ELECTRICALLY WELDED STRAIGHT-SEAM TUBE PRODUCTION METHOD Russian patent published in 2007 - IPC B21C37/06 

FIELD: plastic working of metals, possibly manufacture of electrically welded straight-seam tubes.

SUBSTANCE: method comprises steps of bending tube blank according to two radiuses; monotonously bending central portion of blank by means of decreasing radius of shaped gages from value (20 - 30)Rw till Rw; bending peripheral portions of blank till radius Rw; increasing bending radius of central portion in respective stand till value (1.45 - 4.25)Rw in zone of transition of open gage to closed gage; providing identical shaping effort in all working stands due to design and size of roll grooved passes and determining such effort according to formula : P_i ^Ф_{=(σ i xΔεi xSm xBi x Li ^in.def.)/(KФ x mi) for open gages and Pi ^Ф =( σi ⁿ x Δεi x Sm x Bi x L^in.def. ) /( KФ x mi ) +Bi ^k x Δεi x Sm for closed gages where Pi ^Ф - shaping effort for i-stand, N; σi ⁿ -stress in outer surface of strip determined from stress diagram, MPa; Sm - blank thickness, mm; Bi - blank width being in contact with rolls, mm; Li ^in.def. - length of non-contact deformation zone in i-gage, mm; KФ - coefficient equal to 1 - 3; mi - width of i-gage, mm;Bi ^k - complete perimeter of blank in closed i-stand, mm; Δεi - bending deformation value in i-stand determined as deformations difference between i-gage and (i-1)-gage while taking into account value Δεi= εi -(! - β)εi-1 where β - unspringing factor.}

EFFECT: possibility for achieving identification of shaping efforts in all working stands due to calibration and determining dimensions of grooved rolls.

16 dwg, 7 tbl, 1 ex