High-performance nuclear power heterogeneous composite steel plate and production method thereof

Abstract

The invention belongs to the technical field of metal material production, and particularly relates to a high-performance nuclear power heterogeneous composite steel plate and a production method thereof. The composite steel plate is composed of a base layer steel plate and a composite layer steel plate. The base layer steel plate is prepared from the following chemical components in percentage by weight: 0.13 percent to 0.20 percent of C, 0.10 percent to 0.50 percent of Si, 1.10 percent to 1.85 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.005 percent of S, 0.51 percent to 0.96 percent of Ni, 0.12 percent to 0.45 percent of Cr, 0.26 percent to 0.65 percent of Mo, 0.031 percent to 0.085 percent of V, 0.02 percent to 0.05 percent of Ti, 0.02 percent to 0.05 percent of Al, 0.007 percent to 0.015 percent of N and the balance of Fe and inevitable impurities; the multi-layer steel plate is made of stainless steel. The bonding rate of the obtained composite steel plate reaches 100%, the ultrasonic detection result meets the I-level requirement specified by NB / T47013.3, and the composite steel plate has high structural strength and toughness and has the composite characteristics of corrosion resistance, heat resistance and the like.

Description

Technical Field

[0001] This invention belongs to the field of metal material production technology, and in particular relates to a high-performance nuclear power heterogeneous composite steel plate and its production method. Background Technology

[0002] Most corrosion-resistant equipment in nuclear power units is made of stainless steel. However, stainless steel equipment is more difficult to manufacture, weld, and costly due to the material itself. Therefore, composite steel plates made of stainless steel and carbon steel can be used as a substitute for stainless steel in the design of such equipment. Composite steel plates, through the combination of a base layer (load-bearing strength) and a cladding layer (corrosion resistance), can simultaneously meet the requirements of structural strength and adaptability to the environment, and are relatively cheaper to produce. The base layer of the composite steel plate is carbon steel, and the cladding layer is a thin layer of stainless steel. The base layer and cladding layer must have good bonding during forming, thus requiring sufficient shear strength to prevent the cladding layer from detaching or delaminating. Furthermore, as the thickness of the composite steel plate increases, the strength, toughness, and stability of the steel plate become more difficult to control.

[0003] Existing composite steel plates for nuclear power plants suffer from problems such as insufficient bonding strength, large performance fluctuations after heat treatment, and difficulty in simultaneously achieving good resistance to intergranular corrosion. For example, patent CN102069289A discloses a method for preparing a stainless steel-carbon steel composite plate. The shear strength of this steel plate exceeds 400MPa, indicating a high degree of bonding. However, the maximum thickness of the composite steel plate is only 10.8mm, which cannot meet the manufacturing requirements of large-thickness nuclear power equipment. Patent CN113399457A discloses a "hot rolling process method for duplex stainless steel-carbon steel composite plates," which uses vacuum welding + hot rolling to prepare 2205 duplex stainless steel + Q345 carbon steel single-sided composite plates. The bonding strength of the finished composite plates exceeds 400MPa, but the maximum thickness of the finished steel plates is relatively low, about 10mm, and the substrate strength is low. Patent CN11194... Patent 1003A discloses a method for preparing a warm-rolled stainless steel / carbon steel composite plate, which uses vacuum welding and warm rolling to prepare a single-sided composite plate of 304 stainless steel and Q235 carbon steel. The composite plate has a bonding strength of 280 MPa, which is relatively low. Patent CN101559525A discloses an explosive welding method for 310S austenitic stainless steel composite steel plate. The manufacturing method of this patent is an explosive bonding method. This method obtains a composite steel plate by explosive welding after simple surface treatment of the substrate and composite material. Although the ultrasonic flaw detection is 100% qualified, the explosive bonding method will result in uneven bonding effect due to uneven explosive force. The shear force at the bonding interface is small, which cannot guarantee the safety of nuclear equipment.

[0004] Therefore, it is of great significance to develop a nuclear power heterogeneous composite steel plate that meets the requirements of high performance and its production method. Summary of the Invention

[0005] The purpose of this invention is to overcome the deficiencies of existing technologies and support the smooth construction of large-scale nuclear power units in my country. It provides a high-performance nuclear power heterogeneous composite steel plate and its production method. The interfacial shear strength between the base steel plate and the cladding steel plate of this composite steel plate is >350MPa, and it passes the 180° bending test. The mechanical properties of the base steel plate meet the following requirements: room temperature tensile strength. R p0.2 >655MPa R m >725MPa A 50 >20%, high temperature tensile testing at 350℃ R p0.2 >590MPa R m >640MPa, -20℃ KV 2 > 200J; After intergranular corrosion of the clad steel plate according to GB / T4334-2020, no cracks were generated when the sample was bent 180°, and the Rockwell hardness HRB≤90. In particular, the composite steel plate still maintains good mechanical properties after stress relief heat treatment at a temperature of 615℃ for 10 hours, which can fully meet the high service safety requirements of nuclear power equipment.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In one aspect, the present invention provides a high-performance nuclear power heterogeneous composite steel plate, wherein the composite steel plate is composed of a base steel plate and a cladding steel plate; The chemical composition of the base steel plate by weight percentage is as follows: C: 0.13%~0.20%, Si: 0.10%~0.50%, Mn: 1.10%~1.85%, P≤0.010%, S≤0.005%, Ni: 0.51%~0.96%, Cr: 0.12%~0.45%, Mo: 0.26%~0.65%, V: 0.031%~0.085%, Ti: 0.02%~0.05%, Al: 0.02%~0.05%, N: 0.007%~0.015%, with the remainder being Fe and unavoidable impurities; The cladding steel plate is made of stainless steel.

[0007] In the above technical solution, the chemical composition of the clad steel plate by weight percentage is further as follows: C: 0.012%~0.038%, Mn: 1.61%~1.96%, P≤0.010%, S≤0.005%, Cr: 17.3%~18.7%, Ni: 9.4%~14.7%, Mo: 2.1%~3.2%, N: 0.03%~0.10%, with the remainder being Fe and unavoidable impurities.

[0008] The rationale for designing the chemical composition of the base steel plate in this invention is as follows: Carbon (C) enhances the strength of the base steel plate and improves its hardenability during quenching, promoting the uniform formation of martensite in the thickness direction. It also forms stable carbides with alloying elements, improving microstructure stability and high-temperature strength. However, excessive C content negatively impacts the steel's ductility, toughness, and weldability. Therefore, the C content in the base steel plate of this invention is designed to be 0.13%~0.20%.

[0009] Si: Si is used to improve the hardenability and tempering resistance of steel plates. However, excessive Si content will impair the formability and low-temperature toughness of the steel plates. The Si content in the base steel plate of this invention is designed to be 0.10%~0.50%.

[0010] Mn: Mn is used to improve the hardenability of steel plates, refine the martensitic structure, improve the strength and toughness of steel plates, expand the austenite phase region, and improve the stability of austenite. This helps maintain the high-temperature strength of steel. Furthermore, when used in combination with Cr and Mo, Mn can improve the tempering stability of steel plates and enhance their overall performance after final heat treatment. Therefore, the Mn content in the base steel plate of this invention is designed to be 1.10%~1.85%.

[0011] P: P is a harmful element in steel, which can cause segregation of the structure and has a significant adverse effect on low-temperature toughness. The lower the content, the better. However, considering the steelmaking conditions and costs, this invention controls the P content in the steel to be ≤0.010%.

[0012] S: S is a harmful element in steel. It easily forms sulfide inclusions in steel, reducing the impact toughness of the steel, impairing its weldability, and aggravating defects such as center segregation and porosity. Therefore, this invention requires S ≤ 0.005%.

[0013] Ni: Ni can improve the low-temperature toughness of steel and reduce the brittle transition temperature. At the same time, Ni and Cr work together to promote the formation of Cr2O3 oxide layer and enhance the oxidation resistance of steel. In addition, Ni and an appropriate amount of Ti can promote the precipitation of strengthening phase and improve the high-temperature strength of steel plate. The Ni content in the base steel plate of this invention is designed to be 0.51%~0.96%.

[0014] Cr: Cr is used to improve the strength and hardenability of steel plates, reduce the minimum cooling rate for obtaining martensite, making it easier for the steel plate to obtain and refine martensite, thereby promoting the formation of fine tempered sorbite and maintaining good strength, toughness, and structural stability. Cr is used in combination with Mn and Mo to improve the tempering stability of the steel plate and enhance its overall performance after final heat treatment. However, excessive Cr content will reduce the weldability of the steel. Therefore, the Cr content in the base steel plate of this invention is designed to be 0.12%~0.45%.

[0015] Mo: Mo can inhibit the phase transformation of ferrite and pearlite, expand the cooling rate range for martensite formation, promote the formation of lath martensite, and improve the hardenability of steel plates, promoting the formation and homogenization of martensite along the thickness section. At high temperatures, Mo can also stabilize carbides in steel, delaying their coarsening and decomposition at high temperatures, thereby improving high-temperature strength and structural stability. In addition, Mo, when used in combination with Mn and Cr, improves the tempering stability of steel plates and enhances the overall performance of steel plates after final heat treatment. Therefore, the Mo content in the base steel plate of this invention is designed to be 0.26%~0.65%.

[0016] V: In low-temperature rolling, V is used to precipitate V(C,N), pin grain boundaries, and refine grains; in quenching heat treatment, it dissolves in austenite to improve the hardenability of the steel plate; the dispersed precipitation of V carbides is beneficial to improving the bending performance of the steel plate. Therefore, the V content in the base steel plate of this invention is designed to be 0.031%~0.085%.

[0017] Ti: Ti is used to form fine Ti(C,N) particles, improving the as-cast microstructure; it also forms high-melting-point TiC and TiN particles, pinning austenite grain boundaries, hindering grain coarsening during high-temperature heating or welding, and improving the strength and toughness of the steel. The Ti content in the base steel plate of this invention is designed to be 0.02%~0.05%.

[0018] Al plays a certain role in deoxidation, and also contributes to the formation of fine AlN, promoting the solid solution of V, improving the hardenability of steel, refining grains, and improving the strength and toughness of steel plates. The Al content in the base steel plate of this invention is 0.02~0.05%.

[0019] Nitrogen (N): Nitrogen is used to form nitrides, refine grains, and thus improve the strength and toughness of the steel plate, while also contributing to increased high-temperature strength. Furthermore, N enhances Cr diffusion, promotes the formation of a more stable Cr2O3 oxide film, and improves the oxidation resistance of the steel plate. However, excessive nitrogen content increases the aging tendency of the steel plate, as well as cold and hot brittleness, impairing its weldability. Therefore, the N content in the base steel plate of this invention is designed to be 0.007%~0.015%.

[0020] The rationale for designing the chemical composition of the clad steel plate of this invention is as follows: C: The main function of C is to improve the strength of the cladding layer and inhibit sensitization by reducing the precipitation of chromium carbide, thereby improving the cladding layer's resistance to intergranular corrosion. Simultaneously, a lower carbon content is beneficial for improving long-term high-temperature stability and reducing the harmful precipitation of carbides during long-term service. Therefore, the C content in the cladding steel plate of this invention is designed to be 0.012%~0.038%.

[0021] Mn: Mn is used for deoxidation and desulfurization, improves the purity of steel, increases the high-temperature strength of austenite, and reduces the tendency to crack during hot rolling. The Mn content in the clad steel plate of this invention is designed to be 1.61%~1.96%.

[0022] P and S: Harmful elements in steel, so the lower the content, the better. However, considering steelmaking conditions and costs, P should be controlled to ≤0.010% and S to ≤0.005%.

[0023] Cr: Cr combines with oxygen to form a dense Cr2O3 passivation film on the steel surface, giving the steel plate excellent corrosion resistance. When used synergistically with Mo, it improves the stability of the passivation film, especially in chlorine-containing environments (seawater, coastal areas). When used synergistically with Ni, it balances the ferrite tendency of Cr, stabilizes the austenite phase, and prevents the precipitation of δ-ferrite. The Cr content in the clad steel plate of this invention is designed to be 17.3%~18.7%.

[0024] Ni: Ni is a strong austenitic element that can expand the γ-phase region, allowing the clad stainless steel to maintain a fully austenitic structure at room temperature. It works synergistically with Cr to balance the ferrite tendency of Cr, stabilize the austenitic phase, and prevent the precipitation of δ-ferrite. It reduces the formation of the σ phase (Fe-Cr-Mo brittle phase) and δ-ferrite, avoiding embrittlement problems during long-term high-temperature service. It optimizes the density and self-healing ability of the passivation film, improving the corrosion resistance of the steel plate. Simultaneously, Ni works synergistically with Mo to improve resistance to pitting corrosion. Therefore, the Ni content in the clad steel plate of this invention is designed to be 9.4%~14.7%.

[0025] Mo: The addition of Mo is achieved through the formation of MoO4. 2- Or it may adsorb at defects in the passivation film, blocking Cl - Mo and Cr work synergistically to enhance the stability of the passivation film and delay the precipitation of carbides and σ phases. Furthermore, the combination of Mo and N can improve resistance to pitting corrosion. The Mo content in the clad steel plate of this invention is designed to be 2.1%~3.2%.

[0026] Ni: As a strong austenite-forming element, Ni, together with Ni, maintains the all-austenitic structure and avoids the formation of δ-ferrite; it dissolves in the austenitic matrix, causing lattice distortion and improving the strength of the cladding layer; in a corrosive microenvironment, Ni can dissolve into NH4. + Neutralizes acidity (H) + The N and Mo work synergistically to suppress pitting corrosion propagation; simultaneously, N and Mo work together to improve the stability of the passivation film; furthermore, N, in synergy with the low-C design of this invention, can further reduce chromium carbide (Cr). 23 C6) precipitation reduces the risk of chromium depletion at grain boundaries. Therefore, the N content in the clad steel plate of this invention is designed to be 0.03%~0.10%.

[0027] In the above technical solution, the interfacial shear strength between the base steel plate and the cladding steel plate is greater than 350 MPa, and the composite steel plate passes the 180° bending test.

[0028] In the above technical solution, the metallographic structure of the base steel plate is tempered sorbite, and the metallographic structure of the cladding steel plate is austenite.

[0029] In the above technical solution, the thickness of the composite steel plate is further 10~80mm.

[0030] In the above technical solution, the base steel plate is further subjected to room temperature tensile testing: R p0.2 >655MPa, R m >725MPa, A 50 >20%; 350℃ high-temperature tensile testing: R p0.2 >590MPa, R m >640MPa; Low-temperature toughness: -20℃ KV 2 > 200J.

[0031] In the above technical solution, further, after the composite steel plate undergoes stress-relieving heat treatment at a temperature of 615℃ for 10 hours, the base steel plate is subjected to room temperature tensile testing: R p0.2 >655MPa, R m >725MPa, A 50 >20%; 350℃ high-temperature tensile testing: R p0.2 >590MPa, R m >640MPa; Low-temperature toughness: -20℃ KV 2 > 200J.

[0032] In the above technical solution, further, after the clad steel plate is subjected to intergranular corrosion according to GB / T4334-2020, the sample is bent 180° without cracks and the Rockwell hardness HRB≤90.

[0033] Another aspect of the present invention provides a method for producing the above-mentioned high-performance nuclear power heterogeneous composite steel plate, comprising the following steps: (1) Surface treatment: The base steel billet and the cladding steel billet are surface treated; (2) Composite billet assembly: The base steel billet and the cladding steel billet are assembled to obtain a composite billet. The cladding steel billets of the two composite billets are then stacked together with one side in contact, and a release agent is applied between the adjacent cladding steel billets to obtain a combined billet. (3) Vacuum welding: The adjacent steel billets are welded and sealed around their perimeter by vacuum electron beam welding. (4) Heating, rolling and slow cooling: The heating temperature is 1200-1260℃ and the heating time is 8-16h. After heating, rolling is carried out. The initial rolling temperature is 1140-1210℃ and the final rolling temperature is 990-1070℃. Slow cooling is carried out after the final rolling is completed. (5) Tempering treatment: Offline tempering heat treatment is adopted, wherein the quenching temperature is 940~990℃, the holding time is 1~5min / mm, and after quenching, tempering is performed at a temperature of 600~650℃ and a holding time of 2~5h. After being taken out of the furnace, air cooling is performed. (6) Plate separation: After heat treatment, plate separation is performed to obtain two composite steel plates.

[0034] In the above technical solution, further, in step (1), the base steel plate billet is produced by the converter double-run method, controlling P≤0.010% and S≤0.005% in the molten steel, and then undergoes LF and RH ladle refining treatment to control [H]≤1.5ppm and [O]≤20ppm in the molten steel; in the continuous casting process, the tundish superheat is 29~35℃, and electromagnetic stirring and light reduction are adopted at the end of continuous casting. The electromagnetic stirring current is 330~360A, the light reduction is 7~12mm, the billet pulling speed is 0.7~1.0m / min, and the continuous casting billet is stacked and slowly cooled for more than 24 hours after it is removed from the line.

[0035] In the above technical solution, further, in step (1), after surface treatment, the surface roughness Ra of the base steel plate blank is <7.5μm, and the surface roughness Ra of the cladding steel plate blank is <6.3μm.

[0036] In the above technical solution, further, in step (2), the method for preparing the composite billet is as follows: welding metal strips around the surface-treated base steel billet, and embedding the cladding steel billet into the groove formed by the metal strips and the base steel billet to obtain the composite billet.

[0037] In the above technical solution, further, in step (3), the parameters of the vacuum electron beam welding are: vacuum degree ≤ 0.1 Pa, welding penetration ≥ 20 mm.

[0038] In the above technical solution, further, in step (4), in the rolling process, the deformation amount of the first 3 passes is 30~50mm and the roll speed is 0.8~1.3m / s, and the reduction rate of the subsequent passes is >8% and the roll speed is 1.2~1.9m / s; The thickness of the composite steel plate is 20~160mm.

[0039] In the above technical solution, further, in step (5), the quenching cooling rate is 19~28℃ / s, and the tempering heating rate is 2~4min / mm.

[0040] The beneficial effects of this invention are as follows: (1) The composite steel plate of the present invention has good hardenability and toughness, especially high temperature strength and formability, by adding Mn, Ni, Cr, Mo, V and Ti alloying elements in combination; the cladding steel plate uses Mn, Cr, Ni and Mo alloying elements to ensure the excellent corrosion resistance of the cladding.

[0041] (2) The composite steel plate of the present invention, through chemical composition and production process, produces a 10-80mm thick high-performance nuclear power heterogeneous composite steel plate. The interfacial shear strength between the base layer and the cladding layer of the composite steel plate is >350MPa (currently, the shear strength requirement for composite plates is greater than 200MPa), and it passes the 180° bending test. Simultaneously, the mechanical properties of the base layer meet the following requirements: room temperature tensile strength. R p0.2 >655MPa R m >725MPa A >20%, high temperature tensile testing at 350℃ R p0.2 >590MPa R m >640MPa, -20℃ KV 2 > 200J; After intergranular corrosion of the clad steel plate according to GB / T4334-2020, no cracks were generated when the sample was bent 180°, and the Rockwell hardness HRB≤90. In particular, the steel plate still maintains good mechanical properties after stress relief heat treatment at a temperature of 615℃ for 10 hours, meeting the high service safety requirements of nuclear power equipment.

[0042] (3) Through the effective control of the converter double-strand smelting and continuous casting process, the present invention obtains continuous casting billet steel with pure quality (non-metallic inclusions ≤ grade 1.0), low segregation (≤ grade 1.0), uniform as-cast structure, and large thickness (250~350mm).

[0043] (4) The composite steel plate obtained by the present invention has a bonding rate of 100%, and the ultrasonic test results meet the Class I requirements specified in NB / T47013.3. Compared with carbon steel plate and stainless steel alone, the composite steel plate of the present invention not only has high structural strength and toughness, but also has composite properties such as corrosion resistance and heat resistance. It has obvious advantages in terms of structural performance improvement and equipment weight reduction, which can effectively extend the service life of the equipment and reduce the manufacturing cost of the equipment. Attached Figure Description

[0044] Figure 1 The metallographic structure of the base steel plate in Example 5; Figure 2 The metallographic structure of the clad steel plate in Example 5; Figure 3 The image shows the interface EBSD diagram of the composite steel plate in Example 5. Detailed Implementation

[0045] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0046] Examples 1-10 The chemical composition of the composite steel plates provided in Examples 1-10 is shown in Table 1.

[0047] Table 1. Chemical composition (wt%) of the composite steel plates in Examples 1-10

[0048] The above-mentioned production method for nuclear power heterogeneous composite steel plates includes the following process: billet preparation—surface treatment—composite billet assembly—vacuum welding—heating—rolling—slow cooling—quenching and tempering—plate separation, wherein: (1) Preparation of billet The base steel billet used in this invention is produced by a double-unit converter process, controlling P ≤ 0.010% and S ≤ 0.005% in the steel. After further refining by LF and RH ladle refining, the [H] ≤ 1.5ppm and [O] ≤ 20ppm in the steel are controlled, ensuring that the non-metallic inclusions in the steel are ≤ 1.0 grade. During continuous casting, the superheat of the tundish is controlled at 29~35℃ to improve the fluidity of the molten steel and facilitate casting. At the end of continuous casting, electromagnetic stirring and light reduction are used. The electromagnetic stirring current is 330~360A, the light reduction is 7~12mm, and the billet pulling speed is controlled at 0.7~1.0m / min to improve the as-cast structure and increase the uniformity of the structure, laying the foundation for obtaining good quality steel plates. The thickness of the continuously cast billet is preferably 250~350mm. After leaving the line, it is stacked and slowly cooled for more than 24 hours to further reduce segregation to below 1.0 grade, while promoting the homogenization of the structure and eliminating internal defects in the billet. The multi-layered steel billet used in this invention can be purchased as a finished product or prepared using traditional methods, according to the designed composition. (2) Surface treatment The surfaces of the base steel billet and the cladding steel billet are milled to ensure that there are no defects such as rust, residual iron oxide scale, or oil stains on the surface, so that the surface roughness Ra of the base steel billet is less than 7.5 μm and the surface roughness Ra of the cladding steel billet is less than 6.3 μm. (3) Composite billet assembly Metal strips are welded around the surface-treated base steel billet. The cladding steel billet is then embedded into the groove formed by the metal strips and the base steel billet to obtain a composite billet. The cladding steel billets of the two sets of composite billets are brought into contact on one side and stacked in the order of base-cladding-cladding-base. A release agent is applied between adjacent cladding steel billets to obtain a combined billet. The release agent is a material conventional in the art, including but not limited to zirconium oxide powder, chromium oxide powder, or water glass. (4) Vacuum welding The combined billets are placed in a vacuum chamber, and the vacuum degree is controlled at ≤0.1Pa. Vacuum electron beam welding is used to weld and seal the perimeter of adjacent steel billets. The weld penetration is ≥20mm, the weld is full, the arc initiation and arc termination areas of the weld must be consistent and continuous, the weld discontinuity areas are eliminated, the weld surface is well formed, and there are no cracks, inclusions, pores and surface depressions. (5) Heating, rolling, and slow cooling The composite billet is heated to 1200-1260℃ for 8-16 hours. High-temperature heating ensures full austenitization of the composite billet and promotes the diffusion and migration of active atoms in the base and cladding materials at the interface, forming a metallurgical bond. After descaling, the composite billet is rolled at an initial rolling temperature of 1140-1210℃. The deformation per pass in the first three passes is 30-50mm, and the roll speed is 0.8-1.3m / s. The slow roll speed and large reduction process facilitates the full bonding of the base and cladding layers at high temperatures and effectively improves the thickness performance. After that, the reduction rate per pass is >8%, and the roll speed is 1.2-1.9m / s. Through repeated rolling with a certain reduction rate, austenite recrystallization is promoted, grains are refined, and the microstructure is homogenized. The final rolling temperature is 990-1070℃. After the final rolling, slow cooling is performed with a steel plate cooling rate ≤8℃ / s. The resulting composite steel plate has a thickness of 20-160mm. (5) Conditioning treatment Offline quenching and tempering heat treatment is adopted, with a quenching temperature of 940~990℃, a holding time of 1~5min / mm, and a quenching cooling rate controlled at 19~28℃ / s. The higher quenching temperature facilitates the dissolution of the alloy in austenite, laying the foundation for the formation of uniform martensite during cooling, thereby enhancing high-temperature strength and structural stability. Furthermore, the higher quenching temperature effectively eliminates ferrite or carbide phases, avoiding uneven mechanical properties or decreased high-temperature performance due to undissolved phases. Moreover, the supersaturated martensite obtained through high-temperature quenching significantly improves the high-temperature strength, creep resistance, and oxidation resistance of the steel plate. After tempering, the tempering temperature is 600~650℃, the holding time is 2~5h, and the heating rate is 2~4min / mm. After being taken out of the furnace, it is air-cooled, quenched at high temperature, and then tempered at high temperature to promote the precipitation of finer and more uniform carbides, thereby improving the stability of the steel plate against simulated post-weld heat treatment. High-temperature tempering can also promote the decomposition of residual austenite, preventing it from transforming into a brittle phase during high-temperature service, improving the stability of the structure, promoting the transformation of martensite into stable tempered sorbite, and improving the strength and toughness of the steel plate. In addition, combined with the control of the heating rate, it is beneficial to eliminate structural stress and improve the plate shape. (6) Plate splitting After heat treatment, the welded edges of the two composite steel plates are cut off, the cladding steel plates of the two composite steel plates are separated, and the plates are separated. The final finished composite steel plate has a thickness of 10~80mm, of which the cladding steel plate has a thickness of 2~6mm.

[0049] The billet preparation process parameters for Examples 1-10 are shown in Table 2.

[0050] Table 2. Billet preparation process parameters for Examples 1-10

[0051] The surface treatment and vacuum welding process parameters for Examples 1-10 are shown in Table 3.

[0052] Table 3 Surface treatment and vacuum welding process parameters for Examples 1-10

[0053] The heating and rolling process parameters for Examples 1-10 are shown in Table 4.

[0054] Table 4 Heating and rolling process parameters for Examples 1-10

[0055] The process parameters for the conditioning and tempering treatment in Examples 1-10 are shown in Table 5.

[0056] Table 5. Process parameters for tempering treatment in Examples 1-10

[0057] The properties of the base steel plates in Examples 1-10 are shown in Table 6. The stress-relieving heat treatment process is as follows: the holding temperature is 615℃, the holding time is 10h, and the heating and cooling rate above 425℃ is no more than 80℃ / h.

[0058] Table 6 Mechanical properties of the base steel plates in Examples 1-10

[0059] The properties of the clad steel plates in Examples 1-10 are shown in Table 7.

[0060] Table 7 Properties of the clad steel plates in Examples 1-10

[0061] The properties of the composite steel plates of Examples 1-10 are shown in Table 8.

[0062] Table 8. Properties of composite steel plates in Examples 1-10

[0063] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A high-performance nuclear power heterogeneous composite steel plate, characterized in that, The composite steel plate is composed of a base steel plate and a cladding steel plate; The chemical composition of the base steel plate by weight percentage is as follows: C: 0.13%~0.20%, Si: 0.10%~0.50%, Mn: 1.10%~1.85%, P≤0.010%, S≤0.005%, Ni: 0.51%~0.96%, Cr: 0.12%~0.45%, Mo: 0.26%~0.65%, V: 0.031%~0.085%, Ti: 0.02%~0.05%, Al: 0.02%~0.05%, N: 0.007%~0.015%, with the remainder being Fe and unavoidable impurities; The cladding steel plate is made of stainless steel.

2. The high-performance nuclear power heterogeneous composite steel plate according to claim 1, characterized in that, The chemical composition of the clad steel plate by weight percentage is as follows: C: 0.012%~0.038%, Mn: 1.61%~1.96%, P≤0.010%, S≤0.005%, Cr: 17.3%~18.7%, Ni: 9.4%~14.7%, Mo: 2.1%~3.2%, N: 0.03%~0.10%, with the remainder being Fe and unavoidable impurities.

3. The high-performance nuclear power heterogeneous composite steel plate according to claim 1, characterized in that, The composite steel plate passed the 180° bending test, and the interfacial shear strength between the base steel plate and the cladding steel plate was >350MPa. The metallographic structure of the base steel plate is tempered sorbite, and the metallographic structure of the cladding steel plate is austenite. The thickness of the composite steel plate is 10~80mm.

4. The high-performance nuclear power heterogeneous composite steel plate according to claim 1, characterized in that, The base steel plate is stretched at room temperature: R p0.2 >655Mpa, R m >725MPa, A 50 >20%; 350℃ high-temperature tensile testing: R p0.2 >590MPa R m >640MPa; Low temperature toughness: -20℃ KV 2 > 200J; After stress-relieving heat treatment at 615℃ for 10 hours, the base steel plate is subjected to room temperature tensile testing. R p0.2 >655MPa, R m >725Mpa, A 50 >20%; 350℃ high-temperature tensile testing: R p0.2 >590MPa, R m >640MPa; Low temperature toughness: -20℃ KV 2 > 200J.

5. The high-performance nuclear power heterogeneous composite steel plate according to claim 1, characterized in that, After the clad steel plate was subjected to intergranular corrosion according to GB / T4334-2020, the sample was bent 180° without cracking and the Rockwell hardness HRB≤90.

6. A method for producing a high-performance nuclear power heterogeneous composite steel plate according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Surface treatment: The base steel billet and the cladding steel billet are surface treated; (2) Composite billet assembly: The base steel billet and the cladding steel billet are assembled to obtain a composite billet. The cladding steel billets of the two composite billets are then stacked together with one side in contact, and a release agent is applied between the adjacent cladding steel billets to obtain a combined billet. (3) Vacuum welding: The adjacent steel billets are welded and sealed around their perimeter by vacuum electron beam welding. (4) Heating, rolling and slow cooling: The heating temperature is 1200-1260℃ and the heating time is 8-16h. After heating, rolling is carried out. The initial rolling temperature is 1140-1210℃ and the final rolling temperature is 990-1070℃. After the final rolling is completed, slow cooling is carried out to obtain the composite steel plate. (5) Tempering treatment: Offline tempering heat treatment is adopted, wherein the quenching temperature is 940~990℃, the holding time is 1~5min / mm, and after quenching, tempering is performed at a temperature of 600~650℃ and a holding time of 2~5h. After being taken out of the furnace, air cooling is performed. (6) Plate separation: After heat treatment, plate separation is performed to obtain two composite steel plates.

7. The method for producing high-performance nuclear power heterogeneous composite steel plates according to claim 6, characterized in that, In step (1), the base steel plate billet is produced by the double converter method, and the P in the molten steel is controlled to be ≤0.010% and S to be ≤0.005%. Then, it is refined by LF and RH ladle refining to control the [H] in the molten steel to be ≤1.5ppm and [O] to be ≤20ppm. In the continuous casting process, the tundish superheat is 29~35℃. At the end of the continuous casting, electromagnetic stirring and light reduction are used. The electromagnetic stirring current is 330~360A, the light reduction is 7~12mm, the billet pulling speed is 0.7~1.0m / min, and the continuous casting billet is stacked and slowly cooled for more than 24 hours after it is removed from the line. After surface treatment, the surface roughness Ra of the base steel plate blank is <7.5μm, and the surface roughness Ra of the cladding steel plate blank is <6.3μm.

8. The method for producing high-performance nuclear power heterogeneous composite steel plates according to claim 6, characterized in that, In step (2), the method for preparing the composite billet is as follows: weld metal strips around the surface-treated base steel billet, and embed the cladding steel billet into the groove formed by the metal strips and the base steel billet to obtain the composite billet; in step (3), the parameters for vacuum electron beam welding are: vacuum degree ≤ 0.1 Pa, welding penetration ≥ 20 mm.

9. The method for producing high-performance nuclear power heterogeneous composite steel plates according to claim 6, characterized in that, In step (4), during the rolling process, the deformation amount per single pass in the first 3 passes is 30~50mm and the roll speed is 0.8~1.3m / s, and the reduction rate per single pass thereafter is >8% and the roll speed is 1.2~1.9m / s; During the slow cooling process, the cooling rate of the steel plate is ≤8℃ / s; The thickness of the composite steel plate is 20~160mm.

10. The method for producing high-performance nuclear power heterogeneous composite steel plates according to claim 6, characterized in that, In step (5), the quenching cooling rate is 19~28℃ / s, and the tempering heating rate is 2~4min / mm.

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