The forming methods of straight seam steel pipes include UOE forming method, roll forming method (CFE), CE forming, etc. For most forming methods, the last process is to re-expand the full-length diameter of the welded pipe blank to improve the shape of the welded steel pipe. , Diameter expansion has become an important process in the production of longitudinal welded pipes to ensure finished pipes. The mechanical method is simpler and more efficient than the hydraulic method. Several types of straight seam welding control pipelines are used internationally.

1. The initial round stage. The sector blocks are opened until all sector blocks are in contact with the inner wall of the steel pipe. At this time, the radius of the round pipe in the steel pipe is almost the same within the step size range, and the steel pipe reaches the initial circle.

2.Nominal inner diameter level. The sector block starts from the front until it reaches a predetermined position, which is the circumferential position required for the finished tube.

3. Flexible recovery and compensation stage. The position of the sector block in the second stage will be further reduced until it reaches the required position, that is, the circumferential position of the elastic front steel pipe required by the process design.

Note: a53 grade pipe covers Seamless and Welded, Black and Hot-Dipped Galvanized nominal (average) wall pipe for coiling, bending, flanging and other special purposes and is suitable for welding. Continuous-Welded pipe is not intended for flanging.