An asymmetric double-sided heterogeneous composite steel plate for nuclear power and a method for manufacturing the same

Abstract

The present application relates to a kind of asymmetric double-sided heterogeneous composite steel plate for nuclear power and its preparation method, comprising: preparing the base plate of double-sided heterogeneous composite steel plate;Prepare the complex plate of double-sided heterogeneous composite steel plate;Steel plate group blank;Adjacent slab four edges are welded using vacuum electron beam welding mode;Composite plate rolling;Quenching and tempering treatment.The advantages of the present application are: using asymmetric double-sided heterogeneous composite steel plate, maximum thickness reaches 129mm, applied to the preparation small nuclear power unit containment vessel, can solve the key material "neck" problem of the top head and cylinder of heat and power cogeneration integrated heat supply reactor, promote the key material localization of China's nuclear power unit;Asymmetric double-sided heterogeneous composite steel plate uses less process flow, compared with other preparation processes that need to prepare side plate or inlay groove, production cost is low, and the yield is high;Using double-sided heterogeneous composite plate, the difference of the thickness of upper and lower composite material can be realized, and asymmetric double-sided heterogeneous composite steel plate can replace stainless steel of same thickness.

Description

Technical Field

[0001] This invention relates to composite plates, and more particularly to an asymmetric double-sided heterogeneous composite steel plate for nuclear power and its preparation method. Background Technology

[0002] The integrated heat and power (CHP) reactor (Guohe-3) is a key nuclear power reactor type developed in my country. This technology is particularly suitable for small nuclear power units in northern my country that require winter heating. The containment top head and shell are important nuclear-grade equipment of the integrated CHP reactor. Their overall height exceeds 26m, with the upper shell approximately 16.5m high and having an inner diameter of 6100mm. Both sides are in contact with 0℃ liquid water, making them extremely important for the safe operation of the entire unit. The steel containment vessel operates at high pressure, requiring materials with high strength, good toughness, and corrosion resistance. Currently, 130-140mm thick 304 stainless steel or controlled-nitrogen stainless steel are mainly used. However, both of these materials have disadvantages such as high cost, low strength, and high processing difficulty. To solve this problem, this invention uses a three-layer composite technology of stainless steel + low-alloy steel + stainless steel to prepare an asymmetric heterogeneous composite plate. This effectively addresses the high strength and corrosion resistance requirements of the CHP reactor containment vessel while significantly reducing costs and improving overall economic efficiency. The biggest challenge of this composite plate lies in achieving the thickness differences between the upper and lower layers and the base layer.

[0003] The publication number is CN109591396A, titled "Stainless Steel and Carbon Steel Composite Plates and Their Preparation Methods". It introduces a method for producing carbon steel + stainless steel composite plates using vacuum electron beam welding. The production process requires four layers of steel plates to be stacked, resulting in a large amount of material consumption. Furthermore, it does not describe the thickness range of the finished composite plate.

[0004] The publication number is CN211942395U, entitled "A Stainless Steel / Carbon Steel Composite Plate", which provides a method for preparing a carbon steel + stainless steel composite plate. The characteristic of this method is that it does not need to consider the type of substrate and composite material. However, it requires the preparation of four side plates during the preparation process, which is relatively complicated. Moreover, it can only meet the requirements of single-sided composite and cannot meet the needs of double-sided composite plate preparation.

[0005] The publication number is CN102069289A, titled "A method for preparing a stainless steel-carbon steel composite plate". Judging from the final thickness and properties of the steel plate disclosed, the shear strength of the steel plate exceeds 400MPa, indicating that the composite steel plate has a high degree of bonding. However, the maximum thickness of the composite steel plate is only 10.8mm, which cannot meet the requirements of the containment vessel of a nuclear power plant.

[0006] The patent, with publication number CN107282684A and titled "A Production Method of Extra-Thick Heterogeneous Composite Plate of Stainless Steel and Carbon Steel," describes a method for preparing a single-sided composite plate of 316 stainless steel and Q370 carbon steel. This method requires grooved treatment of the composite material, resulting in higher steel plate production costs. Furthermore, this patent only describes the thickness range of the composite material and the substrate, without mentioning the thickness range of the finished composite plate.

[0007] The publication number is CN113399457A, entitled "A Hot Rolling Process for Duplex Stainless Steel-Carbon Steel Composite Plate". It introduces a method for preparing 2205 duplex stainless steel + Q345 carbon steel single-sided composite plate by vacuum welding and hot rolling. The bonding strength of the finished composite plate exceeds 400MPa, but the maximum thickness of the finished steel plate is relatively low, about 10mm, and it is a single-sided composite. The double-sided composite method is not mentioned.

[0008] The publication number is CN111941003A, entitled "A method for preparing a warm-rolled stainless steel / carbon steel composite plate". It introduces a method for preparing a single-sided composite plate of 304 stainless steel and Q235 carbon steel using vacuum welding and warm rolling. The composite plate has a bonding strength of 280MPa, which is relatively low. Moreover, the maximum thickness of the finished steel plate is only 12mm, which cannot meet the requirements of steel containment vessels for nuclear power plants. Summary of the Invention

[0009] The purpose of this invention is to provide an asymmetric double-sided heterogeneous composite steel plate for nuclear power and its preparation method. It is manufactured using a three-layer composite steel plate of stainless steel + carbon steel + stainless steel. The thickness of the upper and lower composite materials of the finished composite plate is different, i.e., asymmetric. This can effectively solve the "bottleneck" problem of key materials for the top head and shell of the heating reactor, promote the localization of key materials for nuclear power, and reduce production costs.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A type of asymmetric double-sided heterogeneous composite steel plate for nuclear power plants, wherein the base material of the composite steel plate is carbon steel, and its composition by mass percentage is: C: 0.10%~0.30%; Si: 0.10%~0.40%; Mn: 1.30%~1.70%; P≤0.01%; S≤0.002%; Cr: 0.10%~0.30%; Mo: 0.20%~0.60%; Ni: 0.40%~1.00%; N≤0.01%; V: 0.01%~0.05%; Cu≤0.03%, with the balance being Fe and unavoidable impurity elements;

[0012] The composite steel plate is made of stainless steel, with the following composition by mass percentage: C ≤ 0.03%; Si: 0.40-0.70%; Mn: 1.40-1.55%; P ≤ 0.02%; S ≤ 0.004%; Cr: 15.85-17.15%; Mo: 1.95-3.00%; Ni: 10.00-11.05%; N ≤ 0.15%; Co ≤ 0.08%, with the balance being Fe and unavoidable impurity elements.

[0013] Specifically, the following steps are included:

[0014] S1. Preparation of substrate for double-sided heterogeneous composite steel plate: Prepare continuous casting billet according to the composition of the composite steel plate substrate, use the continuous casting billet as electrode to prepare electroslag ingot using electroslag remelting technology, and after forging and rolling, prepare double-sided heterogeneous composite substrate for later use.

[0015] S2. Preparation of double-sided heterogeneous composite steel plate: Stainless steel ingots are made according to the composite material composition of the composite steel plate. The stainless steel ingots are hot rolled into composite plates of different thicknesses at low speed and low pressure according to the required thickness. After solution treatment and pickling passivation, they are used as double-sided heterogeneous composite composite plates for later use.

[0016] S3. Steel plate assembly, specifically including the following:

[0017] 1) Milling is performed on the double-sided heterogeneous composite substrate and the double-sided heterogeneous composite laminate;

[0018] 2) The surfaces of the double-sided heterogeneous composite substrate and the double-sided heterogeneous composite laminate to be laminated are machined and ground to a surface roughness of 0.3 to 0.6 μm;

[0019] 3) Based on the specifications of the finished composite plate, select a double-sided heterogeneous composite base plate with a thickness of 180-500mm and a double-sided heterogeneous composite composite plate with a thickness of 10-30mm, wherein the thickness percentage of stainless steel and carbon steel is 12-67%; stack the slabs in the order of stainless steel / carbon steel / stainless steel in the rolling pressing direction, with the diagonal dimension deviation of each slab being less than 2mm and the maximum gap between the stacked slabs not exceeding 0.5mm;

[0020] S4. Place the assembled composite plate in a vacuum chamber with a vacuum level of less than 10. -2 Pa, the four sides of adjacent slabs are welded using vacuum electron beam welding;

[0021] S5. Composite plate rolling: The welded composite plate is sent into a heating furnace and heated at 1200℃~1230℃. The net holding time is 5~14h. Different rolling passes are set according to the thickness of the finished composite plate. The total reduction rate is 60%~80%, and at least three passes are guaranteed to have a reduction rate ≥20%.

[0022] S6. Conditioning and tempering, specifically including the following:

[0023] Quenching process: Temperature controlled at 910~940℃, net holding time 2~3min / mm;

[0024] Tempering process: Temperature controlled at 610~660℃, net holding time 1.0~2.5min / mm.

[0025] In step S3, the thickness of the double-sided heterogeneous composite substrate is 180-500 mm, and the thickness of the double-sided heterogeneous composite laminate is 10-30 mm.

[0026] In step S4, the vacuum electron beam welding method is as follows: the welding penetration depth is greater than 40mm, and no pits greater than 10mm should appear where the weld melt flows.

[0027] In step S2, the low-speed, low-reduction method is used: the rolling speed is 0.5 m / s; the reduction rate for the first two passes is ≤15%.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. Asymmetric double-sided heterogeneous composite steel plates with a maximum thickness of 129mm are used to prepare containment vessels for small nuclear power units. This can solve the "bottleneck" problem of key materials for the top head and shell of integrated cogeneration reactors and promote the localization of key materials for nuclear power units in my country.

[0030] 2. The asymmetric double-sided heterogeneous composite steel plate uses fewer process steps. Compared with other preparation processes that require the preparation of side plates or inlay grooves, it has lower production costs and higher yield.

[0031] 3. By using double-sided heterogeneous composite plates, the thickness of the upper and lower composite materials can be differentiated. The application of asymmetric double-sided heterogeneous composite steel plates can replace stainless steel of the same thickness, saving manufacturing costs.

[0032] 4. A method for preparing an asymmetric "stainless steel + carbon steel + stainless steel" double-sided heterogeneous composite steel plate is proposed. Considering the compatibility of materials, 316L stainless steel is selected as the composite material and AG728 steel plate is selected as the base material. The average bonding strength of the composite steel plate exceeds 410MPa, which is significantly higher than the value specified in the national standard GB / T8165-2008 "Stainless Steel Composite Plates and Strips" (≥210MPa). Attached Figure Description

[0033] Figure 1 It is a metallographic diagram of the bonding surface of a 46mm thick composite steel plate.

[0034] Figure 2 This is a metallographic diagram of the bonding surface of a 46mm thick composite steel plate.

[0035] Figure 3 It is a metallographic diagram of the bonding surface of a 69mm thick composite steel plate.

[0036] Figure 4 This is a metallographic diagram of the bonding surface of a 69mm thick composite steel plate.

[0037] Figure 5 It is a metallographic diagram of the bonding surface of a 129mm thick composite steel plate.

[0038] Figure 6 This is a metallographic diagram of the bonding surface of a 129mm thick composite steel plate. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0040] A type of asymmetric double-sided heterogeneous composite steel plate for nuclear power applications. The base material of the composite steel plate is AG728 steel plate independently developed by Ansteel, and its composition by mass percentage is: C: 0.10%~0.30%; Si: 0.10%~0.40%; Mn: 1.30%~1.70%; P≤0.01%; S≤0.002%; Cr: 0.10%~0.30%; Mo: 0.20%~0.60%; Ni: 0.40%~1.00%; N≤0.01%; V: 0.01%~0.05%; Cu≤0.03%, with the balance being Fe and unavoidable impurity elements.

[0041] The composite steel plate is made of 316L stainless steel, with the following composition by mass percentage: C ≤ 0.03%; Si: 0.40-0.70%; Mn: 1.40-1.55%; P ≤ 0.02%; S ≤ 0.004%; Cr: 15.85-17.15%; Mo: 1.95-3.00%; Ni: 10.00-11.05%; N ≤ 0.15%; Co ≤ 0.08%, with the balance being Fe and unavoidable impurity elements.

[0042] A method for preparing an asymmetric double-sided heterogeneous composite steel plate for nuclear power plants specifically includes the following steps:

[0043] S1. Preparation of substrate for double-sided heterogeneous composite steel plate: Prepare continuous casting billet according to the composition of the composite steel plate substrate. In order to improve the homogeneity and purity of continuous casting billet, use continuous casting billet as electrode to prepare electroslag ingot using electroslag remelting technology. After forging and rolling, further improve the microstructure and basic properties of the steel plate core to prepare double-sided heterogeneous composite substrate for later use.

[0044] S2. Preparation of double-sided heterogeneous composite steel plate: Stainless steel ingots are made according to the composite material composition of the composite steel plate. The stainless steel ingots are hot rolled into composite plates of different thicknesses at low speed and small reduction (i.e., rolling speed of 0.5m / s; reduction rate of the first two passes ≤15%) according to the required thickness. After solution treatment and pickling passivation, they are used as double-sided heterogeneous composite composite plates for later use.

[0045] S3. Steel plate assembly, specifically including the following:

[0046] 1) Milling is performed on the double-sided heterogeneous composite substrate and the double-sided heterogeneous composite cladding to ensure that there are no residual iron oxide scale, oil stains, dust and other defects on the surface of carbon steel and stainless steel.

[0047] 2) To ensure the bonding strength of the steel plates, the surfaces of the double-sided heterogeneous composite substrate and the double-sided heterogeneous composite laminate to be laminated are machined and ground to a surface roughness of 0.3 to 0.6 μm.

[0048] 3) Based on the specifications of the finished composite plate, select a double-sided heterogeneous composite base plate with a thickness of 180-500mm and a double-sided heterogeneous composite composite plate with a thickness of 10-30mm, wherein the thickness percentage of stainless steel and carbon steel is 12-67%; stack the slabs in the order of stainless steel / carbon steel / stainless steel in the rolling pressing direction, with the diagonal dimension deviation of each slab being less than 2mm and the maximum gap between the stacked slabs not exceeding 0.5mm;

[0049] S4. Place the assembled composite plate in a vacuum chamber with a vacuum level of less than 10. -2 Pa, the four sides of the adjacent slabs are welded using vacuum electron beam welding; the welding penetration depth is required to be more than 40mm, the weld is full, and there should be no pits larger than 10mm where the weld flows. The arc starting and ending areas of the weld must be consistent and continuous, eliminating the discontinuous areas of the weld. The weld surface is well formed and free from cracks, inclusions, pores and surface depressions.

[0050] S5. Composite plate rolling: The welded composite plate is sent into a heating furnace and heated at 1200℃~1230℃. The net holding time is 5~14h. Different rolling passes are set according to the thickness of the finished composite plate. The total reduction rate is 60%~80%, and at least three passes are guaranteed to have a reduction rate ≥20%.

[0051] S6. Conditioning and tempering, specifically including the following:

[0052] Quenching process: Temperature controlled at 910~940℃, net holding time 2~3min / mm;

[0053] Tempering process: Temperature controlled at 610~660℃, net holding time 1.0~2.5min / mm.

[0054] The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the methods used in the following embodiments are conventional methods.

[0055]

Example 1

[0056] An asymmetric double-sided heterogeneous composite steel plate for nuclear power applications is prepared according to the following steps:

[0057] S1. Mill the base plate and cladding plate to ensure that there are no residual iron oxide scale, oil stains, dust, or other defects on the surfaces of the stainless steel and carbon steel, and that the roughness of the steel plate mating surface is 0.3–0.6 μm. The carbon steel plate specifications are 500×450×180 mm, and the stainless steel plate specifications are 500×450×10 mm and 500×450×20 mm, respectively. Stack the slabs in the order of stainless steel / carbon steel / stainless steel in the rolling pressing direction, requiring that the diagonal dimension deviation of each slab be controlled within 2 mm, and the maximum gap between the slabs be no more than 0.5 mm.

[0058] S2. Place the composite slab in a vacuum chamber, ensuring a vacuum level below 10⁻² Pa. Weld the four sides of adjacent steel plates using vacuum electron beam welding. The weld penetration depth should be at least 40 mm, the weld should be full, and there should be no pits larger than 10 mm where the weld melt flows. The arc initiation and termination areas of the weld must be consistent and continuous, eliminating any discontinuous areas. The weld surface should have good shape, free from cracks, inclusions, porosity, and surface depressions.

[0059] S3. The composite billet after assembly is sent to the heating furnace and heated at 1200℃-1230℃ for a net holding time of 5.5h. The composite steel plate is rolled to a thickness of 46mm in 8 passes at a rolling temperature of 1050±10℃. The total reduction rate is 78%, of which the reduction rate of the four passes is ≥20%. The thickness of each layer of the finished composite plate along the rolling reduction direction is 3, 37, and 6mm respectively.

[0060] S4. The obtained steel plate is subjected to quenching at 920℃ with a net holding time of 1.6 min / mm; tempering at 620℃ with a net holding time of 1.5 min / mm.

[0061] The metallographic structure at the upper and lower bonding surfaces of the asymmetric double-sided heterogeneous composite plate prepared in this embodiment is shown in the figure. Figure 1 and Figure 2 The stainless steel matrix has an austenitic microstructure containing numerous twins, while the carbon steel microstructure is bainite. The mechanical properties and bonding strength of the asymmetric double-sided heterogeneous composite plate substrate obtained in this embodiment are shown in Tables 1-3, respectively.

[0062] Table 1: Tensile Properties of 46mm Thick Composite Steel Plate Substrate

[0063]

[0064] Table 2: Impact Performance of 46mm Thick Composite Steel Plate Substrate

[0065]

[0066] Table 3: Shear properties of the upper and lower joint surfaces of 46mm thick composite steel plates

[0067]

[0068]

Example 2

[0069] An asymmetric double-sided heterogeneous composite steel plate for nuclear power applications is prepared according to the following steps:

[0070] S1. Mill the substrate and cladding to ensure that there are no residual iron oxide scale, oil stains, dust, or other defects on the surfaces of the stainless steel and carbon steel, and that the roughness of the steel plate mating surfaces is 0.3–0.6 μm. The carbon steel plate specifications are 500×450×180 mm, and the stainless steel plate specifications are 500×450×10 mm and 500×450×20 mm, respectively. Stack the slabs in the order of stainless steel / carbon steel / stainless steel in the rolling pressing direction, requiring that the diagonal dimension deviation of each slab be controlled within 2 mm, and the maximum gap between the slabs be no more than 0.5 mm.

[0071] S2. Place the composite slab in a vacuum chamber, ensuring the vacuum level is below 10⁻² Pa. Use vacuum electron beam welding to weld the four sides of adjacent steel plates. The weld penetration depth should be more than 40 mm, the weld should be full, and there should be no pits larger than 10 mm where the weld melt flows. The arc initiation and arc termination areas of the weld should be consistent and continuous, eliminating discontinuous areas in the weld. The weld surface should be well formed, without cracks, inclusions, pores, or surface depressions.

[0072] S3. The composite billet after assembly is sent to the heating furnace and heated at 1200℃-1230℃ for a net holding time of 5.5h. The composite steel plate is rolled to a thickness of 69mm in 7 passes at a rolling temperature of 1050±10℃. The total reduction rate is 67%, of which the reduction rate of three passes is ≥20%. The thickness of each layer of the finished composite plate along the rolling reduction direction is 5mm, 55mm, and 9mm respectively.

[0073] S4. The obtained steel plate is subjected to quenching at 940℃ with a net holding time of 2 min / mm; and tempering at 640℃ with a net holding time of 2.2 min / mm.

[0074] The metallographic structure at the upper and lower bonding surfaces of the asymmetric double-sided heterogeneous composite plate prepared in this embodiment is shown in the figure. Figure 3 and Figure 4The stainless steel matrix has an austenitic microstructure containing numerous twins, while the carbon steel microstructure is bainite, with a small amount of precipitates at the bonding surface. The mechanical properties and bonding strength of the asymmetric double-sided heterogeneous composite plate substrate obtained in this embodiment are shown in Tables 4-6, respectively.

[0075] Table 4: Tensile Properties of 69mm Thick Composite Steel Plate Substrate

[0076]

[0077] Table 5: Impact Performance of 69mm Thick Composite Steel Plate Substrate

[0078]

[0079] Table 6: Shear properties of the upper and lower joint surfaces of 69mm thick composite steel plates

[0080]

[0081]

Example 3

[0082] An asymmetric double-sided heterogeneous composite steel plate for nuclear power applications is prepared according to the following steps:

[0083] Step 1: Mill the base plate and cladding plate to ensure that there are no residual iron oxide scale, oil stains, dust or other defects on the surface of stainless steel and carbon steel, and that the roughness of the steel plate mating surface is 0.3 to 0.6 μm; the carbon steel plate is 2000×2200×490 mm, and the stainless steel plates are 2000×2200×15 mm and 2000×2200×25 mm respectively. Stack the slabs in the order of stainless steel / carbon steel / stainless steel according to the rolling pressing direction. The diagonal dimension deviation of each slab should be controlled within 2 mm, and the maximum gap between the slabs should not be greater than 0.5 mm.

[0084] Step 2: Place the composite slab in a vacuum chamber, ensuring the vacuum level is below 10⁻² Pa. Use vacuum electron beam welding to weld the four sides of the adjacent steel plates. The weld penetration depth should be more than 40 mm, the weld should be full, and there should be no pits larger than 10 mm where the weld flows. The arc initiation and arc termination areas of the weld must be consistent and continuous, eliminating discontinuous areas in the weld. The weld surface should be well formed, without cracks, inclusions, pores, or surface depressions.

[0085] Step 3: The assembled composite billet is sent to the heating furnace and heated at 1200℃-1230℃ for a net holding time of 14 hours. The composite steel plate is rolled to a thickness of 129mm in 7 passes at a rolling temperature of 1050±10℃. The total reduction rate is 76%, with the reduction rate of the four passes being ≥20%. The thickness of each layer of the finished composite plate along the rolling reduction direction is 3mm, 120mm, and 6mm, respectively.

[0086] Step 4: The obtained steel plate is subjected to quenching at 940℃ with a net holding time of 2.8 min / mm; tempering at 660℃ with a net holding time of 2.5 min / mm.

[0087] The metallographic structure at the upper and lower bonding surfaces of the asymmetric double-sided heterogeneous composite plate prepared in this embodiment is shown in the figure. Figure 5 and Figure 6 The stainless steel matrix has an austenitic microstructure containing numerous twins, while the carbon steel microstructure is bainite, with a large number of precipitates at the bonding surface. The mechanical properties and bonding strength of the asymmetric double-sided heterogeneous composite plate substrate obtained in this embodiment are shown in Tables 7-9, respectively.

[0088] Table 7: Tensile Properties of 129mm Thick Composite Steel Plate Substrate

[0089]

[0090] Table 8: Impact Performance of 129mm Thick Composite Steel Plate Substrate

[0091]

[0092]

[0093] Table 9: Shear properties of the upper and lower joint surfaces of 129mm thick composite steel plates

[0094]

[0095] This invention employs asymmetric double-sided heterogeneous composite steel plates with a maximum thickness of 129 mm, applied to the fabrication of containment vessels for small nuclear power units. This addresses the critical material bottleneck issue in the top end cap and shell of integrated cogeneration reactors, promoting the localization of key materials for nuclear power units in my country. The asymmetric double-sided heterogeneous composite steel plate utilizes fewer processing steps, resulting in lower production costs and higher yield compared to other fabrication processes that require side plates or recessed mounting. The use of double-sided heterogeneous composite plates allows for differences in the thickness of the upper and lower composite materials, enabling the replacement of stainless steel of equivalent thickness, thus saving on fabrication costs. A method for preparing asymmetric "stainless steel + carbon steel + stainless steel" double-sided heterogeneous composite steel plates is proposed. Considering material compatibility, 316L stainless steel is selected as the composite material, and AG728 steel plate as the base material. The average bonding strength of the composite steel plates exceeds 410 MPa, significantly higher than the value specified in the national standard GB / T8165-2008 "Stainless Steel Composite Plates and Strips" (≥210 MPa).

Claims

1. An asymmetric double-sided heterogeneous composite steel plate for nuclear power plants, characterized in that, The base material of the composite steel plate is carbon steel, and its composition by mass percentage is: C: 0.10%~0.30%; Si: 0.10%~0.40%; Mn: 1.30%~1.70%; P≤0.01%; S≤0.002%; Cr: 0.10%~0.30%; Mo: 0.20%~0.60%; Ni: 0.40%~1.00%; N≤0.01%. V: 0.01%~0.05%; Cu≤0.03%, balance being Fe and unavoidable impurity elements; The composite steel plate is made of stainless steel, with the following composition by mass percentage: C≤0.03%; Si: 0.40-0.70%; Mn: 1.40-1.55%; P≤0.02%; S≤0.004%; Cr: 15.85-17.15%; Mo: 1.95-3.00%; Ni: 10.00-11.05%; N≤0.15%; Co≤0.08%, with the balance being Fe and unavoidable impurity elements. The maximum thickness of the composite steel plate is 129 mm; The asymmetry mentioned refers to the difference in thickness between the upper and lower cladding layers; The yield strength of the composite steel plate is 786 MPa, the tensile strength is 884 MPa, and the bond strength exceeds 410 MPa. The method for preparing an asymmetric double-sided heterogeneous composite steel plate for nuclear power plants specifically includes the following steps: S1. Preparation of substrate for double-sided heterogeneous composite steel plate: Prepare continuous casting billet according to the composition of the composite steel plate substrate, use the continuous casting billet as electrode to prepare electroslag ingot using electroslag remelting technology, and after forging and rolling, prepare double-sided heterogeneous composite substrate for later use. S2. Preparation of double-sided heterogeneous composite steel plate: Stainless steel ingots are made according to the composite material composition of the composite steel plate. The stainless steel ingots are hot rolled into composite plates of different thicknesses at low speed and low pressure according to the required thickness. After solution treatment and pickling passivation, they are used as double-sided heterogeneous composite composite plates for later use. S3. Steel plate assembly, specifically including the following: 1) Milling of the double-sided heterogeneous composite substrate and the double-sided heterogeneous composite laminate; 2) The surfaces of the double-sided heterogeneous composite substrate and the double-sided heterogeneous composite laminate to be laminated are machined and ground to a surface roughness of 0.3~0.6µm; 3) Based on the specifications of the finished composite plate, select a double-sided heterogeneous composite base plate with a thickness of 180~500mm and a double-sided heterogeneous composite composite plate with a thickness of 10~30mm, wherein the thickness percentage of stainless steel and carbon steel is 12~67; stack the slabs in the order of stainless steel / carbon steel / stainless steel in the rolling pressing direction, with the diagonal dimension deviation of each slab being less than 2mm and the maximum gap between the stacked slabs not exceeding 0.5mm; S4. Place the assembled composite plate in a vacuum chamber with a vacuum level of less than 10. -2 Pa, the four sides of adjacent slabs are welded using vacuum electron beam welding; S5. Composite plate rolling: The welded composite plate is sent into a heating furnace, the heating temperature is 1200℃~1230℃, the net holding time is 5~14h, the rolling temperature is 1050±10℃, different rolling passes are set according to the thickness of the finished composite plate, the total reduction rate is 60%~80%, and at least three passes are guaranteed to have a reduction rate ≥20%, and the total rolling passes are 7 or 8. S6. Conditioning and tempering, specifically including the following: Quenching process: Temperature controlled at 910~940℃, net holding time 2~3min / mm; Tempering process: Temperature controlled at 610~660℃, net holding time 1.0~2.5min / mm.

2. The method for preparing an asymmetric double-sided heterogeneous composite steel plate for nuclear power plants according to claim 1, characterized in that, Specifically, the following steps are included: S1. Preparation of substrate for double-sided heterogeneous composite steel plate: Prepare continuous casting billet according to the composition of the composite steel plate substrate, use the continuous casting billet as electrode to prepare electroslag ingot using electroslag remelting technology, and after forging and rolling, prepare double-sided heterogeneous composite substrate for later use. S2. Preparation of double-sided heterogeneous composite steel plate: Stainless steel ingots are made according to the composite material composition of the composite steel plate. The stainless steel ingots are hot rolled into composite plates of different thicknesses at low speed and low pressure according to the required thickness. After solution treatment and pickling passivation, they are used as double-sided heterogeneous composite composite plates for later use. S3. Steel plate assembly, specifically including the following: 1) Milling of the double-sided heterogeneous composite substrate and the double-sided heterogeneous composite laminate; 2) The surfaces of the double-sided heterogeneous composite substrate and the double-sided heterogeneous composite laminate to be laminated are machined and ground to a surface roughness of 0.3~0.6µm; 3) Based on the specifications of the finished composite plate, select a double-sided heterogeneous composite base plate with a thickness of 180~500mm and a double-sided heterogeneous composite composite plate with a thickness of 10~30mm, wherein the thickness percentage of stainless steel and carbon steel is 12~67; stack the slabs in the order of stainless steel / carbon steel / stainless steel in the rolling pressing direction, with the diagonal dimension deviation of each slab being less than 2mm and the maximum gap between the stacked slabs not exceeding 0.5mm; S4. Place the assembled composite plate in a vacuum chamber with a vacuum level of less than 10. -2 Pa, the four sides of adjacent slabs are welded using vacuum electron beam welding; S5. Composite plate rolling: The welded composite plate is sent into a heating furnace, the heating temperature is 1200℃~1230℃, the net holding time is 5~14h, the rolling temperature is 1050±10℃, different rolling passes are set according to the thickness of the finished composite plate, the total reduction rate is 60%~80%, and at least three passes are guaranteed to have a reduction rate ≥20%, and the total rolling passes are 7 or 8. S6. Conditioning and tempering, specifically including the following: Quenching process: Temperature controlled at 910~940℃, net holding time 2~3min / mm; Tempering process: Temperature controlled at 610~660℃, net holding time 1.0~2.5min / mm.

3. The method for preparing an asymmetric double-sided heterogeneous composite steel plate for nuclear power plants according to claim 2, characterized in that, In step S3, the thickness of the double-sided heterogeneous composite substrate is 180~500mm, and the thickness of the double-sided heterogeneous composite laminate is 10~30mm.

4. The method for preparing an asymmetric double-sided heterogeneous composite steel plate for nuclear power plants according to claim 2, characterized in that, In step S4, the vacuum electron beam welding method is as follows: the welding penetration depth is greater than 40mm, and no pits greater than 10mm shall appear where the weld melt flows.

5. The method for preparing an asymmetric double-sided heterogeneous composite steel plate for nuclear power plants according to claim 2, characterized in that, In step S2, the low-speed, low-reduction method involves a rolling speed of 0.5 m / s and a reduction rate of ≤15% for the first two passes.

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