The selection of the mold needs to meet three principles. The mold meets the work requirements of wear resistance, toughness, etc. The mold meets the process requirements, and the mold should meet the economic applicability.
Folding condition requirements
1, wear resistance
When the blank is plastically denatured in the mold cavity, it flows and slides along the surface of the cavity, causing severe friction between the surface of the cavity and the blank, which causes the mold to fail due to wear. Therefore, the wear resistance of the material is one of the most basic and important properties of the mold.
Hardness is a major factor affecting wear resistance. In general, the higher the hardness of the mold part, the smaller the wear amount, and the better the wear resistance. In addition, the wear resistance is also related to the type, quantity, shape, size and distribution of carbides in the material.
2. Strong toughness
Most of the working conditions of the mold are very bad, and some often suffer from a large impact load, resulting in brittle fracture. In order to prevent the mold parts from suddenly breaking during work, the mold must have high strength and toughness.
The toughness of the mold depends mainly on the carbon content, grain size and microstructure of the material.
3. Fatigue fracture performance
During the working process of the mold, under the long-term effect of the cyclic stress, fatigue fracture is often caused. The form has small energy multiple impact fatigue fracture, tensile fatigue fracture contact fatigue fracture and bending fatigue fracture.
The fatigue fracture properties of a mold depend mainly on its strength, toughness, hardness, and the amount of inclusions in the material.
4. High temperature performance
When the working temperature of the mold is higher, the hardness and strength are lowered, resulting in early wear of the mold or plastic deformation and failure. Therefore, the mold material should have high anti-tempering stability to ensure that the mold has high hardness and strength at the working temperature.
5. Resistance to cold and heat fatigue
Some molds are in a state of repeated heating and cooling during the working process, causing the surface of the cavity to be subjected to tensile and pressure-induced stresses, causing surface cracking and spalling, increasing friction, impeding plastic deformation, and reducing dimensional accuracy, thereby resulting in The mold failed. Hot and cold fatigue is one of the main forms of hot work die failure. It should have high resistance to cold and heat fatigue.
6. Corrosion resistance
Some molds, such as plastic molds, when working, due to the presence of chlorine, fluorine and other elements in the plastic, after the heat, the HCI, HF and other strong aggressive gases are resolved, eroding the surface of the mold cavity, increasing its surface roughness and aggravating wear and tear.