Overall bending is the second step of high frequency welded pipe forming, and its purpose is to bend the pipe as a whole to the curvature of the closed lead-in roller. The traditional overall bending adopts flat/vertical roller alternate empty bending forming.

The high-frequency welded pipe is a welded pipe with a high welding speed and a small welding heat-affected zone. Welding can not be cleaned for steel pipes, thin-walled pipes can be welded, and metal pipes can be welded.

The basic principle of magnetic flux leakage flaw detection of seamless pipes is based on the characteristic of high magnetic permeability of ferromagnetic materials. After the ferromagnetic seamless steel pipe is magnetized, its surface and near-surface defects form a leakage magnetic field on the surface of the seamless steel pipe, and the existence of the defect can be detected by detecting the change signal of the leakage magnetic field.

Seamless steel pipes are divided into hot-rolled (extruded) seamless steel pipes and cold-drawn (rolled) seamless steel pipes due to different manufacturing processes. Cold drawn (rolled) tubes are divided into round tubes and special-shaped tubes. Perforation is the most important forming process in the production of hot-rolled tubes, and its task is to perforate a solid billet into a hollow billet (capillary).

The shot blasting machine for the inner and outer walls of the seamless steel pipe is a cleaning machine that combines the inner and outer walls of the steel pipe. The outer surface of the seamless steel pipe is cleaned by shot blasting, and the inner surface is cleaned by shot blasting to remove the scale on the surface.

Both round pipes (seamless pipes and welded pipes) and square (rectangular) cross-sections have the characteristics of biaxial symmetry, section centroid and shear center coincidence. The circular tube and square tube section have the same section moment of inertia for each axis, which has outstanding advantages as a bending and compression member.