A laser filler wire welding process and method for aluminum alloys and steel used in automobiles

Abstract

This invention discloses a laser-assisted wire-filler welding process and method for aluminum alloys and steel used in automobiles, belonging to the field of dissimilar metal welding technology. Addressing the problems of existing automotive aluminum-steel laser welding, such as the easy formation of brittle Fe-Al intermetallic compounds, poor weld mechanical properties, strict requirements on assembly clearance, and high production costs, this invention employs a laser beam biased to the aluminum alloy side combined with a oscillating wire-filler welding technique. This is achieved using a dedicated low-nickel welding wire and a composite shielding gas. Through pre-welding composite pretreatment and precise control of laser power density, welding speed, wire feed speed, and beam oscillation parameters, the thickness of the intermetallic compound layer at the interface is controlled below 5 μm, effectively suppressing the formation of brittle phases. The tensile strength of the welded joint can reach more than 85% of that of the aluminum alloy base material, allowing an assembly clearance of 0.1-0.5 mm. It eliminates the need for pre-removal of the aluminum-silicon coating on the steel surface, improves welding efficiency by more than 30%, and reduces production costs by 25%. This method is suitable for aluminum-steel dissimilar metal connections in key components such as automotive bodies and chassis, and has broad industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of dissimilar metal welding technology, and in particular to a laser filler wire welding process and method for aluminum alloys and steel used in automobiles. Background Technology

[0002] With the rapid development of the automotive industry, energy conservation, emission reduction, and lightweight design have become major trends. Aluminum alloys, with their advantages of low density, high specific strength, and good corrosion resistance, are increasingly widely used in automotive body, chassis, and engine components. However, the strength and stiffness of aluminum alloys are still lower than those of steel. Therefore, automotive manufacturing requires the extensive use of aluminum-steel dissimilar metal connection structures to balance lightweighting and structural strength requirements.

[0003] Currently, the main methods for joining dissimilar metals like aluminum and steel are resistance spot welding, riveting, and bonding. However, these methods suffer from problems such as low joint strength, low production efficiency, and poor sealing. Laser welding, with its advantages of high energy density, low heat input, fast welding speed, and minimal deformation, is an ideal method for achieving high-quality joints between dissimilar metals like aluminum and steel. However, laser welding of aluminum and steel presents the following technical challenges: 1. Aluminum and steel have very different physical and chemical properties, with significant differences in melting point, thermal conductivity, and coefficient of linear expansion. This makes them prone to generating large welding stress and deformation during welding, leading to cracks. 2. Iron has extremely low solid solubility in aluminum, and during the welding process, it is easy to form a series of hard and brittle intermetallic compounds such as FeAl2, FeAl3, and Fe2Al5. The presence of these brittle phases will seriously reduce the plasticity, toughness, and strength of the welded joint. 3. A dense Al2O3 oxide film easily forms on the surface of aluminum alloys. Its melting point is as high as 2072℃, which is much higher than the melting point of aluminum. This will hinder fusion and lead to slag inclusions and incomplete fusion defects in the weld. 4. For hot-formed steel with an aluminum-silicon coating, the aluminum in the coating will enter the weld during welding, forming large skeletal ferrite phases, further reducing the mechanical properties of the weld. Existing technologies typically use pre-removal mechanical or laser methods to remove the coating, but this increases the number of processes and costs; 5. Existing laser wire filler welding processes have very strict requirements for assembly gaps, typically requiring a gap of ≤0.1mm, which places high demands on the precision and cost of welding fixtures; 6. In order to suppress the formation of brittle intermetallic compounds, existing technologies often use welding wires with high nickel or high molybdenum content, but these welding wires are expensive and increase production costs.

[0004] Therefore, developing a laser filler wire welding process and method for automotive aluminum alloys and steel that can effectively suppress the formation of brittle intermetallic compounds, improve the mechanical properties of welded joints, reduce the requirements for assembly clearance, eliminate the need for pre-removal of steel surface coatings, and has low production costs is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a laser filler wire welding process and method for aluminum alloys and steel for automobiles, so as to solve the problems of easy formation of brittle intermetallic compounds, poor mechanical properties of welds, strict requirements on assembly gaps, and high production costs in existing aluminum-steel laser welding.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A laser filler wire welding process and method for automotive aluminum alloys and steel includes the following steps: S1: Pre-welding treatment: Laser cleaning and chemical cleaning are performed on the aluminum alloy and steel areas to be welded to remove surface oxide film, oil and impurities. S2: Clamping and positioning: Clamp the pre-treated aluminum alloy plate and steel plate together, leaving an assembly gap of 0.1-0.5mm. Do not bevel the steel plate side, and make a 30°-45° single-sided bevel on the aluminum alloy side. S3: Welding parameter settings: Use a fiber laser, set the laser power to 1.5-3.5kW, welding speed to 1.0-2.5m / min, wire feed speed to 1.5-4.0m / min, defocusing amount to +1.0-+3.0mm, and laser beam offset to the aluminum alloy side to 0.2-0.8mm; S4: Beam oscillation setting: adopts circular oscillation mode, with an oscillation radius of 0.3-1.0mm and an oscillation frequency of 50-200Hz; S5: Protective gas setting: adopts a mixed protective gas of argon and helium with a volume ratio of 7:3-9:1, a front protective gas flow rate of 15-25L / min, and a back protective gas flow rate of 5-15L / min. S6: Welding Implementation: Perform laser filler wire welding according to the above parameters. During the welding process, the welding wire is fed into the front end of the molten pool from the aluminum alloy side. S7: Post-weld treatment: Perform low-temperature aging treatment on the welded joint at 150-200℃ for 30-60 minutes.

[0007] Furthermore, the laser cleaning in step S1 uses a pulsed fiber laser with a power of 50-200W, a scanning speed of 500-2000mm / s, and a cleaning width of 5-15mm; the chemical cleaning uses anhydrous ethanol to wipe the area to be welded, and then blows it dry with compressed air.

[0008] Furthermore, the aluminum alloy plate mentioned in step S2 is 6061-T6, 5052-H32 or 5083-H112 aluminum alloy with a thickness of 1.0-3.0mm; the steel plate is Q235 low carbon steel, DP590 duplex steel or aluminum-silicon coated hot-formed steel with a thickness of 1.0-3.0mm.

[0009] Furthermore, the welding wire mentioned in step S3 is an ER4047 aluminum-silicon welding wire with a diameter of 1.0-1.6mm, and the silicon content in the welding wire is 11.0-13.0wt%, the copper content is ≤0.30wt%, the iron content is ≤0.80wt%, and the nickel content is ≤0.05wt%.

[0010] Furthermore, in step S3, the ratio of the laser beam offset distance towards the aluminum alloy side to the steel plate thickness is 0.1-0.3.

[0011] Furthermore, the beam oscillation mode described in step S4 can also adopt a figure-eight oscillation or a straight oscillation. When adopting a figure-eight oscillation, the horizontal oscillation amplitude is 0.5-1.5mm, the vertical oscillation amplitude is 0.3-0.8mm, and the oscillation frequency is 80-150Hz.

[0012] Furthermore, 0.5-2.0 vol% of carbon dioxide gas is added to the mixed protective gas in step S5.

[0013] Furthermore, in step S6, the angle between the welding wire and the welding direction is 30°-45°, and the extension length of the welding wire is 8-15mm.

[0014] Furthermore, an infrared thermal imager is used to monitor the molten pool temperature in real time during the welding process, controlling the maximum temperature of the molten pool to 1200-1400℃. When the temperature exceeds 1400℃, the laser power is automatically reduced or the welding speed is increased.

[0015] Furthermore, after welding, the thickness of the intermetallic compound layer at the aluminum-steel interface is 2-5 μm, mainly composed of FeAl3 phase, and the tensile strength of the welded joint is ≥180MPa, with an elongation of ≥8%.

[0016] The beneficial effects of this invention are as follows: 1. This invention employs a laser beam biased to the aluminum alloy side + oscillating filler wire welding technology. By controlling the laser energy input and distribution, the aluminum alloy is completely melted while the steel plate only undergoes surface micro-melting. This effectively reduces the diffusion of Fe elements to the aluminum side, thereby suppressing the formation of brittle Fe-Al intermetallic compounds and controlling the thickness of the intermetallic compound layer at the interface to below 5 μm.

[0017] 2. This invention employs beam oscillation technology, which can stir the molten pool, promote gas escape, reduce porosity defects, and make the temperature field distribution more uniform, reducing welding stress and crack tendency. It can also significantly improve the adaptability to assembly gaps, allowing assembly gaps to reach 0.5mm, greatly reducing the precision requirements of welding fixtures.

[0018] 3. This invention eliminates the need to remove the aluminum-silicon coating from the steel surface beforehand. By optimizing the welding process parameters, the aluminum element in the coating and the silicon element in the welding wire form a eutectic structure. This not only does not reduce the weld performance, but also improves the wettability of liquid aluminum on solid steel, improves the joint quality, simplifies the process, and reduces production costs.

[0019] 4. This invention uses low-cost ER4047 aluminum-silicon welding wire to replace traditional high-nickel or high-molybdenum welding wire, reducing the cost of welding wire by more than 60%. At the same time, it is combined with argon-helium mixed protective gas to improve arc stability and weld formation quality.

[0020] 5. The tensile strength of the welded joint of this invention can reach more than 85% of that of the aluminum alloy base material, the elongation is ≥8%, the welding efficiency is increased by more than 30%, and the production cost is reduced by 25%. It is suitable for aluminum-steel dissimilar metal connection of key components such as automobile body, chassis, doors, and engine hood, and has broad industrial application prospects. Attached Figure Description

[0021] Figure 1 This is a flowchart of the laser filler wire welding process for aluminum alloys and steel used in automobiles according to the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0023] This invention proposes a laser filler wire welding process and method for automotive aluminum alloys and steel, comprising the following steps: S1: Pre-welding treatment: Laser cleaning and chemical cleaning are performed on the aluminum alloy and steel areas to be welded to remove surface oxide film, oil and impurities. This invention abandons traditional mechanical grinding and strong acid pickling processes. Mechanical grinding easily produces surface scratches and abrasive residues, and cannot completely remove the dense Al2O3 oxide film on the aluminum alloy surface; strong acid pickling can cause hydrogen embrittlement of aluminum alloys and cause environmental pollution. It adopts a composite process combining laser cleaning and anhydrous ethanol wiping. Laser cleaning is a dry, non-contact treatment that can accurately remove oxide films and oil layers with a thickness of 5-20μm without damaging the substrate material. Anhydrous ethanol wiping then removes loose particles and residual organic matter generated during laser cleaning, ultimately achieving a surface roughness Ra≤1.6μm for the surface to be welded, significantly improving the wettability of liquid aluminum on the steel surface. S2: Clamping and positioning: Clamp the pre-treated aluminum alloy plate and steel plate together, leaving an assembly gap of 0.1-0.5mm. Do not bevel the steel plate side, and make a 30°-45° single-sided bevel on the aluminum alloy side. This invention innovatively adopts a single-sided bevel design. The steel plate side is not beveled to minimize the amount of steel melting, thereby reducing the diffusion of Fe elements to the aluminum side from the source. The single-sided bevel on the aluminum alloy side not only ensures the smooth feeding of the welding wire but also increases the contact area between the molten pool and the steel surface, improving the interfacial bonding strength. The 0.1-0.5mm assembly gap is reserved to accommodate the thermal expansion deformation generated during welding, avoiding welding deformation and cracks caused by the workpiece being pressed tightly together. At the same time, the capillary effect of the gap promotes the flow of liquid metal, significantly improving the weld formation quality under large gap conditions. S3: Welding parameter settings: Use a fiber laser, set the laser power to 1.5-3.5kW, welding speed to 1.0-2.5m / min, wire feed speed to 1.5-4.0m / min, defocusing amount to +1.0-+3.0mm, and laser beam offset to the aluminum alloy side to 0.2-0.8mm; This invention employs a positive defocus welding mode, which results in a more uniform laser energy distribution and a wide, shallow molten pool, effectively reducing heat input and the width of the heat-affected zone. One of the core technologies of this invention is the biasing of the laser beam towards the aluminum alloy side. By controlling the energy distribution, the aluminum alloy is completely melted while only the surface of the steel plate is slightly melted. The ratio of the bias distance to the steel plate thickness is strictly controlled within the range of 0.1-0.3. If the bias distance is too small, a large amount of the steel plate will melt, generating a thick, brittle phase; if the bias distance is too large, the steel surface cannot obtain sufficient energy to melt, easily leading to incomplete fusion defects.

[0024] S4: Beam oscillation setting: adopts circular oscillation mode, with an oscillation radius of 0.3-1.0mm and an oscillation frequency of 50-200Hz; The oscillation of the beam can generate a strong stirring effect on the molten pool, break the oxide film on the surface of the molten pool, promote the escape of bubbles, and reduce the porosity of the weld to below 0.5%. At the same time, it makes the temperature field distribution of the molten pool more uniform, reduces the temperature gradient and welding stress, and effectively inhibits the generation of hot cracks. In addition, the oscillation of the beam can expand the effective area of ​​the molten pool on the steel surface, making the aluminum-steel interface change from a plane to a wave shape, which significantly improves the mechanical interlocking effect and joint strength. S5: Protective gas setting: Use a mixture of argon and helium as protective gas with a volume ratio of 7:3-9:1. The flow rate of the protective gas on the front is 15-25L / min, and the flow rate of the protective gas on the back is 5-15L / min. Pure argon gas protection is prone to generating plasma clouds that shield laser energy, while pure helium gas protection is ineffective and costly. The argon-helium mixed gas used in this invention can ensure good protection while reducing the impact of plasma clouds, thereby increasing the laser energy utilization rate by more than 20%. S6: Welding Implementation: Perform laser filler wire welding according to the above parameters. During the welding process, the welding wire is fed into the front end of the molten pool from the aluminum alloy side. The welding wire first melts fully in the aluminum alloy molten pool, and then comes into contact with the slightly molten steel surface, which can significantly shorten the high-temperature residence time of the steel and reduce the formation time of Fe-Al intermetallic compounds. S7: Post-weld treatment: Perform low-temperature aging treatment on the welded joint at 150-200℃ for 30-60 minutes; This temperature range can effectively eliminate residual welding stress and cause the supersaturated solid solution in the weld to precipitate fine and dispersed strengthening phases, thus significantly improving its ductility and toughness without reducing the joint strength.

[0025] Furthermore, the laser cleaning in step S1 uses a pulsed fiber laser with a power of 50-200W, a scanning speed of 500-2000mm / s, and a cleaning width of 5-15mm; the chemical cleaning uses anhydrous ethanol to wipe the area to be welded, and then blows it dry with compressed air.

[0026] Further, the aluminum alloy plate mentioned in step S2 is 6061-T6, 5052-H32 or 5083-H112 aluminum alloy with a thickness of 1.0-3.0mm; the steel plate is Q235 low carbon steel, DP590 duplex steel or aluminum-silicon coated hot-formed steel with a thickness of 1.0-3.0mm.

[0027] Furthermore, the welding wire mentioned in step S3 is an ER4047 aluminum-silicon welding wire with a diameter of 1.0-1.6 mm. The welding wire has a silicon content of 11.0-13.0 wt%, a copper content of ≤0.30 wt%, an iron content of ≤0.80 wt%, and a nickel content of ≤0.05 wt%. The high silicon content of the welding wire can reduce the aluminum-silicon eutectic temperature and improve the fluidity of the liquid metal. At the same time, silicon can preferentially combine with Fe to form the Fe-Si phase, inhibiting the formation of the brittle Fe-Al phase.

[0028] Furthermore, in step S3, the ratio of the laser beam offset distance towards the aluminum alloy side to the steel plate thickness is 0.1-0.3.

[0029] Furthermore, the beam oscillation mode described in step S4 can also adopt a figure-eight oscillation or a straight oscillation. When adopting a figure-eight oscillation, the lateral oscillation amplitude is 0.5-1.5mm, the longitudinal oscillation amplitude is 0.3-0.8mm, and the oscillation frequency is 80-150Hz. The figure-eight oscillation is suitable for welding with larger assembly gaps, which can better fill the gaps and avoid the generation of undercut and incomplete penetration defects.

[0030] Furthermore, 0.5-2.0 vol% of carbon dioxide gas is added to the mixed protective gas in step S5. A small amount of carbon dioxide can further stabilize the welding process, improve the weld surface formation, and inhibit the formation of hydrogen pores in the weld.

[0031] Furthermore, in step S6, the angle between the welding wire and the welding direction is 30°-45°, and the extension length of the welding wire is 8-15mm. This parameter range can ensure stable wire feeding, avoid wire sticking or breakage, and at the same time ensure that the shielding gas effectively covers the molten pool.

[0032] Furthermore, an infrared thermal imager is used to monitor the molten pool temperature in real time during the welding process, controlling the maximum temperature of the molten pool to 1200-1400℃. When the temperature exceeds 1400℃, the laser power is automatically reduced or the welding speed is increased. When the temperature exceeds 1400℃, the interdiffusion coefficient between Fe and Al will increase exponentially, resulting in a rapid thickening of the intermetallic compound layer. When the temperature is below 1200℃, the steel surface cannot be fully wetted and fused, resulting in unbonded interface defects.

[0033] The present invention will be further described in detail below with reference to specific embodiments.

[0034] Example 1: A laser filler wire welding process and method for automotive aluminum alloys and steel includes the following steps: S1: Pre-welding treatment: The areas to be welded on 2.0mm thick 6061-T6 aluminum alloy plate and 2.0mm thick DP590 duplex steel plate are subjected to combined laser cleaning and chemical cleaning. Laser cleaning uses a pulsed fiber laser with a power of 100W, a scanning speed of 1000mm / s, and a cleaning width of 10mm. Then, the areas to be welded are wiped with anhydrous ethanol to remove oil and impurities, and finally dried with compressed air. S2: Clamping and positioning: The pre-treated aluminum alloy plate and steel plate are clamped together by butt joint, with a 0.3mm assembly gap. The steel plate side is not beveled, while the aluminum alloy side is beveled at 35° on one side with a bevel depth of 1.0mm. S3: Welding parameter settings: An IPG YLS-4000 fiber laser was used, with a laser power of 2.5kW, welding speed of 1.8m / min, wire feed speed of 2.8m / min, defocusing distance of +2.0mm, and laser beam offset towards the aluminum alloy side by 0.5mm; 1.2mm diameter ER4047 aluminum-silicon welding wire was used, with a silicon content of 12.0wt%. S4: Beam oscillation setting: adopts circular oscillation mode, oscillation radius is 0.6mm, oscillation frequency is 120Hz; S5: Protective gas setting: A mixture of argon and helium is used as the protective gas with a volume ratio of 8:2. The flow rate of the protective gas at the front is 20L / min, and the flow rate of the protective gas at the back is 10L / min. S6: Welding Implementation: Perform laser filler wire welding according to the above parameters. During the welding process, the welding wire is fed into the front end of the molten pool from the aluminum alloy side. The angle between the welding wire and the welding direction is 40°, and the extension length of the welding wire is 12mm. S7: Post-weld treatment: Perform low-temperature aging treatment at 180℃ on the welded joint, and hold for 45 minutes; After welding is completed, the welded joint is subjected to mechanical property testing and microstructure analysis.

[0035] The results show that the welded joint is well formed and free from defects such as porosity, cracks, and lack of fusion; the thickness of the intermetallic compound layer at the aluminum-steel interface is about 3.2 μm, mainly composed of FeAl3 phase; the tensile strength of the welded joint is 192 MPa, reaching 87% of that of the 6061-T6 aluminum alloy base material, and the elongation is 9.2%.

[0036] Example 2: A laser filler wire welding process and method for automotive aluminum alloys and steel includes the following steps: S1: Pre-welding treatment: The areas to be welded on the 1.5mm thick 5052-H32 aluminum alloy plate and the 1.5mm thick aluminum-silicon coated hot-formed steel plate are subjected to a combination of laser cleaning and chemical cleaning. The laser cleaning uses a pulsed fiber laser with a power of 80W, a scanning speed of 1200mm / s, and a cleaning width of 8mm. Then, the areas to be welded are wiped with anhydrous ethanol to remove oil and impurities, and finally dried with compressed air. S2: Clamping and positioning: Clamp the pre-treated aluminum alloy plate and steel plate together, leaving an assembly gap of 0.2mm. Do not bevel the steel plate side, but make a 30° single-sided bevel on the aluminum alloy side with a bevel depth of 0.7mm. S3: Welding parameter settings: IPG YLS-3000 fiber laser is used, with laser power set to 2.0kW, welding speed to 2.0m / min, wire feed speed to 2.2m / min, defocusing distance to +1.5mm, and laser beam offset to the aluminum alloy side to 0.3mm; 1.0mm diameter ER4047 aluminum-silicon welding wire is used, with a silicon content of 11.5wt%. S4: Beam oscillation setting: adopts figure-eight oscillation mode, with a horizontal oscillation amplitude of 0.8mm, a vertical oscillation amplitude of 0.5mm, and an oscillation frequency of 100Hz; S5: Protective gas setting: A mixture of argon, helium and carbon dioxide is used as the protective gas, with a volume ratio of 85:13:2. The flow rate of the protective gas on the front is 18L / min, and the flow rate of the protective gas on the back is 8L / min. S6: Welding Implementation: Perform laser filler wire welding according to the above parameters. During the welding process, the welding wire is fed into the front end of the molten pool from the aluminum alloy side. The angle between the welding wire and the welding direction is 35°, and the extension length of the welding wire is 10mm. S7: Post-weld treatment: Perform low-temperature aging treatment at 160℃ on the welded joint for 50 minutes; After welding is completed, the welded joint is subjected to mechanical property testing and microstructure analysis.

[0037] The results show that the welded joint is well formed and free from defects such as porosity, cracks, and lack of fusion; the thickness of the intermetallic compound layer at the aluminum-steel interface is about 2.8 μm, mainly composed of FeAl3 phase; the tensile strength of the welded joint is 175 MPa, reaching 89% of that of the 5052-H32 aluminum alloy base material, and the elongation is 10.5%.

[0038] Example 3: A laser filler wire welding process and method for automotive aluminum alloys and steel includes the following steps: S1: Pre-welding treatment: The areas to be welded on 2.5mm thick 5083-H112 aluminum alloy plates and 2.5mm thick Q235 low carbon steel plates are subjected to combined laser cleaning and chemical cleaning treatments respectively; the laser cleaning uses a pulsed fiber laser with a power of 150W, a scanning speed of 800mm / s, and a cleaning width of 12mm; then the areas to be welded are wiped with anhydrous ethanol to remove oil and impurities, and finally dried with compressed air; S2: Clamping and positioning: The pre-treated aluminum alloy plate and steel plate are clamped together by butt joint, with a 0.4mm assembly gap. The steel plate side is not beveled, while the aluminum alloy side is beveled at 40° on one side with a bevel depth of 1.2mm. S3: Welding Parameter Settings: An IPG YLS-5000 fiber laser was used, with a laser power of 3.0kW, welding speed of 1.5m / min, wire feed speed of 3.5m / min, defocusing distance of +2.5mm, and laser beam offset towards the aluminum alloy side by 0.6mm. 1.6mm diameter ER4047 aluminum-silicon welding wire was used, with a silicon content of 12.5wt%. S4: Beam oscillation setting: adopts circular oscillation mode, oscillation radius is 0.8mm, oscillation frequency is 150Hz; S5: Protective gas setting: A mixture of argon and helium is used as the protective gas with a volume ratio of 7:3. The flow rate of the protective gas at the front is 22L / min, and the flow rate of the protective gas at the back is 12L / min. S6: Welding Implementation: Perform laser filler wire welding according to the above parameters. During the welding process, the welding wire is fed into the front end of the molten pool from the aluminum alloy side. The angle between the welding wire and the welding direction is 45°, and the extension length of the welding wire is 14mm. S7: Post-weld treatment: Perform low-temperature aging treatment at 200℃ on the welded joint, and hold for 30 minutes; After welding is completed, the welded joint is subjected to mechanical property testing and microstructure analysis.

[0039] The results show that the welded joint has good formation and no defects such as porosity, cracks, or lack of fusion; the thickness of the intermetallic compound layer at the aluminum-steel interface is about 4.1 μm, mainly composed of FeAl3 phase; the tensile strength of the welded joint is 210 MPa, reaching 84% of that of the 5083-H112 aluminum alloy base material, and the elongation is 8.7%.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laser filler wire welding process and method for aluminum alloys and steel used in automobiles, characterized in that, Includes the following steps: S1: Pre-welding treatment: Laser cleaning and chemical cleaning are performed on the aluminum alloy and steel areas to be welded to remove surface oxide film, oil and impurities. S2: Clamping and positioning: Clamp the pre-treated aluminum alloy plate and steel plate together, leaving an assembly gap of 0.1-0.5mm. Do not bevel the steel plate side, and make a 30°-45° single-sided bevel on the aluminum alloy side. S3: Welding parameter settings: Use a fiber laser, set the laser power to 1.5-3.5kW, welding speed to 1.0-2.5m / min, wire feed speed to 1.5-4.0m / min, defocusing amount to +1.0-+3.0mm, and laser beam offset to the aluminum alloy side to 0.2-0.8mm; S4: Beam oscillation setting: adopts circular oscillation mode, with an oscillation radius of 0.3-1.0mm and an oscillation frequency of 50-200Hz; S5: Protective gas setting: adopts a mixed protective gas of argon and helium with a volume ratio of 7:3-9:1, a front protective gas flow rate of 15-25L / min, and a back protective gas flow rate of 5-15L / min. S6: Welding Implementation: Perform laser filler wire welding according to the above parameters. During the welding process, the welding wire is fed into the front end of the molten pool from the aluminum alloy side. S7: Post-weld treatment: Perform low-temperature aging treatment on the welded joint at 150-200℃ for 30-60 minutes.

2. The laser filler wire welding process and method for automotive aluminum alloys and steel according to claim 1, characterized in that, The laser cleaning in step S1 uses a pulsed fiber laser with a power of 50-200W, a scanning speed of 500-2000mm / s, and a cleaning width of 5-15mm; the chemical cleaning uses anhydrous ethanol to wipe the area to be welded, and then blows it dry with compressed air.

3. The laser filler wire welding process and method for automotive aluminum alloys and steel according to claim 1, characterized in that, The aluminum alloy plate mentioned in step S2 is 6061-T6, 5052-H32 or 5083-H112 aluminum alloy with a thickness of 1.0-3.0mm; the steel plate is Q235 low carbon steel, DP590 duplex steel or aluminum-silicon coated hot-formed steel with a thickness of 1.0-3.0mm.

4. The laser filler wire welding process and method for automotive aluminum alloys and steel according to claim 1, characterized in that, The welding wire mentioned in step S3 is an ER4047 aluminum-silicon welding wire with a diameter of 1.0-1.6mm. The silicon content in the welding wire is 11.0-13.0wt%, the copper content is ≤0.30wt%, the iron content is ≤0.80wt%, and the nickel content is ≤0.05wt%.

5. The laser filler wire welding process and method for automotive aluminum alloys and steel according to claim 1, characterized in that, In step S3, the ratio of the distance at which the laser beam is offset toward the aluminum alloy side to the thickness of the steel plate is 0.1-0.

3.

6. The laser filler wire welding process and method for automotive aluminum alloys and steel according to claim 1, characterized in that, The beam oscillation mode described in step S4 can also be a figure-eight oscillation or a straight oscillation. When a figure-eight oscillation is used, the horizontal oscillation amplitude is 0.5-1.5mm, the vertical oscillation amplitude is 0.3-0.8mm, and the oscillation frequency is 80-150Hz.

7. The laser filler wire welding process and method for automotive aluminum alloys and steel according to claim 1, characterized in that, The mixed protective gas in step S5 also contains 0.5-2.0 vol% carbon dioxide gas.

8. The laser filler wire welding process and method for automotive aluminum alloys and steel according to claim 1, characterized in that, In step S6, the angle between the welding wire and the welding direction is 30°-45°, and the extension length of the welding wire is 8-15mm.

9. The laser filler wire welding process and method for automotive aluminum alloys and steel according to claim 1, characterized in that, During the welding process, an infrared thermal imager is used to monitor the temperature of the molten pool in real time, and the maximum temperature of the molten pool is controlled at 1200-1400℃. When the temperature exceeds 1400℃, the laser power is automatically reduced or the welding speed is increased.

10. The laser filler wire welding process and method for automotive aluminum alloys and steel according to claim 1, characterized in that, After welding, the thickness of the intermetallic compound layer at the aluminum-steel interface is 2-5 μm, mainly composed of FeAl3 phase. The tensile strength of the welded joint is ≥180MPa and the elongation is ≥8%.

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