foundry hand tools
TRANSCRIPT
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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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CARBONDIOXIDE MOULDING
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CARBONDIOXIDE MOULDING
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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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SHELL MOLDING PROCESS
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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SHELL MOLDING PROCESS
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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.
VERTICAL CONTINUOUS CASTING
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VERTICALCONTINUOUSCASTING
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.
VERTICAL CONTINUOUS CASTING
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VERTICALCONTINUOUSCASTING
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.
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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