Cold work tool steel include the O-series (oil-hardening), the A-series (air-hardening), and the D-series (high carbon-chromium).  The classification Base on ASTM-A681.

Cold work tool steel place extra emphasis on hardness, wear resistance. High carbon content, alloying elements to increase the hardenability and enhance the wear resistance. Cold work die steel including manufacturing blanking die, blanking punching die and trimming die, punch, scissors) die, cold heading and cold extrusion die, bending die and drawing die, etc.