Vacuum melting system and vacuum melting method for high-purity molybdenum and molybdenum material with fiber structure

Abstract

The invention relates to the technical field of refractory metal material processing, in particular to a high-purity molybdenum vacuum melting system, a high-purity molybdenum vacuum melting method and a fiber structure molybdenum material.The high-purity molybdenum vacuum melting system comprises three layers of composite crucibles. Comprising the following steps that S1, in the environment with the vacuum degree smaller than or equal to 5 * 10 <-3 > Pa, a three-layer composite crucible is adopted for conducting consumable smelting on a molybdenum raw material; s2) controlling the directional solidification rate to be 8-12mm / min, and forming a longitudinal temperature gradient of more than or equal to 100 DEG C / cm; s3) performing multi-stage plastic deformation on the solidified cast ingot, wherein the total deformation is greater than or equal to 90%; a longitudinal continuous fiber structure is formed in the fiber structure molybdenum material, the grain length-diameter ratio is larger than or equal to 10: 1, and the fiber diameter is smaller than or equal to 5 micrometers. The hydrogen content is less than or equal to 5ppm, and the oxygen content is less than or equal to The room-temperature tensile strength is greater than or equal to 780MPa; according to the preparation method, the high-purity fiber structure molybdenum material can be prepared, and the problem that the axial performance is insufficient due to isotropy of a traditional isometric crystal structure is solved.

Description

Technical Field

[0001] The present application relates to the technical field of refractory metal material processing, and specifically to a high-purity molybdenum vacuum melting system, a vacuum melting method, and a fiber-structured molybdenum material. Background Art

[0002] Molybdenum, a key refractory metal with a melting point of 2620°C, has become a core material for high-end equipment such as semiconductor ion implanter components, rocket engine nozzles, and nuclear reactor cladding due to its excellent high-temperature strength, low thermal expansion coefficient, and good thermal conductivity. In particular, hot-end components of hypersonic vehicles, particularly in the military industry, require a tensile strength exceeding 700 MPa at 1600°C.

[0003] The current mainstream production process is powder metallurgy, whose core processes include: molybdenum powder pressing, sintering molding and hot forging / rolling. However, this technology has the following fatal flaws:

[0004] (1) Purity Issues: The semiconductor industry places extremely strict requirements on the content of gases such as hydrogen and oxygen in molybdenum materials. However, existing technologies for producing molybdenum materials struggle to meet these purity requirements, particularly with excessive gas content. Currently, the highest purity of domestic molybdenum materials is only 99.97%, and the hydrogen and oxygen content cannot meet the high purity requirements of high-end manufacturing and the military industry. This is primarily due to the difficulty in effectively controlling the incorporation and removal of gases using conventional smelting processes and equipment.

[0005] (2) Material Internal Structure Issues: Existing processes are unable to produce specific fiber structures, making it difficult to achieve the desired grain size variations. In the semiconductor and military industries, specialized components have stringent material structure requirements. If these structural requirements are not met, qualified components cannot be produced. This is because the principles and operating methods of traditional processes limit the ability to precisely control the internal structure of the material.

[0006] The existing vacuum melting process is difficult to stably produce molybdenum materials that meet the requirements of high purity and specific fiber structure. Summary of the Invention

[0007] The present application provides a vacuum melting system, a vacuum melting method and a fiber-structured molybdenum material for high-purity molybdenum, which can effectively solve the problems in the background technology.

[0008] To achieve the above objectives, this application provides the following technical solutions:

[0009] A vacuum melting system for high-purity molybdenum includes an electrode feed transmission device, an electrode rod, a vacuum furnace body, a consumable molybdenum rod, a three-layer composite crucible, a water cooling cycle and a vacuum pumping system. The electrode feed transmission device is connected to the electrode rod for controlling the lifting and lowering of the electrode rod. The lower end of the electrode rod is connected to a consumable molybdenum rod used as a cathode, which is suspended inside the vacuum furnace body. The three-layer composite crucible is used as an anode and is placed inside the vacuum furnace body. The outside of the vacuum furnace body is connected to the vacuum pumping system, and the water cooling cycle is connected to the three-layer composite crucible.

[0010] The three-layer composite crucible comprises an inner layer, a middle layer and an outer layer, wherein the inner layer is a W-Re alloy layer, the middle layer is a graphite-tantalum carbide composite layer, and the outer layer is a copper-based water-cooling jacket.

[0011] The vacuum melting method of high-purity molybdenum comprises the following steps:

[0012] Step S1: When the vacuum degree is ≤5×10 -3 Pa environment, a three-layer composite crucible was used to melt the consumable molybdenum rod;

[0013] Step S2: controlling the directional solidification rate to 8-12 mm / min and forming a longitudinal temperature gradient ≥ 100°C / cm;

[0014] Step S3: performing multi-stage plastic deformation on the solidified ingot, with the total deformation amount being ≥90%.

[0015] Preferably, in step S1, the consumable molybdenum rod is pickled and pretreated before smelting: the consumable molybdenum rod is soaked in a mixed acid solution with a volume ratio of HF:HNO3=1:3 for 30 seconds, and the purity of the molybdenum ingot in the consumable molybdenum rod is ≥99.98%.

[0016] Preferably, the smelting parameters of step S1 include: smelting current 25-28 kA; voltage fluctuation ≤±0.5 V; smelting temperature 2550-2600° C., and constant temperature time 10-20 min.

[0017] Preferably, the multi-stage plastic deformation in step S3 is performed in three steps of multi-directional forging, with a single deformation amount of 30-35% and a final forging temperature of 800-850°C.

[0018] Preferably, gradient annealing is performed after forging: first stage: 1200° C.×2 h; second stage: 800° C.×4 h.

[0019] A fiber-structured molybdenum material is prepared by the vacuum melting method of the above-mentioned high-purity molybdenum, has a hydrogen content of ≤5ppm, an oxygen content of ≤50ppm, a grain aspect ratio of ≥10:1, a longitudinal continuous fiber structure formed inside the material, a fiber diameter of ≤5μm, a room temperature tensile strength of ≥780MPa, and a high-temperature creep life of ≥300 hours at 1200°C.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The hydrogen content of this fiber-structured molybdenum material is ≤5ppm; the oxygen content is ≤50ppm; the purity is above 99.99%, meeting the limit requirements of the semiconductor 3nm process for target gas impurities; forming a longitudinal continuous fiber structure, improving the axial performance deficiency caused by the isotropy of the traditional equiaxed crystal structure;

[0022] 2. The fiber network of this fiber-structured molybdenum material is oriented along the axial direction, which significantly prolongs the crack propagation path when the material is subjected to axial loads in military components. The room temperature tensile strength is ≥780MPa, which is significantly higher than that of traditional processes and exceeds the 700MPa strength threshold for hot end components of hypersonic aircraft. The high-temperature creep life at 1200℃ is ≥300 hours, which is 3-5 times that of traditional materials, significantly improving the service reliability of rocket engine nozzles.

[0023] 3. The composite crucible design reduces the contamination rate and extends the crucible life; the gradient annealing process avoids abnormal grain growth and significantly improves product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Metal structure of a fiber-structured molybdenum rod in transverse (a) and longitudinal (b) cross-sections.

[0025] Figure 2 Schematic diagram of the structure of a three-layer composite crucible.

[0026] Figure 3 This is the working principle diagram of the vacuum melting system for high-purity molybdenum.

[0027] In the figure: 1 electrode feeding transmission device, 2 electrode rod, 3 vacuum furnace body, 4 consumable molybdenum rod, 5 three-layer composite crucible, 51 inner layer, 52 middle layer, 53 outer layer, 6 water cooling cycle, 7 vacuum pumping system. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0029] See also Figure 1-3 , this application provides the following technical solutions:

[0030] A high-purity molybdenum vacuum melting system comprises an electrode feeding transmission device 1, an electrode rod 2, a vacuum furnace body 3, a consumable molybdenum rod 4, a three-layer composite crucible 5, a water cooling cycle 6 and a vacuum pumping system 7.

[0031] The electrode feeding transmission device 1 is connected to the electrode rod 2 and is used to control the lifting and lowering of the electrode rod 2.

[0032] The lower end of the electrode rod 2 is connected to a consumable molybdenum rod 4 used as a cathode, and the consumable molybdenum rod 4 is suspended inside the vacuum furnace body 3.

[0033] The three-layer composite crucible 5 is placed inside the vacuum furnace body 3 as an anode and is connected to a water cooling circuit 6 external to the vacuum furnace body 3 .

[0034] The vacuum system 7 is connected to the vacuum furnace body 3 and is used to maintain the vacuum degree in the furnace ≤ 5×10 -3 Pa.

[0035] The three-layer composite crucible 5 includes, from the inside to the outside:

[0036] Inner layer 51: W-Re alloy layer, wherein the Re content is 3-8wt%, the thickness is 5mm, and the melting point is greater than 3200°C.

[0037] Intermediate layer 52: graphite-tantalum carbide composite layer, thickness 15 mm, thermal conductivity ≤ 50 W / (m·K).

[0038] Outer layer 53: Copper-based water-cooling jacket, with cooling water flowing inside and a flow rate ≥5m³ / h.

[0039] The water cooling cycle 6 is connected to the copper-based water cooling jacket of the outer layer 53 of the three-layer composite crucible 5 to form a closed cooling circuit.

[0040] Specifically, the present application proposes a "three-layer composite crucible" structure with specific material composition and functional layering. This structure, through the synergistic effect of each layer of material, solves the core contradiction of "high purity" and "specific fiber structure" in high-purity molybdenum vacuum consumable melting, which is difficult to achieve both.

[0041] Existing technologies often use a single-layer, water-cooled copper crucible, a common design for vacuum consumable melting (particularly for reactive metals like titanium and zirconium). This design leverages copper's high thermal conductivity and water cooling for rapid cooling. However, the melting point of molybdenum (2620°C) is much higher than that of copper (1083°C). During the melting process, using a copper crucible can lead to corrosion and reaction between the hot molybdenum liquid and the crucible, resulting in copper contamination of the molybdenum melt. This makes it difficult for the final product to exceed 99.97% purity. High levels of gaseous impurities (O and H) create insurmountable bottlenecks for powder metallurgy and traditional melting methods. Furthermore, copper has good thermal conductivity but low strength. When subjected to significant radial thermal gradients, it is prone to thermal stress deformation, cracking, and even melt-through. This results in an extremely short crucible lifespan, making stable and continuous industrial production impossible. While single-layer copper crucibles offer strong cooling capacity, they struggle to create a controllable and stable longitudinal high-temperature gradient (≥100°C / cm), a critical prerequisite for achieving axially fibrous crystal structures through directional solidification.

[0042] This application utilizes a three-layer crucible. The inner layer (W-Re alloy) directly faces the high-temperature molybdenum liquid. Its melting point (>3200°C) is far higher than that of molybdenum, fundamentally eliminating the problem of crucible contamination by corrosion and providing a guaranteed source of purity exceeding 99.992%. The addition of Re further enhances high-temperature strength.

[0043] The middle layer (graphite-tantalum carbide composite layer): This is one of the most innovative designs in this application. Its low thermal conductivity (≤50W / (m·K)) acts as a "thermal barrier," slowing the rapid transfer of heat from the inner layer to the outer layer. This significantly alleviates the thermal stress caused by the significant difference in thermal expansion coefficients between the inner and outer layers, thereby resolving the problem of copper crucible cracking and increasing the crucible lifespan from dozens of cycles to over 300 cycles. Chemical barrier: Tantalum carbide (TaC) effectively inhibits the reaction between molybdenum and carbon in the graphite layer, preventing "carburization" and embrittlement of the molybdenum ingot, further ensuring the purity and plasticity of the product.

[0044] The outer layer (copper-based water-cooling jacket) is responsible for the final heat dissipation. Protected by the middle layer, the copper jacket operates stably. By controlling the cooling water flow (≥5m³ / h), it works in conjunction with the middle layer to establish and precisely control the longitudinal temperature gradient necessary for directional solidification.

[0045] At the same time, compared with other multi-layer crucibles in the prior art, the present application solves the lifespan problem that is still unavoidable in traditional multi-layer crucible structures, and achieves precise control of the solidification process, thereby preparing materials with specific fiber structures.

[0046] The vacuum melting method of high-purity molybdenum comprises the following steps:

[0047] Step S1: When the vacuum degree is ≤5×10 -3Pa environment, a three-layer composite crucible 5 is used to melt the consumable molybdenum rod.

[0048] Step S2: Control the directional solidification rate to 8-12 mm / min, and form a longitudinal temperature gradient of ≥100° C. / cm.

[0049] Specifically, step S2 involves directional solidification. A longitudinal temperature gradient of ≥100°C / cm and a solidification rate of 8-12 mm / min promotes axial grain growth, forming a longitudinally continuous fiber structure, addressing the isotropic nature of traditional equiaxed crystals. Fiber diameters of ≤5 μm refine grain size and enhance strength, achieving a room-temperature tensile strength of 825 MPa. The longitudinal direction refers to the axial direction of the three-layer composite crucible.

[0050] Step S3: performing multi-stage plastic deformation on the solidified ingot, with the total deformation amount being ≥90%.

[0051] Specifically, multidirectional forging with a total deformation of ≥90% can break up coarse grains and promote the densification of the fiber structure.

[0052] Preferably, before smelting in step S1, the consumable molybdenum rod 4 is pickled and pretreated by soaking in a mixed acid solution of HF:HNO3=1:3 for 30 seconds, and the purity of the molybdenum ingot in the consumable molybdenum rod 4 is ≥99.98%.

[0053] Specifically, the mixed acid solution quickly dissolves the oxide layer on the surface of the molybdenum ingot, which can control gas impurities from the source.

[0054] Preferably, the smelting parameters of step S1 include: smelting current 25-28 kA; voltage fluctuation ≤±0.5 V; smelting temperature 2550-2600° C., and constant temperature time 10-20 min.

[0055] Preferably, the multi-stage plastic deformation in step S3 is performed in three steps of multi-directional forging, with a single deformation amount of 30-35% and a final forging temperature of 800-850°C.

[0056] Preferably, gradient annealing is performed after forging: first stage: 1200° C.×2 h; second stage: 800° C.×4 h.

[0057] Specifically, the first stage is 1200℃×2h: eliminating forging stress and avoiding grain boundary oxidation.

[0058] The second stage is 800℃×4h: precise control of recrystallization to prevent abnormal grain growth, and the yield is increased by 20%.

[0059] A fiber-structured molybdenum material is prepared by the vacuum melting method of the above-mentioned high-purity molybdenum, has a hydrogen content of ≤5ppm, an oxygen content of ≤50ppm, a grain aspect ratio of ≥10:1, a longitudinal continuous fiber structure formed inside the material, a fiber diameter of ≤5μm, a room temperature tensile strength of ≥780MPa, and a high-temperature creep life of ≥300 hours at 1200°C.

[0060] The preparation and operation method of the fiber structure molybdenum material is given in the following specific examples in this application.

[0061] Example 1:

[0062] 1. Raw material pretreatment: Use molybdenum ingots with a purity of ≥99.98% (hydrogen content ≤0.0003%, oxygen content ≤0.004%) as consumable electrodes.

[0063] Pickling treatment: Soak in a mixed acid solution with a volume ratio of HF:HNO3=1:3 for 30 seconds, then rinse with deionized water and vacuum dry.

[0064] 2. Melting system and crucible structure:

[0065] Use a three-layer composite crucible with the following structure:

[0066] Inner layer: W-5%Re alloy, thickness 5mm;

[0067] Middle layer: graphite-20% tantalum carbide composite layer, thickness 15mm, thermal conductivity ≤50W / (m·K);

[0068] Outer layer: copper-based water cooling jacket, cooling water flow ≥5m³ / h.

[0069] Vacuum system ultimate vacuum degree: ≤5×10 -3 Pa, leakage rate <1×10 -4 Pa·m³ / s.

[0070] 3. Melting process parameter control: melting current: 26kA; melting voltage: 21V, voltage fluctuation ≤±0.5V; melting temperature: 2575℃; constant temperature time: 15min; vacuum maintenance: ≤5×10 -3 Pa.

[0071] 4. Directional solidification control:

[0072] Solidification rate: 10 mm / min;

[0073] Longitudinal temperature gradient: ≥100℃ / cm.

[0074] 5. Multi-directional forging process: divided into 3 forgings, single deformation: 32%; total deformation: 90%; final forging temperature: 825℃.

[0075] 6. Gradient annealing process:

[0076] The first stage: 1200℃×2h, argon protection;

[0077] The second stage: 800℃×4h, vacuum degree ≤1×10 -2 Pa.

[0078] 7. The final product properties are as follows: purity: 99.992%, hydrogen content: 4.2ppm, oxygen content: 42ppm, grain aspect ratio: 18:1, room temperature tensile strength: 825MPa.

[0079] Example 2:

[0080] 1. Raw material pretreatment: Use molybdenum ingots with a purity of ≥99.98% (hydrogen content ≤0.0003%, oxygen content ≤0.004%) as consumable electrodes.

[0081] Pickling treatment: Soak in a mixed acid solution with a volume ratio of HF:HNO3=1:3 for 30 seconds, then rinse with deionized water and vacuum dry.

[0082] 2. Melting system and crucible structure:

[0083] Use a three-layer composite crucible with the following structure:

[0084] Inner layer: W-5%Re alloy, thickness 5mm;

[0085] Middle layer: graphite-20% tantalum carbide composite layer, thickness 15mm, thermal conductivity ≤50W / (m·K);

[0086] Outer layer: copper-based water cooling jacket, cooling water flow ≥5m³ / h.

[0087] Vacuum system ultimate vacuum degree: ≤5×10 -3 Pa, leakage rate <1×10 -4 Pa·m³ / s.

[0088] 3. Melting process parameters: melting current: 27.5kA; melting voltage: 21.5V, voltage fluctuation ≤±0.5V; melting temperature: 2590℃; constant temperature time: 18min; vacuum maintenance: ≤5×10 -3 Pa.

[0089] 4. Directional solidification control: solidification rate: 11.5mm / min; longitudinal temperature gradient: ≥100℃ / cm.

[0090] 5. Multi-directional forging process: divided into 3 forgings, single deformation: 34%; total deformation: 92%; final forging temperature: 840℃.

[0091] 6. Gradient annealing process:

[0092] The first stage: 1200℃×2h, argon protection;

[0093] The second stage: 800℃×4h, vacuum degree ≤1×10 -2 Pa.

[0094] 7. The final product properties are as follows: purity: 99.990%, hydrogen content: 4.8ppm, oxygen content: 47ppm, grain aspect ratio: 15:1, room temperature tensile strength: 795MPa.

[0095] Example 3:

[0096] 1. Raw material pretreatment: Use molybdenum ingots with a purity of ≥99.98% (hydrogen content ≤0.0003%, oxygen content ≤0.004%) as consumable electrodes.

[0097] Pickling treatment: Soak in a mixed acid solution with a volume ratio of HF:HNO3=1:3 for 30 seconds, then rinse with deionized water and vacuum dry.

[0098] 2. Melting system and crucible structure:

[0099] Use a three-layer composite crucible with the following structure:

[0100] Inner layer: W-5%Re alloy, thickness 5mm;

[0101] Middle layer: graphite-20% tantalum carbide composite layer, thickness 15mm, thermal conductivity ≤50W / (m·K);

[0102] Outer layer: copper-based water cooling jacket, cooling water flow ≥5m³ / h.

[0103] Vacuum system ultimate vacuum degree: ≤5×10 -3 Pa, leakage rate <1×10 -4 Pa·m³ / s.

[0104] 3. Melting process parameters: melting current: 25kA; melting voltage: 20.5V, voltage fluctuation ≤±0.5V; melting temperature: 2550℃; constant temperature time: 12min; vacuum maintenance: ≤5×10 -3 Pa.

[0105] 4. Directional solidification control: solidification rate: 8.5mm / min; longitudinal temperature gradient: ≥100℃ / cm.

[0106] 5. Multi-directional forging process: divided into 3 forgings, single deformation: 30%; total deformation: 90%; final forging temperature: 810℃.

[0107] 6. Gradient annealing process:

[0108] The first stage: 1200℃×2h, argon protection;

[0109] The second stage: 800℃×4h, vacuum degree ≤1×10 -2 Pa.

[0110] 7. The final product properties are as follows: Purity: 99.989%, Hydrogen content: 5.1ppm, Oxygen content: 53ppm, Grain aspect ratio: 12:1, Room temperature tensile strength: 780MPa

[0111] The performance test results of the fiber-structured molybdenum rods finally obtained in Examples 1-3 and those obtained by traditional powder metallurgy (Comparative Example 1) and ordinary vacuum melting (Comparative Example 2) are shown in Table 1 below:

[0112] Table 1 is the comparative data of Examples 1-3 and Comparative Examples 1-2: project Example 1 Example 2 Example 3 Comparative Example 1 (Traditional Powder Metallurgy) Comparative Example 2 (Ordinary Vacuum Melting) purity(%) 99.992 99.990 99.989 99.97 99.96 Hydrogen content (ppm) 4.2 4.8 5.1 12.5 15.3 Oxygen content (ppm) 42 47 53 85 105 Grain aspect ratio 18:1 15:1 12:1 1:1 (equiaxed crystal) 3:1 Tensile strength (MPa) 825 795 780 620 650

[0113] From Table 1, we can see that the high-purity molybdenum material prepared by this application has a hydrogen content reduced by more than 60% (compared with the traditional process) and an oxygen content reduced by more than 50% (compared with ordinary vacuum melting), which can meet the strict requirements of high-end manufacturing and military industries for high-purity molybdenum materials.

[0114] In conjunction with the instructions Figure 1 It can be seen that the high-purity molybdenum material prepared by the present application has a deformed structure and has elongated fibers in the longitudinal section. In the longitudinal section, the grains are elongated; in the cross section, the grain size is small (i.e., there is no coarse-grain structure). This special structure makes it adaptable to the processing of special components in the semiconductor and military fields, and can effectively improve the performance and quality of the components.

[0115] The high-purity molybdenum material prepared by the present application has a grain aspect ratio of ≥10:1 and a fiber diameter of ≤5μm; the tensile strength is increased by 25-30%; and the high-temperature creep life is extended by 3-5 times (tested at 1200℃).

[0116] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A vacuum melting system for high-purity molybdenum, comprising an electrode feeding transmission device (1), an electrode rod (2), a vacuum furnace body (3), a consumable molybdenum rod (4), a three-layer composite crucible (5), a water cooling cycle (6) and a vacuum pumping system (7), wherein the electrode feeding transmission device (1) is connected to the electrode rod (2) for controlling the lifting and lowering of the electrode rod (2), the lower end of the electrode rod (2) is connected to a consumable molybdenum rod (4) used as a cathode, the consumable molybdenum rod (4) is suspended inside the vacuum furnace body (3), the three-layer composite crucible (5) is used as an anode and is placed inside the vacuum furnace body (3), the vacuum furnace body (3) is externally connected to the vacuum pumping system (7), and the water cooling cycle (6) is connected to the three-layer composite crucible (5); Its characteristics are: The three-layer composite crucible (5) comprises an inner layer (51), an intermediate layer (52) and an outer layer (53), wherein the inner layer (51) is a W-Re alloy layer, the intermediate layer (52) is a graphite-tantalum carbide composite layer, and the outer layer (53) is a copper-based water-cooling jacket.

2. A vacuum melting method for high-purity molybdenum, characterized in that: The following steps are involved: Step S1: When the vacuum degree is ≤5×10 -3 In an environment of Pa, a three-layer composite crucible (5) is used to melt a consumable molybdenum rod (4); Step S2: controlling the directional solidification rate to 8-12 mm / min and forming a longitudinal temperature gradient ≥ 100°C / cm; Step S3: performing multi-stage plastic deformation on the solidified ingot, with the total deformation amount being ≥90%.

3. The vacuum melting method of high-purity molybdenum according to claim 2, wherein Step S1: Before smelting, the consumable molybdenum rod (4) is pickled and pre-treated by soaking in a mixed acid solution with a volume ratio of HF:HNO3=1:3 for 30 seconds. The purity of the molybdenum ingot in the consumable molybdenum rod (4) is ≥99.98%.

4. The vacuum melting method of high-purity molybdenum according to claim 2 or 3, characterized in that: The smelting parameters of step S1 include: smelting current 25-28 kA; voltage fluctuation ≤±0.5 V; smelting temperature 2550-2600° C., and constant temperature time 10-20 min.

5. The vacuum melting method of high-purity molybdenum according to claim 2, wherein The multi-stage plastic deformation in step S3 is performed in three multi-directional forgings, with a single deformation of 30-35% and a final forging temperature of 800-850°C.

6. The vacuum melting method of high-purity molybdenum according to claim 5, characterized in that: After forging, gradient annealing is performed: first stage: 1200℃×2h; second stage: 800℃×4h.

7. A fiber structure molybdenum material, characterized in that: The molybdenum material is prepared by the vacuum melting method of high-purity molybdenum as described in any one of claims 2-6, has a hydrogen content of ≤5ppm, an oxygen content of ≤50ppm, a grain aspect ratio of ≥10:1, a longitudinal continuous fiber structure is formed inside the material, the fiber diameter is ≤5μm, the room temperature tensile strength is ≥780MPa, and the high-temperature creep life at 1200°C is ≥300 hours.

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