Cause of wrong side of spiral steel pipe

　　In production practice, the spiral steel pipe is often degraded by the wrong side margin. Therefore, it is necessary to analyze the causes and preventive measures of the wrong side of the spiral steel pipe.

　　The sickle bending of steel strip is the most important factor that causes the misalignment of spiral steel pipe. In the forming of ASTM A252 SSAW Welded Carbon Spiral Steel Pipe, the sickle bending of steel strip will constantly change the forming angle, resulting in the change of weld clearance, thus resulting in seam opening, misalignment and even lapping.

　　When the butt weld seam of the steel strip head and tail is too high, it is easy to cause large misalignment if it is improperly treated during overforming.

　　The poor edge condition of the steel strip is another important reason for the wrong side.

　　(1) raw materials, namely, steel coil, welding wire and flux. Strict physical and chemical tests must be carried out before putting into operation.

　　(2) Single wire or double wire submerged arc welding is used for butt joint of strip head and tail, and automatic submerged arc welding is used for repair welding after coiled spiral steel pipe.

　　(3) before forming, strip is leveled, trimming, planing, surface cleaning, transportation and bending.

　　(4) The weld gap control device is used to ensure that the weld gap meets the welding requirements. The pipe diameter, staggered edge and weld gap are strictly controlled.

　　(5) external control or internal control roller forming.