METHOD FOR MAKING ELONGATED WELDED TUBES Russian patent published in 2001 - IPC

FIELD: manufacture of elongated welded coupling-free tubes, possibly in oil production industry branch for repairing works and drilling wells. SUBSTANCE: method comprises steps of welding ends of coiled strip by welded seam inclined relative to tube axis by angle different from right one; welding by seam passing along S-shaped curve in such a way that lines tangential to crossing points of lengthwise edges of strip form with said edges right angles and lines tangential to crossing point with strip axis form with strip axis angles equal to 15-45 degrees and formed in vertical plane; shaping strip to tubular blank and welding its lengthwise edges. Such method increases useful life period of elongated welded tubes at repairing well by 20-25%. EFFECT: enhanced strength of welded joint in condition of sign-variable elastoplastic bending at simultaneously applied pressure. 1 tbl, 2 dwg