Pre-hardened steel are mold materials developed for plastic molding and used for dies of presses. These have not been stipulated in JIS standards, and the materials used are those developed under the brand names of the manufacturers. These materials have reasonable hardness and can be machined. The material properties are adjusted to obtain a hardness of about 40 HRC, and precipitation hardened types are used.

Pre-hardened steel is used frequently for punches and dies for blanking or bending in the case of low volume production. In the case of large volume production, pre-hardened steel is used for punch plates, backing plates, etc. This material is commonly used because it can be machined and is convenient because it can be used as is without heat treatment.

* Precipitation hardening:

This is hardening caused by the precipitation of certain constituents when a supersaturated solid solution is heated to an appropriate temperature.