METHOD FOR MANUFACTURE OF PIPES FROM NONFERROUS METALS AND ALLOYS Russian patent published in 1995 - IPC

FIELD: plastic metal working. SUBSTANCE: method involves hot spiral broaching and expansion of mandrels in three-roll passes formed by multiconical rolls whose inclination angle of conical generatrix to rolling axis at pass entry is 7-25 deg larger than it is before the mandrel nose with reduction at the entry portion equal to 0.3-0.8 of reduction before the mandrel nose. The method also involves expansion of broached liner in rolls having two reducing portions (ridges) separated from each other by intermediate calibration and expansion sections, the inclination angle of the generatrix to the rolling axis of one section being 1.5-5.0 deg smaller and that of the other one larger than the inclination angle of the generatrix of the entry portion of broaching rolls to the rolling axis. EFFECT: higher yield of quality product and more efficient stability in working of expanding metals. 2 cl, 2 dwg