A method for improving the corrosion resistance of low activation ferritic / martensitic steels by grain boundary engineering

Abstract

The present application belongs to the technical field of nuclear energy materials, and particularly relates to a grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferrite / martensite steel. The method comprises the following steps: S1, cold rolling of the RAFM steel blank at room temperature, with the deformation amount being controlled to be 8%-12%; S2, air quenching after the cold-rolled steel blank is heated and kept; and S3, tempering of the quenched steel blank at 750-800 DEG C, with the temperature being kept for 60-120 min and then air cooling. Through the precise matching of the three-step process of "cold rolling-quenching-tempering", the deformation energy introduced by cold rolling is used to drive the grain boundary preferential migration and reconstruction in the austenitizing process, and the phase pinning is used to stabilize and optimize the grain boundary structure through tempering. After the treatment, the proportion of low Sigma-CSL grain boundaries along the original austenite grain boundaries of the RAFM steel is significantly improved, the corrosion layer thickness in the high-temperature steam at 550 DEG C is reduced by about 50%, and the corrosion resistance of the RAFM steel in the high-temperature water environment is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of nuclear energy materials technology, specifically relating to a grain boundary engineering treatment method to improve the corrosion resistance of low-activation ferrite / martensitic steel. Background Technology

[0002] Nuclear energy, as a clean and efficient energy source, plays a vital role in addressing the energy crisis and environmental pollution. However, the long-term service performance of nuclear reactor structural materials under high temperature, high pressure, strong radiation, and corrosive environments directly affects the safety and economics of nuclear power plants. This is especially true in nuclear fusion reactors, where structural materials face even harsher operating environments, such as high-dose neutron radiation and high-temperature corrosion. Low-activation ferritic / martensitic (RAFM) steel, due to its excellent resistance to radiation swelling, low coefficient of thermal expansion, and mature manufacturing and processing technologies, is considered one of the main candidate materials for the blanket structures of future nuclear fusion reactors and fourth-generation nuclear fission reactors. RAFM steel significantly reduces the amount of radioactive waste generated under irradiation by reducing the content of activating elements such as cobalt, nickel, and molybdenum in the alloy and using low-activation elements such as tungsten, vanadium, and tantalum in its alloying design. However, the corrosion resistance of RAFM steel in high-temperature water environments still needs further improvement. Studies have shown that RAFM steel undergoes surface oxidation and intergranular corrosion in high-temperature water environments, especially under conditions with high oxygen content, where the corrosion problem is more severe. Furthermore, the synergistic effect of high-temperature water corrosion and irradiation damage may further exacerbate the degradation of material properties, leading to failure modes such as stress corrosion cracking (SCC).

[0003] The grain boundary structure of a material has a significant impact on its corrosion resistance. Grain boundaries are irregularly arranged regions of atoms in crystalline materials, and their energy state and chemical activity are usually higher than those of the grain interior. In high-temperature water environments, grain boundaries often become rapid channels for the diffusion of corrosive media, leading to intergranular corrosion and stress corrosion cracking. Existing research has shown that the type and characteristics of grain boundaries (such as grain boundary orientation difference, grain boundary energy, and grain boundary defect density) have a significant impact on corrosion behavior. For example, high-energy grain boundaries, due to their higher energy and defect density, are more likely to become the preferred pathway for the diffusion of corrosive media, while low-energy grain boundaries (such as lattice boundaries at low Σ-value coincidence sites), due to their more ordered structure and lower energy, exhibit better corrosion resistance. Grain boundary engineering (GBE) is a materials design method that improves the performance of materials by controlling their grain boundary structure. By optimizing material processing parameters (such as deformation, quenching temperature, quenching time, tempering temperature, and tempering time), GBE can significantly increase the proportion of low-energy grain boundaries in the material, thereby improving its corrosion resistance. In recent years, GBE has been widely used in nickel-based alloys, austenitic stainless steels, and other materials, achieving remarkable results. Although GBE has shown great potential in various materials, its application research in RAFM steel is still in its early stages. RAFM steel obtained through traditional heat treatment processes typically has a randomly oriented grain boundary structure, with a high proportion of high-energy grain boundaries, which may lead to insufficient corrosion resistance in high-temperature water environments. Studies have shown that proto-austenite grain boundaries are the preferential corrosion initiation points for ferritic martensitic steels. Therefore, regulating the proto-austenite grain boundary structure to suppress its corrosion susceptibility at the source is an important research direction for improving ferritic martensitic steels. In recent years, some studies have shown that by optimizing the thermomechanical processing technology of RAFM steel (such as controlled rolling and cyclic heat treatment), its grain boundary characteristic distribution can be controlled, increasing the proportion of overlapping lattice grain boundaries with low Σ values ​​along the proto-austenite grain boundaries, thereby improving its corrosion resistance. However, existing research focuses on exploring process parameters and lacks systematic research on the correlation between grain boundary structure design and corrosion performance. In particular, there is a lack of research on the regulation of grain boundary evolution mechanism during austenitization. The development of grain boundary engineering treatment methods for high-temperature water environments still remains a gap.

[0004] To address the insufficient corrosion resistance of RAFM steel in high-temperature water environments, this patent proposes a grain boundary engineering-based treatment method. By controlling the evolution behavior of the original austenite grain boundaries during austenitization, the proportion of low-energy grain boundaries is increased, thereby significantly improving its corrosion resistance. This method aims to provide new optimization goals for the design and development of nuclear reactor structural materials, promote the application of RAFM steel in nuclear fusion reactors, and provide a reference for grain boundary engineering research on other materials. Summary of the Invention

[0005] In view of the above background, the present invention provides a grain boundary engineering treatment method to improve the corrosion resistance of low-activation ferrite / martensitic steel. The method involves performing thermomechanical treatment on RAFM steel blocks by cold rolling, quenching, and tempering. Through the synergistic effect of pre-deformation and subsequent heat treatment, the grain boundary structure of RAFM steel is directionally controlled, especially the evolution path of the original austenite grain boundaries during austenitization, thereby achieving directional optimization of the grain boundary structure and significantly improving the corrosion resistance of low-activation ferrite / martensitic steel in high-temperature and high-pressure steam environments.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferritic / martensitic steel, wherein the composition of the low-activation ferritic / martensitic steel is as follows (by mass percentage): Cr: 8.00%, W: 1.50%, V: 0.30%, Ta: 0.10%, Mn: 0.50%, C: 0.11%; Fe: balance; The processing method includes the following steps: S1. Cold rolling: Cold rolling of low-activation ferritic / martensitic steel billets at room temperature; S2. Quenching: Quenching the cold-rolled steel billet; S3. Tempering: Tempering the quenched steel billet.

[0007] Preferably, the deformation energy storage introduced by the cold rolling drives the preferential migration and reconstruction of the original austenite grain boundaries during the austenitization process, which promotes the transformation of high-energy random grain boundaries into low-Σ value coincident lattice grain boundaries, and the optimized grain boundary structure is stabilized by the dispersed precipitation of carbides at the grain boundaries during the tempering process.

[0008] Preferably, in step S1, the deformation amount of cold rolling is controlled to be 8%-12%.

[0009] Preferably, in step S1, the deformation amount of cold rolling is controlled to be 10%.

[0010] Preferably, this specific range is a critical window for introducing optimal deformation energy storage, providing sufficient driving force for subsequent grain boundary migration, and providing the necessary driving conditions for subsequent original austenite grain boundary migration and reconstruction.

[0011] Preferably, in step S2, quenching involves heating the cold-rolled steel billet to 950-1050°C and holding it at that temperature.

[0012] This step utilizes the deformation energy and dislocation structure stored during cold rolling to drive preferential migration and reorganization of grain boundaries during austenitization. By regulating the migration dynamics of austenite grain boundaries, it guides the original austenite grain boundaries to undergo directional migration and reconstruction, promoting the transformation of high-energy random grain boundaries into low-Σ-value coincident position lattice (CSL) grain boundaries (especially Σ3 twin boundaries), and initially establishing a corrosion-resistant grain boundary characteristic distribution.

[0013] Preferably, the quenching and holding time is controlled within the range of 60-90 minutes. This time range provides sufficient time for the migration and reconstruction of the original austenite grain boundaries, thereby achieving effective control of the grain boundary structure. When the time is too short, the grain boundary migration is insufficient, making it difficult to form a stable low-Σ grain boundary structure. When the time is too long, it is easy to cause grain coarsening, which is not conducive to grain boundary structure optimization.

[0014] Preferably, in step S2, quenching involves heating the cold-rolled steel billet to 1050°C and holding it at that temperature for 90 minutes.

[0015] Preferably, the heating rate of the quenching treatment is 8-12℃ / min.

[0016] Preferably, in step S3, the tempering treatment involves holding the quenched steel billet at 750-800℃ for 60-120 minutes.

[0017] Preferably, in step S3, the tempering process involves holding the quenched steel billet at 780°C for 120 minutes.

[0018] This step promotes the uniform dispersion and precipitation of carbides at the optimized grain boundaries, playing a "pinning" role and effectively reducing grain boundary energy. This locks in and stabilizes the favorable grain boundary structure formed during the quenching stage, preventing it from degrading during use and avoiding its degradation in subsequent use, while also eliminating residual stress.

[0019] The present invention also provides an improved low-activation ferrite / martensitic steel, which is prepared by the grain boundary engineering treatment method described above.

[0020] Compared with the prior art, the positive effects of the present invention are as follows: (1) By using the cold rolling-quenching-tempering process, the proportion of low Σ-CSL grain boundaries is significantly increased, forming a high proportion of special grain boundary network distributed along the original austenite grain boundaries. This result is derived from the effective control of the evolution behavior of the original austenite grain boundaries. (2) After the optimized grain boundary structure was exposed to high-temperature steam at 550℃ for 100h, the thickness of its corrosion layer decreased by about 50% (20μm→10μm), which is significantly better than that of conventional heat-treated steel; (3) It has a wide process window and high repeatability, which overcomes the shortcomings of random grain boundary regulation and limited improvement of corrosion resistance in the existing technology. It has industrial application prospects and is suitable for industrial promotion and other ferritic / martensitic corrosion-resistant alloy systems. Attached Figure Description

[0021] Figure 1 The microstructure and elemental distribution diagrams of the low-activation ferrite / martensite steel billet sample are shown below; (a) is the metallographic structure diagram, (b) is the EBSD grain boundary distribution diagram, (c) is the phase distribution diagram, and (d) is the elemental distribution diagram. Figure 2 The images show the microstructure of the low-activation ferrite / martensitic steel samples prepared in the examples; where (a) is a metallographic image and (b) is an EBSD grain boundary distribution image. Figure 3 Statistical distribution diagram of grain boundary characteristics for low-activation ferrite / martensite steel billet samples and low-activation ferrite / martensite steel samples prepared in the examples. Figure 4 This is a diagram showing the evolution of grain boundary characteristics along the original austenite grain boundaries during each heat treatment stage of the low-activation ferrite / martensitic steel sample prepared in the examples. Figure 5 SEM images of the surface morphology of the low-activation ferrite / martensite steel billet sample and the low-activation ferrite / martensite steel sample prepared in the examples after corrosion in high-temperature steam at 550℃ for 100h; wherein, (a) is the low-activation ferrite / martensite steel billet sample, and (b) is the low-activation ferrite / martensite steel sample prepared in the examples. Figure 6 XRD diffraction patterns of corrosion products of low-activation ferrite / martensitic steel billet samples and low-activation ferrite / martensitic steel samples prepared in the examples. Figure 7 Raman spectra of corrosion products of low-activation ferrite / martensitic steel billet samples and low-activation ferrite / martensitic steel samples prepared in the examples. Figure 8 The corrosion layer structure, thickness, and cross-sectional element distribution of the low-activation ferrite / martensitic steel billet sample are shown in the diagram. Figure 9 The image shows the corrosion layer structure, thickness, and cross-sectional element distribution of the low-activation ferritic / martensitic steel sample prepared in the examples. Detailed Implementation

[0022] The embodiments of the present invention are described in detail below. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art, belonging to the inventors. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0024] This invention provides a grain boundary engineering treatment method to improve the corrosion resistance of low-activation ferrite / martensitic steel. This process aims to introduce prestress through cold rolling, combined with quenching and tempering treatments to optimize the distribution of grain boundary characteristics and the size of precipitated phases, thereby enhancing the corrosion resistance of RAFM steel. The specific process is as follows: First, cold rolling. Introducing high-density dislocations through cold rolling is a key step in the processing of RAFM steel. Pre-stress is introduced through pre-deformation, providing a foundation for subsequent grain boundary migration. The initial material is a hot-rolled RAFM steel sheet with a thickness of 3 mm. Cold rolling is performed at room temperature with a deformation of 10%, resulting in a final thickness controlled between 2.68 and 2.82 mm. Through cold rolling, the dislocation density within the material increases significantly, and the grains elongate along the rolling direction, forming a distinct deformation texture.

[0025] Next, quenching. The purpose of quenching is to improve the corrosion resistance of the material by migrating grain boundaries and optimizing the distribution of grain boundary characteristics through austenitization. The quenching heating temperature is 1050℃, slightly higher than the Ac3 temperature of RAFM steel, to ensure complete austenitization. The heating rate is 10℃ / min, and the holding time is 90min. The specific time is adjusted according to the thickness of the plate to ensure uniform temperature.

[0026] Preferably, the quenching and holding time is controlled within the range of 60-90 minutes. This time range provides sufficient time for the migration and reconstruction of the original austenite grain boundaries, thereby achieving effective control of the grain boundary structure. If the time is too short, the grain boundary migration will be insufficient; if the time is too long, it will easily cause grain coarsening. The cooling method is air cooling.

[0027] After quenching, a uniform equiaxed grain structure is formed, while reducing the deformation texture introduced by cold rolling. In addition, quenching can also increase the proportion of special grain boundaries. This process simultaneously optimizes the grain boundary structure by regulating the migration behavior and reconstruction path of the original austenite grain boundaries, thus providing the material with better corrosion resistance.

[0028] Finally, tempering. Tempering is the final step in optimizing the mechanical and corrosion resistance properties of RAFM steel, mainly achieved by improving the distribution of precipitates and optimizing the distribution of grain boundary characteristics. The tempering temperature is 780℃, lower than the Ac1 temperature to avoid austenitization, the heating rate is 10℃ / min, the holding time is 60-120min, and the cooling method is air cooling.

[0029] The present invention will be described below through specific embodiments. It should be noted that the specific embodiments below are for illustrative purposes only and do not limit the scope of the present invention in any way. In addition, unless otherwise specified, methods that do not specifically describe conditions or steps are conventional methods, and the reagents used are all commercially available.

[0030] In this embodiment of the invention, the equipment used for cold rolling is a 630-650 type rolling mill.

[0031] In this embodiment of the invention, the equipment used for calcination (quenching and tempering) is a GSL-1200X muffle furnace.

[0032] The XRD diffractometer used in this embodiment of the invention is a SmartLab 9kW.

[0033] The Raman device model in this embodiment of the invention is LabRAM HR Evolution.

[0034] In this embodiment of the invention, the SEM equipment used to observe the sample morphology is the Gmini 500 from ZEISS GmbH, Germany, equipped with an Electron Back Scattered Diffraction (EBSD) probe: the equipment model is Symmetry S3. Example

[0035] This embodiment discloses a grain boundary engineering treatment method to improve the corrosion resistance of low-activation ferrite / martensitic steel. The composition of the low-activation ferrite / martensitic steel, by mass percentage, is: Cr: 8.00%, W: 1.50%, V: 0.30%, Ta: 0.10%, Mn: 0.50%, C: 0.11%; Fe: balance. The processing method includes the following steps: S1. Cold rolling: Low-activation ferritic / martensitic steel billets are cold rolled at room temperature, with the deformation controlled at 10%. S2. Quenching: The cold-rolled steel billet is placed in a GSL-1200X vacuum muffle furnace for quenching. The quenching heating rate is 10℃ / min. The temperature is raised to 1050℃ and held for 90 minutes. After quenching, the billet is cooled by air cooling. S3. Tempering: The quenched steel billet is placed in a GSL-1200X vacuum muffle furnace for tempering treatment. The tempering heating rate is 10℃ / min. The temperature is raised to 780℃ and held for 120min. After tempering, it is cooled by air cooling to obtain low-activation ferrite / martensitic steel.

[0036] Microstructure characterization and performance testing: (1) Determination of the microstructure and elemental distribution of low-activation ferrite / martensite steel billet samples: Microstructure characterization of low-activation ferrite / martensite steel billet samples was performed using metallographic observation (OM) and scanning electron microscopy (SEM) equipped with an electron backscatter diffraction (EBSD) probe. Elemental distribution was obtained through energy dispersive spectroscopy (EDS). The results are as follows: Figure 1 As shown. Figure 1 In the image, (a) is the metallographic structure of the low-activation ferrite / martensite steel billet sample, (b) is the EBSD grain boundary distribution diagram of the low-activation ferrite / martensite steel billet sample, (c) is the phase distribution diagram of the low-activation ferrite / martensite steel billet sample, and (d) is the elemental distribution diagram of the low-activation ferrite / martensite steel billet sample. Figure 1 It can be seen that the low-activation ferrite / martensite steel billet sample exhibits a typical tempered martensite structure with random orientation distribution of grain boundaries and a high proportion of high-energy random grain boundaries. All alloying elements are uniformly distributed in the matrix without obvious segregation. The low-activation ferrite / martensite steel billet sample has good compositional homogeneity, which lays the microstructure foundation for subsequent grain boundary engineering treatment.

[0037] (2) The microstructure of the low-activation ferrite / martensitic steel samples prepared in the examples was determined: Metallographic observation (OM) and scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD) probes were used to observe the grain morphology and grain boundary characteristics after treatment. The measurement results are as follows: Figure 2 As shown. Figure 2 In the figures, (a) is the metallographic structure of the low-activation ferrite / martensitic steel sample prepared in the examples, and (b) is the EBSD grain boundary distribution diagram of the low-activation ferrite / martensitic steel sample prepared in the examples. Figure 2 It can be seen that after being treated by the grain boundary engineering method of the present invention, the sample still maintains a uniform tempered martensite structure with uniform grain size (average grain size of about 10 μm), and the distribution of grain boundary characteristics changes significantly, forming a high proportion of special grain boundary network along the original austenite grain boundary.

[0038] Furthermore, based on EBSD data, the GBCD (Grain Boundary Characteristic Distribution) analysis method was used to statistically analyze the proportion of low Σ-CSL grain boundaries (especially Σ3 twin boundaries) in the low-activation ferrite / martensitic steel billet samples and the low-activation ferrite / martensitic steel samples prepared in the examples; the statistical results are as follows. Figure 3 As shown, Figure 3 In this text, "AR" indicates a low-activation ferrite / martensitic steel billet sample, "10%-deformed" indicates a low-activation ferrite / martensitic steel sample prepared in the examples, and PAGB indicates Prior Austenite Grain Boundaries. Figure 3 It can be seen that the proportion of low Σ-CSL grain boundaries in the activated ferrite / martensite steel billet sample is relatively low, and the special grain boundaries along the original austenite grain boundaries are sparsely distributed; while the proportion of low Σ-CSL grain boundaries in the low activated ferrite / martensite steel sample prepared in the examples is significantly increased, with Σ3 twin boundaries being the main component.

[0039] Furthermore, the evolution of grain boundary characteristics along the original austenite grain boundaries was statistically analyzed at each heat treatment stage under a 10% cold rolling deformation process; the statistical results are as follows: Figure 4 As shown, analysis of the evolution of each heat treatment stage under a 10% cold rolling deformation process reveals that after cold rolling introduces deformation energy storage, the quenching stage (austenitization process) is the key stage for preferential grain boundary reconstruction. The original austenite grain boundaries undergo directional migration, and high-energy random grain boundaries gradually transform into low-Σ-CSL grain boundaries. The subsequent tempering stage effectively pins and fixes the formed special grain boundary network through carbide dispersion precipitation, ensuring the stability of the grain boundary optimization effect. This result verifies the effective control capability of the three-step process chain of this invention—"cold rolling to introduce energy storage—quenching to drive reconstruction—tempering to stabilize"—on the evolution behavior of the original austenite grain boundaries.

[0040] (3) High-temperature steam corrosion test: Using a high-temperature steam corrosion device, corrosion tests were conducted on the low-activation ferrite / martensitic steel billet samples and the low-activation ferrite / martensitic steel samples prepared in the examples at 550°C for up to 100 hours. This was to verify the effect of the grain boundary engineering treatment method on the regulation of the original austenitic grain boundary structure and its effect on improving corrosion resistance.

[0041] The surface morphology after etching was observed using scanning electron microscopy (SEM), such as... Figure 5 As shown. Figure 5 In the figures, (a) shows the surface morphology of the low-activation ferrite / martensitic steel billet sample after corrosion at 550℃ for 100h, and (b) shows the surface morphology of the low-activation ferrite / martensitic steel sample obtained in the examples after corrosion at 550℃ for 100h. Figure 5 It can be seen that the corrosion product layer on the surface of the low-activation ferritic / martensitic steel billet sample is relatively thick, and the surface is covered with a loose oxide layer. Local signs of corrosion peeling are visible, indicating that the degree of corrosion is relatively severe. In contrast, the corrosion product layer on the surface of the low-activation ferritic / martensitic steel sample prepared in the example is relatively uniform and dense, the peeling phenomenon is significantly reduced, and the surface integrity is significantly better than that of the low-activation ferritic / martensitic steel billet sample. This indicates that the high-temperature steam corrosion resistance of RAFM steel is significantly improved after treatment by the method of the present invention.

[0042] Furthermore, the phase composition of the corrosion products was characterized using X-ray diffraction (XRD, SmartLab 9kW) and Raman spectroscopy (LabRAM HR Evolution). The XRD results are as follows: Figure 6 As shown, the Raman spectroscopy results are as follows: Figure 7 As shown. Figure 6 and Figure 7 In this text, "AR" indicates a low-activation ferrite / martensitic steel billet sample, and "10%-deformed" indicates a low-activation ferrite / martensitic steel sample prepared in the examples. Figure 6 and Figure 7 It can be seen that the surface corrosion products of both the activated ferrite / martensitic steel billet sample and the low-activated ferrite / martensitic steel sample prepared in the examples are Fe3O4 and FeCr2O4, indicating that the corrosion mechanism has not fundamentally changed. However, the low-activated ferrite / martensitic steel sample prepared in the examples exhibits stronger diffraction peaks and Raman characteristic peak intensities, combined with the cross-sectional morphology ( Figure 8-9 As can be seen, this is because although the corrosion layer is thinned by about 50% after grain boundary optimization, the density and crystallinity are significantly improved. This result shows that the grain boundary engineering treatment method of the present invention effectively changes the growth kinetics of the oxide layer—from preferential intergranular etching to uniform passivation growth, thereby endowing the material with better corrosion resistance.

[0043] Furthermore, cross-sectional samples were prepared from the corroded specimens. Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) was used to observe the corrosion layer structure, measure the corrosion layer thickness, and obtain the elemental distribution of the cross-section. The measurement results for the low-activation ferrite / martensitic steel billet samples are as follows: Figure 8 As shown, the low-activation ferrite / martensitic steel billet sample treated by the grain boundary engineering method of this invention is as follows: Figure 9 As shown. By Figure 8 and Figure 9 It can be seen that both the low-activation ferrite / martensitic steel billet sample and the low-activation ferrite / martensitic steel sample prepared in the examples formed a double-layer corrosion structure, with an outer Fe3O4 layer and an inner FeCr2O4 layer, and a certain thickness of element diffusion layer (Cr, W, and other element enrichment regions) on the matrix side. However, the key difference lies in the corrosion layer thickness: the corrosion layer thickness of the low-activation ferrite / martensitic steel billet sample is about 20 μm, while the corrosion layer thickness of the low-activation ferrite / martensitic steel billet sample (example, deformation amount of 10%) after treatment by the grain boundary engineering method of the present invention is significantly reduced to about 10 μm, with a corrosion layer thinning of up to 50%. The results demonstrate that the present invention, through a three-step grain boundary engineering treatment method of "cold rolling-quenching-tempering," constructs a high-proportion, low-Σ-CSL special grain boundary network in RAFM steel by directionally controlling the evolution behavior of the original austenite grain boundaries. This effectively blocks the rapid diffusion channels of oxygen and corrosive media along the grain boundaries, thereby significantly reducing the oxidation kinetic rate under high-temperature steam conditions and greatly improving the corrosion resistance of RAFM steel. These results fully verify the effectiveness and superiority of the grain boundary engineering treatment method described in this invention.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferrite / martensitic steel, characterized in that, The composition of the low-activation ferritic / martensitic steel, by mass percentage, is: Cr: 8.00%, W: 1.50%, V: 0.30%, Ta: 0.10%, Mn: 0.50%, C: 0.11%; Fe: balance; The processing method includes the following steps: S1. Cold rolling: Cold rolling of low-activation ferritic / martensitic steel billets at room temperature; S2. Quenching: Quenching the cold-rolled steel billet; S3. Tempering: Tempering the quenched steel billet.

2. The grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferrite / martensitic steel according to claim 1, characterized in that, In S1, the deformation amount of cold rolling is controlled to be 8%-12%.

3. The grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferrite / martensitic steel according to claim 2, characterized in that, In S1, the deformation amount of cold rolling is controlled to be 10%.

4. The grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferrite / martensitic steel according to claim 1, characterized in that, In S2, quenching involves heating the cold-rolled steel billet to 950-1050℃ and holding it at that temperature for 60-90 minutes.

5. A grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferrite / martensitic steel according to claim 4, characterized in that, In S2, quenching involves heating the cold-rolled steel billet to 1050°C and holding it at that temperature for 90 minutes.

6. The grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferrite / martensitic steel according to claim 4, characterized in that, The heating rate of the quenching treatment is 8-12℃ / min.

7. The grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferrite / martensitic steel according to claim 1, characterized in that, In step S3, the tempering process involves holding the quenched steel billet at 750-800℃ for 60-120 minutes.

8. The grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferrite / martensitic steel according to claim 7, characterized in that, In step S3, the tempering process involves holding the quenched steel billet at 780°C for 120 minutes.

9. A grain boundary engineering treatment method for improving the corrosion resistance of low-activation ferrite / martensitic steel according to claim 7, characterized in that, The tempering heating rate is 8-12℃ / min.

10. A low-activation ferritic / martensitic steel, characterized in that, It is prepared by the grain boundary engineering treatment method as described in any one of claims 1-9.

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