China's progress in heat treatment production technology (4)

The potential of chemical heat treatment is brought into play

In addition to carburizing, carbonitriding chemical heat treatment, especially the chemical heat treatment of steel in the ferrite state, it is characterized by small distortion of the workpiece, improve the wear resistance and friction reduction of machine parts, improve fatigue resistance and corrosion resistance. It has obvious effects on anti-seizure ability and energy saving. Since the 1960s, the Mechanical Science Research Institute of the Ministry of Machinery has successfully developed the nitrogen bath and the nitriding (soft nitriding) of the salt bath and the non-toxic raw material nitrocarburizing, and since the application in production, it has successively developed the carbon, boron and boron triads. Seepage, ammonia + endothermic atmosphere, ammonia + air, ammonia + carbon dioxide gas nitrocarburizing and nitrogen oxynitridation and low cyanide bath nitriding, polishing, oxidation QPQ technology and LT salt bath nitrocarburizing Automobiles, motorcycles, textile machinery, machine tools, tooling, fasteners, instrumentation, 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-invested enterprises and export-oriented products enterprises listed above.

Although the process cycle of gas nitriding is long, the hardness of the layer is high, the wear resistance of the parts is improved, and the distortion of the workpiece is small, which is widely used in precision parts of machine tools. Professor Pan Jiansheng of Shanghai Jiaotong University conducted a systematic study on controlling nitriding technology in the 1980s. Through the precise control of the ammonia decomposition rate (H2), the expected nitrogen content of the steel layer and the ideal microstructure can be obtained and promoted and applied in production. In the 1970s, Shandong University of Technology (now the School of Materials Engineering of Shandong University) and Jiangsu Machinery Research Institute (now the Institute of Casting and Forging Heat Treatment) developed a solid boronizing method and a granular boronizing agent that can obtain a single-phase Fe2B layer with low brittleness. commodity. The Wuhan Institute of Materials Protection also developed a borax salt bath metal infiltration technology (similar to the Japanese TD method). Both have fully exploited the potential of chemical heat treatment in improving the life of metallurgy, mining machine parts and molds.

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