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20CrMnTi Gear Carburizing Heat Treatment

As anti-wear parts, carburized gears are widely used in mechanical transmission equipment. Carburizing heat treatment and low-temperature tempering can well guarantee the needs of its work.

The carburizing heat treatment of gears has three technical indicators: the carbon content of the carburized layer, the depth of the carburized layer and the organization. He has a direct relationship with the mechanical properties of carburized parts. 20CrMnTi is a carburized steel with good performance and high hardenability. After carburizing heat treatment, it has a hard and wear-resistant surface and a tough core, and has high low-temperature impact toughness.

When using the gas carburizing of the UNICASE sealed box multipurpose furnace independently developed and manufactured by Fengdong Co., Ltd., the furnace temperature will drop rapidly after the product enters the back chamber. A large amount of methanol should be introduced to reduce the carburizing atmosphere to prevent the product from producing carbon black. To avoid coarse crystal grains, the heating temperature is generally 900-920°C.

After reaching the set temperature, the amount of propane should be increased in the strong infiltration stage to ensure that the carburizing has a high carbon potential and has the carburizing conditions to form a carburized layer with a higher surface carbon concentration. In order to reduce the carbon content on the surface and expand the range of the transition zone, the concentration gradient of carbon atoms is gentle. According to the principle of balancing carbon absorption and diffusion of the workpiece, after a certain amount of carburized layer on the surface of the workpiece is kept for a period of time according to the requirements of the carburized layer, Into the amount of measures to reduce the surface carbon concentration. The high temperature of the workpiece will cause the increase of deformation, and the increase of the amount of retained austenite on the surface after quenching will make the surface hardness unqualified. The process of cooling with the furnace reduces the carbon content in the austenite, lowers the Ms point, and reduces the retained austenite after quenching, which can increase the surface hardness. The general quenching temperature is 840-860℃. Taking into account the inconsistency of the internal and external temperature of the workpiece itself and the temperature difference between the internal and external temperatures of the whole furnace, the temperature of the workpiece in the furnace is uniform for a period of time, and then the furnace is quenched and oil-cooled. Generally, the temperature is isothermal for 30-60 minutes.

The 20CrMnTi gear adopts strong infiltration into large flow propane to quickly establish carbon potential, and after a small flow of propane in the diffusion stage to reduce the surface carbon content of the carburizing heat treatment process, excellent mechanical properties are obtained.