Unit I Foundry All

8/13/2019 Unit I Foundry All

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Introduction

Foundry Engineering deals with theprocess of making casting in moulds

prepared by patterns

Stages:1. Pattern making

2. Moulding and core making

3. Melting and casting4. 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 andmelting temperature of the metal severalfurnaces 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

temp and chemical

composition.

Easy tapping.

Consumes easily

available fuels.


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Electric Furnace

High Temp.

Fast Melting.

Controlled atm.

For largequantities.

High cost andmaintenance.

Fumes, smoke andnoise.


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Oil / Gas fired Rotary Furnace


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Moulding

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

Coreis a sand shape exactly similar to the cavitiesto be produced in casting. Generally made

differently in a core box.

Permanent mouldsare made up of ferrous metalsand alloys, normally used for casting of lowmelting point material, costly

Temporary refractory mouldsare made ofrefractory sands and resin, for high melting pointsand bigger objects, Cheap.


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Main constituents of Moulding sand

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.

Additives

Water


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Additives of Moulding sand


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Additives of Moulding sand


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Sand Grains


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Properties of Moulding Sand

Porosity or Permeability Flowability or Plasticity

Refractoriness

Adhesiveness

Cohesiveness Collapsibility

Durability

Fitness

Bench life

Co-efficient of expansion

Chemically Neutral

Reusable, Cheap and Easily available


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Classification of 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 covered withcope 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 makegates 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 through whichthe molten metal enters themould cavity.

Includes:

Pouring basin

Runner

Gate

Riser It has great impact upon the

quality of the castingproduced.


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Requirement of 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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Types of Gates

1. Top Gate2. Bottom Gate

3. Parting Gate

4. Step Gate


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Types of Gates


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Special Casting Processes


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Gravity Die or Permanent Mould Casting

Molten metal is pouredunder gravity only.

Uses permanent moulds;

can be reused many times

Made of grey cast iron;

inner surface coated with

refractories. Made in two halves with

built-in gating system.


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True Centrifugal Casting


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True Centrifugal Casting


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Semi Centrifugal and Centrifuge Casting


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Carbon dioxide 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 immediately

becomes extremely strong bonded as sodiumsilicate becomes a stiff gel giving the necessarystrength to the mould.

Pure dry silica is mixed with 3-5% sodium silicate

and 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 isallowed to come into contact with heated

metallic pattern plate.

A thin and strong shell of mould is formedaround the pattern.

The shell is removed from the pattern and

paced in cope and drag with backing

material and molten metal is poured for

casting.


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Shell Moulding


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Rotational Shell Moulding


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Shell Moulding


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Casting Defects


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Casting Defects1. Blow holes

2. Porosity3. Shrinkage

4. Hot tears

5. Drop

6. Metal Penetration

7. Fusion

8. Shot metal

9. Shift10. Swells

11. Hard Spots

12. Warpage


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Casting Defects


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Casting Defects


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Casting Defects


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Casting Defects


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Casting Defects


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Casting Defects

Cl i f C i (F li )


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Cleaning of Casting (Fettling)

After casting has solidified it is removed form

the mould and is cleaned to remove the runner

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

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Inspection of casting

Destructive

Cutting samples and examining properties

Tensile, Compression and Torsion Testing

Non-Destructive

Visual Inspection

Dimensional Inspection

Pressure Testing Radiographic Inspection

Magnetic Inspection

Unit I Foundry All

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