1. Raw material
The factors affecting the quality of welds are more complex, including the chemical composition of raw materials, inclusions, banded structures, sickle bends, plate edge burrs, etc. will affect the quality of welds, inclusions, banded structures will affect the impact toughness and flattening performance of welds It has a great influence. Excessive inclusions are easy to enrich in the heat-affected zone of the weld, and it is easy to form a crack source to cause cracking. When the camber and edge burrs 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 Huayang 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!
2. High frequency welding process
And its high-frequency welding process. The welding temperature, speed, extrusion amount and opening angle 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.
3. Heat treatment process
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.
