The deep carburizing of large heavy duty gears has a history of more than 10 years in foreign countries, with complete sets of production equipment, process and inspection standards, and the production quality tends to be stable. In China, tests and trial production are also actively organized. A lot of work needs to be done to develop deep carburizing of low speed and heavy duty gears.
Large carburizing furnace and quenching cooling device are the key. In foreign countries, large-scale carburizing furnace is used for deep carburizing of large-scale heavy-duty gears. Endothermic protective gas + propane gas is mostly used, and CO2 infrared analysis controller is used to control the carbon potential in the furnace. In China, it is difficult to supply gas with this method, and it is also difficult to solve in investment and management. It is more economical to adopt drip type, but the uniformity of temperature and atmosphere and the control of carbon potential in large furnace must be well solved.
Quenching and cooling is the key to ensure that the effective hardening layer depth and the hardness of the center are enough after carburizing and quenching of large gear and gear shaft, and also an important means to control gear deformation and increase residual pressure stress on the tooth surface. The fixed part is used in the carburizing and quenching of the large-scale herringbone gear shaft in Japanese rolling mill, and the cooling is carried out by periodic and intense circulation.