The solution to the asymmetry of the open tube of the steel pipe

Causes and effects of asymmetrical edge bending arcs: For W deformed pass, edge deformed pass and double radius deformed pass, most of the reasons are improper use of flat rollers during forming, and insufficient reduction on the side with a large curvature radius on the tube , or the upper roll is biased to the side with the smaller radius of curvature. For the circumferential deformation pass, the problem may be that the roller axes are not parallel on a certain pass of the closed pass, resulting in insufficient deformation of the tube blank on the side with a larger roll gap, and the upper roll of the closed pass Offset, the force applied by the pass to the two edges of the tube blank is not the same, resulting in different degrees of deformation on both sides, and the feed is biased, and the tube blank always tends to the side with the larger radius of curvature.

The influence of the asymmetry of the edge bending arc: mainly manifested in hindering the parallel butt joint of the weld seam, it is easy to form high and low mouths, weld seam dislocation, lap welding, weld seam difficulty in alignment, etc., thereby reducing the strength of the weld seam, affecting the removal of external burrs and weld seam The surface quality and adjustment measures are simply correcting deviation, correcting the asymmetry of the pass, the asymmetry of the feed, and the imbalance of the pressing force.
Causes and effects of unequal height at the edge of the tube billet: First, the amount of reduction of the upper roll in the closed pass of the last pass is insufficient, there is a gap between the edge of the billet and the guide ring, and at the same time, the vertical roll before this pass deviates from the rolling center line; the second is the last pass The axis of the upper and lower flat rollers of the closed pass is not horizontal; adjustment measures: readjust the closed pass rollers and align the fine forming vertical rollers according to the process requirements.

The tube is asymmetrical to the circle, and the formed tube is flat oval or vertical oval. Their common feature is that the tube is symmetrical, but asymmetrical to the circle.
The basic reason for forming the flat ellipse of the tube blank is that the edge of the flat roller with closed holes is severely worn, and the more the pressure is, the more obvious the transverse ellipse is. It should be pointed out that the tube with a thicker wall thickness presents a slightly flattened ellipse, which is not Defects, even the goal pursued by forming, are conducive to the parallel butt joint of thick-walled pipe welds, however, for thin-walled pipes, this decision is a defect that needs to be dealt with. From the point of view of production practice, too flat butt joint Edges make deburring more difficult.

Main adjustment measures: Properly raise the upper roll of the closed pass, do not press down too tightly, properly tighten the front vertical roll of the closed pass, reduce the width of the tube blank entering the closed pass roll, and modify the pass, which is adjusted on site for the welded pipe The means are also the means of last resort.

The reason for the formation of the vertical elliptical tube is that the deformation of the tube tube in the "9 o'clock" direction and the "3 o'clock" direction is insufficient in the rough forming roller. It will form a vertical elliptical tube. In addition, the forming machine with vertical rollers is also easy to form a vertical elliptical tube. In fact, the impact of the vertical elliptical tube on the thin-walled tube forming and welding is not obvious, just because of its vertical The size is too large relative to the opening size of the extrusion roll pass, and the tube blank is easily bitten by the upper and lower edges of the extrusion roll pass when it enters the extrusion roll pass.
The method of adjustment treatment is to strengthen the rolling of the third to fifth flat rolls for rough forming, and at the same time appropriately increase the reduction of the closed-hole type rolls. For thin-walled pipes, it may not be treated as a defect, or as long as the It is enough not to "bite the pipe" until the pass of the extrusion roller is reached, or simply open the opening of the pass of the extrusion roller appropriately. For thick-walled pipes, try to process it into a round~flat oval shape. From the analysis of the cause of the tube blank and its treatment process, it can be seen that some "deficiencies" in the forming of welded pipes are relative. The same tube shape is a defect that needs to be dealt with for some tube types, and for other tube types. In terms of craftsmanship, it is the goal pursued by craftsmanship.