Large Diameter Straight Seam Steel Pipe Expansion Process
The expansion of the straight seam steel pipe is a pressure processing process that applies a hydraulic or mechanical force from the inner wall of the steel pipe to expand and form the steel pipe radially outwardly. The machine mode is more complex and efficient than the hydraulic method, and the most advanced large-diameter straight seam welding control pipelines in the world have been used for the expansion process. The process is:
Expanding the diameter of the machine The diverging fan-shaped block at the end of the dilating machine is expanded in the radial direction so that the tube blank can complete the plastic deformation process of the entire pipe lengthwise in a stepwise manner. Divided into 5 phases
1, the initial round stage. The fan-shaped block is opened until all the fan-shaped blocks come into contact with the inner wall of the steel pipe. At this time, the radius of each point in the pipe within the step length range is almost the same, and the steel pipe loses its initial round shape.
2, nominal diameter stage. The sector block lowers the speed of movement from the previous position until it reaches the required position. This status is the position of the inner circumference of the finished pipe required by the quality.
3, rebound compensation stage. The status of the sector block at the beginning of the stage 2 will further reduce the speed until it reaches the required status. This status is required for the process design to recover the position of the steel pipe on the front side.
4, pressure fluctuations phase. Sector-shaped pieces of steel before the resumption of the inner circle of the steel pipe for a certain period of time to persist, this is the equipment and expansion process requirements of the pressure fluctuation stage.
5, unloading regression stage. The sector block rapidly retracts from the beginning of the inner circumference of the steel pipe before rebound, until it reaches the position of initial expansion, which is the minimum expansion diameter of the sector block required by the expansion process.