Al-cu series welding wire and preparation method and application thereof

Abstract

This invention discloses an Al-Cu welding wire, its preparation method, and its application, belonging to the field of laser welding technology. The welding wire is prepared by weighing various components, including aluminum, aluminum-copper master alloy, aluminum-titanium master alloy, aluminum-magnesium master alloy, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-scandium master alloy, and aluminum-zirconium master alloy, according to a designed welding wire composition ratio. These components are then melted and cast to obtain an ingot. The ingot undergoes multi-stage homogenization treatment, followed by hot rolling and wire cutting. This invention improves the proportion of isometric regions in the weld microstructure by introducing trace amounts of Sc, Si, Ti, and Zr into a low-cost, high-Cu content weld pool system, refining the weld microstructure and enhancing mechanical properties compatible with Al-Cu-Li alloys. Furthermore, by reducing the content of the hard and brittle W phase through appropriate processes, the invention effectively ensures the machinability of the welding wire and the weld performance.

Description

Technical Field

[0001] This invention relates to an Al-Cu welding wire, its preparation method and application, belonging to the field of laser welding technology. Background Technology

[0002] With the increasing demand for lightweight and high-strength materials in the aerospace field, aluminum-lithium alloys (Al-Li) have become a research hotspot in advanced lightweight materials due to their advantages such as low density, high specific strength, and low-temperature toughness. Laser welding, with its advantages of high energy density, low heat input, and narrow heat-affected zone, is widely used in precision welding. Currently, there are reports of using laser welding to weld aluminum-lithium alloy structural components, reducing component weight by approximately 20% and production costs by approximately 25%. There are also reports of using aluminum-lithium alloys to replace tank materials and employing laser welding to replace traditional riveting, significantly reducing fuselage weight and effectively improving spacecraft carrying capacity. Therefore, high-quality welding of aluminum-lithium alloys using laser welding has broad application prospects in the aerospace field.

[0003] Al-Cu-Li alloys are optimized alloys based on 2195 aluminum-lithium alloys through compositional micro-tuning. The main strengthening phase, T1 (Al2CuLi), coarsens during welding, leading to softening of the weld joint. The weld microstructure is influenced by the ratio of liquidus temperature to crystallization rate (G / R) during solidification, consisting of columnar crystals and equiaxed dendrites. Furthermore, a special weld microstructure, the equiaxed fine-grained region, exists during the welding process of Al-Li alloys. This inhomogeneity in the weld microstructure degrades the performance of Al-Cu-Li alloy weld joints. Simultaneously, Al-Cu-Li alloys are highly susceptible to porosity, crystallization cracks, and liquefaction cracks during welding, hindering their engineering applications.

[0004] Currently, when considering how to achieve mechanical properties in welded joints that better match those of the base metal, the composition of the filler wire is designed to be as close to the base metal as possible. For Al-Cu-Li alloys, this means that the Cu content in the filler wire needs to be designed. High Cu content can effectively improve the fluidity of the molten pool, but its performance in improving the weld microstructure has certain limitations. Trace amounts of Sc can play a heterogeneous nucleation role during the solidification process of aluminum alloys. However, adding trace amounts of Sc to high Cu content filler wire presents a new challenge. When high Cu content and trace amounts of Sc coexist in the filler wire, the filler wire ingot will inevitably form a hard and brittle W phase (AlCuSc) during solidification, reducing the machinability of the filler wire and the weld performance.

[0005] Therefore, it is urgent to adjust the composition of the Al-Cu welding wire system and find a suitable process method. Summary of the Invention

[0006] To address the problems of low machinability, inability to match the mechanical properties of the base material, and high cost of existing welding wires used for laser welding of Al-Cu-Li alloys, the first objective of this invention is to provide an Al-Cu welding wire that, by introducing trace amounts of Sc, Si, Ti, and Zr into a low-cost, high-Cu-content weld pool system, synergistically improves the proportion of equiaxed grain regions in the weld microstructure, refines the weld microstructure, and enhances the mechanical properties that match those of Al-Cu-Li alloys.

[0007] The second objective of this invention is to provide a method for preparing Al-Cu welding wire. The method of this invention significantly reduces the content of the hard and brittle W phase (AlCuSc phase) by using an intermediate alloy and introducing multi-stage homogenization treatment in conjunction with multi-pass hot rolling, thereby effectively ensuring the machinability of the welding wire and the weld performance.

[0008] The third objective of this invention is to provide an application of Al-Cu welding wire for laser welding of Al-Cu-Li alloy plates. By using a welding method with a composition similar to the base material and incorporating an I-groove and a protective atmosphere on the back side, the density and size of hydrogen pores and metallurgical pores in the weld are effectively reduced and the mechanical properties of the weld joint are improved.

[0009] To achieve the above technical objectives, this invention provides a method for preparing Al-Cu welding wire. The method involves weighing various components, including aluminum, aluminum-copper master alloy, aluminum-titanium master alloy, aluminum-magnesium master alloy, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-scandium master alloy, and aluminum-zirconium master alloy, according to a designed welding wire composition ratio. These components are then melted and cast to obtain an ingot. The ingot undergoes multi-stage homogenization treatment, followed by hot rolling and wire cutting to obtain the final welding wire. The welding wire is composed of the following components by mass percentage: Cu 5.80~6.80%, Ti 0.12~0.28%, Si 0.18~0.28%, Zr 0.10~0.50%, Sc 0.10~0.30%, Mg≤0.05%, Mn≤0.05%, with the balance being Al and unavoidable impurities.

[0010] This invention can significantly improve the ratio of isometric crystal regions to columnar crystals in the weld microstructure in a low-cost weld pool system, refining the weld microstructure and improving mechanical properties compatible with Al-Cu-Li alloys. The key lies in the synergistic control of alloy composition and preparation method. Specifically, in terms of composition design, a high Cu content matching the base metal is adopted, utilizing Cu's characteristic of improving the fluidity of the weld pool to allow the liquid metal to fully fill the crystal gaps and suppress the generation of hot cracks. Trace amounts of Sc can effectively refine the weld microstructure, improve the formation of columnar crystals, and eliminate microstructure segregation. The combined addition of Sc and Zr forms nanoscale L12-type Al3(Sc, Zr) particles with a core-shell structure, which are highly coherent with the Al matrix, have low lattice mismatch, can pin grain boundaries, refine grains, and also possess excellent thermal stability. The trace amounts of Al3Ti particles also play a role in refining the microstructure, synergistically improving the ratio of isometric crystal regions to columnar crystals in the weld, refining the weld microstructure, and improving mechanical properties compatible with Al-Cu-Li alloys. Furthermore, in this invention, the Si content should not be too high. Excessive Si content will generate V phase (AlSc2Si2) in the alloy, which is not only detrimental to the mechanical properties of the alloy, but also consumes some Sc elements, thereby reducing the formation of Al3(Sc, Zr).

[0011] In terms of preparation method, this invention firstly avoids the formation of element agglomeration and segregation by using an intermediate alloy as raw material. Simultaneously, in the high Cu content and low Si content system of this invention, the formation of a hard and brittle W phase (AlCuSc phase) is inevitable. This invention, through multi-stage homogenization treatment combined with a multi-pass hot rolling process, can significantly reduce the content of this hard and brittle W phase, while ensuring that other elements and strengthening phases improve the ratio between equiaxed and columnar grains and refine the weld microstructure. Specifically, this invention first uses multi-stage homogenization treatment to eliminate the large-sized W phase formed during the casting process, then uses multi-pass hot rolling to mechanically crush the remaining W phase particles, combined with deformation-guided local dissolution effect to further eliminate the W phase. Simultaneously, during the gradual heating and holding process of the multi-stage homogenization treatment, Al3(Sc, Zr) particles and Al3Ti particles gradually precipitate, which pin grain boundaries, refine grains, and improve the ratio between equiaxed and columnar grains in the weld microstructure.

[0012] Further preferred, the ratio of Sc to Zr is 1:(1~2). By controlling the ratio of the two, Al3(Sc,Zr) particles can be further formed, thereby further improving the strengthening effect.

[0013] Furthermore, the weld microstructure of the Al-Cu welding wire contains nanoscale L12-type Al3(Sc,Zr) particles with a core-shell structure, and is coherent with the Al matrix.

[0014] As a preferred embodiment, the welding wire is composed of the following components by mass percentage: Cu 6.20~6.80%, Ti 0.12~0.28%, Si 0.18~0.28%, Zr 0.10~0.30%, Sc 0.10~0.20%, Mg≤0.05%, Mn≤0.05%, with the balance being Al and unavoidable impurities. Under further optimized welding wire composition ranges, combined with the process, welding wire materials with superior performance can be obtained.

[0015] As a preferred embodiment, a covering agent and a refining agent are added during the smelting process, the smelting temperature is 400~830℃, and the resulting melt is subjected to slag removal and settling treatment after smelting.

[0016] As a preferred embodiment, the covering agent comprises NaCl and KCl, and the refining agent comprises C2Cl6.

[0017] As a preferred embodiment, the covering agent is composed of NaCl and KCl in a mass ratio of (1~2):(1~2).

[0018] Further preferably, the melting temperature before adding the covering agent is 400~760℃, the melting temperature before adding the refining agent is 780~830℃, the stirring is performed for 2~5 minutes before slag removal, and the standing time is 20~30 minutes.

[0019] Further preferred, the casting is gravity casting.

[0020] As a preferred embodiment, the temperature of the multi-stage homogenization process is 290~520℃, and the time is 36~68h.

[0021] As a preferred embodiment, the multi-stage homogenization treatment is a two-stage homogenization treatment or a three-stage homogenization treatment; wherein, in the two-stage homogenization treatment, the first stage heat preservation temperature is 300~320℃, and the time is 20~24h, and the second stage heat preservation temperature is 500~520℃, and the time is 20~24h; in the three-stage homogenization treatment, the first stage heat preservation temperature is 330~340℃, and the time is 4~6h, the second stage heat preservation temperature is 450~470℃, and the time is 4~6h, and the third stage heat preservation temperature is 510~530℃, and the time is 40~48h. In the multi-stage homogenization process of this invention, the temperature and duration directly affect the elimination of the brittle W phase and the precipitation of the strengthening phase: short-term holding at lower temperatures can act as a pre-homogenization, inhibiting the rapid formation of harmful phases, while higher temperatures and longer holding times can more effectively eliminate the large-sized W phase formed during the casting process and promote the gradual precipitation of nano-sized Al3(Sc, Zr) particles and Al3Ti particles with core-shell structures. However, excessively high single temperatures or excessively long holding times cannot effectively eliminate the large-sized W phase. A further preferred method is a three-stage homogenization process.

[0022] As a preferred embodiment, the hot rolling temperature is 400~460℃, the deformation per pass is 5%~40%, the total deformation is 85%~95%, and the heat preservation between passes is 15~20min.

[0023] Furthermore, the total number of hot rolling passes is N, where the deformation per pass of N / 2 is greater than the deformation of the first pass and the deformation of the last pass. This invention employs a distribution pattern of large deformation in the middle passes and small deformation in the first and last passes, which can fully guarantee the formability of the welding wire and the sufficient fragmentation and localized remelting effect of the W phase.

[0024] As a preferred embodiment, the wire EDM control wire has a size of 75mm × 1mm × 1mm.

[0025] This invention also provides an Al-Cu welding wire, obtained by the above-described preparation method. The Al-Cu welding wire of this invention, when laser-welded, produces a weld microstructure with a high proportion of isometric crystal regions, a fine and uniform microstructure, and high welding coefficient and machinability.

[0026] As a preferred embodiment, the isoaxial crystalline region accounts for 75% to 90% of the weld microstructure formed by laser welding of the Al-Cu welding wire. In this invention, isoaxial crystalline refers to a crystalline structure in the weld microstructure with an aspect ratio of less than 2.

[0027] Finally, this invention also provides an application of Al-Cu welding wire for laser welding of Al-Cu-Li alloy plates.

[0028] As a preferred embodiment, the laser welding process includes the following steps:

[0029] S1 After cleaning and pre-treatment, Al-Cu-Li alloy plates are spliced ​​and placed; the splicing bevel between the Al-Cu-Li alloy plates uses a type I bevel, and the gap width between the splices is not greater than the thickness of the Al-Cu welding wire.

[0030] S2 provides a protective atmosphere on the back side of the Al-Cu-Li alloy plate for laser welding, and places the Al-Cu welding wire above the plate to be joined, and performs laser welding using a fiber laser.

[0031] The laser welding method of this invention utilizes an Al-Cu welding wire with a composition similar to the base metal, combined with an I-groove, effectively improving the growth pattern of columnar crystals in Al-Cu-Li alloys during solidification and reducing the generation of crystallization cracks. This enhances the weld's forming ability, strength, and mechanical properties that are compatible with the base metal. Furthermore, the high-flow-rate back-side protective atmosphere laser welding method effectively reduces the density and size of hydrogen and metallurgical pores in the weld, while altering the temperature gradient to further refine the weld microstructure, thus significantly improving the performance of the welded joint.

[0032] As a preferred embodiment, the cleaning pretreatment refers to: grinding the welding surfaces of the Al-Cu-Li alloy plates with 80# sandpaper, then using ethanol ultrasonic cleaning to remove impurities and oil stains from the plate surface and air drying and cooling.

[0033] As a preferred embodiment, the Al-Cu-Li alloy plate has a thickness of 1.8~2.2mm.

[0034] In the laser welding operation of this invention, the welding surface is also provided with a protective atmosphere as usual. Further, the flow rate of the protective atmosphere on the welding surface is 15~20 L / min, and the flow rate of the protective atmosphere on the back side of the weld is 25~35 L / min. Within this flow rate range, a better effect of refining the weld microstructure can be achieved.

[0035] Furthermore, the protective atmosphere is high-purity argon (≥99.99%).

[0036] As a preferred embodiment, the laser welding parameters are: defocusing amount -6 to +2 mm, welding power 3 to 6 kW, welding speed 2.8 to 5.8 m / min, duty cycle 75 to 90%, pulse frequency 960 to 1200 Hz, the angle between the protective atmosphere nozzle and the horizontal direction is 40°, and the angle between the laser and the horizontal direction is 70°. By setting a specific angle for the laser, this invention avoids damage to the laser caused by the high reflectivity of the base material during the welding process.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] (1) This invention, through the design of welding wire composition, based on the idea of ​​microalloying the weld structure, introduces trace amounts of Sc, Si, Ti and Zr into the low-cost high Cu content weld pool system to synergistically improve the proportion of equiaxed crystal regions, refine the weld structure, and improve the mechanical properties that match the Al-Cu-Li alloy system.

[0039] (2) By using an intermediate alloy and introducing multi-stage homogenization treatment in conjunction with multi-pass hot rolling, the present invention significantly reduces the content of the W hard and brittle phase (AlCuSc phase), effectively ensuring the machinability of the welding wire and the performance of the weld.

[0040] (3) The present invention uses high flow rate back protective atmosphere splicing laser welding to effectively reduce the density and size of hydrogen pores and metallurgical pores in the weld, while changing the temperature gradient to further refine the weld structure and effectively improve the performance of the welded joint.

[0041] (4) The Al-Cu welding wire provided by the present invention is particularly suitable for laser welding of Al-Cu-Li alloy plates. The Al-Cu welding wire designed with a composition similar to that of the base material and combined with the I-type groove effectively improves the growth mode of columnar crystals in the solidification process of Al-Cu-Li alloy, reduces the generation of crystallization cracks, improves the weld formation ability, and improves the weld strength and mechanical properties that are compatible with the base material.

[0042] (5) The welded joint of the present invention has excellent mechanical properties, simple process steps, and low-cost industrial application prospects. Attached Figure Description

[0043] Figure 1 This is a microstructure diagram of the welding wire after three-stage homogenization treatment in Example 2 of the present invention.

[0044] Figure 2 This is a microstructure diagram of the weld seam of the laser welding head in Embodiment 2 of the present invention.

[0045] Figure 3 This is a microstructure diagram of the weld seam of the laser welding head in Embodiment 3 of the present invention.

[0046] Figure 4 This is a microstructure diagram of the weld seam of the laser welding head in Comparative Example 1 of the present invention.

[0047] Figure 5 This is a microstructure diagram of the fracture surface of the laser-welded head of Comparative Example 2 of the present invention.

[0048] Figure 6 This is a scanning electron microscope image of the fracture surface of the laser-welded head of Comparative Example 5 of the present invention. Detailed Implementation

[0049] The technical solutions in 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. Based on the embodiments of the present invention, all embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0050] In the embodiments and comparative examples of this invention, isometric crystals refer to crystal structures with an aspect ratio of less than 2 in the weld microstructure.

[0051] Example 1

[0052] This embodiment provides an Al-Cu welding wire and its preparation method. The welding wire composition, by mass percentage, is: Cu 6.50%, Ti 0.20%, Si 0.22%, Zr 0.20%, Sc 0.10%, Mg 0.03%, Mn 0.02%, with the balance being Al and unavoidable impurities.

[0053] The preparation method of the welding wire is as follows:

[0054] (1) Ingredients: High-purity aluminum, Al-40Cu, Al-10Ti, Al-20Mg, Al-20Si, Al-10Mn, Al-2Sc, Al-5Zr master alloy, NaCl and KCl covering agent, C2Cl6 refining agent. The master alloy is added first to avoid agglomeration and segregation. All master alloys are wrapped in aluminum foil.

[0055] (2) Melting: The melting temperature is 760℃, until high-purity aluminum is melted;

[0056] (3) Adding materials: Add the intermediate alloy wrapped in aluminum foil, and use a stirrer to press the intermediate alloy below the surface of the molten aluminum. Add a covering agent, wherein the total mass of the covering agent is 0.4% of the total mass of the alloy, and the mass ratio of NaCl to KCl is 1:1.

[0057] (4) Melting: The melting temperature is increased to 780℃ until the intermediate alloy melts;

[0058] (5) Stirring and slag removal: Add C2Cl6 refining agent, the amount of C2Cl6 is 0.3% of the total mass of the alloy, stir the melt with a stirrer for 5 minutes, remove the slag and let the melt stand for 30 minutes.

[0059] (6) Casting: The refined melt is gravity cast to obtain an ingot;

[0060] (7) Homogenization: After cutting off the head and tail and peeling the skin, the three-stage homogenization treatment is carried out in sequence: 335℃ for 4 hours, 460℃ for 4 hours and 520℃ for 48 hours.

[0061] (8) Hot deformation: The hot rolling temperature is 460℃. After each rolling pass, the billet is sent into the heat preservation furnace and kept for 15 minutes. According to the passes of 20mm→19mm→17mm→14mm→10mm→6mm→4mm→3mm→2mm, a 2mm thick hot-rolled plate is prepared.

[0062] (9) Wire cutting: 75mm×1mm×1mm welding wire was prepared by wire cutting. The wire cutting marks were polished with sandpaper. After polishing, the width and thickness of the welding wire were 0.2~0.5mm. It was ultrasonically cleaned with anhydrous ethanol, dried and vacuum stored.

[0063] This embodiment also provides a laser welding method, including laser welding using the above-mentioned welding wire, the workpiece being an Al-Cu-Li alloy (Al-4.05%Cu-1.02%Li-0.51%Ag-0.45%Mg-0.15%Zr, by mass percentage), the workpiece size being 75mm×50mm×2mm; welding is performed using a butt joint with a type I bevel, with a pre-reserved gap of 0.1mm; before welding, the surface is cleaned with acetone and anhydrous ethanol, a protective atmosphere is provided on the back side of the Al-Cu-Li alloy plate for laser welding, and an Al-Cu welding wire is placed on top of the plate to be joined, and laser welding is performed using a fiber laser.

[0064] The specific laser welding process is as follows: laser defocusing amount is -6mm, welding power is 3.8kW, welding speed is 4.8m / min, duty cycle is 85%, pulse frequency is 1000Hz, back protective atmosphere flow rate is 30L / min, top surface protective atmosphere flow rate is 15L / min, the angle between the protective atmosphere nozzle and the horizontal direction is 40°, and the angle between the laser and the horizontal direction is 70°.

[0065] Example 2

[0066] This embodiment provides an Al-Cu welding wire and its preparation method. The welding wire composition, by mass percentage, is: Cu 6.50%, Ti 0.20%, Si 0.22%, Zr 0.15%, Sc 0.15%, Mg 0.03%, Mn 0.02%, with the balance being Al and unavoidable impurities.

[0067] The preparation method of the welding wire is the same as in Example 1, and the microstructure of the welding wire after three-stage homogenization treatment is as follows: Figure 1 As shown.

[0068] This embodiment also provides a laser welding method, including laser welding using the welding wire as described above, the workpiece being an Al-Cu-Li alloy (same as in Embodiment 1), the workpiece size being 75mm×50mm×2mm; welding is performed using a butt joint method with a type I bevel and a pre-reserved gap of 0.1mm; before welding, the surface is cleaned with acetone and anhydrous ethanol, a protective atmosphere is provided on the back side of the Al-Cu-Li alloy plate for laser welding, and an Al-Cu welding wire is placed on top of the plate to be joined, and laser welding is performed using a fiber laser.

[0069] The specific laser welding process is as follows: laser defocusing distance is -6mm, welding power is 3.8kW, welding speed is 4.8m / min, duty cycle is 85%, pulse frequency is 1000Hz, back shielding atmosphere flow rate is 30L / min, top surface shielding atmosphere flow rate is 15L / min, the angle between the shielding atmosphere nozzle and the horizontal direction is 40°, and the angle between the laser nozzle and the horizontal direction is 70°. The weld microstructure is as follows. Figure 2 As shown, the equiaxed crystal ratio of the weld microstructure is 86.5%.

[0070] Example 3

[0071] This embodiment provides an Al-Cu welding wire and its preparation method. The welding wire composition by mass percentage is: Cu 6.50%, Ti 0.20%, Si 0.22%, Zr 0.10%, Sc 0.20%, Mg 0.03%, Mn 0.02%, with the balance being Al and unavoidable impurities.

[0072] The preparation method of the welding wire is as follows: the same as in Example 1.

[0073] This embodiment also provides a laser welding method, including laser welding using the welding wire as described above, the workpiece being an Al-Cu-Li alloy (same as in Embodiment 1), the workpiece size being 75mm×50mm×2mm; welding is performed using a butt joint method with a type I bevel and a pre-reserved gap of 0.15mm; before welding, the surface is cleaned with acetone and anhydrous ethanol, a protective atmosphere is provided on the back side of the Al-Cu-Li alloy plate for laser welding, and an Al-Cu welding wire is placed on top of the plate to be joined, and laser welding is performed using a fiber laser.

[0074] The specific laser welding process is as follows: laser defocusing distance is -6mm, welding power is 3.8kW, welding speed is 4.8m / min, duty cycle is 85%, pulse frequency is 1000Hz, back shielding atmosphere flow rate is 30L / min, top surface shielding atmosphere flow rate is 15L / min, the angle between the shielding atmosphere nozzle and the horizontal direction is 40°, and the angle between the laser nozzle and the horizontal direction is 70°. The weld microstructure is as follows. Figure 3 As shown.

[0075] Example 4

[0076] This embodiment provides an Al-Cu welding wire and its preparation method. The welding wire composition, by mass percentage, is: Cu 6.50%, Ti 0.20%, Si 0.22%, Zr 0.15%, Sc 0.15%, Mg 0.03%, Mn 0.02%, with the balance being Al and unavoidable impurities.

[0077] The preparation method of the welding wire is as follows:

[0078] (1) Ingredients: High-purity aluminum, Al-40Cu, Al-10Ti, Al-20Mg, Al-20Si, Al-10Mn, Al-2Sc, Al-5Zr master alloy, NaCl and KCl covering agent, C2Cl6 refining agent. The master alloy is added first to avoid agglomeration and segregation. All master alloys are wrapped in aluminum foil.

[0079] (2) Melting: The melting temperature is 760℃, until high-purity aluminum is melted;

[0080] (3) Adding materials: Add the intermediate alloy wrapped in aluminum foil, and use a stirrer to press the intermediate alloy below the surface of the molten aluminum. Add a covering agent, wherein the total mass of the covering agent is 0.4% of the total mass of the alloy, and the mass ratio of NaCl to KCl is 1:1.

[0081] (4) Melting: The melting temperature is increased to 780℃ until the intermediate alloy melts;

[0082] (5) Stirring and slag removal: Add C2Cl6 refining agent, the amount of C2Cl6 is 0.3% of the total mass of the alloy, stir the melt with a stirrer for 5 minutes, remove the slag and let the melt stand for 30 minutes.

[0083] (6) Casting: The refined melt is gravity cast to obtain an ingot;

[0084] (7) Homogenization: After cutting off the head and tail and peeling the skin, the two-stage homogenization treatment is carried out in sequence: 310℃ for 24 hours and 520℃ for 24 hours.

[0085] (8) Hot deformation: The hot rolling temperature is 460℃. After each rolling pass, the billet is sent into the heat preservation furnace and kept for 15 minutes. According to the passes of 20mm→19mm→17mm→14mm→10mm→6mm→4mm→3mm→2mm, a 2mm thick hot-rolled plate is prepared.

[0086] (9) Wire cutting: 75mm×1mm×1mm welding wire was prepared by wire cutting. The wire cutting marks were polished with sandpaper. After polishing, the width and thickness of the welding wire were 0.2~0.5mm. It was ultrasonically cleaned with anhydrous ethanol, dried and vacuum stored.

[0087] This embodiment also provides a laser welding method, including laser welding using the welding wire as described above. The workpiece is an Al-Cu-Li alloy (same as in Embodiment 1), and the workpiece size is 75mm×50mm×2mm. The welding is performed by butt welding with a type I bevel and a pre-reserved gap of 0.1mm. Before welding, the surface is cleaned with acetone and anhydrous ethanol. A protective atmosphere is provided on the back side of the Al-Cu-Li alloy plate for laser welding, and an Al-Cu welding wire is placed on top of the plate to be joined. Laser welding is performed using a fiber laser.

[0088] The specific laser welding process is as follows: laser defocusing amount is -6mm, welding power is 3.8kW, welding speed is 4.8m / min, duty cycle is 85%, pulse frequency is 1000Hz, back protective atmosphere flow rate is 30L / min, top surface protective atmosphere flow rate is 15L / min, the angle between the protective atmosphere nozzle and the horizontal direction is 40°, and the angle between the laser and the horizontal direction is 70°.

[0089] Example 5

[0090] This embodiment provides an Al-Cu welding wire and its preparation method. The welding wire composition, by mass percentage, is: Cu 6.50%, Ti 0.20%, Si 0.22%, Zr 0.15%, Sc 0.15%, Mg 0.03%, Mn 0.02%, with the balance being Al and unavoidable impurities.

[0091] The method for preparing the welding wire is as follows: the same as in Example 4.

[0092] This embodiment also provides a laser welding method, including laser welding using the welding wire as described above, the workpiece being an Al-Cu-Li alloy (same as in Embodiment 1), and the workpiece size being 75mm×50mm×2mm; welding is performed using a butt joint method with a type I bevel and a pre-reserved gap of 0.2mm; before welding, the surface is cleaned with acetone and anhydrous ethanol, a protective atmosphere is provided on the back side of the Al-Cu-Li alloy plate for laser welding, and an Al-Cu welding wire is placed on top of the plate to be joined, and laser welding is performed using a fiber laser.

[0093] The specific laser welding process is as follows: laser defocusing amount is -6mm, welding power is 4.0kW, welding speed is 4.8m / min, duty cycle is 85%, pulse frequency is 1000Hz, back protective atmosphere flow rate is 30L / min, top surface protective atmosphere flow rate is 15L / min, the angle between the protective atmosphere nozzle and the horizontal direction is 40°, and the angle between the laser and the horizontal direction is 70°.

[0094] Example 6

[0095] This embodiment provides an Al-Cu welding wire and its preparation method. The welding wire composition, by mass percentage, is: Cu 6.00%, Ti 0.15%, Si 0.18%, Zr 0.15%, Sc 0.15%, Mg 0.03%, Mn 0.02%, with the balance being Al and unavoidable impurities.

[0096] The method for preparing the welding wire is as follows: the same as in Example 4.

[0097] This embodiment also provides a laser welding method, including laser welding using the welding wire as described above. The workpiece is an Al-Cu-Li alloy (same as in Embodiment 1), and the workpiece size is 75mm×50mm×2mm. The welding is performed by butt welding with a type I bevel and a pre-reserved gap of 0.1mm. Before welding, the surface is cleaned with acetone and anhydrous ethanol. A protective atmosphere is provided on the back side of the Al-Cu-Li alloy plate for laser welding, and an Al-Cu welding wire is placed on top of the plate to be joined. Laser welding is performed using a fiber laser.

[0098] The specific laser welding process is as follows: laser defocusing amount is -6mm, welding power is 3.8kW, welding speed is 4.8m / min, duty cycle is 85%, pulse frequency is 1000Hz, back protective atmosphere flow rate is 30L / min, top surface protective atmosphere flow rate is 15L / min, the angle between the protective atmosphere nozzle and the horizontal direction is 40°, and the angle between the laser and the horizontal direction is 70°.

[0099] Comparative Example 1

[0100] In this comparative example, 75mm × 1mm × 1mm welding wire was prepared on an Al-Cu-Li base material using wire cutting. The wire cutting marks were polished with sandpaper, resulting in a welding wire width and thickness of 0.2~0.5mm. The wire was then ultrasonically cleaned with anhydrous ethanol, dried, and vacuum-stored. The chemical formula of the Al-Cu-Li base material is: Al-4.05%Cu-1.02%Li-0.51%Ag-0.45%Mg-0.15%Zr, by mass percentage.

[0101] This comparative example also provides a laser welding method, with welding steps and parameters identical to those in Example 2, and the weld microstructure is as follows: Figure 4 As shown, the proportion of equiaxed grains in the weld microstructure is 42.3%.

[0102] Comparative Example 2

[0103] This comparative example provides a laser welding method that does not use welding wire for laser welding. The workpiece is an Al-Cu-Li alloy (same as in Example 1), and self-fusion welding is used. The workpiece size is 75mm×50mm×2mm. The welding is performed by butt welding with a type I bevel and a pre-reserved gap of 0.2mm. Before welding, the surface is cleaned with acetone and anhydrous ethanol. A protective atmosphere is provided on the back side of the Al-Cu-Li alloy plate for laser welding. A fiber laser is used for laser welding.

[0104] The specific laser welding process is as follows: laser defocusing amount is -1mm, welding power is 2.6kW, welding speed is 4.5m / min, duty cycle is 60%, pulse frequency is 1000Hz, back shielding atmosphere flow rate is 30L / min, top surface shielding atmosphere flow rate is 15L / min, the angle with the horizontal direction is 40°, and the laser's horizontal angle is 70°. The weld microstructure of its tensile fracture surface is as follows: Figure 5 As shown.

[0105] Comparative Example 3

[0106] This embodiment provides an Al-Cu welding wire and its preparation method. The welding wire composition, by mass percentage, is: Cu 6.50%, Ti 0.20%, Si 0.22%, Zr 0.15%, Mg 0.03%, Mn 0.02%, with the balance being Al and unavoidable impurities. The main difference between this embodiment and Embodiment 2 is that Sc is not added to the welding wire composition.

[0107] The method for preparing the welding wire is as follows:

[0108] (1) Ingredients: High-purity aluminum, Al-40Cu, Al-10Ti, Al-20Mg, Al-20Si, Al-10Mn, Al-5Zr master alloy, NaCl and KCl covering agent, C2Cl6 refining agent. The master alloy is added first to avoid agglomeration and segregation. All master alloys are wrapped in aluminum foil.

[0109] (2) Melting: The melting temperature is 760℃, until high-purity aluminum is melted;

[0110] (3) Adding materials: Add the intermediate alloy wrapped in aluminum foil, and use a stirrer to press the intermediate alloy below the surface of the molten aluminum. Add the covering agent, the amount of which is the same as in Example 2.

[0111] (4) Melting: The melting temperature is increased to 780℃ until the intermediate alloy melts;

[0112] (5) Stirring and slag removal: Add C2Cl6 refining agent, the amount is the same as in Example 2, stir the melt with a stirrer for 5 minutes, remove the slag and let the melt stand for 30 minutes;

[0113] (6) Casting: The refined melt is gravity cast to obtain an ingot;

[0114] (7) Homogenization: After cutting off the head and tail and peeling the skin, the product is subjected to a single-stage homogenization treatment at 520℃ for 48 hours.

[0115] (8) Hot deformation: The hot rolling temperature is 460℃. After each rolling pass, the billet is sent into the heat preservation furnace and kept for 15 minutes. According to the passes of 20mm→19mm→17mm→14mm→10mm→6mm→4mm→3mm→2mm, a 2mm thick hot-rolled plate is prepared.

[0116] (9) Wire cutting: 75mm×1mm×1mm welding wire was prepared by wire cutting. The wire cutting marks were polished with sandpaper. After polishing, the width and thickness of the welding wire were 0.2~0.5mm. It was ultrasonically cleaned with anhydrous ethanol, dried and vacuum stored.

[0117] This embodiment also provides a laser welding method, with the same welding steps and parameters as in Embodiment 2.

[0118] Comparative Example 4

[0119] The only difference between this comparative example and Example 2 is that the Si content is increased to 5%, while the other steps and conditions are the same, resulting in an Al-Cu welding wire. The Al-Cu welding wire was then laser-welded using the same welding steps and parameters as in Example 2.

[0120] Comparative Example 5

[0121] The only difference between this comparative example and Example 2 is that a back-side protective atmosphere is not used during the laser welding process; all other steps and conditions are the same as in Example 2. The scanning electron microscope image of the laser-welded joint fracture surface is shown below. Figure 6 As shown.

[0122] Comparative Example 6

[0123] The only difference between this comparative example and Example 2 is that the Cu content is replaced with 5.5%, while the other steps and conditions are the same, resulting in an Al-Cu welding wire. The Al-Cu welding wire was then laser-welded using the same welding steps and parameters as in Example 2.

[0124] The performance parameters for each case are shown in Table 1.

[0125] Table 1 Performance Parameters

[0126]

[0127] As shown in Table 1, the welded joints of Examples 1 to 6 of the present invention have better mechanical properties, and their tensile strength and elongation are significantly higher than those of the comparative examples.

[0128] As can be seen from Example 2 and Comparative Example 1, under the same welding process parameters, adding Sc to the welding wire can effectively improve the tensile strength and elongation of the welded joint. Figure 2 and Figure 4 It is known that the synergistic addition of Sc element to the alloy system of this invention can effectively improve the growth mode of columnar crystals near the fusion line, promote the transformation of columnar crystals to equiaxed crystals in the weld joint, and change the nucleation energy barrier and critical undercooling of aluminum liquid during solidification; Figure 2 It is evident that the addition of Sc element can effectively refine the weld microstructure and improve the mechanical properties of the weld joint. This indicates that the welding wire composition designed in this invention, combined with the laser welding method, can improve the overall performance of the joint.

[0129] As can be seen from the metallographic microstructure of the fracture crack in Comparative Example 2, the boundary between isometric and columnar crystals in the weld microstructure is one of the pathways that guide crack propagation. This further illustrates the advantage of introducing trace amounts of Sc, Si, Ti and Zr into the high Cu content weld pool system of the present invention to synergistically improve the growth mode of columnar and isometric crystals.

[0130] As can be seen from the scanning electron microscope image of the laser-welded head fracture surface in Comparative Example 5, when no protective atmosphere is used on the back side, there are many large pores at the fracture surface.

[0131] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0132] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for preparing Al-Cu welding wire, characterized in that: According to the designed welding wire composition ratio, weigh out each component including aluminum, aluminum-copper master alloy, aluminum-titanium master alloy, aluminum-magnesium master alloy, aluminum-silicon master alloy, aluminum-manganese master alloy, aluminum-scandium master alloy, and aluminum-zirconium master alloy. Then, melt and cast each component to obtain an ingot. After the ingot undergoes multi-stage homogenization treatment, it is hot-rolled and wire-cut to form the final product. The welding wire is composed of the following components by mass percentage: Cu 5.80~6.80%, Ti 0.12~0.28%, Si 0.18~0.28%, Zr 0.10~0.50%, Sc 0.10~0.30%, Mg≤0.05%, Mn≤0.05%, with the balance being Al and unavoidable impurities.

2. The method for preparing an Al-Cu welding wire according to claim 1, characterized in that: The welding wire is composed of the following components by mass percentage Composition: Cu 6.20~6.80%, Ti 0.12~0.28%, Si 0.18~0.28%, Zr 0.10~0.30%, Sc 0.10~0.20%, Mg≤0.05%, Mn≤0.05%, with the balance being Al and unavoidable impurities.

3. A method for preparing an Al-Cu welding wire according to claim 1 or 2, characterized in that: During the smelting process, a covering agent and a refining agent are added, and the smelting temperature is 400~830℃. After smelting, the resulting melt is subjected to slag removal and settling treatment. The covering agent includes NaCl and KCl, and the refining agent includes C2Cl6.

4. The method for preparing an Al-Cu welding wire according to claim 3, characterized in that: The multi-stage homogenization process is carried out at a temperature of 290~520℃ for 36~68h.

5. The method for preparing an Al-Cu welding wire according to claim 4, characterized in that: The multi-level homogenization process is either a two-level homogenization process or a three-level homogenization process. The first stage of the two-stage homogenization treatment has a heat preservation temperature of 300~320℃ and a time of 20~24h, while the second stage has a heat preservation temperature of 500~520℃ and a time of 20~24h. The three-stage homogenization treatment involves a first-stage heat preservation temperature of 330-340℃ for 4-6 hours, a second-stage heat preservation temperature of 450-470℃ for 4-6 hours, and a third-stage heat preservation temperature of 510-530℃ for 40-48 hours.

6. The method for preparing an Al-Cu welding wire according to claim 1, characterized in that: The hot rolling temperature is 400~460℃, the deformation per pass is 5%~40%, the total deformation is 85%~95%, and the heat preservation between passes is 15~20min.

7. An Al-Cu welding wire, characterized in that: It is obtained by the preparation method according to any one of claims 1 to 6.

8. An application of the Al-Cu welding wire as described in claim 7, characterized in that: Laser welding of Al-Cu-Li alloy plates.

9. The application of the Al-Cu welding wire according to claim 8, characterized in that: The laser welding process includes the following steps: S1 After cleaning and pre-treatment, Al-Cu-Li alloy plates are spliced ​​and placed; the splicing bevel between the Al-Cu-Li alloy plates uses a type I bevel, and the gap width between the splices is not greater than the thickness of the Al-Cu welding wire. S2 provides a protective atmosphere on the back side of the Al-Cu-Li alloy plate for laser welding, and places the Al-Cu welding wire above the plate to be joined, and performs laser welding using a fiber laser.

10. The application of the Al-Cu welding wire according to claim 9, characterized in that: The parameters for laser welding are as follows: defocusing amount -6~+2mm, welding power 3~6kW, welding speed 2.8~5.8m / min, duty cycle 75~90%, pulse frequency 960~1200Hz, the angle between the protective atmosphere nozzle and the horizontal direction is 40°, and the angle between the laser and the horizontal direction is 70°.

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