The role of expansion of seamless pipe

After cold expansion, the diameter of the pipes and pipes will increase by about one percent. The diameter, roundness and diameter of the two pipes are greatly improved. The straightness of the pipe is also greatly improved. The length of the pipe has been shortened. At 0.5%, the thickness of the wall was reduced by about 0.8%. Overall and effective maintenance of the overall function of the steel pipe.  The geometric accuracy of seamless pipe and pipe ends is improved, and the difference between the diameter and roundness of the pipe and the diameter of the two pipe is up to the standard requirement, which is convenient for on-site welding.  The tension reduction process is a continuous rolling process, where the hollow base metal does not have a mandrel. On the premise of guaranteeing the welding quality of the mother tube, the seamless tube tension reduction process is to heat the seamless tube to more than 950 degrees C, and then use the tension reducer (24 times) to roll into various types of tensile reducer. The outer diameter and wall thickness of the finished product are essentially different from those of the hot rolled steel pipe and the ordinary seamless pipe produced by this technology. After heating in the reheating furnace, the metallographic structure and mechanical properties of the weld metal and the parent metal can be exactly the same.  Through multiple reducing rolling and automatic control, the size accuracy of the steel pipe is better than that of the seamless steel tubes of the same kind.


The non-uniform deformation of the seamless tube forming and welding reduces the residual stress caused by the forming and welding of the tube, improves its distribution and improves the overall mechanical properties of the steel pipe. These changes should be fully taken into consideration when developing seamless steel tubes. The width, length and thickness of the pipe sheet should be taken into account, and the outer diameter of the steel pipe before expansion should be considered, so that the geometric size of the steel tube after the diameter expansion can not reach the final requirement. For different grids, the cold expansion path also has the effect of improving the straightness of seamless pipes, especially the straight-line effect of small diameter seamless steel tubes is more obvious.