Adjustment of Squeeze Roller for High Frequency Welded Pipe Welding

In the production of high-frequency welded pipes, the forming and jointing state of the tube billet directly affects the quality of the weld seam, and the parallelism of the butt joint surface of the welded joint is particularly important. During the joint welding process of the steel pipe, the parallelism of the seam is ensured mainly 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 extrusion rollers
The pass radius of the upper extrusion roll of the welded extrusion frame is about 10% larger than that of other extrusion rolls. Therefore, there is a gap between the outer roll surface of the upper extrusion roll and the ideal circular section of the steel pipe, commonly known as "heel gap".
If the upper extrusion roll adopts the same pass radius as the other extrusion rolls, when the V-shaped seam is removed by adjusting the reduction of the upper extrusion roller, the outer roll surface of the upper extrusion roller will be pressed hard on the steel pipe surface, which will easily cause pipe surface scars and form a more serious V-shaped seam. Therefore, the setting of the "heel gap" is based on the actual characteristics of the tube blank. By adjusting the reduction of the upper extrusion roller, the V-shaped seam phenomenon, "heel gap" position and shape are removed.
Second, the adjustment method of the upper squeeze roller
According to the standard pass, when setting the position of the extrusion roller, if the forming seam is found to be V-shaped, the reduction of the upper extrusion roller can be adjusted within the range of the "heel gap". The adjustment method is: the reduction of the upper extrusion roller The limit is that the outer roller surface of the upper extrusion roller causes a shallow indentation on the steel pipe surface. According to experience, when this reduction limit is reached, even high-strength pipes can usually form a parallel (I-shaped) forming seam.
When applying the above experience, it is necessary to set the gap between the two upper extrusion rollers strictly according to the design value. The change of this gap will directly cause the change of the "heel gap". If the gap is not set strictly according to the design value every time the roll is changed, it will be difficult to achieve reproducibility in the adjustment of the pass pattern. For the same reason, when the asymmetrical adjustment of the upper roller is performed to remove the wrong side, only the upper roller on the side of the console is adjusted, and the upper roller on the other side is fixed as a reference.
3. Adjustment skills under special circumstances
1. Passage adjustment for thick-walled and high-strength pipes
The greater the wall thickness of the steel pipe, the higher the material strength, and the harder it is to remove the V-shaped seam that appears during welding. If the outer roll surface of the upper roll has obvious indentations but the I-shaped seam cannot be achieved, it means that the adjustment has reached the limit. Continue to press the upper roll. Not only will it cause serious indentations, but it will also form a more serious V-shaped butt seam.
The above phenomenon shows that a larger "heel gap" is needed to allow a larger amount of adjustment for pressing down. For this reason, the gap between the two upper rollers can be enlarged to achieve this purpose.
It should be noted that the ideal upper roll gap value varies with the wall thickness and strength of the steel pipe. For example, when the wall thickness is thin, it is generally necessary to set a smaller upper roll gap to improve welding stability. If the wall thickness is thicker, even if the gap between the upper rolls is appropriately increased, the welding stability will not be affected.
The standard setting value on the pass diagram is selected by the designer based on many years of practical experience. Usually, different wall thicknesses and strengths can be considered. However, if the above-mentioned adjustment range is insufficient, the problem can be solved by appropriately expanding the upper roller gap.
2. Passage adjustment of thin-walled steel pipes For thin-walled steel pipes, under normal circumstances, I-shaped butt joints can be obtained without excessive upper roll reduction. The problem that often occurs is the stability of the formed seam during welding.
The stability of the forming seam is related to many factors, but properly reducing the gap between the upper rolls will generally have the effect of improving the stability of the forming seam. Therefore, the thin-walled steel pipe does not need a large "heel gap". When the forming seam is unstable, the method of appropriately reducing the gap between the upper rolls can be used to solve the problem.