Plastics can be roughly divided into thermosetting plastics and thermoplastic plastics. Due to the different types of pressing plastics and the different requirements for the size, shape, precision and surface roughness of plastic products, there are different requirements for the wear resistance, corrosion resistance, heat resistance, pressure resistance, magnetic properties, micro deformation and mirror polishing properties of plastic mold steel.

1）通用型塑料模具钢  通用型塑料模具钢用于生产通用型塑料，如聚乙烯、聚丙烯。当生产批量较小，尺寸精度和表面粗糙度无特殊要求，而且模具截面不大时，可以采用碳素结构钢SM50、SM55钢或低碳钢10、20钢制造，前者采用调质或正火处理，后者采用渗碳加淬回火处理。低碳钢由于变形抗力低、塑性好，主要适用于采用冷挤压成型的方法压制模具型腔制造模具。

1) General purpose plastic mould steel is used to produce general-purpose plastics, such as polyethylene and polypropylene. When the production batch is small, there are no special requirements for dimensional accuracy and surface roughness, and the die section is not large, carbon structural steel SM50, sm55 or low carbon steel 10, 20 can be used. The former is quenched and tempered or normalized, and the latter is carburized and quenched and tempered. Low carbon steel due to low deformation resistance, good plasticity, mainly suitable for cold extrusion molding method to press mold cavity manufacturing mold.

（2）耐磨塑料模具钢  为了生产强化工程塑料制品（如加入纤维强化的热塑性工程塑料制品）用模具，或热固性塑料挤压成型用的模具，采用耐磨性好的模具钢。当生产量较大时选用4Cr5MoSiV1、Cr12MoV、Cr12Mo1V1等钢种制造，并经淬火、回火后使用。为了提高耐磨性，可进行表面处理。

(2) In order to produce reinforced engineering plastic products (such as thermoplastic engineering plastics products reinforced with fiber), or for extrusion molding of thermosetting plastics, die steel with good wear resistance is used. When the production volume is large, 4Cr5MoSiV1, Cr12MoV, Cr12Mo1V1 and other steel grades are selected for manufacturing, and they are used after quenching and tempering. In order to improve the wear resistance, surface treatment can be carried out.

（3）渗碳型塑料模具钢  采用冷挤压反印法制造模具型腔，可以采用合金渗碳钢。这类钢在退火状态下塑性很好，较容易挤压成型，为提高型腔的耐磨性，冷挤压后需要进行渗碳，然后进行淬火和低温回火。这种模具表面具有高的硬度和耐磨性，而心部具有很好的韧性，而且模具互换性好。

(3) Carburized plastic die steel can be made by cold extrusion reverse printing, and alloyed carburizing steel can be used. In order to improve the wear resistance of the cavity, carburizing, quenching and tempering are needed after cold extrusion. The die surface has high hardness and wear resistance, while the core has good toughness and good interchangeability.