Thin-wall aluminum alloy component welding method based on infrared-blue light composite laser

Abstract

The invention discloses a thin-wall aluminum alloy component welding method based on infrared-blue light composite laser, and belongs to the technical field of laser cladding. The method comprises the steps that firstly, the surface of a to-be-welded thin-wall aluminum alloy component is cleaned and dried to remove an oxidation film and impurities on the surface of the to-be-welded area of the thin-wall aluminum alloy component, and then the to-be-welded area of the thin-wall aluminum alloy component is preheated through blue laser; then, the thin-wall aluminum alloy component is welded according to a preset welding path by taking infrared-blue light composite laser as a heat source, an aluminum alloy welding wire as a filling material and inert gas as protective gas, and after welding is completed, the to-be-welded area is subjected to remelting and heat preservation treatment through the blue light laser; and welding of the to-be-welded thin-wall aluminum alloy component is completed. The method has the remarkable advantages in the aspects of improving the welding efficiency, improving the welding quality, reducing the defect rate, widening the aluminum alloy welding application range and the like, and an efficient and reliable solution is provided for thin-wall aluminum alloy welding.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser cladding, and particularly relates to a welding method for thin-walled aluminum alloy components based on infrared-blue composite laser. Background Art

[0002] Due to the advantages of aluminum alloy such as light weight, high strength, and corrosion resistance, the development of its welding technology is of great significance for realizing the forming of complex structures, improving the design freedom, and promoting lightweight design. There are a rich variety of existing aluminum alloy welding processes, mainly including infrared laser welding, TIG welding (tungsten inert gas welding), MIG welding (metal inert gas welding), plasma arc welding, friction stir welding, electron beam welding, infrared laser-MIG composite welding, etc. and other special welding methods. Among them, infrared laser welding is widely used in the manufacturing of thin-walled and complex components and precision welding fields due to the characteristics of concentrated laser beam energy, fast welding speed, and strong shape adaptability.

[0003] Traditional aluminum alloy laser welding processes usually use infrared lasers with a single wavelength (1064nm). However, aluminum alloy has a low absorption rate for lasers in this wavelength band (usually less than 10%). To ensure the penetration depth and welding strength, high-power infrared lasers are usually required to increase the heat input, which is contradictory to the sensitivity of thin-walled aluminum alloy components to heat input and the easy generation of welding deformation, resulting in some technical difficulties in welding: 1) High reflectivity, aluminum alloy has a high reflectivity to infrared lasers, resulting in low laser energy utilization rate and low welding efficiency. The input of high-power infrared lasers is likely to cause the expansion of the heat-affected zone, leading to an increase in residual stress and component deformation, which is particularly obvious during the welding process of thin-walled aluminum alloy components; 2) Thermal crack tendency, aluminum alloy has a large coefficient of thermal expansion, and thermal stress is easily generated during the welding process, leading to the formation of thermal cracks; 3) Porosity defects, the surface of aluminum alloy is easy to form an oxide film, and porosity defects are easily generated during the welding process, resulting in low weld strength and poor sealing; 4) Aluminum alloy has a high thermal conductivity and fast heat diffusion, making it difficult to control the stability of the molten pool and affecting the welding quality. Summary of the Invention

[0004] To solve the problems in the prior art, the present invention provides a welding method for thin-walled aluminum alloy components based on infrared-blue composite laser.

[0005] The technical solution of the present invention is as follows:

[0006] The present invention discloses a welding method for thin-walled aluminum alloy components based on infrared-blue composite laser, including the following steps:

[0007] 1) Clean and dry the surface of the thin-walled aluminum alloy component to be welded to remove the oxide film and impurities on the surface of the thin-walled aluminum alloy component in the area to be welded, and then preheat the area to be welded of the thin-walled aluminum alloy component with blue laser;

[0008] 2) Use infrared-blue composite laser as the heat source, use aluminum alloy welding wire as the filler material, use inert gas as the shielding gas, and weld the thin-walled aluminum alloy component according to the preset welding path;

[0009] 3) After welding, use blue laser to remelt and keep warm the area to be welded to complete the welding of the thin-walled aluminum alloy component to be welded.

[0010] Compared with the prior art, the specific beneficial effects of the present invention are as follows:

[0011] The present invention adopts the process flow of infrared-blue composite laser combined with preheating-welding-remelting and heat preservation, which can effectively avoid the welding problems caused by the low absorption rate of single infrared laser by aluminum alloy, and the main manifestations are as follows: 1) Blue laser effectively reduces the high reflectivity of the aluminum alloy surface to laser, improves the laser energy utilization rate, and thus greatly improves the welding efficiency; 2) Blue laser can inhibit the generation of pores during the welding process, and at the same time cooperate with infrared laser to refine the weld microstructure, significantly improve the welding quality, and improve the strength and toughness of the weld; 3) Composite laser welding can achieve more precise control of heat input, reduce the heat affected zone of welding, and reduce the tendency of hot cracks, and is especially suitable for thin-walled aluminum alloy materials with high reflectivity, easy oxidation and thermal sensitivity. To sum up, the infrared-blue composite laser welding technology shows significant advantages in improving welding efficiency, improving welding quality, reducing defect rate and expanding the applicable range of aluminum alloy welding, and provides an efficient and reliable solution for thin-walled aluminum alloy welding. Description of the Drawings

[0012] Figure 1 It is a schematic diagram of the welding method;

[0013] Figure 2 It is a schematic cross-sectional view of infrared-blue composite laser;

[0014] Figure 3 It is a flowchart of the welding method;

[0015] Figure 4 It is a diagram of the preheating movement track;

[0016] Figure 5 It is a diagram of the weld appearance after infrared laser welding;

[0017] Figure 6 It is a diagram of the weld appearance after composite laser welding;

[0018] Figure 7It is a cross-sectional view of the weld seam after infrared laser welding;

[0019] Figure 8 It is a cross-sectional view of the weld seam after composite laser welding. Specific embodiments

[0020] The present invention will be further described and explained below in conjunction with specific embodiments. The described embodiments are only illustrative of the present disclosure and do not delimit the scope of limitation. The technical features of each embodiment of the present invention can be combined accordingly without conflict.

[0021] The purpose of the present invention is to provide a welding method for thin-walled aluminum alloy components based on infrared-blue composite laser to solve the problems of low efficiency and poor quality in aluminum alloy laser welding in the prior art. By introducing blue laser, the reflectivity of the aluminum alloy surface to the laser is reduced, the energy absorption rate is increased, and at the same time, the control of heat input during the welding process is optimized to inhibit the generation of pores and refine the weld microstructure, thereby significantly improving the welding efficiency, improving the welding quality, and reducing the tendency of hot cracks. The present invention also designs a preheating process for low-power, large-spot blue laser, which can uniformly heat the weld area and avoid the generation of thermal stress and thermal deformation due to excessive temperature gradient during the welding process. The present invention also designs a remelting and heat preservation process to effectively slow down the temperature drop rate after welding and reduce the thermal shrinkage problem of thin-walled aluminum alloy components due to the sharp temperature drop, which is beneficial to improving the geometric accuracy of the components after welding.

[0022] The schematic diagram of the welding method of the welding method for thin-walled aluminum alloy components based on infrared-blue composite laser designed by the present invention is as Figure 1 shown. The figure mainly shows a workbench 1, a thin-walled aluminum alloy component 2 to be welded, a shielding gas output pipe 3, a blue laser 4, an infrared laser 5, and a wire feeding conduit 6.

[0023] The workbench 1 provides an installation position for the thin-walled aluminum alloy component 2 to be welded and its fixing fixture, and is in a fixed state during the welding process. The thin-walled aluminum alloy component 2 to be welded includes a welding area. Taking the welding area as the boundary, the thin-walled aluminum alloy component 2 to be welded is divided into two units, and the two units will be melted into one after welding. One end of the shielding gas output pipe 3 is connected to a gas cylinder, and the other end acts on the welding area. The shielding gas output pipe 3 is used to transport the inert gas in the gas cylinder to the welding area position to avoid oxidation during the welding process and affect the welding performance; wherein, in a specific embodiment of the present invention, the inert gas is argon or helium.

[0024] The blue laser 4 and the infrared laser 5 are coaxially distributed, and their foci are at the same position. The two are respectively generated by a blue laser and an infrared laser, and are transmitted through an optical fiber and processed by an optical lens to converge into one point. The blue laser 4 is a laser beam with a wavelength range of 450 nm - 470 nm and a maximum power of 500 W. The infrared laser 5 is a laser beam with a wavelength range of 800 nm - 1100 nm and a maximum power of 2000 W. The output powers of the two laser beams can be steplessly adjusted within the maximum power range and have an independent control function, that is, during the welding process, the infrared laser and the blue laser can be output separately, and the infrared-blue composite laser can be output.

[0025] In a specific embodiment of the present invention, the spot diameter of the blue laser 4 at the focus is 2 mm, and the spot diameter of the infrared laser 5 is 1.2 mm. From the cross-section of the laser focus, the two are in an annular distribution, as Figure 2 shown.

[0026] One end of the wire feeding conduit 6 is connected to a wire feeder, and the wire material can be transported by the wire feeding conduit 6 to the laser focus to provide the necessary materials during welding to fill defects and restore the shape and function of the thin-walled aluminum alloy component. The relative positions of the shielding gas output pipe 3, the blue laser 4, the infrared laser 5, and the wire feeding conduit 6 are fixed, and they are all connected to the motion execution mechanism in the welding device and complete the welding work along with the motion execution mechanism according to a preset motion trajectory.

[0027] The welding method designed by the present invention is as Figure 3 shown, mainly including steps such as clamping, cleaning, preheating, welding, remelting, and heat preservation of the thin-walled aluminum alloy component 2 to be welded. The implementation details of each step are as follows.

[0028] Step 1: Clamping of the thin-walled aluminum alloy component 2 to be welded. The thin-walled aluminum alloy component 2 to be welded is fixed on the workbench 1 through tools such as jigs to ensure that the thin-walled aluminum alloy component 2 to be welded does not move during the welding process.

[0029] Step 2: Cleaning. Because a dense aluminum oxide film will form on the surface of aluminum alloy at room temperature, and its melting point is as high as 2050 °C, which is much higher than the melting point of the aluminum alloy itself (about 660 °C). This oxide film will hinder the fusion of metals during welding, resulting in defects such as incomplete fusion and incomplete penetration in the area to be welded. Therefore, the oxide film on the surface of the thin-walled aluminum alloy component needs to be removed by cleaning.

[0030] The cleaning process can be as follows: First, use an alkaline solution to rinse the surface of the thin-walled aluminum alloy component around the area to be welded to remove the oxide film and impurities on the surface of the thin-walled aluminum alloy component; then use an acidic solution for rinsing to neutralize the alkaline solution remaining on the aluminum alloy surface; finally, use anhydrous ethanol for cleaning and drying.

[0031] Specifically, in a specific embodiment of the present invention, the specific steps of cleaning include: rinsing the surface of the thin-walled aluminum alloy component around the area to be welded with a 10% concentration sodium hydroxide solution and standing for 5 minutes to remove the oxide film and impurities on the surface to be welded; then rinsing with a 10% concentration nitric acid solution and standing for 3 minutes to neutralize the residual alkali solution after sodium hydroxide cleaning; finally, cleaning with anhydrous ethanol and naturally drying or wiping with a clean dry cloth to remove the residual moisture after sodium hydroxide and nitric acid rinsing, preventing the generation of pores during the welding process due to moisture residue.

[0032] The work function of the electrons escaping from the oxide film on the aluminum alloy surface is relatively low, and it is easy to emit electrons, resulting in unstable arc drift and affecting the stability of the welding process. Removing the oxide film helps to maintain the stability of the arc and ensure the welding quality. The existence of the oxide film will also exacerbate the thermal stress during the welding process and increase the risk of hot cracks. Removing the oxide film can reduce this tendency and improve the strength and reliability of the weld (i.e., the area to be welded). And after removing the oxide film, the welding process is easier to control, which can improve the welding efficiency and quality.

[0033] Step 3: Preheating. Use a low-power, large-spot blue laser with a power of 100 - 200w, a wavelength of 450nm - 470nm, and a spot diameter of 4 - 6mm combined with a motion actuator to preheat the area to be welded.

[0034] In a specific embodiment of the present invention, the vertical distance between the laser focus and the area to be welded is adjusted through the motion actuator, so that the spot of the blue laser is in a defocused state, and a spot with a diameter of 4mm can be obtained.

[0035] After the blue laser is turned on, the motion actuator starts to control the spot of the blue laser to reciprocate along the preset welding path to achieve preheating. At the same time, it also moves a certain amplitude in the width direction of the welding path so that the width direction of the welding path is also preheated, avoiding local overheating or insufficient heat in the area to be welded. And adopting such a preheating method can effectively expand the range of the heat-affected zone and achieve a gradient diffusion distribution of heat, thus effectively avoiding the band-shaped high-temperature concentration area easily formed by the straight preheating path. The main advantage of this path is its local repeated heating function, which is particularly significant for improving the temperature field distribution of the material.

[0036] In a specific embodiment of the present invention, the spot of the blue laser 4 can perform a spiral reciprocating motion along the preset welding path, and the motion trajectory is as Figure 4 shown. Taking high-reflectivity aluminum alloy as an example, such a preheating path can significantly reduce the total heat input by 15 - 20% compared with the traditional straight path. This characteristic not only improves the energy utilization efficiency but also helps to improve the processing characteristics of the material. Among them, the moving distance in the width direction of the welding path can be 10 - 20mm.

[0037] The low-power, large-spot blue laser can effectively reduce the power density of the laser beam. When combined with the spiral reciprocating motion, it can avoid problems such as local overheating or insufficient heat in the area to be welded, ensuring uniform heating of the area to be welded. When the surface temperature of the thin-walled aluminum alloy component within a range of 10 - 15 mm around the area to be welded reaches 150 - 200 °C, the blue laser is turned off, and the preheating is completed. The motion execution mechanism moves to the starting point of the preset welding path.

[0038] Preheating can reduce the temperature gradient in the area to be welded, reduce the thermal stress generated by rapid heating and cooling, and thus reduce the risk of deformation and thermal cracking of the thin-walled aluminum alloy component during welding.

[0039] Step 4: Welding. The blue laser, infrared laser, gas cylinder, wire feeder, and motion mechanism are turned on simultaneously. The foci of the blue laser 4 and the infrared laser 5 converge at the starting point of the preset welding path. At the same time, the aluminum alloy welding wire also converges at this starting point through the wire feeding conduit 6, and the shielding gas is output to the welding part through the shielding gas output pipe 3.

[0040] Under the action of the infrared-blue composite laser, the base material of the thin-walled aluminum alloy component and the aluminum alloy welding wire at the starting point are melted together to form a molten pool. At the same time, under the action of the motion execution mechanism, the molten pool moves along the preset welding path. After the laser beam moves, the temperature of the melted area behind the molten pool decreases, and the melted base material of the thin-walled aluminum alloy component and the aluminum alloy welding wire solidify into one body to complete the welding. The moving speed of the motion execution mechanism is 10 mm / s.

[0041] Among them, in the infrared-blue composite laser, the power of the blue laser is 350 - 500 w, the wavelength is 450 nm - 470 nm, the power of the infrared laser is 900 - 1200 w, and the wavelength is 800 nm - 1100 nm; the diameter of the spot formed when the blue laser irradiates the surface of the area to be welded is 2 - 3 mm, the diameter of the spot formed when the infrared laser irradiates the surface of the area to be welded is 1.2 - 2 mm, and the center of the spot irradiated by the blue laser coincides with the center of the spot irradiated by the infrared laser.

[0042] In a specific embodiment of the present invention, the power of the blue laser 4 is 350 w, and the power of the infrared laser 5 is 900 w. The two act together to form an annular composite laser with a small power on the outside and a large power in the center at the laser focus. The specific power value can be adjusted according to the thickness of the thin-walled aluminum alloy component 2 to be welded.

[0043] In the infrared-blue composite laser, the blue laser part can reduce the reflection loss of the aluminum alloy to the infrared laser, improve the energy utilization rate, and enhance the welding efficiency. In addition, the large-spot blue laser can effectively stabilize the molten material around the molten pool, improve the fluidity of the molten pool, facilitate the removal of gas and impurities, reduce defects such as pores and slag inclusions, and improve the process stability. After welding is completed, the motion execution mechanism resets and returns to the starting point of the preset welding path.

[0044] Step 5: Remelting and heat preservation. This step is roughly the same as the preheating process in Step 3. Use a low-power, large-spot blue laser with a power of 100 - 200w, a wavelength of 450nm - 470nm, and a spot diameter of 4 - 6mm. Control the spot of the blue laser to reciprocate along the preset welding path, and at the same time, move a certain distance in the width direction of the welding path so that the width direction of the welding path can also be remelted and heat-preserved.

[0045] During the remelting and heat preservation process, dynamically adjust the power of the blue laser according to a preset change rate. Through this non-linear power adjustment strategy, precisely control the surface temperature of the thin-walled aluminum alloy component within a range of 10 - 15mm around the area to be welded, so that the surface temperature of the thin-walled aluminum alloy component within a range of 10 - 15mm around the area to be welded is reduced to 80 - 100°C within 2 - 5 minutes. At this time, the remelting and heat preservation treatment is completed; among them, the absolute value of the change rate is 20W / s - 50W / s; the moving distance in the width direction of the welding path can be 10 - 20mm; the dynamic adjustment includes increasing the power of the blue laser and decreasing the power of the blue laser.

[0046] In a specific embodiment of the present invention, the movement trajectory of the spot of the blue laser can be Figure 4 consistent with the movement trajectory shown.

[0047] This step has the effect of slowing down the temperature drop rate in the area to be welded, promoting grain refinement in the area to be welded, reducing the welding residual stress, being able to improve the mechanical properties of the area to be welded, and reducing the risk of deformation and cracking of the thin-walled aluminum alloy component.

[0048] To verify the advantages of the infrared-blue composite laser in the welding of thin-walled aluminum alloy components, a crack damage with a depth of 1mm is prefabricated in an aluminum alloy (grade: 2024) with a specification of 150*80*2mm. Welding performance tests are carried out respectively with an infrared laser of 1250w and a total power of the composite laser of 1250w (where the infrared laser is 900w and the blue laser is 350w), and comparisons are made from aspects such as the weld appearance, tensile strength, and weld cross-section state.

[0049] During the two welding processes, except for the different laser modes used in the final welding, steps such as cleaning, preheating, and heat preservation are the same. Figure 5 、Figure 6 They are the appearance diagrams of the welds after infrared laser welding and composite laser welding respectively. The black arrows in the figures indicate the welding directions. It can be seen from the appearance diagrams of the welds that the flatness of the welds in the infrared laser mode is worse than that in the composite laser mode.

[0050] Figure 7 、 Figure 8 They are the cross-sectional diagrams of the welds after infrared laser welding and composite laser welding respectively. It can be seen from the figures that under the action of the infrared laser, there is an obvious gap in the middle of the weld, that is, the substrate materials on both sides of the crack are not completely melted, cooled and solidified into one body after welding; under the action of the composite laser, there is no obvious gap in the cross-section of the weld, and the penetration depth (D) and the width (w) of the clad layer of the substrate are both larger than those of the infrared laser, and the height (h) of the clad layer is smaller than that of the infrared laser. In addition, according to the room temperature test method of the tensile test of metallic materials (GB / T 228.1-2021), the tensile strengths of the specimens under the two welding modes are tested. The average tensile strength of the infrared laser welded parts is only 276 MPa, and the average tensile strength of the composite laser welded parts is 383 MPa. The test results of the welding performance show that the weld appearance, cross-sectional state and tensile strength of the components after composite laser welding are all better than those of the infrared laser. This method has practical significance in the welding of thin-walled aluminum alloy components.

[0051] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent of the present invention. For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A thin-walled aluminum alloy component welding method based on infrared-blue light composite laser, characterized in that: The following steps are involved: 1) Clean and dry the surface of the thin-walled aluminum alloy component to be welded to remove the oxide film and impurities on the surface of the thin-walled aluminum alloy component in the welding area, and then use a blue light laser to preheat the welding area of ​​the thin-walled aluminum alloy component; 2) Using infrared-blue light composite laser as heat source, aluminum alloy welding wire as filling material, and inert gas as shielding gas, the welding of thin-walled aluminum alloy components is carried out according to the preset welding path; 3) After welding is completed, the blue light laser is used to remelt and heat-insulate the welding area to complete the welding of the thin-walled aluminum alloy components to be welded.

2. The thin-walled aluminum alloy component welding method based on infrared-blue light composite laser according to claim 1 is characterized in that: In step 1), the surface of the aluminum alloy to be welded is cleaned and dried, comprising: First, the surface of the thin-walled aluminum alloy component around the welding area is rinsed with an alkaline solution to remove the oxide film and impurities on the surface of the thin-walled aluminum alloy component; then it is rinsed with an acidic solution to neutralize the alkaline solution remaining on the surface of the aluminum alloy; finally, it is cleaned and dried with anhydrous ethanol.

3. The thin-walled aluminum alloy component welding method based on infrared-blue light composite laser according to claim 1 is characterized in that: In step 1), the blue laser is used to preheat the area to be welded of the thin-walled aluminum alloy component, comprising: First, adjust the power of the blue laser to 100-200W, and then adjust the diameter of the spot that appears when the blue laser is irradiated on the surface of the area to be welded to 4-6mm; wherein the wavelength of the blue laser is 450nm-470nm; The blue laser spot is controlled to reciprocate along the preset welding path. When the surface temperature of the thin-walled aluminum alloy component within 10-15mm around the welding area reaches 150-200℃, the preheating process is judged to be completed.

4. The thin-walled aluminum alloy component welding method based on infrared-blue light composite laser according to claim 3 is characterized in that: When the blue laser spot reciprocates along the welding path, it also moves a certain amount in the width direction of the welding path so that the width direction of the welding path is also preheated to avoid local overheating or insufficient heating of the area to be welded.

5. The thin-walled aluminum alloy component welding method based on infrared-blue light composite laser according to claim 1 is characterized in that: In step 2), the power of the blue laser in the infrared-blue composite laser is 350-500w, the wavelength is 450nm-470nm, the power of the infrared laser is 900-1200w, the wavelength is 800nm-1100nm; the diameter of the light spot that appears when the blue laser is irradiated on the surface of the area to be welded is 2-3mm, the diameter of the light spot that appears when the infrared laser is irradiated on the surface of the area to be welded is 1.2-2mm, and the center of the light spot irradiated by the blue laser coincides with the center of the light spot irradiated by the infrared laser.

6. The thin-walled aluminum alloy component welding method based on infrared-blue light composite laser according to claim 1 is characterized in that: In step 2), the inert gas is argon or helium.

7. The thin-walled aluminum alloy component welding method based on infrared-blue light composite laser according to claim 1 is characterized in that: In step 3), after the welding is completed, the blue light laser is used to remelt and heat-insulate the welding area, including: First, adjust the power of the blue laser to 100-200W, and then adjust the diameter of the spot that appears when the blue laser is irradiated on the surface of the area to be welded to 4-6mm; wherein the wavelength of the blue laser is 450nm-470nm; The spot of the blue laser is controlled to reciprocate along the preset welding path to achieve remelting and heat preservation treatment. During the remelting and heat preservation process, the power of the blue laser is dynamically adjusted according to the preset change rate, so that the surface temperature of the thin-walled aluminum alloy components within 10-15mm around the welding area is reduced to 80-100℃ within 2-5 minutes, and the remelting and heat preservation treatment is completed; among them, the absolute value of the change rate is 20 W / s -50W / s.

8. The thin-walled aluminum alloy component welding method based on infrared-blue light composite laser according to claim 7 is characterized in that: When the blue laser spot reciprocates along the welding path, it also moves a certain range in the width direction of the welding path, so that the width direction of the welding path is also remelted and heat-insulated, slowing down the temperature drop rate in the area to be welded, promoting grain refinement in the area to be welded, reducing the effect of welding residual stress, improving the mechanical properties of the area to be welded, and reducing the risk of deformation and cracking of thin-walled aluminum alloy components.

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