Nb55Ti plate for radio frequency superconducting cavity and preparation method thereof

Abstract

The application discloses a kind of Nb55Ti plate for radio frequency superconducting cavity and preparation method thereof, belong to superconducting accelerating cavity field, including steps: forging, slab surface treatment, rolling, plate surface treatment, plate heat treatment and finished product processing.The application is reasonably designed to processing procedure and process parameter is limited, in combination with vacuum heat treatment and surface treatment, effectively break Nb55Ti blank original organization, significantly improve the grain size uniformity of product Nb55Ti plate and the uniformity of horizontal and longitudinal organization and performance, improve the hardness of Nb55Ti plate, suitable for radio frequency superconducting cavity, also improve the processing yield of Nb55Ti plate, reduce raw material cost, can be mass production.

Description

Technical Field

[0001] This invention relates to the field of superconducting accelerator cavity technology, and more specifically, to an Nb55Ti substrate for radio frequency superconducting cavities and its preparation method. Background Technology

[0002] A superconducting radio frequency accelerator is a type of radio frequency field accelerator, which is a device that uses radio frequency electromagnetic fields in an accelerating cavity to accelerate charged particles. The 1.3GHz 9cell radio frequency accelerating cavity is mainly composed of a high-purity niobium cavity and a titanium jacket. The Nb55Ti plate is the transition connector between the two parts, which is fitted and welded to the niobium cavity and the titanium jacket respectively, and plays the role of positioning the cavity in the accelerator.

[0003] Nb55Ti alloy possesses characteristics such as high strength, low elastic modulus, good thermal conductivity, excellent plasticity, good cold formability, and good corrosion resistance, exhibiting superior comprehensive performance in the fields of aerospace, chemical engineering, and superconductivity. As a superconducting material, this alloy is used in nuclear magnetic resonance imaging (MRI), high-energy physics accelerators in strong electromagnetic fields, plasma magnetic confinement devices, and superconducting energy storage devices. Due to its good weldability with both titanium and niobium, Nb55Ti alloy has also been widely used in recent years for connecting components made of titanium and niobium alloys.

[0004] In recent years, with the rapid development of radio frequency superconducting technology, the design of superconducting accelerator cavity structures has become increasingly complex, posing new demands on the strength of cavity structures. This places high requirements on the mechanical properties and microstructure of Nb55Ti alloy disks. However, existing domestic research has not focused on the mechanical properties and microstructure of Nb55Ti. For the current novel superconducting cavity structure, the key to processing Nb55Ti plates is to control the uniformity of material properties and microstructure. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an Nb55Ti substrate for radio frequency superconducting cavities and its preparation method.

[0006] To achieve the above technical solution, this invention provides a method for fabricating Nb55Ti substrate for radio frequency superconducting cavities, comprising the following steps:

[0007] S1: Forging, heating a niobium-titanium alloy ingot with dimensions Φ×L, Nb mass fraction of 44~46%, and Ti mass fraction of 54~56% to 850℃~900℃ and holding it at that temperature for (0.5~0.6)×Φ min; then performing blank forging to obtain a slab blank with dimensions H1×B1×L1;

[0008] S2: Surface treatment of slab blank, using a CNC milling machine to remove surface defects from the slab blank obtained in step S1;

[0009] S3: Rolling, the slab blank after machining in step S2 is rolled to obtain a slab blank with dimensions of H2×B2×L2; during the rolling process, the rolling heating temperature is 800℃~850℃, and the heating and holding time is (0.8~1)×H1 min.

[0010] S4: Surface treatment of the board material. The board material obtained in step S3 is sanded using a sander, then placed in an acid solution for pickling for 3 to 5 minutes, then rinsed with clean water and air-dried naturally to ensure that the surface roughness Ra of the board material after treatment is Ra≤1.6μm.

[0011] S5: Plate heat treatment. The surface of the blank after surface treatment in step S4 is wiped with ethanol solution and then placed in a vacuum heat treatment furnace for vacuum heat treatment.

[0012] S6: Finished product processing. The billet after heat treatment in step S5 is machined using a CNC machining center to obtain Nb55Ti plate products with Nb mass fraction of 44~46%, Ti mass fraction of 54~56%, Hv≥150, and recrystallization rate of 100%.

[0013] Further, in step S1, the forging method is axial upsetting with two upsetting and two drawing processes + forming of the billet, and the upsetting deformation is (0.6~0.7)×L min; the thickness H1 of the billet is (0.25~0.35)×Φ min.

[0014] Further, in step S3, the rolling method is as follows: first, roll along the width B1 direction of the slab to the thickness H2, and then change direction by 90° to roll along the length direction of the slab to the thickness H3.

[0015] Furthermore, H2 is (0.3~0.4)×H1 min, and the upper limit of the product thickness tolerance of H3 is +(0.2~0.25) mm.

[0016] Further, in step S4, the acid solution is a uniform mixture of a 30% hydrofluoric acid solution, a 70% nitric acid solution, and water in a volume ratio of 3:1:1.

[0017] Further, in step S5, the vacuum heat treatment method includes the step of: when the vacuum degree inside the furnace is 3×10 -3 Pa ~ 2.5 × 10 -3 The heating process begins at Pa; the heating process includes: heating to 500℃±10℃ within 60 minutes and holding for 30 minutes; after holding, heating to 770℃~800℃±5℃ within 30 minutes and holding for 90 minutes; after holding, cooling with the furnace until the furnace temperature is less than 100℃ before removing from the furnace.

[0018] Furthermore, in step S6, before machining, the heat-treated blank is coated for protection.

[0019] Furthermore, an Nb55Ti substrate for a radio frequency superconducting cavity is fabricated using a method for preparing an Nb55Ti substrate for a radio frequency superconducting cavity.

[0020] In summary, the present invention has the following advantages over the prior art:

[0021] 1. This invention involves forging and rolling Nb55Ti alloy billets sequentially to effectively break down and refine the original microstructure of the Nb55Ti alloy billets. By controlling the total deformation and processing direction in each processing step, the uniformity of the transverse and longitudinal microstructure and properties of the Nb55Ti alloy sheet products is significantly improved. Combined with vacuum heat treatment of the finished product, the recrystallization degree, grain size, and transverse and longitudinal grain difference of the Nb55Ti alloy sheet are effectively controlled, thereby improving the uniformity of grain size in the Nb55Ti alloy sheet. Furthermore, the content of C, H, O, and N gas elements in the sheet is effectively controlled, making it suitable for use in radio frequency superconducting cavities.

[0022] 2. This invention effectively removes surface contaminants introduced during the processing of Nb55Ti alloy plates by performing surface treatment on the billet after each forging and rolling process, resulting in a uniform surface of Nb55Ti alloy plates with a surface roughness that meets the requirement of an average roughness Ra≤1.6μm.

[0023] 3. The difference in mechanical properties and hardness between the perpendicular rolling direction and the rolling direction of the Nb55Ti alloy plate prepared by this invention does not exceed 5%, the recrystallization rate of the plate is 100%, and the difference in grain size between the perpendicular rolling direction and the rolling direction is ≤ASTM 0.5 grade (ASTM E112-13), ensuring that the gas element content, mechanical properties, hardness, grain size and recrystallization rate of the plate meet the requirements for use in a 1.3GHz 9cell radio frequency superconducting cavity. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 This is a metallographic image of the transverse (perpendicular rolling direction) microstructure of the δ3mm Nb55Ti alloy plate prepared in Example 1 of this invention;

[0026] Figure 2 This is a metallographic image of the longitudinal (rolling direction) microstructure of the δ3mm Nb55Ti alloy plate prepared in Example 1 of this invention;

[0027] Figure 3 This is a metallographic image of the transverse (perpendicular rolling direction) microstructure of the δ6mm Nb55Ti alloy plate prepared in Example 2 of this invention;

[0028] Figure 4 This is a metallographic image of the longitudinal (rolling direction) microstructure of the δ6mm Nb55Ti alloy plate prepared in Example 2 of this invention. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form may also include the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0031] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0032] This invention provides a method for fabricating Nb55Ti substrate for radio frequency superconducting cavities, comprising the following steps:

[0033] S1: Forging. A niobium-titanium alloy ingot with dimensions Φ×L, Nb mass fraction of 44~46%, and Ti mass fraction of 54~56% is heated to 850℃~900℃ and held at that temperature for (0.5~0.6)×Φ min. Then, a slab forging process is performed to obtain a slab blank with dimensions H1×B1×L1. Wherein, Φ is the diameter (mm); L is the length of the plate (mm); B1 is the width of the slab blank (mm); H1 is the thickness of the slab blank (mm); and L1 is the length of the slab blank (mm).

[0034] S2: Surface treatment of slab blank. The slab blank obtained in step S1 is machined using a CNC milling machine to remove surface defects. After machining, the surface of the slab blank must be smooth and uniform, without grinding marks, pits, cracks, inclusions or other defects visible to the naked eye.

[0035] S3: Rolling. The slab blank processed in step S2 is rolled to obtain a sheet blank with dimensions H2×B2×L2. During the rolling process, the rolling heating temperature must be maintained at 800℃~850℃, and the heating and holding time must be (0.8~1)×H1 min. Wherein, H2 is the thickness of the rolled sheet (mm); B2 is the width of the rolled sheet (mm); and L2 is the length of the rolled sheet (mm).

[0036] S4: Surface treatment of the board. The board blank obtained in step S3 is sanded with a sander to the product thickness tolerance range. Then it is placed in acid solution for pickling for 3 to 5 minutes. After rinsing with clean water, it is air-dried naturally. After this step, it is necessary to ensure that the surface of the board blank after sanding is smooth and uniform, without grinding marks, pits, cracks, inclusions or other defects that are visible to the naked eye. That is to say, the surface roughness Ra of the board blank must be ≤1.6μm.

[0037] S5: Plate heat treatment. The surface of the blank after surface treatment in step S4 is wiped with ethanol solution and then placed in a vacuum heat treatment furnace for vacuum heat treatment.

[0038] S6: Finished product processing. The heat-treated billet from step S5 is machined to the product length and width tolerance range using a CNC machining center to obtain Nb55Ti plate products with Nb mass fraction of 44~46%, Ti mass fraction of 54~56%, Hv≥150, and recrystallization rate of 100%.

[0039] This method, through the rational design of processing steps and the limitation of process parameters, combined with vacuum heat treatment and surface treatment, effectively breaks down and refines the original microstructure of Nb55Ti billet, significantly improving the uniformity of grain size and the uniformity of transverse and longitudinal microstructure and properties of the Nb55Ti plate, increasing the hardness of the Nb55Ti plate, making it suitable for use in radio frequency superconducting cavities, while also improving the processing yield of Nb55Ti plate, reducing raw material costs, and enabling stable mass production.

[0040] As a preferred embodiment, in step S1, to expedite the forging process, the forging method is axial upsetting followed by two upsetting and two drawing operations, plus forming the billet. The upsetting deformation is (0.6~0.7)×L mm. After forming the billet, the thickness H1 of the billet is (0.25~0.35)×Φ mm to facilitate subsequent processing. In this preferred embodiment, only the thickness H1 needs to be considered during forging; B1 and L1 are addressed in subsequent steps. This method can significantly improve the production speed of Nb55Ti plates.

[0041] As a preferred embodiment, in step S3, the rolling method is as follows: first, roll along the width B1 direction of the slab to thickness H2, then reverse the direction by 90° and roll along the length direction of the slab to thickness H3. Here, H2 is (0.3~0.4)×H1 mm, and the upper limit of the product thickness tolerance for H3 is +(0.2~0.25) mm. By gradually satisfying the dimensional requirements of the slab blank through rolling along the width B1 direction to thickness H2, and then reversing the direction by 90° and rolling along the length direction of the slab to thickness H3, the internal structure of the slab can be made uniform and consistent, with isotropic mechanical properties. This ensures that the difference in mechanical properties and hardness between the transverse and longitudinal directions does not exceed 5%, and the difference in grain size between the transverse and longitudinal directions is ≤ASTM 0.5 grade.

[0042] As a preferred embodiment, in step S4, the acid solution used is a uniform mixture of a 30% hydrofluoric acid solution, a 70% nitric acid solution, and water in a volume ratio of 3:1:1. Practical use has shown that this acid solution ensures that the surface of the sheet material after pickling is smooth, has a uniform metallic color, and is free of acid residue.

[0043] As a preferred embodiment, in step S5, the vacuum heat treatment regime is as follows: when the vacuum degree inside the furnace is 2.5 × 10⁻⁶ -3 Pa~3×10 -3 When Pa, first heat up to 500℃±10℃ within 60min and hold for 30min, then heat up to 770℃~800℃±5℃ within 30min and hold for 90min, then cool with the furnace until the furnace temperature is less than 100℃ before removing from the furnace.

[0044] As a preferred option, in step six, the heat-treated billet is coated with a protective film before machining. The coated billet has an additional thin and transparent plastic film on its surface, which protects it from surface scratches and other defects during machining. It also provides protection against water, dirt, wear, and chemical corrosion.

[0045] In addition, the present invention also provides an Nb55Ti substrate for radio frequency superconducting cavities, which is prepared by the above method.

[0046] Examples of preparing Nb55Ti plates using the above method are as follows:

[0047] Example 1

[0048] This embodiment includes the following steps:

[0049] Step 1: Forging: The Nb55Ti billet with dimensions (diameter × length) of Φ180×300mm is heated to 850℃ for 90min, followed by two upsetting and two drawing processes of Φ180×300→Φ284×120→Φ142×300→Φ284×120→Φ142×300. Finally, the billet is shaped along the axial direction of 300mm to obtain an Nb55Ti slab billet with dimensions (thickness × width × length) of δ45×300×565mm.

[0050] Step 2: Surface Treatment of the Slab: The Nb55Ti alloy slab blank with dimensions (thickness × width × length) of δ45 × 300 × 565 mm from Step 1 is machined and milled along the 565 mm direction to obtain a slab blank with dimensions (thickness × width × length) of δ45 × 300 × 565 mm. Nb55Ti alloy slab blank.

[0051] Step 3, Rolling: Roll the material into a roll with the dimensions (thickness × width × length) from Step 2. The Nb55Ti billet was heated to 800℃ for 35 minutes and then rolled along the 295mm direction to a thickness of δ12mm. The billet was then rotated 90° and rolled along the 560mm direction to a thickness of δ12mm. mm, yielding the dimensions (thickness × width × length) as follows: Plate blanks measuring 983mm × 2240mm.

[0052] Step 4: Surface Treatment of the Board: Use a sander to sand the board blank obtained in Step 3 until it is within the product thickness tolerance range. During sanding, use a 400# sanding belt to sand both sides of the board blank until the thickness is [to be specified]. mm, then placed in acid solution for pickling for 3 minutes, rinsed with clean water and air-dried. The dimensions (thickness × width × length) of the finished blank after surface treatment are: mm×983mm×2240mm.

[0053] Step 5, Plate Heat Treatment: Wipe the surface of the plate blank after surface treatment in Step 4 with an ethanol solution, and then place it in a vacuum heat treatment furnace for vacuum heat treatment; the vacuum heat treatment regime is as follows: the vacuum degree in the furnace does not exceed 3×10 -3After Pa, the temperature is raised to 500℃±10℃ within 60 minutes and held for 30 minutes. Then, the temperature is raised to 770℃±5℃ within 30 minutes and held for 90 minutes. The furnace is then cooled to a temperature below 100℃ before being removed from the furnace.

[0054] Step Six: Finishing Process: Using a CNC machining center, the heat-treated sheet metal blanks from Step Five are machined to within the product's length and width tolerances. Before machining, the CNC machining center equipment is cleaned, and the heat-treated sheet metal blanks are coated for protection, resulting in 8 pieces with dimensions (diameter × thickness) as follows. Nb55Ti plate products with a mass fraction of 44-46% Nb and 54-56% Ti, Hv≥150, and recrystallization rate of 100% (mm).

[0055] In step four of this embodiment, the acid solution used is a uniform mixture of 30% hydrofluoric acid solution, 70% nitric acid solution, and water in a volume ratio of 3:1:1. The surface of the billet after pickling in step four is smooth, has a metallic color, and is uniform, without any traces of acid solution. The surfaces of the slab billet after grinding in step two and the slab billet after sanding in step four are smooth and uniform, without grinding marks, and without defects such as pits, cracks, fissures, or inclusions that are visible to the naked eye.

[0056] Figure 1 This is a metallographic image of the transverse (perpendicular to the rolling direction) microstructure of the δ3mm high-purity niobium plate prepared in Example 1 of this invention. Figure 1 It can be seen that all grains in this structure are 100% recrystallized, and the grains are equiaxed, uniform in size, and the main grain size is ASTM grade 8 (0.022 mm).

[0057] Figure 2 This is a metallographic image of the longitudinal (rolling direction) microstructure of the δ3mm high-purity niobium plate prepared in Example 1 of this invention. Figure 2 It can be seen that all grains in this structure are 100% recrystallized, and the grains are equiaxed, uniform in size, and the main grain size is ASTM grade 8 (0.022 mm).

[0058] The Nb55Ti plate product prepared in this embodiment was subjected to performance component testing, and the test results are shown in Table 1 below.

[0059] Table 1. Composition of Nb55Ti plates obtained in Example 1

[0060]

[0061] The Nb55Ti plate prepared in this embodiment has a uniform surface, and its gas element content, mechanical properties, hardness, grain size and recrystallization rate all meet the requirements for use in radio frequency superconducting cavities.

[0062] Example 2

[0063] This embodiment includes the following steps:

[0064] Step 1: Forging: The Nb55Ti billet with dimensions (diameter × length) of Φ220×400mm is heated to 900℃ for 130min and then subjected to two upsetting and two drawing processes of Φ220×400→Φ400×120→Φ195×400→Φ400×120→Φ195×400. Finally, the billet is shaped along the axial direction of 400mm to obtain an Nb55Ti slab billet with dimensions (thickness × width × length) of δ77×400×493mm.

[0065] Step 2, Slab Surface Treatment: The Nb55Ti alloy slab blank with dimensions (thickness × width × length) of δ77 × 400 × 493 mm from Step 1 is machined and milled along the 493 mm direction to obtain a blank with dimensions (thickness × width × length) of δ77 × 400 × 493 mm. Nb55Ti alloy slab blank.

[0066] Step 3, Rolling: Roll the material into a roll with the dimensions (thickness × width × length) from Step 2. The Nb55Ti billet was heated to 850℃ for 70 minutes and then rolled along the 395mm direction to a thickness of δ31mm. The billet was then rotated 90° and rolled along the 485mm direction to a thickness of δ31mm. mm, yielding the dimensions (thickness × width × length) as follows: Plate blanks measuring 980mm x 2505mm.

[0067] Step 4: Surface Treatment of the Board: Use a sander to sand the board blank obtained in Step 3 until it is within the product thickness tolerance range. During sanding, use a 400# sanding belt to sand both sides of the board blank until the thickness is [to be specified]. mm, then placed in acid solution for pickling for 5 minutes, rinsed with clean water and air-dried. The dimensions (thickness × width × length) of the finished blank after surface treatment are: mm×980mm×2505mm.

[0068] Step 5, Plate Heat Treatment: Wipe the surface of the plate blank after surface treatment in Step 4 with an ethanol solution, and then place it in a vacuum heat treatment furnace for vacuum heat treatment; the vacuum heat treatment regime is as follows: the vacuum degree in the furnace does not exceed 3×10 -3 After Pa, the temperature is raised to 500℃±10℃ within 60 minutes and held for 30 minutes. Then, the temperature is raised to 800℃±5℃ within 30 minutes and held for 90 minutes. The furnace is then cooled to a temperature below 100℃ before being removed from the furnace.

[0069] Step Six: Finished Product Machining: Using a CNC machining center, the heat-treated sheet metal blanks from Step Five are machined to within the product's length and width tolerances. Before machining, the CNC machining center equipment is cleaned, and the heat-treated sheet metal blanks are coated for protection. Ten pieces with dimensions (diameter × thickness) are obtained. Nb55Ti plate products with a mass fraction of 44-46% Nb and 54-56% Ti, Hv≥150, and recrystallization rate of 100% (mm).

[0070] In step four of this embodiment, the acid solution used is a uniform mixture of 30% hydrofluoric acid solution, 70% nitric acid solution, and water in a volume ratio of 3:1:1. The surface of the billet after pickling in step four is smooth, has a metallic color, and is uniform, without any traces of acid solution. The surfaces of the slab billet after grinding in step two and the slab billet after sanding in step four are smooth and uniform, without grinding marks, and without defects such as pits, cracks, fissures, or inclusions that are visible to the naked eye.

[0071] Figure 3 This is a metallographic image of the transverse (perpendicular to the rolling direction) microstructure of the δ6mm high-purity niobium plate prepared in Example 2 of this invention. Figure 3 It can be seen that all grains in this structure are 100% recrystallized, and the grains are equiaxed, uniform in size, and the main grain size is ASTM grade 7 (0.032 mm).

[0072] Figure 4 This is a metallographic image of the longitudinal (rolling direction) microstructure of the δ6mm high-purity niobium plate prepared in Example 2 of this invention. Figure 4 It can be seen that all grains in this structure are 100% recrystallized, and the grains are equiaxed, uniform in size, and the main grain size is ASTM grade 7 (0.032 mm).

[0073] The performance components of the high-purity niobium plate product prepared in this embodiment were tested, and the test results are shown in Table 2 below.

[0074] Table 2. Composition of Nb55Ti plates obtained in Example 2

[0075]

[0076] The Nb55Ti plate prepared in this embodiment has a uniform surface, and its gas element content, mechanical properties, hardness, grain size and recrystallization rate all meet the requirements for use in radio frequency superconducting cavities.

[0077] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating Nb55Ti substrate for radio frequency superconducting cavities, characterized in that, Including the following steps: S1: Forging. A niobium-titanium alloy ingot with dimensions Φ×L, Nb mass fraction of 44~46%, and Ti mass fraction of 54~56% is heated to 850℃~900℃ and held at that temperature for (0.5~0.6)×Φ min. Then, a slab forging process is performed to obtain a slab blank with dimensions H1×B1×L1. The forging method is axial upsetting with two upsetting and two drawing operations followed by forming. The upsetting deformation is (0.6~0.7)×L mm. The thickness H1 of the slab blank is (0.25~0.35)×Φ mm. Wherein, Φ is the diameter (mm); L is the length of the plate (mm); B1 is the width of the slab blank (mm); H1 is the thickness of the slab blank (mm); and L1 is the length of the slab blank (mm). S2: Surface treatment of slab blank, using a CNC milling machine to remove surface defects from the slab blank obtained in step S1; S3: Rolling. The slab blank processed in step S2 is rolled to obtain a sheet blank with dimensions H2×B2×L2. During the rolling process, the rolling heating temperature is 800℃~850℃, and the heating and holding time is (0.8~1)×H1 min. The rolling method is as follows: first, roll along the width B1 direction of the slab to the thickness H2, then change direction by 90° and roll along the length direction of the slab to the thickness H3. Wherein, H2 is the thickness of the rolled sheet (mm); B2 is the width of the rolled sheet (mm); and L2 is the length of the rolled sheet (mm). S4: Surface treatment of the board material. The board material obtained in step S3 is sanded using a sander, then placed in an acid solution for pickling for 3 to 5 minutes, then rinsed with clean water and air-dried naturally to ensure that the surface roughness Ra of the board material after treatment is Ra≤1.6μm. S5: Plate heat treatment. The surface of the blank after surface treatment in step S4 is wiped with ethanol solution and then placed in a vacuum heat treatment furnace for vacuum heat treatment. S6: Finished product processing. The billet after heat treatment in step S5 is machined using a CNC machining center to obtain Nb55Ti plate products with Nb mass fraction of 44~46%, Ti mass fraction of 54~56%, hardness Hv≥150, and recrystallization rate of 100%.

2. The method for fabricating Nb55Ti substrate for radio frequency superconducting cavities according to claim 1, characterized in that, H2 is (0.3~0.4)×H1 mm, and the upper limit of the product thickness tolerance for H3 is +(0.2~0.25) mm.

3. The method for fabricating Nb55Ti substrate for radio frequency superconducting cavities according to claim 1, characterized in that, In step S4, the acid solution is prepared by uniformly mixing a 30% hydrofluoric acid solution, a 70% nitric acid solution, and water in a volume ratio of 3:1:

1.

4. The method for fabricating Nb55Ti substrate for radio frequency superconducting cavities according to claim 1, characterized in that, In step S5, the vacuum heat treatment method includes the step of: when the vacuum degree inside the furnace is 3×10 -3 Pa ~ 2.5 × 10 -3 The heating process begins at Pa; the heating process includes: heating to 500℃±10℃ within 60 minutes and holding for 30 minutes; after holding, heating to 770℃~800℃±5℃ within 30 minutes and holding for 90 minutes; after holding, cooling with the furnace until the furnace temperature is less than 100℃ before removing from the furnace.

5. The method for fabricating Nb55Ti substrate for radio frequency superconducting cavities according to claim 1, characterized in that, In step S6, before machining, the heat-treated blank is coated for protection.

6. An Nb55Ti substrate for radio frequency superconducting cavities, characterized in that, It is manufactured by the method for preparing Nb55Ti substrate for radio frequency superconducting cavity as described in any one of claims 1 to 5.

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