WELDED STRAIGHT-SEAM LARGE-DIAMETER TUBES PRODUCING METHOD Russian patent published in 2007 - IPC B21C37/08 B23K5/02 C21D9/08 

FIELD: tube production, namely manufacture of welded straight-seam large-diameter tubes, possibly production of tubes of given size subjected to expanding of welded seam till level of base metal and to thermal and mechanical working.

SUBSTANCE: method comprises steps of planing sheet along width, preparing edges of sheet for welding, shaping, welding tube blanks under flux layer by one or two lengthwise seams at reinforcing outer and inner seams; heating welded seam till predetermined temperature; hot deformation till complete flattening of welded seam and thermal and mechanical working of seam. Welded seam is expanded at widening along tube perimeter. Widening of tube perimeter with one lengthwise seam is determined at sufficient accuracy according to expression ▵ = aB/S and for tubes with two lengthwise seams according to expression ▵₁ = 2aB/S, where a - averaged summed width of outer and inner seams, mm; B - averaged summed height of reinforcement of outer and inner seams, mm; S-nominal thickness of tube walls, mm. Width of sheet for shaping tube blanks with one lengthwise seam is decreased by value ▵; width of sheet for shaping tube blanks with two lengthwise seams is decreased by value ▵₁.

EFFECT: enhanced operational reliability of pipelines, improved quality of polyethylene cohesion for tubes with corrosion protection coating of tubes without reinforced seams, lowered consumption factor of metal.

2 cl, 1 tbl