The drill pipe is a steel pipe with a threaded tail, which is used to connect the surface equipment of the drilling rig and the drilling and grinding equipment or the bottom hole device at the bottom of the drilling well. The purpose of the drill pipe is to transport the drilling mud to the DTH bit and together with the drill bit raise, lower or rotate the bottom hole device. Drill pipe must be able to withstand enormous internal and external pressure, twisting, bending, and vibration. In the process of oil and gas extraction and refining, the drill pipe can be used many times.

　　Plain and raw steel pipe is made into drill pipe after several processing steps. First, through the steel pipe thickening process, the outer surface of the bare pipe is bent inward, and the steel pipe wall is thickened. Next, it is threaded and plated with copper for added strength. Non-destructive quality control inspections are then performed, followed by welding of the steel pipe body joints. Then, the pipe will undergo welding heat treatment and welding final treatment to eliminate welding residual pressure. Before the finished drill pipe is painted and packaged, other tests are carried out on the finished steel pipe, including a hardness test, pressure test, and non-destructive test.

　　The usual components of the drill string are a drill bit, drill collar, drill pipe, stabilizer, special joint, and kelly. The basic functions of the drill string are: lifting the drill bit; applying drilling pressure; transmitting power; transporting drilling fluid; performing special operations: squeezing cement, dealing with downhole accidents, etc.