METHOD FOR MANUFACTURE OF THICK-WALLED PIPES WITH SMALL INNER DIAMETER AND WIDENED PORTION AT ONE END Russian patent published in 1997 - IPC

FIELD: plastic working of metals. SUBSTANCE: method involves producing basic tubular billet; subjecting billet to hot direct pressing to produce semifinished pipe with smooth surface and central channel of variable section, with central channel having two unequal cylindrical and intermediate cavities with predetermined size ratio; producing ready pipe from semi-finished pipe by cold longitudinal rolling without mandrel. Rolling is conducted in accordance with predetermined rolling modes. Hot pressing of semi-finished pipe is conducted on movable stepped-diameter needle of predetermined size. EFFECT: increased efficiency and improved quality of rolled product. 2 cl, 3 dwg