METHOD FOR MANUFACTURING SEAMLESS HOT-DEFORMED BOILER TUBES OF LARGE AND MEAN DIAMETERS IN TUBE ROLLING AGGREGATES WITH PILGER MILLS FOR STEAM BOILERS, STEAM CONDUITS AND MANIFOLDS OF PLANTS WITH HIGH AND SUPERCRITICAL PARAMETERS OF STEAM FROM INGOTS OF ELECTROSLAG REFINING AND CONTINUOUSLY CAST BILLETS Russian patent published in 2006 - IPC B21B21/00 

FIELD: rolled tube production processes and equipment, namely manufacture of seamless hot deformed tubes of large and mean diameters for steam boilers, steam conduits and manifolds of plants high and supercritical parameters of steam from ingots of electroslag refining and continuously cast billets.

SUBSTANCE: method for producing above mentioned seamless tubes of carbon, low-alloy, alloy and high-alloy steels comprises steps of melting ingots in electric and open-hearth furnaces; forging ingot at forging degree 2 - 3 depending upon steel kind; forming tube blanks by turning and drilling central part of forged pieces; continuously casting billets of steels of given four types for their successive forging at forging degree no less than 1.5 and converting them to blanks or casting ingots by means of electroslag refining; heating blanks and electroslag refining ingots till yielding temperature; piercing blanks in skew rolling mills on mandrels whose diameters depend upon geometry size of sleeve; piercing ingots of electroslag refining at deforming metal in skew rolling mills along crystal arrangement due to guiding ingots to rolling mill by head portion and at fitting 8 - 16% by diameter; rolling sleeves formed of ingots of electroslag refining and of continuously cast billets to tubes in pilger mills with elongation degree depending upon diameter and wall thickness; sizing and straightening tubes; drilling in ingots of electroslag refining and in continuously cast billets central opening whose diameter is determined according to expressions: d_{dr el} = d₀ (D_C /D₀ ), d_drcc= d₁(D_C /D₁ ) where d₀ = 95 mm, diameter of central drilling of ingots of electroslag refining with outer diameter 500 mm; d₁ = 90 mm, diameter of central drilling of continuously cast billets with outer diameter 430 mm; D_C - current values of outer diameter of ingots of electroslag refining and continuously cast billets, mm; D₀ - outer diameter 500 mm of electroslag refining ingots; D₁ - outer diameter 430 mm of continuously cast billets; heating ingots till yielding temperature; piercing them in skew rolling mills to sleeves with elongation degree depending upon geometry size of sleeves; rolling in pilger mills to tubes. Ingots are pierced in skew rolling mills with elongation degree determined according to expressions μ_el = μ_f(0.1 + D_C/D₀), μ_cc = μ_f(D_C /D₁ ) where μ_f - elongation degree in skew rolling mill at rolling tubes of given size of forged blank. Ingots of electroslag refining and continuously cast billets are heated before piercing in skew rolling mills till temperature that is lower by 20 -40°C than that of forged piece (larger values are related to alloy and high alloy steels).

EFFECT: lowered power consumption at piercing process, lowered metal consumption of conversion of electroslag refining ingot and continuously cast billet to boiler tube, rational gas consumption.

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