RU2297891C2 - Method for producing in tube rolling plants with pilger mills seamless hot-deformed large- and mean-diameter tubes for steam boilers, steam pipes and collectors of plants with high and super-critical parameters of steam from ingots of electroslag refining and continuously cast billets - Google Patents

Abstract

FIELD: production of rolled tubes, namely seamless hot deformed tubes of large and mean diameters for steam boilers, steam pipes, collectors of plants with high and super-critical parameters of steam from ingots of electroslag refining and continuously cast billets, possibly in tube rolling plants with pilger mills including helical rolling mills.

SUBSTANCE: method comprises steps of melting ingots in electric and Martin furnaces on base of direct reduction and also with use of stage for treating with liquid slag in ladle; forging ingots at forging ratio 2 - 3 depending upon steel kind; turning and drilling central part of tube blanks; continuously casting steel of predetermined kinds (given in specification) treated with synthetic slag; continuously casting steel of given kinds from evacuated or non-evacuated metal treated with synthetic slag for further forging them to blanks with forging ratio no less than 1.5; melting ingots of given kinds of steel by electroslag refining; drilling central part of ingots of electroslag refining and continuously cast billets; heating billets and ingots till their plastic temperature depending upon steel kind; piercing them in skew rolling mills on mandrels whose diameter depend upon geometry size of sleeves; piercing ingots of electroslag refining while deforming metal in piercing mill with diameter fit in range 8 - 16%; rolling blanks in pilger mills with elongation values depending upon diameter and thickness of wall; calibrating and straightening tubes. Ingots of electroslag refining and continuously cast billets of steels of kinds given in specification are heated till plastic temperature without drilling central opening, pierced in piercing mills to sleeves and rolled in pilger mills to tubes. Bottom portion of ingots of electroslag refining is removed by means of anode-arc cutting. Ingots of electroslag refining are guided to piercing mill forward by their bottom ends. Tubes from sleeves pierced from ingots of electroslag refining are rolled in pilger mills at their bottom end turned forward while forming pilger head from shrinkage portion of ingot. Elongation factors for piercing in piercing mill ingots of electroslag refining and continuously cast billets are determined from expressions: μ_esr = 1.1μ_fbd_{c esr}/d_{o esr,} μ_ccb = 1.1μ_fb d_{c ccb}/d_{o ccb} , where μ_fb -elongation value at rolling tubes of given size from forged blank in piercing mill; d_{c esr} -current value of diameter of ingots of electroslag refining, mm; d_{o ccb} - diameter of ingot of electroslag refining equal to 500 mm; d _{c ccb} - current value of diameters of continuously cast billet; d_{o ccb} - diameter of continuously cast billet equal to 400 mm. Invention provides reduced energy consumption due to elimination of operations for heating ingots for forging and forging ingots to forged pieces, for drilling ingots.

EFFECT: reduced factor of metal consumption at mechanical properties of tube metal equal or higher than those of forged blank metal during conversion such as electroslag refining - boiler tube, lowered cost of boiler tubes.

2 cl, 2 tbl

Description

The invention relates to pipe rolling production, and in particular to a method for the production of seamless hot-deformed boiler pipes of large and medium diameters for steam boilers, steam pipelines and collectors of installations with high and supercritical parameters of steam from electroslag remelting ingots (ESR), and continuously cast billets (NLZ), and can be used in pipe rolling plants with pilgrim mills, which include cross-helical rolling mills.

In the practice of pipe-rolling production, there is a method of manufacturing seamless hot-deformed pipes of large and medium diameters on pipe-rolling plants with pilgrim mills for steam boilers, steam pipelines and manifolds of plants with high and supercritical steam parameters from forged billets of steel grades 20, 15GS, 15XM, 12X1MF, 15X1MF, 15X1MF 10Kh9MFB, 12Kh11 V2MF, 08Kh16N9M2, 12Kh18N12T and 10Kh13G12BS2N2D2 with specified requirements for mechanical properties, including casting of ingots in electric and open-hearth furnaces, their forging (pack structure) with a yoke from 2.0 to 3.0, depending on the steel grade, as well as continuous casting of steel grades 20, 15GS, 12Kh1MF, 15Kh1M1F and 15KhM with their subsequent forging into forgings with a kennel of at least 1.5, mechanical processing (turning with 10-15 mm metal removal to the side and drilling of a central hole with a diameter of 100 ± 5 mm to remove central segregation porosity and non-metallic inclusions), heating to ductility temperature, piercing blanks in oblique rolling mills into sleeves and rolling them into pipes on pilgrim mill with a wall tolerance of + 20 / -5 % (TU 14-1-2560-78 "Forged pipe billet for boiler pipes", TU 14-3-460-2003 and TU 14-ЗР-55-2001 "Seamless steel pipes for steam boilers and pipelines" and TU 14- 3-420-75 "Pipes for steam boilers and pipelines made of steel 15GS and 15X1M1F".

The disadvantage of this method is the high energy intensity of the process associated with heating and deformation (forging) of ingots and NLZ into forgings, followed by turning and drilling of the central hole, heating the workpieces to a ductility temperature, piercing and rolling them into pipes on pilgrim mills with a wall tolerance of +20 / -5%, increased metal consumption (metal consumption coefficient) when redistributing an ingot or NL3 forging - billet - pipe and, as a result, the high cost of pipes.

Known in the pipe-rolling industry are methods for flashing ingots (billets) on lifting (expansion - 3-7%), size in size and posad (settling - 2-5%), where, with a change in the stress-strain state diagram, deformation expressed by the amount of drawing also changes (F.A. Danilov et al. Hot rolling of pipes. Moscow, Metallurgizdat, 1982, p. 300, table 34).

The disadvantage of these methods of firmware is the inability to provide the necessary deformation of the ingot, which allows to obtain the mechanical properties, structure and density of the metal pipes, which are obtained by production from forged billets.

In pipe rolling production, there is also known a method of manufacturing large diameter gas lift pipes from 09G2S steel ingots for ESW and VDP smelting (RF Patent No. 2119395, class B21B 19/04), where the ingots are deformed in the piercing mill along the crystals, setting the ingots in the mill with the head part (shrink) and stitched with a posad in diameter by the amount

D = 2S _r (1-sinα) S _c ,

where S _r is the wall thickness of the sleeve, mm;

S _c - wall thickness of the drilled ingot ESR, mm;

α is the angle of inclination of the crystallization front to the axis of the ingot, deg.

The disadvantage of this method of manufacturing large diameter pipes from ingots of ESR and VDP steel grade 09G2S is the need to manufacture macro templates to determine the angle of inclination of the crystallization front to the axis of the ingot, and the piercing of the ingots with shrink (head) part forward leads to the formation of defects in the form of internal captures at the front ends of the sleeves .

The closest technical solution is a method for the production of large diameter boiler pipes from ESR ingots (patent RU No. 2180874, class B21B 19/04), which reduces energy costs, reduces metal consumption and, as a result, reduces the cost of boiler pipes through the use of large diameter ingots and conducting the firmware process with a posad in diameter equal to 8-16%.

The disadvantages of this method are the constant values of the removed metal layers during machining (turning) of the ingots, the constant value of the drilling of the central hole 100 ± 5 mm and the constant values of the compression of the ingots when piercing, which do not depend on their geometric dimensions (diameters), which leads to an additional expense metal and energy consumption during machining (turning, drilling a central hole and piercing ingots for landing).

The objective of the proposed method (invention) is to reduce energy costs due to the exclusion from the technological process of heating ingots for forging, forging them into forgings, followed by turning the forgings into billets on the outer surface, as well as during flashing, by optimizing the amount of compression, depending on geometric sizes (diameters) of ESR and NLZ ingots, reduction of metal consumption during redistribution of ESR ingots and NL3-boiler pipe due to a decrease in the thickness of the removed metal layer during turning compared to forged billet and proc pipe webs made of higher quality and ductile metal without central segregation porosity and non-metallic inclusions.

The technical result is achieved by the fact that in the known method for the production of seamless hot-deformed pipes of large and medium diameters on tube rolling plants with pilgrim mills for steam boilers, steam pipelines and manifolds of plants with high and supercritical parameters of steam from ESR and NLZ ingots, including ingot smelting in electric and open-hearth furnaces furnaces, based on direct reduction, treatment with liquid synthetic slag in a ladle, forging ingots with a weight from 2.0 to 3.0, depending on the grade of steel forging ingots into pipe billets, or continuous casting of steel grades 20 and 15GS treated with synthetic slag, into continuously cast billets, or continuous casting of steel grades 12X1MF, 15X1M1F and 15XM from vacuum or non-vacuum metal treated with synthetic slag, followed by forging them into billets with a draft of at least 1.5, or the smelting of ingots of these steel grades by electroslag remelting, heating the billets and ingots to a plasticity temperature depending on the grade of steel, piercing them into sleeves in oblique rolling mills on mandrels, the diameter of which depends on the geometrical dimensions of the sleeves, piercing ingots of electroslag remelting with metal deformation in the piercing mill with a diameter of 8-16% in the piercing mill, rolling on pilgrim mills with hoods, depending on the diameter and wall thickness, calibration and dressing pipes, while the electroslag remelting ingots in the piercing mill are set with the bottom end forward, the tubes are rolled on the pilgrim mill from the shells sewn from electroslag remelting ingots, the bottom end is forward, and the ingot is shrunk a pilger forming head extracts the coefficients a piercer in piercing electroslag remelting ingots and continuous - casting blocks is determined from the expression μ = 1,05μ _{ESR of ESR t} d / d _{o ESR,} μ _nlz = 1,1μ _{nlz g of} d / d _{o nlz} , where μ _s is the hood on the piercing mill when rolling pipes of a given size from forged blanks; d _{t eshp} - current value of diameters of electroslag remelting ingots, mm; d _{o eshp} - diameter of the electroslag remelting ingot, equal to 500 mm; d _{g nlz} - the current value of the diameters of continuously cast billets; d _{o NLS} - the diameter of a continuously cast billet equal to 400 mm, and the bottom of the electroslag remelting ingots is removed by anodic-mechanical cutting.

Comparative analysis with the prototype shows that the inventive method for the production of seamless hot-deformed pipes of large and medium diameters on pipe rolling plants with pilgrim mills for steam boilers, steam pipelines and collectors of plants with high and supercritical parameters of steam from ESR and NLZ ingots is characterized in that electroslag ingots are remelted into the piercing mill is set with the bottom end forward, the pipes are rolled on a pilgrim mill from shells sewn from ingots of electroslag remelting, bottom the end forward, and a pilgrim head is formed from the shrinkage part of the ingots, the hood coefficients on the piercing mill when piercing electroslag remelting ingots and continuously _cast billets are determined from the expressions μ _ESR = 1.05 μ _s d _{g ESR} / d _{o ESR} , μ _nlz = 1.1 μ _s d _{g nlz} / d _{o nlz} , where μ _s is the hood on the piercing mill when rolling pipes of a given size from forged billets; d _{g esp} - the current value of the diameters of the ingots of electroslag remelting, mm; d _{o eshp} - diameter of the electroslag remelting ingot, equal to 500 mm; d _{g nlz} - the current value of the diameters of continuously cast billets; d _{o NLS} - the diameter of a continuously cast billet equal to 400 mm, and the bottom of the electroslag remelting ingots is removed by anodic-mechanical cutting. Thus, the claimed method meets the criteria of the invention of "inventive step".

Comparison of the proposed method not only with the prototype, but also with other technical solutions in the art did not allow them to identify signs that distinguish the claimed method from the prototype, which corresponds to the patentability of "inventive step".

The proposed method for the production of large and medium diameter boiler pipes in pipe rolling plants with pilgrim mills for steam boilers, steam pipelines and collectors of plants with high and supercritical parameters of steam from ESHP and NLZ ingots consists in setting the electroslag ingots in the piercing mill to set the bottom end forward, pipe rolling on a pilgrim mill made of sleeves sewn from ingots of electroslag remelting is carried out with the bottom end forward, and from the shrinkage part of the ingots form a pilgrim head Patent Application, extracts the coefficients a piercer in piercing electroslag remelting ingots and continuously cast billets determined from expressions μ _ESR = 1,05μ _{ESR t of} d / d _{o ESR,} μ _nlz = 1,1μ _{nlz g of} d / d _{o nlz,} where μ _s - hood on the piercing mill when rolling pipes of a given size from forged billets; d _{g esp} - the current value of the diameters of the ingots of electroslag remelting, mm; d _{o eshp} - diameter of the electroslag remelting ingot, equal to 500 mm; d _{g nlz} - the current value of the diameters of continuously cast billets; d _{o NLS} - the diameter of a continuously cast billet equal to 400 mm, and the bottom of the electroslag remelting ingots is removed by anodic-mechanical cutting.

A method for the production of seamless hot-deformed pipes of large and medium diameters in tube-rolling plants with pilgrim mills for steam boilers, steam pipelines and collectors of plants with high and supercritical steam parameters from forged billets, ESR ingots and NLZ was tested during rolling of 325 × 40, 377 × 45 and 273 × 30 mm from steel grade 12X1MF at TPA 8-16 "with pilgrim mills of ChTPZ OJSC.

15 forgings of 570 × 1750, 630 × 1750 and 460 × 1750 mm in size (5 forgings of each size), 10 ESR ingots of 550 × 1750 and 610 × 1750 mm in size (5 ingots of each size) and 5 NLZ sizes were set for production 430 × 1750 mm steel grade 12X1MF. The forgings were turned and drilled into blanks of 540 × 100 × 1750, 600 × 100 × 1750 and 540 × 100 × 1750 mm, respectively. ESR ingots are turned and drilled to a size of 540 × 100 × 1750 and 600 × 100 × 1750 mm. Because In Russia, billets with a maximum diameter of 430 mm are currently cast in continuous steel casting plants; for this experiment, 5 NLZ sizes of 430 × 1750 mm were specified. NLZ was not machined (turned) and the central hole was drilled. 5 billets of 540 × 100 × 1750 mm in size and 5 ESR ingots were simultaneously placed in a furnace, heated to a temperature of 1270-1280 ° C, sewn into sleeves and rolled into 325 × 40 mm pipes according to TU 14-3-55R-2001. The blanks were stitched according to the existing technology into sleeves with a hood μ = 1.36 without compression in diameter, i.e. size in size, and ESR ingots were stitched into sleeves, in accordance with the claims, with a hood μ = 1.51 due to compression in diameter by 6.7%, i.e. with a posad in diameter. The bottom part on ESR ingots at ZMZ OJSC was removed by anode-mechanical cutting. ESR ingots were set in the piercing mill with the bottom end forward. Tubes were rolled from sleeves sewn from ESR ingots with the bottom end forward, and a pilgrim head was formed from the shrinkage parts of the ingots. Data on rolling, geometrical dimensions of billets, pipes and expenditure coefficient of metal rolled from forged billets, ingots EShP and NLZ steel grade 12X1MF for existing and proposed technologies are given in table No. 1. The table shows that the expenditure coefficient of the metal from forging to finished through pipes of 325 × 40 mm, when rolling pipes using the existing technology, amounted to 1,430, and according to the proposed 1,284. The metal savings per ton of pipes amounted to 146 kg. The expenditure coefficient of the metal is the main economic indicator in the production of pipes, because the cost of metal (depending on the grade of steel) ranges from 50 to 75% of the market value of pipes. According to a similar scheme, pipes 377 × 45 mm in size were rolled. According to existing technology, the expenditure coefficient of the metal was 1.428, and according to the proposed one, 1.255, i.e. a decrease in metal consumption of 173 kg per ton of pipe was obtained. Pipes 373 × 30 mm in size were rolled according to the existing technology from forgings of 460 × 1750 mm in size, which were turned at ChTPZ OJSC into blanks with a diameter of 430 mm, followed by drilling a central hole to a diameter of 100 ± 5.0 mm. Five forgings with a total weight of 11,409 tons were set into production. Billets on the piercing mill were sewn into sleeves the size of a size with a hood 1.37 and rolled into pipes. 7.775 tons of pipes were delivered from this batch. The expenditure coefficient of the metal from the forgings to the pipe amounted to 1,468. According to the proposed technology, NLZs were not subjected to mechanical processing (turning and drilling), they were set in a furnace for heating along with forged billets, heated to a temperature of 1265-1275 ° C and sewn into sleeves with a fit of 4.7% in diameter and drawing coefficient in accordance with the claims. According to the proposed method, 9.970 tons of metal were set into production. Accepted 7.955 tons of pipes in accordance with TU 14-3-55R-2001. The expenditure coefficient of the metal for this batch was 1.254, i.e. a decrease in metal consumption of 214 kg per ton of pipe was obtained.

Table 2 shows data on the mechanical properties of metal pipes made of steel grade 12X1MF, rolled from forged billets, ingots EShP and NLZ according to the existing and proposed technologies. The table shows that the average values of the mechanical properties of the metal of pipes rolled from ESR ingots according to the proposed technology are higher than from forged billets by 5.0-7.5%, which, in turn, provides a guaranteed opportunity to reduce the positive tolerance field in wall thickness by 5.0% or set the tolerance on the wall + 15 / -10 instead of the existing + 20 / -5.0%. And since the quality of the metal of the ESR ingots is much better, the main criterion for boiler pipes is the long-term strength will be much higher. The average values of the mechanical properties of the metal pipes rolled from NLZ are on the same level as the metal pipes rolled according to the existing technology from forged billets.

Thus, the use of the proposed method for the production of boiler pipes of large and medium diameters from EShP and NLZ ingots will significantly reduce energy costs by eliminating the heating of ingots for forging and forging of ingots into forgings, and reduce the expenditure coefficient of the metal with the mechanical properties of the pipe metal at or higher, compared with forged billet, when redistributing an ingot of ESR and NL3 boiler pipe, and therefore, reduce the cost of boiler pipes.

Table 1 Data on rolling, the geometric dimensions of billets, pipes and the expenditure coefficient of metal, taking into account technological waste at the rental (pilgrim heads and seed ends), rolled from forged billets, EShP and NLZ ingots of steel grade 12X1MF according to existing and proposed technologies The method of arbitrariness. pipes Type of procurement. The size of the forgings, ingots EShP and NLZ (mm) Kolich. forgings, ingots EShP and NLZ (pcs) Weight set. Metal (t) Dimensions (mm) Firmware for ingots and billets Pilgrim mill pipe rolling Expense. coefficient metal Mandrel Diameter (mm) Sleeve Size (mm) Coeff. extractor hood. (μ) Squeezed. by dia. (%) Pipe Size (mm) Delivery pipe dimensions Avg thickness wall (mm) Average length (m) Weight of pipes according to TU (tn) Existence. technol. Forged barbecue. 570 × 1750 5 17,525 540 × 100 × 1750 275 540 × 290 × 2380 1.36 0 325 × 40 43.0 8.2 12,260 1,430 630 × 1750 5 21,410 600 × 100 × 1750 300 600 × 315 × 2560 1.34 0 377 × 45 48,4 7.65 14,995 1,428 460 × 1750 5 11,409 430 × 100 × 1750 225 430 × 240 × 2400 1.37 0 273 × 30 32,3 8.65 7,775 1,468 Proposal technol. ESR ingot 550 × 1750 5 15,830 540 × 100 × 1750 275 520 × 290 × 2750 1.51 3,7 325 × 40 42.8 8.25 12,335 1,284 610 × 1750 5 19,400 600 × 100 × 1750 300 560 × 315 × 2940 1.68 6.7 377 × 45 48.1 7.75 15,462 1,255 NLZ 430 × 1750 5 9,970 430 × 1750 225 410 × 240 × 2920 1,67 4.7 273 × 30 32.1 8.85 7,955 1,254

table 2
Data on the mechanical properties of metal pipes of steel grade 12X1MF, rolled from forged billets, ingots EShP and NLZ according to existing and proposed technologies Method for the production of pipes Type of workpiece Sample Type Temporary resistance σ _in (N / mm ² ) Yield strength σ _0.2 (N / mm ² ) Elongation δ ₅ , (%) Relative Narrowing Ψ, (%) Impact strength KCU (J / cm ² ) no less According to TU 14-3-55R-2001 - transverse 490-686 314 16 45 39 longitudinal 490-686 314 eighteen fifty 49 Existing technology Forged workpiece transverse 547-610 (cf. 578.5) 336-347 (cf. 341.5) 18-23 (cf. 20.5) 48-51 (cf. 49.5) 45-57 (cf. 51.0) longitudinal 537-625 (cf. 581.0) 340-365 (cf. 352.5) 21-25 (cf. 23.0) 55-58 (cf. 56.5) 52-63 (cf. 57.5) Proposed technology
NLZ transverse 538-605 (cf. 571.5) 345-379 (cf. 357.5) 19-21 (cf. 20.0) 47-50 (cf. 48.5) 46-61 (cf. 53.5) longitudinal 540-610 (cf. 575.0) 341-358 (cf. 349.5) 22-24 (cf. 23.0) 56-60 (cf. 58.0) 51-64 (cf. 57.5) ESR ingot transverse 580-635 (cf. 607.5) 347-377 (cf. 362.0) 19-25 (cf. 22.0) 49-56 (cf. 52.5 44-58 (cf. 54.0) longitudinal 585-638 (cf. 611.5) 360-382 (cf. 371.0) 23-26 (cf. 24.5) 58-61 (cf. 59.5) 57-65 (cf. 61.0)

Claims (2)

1. Method for the production of seamless hot-deformed pipes of large and medium diameters in tube rolling plants with pilgrim mills for steam boilers, steam pipelines and manifolds of plants with high and supercritical parameters of steam from electroslag remelting ingots and continuously cast billets, including ingot smelting in electric and open-hearth furnaces based on direct reduction, treatment with liquid synthetic slag in a ladle, forging of ingots with a weft from 2.0 to 3.0 depending on the steel grade, turning turned forging into pipe billets, or continuous casting of steel grades 20 and 15GS treated with synthetic slag, into continuously cast billets, or continuous casting of steel grades 12X1MF, 15X1M1F and 15XM from vacuum or non-vacuum metal treated with synthetic slag, followed by forging them into forgings with a draft of at least 1.5, or the smelting of ingots of these grades of steel by electroslag remelting, heating of the billets and ingots to a plasticity temperature depending on the grade of steel, flashing them into sleeves in oblique rolling mills on a mandrel x, the diameter of which depends on the geometrical dimensions of the sleeves, piercing ingots of electroslag remelting with metal deformation in the piercing mill with a diameter of 8-16% in the piercing mill, rolling on pilgrim mills with hoods, depending on the diameter and wall thickness, calibration and straightening of pipes , while electroslag remelting ingots in the piercing mill are set with the bottom end forward, pipes are rolled on a pilgrim mill from shells sewn from electroslag remelting ingots, with the bottom end forward, and from the shrink part of the ingots, t the pilgrim head, and the hood coefficients on the piercing mill when piercing electroslag remelting ingots and continuously cast billets are determined from the expressions μ _ESR = 1.05 μ _s d _{t ESR} / d _{o ESR} ; μ _nlz ⁼ 1.1μ _s d _{g nlz} / d _{o nlz} , where μ _s - hood on the piercing mill when rolling pipes of a given size from forged billets; d _{g esp} - the current value of the diameters of the ingots of electroslag remelting, mm; d _{o eshp} - diameter of the electroslag remelting ingot, equal to 500 mm; d _{g nlz} - the current value of the diameters of continuously cast billets; d _{o nlz} - the diameter of a continuously cast billet equal to 400 mm 2. The method according to claim 1, characterized in that the bottom of the electroslag remelting ingots is removed by anodic mechanical cutting.