In addition to high strength and toughness, the surface performance of high-precision die parts is very important to the working performance and service life of high-precision die parts. The improvement of these properties is very limited and uneconomical only depending on the improvement and improvement of the matrix material, and the surface treatment technology can often get twice the result with half the effort, which is the reason why the surface treatment technology has developed rapidly. Mold polishing technology is an important part of mold surface engineering and an important post-processing technology in mold manufacturing process. Because there are still some problems in polishing technology and materials in China, for example, the injection mold for lens of fool camera, CD, VCD disc and injection mold with high transparency requirements for tools still rely on import.

The mirror mold material is not only a matter of chemical composition, but also a series of advanced technologies such as vacuum degassing, argon protection ingot, vertical continuous casting and rolling, soft forging, etc. are required during smelting, which make the mirror mold steel have a series of advantages such as less internal defects, fine impurity particle size, high dispersion, fine metal grain size, good uniformity, etc., so as to meet the requirements of mold steel polished to mirror surface. 。 The surface treatment technology of mould parts is a systematic engineering to change the shape, chemical composition, structure and stress state of the surface of high-precision mould parts through surface coating, surface modification or composite treatment technology, so as to obtain the required surface performance. Nitriding process includes gas nitriding, ion nitriding and liquid nitriding. In each nitriding mode, there are several nitriding technologies, which can meet the requirements of different steel grades and different workpieces. From the way of surface treatment, it can be divided into chemical method, physical method, physical chemical method and mechanical method.

It is worth noting that the polishing of die surface is not only affected by the polishing equipment and technology, but also by the specularity of die material, which has not attracted enough attention, that is to say, the polishing itself is restricted by the die material. Although new processing technologies aiming at improving the surface properties of precision die parts are emerging, the main applications in the manufacturing of high-precision die parts are nitriding, carburizing and hardening film deposition. Because the nitriding technology can form the surface with excellent performance, and the nitriding process has good coordination with the quenching process of high-precision die parts steel. At the same time, the nitriding temperature is low, after nitriding, there is no need for intense cooling, and the deformation of high-precision die parts is very small. Therefore, the surface strengthening of high-precision die parts is the earliest and most widely used nitriding technology.