Mould meets working conditions
1. Wear resistance
When the blank is plastic deformed in the die cavity, it flows and slides along the surface of the die cavity, which causes severe friction between the surface of the die cavity and the blank, thus easily leading to the failure of the die due to wear. Therefore, the wear resistance of materials is one of the most basic and important properties of dies.
Hardness is the main factor affecting wear resistance. Generally speaking, the harder the die parts are, the smaller the wear amount is and the better the wear resistance is. In addition, the wear resistance is also related to the type, quantity, morphology, size and distribution of carbides in the material.
2. Strength and tenacity
Most of the working conditions of the dies are very bad, and some of them often bear large impact load, which leads to brittle fracture. In order to prevent the sudden brittle fracture of die parts, the die should have high strength and toughness. The toughness of the die mainly depends on the carbon content, grain size and structure of the material.
3. Fatigue fracture properties
During the working process of the die, fatigue fracture often occurs under the long-term action of cyclic stress. Its forms include low energy multiple impact fatigue fracture, tensile fatigue fracture, contact fatigue fracture and bending fatigue fracture.
The fatigue fracture performance of the die mainly depends on its strength, toughness, hardness and inclusion content in the material.
4. High temperature performance
When the working temperature of the die is higher, the hardness and strength of the die will decrease, leading to early wear or plastic deformation of the die and failure. Therefore, the die material should have high temper resistance stability to ensure that the die has high hardness and strength at working temperature.
5. Cold and thermal fatigue resistance
Some moulds are in the state of repeated heating and cooling in the working process, which makes the surface of the cavity subject to tension and pressure variable stress, causes surface cracking and peeling, increases friction, hinders plastic deformation, reduces dimensional accuracy, and leads to die failure. Thermal and cold fatigue is one of the main failure modes of hot working dies, and the die should have high cold and thermal fatigue resistance.
6. Corrosion resistance
When some moulds such as plastic moulds are working, due to the presence of chlorine, fluorine and other elements in the plastics, HCI, HF and other strong corrosive gases are decomposed and precipitated after heating, which erode the surface of the mould cavity, increase its surface roughness and aggravate wear failure.