Method for improving high-temperature thermal stability of ferrite martensitic steel and application

Abstract

The invention relates to a method for improving high-temperature thermal stability of ferrite martensite steel and application, and relates to the technical field of nuclear structural materials.The method specifically comprises the following steps that an alloy steel ingot is sequentially subjected to forging, rolling, rolling, quenching and air cooling, and an alloy blank with a ferrite martensite structure is obtained; sequentially carrying out austenitizing at 1020-1080 DEG C, quenching, tempering at 700-750 DEG C and air cooling on the alloy blank so as to maintain a ferrite martensite structure in the alloy blank and increase the concentration of solute elements in the alloy blank; and finally, the alloy blank subjected to secondary heat treatment is subjected to severe plastic deformation processing treatment. According to the method, good plasticity can be maintained while the high-temperature tensile strength of the ferritic martensitic steel is improved, the high-temperature thermal stability is improved, and the application prospect of the ferritic martensitic steel in nuclear structural materials is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear structural materials, and in particular relates to a method for improving the high-temperature thermal stability of ferrite martensitic steel and its application. Background Art

[0002] Ferritic martensitic (F / M) steel is considered to be one of the most promising candidate structural materials for nuclear applications due to its excellent thermophysical, mechanical and radiation swelling resistance. However, whether used as a nuclear fusion reactor structural material or a nuclear reactor structural material, it faces the synergistic coupling of neutron irradiation, liquid metal corrosion and high temperature (500-600°C). Therefore, it is urgent to develop ferritic martensitic steel that is more resistant to high temperature, radiation and corrosion.

[0003] In the prior art, patent CN117431370A discloses a high-temperature, high-strength and plastic ferrite martensitic steel and a preparation method thereof, which obtains original ferrite martensitic steel by first heat treating the steel ingot, and then performs cold plastic deformation processing with a total processing strain ≥ 1 on the obtained original ferrite martensitic steel at a low temperature (not higher than 50°C) to obtain nanocrystalline or ultrafine-grained ferrite martensitic steel with a large number of prefabricated dislocations. Subsequently, the dislocation behavior is controlled by controlling the heat treatment process, so that the prefabricated large number of dislocations evolve into dislocation cell structures or substructures such as subgrains, thereby obtaining ferrite martensitic steel with both high strength and plasticity at high temperature (550°C).

[0004] Severe plastic deformation to refine grains is a common means of strengthening material properties. It can significantly increase the volume density of grain boundaries. On the one hand, grain boundaries can absorb point defects generated by neutron irradiation and improve the material's radiation resistance. On the other hand, as a rapid diffusion channel for elements, it can improve the material's corrosion resistance. However, materials that undergo severe plastic deformation at low temperatures usually have poor thermal stability, making it difficult for the deformed materials to meet the requirements of high-temperature service conditions in nuclear fusion reactors or nuclear fission reactors. Summary of the invention

[0005] The purpose of the present invention is to provide a method and application for improving the high temperature thermal stability of ferrite martensitic steel in view of the problems existing in the background technology.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions: The present invention provides a method for improving the high temperature thermal stability of ferrite martensitic steel, the method comprising the following steps: (1) Forging, rolling, quenching and air cooling the alloy steel ingot in sequence to obtain an alloy billet having a ferrite-martensite structure; (2) the alloy billet treated in step (1) is subjected to austenitization at 1020-1080° C., quenching, tempering at 700-750° C., and air cooling in sequence to maintain the ferrite-martensite structure in the alloy billet while increasing the concentration of solute elements in the alloy billet; (3) The alloy blank processed in step (2) is subjected to severe plastic deformation processing.

[0007] As a further optimized solution, the alloy elements of the alloy steel ingot include Fe, C, Cr, W, Si, Mn, V, Ta and Zr, wherein the content of Fe element is ≥80%.

[0008] As a further optimized solution, the austenitizing time is 40-60 minutes, and the tempering time is 1-2 hours.

[0009] As a further optimized solution, the temperature of the severe plastic deformation processing is lower than 300°C.

[0010] As a further optimization scheme, the severe plastic deformation processing treatment selects at least one of rotary forging and equal channel extrusion, the total processing strain is ≥3, the total processing passes and the strain are determined according to the achievable total processing strain, and the purpose of the total processing strain is ≥3 is to introduce high-density dislocations into the alloy billet to ensure that the dislocations interact with the solute atoms in the alloy billet at high temperature to achieve a dynamic strain aging effect.

[0011] As a second aspect of the present invention, there is also provided a high temperature thermal stability ferrite martensitic steel, which is prepared by any of the above methods.

[0012] As a further optimized solution, the high temperature thermal stability means that at 600° C., the tensile strength of the ferrite martensitic steel is 500-515 MPa and the total elongation is 45-50%.

[0013] As a third aspect of the present invention, there is also provided a use of any of the high temperature thermal stability ferrite martensitic steels described above in nuclear structural materials.

[0014] As a further optimized solution, the operating temperature of the nuclear structural material is 600°C.

[0015] The working principle of the present invention is: Different from the prior art, the original ferrite martensitic steel (F / M steel) is first subjected to cold plastic deformation to introduce a large number of dislocations, and then annealed at 300°C to allow the dislocations to undergo a recovery process to form high-temperature thermally stable dislocation cells, thereby achieving an improvement in high-temperature strength and plasticity. The present invention uses commercial steel ingots as raw materials, first undergoes a primary heat treatment including forging, rolling, quenching and air cooling to obtain an alloy billet with a ferrite martensitic structure, namely the original ferrite martensitic steel (F / M steel), and then sequentially performs a secondary heat treatment including austenitization, quenching and tempering on the F / M steel to obtain F / MR steel, so that the M in the F / M steel 23 C 6 After carbides are dissolved, they re-precipitate, increasing the concentration of solute elements in F / MR steel. At the same time, it ensures that the structure of F / MR steel is still ferrite martensite. On this basis, F / MR steel is further subjected to severe plastic deformation with a total strain ≥ 3 to introduce high-density dislocations, which makes the dislocations interact with the solute atoms in F / MR steel at high temperatures to achieve dynamic strain aging effects. As a result, compared with F / ME steel, F / MRE steel has improved high-temperature strength at the expense of a certain plasticity (or total elongation), thereby improving the high-temperature thermal stability of ferrite martensite steel.

[0016] The beneficial effects of the present invention are: For nuclear reactor structural materials, especially nuclear fuel cladding, the operating temperature can reach 600°C. Therefore, maintaining excellent strength and plasticity at 600°C is more conducive to the safety of the nuclear reactor system. In addition, during the service of nuclear structural materials, they will also face neutron irradiation, which will cause radiation embrittlement of the material and aggravate the failure of the material. The ferrite martensitic steel obtained by the method of the present invention has a total elongation of about 50% at 600°C, which is nearly 80% higher than the original ferrite martensitic steel. This provides sufficient space for resisting radiation embrittlement of the material, further improving its service life, and is conducive to improving the application prospects of ferrite martensitic steel in nuclear structural materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A process flow chart for improving the high temperature thermal stability of ferrite martensitic steel provided by the present invention.

[0018] Figure 2 High temperature engineering stress-strain curves of the ferrite martensitic steel (F / M) billet and the ferrite martensitic steel (F / MR) after secondary heat treatment provided in Example 1 of the present invention before and after 4 extrusions at room temperature at 500°C (a) and 600°C (b). DETAILED DESCRIPTION

[0019] The present invention is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Technicians in this field can make some non-essential improvements and adjustments to the present invention based on the above application content.

[0020] Unless otherwise specified, the methods used in the present invention are conventional methods known to those skilled in the art. If no specific conditions are specified, they are carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the materials or instruments are not specified, they are all products that can be purchased commercially.

[0021] In the present invention, the alloy steel ingot is first subjected to a heat treatment to obtain a ferrite martensitic steel (F / M) billet having a ferrite martensitic structure. The primary heat treatment method adopted in the present invention is (but not limited to this process): the alloy steel ingot is homogenized at 1100°C for 3 hours and then forged, the forging deformation ratio is 5:1, and a steel billet is obtained. The steel billet is placed in a heating furnace at 1100°C for 1 hour and then rolled, the deformation amount is 50%, and the sample after rolling is placed in a heating furnace at 800°C for 1 hour and then rolled, the deformation amount is 30%, and the rolling is performed for 2 times. Subsequently, the rolled sample is kept at 1020°C for 1 hour and then quenched in water, and finally kept at 700°C for 1.5 hours and then air-cooled to obtain a ferrite martensitic steel (F / M) billet.

[0022] In the present invention, the alloy steel ingot is a commercially available steel ingot, and its alloy elements include: Fe, C, Cr, W, Si, Mn, V, Ta and Zr, wherein the Fe content is ≥80%. The alloy element composition and proportion (but not limited to this alloy element composition and proportion) of the alloy steel ingot selected in the embodiment of the present invention are 0.04-0.14% C, 7-12% Cr, 1.0-2.0% W, 0-1.0% Si, 0.2-0.6% Mn, 0.1-0.3% V, 0-0.2% Ta, 0-0.03% Zr, and the balance is Fe.

[0023] The process flow charts for improving the high temperature thermal stability of ferrite martensitic steel provided in Examples 1-4 are as follows Figure 1 shown.

[0024] Example 1

[0025] The method for improving the high-temperature thermal stability of ferrite martensitic steel disclosed in this embodiment is specifically: subjecting the ferrite martensitic steel (F / M) billet to secondary heat treatment, that is, austenitizing at 1020°C for 1 hour and then quenching in water, followed by tempering at 700°C for 1.5 hours, and cooling to room temperature in the air outside the heating furnace after tempering. The ferrite martensitic steel that has undergone secondary heat treatment is recorded as F / MR, and then, at room temperature, F / MR is subjected to 4 equal channel angular extrusions with a total strain of 4.12, and the ferrite martensitic steel obtained by the above treatment is recorded as F / MRE. In addition, the ferrite martensitic steel obtained by directly performing 4 equal channel angular extrusions with a total strain of 4.12 without secondary heat treatment is recorded as F / ME.

[0026] High temperature tensile tests were performed on F / M, F / MR, F / MRE and F / ME at 500°C and 600°C.

[0027] Figure 2 a is the high temperature (500°C) engineering stress-strain curve of the ferrite martensitic steel (F / M) billet and the ferrite martensitic steel (F / MR) after secondary heat treatment before and after 4 extrusions at room temperature. The 500°C tensile strength of the ferrite martensitic steel (F / MRE) obtained by the method of the present invention is measured to be about 864MPa, and the total elongation is about 19%. Compared with the ferrite martensitic steel (F / ME) without secondary heat treatment but extruded 4 times, the tensile strength is increased (from about 802MPa to about 864MPa), and the plasticity is reduced (from about 23% to about 19%). Compared with the ferrite martensitic steel (F / MR) without 4 extrusions after secondary heat treatment, the strength is significantly increased (the tensile strength is increased from about 618MPa to about 864MPa), and the total elongation is reduced from about 22% to about 19%. Compared with the ferritic martensitic steel (F / M) billet, the tensile strength is significantly improved (from about 681 MPa to about 864 MPa), and the total elongation is reduced (from about 21% to about 19%).

[0028] Figure 2b is the high temperature (600℃) engineering stress-strain curve of the ferrite martensitic steel (F / M) billet and the ferrite martensitic steel (F / MR) after secondary heat treatment before and after 4 extrusions at room temperature. The 600℃ tensile strength of the ferrite martensitic steel (F / MRE) obtained by the method of the present invention is measured to be about 515MPa, and the total elongation is about 50%. Compared with the ferrite martensitic steel (F / ME) without secondary heat treatment but extruded 4 times, the tensile strength is significantly improved (from about 373MPa to about 515MPa), and the plasticity is reduced (from about 64% to about 50%). Although the total elongation of F / ME steel is higher at this time, its lower tensile strength obviously makes it no longer suitable for nuclear structural materials. Compared with the ferrite martensitic steel (F / MR) without 4-pass extrusion deformation after secondary heat treatment, the strength and plasticity are significantly improved (tensile strength increases from about 433MPa to about 515MPa; total elongation increases significantly from about 28% to about 50%). Compared with the ferrite martensitic steel (F / M) billet, the tensile strength increases slightly (from about 505MPa to about 515MPa), and the total elongation increases significantly (from about 28% to about 50%).

[0029] In general, the ferrite martensitic steel (F / MRE) obtained by the method of the present invention achieves improved high temperature thermal stability.

[0030] Example 2

[0031] The method for improving the high-temperature thermal stability of ferrite martensitic steel disclosed in this embodiment is specifically: subjecting the ferrite martensitic steel (F / M) billet to secondary heat treatment, that is, austenitizing at 1020°C for 1 hour and then quenching in water, followed by tempering at 700°C for 1.5 hours, and cooling to room temperature in the air outside the heating furnace after tempering. The ferrite martensitic steel that has undergone secondary heat treatment is recorded as F / MR, and then, at room temperature, F / MR is subjected to equal channel angular extrusion for 3 times with a total strain of 3.09, and the ferrite martensitic steel obtained by the above treatment is recorded as F / MRE. In addition, the ferrite martensitic steel obtained by directly performing equal channel angular extrusion for 3 times with a total strain of 3.09 without secondary heat treatment is recorded as F / ME.

[0032] The F / M, F / MR, F / MRE and F / ME of this embodiment were subjected to a high temperature tensile test at 500° C.-600° C.

[0033] The tensile strength of the ferritic martensitic steel (F / MRE) at 500℃ was measured to be about 821MPa, and the total elongation was about 24%. Compared with the ferritic martensitic steel (F / ME) without secondary heat treatment but after three extrusions, the strength of F / MRE increased (from about 726MPa to about 821MPa), and the plasticity remained basically unchanged (about 24%). Compared with the ferritic martensitic steel (F / MR) without three extrusions after secondary heat treatment, the strength and plasticity of F / MRE were improved (tensile strength increased from about 618MPa to about 821MPa, and total elongation increased from about 22% to about 24%). Compared with the ferritic martensitic steel (F / M) billet, the tensile strength of F / MRE was significantly improved (from about 681MPa to about 821MPa), and the total elongation was improved (from about 21% to about 24%).

[0034] The tensile strength of the ferritic martensitic steel (F / MRE) at 600℃ was measured to be about 500MPa, and the total elongation was about 46%. Compared with the ferritic martensitic steel (F / ME) without secondary heat treatment but after three extrusions, the strength of F / MRE was significantly improved (from about 387MPa to about 500MPa), and the plasticity decreased (from about 57% to about 45%). Although the total elongation of F / ME was higher at this time, its lower tensile strength obviously made it no longer suitable for nuclear structural materials. Compared with the ferritic martensitic steel (F / MR) without three extrusions after secondary heat treatment, the strength and plasticity of F / MRE were significantly improved (tensile strength increased from about 433MPa to about 500MPa, and total elongation increased from about 28% to about 46%). Compared with the ferritic martensitic steel (F / M) billet, the tensile strength of F / MRE is slightly reduced (from about 505 MPa to about 500 MPa), and the total elongation is significantly increased (from about 28% to about 46%).

[0035] Example 3

[0036] The method for improving the high-temperature thermal stability of ferrite martensitic steel disclosed in this embodiment is specifically as follows: subjecting the ferrite martensitic steel (F / M) billet to secondary heat treatment, that is, austenitizing at 1040°C for 50 minutes and then quenching in water, followed by tempering at 720°C for 1 hour, and cooling to room temperature in the air outside the heating furnace after tempering, and the ferrite martensitic steel subjected to the secondary heat treatment is recorded as F / MR. Then, F / MR is subjected to 13 passes of rotary forging at 200°C to achieve a total equivalent effect variable of approximately 3.2, and the ferrite martensitic steel obtained by the above treatment is recorded as F / MRE. In addition, the ferrite martensitic steel obtained by rotary forging at 200°C for 13 passes without secondary heat treatment to achieve a total equivalent effect variable of approximately 3.2 is recorded as F / ME.

[0037] The F / M, F / MR, F / MRE and F / ME of this embodiment were subjected to high temperature tensile tests at 500° C. and 600° C.

[0038] The tensile strength of the ferritic martensitic steel (F / MRE) at 500℃ was measured to be about 830MPa, and the total elongation was about 23%. Compared with the ferritic martensitic steel (F / ME) without secondary heat treatment but after 13 passes of rotary forging, the tensile strength of F / MRE at 500℃ was significantly improved (from about 740MPa to about 830MPa), and the plasticity was slightly reduced (from about 24% to about 23%). Compared with the ferritic martensitic steel (F / MR) without 13 passes of rotary forging deformation after secondary heat treatment, the strength of F / MRE was significantly improved (tensile strength increased from about 627MPa to about 830MPa), and the total elongation was slightly improved (from about 21% to about 23%). Compared with the ferritic martensitic steel (F / M) billet, the tensile strength is significantly improved (tensile strength increases from about 681 MPa to about 830 MPa), and the total elongation is slightly improved (from about 21% to about 23%).

[0039] The tensile strength of the ferritic martensitic steel (F / MRE) at 600℃ was measured to be about 504MPa, and the total elongation was about 48%. Compared with the ferritic martensitic steel (F / ME) without secondary heat treatment but after 13 passes of rotary forging, the tensile strength of F / MRE at 600℃ was significantly improved (from about 383MPa to about 504MPa), and the plasticity decreased (from about 60% to about 48%). Although the total elongation of the steel was high at this time, its low tensile strength obviously made it no longer suitable for nuclear structural materials. Compared with the ferritic martensitic steel (F / MR) without 13 passes of rotary forging deformation after secondary heat treatment, the strength and plasticity of F / MRE were significantly improved (tensile strength increased from about 453MPa to about 504MPa, and total elongation increased from about 26% to about 48%). Compared with the ferritic martensitic steel (F / M) billet, the tensile strength remains basically unchanged, and the total elongation is significantly improved (from about 28% to about 48%).

[0040] Example 4

[0041] The method for improving the high-temperature thermal stability of ferrite martensitic steel disclosed in this embodiment is specifically: subjecting the ferrite martensitic steel (F / M) billet to secondary heat treatment, that is, quenching in water after austenitizing at 1080°C for 40 minutes, followed by tempering at 750°C for 2 hours, and cooling to room temperature in the air outside the heating furnace after tempering. The ferrite martensitic steel that has undergone secondary heat treatment is recorded as F / MR, and then, F / MR is subjected to three equal channel angular extrusions at room temperature with a total strain of 3.09, and the ferrite martensitic steel obtained by the above treatment is recorded as F / MRE. In addition, the ferrite martensitic steel obtained by directly performing three equal channel angular extrusions with a total strain of 3.09 without secondary heat treatment is recorded as F / ME.

[0042] The F / M, F / MR, F / MRE and F / ME of this embodiment were subjected to high temperature tensile tests at 500° C. and 600° C.

[0043] The tensile strength of the ferritic martensitic steel (F / MRE) at 500℃ was measured to be about 839MPa, and the total elongation was about 21%. Compared with the ferritic martensitic steel (F / ME) without secondary heat treatment but after three extrusions, the strength of F / MRE increased (significantly increased from about 781MPa to about 839MPa), and the plasticity decreased (from about 23% to about 21%). Compared with the ferritic martensitic steel (F / MR) without three extrusions after secondary heat treatment, the strength of F / MRE increased significantly (tensile strength increased from about 670MPa to about 839MPa), and the total elongation increased slightly (from about 20% to about 21%). Compared with the ferritic martensitic steel (F / M) billet, the tensile strength increased significantly (from about 681MPa to about 839MPa), and the total elongation remained basically unchanged.

[0044] The tensile strength of ferritic martensitic steel (F / MRE) at 600℃ was measured to be about 506MPa, and the total elongation was about 45%. Compared with ferritic martensitic steel (F / ME) without secondary heat treatment but after 3-pass extrusion, the strength of F / MRE was significantly improved (from about 380MPa to about 506MPa), and the plasticity decreased (from about 60% to about 45%). Although the total elongation of F / ME was higher at this time, its lower tensile strength obviously made it no longer suitable for nuclear structural materials. Compared with ferritic martensitic steel (F / MR) without 3-pass extrusion deformation after secondary heat treatment, the strength and plasticity of F / MRE were significantly improved (tensile strength increased from about 460MPa to about 506MPa, and total elongation increased from about 25% to about 45%). Compared with the ferritic martensitic steel (F / M) billet, the tensile strength remains basically unchanged, and the total elongation is significantly improved (from about 28% to about 45%).

[0045] Comparative Example 1 The method for improving the high temperature thermal stability of ferritic martensitic steel disclosed in this comparative example is specifically: subjecting the ferritic martensitic steel (F / M) billet to 4-pass equal channel angular extrusion with a total strain of about 4.12 at room temperature, followed by quenching in water after austenitizing at 1020°C for 1 hour, followed by tempering at 700°C for 1.5 hours, and cooling to room temperature in the air outside the heating furnace after tempering. The F / MRE obtained in this comparative example was subjected to a 600°C high temperature tensile test. The results showed that the 500°C tensile strength of the F / MRE was about 681MPa, the total elongation was about 22%, the 600°C tensile strength was about 503MPa, and the total elongation was about 29%, which was close to that of the ferritic martensitic steel (F / M) billet, and the high temperature thermal stability of the ferritic martensitic steel was not improved.

[0046] Comparative Example 2 The method for improving the high temperature thermal stability of ferrite martensitic steel disclosed in this comparative example is specifically: subjecting the ferrite martensitic steel (F / M) billet to rotary forging deformation with a total strain of about 3.2 at 200°C, followed by austenitizing at 1020°C for 1h and quenching in water, followed by tempering at 700°C for 1.5h, and cooling to room temperature in the air outside the furnace after tempering. The F / MRE obtained in this comparative example was subjected to a 600°C high temperature tensile test. The results showed that the tensile strength of F / MRE at 500°C was about 683MPa, the total elongation was about 20%, the tensile strength at 600°C was about 505MPa, and the total elongation was about 27%, which was close to that of the ferrite martensitic steel (F / M) billet, and the high temperature thermal stability of ferrite martensitic steel was not improved.

[0047] The high temperature tensile test results of the products of each process and the final product in Examples 1-4 and Comparative Examples 1-2 at 500° C. and 600° C. are summarized as shown in Table 1-2.

[0048] Table 1 500℃ tensile test results ; Table 2 600℃ tensile test results ; The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for improving the high temperature thermal stability of ferrite martensitic steel, characterized in that: The method comprises the following steps: (1) Forging, rolling, quenching and air cooling the alloy steel ingot in sequence to obtain an alloy billet having a ferrite-martensite structure; (2) the alloy billet treated in step (1) is subjected to austenitization at 1020-1080° C., quenching, tempering at 700-750° C., and air cooling in sequence to maintain the ferrite-martensite structure in the alloy billet while increasing the concentration of solute elements in the alloy billet; (3) The alloy blank processed in step (2) is subjected to severe plastic deformation processing.

2. The method for improving the high temperature thermal stability of ferrite martensitic steel according to claim 1, characterized in that: The alloy elements of the alloy steel ingot include Fe, C, Cr, W, Si, Mn, V, Ta and Zr, among which the content of Fe element is ≥80%.

3. The method for improving the high temperature thermal stability of ferrite martensitic steel according to claim 1, characterized in that: The austenitizing time is 40-60 minutes, and the tempering time is 1-2 hours.

4. The method for improving the high temperature thermal stability of ferrite martensitic steel according to claim 1, characterized in that: The severe plastic deformation process is performed at a temperature lower than 300°C.

5. The method for improving the high temperature thermal stability of ferrite martensitic steel according to claim 1, characterized in that: The severe plastic deformation processing is selected from at least one of rotary forging and equal channel extrusion, and the total processing strain is ≥3.

6. A high temperature thermal stability ferrite martensitic steel, characterized in that: The method is prepared by any one of claims 1 to 5.

7. The high temperature thermal stability ferrite martensitic steel according to claim 6, characterized in that: The high temperature thermal stability means that at 600°C, the tensile strength of the ferrite martensitic steel is 500-515 MPa and the total elongation is 45-50%.

8. Use of the high temperature thermal stability ferrite martensitic steel as claimed in any one of claims 6 to 7 in nuclear structural materials.

9. The use according to claim 8, characterized in that: The operating temperature of the nuclear structural material is 600°C.

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