unit i foundry all
TRANSCRIPT
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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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Carbon dioxide Moulding
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Carbon dioxide Moulding
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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
i f i
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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