Machining forces act on the punches and dies (tools) used in press molds. These machining forces are very close to shocks. Let us now consider the punch and die materials and shock.

（1）Toughness

Tools are expected to maintain their shapes for a very long time so that a large production can be made. This is that "the tool does not wear out and maintains the initial shape for a long time". Hardness has an important role in the wear of the tool.
When the properties of the material are considered, "hard" gives one the image that it resists wear, and "brittle" gives one the image that the material does not get deformed when a force acts on it but it just crumbles.
Also, "soft" gives us the impression that the material can get worn out easily and that it can extend easily (ductility). This is not a desirable property in a tool.
There is one more property of being difficult to get deformed or broken when subjected to a force. While this property is somewhat difficult to understand, this is described as "being tough". This is called "toughness". According to the glossary in JIS, toughness is described as "the degree of being tenacious and difficult to be broken by shock".
The key to the shock resistance of tool steel is the toughness possessed by the material.

(2) Hardening and annealing

It is not true to say that a material becomes tough when it is made soft, and if thermal refining (hardening and tempering) is done, the material goes into a state of being hard and strong against shock compared to an untreated material. Thermal refining is the operation of carrying out tempering at a relatively high temperature (more than 400C) after hardening. Care should be taken about the difference in the temperature compared to that of ordinary annealing (around 200C), There is something that needs to be paid attention to in tempering. It is temper brittleness. This is the reduction in the strength against shock due to tempering. Temper brittleness appears at some temperatures. It is the "low temperature temper brittleness" that appears around 300C, the "primary temper brittleness" that appears around 500C, and the "secondary temper brittleness" that appears at still higher temperatures.