A method for welding a metal vanadium material

Abstract

This invention discloses a welding method for vanadium metal, comprising the following steps: Pre-treatment for impurity removal: the vanadium metal is sequentially subjected to ultrasonic cleaning, plasma polishing, and vacuum drying; Welding: Tungsten inert gas (TIG) welding is employed, using a mixture of 60-80% argon and 20-40% helium by volume as the shielding gas, under conditions of 120-150A current, 18-22V voltage, and a welding speed of 5-8mm / s; Post-treatment: the welded parts are held at 400-500℃ for 1.5-2 hours; then cooled to room temperature in the furnace at a cooling rate of ≤5℃ / min; after non-destructive testing and surface cleaning, the finished product is obtained. The method provided by this invention not only significantly improves the welding quality of vanadium metal, increasing the tensile strength of the joint to over 420MPa, but also maintains high purity; simultaneously, this method is stable and has low equipment costs, making it suitable for industrial mass production.

Description

Technical Field

[0001] This invention relates to the field of metal welding technology, and more specifically to a welding method for vanadium metal materials. Background Technology

[0002] Vanadium metal materials, with their excellent high-temperature resistance, corrosion resistance, and high-temperature mechanical strength, have broad application prospects in high-end industrial fields. However, the welding and processing of vanadium materials has long faced significant technical challenges: vanadium metal is highly chemically reactive, readily reacting with oxygen and water at room temperature to form vanadium oxide; in the high-temperature welding environment (above 1900℃), the oxidation reaction rate accelerates dramatically, easily causing weld embrittlement and a decline in mechanical properties. Simultaneously, vanadium has a relatively low thermal conductivity, only one-third that of iron, making heat dissipation during welding difficult, easily leading to stress concentration and subsequently, welding cracks.

[0003] Currently, conventional welding processes struggle to effectively address these issues. For example, when using argon gas alone for shielded welding, the oxide layer thickness can reach 0.3 μm, with a tensile strength of only 350 MPa, failing to meet industrial requirements. While vacuum welding technology is used abroad to reduce oxidation, the equipment investment is prohibitively high, exceeding 5 million yuan per machine; furthermore, its low production efficiency makes it unsuitable for large-scale mass production. Therefore, the core shortcomings of traditional processes are primarily: inadequate material pretreatment, leaving residual oxidation risks; a single type of shielding gas, failing to simultaneously achieve efficient oxidation protection and heat dissipation; and a lack of targeted stress relief measures, ultimately resulting in poor welding quality and overall poor process economy. Summary of the Invention

[0004] To address the problems of severe weld oxidation, insufficient strength, and high cost in existing methods, a welding method for vanadium metal is provided that balances protective effect, welding strength, and industrial applicability, ensuring that the weld performance meets standards and is suitable for mass production.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A welding method for vanadium metal includes the following steps:

[0007] Impurity removal pretreatment: The vanadium metal material is sequentially subjected to ultrasonic cleaning, plasma polishing and vacuum drying;

[0008] Welding: Tungsten inert gas (TIG) welding is used, with a shielding gas consisting of 60-80% argon and 20-40% helium by volume. Welding of vanadium metal is carried out under the conditions of 120-150A current, 18-22V voltage, and 5-8mm / s welding speed.

[0009] Post-processing: The welded parts are kept at 400-500℃ for 1.5-2 hours; then cooled to room temperature in the furnace at a cooling rate of ≤5℃ / min; after non-destructive testing and surface cleaning, the finished product is obtained.

[0010] In the technical solution provided by this invention, ultrasonic cleaning in the impurity removal pretreatment can remove most of the grease, dust, and particulate matter attached to the metal surface; plasma polishing can efficiently and uniformly remove the surface contamination layer, exposing the pure vanadium matrix; vacuum drying ensures that the surface is absolutely clean and dry before welding, preventing moisture or air residue from causing porosity or secondary contamination during welding. The welding process uses tungsten inert gas (TIG) welding, which has a stable arc, concentrated heat, and no weld slag; an argon-helium mixture is used as the shielding gas. Argon has a high density and good coverage, and as an inert gas, it provides good basic protection, preventing air intrusion. Helium has high thermal conductivity, which can generate a more concentrated high-temperature arc and deeper penetration. Adding helium (20-40%) can improve the weld morphology and increase the penetration depth. Simultaneously, its higher ionization potential helps stabilize the arc. The mixture combines the advantages of both, offering superior protection and thermal efficiency compared to pure argon. The welding parameters (current 120-150A, voltage 18-22V, welding speed 5-8mm / s) are designed to achieve full fusion while avoiding excessive heat input, which could lead to coarse grains in the heat-affected zone and decreased mechanical properties. Post-treatment steps aim to eliminate internal stress and optimize the microstructure. The welding process generates significant thermal and structural stresses. Low-temperature annealing at 400-500℃ effectively relaxes and eliminates most residual welding stresses, preventing workpiece deformation or stress corrosion cracking during use. Subsequent controlled cooling avoids rapid cooling (such as air cooling) that could cause new internal stresses or brittle phase precipitation, ensuring maximum microstructure stability, preventing new stresses due to temperature differences, and achieving more balanced mechanical properties.

[0011] Furthermore, in the impurity removal pretreatment, the process parameters for ultrasonic cleaning are: using anhydrous ethanol as the medium, a frequency of 30-50kHz, and a time of 15-20min.

[0012] Furthermore, in the impurity removal pretreatment, the process parameters for plasma polishing are: power 80-100W, time 3-5min.

[0013] Furthermore, in the impurity removal pretreatment, the process parameters for vacuum drying are: temperature 80-100℃, vacuum degree ≤5Pa, and drying time 2-3h.

[0014] Furthermore, in the welding step, tungsten inert gas welding is used, with a mixture of 65-75% argon and 25-35% helium by volume as the shielding gas, and the metal vanadium material is welded under the conditions of 130-140A current, 19-21V voltage and welding speed of 6-7mm / s.

[0015] Furthermore, in the welding step, the purity of argon and helium in the shielding gas is ≥99.999%, the flow rate of the shielding gas on the front side is 15-20L / min, and the flow rate of the shielding gas on the back side is 8-12L / min.

[0016] Furthermore, in the welding step, the purity of argon and helium in the shielding gas is ≥99.999%, the flow rate of the shielding gas on the front side is 16-19 L / min, and the flow rate of the shielding gas on the back side is 9-11 L / min.

[0017] Furthermore, in the welding step, the tungsten electrode diameter is 2-3 mm and the arc length is 2-4 mm.

[0018] Furthermore, in the post-processing step, the welded parts are held at a temperature of 430-470℃ for 1.5-2 hours; then cooled to room temperature in the furnace at a cooling rate of 2-4℃ / min.

[0019] Furthermore, in the post-processing steps, non-destructive testing is performed using ultrasonic testing, with a defect detection accuracy ≥0.1mm; the tensile strength of the finished weld is ≥420MPa, and the oxide layer thickness is ≤0.08μm.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention is based on the principle of "thorough impurity removal + precise protection + stress control." It thoroughly removes the micron-level oxide layer on the surface of vanadium materials through plasma polishing during pretreatment, combined with vacuum drying to eliminate the sources of oxidation and hydrogen embrittlement. Tungsten inert gas (TIG) welding is performed using an argon-helium mixed shielding gas. Argon provides a stable arc and basic protection, while helium enhances heat conduction efficiency and prevents heat concentration. A low-temperature annealing process further eliminates residual welding stress. This method significantly improves welding quality, increasing the tensile strength of the joint to over 420 MPa, meeting aerospace-grade requirements, while maintaining a purity retention rate of over 99.5%. Furthermore, it utilizes conventional TIG welding equipment, eliminating the need for expensive vacuum equipment, keeping the cost per unit below 500,000 RMB. The welding efficiency reaches 0.5 m / min, with clearly quantified parameters and easily replicable operation, enabling high-quality industrial mass production. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the vanadium metal welding method in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] Example 1

[0025] This embodiment provides a vanadium metal material and its welding method. The process flow diagram of the vanadium metal material welding method is as follows: Figure 1 As shown, the steps are as follows.

[0026] (1) Impurity removal pretreatment

[0027] The 15mm thick industrial-grade vanadium plate raw material was placed in an ultrasonic cleaning tank and cleaned for 18 minutes under 40kHz ultrasound with anhydrous ethanol as the medium to remove surface oil and dust. Then, it was subjected to plasma polishing treatment with a power of 90W for 4 minutes. The high-energy particles of plasma were used to bombard the surface to remove the 0.5-1μm thick oxide layer, so that the surface finish Ra≤0.2μm was achieved. Finally, it was placed in a vacuum drying oven and dried at 90℃ and 5Pa for 2.5 hours to reduce the surface moisture content to ≤0.05% to avoid the generation of hydroxide impurities during welding.

[0028] (2) Welding

[0029] An automatic tungsten inert gas (TIG) welding machine was used, employing a cerium tungsten electrode (2.5mm in diameter). A 99.999% pure argon-helium mixed shielding gas (70% argon, 30% helium by volume) was introduced 10 minutes beforehand. The welding of vanadium metal was performed under conditions of 135A current, 20V voltage, and a welding speed of 6mm / s. During welding, the shielding gas flow rate was 18L / min on the front side and 10L / min on the back side via a dedicated gas hood, ensuring the molten pool and heat-affected zone were under a protective atmosphere throughout the welding process. The arc length was maintained at 3mm during welding to prevent shielding failure due to excessive arc length.

[0030] (3) Post-processing

[0031] Immediately after welding, the weldment is placed in an annealing furnace and held at 450℃ for 2 hours. It is then cooled to room temperature in the furnace at a rate of 4℃ / min to eliminate welding stress through slow atomic diffusion. Subsequently, an ultrasonic testing instrument is used to perform full-section non-destructive testing on the weld to ensure there are no cracks or inclusions ≥0.1mm. Finally, the weld surface is cleaned by wiping with anhydrous ethanol to remove residual welding slag, yielding the finished product.

[0032] Test results: The oxide layer thickness of the weld is 0.06μm, the tensile strength is 435MPa, there are no cracks in the 180° bending test, and the purity retention rate is 99.6%.

[0033] Example 2

[0034] This embodiment provides a vanadium metal material and its welding method, the steps of which are shown below.

[0035] (1) Impurity removal pretreatment

[0036] A 10mm thick industrial-grade vanadium plate raw material was placed in an ultrasonic cleaning tank and cleaned for 20 minutes using anhydrous ethanol as the medium under 30kHz ultrasound. It was then subjected to 5 minutes of plasma polishing with 80W power. Finally, it was vacuum dried for 2 hours in a drying oven at 80℃ and 5Pa.

[0037] (2) Welding

[0038] An automatic tungsten inert gas (TIG) welding machine was used, employing a cerium-tungsten electrode with a diameter of 2mm. A 99.999% pure argon-helium mixed shielding gas mixture (volume percentage composition: 60% argon, 40% helium) was introduced. Welding parameters were set as follows: current 120A, voltage 22V, welding speed 5mm / s, arc length 4mm. The front shielding gas flow rate was 15L / min, and the back shielding gas flow rate was 12L / min.

[0039] (3) Post-processing

[0040] Immediately after welding, the welded parts are placed in an annealing furnace and held at 400℃ for 2 hours, followed by furnace cooling to room temperature at a rate of 5℃ / min. Then, an ultrasonic testing instrument is used to perform full-section non-destructive testing on the weld to ensure there are no cracks or inclusions ≥0.1mm. Finally, the weld surface is cleaned by wiping with anhydrous ethanol to remove residual weld slag, yielding the finished product.

[0041] Test results: The oxide layer thickness of the weld is 0.07μm, the tensile strength is 420MPa, there are no cracks in the 180° bending test, and the purity retention rate is 99.5%.

[0042] Example 3

[0043] This embodiment provides a vanadium metal material and its welding method, the steps of which are shown below.

[0044] (1) Impurity removal pretreatment

[0045] A 20mm thick industrial-grade vanadium plate raw material was placed in an ultrasonic cleaning tank and cleaned for 15 minutes using anhydrous ethanol as the medium under 50kHz ultrasound. It was then subjected to 100W plasma polishing for 3 minutes. Finally, it was vacuum dried for 3 hours in a drying oven at 100℃ and 4Pa.

[0046] (2) Welding

[0047] An automatic tungsten inert gas (TIG) welding machine was used, employing a cerium-tungsten electrode with a diameter of 3mm. A 99.999% pure argon-helium mixed shielding gas mixture (volume percentage composition: 80% argon, 20% helium) was introduced. Welding parameters were set as follows: current 150A, voltage 18V, welding speed 8mm / s, arc length 2mm. The front shielding gas flow rate was 20L / min, and the back shielding gas flow rate was 8L / min.

[0048] (3) Post-processing

[0049] Immediately after welding, the welded parts are placed in an annealing furnace and held at 500℃ for 1.5 hours, followed by furnace cooling to room temperature at a rate of 2℃ / min. Then, an ultrasonic testing instrument is used to perform full-section non-destructive testing on the weld to ensure there are no cracks or inclusions ≥0.1mm. Finally, the weld surface is cleaned by wiping with anhydrous ethanol to remove residual weld slag, yielding the finished product.

[0050] Test results: The oxide layer thickness of the weld is 0.08μm, the tensile strength is 428MPa, there are no cracks in the 180° bending test, and the purity retention rate is 99.6%.

[0051] Comparative Example 1

[0052] This comparative example provides a vanadium metal material and its welding method, the steps of which are shown below.

[0053] (1) Impurity removal pretreatment

[0054] The surface of the 15mm thick industrial-grade vanadium plate raw material was wiped with anhydrous ethanol, and then placed in a vacuum drying oven and dried at 90℃ and 5Pa for 2.5h to reduce the surface moisture content to ≤0.05% and avoid the generation of hydroxide impurities during welding.

[0055] (2) Welding

[0056] An automatic tungsten inert gas (TIG) welding machine was used, employing a cerium tungsten electrode (2.5mm in diameter). A 99.999% pure argon-helium mixed shielding gas (70% argon, 30% helium by volume) was introduced 10 minutes beforehand. The welding of vanadium metal was performed under conditions of 135A current, 20V voltage, and a welding speed of 6mm / s. During welding, the shielding gas flow rate was 18L / min on the front side and 10L / min on the back side via a dedicated gas hood, ensuring the molten pool and heat-affected zone were under a protective atmosphere throughout the welding process. The arc length was maintained at 3mm during welding to prevent shielding failure due to excessive arc length.

[0057] (3) Post-processing

[0058] After welding, the welded parts are air-cooled; finally, the weld surface is cleaned by wiping with anhydrous ethanol to remove residual welding slag and obtain the finished product.

[0059] Test results: The weld surface was severely oxidized, with an oxide layer thickness of 0.21 μm, a tensile strength of 339 MPa, and cracks appeared in the bending test.

[0060] Comparative Example 2

[0061] This comparative example provides a vanadium metal material and its welding method.

[0062] The difference between this comparative example and Example 1 is that an automatic tungsten inert gas (TIG) welding machine is used in the welding process, and a cerium tungsten electrode (2.5 mm in diameter) is selected. 99.999% pure argon gas is introduced 10 minutes in advance for protection.

[0063] Test results: The oxide layer thickness of the weld is 0.15μm, the tensile strength is 390MPa, and cracks appear in the 180° bending test.

[0064] Comparative Example 3

[0065] This comparative example provides a vanadium metal material and its welding method.

[0066] The difference between this comparative example and Example 1 is as follows: In the welding process, an automatic tungsten inert gas (TIG) welding machine was used, with a cerium tungsten electrode (2.5 mm in diameter). A 99.999% pure argon-helium mixed shielding gas (volume ratio 7:3) was introduced 10 minutes in advance. The vanadium metal was welded under the conditions of 110 A current, 24 V voltage, and a welding speed of 9 mm / s. During welding, the shielding gas flow rate on the front side was 22 L / min, and the flow rate on the back side was 5 L / min through a dedicated gas hood, ensuring that the molten pool and heat-affected zone were under a protective atmosphere throughout the process. The arc length was kept stable at 3 mm during welding to avoid shielding failure due to excessive arc length.

[0067] Test results: The oxide layer thickness of the weld is 0.10 μm, the tensile strength is 401 MPa, there are no cracks in the 180° bending test, and the purity retention rate is 99.4%.

[0068] Performance testing

[0069] (1) Method for detecting the thickness of the oxide layer of the weld: Scanning electron microscopy (SEM) + energy dispersive spectroscopy (EDS).

[0070] (2) Method for testing tensile strength: Refer to the transverse tensile test (standard method), cut from the weld seam perpendicular to the weld seam of the welded test plate, with the weld seam located in the middle of the parallel section of the specimen. Equipment: Universal testing machine (accuracy grade 1); speed: 1-2 mm / min (room temperature 23±5℃); result: tensile strength Rm = maximum breaking force Fm / original cross-sectional area A0.

[0071] (3) Bending test method: Refer to the transverse face bend / back bend / side bend (standard method), equipment: three-point bending test machine; speed: 1-2mm / min (room temperature 23±5℃); judgment: bending to 180°, no cracks ≥0.5mm on the tensile surface is qualified; face bend: the front of the weld is under tension; back bend: the root of the weld is under tension; side bend: evaluate the transverse plasticity of the weld.

[0072] (4) Method for detecting purity retention rate: Inductively coupled plasma mass spectrometry (ICP-MS, trace impurities) is used for detection. The process is: acid digestion → plasma ionization → mass spectrometry detection.

[0073] The test results are shown in Table 1.

[0074] Table 1. Performance test results of vanadium metal materials in the examples and comparative examples.

[0075]

[0076] As shown in the table above, the welding method for vanadium materials provided by this invention employs precise impurity removal, welding with a strictly proportioned argon-helium mixed protective gas, and precise low-temperature annealing treatment. This effectively overcomes the industry challenges of easy oxidation and embrittlement and thermal stress cracking in vanadium welding. This method offers stable and controllable processes, yields welds with excellent mechanical properties, and eliminates the need for expensive vacuum welding equipment, making it perfectly suited for the mass production needs of high-end vanadium components in aerospace, nuclear industry, and other fields.

[0077] The foregoing descriptions have outlined some exemplary embodiments of the present invention. It is understood that these embodiments are merely illustrative and do not constitute a limitation on the scope of protection of the present invention. Features in these embodiments can be rearranged in suitable ways, and the resulting solutions remain within the scope of protection claimed by the present invention. All other embodiments obtained by those skilled in the art based on the foregoing embodiments without inventive effort, i.e., all modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A welding method for vanadium metal materials, characterized in that, Includes the following steps: Impurity removal pretreatment: The vanadium metal material is sequentially subjected to ultrasonic cleaning, plasma polishing and vacuum drying; Welding: Tungsten inert gas (TIG) welding is used, with a shielding gas consisting of 60-80% argon and 20-40% helium by volume. Welding of vanadium metal is carried out under the conditions of 120-150A current, 18-22V voltage, and 5-8mm / s welding speed. Post-processing: The welded parts are kept at 400-500℃ for 1.5-2 hours; then cooled to room temperature in the furnace at a cooling rate of ≤5℃ / min; after non-destructive testing and surface cleaning, the finished product is obtained.

2. The welding method for vanadium metal materials according to claim 1, characterized in that, In the impurity removal pretreatment, the ultrasonic cleaning process parameters are: anhydrous ethanol as the medium, frequency 30-50kHz, time 15-20min.

3. The welding method for vanadium metal materials according to claim 1, characterized in that, In the impurity removal pretreatment, the process parameters for plasma polishing are: power 80-100W, time 3-5min.

4. The welding method for vanadium metal materials according to claim 1, characterized in that, In the impurity removal pretreatment, the process parameters for vacuum drying are: temperature 80-100℃, vacuum degree ≤5Pa, and drying time 2-3h.

5. The welding method for vanadium metal materials according to claim 1, characterized in that, In the welding step, tungsten inert gas (TIG) welding is used, with a mixture of 65-75% argon and 25-35% helium by volume as the shielding gas. The welding of vanadium metal is carried out under the conditions of 130-140A current, 19-21V voltage, and 6-7mm / s welding speed.

6. The welding method for vanadium metal materials according to claim 1, characterized in that, In the welding process, the purity of argon and helium in the shielding gas is ≥99.999%, the flow rate of the shielding gas on the front side is 15-20 L / min, and the flow rate of the shielding gas on the back side is 8-12 L / min.

7. The welding method for vanadium metal materials according to claim 1, characterized in that, In the welding process, the tungsten electrode diameter is 2-3 mm and the arc length is 2-4 mm.

8. The welding method for vanadium metal materials according to claim 1, characterized in that, In the post-processing step, the welded parts are held at 430-470℃ for 1.5-2 hours; then cooled to room temperature in the furnace at a cooling rate of 2-4℃ / min.

9. The welding method for vanadium metal materials according to claim 1, characterized in that, In the post-processing step, non-destructive testing is performed using ultrasonic testing, with a defect detection accuracy of ≥0.1mm.

10. A vanadium metal welded product, characterized in that, The vanadium metal weld obtained by welding using the method described in any one of claims 1-9 has a weld tensile strength ≥420MPa and an oxide layer thickness ≤0.08μm.

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