Production of high-strength alloy steel pipes
The production method of seamless steel pipe is roughly divided into the cross-rolling method (Mennesmann method) and the extrusion method. The cross-rolling method (Mennesmann method) is to first perforate the tube blank with a cross-roller, and then extend it with a rolling mill. This method has a fast production speed, but requires higher machinability of the tube blank, and is mainly suitable for the production of carbon steel and low-alloy steel tubes
The extrusion method is to perforate the tube blank or ingot with a piercing machine, and then extrude it into a steel pipe with an extruder. This method is less efficient than the skew rolling method and is suitable for the production of high-strength alloy steel pipes.
Both the skew rolling method and the extrusion method must first heat the tube blank or ingot, and the produced steel tube is called a hot-rolled tube. Steel pipes produced by hot working methods can sometimes be cold worked as needed.
There are two methods of cold working: one is the cold drawing method, which is to draw the steel pipe through a drawing die to gradually thin and elongate the steel pipe;
Another method is the cold rolling method, which is a method of applying the hot rolling mill invented by the Mennesmann Brothers to cold working. The cold working of seamless steel pipe can improve the dimensional accuracy and processing finish of the steel pipe, and improve the mechanical properties of the material.
Production process of seamless steel pipe (hot-rolled steel pipe)
The seamlessness of the steel pipe is mainly completed by tension reduction, and the tension reduction process is a continuous rolling process of the hollow base metal without a mandrel. Under the condition of ensuring the welding quality of the parent pipe, the welding pipe tension reduction process is to heat the welded pipe as a whole to more than 950 degrees Celsius, and then roll it into various outer diameters and walls by a tension reducer (a total of 24 passes of the tension reducer). For thick finished pipes, the hot-rolled steel pipes produced by this process are fundamentally different from ordinary high-frequency welded pipes. The secondary tension reducer rolling and automatic control make the dimensional accuracy of the steel pipe (especially the roundness and wall thickness accuracy of the pipe body) better than that of similar seamless pipes.