Plastic mold processing requirements for materials
The processing conditions of plastic molds are different from those of cold stamping die. Generally, it must be operated at 150 °C-200 °C. In addition to being subjected to a certain pressure, it must also withstand the temperature influence. According to the different conditions and processing methods of plastic molding dies, the basic functions of plastic mold steel are summarized as follows:
1. Satisfactory surface hardness and wear resistance
The hardness of the plastic mold processing die is generally below 50-60HRC, and the heat-treated mold should have a satisfactory surface hardness to ensure satisfactory rigidity of the mold. In the work, the mold is subjected to large compressive stress and friction due to the filling and activity of the plastic. The mold is insisted on the accuracy of the shape and the stability of the standard precision to ensure the satisfactory service life of the mold. The wear resistance of the mold depends on the chemical composition of the steel and the heat treatment hardness, so the hardness of the advance mold is favorable for advancing its wear resistance.
2, excellent machinability
Most plastic molding dies require a certain amount of cutting and trimming in addition to EMD processing. In order to extend the service life of the cutting tool, advance the cutting function, reduce the surface roughness, and the hardness of the steel for the plastic mold is necessary.
3, excellent polishing function
High-quality plastic products, which require a small roughness value on the surface of the cavity. For example, the surface roughness value of the injection mold cavity is less than Ra 0.1 to 0.25, and the optical surface is required to be Ra<0.01 nm. The cavity must be polished to reduce the surface roughness value. The steel material selected for this purpose has less impurities, fine tissue uniformity, no fiber orientation, and should not exhibit pitting or orange peel defects during polishing.
4, excellent thermal stability
The shape of the parts of the plastic injection mold is generally complicated, and it is difficult to process after quenching. Therefore, it should be selected with excellent thermal stability. When the mold is formed by heat treatment, the linear expansion coefficient is small, the heat treatment deformation is small, and the standard variation caused by the temperature difference is caused. The rate is small, the metallographic organization and the mold standard are stable, and the processing can be reduced or no longer processed to ensure the standard precision and surface roughness of the mold.
5. The trademark carbon steel has certain strength and wear resistance, and is mostly used for formwork materials after quenching and tempering treatment. High carbon tool steel and low alloy tool steel have high strength and wear resistance after heat treatment, and are mostly used for forming parts. However, high carbon tool steels are only suitable for the manufacture of molded parts with small standards and simple shapes due to their large heat treatment deformation.
In addition, when selecting materials, it is necessary to consider avoiding scratches and gluing. For example, if there is relative motion between the two surfaces, try to avoid selecting materials with the same structure. In special cases, one side may be plated or nitrided to make both sides have Not the same surface structure.
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