Manufacturing Techniques of Longitudinal Submerged Arc Welding Pipes (LSAW)

The time of issue:2013-11-20 9:09:59       Author:

The longitudinal submerged arc welding pipe (LSAW), as a kind of welded steel pipe, has been applied in domestic heavy steel structure engineering, fluid pipeline engineering, and in the foundation pile engineering. And this article is to introduce its manufacturing techniques in details.

The biggest advantage of the longitudinal submerged arc welding pipes (LSAW) is that it can produce specifications that high-frequency longitudinal-seam steel pipes, spiral welded steel pipes and seamless steel pipes can't manufacture. At present, the manufacture techniques of the longitudinal submerged arc welding pipes(LSAW)mainly have UOE, CFE, RBE, JCOE and PFP etc. Among them, there are only UOE and JCOE belonging to the country's main forming methods. UOE is one of the most advanced molding method in the world, and it is famous for its high production efficiency and quality, but it also needs expensive equipments well as large amount of investment. JCOE, its product quality is the same as those made with UOE, but its unit price is much lower than that of the UOE unit, has low production efficiency.

And a more newly introduced manufacturing technique is to use steel coils to form longitudinal submerged arc welding pipes continuously. A domestic welded pipe manufacturer developed two production lines using this kind of technique, and it has applied for national invention patent. The main process is as follows: after uncoiling the steel coils, it needs to carry out 3 groups of flattening, edge milling with plain-barrelled roll. And make it bend gradually through 16 groups of edge bending rolls and 12 groups of rack of plain-barrelled roll to reach C molding and D molding. At the same time, to finish the welding of automatic submerged arc of the inside welding line in the way of flat welding. And then mill the outer welding line of the steel pipe to be a V, cutting into the required length. Finally, put the welding line upwards and weld up the automatic submerged arc of the outside welding line adopting flat welding method.

And the LSAW made with this kind of manufacturing technique has many advantages. First, it has good stability. Due to the steel coils being raw materials, it can undertake continuous forming and welding. So if the welding quality is stable, the performance of welding line willi be stable, too. Because this process is mainly used for manufacturing thin-walled the longitudinal submerged arc welding pipe (LSAW) with minor diameter, it can have access to full inside welding lines; the use of flat welding makes straight inside welding lines can be obtained. Second, for different steel mills, because of the difference of cost control and production level, the market price of the same products will be slightly different. But for one steel mill, under the same steel coil (steel plate) technical conditions, the steel coil is 700 yuan/t lower than the steel plate of the same grade. Therefore, the longitudinal-seam steel pipes manufactured with the use of steel coils to form continuously has great cost advantage. Because of the low price of domestic pipeline steel and its low yield, the steel mills are reluctant to put too much effort in this area, leading to continued shortage of pipeline steels in the domestic market in recent years. And unstable source of steel plate has become bottleneck which restricts production and operation of the domestic the longitudinal submerged arc welding pipes (LSAW). So, adopting the way that the longitudinal submerged arc welding pipes are manufactured to produce thin-walled the longitudinal submerged arc welding pipes with minor diameter has bright market prospects.

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