Calibration for the rolls of a skew-rolling mill

摘要

The invention concerns set-up of the rolls of a skew rolling mill, in particular, an Assel mill for production of pipes out of pre-pierced hollow blanks on a mandrel by means of at least three rolls. Such rolls are separated from one another by a circumferential angle of 120 deg., incline at a spreader angle towards the rolling axis, and are additionally pivoted through a transport angle (alpha ) relative to this axis. Each roll consists of a run-in cone (2), a shoulder (3), a smoothing section (4) and a rounding cone (5). Roll set-up is characterised by combination of the following features; a) the pivot axis of each roll for forming the transport angle (alpha ) cuts the axis of the blank at a right angle, and passes through the middle of the smoothing section (4); b) the section (4) has a concave shape corresponding to the local pipe diameter; c) the length of the section (4) is chosen so that the overlap of three rolls varies from 115 to 150%; d) the transport angle (alpha ) varies from 7 to 15 deg., and preferably is 10 deg.