Manufacturing Technique of Seamless Steel Pipes

The common seamless steel pipe production process can be divided into two ways: cold drawing and hot rolled. The cold rolled seamless steel pipe production process is generally more complicated than the hot rolled one. The three-roll rolling should be done first on the tube billets. The sizing test should be done after the extrusion. If there is no response after cracking on the surface of pipes which have to be cut after cutting machine, the billet should be cut into one with the length of about one meter.
 
The main production procedures of hot rolled seamless steel pipes (△ The main testing procedures): 
Preparation and inspection of billets △→ heating of billet → perforation → rolling of pipes → reheating of steel pipes → sizing (reducing) → heat treatment △→ straightening of finished pipes→ finishing → testing △→ storage
　
The main production procedures of cold rolling (drawing) seamless steel pipes:
Preparation of billets→ pickling and lubrication → cold rolling (drawing)→ heat treatment → straightening → finishing → inspection
 
The delivery state of hot rolled seamless steel pipes is generally hot rolled state after heat treatment for delivery. The strict manual selection of hot rolled seamless steel pipes needs to be done after quality inspection by staff. After quality inspection, the surface should be coated, and then followed by many cold drawing experiments. The perforation experiment needs to be done after hot rolling treatment. If the perforation enlargement is too large, the straightening should be done. After straightening, it is transmitted to the flaw detector by the conveyor device for flaw detection test, and then it is labeled and placed in the warehouse after specification arrangement.
 
Round tube billets → heating → perforation → three-roll cross rolling→ tube stripping → sizing (or reducing)→ cooling → straightening → hydraulic test (or inspection)→ marking → storage 

The seamless steel pipe is made of ingot or solid tube billet by perforation, and then made by hot rolling, cold rolling or cold drawing. The specifications of seamless steel pipes are expressed in millimeters of outside diameters and wall thicknesses.
 
The outer diameter of the hot rolled seamless tube is generally greater than 32mm. The wall thickness is 2.5-200mm. The outer diameter of the cold rolled seamless steel pipe can be up to 6mm. The wall thickness can be up to 0.25mm. The outer diameter of the thin-walled tube can be up to 5mm. The wall thickness is less than 0.25mm. The size accuracy of the cold rolling is higher than that of the hot rolling.
 
The general seamless steel pipes are made of superior carbon steel like 10, 20, 30, 35 and 45 and other low alloy structural steels such as 16Mn and 5MnV by hot rolled ways or cold rolled ways. 10, 20 and other low carbon steel seamless pipes are mainly used for fluid delivery pipeline. 45, 40Cr and other medium carbon steel made of seamless pipes are used for the manufacture of mechanical parts, such as cars, tractors stress parts.