METHOD FOR PRODUCING INGOT-BLANKS BY ELECTROSLAG REFINING OF HARD-TO-FORM STEELS AND ALLOYS AND FOR ROLLING OF THEM COMMERCIAL TUBES OF LARGE AND MEAN DIAMETERS IN TUBE ROLLING PLANTS WITH PILGER MILLS AND CONVERSION TUBES FOR REROLLING IN TUBE COLD ROLLING MILLS

摘要

FIELD: production of ingot-blanks by electroslag refining of hard-form steels and alloys, rolling commercial tubes of large and mean diameters in tube rolling plants with pilger mill and conversion tubes for further rerolling in tube cold rolling mills.;SUBSTANCE: method comprises steps of casting ingots with size 420 -620 x 1750 50 mm by electroslag refining; mechanically working - turning them to ingot-blanks with size 400 -600 x 1750 50 mm; heating till yielding temperature of ingot-blanks and expanding in radial forging machines to sleeve-blanks for further turning and boring till removing forging flaws; boring inner diameter of ingot-blanks to sleeve-blanks with inner diameter exceeding diameter of drift by 30 - 35 mm; heating ingot-blanks and sleeve-blanks till yielding temperature; piercing ingot-blanks with diameter 400 - 500 mm in skew rolling mill to sleeves; rolling sleeves; rolling expanded and turned sleeve-blanks in pilger mill with use of backing carbonaceous rings to commercial or conversion tubes with diameter 219 - 426 mm; performing first piercing of ingot-blanks with diameter 540 - 600 mm to sleeves on mandrel with diameter 250 - 275 mm; again heating sleeves from hot or cold fit till yielding temperature; secondary piercing-rolling out of them in skew rolling mill on mandrel with diameter exceeding that of drift by 20 - 25 mm; rolling sleeves to commercial or conversion tubes with diameter 351 - 450 mm in pilger mill with backing carbonaceous rings. Ingots cast by electroslag refining are hollow ones, they have relation of diameter to wall thickness D/S = K1 and height H = K2*D where D - outer diameter of hollow ingot of electroslag refining, mm; S - wall thickness of hollow ingot of electroslag refining, mm; H = 2500 - 3000 - height of hollow ingot of electroslag refining, mm; K1 = (4.0 -6.0) -coefficient whose larger values correspond to hollow ingots of larger diameters; K2 = (4.0 - 7.0) -coefficient whose larger values correspond to hollow ingots of less diameters. Hollow ingots of electroslag refining are bored and turned to sleeve-blanks till removing flux and casting-origin flaws with inner surface roughness Rz 40 micrometers and outer surface roughness Rz 60 micrometers. Hollow ingot-blanks are heated till yielding temperature and rolled in pilger mill to commercial tubes with diameter 219 - 426 mm and elongation value 6.0 and to conversion tubes with diameter 273 - 450 mm and elongation value 4.0.;EFFECT: lowered consumption of high-cost metals of hard-to-form steels and alloys, reduced cost of hollow ingot-blanks in comparison with expanded sleeve-blanks, decreased cost of commercial and conversion tubes of given assortment.;3 cl, 1 tbl