Today, 45# steel is a kind of high-quality carbon structural steel, which is also often called oil cylinder. It belongs to medium carbon steel. The carbon content is between 0.4% - 0.5%, the hardness is not high, and it is easy to cut. It is generally formed by hot rolling or cold rolling. According to the requirements of 45 steel parts under different working conditions, if adjusted and combined with high-frequency quenching, the fire hardness is controlled between 48 and 52, The surface hardness of parts can be improved, and carburizing treatment can increase the wear resistance of parts. The service hardness of 45 polished plate after processing is generally between hrc20 and 34. 45# steel is widely used as unimportant gears on machine tools or medium load drilling machine transmissions, but it can not be used as high-speed or high load gears