The Effect of Seamless Steel Pipe Expansion

After the cold expansion of the seamless steel pipes, the diameter of the pipe body and the pipe will increase by about one percent. The diameter, the roundness and the difference between the diameters of the steel pipes are greatly improved, and the straightness of the steel pipe is also greatly improved. The length is reduced by about 0.5%, and the wall thickness is reduced by about 0.8%. Comprehensive and effective maintenance of the overall function of the steel pipe. Improve the geometrical dimensional accuracy of the pipe and pipe end of the seamless steel pipe, so that the diameter difference between the pipe body and the pipe, the roundness and the diameter of the steel pipe can reach the scale requirement, which is convenient for on-site welding construction. The tension reduction process is a continuous rolling process in which the hollow base metal does not have a mandrel. Under the premise of ensuring the quality of the mother tube welding, the seamless pipe tension reducing process is to heat the seamless pipe to more than 950 degrees Celsius, and then roll it into various kinds through the tension reducer (the tension reducer has 24 passes). The finished pipe with outer diameter and wall thickness, the hot-rolled steel pipe produced by this process is intrinsically different from the ordinary seamless pipe. After heating by the heating furnace, the metallographic structure and mechanical properties of the weld bead and the parent body can be completely consistent. Through multi-pass tension reducer rolling and automatic control, the dimensional accuracy of steel pipes is superior to similar seamless steel pipes.

Uneven deformation of the seamless steel tube forming and welding process, reducing the residual stress of the pipe body caused by molding and welding, and improving its distribution, and improving the overall mechanical performance of the steel pipe. In the development of seamless steel pipe process, these changes should be fully considered to determine the width, length and thickness of the pipe sheet and the outer diameter of the steel pipe before the diameter expansion, so as to avoid the geometrical size of the steel pipe after the expansion is not up to the ultimate requirement. The divergence and cold expansion also have the effect of improving the straightness of the seamless steel pipe, especially for the straightening effect of the smaller diameter seamless steel pipe.

After the welding is completed, the roundness and straightness of the steel pipe usually cannot meet the relevant standards and technical requirements. The sizing and straightness are used in the pipe making factory and are completed by the mechanical cold expansion method.

The sizing and reducing diameter of steel pipe is the last heat pipe deformation process in the production of hot rolled seamless steel pipe. Its main function is to eliminate the outer diameter difference caused by the rolling process in the previous process to improve the outer tube of hot rolled product. Diameter accuracy and roundness. The sizing, reducing and tension reducing process of steel pipe is a continuous rolling process of hollow body without core rod. At present, the domestic advanced fixed (reducing) diameter machines adopt three-roller 120° halving rolls. After using this type of fixed (reduced) diameter machine, the surface quality of the pipe is good, and the finished pipe has more specifications.

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