The production method of seamless steel tube is roughly divided into oblique rolling (mannesmann method) and extrusion method.
1. The oblique rolling method (mannesmann method) is to first use the slant roll to perforate the pipe and then extend it with rolling mill. This method is fast in production, but it has higher machinability requirement for billet, which is mainly suitable for producing carbon steel and low alloy steel pipe.
2. The extrusion rule is to use the perforator to perforate the billet or ingot, and then extrude the steel pipe by extruding machine. This method is less efficient than the oblique rolling method and is suitable for the production of high-strength alloy steel pipe.
Both the slanting and extruding methods must first heat the billet or ingots, and the steel pipes are called hot rolled pipes. Steel tubes made by hot processing can sometimes be cold-processed as needed. There are two methods for cold processing: one is cold drawing, which is to draw the steel tube through drawing, so that the steel tube gradually becomes thin and elongated. Another method is cold rolling, which is used in cold machining for hot mills invented by the mannesmann brothers. The cold machining of seamless steel tube can improve the dimension precision and finish of the steel tube, improve the mechanical properties of the material.