A laser-MIG hybrid welding method for thick titanium alloy plates

Abstract

A laser-MIG hybrid welding method for thick titanium alloy plates, wherein the thick titanium alloy plate has a thickness of ≥20mm, is disclosed. The laser-MIG hybrid welding method comprises the following steps: S1, machining the weld joint of the thick titanium alloy plate to be welded into a U-shaped bevel; S2, grinding the U-shaped bevel and the surrounding area of ​​the weld joint; S3, placing the thick titanium alloy plate to be welded in a gas shielded device and fixing it in place; S4, using a laser-MIG hybrid heat source to perform multi-layer welding on the weld joint of the thick titanium alloy plate to be welded. After each layer of welding is completed, the welding torch is withdrawn from the shielded gas chamber and the weld bead is cleaned. After the weld cools to room temperature, the next layer of welding is immediately performed until the bevel is filled. This invention provides a welding method with good gas shielding effect and ease of operation, solves the technical problem of easy oxidation in narrow gap bevel welding of thick titanium alloy plates, and achieves welding formation for butt welding of thick titanium alloy plates.

Description

Technical Field

[0001] This invention belongs to the field of welding processing technology, specifically relating to a laser-MIG hybrid welding method for thick titanium alloy plates. Background Technology

[0002] Titanium alloys possess advantages such as high specific strength, high fatigue strength, and corrosion resistance, making them widely used as core materials in aerospace engineering, marine engineering, the automotive industry, and medical equipment. Based on modular and integrated structural design concepts, titanium alloys are now widely used in rail transportation, aerospace, and nuclear power products, often employing large and complex structural components, making thick-plate welding a key research focus. Laser-MIG hybrid welding offers advantages such as high welding speed, deep penetration, and good process stability, overcoming the limitations of welding with a single heat source. It is a widely adopted, high-efficiency, and low-cost welding method for thick titanium alloys. However, due to the unique welding characteristics of titanium alloys, the laser-arc hybrid welding process, especially for thick titanium alloys, is unstable. Titanium alloys are highly susceptible to oxidation at high temperatures, affecting weld quality and severely hindering the application of thick titanium alloys in large components.

[0003] Current research reports on composite welding processes for thick titanium alloy plates exist. For example, Chinese publication CN103831533A, "Laser-MIG Composite Welding Method for Titanium Alloys," describes a method using an I-groove and adding a weld protection shield to achieve butt welding of 6mm thick titanium alloy plates. Chinese publication CN106553012A, "Post-Weld Protection Shield and Welding Method for Laser-MIG Composite Welding of Titanium Alloys," describes welding 4.2mm thick TA2 plates. Chinese publication CN102225485A, "Laser-Targon Arc Composite Heat Source Welding Process for TC18 Titanium Alloys," describes a laser-TIG composite welding method with a specific groove to achieve single-sided welding and double-sided forming of 8-18mm thick TC18 titanium alloy forged plates. Currently, in literature research on titanium alloy welding, the thickness of the titanium alloy plates does not exceed 20mm, which is insufficient to meet some special requirements.

[0004] Titanium and titanium alloys react violently with many gases, especially common gases such as O2, H2, N2, and CO2, under high-temperature welding conditions. This causes weld embrittlement, a decrease in the plasticity and toughness of the joint, and a severe deterioration of the overall performance of the joint. Therefore, gas protection for the molten pool and the solidified weld is essential during the welding process. Current gas protection methods mainly include coaxial gas protection and gas chamber protection, which use argon, helium, or a mixture of both to isolate and protect the molten pool and weld. Coaxial gas protection devices often consist of a main nozzle and a rear auxiliary flat gas nozzle. However, the airflow from the rear flat gas nozzle and the main nozzle blows directly onto the molten pool, causing plasma drift above the molten pool, disrupting the laser and arc coupling effect, and disturbing the flow state of the molten pool, affecting welding stability. Furthermore, the rear nozzle requires manual adjustment, which is cumbersome.

[0005] The patent technology, with application number 201410085830.9 and titled "A Laser-Arc Hybrid Welding Gun Suitable for Narrow Gap Welding of Thick Plates," combines a flat rectangular tubular nozzle with a laser welding head for narrow-gap laser-arc hybrid welding. This device is an extended nozzle mechanism. Due to the large size of the nozzle, the adjustable range of the heat source distance between the laser and the arc is limited, which has a certain impact on the optimization of process parameters. Furthermore, the minimum bevel width can only be reduced to 11mm, and welding efficiency needs further improvement.

[0006] The patented technology with application number 201711164562.X and title "Retractable Nozzle Device and Adjustment Method for Narrow Gap Welding" consists of a main nozzle assembly and a rear auxiliary gas flat nozzle. The rear auxiliary gas flat nozzle extends into the groove. Since the laser is in front, the rear auxiliary nozzle cannot guarantee the protection of the molten pool in the laser action zone. In addition, the orifice of the rear auxiliary gas flat nozzle is too narrow, resulting in low flow rate and high flow velocity, which easily causes turbulence. The rear auxiliary gas flat nozzle assembly continuously adjusts the nozzle height according to the groove depth, making the operation cumbersome. This device still needs further improvement. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies and overcome the difficulty in welding thick titanium alloys. It provides a laser-MIG hybrid welding method for thick titanium alloy plates. This welding method has good gas protection effect, is easy to operate, solves the problem of easy oxidation in narrow gap groove welding of thick titanium alloy plates, and realizes the welding formation of butt welding of thick titanium alloy plates.

[0008] To achieve its objective, this invention provides a laser-MIG hybrid welding method for thick titanium alloy plates, wherein the thick titanium alloy plate has a thickness of 20 mm or more. The steps of the laser-MIG hybrid welding method are as follows:

[0009] S1. The weld joint of the titanium alloy plate to be welded is processed into a U-shaped bevel with a pre-defined bevel angle of 2° to 4°, a blunt edge thickness of 1-3mm, and a bevel gap of no more than 10mm. When the thickness of the titanium alloy plate to be welded is greater than or equal to 20mm and less than 40mm, a bevel is designed on one side of the titanium alloy plate to be welded. When the thickness of the titanium alloy plate to be welded is greater than or equal to 40mm, a bevel is designed on both sides of the titanium alloy plate to be welded.

[0010] S2. Grind the U-shaped bevel of the joint to be welded and the area around the bevel, and clean it.

[0011] S3. Place the titanium alloy plate to be welded in a gas protection device and fix it together.

[0012] The gas protection device comprises a protective gas chamber consisting of a protective gas chamber base plate, two fixed side plates on the left and right sides of the protective gas chamber base plate, two sealing baffles connected to the protective gas chamber base plate by hinges on the front and rear sides of the protective gas chamber base plate, and a protective gas chamber top cover plate. The protective gas chamber base plate has symmetrically distributed fixing bolts at its four corners and a jaw iron for supporting the thick titanium alloy plate to be welded in the middle. The two sealing baffles have densely arranged uniformly spaced small gas guide holes near the bottom for connecting to the protective gas guide pipe, filling with protective gas to create a protective atmosphere. The top of the two sealing baffles has a vertically oriented elongated groove. The protective gas chamber top cover plate has bolt holes at its four corners that mate with the fixing bolts, a slidable sliding cover through-hole device for passing through the laser beam and MIG welding torch in the middle, and butterfly nuts and locking bolt holes corresponding to the positions of the elongated grooves on its sides.

[0013] The specific operation of placing the titanium alloy plate to be welded in the gas protection device is as follows: Place the titanium alloy plate to be welded on the jaw iron in the protective gas chamber, so that the weld direction is parallel and perpendicular to the sliding direction of the sliding cover through hole device; clamp the protective gas chamber top cover plate, the titanium alloy plate to be welded, the jaw iron and the protective gas chamber bottom plate with fixing bolts, and then seal and clamp the sealing baffle and the protective gas chamber top cover plate by passing butterfly nuts through the long through groove on the sealing baffle and the locking bolt hole on the side of the protective gas chamber top cover plate in sequence; connect the protective gas guide pipe to the gas guide holes evenly arranged on the two sealing baffles, open the gas valve to adjust the gas flow rate, so that the protective gas chamber is filled with a stable flow of protective gas.

[0014] S4. Use a laser-MIG composite heat source to perform multi-layer welding on the thick titanium alloy plate to be welded. After each layer of welding is completed, control the welding torch to exit the protective gas chamber and clean the weld bead. After the weld cools to room temperature, immediately perform the next layer of welding until the bevel is filled.

[0015] The welding process parameters are as follows: the laser beam defocusing amount is -2 to 2 mm, the laser power is 1.2 to 2.5 kW; the welding wire diameter of the MIG welding torch is 1.2 mm, the welding wire length is 12 to 18 mm, the pulse current is 170 to 190 A, and the welding voltage is 20 to 24 V; during welding, the laser beam is in front and the MIG welding torch moves synchronously behind, the laser beam is tilted in the welding direction with an angle of 10° with the vertical direction, the MIG welding torch is tilted in the opposite welding direction with an angle of 50° to 60° with the vertical direction, the wire spacing is 2 to 3 mm, the welding speed is 8 to 12 mm / s, and the wire feed speed is 6 to 7 m / min.

[0016] Furthermore, the sliding cover through-hole device of the present invention includes an elongated opening provided on the upper cover plate of the protective gas chamber, a guide groove device parallel to the elongated opening, and a sliding cover that can slide along the guide groove device. The sliding cover has a sliding cover opening that allows the MIG welding torch and the laser beam to pass through. When the sliding cover slides along the guide groove device, the sliding cover opening slides along the elongated opening.

[0017] Furthermore, the guide groove device of the present invention comprises two upper and lower guide groove platforms and a guide groove composed of two limiting strips sandwiched between the two guide groove platforms.

[0018] Furthermore, the sliding cover of the present invention is also provided with a welding gun sliding cover connecting rod for fixing the laser head and the MIG welding gun, so as to ensure that the sliding cover moves synchronously with the laser head and the MIG welding gun.

[0019] Furthermore, the protective gas described in this invention is argon gas with a purity of 99% or higher, and the flow rate of the protective gas introduced into the protective gas chamber during the welding process is 20-30 L / min.

[0020] Furthermore, the protective gas described in this invention is argon gas with a purity of 99% or higher, and the flow rate of the protective gas introduced into the protective gas chamber during the welding process is 25 L / min.

[0021] Furthermore, the welding wire length of the MIG welding torch described in this invention is 15mm.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention targets titanium alloy thick plate structural components with a thickness greater than or equal to 20 mm. It employs a specific U-shaped bevel, laser-MIG hybrid welding method, gas shielding device, and welding parameters to achieve single-sided welding and double-sided forming during butt welding of thick titanium alloy plates, providing a good foundation for subsequent filler welding. The welding method and apparatus of this invention feature large weld penetration, high welding efficiency, low assembly requirements, stable weld performance, and ease of automation. Butt welding of thick titanium alloy plates according to this invention yields aesthetically pleasing welds free from defects such as cracking, undercut, and porosity.

[0024] The gas protection device of this invention ensures continuous protection of the weld from pre-weld to post-weld, forming a large-scale, stable laminar flow protection. The protection range completely covers the laser-affected zone, the arc-affected zone, and the weld pool. Furthermore, the high concentration of the protective gas minimizes the possibility of the weld coming into contact with air during welding, eliminating adverse factors such as oxygen and hydrogen absorption, and thus better ensuring weld quality. Compared to coaxial gas protection, the symmetrical multi-hole jetting method on the side bottom of this invention avoids the welding instability caused by direct nozzle airflow disturbing the weld pool flow and the laser-arc coupling state. Simultaneously, it forms a stable laminar gas flow inside the gas chamber, avoiding unstable protection effects caused by turbulent airflow. Therefore, the gas flow rate and velocity can be appropriately increased for better protection. This bottom-up gas flow method effectively protects three high-temperature zones: the weld pool area during welding, the high-temperature solidification zone after welding, and the back side of the weld. The protection effect is more comprehensive and can replace commonly used back-side argon gas protection devices, reducing production costs. In addition, the design of the sliding cover through hole device and the welding torch sliding cover connecting rod of the present invention can realize the sliding cover opening of the gas protection device and the follow-up function of the welding torch, avoid the length and width opening design required to prevent the welding torch from moving and limiting, minimize the opening area of ​​the gas chamber, and ensure the airtightness of the gas chamber cavity throughout the welding process.

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the U-shaped bevel cross-section structure of the titanium alloy thick plate of the present invention.

[0027] Figure 2 This is a schematic diagram of the overall structure of the gas protection device of the present invention.

[0028] Figure 3 This is a schematic diagram of the structure of the protective air chamber cover plate and the sliding cover through hole device provided on it according to the present invention.

[0029] Figure 4 This is a schematic diagram of the internal structure of the gas protection device of the present invention.

[0030] Figure 5 This is a schematic diagram simulating the internal airflow of the gas protection device of the present invention.

[0031] Figure 6 This is a schematic diagram showing the positions of the laser beam and MIG welding torch of the present invention.

[0032] Figure 7 This is a schematic diagram of the quality of a single-sided bevel weld on a 25mm thick titanium alloy plate in Embodiment 1 of the present invention.

[0033] Figure 8 This is a macroscopic morphology diagram of the cross-section of the multi-welded joint of the 45mm thick titanium alloy plate in Embodiment 2 of the present invention. Detailed Implementation

[0034] A laser-MIG hybrid welding method for thick titanium alloy plates, wherein the thick titanium alloy plate has a thickness of 20 mm or more, and the laser-MIG hybrid welding method comprises the following steps:

[0035] S1. The weld joint of the titanium alloy plate 8 to be welded is processed into a U-shaped bevel with a preset shape. Figure 1 This is a schematic diagram of the U-shaped bevel cross-section structure, as shown below. Figure 1 As shown, the bevel angle 9 is 2° to 4°, the blunt edge thickness 12 is 1-3mm, and the maximum bevel gap 10 does not exceed 10mm; when the thickness of the titanium alloy plate 8 to be welded is greater than or equal to 20mm and less than 40mm, a bevel is designed on one side of the titanium alloy plate 8 to be welded; when the thickness of the titanium alloy plate 8 to be welded is greater than or equal to 40mm, a bevel is designed on both sides of the titanium alloy plate 8 to be welded.

[0036] S2. Grind the U-shaped bevel of the joint to be welded and the area around the bevel, and clean it.

[0037] S3. Place the titanium alloy plate 8 to be welded in the gas protection device and fix it together.

[0038] Figure 2 This is a schematic diagram of the overall structure of the gas protection device of the present invention. Figure 4 This is a schematic diagram of the internal structure of the gas protection device of the present invention. Figure 2 and Figure 4 As shown, the gas protection device includes a protective gas chamber consisting of a protective gas chamber base plate 2, two fixed side plates on the left and right sides of the protective gas chamber base plate 2, two sealing baffles 1 connected to the protective gas chamber base plate 2 by hinges on the front and rear sides of the protective gas chamber base plate 2, and a protective gas chamber top cover plate 3. The protective gas chamber base plate 2 has four symmetrically distributed fixing bolts 4 at its four corners, and a jaw iron 2a for supporting the titanium alloy plate 8 to be welded is provided in the middle. The two sealing baffles 1 have densely arranged uniformly spaced small gas guide holes 1a near their bottom positions for connecting to the protective gas guide pipe, filling with protective gas to create a protective atmosphere. The top of the two sealing baffles 1 has a vertically oriented elongated groove 1b. The protective gas chamber top cover plate 3 has bolt holes at its four corners that mate with the fixing bolts 4, a sliding cover through-hole device for passing through the laser beam and MIG welding torch in the middle, and butterfly nuts 6 and locking bolt holes corresponding to the positions of the elongated grooves 1b on its sides.

[0039] Preferably, the sliding cover 5 is further provided with a welding gun sliding cover connecting rod 7 for fixing the laser head and the MIG welding gun, so as to ensure that the sliding cover 5 moves synchronously with the laser head and the MIG welding gun.

[0040] Preferably, the structural schematic diagram of the protective air chamber cover plate and the sliding cover through hole device provided thereon in this invention is as follows: Figure 3 As shown, the sliding cover through-hole device includes an elongated opening 3b on the upper cover plate 3 of the protective gas chamber, a guide groove device parallel to the elongated opening 3b, and a sliding cover 5 that can slide along the guide groove device. The sliding cover has a sliding cover opening 5a that allows the MIG welding torch and laser beam to pass through. When the sliding cover 5 slides along the guide groove device, the sliding cover opening 5a slides along the elongated opening 3b.

[0041] Preferably, the guide groove device consists of two upper and lower guide groove platforms 3a and a guide groove composed of two limiting strips sandwiched between the two guide groove platforms 3a;

[0042] The specific operation of placing the titanium alloy plate 8 to be welded in the gas protection device is as follows: Place the titanium alloy plate 8 to be welded on the jaw iron 2a in the protective gas chamber, so that the weld direction is parallel and perpendicular to the sliding direction of the sliding cover through hole device; clamp the protective gas chamber top cover plate 3, the titanium alloy plate 8 to be welded, the jaw iron 2a and the protective gas chamber bottom plate 2 by fixing bolts 4, and then seal and clamp the sealing baffle 1 and the protective gas chamber top cover plate 3 by passing the butterfly nut 6 through the long through groove 1b on the sealing baffle 1 and the locking bolt hole on the side of the protective gas chamber top cover plate 3 in sequence; connect the protective gas guide pipe to the small gas guide hole 1a set on the two sealing baffles 1, open the gas valve to adjust the gas flow rate, so that the protective gas chamber is filled with a stable flow of protective gas.

[0043] Figure 5 This is a schematic diagram simulating the internal airflow of the gas protection device of the present invention. As can be seen from the diagram, the airflow is injected through the gas guide hole 1a and flows upwards, escaping through the opening 3b in the upper cover plate. The airflow is stable and laminar, with a high concentration of protective gas. The protection range completely covers the laser-affected area, the arc-affected area, and the weld pool of the workpiece 8 to be welded, effectively protecting three high-temperature areas: the weld pool area during welding, the high-temperature solidification area after welding, and the back surface area of ​​the weld. Compared with coaxial gas protection, this method avoids the welding instability caused by the direct blowing of the nozzle airflow disturbing the weld pool flow and the laser-arc coupling state. Therefore, the gas flow rate and velocity can be appropriately increased to achieve better protection.

[0044] S4. Use a laser-MIG composite heat source to perform multi-layer welding on the titanium alloy plate 8 to be welded. After each layer of welding is completed, control the welding torch to exit the protective gas chamber and clean the weld bead. After the weld cools to room temperature, immediately perform the next layer of welding until the bevel is filled.

[0045] The welding process parameters are as follows: the defocusing amount of the laser beam is -2 to 2 mm, the laser power is 1.2 to 2.5 kW; the diameter of the welding wire of the MIG welding torch is 1.2 mm, the length of the welding wire is 12 to 18 mm, preferably 15 mm, the pulse current is 170 to 190 A, and the welding voltage is 20 to 24 V; during welding, the laser beam is in front and the MIG welding torch moves synchronously behind, the laser beam is tilted in the welding direction with an angle of 10° with the vertical direction, the MIG welding torch is tilted in the opposite welding direction with an angle of 50° to 60° with the vertical direction, the wire spacing is 2 to 3 mm, the welding speed is 8 to 12 mm / s, and the wire feed speed is 6 to 7 m / min. Figure 6 This is only to clearly illustrate the positional relationship between the laser beam and the MIG welding torch, and does not represent the actual welding situation of thick titanium alloy plates. In the figure, A is the angle between the laser beam and the vertical direction, A = 10°, and B is the angle between the MIG welding torch and the vertical direction, B = 50°-60°.

[0046] Preferably, the protective gas is argon with a purity of 99% or higher, and during the welding process, the flow rate of the protective gas introduced into the protective gas chamber is 20-30 L / min, preferably 25 L / min.

[0047] Example 1

[0048] A laser-MIG hybrid welding method for thick titanium alloy plates, wherein the thick titanium alloy plate is 25mm thick, and the laser-MIG hybrid welding method steps are as follows:

[0049] S1. The weld joint of the titanium alloy plate 8 to be welded is processed into a U-shaped bevel with a preset shape, the bevel angle 9 is 4°, the blunt edge thickness 12 is 2mm, the bottom bevel gap is 6mm, and the maximum bevel gap is less than 10mm; a bevel is designed on one side of the titanium alloy plate 8 to be welded.

[0050] S2. Grind the U-shaped bevel of the joint to be welded and the area around the bevel, and clean it.

[0051] S3. Place the titanium alloy plate 8 to be welded in the gas protection device and fix it together.

[0052] The gas protection device comprises a protective gas chamber consisting of a protective gas chamber base plate 2, two fixed side plates on the left and right sides of the protective gas chamber base plate 2, two sealing baffles 1 connected to the protective gas chamber base plate 2 by hinges on the front and rear sides of the protective gas chamber base plate 2, and a protective gas chamber top cover plate 3. The protective gas chamber base plate 2 has four symmetrically distributed fixing bolts 4 at its four corners, and a jaw iron 2a in the middle for supporting the titanium alloy plate 8 to be welded. The two sealing baffles 1 have densely arranged uniformly spaced small gas guide holes 1a near their bottom positions for connecting to the protective gas guide pipe and filling with protective gas to create a protective atmosphere. The top of the two sealing baffles 1 has a vertically oriented elongated groove 1b. The protective gas chamber top cover plate 3 has bolt holes at its four corners that mate with the fixing bolts 4, a sliding cover through-hole device in the middle for passing through the laser beam and MIG welding torch, and butterfly nuts 6 and locking bolt holes corresponding to the positions of the elongated grooves 1b on its sides.

[0053] The specific operation of placing the titanium alloy plate 8 to be welded in the gas protection device is as follows: Place the titanium alloy plate 8 to be welded on the jaw iron 2a in the protective gas chamber, so that the weld direction is parallel and perpendicular to the sliding direction of the sliding cover through hole device; clamp the protective gas chamber top cover plate 3, the titanium alloy plate 8 to be welded, the jaw iron 2a and the protective gas chamber bottom plate 2 by fixing bolts 4, and then seal and clamp the sealing baffle 1 and the protective gas chamber top cover plate 3 by passing the butterfly nut 6 through the long through groove 1b on the sealing baffle 1 and the locking bolt hole on the side of the protective gas chamber top cover plate 3 in sequence; connect the protective gas guide pipe to the small gas guide hole 1a set on the two sealing baffles 1, open the gas valve to adjust the gas flow rate, so that the protective gas chamber is filled with a stable flow of protective gas.

[0054] S4. Use a laser-MIG composite heat source to perform multi-layer welding on the titanium alloy plate 8 to be welded. After each layer of welding is completed, control the welding torch to exit the protective gas chamber and clean the weld bead. After the weld cools to room temperature, immediately perform the next layer of welding until the bevel is filled.

[0055] The welding process parameters are as follows: laser beam defocusing amount is 0mm, laser power is 2kw; MIG welding torch welding wire diameter is 1.2mm, welding wire length is 15mm; pulse current is 180A, welding voltage is 22V; during welding, the laser beam is in front and the MIG welding torch moves synchronously behind, the laser beam is tilted in the welding direction with an angle of 10° with the vertical direction, the MIG welding torch is tilted in the opposite welding direction with an angle of 60° with the vertical direction, the wire spacing is 2mm, the welding speed is 10mm / s, and the wire feed speed is 6m / min.

[0056] In this example, the sliding cover through-hole device includes an elongated opening 3b on the upper cover plate 3 of the protective gas chamber, a guide groove device parallel to the elongated opening 3b, and a sliding cover 5 that can slide along the guide groove device. The sliding cover 5 has a sliding cover opening 5a that allows the MIG welding torch and laser beam to pass through. When the sliding cover 5 slides along the guide groove device, the sliding cover opening 5a slides along the elongated opening 3b.

[0057] In this example, the guide groove device consists of two upper and lower guide groove platforms 3a and a guide groove composed of two limiting strips sandwiched between the two guide groove platforms 3a.

[0058] In this example, the sliding cover 5 is also provided with a welding gun sliding cover connecting rod 7 for fixing the laser head and the MIG welding gun, so as to ensure that the sliding cover 5 moves synchronously with the laser head and the MIG welding gun.

[0059] In this example, the protective gas is argon with a purity of over 99%, and the flow rate of the protective gas introduced into the protective gas chamber during the welding process is 25 L / min.

[0060] Figure 7 This is a schematic diagram illustrating the quality of a single-sided bevel weld on a 25mm thick titanium alloy plate, as shown in Example 2. Figure 7 (a) shows the surface morphology of the weld. The weld surface is bright and uniform, without defects such as humps, undercut, or lack of fusion. There is no spatter adhering to the sidewall of the bevel, indicating that the droplet transition is smooth, the molten pool is stable, and the gas protection effect is good. (b) shows the X-ray porosity measurement results of the weld. It can be found that there are no obvious porosity defects inside the weld, indicating that the arc and molten pool are highly stable during the welding process. Figure 7 (c) is a metallographic image of the weld cross section. It can be seen that the weld and the bevel sidewall are well fused, with no defects such as incomplete fusion or undercut. The microstructure is a typical columnar grain growing along the direction of the maximum temperature gradient, indicating good metallurgical quality of the weld.

[0061] Example 2

[0062] A laser-MIG hybrid welding method for thick titanium alloy plates, wherein the thick titanium alloy plate is 45mm thick, and the laser-MIG hybrid welding method steps are as follows:

[0063] S1. The weld joint of the titanium alloy plate 8 to be welded is processed into a U-shaped bevel with a preset shape, the bevel angle 9 is 3°, the blunt edge thickness 12 is 2mm, the bottom bevel gap is 3mm, and the maximum bevel gap is less than 6mm; bevels are designed on both sides of the titanium alloy plate 8 to be welded.

[0064] S2. Grind the U-shaped bevel of the joint to be welded and the area around the bevel, and clean it.

[0065] S3. Place the titanium alloy plate 8 to be welded in the gas protection device and fix it together.

[0066] The gas protection device comprises a protective gas chamber consisting of a protective gas chamber base plate 2, two fixed side plates on the left and right sides of the protective gas chamber base plate 2, two sealing baffles 1 connected to the protective gas chamber base plate 2 by hinges on the front and rear sides of the protective gas chamber base plate 2, and a protective gas chamber top cover plate 3. The protective gas chamber base plate 2 has four symmetrically distributed fixing bolts 4 at its four corners, and a jaw iron 2a in the middle for supporting the titanium alloy plate 8 to be welded. The two sealing baffles 1 have densely arranged uniformly spaced small gas guide holes 1a near their bottom positions for connecting to the protective gas guide pipe and filling with protective gas to create a protective atmosphere. The top of the two sealing baffles 1 has a vertically oriented elongated groove 1b. The protective gas chamber top cover plate 3 has bolt holes at its four corners that mate with the fixing bolts 4, a sliding cover through-hole device in the middle for passing through the laser beam and MIG welding torch, and butterfly nuts 6 and locking bolt holes corresponding to the positions of the elongated grooves 1b on its sides.

[0067] The specific operation of placing the titanium alloy plate 8 to be welded in the gas protection device is as follows: Place the titanium alloy plate 8 to be welded on the jaw iron 2a in the protective gas chamber, so that the weld direction is parallel and perpendicular to the sliding direction of the sliding cover through hole device; clamp the protective gas chamber top cover plate 3, the titanium alloy plate 8 to be welded, the jaw iron 2a and the protective gas chamber bottom plate 2 by fixing bolts 4, and then seal and clamp the sealing baffle 1 and the protective gas chamber top cover plate 3 by passing the butterfly nut 6 through the long through groove 1b on the sealing baffle 1 and the locking bolt hole on the side of the protective gas chamber top cover plate 3 in sequence; connect the protective gas guide pipe to the small gas guide hole 1a set on the two sealing baffles 1, open the gas valve to adjust the gas flow rate, so that the protective gas chamber is filled with a stable flow of protective gas.

[0068] S4. Use a laser-MIG composite heat source to perform multi-layer welding on the titanium alloy plate 8 to be welded. After each layer of welding is completed, control the welding torch to exit the protective gas chamber and clean the weld bead. After the weld cools to room temperature, immediately perform the next layer of welding until the bevel is filled.

[0069] The welding process parameters are as follows: the joint consists of 18 weld seams, formed by alternating double-sided welding. Due to the gradual increase in bevel gap along the plate thickness direction, the required filler volume increases, and the risk of weld incomplete fusion defects also increases. Therefore, the welding speed of the intermediate filler layer is reduced to 9 mm / s, and the laser power is increased to 2 kW to appropriately increase the heat input. The laser spot defocusing amount is 0 mm, the wire spacing is 2 mm, and the wire extension is 15 mm. Specific welding process parameters for each weld seam are shown in Table 1.

[0070] Table 1

[0071]

[0072]

[0073] In this example, the sliding cover through-hole device includes an elongated opening 3b on the upper cover plate 3 of the protective gas chamber, a guide groove device parallel to the elongated opening 3b, and a sliding cover 5 that can slide along the guide groove device. The sliding cover 5 has a sliding cover opening 5a that allows the MIG welding torch and laser beam to pass through. When the sliding cover 5 slides along the guide groove device, the sliding cover opening 5a slides along the elongated opening 3b.

[0074] In this example, the guide groove device consists of two upper and lower guide groove platforms 3a and a guide groove composed of two limiting strips sandwiched between the two guide groove platforms 3a.

[0075] In this example, the sliding cover 5 is also provided with a welding gun sliding cover connecting rod 7 for fixing the laser head and the MIG welding gun, so as to ensure that the sliding cover 5 moves synchronously with the laser head and the MIG welding gun.

[0076] In this example, the protective gas is argon with a purity of over 99%, and the flow rate of the protective gas introduced into the protective gas chamber during the welding process is 25 L / min.

[0077] Figure 8 This is a macroscopic morphological image of the cross-section of a multi-welded joint in a 45mm thick titanium alloy plate according to Embodiment 2 of the present invention. Figure 8 It can be seen that the overall joint has no obvious welding deformation, cracks, porosity, lack of fusion and other defects. The weld is uniform and the transition between weld beads is smooth, showing an I-shaped morphology.

[0078] The above embodiments are typical implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and included within the protection scope of the present invention.

Claims

1. A laser-MIG hybrid welding method for thick titanium alloy plates, characterized in that: The titanium alloy plate is a titanium alloy plate with a thickness of 20 mm or more. The laser-MIG hybrid welding method steps are as follows: S1. The weld joint of the titanium alloy thick plate (8) to be welded is processed into a U-shaped bevel with a preset shape. The bevel angle (9) is 2° to 4°, the blunt edge thickness (12) is 1-3mm, and the bevel gap (10) is no more than 10mm. When the thickness of the titanium alloy thick plate (8) to be welded is greater than or equal to 20mm and less than 40mm, a bevel is designed on one side of the titanium alloy thick plate (8) to be welded. When the thickness of the titanium alloy thick plate (8) to be welded is greater than or equal to 40mm, a bevel is designed on both sides of the titanium alloy thick plate (8) to be welded. S2. Grind the U-shaped bevel of the joint to be welded and the area around the bevel, and clean it. S3. Place the titanium alloy thick plate (8) to be welded in the gas protection device and fix it together; The gas protection device includes a protective gas chamber consisting of a protective gas chamber base plate (2), two fixed side plates on the left and right sides of the protective gas chamber base plate (2), two sealing baffles (1) connected to the protective gas chamber base plate (2) by hinges on the front and rear sides of the protective gas chamber base plate (2), and a protective gas chamber top cover plate (3); the protective gas chamber base plate (2) has four symmetrically distributed fixing bolts (4) at its four corners, and a clamping iron (2a) for supporting the titanium alloy thick plate (8) to be welded is provided in the middle; the two sealing baffles (1) are close to the bottom The part is densely arranged with uniform gas guide holes (1a) in the radial direction for connecting the protective gas guide pipe and filling the protective gas to create a protective atmosphere; the top of the two sealing baffles (1) is provided with a vertical long through groove (1b); the four corners of the protective gas chamber cover plate (3) are provided with bolt holes that cooperate with the fixing bolts (4), the middle is provided with a sliding cover through hole device for passing through the laser beam and MIG welding gun, and the side is provided with butterfly nuts (6) and locking bolt holes corresponding to the position of the long through groove (1b); The specific operation of placing the titanium alloy thick plate (8) to be welded in the gas protection device is as follows: Place the titanium alloy thick plate (8) to be welded on the jaw iron (2a) in the protective gas chamber, so that the weld direction is parallel and perpendicular to the sliding direction of the sliding cover through hole device; clamp the protective gas chamber upper cover plate (3), the titanium alloy thick plate (8), the jaw iron (2a) and the protective gas chamber bottom plate (2) by fixing bolts (4), and then seal and clamp the sealing baffle (1) and the protective gas chamber upper cover plate (3) by passing the butterfly nut (6) through the long through groove (1b) on the sealing baffle (1) and the locking bolt hole on the side of the protective gas chamber upper cover plate (3); connect the protective gas guide pipe to the small guide hole (1a) set on the two sealing baffles (1), open the gas valve to adjust the gas flow rate, so that the protective gas chamber is filled with a stable flow of protective gas; S4. Use laser-MIG composite heat source to perform multi-layer welding on the weld joint of the titanium alloy thick plate (8). After each layer of welding is completed, control the welding gun to exit the protective gas chamber and clean the weld. After the weld cools to room temperature, immediately perform the next layer of welding until the groove is filled. The welding process parameters are as follows: the laser beam defocusing amount is -2 to 2 mm, the laser power is 1.2 to 2.5 kW; the welding wire diameter of the MIG welding torch is 1.2 mm, the welding wire length is 12 to 18 mm, the pulse current is 170 to 190 A, and the welding voltage is 20 to 24 V; during welding, the laser beam is in front and the MIG welding torch moves synchronously behind, the laser beam is tilted in the welding direction with an angle of 10° with the vertical direction, the MIG welding torch is tilted in the opposite welding direction with an angle of 50° to 60° with the vertical direction, the wire spacing is 2 to 3 mm, the welding speed is 8 to 12 mm / s, and the wire feed speed is 6 to 7 m / min.

2. The laser-MIG hybrid welding method for thick titanium alloy plates according to claim 1, characterized in that: The sliding cover through hole device includes an elongated opening (3b) on the upper cover plate (3) of the protective gas chamber, a guide groove device parallel to the elongated opening (3b), and a sliding cover (5) that can slide along the guide groove device. The sliding cover (5) has a sliding cover opening (5a) that allows the MIG welding gun and laser beam to pass through. When the sliding cover (5) slides along the guide groove device, the sliding cover opening (5a) slides along the elongated opening (3b).

3. The laser-MIG hybrid welding method for thick titanium alloy plates according to claim 2, characterized in that: The guide groove device consists of two upper and lower guide groove platforms (3a) and a guide groove composed of two limiting strips sandwiched between the two guide groove platforms (3a).

4. The laser-MIG hybrid welding method for thick titanium alloy plates according to claim 2, characterized in that: The sliding cover (5) is also provided with a welding gun sliding cover connecting rod (7) for fixing the laser head and the MIG welding gun, so as to ensure that the sliding cover (5) moves synchronously with the laser head and the MIG welding gun.

5. The laser-MIG hybrid welding method for thick titanium alloy plates according to claim 1, characterized in that: The protective gas is argon with a purity of over 99%. During the welding process, the flow rate of the protective gas introduced into the protective gas chamber is 20-30 L / min.

6. The laser-MIG hybrid welding method for thick titanium alloy plates according to claim 1, characterized in that: The protective gas is argon with a purity of 99% or higher. During the welding process, the flow rate of the protective gas introduced into the protective gas chamber is 25 L / min.

7. The laser-MIG hybrid welding method for thick titanium alloy plates according to claim 1, characterized in that: The welding wire length of the MIG welding gun is 15mm.

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