Development of pipe rolling technology for continuous rolling mill with retained mandrel

Every year hot-rolled seamless pipes tighten requirements for accuracy of wall thickness, limit deviations in internal or external diameters, ovality and curvature. Therefore, the problem of increasing the accuracy of the geometric parameters of pipes is one of the main problems in the pipe-rolling industry. The process of rolling seamless pipes on a mandrel and without mandrel using continuous mills is widely used on modern pipe-rolling machines. On a continuous rolling mill with a retained mandrel, seamless pipes with different external diameters are rolled, the dimensions of which indicate the corresponding caliber system. The whole assortment of pipes is obtained at the extraction-calibration, reduction-stretching and calibration mills. In this case, the rolling technology on a continuous rolling mill largely determines the state of the surface and the accuracy of the geometric parameters of the finished pipes. This article presents a set of works to improve the technology of rolling seamless pipes on a continuous rolling mill with a retained mandrel. The complex of works includes: development and investigation of the influence of different calibrations of continuous roll mill rolls on pipe accuracy and surface condition, investigation of the influence of the parameters of the rolling process on the formation of the end cutting of pipes at hot redistribution, determination and adjustment of the spatial position of the technological equipment of a continuous rolling mill of the relative design axis rolling, the determination of the rational position of the mandrel of a continuous rolling mill in the process of rolling shells. In the work formulas are given for calculating the speed of moving the mandrel of a continuous rolling mill, taking into account the structural composition of the equipment. The formulas are universal and allow you to determine the length of the working part of the mandrel, as well as the minimum and maximum speed of moving the mandrel of a continuous rolling mill. It is shown that the results of the performed work should be taken into account when designing new pipe-rolling units.