Straight seam steel pipe expansion technology

1. Preliminary rounding stage: the fan-shaped blocks are opened until all the fan-shaped blocks are in contact with the inner wall of the steel pipe. At this time, the radius of each point in the inner circular pipe of the steel pipe within the step range is almost the same, and the steel pipe is initially rounded.
2. Nominal inner diameter stage: The fan-shaped block starts to reduce the movement speed from the front position until it reaches the required position, which is the required inner circumference position of the finished pipe.
3. Rebound compensation stage: The fan-shaped block starts to further reduce the speed at the position of stage 2 until it reaches the required position, which is the inner circumference position of the steel pipe before the rebound required by the process design.
4. Stable pressure holding stage: The inner circumference of the steel pipe remains stationary for some time before the sector block is bounced back. This is the stable pressure holding stage required by the equipment and diameter expansion process.
5. Unloading and regression stage: The sector block starts to retract rapidly from the inner circumference of the steel pipe before rebounding until it reaches the initial expansion position, which is the small shrinkage diameter of the sector block required by the expansion process.