Small-diameter seamless pipes can be called small-diameter seamless pipes. Small-diameter seamless pipes can also be divided into: seamless small-diameter steel pipes and straight seam (also called welding) small-diameter seamless pipes. Generally The outer diameter of the steel pipe is less than 89mm, and the diameter is more than 4mm; they can be collectively referred to as small-diameter seamless pipes. Small-caliber seamless pipe is a round, square, rectangular steel with a hollow section and no seams on the periphery. Seamless tubes are made of steel ingots or solid tube blanks through perforation to make capillary tubes, and then made by hot rolling, cold rolling or cold drawing. Seamless pipe has a hollow section and is widely used as a pipeline for conveying fluids. Compared with solid steel such as round steel, steel pipe has a low bending and torsional strength and is lighter. And mechanical parts, such as oil drill pipes, automobile drive shafts, bicycle frames, and steel scaffolding used in building construction.

According to different production methods, it can be divided into hot rolled tubes, cold rolled tubes, cold drawn tubes, extruded tubes, etc. Hot rolled seamless tubes are generally produced on automatic tube rolling units.

The solid tube blank is cut to the required length after inspection and removal of surface defects, centered on the end face of the perforated end of the tube blank, and then sent to a heating furnace to be heated on the piercing machine. The perforation is continuously rotated and advanced while perforating. Under the action of the roller and the head, Inside the tube blank, a cavity called a capillary is gradually formed, and then it is sent to an automatic tube rolling machine to continue rolling. Finally, the thickness is uniformized by the sizing machine, and the diameter is reduced by a sizing (reducing) machine to meet the specifications. Hot rolled seamless pipe is an advanced method. If you want to obtain seamless pipe with smaller size and better quality, you must use cold rolling or cold drawing or a combination of the two methods. Cold rolling is usually performed on a two-roll mill. Rolled in a ring-shaped pattern consisting of a circular hole slot with a variable cross-section and a fixed conical head. Cold drawing is usually performed on a single-chain or double-chain cold-drawing machine. The perforated rod in the extruded cylinder moves together with the extruded rod, so that the extruded part is extruded from the smaller die hole. This method can produce a steel pipe with a smaller diameter.