METHOD FOR PRODUCING CASING TUBES FOR THREADING IN TUBE ROLLING AGGREGATES WITH PILGER MILLS

FIELD: rolled tube production, namely production of casing tubes for thread cutting, possibly in well known tube rolling aggregates with pilger mills and also in tube rolling aggregates with new generation of pilger mills controlled by means of computers. ^ SUBSTANCE: method comprises steps of heating ingots and continuously cast billets till yielding temperature; piercing them to sleeves in skew rolling mills; rolling tubes on long mandrel in pilger mills and sizing them in calibration mill. Deformation value along rolled tube lengths in pilger mill is cyclically decreased by (n+1) times where n - number of multiple tubes, pieces. Said deformation is decreased due to opening rolls by value determined according to expression Delta = (1.0 - 2.0)H where H - height of initial thread profile, mm. Deformation is decreased in portions of tubes whose lengths are determined according to expression L = Lc + K where Lc - length of coupling, mm; K = 50 - 150 mm, factor taking into account waste value and allowance along length of multiple tubes at working their ends with thickened wall, mm. Tube lengths are cut by multiple tubes along center of thickened portions. Nominal inner diameter of tube end portions is lowered at calibration by value determined with use of expression Din = Dnom - K1, where Dnom - nominal inner diameter of tube, mm; K1 - coefficient taking into account lowered inner diameter of end portions of casing tubes at calibration, mm; K1