In addition to carburizing and carbonitriding, chemical heat treatment, especially the chemical heat treatment of steel in the ferrite state, is characterized by less distortion of the workpiece, which improves the wear resistance and friction reduction performance of machine parts, and improves fatigue and corrosion resistance. It has obvious effects on anti-seize ability, energy saving and consumption reduction. Since the successful development of salt bath nitrocarburizing (soft nitriding) and non-toxic raw material nitrocarburizing in the 1960s in the 1960s, the Institute of Mechanical Sciences of the Ministry of Machinery has successively developed carbon, nitrogen and boron ternary systems. Infiltration, ammonia + endothermic atmosphere, ammonia + air, ammonia + carbon dioxide gas nitrocarburizing and nitrogen-oxygen co-carburizing and low-cyanide salt bath nitriding, polishing, oxidation QPQ technology and LT salt bath nitrocarburizing Automobiles, motorcycles, textile machinery, machine tools, molds, fasteners, instruments, weapons and other industries have been widely used. Because of its good effect, low cost, simple process and low toxicity, it is especially favored by foreign-funded enterprises and export-sale products enterprises in the above industries.
Although gas nitriding has a long process cycle, it is widely used in precision parts of machine tools because of the high hardness of the infiltration layer, the good effect of improving the wear resistance of parts, and the small distortion of the workpiece. Professor Pan Jiansheng of Shanghai Jiaotong University carried out systematic research on the control nitriding technology in the 1980s. Through precise control of the ammonia decomposition rate (H2), the expected nitrogen content and ideal structure of the steel layer can be obtained, which can be popularized and applied in production. In the 1970s, Shandong University of Technology (now the School of Materials Engineering, Shandong University) and Jiangsu Institute of Machinery (now the Institute of Casting and Forging Heat Treatment) developed a solid boronizing method and granular boronizing agent that can obtain a single-phase Fe2B layer with small brittleness. commodity. The Wuhan Institute of Materials Protection also developed the borax salt bath metal infiltration technology (similar to Japan’s T.D method) at the same time. Both of them give full play to the potential of chemical heat treatment in improving the life of metallurgy, mining machine parts and molds.