Gear as an important transmission equipment in mechanical equipment, widely used in machine tools, automotive and other industries. Manufacture of gears commonly used steel with quenched and tempered steel, hardened steel, carburized steel and nitriding steel. According to the hardness to divide, gear tooth surface can be divided into soft and hard tooth surface two.

Soft tooth surface bearing capacity is low, but the manufacture is relatively easy, running good, and more for the transmission size and weight without strict restrictions, and small production of general machinery. Hardness around HRC30.

Hard tooth surface bearing capacity is high, it is fine after the gear, and then quenching, surface hardening or carburizing quenching to improve the hardness. However, in the heat treatment, the gear will inevitably produce deformation, so after the heat treatment to be grinding, grinding or finishing, in order to eliminate the deformation caused by the error, improve the accuracy of the gear. Hardness above HRC45, or even up to HRC60 or more.