Adjustment of extrusion roller for high-frequency welded pipe welding

In the production of high-frequency welded pipes, the formation of the pipe blank and the state of the seam directly affect the quality of the weld, and the parallelism of the weld butt surfaces is particularly important. During the joint welding process of steel pipes, the parallelism of the joints is mainly ensured by adjusting the reduction of the upper roller of the extrusion roller and the gap between the two upper rollers.

1. Passage characteristics of welded squeeze rollers
The hole radius of the upper extrusion roller of the welded extrusion frame is larger than that of the other extrusion rollers. Therefore, there is a gap between the outer roller surface of the upper squeeze roller and the ideal circular cross-section of the steel pipe. This gap is often called the "heel gap."
In actual forming, the cross-section of the steel pipe cannot be ideally circular. Under normal circumstances, due to insufficient deformation at the edge of the strip, its cross-section tends to be peach-shaped. If no adjustments are made, the butt surfaces will not be parallel butts, which will seriously affect the welding quality.
If the upper squeezing roller and other squeezing rollers use the same hole radius, when the V-shaped joint is eliminated by adjusting the pressing amount of the upper squeezing roller, the outer surface of the upper squeezing roller will be squeezed hard, and it is easy to press the pipe The surface is scarred and a more severe V-shaped joint is formed.
Therefore, the setting of the "heel gap" is based on the actual characteristics of the tube blank forming and by adjusting the reduction rate of the upper pressure roller to effectively eliminate the V-shaped joining phenomenon.
2. Adjustment method of upper squeeze roller
When setting the position of the pressure roller according to the standard hole pattern, if the formed joint is found to be V-shaped, the amount of compression of the upper pressure roller can be adjusted within the "gap" range.
The limit of reducing the upper squeeze roller is that the outer surface of the upper squeeze roller produces shallow dents on the surface of the steel pipe. As a rule of thumb, even stronger pipes will often develop parallel (I-shaped) formed joints when this lower limit is reached.
Based on the above experience, the gap between the two upper squeeze rollers must be set strictly according to the design value. Changes in this gap will directly lead to changes in the "heel gap". If the gap is not set strictly according to the design value every time the roller is replaced, it will be difficult to achieve repeatability in the adjustment of the hole pattern.
For the same reason, when making asymmetrical adjustments to the upper roller to eliminate misalignment, be sure to adjust only the upper roller on the console side and always use the upper roller on the other side as a reference. If the upper rollers on both sides are adjusted arbitrarily, the gap between the upper rollers may gradually deviate from the set value.
3.Adjustment skills under special circumstances
The thicker the wall thickness of the steel pipe and the higher the strength of the material, the more difficult it is to eliminate the V-joint during the welding process. If obvious indentations have been caused on the outer roller surface of the upper roller, but the I-shaped seam still cannot be achieved, it means that the adjustment has reached the limit. Continuing to press the upper roller downward will not only cause severe indentation, but also cause a more severe V-shaped seam.
The above phenomena indicate that a larger "heel clearance" is required for larger pressure adjustments. Therefore, the gap between the two upper rollers can be expanded to achieve this purpose.