Hot Rolled Steel Pipe Production Process

General process flow

 

The production process of hot rolled seamless steel pipe includes several basic processes, such as preparation of billet before rolling, heating of tube billet, perforation, rolling, diameter reduction, cooling and finishing of steel pipe, etc.

 

There are three main deformation processes in the production of hot rolled seamless steel tube: perforation, rolling and diameter reduction; Their respective process objectives and requirements are:

 

 

 

1 perforation

 

Change the solid tube blank into hollow capillary; We can understand as shaping, both the rolling section as a circular ring; The device is called a puncher. The requirements of the perforation process are: first of all, it is necessary to ensure the uniform thickness of the capillary wall, small ellipticity and high precision of geometric dimensions; Secondly, the inner and outer surface of the capillary should be smooth, without scarring, folding, cracks and other defects; The third is to have the corresponding perforation speed and rolling period, in order to adapt to the production rhythm of the whole unit, so that the final rolling temperature of the wool tube can meet the requirements of the rolling machine.

 

2 tube rolling

 

The thick wall of the capillary into thin wall (close to the finished wall thickness) of the waste pipe; We can regard it as fixed wall, that is, according to the following process diameter reduction and empirical formula to determine the wall thickness value of the process waste pipe; The equipment is called a pipe mill. The requirements of pipe rolling process are as follows: first, when thick-walled capillary tube is changed into thin-walled waste tube (reducing wall extension), it is necessary to ensure that the waste tube has a higher uniformity of wall thickness; Secondly, the pipe has good internal and external surface quality.

 

3. Fixed diameter reduction (including tension reduction)

 

Big circle small circle, referred to as sizing; The corresponding equipment is the sizing machine. The requirements of sizing and reducing process are as follows: firstly, sizing can be achieved under the conditions of a certain total reducing rate and a small single-frame reducing rate; secondly, it can realize the task of producing finished tubes of various specifications by using one specification blank; thirdly, it can further improve the outer surface quality of steel tubes.

 

At the end of 1980s, there was an attempt to cancel the rolling process and only use the method of perforation plus constant reduction to produce seamless steel pipe, CPS, that is, the English abbreviation of cross rolling perforation and tension reduction), and the industrial test was carried out in The Tosa factory in South Africa, which was used to produce steel pipe with outer diameter :33.4 ~ 179.8mm, wall thickness 3.4 ~ 25mm. The minimum outer diameter of sizing is 101.6mm; I reduce the maximum outside diameter of 101.6mm. The quality of steel pipe with wall thickness greater than 10mm is acceptable, but the helix of perforated capillary can not be completely eliminated by sizing and tensioning when steel pipe with wall thickness less than 8mm is produced, which affects the appearance quality of steel pipe. In the subsequent transformation, a Mini-MPM (4 racks) had to be added between the punch machine and the sizing machine to ensure product quality.