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What is the cold expansion technology of straight seam steel pipes?

Views:4     Author:Site Editor     Publish Time: 2020-07-13      Origin:Site

    Straight seam steel pipe 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 and expand the steel pipe radially outward. The mechanical method is simpler and has a higher speed than the hydraulic method. Several large diameter straight seam steel pipe pipeline expansion procedures are used in the world. The process is: mechanical expansion uses the split fan shape of the end of the expansion machine The block expands in the radial direction, so that the tube blank is stepped along the length to achieve the process of plastic deformation of the entire tube length.


Summarize the deformation process principles of straight seam steel pipes:

1. Pressure holding and stabilization phase: The fan-shaped block remains stationary for a period of time before the rebound of the steel pipe. This is the pressure holding and stability phase required by the equipment and the diameter expansion process.

2. Springback compensation stage: The fan-shaped block starts at the position of stage 2 and will further reduce the speed until it reaches the required position, which is the inner circumferential position of the steel pipe before springback required by the process design.

3. 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 inner tube of the steel tube is almost the same within the step size, and the steel tube is initially rounded.

4. Unloading regression stage: The fan-shaped block is rapidly retracted from the inner circumferential position of the steel pipe before rebounding until it reaches the initial diameter expansion position, which is the smaller contraction diameter of the fan-shaped block required by the diameter expansion process.

5. Nominal inner diameter stage: The sector-shaped block starts to decrease the movement speed from the previous position until it reaches the required position, which is the required inner circumferential position of the finished pipe.

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