Showing posts with label
Longitudinal submerged arc welded pipe.
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Showing posts with label
Longitudinal submerged arc welded pipe.
Show all posts
First, reasonable selection. Straight pipe joints should choose a good micro deformable material straight seam steel pipe steel, for carbide segregation serious straight seam steel casting steel should be reasonable and transfer of heat treatment, larger and unable to cast a straight seam steel pipe steel may be solution bis refined heat treatment. Reasonable choice of heating temperature control heating rate, on a straight seam steel pipe can be heated slowly, preheat and other ways to reduce heating balanced straight seam steel pipe heat deformation.
Second, the correct heat treatment process operation and reasonable heat treatment process is also a useful way to reduce the distortion of straight pipe joints. Straight seam steel pipe deformation reason is often messy, but we only need to master the rules of the deformation analysis of the onset of the reason, the choice of avoiding abnormal deformation method of straight pipe joints can be reduced, and also can be controlled.
Third, straight seam steel pipe to be pre-heat treatment to eliminate the machining process of the remaining episodes of stress. For straight seam steel pipe, in the case of the conditions allow, try to use cryogenic vacuum heat treatment and quenching after quenching. In ensuring straight seam steel hardness of the premise, try to use pre-cooling, grading cooling quenching or austempering process.
Fourth, straight seam steel pipe planning portrayed to be reasonable, not too poor thickness, shape to symmetrical, straight pipe joints on large deformation deformed to master the rules, to reserve allowance, on a large, straight seam steel pipe can be used in combination plan. For some precision messy straight seam steel pipe can be used pre-heat treatment, aging heat treatment, quenching and nitriding heat treatment to control the accuracy of straight pipe joints. When the patch straight seam steel trachoma, porosity, wear and other defects, the choice of cold welding and other small heat-affected patch repair equipment, to prevent the onset of deformation process.
Surface microcracks of lsaw steel pipe impact on product quality greatly, ranging from commuted, while in retirement, especially niobium, vanadium, titanium Longitudinal most prominent, has seriously affected the improvement of product quality and finished product rate. This not only gives the enterprise has brought huge economic losses, but also restricts the development of varieties of plate production line. Longitudinal surface microcracks mainly has edge crack, longitudinal, star cracks, its causes both improper rolling process parameter control, there are abnormal production of continuous casting process, the slab cracks genetic, residual element enrichment.
Longitudinal surface microcracks severely affect product quality. Longitudinal surface micro cracks main reason is the continuous casting mold copper coating off. This aspect will lead to copper penetration into the solidified shell austenite grain boundaries, grain boundary cracks; on the other hand will be uneven due to thermal stress cracks and crack sensitivity containing titanium steel strong performance is particularly evident . Control measures: To improve the quality of mold copper, copper to prevent dew; strengthen inspection before production of slab quality and production after Longitudinal; Longitudinal protection through good casting and other measures to improve Longitudinal steel cleanliness.
LSAW steel pipes (UOE, JCOE) manufacturing processes, welding processes are set to continuous advance. Its role is to be finalized after the tube forming, shaping and positioning within the weld seam on the back cover, in order to ensure the pipe dimensions and is conducive to tube welded pipe to improve quality and production efficiency.
Pre-welding process
After forming the tube by the next roller conveyor transported to a pre-welder's torch, rising rotating roll, rotate to adjust an open position to weld at the top of both sides of the pressure on the pressure roller and the pressure roller so that the tube seam, drop gun and adjust the tracking of the weld seam, open the protective gas and cooling water, start welding, welding condition monitoring, welded to the tube end welding arc stops (automatic delay stop gas), lift the gun and the top pressure rollers, pipe welder pre sent , pipe ends and welding defects.
Pre-welding process characteristics
Pre-welding using Ar + CO2 mixed gas shielded arc welding, continuous welding seam on the back of the tube to move at a faster speed. Since the bevel angle, tube shape, the tube along the longitudinal direction of the opening and both sides of the plate edge distortion factors of inequality, forming the seam after seam quality is not stable, larger changes. Need to change the tube seam welding, the arc of a steady state, the weld position deviated from the case and other real-time tracking and adjusted accordingly. Thus presoldered have welding speed, impact seam quality factors, changes and adjustments randomness and other characteristics.
