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生产大直径螺旋焊管采用热轧带钢或钢板作原料。热轧带钢一般都存在不同程度的镰刀弯,从而对螺旋焊管的成型、焊接和尺寸精度造成不良影响。在焊管成型过程中,带钢的镰刀弯会不断地改变接合缝隙,使焊接边缘不能很好吻合,以致产生开缝或搭接。此时,焊管直径也相应有所改变。在焊接过程中,接合缝隙大会产生过焊现象;缝隙小会产生未焊透现象,从而降低了焊接质量。焊管直径不同使其在现场的管端对接产生困难。因此,近几年来对直径1220～1420毫米的螺旋焊管,其管径公差已从±4～5毫米减
Production of large diameter spiral welded steel or hot-rolled strip as raw material. Hot-rolled strip generally have different degrees of sickle bend, which spiral welded pipe forming, welding and dimensional accuracy adversely affected. In the pipe forming process, the sickle bend strip will continue to change the joint gap, the welding edge can not be well matched, resulting in a slit or lap. At this point, the pipe diameter has also changed accordingly. In the welding process, the joint gap assembly produces over-welding phenomenon; small gap will produce incomplete penetration phenomenon, thus reducing the welding quality. Different pipe diameters make it difficult to dock pipe ends in the field. Therefore, in recent years, the diameter of 1220 ~ 1420 mm spiral welded pipe, the diameter of the tolerance from ± 4 to 5 mm less