How to carry out weld treatment for spiral steel pipe?

The spiral steel pipe sends the strip steel into the welded pipe mill. After rolling by multiple rollers, the strip steel is gradually rolled up to form a round tube blank with opening gap. The reduction of kneading roller is adjusted to control the weld gap within 1 ~ 3 mm, and the two ends of the weld joint are flush.

1. If the gap is too large, it will cause the reduction of nearby effect, the lack of eddy current heat, and the poor intergranular joint of weld, resulting in incomplete fusion or cracking.

2. If the gap is too small, it will increase the nearby effect, and if the welding heat is too large, it will cause the weld burn out; maybe the weld will form a deep pit after kneading and rolling, which will affect the appearance quality of the weld.

After the two edges of the tube blank are heated to the welding temperature, under the kneading of the kneading roller, the metal grains formed together infiltrate and crystallize with each other, and finally form a firm weld. If the kneading force of spiral steel pipe is too small, the number of crystals will be small, the strength of weld metal will be reduced, and cracks will occur after stress.

If the kneading force is too large, the molten metal will be squeezed out of the weld, which not only reduces the weld strength, but also causes a lot of surface and interior burr, and even the formation of welding lap joint and other defects.