Laser flexible heat source hybrid welding and heat treatment method for 7A52 aluminum alloy medium plate

Abstract

The invention relates to a laser flexible heat source hybrid welding and heat treatment method for a 7A52 aluminum alloy medium plate. Firstly, a laser flexible heat source composite wire filling welding technology is selected, and a well-formed and low-porosity welding joint is obtained by regulating and controlling the relative spatial position of pulse laser, a welding arc and a welding wire, dynamically combining a flexible heat source with controllable welding arc deflection and optimizing three-dimensional heat distribution of a welding seam; the nano ceramic particles are filled to reinforce the composite welding wire, so that crystal grains in a weld zone are promoted to be converted into a double-peak layered structure in which fine columnar crystals and equiaxed crystals are alternately distributed from thick columnar crystals growing in the heat dissipation direction, tensile deformation is effectively buffered, and the tensile strength and the elongation of a welded joint are improved; and then T6 heat treatment is carried out on the welded joint, so that a thick eutectic phase is fully dissolved, a strengthening phase MgZn2 phase (eta ') in a semi-coherent relationship with the matrix is promoted to be uniformly dispersed and separated out, and the tensile strength and the elongation of the welded joint are further improved. The method has important engineering application value.

Description

Technical Field

[0001] The present invention relates to the technical field of material processing, and relates to the application of 7A52 aluminum alloy medium and heavy plates in engineering structures. Specifically, it relates to a laser flexible heat source composite welding and heat treatment method for 7A52 aluminum alloy medium and heavy plates, realizing high-quality welding of 7A52 aluminum alloy medium and heavy plates. Background Art

[0002] As a high-strength weldable aluminum alloy independently developed in China, 7A52 aluminum alloy medium and heavy plates have the advantages of high strength, low density, good corrosion resistance, etc., and show irreplaceable application value in large and complex key components in military facilities, light equipment, gun mounts, aerospace and other fields. However, its application in the above fields requires the support of advanced welding technology.

[0003] However, there are still many technical challenges in the high-quality welding of medium and thick plates of 7A52 aluminum alloy, which are specifically manifested in the following aspects: First, the formation of coarse columnar crystals and coarse equiaxed crystals in the weld seam will significantly reduce the performance of the welded joint, and heat cracks are likely to be induced along the grain boundaries under the action of solidification shrinkage stress; Second, during the welding of medium and thick plates, due to the uneven distribution of heat input, it is easy to cause defects such as poor sidewall fusion (JIANG N, JIANG M, CHEN X, et al. Effect of beam oscillation on weld formation, microstructure and mechanical properties in vacuum laser beam welding of thick section 5083 aluminum alloy[J]. Optics and laser technology, 2024, 171:110408.) and lack of interlayer fusion. These defects and pores will significantly reduce the load-bearing capacity of the welded joint and are likely to become stress concentration sources, accelerating the failure of structural components; Third, the formation of eutectic phases in the weld area and the aging coarsening in the heat-affected zone lead to joint softening (DUAN C, HAO X, LUO X, et al. Microstructure and fatigue properties of laser-MIG hybrid welding of medium-thickness 6005A aluminum alloy[J]. Engineering failure analysis, 2024, 165:108753.). At present, the fusion welding of 7A52 aluminum alloy mainly uses 4XXX and 5XXX series aluminum alloy welding wires. Although these welding wires can compensate for the loss of low-melting-point elements such as Mg and Zn to a certain extent during the welding process, the improvement of the mechanical properties of the welded joint after welding is limited. Its tensile strength ranges from 268 to 284 MPa, which is 54 to 60% of the base metal, and the elongation after fracture is less than 40% of the base metal, making it difficult to meet the requirements of 7A52 aluminum alloy for medium and thick plates as high-performance components (DUAN C, HAO X, LUO X, et al. Microstructure and fatigue properties of laser-MIG hybrid welding of medium-thickness 6005A aluminum alloy[J]. Engineering failure analysis, 2024, 165:108753.). Therefore, achieving a comprehensive improvement in the mechanical properties of the welded joint of 7A52 aluminum alloy medium and thick plates has become an urgent need to expand its application in key engineering fields.

[0004] The invention patent with the application number 202411231767.5 proposes a method of backside laser conduction welding to improve the strength and plasticity of the welded joints of medium-thick plates of 7050 high-strength aluminum alloy. However, this method still has significant limitations in engineering applications: First, the effect of improving the strength of the welded joints is limited. The strength is increased to 65% of the base material, and the elongation after fracture is increased to 50% of the base material, making it difficult to meet the strength requirements of high-load structural components. Second, during the manufacturing process of large structural components, it is difficult to assemble and precisely control the laser beam on the backside of the welded parts, which limits its industrial application scope.

[0005] Therefore, there is an urgent need for a new technology to improve the poor welding performance of medium-thick plates of 7A52 aluminum alloy and expand the practical application of medium-thick plates of 7A52 aluminum alloy in the engineering field. Summary of the Invention

[0006] In view of the above-mentioned technical problems, a laser flexible heat source composite welding and heat treatment method for medium-thick plates of 7A52 aluminum alloy is provided.

[0007] The technical means adopted in the present invention are as follows:

[0008] A laser flexible heat source composite welding and heat treatment method for medium-thick plates of 7A52 aluminum alloy,

[0009] adopts a laser flexible heat source composite wire filling welding technology;

[0010] During welding, a 7-series aluminum alloy welding wire with a composition close to that of the to-be-welded medium-thick plate of 7A52 aluminum alloy and added with nano-ceramic particles is selected.

[0011] During the welding process, a multi-layer and multi-pass welding method is used to weld the 10-20 mm thick medium-thick plate of 7A52 aluminum alloy, and the flexible regulation of the heat source is realized by changing the spatial position of the tungsten electrode and the laser beam.

[0012] After welding, the welded joint is subjected to T6 heat treatment to dissolve the coarse eutectic phase and then precipitate it as a uniform aging phase.

[0013] Furthermore, the welding wire is a 7A52 aluminum alloy welding wire reinforced with nano-TiC.

[0014] Furthermore, for the nano-TiC ceramic reinforced 7A52 aluminum alloy welding wire, the chemical composition is by mass percentage: Mg: 2.2% - 2.8%; Zn: 4.2% - 4.8%; Cu: 0.05% - 0.18%; pure Ti: 0.96% - 1.00%; Zr: 0.06% - 0.15%; Cr: 0.15% - 0.25%; Mn: 0.2% - 0.5%; Fe ≤ 0.3%; Si ≤ 0.25%; TiC particles: 1.2% - 1.5%, and the balance is Al and unavoidable impurities. The particle size range of the TiC particles is 300 - 900 nm.

[0015] Furthermore, the multi-layer and multi-pass welding includes root pass welding, filler pass welding, and capping pass welding.

[0016] Furthermore, the process parameters for root pass welding are as follows: the laser power range is 500 - 700 W, the laser defocusing amount range is -2 - 2 mm, the arc pulse current range is 180 - 220 A, the arc pulse frequency range is 0 - 40 HZ, the welding speed range is 180 - 220 mm / min, the TIG torch angle range is 35 - 50°, the tungsten electrode height range is 1 - 3 mm, D la range is 0 - 3 mm, Malp range is 0 - 3 mm, the shielding gas flow rate range is 10 - 15 L / min, and the welding wire height range is 0 - 3 mm.

[0017] Furthermore, the process parameters for filler pass welding are as follows: the laser power range is 500 - 700 W, the laser defocusing amount range is -2 - 2 mm, the arc pulse current range is 200 - 260 A, the arc pulse frequency range is 0 - 40 HZ, the welding speed range is 280 - 350 mm / min, the wire feeding speed range is 1500 - 1800 mm / min, the TIG torch angle range is 35 - 50°, the tungsten electrode height range is 1 - 3 mm, the Dla range is 0 - 3 mm, the Malp range is 0 - 3 mm, the distance between the laser and the wire range is 2 - 3 mm, the shielding gas flow rate range is 0 - 15 L / min, and the welding wire height range is 0 - 3 mm.

[0018] Furthermore, the process parameters for capping pass welding are as follows: the laser power range is 500 - 700 W, the laser defocusing amount range is -2 - 2 mm, the arc pulse current range is 180 - 240 A, the arc pulse frequency range is 0 - 40 HZ, the welding speed range is 300 - 380 mm / min, the wire feeding speed range is 1500 - 1800 mm / min, the TIG torch angle range is 35 - 50°, the tungsten electrode height range is 1 - 3 mm, the Dla range is 0 - 3 mm, the Malp range is 0 - 3 mm, the distance between the laser and the wire range is 2 - 3 mm, the shielding gas flow rate range is 0 - 15 L / min, and the welding wire height range is 0 - 3 mm.

[0019] Furthermore, heat treatment is carried out by adopting the T6 single-stage aging process, including solution treatment, water quenching and aging treatment, and the process parameter ranges meet the following:

[0020] For the solution treatment of the welded joint of 7A52 aluminum alloy, the temperature range is 460 - 480 °C and the holding time range is 2 - 3 h;

[0021] Water quenching is carried out. The welded joint after solution treatment is quickly put into water for quenching, and the time range is 1 - 5 min;

[0022] Single-stage aging treatment is carried out, the temperature range is 120 - 130 °C, and the holding time range is 24 - 30 h.

[0023] Compared with the prior art, the present invention has the following advantages: The present invention proposes a comprehensive solution aiming to improve the comprehensive performance of the welded joint of medium and thick plates of 7-series aluminum alloy. Firstly, the laser flexible heat source composite wire filling welding technology is adopted. By controlling the relative positions of the laser beam, welding arc and welding wire, the distribution of heat on the base metal and the welding wire is optimized, effectively improving the problems of sidewall non-fusion and poor interlayer fusion commonly found in the welding of medium and thick plate aluminum alloy. Secondly, the 7-series aluminum alloy composite welding wire filled with nano-TiC particles is used to form a bimodal structure with alternating distribution of fine equiaxed grains and fine columnar grains in the weld, effectively suppressing the formation tendency of welding hot cracks in 7-series aluminum alloy. Finally, solution treatment is adopted to promote the full re-dissolution of the coarse eutectic phase at the grain boundary into the weld structure, and then aging treatment is used to control the uniform and dispersed precipitation of nano-fine aging phases in the weld and the heat affected zone. The maximum tensile strength of the welded joint of the medium and thick plate of 7A52 aluminum alloy obtained by the above process is greater than 83% of the base metal, and the elongation after fracture is greater than 50% of the base metal. Brief Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 Schematic diagrams of a welding fixture for 10-mm-thick 7A52 aluminum alloy (a), the taking position of the tensile specimen (b), and the dimensions of the tensile specimen (c).

[0026] Figure 2 Schematic diagrams of a welding groove for 10-mm-thick 7A52 aluminum alloy (a) and the distribution of laser-arc composite wire filling weld beads (b).

[0027] Figure 3Microstructures of the upper and lower regions of the cross-section of a 10-mm-thick 755A aluminum alloy welded joint, including the average grain size and the grain boundary distribution.

[0028] Figure 4 Microtopographies of the cross-section of a 10-mm-thick 7A52 aluminum alloy welded joint before and after heat treatment, where the upper, middle, and lower parts correspond to Figure 1 the positions selected for the tensile specimens. Among them, (a), (b), and (c) are the microtopographies before heat treatment of the upper, middle, and bottom parts respectively, and (d), (e), and (f) are the microtopographies after heat treatment of the upper, middle, and bottom parts respectively.

[0029] Figure 5 Engineering stress-strain curves of a 10-mm-thick 7A52 aluminum alloy welded joint before and after heat treatment. Among them, (a) and (c) are the stress-strain curves of the upper, middle, and bottom regions of the welded joint before and after heat treatment; (b) and (d) are the tensile strength and elongation values of the upper, middle, and bottom parts of the welded joint before and after heat treatment.

[0030] Figure 6 Schematic diagram of the welding groove of a 30-mm-thick 7A52 aluminum alloy (a), schematic diagram of the bead distribution of laser-arc hybrid wire filling welding (b), and sampling positions of tensile specimens (c).

[0031] Figure 7 Schematic diagram of the specific process method of Embodiment 1 of the present invention. Specific implementation manners

[0032] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The description of at least one exemplary embodiment below is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods, and devices should be regarded as part of the specification. In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not require further discussion in subsequent drawings.

[0036] An embodiment of the present invention discloses a method for laser flexible heat source composite welding and heat treatment of 7A52 aluminum alloy medium-thick plates. Taking Embodiment 1 as an example, as Figure 7 shown,

[0037] The laser flexible heat source composite heat source wire filling welding technology is adopted; the "flexible heat source" mentioned in the present invention realizes good distribution of the heat source on the wire and the base material by changing the relative positions of the laser and the arc, which is beneficial to promoting sidewall and interlayer fusion. It promotes good sidewall and interlayer fusion, and there are no obvious pores and lack of fusion.

[0038] During welding, a 7-series aluminum alloy wire filled with nano-ceramic particles, which is preset and has a composition close to that of the 7A52 aluminum alloy medium-thick plate to be welded, is selected;

[0039] During the welding process, the multi-layer and multi-pass welding method is used to weld the 10-20 mm thick 7A52 aluminum alloy medium-thick plate, and the flexible regulation of the heat source is realized by changing the spatial position of the tungsten electrode and the laser beam;

[0040] After welding, the welded joint is subjected to T6 heat treatment to dissolve the coarse eutectic phase and then precipitate it as a uniform aging phase, so as to achieve the coordinated improvement of the strength and plasticity of the welded joint and realize the high-quality connection of the 7A52 aluminum alloy medium-thick plate.

[0041] Further, the wire is a 7A52 aluminum alloy wire reinforced with nano-TiC.

[0042] Furthermore, for the nano-TiC ceramic reinforced 7A52 aluminum alloy welding wire, the chemical composition is by mass percentage: Mg: 2.2% - 2.8%; Zn: 4.2% - 4.8%; Cu: 0.05% - 0.18%; pure Ti: 0.96% - 1.00%; Zr: 0.06% - 0.15%; Cr: 0.15% - 0.25%; Mn: 0.2% - 0.5%; Fe ≤ 0.3%; Si ≤ 0.25%; TiC particles: 1.2% - 1.5%, and the balance is Al and inevitable impurities. The particle size range of the TiC particles is 300 - 900 nm.

[0043] Furthermore, the multi-layer and multi-pass welding includes root pass welding, filler pass welding, and cap pass welding.

[0044] Furthermore, the process parameters for root pass welding are: the laser power range is 500 - 700 W, the laser defocusing amount range is -2 - 2 mm, the arc pulse current range is 180 - 220 A, the arc pulse frequency range is 0 - 40 HZ, the welding speed range is 180 - 220 mm / min, the TIG torch angle range is 35 - 50°, the tungsten electrode height range is 1 - 3 mm, D la range is 0 - 3 mm, Malp range is 0 - 3 mm, the shielding gas flow rate range is 10 - 15 L / min, and the welding wire height range is 0 - 3 mm.

[0045] Furthermore, the process parameters for filler pass welding are: the laser power range is 500 - 700 W, the laser defocusing amount range is -2 - 2 mm, the arc pulse current range is 200 - 260 A, the arc pulse frequency range is 0 - 40 HZ, the welding speed range is 280 - 350 mm / min, the wire feeding speed range is 1500 - 1800 mm / min, the TIG torch angle range is 35 - 50°, the tungsten electrode height range is 1 - 3 mm, the Dla range is 0 - 3 mm, the Malp range is 0 - 3 mm, the optical wire spacing range is 2 - 3 mm, the shielding gas flow rate range is 10 - 15 L / min, and the welding wire height range is 0 - 3 mm.

[0046] Furthermore, the process parameters for cap pass welding are: the laser power range is 500 - 700 W, the laser defocusing amount range is -2 - 2 mm, the arc pulse current range is 180 - 240 A, the arc pulse frequency range is 0 - 40 HZ, the welding speed range is 300 - 380 mm / min, the wire feeding speed range is 1500 - 1800 mm / min, the TIG torch angle range is 35 - 50°, the tungsten electrode height range is 1 - 3 mm, the Dla range is 0 - 3 mm, the Malp range is 0 - 3 mm, the optical wire spacing range is 2 - 3 mm, the shielding gas flow rate range is 10 - 15 L / min, and the welding wire height range is 0 - 3 mm.

[0047] Furthermore, heat treatment is carried out by adopting the T6 single-stage aging process, including solution treatment, water-cooled quenching and aging treatment, and the process parameter ranges meet:

[0048] For solution treatment of the 7A52 aluminum alloy welded joint, the temperature range is 460 - 480 °C and the holding time range is 2 - 3 h;

[0049] Water-cooled quenching is carried out. After solution treatment, the welded joint is quickly put into water for quenching, and the time range is 1 - 5 min;

[0050] Single-stage aging treatment is carried out, the temperature range is 120 - 130 °C, and the holding time range is 24 - 30 h.

[0051] The present invention selects the laser flexible heat source composite wire filling welding technology. By regulating the relative spatial positions of the pulsed laser, welding arc and welding wire, the dynamic flexible heat source composite controllable welding arc deflection is realized, the three-dimensional heat distribution of the weld is optimized, and a welded joint with good forming and low porosity is obtained; the nano-ceramic particle-reinforced composite welding wire is filled, which promotes the transformation of the grains in the weld zone from the coarse columnar grains growing along the heat dissipation direction to the bimodal layered structure with alternating fine columnar grains and equiaxed grains, effectively buffering the tensile deformation and improving the tensile strength and plasticity of the welded joint; then the welded joint is subjected to T6 heat treatment to fully dissolve the coarse eutectic phase and promote the uniform and dispersed precipitation of the strengthening phase MgZn2 phase (η′) with a semi-coherent relationship with the matrix. Further improve the tensile strength and elongation of the welded joint. Through the synergistic effect of the above welding process optimization, nano-particle reinforcement and heat treatment strengthening, the strength and plasticity of the 7A52 aluminum alloy welded joint can be greatly improved. The strength of the welded joint is greater than 80% of the base metal, and the elongation after fracture is greater than 50% of the base metal. The present invention realizes the high-quality connection of the 7A52 aluminum alloy medium-thick plate and has important engineering application value.

[0052] Example 1 Laser-arc composite wire filling welding of 10-mm-thick 7A52-T6 aluminum alloy plate

[0053] As Figure 1 shown, take two 7A52-T6 aluminum alloy plates with a thickness of 10 mm, open a "U"-shaped groove in the aluminum alloy plates, with a blunt edge of 1 mm, an assembly gap of 0 mm, a bilateral groove angle of 10°, and a straight edge of 3.5 mm. The macroscopic morphology of the cross-section of the welded joint after welding and the taking position of the tensile specimen, and the dimensions of the tensile specimen are as Figure 1 shown. The welding groove angle and the weld bead distribution schematic diagram are as Figure 2As shown, where the shaded area is the backing weld, 1-3 are the filler wire welds, and 4-5 are the capping welds. A nano-TiC ceramic particle-reinforced 7-series aluminum alloy composite wire is used, and its chemical composition by mass percentage is: Mg: 2.2%; Zn: 4.2%; Cu: 0.05%; pure Ti: 1.00%; Zr: 0.06%; Cr: 0.15%; Mn: 0.5%; Fe: 0.3%; Si: 0.2%; TiC particles: 1.2%, and the balance is Al and unavoidable impurities. The particle size of the TiC particles formed in-situ in the weld is 400 nm. Cold wire feeding and free forming are adopted.

[0054] Backing welding process parameters: laser power 520 W, laser defocus -2 mm, arc pulse current 200 A, arc pulse frequency 0 HZ, welding speed 180 mm / min, TIG torch angle 45°, tungsten electrode height 2 mm, the lateral distance between the wire tip and the tungsten electrode, i.e., D la is 2 mm, the longitudinal misalignment between the tungsten electrode tip and the laser beam focus, i.e., Malp is 0 mm, and the shielding gas is argon with a purity of 99%, and the shielding gas flow rate is 15 L / min. Filler welding process parameters: laser power 520 W, laser defocus -2 mm, arc pulse current 220 A, arc pulse frequency 0 HZ, welding speed 300 mm / min, wire feeding speed 1800 mm / min, TIG torch angle 45°, tungsten electrode height 2 mm, D la is 2 mm, Malp is 2 mm, the distance between the laser and the wire is 2 mm, and the shielding gas flow rate is 15 L / min, and the wire height is 2 mm. Capping welding process parameters: laser power 600 W, laser defocus -2 mm, arc pulse current 180 A, arc pulse frequency 20 HZ, welding speed 320 mm / min, wire feeding speed 1600 mm / min, TIG torch angle 40°, tungsten electrode height 2 mm, D la is 1 mm, Malp is 1 mm, the distance between the laser and the wire is 2 mm, and the shielding gas flow rate is 15 L / min, and the wire height is 2 mm.

[0055] Figure 3It is the grain and grain boundary distribution map of the upper and lower regions of the welded joint. Obviously, near the fusion line close to the weld, the microstructure of the weld region and the interlayer region consists of alternating fine columnar grains and equiaxed grains, and the average grain size is less than 11 μm. The average grain size of the lower region of the welded joint is slightly larger than that of the upper region. When welding the upper layer, it is equivalent to "heat treatment" of the lower weld. Under the action of a new thermal cycle, grain growth is caused. In addition, under the action of the multiple laser-arc flexible heat sources, the dislocation density of the lower weld increases significantly, manifested as an obvious increase in the proportion of small-angle grain boundaries (LAGBs). After welding, the joint is solution-treated at a temperature of 475 °C for a holding time of 2 h, and immediately water-cooled and quenched after being taken out. Then aging treatment is carried out: the temperature is 130 °C and the time is 24 h; the microstructure of the welded joint before and after heat treatment is as Figure 4 shown. The continuous grain boundaries existing in the upper, middle and lower regions are remelted, there is almost no remaining eutectic phase, and only a small amount of impurity phases exist.

[0056] Figure 5 It is the engineering stress-strain curve of the welded joint before and after heat treatment. Before heat treatment, the maximum tensile strength of the welded joint is 65.2% - 70.5% of the base metal, and the elongation after fracture is 46.3% - 51.5% of the base metal; after heat treatment, the welded joint is 87.8% - 92.1% of the base metal, and the elongation after fracture is 59.5% - 64.8% of the base metal.

[0057] Example 2 Laser-arc composite wire filling for 30-mm-thick 7A52-T6 aluminum alloy plate

[0058] Take two 30-mm-thick 7A52-T6 aluminum alloy plates, make a "double U" groove on the aluminum alloy workpiece, with a blunt edge of 2 mm, an assembly gap of 0 mm, a bilateral groove angle of 10°, and a straight edge of 3.5 mm. The schematic diagram of the welding groove, weld bead distribution and the position of the tensile specimen taking are as Figure 6 shown, where the shaded part is the root pass welding, 1 - 3, 6 - 8 are wire filling welding, and 4 - 5, 9 - 10 are capping welding. A nano-TiC ceramic particle-reinforced 7-series aluminum alloy composite wire is used, and its chemical composition by mass percentage is: Mg: 2.5%; Zn: 4.5%; Cu: 0.1%; pure Ti: 0.96%; Zr: 0.08%; Cr: 0.18%; Mn: 0.3%; Fe: 0.2%; Si: 0.2%; TiC particles: 1.5%, and the balance is Al and unavoidable impurities. The particle size of the TiC particles formed in-situ in the weld is 300 nm. Cold wire feeding, free forming. Cold wire feeding, free forming.

[0059] Backing welding process parameters: laser power 700W, laser defocusing amount 0mm, arc pulse current 220A, arc pulse frequency 20HZ, welding speed 180mm / min, TIG torch angle 35°, tungsten electrode height 1mm, D la is 0mm, Malp is 0mm, shielding gas flow rate 10L / min. Filling welding process parameters: laser power 700W, laser defocusing amount 2mm, arc pulse current 260A, arc pulse frequency 40HZ, welding speed 350mm / min, wire feeding speed 1800mm / min, TIG torch angle 35°, tungsten electrode height 1mm, D la is 0mm, Malp is 0mm, optical wire spacing 2mm, shielding gas flow rate 10L / min, wire height 3mm. Surfacing welding process parameters: laser power 700W, laser defocusing amount 0mm, arc pulse current 180A, arc pulse frequency 0HZ, welding speed 300mm / min, wire feeding speed 1500mm / min, TIG torch angle 35°, tungsten electrode height 1mm, D la is 0mm, Malp is 0mm, optical wire spacing 2mm, shielding gas flow rate 10L / min, wire height 3mm.

[0060] Before heat treatment, the maximum tensile strength of the welded joint is 66.2% - 68.0% of the base metal, and the elongation after fracture is 43.5% - 46.1% of the base metal; after heat treatment, the welded joint is 86.8% - 89.2% of the base metal, and the elongation after fracture is 58.5% - 60.8% of the base metal.

[0061] Example 3 Laser-arc hybrid wire filling of 30mm thick 7A52-T6 aluminum alloy plate

[0062] Take two 30mm thick 7A52-T6 aluminum alloy plates, open a "double U" groove for the aluminum alloy workpiece, with a blunt edge of 3mm and an assembly gap of 0mm. Use a nano-TiC ceramic particle-reinforced 7-series aluminum alloy composite wire. The chemical composition by mass percentage is: Mg: 2.8%; Zn: 4.8%; Cu: 0.18%; pure Ti: 0.98%; Zr: 0.15%; Cr: 0.25%; Mn: 0.5%; Fe: 0.3%; Si: 0.2%; TiC particles: 1.4%, and the balance is Al and unavoidable impurities. The particle size of the TiC particles formed in-situ in the weld is 900nm. Cold wire feeding, free forming.

[0063] Backing welding process parameters: laser power 500W, laser defocusing amount 2mm, arc pulse current 180A, arc pulse frequency 40HZ, welding speed 220mm / min, TIG torch angle 50°, tungsten electrode height 3mm, Dla is 3 mm, Malp is 3 mm, the shielding gas flow rate is 15 L / min. Filling welding process parameters: laser power is 500 W, laser defocus amount is -2 mm, arc pulse current is 200 A, arc pulse frequency is 0 HZ, welding speed is 280 mm / min, wire feeding speed is 1500 mm / min, TIG torch angle is 50°, tungsten electrode height is 3 mm, D la is 3 mm, Malp is 3 mm, the distance between the laser and the wire is 3 mm, the shielding gas flow rate is 15 L / min, and the wire height is 0 mm. Surfacing welding process parameters: laser power is 500 W, laser defocus amount is 2 mm, arc pulse current is 240 A, arc pulse frequency is 40 HZ, welding speed is 380 mm / min, wire feeding speed is 1800 mm / min, TIG torch angle is 50°, tungsten electrode height is 3 mm, D la is 3 mm, Malp is 3 mm, the distance between the laser and the wire is 3 mm, the shielding gas flow rate is 15 L / min, and the wire height is 0 mm

[0064] Before heat treatment, the maximum tensile strength of the welded joint is 65.8% - 68.7% of the base material, and the elongation after fracture is 44.2% - 47.3% of the base material; after heat treatment, the welded joint is 85.6% - 87.9% of the base material, and the elongation after fracture is 57.8% - 61.4% of the base material.

[0065] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser flexible heat source composite welding and heat treatment method for 7A52 aluminum alloy medium - thick plates, characterized in that: The laser flexible heat source composite wire - filling welding technology is adopted; During welding, a 7 - series aluminum alloy welding wire with a composition close to that of the to - be - welded 7A52 aluminum alloy medium - thick plate and added with nano - ceramic particles is selected as the preset; During the welding process, the multi - layer and multi - pass welding method is used to weld the 7A52 aluminum alloy medium - thick plate with a thickness of 10 - 20 mm, and the flexible regulation of the heat source is realized by changing the spatial position of the tungsten electrode and the laser beam; After welding, the welded joint is subjected to T6 heat treatment to dissolve the coarse eutectic phase and then precipitate it as a uniform aging phase.

2. The method according to claim 1, characterized in that, The welding wire is a 7A52 aluminum alloy welding wire reinforced with nano - TiC.

3. The method according to claim 1, characterized in that The nano - TiC ceramic - reinforced 7A52 aluminum alloy welding wire, the chemical composition is calculated by mass percentage as follows: Mg: 2.2% - 2.8%; Zn: 4.2% - 4.8%; Cu: 0.05% - 0.18%; Pure Ti: 0.96% - 1.00%; Zr: 0.06% - 0.15%; Cr: 0.15% - 0.25%; Mn: 0.2% - 0.5%; Fe ≤ 0.3%; Si ≤ 0.25%; TiC particles: 1.2% - 1.5%, the balance is Al and inevitable impurities, and the particle size range of TiC particles is 300 - 900 nm.

4. The method according to claim 1, wherein The multi - layer and multi - pass welding includes root pass welding, filler pass welding and capping welding.

5. The method according to claim 1, wherein The welding process parameters of the root pass are: the laser power range is 500 - 700 W, the laser defocusing amount range is - 2 - 2 mm, the arc pulse current range is 180 - 220 A, the arc pulse frequency range is 0 - 40 HZ, the welding speed range is 180 - 220 mm / min, the TIG welding gun angle range is 35 - 50°, the tungsten electrode height range is 1 - 3 mm, the Dla range is 0 - 3 mm, the Malp range is 0 - 3 mm, the shielding gas flow rate range is 10 - 15 L / min, and the welding wire height range is 0 - 3 mm.

6. The method according to claim 1, wherein The welding process parameters of the filler pass are: the laser power range is 500 - 700 W, the laser defocusing amount range is - 2 - 2 mm, the arc pulse current range is 200 - 260 A, the arc pulse frequency range is 0 - 40 HZ, the welding speed range is 280 - 350 mm / min, the wire feeding speed range is 1500 - 1800 mm / min, the TIG welding gun angle range is 35 - 50°, the tungsten electrode height range is 1 - 3 mm, the Dla range is 0 - 3 mm, the Malp range is 0 - 3 mm, the light - wire spacing range is 2 - 3 mm, the shielding gas flow rate range is 10 - 15 L / min, and the welding wire height range is 0 - 3 mm.

7. The method according to claim 1, wherein The process parameters for surfacing welding are as follows: the laser power ranges from 500 to 700 W, the laser defocusing amount ranges from -2 to 2 mm, the arc pulse current ranges from 180 to 240 A, the arc pulse frequency ranges from 0 to 40 HZ, the welding speed ranges from 300 to 380 mm / min, the wire feeding speed ranges from 1500 to 1800 mm / min, the TIG torch angle ranges from 35 to 50°, the tungsten electrode height ranges from 1 to 3 mm, the Dla ranges from 0 to 3 mm, the Malp ranges from 0 to 3 mm, the optical wire spacing ranges from 2 to 3 mm, the shielding gas flow rate ranges from 10 to 15 L / min, and the wire height ranges from 0 to 3 mm.

8. The method according to claim 1, wherein Heat treatment is carried out using the T6 single-stage aging process, including solution treatment, water quenching, and aging treatment. The process parameter ranges meet the following requirements: Solution treatment of the 7A52 aluminum alloy welded joint, the temperature range is 460 - 480 °C, and the holding time range is 2 - 3 h; Water quenching is carried out. The welded joint after solution treatment is quickly put into water for quenching, and the time range is 1 - 5 min; Single-stage aging treatment is carried out, the temperature range is 120 - 130 °C, and the holding time range is 24 - 30 h.

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