TUBE ROLLING METHOD Russian patent published in 2000 - IPC

FIELD: manufacture of tubes, namely production of seamless tubes by lengthwise hot rolling in automatic tube rolling mills. SUBSTANCE: method comprises steps of deforming tube blank in deformation zone in pass restricted by two rolls and stationary mandrel in such a way that at first blank is reduced until plane passing through roll axes, then walls of blank are reduced for simultaneously increasing its diameter. Walls of blank at simultaneous increase of its diameter are reduced at lowering deformation degree from its maximum value until minimum one in place of outlet of ready tube from deformation zone. Values of reducing walls, increasing its diameter and length of deformation zone under plane passing through roll axes are mutually related by expression 0.5 x Δd x l = ΔS(Ru-r) x Sinα, where Δd- value of increasing diameter, mm; ΔS- wall reduction degree, mm; Ru - ideal radius of roll, mm; r - radius of ready tube, mm; l - length value of deformation zone behind plane passing through roll axes; α- biting angle behind plane passing through roll axes, degrees. EFFECT: enhanced accuracy of wall thickness value of rolled tubes, high deformation capability of process due to possibility of acting upon pattern of stressed-deformed state of metal in deformation zone. 4 dwg, 1 ex