Factors affecting the welding quality of ERW pipes

With the development of ERW pipe technology, its application fields are constantly expanding. ERW steel pipes use the skin effect and proximity effect of electric current to quickly heat the edge of the pipe blank to the welding temperature for extrusion and welding. Compared with seamless pipes, it is obvious that ERW pipes have a weld seam, and their performance depends largely on the quality of the weld seam.

The factors that affect the quality of welds are relatively complex, including the chemical composition of raw materials, inclusions, banded structures, sickle bends, plate edge burrs, etc., which will affect the quality of welds. Inclusions and banded structures affect the impact toughness and flattening performance of welds. It has a great influence. Excessive inclusions are easy to accumulate in the heat-affected zone of the weld, which can easily form a crack source and cause cracking. When the sickle bend and plate edge burrs are serious, it will cause misalignment, arc ignition, weld deviation, difficulty in discharging inclusions, etc., and reduce the quality of the weld. The raw materials of HSCO steel pipes are directly supplied by large steel mills. The raw materials entering the factory undergo chemical analysis, mechanical properties, surface defects, etc., and they can only be put into storage if they pass the inspection!

High-frequency welding process is also one of the factors affecting the welding quality of ERW pipes. Welding temperature, speed, extrusion amount and opening angle will all affect the quality of the weld. The temperature is too high, the burrs have no convex shape, the weld is flat, the temperature is too low, the top of the outer burr is not rounded, and there are no intermittent convex shapes on the burr line; faster welding speed can easily ensure the quality of the weld; in general, The extrusion amount should refer to the wall thickness. It is better to control it at around 5.0mm. For thick-walled pipes such as 10mm or above, the extrusion amount can be appropriately increased by 0.5-1mm. As the pipe diameter and thickness change, the opening angle should also be adjusted appropriately. .

The stability of high-frequency welding is also the key to stable weld quality. Excessive impurities and burrs on the edge of the plate will cause instant short circuit and ignition during high-frequency welding, and local cold welding will occur in the weld. To prevent this defect, frequent inspections should be carried out. Whether the installation of the high-frequency coil is reliable, whether the coolant is filtered cleanly, whether the welding opening angle is appropriate, and whether the burrs on the edge of the plate coil are removed. Secondly, the water pressure and ultrasonic inspections are strengthened to strictly control the quality of the steel pipe.

In addition, the heat treatment process is also one of the influencing factors. Heat treatment generally uses online medium-frequency weld heat treatment. The impact of the length of the air-cooling section after medium-frequency heating on the quality of the weld is easily ignored. Excessive water inlet temperature will cause a sharp decrease in the impact toughness of the weld. If the water inlet is too low, the impact toughness will also decrease. The operating speed of the production line must be comprehensively considered to determine the length of the air cooling section.

HSCO focuses on customer needs, uses ERW high-frequency welding technology to achieve automated production, and has passed national standards, American standards and other certifications. In the production of welded pipes, all factors that may affect the quality of steel pipe welds are comprehensively prevented. Online non-destructive testing equipment such as hydraulic testing, ultrasonic testing, and X-ray testing protect our quality.

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