THEORETICAL STUDY OF SHAPE CHANGES OF THE SINK MARK ON THE BACK END OF THE MATERIAL BLANK DURING BROACHING

Abstract

In connection with the use of an uninterruptedly-casted blank in the line of a pipe-rolling plant it is appropriate to carry out blank cobbing before broaching achieving increase of the structure quality and technological properties of steel. For this goal on the TPA-80 LLC Sinarskiy Trubniy Zavod a three-high unit of screw rolling for blank cobbing was installed. In a new technological process there was a problem of defects increase due to compression marks caused by formation of a the sink mark on the back end of the material blank during cobbing and subsequent formation of semirings during broaching, their detachment to the deformation zone. The causes of sink marks formation on the pipes and rolling are investigated. The results of mathematical simulation of the process of blanks broaching on the piercing mill of screw rolling are given, recommendation for reduction of surface defects formation on the pipes during rolling on TPA-80 with cogging mill is provided.