Mold selection is a very important part of the entire mold making process. The mold selection 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. Condition requirements 1. When the wear-resistant 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. The working conditions of the toughness mold are mostly 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 the 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 will decrease, resulting in early wear or plastic deformation of the mold 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, resulting in mold failure. Hot and cold fatigue is one of the main forms of hot work die failure, and it should have high resistance to cold and heat fatigue. 6. Corrosion resistance Some molds such as plastic molds work, due to the presence of chlorine, fluorine and other elements in the plastic, after the heat, the HCI, HF and other strong corrosive gases are resolved, eroding the surface of the mold cavity, increasing its surface roughness, intensifying Wear and tear failure. Process performance Molds are generally manufactured through several processes such as forging, cutting, and heat treatment. In order to ensure the quality of the mold and reduce the production cost, the material should have good forgeability, machinability, hardenability, hardenability and grindability; it should also have small oxidation, decarburization sensitivity and quenching. Deformation cracking tendency. 1. Forgeability has low hot forging deformation resistance, good plasticity, wide forging temperature range, low tendency for forging cracking and precipitation of reticulated carbides. 2. The annealing process spheroidizing annealing has a wide temperature range, low annealing hardness, small fluctuation range, and high spheroidization rate. 3. The cutting process has a large amount of cutting, low tool loss, and low surface roughness. 4. Oxidation and decarburization sensitivity When the high temperature heating is high, the oxidation resistance is good, the decarburization speed is slow, the heating medium is not sensitive, and the pitting point tends to be small. 5. Uniform and high surface hardness after hardened quenching. 6. After hardenability quenching, a deep hardened layer can be obtained, which can be hardened with a mild quenching medium. 7. Quenching deformation cracking tendency The conventional quenching volume change is small, the shape is warped, the distortion is slight, and the abnormal deformation tendency is low. Conventional quenching cracking has low sensitivity and is not sensitive to quenching temperature and workpiece shape. 8. The grindable grinding wheel has a relatively low loss, no wear limit, and a large amount of grinding. It is not sensitive to the quality of the grinding wheel and the cooling conditions, and is not prone to wear and grinding cracks.