Steel pipe oblique rolling piercing process and quality defects and their prevention

The steel pipe oblique rolling piercing process is the most widely used in seamless steel pipe production. It was invented by the German Mannesmann brothers in 1883. Oblique rolling piercing machines include two-roll oblique rolling piercing machines and three-roll oblique rolling piercing machines. The rough pipe quality defects caused by the oblique rolling piercing of the tube billet mainly include the inner fold, outer fold, uneven wall thickness, and surface scratches of the rough pipe.

The inner fold of the rough pipe of the steel pipe:

The rough pipe of the steel pipe is the most likely defect in oblique rolling piercing. It is closely related to the piercing performance of the tube billet, the adjustment of the piercing process parameters of the perforation hole type machine, and the quality of the perforation head.

Inner fold Factors affecting the inner fold of the rough pipe of the steel pipe:

First, the amount (rate) of the head before the compression, the number of compressions;

Second, the hole shape;

Third, the surface quality of the head.

Outer fold of steel pipe:

The outer fold of steel pipe is mostly caused by surface defects of tube blank, which is another surface quality defect that is easily caused by tube blank during oblique rolling and perforation.

Factors affecting the outer fold of steel pipe:

A. Plasticity of tube blank and perforation deformation;

B. Surface defects of tube blank;

C. Quality of perforation tool and hole shape;

The uneven wall thickness of steel pipe: There are uneven transverse wall thicknesses and uneven longitudinal wall thicknesses. During oblique rolling and perforation, uneven transverse wall thickness is most likely to occur. The main factors affecting the uneven transverse wall thickness of the tube are the heating temperature of the tube blank, centering of the tube end, hole adjustment of the perforator, and tool shape.

Surface scratch of steel pipe:

Although the requirements for the surface quality of perforated steel pipe are not as strict as those of tube rolling mill and sizing mill, serious surface scratches of the tube will also affect the surface quality of steel pipe.

Factors that affect the rough surface scratches of steel pipes:

Mainly due to serious wear and tear of the perforating tool the roller surface of the perforator outlet, or the roller surface not rotating. To prevent the rough surface of the perforating tool from being scratched due to the surface defects of the perforating tool, the perforating tool (guide tube and material trough) should be inspected and polished.