Roller bending of edges of steel tubal billet. Part 2. Involute profile of rolls

The bending of the steel pipe billet’s edges on the roller edge bending machine can be carried out with the different surface profiles of the upper pressing roller. In the first part of our paper, we examined the bending of the pipe billet’s edges with a two-radius profile of the upper pressing roller. With this profile, the surface of the bent edge is smooth (it has a continuous tangent line on the neutral surface of the steel sheet), but the sheet’s curvature has breaks at the points of contact of two different profiles of the upper roll. Later, this disadvantage is significantly corrected when forming the pipe billet on the expander. The advantage of the two-radius bending of edges is the simplicity of the analytical calculation of the profiles of the upper roller and lower roller of the edge bending machine and the profile of the pipe billet’s edge during and after forming. In the second part of our paper, we will consider bending the pipe billet’s edges with an involute profile of the upper pressing roller. This profile of edge bending on presses was first proposed by the German company SMS Meer. At the involute profile of the upper roller surface, the surface of the bent edge is especially smooth, since the sheet’s curvature has no breaks in the area of edge bending. The disadvantage of the involute bending of the pipe billet’s edges is the impossibility of analytical calculation and the complexity of numerical calculation of the profiles of the upper roll and lower roller of the edge bending machine. In this case, a complex numerical calculation of the neutral plane’s profile of the pipe billet’s wall after its edges bending is also required. Below we constructed the new mathematical model for calculating the residual curvature of the steel pipe billet’s edges during and after its forming on the roller bending machine with an involute surface profile of the upper roller.