Tool steels - normalized numerical data

The cost of tooling represents between 5 and 15% of the manufacturing cost of the parts used, depending on the industry. In many cases (forging and coining tools, sheet metal working tools, molds used in plastics processing, die-casting and the glass industry), the use of calculation codes has enabled a significant reduction in the unit cost of tools, resulting in an increase in their service life of several tens of percent. These codes have made it possible to modify tool design by reducing thermal and mechanical stresses, and have helped in the development of simulation tests for the various modes of degradation, leading to the possibility of optimizing steel grades for a given use, as well as heat treatment and surface treatment.

The use of these codes, however, requires a thorough understanding of the physical and mechanical properties of tool steels, both at room temperature and when hot. The standardized numerical data presented in this article provide an initial response to the problem posed by users of calculation codes. They must, of course, be supplemented by boundary conditions (heat exchange coefficients in particular) which can only be determined by experimental methods.

The aim of this article is to provide users of tool steels with a coherent set of data to help them choose the right grades. This document covers the classification, standardization and mechanical properties of tool steels, based on the NF EN ISO 4957 standard of May 2000. This set of data provides the user with indications on the chemical composition of the grades, their most common heat treatment and the evolution of hardness as a function of tempering temperature. This document also deals with equivalence with the best-known foreign standards, in particular American and Japanese standards.