1.Good machining performance. Steel grades that are easy to cut and can obtain
high-precision parts after processing must be selected.
2. Excellent polishing performance. The working surface of injection molded parts needs to be polished to reach the mirror surface, Ra≤0.05μm. The hardness of the steel is preferably HRC35-40. Too hard surfaces can make polishing difficult. The microstructure of the steel should be uniform and dense, with few impurities, no spots and needle points.
3. Good wear resistance and fatigue resistance. The injection mold cavity is not only scoured by the high-pressure plastic melt, but also by the alternating hot and cold temperature stress. General high carbon alloy steel can be heat treated to obtain high hardness, but poor toughness is easy to form surface cracks, so it is not used. The steel type selected should enable the injection mold to reduce the number of polishing repairs, maintain the dimensional accuracy of the cavity for a long time, and reach the planned service life of mass production.
4. Has corrosion resistance. For some types of plastics, such as polyvinyl chloride and flame retardant plastics, steel grades with corrosion resistance must be considered.
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