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 tube. At this time, the radius of each point in the steel tube within the step range is almost the same, and the steel tube is initially rounded.

2. The stage of nominal inner diameter. The fan-shaped block reduces the speed of movement from the front position until it reaches the required position, which is the required inner circumferential position of the finished pipe.

3. The stage of rebound compensation. At the stage 2 position, the fan-shaped block starts to move further at a low speed until it reaches the required position, which is the inner circumferential position of the steel pipe before the springback required by the process design.

4. Stable pressure holding stage. The fan-shaped block remains stationary for a period of time before the rebound, which is the pressure-holding and stable stage required by the equipment and the diameter expansion process.

5.Unloading regression stage. The fan-shaped block rapidly retracts from the position of the inner circumference of the steel pipe before rebounding, until it reaches the initial diameter expansion position, which is the smaller shrinking diameter of the fan-shaped block required by the diameter expansion process.