Where do cracks occur?
At a hot spot in the castings ( ingate, hot riser, heavysection)
Under a riser, on the riser contact surface
Heavy section (greater than 6”inscribed sphere)
At a stress-raiser on a casting surface (small radii,change of section)
Inside a cored surface
Adjacent to an ingate
Adjacent to a chill
When do Cracks Occur?
During solidification and cooling (visible aftershakeout & blast)
During processing (grinding, arc air, welding)
After heat-treatment (especially Q&T)
Many days after Q&T (“delayed cracking”)
Causes of Craze Cracking
1. In green sand molds, due to high-temperatureoxidation at prior-austenite grain boundaries
2. Excessively high shakeout temperatures above 2000F
? Can be caused by combustion of binder and sand falling away from cast surface
3. Oxidation damage at austenite grains due to excessive austenitizing time and/or temperature
4. In very heavy sections, due to surface nitriding from PUN binder
Cures for Craze Cracks
1. In green sand mold, reduce moisture or skin-dry mold surface
2. In PUN, increase Fe3O4 addition to 5%
3. Reportedly worse at low levels of C, increase C to .25%
4. Reportedly worse in steels with high Ni
5. Usually can be removed by light grinding
ABOUT KEVA
Keva Casting is a professional casting company that focuses on Construction, Machinery, Automobile, Hardware, Pipeline and many other industries.
We provide top quality products with the best service based on our complete production chain including our own mold design, advanced production techniques, and full management of the supply chain. Keva Casting has two factories located in Zhucheng, China's Shandong province.
We use "shell molding", which is a new technique that has been developed in recent years.This new technique has simplified production procedures and reduced air pollution compared with traditional sand casting and investment casting. Shell making and core making are faster to ensure production in enormous quantities. The dimensions and surface finishing are satisfactory for all kinds of industrial requirements. Besides supplying our own formwork & scaffolding systems, our casting products also supply OEM services in various industries.