1. The gloss and accuracy of the surface of injection molded products are directly related to the wear resistance of the surface of the injection mold cavity, especially when glass fibers, inorganic fillers and certain pigments are added to certain plastics. They melt in the runner together with the plastic, and the mold cavity flows at a high speed, causing great friction on the surface of the cavity. If the material is not wear-resistant, it will wear out quickly, which will damage the quality of the plastic part.

2. Resins and additives with high corrosion resistance have a corrosive effect on the surface of the cavity. This corrosion causes the metal on the surface of the cavity to dissolve and peel off, the surface condition is deteriorated, and the quality of the plastic parts is deteriorated. Therefore, it is best to use corrosion-resistant steel, or to treat the surface of the cavity with chromium or nickel cyanide.

3. In order to shorten the production cycle and improve production efficiency, mold materials are required to be easy to process into the shape and accuracy required by the drawings.

4. The dimensional stability of injection molding is good, and the cavity temperature of the injection mold can reach above 300°C. Therefore, it is best to choose tool steel (heat-treated steel) that has been properly tempered, otherwise it will cause changes in the microstructure of the material and the size of the injection mold.

5. Injection molded parts with good polishing performance are usually required to have good gloss and surface condition, so the roughness of the cavity surface is very small, so the cavity surface must be polished and ground. Therefore, the selected steel should not contain coarse impurities and pores.

6. The effect of heat treatment is not significant. In order to improve the hardness and wear resistance, the injection mold should generally be heat treated, but this heat treatment should make the size change little, so it is best to use machinable pre-hardened steel.