Case study of defects in casting and forging Project guide: Prof. R. K. Mahajan

Group no.-11

Munish kumar(071425)

Mahander Pratap Singh (071577)

What done up till now

1. Literature review of various practices in gray cast iron.2. Visited Mahindra and Mahindra foundry section.3. Literature review of Forging practices and Forging defects.4. Asked for the permission in Forging section for various

industries.

Defects in gray cast iron castingMahindra and Mahindra Foundry section

Various shops in foundry where defects generally comes.

MELT SHOP

CORE SHOP

MOLD SHOP

SAND SHOP

MELT SHOP COLD SHUT SHORT PORE SHRINKAGE LOW HARDNESS HIGH HARDNESS

MOLD SHOP

MOLD SCAB SAND DROP MOLD CRACK MOLD LEAK BLOW HOLE (VERY COMMON)

CORE SHOP CORE SCAB CORE CRUSH CORE SHIFTING

Sand plant Moisture Sand fusion

Defects in foundry

Typical forging defects Incomplete die filling. Die misalignment. Forging laps. Incomplete forging penetration- should

forge on the press. Microstructural differences resulting in

pronounced property variation. Hot shortness, due to high sulphur

concentration in steel and nickel. Pitted surface, due to oxide scales occurring

at high temperature stick on the dies.

Buckling, in upsetting forging. Subject to high compressive stress.

Surface cracking, due to temperature differential between surface and centre, or excessive working of the surface at too low temperature.

Microcracking, due to residual stress. Flash line crack, after trimming-occurs more

often in thin workpieces. Therefore should increase the thickness of the flash.

Cold shut or fold , due to flash or fin from prior forging steps is forced into the workpiece.

Internal cracking, due to secondary tensile stress.

Casting Quality There are numerous opportunities for

things to go wrong in a casting operation, resulting in quality defects in the product

The defects can be classified as follows: Defects common to all casting processes Defects related to sand casting process

Misrun A casting that has solidified before completely

filling mold cavity

Figure 11.22 ‑ Some common defects in castings: (a) misrun

Cold Shut Two portions of metal flow together but there is a

lack of fusion due to premature freezing

Figure 11.22 ‑ Some common defects in castings: (b) cold shut

Cold Shot

Metal splatters during pouring and solid globules form and become entrapped in casting

Figure 11.22 ‑ Some common defects in castings: (c) cold shot

Shrinkage Cavity Depression in surface or internal void caused by

solidification shrinkage that restricts amount of molten metal available in last region to freeze

Figure 11.22 ‑ Some common defects in castings: (d) shrinkage cavity

Sand Blow Balloon‑shaped gas cavity caused by release of

mold gases during pouring

Figure 11.23 ‑ Common defects in sand castings: (a) sand blow

Pin Holes Formation of many small gas cavities at or

slightly below surface of casting

Figure 11.23 ‑ Common defects in sand castings: (b) pin holes

Penetration

When fluidity of liquid metal is high, it may penetrate into sand mold or sand core, causing casting surface to consist of a mixture of sand grains and metal

Figure 11.23 ‑ Common defects in sand castings: (e) penetration

Mold Shift

A step in cast product at parting line caused by sidewise relative displacement of cope and drag

Figure 11.23 ‑ Common defects in sand castings: (f) mold shift