High precision tooling and tooling components often operate under harsh conditions. Some are usually subjected to large impact loads that result in brittle fractures. Therefore, precision molds should have high strength and toughness. This is to prevent the mold parts from breaking suddenly during the working process. And the toughness of molds and tools mainly depends on the carbon content, grain size and microstructure of the material.

High-precision injection mold parts often fatigue fracture when working. This is due to the long-term effects of cyclic stress. Forms include multiple small energy impact, tensile, contact and bending fatigue fracture. In general, this characteristic of custom molding and tooling depends on these factors. For example, its strength, toughness, hardness, and the content of inclusions in the material.

When the working temperature of precision molds and dies is high, the hardness and strength will be reduced. And it will lead to early mold wear or failure due to plastic deformation. Therefore, the mold material should have high tempering stability. It can ensure the mold has high hardness and strength at working temperature.

Some molds are in the state of repeated heating and cooling during the working process. Then, it causes the cavity surface to be pulled and stressed, leading to surface cracking and spalling. As a result, it increases the friction force. In addition, it prevents plastic deformation and reduces dimensional accuracy. Finally, it leads to mold failure. Hot and cold fatigue is one of the main forms of hot working tool failure.

In the working process of some molds, such as plastic injection molding, they produce strong corrosive gases. As the plastic contains chlorine, fluorine and other elements, it will decompose and precipitate HCI and HF. they erode the cavity surface, increase the surface roughness and intensify the wear loss effect.