The forming of high strength steel plate needs higher punching and working force. Therefore, the hardness and toughness of cold working die steel are required to be higher. The current performance characteristics and future development of high-strength steel plate require the study of higher performance die materials to meet the processing requirements of high-strength steel plate.

Generally speaking, cold working die steel needs high hardness, because high hardness can prevent the plastic deformation or serious wear of the die. High hardness requires higher carbon content in cold work die steel than in hot work and plastic die steel.

Because carbon is the main element to obtain high hardness, but the toughness of the material will decrease. Cold working die steel needs good wear resistance, high compressive strength, and enough toughness and ductility. High wear resistance can increase the service life of the mold and reduce the downtime caused by maintenance; high compressive strength can prevent plastic deformation of the mold; enough toughness and ductility can prevent the early cracking and chipping of the material. High wear resistance requires not only high carbon content but also hard carbide. These carbides are compounds of carbon and carbide forming elements such as chromium, vanadium, molybdenum, tungsten, etc. Generally, the harder the carbide is, the more the quantity is, the larger the size is, the better the wear resistance is.

But the high hardness makes the notch effect more sensitive. Large carbides are usually the origin of fatigue cracks. Most die failures are due to fatigue cracking. Fatigue cracks usually originate in places with notch effect, where stress concentration is relatively strong. Generally, the high hardness of the material makes the fatigue crack propagation very fast, that is, the overall crack of the material is very fast.