Extreme wide specification nuclear power steel plate for high temperature gas-cooled reactor plate components and preparation method thereof

Abstract

The present invention provides a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor platen component and a preparation method thereof. The chemical composition and mass percentage of the nuclear power steel plate are as follows: C: 0.10% to 0.14%, Si: 0.10% to 0.30%, Mn: 0.30% to 0.60%, P≤0.006%, S≤0.002%, Cr: 2.05% to 2.55%, Mo: 0.80% to 1.10%, Nb: 0.01% to 0.03%, Alt: 0.020% to 0.045%, and the balance is Fe and unavoidable inclusions. The preparation method comprises smelting, refining, vacuum degassing, casting, stacking slow cooling, heating, rolling, and heat treatment, so as to obtain a nuclear power steel plate with an extreme wide specification, high temperature resistance of 570°C, and excellent processing performance, which meets the use conditions of the high temperature gas-cooled reactor platen component.

Description

Technical Field

[0001] The present invention relates to the technical field of steel for high temperature gas-cooled reactor platen components, and in particular to an extreme wide specification nuclear power steel plate for high temperature gas-cooled reactor platen components and a preparation method thereof. Background Art

[0002] The high-temperature gas-cooled reactor is recognized by the world as one of the fourth-generation nuclear power reactor technologies. Different from the working principle of the third-generation water reactor nuclear power unit, it adopts modular high-temperature gas-cooled reactor technology to generate electricity through the conversion of nuclear energy-thermal energy-mechanical energy-electrical energy. In addition, the high-temperature gas-cooled reactor can reach the coolant outlet temperature that other reactor types cannot reach, allowing it to not only generate electricity efficiently, but also use the high-temperature characteristics to develop non-electric applications of nuclear energy, such as cogeneration, hydrogen production, heavy oil thermal recovery, chemical industry, metallurgy and other fields, to achieve comprehensive utilization and kill two birds with one stone. Therefore, the high-temperature gas-cooled reactor will become the main battlefield for the struggle between nuclear power powers in the 21st century with its inherent safety, simple system, high power generation efficiency and wide range of uses. my country is one of the countries that started research and construction of high-temperature gas-cooled reactors earlier, and in 2021, it achieved grid-connected power generation of two high-temperature gas-cooled reactors. It is the first country in the world to actually build such a nuclear power plant and realize the localization of all key materials. With the successful operation of the first two reactors, the 2022 high-temperature gas-cooled reactor project continues to advance. The designers summarized the problems existing in the first phase of construction and made improvements in the subsequent design. The core pressure plate components were changed from two semicircular welded parts to a whole circular plate with a size of 65mm×5100mm×5100mm. This design not only eliminates the waste of manpower, material and financial resources such as beveling, welding, flaw detection, post-weld stress relief and witnessing in the original design process, but also shortens the manufacturing cycle and greatly improves the safety of equipment operation. However, there is still a technical gap in the development of such large-scale and extremely wide-specification materials.

[0003] The disclosed invention patent "A nickel-based corrosion-resistant alloy pipe for a high-temperature gas-cooled reactor steam generator and its manufacturing method" (publication number CN107557616A) shows, from the disclosed composition, production method and beneficial effects, that the patented product is an alloy material mainly containing Cr and Ni elements, not a steel material. It is used in the piping system of the secondary-loop steam generator of a high-temperature reactor equipment. It is essentially different from the plate material for the core pressure plate developed by the present invention in terms of material, use and shape, and cannot be substituted for each other.

[0004] The disclosed invention patent "Large-sized nuclear graphite material and preparation method for high-temperature gas-cooled reactor internal components" (publication number CN108341669A), judging from the disclosed ingredients, production methods and beneficial effects, this patented product is a graphite material. Although it is used for internal components of the reactor and is of large size, its use in a high-temperature gas-cooled reactor is different from that of the product of the present invention, and both are indispensable. Therefore, the two are essentially different in raw material composition, manufacturing method and use, and are irreplaceable.

[0005] The disclosed invention patent "A wide and thick steel plate for nuclear power and its manufacturing method" (publication number CN201910725047.7), judging from the disclosed composition, production method and beneficial effects, although the patent can develop wide and thick steel for nuclear power, the maximum thickness in the embodiment is 101mm and the maximum width is 4300mm. The mechanical properties involved can only guarantee the use requirements at an operating environment temperature of 150°C. There is no description or guarantee for higher operating temperatures, and it is clearly stated that the patent is used for the manufacture of SA738Gr.B, a third-generation nuclear power containment steel.

[0006] Although the main contents of the above-mentioned invention patents involve the development of key materials and processes for high-temperature gas-cooled reactors, they mainly involve nickel-based materials and graphite materials, and no relevant process research has been conducted on key steel materials with regard to size specifications. The present invention mainly solves the development of large-scale, extreme wide-specification heat-resistant alloy plates and extreme production processes for high-temperature gas-cooled reactor core plate components, develops key core materials required for high-temperature gas-cooled reactor nuclear power plants, and solves the "bottleneck" problem of major nuclear power equipment in my country. Summary of the invention

[0007] According to the above technical problems, a nuclear power steel plate with extreme wide specifications for high temperature gas-cooled reactor plate components and a preparation method are provided. The present invention adopts a new chemical composition design and a specific production and manufacturing process to obtain an excellent steel plate with excellent plate shape of (50-70) mm × (5000-5300) mm × (5000-5300) mm, high temperature resistance of 570°C, high temperature toughness and excellent processing performance, which meets the manufacturing and use requirements of steel for high temperature gas-cooled reactor core plate.

[0008] The technical means adopted by the present invention are as follows:

[0009] A nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor plate component, the chemical composition and mass percentage of the nuclear power steel plate are:

[0010] C: 0.10%~0.14%, Si: 0.10%~0.30%, Mn: 0.30%~0.60%, P≤0.006%, S≤0.002%, Cr: 2.05%~2.55%, Mo: 0.80%~1.10%, Nb: 0.01%~0.03%, Alt: 0.020%~0.045%, the balance is Fe and unavoidable inclusions.

[0011] The nuclear power steel plate has a complex phase structure of 15-25% equiaxed ferrite, 2-5% fine subgrains and 70-80% bainite tempered structure.

[0012] The specifications of the nuclear power steel plate are (50-70) mm×(5000-5300) mm×(5000-5300) mm, the surface unevenness is ≤10 mm / m, and the plate thickness tolerance is 1.0-2.0 mm.

[0013] The mechanical properties of the nuclear power steel plate are 475MPa≤R eL ≤515MPa、620MPa≤R m ≤655MPa; 370MPa at 570℃≤R m ≤385MPa; (100℃)KV2≥300J, HBW≤195, small performance difference in thickness direction, excellent machining performance.

[0014] The reasons for limiting the amount of each chemical element in steel plates, including C, Si, Mn, P, S, Cr, Mo, Nb and Alt, are detailed as follows:

[0015] C is the most important element for improving the strength of steel. It strengthens the strength of the matrix through solid solution and ensures the room temperature and high temperature strength of the steel plate. However, too high a carbon content will affect the machining performance of the steel. Therefore, the present invention sets the C content range to 0.10% to 0.14%.

[0016] Si is used as a reducing agent and deoxidizing agent in the steelmaking process. However, when the silicon content exceeds 0.5%, the toughness of the steel will decrease. Therefore, the Si content range is set to 0.20% to 0.30% in the present invention.

[0017] Mn can increase the strength and hardness of steel and is an element that strongly stabilizes austenite. It can effectively reduce the decomposition rate of austenite and improve the hardenability of steel. However, a high Mn content will enhance temper brittleness. Therefore, the present invention sets the Mn content range to 0.30% to 0.60%.

[0018] S and P are harmful elements in steel and must be strictly controlled to ensure comprehensive indicators such as purity and mechanical properties of steel. Therefore, the present invention limits S to ≤ 0.002% and P to ≤ 0.008%.

[0019] Cr is a strong carbide-forming element. It forms stable carbides with C in steel, which improves the room temperature and high temperature strength of the platen structural steel. In addition, adding Cr to steel can make the steel have high temperature oxidation resistance and oxidative medium corrosion resistance. Therefore, the present invention sets the Cr content range to 2.05% to 2.55%.

[0020] Mo in steel can delay the austenite transformation incubation time, shift the pearlite and ferrite transformation curves to the right, promote medium-temperature transformation, and improve hardenability. At the same time, molybdenum is a strong carbide-forming element. Molybdenum dissolved in the matrix during tempering easily forms alloy compounds such as MxC to ensure the strength after tempering. However, too high Mo content will lead to embrittlement of the steel. The present invention sets the Mo content range to 0.80% to 1.10%.

[0021] Nb can generate highly dispersed strong carbide NbC, which has the effect of refining grains. When heated to 1100-1200℃, it can still prevent grain growth, thereby improving the strength and toughness of steel. However, when the content is too high, ferrite δ phase or other brittle phases will be generated, which will reduce its toughness. Therefore, the Nb content is limited to 0.01%-0.03%.

[0022] Alt is a commonly used deoxidizer in steel. Adding a small amount of aluminum to steel can refine the grains and improve impact toughness. Too much aluminum will affect the cutting performance of steel, so the Alt content is limited to 0.020% to 0.045%.

[0023] The present invention also provides a method for preparing an extreme wide specification nuclear power steel plate for a high temperature gas-cooled reactor platen component, comprising the following steps:

[0024] (1) According to the composition design of the nuclear power steel plate, the raw materials are smelted in a converter, the raw materials mainly use high-quality scrap steel and molten iron, the molten iron content is controlled at 70-80%, and in order to effectively reduce the content of harmful elements P, dephosphorization and decarburization are smelted separately in a converter, wherein the dephosphorization oxygen blowing is controlled at 7-10 minutes, and the decarburization oxygen blowing is controlled at 8-12 minutes, and finally the phosphorus mass fraction is reduced to less than 0.006%;

[0025] (2) The molten steel is subjected to deep desulfurization treatment in the LF refining furnace, and the sulfur content is controlled below 0.002%;

[0026] (3) The molten steel is vacuum degassed in the VD furnace, with a net cycle time of 10 to 15 minutes;

[0027] (4) Vacuum casting, and the molten steel is calmed in the VD furnace for 3 to 5 minutes before casting. The casting superheat is set at 20 to 30°C, the cross-section of the continuous casting billet is (250 to 300) mm × (1500 to 1650) mm, the billet drawing rate during casting is 1.0 to 1.4 m / s, and the online cutting length of the billet is between 5100 and 5300 mm.

[0028] (5) The ingots are stacked and slowly cooled to obtain steel ingots. The stacking slow cooling time is 24 to 36 hours and the ingots are unstacked below 400°C to prevent defects such as cracks in the ingots caused by rapid cooling.

[0029] (6) Heating: the heating temperature is controlled at 1180-1230° C., and the total heating time is 4-6 hours.

[0030] (7) rolling, using the length of the heated steel billet as the target rolled plate width, adopting a rolling method of rolling to the bottom, adopting a three-stage rolling method, and not rotating the steel during the rolling process;

[0031] The first stage of high-temperature rolling is completed at above 1000°C. In order to fully crush the core structure of the steel billet, the single-pass reduction is ≥40mm, the roller speed is 0.6-0.8m / s, and the rolling passes are 3-4 times.

[0032] The second stage of rolling is carried out in the range of 830-930°C with a roller speed of 0.8-1.0 m / s. At this time, the austenite grains are further flattened and elongated. With the increase of grain boundary area, the ferrite nucleation rate increases in the subsequent phase transformation process, and the grains are fully refined.

[0033] The third stage of rolling is completed in the two-phase region of 770-800℃. At this time, a part of fine equiaxed crystals transformed from austenite phase transformation are obtained, which have good strength and toughness, and their proportion is about 25-28%. In addition, the ferrite that has completed the phase transformation is elongated and the size becomes very fine. This part of the organizational structure is called subgrain, which plays a very important role in strengthening and toughening steel, and its proportion is about 2-5%. The number of rolling passes in the third stage should not be too many, 2-3 times is the best, the pass reduction is 3-8mm, and the roller speed is 1.0-1.3m / s to ensure the flatness of the ultra-wide steel plate. At the same time, the CVC string roller process is used to control the thickness tolerance in the width direction to ≤1.5mm. The entire rolling process is not less than 10 passes, and the target rolling plate specifications are (50-70)mm×(5000-5300)mm×(5000-5300)mm;

[0034] (8) Heat treatment: Nuclear power steel plates need to be cut and drilled when processing core pressure plates, which places strict requirements on the machining performance of steel. The target rolled plate has a microstructure of equiaxed fine first precipitated ferrite, fine subgrains and bainite. At this time, the density dislocation in the bainite is high, the carbides are not fully precipitated, and the structural stability is poor, resulting in high strength of the steel plate, poor plastic toughness and machining performance. In order to meet the machining and application performance of the product of the present invention, the target rolled plate needs to be heated to 720-750°C and kept at a tempering temperature of 2.0-4.0min / mm (the holding time is determined according to the thickness of the target rolled plate, and the 1mm thick target rolled plate is kept at a tempering temperature of 2.0-4.0min) to finally obtain the nuclear power steel plate. The nuclear power steel plate contains a complex phase structure of 15-25% equiaxed ferrite, 2-5% fine subgrains and 70-80% bainite tempered structure. The high temperature performance of the structure is stable, the high temperature toughness is excellent and the cold working performance is excellent.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) On the basis of strengthening elements C, Si, and Mn, by compositely adding alloying elements Cr, Mo, and Nb, and strictly controlling the content of harmful elements P and S, a complex phase structure containing 15-25% equiaxed ferrite, 2-5% fine subgrains, and 70-80% bainite tempering structure is obtained in combination with the preparation method, which ensures the comprehensive mechanical and cold working properties of nuclear power steel plates for high-temperature gas-cooled reactor plate components with extremely wide specifications.

[0037] (2) The mechanical properties of the extreme wide specification steel plate for high temperature gas-cooled reactor plate components obtained through a unique production process are 475MPa≤R eL ≤515MPa、620MPa≤R m ≤655MPa, 370MPa≤Rm≤385MPa at 570℃; (100℃)KV2≥300J, HBW≤195, small performance difference in thickness direction, excellent machining performance.

[0038] (3) The present invention obtains a steel plate with an extreme width of (50-70) mm × (5000-5300) mm × (5000-5300) mm, which has a flat plate shape, a surface unevenness of ≤10 mm / m, and a full plate thickness tolerance of 1.0-2.0 mm, which meets the use requirements of high-temperature gas-cooled reactor pressure plates and realizes a welding-free manufacturing process for high-end large-scale nuclear power equipment.

[0039] Based on the above reasons, the present invention can be widely promoted in the fields of steel for high temperature gas-cooled reactor plate components, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1This is a typical metallographic structure diagram of an extremely wide specification nuclear power steel plate used for high-temperature gas-cooled reactor pressure plate components. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] The present invention provides a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor platen component, wherein the chemical composition and mass percentage of the nuclear power steel plate are:

[0043] C: 0.10%~0.14%, Si: 0.10%~0.30%, Mn: 0.30%~0.60%, P≤0.006%, S≤0.002%, Cr: 2.05%~2.55%, Mo: 0.80%~1.10%, Nb: 0.01%~0.03%, Alt: 0.020%~0.045%, the balance is Fe and unavoidable inclusions.

[0044] The present invention also provides a method for preparing an extreme wide specification nuclear power steel plate for a high temperature gas-cooled reactor platen component, comprising the following steps:

[0045] (1) According to the composition design of the nuclear power steel plate, the raw materials are smelted in a converter, the raw materials mainly use high-quality scrap steel and molten iron, the molten iron content is controlled at 70-80%, and in order to effectively reduce the content of harmful elements P, dephosphorization and decarburization are smelted separately in a converter, wherein the dephosphorization oxygen blowing is controlled at 7-10 minutes, and the decarburization oxygen blowing is controlled at 8-12 minutes, and finally the phosphorus mass fraction is reduced to less than 0.006%;

[0046] (2) Deep desulfurization treatment is carried out in the LF refining furnace, and the sulfur content is controlled below 0.002%;

[0047] (3) Vacuum degassing in a VD furnace, with a net cycle time of 10 to 15 minutes;

[0048] (4) Vacuum casting, and the molten steel is calmed in the VD furnace for 3 to 5 minutes before casting. The casting superheat is set at 20 to 30°C, the cross-section of the continuous casting billet is (250 to 300) mm × (1500 to 1650) mm, the billet drawing rate during casting is 1.0 to 1.4 m / s, and the online cutting length of the billet is between 5100 and 5300 mm.

[0049] (5) The ingots are stacked and slowly cooled to obtain steel ingots. The stacking slow cooling time is 24 to 36 hours and the ingots are unstacked below 400°C to prevent defects such as cracks in the ingots caused by rapid cooling.

[0050] (6) Heating: the heating temperature is controlled at 1180-1230° C., and the total heating time is 4-6 hours.

[0051] (7) rolling, using the length of the heated steel billet as the target rolled plate width, adopting a rolling method of rolling to the bottom, adopting a three-stage rolling method, and not rotating the steel during the rolling process;

[0052] The first stage of high-temperature rolling is completed at above 1000°C. In order to fully crush the core structure of the steel billet, the single-pass reduction is ≥40mm, the roller speed is 0.6-0.8m / s, and the rolling passes are 3-4 times.

[0053] The second stage rolling is carried out in the range of 830-930°C, with a roller speed of 0.8-1.0 m / s.

[0054] The third stage of rolling is completed in the two-phase region of 770-800℃, with 2-3 rolling passes, 3-8mm reduction per pass, and a roller speed of 1.0-1.3m / s to ensure the flatness of the ultra-wide steel plate. At the same time, the CVC roller stringing process is used to control the thickness tolerance in the width direction to ≤1.5mm. The entire rolling process is no less than 10 passes, and the target rolling plate specification is (50-70)mm×(5000-5300)mm×(5000-5300)mm.

[0055] (8) Heat treatment: The target rolled plate is subjected to a tempering heat treatment by heating at 720-750° C. and keeping the temperature for 2.0-4.0 min / mm (the keeping time is determined according to the thickness of the target rolled plate, and the keeping time for a 1 mm thick target rolled plate is 2.0-4.0 min) to finally obtain the nuclear power steel plate.

[0056] To further describe the present invention, the present invention is described in detail with the following 10 embodiments:

[0057] The ingredients of the 10 examples are shown in Table 1.

[0058] Table 1 Chemical composition of the examples (wt, %)

[0059] Example C Si Mn P S Cr Mo Nb Alt 1 0.12 0.15 0.48 0.006 0.001 2.55 1.03 0.02 0.039 2 0.11 0.28 0.44 0.006 0.002 2.12 1.10 0.03 0.022 3 0.14 0.10 0.30 0.005 0.001 2.08 0.88 0.03 0.033 4 0.13 0.18 0.52 0.005 0.001 2.29 0.90 0.01 0.028 5 0.10 0.25 0.35 0.005 0.002 2.05 0.99 0.02 0.045 6 0.14 0.20 0.60 0.006 0.001 2.43 0.80 0.03 0.031 7 0.11 0.30 0.40 0.006 0.001 2.38 0.96 0.01 0.028 8 0.10 0.27 0.36 0.004 0.002 2.16 1.07 0.02 0.020 9 0.14 0.12 0.57 0.006 0.001 2.24 0.84 0.03 0.023 10 0.13 0.10 0.55 0.005 0.001 2.49 0.90 0.01 0.040

[0060] The process parameters of the preparation methods of the 10 embodiments are shown in Table 2.

[0061] Table 2 Example process parameters

[0062]

[0063]

[0064] The structures and properties of the nuclear power steel plates of the 10 embodiments are shown in Table 3. The typical metallographic structure diagram of the nuclear power steel plates is shown in Figure 1 shown.

[0065] Table 3 Example organization, performance and final effect

[0066]

[0067]

[0068] The full steel plate surface thickness tolerances of the nuclear power steel plates of the 10 embodiments are shown in Table 4.

[0069] Table 4 Thickness tolerance of all steel plate surface in the example

[0070]

[0071] According to the above results, it can be concluded that the nuclear power steel plate with a maximum wide specification for high temperature gas-cooled reactor plate components provided by the present invention has high internal purity, extremely low content of harmful elements P and S, and a room temperature of 475MPa≤R eL ≤515MPa、620MPa≤R m ≤655MPa, 370MPa≤R at 570℃ m ≤385MPa; (100℃) KV2≥300J, HBW≤195. Specification limit: Wide specification steel plate (50~70)mm×(5000~5200)mm×(5300~5500)mm has a flat plate shape, surface unevenness ≤10mm / m, and full plate thickness tolerance 1.0~2.0mm.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor plate component, characterized in that: The chemical composition and mass percentage of the nuclear power steel plate are: C: 0.10%~0.14%, Si: 0.10%~0.30%, Mn: 0.30%~0.60%, P≤0.006%, S≤0.002%, Cr: 2.05%~2.55%, Mo: 0.80%~1.10%, Nb: 0.01%~0.03%, Alt: 0.020%~0.045%, the balance is Fe and unavoidable inclusions; The preparation method comprises: According to the composition design of the nuclear power steel plate, the raw materials are sequentially smelted, refined, and vacuum degassed to obtain molten steel, and the molten steel is cast, stacked, slowly cooled, and heated to obtain heated steel billets; The heated steel billet is rolled: the length of the heated steel billet is used as the target rolling plate width, a rolling method of rolling to the bottom is adopted, a three-stage rolling method is adopted for rolling, and the steel is not rotated during the rolling process; the first stage of high-temperature rolling is completed at above 1000°C, the single-pass reduction is ≥40mm, the roller speed is 0.6~0.8m / s, and the rolling passes are 3~4 times; the second stage of rolling is carried out in the range of 830~930°C, the roller speed is 0.8~1.0m / s; the third stage of rolling is carried out in the range of 770~800°C, the rolling passes are 2~3 times, the pass reduction is 3~8mm, and the roller speed is 1.0~1.3m / s; the whole rolling process is not less than 10 passes; The target rolled plate is heat treated: the target rolled plate is heat treated at a tempering temperature of 720-750° C., and the holding time is determined according to the thickness of the target rolled plate: 2.0-4.0 min / mm; and the nuclear power steel plate is finally obtained.

2. The method for preparing a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor press plate component according to claim 1, characterized in that: The nuclear power steel plate has a complex phase structure of 15-25% equiaxed ferrite, 2-5% fine subgrains and 70-80% bainite tempered structure.

3. The method for preparing a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor press plate component according to claim 1, characterized in that: The specifications of the nuclear power steel plate are (50~70) mm×(5000~5300) mm×(5000~5300) mm, the surface unevenness is ≤10 mm / m, and the plate thickness tolerance is 1.0~2.0 mm.

4. The method for preparing a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor press plate component according to claim 1, characterized in that: In the casting process, a slab continuous casting machine is used to cast the molten steel after breaking the vacuum to obtain a cast billet. The superheat degree during the casting process is 20-30° C. The cross-section of the continuous casting billet is (250-300) mm×(1500-1650) mm. The billet drawing rate is 1.0-1.4 m / s. The online cutting length of the continuous casting billet is 5100-5300 mm.

5. The method for preparing a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor press plate component according to claim 1, characterized in that: During the stacking slow cooling process, the stacking slow cooling time is 24 to 36 hours, and the stacks are unpacked when the temperature is below 400°C to obtain steel billets.

6. The method for preparing a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor press plate component according to claim 1, characterized in that: During the third stage of rolling, the CVC roller-string process is simultaneously used to ensure that the thickness tolerance of the target rolled plate in the width direction is ≤1.5mm.

7. The method for preparing a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor press plate component according to claim 1, characterized in that: During the heating process, the heating temperature is 1180-1230°C, and the total heating time is 4-6 hours.

8. The method for preparing a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor press plate component according to claim 1, characterized in that: During the smelting process, a converter is used, and dephosphorization and decarburization are smelted separately in the converter. The dephosphorization oxygen blowing time is 7 to 10 minutes, and the decarburization oxygen blowing time is 8 to 12 minutes.

9. The method for preparing a nuclear power steel plate with an extreme wide specification for a high temperature gas-cooled reactor press plate component according to claim 1, characterized in that: Vacuum degassing uses a VD furnace with a net cycle time of 10~15min and a calming time before casting of 3~5min.

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