When the mold is made, the required characteristics of the mold steel are machinability, mold forming surface carving, and electrical discharge machining.
1. Machinability
The structure of the plastic molding die is relatively complicated,plastic injection molding service， and the amount of cutting is large. The degree of easy cutting of the mold directly affects the delivery time of the mold and the cost of mold manufacturing. Therefore, for molds that do not require particularly high specularity, mold steels with good machinability added with free-cutting elements such as sulfur are used.
2. Carving and EDM
Carving processing is used for the molding processing of automotive interior decoration parts, home appliance exterior decoration parts, office equipment and other parts that require beautiful appearance. Generally, a photolithography etching method is used to make the molding surface of the mold into a complex convex-concave shape. Due to the corrosion processing of steel, it is required that the steel should have a small segregation of components, a uniform structure, and a small amount of coarse non-metallic inclusions and carbides.
In order to obtain good electrical discharge machining, it is necessary to reduce the coarse non-metallic inclusions and carbides in the steel. Electrical discharge machining is a method of melting the surface of the steel material, and then processing the shape of the steel material. After the processing surface is melted, quenching occurs, the quenching layer becomes hard, and many macroscopic cracks will be generated after processing. These cracks become the source of cracks in the mold. Therefore, the mold must be ground before use.
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