In order to ensure that "tube pulling" and "tube stacking" do not occur in the forming section, welding section and sizing section, according to the rolling principle of
high-frequency straight seam welded pipe (ERW), it is necessary to ensure that the welded tube blank maintains proper tension in each section.
In addition to the pass speed and rolling force, the factors that affect the tension are the sizing allowance, the outer diameter of the welded pipe, the wall thickness, the deformation method, the raw material of the tube blank, the coolant, the pass shape and the surface roughness, etc. If it is large, the hole pattern is easy to wear, the strip joint is broken, and the tension is too small, and the welded pipe cannot run stably in the sizing roller, resulting in "tube stacking".
Coordination of tension between sizing section and welding section:
During the welding process, the perimeter of the welded pipe blank in the welding section is shortened after being squeezed by the extrusion roller, and transformed into internal and external burrs or thickness increments. If the converted length is not absorbed in this section, the thrust and sizing in the forming section will be reduced. Under the combined effect of section resistance, the continuous accumulation of longitudinal growth will inevitably lead to the arching of the welded pipe between the sizing roller and the squeeze roller, and the production cannot be continued. Therefore, the sizing section must maintain a certain tension to digest and absorb the length increment.
The adjustment method of the tension of the welding section can be adjusted according to the power supply method of the welded pipe unit.
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
In terms of controlling the longitudinal tension of the welding section, there is no essential difference between this type of unit and the previous one. The speed ratio is constant, and the linear speed of the forming section and the welding section is also a fixed value. You can refer to the tension control method for reference.
Whole line tension control:
The tension coordination of the whole line of the welded pipe unit is the premise and guarantee for the smooth operation of the welded pipe unit.
Appropriate standard for measuring sizing tension:
1. The welded pipe runs in a straight line in the cooling water tank without shaking and waves left and right.
2. The welding position is basically fixed in the cooling section and the sizing machine, without torsion and left-right yaw.
3. There is no wear protrusion on the edge of the pass of the sizing flat roll. If the direction of the wear protrusion is consistent with the rotation direction of the pass, it means that the sizing rolling force is too large, otherwise it is too small.
Tips: ASTM A53 ERW pipe is a typical carbon steel pipe. It is largely used to convey fluids at low / medium pressures such as oil, gas, steam, water, air and also for mechanical applications.
