Molding method for manufacturing large diameter lsaw steel pipe are UOE molding method, a row of roll forming method (CFE), CE molding. For the vast majority of the final steps of the molding process is to conduct a post-weld tube expanding full-length, in order to improve the quality of welded steel pipe shape. Expanding become large-caliber Longitudinal production to ensure the quality of the finished tube an important process.
Expanding is a use of hydraulic or mechanical means from urging the steel pipe along the pipe wall bulged radially outward pressure molding process. Mechanical than hydraulic mode, the device is simple and more efficient, the world's most advanced large-caliber Longitudinal several enlarged diameter pipeline system processes are adopted, the process is as follows: Mechanical expanding the use of the split-side portion of the enlarged diameter of the segments radially expand, so the tube along the longitudinal direction in a stepwise manner to achieve the full length of the tube segments of plastic deformation process. It is divided into five stages
1. Initial stage full circle. Segments open until all the segments are exposed to the pipe wall, this time within the range of steps at various points within the steel tube radius are almost identical, steel preliminary full circle.
2. The nominal inside diameter of the stage. Segments from the front position began to decrease velocity, until you reach the desired position, this position is within the quality requirements of the finished pipe circumferential position.
3. Springback compensation stage. Segments in position to start the second stage further low speed until you reach the desired position, this position is within the missile complex process design requirements of previous pipe circumferential position.
