There are many requirements for materials on plastic molds. Today we will understand the requirements of plastic molds.
Sufficient surface hardness and wear resistance: The general hardness of plastic molds is usually below 50-60HRC. After heat treatment, the mold should have sufficient surface hardness to ensure sufficient rigidity of the mold. The mold is subjected to large compressive stress and friction during operation due to the filling and flowing plastic, and the mold is required to maintain the accuracy of its shape and the dimensional accuracy to ensure that the mold has a sufficient service life. The wear resistance of the mold depends on the chemical composition of the steel and the heat treatment hardness, so increasing the hardness of the mold is beneficial to improve its wear resistance.
Excellent machinability: Most plastic molds require a certain degree of cutting and fitter repair in addition to EMD processing. In order to prolong the service life of the cutting tool, improve the cutting performance and reduce the surface roughness, the hardness of the plastic mold steel must be appropriate.
Good polishing performance: high quality plastic products, requiring low surface roughness. For example, the surface roughness of the injection cavity is less than the level of Ra 0.1 0.25, the optical surface requires Ra < 0.01 nm, and the cavity must be polished to reduce the surface roughness value. The steel used for this purpose requires less material impurities, finely organized microstructure, no fiber direction, and no pitting or orange peel-like defects in polishing.
Good thermal stability: The shape of the injection mold parts is often complicated. It is difficult to process after quenching. It should be used with good thermal stability. When the mold is processed and heat treated, the coefficient of linear expansion is small, the heat treatment deformation is small, and the dimensional change rate is small. The metallographic structure and the dimensional stability of the mold can reduce or no longer process the temperature difference, which can ensure the dimensional accuracy and surface roughness of the mold.