Workmanship of spiral submerged arc welding pipe
Hot-rolled steel spiral welded pipe is generally based on volume for the tube, the spiral shape, the use of high frequency resistance welding or submerged arc welding molding method. The process can narrow the billet production of large diameter pipe, you can also use the same width of the billet production of different pipe diameters. Spiral welded pipe in the oil and gas transportation is being challenged in the reason is because of its technology can not overcome the inherent shortcomings. Main features: Longitudinal seam weld length longer than the 30% to 100%. Mainly in the pipe weld defects, weld length means that the reliability is poor, and forming and welding the same time, significantly higher risk of weld defects, weld quality assurance is not easy. Spiral pipe welding on the surface, poor weld shape, internal and external weld seam of the saddle shape of the back are difficult to overcome, is difficult to avoid stress concentration. Spiral welded pipe weld heat-affected zone is big and high hardness, toughness and stress corrosion resistance decreased.
LSAW pipe technology become mainstream
Large diameter LSAW pipe (LSAW) steel as raw material is generally through different molding process, using double-sided submerged arc welding and after welding processes of the formation of expanded diameter pipe. Basically, LSAW pipe technology to overcome the lack of spiral welded pipe technology. LSAW pipe production process regardless of what kind of production methods, the preparatory process for the steel, such as steel ultrasonic inspection, trimming, edge of the tube after the molding process and spot welding, inside and outside the buried arc welding, ultrasonic testing, expansion diameter, pressure tubes and other processes are basically similar, the key is different molding process. Thus, according to molding process, LSAW and can be divided into specific roll forming process (RBE), JCOE molding, C molding process, a continuous molding process and reverse the UOE forming process five, which JCOE and C forming method is basically the same. Row of roll forming process (CFE) can also be used LSAW steel pipe forming. But it is mainly used for resistance welding of steel pipe forming.
