1. Medium carbon steel and medium carbon alloy steel are usually used for surface hardening. After the surface is hardened, the tooth surface hardness is generally 40-55HRC. It has the characteristics of anti-fatigue pitting corrosion, strong resistance to adhesion, and good wear resistance. As the bare core will eventually harden, the gear still has enough toughness to withstand a small impact load. 2. Carburizing and quenching are often used for low-carbon steel and low-carbon general steel. After carburizing and quenching, the hardness of the tooth surface can reach 56-62hrc, while the center of the tooth still maintains high toughness. After the gear is hardened by carburizing, the gear teeth are deformed. There should be a larger break-in. 3. Nitriding is a kind of surface chemical heat treatment. No other heat treatment is required after nitriding, and the tooth surface hardness can reach 700~900hv. Nitrided gear has the characteristics of high hardness, low processing temperature, small deformation, etc., which is suitable for difficult-grinding processing of gears, and is often used in nitrided steels containing alloy elements such as chromium, copper, and lead. Changzhou sprocket manufacturers 4. Medium-carbon steel and medium-carbon alloy steel are generally quenched and tempered, and the hardness of the tooth surface after quenching and tempering is 220×280 HBS. Due to the low hardness, the gear can be trimmed after heat treatment. 5. Normalizing can eliminate internal stress, refine grains, and improve mechanical properties and cutting performance. Gears with low mechanical strength requirements can be standardized with medium carbon steel, and large-diameter gears can be standardized with cast steel.