1. Low pressure vacuum carburizing
The conventional gas carburizing in Guangdong machining plant is easy to produce surface oxidation (Igo), and non martensitic structure appears in the thin layer of the surface of the carburizing layer, which reduces the fatigue performance of gears. Low pressure vacuum (1333-1.33 × The carburizing can improve the quality of carburizing layer and no internal oxidation on the surface. The vacuum carburizing process controlled by computer simulation is adopted. The short treatment time and less carburizing gas consumption are used in Guangdong Machinery processing plant to ensure good carburizing effect: the depth deviation of carburizing layer is ＜ ± 0.05mm, and the surface carbon content uniformity is ＜ ± 0.05%. The replacement of acetylene for propane carburization has become the development trend of vacuum carburizing. The conventional carburizing heat treatment period is long, and the technology can realize carburizing at high temperature (950-1050 ℃), thus improving the carburizing speed.
2. High pressure gas quenching technology
After carburizing, the cooling of gears and other parts in Guangdong Machinery Factory is even than that in liquid, so the quenching distortion is small. Many gases can be used as gas quenching gases, such as argon, helium, hydrogen, nitrogen and their mixtures. It is economical to use nitrogen to quench gears. At present, 85% - 95% of the gas quenching chamber is nitrogen, and the quenching pressure is usually 2MPa. High pressure gas quenching can control the pressure and flow of (inert) gas, change the cooling characteristics of gas, and combine with the phase diagram of supercooled austenite transformation of steel to achieve good quenching cooling effect, thus reducing gear distortion and improving the strength of the center.
3. Combination of low pressure vacuum carburizing and high pressure gas quenching technology
Low pressure vacuum carburizing can not only effectively avoid surface non martensite and other defects, but also improve surface quality of gears and other parts, but also can reduce heat treatment distortion by combining with high pressure gas quenching. By increasing carburizing temperature, treatment time can be reduced, thus energy consumption and gas consumption can be reduced. Therefore, the combination of vacuum low pressure carburizing and high pressure gas quenching is an advanced carburizing quenching technology, which can be called the real environmental protection green heat treatment technology