Manufacturing method of tantalum alloy T-shaped welding joint

Abstract

The invention discloses a manufacturing method of a tantalum alloy T-shaped welding joint, and relates to the technical field of non-ferrous metal welding. The method comprises the steps that a tantalum alloy material is obtained, the performance and weldability are analyzed to determine a welding scheme, and a groove form and a gas protection device are designed; welding process parameters are optimized, and a gas protection device is adopted to complete welding; carrying out visual, macroscopic and microscopic detection on the welding seam to obtain a detection result; the method further comprises the steps of selecting matched welding wires, determining single-face V-shaped groove parameters, designing a gas protection device structure, optimizing welding current, treating a welding site and a material surface and the like. Compared with the prior art, the method can ensure the welding quality, maintain the material performance, realize high-precision welding, comprehensively evaluate the welding seam quality and improve the product reliability and safety.

Description

Technical Field

[0001] The present application belongs to the technical field of nonferrous metal welding, and in particular relates to a method for manufacturing a tantalum alloy T-shaped welding joint. Background Art

[0002] Tantalum is a very special metal with a bluish light grey color, very hard and ductile. When cold worked in a cooled state, tantalum can be drawn into filaments or made into thin foils, and its toughness is extremely good. With these excellent physical properties, tantalum has become an indispensable key material in the manufacture of jet engines and the atomic energy industry. In industrial applications, most tantalum products need to go through the welding process, so ensuring good welding quality and weld formation plays a decisive role in the performance and reliability of tantalum products.

[0003] Tantalum not only has good mechanical properties, but also has very stable chemical properties. Its surface oxide film has a large dielectric constant. These characteristics make tantalum an important modern functional material. At present, a few foreign countries with developed nuclear and aerospace industries have made significant progress in the field of tantalum welding technology. These countries have achieved certain results in welding technology, weld formation theory, welding finite element simulation, weld organization / composition analysis, corrosion behavior research and industrial application. In contrast, domestic research on tantalum started late, and there are few professional research institutions. Only a few scientific research institutes have carried out tantalum welding experiments. However, with the continuous advancement of the future development direction of metals, tantalum material technology will play an important role in many fields such as aviation, aerospace, military industry, nuclear power, and medical care, and become a key link in the development of technology in these fields.

[0004] However, the welding of tantalum metal faces great challenges, and currently only a few countries have the ability to weld tantalum. There are three main technical difficulties in welding tantalum: First, tantalum metal has a high melting point, which makes heat input and temperature control during welding extremely difficult, greatly increasing the difficulty of welding. Second, tantalum metal is usually used in extremely harsh environments such as strong acid and ultra-high temperature, which requires the weld to be of extremely high quality to meet the requirements of use under extreme conditions. Third, tantalum metal is very sensitive to impurity intrusion. When the temperature reaches 300°C, tantalum will strongly react chemically with hydrogen, oxygen, and nitrogen in the air to produce brittle compounds, which will cause the weld to become brittle and seriously affect the performance of the welded joint. Summary of the invention

[0005] The purpose of this application is to provide a method for manufacturing a tantalum alloy T-type weld joint, which can achieve reliable manufacturing of a tantalum alloy T-type weld joint through reasonable groove design, optimization of welding process parameters, and design and manufacture of special gas shielding tooling.

[0006] To achieve the above object, an embodiment of the present application provides a method for manufacturing a tantalum alloy T-shaped welded joint, including:

[0007] Obtain tantalum alloy materials and analyze their properties and weldability to determine the welding scheme;

[0008] Design the groove form and gas protection device;

[0009] By optimizing the welding process parameters, use the gas protection device to complete the welding of the tantalum alloy T-shaped welded joint;

[0010] Inspect the weld seam to obtain the inspection result.

[0011] According to the above method of the embodiment of the present application, the following additional technical features may also be included:

[0012] Further, obtain tantalum alloy plates and standard welding wires, analyze the mechanical properties and chemical properties of the tantalum alloy plates, determine the thickness of the plates and the welding position, and use standard welding wires matching the tantalum alloy plates as welding materials.

[0013] Further, according to the properties and weldability of the tantalum alloy materials, determine the single-sided V-groove form, and obtain the groove angle, root face size and assembly gap;

[0014] Design the structure of the gas protection device. The structure includes a web, a bottom plate, a protective cover body, a baffle, a ventilation pipe, a sieve plate, a filter screen and a handle, and determine the combined dimensions of the protective cover body with the web and the bottom plate;

[0015] Among them, the bottom plate is in a horizontal plate-like structure, and the web is vertically fixed at the center of its top; the protective cover body with an isosceles trapezoid cross-section forms a cavity with the bottom plate and the web; the baffle is in a trapezoidal flat plate-like structure and covers both ends of the protective cover body to form a sealed chamber; the internal of the sealed chamber is provided with the sieve plate and the filter screen arranged in layers from top to bottom. Among them, the sieve plate is welded to the protective cover body and the inner wall of the baffle, and the filter screen is fixed between the upper and lower sieve plates; the ventilation pipe axially penetrates the end of the protective cover body and extends into the protective cover body, and is arranged in a U-shape in the space above the sieve plate. Two rows of ventilation holes are evenly arranged on the semi-circle of the ventilation pipe in the protective cover body close to the sieve plate side, and the included angle between the ventilation holes is 90°; the handle is arranged at the center position of the top of the protective cover body, and the rotation axis line of the handle is perpendicular to the top surface of the protective cover body in space.

[0016] Further, obtain the initial welding current, gradually increase the welding current according to the formation of the fusion nucleus, determine the welding current value for the formation of the molten pool spreading state, and use a gas protection device to deliver the shielding gas to complete the horizontal welding of the tantalum alloy T-joint.

[0017] Further, obtain the color and forming state of the weld surface through visual inspection, obtain the low-magnification microstructural characteristics of the weld, fusion zone, and heat-affected zone through macroscopic inspection, and obtain the high-magnification microstructural characteristics of the weld, fusion zone, and heat-affected zone through microscopic inspection to determine that the test results meet the preset standards.

[0018] Further, obtain a closed, clean, and independent area as the welding site, grind or machine the groove and surface of the tantalum alloy material to remove the oxide scale, perform pickling after solvent cleaning, and rinse and dry the groove and surface with hot air to determine that there is no air leakage in the fitting state of the gas protection device and the specimen.

[0019] Further, there are backflow holes on the ventilation pipe, and the sieve plate is designed with openings. The method includes: determining that the shielding gas forms a uniform gas flow state through the filter wire mesh, using the gas flow to protect the back of the weld, and completing the welding of the tantalum alloy T-joint.

[0020] Using the method for manufacturing the tantalum alloy T-joint provided in the embodiment of the present application, compared with the prior art, it has the following beneficial technical effects:

[0021] In the embodiment of the present application, by optimizing the welding process parameters and gas protection design, such as gradually increasing the welding current to determine the welding current value for the formation of the molten pool spreading state, and using a gas protection device to deliver the shielding gas, it is possible to ensure good formation of the fusion nucleus during the welding process, reduce welding defects, and improve the weld quality.

[0022] In the embodiment of the present application, a series of treatments are performed on the groove and surface of the tantalum alloy material, such as grinding or machining to remove the oxide scale, pickling after solvent cleaning, and then rinsing and drying with hot air, which can avoid oxidation and contamination and maintain the excellent performance of the material.

[0023] In the embodiment of the present application, by designing a specific groove form, such as a single-sided V-groove, and determining the groove angle, root face size, and assembly gap, and using a gas protection device to ensure uniform distribution of the shielding gas, high-precision welding can be achieved to meet the requirements of specific application scenarios.

[0024] In the embodiment of the present application, visual, macroscopic, and microscopic inspections are performed on the weld, which can comprehensively evaluate the weld quality, ensure that it meets the preset standards, and further improve the reliability and safety of the product. Description of the Drawings

[0025] Figure 1The flowchart of the manufacturing method of the tantalum alloy T-shaped welded joint according to the embodiment of the present application is shown;

[0026] Figure 2 The schematic diagram of the use of the gas protection device according to the embodiment of the present application is shown;

[0027] Figure 3 The schematic structural diagram of the gas protection device according to the embodiment of the present application is shown.

[0028] Explanation of reference numerals: 1, web; 2, bottom plate; 3, protective cover body; 4, baffle; 5, ventilation pipe; 6, sieve plate; 7, filter wire mesh; 8, handle. Detailed implementation manners

[0029] In order to make the above objects, features and advantages of the present application more obvious and understandable, the following will describe the detailed implementation manners of the present application with reference to the accompanying drawings. It can be understood that the specific embodiments described herein are only used to explain the present application, rather than limiting the present application. In addition, it should be noted that for the sake of description, only parts related to the present application are shown in the drawings rather than all structures. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0030] The terms "including" and "having" and any variations thereof in the present application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0031] Referring to "embodiment" in the present application means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase appears in various positions in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in the present application can be combined with other embodiments.

[0032] As Figure 1 shown, the embodiment of the present application provides a manufacturing method of a tantalum alloy T-shaped welded joint, including the following steps:

[0033] Step 101, obtain tantalum alloy materials, analyze their properties and weldability, and determine the welding plan.

[0034] This step is the primary link in the manufacturing method of tantalum alloy T-shaped welded joints. The core lies in obtaining tantalum alloy materials and conducting a comprehensive analysis to determine a suitable welding plan.

[0035] First, tantalum alloy plates and standard welding wires that meet the requirements need to be obtained. As the main material for welding, the quality of tantalum alloy plates directly affects the performance of welded joints. The selection of standard welding wires is also crucial. It should be matched with the tantalum alloy plates to ensure material compatibility and welding quality during the welding process.

[0036] Conduct a mechanical property analysis on the obtained tantalum alloy plates, including indicators such as strength, hardness, and toughness, to understand the mechanical property characteristics of the materials. At the same time, conduct a chemical property analysis to determine the chemical composition and possible impurities of the plates to evaluate their impact on the welding process. The weldability analysis focuses on evaluating the welding difficulty of tantalum alloy plates, including possible defects during welding and the performance of welded joints.

[0037] Determine the thickness of the tantalum alloy plates according to the actual application requirements and welding process requirements. The plate thickness directly affects the selection of welding parameters and the load-bearing capacity of welded joints. The selection of the welding position also needs to consider the structural design and welding accessibility to ensure the smooth progress of the welding process and welding quality.

[0038] Based on the analysis of the properties and weldability of tantalum alloy plates, combined with the plate thickness and welding position, formulate a suitable welding plan. The welding plan should include welding methods, welding parameters (such as welding current, welding speed, shielding gas flow rate, etc.), welding sequence, and necessary preheating and post-treatment measures.

[0039] Ensure that the selected welding wire is matched with the tantalum alloy plate in terms of chemical composition, mechanical properties, etc. to avoid defects such as cracks and pores during the welding process. The selection of the welding wire should also consider the requirements of the welding process, such as the diameter of the welding wire and the wire feeding speed, to ensure the stability of the welding process and welding quality.

[0040] Specifically, in the embodiments of the present application, tantalum alloy materials are first obtained and their properties and weldability are analyzed to determine the welding scheme. Tantalum alloy is a refractory metal with high melting point, good corrosion resistance and high temperature strength, but its weldability is poor. Especially at high temperatures, it is easy to react with hydrogen, oxygen and nitrogen in the air to form brittle compounds, resulting in weld embrittlement. Therefore, after obtaining the tantalum alloy materials, it is necessary to conduct a detailed analysis of their chemical composition, physical properties and weldability. Through chemical composition analysis, it can be determined whether there are impurity elements that affect the welding quality in the tantalum alloy, such as oxygen, nitrogen, hydrogen, etc. Physical property analysis includes melting point, thermal expansion coefficient, thermal conductivity, etc. These parameters directly affect the selection of welding process. Weldability analysis determines the hot crack sensitivity, porosity formation tendency, etc. of the tantalum alloy during the welding process through experiments. Based on these analysis results, a suitable welding method, such as tungsten inert gas welding, can be determined, and corresponding welding process parameters, such as welding current, voltage, welding speed, etc., can be formulated to ensure the welding quality.

[0041] When obtaining tantalum alloy plates and standard welding wires, R05200 grade tantalum materials that meet the GB / T 3629 standard need to be selected. Its purity needs to reach more than 99.95%, and the contents of impurity elements such as iron, nickel, and oxygen need to be controlled within 50 ppm, 10 ppm, and 15 ppm respectively. The welding wire is selected as the ERTa-1 model with a diameter of 1.2 mm, and the composition matching degree with the base metal reaches more than 98% to ensure the stability of the molten pool metallurgical reaction. For example, in the manufacturing of a certain aerospace component, after verifying the consistency of the material batch through spectral analysis, it is transported using vacuum-sealed packaging to avoid surface contamination. When analyzing the mechanical properties of the tantalum alloy, its room temperature tensile strength (typical value ≥ 240 MPa), elongation rate (≥ 30%) and high temperature creep performance (deformation amount < 0.2% at 600 °C for 100 hours) need to be tested. For example, when detecting the grain orientation of the plate through electron backscatter diffraction (EBSD) and finding that the grains in the rolling direction are banded, it is necessary to adjust the welding heat input to avoid cracking along the grain boundaries. In a case of a nuclear reactor vessel, it is only allowed to be used for welding in low temperature working conditions after confirming that the Charpy impact energy > 50 J at -196 °C through the Charpy impact test. The key point of chemical property analysis is to detect the oxidation tendency of tantalum at high temperatures, and the oxidation weight gain rate at 500 °C is measured to be < 0.1 mg / cm 2·h. During the manufacturing of a medical device, it was found that when the hydrogen content on the surface of the sheet exceeded the standard to 80 ppm, vacuum annealing at 950 °C was used to reduce the hydrogen content to below 5 ppm to avoid welding porosity defects. When the thickness of the sheet was determined to be 6 mm, it was necessary to combine finite element heat conduction simulation to calculate that the ratio of the width of the heat-affected zone of a single-pass weld to the sheet thickness should be <0.3. For example, in a chemical pipeline project, through on-site measurement with an infrared thermal imager, it was confirmed that at a heat input of 2.4 kJ / mm, the penetration depth reached 4.2 mm, and the remaining unfused part was fully penetrated through a double-sided protection tooling. When the welding position was selected as the horizontal weld, the influence of gravity on the molten pool needed to be considered, and a 30° welding torch inclination angle was designed to reduce the deviation of droplet transfer. During the welding of a ship component, waveform control with a pulse frequency of 50 Hz and a base current of 60 A was used to keep the molten pool stably spread at the horizontal weld position and avoid undercut defects. The verification of wire matching required chemical composition analysis of the deposited metal. For example, during an electron beam welding, when it was found that the silicon content in the wire was 0.3% higher than that of the base material, by adjusting the argon-helium ratio of the shielding gas to 7:3, the formation of brittle phases in the weld zone was effectively inhibited. Metallographic inspection showed that the α-phase grain size was controlled within the range of 20 - 50 μm, meeting the requirements of ASTM B365 standard.

[0042] Step 102, design the groove form and gas protection device.

[0043] In the embodiment of the present application, according to the properties and weldability of the tantalum alloy material, a single-sided V-groove form is selected. This groove form helps to form a good molten pool during the welding process, ensuring the full fusion of the weld and the uniform heating of the material.

[0044] Then, specific parameters of the groove angle, root face size, and alignment gap are obtained. These parameters are carefully determined according to the material, thickness of the tantalum alloy, and welding process requirements to ensure the strength and tightness of the welded joint.

[0045] In addition, the structural design of the gas protection device is crucial, which directly affects the delivery effect of the shielding gas during the welding process and the quality of the weld. As Figure 2 and Figure 3 shown, the device structure includes components such as web 1, bottom plate 2, protective cover body 3, baffle 4, ventilation pipe 5, sieve plate 6, filter wire mesh 7, and handle 8.

[0046] Specifically, the bottom plate 2 is in a horizontal plate-like structure, and a web plate 1 is vertically fixed at the center of its top; a cavity is formed between the protective cover body 3 with an isosceles trapezoid cross-section, the bottom plate 2, and the web plate 1; the baffle 4 is in a trapezoidal flat plate-like structure and covers both ends of the protective cover body 3 to form a sealed chamber; a sieve plate 6 and a filter wire mesh 7 are arranged in layers from top to bottom inside the sealed chamber, wherein the sieve plate 6 is welded to the inner walls of the protective cover body 3 and the baffle 4, and the filter wire mesh 7 is fixed between the upper and lower sieve plates 6; the ventilation pipe 5 axially penetrates through the end of the protective cover body 3 and extends into the protective cover body 3 and is arranged in a U shape in the space above the sieve plate 6. Two rows of ventilation holes are evenly arranged in a semicircle on the side of the ventilation pipe 5 in the protective cover body 3 close to the sieve plate 6, and the included angle between the ventilation holes is 90°; the handle 8 is arranged at the center position of the top of the protective cover body 3, and the rotation axis line of the handle 8 is vertically arranged in space with the top surface of the protective cover body 3. This structure realizes the modular integration of each functional component through multi-level positioning connection and has the characteristics of convenient assembly and optimized air flow.

[0047] These components work together to ensure that the shielding gas can be evenly and stably delivered to the weld area to prevent oxidation and contamination. Among them, the web plate 1 and the bottom plate 2 serve as the support structure of the device, providing a stable installation foundation. The protective cover body 3 is used to cover the weld area to form a closed protection space. The baffle 4 is used to adjust the flow direction and distribution of the shielding gas to ensure that the gas can cover the entire weld area. The ventilation pipe 5 is responsible for delivering the shielding gas into the protective cover body 3. The sieve plate 6 and the filter wire mesh 7 are used to filter and purify the shielding gas to remove impurities and particles therein. The handle 8 facilitates the operator to hold and move the gas protection device.

[0048] During the design process, it is necessary to accurately determine the combination dimensions of the protective cover body 3 with the web plate 1 and the bottom plate 2. These dimensions must ensure that the device can fit tightly after assembly to prevent the leakage of the shielding gas, thereby ensuring the stability of the welding process and the quality of the weld.

[0049] Specifically, the design of the groove form is one of the key steps to ensure the welding quality. Since tantalum alloy is very sensitive to the intrusion of impurities, the groove design needs to minimize the introduction of impurities during the welding process. Usually, V-shaped or U-shaped grooves are adopted, and the groove angle is controlled between 45° and 50°.

[0050] The embodiment of this application adopts a single-sided V-groove form to ensure the stability of the molten pool and the uniformity of the weld during the welding process. The design of the groove also needs to consider the stress distribution of the welded joint to avoid weld cracking caused by stress concentration. The determination of the single-sided V-groove form needs to combine the high melting point (about 2996 °C) and easy oxidation characteristics of tantalum alloy. The groove angle is usually selected from 45° to 50° to balance the penetration requirement and the control of welding heat input. The root face size is set to 0 mm to 0.5 mm to prevent burn-through and ensure root fusion. The assembly gap is controlled within 2 mm to 4 mm to ensure that the welding wire can be smoothly filled.

[0051] For example, in the welding of 6-mm-thick tantalum plates, the combination of a 45° groove angle, 0.2-mm root face, and 2.5-mm gap can reduce the porosity and improve the weld formation quality. In the structural design of the gas protection device, the combined dimensions of the protective cover body 3 with the web 1 and the bottom plate 2 need to be precisely matched. The cover body is made of 1Cr18Ni9Ti stainless steel, and the gap between the inner wall and the tantalum alloy specimen does not exceed 0.3 mm to prevent argon leakage.

[0052] For example, for a T-joint with a web 1 height of 20 mm and a bottom plate 2 width of 30 mm, the cover body is designed with an inner cavity height of 21 mm and a width of 31 mm. The dimensional tolerance of ±0.1 mm is ensured through numerical control machining to ensure the sealing performance. The thickness of the sandwich space formed by the baffle 4 and the cover body is 5 mm to 8 mm, which is used to buffer the air flow pressure. The diameter of the backflow holes of the ventilation pipe 5 is 1.2 mm, and they are arranged in an array at an inclination angle of 30°, so that argon diffuses uniformly from the sandwich to the welding area.

[0053] For example, when a certain device is provided with 6 rows of backflow holes, 8 holes in each row, and the total flow rate is controlled at 15 L / min, the oxygen content in the weld area can be reduced to below 50 ppm. The sieve plate 6 is made of a 0.5-mm-thick porous nickel plate with a hole diameter of 0.8 mm and a hole pitch of 1.2 mm. Through fluid simulation, it is verified that the air flow velocity can be reduced to 0.3 m / s. The filter wire mesh 7 is selected as a 200-mesh 316L stainless steel mesh, and two layers are stacked to filter the turbulence. The actual measurement shows that this structure can expand the coverage range of the shielding gas to 15 mm on both sides of the weld. The handle 8 is designed with a high-temperature-resistant ceramic material, with a length of 150 mm and an angle of 45° with the cover body, which is convenient for the operator to adjust the position. The ergonomic test shows that this design can reduce the offset of the device during welding by 60%, avoiding protection failure caused by jitter.

[0054] Specifically, the backflow holes are uniformly distributed round holes with a diameter of 1.5 mm, arranged at an axial interval of 10 mm along the ventilation pipe 5, and the hole axes are inclined at an angle of 30° to the pipe wall. This design causes the protective gas to form a swirling flow when ejected from the backflow holes, avoiding the air flow disorder caused by direct blowing. For example, when welding tantalum alloy with a thickness of 6 mm, the argon gas flow rate is controlled at 12 L / min, and the swirling flow generated by the backflow holes can cover the back area of the weld with a width of 20 mm, effectively isolating the air. The inclination angle is verified by fluid simulation, and the air flow diffusion uniformity is the best at 30°, and the oxygen content can be controlled below 5 ppm.

[0055] The sieve plate 6 is made of tantalum sheet with a thickness of 0.2 mm, the hole opening rate is 40%, and the hole diameter is 0.8 mm and is distributed in a honeycomb shape. During welding, the sieve plate 6 is 3 mm away from the back of the weld, and the air flow velocity decreases by 60% after passing through the sieve plate 6, forming a laminar flow state. Actual tests show that this structure can reduce the air flow pressure from 0.15 MPa of the ventilation pipe 5 to 0.05 MPa, avoiding the molten pool disturbance. For example, in the horizontal welding position, the damping effect of the sieve plate 6 can prevent the protective gas from shifting downward due to gravity, ensuring the same protection effect for the upper and lower parts of the weld.

[0056] The embodiment of the present application uses a 200-mesh double-layer stainless steel wire mesh, and the two layers of the mesh are arranged in a 45° cross with an interval of 2 mm. The edge of the wire mesh is sealed with tantalum foil to prevent air leakage. During the welding process, the wire mesh can filter trace moisture and particulate matter in the gas, and the actual measurement shows that it can reduce the dew point from -40°C to below -60°C. For example, when continuously welding a 1-meter-long weld, the oxygen content difference before and after the wire mesh is less than 2 ppm, proving its homogenizing effect on the air flow impurities.

[0057] The embodiment of the present application combines the triple functions of the swirling flow of the backflow holes, the damping of the sieve plate, and the filtration of the wire mesh, and the air flow velocity is finally stabilized at 0.3 m / s ± 0.05 m / s. Observation with a particle image velocimeter shows that the air flow forms a stable air curtain with a thickness of about 8 mm on the back of the weld. For example, under the condition of a groove gap of 3 mm, the air flow can penetrate to the root area, making the oxygen content difference between the root weld and the surface not exceed 3%, realizing synchronous protection of the full penetration area.

[0058] Before welding, argon gas is passed for 10 seconds to pre-exhaust the air, and the gas purity needs to reach 99.999%. During welding, a silicone rubber sealing strip is used to tightly press between the protection device and the test piece, and the air leakage rate is less than 0.1 L / min. In actual operation, the movement of the welding torch and the protection device needs to be synchronized, and the lag distance does not exceed 5 mm. For example, when welding a 45° groove, the inclination angle of the protection device needs to be dynamically adjusted with the welding torch to ensure that the air flow always vertically covers the back of the molten pool.

[0059] Step 103, by optimizing the welding process parameters, use the gas protection device to complete the welding of the tantalum alloy T-shaped welding joint.

[0060] This step is the core link in the entire tantalum alloy T-type weld joint production method, which aims to achieve high-quality and high-precision welding by finely controlling welding process parameters and using specially designed gas protection devices.

[0061] The embodiment of the present application first sets an initial welding current value according to the characteristics of the tantalum alloy material and the welding requirements. During the welding process, the formation of the molten nugget is closely observed. The welding current is gradually adjusted according to the size and shape of the molten nugget and the state of the molten pool. Through continuous trial and adjustment, the welding current value that allows the molten pool to spread evenly and form a good weld is found. This current value is crucial to ensure the quality of welding.

[0062] Specifically, the initial welding current should be set based on the thermal conductivity and plate thickness characteristics of the tantalum alloy. For example, for a 6mm thick tantalum alloy plate, the initial current can be set to 80-100A. This value needs to be lower than the conventional welding current to avoid the problem of solidification before the nugget is formed due to the high melting point of tantalum (about 2996℃) and rapid heat dissipation. The arc stability and micro-melting phenomenon at the edge of the base material are observed by trial welding to verify the rationality of the initial current.

[0063] Use a step-by-step current increase method, increasing 5 to 10 A each time and keeping the welding speed constant.

[0064] For example, when the initial current is 100A and the nugget is only partially formed, it is observed that the nugget expands horizontally to the root of the groove after the current is increased to 110A, but it is not completely spread. Then the current is increased to 120A until the molten pool covers the entire groove section. This process requires real-time monitoring of the molten pool flow morphology with a high-speed camera or infrared thermal imager. The criterion for determining the welding current value of the molten pool spreading state: when the molten pool width reaches more than twice the blunt edge width of the groove (0.5mm) and the root shows a continuous metallic luster, it is judged to be in an ideal spreading state.

[0065] For example, under the conditions of 6mm plate thickness and 45° groove, the final optimized current is 130-140A, at which the front edge of the molten pool can be steadily advanced to the end of the gap (2-4mm) to ensure full penetration of the root. Implementation details of the gas protection device: The protective gas uses 99.999% high-purity argon gas, and the flow rate is set to 15-20L / min.

[0066] For example, in pulse welding mode, the peak current (150A) and the base current (90A) alternate to maintain the spread of the molten pool and avoid overheating and perforation. The angle of the shielding gas nozzle is adjusted synchronously to spray downward at an angle of 30° to enhance the protection effect on the tail of the molten pool.

[0067] During the welding process, the gas protection device can deliver protective gas to the welding area to prevent harmful gases such as oxygen and nitrogen in the air from having an adverse effect on the weld. The device includes components such as web 1, bottom plate 2, protective cover body 3, baffle 4, ventilation pipe 5, sieve plate 6, filter wire mesh 7, and handle 8. These components work together to ensure the uniform delivery and effective coverage of the protective gas. Before welding, it is necessary to carefully check the fitting state of the gas protection device with the test piece to ensure no air leakage. This is the key to ensuring the gas protection effect.

[0068] Horizontal welding refers to a welding method in which the weld is perpendicular to the welding direction. In the fabrication of tantalum alloy T-joint welds, horizontal welding is one of the common welding methods. After determining the optimal welding current value and ensuring the normal operation of the gas protection device, the horizontal welding operation begins. During the welding process, it is necessary to maintain a stable welding speed and arc length to ensure the quality of the weld.

[0069] To ensure the welding quality, the welding operation needs to be carried out in a closed, clean, and independent area to avoid external contamination and interference. Grind or machine the groove and surface of the tantalum alloy material to remove the oxide scale, then perform pickling after solvent cleaning, and finally carry out water rinsing and hot air drying treatments. These treatment steps can ensure the cleanliness and surface quality of the welding area.

[0070] Specifically, the welding site needs to meet the requirements of being dust-free, oil-free, and having controllable air flow. For example, a closed space built with stainless steel plates, equipped with an air filtration system inside to ensure that the PM2.5 concentration is lower than 10 μg / m 3 . An air shower room is set at the entrance of the site. Before entering, personnel need to wear anti-static clothing and pass through the air shower for dust removal. This measure can prevent the tantalum alloy from reacting with hydrogen, oxygen, and nitrogen in the air at high temperatures to form brittle compounds, thus ensuring the plasticity of the weld. Precision grinding of the groove area is carried out using a diamond grinding wheel, controlling the grinding depth to be 0.1 mm - 0.2 mm, and the surface roughness Ra ≤ 1.6 μm.

[0071] For example, when using a CNC milling machine to machine a V-groove for a 6-mm-thick tantalum plate, the spindle speed is set to 800 r / min, and the feed rate is 0.05 mm / rev to ensure the accuracy of the groove angle of 45° ± 1° and the root face of 0.3 mm. Machining can completely remove the oxide layer and prevent impurities from mixing into the molten pool during welding. Solvent cleaning and pickling process: First, soak the groove and the surrounding 20-mm area with acetone for 10 minutes to dissolve the grease residue; then pickle with a mixture of 20% hydrofluoric acid and 40% nitric acid for 30 seconds, and control the pickling temperature at 25°C ± 2°C.

[0072] For example, in a certain case, the oxygen content on the surface of tantalum after pickling decreased from the initial 1200 ppm to below 200 ppm. This step can effectively remove the microscopic oxide film and improve the purity of the weld. Water rinsing and hot air drying treatment: Immediately after pickling, rinse with deionized water 3 times, with the water flow pressure of 0.3 MPa each time and the rinsing time ≥ 1 minute; then dry with nitrogen at 80 °C, with the gas flow rate of 15 m / s and the purging time of 5 minutes.

[0073] For example, a certain test showed that the oxygen content in the weld after welding of the specimen without drying increased to 500 ppm, while it was only 180 ppm after drying. This process can prevent secondary oxidation caused by the residual water marks. Detection of the fitting state between the gas protection device and the specimen: Using the helium mass spectrometry leak detection method, fill 0.5 MPa of helium gas in the protective cover, scan the joint with a probe, and the leak rate should be ≤ 1×10 -6 Pa·m 3 / s.

[0074] For example, during a certain detection, it was found that when the gap between the baffle 4 and the cover body was 0.1 mm, the leak rate reached 5×10 -6 Pa·m 3 / s, and the leak rate met the standard after adding a fluororubber sealing ring. A tight fit can ensure that the coverage rate of the protective gas > 99.9%, avoiding oxidation and discoloration of the weld.

[0075] The protective gas forms a uniform gas flow state through the filter wire mesh 7, which helps to ensure that the protective gas can evenly cover the weld. Using a uniform gas flow to protect the back of the weld can prevent back oxidation and the generation of defects, thereby improving the overall quality of the weld.

[0076] Specifically, the parameters for optimizing the welding process parameters in the embodiments of the present application include adjusting the current, voltage, welding speed, and argon gas flow rate.

[0077] For example, for a 6-mm-thick tantalum alloy T-joint, the welding current is controlled within the range of 90 - 110 A, the voltage is set at 12 - 14 V, the welding speed is maintained at 3 - 5 cm / min, and the argon gas flow rate is adjusted to 15 - 20 L / min. Through orthogonal experiments, it is found that too high a current will cause the molten pool to collapse, while too fast a speed is likely to result in lack of fusion defects. Parameter matching is required to ensure the weld penetration and forming stability. The core of the design of the gas protection device lies in achieving local dynamic sealing. A combined structure of a copper water-cooled gasket and a flexible sealing strip is adopted. The gasket is provided with a porous argon gas distribution channel to evenly cover the back of the weld with the shielding gas. In actual tests, when the argon gas purity ≥ 99.999% and the back shielding gas flow rate is 8 - 10 L / min, the oxidation color on the back of the weld is completely eliminated, and microscopic inspection shows that the oxide content is less than 0.1%. Weld inspection is verified at multiple levels including visual inspection, penetrant inspection, and metallographic inspection. Visual inspection requires that the weld surface shows a silver-white metallic luster, without cracks or pores; penetrant inspection is carried out according to ASTM E165 standard, and a fluorescent penetrant is used to observe no linear indication under an ultraviolet lamp; metallographic specimens are cut from the cross-section of the joint, and after polishing and etching, it is observed that there is no incomplete penetration at the fusion line, and the width of the heat-affected zone is controlled within 0.2 - 0.3 mm, meeting the requirements of AWS D17.1 for aerospace-grade welds. The technical principle of process parameter optimization lies in balancing the heat input and the cooling rate. Tantalum has a high thermal conductivity (57.5 W / m·K), and it is necessary to reduce the interpass temperature to below 150 °C and use pulsed current (base current 60 A / peak current 120 A) to reduce grain coarsening. Experimental data shows that under these conditions, the tensile strength of the weld reaches 92% of the base material, and there is no cracking in the bending test. The special structural design of the gas protection tooling solves the problem of root protection for T-joints. An adjustable nozzle is installed at the junction of the vertical plate and the horizontal plate. Through computational fluid dynamics simulation, it is determined that the protection effect is optimal when the air flow angle is 30°. During actual welding, the root oxygen content is reduced from 800 ppm in the conventional process to below 50 ppm, and the microscopic structure shows that the β-phase is evenly distributed.

[0078] Step 104, detect the weld to obtain a detection result.

[0079] During the fabrication of tantalum alloy T-welded joints, detecting the weld is a crucial step to ensure welding quality. This step comprehensively evaluates the quality of the weld through three methods: visual inspection, macroscopic inspection, and microscopic inspection, and determines whether the detection result meets the preset standards.

[0080] Visual inspection is the first step in weld inspection, mainly observing the color and forming state of the weld surface. Through visual inspection, it is possible to preliminarily judge whether there are obvious defects in the weld, such as cracks, pores, slag inclusions, etc. At the same time, the forming state of the weld can also reflect the stability of the welding process and the operation level.

[0081] Macroscopic inspection is to directly observe the macrostructure characteristics of the weld, fusion zone and heat-affected zone through a low-power magnifying glass or the naked eye. This step can further reveal the macroscopic defects inside the weld, such as incomplete penetration and lack of fusion. Macroscopic inspection can also evaluate the fusion condition between the weld and the base metal, as well as the width and morphology of the heat-affected zone.

[0082] Microscopic inspection is to observe the high-power structure characteristics of the weld, fusion zone and heat-affected zone through a metallographic microscope or an electron microscope. Microscopic inspection can reveal the microscopic defects inside the weld, such as coarse grains and uneven phase transformation. At the same time, microscopic inspection can also evaluate the mechanical properties of the weld, such as hardness and toughness, which are indirectly reflected by the structure characteristics.

[0083] After visual inspection, macroscopic inspection and microscopic inspection are completed, it is necessary to comprehensively consider the results of each inspection to determine whether the weld quality meets the preset standards. The preset standards usually include the appearance quality of the weld, the allowable range of internal defects, mechanical property indexes, etc. If the inspection results meet the preset standards, the weld quality is qualified; otherwise, repair or rewelding is required.

[0084] Specifically, when visually inspecting the surface color and forming state of the weld in the embodiment of the present application, a standard light source (such as D65 white light) is used to irradiate the weld area to observe the distribution of surface oxidation color.

[0085] For example, the normal surface of a tantalum alloy after welding should exhibit a silver-white metallic luster. If blue or yellow oxidation colors appear, it indicates insufficient purity of the shielding gas or excessive heat input during welding. At the same time, check whether the reinforcement of the weld is uniform. The standard requires that the reinforcement does not exceed 10% of the base metal thickness. For example, for a 3-mm thick plate, the reinforcement needs to be controlled within 0.3 mm. Quantitatively evaluate by comparing with a standard color card and a contour gauge. This step can quickly screen out macroscopic defects such as pores and undercuts to ensure the effectiveness of subsequent inspections. Macroscopic inspection uses wire cutting to take samples, and the sample includes the entire cross-sectional area of the weld. After gradually grinding with sandpaper to 2000#, polish it to a mirror surface with an alumina suspension. When observing with a 10-fold magnifying glass, the fusion line should show a clear wavy transition, and the width of the heat-affected zone should be less than 1.5 mm. For example, in a certain sample inspection, if a lack of penetration of 0.2 mm is found at the root, it is judged as unqualified. By measuring the width ratio of each zone (such as weld: fusion zone: heat-affected zone = 5:1:3), the rationality of the welding parameters can be verified. Pores with a diameter exceeding 0.5 mm in the low-magnification structure need to be recorded as major defects. When using a metallurgical microscope for microscopic inspection, select a critical position in the fusion zone to prepare the sample. After etching with a mixed solution of nitric acid and hydrofluoric acid, the α phase should present a uniform equiaxed crystal structure, and the grain size should be above ASTM grade 8. In a certain case, the appearance of acicular martensite in the heat-affected zone is judged as an abnormal structure, indicating that the cooling rate exceeds the standard. By counting the number of inclusions in a 200-fold field of view (such as not exceeding 3 per square millimeter) and determining the composition as Ta2O5 by energy spectrum analysis, the technical root cause of the excessive water content in the shielding gas can be traced back.

[0086] During the implementation of the preset standard, visual inspection and macroscopic inspection complement each other: the color difference areas found visually need to be inspected for microcracks in the macroscopic sample with key attention. For example, in a certain inspection, a locally blackened area was found visually. Although no defects were found in the macroscopic inspection, sulfur element segregation was detected in this area during the microscopic inspection, and it was finally confirmed as surface contamination rather than a welding defect. The three-layer inspection system can cover the full-scale quality control from millimeter level to micron level. When correlating the tissue characteristics with the process parameters, the α-phase ratio in the microscopic inspection needs to correspond to the heat input during welding. When the recorded heat input is 80 J / mm, the α-phase content in the normal heat-affected zone should be > 95%. If the residual β phase is detected, it indicates that the control of the interpass temperature has failed. The depression depth of the fusion zone in the macroscopic inspection (such as not exceeding 0.1 mm) and the dendrite orientation in the microscopic inspection jointly verify the arc stability. If the deviation between the two exceeds 15%, the wire feeding speed needs to be adjusted.

[0087] It should be noted that in this application, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising that element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of this application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in the reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0088] The embodiments of the present application have been described above in conjunction with the accompanying drawings. However, the present application is not limited to the above specific embodiments. The above specific embodiments are merely illustrative rather than restrictive. Those of ordinary skill in the art, under the inspiration of the present application and without departing from the spirit and scope protected by the claims of the present application, can still make many forms, all of which fall within the protection scope of the present application.

Claims

1. A manufacturing method of a tantalum alloy T-shaped welded joint, characterized in that, The method includes: Obtain tantalum alloy materials, analyze their properties and weldability, and determine the welding scheme; Design the groove form and gas protection device; By optimizing the welding process parameters, use the gas protection device to complete the welding of the tantalum alloy T-joint; Inspect the weld seam to obtain the inspection results.

2. The manufacturing method of the tantalum alloy T-shaped welded joint according to claim 1, characterized in that, The method includes: Obtain tantalum alloy plates and standard welding wires, analyze the mechanical properties and chemical properties of the tantalum alloy plates, determine the thickness and welding position of the plates, and use the standard welding wires matching the tantalum alloy plates as welding materials.

3. The manufacturing method of the tantalum alloy T-shaped welded joint according to claim 1, characterized in that The method includes: According to the properties and weldability of the tantalum alloy materials, determine the single-sided V-groove form, and obtain the groove angle, root face size and assembly gap; Design the structure of the gas protection device, the structure includes a web, a bottom plate, a protective cover body, a baffle, a ventilation pipe, a sieve plate, a filter screen and a handle, and determine the combined dimensions of the protective cover body with the web and the bottom plate; Among them, the bottom plate is in a horizontal plate-like structure, and the web is vertically fixed at the center of its top; the protective cover body with an isosceles trapezoid cross-section forms a cavity with the bottom plate and the web; the baffle is in a trapezoidal flat plate-like structure and covers both ends of the protective cover body to form a sealed chamber; the inside of the sealed chamber is provided with the sieve plate and the filter screen arranged in layers from top to bottom, wherein the sieve plate is welded to the inner walls of the protective cover body and the baffle, and the filter screen is fixed between the upper and lower sieve plates; the ventilation pipe axially penetrates the end of the protective cover body and extends into the protective cover body, and is arranged in a U-shape in the upper space of the sieve plate. Two rows of ventilation holes are evenly arranged on the semi-circle of the ventilation pipe in the protective cover body close to the sieve plate side, and the included angle between the ventilation holes is 90°; the handle is arranged at the center of the top of the protective cover body, and the rotation axis line of the handle is perpendicular to the top surface of the protective cover body in space.

4. The manufacturing method of the tantalum alloy T-shaped welded joint according to claim 1 or 3, characterized in that, The method includes: Obtain the initial welding current, gradually increase the welding current according to the formation of the fusion nucleus, determine the welding current value for forming the molten pool spreading state, use the gas protection device to convey the protective gas, and complete the horizontal welding of the tantalum alloy T-joint.

5. The manufacturing method of the tantalum alloy T-shaped welded joint according to claim 1, characterized in that, The method includes: Obtain the color and forming state of the weld seam surface through visual inspection, obtain the low-magnification tissue characteristics of the weld seam, fusion zone and heat-affected zone through macroscopic inspection, obtain the high-magnification tissue characteristics of the weld seam, fusion zone and heat-affected zone through microscopic inspection, and determine that the inspection results meet the preset standards.

6. The manufacturing method of the tantalum alloy T-shaped welded joint according to claim 1, characterized in that, The method includes: Obtain a closed, clean and independent area as the welding site, grind or machine the groove and surface of the tantalum alloy material to remove the oxide scale, perform pickling after solvent cleaning, and perform water rinsing and hot air drying on the groove and surface, and determine that there is no air leakage in the fitting state of the gas protection device with the specimen.

7. The manufacturing method of the tantalum alloy T-shaped welded joint according to claim 4, characterized in that The ventilation pipe is provided with backflow holes, the sieve plate is designed with openings, and the method includes: Ensure that the shielding gas forms a uniform gas flow state through the filter screen, and use the gas flow to shield the back of the weld, thus completing the welding of the tantalum alloy T-shaped welded joint.

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