Plastic mold steel can generally be divided into six categories: age hardening plastic mold steel (including mirror mold steel), corrosion-resistant plastic mold steel, carburized plastic mold steel, pre hardened embedded mold steel (including free cutting steel), Quenched and tempered plastic mold steel and hardened plastic mold steel. Age hardening plastic die steel, carburizing plastic die steel and pre hardening plastic die steel are widely used. With the more and more extensive application of plastic products in industry and daily life, the demand of plastic mold industry for mold steel is also growing. In plastic molding and processing, the quality of the mold plays an important role in ensuring the product quality. At present, plastic molds have developed in the direction of precision, large-scale and multi cavity. The requirements for the performance of plastic mold steel are higher and higher. The performance of plastic mold steel should be determined according to the requirements of plastic type, product use, production batch, dimensional accuracy and surface quality.