CN114749508B - Large-caliber austenitic stainless steel seamless pipe and manufacturing method and application thereof - Google Patents
Large-caliber austenitic stainless steel seamless pipe and manufacturing method and application thereof Download PDFInfo
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- 229910000963 austenitic stainless steel Inorganic materials 0.000 title claims abstract description 112
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 31
- 238000011282 treatment Methods 0.000 claims abstract description 135
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- 238000010622 cold drawing Methods 0.000 claims abstract description 68
- 238000000034 method Methods 0.000 claims abstract description 40
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- 238000009849 vacuum degassing Methods 0.000 claims abstract description 13
- 238000000265 homogenisation Methods 0.000 claims abstract description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000007664 blowing Methods 0.000 claims abstract description 10
- 239000001301 oxygen Substances 0.000 claims abstract description 10
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 73
- 238000010438 heat treatment Methods 0.000 claims description 56
- 239000006104 solid solution Substances 0.000 claims description 25
- 239000000243 solution Substances 0.000 claims description 25
- 229910001220 stainless steel Inorganic materials 0.000 claims description 25
- 239000010935 stainless steel Substances 0.000 claims description 25
- 230000009467 reduction Effects 0.000 claims description 20
- 239000012298 atmosphere Substances 0.000 claims description 12
- 238000005520 cutting process Methods 0.000 claims description 12
- 238000001816 cooling Methods 0.000 claims description 9
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- 230000003746 surface roughness Effects 0.000 claims description 5
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 abstract description 19
- 229910052708 sodium Inorganic materials 0.000 abstract description 19
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- 239000012300 argon atmosphere Substances 0.000 description 7
- 239000013078 crystal Substances 0.000 description 7
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
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- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
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- ALKZAGKDWUSJED-UHFFFAOYSA-N dinuclear copper ion Chemical compound [Cu].[Cu] ALKZAGKDWUSJED-UHFFFAOYSA-N 0.000 description 1
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
- B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/02—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
- B21B1/024—Forging or pressing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/02—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling heavy work, e.g. ingots, slabs, blooms, or billets, in which the cross-sectional form is unimportant ; Rolling combined with forging or pressing
- B21B1/026—Rolling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C1/00—Manufacture of metal sheets, metal wire, metal rods, metal tubes by drawing
- B21C1/16—Metal drawing by machines or apparatus in which the drawing action is effected by other means than drums, e.g. by a longitudinally-moved carriage pulling or pushing the work or stock for making metal sheets, bars, or tubes
- B21C1/22—Metal drawing by machines or apparatus in which the drawing action is effected by other means than drums, e.g. by a longitudinally-moved carriage pulling or pushing the work or stock for making metal sheets, bars, or tubes specially adapted for making tubular articles
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/068—Decarburising
- C21C7/0685—Decarburising of stainless steel
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
- C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
- C22B9/16—Remelting metals
- C22B9/18—Electroslag remelting
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L9/00—Rigid pipes
- F16L9/02—Rigid pipes of metal
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
The invention provides a large-caliber austenitic stainless steel seamless pipe, a manufacturing method and application thereof, wherein the outer diameter of the large-caliber austenitic stainless steel seamless pipe is 610-914 mm, and the diameter-wall ratio is more than 45; according to the preparation method, a first austenitic stainless steel blank is obtained through a steelmaking process of electric furnace steelmaking, vacuum oxygen blowing decarburization, vacuum degassing, casting and electroslag remelting, and then a series of treatment processes of homogenization, upsetting drawing, forging, hot rolling, hot expansion, cold drawing and the like are carried out, so that the large-caliber austenitic stainless steel seamless pipe with a wide size range, comprehensive performance and metallographic structure meeting the technical protocol requirements of a safety-level high-temperature sodium pipeline in a sodium-cooled fast reactor is obtained. The manufacturing method has compact, flexible and convenient overall process, high yield of products and low energy consumption; the large-caliber austenitic stainless steel seamless pipe is used for a sodium-cooled fast neutron reactor of a nuclear power system.
Description
Technical Field
The invention relates to the technical field of seamless steel pipes, in particular to a large-caliber austenitic stainless steel seamless pipe, and a manufacturing method and application thereof.
Background
A Sodium-cooled fast neutron reactor (Sodium-cooledFastReactor, SFR) is a fast neutron breeder reactor, which uses liquid Sodium as a coolant. The sodium-cooled fast reactor is the main reactor type of a fourth generation advanced nuclear energy system, can greatly improve the utilization rate of natural uranium resources and effectively solves the technical problem that nuclear waste is difficult to treat. The service working condition of the sodium-cooled fast reactor is extremely harsh, and the sodium-cooled fast reactor is in harsh environments such as high temperature, corrosion, irradiation and the like for a long time, so that the requirement on stainless steel pipeline materials which are in service under the working condition is very high. The design life of the safe two-stage and three-stage high-temperature sodium pipelines in the sodium-cooled fast reactor is not less than 40 years, and the safe two-stage and three-stage high-temperature sodium pipelines have high requirements on the metallographic structure and the comprehensive performance of the stainless steel pipes. Meanwhile, in order to meet the increasing installed capacity, the diameter of the pipeline is increasingly larger.
The traditional hot punching, cold rolling, cold drawing/hot extrusion, cold rolling, hot extrusion, cold rolling and cold drawing processes cannot meet the requirements of the size specification, the metallographic structure and the comprehensive performance of a high-temperature sodium pipeline in a sodium-cooled fast reactor. The maximum outer diameter of the stainless steel pipe rolled by the domestic stainless steel cold rolling unit is 720mm, and the pipe specification required by the sodium-cooled fast reactor cannot be achieved. The deformation of each pass of the cold expansion process is small, and the stainless steel seamless steel pipe with the outer diameter larger than 720mm is manufactured by adopting the cold expansion process, so that the stainless steel seamless steel pipe is usually required to be subjected to cold expansion in multiple passes, each cold expansion process is required to be subjected to annealing treatment, the production efficiency is low, and the energy consumption of multiple heat treatments is high. The pierced billet produced by hot extrusion has small diameter-wall ratio, low dimensional accuracy and large metal loss, is difficult to produce large-caliber thin-wall seamless steel pipes, and because the crystal grains at the end part of the pierced billet after hot extrusion are coarse, the metallographic structure of the finished product is difficult to reach the standard even through subsequent cold rolling or cold drawing, the cutting amount of the end part of the pierced billet is large, and the utilization rate of materials is reduced.
In addition, the prior art manufacturing process cannot effectively ensure the grain size grade and uniformity required by the high-temperature sodium stainless steel seamless tube. A significant problem is the presence of edge grain growth or core coarse grain in the blank, intermediate or product. Edge grain growth is generated by continuous small deformation in subsequent processing because the blank is not forged, or is forged but the forging ratio is insufficient or the final forging temperature is low; the coarse grain at the core is caused by insufficient processing deformation, insufficient breaking of crystal grains or continuous high-temperature large deformation, and growth of the crystal grains.
CN104368623a discloses a method for producing a large-caliber stainless steel seamless steel pipe, which uses a method of punching, reaming and wall reducing of 508 machine sets to produce the large-caliber stainless steel seamless steel pipe, wherein the outer diameter of the stainless steel seamless steel pipe is 380-650 mm, the wall thickness is 20-60 mm, and the length is 3000-8000 mm. However, the method does not perform forging treatment, cold rolling or cold drawing processing and solution treatment on the blank, and it is difficult to ensure that the obtained large-caliber stainless steel seamless steel pipe meets the grain size and performance requirements required by a sodium-cooled fast reactor system.
CN107803411a discloses a method for manufacturing a large-diameter seamless steel pipe of super austenitic stainless steel, which uses a hollow ingot cylinder blank to be subjected to diameter expansion and perforation by a bacterial perforation machine, then uses a conical roller oblique rolling mill set to carry out secondary oblique rolling and diameter expansion, and uses a cold rolling mill set to carry out twice cold rolling to manufacture the large-diameter seamless steel pipe of super austenitic stainless steel. However, the hollow ingot cylindrical tube blank obtained by direct casting through the method has loose structure, micro component segregation caused by macrosegregation and alloy element selective crystallization can cause the ferrite content to exceed the standard, the grain size grade and uniformity of the finished tube and the comprehensive performance of the finished tube can be seriously influenced, the taper roller oblique rolling and expanding rolling is lower, and cracks are easily generated on the inner surface of the pierced tube during the piercing and rolling process.
Therefore, in order to meet the increasing requirements of a nuclear power system on the large-caliber austenitic stainless steel seamless pipe, development of a production process which is economical, flexible, energy-saving, environment-friendly, practical, efficient and capable of preparing and obtaining the large-caliber austenitic stainless steel seamless pipe with high precision is urgently needed.
Disclosure of Invention
In view of the problems existing in the prior art, the invention provides a large-caliber austenitic stainless steel seamless pipe and a manufacturing method and application thereof, wherein an austenitic stainless steel blank with components and structures meeting requirements is obtained through a steelmaking process of electric furnace steelmaking, vacuum oxygen blowing decarburization, vacuum degassing, casting and electroslag remelting, and then a series of treatment processes of homogenization, upsetting drawing, forging, hot rolling, hot expansion, cold drawing and the like are carried out, so that the large-caliber austenitic stainless steel seamless pipe with wide size range, comprehensive performance and metallographic structure meeting the technical protocol requirements of a safety-level high-temperature sodium pipeline in a sodium-cooled fast reactor is obtained.
To achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a large-caliber austenitic stainless steel seamless pipe, wherein the outer diameter of the large-caliber austenitic stainless steel seamless pipe is 610-914 mm, and the diameter-wall ratio is more than 45.
The large-caliber austenitic stainless steel seamless pipe has the advantages of wide size range, high geometric precision, good internal and external surface quality, ferrite content of less than 1%, and capability of meeting the technical protocol requirements of a safety-level high-temperature sodium pipeline in a sodium-cooled fast reactor, along with tensile property, bending property, lasting strength property, fatigue resistance, inter-crystal corrosion resistance and the like.
The outer diameter of the large-caliber austenitic stainless steel seamless pipe is 610-914 mm, for example, 610mm, 630mm, 660mm, 711mm, 720mm, 762mm, 813mm, 864mm or 914mm; the radial wall ratio is greater than 45 and may be 46, 49, 50, 55, 60, 80 or 90, for example.
Preferably, the surface roughness of the large caliber austenitic stainless steel seamless pipe is lower than 6.3 μm, for example, 6.2 μm, 6 μm, 5.8 μm, 5.5 μm, 5 μm, 4 μm, 3 μm or 1 μm.
Preferably, the ferrite content of the large caliber austenitic stainless steel seamless tube is less than 1%, for example, 0.9%, 0.7%, 0.6%, 0.5%, 0.3%, 0.2% or 0.1%.
Preferably, the large-caliber austenitic stainless steel seamless tube has a grain size of 5 or more, for example, 5, 6 or 7 grades; the difference between the maximum level and the minimum level of the grain size is not more than 2 levels, and the mixed crystal phenomenon is avoided.
In a second aspect, the present invention also provides a method for manufacturing a large-caliber austenitic stainless steel seamless pipe, the method comprising the steps of:
(1) The stainless steel water is subjected to primary refining by an electric furnace, vacuum oxygen blowing decarburization treatment and vacuum degassing treatment in sequence, and then is cast to obtain an electrode ingot;
(2) Electroslag remelting is carried out on the electrode ingot in an inert atmosphere to obtain a first austenitic stainless steel blank;
(3) Carrying out homogenization treatment and upsetting and drawing treatment on the first austenitic stainless steel blank, and sequentially carrying out cooling, peeling and positioning hole punching treatment to obtain a second austenitic stainless steel blank;
(4) The second austenitic stainless steel blank is subjected to forging treatment, first solid solution treatment and hot rolling in sequence to obtain a pierced billet;
(5) Sequentially carrying out second solid solution treatment, first cold drawing, heat expansion treatment and third solid solution treatment on the pierced billet to obtain a capillary;
(6) And sequentially carrying out second cold drawing and fourth solution treatment on the capillary tube to obtain the large-caliber austenitic stainless steel seamless tube.
According to the manufacturing method of the large-caliber austenitic stainless steel seamless pipe, firstly, nonmetallic inclusion, impurity elements, residual elements and harmful elements are effectively controlled through a steelmaking process of electric furnace steelmaking, vacuum oxygen blowing decarburization, vacuum degassing, casting and electroslag remelting, so that the purity of the stainless steel is ensured, strict chemical component requirements can be met, the cutting amount of an electroslag ingot is greatly reduced, and the yield of a final product is improved; then, homogenizing the first austenitic stainless steel blank to eliminate micro segregation caused by high alloy element selective crystallization, reduce the component difference between the dendrite and the inter-dendrite of the as-cast structure, obtain a structure with uniform components, and ensure that the ferrite content reaches the standard; and then upsetting and drawing the first austenitic stainless steel blank, fully crushing coarse grains, eliminating looseness, shrinkage cavity and anisotropism, and rapidly cooling after forging to pass through a sensitization temperature zone so as to prevent carbide from precipitating along a grain boundary or the grains at the center of the blank from growing. According to the invention, the forging treatment and the hot expansion treatment are matched to prepare the high-temperature sodium pipeline with the outer diameter of 610-914 mm, and the metallographic structure and the comprehensive performance meet the technical requirements of safe two-stage and three-stage high-temperature sodium pipelines in the sodium-cooled fast reactor. The manufacturing method of the invention carries out cold drawing treatment after the hot expansion treatment, further refines crystal grains by utilizing deformation generated in the cold drawing process, and improves the dimensional accuracy of the final product. The manufacturing method disclosed by the invention has the advantages of compact, flexible and convenient overall process, high yield of products, low energy consumption and suitability for large-scale popularization and application.
The casting of the electrode ingot obtained in step (1) of the present invention is performed under an inert atmosphere comprising any one or a combination of at least two of a nitrogen atmosphere, an argon atmosphere, or a helium atmosphere, wherein typical but non-limiting combinations include combinations of a nitrogen atmosphere and an argon atmosphere, combinations of a nitrogen atmosphere and a helium atmosphere, combinations of an argon atmosphere and a helium atmosphere, or combinations of three of a nitrogen atmosphere, an argon atmosphere, and a helium atmosphere.
Preferably, the electroslag ingot is cut end to end by an amount not greater than 3.0% of nominal diameter, for example, 3.0%, 2.9%, 2.8%, 2.5%, 2.3%, 2.1%, 2.0%, 1.5%, 1.0% or 0.5%; and not more than 10mm, for example, may be 10mm, 9mm, 8mm, 7mm, 6mm, 5mm, 3mm, 2mm or 1mm.
Preferably, the homogenization treatment in the step (3) is performed in three stages, wherein the first stage is a slow heating stage, the temperature is raised to 550-600 ℃ at a heating rate of 80-90 ℃/h, and the temperature is kept for 1-2 h, so that the internal temperature of the first stainless steel blank is uniform, and the preparation is made for the rapid heating in the second stage; the second stage is a rapid heating stage, wherein the temperature is raised to 950-1000 ℃ at a heating rate of 130-150 ℃/h, and the temperature is kept for 2-3 h, so that the first stainless steel blank is thoroughly heated, and carbide precipitation is prevented; the third stage is a high-temperature diffusion stage, the temperature is raised to 1200-1230 ℃ at the heating rate of 90-100 ℃/h, and the temperature is kept for 40-50 h, so that the elements are fully diffused, the element segregation of the as-cast structure dendrite and the dendrite is eliminated, the structure is uniform, and the ferrite content is ensured to be qualified. The larger the diameter of the first stainless steel blank, the longer the heat preservation time at each stage. And then, when the first stainless steel blank is cooled to 1160-1190 ℃ along with the furnace, upsetting and drawing out are carried out.
The temperature rising rate of the first stage of the homogenization treatment is 80-90 ℃ per hour, for example, 80, 82, 85, 88, 89 or 90 ℃ per hour; heating to 550-600 deg.c, such as 550 deg.c, 560 deg.c, 570 deg.c, 580 deg.c, 590 deg.c or 600 deg.c; the heat preservation time is 1 to 2 hours, for example, 1 hour, 1.3 hours, 1.5 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours.
The temperature rising rate of the second stage of the homogenization treatment is 130-150 ℃ per hour, for example, 130, 135, 138, 140, 145 or 150 ℃ per hour; heating to 950-1000 deg.c, such as 950 deg.c, 960 deg.c, 970 deg.c, 980 deg.c, 990 deg.c or 1000 deg.c; the heat preservation time is 2 to 3 hours, for example, 2 hours, 2.3 hours, 2.5 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3 hours.
The temperature rising rate of the third stage of the homogenization treatment is 90-100 ℃ per hour, for example, 90, 92, 95, 98, 99 or 100 ℃ per hour; heating to 1200-1230 ℃, such as 1200-1210 ℃, 1215 ℃, 1220 ℃, 1225 ℃ or 1230 ℃; the heat preservation time is 40-50 h, for example, 40h, 41h, 43h, 45h, 48h, 49h or 50h.
Preferably, the upsetting and drawing process of step (3) is performed in a rapid forging machine.
Preferably, the forging temperature before the upsetting drawing process is 1160 ℃ to 1190 ℃, for example, 1160 ℃, 1165 ℃, 1170 ℃, 1175 ℃, 1180 ℃, 1185 ℃ or 1190 ℃. The high-temperature ferrite is easy to generate when the forging temperature is too high, the precipitated harmful phase influences the plasticity of the material, and the cracking is easy to occur in the upsetting and drawing process.
Preferably, the upsetting elongation process is not less than 3 passes, and may be 3 passes, 4 passes, 5 passes, 6 passes, 7 passes, or 8 passes, for example.
Preferably, the total forging ratio after the upsetting drawing process is greater than 5, and may be 6, 7, 8, 9, 10, 11 or 12, for example.
In the upsetting and drawing process, when the temperature of the first austenitic stainless steel blank is lower than 860 ℃, furnace returning heating is carried out again, the initial forging temperature of the last upsetting and drawing process is controlled to be not higher than 1100 ℃, the final forging temperature is controlled to be not lower than 860 ℃, and the blank is forged and formed.
Preferably, the cooling of step (3) comprises: transferring the first austenitic stainless steel blank subjected to upsetting and drawing treatment to water with the initial temperature not exceeding 25 ℃ for cooling in 60 seconds.
Preferably, the second austenitic stainless steel blank of step (4) is heated to 1190 ℃ to 1210 ℃ in a heating furnace and then subjected to forging treatment, and may be 1190 ℃, 1193 ℃, 1195 ℃, 1197 ℃, 1200 ℃, 1205 ℃, 1208 ℃ or 1210 ℃.
Preferably, the forging process is performed in a radial forging machine. And (3) carrying out enveloping forging on the second austenitic stainless steel blank at the same time according to the frequency of not less than 120 times/min by a plurality of hammerheads of the radial forging machine, and compensating the heat taken away by cooling water in the core rod by the heat generated by forging by controlling the integral deformation and the forging frequency, so as to realize isothermal forging and ensure one-fire forming. In the forging process, the second austenitic stainless steel blank is forged while rotating, so that the radial forging pierced billet with uniform wall thickness and good inner and outer surface quality can be obtained.
Preferably, the forging process has a total elongation of greater than 5, which may be, for example, 6, 7, 8, 9, 10, 11 or 12.
The forging treatment of the invention promotes the metal to be completely and dynamically recrystallized for many times under the conditions of specific temperature 1190-1210 ℃ and total elongation coefficient more than 5, eliminates segregation and achieves the purposes of uniform structure and grain refinement.
Preferably, the temperature of the first solution treatment is 1050 ℃ to 1150 ℃, and may be 1050 ℃, 1055 ℃, 1060 ℃, 1065 ℃, 1070 ℃, 1090 ℃, 1100 ℃, or 1150 ℃, for example.
The first solution-treated, diameter-forged blank is preferably heated to 1170 to 1200 ℃ and then hot-rolled, and may be 1170 ℃, 1175 ℃, 1180 ℃, 1185 ℃, 1190 ℃ or 1200 ℃.
The hot rolling of the invention is to use a conical roller skew rolling mill unit to carry out the wall-reducing hot rolling, improve the rolling compression ratio and promote the full breaking of large grains.
The second solid solution treatment is carried out after hot rolling, and the main function of the invention is to obtain a single uniform austenite structure, and to soften the hot rolled pierced billet to the greatest extent, thereby facilitating the first cold drawing treatment.
Preferably, the temperature of the second solution treatment is 1050 ℃ to 1150 ℃, and may be 1050 ℃, 1055 ℃, 1060 ℃, 1065 ℃, 1070 ℃, 1090 ℃, 1100 ℃, or 1150 ℃, for example.
The first cold drawing is carried out after the first lubricant is coated on the inner wall of the pierced billet, which is a conventional operation in the field, and the lubricating agent of the tallow lime can be adopted, which is well known to the person skilled in the art.
In the invention, a 1600t hydraulic precision cold drawing unit is used for carrying out first cold drawing on the pierced billet after the first lubricant is smeared.
Preferably, the speed of the first cold drawing in the step (5) is 0.8-1.0 m/min, for example, 0.8m/min, 0.85m/min, 0.88m/min, 0.9m/min, 0.95m/min, 0.98m/min or 1.0m/min.
Preferably, the reduction of the outer diameter of the pierced blank after the first cold drawing is 2-6 mm, and may be 2mm, 2.5mm, 3mm, 3.6mm, 4mm, 4.2mm, 5mm or 6mm, for example.
Preferably, the wall thickness of the pierced blank after the first cold drawing is reduced by 1.5-3.0 mm, for example, 1.5mm, 1.8mm, 2.0mm, 2.2mm, 2.5mm, 2.7mm or 3.0mm.
The invention also needs to check the inner and outer surfaces of the pierced billet, and if visual appearance defects exist, the pierced billet is removed by a local polishing mode.
The invention carries out heat expansion treatment after the second lubricant is smeared on the inner wall of the pierced billet, and the adopted second lubricant is a mixed solution prepared by powdery graphite powder with the particle size of 60-70 mu m and crystalline flake graphite powder with the particle size of 85-95 mu m and water according to the mass ratio of 1:2:3.
Preferably, the temperature of the thermal expansion treatment is 860 ℃ to 1000 ℃, and may be 860 ℃, 880 ℃, 890 ℃, 900 ℃, 950 ℃, 980 ℃ or 1000 ℃, for example.
Preferably, the expansion ratio of the thermal expansion treatment is 1.1 to 1.4, and may be, for example, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.38 or 1.4.
Preferably, the pipe expanding advancing speed of the thermal expansion treatment is 20-70 mm/min, for example, 20mm/min, 25mm/min, 30mm/min, 35mm/min, 40mm/min, 50mm/min, 60mm/min, 65mm/min or 70mm/min.
The heat expansion treatment is intermediate frequency heat expansion treatment, the frequency of intermediate frequency current is 500-1000 Hz, and generally, the larger the outer diameter of a steel pipe is, the thicker the wall thickness is, and the lower the intermediate frequency is selected.
The temperature, the diameter expansion ratio and the pipe expansion advancing speed of the hot expansion treatment are determined according to the material of the pierced billet, the wall thickness of the pierced billet and the wall thickness of the pierced billet after the hot expansion, and the conical core rod used for the hot expansion treatment is a main body material of the conical core rod, wherein the heat-resistant stainless steel with the carbon content close to that of the pierced billet is selected according to the material of the pierced billet and the temperature of the hot expansion treatment.
Preferably, the length of the induction heating coil in the heat expansion process covers the deformation zone of the pierced blank and extends 300-500 mm each in the front-rear direction, and may be 300mm, 350mm, 380mm, 400mm, 470mm, 490mm or 500mm, for example.
Preferably, the outer diameter of the induction heating coil in the heat expansion treatment is 80-120 mm larger than the outer diameter of the thermally expanded pierced billet, and may be 80mm, 85mm, 90mm, 95mm, 100mm, 110mm or 120mm, for example.
In the process of heat expansion treatment, the temperature change range of the deformation zone of the pierced billet is stabilized in the range of-5 ℃ to 5 ℃ by a PLC intelligent constant temperature system, and can be-5 ℃, -4 ℃, -3 ℃, -2 ℃, -1 ℃, 0 ℃, 1 ℃, 3 ℃, 4 ℃ or 5 ℃ for example.
According to the invention, the material of the core rod for the thermal expansion treatment and the size of the induction heating coil are selected, the temperature, the diameter expansion ratio and the pipe expansion propelling speed of the thermal expansion treatment are strictly controlled, and the thermal expansion treatment is successfully applied to the production of the austenitic stainless steel seamless pipe, so that the large-diameter variable rate processing of the large-caliber austenitic stainless steel seamless pipe is realized, and the production efficiency and the metal utilization rate are improved.
Preferably, the temperature of the third solution treatment is 1050 to 1150 ℃, and may be 1050 ℃, 1055 ℃, 1060 ℃, 1065 ℃, 1070 ℃, 1090 ℃, 1100 ℃, or 1150 ℃, for example.
Preferably, the second cold drawing in step (6) is performed in 1-3 passes, for example, 1 pass, 2 passes or 3 passes may be performed.
The invention carries out solution treatment before cold drawing twice, and aims to soften the pierced billet to the maximum extent and facilitate cold drawing operation.
Preferably, the last cold drawing in the second cold drawing adopts equal-diameter cold drawing, and other passes adopt reducing cold drawing.
Preferably, the reduction of the outer diameter of the capillary after the second cold drawing is 2-5 mm, for example, 2mm, 2.5mm, 3mm, 3.6mm, 4mm, 4.2mm or 5mm.
Preferably, the wall thickness of the second cold drawn capillary is reduced by 1.5-3.0 mm, for example, 1.5mm, 1.8mm, 2.0mm, 2.2mm, 2.5mm, 2.7mm or 3.0mm.
The invention carries out the second cold drawing after the hot expansion treatment, further refines the crystal grains by utilizing enough cold drawing deformation and improves the dimensional accuracy of the large-caliber austenitic stainless steel seamless tube of the final product.
Preferably, the temperature of the fourth solution treatment is 1050 to 1150 ℃, and may be 1050 ℃, 1055 ℃, 1060 ℃, 1065 ℃, 1070 ℃, 1090 ℃, 1100 ℃, or 1150 ℃, for example.
The fourth solution treatment can obtain a single uniform austenite structure, the structure and the performance of the finally obtained large-caliber austenitic stainless steel seamless tube are directly affected, the tolerance of the outer diameter of the large-caliber austenitic stainless steel seamless tube is +/-0.8%, the tolerance of the wall thickness is 0-15%, the straightness is less than 1.5mm/m, and the ovality is less than 1.0% of the average diameter after the fourth solution treatment; the grain size reaches more than 5 levels, and the difference between the maximum level and the minimum level of the grain size is not more than 2 levels; ferrite content is less than 1%; the average breaking stress of the high-temperature sodium pipeline with the permanent strength of 650 ℃ for 3000 hours is not less than 134MPa, and the high-temperature sodium pipeline can meet the technical requirements of safe two-level and three-level high-temperature sodium pipelines in a sodium-cooled fast reactor.
In the first solid solution treatment, the second solid solution treatment, the third solid solution treatment and the fourth solid solution treatment, a special heat treatment lifting appliance is used for lifting and transferring.
And (3) carrying out grain size inspection after upsetting and drawing and after solution treatment, timely knowing the change of grain size, and adjusting the processing deformation and the processing temperature of the next working procedure according to the grade of the grain size to ensure that the grain size of the final product reaches the standard.
The numerical ranges recited herein include not only the recited point values, but also any point values between the recited numerical ranges that are not recited, and are limited to, and for the sake of brevity, the invention is not intended to be exhaustive of the specific point values that the recited range includes.
As a preferred technical solution of the present invention, the manufacturing method includes the steps of:
(1) The stainless steel water is subjected to primary refining by an electric furnace, vacuum oxygen blowing decarburization treatment and vacuum degassing treatment in sequence, and then is cast to obtain an electrode ingot;
(2) After electroslag remelting is carried out on the electrode ingot in inert atmosphere, cutting off the head and the tail of the electroslag ingot, wherein the cutting-off angle of the end part is not more than 3.0% of the nominal diameter and is not more than 10mm, so as to obtain a first austenitic stainless steel blank;
(3) Homogenizing the first austenitic stainless steel blank, upsetting and drawing the blank in a rapid forging machine for at least 3 times at the forging temperature of 1160-1190 ℃, and then peeling and punching positioning holes to obtain a second austenitic stainless steel blank;
the homogenization treatment is carried out in three stages, wherein the temperature is raised to 550-600 ℃ at the temperature rising rate of 80-90 ℃ per hour in the first stage, and the temperature is kept for 1-2 hours; the second stage is to heat up to 950-1000 ℃ at a heating rate of 130-150 ℃/h, and keep the temperature for 2-3 h; in the third stage, the temperature is raised to 1200-1230 ℃ at a heating rate of 90-100 ℃/h, and the temperature is kept for 40-50 h; the total forging ratio after the upsetting and drawing treatment is more than 5;
(4) Heating the second austenitic stainless steel blank to 1190-1210 ℃ in a heating furnace, forging in a radial forging machine, performing first solution treatment at 1050-1150 ℃, heating to 1170-1200 ℃ and hot rolling to obtain a pierced billet; the total elongation coefficient of the forging treatment is more than 5;
(5) Sequentially performing second solid solution treatment at 1050-1150 ℃ on the pierced billet, then sequentially performing first cold drawing at 0.8-1.0 m/min, thermal expansion treatment at 860-1000 ℃ with an expansion ratio of 1.1-1.4 and an expansion advancing speed of 20-70 mm/min, and third solid solution treatment at 1050-1150 ℃ to obtain a capillary;
the reduction of the outer diameter of the pierced billet after the first cold drawing is 2-6 mm, and the reduction of the wall thickness is 1.5-3.0 mm; the length of the induction heating coil in the thermal expansion treatment covers the deformation area of the pierced billet and extends 300-500 mm forwards and backwards respectively; the outer diameter of the induction heating coil in the thermal expansion treatment is 80-120 mm larger than the outer diameter of the thermally expanded pierced billet;
(6) Sequentially carrying out second cold drawing of 1-3 times and fourth solution treatment at 1050-1150 ℃ on the blank pipe to obtain the large-caliber austenitic stainless steel seamless pipe;
The last cold drawing in the second cold drawing adopts equal-diameter cold drawing, and other passes adopt reducing cold drawing; the outer diameter reduction of the capillary after the second cold drawing is 2-5 mm, and the wall thickness reduction is 1.5-3.0 mm.
In a third aspect, the invention also provides the use of a large caliber austenitic stainless steel seamless tube for a nuclear power system, preferably for a sodium-cooled fast neutron reactor.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) The large-caliber austenitic stainless steel seamless pipe provided by the invention has the advantages of good surface quality, high grain size grade, high purity, low inclusion content, good comprehensive performance of products, high-temperature strength and lasting strength exceeding the requirements of technical protocols, and size, structure and performance of the products meeting the technical requirements of austenitic stainless steel seamless pipes for sodium-cooled fast reactor high-temperature sodium pipelines;
(2) The manufacturing method of the large-caliber austenitic stainless steel seamless pipe provided by the invention can obtain larger reducing rate by adopting one-time medium-frequency heat expansion treatment, improves the working efficiency, has flexible production mode, and is suitable for producing large-caliber austenitic stainless steel seamless pipes with multiple varieties and multiple specifications.
Detailed Description
The present invention will be described in further detail below. The following examples are merely illustrative of the present invention and are not intended to represent or limit the scope of the invention as defined in the claims.
The chemical composition and mass content (%) of the stainless steel water in the following examples are shown in table 1:
TABLE 1
The mass contents of Ti and Nb are not specifically required in table 1, but the mass contents of Ti and Nb need to be detected, and specific data of the detection are noted in the report.
Example 1
The embodiment provides a manufacturing method of a large-caliber austenitic stainless steel seamless pipe, which comprises the following steps:
(1') the stainless steel water is subjected to primary refining by an electric furnace, the carbon content is controlled to be 0.08-0.12%, then vacuum oxygen blowing decarburization treatment is carried out, the decarburization time is 40min, and the process is stopped when the C is less than or equal to 0.05%;
(2') vacuum degassing treatment is carried out by utilizing a vacuum degassing furnace, the required vacuum degree is less than or equal to 66.7Pa, the high vacuum holding time is 25min, the degassing time is 30min, the soft stirring time after breaking is 40min, the components and the temperature of molten steel are ensured to be uniform, then an electrode ingot is poured under the protection atmosphere of argon, sampling is carried out during molten steel pouring for smelting analysis, and the chemical components are ensured to meet the technical requirements of an austenitic stainless steel seamless pipe for a sodium-cooled fast reactor high-temperature sodium pipeline;
(3') the outer trolley of the electrode ingot is fully peeled off and the head and the tail are thoroughly cut off, and electroslag remelting casting is carried out in argon atmosphere to obtain an electroslag ingot with the diameter of 500 mm;
(4') peeling the electroslag ingot, and cutting off head and tail parts, wherein the shrinkage cavities at the head and tail parts must be completely cut off, and the cutting angle of the end part is not more than 3.0% of the nominal diameter and not more than 10mm, so as to obtain a first austenitic stainless steel blank;
(5') removing all oil films, stains and other compounds from the surface of the first austenitic stainless steel blank; homogenizing the first austenitic stainless steel blank, wherein the homogenizing is performed in three stages, the temperature is raised to 550 ℃ at a heating rate of 80 ℃/h in the first stage, and the temperature is kept for 1h; the second stage is to heat up to 950 ℃ at a heating rate of 150 ℃/h, and keep the temperature for 2 h; the third stage is to raise the temperature to 1200 ℃ at a heating rate of 100 ℃/h, and keep the temperature for 40h and then cool along with the furnace; cooling to 1160 ℃ and discharging from the furnace;
(6') upsetting and drawing processing for 4 times is carried out in a rapid forging machine, and the final forging temperature is not lower than 860 ℃; the total forging ratio after the upsetting and drawing treatment is 5.2; returning to the furnace again for heating when the forging temperature is close to 860 ℃; forging the blank to form at the initial forging temperature of not more than 1100 ℃ and the final forging temperature of not less than 860 ℃ in the last forging; peeling by a peeler, processing into a blank with the diameter of 500mm, and punching a positioning hole to obtain a second austenitic stainless steel blank;
(7') heating the second austenitic stainless steel blank in a heating furnace to 1190 ℃ and preserving heat for 90min, discharging, and forging in a radial forging machine to obtain a pierced billet with the diameter of phi 480 multiplied by 22mm, wherein the total extension coefficient is 6.20;
(8') carrying out first solution treatment at 1060 ℃ and preserving heat for 60min, wherein the temperature deviation of a heat preservation section is controlled within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; the temperature of water is not more than 40 ℃ during quenching, the water is fully flowed and cooled by a circulating water pump, and the water quenching time is 12min;
(9') continuing to heat to 1170 ℃ and hot-rolling to phi 508 multiplied by 18mm by using a taper roll skew rolling mill;
(10') carrying out second solid solution treatment at 1060 ℃, preserving heat for 50min, and controlling the temperature deviation of a heat preservation section within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; the temperature of water is not more than 40 ℃ during quenching, the water is fully flowed and cooled by a circulating water pump, and the water quenching time is 10min;
(11') uniformly coating a layer of butter lime lubricant on the inner wall of the pierced billet;
(12') performing first cold drawing on the pierced blank at a speed of 0.9m/min by using a 1600t hydraulic precision cold drawing unit, wherein the reduction of the outer diameter is 4mm, and the reduction of the wall thickness is 3.0mm, so as to obtain a pierced blank with the diameter of phi 503 multiplied by 15 mm;
(13') inspecting the inner and outer surfaces of the pierced billet, if visual appearance defects exist, removing the pierced billet by using a local polishing mode, and removing all oil films, stains and other compounds on the surface of the pierced billet;
(14') uniformly coating a lubricant on the inner wall of the pierced billet, wherein the lubricant is a mixture formed by mixing powdery graphite powder with the particle size of 60 mu m, flake graphite powder with the particle size of 90 mu m and water according to the mass ratio of 1:2:3;
(15') determining the intermediate frequency to be 900Hz, selecting a conical mandrel for thermal expansion treatment, wherein the mandrel is made of 06Cr25Ni20, the coil has an outer diameter of 720mm, the coil length covers the deformation area of the pierced billet, and extends forward (the undeformed area of the pierced billet) for 420mm and backward (the deformed area of the pierced billet) for 350mm, so as to ensure that the pierced billet is fully preheated, and when reaching the deformation area, the pierced billet reaches a specified thermal expansion temperature, performing thermal expansion treatment on the pierced billet coated with the lubricant by adopting a thermal expansion unit, wherein the thermal expansion temperature is 860 ℃, the expansion ratio is 1.21, the expansion advancing speed is 20mm/min, and the specification of the pierced billet after thermal expansion is phi 610 multiplied by 14.5mm;
(16') carrying out third solid solution treatment at 1060 ℃ on the thermally expanded pierced billet, and preserving heat for 50min, wherein the temperature deviation of a heat preservation section is controlled within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; the temperature of water is not more than 40 ℃ during quenching, the water is fully flowed and cooled by a circulating water pump, and the water quenching time is 9min, so that a capillary tube is obtained;
(17') performing a second cold drawing on the capillary, wherein the specification of the capillary after the first cold drawing is phi 610 multiplied by 12mm;
(18') carrying out fourth solid solution treatment at 1060 ℃ on the final cold drawn capillary, and preserving heat for 60min, wherein the temperature deviation of a heat preservation section is controlled within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; and (3) when quenching, the temperature of water is not more than 40 ℃, the water is fully flowed and cooled by using a circulating water pump, and the water quenching time is 7min, so that the large-caliber austenitic stainless steel seamless pipe is obtained.
The large-caliber austenitic stainless steel seamless pipe obtained in the example has an outer diameter of 610mm, a nominal wall thickness of 12mm and a surface roughness of 6.0 μm.
Example 2
The embodiment provides a manufacturing method of a large-caliber austenitic stainless steel seamless pipe, which comprises the following steps:
(1') the stainless steel water is subjected to primary refining by an electric furnace, the carbon content is controlled to be 0.08-0.12%, then vacuum oxygen blowing decarburization treatment is carried out, the decarburization time is 30min, and the process is stopped when the C is less than or equal to 0.05%;
(2') vacuum degassing treatment is carried out by utilizing a vacuum degassing furnace, the required vacuum degree is less than or equal to 66.7Pa, the high vacuum holding time is 18min, the degassing time is 25min, the soft stirring time after breaking is 30min, the components and the temperature of molten steel are ensured to be uniform, then an electrode ingot is poured under the protection atmosphere of argon, sampling is carried out during molten steel pouring for smelting analysis, and the chemical components are ensured to meet the technical requirements of an austenitic stainless steel seamless pipe for a sodium-cooled fast reactor high-temperature sodium pipeline;
(3') the outer trolley of the electrode ingot is fully peeled off and the head and the tail are thoroughly cut off, and electroslag remelting casting is carried out in argon atmosphere to obtain an electroslag ingot with the diameter of 600 mm;
(4') peeling the electroslag ingot, and cutting off head and tail parts, wherein the shrinkage cavities at the head and tail parts must be completely cut off, and the cutting angle of the end part is not more than 3.0% of the nominal diameter and not more than 10mm, so as to obtain a first austenitic stainless steel blank;
(5') removing all oil films, stains and other compounds from the surface of the first austenitic stainless steel blank; homogenizing the first austenitic stainless steel blank, wherein the homogenizing is performed in three stages, the temperature is raised to 580 ℃ at the heating rate of 90 ℃/h in the first stage, and the temperature is kept for 1.5h; in the second stage, the temperature is increased to 980 ℃ at the heating rate of 138 ℃/h, and the temperature is kept for 2.5 h; in the third stage, the temperature is raised to 1215 ℃ at a heating rate of 95 ℃/h, and the furnace is cooled after heat preservation for 45 h; cooling to 1170 ℃ and discharging;
(6') upsetting and drawing processing for 5 times is carried out in a rapid forging machine, and the final forging temperature is not lower than 860 ℃; the total forging ratio after the upsetting and drawing treatment is 5.5; returning to the furnace again for heating when the forging temperature is close to 860 ℃; forging the blank to form at the initial forging temperature of not more than 1100 ℃ and the final forging temperature of not less than 860 ℃ in the last forging; peeling by a peeler, processing into a blank with the diameter of 710mm, and punching a positioning hole to obtain a second austenitic stainless steel blank;
(7') heating the second austenitic stainless steel blank in a heating furnace to 1200 ℃, preserving heat for 110min, discharging, and forging in a radial forging machine to obtain a pierced billet with the diameter of 666 multiplied by 35mm, wherein the total elongation coefficient is 5.71;
(8') carrying out first solution treatment at 1070 ℃, preserving heat for 70min, and controlling the temperature deviation of a heat preservation section within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; the temperature of water is not more than 40 ℃ during quenching, the water is fully flowed and cooled by a circulating water pump, and the water quenching time is 12min;
(9') continuing to heat to 1180 ℃ and hot-rolling to phi 720 multiplied by 28mm by using a conical roll skew rolling mill;
(10') carrying out second solid solution treatment at 1070 ℃, and preserving heat for 60min, wherein the temperature deviation of a heat preservation section is controlled within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; the temperature of water is not more than 40 ℃ during quenching, the water is fully flowed and cooled by a circulating water pump, and the water quenching time is 10min;
(11') uniformly coating a layer of butter lime lubricant on the inner wall of the pierced billet;
(12') performing first cold drawing on the pierced blank at a speed of 0.8m/min by using a 1600t hydraulic precision cold drawing unit, wherein the reduction of the outer diameter is 5mm, and the reduction of the wall thickness is 3.0mm, so as to obtain a pierced blank with the diameter of phi 715 multiplied by 25 mm;
(13') inspecting the inner and outer surfaces of the pierced billet, if visual appearance defects exist, removing the pierced billet by using a local polishing mode, and removing all oil films, stains and other compounds on the surface of the pierced billet;
(14') uniformly coating lubricant on the inner wall of the pierced billet, wherein the lubricant is a mixture formed by mixing powdery graphite powder with the particle size of 65 mu m, flake graphite powder with the particle size of 90 mu m and water according to the mass ratio of 1:2:3;
(15') determining the intermediate frequency to be 750Hz, selecting a conical mandrel for heat expansion treatment, wherein the mandrel is made of 06Cr25Ni20, the coil has an outer diameter of 910mm, the coil length covers the deformation area of the pierced billet, and extends forward (the undeformed area of the pierced billet) for 500mm and backward (the deformed area of the pierced billet) for 300mm, so as to ensure that the pierced billet is fully preheated, and when reaching the deformation area, the pierced billet reaches a specified heat expansion temperature, performing heat expansion treatment on the pierced billet coated with the lubricant by adopting a heat expansion unit, wherein the heat expansion temperature is 940 ℃, the expansion ratio is 1.15, the expansion advancing speed is 30mm/min, and the specification of the pierced billet after heat expansion is phi 820 multiplied by 23mm;
(16') carrying out third solid solution treatment at 1070 ℃ on the thermally expanded pierced billet, and preserving heat for 60min, wherein the temperature deviation of the heat preservation section is controlled within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; the temperature of water is not more than 40 ℃ during quenching, the water is fully flowed and cooled by a circulating water pump, and the water quenching time is 9min, so that a capillary tube is obtained;
(17') performing secondary cold drawing on the capillary tube twice, wherein the specification after one cold drawing is phi 813 multiplied by 20mm, and the specification after the secondary cold drawing is phi 813 multiplied by 18mm;
(18') carrying out fourth solid solution treatment at 1070 ℃ on the final cold drawn capillary, and preserving heat for 70min, wherein the temperature deviation of a heat preservation section is controlled within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; and (3) when quenching, the temperature of water is not more than 40 ℃, the water is fully flowed and cooled by using a circulating water pump, and the water quenching time is 7min, so that the large-caliber austenitic stainless steel seamless pipe is obtained.
The large-caliber austenitic stainless steel seamless pipe obtained in this example has an outer diameter of 813mm, a nominal wall thickness of 18mm and a surface roughness of 5.5. Mu.m.
The large-caliber austenitic stainless steel seamless pipe obtained in the embodiment is subjected to instantaneous high-temperature tensile test according to GB/T228.2-2015, and the test results are shown in Table 2.
TABLE 2
| Temperature/. Degree.C | 350 | 400 | 450 | 550 | 650 | 700 |
| Drawing strength/MPa | 518 | 492 | 471 | 438 | 392 | 363 |
| Yield strength/MPa | 159 | 143 | 138 | 129 | 117 | 111 |
As can be seen from Table 2, the large-caliber austenitic stainless steel seamless pipe obtained by the embodiment meets the technical requirements of safe two-stage and three-stage high-temperature sodium pipelines in a sodium-cooled fast reactor.
Example 3
The embodiment provides a manufacturing method of a large-caliber austenitic stainless steel seamless pipe, which comprises the following steps:
The embodiment provides a manufacturing method of a large-caliber austenitic stainless steel seamless pipe, which comprises the following steps:
(1') the stainless steel water is subjected to primary refining by an electric furnace, the carbon content is controlled to be 0.08-0.12%, then vacuum oxygen blowing decarburization treatment is carried out, the decarburization time is 50min, and the process is stopped when the C is less than or equal to 0.05%;
(2') vacuum degassing treatment is carried out by utilizing a vacuum degassing furnace, the required vacuum degree is less than or equal to 66.7Pa, the high vacuum holding time is 30min, the degassing time is 30min, the soft stirring time after breaking is 30min, the molten steel components and the temperature are ensured to be uniform, then an electrode ingot is poured under the protection atmosphere of argon, sampling is carried out during molten steel pouring for smelting analysis, and the chemical components are ensured to meet the technical requirements of an austenitic stainless steel seamless pipe for a sodium-cooled fast reactor high-temperature sodium pipeline;
(3') the outer trolley of the electrode ingot is fully peeled off and the head and the tail are thoroughly cut off, and electroslag remelting casting is carried out in argon atmosphere to obtain an electroslag ingot with the diameter of phi 690 mm;
(4') peeling the electroslag ingot, and cutting off head and tail parts, wherein the shrinkage cavities at the head and tail parts must be completely cut off, and the cutting angle of the end part is not more than 3.0% of the nominal diameter and not more than 10mm, so as to obtain a first austenitic stainless steel blank;
(5') removing all oil films, stains and other compounds from the surface of the first austenitic stainless steel blank; homogenizing the first austenitic stainless steel blank, wherein the homogenizing is performed in three stages, the temperature is raised to 600 ℃ at a heating rate of 88 ℃/h in the first stage, and the temperature is kept for 2h; the second stage is to heat up to 1000 ℃ at a heating rate of 130 ℃/h, and keep the temperature for 3 h; the third stage is to heat up to 1230 ℃ at a heating rate of 100 ℃/h, keep the temperature for 50h and then cool with the furnace; cooling to 1190 ℃ and discharging;
(6') upsetting and drawing processing is carried out for 6 times in a rapid forging machine, and the final forging temperature is not lower than 860 ℃; the total forging ratio after the upsetting and drawing treatment is 6.5; returning to the furnace again for heating when the forging temperature is close to 860 ℃; forging the blank to form at the initial forging temperature of not more than 1100 ℃ and the final forging temperature of not less than 860 ℃ in the last forging; peeling by a peeler, processing into blank with phi of 800mm, and punching a positioning hole to obtain a second austenitic stainless steel blank;
(7') heating the second austenitic stainless steel blank to 1210 ℃ in a heating furnace, preserving heat for 120min, discharging, and forging in a radial forging machine to obtain a pierced billet with phi 760 multiplied by 38mm, wherein the total elongation coefficient is 5.83;
(8') carrying out first solution treatment at 1090 ℃, preserving heat for 80min, and controlling the temperature deviation of a heat preservation section within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; the temperature of water is not more than 40 ℃ during quenching, the water is fully flowed and cooled by a circulating water pump, and the water quenching time is 12min;
(9') continuing to heat to 1185 ℃, and hot-rolling to phi 820 multiplied by 31mm by using a conical roll skew rolling mill;
(10') carrying out second solid solution treatment at 1080 ℃, and preserving heat for 70min, wherein the temperature deviation of a heat preservation section is controlled within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; the temperature of water is not more than 40 ℃ during quenching, the water is fully flowed and cooled by a circulating water pump, and the water quenching time is 10min;
(11') uniformly coating a layer of butter lime lubricant on the inner wall of the second pierced billet;
(12') performing first cold drawing on the pierced blank at a speed of 1.0m/min by using a 1600t hydraulic precision cold drawing unit, wherein the reduction of the outer diameter is 6mm, and the reduction of the wall thickness is 2.2mm, so as to obtain a pierced blank with the diameter of phi 813 multiplied by 28 mm;
(13') inspecting the inner and outer surfaces of the pierced billet, if visual appearance defects exist, removing the pierced billet by using a local polishing mode, and removing all oil films, stains and other compounds on the surface of the pierced billet;
(14') uniformly coating a lubricant on the inner wall of the pierced billet, wherein the lubricant is a mixture formed by mixing powdery graphite powder with the particle size of 60 mu m, flake graphite powder with the particle size of 90 mu m and water according to the mass ratio of 1:2:3;
(15') determining the intermediate frequency to be 650Hz, selecting a conical mandrel for thermal expansion treatment, wherein the mandrel is made of 06Cr25Ni20, the coil has an outer diameter of 1000mm, the coil length covers the deformation area of the pierced billet, and extends forward (the undeformed area of the pierced billet) for 400mm and backward (the deformed area of the pierced billet) for 450mm, so as to ensure that the pierced billet is fully preheated, and when reaching the deformation area, the pierced billet reaches a specified thermal expansion temperature, carrying out thermal expansion treatment on the pierced billet coated with the lubricant by adopting a thermal expansion unit, wherein the thermal expansion temperature is 1000 ℃, the expansion ratio is 1.13, the expansion advancing speed is 70mm/min, and the pierced billet specification after thermal expansion is phi 920 multiplied by 26mm;
(16') carrying out third solid solution treatment at 1080 ℃ on the thermally expanded pierced billet, and preserving heat for 65min, wherein the temperature deviation of a heat preservation section is controlled within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; the temperature of water is not more than 40 ℃ during quenching, the water is fully flowed and cooled by a circulating water pump, and the water quenching time is 9min, so that a capillary tube is obtained;
(17') performing 2-pass second cold drawing on the capillary, wherein the specification after one cold drawing is phi 914 multiplied by 23mm, and the specification after two cold drawing is phi 914 multiplied by 20mm;
(18') carrying out fourth solid solution treatment at 1080 ℃ on the final cold drawn capillary tube, and preserving heat for 75min, wherein the temperature deviation of a heat preservation section is controlled within +/-10 ℃; the allowable deviation of the heat preservation time is +/-1 min; the time of discharging from the furnace and charging water is less than 1min; and (3) when quenching, the temperature of water is not more than 40 ℃, the water is fully flowed and cooled by using a circulating water pump, and the water quenching time is 7min, so that the large-caliber austenitic stainless steel seamless pipe is obtained.
The large-caliber austenitic stainless steel seamless pipe obtained in the example has an outer diameter of 914mm, a nominal wall thickness of 20mm and a surface roughness of 4.8 μm.
The large-caliber austenitic stainless steel seamless pipes obtained in the above examples 1 to 3 were rated according to GB/T6394-2017 in grain size, 5 and 6 grades respectively.
The large-diameter austenitic stainless steel seamless pipes obtained in examples 1 to 3 were sampled and subjected to nonmetallic inclusion inspection and rating according to GB/T10561-2005A method, wherein A fine fraction, B fine fraction, C fine fraction, D fine fractionAnd D S The test value of the level is not more than 1.0, and the test result is qualified.
The large-diameter austenitic stainless steel seamless pipes obtained in examples 1 to 3 were subjected to ferrite detection by cutting out a full-thickness sample from each of the ends of the pipe, and the ferrite contents were 0%, 0% and 0.1%, respectively, as observed under a microscope having a magnification of 400 times according to GB/T13298-2015.
The surface hardness of the large-diameter austenitic stainless steel seamless pipes obtained in examples 1 to 3 was measured and the brinell hardness was 141 (HBW 10/3000), 153 (HBW 10/3000) and 132 (HBW 10/3000), respectively.
The large-caliber austenitic stainless steel seamless pipes obtained in examples 1 to 3 were subjected to a room temperature tensile test, a room temperature impact test, and a bending test, and the test results were all acceptable.
The large-caliber austenitic stainless steel seamless pipes obtained in the examples 1 to 3 were subjected to a endurance strength test according to GB/T2039-2012, and were not broken after 6000 hours under test stress conditions of 650 ℃ and 134 MPa.
The large-diameter austenitic stainless steel seamless pipes obtained in examples 1 to 3 were subjected to an intergranular corrosion test according to the method E prescribed in GB/T4334-2020. The sensitization treatment is carried out at 650+/-10 ℃ for 2 hours, then air cooling is carried out, the boiling test is carried out in a copper-copper sulfate-16% sulfuric acid solution for 16 hours, then the test is carried out in a magnifying glass of 10 times after bending, and the surfaces are free from intergranular corrosion cracks.
In conclusion, the structure, the performance and the size of the large-caliber austenitic stainless steel seamless pipe obtained by the preparation method of the large-caliber austenitic stainless steel seamless pipe provided by the invention all meet the requirements of the technical protocol of the austenitic stainless steel seamless pipe for the high-temperature sodium pipeline of the sodium-cooled fast neutron reactor.
The applicant declares that the above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that are easily conceivable within the technical scope of the present invention disclosed by the present invention fall within the scope of the present invention and the disclosure.
Claims (9)
1. A method for manufacturing a large-caliber austenitic stainless steel seamless pipe, which is characterized by comprising the following steps:
(1) The stainless steel water is subjected to primary refining by an electric furnace, vacuum oxygen blowing decarburization treatment and vacuum degassing treatment in sequence, and then is cast to obtain an electrode ingot;
(2) Electroslag remelting is carried out on the electrode ingot in an inert atmosphere to obtain a first austenitic stainless steel blank;
(3) Carrying out homogenization treatment and upsetting and drawing treatment on the first austenitic stainless steel blank, and sequentially carrying out cooling, peeling and positioning hole punching treatment to obtain a second austenitic stainless steel blank;
the homogenization treatment is carried out in three stages, wherein the temperature is raised to 550-600 ℃ at a heating rate of 80-90 ℃ per hour in the first stage, and the temperature is kept for 1-2 hours; the second stage is to heat up to 950-1000 ℃ at a heating rate of 130-150 ℃/h, and keep the temperature for 2-3 h; in the third stage, the temperature is raised to 1200-1230 ℃ at a heating rate of 90-100 ℃ per hour, and the temperature is kept for 40-50 hours;
the upsetting and drawing process is carried out in a rapid forging machine;
the forging temperature before upsetting and pulling is 1160-1190 ℃;
the upsetting and pulling length is processed for not less than 3 times;
the total forging ratio after the upsetting and drawing treatment is more than 5;
(4) The second austenitic stainless steel blank is subjected to forging treatment, first solid solution treatment and hot rolling in sequence to obtain a pierced billet;
(5) Sequentially carrying out second solid solution treatment, first cold drawing, heat expansion treatment and third solid solution treatment on the pierced billet to obtain a capillary;
(6) Sequentially carrying out second cold drawing and fourth solution treatment on the capillary tube to obtain the large-caliber austenitic stainless steel seamless tube;
the outer diameter of the large-caliber austenitic stainless steel seamless pipe is 610-912 mm, and the diameter-wall ratio is greater than 45.
2. The method of manufacturing according to claim 1, wherein the large-caliber austenitic stainless steel seamless tube has a surface roughness of less than 6.3 μm;
the grain size of the large-caliber austenitic stainless steel seamless pipe is more than 5 grades.
3. The method according to claim 1, wherein the electroslag ingot obtained by electroslag remelting the electrode ingot in step (2) is cut from the head to the tail, and the end cutting amount is not more than 3.0% of the nominal diameter and not more than 10mm.
4. The method according to claim 1, wherein the second austenitic stainless steel billet in step (4) is heated to 1190 ℃ to 1210 ℃ in a heating furnace and then subjected to forging treatment;
the forging treatment is performed in a radial forging machine;
the total elongation coefficient of the forging treatment is more than 5;
the temperature of the first solution treatment is 1050-1150 ℃;
And heating the diameter forging pierced billet subjected to the first solution treatment to 1170-1200 ℃ and then carrying out hot rolling.
5. The method of claim 1, wherein the second solution treatment in step (5) is performed at a temperature of 1050 ℃ to 1150 ℃;
the speed of the first cold drawing is 0.8-1.0 m/min;
the reduction of the outer diameter of the pierced billet after the first cold drawing is 2-6 mm;
the wall thickness reduction of the first cold drawn pierced billet is 1.5-3.0 mm;
the temperature of the thermal expansion treatment is 860-1000 ℃;
the expansion ratio of the thermal expansion treatment is 1.1-1.4;
the pipe expanding pushing speed of the thermal expansion treatment is 20-70 mm/min;
the length of the induction heating coil in the thermal expansion treatment covers the deformation area of the pierced billet and extends forward and backward for 300-500 mm respectively;
the outer diameter of the induction heating coil in the thermal expansion treatment is 80-120 mm larger than the outer diameter of the thermally expanded pierced billet;
the temperature of the third solid solution treatment is 1050-1150 ℃.
6. The method according to claim 1, wherein the second cold drawing in step (6) is performed for 1 to 3 passes;
the last cold drawing in the second cold drawing adopts equal-diameter cold drawing, and other passes adopt reducing cold drawing;
the outer diameter reduction of the capillary after the second cold drawing is 2-5 mm;
The wall thickness reduction of the capillary after the second cold drawing is 1.5-3.0 mm;
the temperature of the fourth solution treatment is 1050-1150 ℃.
7. The manufacturing method according to claim 1, characterized in that the manufacturing method comprises the steps of:
(1) The stainless steel water is subjected to primary refining by an electric furnace, vacuum oxygen blowing decarburization treatment and vacuum degassing treatment in sequence, and then is cast to obtain an electrode ingot;
(2) After electroslag remelting is carried out on the electrode ingot under inert atmosphere, cutting off the head and the tail of the obtained electroslag ingot, wherein the cutting-off amount of the end part is not more than 3.0% of the nominal diameter and is not more than 10mm, and obtaining a first austenitic stainless steel blank;
(3) Homogenizing the first austenitic stainless steel blank, upsetting and drawing the blank in a rapid forging machine for at least 3 times at the forging temperature of 1160-1190 ℃, and then peeling and punching positioning holes to obtain a second austenitic stainless steel blank;
the homogenization treatment is carried out in three stages, wherein the temperature is raised to 550-600 ℃ at a heating rate of 80-90 ℃ per hour in the first stage, and the temperature is kept for 1-2 hours; the second stage is to heat up to 950-1000 ℃ at a heating rate of 130-150 ℃/h, and keep the temperature for 2-3 h; in the third stage, the temperature is raised to 1200-1230 ℃ at a heating rate of 90-100 ℃ per hour, and the temperature is kept for 40-50 hours; the total forging ratio after the upsetting and drawing treatment is more than 5;
(4) Heating the second austenitic stainless steel blank to 1190-1210 ℃ in a heating furnace, forging in a radial forging machine, performing first solution treatment at 1050-1150 ℃, heating to 1170-1200 ℃ and hot rolling to obtain a pierced billet; the total elongation coefficient of the forging treatment is more than 5;
(5) After the pierced billet is subjected to second solid solution treatment at 1050-1150 ℃, sequentially performing first cold drawing at a speed of 0.8-1.0 m/min, hot expanding treatment at 860-1000 ℃ with an expanding ratio of 1.1-1.4 and an expanding pushing speed of 20-70 mm/min and third solid solution treatment at 1050-1150 ℃ to obtain a blank pipe;
the reduction amount of the outer diameter of the pierced billet after the first cold drawing is 2-6 mm, and the reduction amount of the wall thickness is 1.5-3.0 mm; the length of the induction heating coil in the thermal expansion treatment covers the deformation area of the pierced billet and extends forward and backward for 300-500 mm respectively; the outer diameter of the induction heating coil in the thermal expansion treatment is 80-120 mm larger than the outer diameter of the thermally expanded pierced billet;
(6) Sequentially carrying out second cold drawing for 1-3 times and fourth solution treatment at 1050-1150 ℃ on the blank pipe to obtain the large-caliber austenitic stainless steel seamless pipe;
the last cold drawing in the second cold drawing adopts equal-diameter cold drawing, and other passes adopt reducing cold drawing; the outer diameter reduction of the capillary after the second cold drawing is 2-5 mm, and the wall thickness reduction is 1.5-3.0 mm.
8. Use of the large-caliber austenitic stainless steel seamless pipe obtained by the manufacturing method of the large-caliber austenitic stainless steel seamless pipe according to any one of claims 1 to 7, wherein the large-caliber austenitic stainless steel seamless pipe is used for a nuclear power system.
9. Use of the large-caliber austenitic stainless steel seamless pipe obtained by the method for manufacturing a large-caliber austenitic stainless steel seamless pipe according to claim 8, wherein the large-caliber austenitic stainless steel seamless pipe is used for a sodium-cooled fast neutron reactor.
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