In addition to high-precision mold parts requiring high enough strength and toughness at work, their surface properties are critical to the working performance and service life of high-precision mold parts. The improvement of these performances is very limited and uneconomical by relying solely on the improvement and improvement of the base material. Surface treatment technology can often get twice the result with half the effort, which is the reason why surface treatment technology has developed rapidly. Mold polishing technology is an important part of mold surface engineering and an important process of post-processing in the mold manufacturing process. Because there are still certain problems in domestic polishing technology and materials, a large part of injection molds such as point-and-shoot camera lens injection molds, CD, VCD discs and tools with high transparency requirements still rely on imports.

Mirror mold material is not only a problem of chemical composition, but more importantly, a series of advanced processes such as vacuum degassing, argon protection ingot, vertical continuous casting and rolling, and soft forging are required during smelting, so that there are fewer internal defects in the mirror mold steel. A series of advantages, such as fine particle size of impurities, high degree of dispersion, fine metal grain size, and good uniformity, can meet the requirements of mold steel polished to mirror surface. The surface treatment technology of mold parts is a systematic engineering of changing the surface morphology, chemical composition, structure and stress state of high-precision mold parts through surface coating, surface modification or composite treatment technology to obtain the required surface properties. The nitriding process includes gas nitriding, ion nitriding, liquid nitriding, etc. There are several nitriding technologies in each nitriding method, which can meet the requirements of different steel types and different workpieces. From the surface treatment method, it can be divided into: chemical method, physical method, physical chemical method and mechanical method.

It is worth noting that the mold surface polishing is not only affected by the polishing equipment and process technology, but also by the mirror finish of the mold material. This has not attracted enough attention, that is, the polishing itself is restricted by the mold material. Although new processing technologies aimed at improving the surface performance of precision mold parts are constantly emerging, the main applications in the manufacture of high-precision mold parts are nitriding, carburizing and hardened film deposition. Because the nitriding technology can form a surface with excellent performance, and the nitriding process has good coordination with the quenching process of high-precision mold parts steel, at the same time, the nitriding temperature is low, no intense cooling is required after nitriding, and the high-precision mold parts are deformed It is extremely small, so the surface strengthening of high-precision mold parts adopts nitriding technology earlier and is also the most widely used.