Seamless Steel Pipe Manufacturing Process

Seamless Steel Pipe Manufacturing Process

The cross-rolling method (Mennesmann method) first pierces the steel pipe with a skew roller and then extends it with a rolling mill. This method has fast production speed, but requires high processability of the tube blank. It is mainly suitable for the production of carbon steel and low alloy steel tubes. The extrusion method uses a piercing machine to pierce the tube blank or steel ingot, and then uses an extruder to extrude it into a steel pipe. This method is less efficient than the cross-rolling method and is suitable for producing high-strength alloy steel pipes.

Regardless of the cross rolling method or the extrusion method, the tube blank or steel ingot must be heated first, and the steel pipe produced is called a hot-rolled steel pipe. Steel pipes produced by hot processing can sometimes be cold processed as needed. There are two methods of cold working: one is the cold drawing method, which is to pull the steel pipe through the extrusion die to make the steel pipe thinner and longer; the other is the cold rolling method, invented by the Mennesmann brothers. Hot rolling mills are suitable for cold working methods. Cold processing of seamless steel pipes can improve the dimensional accuracy and processing finish of the steel pipes and improve the mechanical properties of the material.

The production process of seamless steel pipes (hot-rolled steel pipes): The seamlessness of steel pipes is mainly achieved through tension reduction. The tension reduction process is a continuous rolling process of coreless hollow base metal. Under the condition of ensuring the welding quality of the parent pipe, the steel pipe tension reduction process is to heat the entire welded pipe to more than 950 degrees Celsius, and then reduce it to various outer diameters and pipe walls through a tension reduction machine (a total of 24 times of tension reduction are required ).

The hot-rolled steel pipes produced using this process are essentially different from ordinary high-frequency welded pipes. After being heated in the heating furnace, the metallographic structure and mechanical properties of the weld are completely consistent with those of the parent body. In addition, multiple passes of tension reduction were achieved. Machine rolling and automatic control make the dimensional accuracy of the steel pipe (especially the roundness and wall thickness accuracy of the steel pipe) superior to similar seamless steel pipes.