Control of weld seam gap: Send the strip steel into the welded pipe unit, roll up the strip steel gradually with roller rolling to form a round tube billet with open gap, adjust the pressure drop of the extrusion roller, so that the weld seam gap is controlled at 1~3mm , both ends of the welding joint are flat, and the gap is too large, thereby reducing the proximity effect.

Dimensional tolerance defects, surface defects and straightness defects are common defects of sizing section welded pipes.

In the high-frequency straight seam welded pipe, the cracks appear in the form of long cracks, local periodic cracks, and irregular intermittent cracks. Some steel pipes have no cracks on the surface after welding, but after flattening, straightening or hydraulic test after the crack

Forming adjustment is the basis of welded pipe adjustment. The industry recognizes that welded pipe adjustment is an art. Among them, forming adjustment is the jewel in the art palace.

Common problems in the removal process of internal burrs include scraping, deep scraping, shallow scraping, etc., any of which will affect the quality of weld flaw detection and reduce the yield of welded pipes, especially the thickness of the weld at the weld due to deep scraping of internal burrs. If the requirements are not met, the bearing capacity here is insufficient.

The strip steel is fed into the welded pipe mill, rolled by multiple rollers, and the strip steel is gradually rolled up to form a round billet with open gap. The reduction of extrusion roller is adjusted to control the weld gap at 1 ~ 3mm, and the two ends of the weld joint are flush. If the gap is too large, the proximity effect will be reduced, the eddy current heat is insufficient, and the weld is not fused or cracked due to poor intergranular bonding.

High frequency welding was invented in the early 1950s and has been rapidly applied in industrial production. It uses 10 ~ 500KHz At present, high frequency welding is mainly used in pipe and profile production lines with high degree of mechanization or automation.

Weld reinforcement refers to the height of the part of metal on the connecting line between the two welding toes on the weld surface. Generally speaking, reinforcement refers to the part protruding from the base metal surface or the deposited metal above the connecting line at the end of fillet welding (i.e. welding toe).

Steel pipe is generally divided into seamless steel pipe and welded steel pipe according to production methods.

Welding heat affected zone (HAZ) is different from weld. The performance of weld is guaranteed by chemical composition adjustment, redistribution and proper welding process. However, the performance of HAZ can not be adjusted by chemical composition.