High frequency straight seam welded steel pipe welding quality defects are cracks, welding, water leakage, scratches and so on.
First, cracks
Fracture is the main defect of welded pipe, its manifestation can be by the usual cracks, local periodic cracks, irregular intermittent cracks. Some of the steel pipe after welding surface without cracks, but by the flattening, straightening or hydrostatic test cracks. Severe leakage will leak. There are many causes of cracks. Elimination of cracks is one of the most difficult problems in welding adjustment operations.
Second, take the welding
Lap welding is the edge of the tube in the welding when the dislocation, although the curette can still see the traces of dislocation.
1) Molding quality is not good. Forming the edge of the tube is not usually appear on both sides of the usual lap welding, forming the edge of the wave and the drum package, the local small lap.
2) The production of thin-walled tube, the squeeze pressure properly, easily lead to drought. In the squeeze roll hole type center tube inside the installation of a small roller, can effectively overcome the thin-walled pipe lap welding.
3) Extrusion roller installation uneven, a high and one low, resulting in welding.
4) Strip edge slitting bad, curling or edge burr is too large, resulting in lap welding.
5) Forming vertical roller, horizontal roller and squeeze roll rolling center line is not a straight line, or a sickle with steel bends, resulting in unstable molding, weld reverse, resulting in lap welding.
6) When the position of the front end of the resistor is just at the center of the squeeze roll, the flaring strength value and the crushing strength value are the best. When the center line than the extrusion roller, stretching to the sizer side, the flaring strength and crush strength are significantly reduced. When less than the center line in the molding machine side, but also reduce the welding strength.
