casting process ( mp 2 / sem 4 / gtu )

LD COLLEGE OF ENGINEERING

TOPIC : CASTING PROCESS

NAME ENROLL NO TEJAS PATEL 140280119081 TRUPAL PATEL 140280119082 NIMESH PATEL 140280119075

STEPS INVOLVED IN MAKING CASTING

making pattern and core box Making mould Melting and pouring the metal Cleaning Inspection and testing Reclaiming sand

CASTING PROCESS : Casting is the process of pouring molten

metal into the previously made cavity to the desired

shape and allow it to solidify.

PATTERN Pattern is the solid form that used to make the

mould. Types of pattern1. Loose pattern2. Gated pattern3. Match plate pattern 4. Cope and drag pattern5. Pattern devices6. Shell pattern7. Built up pattern8. Lagged up pattern

LOOSE PATTERN Not connected to other patterned or

mounted on a plate. Classified in to 1. Solid piece pattern2. Self core pattern3. Split pattern4. Loose piece pattern

GATED PATTERN They are number of loose pattern connected with

gatting system. Reduce moulding time. Extra cost for operation of separating individual casting.

COPE AND DRAG PATTERN Used for medium and large size casting. Separate pattern plates are made for cope and drag

halves.

PATTERN DEVICES When the size of casting is too large

and number casting to produce is only two or one then full pattern prove uneconomical.

In such case sweeps, segments, skeletons and follow boards are used.

SHELL PATTERN U-used mostly for piping work C -consist of a thin cylindrical or curved metal piece

BUILT UP PATTERN Intricate patterns are built op by

joining segments of wooden strips. These segments are cutting strip of

wood to the curvature required and gluied together to form the desired size of the pattern.

MATCH PLATE PATTERN Designed to work with match

plate moulding machine for high production rate.

They are expensive. Accuracy is more than those

made by hand moulding.

LAGGED UP PATTERN

Used for cylinders, pipes and columns.

PATTERN MATERIAL Following material can be used for

pattern making 1. Wood2. Metal3. Plastic4. Plaster

WOOD Most commonly used Readily available Worked easily Can join by glue Can preserved with shellac Repaired easily Hard , strong and less likely to wrap

METALS Used in mass production Can hold dimension and don’t wrap Are not effected by moisture More wear resistance Can get good surface finish Used: aluminium, white metal,cast iron,

brass , mild steel Are expensive as compare to wooden Heavier

PLASTICS Good wear resistance Are not effected by moisture Give good surface finish Light in weight Because of glossy surface pattern withdrawn is easy Can’t withstand shock

PLASTER• Easy to cast• It is brittle• It expands on solidifications

PATTERN ALLOWANCE PATTERN DRAFT

• Taper provided to facilitate its withdrawal

• It may be positive or negative according to shape of cavity.

MACHINING ALLOWANCE

Provided to take care of the surface finish and dimensional requirement of casting.

Depends on material of the casting ,size, and surface of casting, the method of casting and moulding.

SHAKE ALLOWANCE Cause : rapping of pattern before they

are withdrawn. A negative allowance is applied to the

dimension which are parallel to the parting plane.

DISTORTION AND CHAMBER ALLOWANCES

Certain casting like large flat plates and V OR U shape castings have tendency to wrap or distort on cooling

Cause: uneven metal thickness

SHRINKAGE ALLOWANCES

Liquid shrinkage Solidification shrinkage can make good by gating

and risering system Solid shrinkage Can’t remove easily Can compensated by

making the pattern larger than the requires

MOULDING SAND Green sand Contain : 15-25 % clay , 6-8%water Used to produce small to medium size

mould

Dry sand It is the green sand that has been dried

after preparing the mould Give strength to mould Used for large casting

Loam sand Contain 50% clay Used for heavy casting with the help of

sweep and skeleton pattern

Parting sand Stickness Contain :clay free dry silica sand, sea

sand , parting compound

Facing sand Made of silica sand and clay without

addition of any used sand Thickness: 20 to 30mm

Backing sand Consist of old repeatedly used mould sand Reduce cost

System sand More strength , permeability ,refractiness Used: for filling whole flask in mechanized

foundries

Core sand(oil sand) Silica sand mixed with core oil Used: for making larger cores

System sand Used in mechanized foundries. Due to absence of fresh sand system

sand must have more strength ,permeability and refractiness compared to backing sand.

VARIABLES AFFECTING SAND PROPERTIES

GRAIN TEXTURE :

Permeability decrease from left to right. Compounded grains are least desirable at high

temp. bec. They tends to disintegrate. Uniform grain size => more permeability

CLAY TYPE AND AMOUNT

As the amount of clay increases , strength of mould will increase.

Amount of water & max. strength available = f ( type of clay )

MOISTURE CONTENT : Active the bonding action

MEATHOD OF PREPARING THE MOULD : Intensity of ramming (high degree of ramming

increase the bulk density & reduce permeability )

PROPERTIES OF MOULDING SAND

Strength Should have adequate strength in its

green , dry and hop state Depends: grain size and shape : moisture content : density of sand

Thermal stability Dimensional stability under rapid

heating ,cracks, buckling, and flaking off of sand.

Permeability Natural porosity of sand which will permit

steam and other mould gases to escape. Higher if clay content is less and grain size

is large.

Refractoriness Ability to withstand the temperature of

liquid metal. Measured by sinter point.

Reusability Important to reuse of sand otherwise apart

from cost it will create disposal problem.

Flowability Ability to flow all around the pattern and

take desired mould shape. Increase as clay and water content are

increased.

Collapsibility Sand should collapse after the casting is

solidified . The property is very important for core sand

which forms interior detail of casting.

Conductivity Sand should have enough conductivity to

permit removal of heat from the casting.

SAND TESTING Clay content test For testing purpose clay content is

defined as all substance which settle at a rate less than 25 mm per minute when suspended in water.

Moisture content test

Determined by drying 50 gm of moist sand to constant weight between 105 to 110 c in a uniformly heated oven ,cooling to room temperature and weighing dry sample.

The difference in weights gives the moisture content.

Permeability test

For purpose of comparison permeability is quantified as a permeability number

 Permeability number (N) = ((V x H) / (A x P x T)) Where,

V-Volume of air (cc) H-Height of the specimen (mm) A-Area of the specimen (mm2) P-Air pressure (gm / cm2) T-Time taken by the air to pass

through the sand (seconds)

CORE AND CORE MAKING Core To produce inside detail, recess , cavity in a casting a

suitable solid mass should be placed in the mould to prevent the metal from pouring in these place resulting in a cavity.

This solid mass in a mould is called core.

Core material Sand : green sand : Dry sand metal

Method of core making1. Preparation of core sand mix2. Core making3. Core drying or backing4. Core finishing

MOULDING PRACTICE Green sand moulding They are moulds by using conventional

clay sands and poured with the moulds in wet sand.

Composition : 60% floor sand, 30% new sand, 10% coal dust.

Least expensive method of moulding. Lack of permeability and strength due

to moisture.

How to prepare a mould for green sand moulding…???

Dry sand moulds

They are completely dried in ovens before pouring.

Composition: 53% floor sand, 42% new sand, 5% horse manure or saw dust and blinders like flour, resin, molasses or clay.

Used for large casting requiring strong mould .

More dimensional accuracy compared to green sand moulding.

They are more susceptible to distortion and hot tears , longer production cycle.

Process of preparation of the dry sand mould…..

Loam sand moulds They are built up with unburnt bricks or large

cast iron parts and plasters with loam mortar. Chopped straw may be added for strength

and cow dung added to enhance workability. Large cylinders , heavy bells, chemical plant

pans are cast using loam sand moulds. It is time consuming.

Carbon dioxide moulds The mould is prepared by

ramming clean sand mixed with sodium silicates around the pattern .

The carbon dioxide is added to harden the mould.

It has high accuracy and good surface finish.

Reduce the manual work and cost.

Floor moulding

The moulding is done on the foundry floor , is known as floor moulding.

It is used for medium and large size casting .

Metal flask is used for holding the sand.

Pit moulding

Very large moulds are made in pits below the foundry floor, is known as pit moulding.

The pit acts as the drag part of the mould while a separate cope is used above it.

The sides of pit are lined with bricks while its bottom is covered with a thick layer of cinders.

Reduces the efforts and cost of casting.

PREPARE A MOULD

POUR A MOLTEN METAL

REFERENCES [ FROM WHERE ??? ]

PICS REFERENCE REFERENCES FOR VIDEO

MOULDING : Westpointfoundry.org Metalworkingnews.info SAND TESTING : Slideshare.net Hnsa.org PATTERNS : Mechanicalinventions.blogsp

ot.com

Chinasavvy ( casting process )

YOUTUBE : UNIVERSITY OF ARKANSAS (permeability test )

THANK YOU