Pipe fitting is the general name of the parts and components that play the roles of connection, control, direction change, diversion, sealing and support in the pipeline system.Steel pipe fittings are all pressure fittings. According to different processing technology, it can be divided into four categories: butt welded pipe fittings (welded and non-welded), socket welded pipe fittings, threaded pipe fittings and flanged pipe fittings.