Production technology of seamless steel tube
It is roughly divided into oblique rolling method (Mannesman method) and extrusion method.
The cross rolling method (Mennesmann method) is to perforate the pipe with the cross roll first, and then extend it with the mill. This method can produce carbon steel and low alloy steel pipe with high speed, but it requires high machinability.
The extrusion method is to perforate the tube billet or steel ingot with a punch and then extrude it into steel tube with an extruder. This method is less efficient than the cross-rolling method and is suitable for producing high-strength alloy steel tube.
In both oblique rolling and extrusion methods, the billet or ingot must be heated first, and the steel pipe produced is called hot rolled pipe. Steel pipes produced by hot working can sometimes be reworked by cold working as needed. There are two methods of cold processing: one is cold drawing method, that is, the steel pipe is drawn through the drawing die, so that the steel pipe gradually becomes thin and elongated; The other method is cold rolling, which is the hot mill invented by the Mennesmann brothers and applied to cold processing. The cold processing of seamless steel tube can improve the dimensional accuracy and machining finish of steel tube, and improve the mechanical properties of the material.
Seamless steel tube (hot rolled steel tube) production process
The seamless steel pipe is mainly completed by tension reduction, which is a continuous rolling process of hollow base material without mandrel. On the premise of ensuring the welding quality of the master pipe, the welded pipe tension reducing process is to heat the welded pipe to more than 950 degrees Celsius, and then roll the welded pipe into a variety of outer diameter and wall thickness finished pipe by the tension reducing machine (a total of 24 passes). Adopting this process by the production of hot-rolled steel pipe with ordinary high-frequency welded pipe have substaintial distinction through heating furnace after its weld and the microstructure and mechanical properties of matrix can achieve the same in addition, through many times of tension reducing mill rolling and automatic control makes the size precision of steel tube (especially the tube roundness and wall thickness accuracy) is superior to the same kind of seamless tube. The seamless welded pipe technology has been adopted in a large number of fluid tubes produced in developed countries in the world. With the development of society, the situation that domestic hot rolled welded pipe gradually replaces seamless pipe has been formed.