Plastic products have been widely used in industry and daily life. Plastic mold has been developed to the direction of precision, large-scale and multi cavity. The performance requirements of plastic mold steel are higher and higher. Some industrial developed countries have independent plastic mold steel series.

塑料模具钢的性能应根据塑料种类、制品用途、成型方法和生产批量大小而定。一般要求热处理工艺简便，热处理变形小或者不变形，预硬状态的切削加工性能好，镜面抛光性能和图案蚀刻性能优良，表面粗糙度低，使用寿命长

The properties of plastic mould steel should be determined according to the type of plastic, the use of products, the forming method and the production batch size. In general, it is required that the heat treatment process is simple, the heat treatment deformation is small or no deformation, the cutting performance of pre hardened state is good, the mirror polishing performance and pattern etching performance are excellent, the surface roughness is low, and the service life is long

① 切削加工性能 对于大型、复杂和精密的挤压和注射模具，通常预硬化到28-35HRC之间，再进行切削和磨削加工所要求的尺寸和精度后，直接投入使用，从而避免了热处理变形、氧化和脱碳的缺陷。加入易切削元素S、Co和稀土，用以改善硬钢的切削加工性能。

① Machinability for large, complex and precise extrusion and injection molds, usually pre hardened to 28-35hrc, then cut and ground to the required size and accuracy, and then directly put into use, so as to avoid the defects of heat treatment deformation, oxidation and decarbonization. Free cutting elements s, CO and re are added to improve the machinability of hard steel.

② 镜面加工性能 激光盘和塑料透镜等塑料制品的表面粗糙度要求很高，主要由模具型腔的粗糙度来保证，一般模具型腔的粗糙度要比塑料制品的高一级。模具钢的镜面加工性能与钢的纯洁度、组织、硬度和镜面加工技术有关。硬度高、显微组织细小而均匀、非金属夹杂少，均有利于提高镜面抛光性。镜面抛光性要求高的塑料模具钢常采用真空熔炼或真空除气。

② The surface roughness of plastic products such as optical disk and plastic lens is very high, which is mainly guaranteed by the roughness of mold cavity. Generally, the roughness of mold cavity is one level higher than that of plastic products. The mirror finishing performance of die steel is related to the purity, microstructure, hardness and mirror finishing technology of the steel. High hardness, fine and uniform microstructure, less non-metallic inclusions are conducive to improve the mirror polishing. Vacuum melting or degassing is often used for plastic mould steel with high requirement of mirror polishing.

③ 图案蚀刻性能 某些塑料制品表面要求呈现清晰而丰满的图案花纹，还有皮革工业中的大型皮纹压花版，都要求模具钢有良好的图案光刻性能，图案光刻性能对材质的要求与镜面抛光性能相似，钢的纯洁订要高，组织要致密，硬度要高。

③ Pattern etching performance some plastic products require clear and full patterns on the surface, as well as the large-scale leather embossing plate in the leather industry, all require mold steel to have good pattern lithography performance. The requirements of pattern lithography performance for material are similar to mirror polishing performance. The purity of steel should be high, the structure should be compact, and the hardness should be high.

④ 耐蚀性能 含氯和氟的树脂以及在ABS树脂中添加抗燃剂时，在成型过程中将释放出有腐蚀性的气体。对于这类塑料模具要选用耐蚀塑料模具钢或表面镀铬或采用镍磷非晶态表面涂层。

④ The corrosion resistance of resin containing chlorine and fluorine and the addition of flame retardant in ABS resin will release corrosive gas during the molding process. For this kind of plastic mould, corrosion-resistant plastic mould steel or chromium plating or nickel phosphorus amorphous surface coating should be selected.