Patent ID: 8316680
Filing Date: 2012-11-27
Classification: B21B

Abstract:
1. A method of making a seamless hollow body from a solid round block of steel with a diameter <95% of the solid round block diameter, by means of a two-roll cross rolling mill with a piercing mandrel held between inclined rolls and including a piercer and at least one smoothing part, while using pass-closing guides, wherein a roll spacing of the rolls in a narrowest cross section defining a high-point is adjusted in relation to the solid round block diameter, and a position of the piercing mandrel is adjusted in relation to the high-point, said method comprising the steps of: maintaining a forming limit X for the incoming solid round block anteriorly of a tip of the piercing mandrel, with the forming limit X being dependent on a deformability of a steel material of the round block, on an adjusted transport angle, and on a run-in angle of the rolls; and determining tool distances through approximation (<3%) on the basis of the equations: wherein the forming limit X is defined as (1−ratio of a roll spacing at the piercing mandrel tip position to the diameter of the round block) in %.