A high-boron, rich-gadolinium stainless steel for shielding in a vacuum chamber of a fusion reactor and a method for preparing the same

Abstract

This invention discloses a gadolinium-rich high-boron stainless steel for shielding in the vacuum chamber of a fusion reactor and its preparation method, belonging to the technical field of nuclear fusion radiation shielding materials. Based on the total weight of the gadolinium-rich high-boron stainless steel, the weight percentages of each component are: Cr 10-20%, Ni 8-18.5%, B 0.8-3%, Gd 0.2-3%, with the balance being Fe and unavoidable impurities. This invention significantly improves the shielding performance of high-boron steel by adding Gd, optimizes the elemental ratio to improve the uniformity and density of the material composition, and achieves efficient shielding of neutrons and gamma rays while ensuring processing stability.

Description

Technical Field

[0001] This invention belongs to the field of nuclear fusion radiation shielding materials technology, specifically relating to a gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of a fusion reactor and its preparation method. Background Technology

[0002] In recent years, with the rapid development of controlled nuclear fusion technology and its supporting technologies (such as superconducting technology), nuclear fusion research has entered a critical stage of rapid advancement. Against this backdrop, the demand for high-performance shielding materials has become increasingly prominent. These materials need to simultaneously and efficiently shield the high-energy neutrons and gamma rays produced by the deuterium-tritium fusion reaction to avoid damage to the superconducting magnet or quenching failure caused by radiation energy deposition, while minimizing the harm of radiation to operators and the environment.

[0003] High-boron stainless steel, with its superior neutron moderation and absorption capabilities, as well as the mature manufacturing processes and extensive application experience accumulated in the field of fission reactors, has become one of the important candidates for nuclear fusion shielding materials. Its outstanding neutron shielding performance and excellent engineering applicability provide a reliable technical advantage in the field of nuclear fusion device shielding.

[0004] Boron (B) is valued for its excellent neutron moderation and absorption capabilities, especially... 10 Boron (B) exhibits a high cross-section in its (n, α) neutron absorption reaction and is widely used in nuclear shielding materials. High-boron steel, based on this property, has become an important candidate for nuclear fusion shielding materials. Gadolinium (Gd) has an even higher neutron absorption cross-section (…). ), far exceeding that of natural boron ( 10 A neutron absorption cross section (760b) with a boron content of approximately 19.8% (B≈19.8%) can effectively improve neutron shielding performance. Through specific process control, gadolinium-rich high-boron steel exhibits excellent neutron and gamma-ray shielding capabilities, as well as good mechanical properties and processing adaptability in nuclear fusion devices, providing a new path for the development of nuclear fusion shielding materials. However, existing high-boron stainless steels still face challenges in large-scale production due to insufficient processing performance, especially significant brittleness at high boron contents. Adding gadolinium to reduce boron content can ensure shielding performance while reducing brittle fracture, thus improving mechanical and processing properties. Therefore, further optimization of composition design and process innovation are urgently needed to enhance overall performance.

[0005] Currently, 304B4 and 304B7 high-boron stainless steels used in ITER are the mainstream shielding materials. However, with the development of CFETR reactors and miniaturized fusion devices, higher requirements are being placed on shielding materials, including superior neutron and gamma-ray shielding performance, stronger mechanical properties, and lower manufacturing costs. Existing preparation methods have limitations: powder metallurgy offers superior performance but is costly; while smelting is economical, the brittleness caused by high boron content increases production difficulty. Therefore, there is an urgent need to develop new shielding materials that can improve shielding performance, significantly enhance mechanical properties, and simultaneously consider economy and manufacturability. Future research on shielding materials will focus on balancing shielding performance, processability, and cost to meet the comprehensive needs of fusion reactors for both shielding performance and economy, providing a more efficient solution for the development of nuclear fusion technology. Summary of the Invention

[0006] To meet the shielding requirements for neutron and gamma-ray nuclear radiation in fusion reactor vacuum chambers, and to ensure material machinability and economy, this invention provides a gadolinium-rich, high-boron stainless steel for shielding fusion reactor vacuum chambers and its preparation method. This material improves shielding performance, enhances mechanical properties, and adjusts density by optimizing gadolinium and boron content, thereby strengthening its overall shielding performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A gadolinium-rich high-boron stainless steel for shielding a vacuum chamber in a fusion reactor, wherein the weight percentage of each component based on the total weight of the gadolinium-rich high-boron stainless steel is: Cr 10-20%, Ni 8-18.5%, B 0.8-3%, Gd 0.2-3%, with the balance being Fe and unavoidable impurities.

[0009] The weight percentages of each component are as follows: Cr 12-15%, Ni 9-12%, B 1-1.7%, Gd 0.4-0.8%, with the balance being Fe and unavoidable impurities.

[0010] Preferably, the weight percentages of each component are: Cr 13.5-15%, Ni 10-12%, B 1.2-1.7%, Gd 0.5-0.8%, with the balance being Fe and unavoidable impurities.

[0011] The substrate of the gadolinium-rich high-boron stainless steel used for shielding the vacuum chamber of the fusion reactor is an austenitic matrix.

[0012] In the gadolinium-rich high-boron stainless steel used for shielding the vacuum chamber of the fusion reactor, B and Fe form particulate borides; and the particulate borides are uniformly dispersed in the austenitic matrix.

[0013] The particulate borides are a single-phase structure composed of Fe and B elements.

[0014] The Gd element is concentrated in the particulate borides.

[0015] The above-mentioned method for preparing gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of a fusion reactor includes the following steps:

[0016] a. Smelting: Under the protection of an inert atmosphere, chromium-containing raw materials, nickel-containing raw materials, gadolinium-containing raw materials and iron raw materials are mixed and smelted to obtain an alloy liquid;

[0017] b. Refining: Under the protection of an inert atmosphere, boron-containing raw materials are added to the alloy liquid for refining;

[0018] c. Casting: The refined alloy liquid is cast and then cooled to obtain alloy castings;

[0019] d. Forging: The alloy casting obtained in step c is heated to the forging temperature, and the alloy obtained after heating is forged to obtain gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of the fusion reactor.

[0020] In step a, the melting temperature is 1500–1630℃; in step b, the refining time is 2–15 min and the refining temperature is 1550–1600℃; in step c, the casting temperature is 1510–1610℃; and in step d, the forging temperature is 1100–1200℃.

[0021] The preparation method further includes the following steps:

[0022] e. Rolling: The forged and cooled gadolinium-rich high-boron stainless steel for the fusion reactor vacuum chamber shield is rolled to obtain gadolinium-rich high-boron stainless steel for the fusion reactor vacuum chamber shield of engineering application specifications.

[0023] The chromium-containing raw material is ferrochrome, the nickel-containing raw material is ferronickel, the gadolinium-containing raw material is gadolinium iron, the iron raw material is pure iron, and the boron-containing raw material is ferroboron powder.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) This invention improves the uniformity and density of material composition by optimizing the element ratio, thereby ensuring processing stability while achieving efficient shielding of neutrons and gamma rays.

[0026] (2) Traditional iron-based boron-containing materials have insufficient deformation capacity due to the presence of iron-boron compounds, and tend to form a network precipitate phase at the matrix interface during smelting, which significantly reduces fracture strength and toughness. This invention optimizes the overall performance by controlling the content of boron (B) and gadolinium (Gd) so that Gd is enriched in the dispersed boron compound strengthening phase.

[0027] (3) The gadolinium-rich high boron stainless steel for shielding the vacuum chamber of the fusion reactor of the present invention is not only a preferred shielding material for nuclear radiation in fusion reactors, but also applicable to other fields that require shielding of neutrons and gamma rays, such as fission reactors, nuclear power plants and nuclear waste storage facilities.

[0028] (4) The preparation method of the present invention adopts a mature smelting process to ensure that the material is feasible for large-scale production.

[0029] (5) The gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of the fusion reactor prepared by this invention has a density greater than 99%, and the boron density in the material is 0.08-0.3 g / cm³. 3 After rolling, the material exhibits superior key properties compared to ITER's current 304B4 and 304B7 materials. This material can meet the urgent need for efficient radiation shielding in key components of fusion reactors, and can also be extended to other fields requiring strong radiation protection. Attached Figure Description

[0030] Figure 1 This is an elemental and phase distribution diagram of gadolinium-rich high-boron stainless steel used for shielding the vacuum chamber of a fusion reactor, obtained in Embodiment 1 of the present invention.

[0031] Figure 2 This is a tensile curve of gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of a fusion reactor, obtained in Embodiment 1 of the present invention.

[0032] Figure 3 This is an elemental and phase distribution diagram of gadolinium-rich high-boron stainless steel used for shielding the vacuum chamber of a fusion reactor, obtained in Embodiment 2 of the present invention.

[0033] Figure 4 This is a tensile curve of gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of a fusion reactor obtained in Embodiment 2 of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0035] This invention provides a gadolinium-rich, high-boron stainless steel for shielding fusion reactor vacuum chambers, wherein the weight percentages of each component are: Cr 10-20%, Ni 8-18.5%, B 0.8-3%, Gd 0.2-3%, with the balance being iron (Fe) and unavoidable impurities. The matrix of this gadolinium-rich, high-boron stainless steel for shielding fusion reactor vacuum chambers is an austenitic matrix.

[0036] By weight percentage, the gadolinium-rich high-boron stainless steel for shielding fusion reactor vacuum chambers provided by this invention contains 10-20% chromium (Cr), preferably 12-15%. Controlling Cr within this range in this invention is beneficial for improving the alloy's corrosion resistance.

[0037] By weight percentage, the gadolinium-rich high-boron stainless steel for shielding fusion reactor vacuum chambers provided by this invention contains 8-18.5% nickel (Ni), preferably 9-12%. Controlling Ni within this range facilitates the formation of room-temperature austenite, eliminates the alloy's magnetism, and improves its mechanical properties.

[0038] By weight percentage, the gadolinium-rich boron-rich stainless steel for shielding fusion reactor vacuum chambers provided by this invention contains 0.8-3% B, preferably 1-1.7%. Controlling the B content within this range is beneficial for shielding moderated thermal neutrons and for improving the material's mechanical properties.

[0039] The gadolinium-rich high-boron stainless steel for shielding fusion reactor vacuum chambers provided by this invention contains 0.2-3% Gd, preferably 0.4-0.8%, by weight percentage. Controlling Gd within this range in this invention facilitates the formation of granular borides, optimizes grain boundaries, and improves ductility and toughness.

[0040] The preparation process of the gadolinium-rich, high-boron stainless steel for shielding the vacuum chamber of a fusion reactor according to the present invention includes: smelting, refining, casting, forging, and rolling processes to obtain the bulk shielding material. The above steps include:

[0041] a. Smelting: Under the protection of an inert atmosphere, ferrochrome, ferronickel, gadolinium iron and pure iron raw materials are mixed and smelted to obtain an alloy liquid;

[0042] b. Refining: Under the protection of an inert atmosphere, ferroboron powder is added to the alloy liquid for refining;

[0043] c. Casting: The refined alloy liquid is cast and then cooled to obtain alloy castings;

[0044] d. Forging: Heat the alloy casting obtained in step c to the alloy forging temperature, forge the alloy obtained after heating and air cool it to obtain the alloy.

[0045] e. Rolling: The alloy after forging and cooling is rolled to obtain gadolinium-rich high-boron stainless steel of engineering application specifications.

[0046] Preferably, the melting temperature in step a is 1550–1600℃; the refining time in step b is 5–10 min; the casting temperature in step c is 1530–1580℃; and the forging temperature in step d is 1100–1200℃.

[0047] Example 1:

[0048] The gadolinium-rich high-boron stainless steel used for shielding the fusion reactor vacuum chamber in this embodiment has the following composition: B: 1.23 wt.%, Ni: 10.3 wt.%, Cr: 13.5 wt.%, Gd: 0.52 wt.%, with the balance being Fe and unavoidable impurities.

[0049] The preparation of this alloy includes the following steps:

[0050] First, ferrochrome (FeCr65C0.3), ferronickel (FeNi50C), gadolinium iron (FeGd20), and iron powder are added to a crucible. The crucible is then evacuated to a vacuum level of 0.6 Pa and filled with argon gas for protection. The raw materials are then melted completely at 1600°C to form an alloy liquid.

[0051] Then, ferroboron (FeB23C0.5) powder was added to the alloy liquid and refined at 1600℃ for 8 minutes.

[0052] The refined molten alloy is poured into a mold at 1550°C and cooled to room temperature to obtain an alloy casting.

[0053] The casting is heated to 1140℃ for multi-directional forging, followed by forging and drawing with a drawing ratio of 4.

[0054] The forged steel block was uniaxially rolled to obtain a 50mm thick alloy plate.

[0055] The density of the gadolinium-rich high-boron stainless steel used for shielding the vacuum chamber of the fusion reactor prepared in this embodiment is 8.7 g / cm³.

[0056] like Figure 1 As shown, the particulate borides are uniformly distributed in the austenitic matrix, with Gd elements concentrated in the particulate borides. The borides are composed of a single-phase structure of Fe and B elements.

[0057] like Figure 2 As shown, the gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of the fusion reactor prepared in this embodiment has an elongation of more than 15% and a tensile strength of more than 620 MPa (tested according to GB / T 228.1).

[0058] The gadolinium-rich high-boron stainless steel for fusion reactor vacuum chamber shielding prepared in this embodiment not only has excellent neutron and gamma-ray shielding performance, but also exhibits good plasticity, toughness and processing adaptability. Its mechanical properties are significantly better than 304B7, especially the elongation at room temperature can reach more than 15% and the strength exceeds 515 MPa. It significantly improves the shielding performance while increasing the yield and ensuring the economic efficiency of engineering applications.

[0059] Example 2:

[0060] The gadolinium-rich high-boron stainless steel used for shielding the fusion reactor vacuum chamber in this embodiment has the following composition: B: 1.62 wt.%, Ni: 11.2 wt.%, Cr: 14.8 wt.%, Gd: 0.78 wt.%, with the balance being Fe and unavoidable impurities.

[0061] The preparation of this alloy includes the following steps:

[0062] First, ferrochrome (FeCr65C0.3), ferronickel (FeNi50C), gadolinium iron (FeGd20), and iron powder are added to a crucible. The crucible is then evacuated to a vacuum level of 0.6 Pa and filled with argon gas for protection. The raw materials are then melted completely at 1590°C to form an alloy liquid.

[0063] Then, ferroboron (FeB23C0.5) powder was added to the alloy liquid and refined at 1590℃ for 8 minutes.

[0064] The refined molten alloy was poured into a mold at 1560°C and cooled to room temperature to obtain an alloy casting.

[0065] The casting is heated to 1160℃ for multi-directional forging, followed by forging and drawing with a drawing ratio of 3.5.

[0066] The forged steel block was uniaxially rolled to obtain a 50mm thick alloy plate.

[0067] The density of the gadolinium-rich high-boron stainless steel used for shielding the vacuum chamber of the fusion reactor prepared in this embodiment is 8.75 g / cm³.

[0068] like Figure 3 As shown, the particulate borides are uniformly distributed in the austenitic matrix, with Gd elements concentrated in the particulate borides. The borides are composed of a single-phase structure of Fe and B elements.

[0069] like Figure 4 As shown, the gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of the fusion reactor prepared in this embodiment has an elongation of more than 15% and a tensile strength of more than 620 MPa (tested according to GB / T 228.1 standard).

[0070] The gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of the fusion reactor prepared in this embodiment not only has excellent neutron and gamma-ray shielding performance, but also exhibits good plasticity, toughness and processing adaptability. Its mechanical properties are significantly better than 304B7, with an elongation of more than 15% at room temperature and a strength of more than 515 MPa, improving processing performance and yield, and ensuring economic efficiency.

[0071] This invention, based on existing high-boron stainless steel, effectively improves neutron absorption performance and significantly enhances the shielding performance of the material by introducing gadolinium (Gd), a rare earth element with a higher neutron absorption cross section.

[0072] The gadolinium-rich, high-boron stainless steel for shielding the vacuum chamber of a fusion reactor prepared in this embodiment of the invention has adjustable density and high density characteristics. The addition of Gd and B can effectively absorb neutrons, and Gd has a higher neutron absorption cross-section. This material significantly improves shielding performance by optimizing the gadolinium and boron content, while also enhancing its mechanical and processing properties, increasing yield, and ensuring economic viability in engineering applications. The stainless steel material of this invention can be economically and efficiently prepared using the aforementioned smelting process, providing crucial support for the development of components for the China Fusion Engineering Experimental Reactor (CFETR), compact fusion reactors, and other fields requiring shielding.

[0073] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A gadolinium-rich high-boron stainless steel for shielding a fusion reactor vacuum chamber, characterized in that, Based on the total weight of gadolinium-rich high-boron stainless steel, the weight percentages of each component are as follows: Cr 10-20%, Ni 8-18.5%, B 0.8-3%, Gd 0.2-3%, with the balance being Fe and unavoidable impurities.

2. The gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of a fusion reactor according to claim 1, characterized in that, The weight percentages of each component are: Cr 12-15%, Ni 9-12%, B 1-1.7%, Gd 0.4-0.8%, with the balance being Fe and unavoidable impurities.

3. The gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of a fusion reactor according to claim 1, characterized in that, The matrix of the gadolinium-rich high-boron stainless steel used for shielding the vacuum chamber of the fusion reactor is an austenitic matrix.

4. The gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of a fusion reactor according to claim 3, characterized in that, The shielding inside the fusion reactor vacuum chamber uses gadolinium-rich high-boron stainless steel B to form particulate borides with Fe, and the particulate borides are uniformly dispersed in the austenitic matrix.

5. The gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of a fusion reactor according to claim 4, characterized in that, The particulate borides are a single-phase structure composed of Fe and B elements.

6. The gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of a fusion reactor according to claim 4, characterized in that, Gd elements are concentrated in granular borides and significantly improve neutron shielding performance.

7. The method for preparing gadolinium-rich boron-rich stainless steel for shielding the vacuum chamber of a fusion reactor according to any one of claims 1 to 6, characterized in that, The preparation method specifically includes the following steps: a. Smelting: Under the protection of an inert atmosphere, chromium-containing raw materials, nickel-containing raw materials, gadolinium-containing raw materials and iron raw materials are mixed and smelted to obtain an alloy liquid; b. Refining: Under the protection of an inert atmosphere, boron-containing raw materials are added to the alloy liquid for refining; c. Casting: The refined alloy liquid is cast and then cooled to obtain alloy castings; d. Forging: The alloy casting obtained in step c is heated to the forging temperature, and the alloy obtained after heating is forged to obtain gadolinium-rich high-boron stainless steel for shielding the vacuum chamber of the fusion reactor.

8. The method for preparing gadolinium-rich high-boron stainless steel for shielding in the vacuum chamber of a fusion reactor according to claim 7, characterized in that, The melting temperature in step a is 1500-1630℃; the refining time in step b is 2-15 minutes, and the refining temperature is 1550-1600℃; the casting temperature in step c is 1510-1610℃; and the forging temperature in step d is 1100-1200℃.

9. The method for preparing gadolinium-rich high-boron stainless steel for shielding in the vacuum chamber of a fusion reactor according to claim 7, characterized in that, The preparation method further includes the following steps: e. Rolling: The forged and cooled gadolinium-rich high-boron stainless steel for the fusion reactor vacuum chamber shield is rolled to obtain gadolinium-rich high-boron stainless steel for the fusion reactor vacuum chamber shield of engineering application specifications.

10. The method for preparing gadolinium-rich high-boron stainless steel for shielding in the vacuum chamber of a fusion reactor according to claim 7, characterized in that, The chromium-containing raw material is ferrochrome, the nickel-containing raw material is ferronickel, the gadolinium-containing raw material is gadolinium iron, the iron raw material is pure iron, and the boron-containing raw material is ferroboron powder.

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