Stainless steels are distinguished from other steels by a minimum chromium content of 10.5%, which makes them more resistant to corrosive aqueous environments and to oxidation. Although there are exceptions, stainless steel casting is classified as “corrosion resistant” when used in aqueous environments and vapors below 1200°F (650°C) and “heat resistant” when used above this temperature.
The usual distinction between the heat and corrosion resistant casting grades is carbon content. For a stainless steel casting to perform well in a corrosive environment, the carbon content must be low. Heat resistant grades have higher carbon contents to improve elevated temperature strength.
Cast stainless steels generally have equivalent corrosion resistance to their wrought equivalents, but they can become less corrosion resistant due to localized contamination, microsegregation or lack of homogeneity. For example, mold quality may cause superficial compositional changes that influence performance, and carbon pick-up from mold release agents can affect corrosion resistance. Heat treatment and weld repair procedures can influence the performance of some cast grades and should be taken into consideration during grade selection.
Stainless steel casting can be produced by centrifugal, sand, shell-mold, ceramic-mold, and investment casting.