With the development of
ERW welded pipe technology, its application fields continue to expand. ERW welded pipe uses the skin effect and proximity effect of the current to heat the edge of the tube blank to the welding temperature for extrusion and welding. Compared with seamless pipe, it is obvious that ERW pipe has a weld seam, and its performance depends largely on the quality of the weld seam.
The factors affecting the quality of welds are more complicated, including the chemical composition of raw materials, inclusions, banded structures, sickle bends, and edge burrs, which will all affect the quality of welds.
a. Inclusions and banded structures have a great influence on the impact toughness and flattening performance of welds. Excessive inclusions are easy to accumulate in the heat-affected zone of welds and easily form crack sources to cause cracking.
b. When the sickle bend and the edge burr are serious, it will cause misalignment, arc strike, weld deviation, inclusions are difficult to discharge, etc., which will reduce the quality of the weld.
The raw materials of PMC steel pipes are directly supplied by large steel mills such as Shougang, Jinan Iron and Steel, Puyang, Ruifeng, Nangang, and Handan Iron and Steel. The raw materials enter the factory after chemical analysis, mechanical properties, surface defects and other inspections, and can only be put into storage after passing the inspection!
Factors of high-frequency welding process level. The temperature, speed, extrusion amount and opening angle during welding will all affect the quality of the weld.
If the temperature is too high, the burr does not have a raised shape, the weld seam is flat, and the temperature is too low, the top of the outer burr is not smooth, and there is no intermittent raised shape on the burr line; the faster welding speed, it is easier to ensure the quality of the weld seam; in general, The amount of extrusion should refer to the wall thickness, and it is better to control it at about 5.0mm. For thick-walled pipes such as 10mm or more, the extrusion amount can be increased by 0.5-1mm; as the diameter and thickness of the pipe change, the opening angle should also be adjusted appropriately.
The stability of high-frequency welding is also the key to the stability of weld quality. Too many impurities and burrs on the edge of the plate will cause instantaneous short-circuit ignition during high-frequency welding, and local cold welding of the weld. To prevent this defect, regular inspections should be made. Whether the installation of the high-frequency coil is reliable, whether the coolant is filtered clean, whether the welding opening angle is appropriate, whether the edge burrs of the coil are removed, and then strengthen the inspection of water pressure and ultrasonic to strictly control the quality of the steel pipe.
The heat treatment process is also one of the influencing factors. Heat treatment generally adopts online intermediate frequency weld heat treatment. The influence of the length of the air-cooled section after intermediate frequency heating on the quality of the weld is easily overlooked. Too high water entry temperature will cause a sharp decline in the impact toughness of the weld. Low, the impact toughness will also decrease, it is necessary to consider the running speed of the production line to determine the length of the air-cooling section.
In the production of
welded steel pipes, PMC comprehensively prevents all factors that may affect the quality of welded seams of steel pipes. On-line non-destructive testing equipment such as hydrostatic testing, ultrasonic testing, and X-ray testing ensure our quality. PMC always adheres to the production of high-quality steel pipes, and vigorously promotes the application of ERW steel pipes in a wider range of fields.
