Investigation of the influence on the cross-wall difference of tubes of the double-feed and return cold pillar rolling process at the present conditions

Abstract

Purpose. An experimental study on modern cold rolling mills with double feed and turning on the effect of the cold rolling process on the change in the cross-wall variation in a batch of pipes and on the change in the value of the cross-wall variation at the ends of the pipes from the blank pipe to the finished pipe. The methodology is an industrial experiment on modern industrial equipment using modern devices. The study of changes in the cross-sectional variation in a batch of pipes was carried out during pipe rolling on the HPT -40-8 mill with feeding and turning the pipe in both extreme positions of the cage when rolling pipes measuring 25.4x2.11 mm. The study of the change in the cross-wall variation along the ends of the tubes from the blank tubes to the finished tube during rolling with double feed and rotation was carried out on the KPW-25 mill with feed and rotation in both extreme positions of the cage along the route of 33.7x3.2 → 16x1.5 mm steel pipes 08Х18Н10Т. The methods. The study of the change in transverse thickness from the billet to the pipe in a batch of pipes showed that the maximum value of the transverse thickness among the sample of pipes is 5.64%, the minimum is 0.85%. The average value is 3.51%, the root mean square deviation of the values of diversity is 1.174%. It is not always possible to obtain these accuracy values even at the state of the HPT, and when conducting the HPT process, where the feed is performed before the forward stroke, and the pipe is turned before the reverse stroke, it is practically impossible to obtain such indicators. The study of the change in the cross-wall difference along the ends of the pipes from the billet pipes to the finished pipe during pipe rolling on the KPW-25 mill with feed and rotation of the billet in both extreme positions of the cage showed that although the minimum values of the relative difference slightly increased, but in general the wall difference along the ends of the pipes significantly decreased. This makes it possible to reduce the cut at the ends of the pipes and, accordingly, the consumption coefficient of the metal. The originality. Additional experimental dependences were obtained on the change of the cross-wall variation from the billet pipe to the finished pipe in a batch of pipes and the change of the variation along the ends of the pipes during rolling with the execution of feed and rotation before the forward and reverse motion of the cage. Practical implementation. The conducted studies allow us to use the obtained experimental dependencies in the design of routes, deformation modes and determination of roll calibration in the manufacture of pipes with increased requirements for the accuracy of pipes in cold rolling mills, which have the ability to feed and turn the pipe before the forward and reverse movement of the cage.