Gear as an important mechanical components in the transmission components, widely used in machine tools, automobiles and other industries. Commonly used steel gear made of quenched and tempered steel, hardened steel, carburized hardened steel and nitrided steel. According to the hardness to be divided, the gear tooth surface can be divided into two kinds of soft tooth surface and hardened tooth surface.

Soft tooth surface gear carrying capacity is lower, but easier to manufacture, with good running, and more for transmission size and weight without strict restrictions, and small quantities of general machinery. Hardness around HRC30.

Hardened gear gear carrying capacity is high, it is after the gear cutting, and then quenching, surface hardening or carburizing quenching to increase the hardness. However, in the heat treatment, the gear will inevitably be deformed, so after the heat treatment must be grinding, grinding or finishing, in order to eliminate the error due to deformation, improve gear accuracy. Hardness above HRC45, even up to HRC60 above.