Tension adjustment of sizing section of high frequency straight seam welded pipe

In order to ensure that the forming section, welding section and sizing section do not produce "pipe pulling" and "stacking", according to the rolling principle of high frequency straight seam welded pipe, it is necessary to ensure that the welding tube blank maintains proper tension in each section.

In addition to pass speed and rolling force, the factors that affect the tension are sizing allowance, welded pipe outer diameter, wall thickness, deformation mode, billet raw materials, coolant, pass shape and surface roughness, etc. if the tension is too large, the pass is easy to wear, the strip joint is broken, and the tension is too small, the welded pipe can not run stably in the sizing roll, resulting in "pipe stacking".

Tension coordination between sizing section and welding section

In the welding process, the circumference of the welded tube billet in the welding section becomes shorter after extrusion by the extrusion roller, and changes into internal and external burr or thickness increment. If the transformed length is not absorbed in this section, under the joint action of the forming section thrust and the sizing section resistance, the accumulated longitudinal growth will inevitably cause the welded tube to arch between the sizing and extrusion roller, and the production can not continue, Therefore, the sizing section should maintain a certain tension to digest and absorb the length increment.

According to the power supply method of welding pipe unit, the adjustment measures can be taken for the tension adjustment method of welding section.

1.Single drag + forming, sizing speed ratio of the same unit

There should be a reasonable difference between the bottom diameter of the first pass flat roller and that of the last pass flat roller; By increasing the rolling force of the sizing flat roll and decreasing the rolling force of the sizing vertical roll, the tension on the welded pipe in the welding section is increased; If the pressure of forming flat roll is reduced properly, the rolling force of forming vertical roll can be increased appropriately.

2.Single drag + forming, sizing speed ratio different units

For controlling the longitudinal tension of the welding section, there is no essential difference between this kind of unit and the previous type of unit, the speed ratio is fixed, and the linear speed of the forming section and the welding section is also a fixed value, which can be used for reference.

Tension control of the whole line

The whole line tension coordination is the premise and guarantee for the smooth operation of the welded pipe unit. The whole line adjustment is usually carried out after a complete set of roll change or half set of roll change.

The proper standard for measuring sizing tension

1.The welded pipe runs in a straight line in the cooling water tank without left and right shaking and waves.

2.The welding position is basically fixed in the cooling section and sizing machine, without torsion and left-right deflection.

3.There is no wear bulge on the pass edge of sizing flat roll. If the direction of wear bulge is consistent with the rotation direction of pass, it means that the sizing rolling force is too large, otherwise it is too small.