METHOD FOR SHAPING TUBULAR BLANK AND SLOT WASHER FOR PERFORMING THE SAME Russian patent published in 2000 - IPC

FIELD: tube production, possibly shaping tubular blanks at making electrically welded tubes. SUBSTANCE: method for shaping tubular blank comprises steps of smoothly bending blank in stands with opened roll grooved passes and bending blank with reduction along perimeter in stands having closed roll grooved passes and slot washers. In stands with closed roll passes blank is reduced by perimeter non-uniformly along its thickness in such a way that reduction value increases from outer surface of blank towards its inner surface. Reduction value is normalized according to mathematical expression. Slot washer for performing the method is in the form of disc with tapered working surfaces. Tapered portions are inclined by the same normalized angles relative to end surfaces of washer. EFFECT: desired convergence angle of edges of tubular blank cross section before welding and therefore reduced inner burr. 2 cl, 3 dwg