FIELD: production of ingot-blanks by electroslag refining of hard-to-form steels and alloys, 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.
SUBSTANCE: method comprises steps of casting ingots by electroslag refining with size 420-620 x 1750±50 mm; mechanically working-turning them to blanks with size 400-600 x 1750±50 mm; boring inner diameter by 30 - 35 mm more than drift diameter; heating them till yielding temperature; piercing ingot-blanks with diameter 400-500 mm in skew rolling mill to sleeves; rolling sleeves and bored ingot-blanks in pilger mill with backing carbon rings to commercial or conversion tubes with diameter 219 - 325 mm; subjecting ingot-blanks with diameter 540 -600 mm to first piercing to sleeves on mandrel with diameter 250 - 275 mm; secondary heating of sleeves from hot or cold fit till yielding temperature; secondary piercing- rolling out of sleeves in skew rolling mill on mandrel with diameter exceeding drift diameter by 20-25 mm; rolling sleeves to commercial or conversion tubes in pilger mill with backing carbon rings. Hollow ingots of electroslag refining are made built-up -bimetallic along height; bottom portion of refining ingots forming pilger head at rolling tubes in pilger mill is cast of ductile carbon steel kinds and main part of ingot is cast of steels and alloys according to orders. Height of bottom portion of ductile carbon steel is determined from expression Lb = KH where H -total height of hollow electroslag refining ingot of hard-to-form steels and alloys,mm; Lb - height of bottom portion of hollow ingot of ductile carbon steel, mm; K = 0.15 -0.20 - coefficient for determining height of bottom portion of hollow ingot of ductile carbon steel whose larger values correspond to larger diameter ingots and larger wall thickness. Hollow ingots are turned and bored to hollow ingot-blanks at taking metal of hard-to-form steels and alloys from shrinkage part till fusion boundary of two metals or at shifting to side of ductile carbon steel along length 50 - 100 mm. Transition along outer diameter of ingot-blanks from basic metal to ductile carbon steel is made smooth in the form of truncated cone along length 80 - 100 mm. Heating of built-up hollow ingot-blanks of electroslag refining is realized in mode of heating steel of main kind. On shrinkage end portions of hollow ingot-blanks on outer surface along length Lc = (1.5 - 2.0)Sw cone is formed with blunting h > 2.0Sc where Sw -wall thickness of hollow ingot-blanks of electroslag refining, mm; Sc - wall thickness of commercial or conversion tube, mm; Lc - length of cone portion on outer surface of hollow ingot-blanks at transition of main metal to ductile carbon steel,mm; h - blunting value of hollow blanks of electroslag refining, mm. Commercial and conversion tubes are rolled with their shrinkage end turned forward.
EFFECT: lowered consumption of metal, improved efficiency.
8 cl, 1 tbl.
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