Pipe rolling on a short mandrel with kinematic tension

Abstract

Improvement in pipe production on a longitudinal rolling mill is proposed. The tandem longitudinal pipe rolling mill in the pipe-mill aggregate (PMA)-140 at PJSC (public joint-stock company) Sinarsky Pipe Works is considered. Currently, pipe is produced both from rolled billet (diameter 120 mm) and from continuous-cast billet. To reduce costs, it would make sense to discontinue the use of rolled billet and to produce all of the pipe from continuous-cast billet in the existing PMA-140. In order to employ continuous-cast billet, more profound reduction in the tandem mill is necessary. At present, the reduction is 1.16–1.5 in longitudinal rolling mill 1 and 1.07–1.15 in longitudinal rolling mill 2. With greater reduction, longitudinal guide marks may appear on the pipe surface. A possible approach to decreasing the pipe wall thickening in the groove taper and hence reducing the rejection rate due to longitudinal guide marks is to employ kinematic tension in rolling an oval sleeve on a short mandrel. The influence of the kinematic tension on the pipe shaping in grooves during longitudinal rolling of an oval sleeve is investigated. This method is found to diminish the thickening of the sleeve wall in the groove taper in longitudinal rolling mill 1. That lowers the likelihood of longitudinal guide marks on the pipe’s internal surface. The possibility of increasing the reduction in rolling on an automatic tandem mill is confirmed.