Steel plate for evaporator of advanced nuclear power unit and its manufacturing method

Abstract

The present invention provides a steel plate for an evaporator 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: 0.10%-0.25%, Mn: 0.25%-0.50%, P≦0.006%, S≦0.002%, Cr: 1.80%-2.10%, Mo: 1.00%-1.35%, Ni: 0.80%-1.20%, Nb: 0%-0.04%, V: 0.05%- 0.10%, Ti: 0.03%~0.06%, 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 manufacturing method of the present invention can ensure the comprehensive performance requirements of the evaporator steel plate 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 an evaporator of an advanced nuclear power unit and a manufacturing method thereof. [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) 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, very high requirements are placed on nuclear technology and nuclear equipment, for example, the outlet temperature of the evaporator reaches a high temperature of 530℃, and very high technical index requirements are placed on the steel used to manufacture the evaporator. Therefore, the development of key nuclear equipment and key nuclear materials to meet the needs of the fourth generation advanced nuclear power plants has become a core challenge that the world's current nuclear powers need to solve urgently.

[0004] In Patent Document 1 (Method for refining grains of large forged steel for nuclear reactor evaporator, China Patent Application No. 201110224501.4), it can be seen from the disclosed ingredients, manufacturing method and beneficial effects that this patent is related to the standard of SA508Gr.3Cl.2, which is a material required for manufacturing evaporators for third generation nuclear power generation, and the production process is a forging method, and its performance index does not apply to the performance indexes of fourth generation nuclear power generation.

[0005] In Patent Document 2 (Steel for pressure boundary members of evaporators in nuclear power plants and its manufacturing method, China Patent Application No. 201811165268.5), it can be seen from the disclosed ingredients, manufacturing method and beneficial effects that the mechanical performance of this patent can only ensure the usage requirements at the operating environment temperature of 350°C, and there is no explanation or guarantee for higher usage temperatures. It is also clearly stated that this patent is used for the steel and manufacturing of third-generation nuclear power evaporators.

[0006] The inventions disclosed in the above Patent Documents 1 and 2 mainly relate to metal materials required for third generation nuclear power generation equipment, and compared to the component materials required for fourth generation nuclear power generation technology, they have low parameter requirements, such as an outlet temperature of 150°C to 350°C, a low post-weld heat treatment temperature (620°C or less), and a short heat retention time (15 hours or less). Therefore, they cannot meet the demand of advanced fourth generation nuclear power plants, and there is an urgent need to develop component materials required to meet the important equipment of fourth generation nuclear power plants.

[0007] Therefore, the present invention invents new materials and new processes required for key equipment of advanced nuclear power generation units, in order to meet the characteristics of the materials for the steam generators of fourth-generation nuclear power plants, which require high internal cleanliness, small anisotropy, and excellent high-temperature toughness and fatigue fracture resistance performance characteristics after post-weld heat treatment at 700°C for 16 hours. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] China Patent Application Publication No. 102234706 [Patent Document 2] China Patent Application Publication No. 109136767 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in view of the above technical problems, and provides an advanced steel plate for evaporator of nuclear power unit and its manufacturing method. The present invention adopts a brand new chemical composition design and appropriate production process, based on medium to low C, Si, Mn composition, with Cr, Mo, Ni, Nb, V, Ti and N as alloying elements added in combination, strictly controlling the content of harmful elements P, S, Sn and gas O, H, and further adopts unique smelting, rolling and heat treatment production process, obtains a homogeneous steel plate with high strength, good high temperature fatigue resistance, low temperature toughness and high purity that can withstand high temperature heat treatment at 530℃ after welding, and meets the manufacturing and use requirements of the evaporator of the fourth generation nuclear power plant. [Means for solving the problem]

[0010] The technical means of the present invention are as follows: One embodiment of the present invention is a steel plate for an evaporator of an advanced nuclear power unit, the composition of which is, in mass%, C: 0.10% to 0.14%, Si: 0.10% to 0.25%, Mn: 0.25% to 0.50%, P≦0.006%, S≦0.002%, Cr: 1.80% to 2.10%, Mo: 1.00% to 1.35%, Ni: 0.80% to 1.20%, Nb: 0% ~0.04%, V: 0.05%~0.10%, Ti: 0.03%~0.06%, 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.

[0011] Furthermore, in the delivered state, the yield strength at room temperature is 407MPa≦R el≦431MPa, tensile strength is 573MPa≦R m ≦586MPa, and the tensile strength at 530℃ is 422MPa ≦R m ≦435MPa, HBW≦180, and in the post-weld heat treatment state of 700℃×16h, the tensile strength is 407MPa≦R m (530℃)≦418MPa, impact energy KV2≧320J at -20℃, and number of cycles at 530℃ is 1.1 million or more.

[0012] Furthermore, a composite structure containing (5wt%~10wt%) ferrite + pearlite and tempered bainite was obtained, with the fine system being A+B+C+D≦0.5 grade, the coarse system being A+B+C+D being 0 grade, and the band structure evaluation grade being 0 grade.

[0013] The principles for selecting each chemical component and the reasons for designing the content thereof in the present invention are as follows:

[0014] C: The main solute C and compound C in the present invention ensure the high temperature strength and tensile strength of the steel during heat treatment and post-weld heat treatment, and are also elements that improve fatigue strength. However, since too much carbon content is detrimental to the toughness and weldability of the steel, the present invention sets the C content range to 0.10% to 0.14%.

[0015] Si: A good reducing agent and deoxidizer in the steelmaking process. When used in combination with Alt, it can significantly increase the deoxidizing ability of Alt. 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, the Mo / Si ratio in the present invention is limited to between 4.05 and 13.30 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 favor excessive addition of silicon element, and therefore the present invention sets the Si content range to 0.10% to 0.25%.

[0016] 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 an element that affects temper embrittlement, and therefore must be strictly controlled in the present invention. Therefore, the present invention sets the Mn content range to 0.25% to 0.50%.

[0017] S, P: As harmful elements in steel, they must be strictly controlled to guarantee the purity of steel quality and comprehensive indexes such as J coefficient, so the contents are limited to S≦0.002% and P≦0.006%.

[0018] Cr: A strong carbide-forming element that combines with Fe, Mn, and Mo in steel to form stable M 23 It produces alloy carbide with C6 structure, where M is a combination of Fe, Mn, Cr and Mo, which ensures high temperature performance in the long-term post-weld heat treatment state, and also plays an affinity role between Cr and oxygen, and can form dense metal oxide on the metal surface at high temperature, improving the high temperature oxidation resistance and oxidation corrosion resistance of the steel. However, if the Cr content is too high, the brittle transition temperature of the steel will increase, so the present invention sets the Cr content range to 1.80%-2.10%.

[0019] 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, which plays a role in high temperature strengthening. In addition, in this application, a large amount of Cr and a certain amount of Mn are added, which are prone to co-polymerization with impurity elements such as P and Sn at the grain boundary, 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 it precipitates P in the crystal to prevent grain boundary segregation. Therefore, the present invention limits (Cr+Mn) / Mo to 1.70-2.50 to ensure the stability of the structure and performance of the evaporator steel when it is operated at 530°C. However, if the Mo content is too high, the steel will become embrittled, so the present invention sets the Mo content range to 1.00%-1.35%.

[0020] Ni: In the present invention, the Ni element mainly increases the plasticity and toughness of the steel. However, if the Ni content is too high, the radiation resistance of the material is reduced. Therefore, the present invention sets the Ni content range to 0.80% to 1.20%.

[0021] Nb: In the present invention, Nb acts to refine crystal grains, and since Nb is present as a participating element or a small amount of added element in the present invention, the Nb content is limited to 0% to 0.04%.

[0022] V: In the present invention, the amount of V is large. One of the main effects is that the carbon and nitrogen complex compounds formed with C and N elements during the long-term and high-temperature post-weld tempering process are very stable, ensuring high-temperature strength in the high-temperature post-weld heat treatment state. In addition, the addition of V alloy effectively suppresses grain boundary segregation of Cr and Mn elements due to irradiation, so the V content is limited to 0.05% to 0.10%.

[0023] Ti: One of the elements that form strong ferrite, it strongly increases the A1 and A3 temperatures of steel. Titanium can increase the plasticity and toughness of steel. Titanium bonds carbon and nitrogen to form titanium carbide and titanium nitride, which improves the strength of steel. After normalizing and heat treatment, the grains are refined and carbides are precipitated, which significantly improves the plasticity and impact toughness of steel, so the Ti content is limited to 0.03% to 0.06%.

[0024] Sn: A residual element in steel. It not only affects the purity of the steel, but is also an important element that influences the temper brittleness coefficient J. Therefore, the Sn content is limited to 0.001% or less.

[0025] 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 cleanliness of the steel and prevent the formation of aluminum oxide from affecting fatigue performance, and the Alt content is limited to 0%~0.02%.

[0026] 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 deformed at the rolling temperature of the steel, and remain spherical even after rolling. 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. Therefore, the present invention sets the Ca content range to 0.001% to 0.004%.

[0027] N: Nb, V and other elements form nitrides, which are precipitated at grain boundaries and pin the grain boundaries to refine 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%.

[0028] 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 brittle non-metallic oxides with Al and Si elements, which can affect the purity of steel and the fatigue limit performance 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.

[0029] In order to achieve the object of the present invention, the present invention further provides a manufacturing method for steel plate for evaporator of 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--slab cleaning--electroslag remelting--electroslag steel ingot cooling--slab heating--controlled rolling and controlled cooling--hot straightening--slow cooling--heat treatment--flaw detection--inspection and verification, and the main specific steps of the present invention are as follows:

[0030] 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 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 low-temperature toughness and high-temperature fatigue 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 3-6min.

[0031] 2) Casting process: After breaking the vacuum, a continuous casting machine is used for casting. 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 24~48 hours. The stack is dismantled at 400℃ or less to prevent cracks from occurring inside the billet due to rapid cooling.

[0032] 3) Electroslag remelting process: In order to further increase the purity of steel, homogenize the casting structure, and reduce non-metallic inclusions, the incorporation of the electroslag remelting process is extremely important for high-temperature fatigue resistance and low-temperature toughness. In this invention, an electroslag steel ingot with a thickness of 280 to 350 mm is rolled to a thickness of 50 mm or less to form a steel plate for an evaporator. After demolding, the electroslag steel ingot is stacked and cooled slowly for 48 to 72 hours, and the stack is disassembled at 400°C or less and air-cooled.

[0033] 4) Heating process: By controlling the heating process of the steel billet, 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 6-8 hours, and the soaking time is controlled at 0.5-1.0 hours.

[0034] 5) Controlled rolling and controlled cooling process: The rolling start temperature of recrystallization is 1050-1150°C, the single pass deformation rate of the recrystallized region is 10-14%, and the first three passes each adopt a pass reduction rate of 11%-13% or more, the total deformation rate is 50% or more, the thickness of the intermediate blank is 2.0-5.0 times that of the finished steel plate, the rolling start temperature of non-recrystallization is 850-920°C, the rolling end temperature of non-recrystallization is 800-850°C, the rolling in the non-recrystallized region is 6 passes or more, and the cumulative deformation rate is 50% or more. In the accelerated cooling process (ACC controlled cooling process) of the steel plate after rolling, the cooling start temperature is 800-830°C, the self-tempering temperature is 400-500°C, and the cooling rate is 20-25°C / s. The micro-alloy elements Nb, V, and Ti added to the steel are organically bonded with the elements C and N to maximize the dispersion strengthening and grain refinement effects, resulting in a fine rolling structure and a finished product thickness of 20 to 50 mm after rolling.

[0035] 6) Heat treatment process: In order to obtain a structure that satisfies the strict performance requirements of the present invention, it is necessary to complete the final heat treatment process. The present invention adopts multiple heat treatment processes of high temperature normalization + secondary normalization + high temperature tempering, and the A of the steel type 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 temperature is 0.5min / mm~1.0min / mm, and the air is cooled to room temperature. This process eliminates the grain difference and structure segregation caused by the temperature unevenness of the rolled material, and ensures the homogenization of the components and performance of the product of the present invention. The secondary normalizing temperature is 930~960℃, the temperature is 0.5~1.5min / mm, and the product is cooled to room temperature by air, and the content of ferrite + pearlite is 5~10wt% to meet the high temperature strength and high temperature fatigue resistance, and a multi-phase structure in which bainite is the main component and ferrite and pearlite are mixed is obtained.

[0036] 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 586MPa based on the design allowable stress, and to ensure that the tensile strength of the material in the post-weld heat-treated state at 530°C is 422MPa or more, so that the structure and performance of the process must be adjusted and controlled by accurate tempering heat treatment. The present invention designs a tempering temperature of 730-760°C and a heat retention time of 120min+1.0-2.0min / mm, and the structure in this process has excellent high-temperature stability, and no essential changes occur even after post-weld heat treatment at 700°C for 16h, so that the comprehensive performance of the long-term post-weld heat treatment of the steel plate is guaranteed, especially the high-temperature plasticity, low-temperature toughness and high-temperature fatigue resistance. Effect of the Invention

[0037] The present invention has the following advantages: 1. Based on medium to low C, Si, Mn composition, the harmful elements P, S, Sn and gases O, H contents are strictly controlled, the high temperature tempering embrittlement coefficient is controlled below 40, Cr, Mo, Ni, Nb, V, Ti and N alloying elements are added in combination, and a structure containing 5wt%~10wt% (ferrite + pearlite) and tempered bainite is obtained through a unique manufacturing process, where the (A+B+C+D) fine system of the structure is below grade 0.5, the (A+B+C+D) coarse system is grade 0, and the evaluation grade of the band structure is grade 0, which ensures the irradiation resistance and comprehensive mechanical performance of the evaporator steel plate. 2. The mechanical properties of the steel plate for the evaporator of advanced nuclear power unit obtained through the unique manufacturing process are 407MPa≦R at room temperature in the delivered state. el ≦431MPa, 573MPa≦R m ≦586MPa, and 422MPa ≦R at 530℃ m ≦435MPa, HBW≦180, and after heat treatment at 700℃×16h after welding, 407MPa≦R m (530℃)≦418MPa, KV2(-20℃)≧320J, and the number of cycles at 530℃ is more than 1.1 million times. This has resulted in the production of evaporator steel plates with thickness standards of 20~50mm, filling the gap in this type of product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] 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.

[0039] The chemical compositions of the examples of the present invention are shown in Table 1. The process parameters for each example are shown in Table 2. The final effect of the structural performance of the examples is shown in Table 3. The evaluation effect of non-metallic inclusions of the examples is shown in Table 4. The fatigue performance results of the examples are shown in Table 5.

[0040] [Table 1]

[0041] [Table 2]

[0042] [Table 3]

[0043] [Table 4]

[0044] [Table 5]

[0045] As can be seen from the above results, the steel plate for the evaporator 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 407MPa≦R el ≦431MPa, 573MPa≦R m ≦586MPa, and 422MPa ≦R at 530℃ m ≦435Mpa, (A+B+C+D) fine grain ≦0.5, (A+B+C+D) coarse grain 0, 5wt%≦(pearlite+ferrite)≦10wt%, the evaluation grade of the band structure is grade 0, HBW≦180, and 407MPa≦R in the post-weld heat treatment state of 700℃×16h. m (530℃)≦418MPa, KV2(-20℃)≧320J, and the number of cycles at 530℃ is 1.1 million or more.

[0046] 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.

[0047] (Appendix 1) The composition, in mass%, is C: 0.10%~0.14%, Si: 0.10%~0.25%, Mn: 0.25%~0.50%, P≦0.006%, S≦0.002%, Cr: 1.80%~2.10%, Mo: 1.00%~1.35%, Ni: 0.80%~1.20%, Nb: 0%~0.04%, V: 0.05%~0. 10%, Ti: 0.03%~0.06%, 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 for an evaporator of an advanced nuclear power unit is characterized by:

[0048] (Appendix 2) In the delivered state, the yield strength at room temperature is 407MPa or less R el ≦431MPa, and the tensile strength is 573MPa ≦R m ≦586MPa, and the tensile strength at 530℃ is 422MPa ≦R m ≦435MPa, After heat treatment at 700℃ for 16h after welding, the tensile strength at 530℃ is 407MPa≦R m ≦418MPa, impact energy KV2 ≧320J at -20℃, and cycle count at 530℃ ≧1.1 million times; 2. A steel plate for an evaporator of an advanced nuclear power unit according to claim 1,

[0049] (Appendix 3) Obtain a composite structure containing ferrite + pearlite and tempered bainite, in which the content of ferrite + pearlite is 5 to 10 wt%, the fine system A + B + C + D is ≦ 0.5 grade, the coarse system A + B + C + D is 0 grade, and the evaluation grade of the band structure is 0 grade; 2. A steel plate for an evaporator of an advanced nuclear power unit according to claim 1,

[0050] (Appendix 4) Mo / Si is 4.05~13.30, (Cr+Mn) / Mo is 1.70~2.50; 2. A steel plate for an evaporator of an advanced nuclear power unit according to claim 1,

[0051] (Appendix 5) The smelting process is as follows: molten steel is smelted in a converter, dephosphorization and decarburization are separately smelted using a converter, where the oxygen blowing for dephosphorization is controlled to 7-10min, and the oxygen blowing for decarburization is controlled to 8-12min, and the phosphorus mass fraction is finally reduced to within 0.006%; deep desulfurization is performed in an LF refining furnace to control the sulfur content to 0.002% or less; and at the same time, calcium treatment is performed by feeding CaSi wire into the steel, and the thickness of the generated slag layer is 60-90mm; degassing is completed in an RH furnace; the net circulation time is 10-15min; and the settling time before the start of casting is 3-5min. 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 280-350 mm electroslag steel ingot is rolled to a standard evaporator steel plate of 50 mm or less, the electroslag steel ingot is released from the mold, stacked, cooled slowly, and disassembled at a specified 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 6 to 8 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%, the total deformation rate is 50% or more, the thickness of the intermediate blank is 2.0-5.0 times that of the finished steel plate, the rolling start temperature of the non-recrystallized region is 850-920°C, the rolling end temperature of the non-recrystallized region is 800-850°C, the cumulative deformation rate of the non-recrystallized region is 50% or more, and the thickness of the finished product after rolling is 20-50 mm; A C3A heat treatment process in which high-temperature normalization is performed based on +(80 to 130) ° C, the heat retention time is 0.5 to 1.0 min / mm, air cooling to room temperature, secondary normalization is performed at a temperature of 930 to 960 ° C, the heat retention time is 0.5 to 1.5 min / mm, air cooling to room temperature, and then high-temperature tempering heat treatment is performed. 5. A method for producing a steel plate for an evaporator of an advanced nuclear power unit according to any one of claims 1 to 4.

[0052] (Appendix 6) In the smelting process, scrap steel and molten iron are used as raw materials, and the molten iron content is controlled to 70-80%. During calcium treatment, the wire feed speed is 200-350m / min, and the wire feed depth is 1-2m below the slag layer; The manufacturing method according to claim 5,

[0053] (Appendix 7) In the casting process, the billets are stacked to form a stack, which is slowly cooled for 24 to 48 hours, and the stack is dismantled at 400°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 400°C or less. The manufacturing method according to claim 5,

[0054] (Appendix 8) In the rolling process, the first three passes of the recrystallized region each adopt a pass reduction rate of 11% to 13%, and the rolling in the non-recrystallized region is 6 passes or more; The manufacturing method according to claim 5,

[0055] (Appendix 9) In the rolling process, in the ACC controlled cooling process after rolling, the cooling start temperature is 800 to 830 ° C, the self-tempering temperature is 400 to 500 ° C, and the cooling rate is 20 to 25 ° C / s; The manufacturing method according to claim 5,

[0056] (Appendix 10) The high-temperature tempering heat treatment has a tempering temperature of 730 to 760°C and a heat retention time of 120min + 1.0 to 2.0min / mm; The manufacturing method according to claim 5,

Claims

1. The composition, in mass%, is C: 0.10% to 0.14%, Si: 0.10% to 0.25%, Mn: 0.25% to 0.50%, P≦0.006%, S≦0.002%, Cr: 1.80% to 2.10%, Mo: 1.00% to 1.35%, Ni: 0.80% to 1.20%, Nb: 0% to 0.04%, V: 0.05% to 0. 10%, Ti: 0.03% to 0.06%, 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; The steel plate for an evaporator of an advanced nuclear power unit is characterized by:

2. In the delivered state, the yield strength at room temperature is 407MPa≦R ｅｌ ≦431MPa, and the tensile strength is 573MPa≦R ｍ ≦586 MPa, and the tensile strength at 530 ° C. is 422 MPa ≦ R ｍ ≦435 MPa, In the post-weld heat treatment state of 700°C x 16h, the tensile strength at 530°C is 407MPa≦R ｍ ≦418MPa, impact energy KV at -20°C ２ ≧320 J and the number of cycles at 530° C. is 1.1 million or more; The steel plate for an evaporator of an advanced nuclear power unit according to claim 1.

3. A composite structure containing ferrite + pearlite and tempered bainite is obtained, in which the content of ferrite + pearlite is 5 to 10 wt%, the fine system A + B + C + D is ≦ 0.5 grade, the coarse system A + B + C + D is 0 grade, and the evaluation grade of the band-shaped structure is 0 grade. The steel plate for an evaporator of an advanced nuclear power unit according to claim 1.

4. Mo / Si is 4.05 to 13.30, and (Cr+Mn) / Mo is 1.70 to 2.

50. The steel plate for an evaporator of an advanced nuclear power unit according to claim 1.

5. A smelting process in which molten steel is smelted in a converter, dephosphorization and decarburization are separately performed using a converter, in which the oxygen blowing for dephosphorization is controlled to 7-10 min, and the oxygen blowing for decarburization is controlled to 8-12 min, and the phosphorus mass fraction is finally reduced to 0.006% or less, and deep desulfurization is performed in an LF refining furnace to control the sulfur content to 0.002% or less, and at the same time, a CaSi wire is fed into the steel to perform calcium treatment, and the thickness of the generated slag layer is 60-90 mm, and 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 steel plate for an evaporator made by rolling an electroslag steel ingot of 280 to 350 mm to 50 mm is used, the electroslag steel ingot is released from the mold, stacked up, cooled slowly, and disassembled 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 6 to 8 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%, the total deformation rate is 50% or more, the thickness of the intermediate blank is 2.0-5.0 times that of the finished steel plate, the rolling start temperature of the non-recrystallized region is 850-920°C, the rolling end temperature of the non-recrystallized region is 800-850°C, the cumulative deformation rate of the non-recrystallized region is 50% or more, and the thickness of the finished product after rolling is 20-50 mm; A Ｃ３ A heat treatment process of performing high-temperature normalization based on + (80 to 130) ° C., a heat-holding time of 0.5 to 1.0 min / mm, air-cooling to room temperature, a secondary normalization temperature of 930 to 960 ° C., a heat-holding time of 0.5 to 1.5 min / mm, air-cooling to room temperature, and then performing high-temperature tempering heat treatment. A method for manufacturing a steel plate for an evaporator of an advanced nuclear power unit according to any one of claims 1 to 4.

6. In the smelting process, scrap steel and molten iron are used as raw materials, and the molten iron content is controlled to 70-80%. During calcium treatment, the wire feed speed is 200-350 m / min, and the wire feed depth is 1-2 m below the slag layer; The method according to claim 5 .

7. In the casting process, the billets are stacked to form a stack, which is slowly cooled for 24 to 48 hours, and the stack is dismantled at 400°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 400°C or less. The method according to claim 5 .

8. In the rolling process, the first three passes of the recrystallized region each adopt a pass reduction rate of 11% to 13%, and the rolling in the non-recrystallized region is 6 passes or more. The method according to claim 5 .

9. In the rolling process, in the ACC controlled cooling process after rolling, the cooling start temperature is 800 to 830 ° C, the self-tempering temperature is 400 to 500 ° C, and the cooling rate is 20 to 25 ° C / s; The method according to claim 5 .

10. The high-temperature tempering heat treatment has a tempering temperature of 730 to 760°C and a heat retention time of 120min + 1.0 to 2.0min / mm; The method according to claim 5 .

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