RU2553729C1 - Method of fabrication of seamless hot-rolled machined pipes with extended precision size 530(16 mm from steel grade "08x18h10t" for nuclear power facilities - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: ingots are casted with the size 680×out495×2600±100 mm which are bored out and grinded in work piece ingots with the size 660×out510×2600±100 mm, heated up to the temperature 1260-1270°C, blown with compressed air, into work piece ingots the greasing graphite mix is injected with table salt in the ratio 50/50, weight 1000-1500 g and rolled into process pipes with the size 542×30×5800-6350 mm on a pilger mill with the calibre 550 mm into rolls with the diameter of barrel 1150 mm, on conical mandrels with the diameter 489/491 mm with the coefficient of polishing "К_п" = 7.0-7.5, elongation ratio µ_"п" = 2.8 and diameter crimping Δ = 17.88% then the boring and grinding of the process pipes into commodity seamless hot-rolled pipes with the tolerance by diameter ±0.8% and by wall ±10.0% are performed.

EFFECT: improvement of accuracy of geometrical sizes of pipes, quality of their surface and mechanical properties.

3 cl, 1 tbl

Description

The invention relates to pipe rolling production, and in particular to a method for the production of seamless hot-formed mechanically machined pipes of size 530 × 16 mm of high accuracy from steel grade 08X18H10T for nuclear power facilities at TPU with pilgrim mills from hollow ingots-billets of electroslag remelting, and can be used in the production hollow ingots-billets of electroslag remelting at OJSC "ZMZ" and rolling them into conversion pipes at TPU 8-16 "OJSC" ChTPZ "followed by machining - turning and turning astochkoy in commodity pipes.

In the practice of pipe production, there is a method of manufacturing pipes of large and medium diameters in tube rolling plants with pilgrim mills from steel grades 08X18H12T, 08X10H20T2, including heating a hollow (centrifugal cast) billet and rolling it on a pilgrim mill (TI 158-Tr. TB1-63- 98. "Production of seamless hot-rolled pipes from steel 08Kh18N12T for chemical engineering according to TU14-3-743-78." TI 158 Tp.TB1-6-94. "Production of steel pipes from 08Kh10N20T2 and 08Kh10N16T2 grades for sliding systems according to TU 14-3 -1564-88 ").

The disadvantage of this method is the use of a hollow centrifugal cast billet of low quality due to the lack of firmware technology on the cross helical mills of workpieces with a diameter of more than 460 mm for one firmware with a high content of Cr and Ni, and also due to the low power of the drive of the piercing mill.

Known methods for the production of pipes with a diameter of 530-550 mm with a ratio D / S≤20 on TPU 8-16 ″ with pilgrim mills of OAO ChTPZ from carbon and low-alloy steel grades and pipes with a diameter of 351 mm and more from ESR ingots of hardly deformable steel and alloy grades consisting in the fact that heated ingots and billets are flashed (deformed) in a cross-screw mill in two firmwares (TI 158-Tr. TB1-38-97 "Production of seamless hot-rolled pipes for steam boilers and pipelines according to TU 14-3- 460-75 and TU 14-3-420-75 ". TI 158-Tr. TB 1-56-97" Production of seamless hot of steel pipes of grade 20 steel for the oil refining industry according to TU 14-3-587-77 ", TI 158-Tr. TB1-51-2002" Production of seamless hot-rolled pipes from steel 15X5M according to TU 14-3R-62-2002 "and TI 158-Tr. TB1-53-2002 "Production of seamless hot-rolled pipes from corrosion-resistant steel grades with high surface quality according to TU 14-3R-197-2001").

When piercing blanks with a diameter of more than 460 mm from corrosion-resistant hard-to-deform grades of steel and alloys, due to increased deformations under the influence of tensile stresses, cracks and tears arise on the sleeves, which leads to marriage and does not allow further redistribution, as well as due to increased loads during firmware to stop the engine of the piercing mill and terminate the process. The disadvantage of these methods is that double flashing of ingots and billets (flashing in a cross-helical mill in thick-walled sleeves + reheating + flashing-rolling of thick-walled sleeves in a cross-helical rolling mill in thin-walled sleeves) is performed without considering the technological capabilities of the cross-section mill screw rolling and pilgrim mills, i.e. the maximum possible length of thick-walled sleeves, which can be set in the mill for rolling-rolling the maximum diameter of thin-walled sleeves, which can be issued from the cross-helical rolling mill and the maximum length of sleeves, which can be rolled on a pilgrim mill without crushing the front end of the pipe, which leads to an increase the proportion of technological waste (mass of pilgrim heads and seed ends). Flashing-rolling of sleeves on mandrels with a diameter of 500 mm or more with a ratio D / S≥10 leads to their uneven cooling in the cross-helical rolling mill and increased curvature, which in turn leads to an increased difference in pipes on the pilgrim mill and, as a result, to increased consumption of metal during redistribution (ingot-billet) - finished pipe.

In the pipe industry, there is a known method for the production of seamless hot-deformed machined pipes with a diameter of 530-550 mm from corrosion-resistant hard-deformed steel grades and alloys on TPU 8-16 ″ with pilgrim mills, including casting ESR ingots 610 × 1725 ± 25 mm in size, machining - turning of ingots into ingots-blanks of size 590 ± 5.0 × 1725 mm, drilling in blanks-blanks of a central hole with a diameter of 100 ± 5.0 mm, boring of ingots-blanks to a size of 590 ± 5.0 × vn220 ± 5.0 × 1750 ± 25 mm, heating ingot blanks to pace plasticity ratios, piercing in a cross-helical rolling mill into billet sleeves of size 620 × extra 365 × 1950-2000 mm on a mandrel with a diameter of 350 mm with a diameter rise of δ = 4.0-6.0%, heating the sleeve blanks from cold or hot-rolled to plasticity temperature, firmware-rolling in a cross-helical rolling mill into sleeves of size 660 × 505-515 × 2950-3100 mm on a mandrel with a diameter of 490-500 mm with a rise in diameter of δ = 5.5-6.5%, rolling of sleeves on TPU 8-16 ″ with pilgrim mills into pig tubes with a diameter of 530-550 mm with a ratio D / S = 13.5-15.0 with an allowance for wall thickness under anicheskuyu processing - boring and turning, determine the thickness filmed metal layers in the turning and boring of expression Δ = D / S * K, Δ ₁ = D / S * K ₁ where Δ - thickness of metal removed layer in the turning of hot tubes on the outer surface, mm; Δ ₁ - the thickness of the removed metal layer when boring hot rolled pipes on the inner surface, mm; D is the outer diameter of the hot rolled pipes, mm; S is the wall thickness of the hot rolled pipes, mm; K = 0.5-0.7 - coefficient for determining the thickness of the removed metal layer when turning pipes, large values of which apply to pipes with thicker walls; K ₁ = 0.4-0.5 - coefficient for determining the thickness of the removed metal layer when boring pipes, large values of which relate to pipes with thicker walls (Patent No. 2387501, publ. 07.27.2010. Bull. No. 12).

The disadvantage of this method is that it solves the general issues of the production of seamless hot-deformed pipes from corrosion-resistant hard-deformed steel grades and alloys with a ratio of D / S = 13.5-15.0 for subsequent machining - boring and turning them into commodity pipes with a diameter of 530-550 mm with a wall thickness of more than 20 mm, a length of not more than 4700 mm and does not solve the technological issues of the production of limit and machined pipes of 530 × 16 mm in size from steel grade 08X18H10T of increased length and increased accuracy in diameter and wall for nuclear facilities.

In the pipe industry, there is a known method for the production of seamless hot-deformed long pipes with a diameter of 500 mm and more on TPU with pilgrim mills for steam boilers, steam pipelines and manifolds of plants with high and supercritical steam parameters (patent RU No. 2322315, class B21B 19/04, published 27.11. 2007). The method includes casting hollow ESR ingots with a ratio of diameter to wall thickness D / S = K ₁ , height H = K ₂ D and H ₁ = K ₃ D, where D = 680 is the outer diameter of the hollow ESR ingot, mm; S is the wall thickness of the hollow ESR ingot, mm; K ₁ = 4.8–9.2 is a coefficient whose large values are taken for hollow ingots with a smaller wall thickness; H = 3000-3500 - the height of the hollow ESR ingot for rolling pipes with a ratio of D / S≤20, mm; K ₂ = 4.4-5.2 - the values of the coefficients for rolling pipes with a ratio of D / S≤20, mm; H ₁ = 2000-2100 - the height of the hollow ingot ESR for rolling pipes with a ratio of D / S≥20, mm; K ₃ = 2.9-3.1 - the values of the coefficients for rolling pipes with a ratio of D / S≥20, mm; casting of hollow ingots for rolling boiler pipes with a ratio D / S≥20 with an inner diameter of D _int = D _d ± 5.0, where D _d is the mandrel diameter, mm, turning and boring of hollow ESR ingots into ingots with metal removal of thickness 8 ± 2 mm to remove welding slag and casting defects, heating hollow ingots to a ductile temperature and rolling on a pilgrim mill to pipes with a D / S≥20 ratio with a tolerance of ± 1.0% in diameter and +15 wall thickness, 0 / -10.0%, casting of hollow ingots of ESR for rolling boiler pipes with a ratio of D / S = 20 with an internal diameter trom 300 ± 10 mm, which are machined and bored into hollow ingots with metal removal of 8 ± 2 mm thick to remove welding slag and casting defects, heating hollow ESR ingots to plasticity temperature, piercing-rolling in a cross-screw mill rolling in sleeves on a mandrel with a diameter larger than the mandrel diameter by 15-20 mm and rolling on a pilgrim mill in pipes with a D / S ratio of ≤20 with a diameter tolerance of ± 1.0% and a wall thickness of + 15.0 / -10.0% . The invention provides an increase in the length of pipes with a wall thickness of more than 40 mm by (20-30)%, a reduction in energy consumption, an increase in the performance of pilgrim mills, a decrease in the transverse and longitudinal difference of pipes with a wall thickness of less than 30 mm, and a partial decrease in the expenditure coefficient of the metal due to rolling of pipes with the ratio D / S≥20 of hollow ingots-blanks without piercing ingots-blanks into blanks sleeves and rolling in a cross-helical rolling mill.

One of the main disadvantages of this method is that it is aimed at the production of boiler pipes and does not solve the technological issues of the production of pipes with a size of 530 × 16 mm from steel grade 08X18H10 for nuclear power facilities.

The disadvantages of this method are: the dimensions of the hollow ingots-blanks ESR, which depend on the coefficients K ₁ , K ₂ and K ₃ having large intervals of significance, which makes it difficult to determine the geometric dimensions of hollow ingots-blanks for rolling pipes of the required size; the inner diameters of hollow ingots-billets, taking into account the removal of metal with a bore of 8 mm per side, have underestimated results, which when rolling thick-walled pipes leads to tightening mandrels; rolling of pipes with a wall thickness of more than 30 mm is associated with additional firmware-rolling of hollow ingots-blanks in a cross-helical rolling mill, which is likely to lead to increased curvature and difference in sleeves during uneven heating of ingots-blanks in methodical furnaces, and therefore to the difference in the pipes.

The closest technical solution is a method for the production of hot-rolled commodity and conversion pipes of large and medium diameters from hard-to-deform grades of steel and alloys on pipe rolling plants with pilgrim mills, including casting hollow ingots 2000-3200 mm high on electroslag remelting plants, boring and turning them into ingots workpieces to remove scale and microcracks to a diameter of 400-620 mm with a ratio of diameter to wall thickness D / S = 4.5-7.0, the larger values of which correspond to smaller ingots diameter, heating hollow ingot billets with a ratio D / S = 5.0-7.0 and a height of 2000-2750 mm to ductility temperature, rolling on a pilgrim mill in commodity and conversion pipes with wall thicknesses up to 30 mm, heating ingot billets with a ratio D / S = 4.5-5.5 and a height of 2750-3200 mm to the ductility temperature and rolling them on a pilgrim mill to conversion tubes with a wall thickness of more than 30 mm (patent RU No. 2311980, class B21B 21/00, published on December 10, 2007).

The disadvantage of this prototype, as well as the above analogues, is that it solves the general issues of the production of hot-rolled commodity and conversion pipes of large and medium diameters from hard-to-deform grades of steel and alloys in pipe rolling plants with pilgrim mills and does not solve the technological issues of the production of pipes 530 × 16 in size mm from steel grade 08X181-110 for nuclear facilities.

The objective of the proposed method for the production of seamless hot-formed mechanically machined pipes made of 08Kh18N10T steel is to produce pipes measuring 530 × 16 × 5800-6300 mm with improved surface quality and geometric dimensions for nuclear power facilities.

The technical result is achieved by the fact that in the known method for the production of seamless hot-formed mechanically machined pipes of size 530 × 16 mm of increased accuracy from steel grade 08X18H10T for nuclear facilities, including casting ingots by electroslag remelting size 610 × 1725 ± 25 mm, machining - turning of ingots into ingot blanks measuring 590 ± 5.0 × 1725 ± 25 mm, drilling into ingot blanks of a central hole with a diameter of 100 ± 5 mm, boring ingot blanks to a size of 590 ± 5.0 × vn220 ± 5.0 × 1725 ± 25 mm heating tkov blanks to plasticity temperature, firmware ingots-mill blanks in a helical rolling in the sleeve-blank size of 620 × × vn365 1950-2090 mm diameter elevation δ _pr from 4.20 to 5.88%, and _{so forth} from an extract μ 1,146 to 1,192, heating of the sleeve blanks from a hot or cold embankment to a temperature of ductility, firmware-rolling of the sleeve blanks in a cross-helical rolling mill into sleeves of size 650 × H505 × 2870-3070 mm with a diameter rise of δ _p = 4.84 % stretch μ _p = 1.47, for the rolling of sleeves in pilger 558 mm caliber, embedded in rolls with a diameter Boch and 1045 mm, in steel making pipe size 550 × 40 mm × 4700-5100 polishing coefficient K _n = 3,5-4,0, hoods coefficient μ _n = 2,05 and reducing the diameter of Δ _n = 15,39%, machining - boring and turning into commodity pipes measuring 530 ± 6.6 × 16 ± 2.0 × 4700-5100 mm with a roughness of the turned outer surface Ra of not more than 6.3 microns, and of bored - not more than 2.5 microns, ingots electroslag remelting is cast hollow with a size of 680 × vn495 × 2600 ± 100 mm, ingots are bored and turned into ingots-blanks of 660 × vn510 × 2600 ± 100 mm in size, ingots-billets are heated to a temperature of 1260-1270 ° C, and From the furnace to the ingot trolley, ingot billets are blown with compressed air, lubricant is injected into the ingot billets - a mixture of graphite with 50/50 common salt weighing 1000-1500 g and a crane is fed to the entrance side of the piligim mill, hollow ingots are rolled on the pilgrim mill in a caliber of 550 mm, cut into rolls with a barrel diameter of 1150 mm, into conversion tubes of 542 × 30 × 5800-6350 mm in size on cone mandrels with a diameter of 489/491 mm with a polishing coefficient K _n = 7.0-7.5, an extraction coefficient µ _n = 2.8 and compression in diameter Δ = 17.88%, conversion pipes are bored and turned 530 × 16 × 5800-6350 mm in commodity seamless hot-deformed pipes with a diameter tolerance of ± 0.8% and a wall of ± 10.0%, hollow ingots are placed on the grate of the furnace in a row in the amount of 5-6 pieces, heated without tilting for 40-50 minutes, then heated at a speed of 3.0-3.5 ° C per minute to 1260-1270 ° C with uniform tilting from 22 windows to 4 windows in 14-16 minutes at an angle of 200-220 °, maintained at a temperature of 1260-1270 ° C for 50-60 minutes with a uniform pitching from the 4th window to the furnace pit after 12-15 minutes and issued from the furnace pit with a temperature of 1260-1270 ° C, seed during rolling conversion tubes are produced with a smooth increase in feed from m 0 to 25-30 mm, the steady rolling process is carried out with a feed value of m = 25-30 mm, and during rolling-rolling of the pilgrim head, the feed rate is smoothly reduced to m = 8-10 mm.

Comparative analysis with the prototype showed that the inventive method for the production of seamless hot-deformed machined pipes of 530 × 16 mm in size with increased accuracy from 08Kh18N10T steel for nuclear power facilities differs from the well-known one in that electroslag remelting ingots are cast by hollow 680 × vn495 × 2600 ± 100 mm , the ingots are bored and turned into ingots-blanks with a size of 660 × vn510 × 2600 ± 100 mm, the ingots-blanks are heated to a temperature of 1260-1270 ° C, they are delivered from the furnace to an ingot cart, the ingots-blanks are blown compress grease is injected into the ingot blanks - a mixture of graphite with 50/50 common salt weighing 1000-1500 g and a crane are fed to the inlet side of the pilgrim mill, hollow ingot blanks are rolled on a pilgrim mill in a caliber of 550 mm cut into rolls with a diameter barrels 1150 mm, into conversion pipes 542 × 30 × 5800-6350 mm in size on cone mandrels with a diameter of 489/491 mm with a polishing coefficient K _n = 7.0-7.5, a drawing coefficient µ _n = 2.8 and compression in diameter Δ = 17.88%, conversion pipes are bored and turned into commodity seamless hot-formed pipes p 530 × 16 × 5800-6350 mm with a tolerance of ± 0.8% in diameter and ± 10.0% in the wall, hollow ingots are placed on the grate of the furnace in a row in the amount of 5-6 pieces, heated without tilting for 40 -50 minutes, then heated at a speed of 3.0-3.5 ° C per minute to 1260-1270 ° C with uniform pitching from 22 windows to 4 windows after 14-16 minutes at an angle of 200-220 °, kept at a temperature of 1260 -1270 ° C for 50-60 minutes with a uniform pitching from the 4th window to the furnace pit after 12-15 minutes and dispensed from the furnace pit with a temperature of 1260-1270 ° C, the seed during rolling of the conversion pipes is made with a smooth increase in feeds m from 0 to 25-30 mm, steady rolling process to produce the feed quantity m = 25-30 mm, while the run-dokatka pilger-head feed rate is gradually reduced until m = 8-10 mm. Thus, these differences allow us to conclude that the criterion of "inventive step" is met.

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

The method has been tested on a pipe-rolling installation with 8-16 ′ ′ pilgrim mills of ChTPZ OJSC when rolling pig tubes of 542 × 30 × 6000 mm in size from steel grade 08Kh18N10T-Sh for machining to produce marketable pipes of 530 × 16 × 6000 mm in height and surface quality for nuclear facilities.

The data on the production of seamless hot-deformed machined pipes of 530 × 16 mm in size from steel grade 08X18H10T for nuclear power facilities according to the existing and proposed technologies are given in Table 1.

According to the existing technology, 5 ESR ingots with a size of 610 × 1725 mm with a total weight of 19.786 tons were set into production, which were turned into blanks with a size of 590 × 1725 mm at OAO ZMZ. Billets of billets at ChTPZ OJSC were drilled to a diameter of 100 ± 5 mm, and then bored to a size of 590 × vn220 × 1725 mm. The total weight of the ingot billets after boring was 16.03 tons. The ingot billets were heated to a plasticity temperature in a methodical furnace and stitched in a cross-screw mill on a mandrel with a diameter of 350 mm into blanks 620 × v365 × 2015 mm in diameter with a hood µ _CR = 1,169 and the rise of the sleeve blanks in diameter δ _CR = 5.08%. The billet sleeves from a cold embankment were heated to ductility temperature and stitched — rolled out in a helical rolling mill on a mandrel with a diameter of 490 mm into sleeves of 650 × vn505 × 2960 mm in size with a hood µ _p = 1.47 and a diameter rise of δ _p = 4.84%. The sleeves were rolled on a pilgrim mill in rolls with a barrel diameter of 1045 mm in a caliber of 558 mm with a polishing coefficient K _n = 3.5-4.0 into pig tubes of 550 × 40 × 4870 mm in size with a hood µ _n = 2.05 and compression diameter Δ _n = 15.39%. Conversion pipes were bored and turned into commodity pipes measuring 530 × 16 × 4700 mm. Accepted 23.5 m of pipes with a total weight of 4.127 tons. The expenditure coefficient of the metal of the ESR ingot - commodity pipe - was 4.127, and the expenditure coefficient of the metal of the ingot-blank of the ESR - commodity pipe was 3.343.

According to the proposed method (technology), 5 hollow ESR ingots of 680 × vn495 × 2600 mm in size were cast at ZMZ OJSC. The mass of hollow ESR ingots amounted to 17.525 tons. At ZMZ OJSC, the ingots were bored and turned into hollow ingots-blanks measuring 660 × vn610 × 2600 mm. The mass of hollow ingot blanks was 14.149 tons. At Chelyabinsk Pipe Rolling Plant, hollow ingot blanks were heated in a method furnace to a temperature of 1269–1280 ° C. The process of heating hollow ingots-blanks was carried out in accordance with paragraph 2 of the claims. Hollow ingot blanks were dispensed from the furnace onto an ingot trolley, purged with compressed air. A lubricant in the form of a mixture of graphite with sodium chloride weighing 1000-1500 was set inside the ingot billets. The ingot billets were fed by a crane to the inlet side of the pilgrim mill and rolled in a caliber of 550 mm, cut into rolls with a barrel diameter of 1150 mm, into transfer tubes of size 542 × 30 × 6000 mm on conical mandrels with a diameter of 489/491 mm with a polishing coefficient K _n = 7.0-7.5, a drawing coefficient µ = 2.8 and a diameter reduction Δ = 17.88%. Pipe rolling on a pilgrim mill was made in accordance with paragraph 3 of the claims. 30 m pipes were delivered with a tolerance of ± 0.8% in diameter and ± 10.0% in wall. The expenditure coefficient of the metal hollow ingot ESR - commodity pipe - amounted to 2.864, and the expenditure coefficient of the metal hollow ingot-blank ESR - commodity pipe - amounted to 2,312.

Using the proposed method allowed to master at TPU 8-16 ″ with pilgrim mills from hollow ingots-blanks EShP of 660 × vn510 × 2600 mm in size the production of seamless hot-deformed conversion tubes with a size of 542 × 30 × 6000 mm for subsequent machining-boring and turning them into commodity 530 × 16 × 6100 mm in size with increased requirements for geometric dimensions, surface quality and mechanical properties, reduce the expenditure coefficient of the metal by 1031 kg per ton of commodity pipes and increase their length by 30%, and the investigator but to reduce their cost.

Data on the production of seamless hot-deformed machined pipes of 530 × 16 mm in size from steel grade 08X18H10T for nuclear power facilities according to the existing and proposed technologies are given in Table 1.

Claims (3)

1. Method for the production of seamless hot-formed mechanically machined pipes of size 530 × 16 × 5800-6350 mm of increased accuracy from 08Kh18N10T steel for nuclear power facilities, including casting of hollow ingots of electroslag remelting of 680 × v495 × 2600 ± 100 mm in size, which are bored and turned into ingot blanks with a size of 660 × bh510 × 2600 ± 100 mm, heated to a temperature of 1260-1270 ° C, purged with compressed air, grease in the form of a mixture of graphite with sodium chloride in a ratio of 50/50 weighing 1000-1500 g and rolled in front flax tube size 542 × 30 mm × 5800-6350 pilger caliber rolls 550 mm in diameter with the barrel 1150 mm, a diameter at the tapered Dornach 489/491 mm polishing coefficient K _n = 7.0-7.5, reduction ratio µ _p = 2.8 and a compression in diameter Δ = 17.88%, after which a boring is made - turning the conversion pipes into commodity seamless hot-deformed pipes with a tolerance of ± 0.8% in diameter and ± 10.0% in wall. 2. The method according to claim 1, characterized in that the heating of the hollow ingots-billets is carried out by placing them on the grate of the furnace in a row in the amount of 5-6 pieces, heating without canting for 40-50 minutes, heating at a speed of 3.0 -3.5 ° C per minute to 1260-1270 ° C with uniform pitching from 22 windows to 4 windows in 14-16 minutes at an angle of 200-220 ° and holding at a temperature of 1260-1270 ° C for 50-60 minutes with uniform pitching from the 4th window to the furnace pit after 12-15 minutes. 3. The method according to claim 1, characterized in that the rolling tubes are produced at the seed stage with a smooth increase in the feed m from 0 to 25-30 mm, at the stage of the steady-state process, with the feed value m = 25-30 mm, and at the stage running-in - rolling of the pilgrim head feed rate m gradually decreases to 8-10 mm.