CN118028703A - Steel for advanced nuclear power unit pressure vessel and manufacturing method thereof - Google Patents

Steel for advanced nuclear power unit pressure vessel and manufacturing method thereof Download PDF

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Publication number
CN118028703A
CN118028703A CN202410159616.7A CN202410159616A CN118028703A CN 118028703 A CN118028703 A CN 118028703A CN 202410159616 A CN202410159616 A CN 202410159616A CN 118028703 A CN118028703 A CN 118028703A
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steel
controlled
nuclear power
temperature
power unit
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Inventor
颜秉宇
王勇
孙殿东
王爽
陈捷
胡海洋
张瀚宁
高天宇
欧阳鑫
胡昕明
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Angang Steel Co Ltd
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Angang Steel Co Ltd
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Priority to CN202410159616.7A priority Critical patent/CN118028703A/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • B21B3/02—Rolling special iron alloys, e.g. stainless steel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/1206—Accessories for subsequent treating or working cast stock in situ for plastic shaping of strands
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/12—Accessories for subsequent treating or working cast stock in situ
    • B22D11/122—Accessories for subsequent treating or working cast stock in situ using magnetic fields
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/18—Controlling or regulating processes or operations for pouring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/20—Controlling or regulating processes or operations for removing cast stock
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/16—Controlling or regulating processes or operations
    • B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
    • B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
    • 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
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C21C5/30—Regulating or controlling the blowing
    • C21C5/32—Blowing from above
    • 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
    • C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
    • 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
    • C21C7/064—Dephosphorising; Desulfurising
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • 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
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • 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
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Abstract

The invention relates to steel for an advanced nuclear power unit pressure vessel and a manufacturing method thereof, wherein the steel for the advanced nuclear power unit pressure vessel comprises the following components ,C：0.079％～0.149％,Mn：0.31％～1.24％,P≤0.022％,S≤0.010％,Cr：1.26％～3.20％,N i：1.60％～3.80％,Mo：0.001％～0.120％,Cu：0.001％～0.180％,Nb：0.020％～0.060％,V:0.001％～0.030％,T i：0.001％～0.030％,CaO≤0.060,B:0.0001％～0.0039％,Nd：5ppm～15ppm,Pr:1ppm～15ppm, by weight percent, and the balance of Fe and unavoidable impurities; the method comprises the following steps: smelting process, rolling process and heat treatment process. The method ensures that the delivered-state steel plate achieves good toughness matching through strict chemical components and production process design, and can meet the requirements of technical indexes; in particular, the normal temperature mechanical property, 320 ℃ high temperature state, low temperature toughness and drop hammer property are all kept at higher level, and the requirements of the steel for the pressure vessel of the nuclear power station are completely met.

Description

Steel for advanced nuclear power unit pressure vessel and manufacturing method thereof
Technical Field
The invention belongs to the field of ferrous metal materials, and relates to steel for an advanced nuclear power unit pressure vessel and a manufacturing method thereof.
Background
The pressure vessel filled with nuclear fuel can be said to be the heart of the whole nuclear power plant, is the central importance of nuclear power safety, and is the embodiment of the advanced technology in the industrial field. The nuclear reactor pressure vessel is the most central equipment of a nuclear power plant, and the importance of the technical design is its safety. The safety of the nuclear power plant is ensured, the safety of the pressure vessel is ensured at the most core, and if the pressure vessel is safe, the nuclear power plant can be said to be safe.
This patent is through the demand of design unit to the steel performance for nuclear power pressure vessel, and then has designed in the aspect of the alloying element, and the appropriate rolling of cooperation and heat treatment technology again to guarantee that the performance of steel sheet satisfies the requirement under different states.
Disclosure of Invention
In order to solve the problems, the invention adopts the following technical scheme: a steel for an advanced nuclear power unit pressure vessel and a manufacturing method thereof, wherein the steel for the advanced nuclear power unit pressure vessel comprises the following components ,C：0.079％～0.149％,Mn：0.31％～1.24％,P≤0.022％,S≤0.010％,Cr：1.26％～3.20％,N i：1.60％～3.80％,Mo：0.001％～0.120％,Cu：0.001％～0.180％,Nb：0.020％～0.060％,V:0.001％～0.030％,T i：0.001％～0.030％,CaO≤0.060,B:0.0001％～0.0039％,Nd：5ppm～15ppm,Pr:1ppm～15ppm, by weight percent, and the balance of Fe and unavoidable impurities.
Further: the width range of the medium plate is as follows: 3000-4500 mm.
Further: the thickness range of the medium plate is 10-150 mm.
The manufacturing method of the steel for the advanced nuclear power unit pressure vessel based on any one of the above steps comprises the following steps:
S1: the smelting process comprises the following steps: molten steel smelting is carried out in a converter, waste steel and molten iron are adopted as raw materials, the content of molten iron is controlled to be 70-90%, dephosphorization and oxygen blowing are controlled to be 10-16 min, desulfurization and oxygen blowing are controlled to be 11-17 min, and finally the mass fraction of phosphorus is reduced to be within 0.005% and the mass fraction of sulfur is reduced to be within 0.004% in the converter;
reducing slag is manufactured in an LF refining furnace, and the thickness of a slag layer is 90-120 mm;
Degassing is completed in an RH furnace, the net circulation time is 10-15 min, the vacuum degree is 32-56 Pa, the calm time before casting is 9-12 min, the hydrogen content of the gas is controlled to be less than or equal to 0.0001%, the oxygen content is controlled to be less than or equal to 0.0012%, and the nitrogen content is controlled to be less than or equal to 0.0015;
In casting, the superheat degree of a tundish is controlled to be 30-50 ℃, the temperature of secondary cooling water is controlled to be 20-30 ℃, the flow rate is 220-350 t/h, the temperature of cooling water of a crystallizer is 25-35 ℃, the flow rate is 200-290 t/h, an electromagnetic stirring and heavy pressing mode is adopted at the tail end of continuous casting, the heavy pressing is 15-30 mm, the electromagnetic stirring current is 390-520A, the frequency is 15-25 HZ, the pressing amount is 15-30 mm, and the blank pulling speed is controlled to be 0.6-1.0 m/min;
Through the process control, casting blank fine crystals are 10-20%, and equiaxed crystals are 25-35%;
Stacking and slowly cooling for more than 24 hours after offline;
S2: the rolling process comprises the following steps: the rolling of the steel plate adopts two-stage controlled rolling, wherein the rolling temperature is 1050-1150 ℃ in the first stage, and the average rolling reduction rate of the first 4 passes is controlled to be 15-25%;
the initial rolling temperature of the second stage is 980-1050 ℃, the later 5 passes adopt small deformation, and the average reduction rate is 3-6%;
The finishing temperature is controlled to be 950-1000 ℃;
S3: the heat treatment process comprises the following steps: stacking and slow cooling are carried out after the steel plate is rolled, and quenching and tempering are carried out on the steel plate after the slow cooling is finished;
quenching: the temperature is 870-930 ℃ and the heat preservation time is 2-6 min/mm, and water cooling is immediately carried out after the steel plate is discharged until the temperature of the steel plate is lower than 100 ℃;
tempering: the temperature is 615-660 ℃ and the heat preservation time is 4-8 min/mm.
Further: the continuous casting billet also comprises a preferable thickness of 200-300 mm.
According to the steel for the advanced nuclear power unit pressure vessel and the manufacturing method thereof, provided by the invention, the delivered-state steel plate can achieve good toughness matching through strict chemical components and production process design, and the requirements of technical indexes can be met; in particular, the normal temperature mechanical property, 320 ℃ high temperature state, low temperature toughness and drop hammer property are all kept at higher level, and the requirements of the steel for the pressure vessel of the nuclear power station are completely met.
Compared with the prior art, the beneficial effects are as follows:
(1) The purity of the steel is further improved by a smelting and continuous casting control technology, internal defects such as segregation, looseness and the like are eliminated, nonmetallic inclusion is reduced, an as-cast structure is homogenized, nonmetallic inclusion A is less than or equal to 0.5, nonmetallic inclusion B is less than or equal to 0.5, C is less than or equal to 0.5, D is less than or equal to 0.5, and the total sum of nonmetallic inclusion is less than or equal to 1.0; the hydrogen content of the gas is less than or equal to 0.0001%, the oxygen content is less than or equal to 0.0012%, and the nitrogen content is less than or equal to 0.0015; the central porosity of the continuous casting billet is less than or equal to 1.0, the central crack is less than or equal to 1.0, and the fine grain proportion of the continuous casting billet is as follows: 10-20% of equiaxed crystal proportion: 25-35%.
(2) The average mechanical properties of the manufactured steel plate are as follows: the room temperature tensile yield strength is more than or equal to 392MPa, the tensile strength is more than or equal to 550MPa, and the elongation is more than or equal to 20%; the high-temperature tensile yield strength is more than or equal to 311MPa, the tensile strength is more than or equal to 455MPa, and the T NDT/-35 ℃.
Detailed Description
The invention provides steel for an advanced nuclear power unit pressure vessel and a manufacturing method thereof, and the specific technical scheme is as follows:
The alloy comprises the following components ,C：0.079％～0.149％,Mn：0.31％～1.24％,P≤0.022％,S≤0.010％,Cr：1.26％～3.20％,N i：1.60％～3.80％,Mo：0.001％～0.120％,Cu：0.001％～0.180％,Nb：0.020％～0.060％,V:0.001％～0.030％,T i：0.001％～0.030％,CaO≤0.060,B:0.0001％～0.0039％,Nd：5ppm～15ppm,Pr:1ppm～15ppm, in percentage by weight, and the balance of Fe and unavoidable impurities.
The reason for adopting the components is as follows:
(1) Carbon: carbon C is one of five basic elements in steel, carbon has influence on the strength, hardenability, hardness and the like of the steel, and the carbon content in the invention is used for ensuring the ductile-brittle transition temperature and the welding performance of the steel plate, so the invention C:0.079 to 0.149 percent.
(2) Manganese: mn element can strengthen ferrite in a steel grade in a solid solution strengthening mode, C-Mn strengthening is also a main mode for improving the strength of low-carbon steel, but the Mn content is too high, so that the Mn element is easy to combine with S element to generate MnS while the production cost is increased, and the crack resistance of the material is reduced, so that the Mn:0.31 to 1.24 percent.
(3) P, S: the steel of the invention is harmful element, which can have adverse effect on the low temperature impact toughness and lamellar tearing resistance of the steel plate, and increases the brittleness of the steel. Phosphorus reduces the welding performance, reduces the plasticity and deteriorates the cold bending performance; sulfur reduces the ductility and toughness of steel, causing cracking during forging and rolling. Therefore, the lower the control content, the better, but the invention requires controlling P.ltoreq.0.022% and S.ltoreq.0.010% in steel in view of steelmaking conditions and costs.
(4) Chromium: the hardenability of the steel plate can be improved, the effect is not as good as Mn and Mo elements, but the cost effect is better; the corrosion resistance and the oxidation resistance of the steel plate can be obviously improved; cr in the invention: 1.26 to 3.20 percent.
Nickel: the solid solution strengthening elements in the steel can improve the strength of the steel, N i can relax the stress by reducing the dislocation movement resistance of the steel, and further change the substructure of the matrix structure, so that the toughness of the steel, particularly the low-temperature toughness, is improved, and therefore N i:1.60 to 3.80 percent.
(6) Molybdenum: the element with strong hardenability is beneficial to the hardenability of the steel plate with large thickness along the thickness direction, improves the tempering stability of the steel plate, and can temper the steel plate at a higher temperature so as to improve the plasticity and toughness of the steel plate; the method can improve the solubility of the micro-alloy element in austenite, reduce the precipitation of the carbonitride of the micro-alloy element, enable the micro-alloy element to be precipitated from ferrite at a lower temperature, and enhance the precipitation strengthening effect. Therefore, the present invention requires that the Mo content in the steel be controlled to 0.001% -0.120%.
(7) Copper: the quenching degree of the steel can be improved, the core strength of the thick steel plate can be obviously improved, the steel plate is also an important element for improving weather resistance, and during the slow cooling process of the thick steel plate, a proper amount of Cu can be separated out epsilon-Cu through self tempering, so that the strength of the steel plate is improved. When the Cu content is too high, hot cracks are generated in the steel sheet, and the plasticity of the steel sheet is lowered. Thus in the present invention Cu:0.001 to 0.180 percent.
(8) Niobium: precipitation and pinning of grain boundary are carried out in the rolling process, nucleation is promoted, grains are effectively refined, and therefore strength and toughness are improved; the austenite transformation temperature is reduced, the recrystallization temperature can be increased, grains are refined under high-temperature rolling, the strength of the steel plate is improved, and the plate type rolling control is facilitated; part of C, N compounds of Nb exist in the tempering process, so that the strength of the steel plate is ensured. However, an excessive Nb content deteriorates weld joint and heat affected zone toughness and also increases costs. Nb in the steel of the invention: 0.020-0.060 percent.
(9) Vanadium: in quenched and tempered steel, the effects of improving the strength and yield ratio of the steel, refining grains and improving the toughness are mainly achieved, but vanadium has stronger affinity with carbon and oxygen, and when the vanadium exists in a carbide form, the hardenability is affected, so that V in the invention: 0.001% -0.030.
(10) Titanium: in the common low alloy steel, the plasticity and toughness can be improved, and as the carbon fixes nitrogen and sulfur to form titanium carbide, the strength of the steel is improved, so T i in the invention: 0.001% -0.030.
(11) Calcium oxide: the calcium oxide plays a role of nucleation point in steelmaking, is beneficial to refining grains, and can improve lamellar tearing resistance and fatigue strength. Therefore, caO is required to be less than or equal to 0.060.
(12) Neodymium: purifying the steel and deteriorating impurities in the steel, thereby playing a role in improving the purity of the steel; the high temperature performance of the material can be improved, so the content of Nd is 5ppm to 15ppm.
(13) Praseodymium: more equiaxed grain structures can be formed in the central region of the steel, and the grain size of the steel is thinned, so that the steel has higher tensile strength and impact resistance. Can also react with A l 2O3, mnS inclusions and the like in the steel matrix, change the inclusion components, size parameters, appearance structure, distribution form and quantity in the steel, and convert the irregular appearance inclusions with larger original size into spherical rare earth inclusion with smaller size, thereby achieving the effect of improving the mechanical strength of the steel. Pr in the steel of the invention: 1ppm to 15ppm.
(14) Boron: the hardenability improving element is easy to adsorb on a crystal boundary to reduce the crystal boundary energy, so that the proeutectoid ferrite is not easy to nucleate, the incubation period of transformation between the proeutectoid ferrite and the upper bainite is prolonged, the ferrite transformation is restrained and delayed, the hardenability is further improved, and the method is particularly suitable for improving the hardenability of a special thick plate; however, the solubility of the modified alloy in steel is low, and the modified alloy is influenced by the existence form of the modified alloy, so that B brittleness is easy to form, and the plasticity of the steel is not good, and therefore, the modified alloy disclosed by the invention has the following characteristics: 0.0001-0.0039%.
The invention relates to steel for an advanced nuclear power unit pressure vessel and a manufacturing method thereof, comprising the following steps:
(1) The smelting process comprises the following steps: smelting molten steel in a converter, wherein high-quality scrap steel and molten iron are adopted as raw materials, the content of the molten iron is controlled to be 70-90%, dephosphorization and oxygen blowing are controlled to be 10-16 min, desulfurization and oxygen blowing are controlled to be 11-17 min, and finally the mass fraction of phosphorus is reduced to be within 0.005% and the mass fraction of sulfur is reduced to be within 0.004% in the converter; reducing slag is manufactured in an LF refining furnace, the thickness of a slag layer is 90-120 mm, and the inclusion is ensured to float upwards fully; degassing is completed in an RH furnace, the net circulation time is 10-15 min, the vacuum degree is 32-56 Pa, the calm time before casting is 9-12 min, the hydrogen content of the gas is strictly controlled to be less than or equal to 0.0001%, the oxygen content is less than or equal to 0.0012%, and the nitrogen content is less than or equal to 0.0015.
In casting, the superheat degree of the tundish is controlled to be 30-50 ℃, the temperature of secondary cooling water is controlled to be 20-30 ℃, the flow rate is 220-350 t/h, the temperature of cooling water of a crystallizer is 25-35 ℃, the flow rate is 200-290 t/h, an electromagnetic stirring and heavy pressing mode is adopted at the tail end of continuous casting, the electromagnetic stirring current is 390-520A, the frequency is 15-25 HZ, the pressing amount is 15-30 mm, and the blank pulling speed is controlled to be 0.6-1.0 m/min. Through process control, 10-20% of casting blank fine crystals and 25-35% of equiaxed crystals, the as-cast structure is effectively improved, the structure uniformity is improved, and a foundation is laid for obtaining excellent performance of the steel plate. The thickness of the continuous casting billet is preferably 200-300 mm, and the continuous casting billet is stacked and slowly cooled for more than 24 hours after being taken off line, so that the homogenization of tissues and precipitates is further promoted, and the component segregation is reduced.
(2) The rolling process comprises the following steps: the rolling of the steel plate adopts two-stage controlled rolling, the initial rolling temperature of the first stage rough rolling is 1050-1150 ℃, the average rolling reduction of the first 4 passes is controlled to be 15-25%, the steel plate is plastically deformed at low temperature, the dynamic recrystallization is promoted, the deformation resistance is increased, and the crystal grains are broken;
the initial rolling temperature of the second stage finish rolling is 980-1050 ℃, and the later 5 passes adopt small deformation, the average reduction rate is 3-6%, which is beneficial to eliminating the rolling orientation of the crystal grains. The final rolling temperature is 950-1000 ℃. The thickness of the rolled steel plate is 10-150 mm.
(3) And (3) heat treatment: and (3) stacking and slow cooling after the steel plates are rolled, and quenching and tempering the steel plates after the slow cooling is finished.
Quenching: the temperature is 870-930 ℃ and the heat preservation time is 2-6 min/mm, the complete austenitizing temperature of the steel plate is reached, the heat preservation is fully carried out, and the steel plate is immediately cooled until the temperature of the steel plate is lower than 100 ℃ after being discharged from the furnace;
Tempering: the temperature is kept between 615 ℃ and 660 ℃ for 4 min/mm to 8min/mm, and the temperature is kept in the temperature range to ensure that carbide in the steel is separated out and form a high-temperature tempered sorbite structure;
The specific implementation mode is as follows:
wherein Table 1 is the chemical composition of the example steel; table 2 shows the smelting process system of the example steel; table 3 example steel continuous casting process; table 4 shows the rolling and heat treatment methods of the example steels; table 5 shows the properties of the steel sheets of examples.
TABLE 1 chemical composition (wt%) of example steels
Table 2 smelting process system of example steel
Table 3 example continuous casting process parameters
Table 4 method for rolling and heat treating example steels
Table 5 example steel sheet properties
The example shows that the average mechanical properties of the steel plate are as follows: the room temperature tensile yield strength is more than or equal to 392MPa, the tensile strength is more than or equal to 550MPa, and the elongation is more than or equal to 20%; high-temperature tensile yield strength of not less than 311MPa, tensile strength
≥455MPa，TNDT/≥-35℃。
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims (5)

1. The utility model provides an advanced nuclear power unit steel for pressure vessel which characterized in that: the steel for the advanced nuclear power unit pressure vessel comprises the following components ,C：0.079％～0.149％,Mn：0.31％～1.24％,P≤0.022％,S≤0.010％,Cr：1.26％～3.20％,Ni：1.60％～3.80％,Mo：0.001％～0.120％,Cu：0.001％～0.180％,Nb：0.020％～0.060％,V:0.001％～0.030％,Ti：0.001％～0.030％,CaO≤0.060,B:0.0001％～0.0039％,Nd：5ppm～15ppm,Pr:1ppm～15ppm, by weight percent, and the balance of Fe and unavoidable impurities.
2. The steel for advanced nuclear power unit pressure vessels of claim 1, wherein: the width of the stainless steel medium plate ranges from 3000 mm to 4500mm.
3. The steel for advanced nuclear power unit pressure vessels of claim 1, wherein: the thickness range of the medium plate is 10-150 mm.
4. A method for manufacturing steel for advanced nuclear power unit pressure vessels according to any one of claims 1 to 3, characterized in that: the method comprises the following steps:
S1: the smelting process comprises the following steps: molten steel smelting is carried out in a converter, waste steel and molten iron are adopted as raw materials, the content of molten iron is controlled to be 70-90%, dephosphorization and oxygen blowing are controlled to be 10-16 min, desulfurization and oxygen blowing are controlled to be 11-17 min, and finally the mass fraction of phosphorus is reduced to be within 0.005% and the mass fraction of sulfur is reduced to be within 0.004% in the converter;
reducing slag is manufactured in an LF refining furnace, and the thickness of a slag layer is 90-120 mm;
Degassing is completed in an RH furnace, the net circulation time is 10-15 min, the vacuum degree is 32-56 Pa, the calm time before casting is 9-12 min, the hydrogen content of the gas is controlled to be less than or equal to 0.0001%, the oxygen content is controlled to be less than or equal to 0.0012%, and the nitrogen content is controlled to be less than or equal to 0.0015;
In casting, the superheat degree of a tundish is controlled to be 30-50 ℃, the temperature of secondary cooling water is controlled to be 20-30 ℃, the flow rate is 220-350 t/h, the temperature of cooling water of a crystallizer is 25-35 ℃, the flow rate is 200-290 t/h, an electromagnetic stirring and heavy pressing mode is adopted at the tail end of continuous casting, the heavy pressing is 15-30 mm, the electromagnetic stirring current is 390-520A, the frequency is 15-25 HZ, the pressing amount is 15-30 mm, and the blank pulling speed is controlled to be 0.6-1.0 m/min;
Through the process control, casting blank fine crystals are 10-20%, and equiaxed crystals are 25-35%;
Stacking and slowly cooling for more than 24 hours after offline;
S2: the rolling process comprises the following steps: the rolling of the steel plate adopts two-stage controlled rolling, wherein the rolling temperature is 1050-1150 ℃ in the first stage, and the average rolling reduction rate of the first 4 passes is controlled to be 15-25%;
the initial rolling temperature of the second stage is 980-1050 ℃, the later 5 passes adopt small deformation, and the average reduction rate is 3-6%;
The finishing temperature is controlled to be 950-1000 ℃;
S3: the heat treatment process comprises the following steps: stacking and slow cooling are carried out after the steel plate is rolled, and quenching and tempering are carried out on the steel plate after the slow cooling is finished;
quenching: the temperature is 870-930 ℃ and the heat preservation time is 2-6 min/mm, and water cooling is immediately carried out after the steel plate is discharged until the temperature of the steel plate is lower than 100 ℃;
tempering: the temperature is 615-660 ℃ and the heat preservation time is 4-8 min/mm.
5. The method for manufacturing steel for pressure vessels of advanced nuclear power units as claimed in claim 4, wherein: the continuous casting billet also comprises a preferable thickness of 200-300 mm.
CN202410159616.7A 2024-02-04 2024-02-04 Steel for advanced nuclear power unit pressure vessel and manufacturing method thereof Pending CN118028703A (en)

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