Single-gun dual-tungsten inert gas (TIG) welding method and system for thick titanium alloys with narrow gaps

Abstract

This invention provides a single-gun dual-tungsten inert gas (TIG) welding method and system for thick titanium alloys with narrow gaps. The single-gun dual-tungsten inert gas (TIG) welding method includes the following steps: S1, blunt edge design and processing; S2, cleaning the titanium alloy welding test plate, adjusting the assembly spacing of the titanium alloy welding test plate, and arranging it along the welding axis; setting the integrated dual-tungsten inert gas welding gun shaft and rotating it to the flat welding position; S3, teaching the titanium alloy welding test plate; S4, performing root pass welding on the taught titanium alloy welding test plate; S5, performing fill pass welding on the titanium alloy welding test plate after root pass welding; S6, performing cap pass welding on the titanium alloy welding test plate after fill pass welding. The single-gun dual-tungsten inert gas (TIG) welding method of this invention, with steps S1 to S6 being interconnected and inseparable, improves: 1. the stability of the dual-tungsten inert gas coupled arc, improves the quality of the weld joint, and solves the problem of incomplete fusion of the inner sidewalls in narrow gaps; 2. significantly improves the welding cladding rate.

Description

Technical Field

[0001] This invention relates to the field of narrow-gap TIG welding technology for titanium alloys, and more specifically, to a single-gun dual-tungsten electrode TIG welding method and system for narrow-gap welding of thick titanium alloys. Background Technology

[0002] Titanium alloys, due to their stable performance at high and low temperatures, high specific strength, good weldability, good corrosion resistance, low thermal conductivity, and low density, are increasingly widely used in equipment manufacturing, aviation, aerospace, marine, power, and chemical industries. Non-consumable electrode tungsten inert gas (TIG) welding offers advantages such as high weld quality, less spatter, low cost, and stable joint performance, and is widely used in titanium alloy welding applications requiring high precision, form, and performance. In recent years, with the development of full-ocean-depth diving equipment and other special technical equipment, the application of thick titanium alloy narrow-gap welding technology has become increasingly common; however, the deposition efficiency of thick titanium alloy narrow-gap TIG welding technology is low, with a single layer filling only about 2mm, and the small weld width easily leads to defects such as sidewall incomplete fusion during the welding process.

[0003] Existing narrow-gap welding technologies include dual tungsten inert gas (TIG) welding. For example, patent application CN201811135886.5 discloses a high-efficiency, high-speed dual tungsten inert gas (TIG) narrow-gap welding method. This method uses two welding torches arranged one in front of the other, with the front torch stationary and the rear torch equipped with a rotating device. During welding, both torches are equidistant from the workpiece, and the arc is struck simultaneously, resulting in good weld formation without undercut or other defects. However, this existing technology has the following problems:

[0004] (1) It requires the addition of a rotating device, a welding torch angle adjustment device, and another welding torch, which takes up a lot of space, has a complex structure, and is costly.

[0005] (2) The horizontal distance between the tungsten electrodes of the two welding torches is large, and the electric arc does not couple. However, the energy density of a single electric arc is small, and the improvement in cladding efficiency is only the sum of the cladding amount of a single heat source, so the improvement in cladding efficiency is limited.

[0006] (3) This method is mainly applicable to steel with a thickness of about 25mm. However, for titanium alloys, especially ultra-thick titanium alloys with a thickness of more than 60mm, due to the spatial constraint effect and spatial position limitation of the electric arc, it is not advisable to use a double gun arrangement.

[0007] (4) Titanium alloys begin to absorb H at 250℃, O at 400℃, and N at 600℃. These three elements have a huge impact on the performance of titanium alloys. Due to the excessively wide distance between the front and back of the welding torch, it is not conducive to applying front welding protection during the welding process.

[0008] (5) The double gun or the existing double tungsten ultra-narrow gap welding technology can only perform flat welding and cannot perform all-position welding.

[0009] In view of this, the present invention is hereby proposed. Summary of the Invention

[0010] The purpose of this invention is to propose a single-gun dual-tungsten inert gas (TIG) welding method and system for thick titanium alloys with narrow gaps, in order to solve the problems of incomplete fusion of the narrow gap weld sidewalls and low welding cladding efficiency in the existing technology for thick titanium alloys with narrow gaps.

[0011] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0012] A method for single-gun dual-tungsten inert gas (TIG) welding of thick titanium alloys with narrow gaps, comprising the following steps:

[0013] S1. Blunt edge design and processing:

[0014] Machining titanium alloy welding test plates involves opening double U-shaped bevels and reserving a 2-3mm blunt edge.

[0015] S2. Clean the titanium alloy welding test plate, adjust the assembly spacing of the titanium alloy welding test plate, and arrange it along the welding axis; set the gun shaft of the integrated dual tungsten inert gas welding gun and rotate it to the flat welding position.

[0016] S3. Demonstrate the welding test plate of titanium alloy;

[0017] S4. Perform the root pass welding on the titanium alloy welding test plate that has been demonstrated:

[0018] Along the welding direction, adjust the double tungsten electrode tips to be aligned with the front cone and rear oblique angle, adjust the distance between the front and rear tungsten electrode tips to 2-3 mm, and the distance between the double tungsten electrode tips and the titanium alloy welding test plate to 5-7 mm; the root pass welding is performed using DC without pulse, with single-sided welding and double-sided forming; after adjusting the root pass current, root pass welding speed, wire feed speed and shielding gas flow rate, start the arc for root pass welding;

[0019] S5. Fill the titanium alloy welding test plate that has been prepared with the base layer with filler welding:

[0020] Along the welding direction, adjust the double tungsten electrode tips to be arranged with the front and rear slanted tips aligned. Rotate the slanted tips until the double tungsten electrode tips are close to each other on one side, and adjust the distance between the front and rear tungsten electrode tips. Turn on the vibratory wire feeder and use pulse filling. Adjust the filling current, filling welding speed, vibration frequency, wire feed speed, pulse frequency, and duty cycle. Adjust the helium-argon mixture ratio and flow rate. Start the arc and perform welding filling.

[0021] S6. Perform cover welding on the filled titanium alloy welding test plate:

[0022] During cover welding, the double tungsten electrode tips are adjusted to be arranged with the front and rear slanted sides aligned, and the slanted tips are rotated until the double tungsten electrode tips are close to each other on one side; the distance between the front and rear tungsten electrode tips is adjusted to 1-3mm, and DC low-frequency pulses are used for cover welding; the cover current, cover welding speed, wire feed speed, shielding gas flow rate, pulse frequency and duty cycle are adjusted.

[0023] The present invention discloses a single-gun dual-tungsten electrode TIG welding method for thick titanium alloys with narrow gaps. Steps S1 to S6 are interconnected and inseparable. Through the interrelationship and combined effect of the dual-tungsten electrode tip state, the distance between the dual-tungsten electrodes, the pulse coordination between the dual-tungsten electrodes, the wire feed speed, the shielding gas flow rate, and the mixed gas flow rate in the root pass welding (S4), the fill pass welding (S5), and the cap pass welding (S6), the following benefits are achieved: First, the stability of the dual-tungsten electrode coupled arc is improved, solving the problem of incomplete fusion on the narrow gap sidewalls; second, the quality of the weld joint is improved, further solving the problem of incomplete fusion on the inner sidewalls of the narrow gap; and third, the weld cladding rate is greatly improved.

[0024] Furthermore, in step S4, the dual tungsten electrode root pass current is adjusted to 90-140A; the root pass welding speed is 110-130mm / min; when using 1.6mm diameter coiled wire, the wire feeding speed is 600-800mm / min; the integrated dual tungsten electrode welding torch uses pure argon gas protection, and the shielding gas flow rate is 15-25L / min.

[0025] Furthermore, in step S5, when performing flat filler welding, the distance between the front and rear tungsten electrodes is 2-3 mm; when performing horizontal and vertical filler welding, the shaft of the integrated dual tungsten electrode welding gun is rotated to the vertical plane of the weld, and the distance between the front and rear tungsten electrodes is adjusted to 3-5 mm; the dual tungsten electrode welding filler current is adjusted to 100-320 A, the filler speed is 90-110 mm / min, the vibration frequency of the vibrating wire feed is 250 times / min, and the wire feed speed is 2600-3600 mm / min; during the filler welding process, flat and horizontal welding use dual high-frequency pulses with a pulse frequency of 50-80 Hz and a duty cycle of 60%-80%; during the filler welding process, vertical welding uses alternating pulses with a pulse frequency of 1-3 Hz and a duty cycle of 40%-60%.

[0026] Furthermore, in step S5, when performing all-position welding, the integrated dual tungsten inert gas welding torch is turned on. Helium is sprayed when the amplitude is high and argon is sprayed when the amplitude is low. The average ratio of the mixed shielding gas is helium:argon = 7:3, and the average flow rate is 25-35 L / min.

[0027] Furthermore, in step S5, the filler welding is completed when the filler welding reaches 2-3 mm from the surface of the titanium alloy welding test plate.

[0028] Furthermore, in step S6, the current of the dual tungsten electrode capping is adjusted to 100-280A; the capping welding speed is 90-110mm / min; the wire feeding speed is 3600-5200mm / min; and the capping welding uses dual DC low-frequency pulses with a pulse frequency of 2-5Hz and a duty cycle of 60%-80%.

[0029] Furthermore, in step S6, the integrated dual tungsten inert gas welding torch is protected by pure argon gas with a flow rate of 30-50 L / min.

[0030] Furthermore, in step S2, the assembly spacing of the titanium alloy welding test plate is ≤0.2mm, and the misalignment is ≤0.5mm.

[0031] Furthermore, in step S3, during the welding process of the titanium alloy welding test plate, high-purity argon gas with a purity of 99.99% needs to be continuously introduced into the upper and lower parts of the weld, with a gas flow rate ≥25L / min.

[0032] In a second aspect, the present invention provides a single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps. This system utilizes any one of the methods described above. The system includes two welding machines and an integrated dual-tungsten inert gas (TIG) welding torch. Each welding machine is equipped with a welding power source. Both welding machines are connected to the integrated dual-tungsten inert gas (TIG) welding torch. The two welding machines respectively control the magnitude, type, and pulse pattern of the two tungsten inert gas currents. The system also includes a front shielding gas shroud, a back shielding gas device, and a vibrating wire feeder.

[0033] Compared with existing technologies, the single-gun dual-tungsten electrode TIG welding method and system for thick titanium alloys with narrow gaps described in this invention has the following advantages:

[0034] 1) The single-gun dual-tungsten electrode TIG welding method and system for thick titanium alloys with narrow gaps described in this invention comprises steps S1 to S6, which are interconnected and inseparable. Through the interrelationship and combined effect of the dual-tungsten electrode tip state, the distance between the dual-tungsten electrode tips, the pulse coordination form between the dual-tungsten electrodes, the wire feed speed, the shielding gas flow rate, and the mixed gas flow rate during the root pass welding in step S4, the fill pass welding in step S5, and the cap pass welding in step S6, the following benefits are achieved: First, the stability of the coupled arc of the dual-tungsten electrodes is improved, solving the problem of incomplete fusion of the sidewalls in narrow gaps; second, the quality of the welded joint is improved, further solving the problem of incomplete fusion of the inner sidewalls in narrow gaps; third, the high arc energy after coupling greatly improves the welding cladding rate.

[0035] 2) The single-gun dual-tungsten electrode TIG welding method and system for thick titanium alloy with narrow gap described in this invention improves the quality of the welded joint by the interrelation and synergistic effect of the protective gas flow rate and mixed gas flow rate in the root pass welding in step S4, the fill pass welding in step S5, and the cap pass welding in step S6, and further solves the problem of fusion of the inner sidewall of the narrow gap.

[0036] 3) The single-gun dual-tungsten inert gas (TIG) welding method and system for thick titanium alloys with narrow gaps described in this invention can realize all-position welding of thick titanium alloys and obtain welded joints with reliable welding quality.

[0037] 4) The single-gun dual-tungsten electrode TIG welding method and system for thick titanium alloys with narrow gaps described in this invention has the advantages of simple operation, high efficiency, low cost, high welding quality, and all-position welding capability. It has good technical application and market prospects in the fields of large equipment manufacturing, full ocean depth, and chemical industry. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the process structure of a single-gun dual-tungsten electrode TIG welding method for thick titanium alloys with narrow gaps, as described in an embodiment of the present invention.

[0039] Figure 2 This is a schematic diagram of the processing of a titanium alloy welding test plate for a single-gun dual-tungsten inert gas (TIG) welding method for thick titanium alloys with narrow gaps, as described in an embodiment of the present invention.

[0040] Figure 3 This is a schematic diagram of the structure of a single-gun dual-tungsten electrode TIG welding system for thick titanium alloys with narrow gaps, as described in an embodiment of the present invention.

[0041] Figure 4 This is a schematic diagram of the integrated dual tungsten electrode welding torch of a single-gun dual tungsten electrode TIG welding system for thick titanium alloys with narrow gaps, as described in an embodiment of the present invention.

[0042] Figure 5 One of the schematic diagrams of the morphology and structure of the dual tungsten electrodes in a single-gun dual tungsten electrode TIG welding method for thick titanium alloys with narrow gaps, as described in an embodiment of the present invention;

[0043] Figure 6 for Figure 5 A photograph of the coupled arc obtained from the morphology and structure of the two tungsten electrodes;

[0044] Figure 7 The second schematic diagram of the morphology and structure of the dual tungsten electrodes in the single-gun dual tungsten electrode TIG welding method for thick titanium alloys with narrow gaps, as described in this embodiment of the invention;

[0045] Figure 8 for Figure 7A photograph of the coupled arc obtained from the morphology and structure of the two tungsten electrodes;

[0046] Figure 9 The image shows the low-magnification microstructure of the titanium alloy obtained by the welding method in Comparative Example 1.

[0047] Figure 10 The image shows the low-magnification microstructure of the titanium alloy obtained by the welding method in Comparative Example 2.

[0048] Figure 11 This is a low-magnification microstructure of the titanium alloy used in the single-gun dual-tungsten electrode TIG welding method for thick titanium alloys with narrow gaps, as described in three embodiments of the present invention.

[0049] Explanation of reference numerals in the attached figures:

[0050] 1. Three-axis slide; 2. Welding torch tilting device; 3. Integrated dual tungsten inert gas (TIG) welding torch; 4. Welding power supply; 5. Power supply cooling water tank; 6. High-purity argon gas storage device; 7. High-purity helium gas storage device; 8. Pulse precision control and helium-argon gas regulation device; 9. Welding parameter precision adjustment system; 10. Main parameter and welding process monitor; 11. Vibrating wire feeder; 12. Manual welding parameter controller; 13. Insulating support plate and wire feed frame; 14. Titanium alloy welding test plate; 15. Front protective gas shroud; 16. Back protective gas device. Detailed Implementation

[0051] It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. The descriptions of "first," "second," etc., mentioned in the embodiments of the present invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0052] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0053] This invention proposes a single-gun dual-tungsten electrode TIG welding method for thick titanium alloys with narrow gaps.

[0054] The "large thickness" referred to in this invention means that the thickness of the test plate is greater than 40 mm.

[0055] Narrow gap welding is defined as follows: when the plate thickness is less than 200mm, the gap is less than 20mm; when the plate thickness is more than 200mm, the gap is less than 30mm; for conventional thick plates of about 30mm, a bevel size of 8-10mm or less is considered a narrow gap, and less than 6mm is considered an ultra-narrow gap.

[0056] like Figure 1 As shown, the single-gun dual-tungsten inert gas (TIG) welding method for thick titanium alloys with narrow gaps includes the following steps:

[0057] S1. Blunt edge design and processing:

[0058] Machining titanium alloy welding test plate 14, opening a double U-shaped bevel, and leaving a 2-3mm blunt edge;

[0059] S2. Clean the titanium alloy welding test plate 14, adjust the assembly spacing of the titanium alloy welding test plate 14, and arrange it along the welding axis; set the gun shaft of the integrated dual tungsten inert welding gun 3 and rotate it to the flat welding position.

[0060] Specifically, in step S2, the oil and dust on the surface and the whole of the titanium alloy welding test plate 14 are cleaned; before the welding test, the bevel and the surrounding 10-15mm area of ​​the titanium alloy welding test plate 14 are mechanically cleaned to remove the surface oxide scale, and then wiped clean with a silk cloth dipped in an appropriate amount of acetone; the assembly spacing of the titanium alloy welding test plate 14 is adjusted and arranged along the welding axis; the gun shaft of the integrated dual tungsten inert gas welding gun 3 is set and rotated to the flat welding position;

[0061] S3. Demonstrate the titanium alloy welding test plate 14:

[0062] The welding machine is set to provide gas in advance and cut off gas later; the vibratory wire feeder 11 is set to provide delayed wire feeding and wire pulling after arc interruption; the front shielding gas shroud 15 and the back shielding gas device 16 are turned on; the titanium alloy welding test plate 14 is used for demonstration to ensure that the double tungsten electrodes are always in the center of the weld during the welding process; the front shielding gas shroud 15 and the back shielding gas device 16 are turned on, and the shielding gas flow rate is adjusted so that the surface color of the weld and the heat-affected zone is silver-white or light yellow. When the surface color of the weld and the heat-affected zone is silver-white or light yellow, it indicates that the welding of the titanium alloy welding test plate 14 is normal.

[0063] S4. Perform root pass welding on the titanium alloy welding test plate 14 that has been demonstrated:

[0064] Along the welding direction, adjust the double tungsten electrode tips to be aligned with the front cone and rear oblique angle, adjust the distance between the front and rear tungsten electrode tips to 2-3 mm, and the distance between the double tungsten electrode tips and the titanium alloy welding test plate 14 to 5-7 mm; the root pass welding is performed using DC without pulse, with single-sided welding and double-sided forming; after adjusting the root pass current, root pass welding speed, wire feed speed and shielding gas flow rate, start the arc for root pass welding;

[0065] S5. Fill the gap by welding the titanium alloy welding test plate 14 that has been prepared with the base layer:

[0066] Along the welding direction, adjust the double tungsten electrode tips to be arranged with the front and rear slanted tips aligned. Rotate the slanted tips until the double tungsten electrode tips are close to each other on one side, and adjust the distance between the front and rear tungsten electrode tips. Turn on the vibrating wire feeder 11 and use pulse filling. Adjust the filling current, filling welding speed, vibration frequency, wire feed speed, pulse frequency, and duty cycle. Adjust the helium-argon mixture ratio and flow rate. Start the arc and perform welding filling.

[0067] S6. Perform cover welding on the filled titanium alloy welding test plate 14:

[0068] During cover welding, the double tungsten electrode tips are adjusted to be arranged with the front and rear slanted sides aligned, and the slanted tips are rotated until the double tungsten electrode tips are close to each other on one side; the distance between the front and rear tungsten electrode tips is adjusted to 1-3mm, and DC low-frequency pulses are used for cover welding; the cover current, cover welding speed, wire feed speed, shielding gas flow rate, pulse frequency and duty cycle are adjusted.

[0069] When the two tungsten electrodes are distributed at different heights, the arc tends to shift to the lower electrode, resulting in a narrow arc width. This can easily lead to burn-out of one electrode and incomplete fusion of the sidewalls. When the tip of the tungsten electrode is biconical, the arc stiffness is poor, the penetration depth is shallow, and the stability is poor, especially within a deep and narrow gap where arc drift is severe at lower currents. Using one DC and one pulse with the two tungsten electrodes also increases the likelihood of electrode burn-out. When using two DC electrodes without a pulse, the fusion line is jagged, easily leading to incomplete fusion defects. Furthermore, the combined arc energy is high, resulting in a large welding heat input and relatively poor joint performance.

[0070] Therefore, in step S4 of the present invention, as Figure 5 As shown, when the dual tungsten electrode tips are adjusted to be arranged with a conical front and a sloping rear, and the front end is conical and the rear end is sloping, as... Figure 6 As shown, the resulting electric arc has high stiffness and moderate penetration depth.

[0071] In step S5, as Figure 7 As shown, the two tungsten electrode tips are arranged flush front to back, and the oblique tip is rotated until the two tungsten electrode tips are close to each other on one side; when the spacing between flat-welded tungsten electrodes is 2-3 mm, and the spacing between horizontal and vertical-welded tungsten electrodes is 3-5 mm, as... Figure 8 As shown, an elliptical arc with its major axis perpendicular to the weld direction can be obtained, which can solve the problem of incomplete fusion of the narrow gap sidewall. Moreover, the energy is greatly increased after the arc is coupled, which can significantly improve the weld filling cladding rate. The double tungsten electrode tips are arranged in a double oblique manner, and the arc has a certain stiffness and relatively high stability, which is suitable for weld filling. When pulse is used, the welding heat input is relatively reduced, which is beneficial to improving the joint performance. In addition, the weld formation is more beautiful after adding pulse.

[0072] In step S6, as Figure 7 As shown, the two tungsten electrode tips are arranged obliquely and evenly at the front and back. The oblique tips are rotated until the two tungsten electrode tips are close to each other on one side. When the distance between the front and back tungsten electrode tips is adjusted to 1-3 mm, as shown... Figure 8 As shown, an elliptical arc with its major axis perpendicular to the weld direction can be obtained, which can solve the problem of incomplete fusion of the narrow gap sidewall. Moreover, the energy is greatly increased after the arc is coupled, which can significantly improve the welding filler cladding rate. When a double oblique arrangement is used, the arc has a certain stiffness and relatively high stability, which is suitable for welding filler. When a pulse is used, the welding heat input is relatively reduced, which is beneficial to improving the joint performance. In addition, the weld formation is more aesthetically pleasing after adding a pulse.

[0073] The present invention discloses a single-gun dual-tungsten electrode TIG welding method for thick titanium alloys with narrow gaps. Steps S1 to S6 are interconnected and inseparable. Through the interrelationship and combined effect of the dual-tungsten electrode tip state, the distance between the dual-tungsten electrodes, the pulse coordination between the dual-tungsten electrodes, the wire feed speed, the shielding gas flow rate, and the mixed gas flow rate in the root pass welding (S4), the fill pass welding (S5), and the cap pass welding (S6), the following benefits are achieved: First, the stability of the dual-tungsten electrode coupled arc is improved, solving the problem of incomplete fusion on the narrow gap sidewalls; second, the quality of the weld joint is improved, further solving the problem of incomplete fusion on the inner sidewalls of the narrow gap; and third, the weld cladding rate is greatly improved.

[0074] Specifically, in step S2, the assembly spacing of the titanium alloy welding test plate 14 is ≤0.2mm, and the misalignment is ≤0.5mm.

[0075] More specifically, the assembly spacing between the two titanium alloy welded test plates 14 is ≤0.2mm, and the misalignment is ≤0.5mm.

[0076] Specifically, in step S3, during the welding process of the titanium alloy welding test plate 14, high-purity argon gas with a purity of 99.99% needs to be continuously introduced into the upper and lower parts of the weld, with a gas flow rate ≥25L / min; after one welding is completed, the gas is cut off for a delay of 40-60 seconds.

[0077] Specifically, in step S4, the dual tungsten electrode root pass current is adjusted to 90-140A; the root pass welding speed is 110-130mm / min; when using 1.6mm diameter coiled wire, the wire feeding speed is 600-800mm / min; the integrated dual tungsten electrode welding torch uses pure argon gas protection, and the shielding gas flow rate is 15-25L / min.

[0078] In step S4, the dual tungsten electrode tips are adjusted to be aligned with a conical front and a slanted rear, resulting in a high arc stiffness and moderate weld penetration. When the shielding gas flow rate is too low, the joint protection effect is poor, leading to problems such as bluing, graying, and cracking. Excessive shielding gas flow rate wastes gas and causes arc instability and severe blow-out of the weld pool, affecting welding quality. The shielding gas flow rate setting in step S4 achieves two goals: first, good protection, preventing bluing, graying, and cracking; second, it promotes arc stability, improves welding quality, and avoids gas waste.

[0079] Specifically, in step S5, the tips of the dual tungsten electrodes are adjusted to a double-slanted, flush arrangement, and the slanted tips are rotated until the dual tungsten electrodes are close to each other on one side. When performing flat welding filler, the distance between the front and rear tungsten electrodes is 2-3 mm. When performing horizontal and vertical welding filler, the shaft of the integrated dual tungsten electrode welding gun 3 is rotated to the vertical plane of the weld, and the distance between the front and rear tungsten electrodes is adjusted to 3-5 mm. The dual tungsten electrode welding filler current is adjusted to 100-320 A, the filler speed is 90-110 mm / min, the vibration frequency of the vibrating wire feed is 250 times / min, and the wire feed speed is 2600-3600 mm / min. During the filler welding process, flat welding and horizontal welding use dual high-frequency pulses with a pulse frequency of 50-80 Hz and a duty cycle of 60%-80%. During the filler welding process, vertical welding uses alternating pulses with a pulse frequency of 1-3 Hz and a duty cycle of 40%-60%.

[0080] In step S5, as Figure 7 As shown, the tips of the two tungsten electrodes are arranged flush with each other. When the spacing between the tungsten electrodes in flat welding is 2-3 mm, and the spacing between the tungsten electrodes in horizontal and vertical welding is 3-5 mm, an elliptical arc with its major axis perpendicular to the weld direction can be obtained. This can solve the problem of incomplete fusion of the sidewalls in narrow gaps. Moreover, the energy is greatly increased after the arc is coupled, which can significantly improve the weld filling cladding rate. When a double oblique arrangement is used, the arc has a certain stiffness and relatively high stability, which is suitable for weld filling. When a pulse is used, the welding heat input is relatively reduced, which is beneficial to improving the joint performance. In addition, the weld formation is more aesthetically pleasing after adding a pulse.

[0081] Specifically, in step S5, when performing all-position welding, the integrated dual tungsten inert gas welding torch 3 is turned on. When the amplitude is high, helium is sprayed out, and when the amplitude is low, argon is sprayed out. The average ratio of the mixed protective gas is helium:argon = 7:3, and the average flow rate is 25-35 L / min.

[0082] Setting the shielding gas flow rate in step S5 has two main benefits: first, it provides excellent protection, preventing issues like bluing, graying, and cracking; second, it promotes arc stability, improves welding quality, and avoids gas waste. Using helium shielding significantly improves arc stability, resulting in a more stable and uniform molten pool, which facilitates droplet transfer, increases the cladding rate, and improves welding quality. Furthermore, helium shielding slightly increases the molten pool width within narrow gaps, further mitigating the problem of incomplete fusion on the sidewalls of narrow gaps.

[0083] Specifically, in step S5, the filler welding is completed when the filler welding reaches a distance of 2-3 mm from the surface of the titanium alloy welding test plate 14.

[0084] Specifically, in step S6, the current of the dual tungsten electrode capping is adjusted to 100-280A; the capping welding speed is 90-110mm / min; the wire feeding speed is 3600-5200mm / min; and the capping welding uses dual DC low-frequency pulses with a pulse frequency of 2-5Hz and a duty cycle of 60%-80%.

[0085] Specifically, in step S6, the integrated dual tungsten inert gas welding torch 3 is protected by pure argon gas with a flow rate of 30-50 L / min.

[0086] Setting the protective gas flow rate in step S6 has two advantages: first, it provides good protection and avoids problems such as blueing, graying, and cracking; second, it helps stabilize the arc, improves welding quality, and avoids gas waste.

[0087] The present invention also proposes a single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps, wherein the single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps uses any one of the single-gun dual-tungsten inert gas (TIG) welding methods for thick titanium alloys with narrow gaps.

[0088] like Figure 3 As shown, the single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps includes two welding machines and an integrated dual-tungsten inert gas (TIG) welding torch 3. Each welding machine is equipped with a welding power source 4 and a power cooling water tank 5. Both welding machines are connected to the integrated dual-tungsten inert gas (TIG) welding torch 3. The two welding machines control the magnitude, type, and pulse mode of the two tungsten electrode currents, respectively. The single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps also includes a front shielding gas shroud 15, a back shielding gas device 16, and a vibratory wire feeder 11. The structure of the integrated dual-tungsten inert gas (TIG) welding torch 3 is as follows: Figure 4 As shown, the integrated dual tungsten electrode welding torch 3 integrates two tungsten electrodes, two protective gas tubes, and four circulating water tubes into one unit. By adjusting the arrangement, tip condition, and distance of the two tungsten electrodes, a high-energy elliptical arc suitable for filling thick titanium alloys after coupling can be obtained, which can solve the problem of incomplete fusion of sidewalls in narrow gap welding.

[0089] The front protective gas shroud 15 and the back protective gas device 16 work together to protect the weld during the welding process and improve the weld formation quality.

[0090] The vibrating wire feeding device 11 can realize the vibrating wire feeding in the welding process, thereby controlling the welding heat input and stirring the molten pool to obtain a high-quality weld with reliable quality.

[0091] The single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloy with narrow gap also includes a three-axis carriage 1 and a welding torch tilting device 2. When the torch shaft of the integrated dual-tungsten inert gas welding torch 3 is not tilted, it can achieve flat welding. When the torch shaft of the integrated dual-tungsten inert gas welding torch 3 is tilted, it can achieve vertical welding, horizontal welding and fixed-angle welding, thus achieving the purpose of all-position welding.

[0092] The thick titanium alloy narrow gap single-gun dual tungsten inert gas (TIG) welding system also includes a welding parameter precision adjustment system 9, which can achieve precise control of key parameters such as welding current, pulse frequency, welding speed, wire feed speed, and shielding gas flow rate.

[0093] The single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps also includes a pulse precision control and helium-argon regulation device 8, two high-purity argon gas storage devices 6, and a high-purity helium gas storage device 7. The high-purity helium gas storage device 7 is connected to the pulse precision control and helium-argon regulation device 8. One of the high-purity argon gas storage devices 6 is connected to the pulse precision control and helium-argon regulation device 8, and the other high-purity argon gas storage device 6 is connected to the front protective gas shield 15 and the back protective gas device 16.

[0094] The pulse precision control and helium-argon regulation device 8 can switch between argon and helium in real time during welding, alternating according to the pulse amplitude, to further improve the problem of incomplete fusion of the sidewall and improve the quality of the welded joint.

[0095] like Figure 3 As shown, the single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloy with narrow gap also includes a main parameter and welding process monitor 10, a manual welding parameter controller 12, and an insulating support plate and wire feeding frame 13.

[0096] The single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps is interconnected with the single-gun dual-tungsten inert gas (TIG) welding method for thick titanium alloys with narrow gaps, and they work together:

[0097] I. By utilizing the high energy and wide arc characteristics of double TIG arc coupling, the cladding rate of narrow gap welding of titanium alloys is greatly improved, while solving the problem of sidewall incomplete fusion that is very easy to occur during narrow gap TIG welding.

[0098] Second, by utilizing pulses and optimizing the type and ratio of shielding gas, the welding cladding rate was further improved, and the welding quality was also enhanced.

[0099] Third, in traditional single TIG narrow gap welding, the single-pass filler is about 2mm, and the cladding rate is generally 7.2 to 8.2 g / min; while the present invention can achieve a single-pass filler of 6 to 7mm, and the cladding rate reaches 26.4 to 32.2 g / min, which improves the efficiency by nearly 4 times.

[0100] IV. The integrated dual tungsten electrode welding torch 3 has flexible and convenient adjustment of the relative position of the internal tungsten electrodes. Compared with the arrangement of two welding torches in front and behind, it is more convenient to operate, more flexible in welding adjustment, occupies less space, and has a relatively low welding cost. The welding torch shaft can meet the requirements of all-position welding of thick titanium alloys with narrow gaps.

[0101] 5. The shape of the tungsten electrode tip can be matched by a perfect conical or eccentric conical shape according to welding needs. This can further improve the coupling state of the dual arcs, further eliminate internal defects such as incomplete fusion, improve the stability of the molten pool, and meet the needs of all-position welding.

[0102] VI. After welding, the base metal and the weld are smoothly transitioned, the weld surface has obvious fish scale pattern, and there are no defects such as cracks, lack of fusion, porosity, undercut, arc crater and inclusions, spatter, concavity, weld slip;

[0103] 7. The weld surface is silvery-white after welding. No obvious defects were found in QT and RT tests. The weld quality meets the Class I requirements of NB / T47013.2-2015 standard. The tensile strength of the joint can reach 96% of the base material, and the impact and bending performance can also fully meet the usage requirements.

[0104] Example 1

[0105] This embodiment proposes a single-gun dual-tungsten inert gas (TIG) welding method for thick titanium alloys with narrow gaps. The single-gun dual-tungsten inert gas (TIG) welding method for thick titanium alloys with narrow gaps includes the following steps:

[0106] S1. Blunt edge design and processing:

[0107] Machining titanium alloy welding test plate 14, opening a double U-shaped bevel, and leaving a 2-3mm blunt edge;

[0108] More specifically, in step S1, a pair of double U-shaped bevel test plates made of TC4ELI titanium alloy with dimensions of 42×150×400mm are processed, such as... Figure 2 As shown, the bottom width of the bevel is 8mm, the top width is 12mm, the blunt edge is 2mm, and the bottom and sidewall are connected by a 3mm radius arc.

[0109] S2. Clean the titanium alloy welding test plate 14, adjust the assembly spacing of the titanium alloy welding test plate 14, and arrange it along the welding axis; set the gun shaft of the integrated dual tungsten inert gas welding gun 3 and rotate it to the flat welding position.

[0110] Specifically, the surface and overall surface of the titanium alloy welding test plate 14 are cleaned of oil and dust. Before the welding test, the bevel and surrounding area of ​​the alloy welding test plate 14 within 10-15mm are mechanically cleaned to remove the surface oxide scale, and then wiped clean with a silk cloth dampened with an appropriate amount of acetone. The assembly spacing of the welding test plates is adjusted so that the assembly spacing between two titanium alloy welding test plates 14 is ≤0.2mm and the misalignment is ≤0.5mm. After adjustment, the test plates are arranged along the welding axis, with the tungsten electrode tip 5mm away from the weld. The welding torch axis is set and rotated to the flat welding position.

[0111] S3. Demonstrate the titanium alloy welding test plate 14:

[0112] The titanium alloy welding test plate 14 was taught the trajectory, and the parameters of the welding machine and wire feeding mechanism were set. The welding machine was set to provide gas in advance and cut off gas after delay. The vibration wire feeding device 11 was set to provide delayed wire feeding and wire pulling after arc interruption. The front shielding gas shroud 15 and the back shielding gas device 16 were opened. The titanium alloy welding test plate 14 was taught to ensure that the double tungsten electrodes were always in the center of the weld during the welding process. The front shielding gas shroud 15 and the back shielding gas device 16 were opened and gas was introduced into the front shielding gas shroud 15 and the back shielding gas device 16 at a gas flow rate of 25 L / min.

[0113] S4. Perform root pass welding on the titanium alloy welding test plate 14 that has been demonstrated:

[0114] Along the welding direction, adjust the tips of the dual tungsten electrodes to be aligned with a front cone and a rear slant, and adjust the distance between the front and rear tungsten electrode tips to 2mm; the distance between the dual tungsten electrode tips and the titanium alloy welding test plate 14 is 5mm; the root pass welding is performed using DC without pulse, with single-sided welding and double-sided forming; the root pass current of both tungsten electrodes is adjusted to 120A; the root pass speed is 120mm / min; a 1.6mm diameter wire is used, and the wire feed speed is 600mm / min; the integrated dual tungsten electrode welding torch 3 uses pure argon gas protection, with a shielding gas flow rate of 20L / min; after adjusting the main parameters, start the arc and perform the root pass welding;

[0115] S5. Fill the gap by welding the titanium alloy welding test plate 14 that has been prepared with the base layer:

[0116] Along the welding direction, adjust the double tungsten electrode tips to be arranged with the front and rear angled sides aligned. Rotate the angled tips until the double tungsten electrode tips are close to each other on one side. When performing flat filler welding, the distance between the front and rear tungsten electrodes is 2mm. When performing horizontal and vertical filler welding, rotate the gun shaft of the integrated double tungsten electrode welding gun 3 to the vertical plane of the weld seam and adjust the distance between the front and rear tungsten electrodes to 4mm. Turn on the vibrating wire feeder 11 and adjust the vibration frequency to 250 times / min, using pulse filler welding. Adjust the filler current, filler welding speed, vibration frequency, wire feed speed, pulse frequency, and duty cycle. Adjust the helium-argon mixed gas ratio and flow rate. Start the arc and perform filler welding.

[0117] The first layer of welding filler current is 240A, and the wire feed speed is 2600mm / min; the filler current for other filler layers of double tungsten inert gas welding is adjusted to 260A, and the wire feed speed is 3200mm / min; the welding filler speed is 100mm / min, the pulse frequency is 60Hz, and the duty cycle is 80%; the gas flow rate of the integrated double tungsten inert gas welding torch 3, the front shielding gas shroud 15, and the back shielding gas device 16 is adjusted to 30L / min; the filling process adopts alternating filling from both sides, and the filling welding is completed when the filling welding reaches 2-3mm away from the surface of the titanium alloy welding test plate 14.

[0118] S6. Perform cover welding on the filled titanium alloy welding test plate 14:

[0119] During cover welding, the double tungsten electrode tips are adjusted to be arranged in a front-to-back oblique and parallel configuration, and the oblique tips are rotated until the double tungsten electrode tips are close to each other on one side; the distance between the front and rear tungsten electrode tips is adjusted to 2mm, and double DC low-frequency pulses are used for cover welding at a frequency of 5Hz; duty cycle of 80%; current is adjusted to 240A; welding speed is 110mm / min; wire feed speed is 4000mm / min; shielding gas flow rate is 40L / min.

[0120] The single-gun dual-tungsten inert gas (TIG) welding method for thick titanium alloys with narrow gaps described in this embodiment uses a single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps.

[0121] like Figure 1As shown, the single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps includes two welding machines and an integrated dual-tungsten inert gas (TIG) welding torch 3. Each welding machine is equipped with a welding power source 4 and a power cooling water tank 5. Both welding machines are connected to the integrated dual-tungsten inert gas (TIG) welding torch 3. The two welding machines control the magnitude, type, and pulse form of the two tungsten inert gas currents, respectively. The single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps also includes a front shielding gas shroud 15, a back shielding gas device 16, and a vibrating wire feeder 11. The integrated dual-tungsten inert gas (TIG) welding torch 3 integrates two tungsten inert gases, two shielding gas tubes, and four circulating water tubes into one unit. By adjusting the arrangement, tip condition, and distance of the two tungsten inert gases, a high-energy elliptical arc suitable for thick titanium alloy filling is obtained after coupling, which can solve the problem of incomplete fusion of the sidewalls in narrow-gap welding.

[0122] The front protective gas shroud 15 and the back protective gas device 16 work together to protect the weld during the welding process and improve the weld formation quality.

[0123] The vibrating wire feeding device 11 can realize the vibrating wire feeding in the welding process, thereby controlling the welding heat input and stirring the molten pool to obtain a high-quality weld with reliable quality.

[0124] The single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloy with narrow gap also includes a three-axis carriage 1 and a welding torch tilting device 2. When the torch shaft of the integrated dual-tungsten inert gas welding torch 3 is not tilted, it can achieve flat welding. When the torch shaft of the integrated dual-tungsten inert gas welding torch 3 is tilted, it can achieve vertical welding, horizontal welding and fixed-angle welding, thus achieving the purpose of all-position welding.

[0125] The thick titanium alloy narrow gap single-gun dual tungsten inert gas (TIG) welding system also includes a welding parameter precision adjustment system 9, which can achieve precise control of key parameters such as welding current, pulse frequency, welding speed, wire feed speed, and shielding gas flow rate.

[0126] The single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps also includes a pulse precision control and helium-argon regulation device 8, a high-purity argon gas storage device 6, and a high-purity helium gas storage device 7. Both the high-purity argon gas storage device 6 and the high-purity helium gas storage device 7 are connected to the pulse precision control and helium-argon regulation device 8. The pulse precision control and helium-argon regulation device 8 can achieve real-time switching between argon and helium gases according to the pulse amplitude during welding, further improving the problem of incomplete fusion on the sidewalls and enhancing the quality of the weld joint.

[0127] like Figure 1 As shown, the single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloy with narrow gap also includes a main parameter and welding process monitor 10, a manual welding parameter controller 12, and an insulating support plate and wire feeding frame 13.

[0128] The single-gun dual-tungsten inert gas (TIG) welding system for thick titanium alloys with narrow gaps is interconnected with the single-gun dual-tungsten inert gas (TIG) welding method for thick titanium alloys with narrow gaps. Their combined action results in a coupled elliptical arc with the major axis of the ellipse located perpendicular to the weld, leading to a weld with good sidewall fusion. The coupled arc energy is high, significantly increasing the cladding rate and thus improving welding efficiency. The addition of vibration wire feeding and high-frequency pulses during the filler welding process stirs the weld pool, inhibiting grain growth and improving the mechanical properties of the weld joint. Low-frequency pulses are used for the capping welding, and shielding gas is simultaneously introduced from both the top and bottom of the test plate, resulting in a high-quality silver-white fish-scale textured surface. This example demonstrates efficient single-gun dual-tungsten inert gas (TIP-TIG) planar welding of 36mm–48mm thick titanium alloys with narrow gaps, significantly improving the cladding rate and producing reliable weld joints.

[0129] Example 2

[0130] In this embodiment, unlike in embodiment 1,

[0131] In step S1, a 52mm thick TC4 titanium alloy is used;

[0132] In step S5, before the filler welding, the shaft of the integrated dual tungsten electrode welding gun 3 needs to be rotated to the horizontal or vertical welding surface; the spacing between the dual tungsten electrodes is adjusted to 4mm; the filler current for the first layer of welding remains unchanged.

[0133] The wire feed speed is reduced to 2400 mm / min; the welding current for other layers is adjusted to 270 A; the wire feed speed is 3400 mm / min; the pulse frequency is 50 Hz and the duty cycle is 70%; the integrated dual tungsten electrode welding torch 3 is turned on, and the average ratio of mixed protective gas is helium:argon = 7:3, with an average flow rate of 30 L / min, through the pulse precision control and helium-argon gas regulation device 8.

[0134] Based on Example 1, this embodiment uses a helium-argon mixed protective gas and adjusts the welding process parameters to achieve high-efficiency single-gun dual-tungsten electrode TIP-TIG transverse and vertical welding of 44mm-60mm thick titanium alloys with narrow gaps. This can significantly improve the welding cladding rate and obtain a welded joint with reliable welding quality.

[0135] Example 3

[0136] In this embodiment, unlike in embodiment 1,

[0137] In step S1, 87mm thick TC4 titanium alloy is used;

[0138] In step S5, for the first layer of welding filler, the dual tungsten electrode current remains unchanged, and the wire feed speed is reduced to 2200 mm / min; for subsequent filler layers, the dual tungsten electrode welding current decreases sequentially from 320A, decreasing by 10A for each layer, while the wire feed speed remains unchanged at 3600 mm / min; after filling 4 layers, the welding current remains unchanged at 270A, and the wire feed speed remains unchanged at 3400 mm / min; the pulse frequency is 50 Hz, and the duty cycle is 70%; the integrated dual tungsten electrode welding torch 3 is turned on, and the pulse precision control and helium-argon gas regulation device 8 are used to mix the shielding gases. The average ratio of helium to argon is 7:3, and the average flow rate is 35 L / min.

[0139] Based on Example 1, this embodiment improves the spatial constraint effect that significantly affects arc energy by using a helium-argon mixed protective gas and a stepped current distribution. It enables high-efficiency TIP-TIG welding of narrow gaps in 76mm to 94mm thick titanium alloys using a single gun with dual tungsten electrodes in all positions, which can greatly improve the welding cladding rate and obtain a welded joint with reliable welding quality.

[0140] Comparative Example 1

[0141] The TC4 titanium alloy with a thickness of 80mm and a double U-shaped bevel was welded using a traditional automatic narrow gap welding torch. The welding filling process adopted the same multi-layer welding as the present invention.

[0142] Comparative Example 2

[0143] A handheld TIG welding torch was used to weld 92mm thick TC4 titanium alloy with a double U-shaped bevel. The welding filling process adopted the same multi-layer welding as the present invention.

[0144] Performance Comparison

[0145] The titanium alloy welded test plate 14 obtained by the welding methods of Example 3, Comparative Example 1, and Comparative Example 2 was tested and the results were as follows: Figures 9-11 Low-magnification tissue diagram.

[0146] pass Figures 9-11 The low-magnification microstructure shows that, in Comparative Example 1, the automatic narrow gap welding required 40 passes on both sides to completely fill the bevel, while in Comparative Example 2, the handheld TIG welding required 76 passes on both sides. The welding time was relatively long, and there were a few dot-like unfusion defects on the side wall. Example 3: 14 layers of automatic narrow gap welding sample.

[0147] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A large thickness titanium alloy narrow gap single gun dual tungsten electrode TIG welding method characterized by, The large-thickness titanium alloy narrow-gap single-gun double-tungsten electrode TIG welding method comprises the following steps: S1, the design and processing of the blunt edge: Process the titanium alloy welding test plate (14), open a double-U-shaped groove, and reserve a 2-3mm blunt edge; S2, clean the titanium alloy welding test plate (14), adjust the assembly spacing of the titanium alloy welding test plate (14), and arrange along the welding axis; set the gun shaft of the integrated double-tungsten electrode welding gun (3) and rotate to the flat welding position; S3, teach the titanium alloy welding test plate (14); S4, perform backing welding on the taught titanium alloy welding test plate (14): Along the welding direction, adjust the double-tungsten electrode tip to be arranged in front of the cone and behind the inclined flat, adjust the distance between the front and rear tungsten electrode tips to be 2-3mm, and the distance between the double-tungsten electrode tip and the titanium alloy welding test plate (14) to be 5-7mm; the backing welding is performed by direct current without pulse, single-sided welding with double-sided forming; adjust the backing current, backing welding speed, wire feeding speed and protective gas flow to start the arc and perform backing welding; S5, perform filling welding on the backed titanium alloy welding test plate (14): Along the welding direction, adjust the double-tungsten electrode tip to be arranged in front of the cone and behind the inclined flat, rotate the inclined tip to the side where the double-tungsten electrode tips are close to each other, and adjust the distance between the front and rear tungsten electrode tips; open the vibration wire feeding device (11) and perform filling by pulse; adjust the filling current, filling welding speed, vibration frequency, wire feeding speed, pulse frequency and duty cycle; adjust the helium-argon mixed gas ratio and flow; start the arc and perform welding filling; S6, perform cover welding on the filled titanium alloy welding test plate (14): During cover welding, the double-tungsten electrode tip is adjusted to be arranged in front of the cone and behind the inclined flat, and the inclined tip is rotated to the side where the double-tungsten electrode tips are close to each other; adjust the distance between the front and rear tungsten electrode tips to be 1-3mm, and perform cover welding by direct current low-frequency pulse; adjust the cover current, cover welding speed, wire feeding speed, protective gas flow, pulse frequency and duty cycle.

2. A method of single gun narrow gap TIG welding of thick titanium alloy according to claim 1, characterized in that, In step S4, the double-tungsten electrode backing current is adjusted to be 90-140A; the backing welding speed is 110-130mm / min; when a 1.6mm diameter disc wire is used, the wire feeding speed is 600-800mm / min; the integrated double-tungsten electrode welding gun (3) uses pure argon gas protection, and the protective gas flow is 15-25L / min.

3. A method of single gun narrow gap TIG welding of thick titanium alloy according to claim 1, wherein In step S5, when performing flat welding filling, the distance between the front and rear tungsten electrodes is 2-3mm; when performing horizontal welding and vertical welding filling, rotate the gun shaft of the integrated double-tungsten electrode welding gun (3) to be perpendicular to the welding seam surface and adjust the distance between the front and rear tungsten electrodes to be 3-5mm; the double-tungsten electrode welding filling current is adjusted to be 100-320A, the filling speed is 90-110mm / min, the vibration frequency of the vibration wire feeding is 250 times / min, and the wire feeding speed is 2600-3600mm / min; during the filling welding process, the flat welding and horizontal welding use double high-frequency pulse, the pulse frequency is 50-80Hz, and the duty cycle is 60%-80%; during the filling welding process, the vertical welding uses alternating pulse, the pulse frequency is 1-3Hz, and the duty cycle is 40%-60%.

4. The method of claim 3, wherein the method is a single pass narrow gap TIG welding method of thick titanium alloy using a single torch with two tungsten electrodes. In step S5, when full position welding is performed, the integrated double-tungsten electrode welding gun (3) is opened, helium is sprayed at the high position, argon is sprayed at the low position, the average proportion of the mixed shielding gas is helium:argon=7:3, and the average flow rate is 25-35 L / min.

5. A method of single gun narrow gap TIG welding of thick titanium alloy according to claim 4, wherein In step S5, the filling welding is completed when the filling welding is filled to a distance of 2-3 mm from the surface of the titanium alloy welding test plate (14).

6. A method of single gun narrow gap TIG welding of thick titanium alloy according to claim 1, wherein, In step S6, the double-tungsten electrode cover surface current is adjusted to 100-280 A; the cover surface welding speed is 90-110 mm / min; the wire feeding speed is 3600-5200 mm / min; the cover surface welding selects double direct current low frequency pulse, the pulse frequency is 2-5 Hz, and the duty cycle is 60%-80%.

7. A method of single gun narrow gap TIG welding of thick titanium alloy according to claim 6, wherein In step S6, the integrated double-tungsten electrode welding gun (3) uses pure argon protection, and the shielding gas flow rate is 30-50 L / min.

8. A method of single gun narrow gap TIG welding of thick titanium alloy according to claim 1, characterized in that, In step S2, the assembly spacing of the titanium alloy welding test plate (14) is ≤0.2 mm, and the misalignment amount is ≤0.5 mm.

9. The method of claim 1, wherein the method is a single pass narrow gap TIG welding method of thick titanium alloy using a single torch with two tungsten electrodes. In step S3, during the welding process of the titanium alloy welding test plate (14), pure argon gas with a purity of 99.99% needs to be continuously supplied to the upper and lower parts of the weld, and the gas flow rate is ≥25 L / min.

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