defects in gray cast iron casting
TRANSCRIPT
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