Plastic product molds need to have characteristics:

1. Sufficient surface hardness and wear resistance

The hardness of the plastic product mold is generally below 50-60hrc, and the heat-treated mold should have sufficient surface hardness to ensure that the mold has sufficient rigidity. Since the filling and flow of plastic in the mold have to withstand greater compressive stress and friction, the mold is required to maintain the stability of shape accuracy and dimensional accuracy, so as to ensure that the mold has sufficient service life. The wear resistance of the mold depends on the chemical composition and heat treatment hardness of the steel. Increasing the hardness of the mold is beneficial to improve its wear resistance.

2. Excellent machinability

In addition to EMD processing, most plastic molding molds also need to be cut and repaired. In order to extend the service life of the tool, improve the cutting performance, and reduce the surface roughness, the hardness of the steel used for plastic molds must be appropriate.

3. Good polishing performance

For high-quality plastic products, the roughness of the cavity surface is required to be small. For example, the surface roughness of the injection mold cavity is required to be less than ra0.1-0.25, and the optical surface is required to be less than 0.01nm. The cavity must be polished to reduce the surface roughness. Therefore, the selected steel requires less impurities, fine and uniform microstructure, no fiber directionality, and no pitting or orange peel defects during polishing.

4. Good thermal stability

The shapes of injection mold parts are complex and difficult to process after quenching. Therefore, parts with good thermal stability should be selected as far as possible. After heat treatment, due to the small linear expansion coefficient, small heat treatment deformation, small dimensional change rate caused by temperature difference, metallographic structure and mold size are stable, processing can be reduced or stopped to ensure the dimensional accuracy and surface roughness of the mold.