What are the plastic mold material requirements

Plastic mold material requirements

The working conditions of plastic moulds are different from those of cold punching moulds.-200°C, in addition to being subject to a certain pressure, it also In addition to a certain pressure, but also to withstand the influence of temperature. Now according to the plastic molding mold use conditions, processing methods, the plastic mold with Processing method of the different plastic mold with the basic performance requirements of steel is summarized below:

1, sufficient surface hardness and wear resistance

Plastic mold hardness is usually below 50-60 HRC, after heat treatment，The mold should have enough surface hardness to ensure that the mold has enough rigidity. Mold in the work due to the filling and flow of plastic to withstand large compressive stress and friction, the mold is required to maintain the accuracy of the shape and dimensional accuracy to ensure the mold has sufficient service life.The wear resistance of the mold depends on the chemical properties of the steel. The wear resistance of the mold depends on the chemical composition and heat treatment hardness of the steel.Therefore, improving the hardness of the mold is conducive to improving its wear resistance.

2、Excellent cutting processability

Most of the plastic molding molds, in addition to EMD processing also need to carry out certain，The cutting process and clamp repair. In order to extend the life of cutting tools life, improve cutting performance, reduce surface roughness, plastic mold with Steel hardness must be appropriate 

3、Good polishing performance

High-quality plastic products require small roughness value of the cavity surface.For example, the injection mold cavity surface roughness value required less than Ra0.1 ~ 0.25 level, the optical surface requires Ra<0.01nm, the cavity shall be polishing to reduce the surface roughness value. For this reason, the steel used must be material impurities, tissue microfine uniformity, no fiber directional, polishing Should not appear pockmark or orange peel defects.

4、Good thermal stability

Plastic injection mold parts are often complex in shape, hard to quench after processing, so should try to use a good thermal stability, when Mold molding process after heat treatment due to the coefficient of linear expansion is small, heat treatment deformation is small, the temperature difference caused by the small rate of change in size, metallographic organization and mold size stability, can be reduced or no longer processed, can ensure ，The mold size accuracy and surface roughness requirements can be guaranteed.45, 50 grades of carbon steel has a certain strength and wear resistance, by After tempering treatment, it is mostly used for mold frame material. High carbon tool steel, low alloy tool steel after heat treatment has high strength and wear resistance, mostly Used for forming parts. However, high-carbon tool steel is only suitable for the manufacture of small-sized, shaped parts because of its large heat treatment deformation. Only suitable for the manufacture of small size, simple shape of the molded parts.With the development of the plastics industry, the complexity of plastic products, precision, etc. The requirements are getting higher and higher, and higher requirements are put forward for the mold materials. For manufacturing complex, precise and corrosion-resistant plastic mold, can use pre-hardened steel (such as PMS), corrosion-resistant steel (such as PCR) and low-carbon martensitic time effect steel (such as 18Ni-250), all have good cutting, heat Processing and polishing properties and higher strength. In addition, the selection of materials must also be considered to prevent scuffing and gluing, such as If there is a relative movement of the two surfaces, try to avoid choosing the organization structure of the same material, special conditions can be plated or nitride on one side In special cases, one side can be plated or nitrided so that the two sides have different surface structures.