longitudinally welded tubes

Longitudinally welded tubes are manufactured from sheet steel drawn from a coil(hot-rolled strip usually 2.75–5 mm thick and 65–300 mm wide). The diameter is determined by the width of the sheet; the correct width is slit at the factory and then formed to create a tube. Rollers/formers shape the sheet gradually to create the tube and finally the edges are welded together in a continuous welding process to form a single longitudinal seam. Process of manufacturing longitudinally welded tubes is ERW and CBW.

However, longitudinally welded pipes such as LSAW (JCOE) are able to achieve up to 50mm thickness and the longest length possible is 18m. The welding of longitudinally tubes is by automatic MAG welder. The tube is then conveyed to the submerged arc welding (SAW) stands where both internal and external welding takes place. The as-welded tube is transferred to the finishing department where it undergoes the first inspection and mechanical or hydraulic expanding, in order to fulfil the diameter and roundness tolerances. Afterwards, the hydrostatic test and precise inspection of the weld zone and the tube edges are performed. Finally, the tube ends are subjected to some machining operations.

Hunan great steel pipe co.,ltd can supply an extensive range of longitudinally welded tube in various steel grades from stock. The advantage of longitudinally welded tube is the smooth exterior surface which is optically more appealing. Furthermore, the external welds are also ground down externally and internally in the case of many tube sizes. As a result the external weld bead and, if required, the internal bead can be made practically invisible and more or less undetectable by touch.