What are the deformation processes of seamless steel pipes?

Posted by chase Liu on April 10th, 2023

Seamless pipe is a steel pipe that is perforated by a whole round steel and has no welds on the surface. Mainly used as petroleum geological drilling pipes, cracking pipes for petrochemical industry, boiler pipes, bearing pipes, octg pipes, high-precision structural steel pipes for automobiles, tractors, and aviation, etc. Compared with solid steel such as round steel, it is lighter in weight when the bending and torsional strength is the same, and it is an economical section steel.

The production process of seamless steel pipe includes

Billet pre-rolling preparation→pipe heating→piercing→rolling→diameter reduction→pipe cooling→pipe cutting→segmentation→straightening→flaw detection→manual inspection→label printing→bundling and packaging.

There are generally three main deformation processes in the production of seamless steel pipes today: piercing, rolling and diameter reduction, and their respective process objectives and requirements are as follows:

1. Perforation

Piercing is to punch a solid tube blank into a hollow capillary, and its equipment is called a piercing machine. The requirements for the perforation process are:

1) It is necessary to ensure uniform wall thickness of the capillary tube, small ellipticity and high geometric precision;

2) The inner and outer surfaces of the capillary are relatively smooth, without scars, folds, cracks and other defects;

3) There must be a corresponding piercing speed and rolling cycle to adapt to the production rhythm of the entire unit, so that the final rolling temperature of the capillary can meet the requirements of the rolling mill.

2. Tube rolling

Rolled pipe is to press the perforated thick-walled capillary pipe into thin-walled steel pipe to achieve the required thermal size and uniformity of the finished pipe. That is, the wall thickness of the steel pipe is determined according to the diameter reduction amount of the subsequent process and the empirical formula to process the wall thickness. This equipment is called a pipe rolling mill. The requirements for the rolling process are:

1) When changing the thick-walled capillary into a thin-walled steel pipe (reduced wall extension), it is first necessary to ensure that the steel pipe has a high wall thickness uniformity;

2) The steel pipe has good internal and external surface quality. The selection of the pipe rolling mill and its reasonable matching with the deformation of the piercing process is the key to determine the product quality, output and technical and economic indicators of the unit.

3. Fixed diameter reduction (including tension reduction)

The main function of fixed diameter reduction is to eliminate the difference in the outer diameter of the steel pipe caused by the rolling process of the previous process, so as to improve the outer diameter accuracy and roundness of the hot-rolled finished pipe. Diameter reduction is to reduce the large pipe diameter to the required seamless pipe size and accuracy.