Technology of Cold Expansion

Straight seam welded steel pipe with cold expansion diameter is for the following purposes:(1) To improve the straight seam submerged arc welded pipe body and pipe end geometric dimensional accuracy, so that the pipe body and pipe end diameter, roundness and diameter difference between the two ends of the pipe to meet the standard requirements for easy on-site welding construction.(2) To reduce the forming and uneven deformation in welding process of submerged arc welded pipe, reduce the formation and welding caused by residual stress, and improve its distribution, improve the overall mechanical properties of steel.(3) The overall performance of the steel pipe to conduct a comprehensive and effective inspection.(4) Cold expansion also improve the straightening of DSAW steel pipe, especially for the smaller diameter of the straight seam submerged arc welded pipe is more obvious role.Straight submerged arc welded pipe after cold expansion, the pipe body and pipe end diameter will increase by about one percent, diameter, roundness and diameter difference between the two ends of the steel pipe are greatly improved, the pipe straightness is also greatly improved, the length is reduced by about 0.5 percent, the wall thickness is reduced by about 0.8 percent. In the development of straight seam submerged arc welded pipe technology should take full account of these changes to determine the width of the pipe plate, length and thickness, and the diameter of the pipe before the expansion, so as not to expand the diameter of the structural steel pipe does not meet the final requirements and cause unqualified.