The designation “Calm steel” (or sometimes also called “resting steel”), is a steel subjected to a deoxidizing treatment by adding manganese, silicon or aluminum before casting. The objective of this operation is to significantly reduce or completely eliminate the oxygen content of the steel so that no gas is formed during the subsequent solidification process. This process for calm steel allows perfect pieces to be obtained since it does not produce gases during solidification, so that such addition prevents the formation of blowholes. With this process the aging phenomena are avoided, but the impurities are now on the surface instead of in the nucleus.
Calmed steel is mainly used where the quality of the core is important, that is, for this type of parts: