The material of molding parts is directly related to the quality and service life of the mold, and determines the appearance and internal quality of the molded plastic products. It must be very careful. Generally, it should be selected according to the requirements and characteristics of the products and mold on the basis of the contract provisions and customer requirements.

成型零部件材料的选用原则是：根据所成型塑料的种类、制品的形状、尺寸精度、制品的外观质量及使用要求、生产批量大小等，兼顾材料的切削、抛光、蚀纹、变形、耐磨等各项性能，同时考虑经济性以及模具的制造条件和加工方法，以选用不同类型的钢材。

The selection principle of forming parts materials is: according to the type of plastic, product shape, dimensional accuracy, product appearance quality and use requirements, production batch size, etc., taking into account the cutting, polishing, erosion, deformation, wear resistance and other properties of the material, and taking into account the economy, manufacturing conditions and processing methods of the mold, in order to select different types of steel.

对于制品外观质量要求一般的模具，其成型零部件材料选择如下：

For the mold with general appearance quality requirements, the material selection of forming parts is as follows:

a)小型模具型腔和型芯均选用中档进口P20或P20+Ni类钢材。

a) Medium grade imported P20 or P20 + Ni steel is used for small mold cavity and core.

b)大中型模具，所成型塑料对钢材无特殊要求，型腔可选用中低档进口P20或P20+Ni类钢材；型芯可选用低档进口P20类钢材或进口优良碳素钢S50C、S55C等，也可选用国产塑料模具钢。

b) For large and medium-sized mold, the plastic formed has no special requirements for steel, and the cavity can be made of medium and low grade imported P20 or P20 + Ni steel; The core can be made of low-grade imported P20 steel, imported excellent carbon steel S50C, S55C, etc., or domestic plastic die steel.

c)对于蚀皮纹的型腔，当蚀梨地纹时应争取避免选用P20+Ni类的2738（738）牌号。

c) For the cavity with skin erosion, the P20 + Ni type 2738 (738) should be avoided.

对无外观质量要求的内部结构件，成型材料对钢材亦无特殊要求的模具，其成型零部件材料选择如下：

For the internal structural parts without appearance quality requirements and the molds with no special requirements for steel, the material selection of the molding parts is as follows:

a)对于大中型模具，型腔可选用低档的进口P20或P20+Ni类钢材，也可选用进口优良碳素钢S55C、S50C或国产P20或P20+Ni类塑料模具钢；型芯可选用进口或国产优良碳素钢。

a) For the large and medium-sized mold, the low-grade imported P20 or P20 + Ni steel can be selected for the cavity, and the imported excellent carbon steel S55C, S50C or domestic P20 or P20 + Ni plastic mold steel can also be selected; The core can be made of imported or domestic excellent carbon steel.

b)对于小型模具，若产量较高，结构较复杂，型腔可选用低档的进口P20或P20+Ni类钢材，也可选用国产P20或P20+Ni类塑料模具钢；型芯可选用国产塑料模具钢。

b) For the small mold, if the output is high and the structure is complex, the low-grade imported P20 or P20 + Ni steel can be selected for the cavity, and the domestic P20 or P20 + Ni plastic mold steel can also be selected; The core can be made of domestic plastic die steel.

c)对于结构较简单，产量不高的小型模具，型腔型芯均可选用国产塑料模具钢或优良碳素钢。

c) For the small mold with simple structure and low output, the cavity and core can be made of domestic plastic mold steel or excellent carbon steel.