Performance requirements of plastic molds for materials used

2020-01-03

Excellent cutting processability: Most of the plastic molds that are formed need to be cut and machined apart from EMD processing. In order to extend the service life of cutting tools, enhance cutting functions, and reduce surface roughness, the hardness of steel for plastic molds needs to be appropriate. In addition, when selecting materials, you must also consider preventing scratches and gluing. If there is relative movement between the two surfaces, try to prevent the selection of materials with the same structure. In special cases, one side can be plated or nitrided to make the two sides different Appearance structure.

Outstanding thermal stability: Plastic injection mold parts often have complex shapes and are difficult to process after quenching. Therefore, they should be selected with excellent thermal stability. When the two-color mold forming process is heat treated, the linear expansion coefficient is small and the heat treatment deformation is small. , The temperature change rate caused by the temperature difference is small, the metallographic arrangement and the mold size are stable, which can be reduced or no longer processed, and the mold scale accuracy and appearance roughness requirements can be guaranteed.

Satisfied appearance hardness and abrasion resistance: The hardness of plastic molds is usually below 50-60HRC, and the heat treated molds should have satisfactory appearance hardness to ensure that the mold has a satisfactory rigidity. Due to the large compressive stress and friction force of the mold during the filling and flow of plastic, the mold is required to adhere to the stability of shape accuracy and scale accuracy to ensure that the mold has a satisfactory service life.

The wear resistance of the mold depends on the chemical composition and heat treatment hardness of the steel, so increasing the hardness of the mold is conducive to enhancing its wear resistance. Carbon steel has a certain strength and abrasion resistance: after quenching and tempering, it is mostly used for mold base materials, and high-carbon tool steel and low-alloy tool steel have high strength and abrasion resistance after heat treatment, and are mostly used for forming parts.

However, high-carbon tool steel is only suitable for making small-sized and simple-shaped shaped parts because of its large heat treatment deformation. With the development of the plastic mold industry, the requirements for the complexity and accuracy of plastic products have become higher and higher, and higher requirements have been placed on the two-color injection mold materials. For the production of complex and corrosion-resistant plastic molds, pre-hardened steel, corrosion-resistant steel and low-carbon maraging steel can be used, all of which have good cutting, heat treatment and polishing functions and high strength.

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