The Essentials of Straight Seam Steel Pipe Welding

The forming methods of manufacturing large-diameter longitudinally welded pipes include UOE forming method, roll forming method (CFE), CE forming, and so on. For most of the farming methods, the latter process is to perform a full-length expansion of the welded tube blank to improve the welded steel tube shape. Diameter expansion has become an important process of the production of large-diameter longitudinally welded pipes to ensure finished pipes. Diameter expansion is a pressure processing technology that uses hydraulic or mechanical means to apply force from the inner wall of the steel pipe to expand the steel pipe radially outward. The mechanical method is simpler and more efficient than the hydraulic method. The expansion process of several large-diameters longitudinally welded pipelines in the world is adopted. The mechanical expansion uses the split sector block of the end of the expander to expand radially. , Make the tube blank step by step along the length direction to realize the plastic deformation process of the whole tube length in sections.

1. The preliminary rounding stage. The fan-shaped block is opened until all the fan-shaped blocks touch the inner wall of the steel pipe. At this time, the radius of each point in the inner tube of the steel pipe within the step length is almost the same, and the steel pipe is initially round.

2. Nominal diameter stage. The sector block starts to reduce the movement speed from the previous position until it reaches the required position, which is the required inner circumferential position of the finished pipe.

3. Rebound compensation stage. The fan-shaped block will further slow down at the position of stage 2 until it reaches the required position, which is the position of the inner circumference of the steel pipe before rebound required by the process design.