The thermal expansion seamless steel pipe
adopts the expansion technology of the original pipe. The expansion is a pressure processing process that uses hydraulic or mechanical means to force the steel pipe to expand outward along the radial direction. The mechanical method is simpler and more efficient than the hydraulic method. The world's most advanced large-diameter seamless steel pipe pipeline expansion process is adopted. The process is:
The mechanical expansion diameter is expanded in the radial direction by the segmented fan-shaped block at the end of the expanding machine, so that the tube blank is stepwisely formed in a stepwise manner to realize the process of plastic deformation of the entire pipe length, thereby producing a thermally expanded seamless steel pipe. It is divided into 5 phases:
1. Initial rounding stage: The fan-shaped block is 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 pipe of the steel pipe is almost the same in the step length, and the steel pipe is initially rounded.
2. Nominal inner diameter stage: The fan block reduces the speed of movement from the front position until it reaches the required position, which is the inner circumference position of the finished product of the quality requirement.
3. Rehabilitation compensation phase: The fan-shaped block starts to move at a lower speed in the 2-stage position until it reaches the required position, which is the inner circumferential position of the steel pipe before the rebound of the process design.
4. Pressure-stabilizing stage: The fan-shaped block remains in the inner circumferential position of the steel pipe for a period of time before the rebound, which is the pressure-stabilizing stage required by the equipment and the expansion process.
5. Unloading return phase: The fan-shaped block is rapidly retracted from the inner circumferential position of the steel pipe before the rebound, until reaching the position of the initial expansion, which is the minimum shrinkage diameter of the segment required by the expansion process.
In practical applications, in the process simplification, the steps 2 and 3 can be combined and simplified, which has no effect on the diameter of the steel pipe.