1. Classification of tool steels

In the field of shaping with or without chip removal, the decisive criterion for the tool is the maintenance of hardness, toughness and surface finish at the temperature reached by its active part. If this temperature is relatively low, e.g. less than or equal to 200°C, cold-work steels are used, whereas if it is above 250°C, hot-work steels or high-speed steels are used.

The classification of tool steels between cold and hot working is therefore essentially based on the criterion of hot hardness.

• Cold-work steels are characterized by very high hardness at room temperature, equal to or greater than 55 HRC, but low hardness when hot. They are divided, according to their alloying element content, into two groups:

  • unalloyed tool steels for cold working ;

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