FIELD: processes and equipment for producing in tube rolling plants with pilger mills seamless hot-deformed tubes with diameters 500 mm and more for steam boilers, steam conduits and manifolds of plants with high and super-critical parameters of steam from hollow ingots of electroslag refining.
SUBSTANCE: method comprises steps of melting ingots in electric or in open-hearth furnaces on base of direct reduction and also with use of liquid synthetic-slag treatment in ladle, electroslag or direct reduction; forging ingots to forged pieces with forging reduction ratio 2.0 - 3.0 depending upon steel kind; chopping ends of forged pieces for removing bottom and shrinkage portions; melting ingots by electroslag refining; mechanically working forged pieces and ingots of electroslag refining for preparing blanks with predetermined diameter with allowance -10/+5 mm; heating blanks and ingots till yielding temperature depending upon kind of steel; performing their first piercing in skew rolling mill on mandrel with diameter 300-350 mm depending upon steel kind and load value of rolls drive unit to sleeves with length no more than 2000 mm; again heating sleeves from hot or cold fit till yielding temperature; secondary piercing-rolling out sleeves in skew rolling mill on mandrel whose diameter exceeds that of drift by 25 - 30 mm; rolling sleeves in pilger mill to tubes with diameter 500 mm and more at allowance by diameter ±1.0% and by wall thickness +20/-5.0%. Hollow ingots of electroslag refining are melt with relation of diameter to wall thickness D/S = K1 and with height H =K2*D, H1= K3*D where D = 680 - outer diameter of hollow ingots of electroslag refining, mm; S - wall thickness of hollow ingot of electroslag refining, mm; K1 = (4.8 - 9.2)-coefficient whose larger values correspond to hollow ingots with less wall thickness; H =( 3000-3500) height of hollow ingot of electroslag refining for rolling tubes with relation D/S ≤ 20, mm; K2 =(4.4 -5.2) - coefficient values for rolling tubes at relation D/S≤20, mm; H1 = (2000-2100) - height of hollow ingot of electroslag refining for rolling tubes with relation D/S > 20, mm; K3 = (2.9 - 3.1) - coefficient values for rolling tubes with relation D/S > 20,mm. Hollow ingots of electroslag refining for rolling boiler tubes at relation D/S > 20 are melt with inner diameter Din = Dd ± 5.0 where Dd -diameter of drift, mm. Hollow ingots of electroslag refining for rolling boiler tubes are turned and bored to sleeve-blanks at taking off metal layer thickness 8 ± 2.0 mm for removing welding slag and casting -origin flaws. Hollow sleeve-blanks of electroslag refining are heated till yielding temperature and they are rolled in pilger mill to tubes with relation of D/S > 20, allowance by diameter ± 1.0% and wall thickness +15.0/ -10.0%. Hollow ingots of electroslag refining for rolling boiler tubes with relation D/S 20 are cast with inner diameter 300 ± 10 mm, turned and bored to hollow sleeve-blanks at taking off metal layer thickness 8 ± 2.0 mm for removing welding slag and casting -origin flaws. Hollow sleeve-blanks of electroslag refining are heated till yielding temperature, pierced and rolled out in skew rolling mill to sleeve on mandrel with diameter exceeding that of drift by 15 - 20 mm and then they are rolled in pilger mill to tubes with relation D/S <20, allowance by diameter ±1.0% and wall thickness +15.0/-10.0%. Invention provides possibility for increasing tube length by 20 - 30%.
EFFECT: increased length of tubes, lowered energy consumption, decreased cost of boiler tubes.
6 cl, 1 tbl
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