Thermal expansion of seamless steel pipe is the use of the original tube diameter expansion technology, expansion is a use of hydraulic or mechanical way from the inner wall of the steel tube to the radial outward expansion of the pressure forming process. Mechanical way than the hydraulic way, the equipment is simple and more efficient, in the world's most advanced several large-caliber seamless steel pipe expansion processes have been used, the process is:
Mechanical expansion of the use of expanding machine end of the fan-shaped segment radially expanded, so that the tube along the length of the stepping manner, the whole pipe length plastic deformation process, thus producing seamless hot-expanded seamless steel pipe. Which is divided into five stages:
1. Initial rounding stage. The segments open until all the segments contact the inner wall of the tube. At this point, the radius of each point in the inner tube of the tube is almost the same, and the tube is initially rounded.
Nominal diameter stage. The segment begins to decelerate from the front position until it reaches the desired position, which is the quality required inner circumference of the finished tube.
3 rebound compensation phase. The segment begins to move further down the 2-stage until it reaches the desired position, which is the inner circumference of the pre-rebound steel required by the process design.
4 pressure stability stage. Sector in the pre-complex steel tube within the circumferential position for some time remain intact, this is the device and diameter requirements of the steady-pressure stability stage.
Unloading return to the stage. The segments rapidly retract from the inner circumference of the steel tube before the rebound until they reach the initial diameter expansion, which is the minimum shrinkage of the segments required by the expansion process.
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