METHOD FOR PRODUCING HOT ROLLED COMMERCIAL AND CONVERSION TUBES OF LARGE- AND MEAN-DIAMETERS OF HARD-TO-FORM STEELS AND ALLOYS IN TUBE ROLLING PLANTS WITH PILGER MILLS

摘要

FIELD: rolled tube production, namely processes for producing hot rolled commercial and conversion tubes of large and mean diameters of hard-to-form steels and alloys, possibly in tube rolling plants with pilger mills.;SUBSTANCE: method comprises steps of casting ingots by electroslag refining; drilling central opening with diameter 100 ± 5.0 mm; heating them till yielding temperature; piercing ingots to sleeves; rolling mean-diameter tubes in pilger mills to commercial or conversion tubes; secondary heating sleeves till yielding temperature; rolling them out in skew rolling mill to sleeves at thinning their walls; rolling commercial or conversion tubes of large and mean diameters in pilger mills depending upon kind of steel; or drilling and boring electroslag refining ingots to hollow ingots whose inner diameter exceeds by 40 - 50 mm diameter of mandrel; heating them till yielding temperature and rolling in pilger mills to hot rolled commercial or conversion tubes. Tubes rolled in pilger mills from hollow ingots of electroslag refining at elongation factor more than 5 are used as commercial tubes. Tubes rolled at elongation factor less than 5 are used as conversion tubes. Rolling of tubes from hollow billets in pilger mill is realized at bottom end of tubes turned forward and pilger head is formed from contracted portion. Invention provides lowered metal consumption, reduced quantity of flaws such as slivers and scabs, lowered load of drive unit of pilger mills due to optimal deformation parameters, eliminate breakage of spindles and rolls.;EFFECT: lowered cost of producing tubes of high-cost hard-to-form steels and alloys in tube rolling aggregates with pilger mill.;3 cl, 1 tbl