METHOD OF MAKING STRAIGHT-SEAM ELECTRICALLY WELDED TUBES Russian patent published in 1996 - IPC

FIELD: welded tube production. SUBSTANCE: method comprises steps of continuously forming an initial belt to tube blank in a row of successive roll passes; bringing edges of the belt together and welding them; in a first forming roll pass upbending terminal portions of the belt along its perimeter; performing unbending along the perimeter of a portion of the blank, arranged opposite the edges along a length value, equal to a radius of a ready tube; upbending the above mentioned terminal portions of the belt in the first forming roll pass along a length of a contact zone of the belt with the roll pass, equal to the radius of the ready tube, with a radius value, consisting (1.05-1.1)R_t, and in the last roll pass bending a central portion of the blank along the same length of the contact zone with a radius, equal to (0.85-0.9)R_t; unbending the blank in a welding roll pass, whose radius value consists (1.01-1.10)R_t and spacing an axis of the welding roll pass by a distance, equal to (10-16)R_t from an axis of the last forming roll pass, R_t- the radius of the ready tube. EFFECT: enhanced quality of welded seam of thin-wall tubes of high-strength elastic material, increased welding rate. 1 cl, 5 dwg