The cross-rolling method is to first pierce the tube with a diagonal roll and then extend it with a rolling mill. This method has a high production speed, but has high requirements on the processability of the tube blank, and is mainly suitable for the production of carbon steel and low alloy steel tubes. The extrusion method uses a piercing machine to perforate a tube blank or a steel ingot, and then extrudes it into a steel tube by an extruder. This method is less efficient than the cross-rolling method and is suitable for producing a high-strength alloy steel tube.


Both the cross-rolling method and the extrusion method must first heat the tube blank or the ingot, and the produced steel tube is called a hot rolled tube. Steel pipes produced by hot working can sometimes be cold worked as needed. There are two methods for cold working: one is cold drawing, which is to pull the steel pipe through the extruding die to make the steel pipe become thinner and longer; the other method is cold rolling, which is invented by the Mengnesmann brothers. The hot rolling mill is applied to the method in cold working. The cold working of seamless steel tubes can improve the dimensional accuracy and processing finish of steel pipes and improve the mechanical properties of materials.