CN116121646B - High-strength low-carbon equivalent steel for nuclear reactor containment vessel and manufacturing method thereof - Google Patents

High-strength low-carbon equivalent steel for nuclear reactor containment vessel and manufacturing method thereof Download PDF

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CN116121646B
CN116121646B CN202211665169.XA CN202211665169A CN116121646B CN 116121646 B CN116121646 B CN 116121646B CN 202211665169 A CN202211665169 A CN 202211665169A CN 116121646 B CN116121646 B CN 116121646B
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steel
temperature
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equal
steel plate
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CN116121646A (en
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胡海洋
郑明光
孟劲松
王永东
王义栋
王勇
孙殿东
宁冬
颜秉宇
王谊清
管吉春
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Angang Steel Co Ltd
Shanghai Nuclear Engineering Research and Design Institute Co Ltd
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Angang Steel Co Ltd
Shanghai Nuclear Engineering Research and Design Institute Co Ltd
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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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • 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
    • 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
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/001—Heat treatment of ferrous alloys containing Ni
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • C21D2211/002—Bainite
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

Abstract

The invention provides a high-strength low-carbon equivalent steel for a nuclear reactor containment vessel and a manufacturing method thereof, wherein the steel comprises the following components in percentage by weight: c:0.07 to 0.11 percent; si:0.10 to 0.30 percent; mn:0.80 to 1.20 percent; p is less than or equal to 0.010 percent; s is less than or equal to 0.005%; ni:0.30 to 0.55 percent; cu:0.25 to 0.45 percent; mo:0.25 to 0.55 percent; v:0.08 to 0.12 percent; nb:0.065% -0.090%; ti:0.020 to 0.040 percent; al:0.020 to 0.050 percent; n:0.020 to 0.035 percent; V/N is more than 3; b:0.001 to 0.003 percent; the content of [ O ] is less than or equal to 10ppm; [H] less than or equal to 2ppm, ceq less than or equal to 0.41 percent, and the balance of Fe and unavoidable impurities. The manufacturing method comprises smelting, continuous casting, heating, controlled rolling and cooling, slow cooling and off-line tempering heat treatment, and the steel plate produced by the method has the impact energy of welded joint at-45 ℃ of more than or equal to 150J under the welding heat input of 10-200 kJ/cm.

Description

High-strength low-carbon equivalent steel for nuclear reactor containment vessel and manufacturing method thereof
Technical Field
The invention belongs to the field of metal materials, and particularly relates to steel for a high-strength low-carbon equivalent nuclear reactor containment vessel and a manufacturing method thereof.
Background
Compared with a second generation nuclear power unit and a second generation nuclear power unit, the third generation pressurized water reactor nuclear power unit built by adopting the AP1000 and CAP1400 nuclear power technology has the advantages that the power is higher, and in addition, the safety performance is greatly improved. The AP1000 and CAP1400 third-generation pressurized water reactor nuclear motor unit adopts a double-layer containment design, wherein the outer layer is of a reinforced concrete structure, the inner layer is of a steel containment, and the last safety line of the whole nuclear power unit is formed. The steel containment is currently built by ASME SA-738Gr.B steel plates, the steel plates have good comprehensive performance and the tensile strength grade is 585 MPa. However, with the proposal of the higher power nuclear power technology CAP1700, the requirements on the steel materials of the constructed nuclear power plant are also improved, and the design strength of the steel containment can reach 685MPa, so that the ASME SA-738Gr.B steel can not meet the application requirements any more.
The new generation steel for the steel containment vessel not only needs to have higher strength (685 MPa level), good low-temperature toughness, but also needs to have lower carbon equivalent so as to meet the requirements of engineering welding of a large-scale nuclear power unit. The existing invention patents related to the steel have the problems of poor comprehensive performance, low strength and the like, and similar patents are different from the composition design and the process design of the invention.
The invention relates to a high-strength steel plate for a nuclear reactor containment and a manufacturing method thereof (CN 102264936A), which provides a high-strength steel plate, wherein the steel comprises the following components: c:0.03 to 0.20 percent; si:0.15 to 0.55 percent; mn:0.9 to 1.5 percent; al:0.001 to 0.05 percent; p is less than or equal to 0.030%; s is less than or equal to 0.030%; cr is less than or equal to 0.30 percent; mo is less than or equal to 0.20 percent; ni is less than or equal to 0.60%; v is less than or equal to 0.07%; nb is less than or equal to 0.04 percent; 0.005 to 0.025 percent of Ti; n:0.0020 to 0.0060 percent; b:0.0005 to 0.0020 percent, ca:5ppm to 50ppm, and the balance of Fe and unavoidable impurities. The manufacturing adopts a recrystallization control and off-line tempering mode to obtain the tensile yield strength 621-648 MPa and the tensile strength 670-700 MPa of the steel plate; the method has the defects that the strength is low, and the high-temperature tensile property and the simulated post-welding heat treatment property and the welding property of the steel plate are not clear.
The invention discloses a steel plate for a low-carbon equivalent nuclear containment and a production method thereof (CN 108251748N), and discloses a steel plate for a low-carbon equivalent nuclear containment with the thickness of 20-45mm and a production method thereof, wherein the steel plate comprises the following components: c:0.09 to 0.13 percent; si:0.25 to 0.40 percent; mn:1.0 to 1.35 percent; p is less than or equal to 0.010 percent; s is less than or equal to 0.005%; ni:0.15 to 0.35 percent; 0.15 to 0.30 percent of Cr; mo:0.15 to 0.25 percent; v is less than or equal to 0.10 percent; nb is 0.02-0.04%; cu is less than or equal to 0.10 percent; al is more than or equal to 0.020%; the balance being Fe and unavoidable impurities. The room-temperature tensile yield strength of the steel plate is more than or equal to 415MPa, the tensile strength is 585-705 MPa, and the steel plate is produced by adopting a two-stage controlled rolling, two-time quenching and tempering process; the steel plate has the defects that the strength is lower, and the strength requirement of the steel for the new-generation steel containment vessel cannot be met.
The invention relates to a high-strength steel plate for a containment head of a pressurized water reactor nuclear power plant and a manufacturing method thereof (CN 111020405A), and discloses a high-strength steel plate for the containment head of the pressurized water reactor nuclear power plant with the thickness of 20-90 mm and a manufacturing method thereof, wherein the components of the steel are designed as C:0.10 to 0.17 percent; si:0.15 to 0.35 percent; mn:1.10 to 1.60 percent; p is less than or equal to 0.015 percent; s is less than or equal to 0.008 percent; ni:0.20 to 0.60 percent; cr:0.20 to 0.50 percent; mo:0.65 to 0.95 percent; al:0.015 to 0.035 percent; nb:0.032 to 0.045 percent; cu is less than or equal to 0.050%; v is less than or equal to 0.020%; the balance of Fe and unavoidable impurities. The steel plate is manufactured by adopting a mode of hot rolling and off-line tempering. The steel of the invention has different composition design, higher carbon equivalent and no welding performance data.
Disclosure of Invention
The invention aims to overcome the problems and the shortcomings and provide the high-strength low-carbon equivalent steel for the nuclear reactor containment vessel, which has the advantages of excellent toughness, low-carbon equivalent, easy welding, uniform and stable structural performance and the like, and completely meets the use requirements of the steel for the containment vessel of the new generation of steel and the manufacturing method thereof.
The invention aims at realizing the following steps:
a high-strength low-carbon equivalent steel for a nuclear reactor containment vessel comprises the following components in percentage by weight: c:0.07 to 0.11 percent; si:0.10 to 0.30 percent; mn:0.80 to 1.20 percent; p is less than or equal to 0.010 percent; s is less than or equal to 0.005%; ni:0.30 to 0.55 percent; cu:0.25 to 0.45 percent; mo:0.25 to 0.55 percent; v:0.08 to 0.12 percent; nb: 0.065-0.090%; ti: 0.020-0.040%; al:0.020 to 0.050 percent; n:0.020 to 0.035 percent; V/N is more than 3; b:0.001 to 0.003 percent; the content of [ O ] is less than or equal to 10ppm; [H] less than or equal to 2ppm, and the balance of Fe and unavoidable impurities.
The microstructure of the steel plate is lath bainite and a small amount of granular bainite, wherein the lath bainite accounts for 94-98%, the granular bainite accounts for 2-6%, the microstructure is fine and uniform, and the grain size reaches 10 grade or more.
The thickness of the steel plate is less than or equal to 60mm.
The tensile strength of the steel plate at room temperature is more than 730MPa, the yield strength is more than 660MPa, and the elongation after fracture is more than or equal to 21%; high-temperature tensile strength at 200 ℃ is more than 710MPa, and yield strength is more than 620MPa; impact energy at-45 ℃ is more than 240J.
The tensile strength of the steel plate at room temperature after high-temperature simulated post-welding heat treatment is more than 700MPa, the yield strength is more than 610MPa, and the elongation after fracture is more than or equal to 22%; high-temperature tensile strength at 200 ℃ is more than 670MPa, and yield strength is more than 580MPa; impact energy at-45 ℃ is more than 230J.
The steel plate has good welding performance that the impact energy of a welding joint at the temperature of minus 45 ℃ is more than or equal to 150J under the welding heat input of 10-200 kJ/cm.
The reason for designing the components of the invention is as follows:
c: carbon is the most basic strengthening element in steel, can form tiny carbide with alloy elements such as V, nb, ti and the like, refines grains, effectively improves the toughness of the steel plate, but the improvement of the carbon content can directly influence the increase of the carbon equivalent, thereby influencing the welding performance of the steel plate. Therefore, the C content in the steel of the present invention is designed to be 0.07 to 0.11%.
Si: the silicon is mainly used as a reducing agent and a deoxidizing agent in the steel, plays a certain solid solution strengthening role, and the content is controlled to be 0.10-0.30%.
Mn: in the invention, a proper amount of manganese is added for improving the hardenability of the steel plate in quick cooling, refining the lath bainite structure and improving the toughness of the steel plate; in addition, the invention can enlarge the non-recrystalized area of austenite by controlling the manganese content of proper amount, and promote the generation of dislocation substructure and deformation zone in rolling. Therefore, the Mn content is designed to be 0.80 to 1.20%.
(4) P, S: the steel of the invention is harmful element, the lower the control content is, the better, but the invention requires to control P in the steel to be less than or equal to 0.010 percent and S to be less than or equal to 0.005 percent in consideration of steelmaking conditions and cost.
(5) Ni: in the invention, a proper amount of nickel is added for forming and stabilizing austenite, so that the tissue stability and uniformity are improved; the strength of the steel plate is improved, the carbon content is reduced, and the welding performance of the steel plate is improved; since nickel has a tendency to inhibit the desolventization of carbon from austenite, too high nickel is unfavorable for precipitation of grain boundary carbides, thereby reducing the number of inter-grain carbides, severely affecting the toughness of the steel of the present invention. Therefore, the Ni content is designed to be 0.30-0.55%.
(6) Cu: the method is used for inhibiting austenite recrystallization, expanding an austenite unrecrystallized region to refine grains, improving the hardenability of the steel plate and improving the precipitation strengthening effect; a certain amount of copper is also beneficial to refining the as-cast structure, reducing the segregation degree and improving the structure uniformity; the high-temperature oxidation resistance of the steel plate is improved, and the strength loss of the steel plate after high-temperature and long-time simulated post-welding heat treatment is reduced. The embrittlement phenomenon is easy to occur when the copper content is too high, so the invention designs Cu:0.25 to 0.45 percent.
(8) Mo: the role of molybdenum in the steel of the invention is mainly: 1) The ferrite and pearlite transformation is inhibited, the cooling speed range of bainite formation is enlarged, and the formation of lath bainite is promoted; 2) The austenite recrystallization temperature is increased, the austenite unrecrystallized rolling effect is improved, and grains are refined; 3) Inhibit the aggregation growth of carbide in steel and maintain the precipitation dispersion strengthening effect of carbide after simulated post-welding heat treatment. Therefore, the Mo content is designed to be 0.25-0.55%.
(9) V: the method is used for forming carbonitride, deformation is induced to separate out in rolling, a grain boundary is pinned, and grains are refined; separating out in the controlled cooling and tempering to play a role in precipitation strengthening; the invention adds proper amount of N, strengthens the action mechanism of V, N by controlling V/N to be more than 3, improves the stability of tiny VN and nitrogen-rich V (C, N), refines the bainitic structure to the greatest extent, improves the toughness of the steel plate and effectively improves the welding performance of the steel plate. According to the requirement, the V content is 0.08-0.012%.
(10) Nb: the role of niobium in the steel of the invention is mainly: 1) The high-content niobium can prevent coarsening of austenite grains in heating of the steel billet, and keep smaller original grain size; 2) The method is used for inhibiting recrystallization in the high-temperature deformation process and expanding the range of the non-recrystallized region of the austenite, thereby being beneficial to multi-pass rolling of the non-recrystallized region of the austenite and playing a good role in refining grains; 3) Part of the solution is dissolved into solid solution to play a role in solid solution strengthening; 4) The tempering resistance of the steel plate is improved, and the high-temperature strength is improved. The Nb content in the steel is designed to be 0.065-0.090%.
(11) Ti: the method is used for forming fine TiC and TiN, improving an as-cast structure, reducing segregation and improving the quality of a casting blank; increasing the coarsening temperature of the crystal grains in heating; and a part of N is fixed, so that the utilization rate of B is improved. The Ti content in the steel is designed to be 0.020-0.040%.
(12) Al: the alloy is mainly used for deoxidizing and refining grains, and the Al content is controlled to be 0.020-0.050% according to the requirement.
(13) N: the action mechanism of V, N is strengthened by controlling V/N to be more than 3, the stability of tiny VN and nitrogen-rich V (C, N) is improved, the bainitic structure is refined to the greatest extent, the toughness of the steel plate is improved, and the welding performance of the steel plate is effectively improved; the method is used for improving the strengthening effect of Nb, ti and the like and improving the comprehensive performance of the steel plate; for improving the high-temperature strength of the steel plate; the excessively high nitrogen content increases the ageing tendency, cold brittleness and hot brittleness of the steel plate and damages the welding performance of the steel plate, so the design N content of the invention is 0.020-0.035%.
(14) B: for increasing hardenability of the steel sheet; and is also used for inhibiting ferrite nucleation, so that the ferrite generation area is obviously moved to the right and bainite formation is promoted. The content of B in the invention is designed to be 0.001-0.003%.
(15) H and O: hydrogen and oxygen are harmful elements in steel, and hydrogen dissolved in steel can cause defects such as hydrogen embrittlement, white spots and the like of steel. Oxygen is easy to form oxide inclusion in steel, and the strength and plasticity of the steel are reduced, so that the invention controls [ H ] < 2ppm and [ O ] < 10ppm.
The second technical proposal of the invention is to provide a manufacturing method of the steel for the high-strength low-carbon equivalent nuclear reactor containment vessel, which comprises smelting, continuous casting, heating, controlled rolling and cooling, slow cooling and off-line tempering heat treatment;
smelting:
the steel adopts a high-cleanness steel smelting process, and the P in the steel is strictly controlled to be less than or equal to 0.010 percent; s is less than or equal to 0.005%, and then the steel is subjected to LF and RH external refining treatment, so that [ H ] is less than or equal to 2.0ppm and [ O ] is less than or equal to 10ppm, and nonmetallic inclusion in the steel is ensured to be below 1.0 level. The thickness of the continuous casting billet is preferably 250-300 mm.
Continuous casting and heating:
the continuous casting blank is heated in a walking furnace, the heating temperature is 1120-1160 ℃, the heating speed is 8-11 min/cm, the austenitizing of the continuous casting blank is effectively ensured to be full, and the growth of austenite grains is restrained.
Rolling and cooling control:
the rolling of the steel plate adopts two-stage controlled rolling, the rolling is carried out in an austenite recrystallization zone in the first stage, the initial rolling temperature is 1050-1090 ℃, the single-pass rolling reduction rate is more than 14%, the interval time after each pass of rolling is less than or equal to 5s, and the thickness of a rolled intermediate billet is more than 3t (t: the thickness of a finished steel plate). The large deformation rolling of the austenite recrystallization region can promote the repeated recrystallization of austenite, and the precipitates such as NbN, tiN and the like are utilized to prevent the growth of austenite grains, so that the austenite grains are fully refined. The steel plate is cooled by water after being rolled in the recrystallization zone, and the cooling rate is 5-10 ℃/s so as to prevent austenite grains from growing up. And controlling the temperature to 860-900 ℃ to roll in a second-stage austenite non-recrystallization zone, controlling the total reduction ratio to be more than 68%, and controlling the final rolling temperature to be 680-710 ℃ and the thickness of the finished steel plate to be not more than 60mm. The multi-pass accumulated deformation of the austenite non-recrystallized region can promote the generation of a large number of dislocation substructures and deformation bands in austenite grains, so that the transformation and refinement of bainite are promoted, and the lower finishing temperature is favorable for the effective inheritance of the dislocation substructures in the austenite grains.
Slowly cooling:
after finishing rolling, the steel plate is cooled to 400-450 ℃ at a cooling speed of 15-25 ℃/s after the temperature is 620-650 ℃. And the proper temperature after finish rolling is beneficial to forming ultrafine structures by high-density dislocation in the rolled steel plate, and is beneficial to further precipitation of carbonitride, thereby playing a role in precipitation strengthening. The higher cooling speed is to promote the phase change of the ultra-fine lath bainite, prevent coarsening of the precipitate and keep the strengthening effect.
Off-line tempering heat treatment:
the finished steel plate is subjected to off-line tempering heat treatment, the tempering temperature is 600-640 ℃, the heat preservation time is 3-6 min/mm, and the steel plate is cooled to room temperature after being discharged from the furnace. And by adopting a proper tempering process, the structure is homogenized and the performance is stabilized, meanwhile, the precipitation of carbonitride is promoted, and the toughness of the steel plate is improved.
The final structure of the steel plate is lath bainite and a small amount of granular bainite, wherein the lath bainite accounts for 94-98%, the granular bainite accounts for 2-6%, the structure is fine and uniform, and the grain size of the steel plate reaches 10 grade or more.
The invention has the beneficial effects that:
1. the invention realizes the production and manufacture of the steel for the 685 MPa-level nuclear reactor containment with low carbon equivalent and easy welding by adopting the innovative design of the microalloy steel component system and combining the two-stage controlled rolling, controlled cooling and high-temperature tempering process, and the structure and the performance of the steel plate are uniform and stable.
2. The steel plate manufactured by the invention has high toughness and good welding performance that the impact energy of a welding joint at-45 ℃ is more than or equal to 150J under the welding heat input of 10-200 kJ/cm.
3. The invention skillfully utilizes deformation induction precipitation and medium temperature control, and obtains an ultrafine bainite structure with excellent strength and toughness through controlled rolling of an austenite recrystallization region and a non-recrystallization region and controlled cooling at a lower temperature.
4. The room-temperature tensile strength of the steel plate manufactured by the method is more than 730MPa, the yield strength is more than 660MPa, and the elongation after fracture is more than or equal to 21%; high-temperature tensile strength at 200 ℃ is more than 710MPa, and yield strength is more than 620MPa; impact energy at-45 ℃ is more than 240J. Especially, the mechanical properties after long-time and high-temperature simulated post-welding heat treatment are kept good, wherein the room-temperature tensile strength is more than 700MPa, the yield strength is more than 610MPa, and the elongation after fracture is more than or equal to 22%; high-temperature tensile strength at 200 ℃ is more than 670MPa, and yield strength is more than 580MPa; impact energy at-45 ℃ is more than 230J. Can effectively meet the use safety of the steel for the nuclear reactor containment.
Drawings
FIG. 1 is a golden phase diagram of a microstructure according to example 1 of the present invention.
Detailed Description
The invention is further illustrated by the following examples.
According to the component proportion of the technical scheme, smelting, continuous casting, heating, controlled rolling and cooling, slow cooling and off-line tempering heat treatment are carried out.
Heating:
the heating temperature of the casting blank is 1120-1160 ℃, and the heating speed is 8-11 min/cm;
rolling and cooling control:
adopting two-stage controlled rolling, wherein the initial rolling temperature of the first stage is 1050-1090 ℃, the single-pass rolling reduction is more than 14%, and the interval time after each pass of rolling is less than or equal to 5s; the thickness of the rolled intermediate billet is more than 3t (t: the thickness of the finished steel plate); the temperature of the rolled steel plate is controlled by water cooling; rolling in the second stage at 860-900 deg.c with total rolling reduction over 68% and final rolling temperature of 680-710 deg.c;
slowly cooling:
after finishing rolling, the steel plate starts to be cooled after the temperature reaches 620-650 ℃, and is finally cooled to 400-450 ℃ at a cooling speed of 15-25 ℃/s;
off-line tempering heat treatment:
the steel plate is subjected to off-line tempering heat treatment, the tempering temperature is 600-640 ℃, the heat preservation time is 3-6 min/mm, and the steel plate is cooled to room temperature after being discharged from the furnace.
Further, the thickness of the continuous casting billet is 250-300 mm.
Further, the water cooling temperature control after the first stage rolling is to control the cooling rate of the intermediate billet to be 5-10 ℃/s.
The composition of the steel of the example of the invention is shown in Table 1. The main process parameters of the steel of the example of the invention are shown in Table 2. The properties of the inventive example steels are shown in Table 3. The post-weld heat treatment performance of the steel mold of the example of the invention is shown in Table 4. The microstructure of the steel of the example of the invention is shown in Table 5.
TABLE 1 composition (wt%) of the inventive example steel
Examples C Si Mn P S Ni Cu Mo
1 0.1 0.15 1.0 0.01 0.004 0.35 0.3 0.25
2 0.07 0.1 1.2 0.007 0.003 0.31 0.25 0.32
3 0.11 0.3 0.85 0.008 0.004 0.45 0.28 0.29
4 0.09 0.2 0.96 0.01 0.003 0.55 0.26 0.26
5 0.07 0.25 1.0 0.01 0.005 0.3 0.45 0.4
6 0.08 0.22 0.8 0.008 0.003 0.4 0.33 0.55
7 0.09 0.15 0.96 0.008 0.004 0.33 0.4 0.28
8 0.11 0.24 0.83 0.01 0.005 0.51 0.25 0.35
9 0.08 0.13 0.95 0.009 0.005 0.3 0.42 0.45
10 0.07 0.2 1.2 0.008 0.003 0.42 0.35 0.3
Examples V Nb Ti Al N V/N B Ceq
1 0.086 0.075 0.025 0.03 0.025 3.4 0.0015 0.38
2 0.09 0.065 0.03 0.02 0.028 3.2 0.001 0.39
3 0.08 0.08 0.02 0.035 0.02 4.0 0.002 0.37
4 0.096 0.085 0.034 0.05 0.031 3.1 0.0015 0.37
5 0.1 0.07 0.025 0.03 0.029 3.4 0.0025 0.39
6 0.09 0.075 0.03 0.028 0.026 3.5 0.0021 0.39
7 0.084 0.09 0.02 0.045 0.023 3.7 0.003 0.37
8 0.11 0.065 0.03 0.04 0.035 3.1 0.0028 0.39
9 0.1 0.066 0.04 0.035 0.03 3.3 0.0019 0.40
10 0.12 0.07 0.02 0.025 0.032 3.8 0.0026 0.41
Note that: (1) above examples [ O ] is less than or equal to 10ppm and [ H ] is less than or equal to 2ppm. (2) ceq=c+mn/6+ (cr+mo+v)/5+ (ni+cu)/15.
TABLE 2 main process parameters of the inventive example steel
Note that: t is the thickness of the component steel plate
TABLE 3 Properties of the inventive example Steel
TABLE 4 post-weld heat treatment performance of the Steel die of the inventive example
Note that samples were taken from each example for a simulated post-weld heat treatment test, the process being: the temperature is kept at 605 ℃, the temperature keeping time is 15h, and the temperature rising and falling rate above 420 ℃ is not more than 58 ℃/h.
TABLE 5 microstructure of inventive example steel
As is clear from the above, the room temperature tensile strength of the steel plate is more than 730MPa, the yield strength is more than 660MPa, and the elongation after fracture is more than or equal to 21%; high-temperature tensile strength at 200 ℃ is more than 710MPa, and yield strength is more than 620MPa; impact energy at-45 ℃ is more than 240J. The tensile strength of the steel plate at room temperature after high-temperature simulated post-welding heat treatment is more than 700MPa, the yield strength is more than 610MPa, and the elongation after fracture is more than or equal to 22%; high-temperature tensile strength at 200 ℃ is more than 670MPa, and yield strength is more than 580MPa; impact energy at-45 ℃ is more than 230J. The steel plate has good welding performance that the impact energy of a welding joint at the temperature of minus 45 ℃ is more than or equal to 150J under the welding heat input of 10-200 kJ/cm.
The present invention has been properly and fully described in the foregoing embodiments by way of example only, and not by way of limitation, and various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, any modification, equivalent substitution, improvement, etc. should be included in the scope of the invention, and the scope of the invention is defined by the claims.

Claims (8)

1. A high-strength low-carbon equivalent steel for a nuclear reactor containment vessel is characterized by comprising the following components in percentage by weight: c:0.07% -0.11%; si:0.10% -0.30%; mn:0.80% -1.20%; p is less than or equal to 0.010 percent; s is less than or equal to 0.005%; ni:0.30% -0.55%; cu:0.25% -0.45%; mo:0.25% -0.55%; v:0.08% -0.12%; nb:0.065% -0.090%; ti:0.020% -0.040%; al:0.020% -0.050%; n:0.020% -0.035%; V/N is more than 3; b:0.001% -0.003%; the content of [ O ] is less than or equal to 10ppm; [H] less than or equal to 2ppm, ceq less than or equal to 0.41 percent, and the balance of Fe and unavoidable impurities; the microstructure of the steel plate is lath bainite and a small amount of granular bainite, wherein the lath bainite accounts for 94% -98%, and the granular bainite accounts for 2% -6%; the grain size of the steel plate reaches 10 grade or above.
2. The high strength low carbon equivalent weight steel for nuclear reactor containment according to claim 1, wherein the thickness of the steel sheet is no greater than 60mm.
3. The high-strength low-carbon equivalent steel for a nuclear reactor containment vessel according to claim 1, wherein the tensile strength of the steel plate at room temperature is more than 730MPa, the yield strength is more than 660MPa, and the elongation after break is more than or equal to 21%; high-temperature tensile strength at 200 ℃ is more than 710MPa, and yield strength is more than 620MPa; impact energy at-45 ℃ is more than 240J.
4. The high-strength low-carbon equivalent steel for a nuclear reactor containment vessel according to claim 1, wherein the tensile strength of the steel plate at room temperature after high-temperature simulated post-weld heat treatment is more than 700MPa, the yield strength is more than 610MPa, and the elongation after break is more than or equal to 22%; high-temperature tensile strength at 200 ℃ is more than 670MPa, and yield strength is more than 580MPa; impact energy at-45 ℃ is more than 230J; the simulated post-welding heat treatment test comprises the following steps: the temperature is kept at 605 ℃, the temperature keeping time is 15h, and the temperature rising and falling rate above 420 ℃ is not more than 58 ℃/h.
5. The steel for a high-strength low-carbon equivalent nuclear reactor containment vessel according to claim 1, wherein the steel plate has a welded joint with an impact energy of not less than 150J at-45 ℃ at a welding heat input of 10 to 200 kj/cm.
6. A method of manufacturing a high strength low carbon equivalent weight steel for a nuclear reactor containment vessel as claimed in any one of claims 1 to 5, comprising smelting, continuous casting, heating, controlled rolling and cooling, slow cooling, off-line tempering heat treatment; the method is characterized in that:
heating:
the heating temperature of the casting blank is 1120-1160 ℃, and the heating speed is 8-11 min/cm;
rolling and cooling control:
adopting two-stage controlled rolling, wherein the initial rolling temperature of the first stage is 1050-1090 ℃, the single-pass rolling reduction is more than 14%, the interval time after each pass of rolling is less than or equal to 5s, the thickness of a rolled intermediate billet is more than 3t, and t is the thickness of a finished steel plate; the temperature of the rolled steel plate is controlled by water cooling; controlling the temperature to 860-900 ℃ for second-stage rolling, controlling the total rolling reduction to be more than 68%, and controlling the final rolling temperature to be 680-710 ℃;
slowly cooling:
after finishing rolling, the steel plate starts to be cooled after the temperature reaches 620-650 ℃, and is finally cooled to 400-450 ℃ at a cooling speed of 15-25 ℃/s;
off-line tempering heat treatment:
the steel plate is subjected to off-line tempering heat treatment, the tempering temperature is 600-640 ℃, the heat preservation time is 3-6 min/mm, and the steel plate is cooled to room temperature after being discharged from the furnace.
7. The method for manufacturing high strength low carbon equivalent weight steel for nuclear reactor containment according to claim 6, wherein: the thickness of the continuous casting billet is 250-300 mm.
8. The method for manufacturing high strength low carbon equivalent weight steel for nuclear reactor containment according to claim 6, wherein: and the water cooling temperature control after the first stage rolling is to control the cooling rate of the intermediate billet to be 5-10 ℃/s.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101096738A (en) * 2006-06-26 2008-01-02 舞阳钢铁有限责任公司 Steel plate with low welding crack sensitivity and production method thereof
JP2015124435A (en) * 2013-12-27 2015-07-06 Ｊｆｅスチール株式会社 Thick steel plate for reactor storage container excellent in brittle crack propagation stopping property

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KR101091398B1 (en) * 2008-12-26 2011-12-07 주식회사 포스코 High Strength Steel Sheet with Excellent Low-Temperature Toughness for Pressure Vessel and Manufacturing Method Thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101096738A (en) * 2006-06-26 2008-01-02 舞阳钢铁有限责任公司 Steel plate with low welding crack sensitivity and production method thereof
JP2015124435A (en) * 2013-12-27 2015-07-06 Ｊｆｅスチール株式会社 Thick steel plate for reactor storage container excellent in brittle crack propagation stopping property

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