Material selection for mould processing is very important. If the material is not superior, the performance of the developed workpiece will not be better. Therefore, material selection for mould processing is very important and it must meet the requirements of the six major working conditions.
1. When the abrasion-resistant blank is plastically deformed in the mould cavity, it flows and slides along the cavity surface, causing severe friction between the cavity surface and the blank, which causes the mould to fail due to wear. Therefore, the wear resistance of the material is one of the most basic and important properties of the mould. Hardness is the main factor affecting wear resistance. In general, the higher the hardness of the mould parts, the smaller the amount of wear and the better the wear resistance. In addition, abrasion resistance is also related to the type, quantity, form, size and distribution of carbides in the material.
2. The working conditions of strong and tough moulds are mostly very harsh, and some often bear large impact loads, which leads to brittle fracture. In order to prevent the mould parts from being suddenly brittle during work, the mould must have high strength and toughness. The toughness of the mould mainly depends on the carbon content, grain size and microstructure of the material.
3. Fatigue and fracture performance During the work of the mould, under the long-term effects of cyclic stress, fatigue fracture often occurs. Its forms are small energy multiple impact fatigue fracture, tensile fatigue fracture contact fatigue fracture and bending fatigue fracture. The fatigue fracture performance of a mould mainly depends on its strength, toughness, hardness, and the content of inclusions in the material.
4. High temperature performance When the working temperature of the mould is higher, the hardness and strength will be reduced, resulting in early wear of the mould or plastic deformation and failure. Therefore, the mould material should have high resistance to tempering to ensure that the mould has higher hardness and strength at the working temperature.
5.Cold and hot fatigue resistanceSome moulds are repeatedly heated and cooled during the work process, which causes the surface of the cavity to be stretched and pressure to change the stress, causing surface cracks and peeling, increasing friction, and hindering plastic deformation Reduced dimensional accuracy, resulting in mould failure. Cold and hot fatigue is one of the main forms of failure of hot work moulds, and this type of mould should have high cold and hot fatigue resistance.
6.Corrosion resistanceWhen some moulds, such as plastic moulds, are working, due to the presence of chlorine, fluorine and other elements in the plastic, they will be separated into strong aggressive gases such as HCI and HF after heating, which will erode the mould cavity surface and increase its surface roughness Exacerbated wear failure.