Carbon steel pipe fittings is the most widely used pipe fitting product at present. The main products include carbon steel elbow, carbon steel three links, carbon steel four links, carbon steel reducer (big head), carbon steel head (Guan Mao) and so on. The main implementing standards include GB, US standard and Japanese standard. Among them, GB also includes the Ministry of chemical industry standards, Sinopec standard of fittings and power fittings standards.