Thermal cracking
1. The characteristics and discovery methods of thermal cracking:
The places with thermal cracks have dark or almost black oxidized surfaces. Such thermal cracks can be found by visual inspection, light transmission method, and pressure test.
2. Causes of thermal cracks:
1) If the chemical composition of the molten iron does not meet the requirements, the shrinkage value of the solid will be relatively large, such as low carbon, high sulfur and so on.
2) If the casting contains low-melting slag inclusions, it will reduce the high-temperature strength, because when the thermal cracks are generated near the end of solidification, the shrinkage at the hot joints of the castings will be mechanically hindered to produce thermal cracks.
3. Prevention methods of thermal cracks
1) Cast iron manufacturers should try their best to control the chemical composition in the castings, and the sulfur content in the molten iron must be low;
2) When pouring, avoid molten slag entering the cavity;
Cold cracking
1. The characteristics and discovery methods of cold cracks:
In cold cracks, there will be a clean or slightly oxidized surface with a dark red color; the method of discovery is the same as that of hot cracks.
2. Causes of cold cracks:
1) The chemical composition of the metal liquid is unqualified, which causes the solid shrinkage value to be relatively large;
2) The phosphorus content in the molten metal is relatively high, which increases the brittleness and reduces the tensile strength of the cast iron. The cold cracks mainly occur at the stress concentration of the thick and thin castings.
3. Prevention methods of cold cracks:
1) Control the chemical composition in the castings, and the cast iron manufacturers should also try to reduce the sulfur content in the molten metal;
2) The ωp in the molten iron should be controlled below 0.15%.
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.