold coating,

quartz sand is poured into the mixer

and then the solution of powdered bakelite in

acetone and ethyl aldehyde are added. The typical mixture is 92% quartz sand, 5%

bakelite, 3% ethyl aldehyde.

During mixing of the ingredients, the resin

envelops the sand grains and the solventevaporates, leaving a thin film that uniformlycoats the surface of sand grains, therebyimparting fluidity to the sand mixtures.


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In the method of hot coating,

the mixture is heated to 150-180 o C prior toloading the sand.

In the course of sand mixing, the soluble phenolformaldehyde resin is added.

The mixer is allowed to cool up to 80 90 o C.

This method gives better properties to the

mixtures than cold method.

HOTCOATING.


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SHELL MOULDING


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Shell For

Moulding

Rotational Shell Moulding


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SHELL MOULDING


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INVESTMENT CASTING

-The basic steps of the investment casting process are

Production of heat-disposable wax, plastic, orpolystyrene patterns

Assembly of these patterns onto a gating system

?Investing,? or covering the pattern assembly withrefractory slurry

Melting the pattern assembly to remove the patternmaterial

Firing the mold to remove the last traces of thepattern material

Pouring

Knockout, cutoff and finishing.

INVESTMENT CASTING


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INVESTMENT CASTING

The investment casting process also called lost wax processbegins with the production of wax replicas or patterns of the

desired shape of the castings. A pattern is needed for every casting to be produced.

The patterns are prepared by injecting wax or polystyrene in ametal dies.

A number of patterns are attached to a central wax sprue toform a assembly.

The mold is prepared by surrounding the pattern withrefractory slurry that can set at room temperature.

The mold is then heated so that pattern melts and flows out,

leaving a clean cavity behind. The mould is further hardened by heating and the molten

metal is poured while it is still hot.

When the casting is solidified, the mold is broken and thecasting taken out.


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INVESTMENT CASTING

(a) Wax patterns are produced by

injection molding

(b) Multiple patterns are assembled

to a central wax sprue

Steps in the investment casting process


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(c) A shell is built by immersing the

assembly in a liquid ceramic slurry and

then into a bed of extremely fine sand.

Several layers may be required.

(d) The ceramic is dried; the wax is melted

out; ceramic is fired to burn all wax.


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wax(e) The shell is filled with molten metal by

gravity pouring. On solidification, the parts, gates,

sprueand pouring cup become one solid casting.Hollow casting can be made by pouring out excess

metal before it solidifies.

(f) After metal solidifies, the ceramic shell is

broken off by vibration or water blasting


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(g) The parts are cut away from the

sprue using a high speed friction saw.

Minor finishing gives final part.


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Continuous casting is a casting method, in whichthe steps of pouring, solidification and withdrawal

(extraction) of the casting from an open end mold are

carried out continuously.

Cross-sectional dimensions of a continuous casting

are constant along the casting length and they are

determined only by the dimensions of the mold

cavity.The length of a continuous casting is limited by

the life time of the mold.

Continuous casting technology is used for both

ferrous and non-ferrous alloys.


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Traditional continuous casting processes usestationary (or oscillating) molds, in which the

solidified bar moves relative to the mold surface.

Friction caused by the movement results in

formation of micro-cracks and other defects in the

surface regions of the casting.


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Lubricating oil supplied to the mold surface and self-lubricating graphite molds decrease the friction/sticking and

reduce the defective surface zone.

This defective zone is commonly machined (milled) prior

to Rolling

The alternative continuous casting methods use moving

endless molds (rolls, belts, wheels) characterized by zero

relative movement between the mold and casting surfaces.

Strips and slabs fabricated by Continuous casting in

traveling mold have low defect surface. The castings may befurther processed (rolled) without surface machining.


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Depending on the mold position (vertical or horizontal)

continuous casting machines may bevertical

horizontal.

VERTICAL CONTINUOUS CASTING


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VERTICALCONTINUOUSCASTING

Steels are commonly cast in vertical

continuous casting machines

Molten metal is continuously supplied

from the ladle to the intermediate ladle

(tundish) from which it is continuouslypoured into the mold at a controllable rate

keeping the melt level at a constant

position.

The water-cooled copper mold

(primary cooling zone) extracts the heat

of the metal causing its solidification. The

mold oscillates in order to prevent

sticking with the casting.

http://www.substech.com/dokuwiki/lib/exe/fetch.php?cache=cache&media=vertical_continuous_casting.png


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When the casting goes out from the

mold it is cooled in the secondarycooling zone by water (or water with air)

sprayed on the casting surface.

Most of vertical continuous castingmachines are equipped with strand guide

units bending the casting and changing its

configuration from vertical to horizontal.

The casting is continuously extracted

from the mold by the withdrawal unit

followed by a cut-off unit.



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The casting process begins from

inserting a dummy (primary) bar into themold.

Then a molten metal is poured into the

mold where it solidifies and grips the endof the dummy bar.

The dummy bar is disconnected from

the casting after passing the withdrawal

unit.


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HORIZONTALCONTINUOUSCASTING

Horizontal continuous castingmachine is generally used for casting non-

ferrous alloys.

Horizontal continuous casting in

stationary mold with graphite water-cooledmolds, Twin-roll caster and Twin-belt

caster are most popular methods of this

type.

Due to the water cooling (primary and

secondary) solidification rate provided by

continuous casting is higher than in other

casting methods therefore continuous

castings have more uniform and finer grain

structure and enhanced mechanical

properties.
http://www.substech.com/dokuwiki/lib/exe/detail.php?id=continuous_casting&cache=cache&media=horizontal_continuous_casting.png


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CASTING DEFECTS

C D


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CASTING DEFECTS

1. Blow holes

2. Porosity3. Shrinkage4. Hot tears5. Drop6. Metal Penetration7. Fusion8. Shot metal9. Shift10. Swells11. Hard Spots12. Warpage

C D


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CASTING DEFECTS


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CASTING DEFECTS

CASTING DEFECTS


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CASTING DEFECTS

CASTING DEFECTS


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CASTING DEFECTS

CASTING DEFECTS


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CASTING DEFECTS


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CASTING DEFECTS

CLEANING OF CASTING (FETTLING)


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CLEANINGOF CASTING (FETTLING)

After casting has solidified it is removedform the mould and is cleaned to remove therunner risers cores etc.

1. Rough Cleaning

2. Surface cleaning Wire brush

Sand blasting

Shot Blasting

3. Finishing

4. Inspection of casting

Destructive and Non-Destructive

I


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INSPECTIONOFCASTING

Destructive

Cutting samples and examining properties

Tensile, Compression and Torsion Testing

Non-DestructiveVisual Inspection

Dimensional Inspection

Pressure Testing

Radiographic Inspection

Magnetic Inspection


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THE END

Self Reading assignment:

Chills and ChapletsContinuous Casting

Investment casting and Injection

casting

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