1967 Volume 53 Issue 6 Pages 599-610
Three typical passes i. e. square-oval pass, square-dia. pass and box-pass for caliber rolling were designed which had concave-, convex-and normal shapes of projected contact surface respectively. Model billetsbuiltup of alternate layers of gray and white plasticine were prepared and part-rolled between smooth plastercast rolls using CaCO3 powder as lubricant whose condition was well known to give a good simulationof hot rolling of steel and the deformation patterns were analyzed so as to reveal the deformation processof caliber rolling.
The results were as follows:
(1) The deformations of equidistant lines perpendicular to the direction of rolling on the billet surfaceare characterized by the shape of contact surface, i. e. in square-oval pass of concave-shaped contact surfacethe lines bend backward. In square-dia. pass of convex-shaped contact surface, however, bending is forwardinstead of backward. There is no bending in box-pass of normal contact surface.
(2) The elastic wedge in the material at the entry side shortens its length or eventually vanishes if itslocation is near the middle of billet for square-oval pass or near the edge for square dia. pass. This effectmeans that there is such interaction between the parts of long contact-arc and short one that the deformation of the former facilitates the deformation of the latter. In other words, the deformation of the formeris restrained by the latter.
(3) In all cases, adhesion of material to the rolls occurs over a wide area of contact surface except narrowzones near entry and exit.
(4) The neutral point for caliber rolling can be determined from normal strain distribution in the directionof rolling because at the neutral point the velocities of roll-surface and the material are equal, thusnormal strains along the arc of contact and along the center line of material must be equal. This point approximatelycoincides with the point of maximum bending of line perpendicular to the direction of rollingin the plane normal to the roll axis. The neutral lines in both caliber rollings except box-pass are slightlybent backward.
(5) The normal strain in the direction of spreading along the horizontal center line of the cross-sectionof rolled billet is relatively small and uniform in square-dia. pass. In square-oval pass, however, it isextremely large near the edge and small in the middle.