METHOD FOR PRODUCING LARGE- AND MEAN-DIAMETER TUBES OF COLD-RESISTANT AND CORROSION-RESISTANT STEELS IN TUBE ROLLING PLANTS WITH PILGER MILLS Russian patent published in 2007 - IPC B21B21/00 B21B21/04 

FIELD: rolled tube production, namely rolling of large- and mean-diameter tubes of cold-resistant and corrosion-resistant steels, possibly in tube rolling plants with pilger mills including helical rolling mills.

SUBSTANCE: method comprises steps of casting ingots; drilling central opening with diameter 100±5.0 mm; heating ingots till yielding temperature; piercing ingots to sleeves in skew rolling mills; rolling tubes in pilger mills. Tubes of cold resistant and corrosion resistant steels are rolled from continuously cast billet with diameter 430 mm without central opening; tubes with diameter 273 and 299 mm are rolled in pilger mill from sleeves pierced in skew rolling mills at diameter raise 4.5 - 5.0% ; tubes with diameters 325 and 351 mm are rolled from sleeves pierced at diameter raise 15 - 20% and tubes with diameters 377 and 426 mm rolled of sleeves pierced at diameter raise 21 - 30%. Continuously cast billets are heated for piercing at rolling tubes with diameters 273 and 299 mm till temperature 1230 -1250°C; at rolling tubes with diameters 325 and 351 mm - till temperature 1250 -1270°C; at rolling tubes with diameters 377 and 426 mm - till temperature 1270 - 1290°C. Continuously cast billets are pierced in skew rolling mill at elongation factor 1.5 - 1.6; tubes are rolled in pilger mill at elongation in range 7.5 - 15.0 while rolling tubes with diameter 273 mm at large elongation values and tubes with diameter 426 are rolled with less elongation values. Tubes with diameters 273 and 299 mm are rolled with triple length and tubes with diameters 325, 351, 377 and 426 mm are rolled with double length. Continuously cast billets are pierced to sleeves with diameter raise 4.5 - 5.0% at revolution number of rolling rolls 44-40 rev/min; with diameter raise 15 - 20% at revolution number of rolling rolls 40 - 38 rev/min and with diameter raise 21 - 30% at revolution number of rolling rolls 38 - 36 rev/min.

EFFECT: lowered metal consumption for making tubes, simplified operations for restoring tubes by removing outer and inner flaws before and after ultrasound flaw detection, reduced cost of conversion continuously cast billet - cold resistant tube, improved effectiveness of producing tubes of given assortment.

5 cl, 1 tbl