Steel plate for the core casing of an advanced nuclear power unit and its manufacturing method

Abstract

The present invention provides a steel plate for a cylindrical body of a core casing of an advanced nuclear power unit and a manufacturing method thereof. The composition of the present invention is, in mass%, C: 0.10%-0.14%, Si: 0.20%-0.30%, Mn: 0.30%-0.60%, P≦0.006%, S≦0.002%, Cr: 1.65%-1.95%, Mo: 0.80%-1.20%, Ni: 0.80%-1.20%, Nb: 0.04%-0.08%, V: 0.1 0%~0.20%, Ti: 0%~0.03%, Alt: 0%~0.02%, Ca: 0.001%~0.004%, N: 0.01%~0.03%, Sn≦0.001%, H≦0.0001%, O≦0.0020%, balance: Fe and unavoidable impurities. High temperature temper embrittlement resistance coefficient J=(Si+Mn)×(P+Sn)×10 4 ≦50. The steel plate and its manufacturing method according to the present invention can ensure the comprehensive performance requirements of the steel plate for the core casing cylinder of advanced nuclear power unit.

Description

[Technical field]

[0001] The present invention relates to the field of metallic materials, in particular to a steel plate for the cylinder of the core casing of an advanced nuclear power unit and a method for manufacturing the same. [Background technology]

[0002] Nuclear power has been used by mankind for more than 70 years as one of the clean and efficient energy sources in the world. Since the 2000s, the contradiction between the frequent activities of mankind and the development of the world economy on the one hand and the energy shortage and extreme climate on the other hand has become increasingly evident, and the advantages of nuclear power seem to be even more prominent in such an integrated world. Therefore, the peaceful development of more advanced nuclear power is still a requirement of the times. Currently, nuclear power technology has gone through the development of the first generation prototype reactor, the second generation pressurized water reactor, and the third generation advanced light water reactor, and the fourth generation advanced nuclear technologies such as sodium-cooled fast reactor, air-cooled fast reactor, lead-cooled fast reactor, very high temperature gas reactor, molten salt reactor, and supercritical pressure light water reactor have been proposed by nuclear power experts around the world, and are the direction of the future development of nuclear power technology.

[0003] The main features of the fourth generation nuclear technology are better safety, better economy, less nuclear waste, and effective prevention of nuclear proliferation. Therefore, it puts very high requirements on nuclear technology and nuclear equipment. For example, the structural steel for the core support of the nuclear safety grade I part is not only exposed to high temperature and hydrogen atmosphere, but also to strong irradiation of fast neutrons, and the risk of base embrittlement and hydrogen erosion caused by water decomposition is several times higher than that of the previous generation nuclear power units, so very high technical index requirements are put forward for the component materials. Therefore, the development of key nuclear equipment and key nuclear materials to meet the needs of the fourth generation advanced nuclear power plant has become a core challenge that the world's current nuclear powers need to solve urgently.

[0004] In Patent Document 1 (Heat Treatment Method for Forgings of Core Cylinder of Nuclear Reactor Pressure Vessel, China Patent Application No. 200910057359.1), it can be seen from the disclosed ingredients, manufacturing methods and beneficial effects that the patent specifies a standard of 16MND5, which is widely used in the manufacture of Gen 3 nuclear power equipment, with an operating temperature of 350°C, and does not apply to Gen 4 nuclear power equipment, which has higher operating temperatures and technical requirements.

[0005] The above-mentioned Patent Document 1 mainly relates to metal materials required for third generation nuclear power generation equipment, which, compared with the component materials required for fourth generation nuclear power generation technology, has the characteristics of relatively low high temperature use temperature, no hydrogen in the contact atmosphere, short post-weld heat treatment time, and relatively uniform material mechanical property index. Therefore, the development of component materials required to meet the important equipment of fourth generation nuclear power plants is urgently required.

[0006] Therefore, the present invention invents new materials and new processes required for important equipment of advanced nuclear power units in order to meet the high purity requirements for the steel material of the core casing cylinder of 4th generation nuclear power generation equipment, as well as technical features such as thermal strength and fracture toughness at 500°C, low NDT temperature, excellent hydrogen-induced cracking prevention performance, stable structural performance after long-term post-welding heat treatment at high temperatures, and good processing and forming properties. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] China Patent Application Publication No. 101906523 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the above technical problems, and provides a steel plate for the cylinder of the core casing of advanced nuclear power unit and its manufacturing method. The present invention adopts a brand new chemical composition design and appropriate production process, based on medium and low C, Si, Mn composition, and adds Cr, Mo, Ni, Nb, V, Ti and N as alloying elements, strictly controls the content of harmful elements P, S, Sn and gas O, H, and further adopts unique smelting, rolling and heat treatment production processes to obtain a steel plate with high strength at 500℃, good high-temperature fracture toughness, and excellent low-temperature ball drop and hydrogen-induced cracking prevention performance, which meets the manufacturing and use requirements of the cylinder of the core casing of the fourth generation advanced nuclear power unit. [Means for solving the problem]

[0009] The technical means of the present invention are as follows: One embodiment of the present invention is a steel plate for a cylindrical body of a core casing of an advanced nuclear power unit, the composition of which is, in mass%, C: 0.10% to 0.14%, Si: 0.20% to 0.30%, Mn: 0.30% to 0.60%, P≦0.006%, S≦0.002%, Cr: 1.65% to 1.95%, Mo: 0.80% to 1.20%, Ni: 0.80% to 1.20%, Nb: 0.10% to 0.14%, Si: 0.20% to 0.30%, Mn: 0.30% to 0.60%, P≦0.006%, S≦0.002%, : 0.04%~0.08%, V: 0.10%~0.20%, Ti: 0%~0.03%, Alt: 0%~0.02%, Ca: 0.001%~0.004%, N: 0.01%~0.03%, Sn≦0.001%, H≦0.0001%, O≦0.0020%, balance: Fe and unavoidable impurities, and the high temperature temper embrittlement resistance coefficient J=(Si+Mn)×(P+Sn)×10 4 <=50.

[0010] Furthermore, in the delivered state, 500MPa≦R at room temperature el ≦520MPa, 610MPa≦R m ≦640MPa, and 470MPa≦R at 500℃ m ≦485MPa, and in the post-weld heat treatment state of 700℃×26h, 450MPa≦R m (500℃)≦470MPa, KV2 (80℃)≧420J, T NDT≦-40℃, CSR of HIC (solution A) is 0%, and 280MPa m 1 / 2 ≦K IC ≦285MPa m 1 / 2 As a result, steel plates for cylinders with thickness standards of 40 to 65 mm were obtained.

[0011] The principles for selecting each chemical component and the reasons for designing the content thereof in the present invention are as follows:

[0012] C: In the present invention, the main solute C and compound C ensure the high temperature tensile strength of the steel during heat treatment and post-weld heat treatment. However, a relatively high carbon content affects the steel toughness and weldability, so the present invention sets the C content range to 0.10% to 0.14%.

[0013] Si: A good reducing agent and deoxidizer in the steelmaking process. In particular, when used in combination with Alt, the deoxidizing ability of Alt can be significantly increased. Si forms a dense SiO2 protective film on the surface at high temperatures that is resistant to oxidation. In addition, due to the cooperative action of Si and Mo, the atomic bonds in the crystal structure show the characteristics of coexistence of metallic bonds and covalent bonds, and an intermetallic compound MoSi2 with excellent high-temperature oxidation resistance is formed. Therefore, in a preferred embodiment, the Mo / Si ratio of the present invention is limited to between 2.80 and 5.50 to ensure the formation of a certain amount of MoSi2 structure. However, in the temper embrittlement temperature range of 350 to 550 ° C, if the silicon content is too high, the temper embrittlement sensitivity of the steel increases, so the present invention does not prefer to add excessive silicon element, and therefore the present invention sets the Si content range to 0.20% to 0.30%.

[0014] Mn: In the present invention, the amount of deoxidizers such as Si and Alt added is small, so the addition of Mn compensates for the insufficient deoxidization effect. In addition, Mn is an alloying element with strong solid solution strengthening ability and can increase the strength of the matrix. However, Mn is a sensitive element that increases temper brittleness and must be strictly controlled in the present invention. Therefore, the present invention sets the Mn content range to 0.30% to 0.60%.

[0015] S, P: As harmful elements in steel, they must be strictly controlled to guarantee the overall indexes of steel such as purity, J coefficient and fracture toughness. Therefore, the contents are limited to S≦0.002% and P≦0.006%.

[0016] Cr: A strong carbide-forming element that combines with Fe, Mn, and Mo in steel to form stable M 23 It produces alloy carbides with a C6 structure, which ensures high-temperature performance during long-term post-weld heat treatment, and also fulfills the high-temperature antioxidant and oxidation corrosion functions of Cr. However, if the Cr content is too high, the brittle transition temperature of the steel increases, so the present invention sets the Cr content range to 1.65% to 1.95%.

[0017] Mo: improves the hardenability of steel and ensures the strength of the steel matrix. Mo is a strong carbide forming element, and forms a stable Mo2C heat strengthening phase together with carbon element, and plays a high temperature strengthening role. In addition, in this application, many Cr elements and a certain amount of Mn elements are added, which are prone to co-polymerization with impurity elements such as P and Sn at grain boundaries, which causes high temperature tempering embrittlement and affects the high temperature performance of the steel. On the other hand, the function of Mo is completely opposite, and precipitates P in the crystal to prevent grain boundary segregation. In the preferred embodiment, the present invention limits (Cr+Mn) / Mo to 1.65-2.90 to ensure the stability of the structure and performance of the core casing cylinder steel during operation at 500°C. However, if the Mo content is too high, the steel will become embrittled, so the present invention sets the Mo content range to 0.80%-1.20%.

[0018] Ni: In the present invention, the Ni element mainly enhances the hydrogen corrosion resistance, plasticity and toughness of steel, reduces the brittle transition temperature of ferrite, and prevents the rise in the non-ductile transition temperature due to the effect of radiation irradiation. However, if the Ni content is too high, the radiation resistance of the material is reduced, so the present invention sets the Ni content range to 0.80% to 1.20%.

[0019] Nb: In the present invention, Nb has the effect of refining crystal grains, which improves the toughness and hydrogen-induced cracking resistance of the steel, and also forms carbides to consume carbon, which allows the steel to have good hydrogen resistance. Therefore, the Nb content is limited to 0.04% to 0.08%.

[0020] V: Added in large quantities in the present invention. One of its main functions is that the carbon and nitrogen complex compounds formed with C and N elements are very stable during the long-term and high-temperature post-weld tempering process, ensuring high-temperature strength in the high-temperature post-weld heat treatment state. Secondly, V fixes C to vanadium carbide, greatly improving the stability of hydrogen resistance of steel under high temperature and pressure. In addition, the addition of V alloy effectively suppresses the grain boundary segregation of Cr and Mn elements due to irradiation, so the V content is limited to 0.10% to 0.20%.

[0021] Ti: One of the elements that strongly forms ferrite. In the present invention, the Ti element exists as a participating element or a small amount of added element. When added, the A1 and A3 temperatures of the steel are strongly increased. Titanium can increase the plasticity and toughness of the steel. Titanium bonds carbon and nitrogen to form titanium carbide and titanium nitride, improving the strength of the steel. The Ti content is limited to 0% to 0.03% because the grains are refined and carbides are precipitated and formed after normalizing and heat treatment, significantly improving the plasticity and impact toughness of the steel.

[0022] Alt: In the present invention, the Alt element exists as a related element or a small amount of added element and acts as a deoxidizer. The main purpose of not adding Alt or adding a small amount of Alt is to ensure the purity of the steel and prevent the formation of aluminum oxides from affecting fatigue performance, so the Alt content is limited to 0%~0.02%.

[0023] Ca: The inclusions of the present invention are spheroidized with Ca, and the MnS inclusions are changed to CaS or composite inclusions containing CaS, so that the Al2O3 inclusions become calcium aluminate oxide inclusions, and such inclusions are spherical and distributed in a dispersed manner, hardly deform at the rolling temperature of the steel, and remain spherical even after rolling, so that the hydrogen-induced cracking sensitivity of the steel can be reduced by Ca treatment. However, if too much Ca is added, the size of the formed Ca(O,S) is too large, and the brittleness increases, which can become the starting point of fracture cracks, reducing the low-temperature toughness, ductility, and weldability of the steel, as well as reducing the purity of the steel, so the present invention sets the Ca content range to 0.001% to 0.004%.

[0024] N: Forms nitrides with elements such as Nb and V, which precipitate and deposit at grain boundaries, pinning the grain boundaries and refining the crystal grains, thereby enhancing the high-temperature strength of the grain boundaries. Therefore, the N content is limited to 0.01% to 0.03%.

[0025] Sn: A residual element in steel. It not only affects the purity of steel, but is also an important element that affects the temper brittleness coefficient J, and therefore must be strictly controlled. Therefore, the Sn content is limited to 0.001% or less.

[0026] H, O: exist as harmful gases. For example, H can cause defects such as "white spots" or "hydrogen embrittlement" in steel, which can have serious effects on the service life of materials and the safety of equipment. O can form non-metallic oxides with Al and Si elements, which can affect the purity of steel and the mechanical properties of materials, and can cause many other defects. Therefore, they must be strictly controlled. The O content is limited to 0.0020% or less, and the H content to 0.0001% or less.

[0027] In order to achieve the object of the present invention, the present invention further provides a method for manufacturing a steel plate for the cylindrical body of the core casing of an advanced nuclear power unit, which includes the steps of hot metal pretreatment--converter dephosphorization--converter decarburization--out-of-furnace refining (LF+RH)--slab continuous casting--slow cooling of the stack--billet cleaning--electroslag remelting--slow cooling of the electroslag steel ingot--slab heating--finished product rolling--hot straightening--slow cooling--heat treatment--flaw detection--inspection and verification, and the main specific steps of the present invention are as follows:

[0028] 1) Smelting process: Molten steel is smelted in a converter, and high-quality scrap steel and molten pig iron are used as raw materials. The content of the molten pig iron is controlled to 70-80%. In order to effectively reduce the content of the harmful element P, dephosphorization and decarburization are separately performed using a converter, where the oxygen blowing time for dephosphorization is controlled to 7-10 minutes, and the oxygen blowing time for decarburization is controlled to 8-12 minutes, and the phosphorus mass fraction is finally reduced to within 0.006%. Deep desulfurization is performed in the LF refining furnace to control the sulfur content to below 0.002%, and at the same time, calcium treatment is performed by feeding CaSi wire into the steel, the wire feed speed is 200-350m / min, and the wire feed depth is 1.0-2.0m below the slag layer. This treatment changes the morphology of non-metallic inclusions, forming fine CaS or calcium aluminate spherical inclusion mass points, increasing the axial ratio of steel billets, etc., while purifying the steel quality, improving the purity, improving the hydrogen resistance of steel, and ensuring sufficient floating of inclusions. Degassing is completed in the RH furnace, the net circulation time is 10-15min, and the settling time before starting casting is 3-5min.

[0029] 2) Casting process: After breaking the vacuum, casting is carried out using a continuous casting machine. The superheat is 20~30℃, and the casting process is stable at a constant speed. The billets taken off the production line are piled up into stacks and slowly cooled. The cooling time for the stack is 36~54 hours. The stack is dismantled at 300℃ or less to prevent cracks from occurring inside the billet due to rapid cooling.

[0030] 3) Electroslag remelting process: In order to further increase the purity of steel, remove internal defects such as segregation and porosity, reduce nonmetallic inclusions, and homogenize the cast structure, the incorporation of the electroslag remelting process is extremely important for high-temperature performance and prevention of hydrogen-induced cracking. In this invention, a cylindrical steel plate made by rolling an electroslag steel ingot with a thickness of 300 to 400 mm to a thickness of 65 mm or less is used, and the electroslag steel ingot is stacked after demolding and cooled slowly for 48 to 72 hours, and the stack is disassembled at 300°C or less and air-cooled.

[0031] 4) Heating process: By controlling the heating process of the steel slab, sufficient solid solution of alloying elements is ensured, and the growth of prior austenite grains is effectively inhibited. The heating temperature of the electroslag steel ingot is controlled at 1180-1250°C, the heating time is controlled at 8-10 hours, and the soaking time is controlled at 0.5-1.0 hours.

[0032] 5) Rolling process: the rolling start temperature of the recrystallized region is 1050-1150°C, the single pass deformation rate of the recrystallized region is 10-14%, and the rolling reduction rate of each of the first three passes is more than 12%, the total deformation rate is more than 50%, the thickness of the intermediate blank is 2.0-4.0 times that of the finished steel plate, the rolling start temperature of the non-recrystallized region is 850-900°C, the rolling end temperature of the non-recrystallized region is 820-850°C, and the cumulative deformation rate of the non-recrystallized region is more than 50%. The design of the above parameters is determined based on the composition and performance requirements of the steel type, and the organic bond between the micro-alloy elements Nb, V, and Ti added to the steel and the elements C and N maximizes the effect of dispersion precipitation strengthening and grain refinement, resulting in a relatively fine rolling structure, and providing a relatively homogeneous rolling structure for the subsequent heat treatment, and the thickness of the finished product is 40-65mm.

[0033] 6) Heat treatment process: In order to obtain a structure that satisfies the strict performance requirements of the present invention, a final heat treatment process is required. The present invention uses multiple heat treatment processes of high temperature normalizing + two-phase quenching + high temperature tempering, and the A steel of the present invention is C3 The temperature is about 870℃, and the high temperature normalization temperature is A C3+(80~130)℃, that is, 950℃~1000℃, the heat-holding time is 0.5min / mm~1.0min / mm, and air-cooled to room temperature. This process eliminates the grain difference and structure segregation caused by temperature unevenness of the rolled material, and the occurrence of relatively large grain difference and segregation bands is likely to greatly reduce the hydrogen-induced cracking prevention performance of the product. The two-phase region quenching temperature is 800~850℃, the heat-holding time is 1.0~1.5min / mm, the cooling rate is 5~10℃ / s, and the self-tempering temperature is 350~450℃, and then cooled to room temperature by air. The two-phase region heating makes it easier to refine the grains of undissolved ferrite, and obtains a two-phase structure mixed with ferrite and bainite.

[0034] In order to obtain the excellent processing and use performance of the product of the present invention, it is necessary to estimate that the upper limit of the tensile strength of the material in the heat-treated state does not exceed 640MPa based on the design allowable stress, and to ensure that the tensile strength in the heat-treated state after welding at 500°C is 450MPa or more, so that the structure and performance of the process must be adjusted and controlled by accurate tempering heat treatment. The present invention is designed with a tempering temperature of 710-730°C and a heat retention time of 60min + 2.0-4.0min / mm, and in this tempering process, the bainite structure recovers its softening and (Fe, Mn, Cr, Mo) 23 The alloy carbides of the C6 structure grow without agglomeration, and are distributed in the bainite ferrite matrix or grain boundaries with a high degree of spherical dispersion. The characteristic of this microstructure is that it has extremely strong high-temperature stability, and the microstructure does not change even after post-weld heat treatment at 700℃ for 26 hours. This ensures the overall performance of long-term post-weld heat treatment, especially high-temperature toughness, fracture toughness, and low-temperature ball drop performance. Effect of the Invention

[0035] The present invention has the following advantages: 1. Based on medium to low C, Si, and Mn components, the content of harmful elements P, S, Sn and gases O and H are strictly controlled, the tempering embrittlement coefficient is controlled to 50 or less, and alloy elements Cr, Mo, Ni, Nb, V, Ti, and N are added in combination. In addition, a complex structure containing 10% to 15% undissolved ferrite and tempered bainite is obtained through a unique manufacturing process, where the bainite structure contains a large amount of dispersed precipitates (Fe, Mn, Cr, Mo). 23 The C6 structure alloy carbides are included to ensure the irradiation resistance and comprehensive mechanical properties of the core casing cylindrical steel plate. 2. The mechanical properties of the steel plate for the core casing of advanced nuclear power units, obtained through a unique manufacturing process, are 500MPa≦R at room temperature in the delivered state. el ≦520MPa, 610MPa≦R m ≦640MPa, and 470MPa≦R at 500℃ m ≦485MPa, and in the post-weld heat treatment state of 700×26h, 450MPa≦R m (500℃)≦470MPa, KV2 (80℃)≧420J, T NDT ≦-40℃, CSR of HIC (solution A) is 0%, and 280MPa m 1 / 2 ≦K IC ≦285MPa m 1 / 2 It has been proved that this is the case, and a steel plate for cylinders with a thickness standard of 40~65mm has been obtained, filling the gap in this type of product regardless of its excellent overall performance and dimensional standard. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described more clearly and completely below, but it should be understood that the described embodiments are only some of the embodiments of the present invention, not all of the embodiments. Any other embodiments that a person skilled in the art can obtain based on the embodiments of the present invention without creative effort shall be included in the scope of protection of the present invention.

[0037] The chemical compositions of the examples of the present invention are shown in Table 1. The process parameters of each example are shown in Table 2. The final effect of the structural performance of the examples is shown in Table 3. The hydrogen induced cracking prevention HIC test results are shown in Table 4. The high temperature fracture toughness test results are shown in Table 5.

[0038] [Table 1]

[0039] [Table 2-1]

[0040] [Table 2-2]

[0041] [Table 3]

[0042] [Table 4]

[0043] [Table 5]

[0044] As can be seen from the above results, the steel plate for the cylindrical body of the core casing of the advanced nuclear power unit according to the present invention has high internal purity, the content of harmful elements P and S is controlled to be extremely low, the temper embrittlement prevention coefficient J≦50, and the thermal resistance at room temperature in the delivered state is 500MPa≦R el ≦520MPa, 610MPa≦R m ≦640MPa, and 470MPa≦R at 500℃ m ≦485MPa, and 450MPa≦R at 500℃ after heat treatment at 700℃ for 26h. m ≦470MPa, KV2 ≧420J at 80℃, T NDT≦-40℃, CSR of HIC (solution A) is 0%, and 280MPa m 1 / 2 ≦K IC ≦285MPa m 1 / 2 It is.

[0045] Finally, the following should be mentioned: the above embodiments are only for explaining the technical means of the present invention, and are not limited thereto. Although the present invention has been described in detail with reference to the above embodiments, it is also possible to modify the technical means described in the above embodiments, or to carry out equivalent replacements for part or all of the technical features, and it is understood by those skilled in the art that the essence of the corresponding technical means does not depart from the scope of the technical means of the embodiments of the present invention through such modification or replacement.

[0046] (Additional Note) (Appendix 1) The composition, in mass%, is C: 0.10%~0.14%, Si: 0.20%~0.30%, Mn: 0.30%~0.60%, P≦0.006%, S≦0.002%, Cr: 1.65%~1.95%, Mo: 0.80%~1.20%, Ni: 0.80%~1.20%, Nb: 0.04%~0.08%, V: 0.10%. ~0.20%, Ti: 0%~0.03%, Alt: 0%~0.02%, Ca: 0.001%~0.004%, N: 0.01%~0.03%, Sn≦0.001%, H≦0.0001%, O≦0.0020%, balance: Fe and unavoidable impurities. High temperature temper embrittlement resistance coefficient J=(Si+Mn)×(P+Sn)×10 4 ≦50, 1. A steel plate for a cylindrical body of a core casing of an advanced nuclear power unit, comprising:

[0047] (Appendix 2) The steel plate, as delivered, has a yield strength of 500MPa or less at room temperature. el ≦520MPa, and the tensile strength is 610MPa≦R m ≦640Mpa, and the tensile strength at 500℃ is 470MPa≦R m ≦485Mpa; 2. A steel plate for a cylindrical body of a core casing of an advanced nuclear power unit according to claim 1.

[0048] (Appendix 3) After heat treatment at 700℃ for 26h after welding, the tensile strength at 500℃ is 450MPa≦R m ≦470MPa, impact energy KV2 at 80℃ ≧420J, non-ductile transition temperature T NDT ≦-40℃, the CSR of the HIC A solution is 0%, and the fracture toughness is 280MPa m 1 / 2 ≦K IC ≦285MPa m 1 / 2 That is, 2. A steel plate for a cylindrical body of a core casing of an advanced nuclear power unit according to claim 1.

[0049] (Appendix 4) A structure containing 10% to 15% undissolved ferrite and tempered bainite was obtained. The bainite structure contained dispersed precipitates of M 23 The alloy carbides have the C6 structure, where M is a combination of Fe, Mn, Cr and Mo; 2. A steel plate for a cylindrical body of a core casing of an advanced nuclear power unit according to claim 1.

[0050] (Appendix 5) Mo / Si is 2.80~5.50, (Cr+Mn) / Mo is 1.65~2.90, 2. A steel plate for a cylindrical body of a core casing of an advanced nuclear power unit according to claim 1.

[0051] (Appendix 6) A smelting process in which deep desulfurization is performed in an LF smelting furnace to control the sulfur content below 0.002%, and at the same time, calcium treatment is performed by feeding a CaSi wire into the steel, the thickness of the generated slag layer is 60-90 mm, degassing is completed in an RH furnace, the net circulation time is 10-15 min, and the settling time before the start of casting is 3-5 min; After breaking the vacuum, a continuous casting machine is used to cast the billets at a constant speed with a superheat of 20 to 30°C, and the billets are stacked to form a stack, which is cooled slowly and the stack is dismantled at a predetermined temperature. An electroslag remelting process is a process in which a 300-400 mm electroslag steel ingot is rolled to a standard steel plate for a cylinder of 65 mm or less, the electroslag steel ingot is released from the mold, stacked, cooled slowly, and dismantled at a predetermined temperature. a heating process in which the heating temperature of the electroslag steel ingot is controlled to 1180 to 1250°C, the heating time is controlled to 8 to 10 hours, and the soaking time is controlled to 0.5 to 1.0 hours; A rolling process in which the rolling start temperature of the recrystallized region is 1050-1150°C, the single pass deformation rate of the recrystallized region is 10-14%, and the rolling reduction rates of the first three passes are all 12% or more, the total deformation rate is 50% or more, the thickness of the intermediate blank is 2.0-4.0 times that of the finished steel plate, the rolling start temperature of the non-recrystallized region is 850-900°C, the rolling end temperature of the non-recrystallized region is 820-850°C, the cumulative deformation rate of the non-recrystallized region is 50% or more, and the thickness of the finished product after rolling is 40-65 mm; A C3 and a heat treatment process in which high-temperature normalization is performed based on +(80-130)°C, the heat retention time is 0.5-1.0min / mm, air cooling is performed to room temperature, the two-phase region quenching temperature is 800-850°C, the heat retention time is 1.0-1.5min / mm, the cooling rate is 5-10°C / S, the self-tempering temperature is 350-450°C, air cooling is performed to room temperature, and then high-temperature tempering heat treatment is performed. 6. A method for manufacturing a steel plate for a cylindrical body of a core casing of an advanced nuclear power unit according to any one of claims 1 to 5.

[0052] (Appendix 7) In the smelting process, molten steel is smelted in a converter, using molten pig iron and scrap steel as raw materials, controlling the molten pig iron content to 70-80%, and smelting dephosphorization and decarburization separately using a converter. The oxygen injection time for dephosphorization is controlled to 7-10 min, and the oxygen injection time for decarburization is controlled to 8-12 min, so that the phosphorus mass fraction is finally reduced to within 0.006%. The manufacturing method according to claim 6,

[0053] (Appendix 8) In the smelting process, during calcium treatment, the wire feed speed is 200 to 350 m / min, and the wire feed depth is 1.0 to 2.0 m below the slag layer; The manufacturing method according to claim 6,

[0054] (Appendix 9) In the casting process, the billets are stacked to form a stack, which is slowly cooled for 36 to 54 hours, and the stack is dismantled at 300°C or less. In the electroslag remelting process, the electroslag steel ingot is released from the mold, stacked to form a stack, which is slowly cooled for 48 to 72 hours, and the stack is dismantled at 300°C or less. The manufacturing method according to claim 6,

[0055] (Appendix 10) The specific process parameters of the high-temperature tempering heat treatment are: tempering temperature is 710-730°C, and heat retention time is 60min+2.0-4.0min / mm; The manufacturing method according to claim 6,

Claims

1. The composition, in mass%, is C: 0.10% to 0.14%, Si: 0.20% to 0.30%, Mn: 0.30% to 0.60%, P≦0.006%, S≦0.002%, Cr: 1.65% to 1.95%, Mo: 0.80% to 1.20%, Ni: 0.80% to 1.20%, Nb: 0.04% to 0.08%, V: 0.10%. 0.20%, Ti: 0% to 0.03%, Alt: 0% to 0.02%, Ca: 0.001% to 0.004%, N: 0.01% to 0.03%, Sn≦0.001%, H≦0.0001%, O≦0.0020%, balance: Fe and inevitable impurities, and high-temperature temper embrittlement resistance coefficient J=(Si+Mn)×(P+Sn)×10 ４ ≦50; 1. A steel plate for a cylindrical body of a core casing of an advanced nuclear power unit, comprising:

2. The steel plate has a yield strength of 500 MPa or less at room temperature as delivered. ｅｌ ≦520MPa, and the tensile strength is 610MPa≦R ｍ ≦640 MPa, and the tensile strength at 500 °C is 470 MPa ≦ R ｍ ≦485 MPa; The steel plate for the cylinder of the core casing of an advanced nuclear power unit according to claim 1.

3. In the post-weld heat treatment state of 700°C x 26h, the tensile strength at 500°C is 450MPa≦R ｍ ≦470MPa, impact energy KV at 80°C ２ ≧420 J, and the non-ductile transition temperature T ＮＤＴ ≦-40°C, the CSR of HIC A solution is 0%, and the fracture toughness is 280 MPa m １／２ ≦K ＩＣ ≦285MPa·m １／２ That is, The steel plate for the cylinder of the core casing of an advanced nuclear power unit according to claim 1.

4. A structure containing 10% to 15% undissolved ferrite and tempered bainite was obtained. The bainite structure contained dispersed precipitates of M ２３ C ６ The alloy carbide includes an alloy carbide having the structure, wherein M is a combination of Fe, Mn, Cr and Mo; The steel plate for the cylinder of the core casing of an advanced nuclear power unit according to claim 1.

5. Mo / Si is 2.80 to 5.50, and (Cr+Mn) / Mo is 1.65 to 2.

90. The steel plate for the cylinder of the core casing of an advanced nuclear power unit according to claim 1.

6. A smelting process in which deep desulfurization is performed in an LF smelting furnace to control the sulfur content to 0.002% or less, and at the same time, calcium treatment is performed by feeding a CaSi wire into the steel, the thickness of the generated slag layer is 60-90 mm, degassing is completed in an RH furnace, the net circulation time is 10-15 min, and the settling time before starting casting is 3-5 min; After breaking the vacuum, a continuous casting machine is used to cast the billets at a constant speed with a superheat of 20 to 30°C, and the billets are stacked to form a stack, which is then slowly cooled and dismantled at a predetermined temperature. an electroslag remelting process in which a 300-400 mm electroslag steel ingot is rolled to a standard steel plate for a cylindrical body of 65 mm or less, the electroslag steel ingot is demolded and then stacked to form a stack, which is then slowly cooled and dismantled at a predetermined temperature; a heating step in which the heating temperature of the electroslag steel ingot is controlled to 1180 to 1250°C, the heating time is controlled to 8 to 10 hours, and the soaking time is controlled to 0.5 to 1.0 hours; a rolling process in which the rolling start temperature of the recrystallized region is 1050-1150°C, the single pass deformation rate of the recrystallized region is 10-14%, and the rolling reduction rates of the first three passes are all 12% or more, the total deformation rate is 50% or more, the thickness of the intermediate blank is 2.0-4.0 times that of the finished steel plate, the rolling start temperature of the non-recrystallized region is 850-900°C, the rolling end temperature of the non-recrystallized region is 820-850°C, the cumulative deformation rate of the non-recrystallized region is 50% or more, and the thickness of the finished product after rolling is 40-65 mm; A Ｃ３ and a heat treatment process in which high-temperature normalization is performed based on +(80-130) ° C, the heat-holding time is 0.5-1.0 min / mm, air-cooling to room temperature, the two-phase region quenching temperature is 800-850 ° C, the heat-holding time is 1.0-1.5 min / mm, the cooling rate is 5-10 ° C / S, the self-tempering temperature is 350-450 ° C, air-cooling to room temperature, and then high-temperature tempering heat treatment is performed. A method for manufacturing steel plates for the cylindrical body of the core casing of an advanced nuclear power unit according to any one of claims 1 to 5.

7. In the smelting process, molten steel is smelted in a converter, using molten pig iron and scrap steel as raw materials, controlling the molten pig iron content to 70-80%, and smelting dephosphorization and decarburization separately using a converter, The oxygen blowing time for dephosphorization is controlled to 7-10 min, and the oxygen blowing time for decarburization is controlled to 8-12 min, and the phosphorus mass fraction is finally reduced to within 0.006%. The method according to claim 6 .

8. In the smelting process, during calcium treatment, the wire feed speed is 200 to 350 m / min, and the wire feed depth is 1.0 to 2.0 m below the slag layer; The method according to claim 6 .

9. In the casting process, the billets are stacked to form a stack, which is slowly cooled for 36 to 54 hours, and the stack is dismantled at 300°C or less. In the electroslag remelting process, the electroslag steel ingot is released from the mold, stacked to form a stack, which is slowly cooled for 48 to 72 hours, and the stack is dismantled at 300°C or less. The method according to claim 6 .

10. The specific process parameters of the high-temperature tempering heat treatment are: tempering temperature is 710-730°C, and heat retention time is 60min+2.0-4.0min / mm; The method according to claim 6 .

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