Patent ID: 9156074
Filing Date: 2015-10-13
Classification: B21C,B21D

Abstract:
1. A method for producing a steel tube, comprising: forming a tubular body having a round cross section from a metal sheet or coil in a bending process; welding the metal sheet or coil along longitudinal edges facing one another to produce a continuous seam; processing the tubular body in a concentric straightening operation, wherein the concentric straightening is performed by at least three hydraulically adjustable straightening devices offset in the circumferential direction and pressing from an outside in the radial direction toward a tube axis, and that have straightening shells adapted in some portions to the circumferential contour of the tubular body; subjecting the tubular body to a stress-relieving treatment by combining the concentric straightening operation with the stress-relieving treatment comprising cold forming by upsetting along a circumference in at least one portion with respect to a longitudinal axis, wherein the stress-relieving treatment is performed by plastic deformation of the tubular body via hydraulic adjustment of the at least three straightening devices; and the stress-relieving treatment further comprising a step of hydraulic stress relief following the step of cold forming by upsetting, the hydraulic stress relief comprising generating an outward-oriented pressure on an inner tube surface by a pressure medium within the tube interior.