A universal aluminum alloy welding wire and its preparation method and application

Abstract

The present invention relates to a universal aluminum alloy welding wire and a preparation method and application thereof, belonging to the field of welding technology. The universal aluminum alloy welding wire of the present invention has the following elemental composition and mass percentage: Si is 1.5%-3.5%, Fe is 1.0%-3.0%, Mg is 3.0%-5.0%, Mn is 0.5%-2.5%, Cr is 0.3%-1.5%, and the balance is Al and other inevitable impurities; the mass ratio of Mn / Fe is 0.9-1.1; the mass ratio of Cr / Mn is 0.25-0.4; the mass ratio of Mg / Si is 1.5-1.7; the mass ratio of (Fe+Si) / (Mn+Cr) does not exceed 2.5; and the mass ratio of (Mn+Cr) / Fe is not less than 1. After being used for aluminum alloy welding, the grain morphology and size distribution are optimized to a certain extent, thereby improving the mechanical properties and stability of the weld.

Description

Technical Field

[0001] The present invention belongs to the technical field of welding, and in particular relates to a universal aluminum alloy welding wire and a preparation method and application thereof. Background Art

[0002] With the growing demand for high-performance aluminum alloy welding in areas such as lightweighting in automobiles, rail transit, aerospace, and building structures, aluminum alloy welding wire, as a key connecting material, has a direct impact on the quality and service life of welded structures. However, the mainstream aluminum alloy welding wire currently on the market is mostly made from primary aluminum resources. While these wires offer acceptable welding performance, they consume large amounts of resources and remain expensive, running counter to the current principles of green manufacturing and energy conservation and emission reduction.

[0003] Against this backdrop, recycled aluminum, with its outstanding advantages such as low energy consumption, reduced carbon emissions, and low cost, has become a highly sought-after secondary resource. However, the difficulty in completely removing impurities (such as Fe and Si) from recycled aluminum has severely limited its application in demanding welding alloy wires. This is primarily manifested by problems such as thermal cracking, porosity, and a decline in weld mechanical properties during the welding process. Therefore, the efficient development and utilization of recycled aluminum resources, and the development of aluminum alloy welding wires with both excellent welding performance and stable structure, have become key challenges in the field of aluminum alloy welding materials.

[0004] While current research attempts to improve the weldability of recycled aluminum-based alloys through trace element adjustments, smelting and refining, and modification, these alloys still suffer from significant compositional fluctuations, difficulty in precisely controlling impurities, and unstable weld formability and mechanical properties. Furthermore, conventional welding wires are often designed for specific aluminum alloy grades, resulting in poor versatility and difficulty adapting to the diverse requirements of various aluminum alloy base materials.

[0005] In general, the development of aluminum alloy welding wire based on recycled aluminum, through the rational design of Si, Fe, Mg, Mn, Cr and other alloying elements to give it excellent welding performance and structural stability, has become an important research direction with great prospects and urgently needs to be promoted in this field. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a universal aluminum alloy welding wire and its preparation method and application. The welding wire adopts a high-speed iron setting and a structural control mechanism, but there is a synergistic effect between the alloy elements in its composition system, which has a certain regulatory effect on the solidification behavior and grain growth of the weld zone. After welding, a structure with a smooth structural transition and a continuous distribution of the second phase can be formed, which significantly improves the welding compatibility of dissimilar aluminum alloys. At the same time, the weld is uniformly formed and the joint quality is high. The welding wire is designed based on recycled aluminum resources, and has both high performance and environmental protection characteristics. Its material formula is suitable for secondary manufacturing and repair welding of industrial recycled aluminum alloy components, which can effectively increase the added value of recycled materials.

[0007] A first object of the present invention is to provide a universal aluminum alloy welding wire, wherein the element composition and mass percentage of the universal aluminum alloy welding wire are as follows: Si 1.5%-3.5%, Fe 1.0%-3.0%, Mg 3.0%-5.0%, Mn 0.5%-2.5%, Cr 0.3%-1.5%, and the balance Al and other inevitable impurities, each inevitable impurity being less than 0.05% and the total impurities being less than 0.15%;

[0008] The mass ratio of Mn / Fe is 0.9-1.1; under this condition, Mn can form a stable α-Al(Fe,Mn)Si phase with Fe, thereby promoting the transformation of the brittle β-Al5FeSi phase to the α phase with better plasticity and toughness.

[0009] The mass ratio of Cr / Mn is 0.25-0.4. Under this condition, Cr and Mn can coexist in the microstructure to form an α-Al(Fe,Mn,Cr)Si composite intermetallic compound. This α phase has good thermal stability and dispersion distribution, which can effectively improve the phase uniformity and thermal cycling stability of the weld area.

[0010] The mass ratio of Mg / Si is 1.5-1.7; this ratio is slightly lower than the theoretical eutectic ratio of 1.73. It can maintain appropriate Mg2Si precipitation strengthening while avoiding the weld softening problem caused by excessive Mg volatilization, achieving a balance between eutectic strengthening and solid solution strengthening, and ensuring mechanical properties.

[0011] The mass ratio of (Fe+Si) / (Mn+Cr) does not exceed 2.5; this ensures that the number of regulating elements has sufficient phase equilibrium capacity, restricts the precipitation of harmful phases from the metallurgical phase control level, and ensures the formation of a stable structure;

[0012] The mass ratio of (Mn+Cr) / Fe is not less than 1; a higher ratio reflects that the alloy system has the ability to stably utilize Fe for tissue adsorption, thereby reducing the risk of weld embrittlement and improving the overall mechanical properties.

[0013] In one embodiment of the present invention, the diameter of the universal aluminum alloy welding wire is 1.0 mm-1.2 mm.

[0014] A second object of the present invention is to provide a method for preparing the universal aluminum alloy welding wire, comprising the following steps:

[0015] S1. Adding pure aluminum, Al-Si master alloy, Al-Fe master alloy, Al-Mn master alloy, Al-Cr master alloy and pure magnesium into a smelting furnace in proportion, melting and refining, and then standing and casting to obtain an aluminum alloy ingot; the Al-Fe master alloy is recycled aluminum with an Fe content of 1.5%-2.5%;

[0016] S2. Annealing the aluminum alloy ingot described in S1, and extruding to obtain a first aluminum alloy wire having a diameter of 9 mm to 10 mm;

[0017] S3. Performing multiple drawing processes on the first aluminum alloy wire described in S2, and performing intermediate annealing after each drawing process to obtain a second aluminum alloy wire having a diameter of 2.0 mm to 2.2 mm;

[0018] S4. Roughly scraping, drawing, and finely scraping the second aluminum alloy wire described in S3 to obtain a third aluminum alloy wire with a diameter of 1.1 mm to 1.3 mm;

[0019] S5. Surface cleaning is performed on the third aluminum alloy wire described in S4 to obtain a universal aluminum alloy welding wire.

[0020] In one embodiment of the present invention, in S1, the melting temperature is 820°C-840°C, and the rotation speed is 150rpm-300rpm;

[0021] The refining is carried out under an argon atmosphere at a gas flow rate of 1.5 L / min to 2.5 L / min for 8 min to 12 min;

[0022] The standing time is 5 min-10 min.

[0023] In one embodiment of the present invention, in S1, refining is performed under an argon atmosphere, which can fully remove gases and inclusions. Combined with the melting temperature and the sequential addition of alloy elements, element segregation and oxidation reactions are effectively avoided, the composition uniformity is improved, and the prerequisite for tissue homogenization during welding is provided.

[0024] In one embodiment of the present invention, in S2, the annealing temperature is 460°C-480°C and the time is 6h-18h. Under these conditions, homogenization annealing treatment is performed to promote full dispersion of the primary second phase and eliminate severe segregation in the cast structure, so that the elements are redistributed evenly in the grain boundaries and the matrix, laying the foundation for subsequent extrusion deformation and grain control.

[0025] In one embodiment of the present invention, in S3, the diameter reduction rate of each drawing process is 6%-8% to maintain the continuity of the structure and reduce the work hardening;

[0026] The intermediate annealing temperature is 370° C.-390° C., and the time is 1.5 h-2.5 h.

[0027] In one embodiment of the present invention, in S3, the reduction rate of each drawing process is controlled to avoid the accumulation of work hardening, and at the same time, recrystallization and reorganization adjustment are achieved through intermediate annealing to ensure uniform grain morphology and good organizational continuity, thereby providing good wire feeding stability and formability for the subsequent welding process.

[0028] In one embodiment of the present invention, in S4, the speed of the rough scraping is 4.0 m / s-5.5 m / s, and the diameter reduction is 0.15 mm-0.25 mm;

[0029] The speed of the fine scraping is 3.5m / s-4.0m / s, and the diameter reduction is 0.4mm-0.6mm.

[0030] In one embodiment of the present invention, in S4, rough drawing, fine drawing and sizing are used in series to ensure that the welding wire size is consistent and the surface tension is controllable, which greatly improves the metal wettability, droplet transfer stability and shielding gas coverage efficiency during the welding process, and ultimately improves the weld density and defect resistance.

[0031] In one embodiment of the present invention, in S5, the cleaning temperature is 45°C-55°C and the cleaning time is 2 min-5 min;

[0032] The cleaning liquid used in the cleaning is an alkaline solution or a surfactant solution.

[0033] Furthermore, the alkaline solution is a sodium carbonate solution with a concentration of 1wt%-5wt%;

[0034] The surfactant solution is a polyethylene glycol solution with a concentration of 0.2 wt % to 2 wt %.

[0035] The third object of the present invention is to provide an application of the universal aluminum alloy welding wire in aluminum alloy welding.

[0036] In one embodiment of the present invention, the aluminum alloy is selected from 4XXX series aluminum alloy and / or 6XXX series aluminum alloy.

[0037] The technical solution of the present invention has the following advantages over the prior art:

[0038] The universal aluminum alloy welding wire described in this invention forms a stable secondary phase primarily composed of α-Al(Fe, Mn, Cr)Si during the solidification process by controlling the Mn / Fe and Cr / Mn mass ratios. Mn and Cr occupy Fe sites and regulate the eutectic morphology, promoting the transformation of the crystal structure from the needle-like or flaky β-Al5FeSi phase to the massive or spherical α-Al(Fe, Mn, Cr)Si phase, significantly improving the weld's plasticity, toughness, and crack resistance.

[0039] The universal aluminum alloy welding wire described in this invention effectively avoids embrittlement caused by excessive Si by controlling the Mg / Si mass ratio (slightly lower than the Mg2Si eutectic ratio of 1.73), while also preventing weld softening caused by excessive Mg volatilization. This welding wire comprehensively considers the evaporation behavior of alloying elements during welding and the precipitation strengthening of Mg2Si, promoting the formation of Mg2Si precipitation phases. This achieves the dual effects of solid solution strengthening and precipitation strengthening, while ensuring weld hardness through precise control of the eutectic ratio.

[0040] The universal aluminum alloy welding wire described in the present invention controls the mass ratios of (Fe+Si) / (Mn+Cr) and (Mn+Cr) / Fe so that the total amount of regulating elements is higher than the total amount of harmful elements, ensuring that the regulating elements preferentially combine with Fe and Si to form favorable phases in the metallurgical reaction, thereby converting Fe from an impurity into a controllable strengthening element; Cr combines with Si, Fe, and Mn to form a composite second phase with good dispersion distribution and thermal stability.

[0041] (2) The universal aluminum alloy welding wire described in the present invention is suitable for a variety of welding processes, has good droplet transfer stability and forming performance, and can form weld structures with low thermal crack sensitivity in welding a variety of aluminum alloy base materials. At the same time, by rationally controlling the Fe content and introducing appropriate amounts of Mn and Cr elements, the transformation of β-Al5FeSi to α-Al(Fe,Mn,Cr)Si phase is promoted, the formation of brittle intermetallic compounds is effectively suppressed, and the density and stability of the weld zone structure are improved.

[0042] (3) The universal aluminum alloy welding wire described in the present invention changes the solidification path of the molten pool after being used in aluminum alloy welding, affecting the nucleation conditions and growth mode of the grains, thereby optimizing the grain morphology and size distribution to a certain extent, and improving the mechanical properties and stability of the weld. The microstructure of the weld includes α-Al matrix, eutectic Si, β-AlFeSi phase, α-Al(Fe,Mn)Si phase, α-Al(Fe,Mn,Cr)Si phase, π-AlFeMgSi phase and strip-shaped Mg2Si phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0044] Figure 1 The microscopic morphology of the weld in Test Example 1 of the present invention; wherein (a) is Comparative Example 1, and (b) is Example 1;

[0045] Figure 2 is the microhardness of the weld in Test Example 2 of the present invention;

[0046] Figure 3 The macroscopic morphology of the weld in Test Example 3 of the present invention is shown in FIG. 1 , wherein (a) is Example 1, (b) is Comparative Example 1, (c) is Comparative Example 2, and (d) is Comparative Example 3.

[0047] Figure 4 These are microscopic morphologies of the weld in Test Example 3 of the present invention; wherein, (a) is Example 1, (b) is Comparative Example 1, (c) is Comparative Example 2, and (d) is Comparative Example 3. DETAILED DESCRIPTION

[0048] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0049] In the present invention, unless otherwise specified, the Al—Fe master alloy used in the embodiments of the present invention is recycled aluminum with an Fe content of 2%.

[0050] In the present invention, unless otherwise specified, the element composition and mass percentage of the A356 aluminum alloy used in the embodiments of the present invention are: Si: 7.92%, Mg: 0.363%, Fe: 0.124%, Mn: 0.002%, Cu: 0.004%, Zn: 0.002%, Ti: 0.119%, Ni: 0.007%, and the balance is Al and other inevitable impurities.

[0051] In the present invention, unless otherwise specified, the element composition and mass percentage of the 6082 aluminum alloy used in the embodiments of the present invention are: Si: 0.946%, Mg: 0.636%, Fe: 0.153%, Mn: 0.477%, Cu: 0.1%, Cr≤0.25%, Zn: 0.004%, Ti: 0.017%, Ni: 0.003%, and the balance is Al and other inevitable impurities.

[0052] Example 1

[0053] The universal aluminum alloy welding wire and its preparation method of this embodiment specifically include the following steps:

[0054] S1. Pure aluminum, Al-20Si master alloy, Al-Fe master alloy, Al-10Mn master alloy, Al-10Cr master alloy, and pure magnesium were added to a melting furnace in proportion and melted at 830° C. and 250 rpm. The mixture was then refined under an argon atmosphere at a gas flow rate of 2.0 L / min for 10 min, allowed to stand for 8 min, and then cast to obtain an aluminum alloy ingot.

[0055] S2, homogenizing and annealing the aluminum alloy ingot at 470° C. for 12 hours, and then extruding the ingot to obtain a first aluminum alloy wire having a diameter of 9.5 mm;

[0056] S3, performing multiple drawing processes on the first aluminum alloy wire and intermediate annealing at 380° C. for 2 hours after each drawing process to obtain a second aluminum alloy wire with a diameter of 2.1 mm; wherein the diameter reduction rate of each drawing process is 6%-8%;

[0057] S4. Rough-scraping, wire drawing, and fine-scraping the second aluminum alloy wire to obtain a third aluminum alloy wire with a diameter of 1.3 mm; wherein the rough-scraping speed is 4.8 m / s and the diameter reduction is 0.20 mm; the fine-scraping speed is 3.8 m / s and the diameter reduction is 0.5 mm;

[0058] S5. The third aluminum alloy wire is surface cleaned with a 3 wt % sodium carbonate solution at a temperature of 50° C. for 3 min to obtain a universal aluminum alloy welding wire with a diameter of 1.2 mm; the element composition and mass percentage of the universal aluminum alloy welding wire are as follows: Si: 2.5%, Fe: 1.5%, Mg: 4.0%, Mn: 1.4%, Cr: 0.4%, and the balance is Al and other inevitable impurities, each inevitable impurity is <0.05%, and the total impurities are <0.15%.

[0059] Comparative Example 1

[0060] The present invention is basically the same as Example 1, except that the element composition and mass percentage of the aluminum alloy welding wire with high iron content are as follows: Si is 2.5%, Fe is 1.5%, Mn is 1.4%, Cr is 0.4%, and the balance is Al and other inevitable impurities, each inevitable impurity is less than 0.05%, and the total impurities are less than 0.15%.

[0061] Comparative Example 2

[0062] The present invention is basically the same as Example 1, except that the element composition and mass percentage of the aluminum alloy welding wire with high iron content are as follows: Si is 2.5%, Fe is 1.5%, Mg is 5.0%, Mn is 1.4%, Cr is 0.4%, and the balance is Al and other inevitable impurities, each inevitable impurity is less than 0.05%, and the total impurities are less than 0.15%.

[0063] Comparative Example 3

[0064] The present invention is basically the same as Example 1, except that the element composition and mass percentage of the aluminum alloy welding wire with high iron content are as follows: Si is 2.5%, Fe is 1.5%, Mg is 3.0%, Mn is 1.4%, Cr is 0.4%, and the balance is Al and other inevitable impurities, each inevitable impurity is less than 0.05%, and the total impurities are less than 0.15%.

[0065] Comparative Example 4

[0066] The present invention is basically the same as Example 1, except that the element composition and mass percentage of the aluminum alloy welding wire with high iron content are as follows: Si is 2.5%, Fe is 1.5%, Mg is 4.0%, Mn is 3%, Cr is 0.4%, and the balance is Al and other inevitable impurities, each inevitable impurity is less than 0.05%, and the total impurities are less than 0.15%.

[0067] Comparative Example 5

[0068] The present invention is basically the same as Example 1, except that the element composition and mass percentage of the aluminum alloy welding wire with high iron content are as follows: Si is 2.5%, Fe is 1.5%, Mg is 4.0%, Mn is 1.4%, Cr is 1.8%, and the balance is Al and other inevitable impurities, each inevitable impurity is less than 0.05%, and the total impurities are less than 0.15%.

[0069] Test Example 1

[0070] The aluminum alloy welding wires prepared in Example 1 and Comparative Example 1 were used to perform laser arc hybrid welding on A356 aluminum alloy and 6082 aluminum alloy base materials, respectively, with a power of 2.6 kW, a welding speed of 38 mm / s, a wire feeding speed of 4.5 m / min, an oscillation frequency of 100 Hz, and an oscillation diameter of 1.6 mm.

[0071] The welds prepared by the aluminum alloy welding wires of Example 1 and Comparative Example 1 were characterized by microscope. Figure 1 As shown. Figure 1 As can be seen from (b) in the figure, no needle-shaped or flaky β-Al5FeSi brittle phases were found in the fusion zone of the weld in Example 1. Instead, a large amount of Mg2Si phase and α-Al(Fe,Mn,Cr)Si phase were found. This is because there is a critical threshold for the addition of Mn elements in the weld. When the Mn content exceeds this threshold, the formation of needle-shaped β-Al5FeSi phase can be effectively suppressed. Under certain conditions, the Mn / Fe ratio contributes to the complete transformation of the β phase to the α phase, refines the intermetallic compounds and eliminates the brittle β-Al5FeSi phase, thereby improving the mechanical properties of the joint at the organizational level. In the Al-Mg-Si-Mn-Fe system, Si reacts with Mg to form the Mg2Si phase, and at the same time participates with Fe and Mn to form the α-Al(Fe,Mn,Cr)Si phase, and further promotes the formation of the π-AlFeMgSi phase. In Si-rich alloys, Si is mainly consumed by the above reactions. By controlling the Mg content, the Mg element can be fully utilized, completely converted into the Mg2Si phase and dissolved into the matrix during the solution treatment, thereby improving the overall performance of the alloy. The introduction of Cr plays a role similar to that of Mn in the alloy, namely balancing the Fe content and promoting the transformation of the β phase to the α phase, thereby effectively improving the ductility and fracture toughness of the weld.

[0072] from Figure 1 As can be seen from (a) in the figure, there is a large amount of β-Al5FeSi brittle phase in the fusion zone of the weld of Comparative Example 1, while the content of Mg2Si phase and α-Al(Fe,Mn,Cr)Si phase is relatively small, and the weld structure is relatively coarse as a whole. This is mainly due to the fact that no Mg element was added, resulting in only a very small amount of Mg in the weld reacting with Si to form dispersed Mg2Si second phase particles, thus lacking an effective precipitation strengthening mechanism and unable to suppress grain coarsening through a refinement mechanism. Therefore, there is a lack of strengthening phase distribution in the α-Al matrix of the weld, and the overall structure is coarse, which leads to a significant decrease in its tensile strength and plasticity. At the same time, the large amount of residual brittle β phase greatly weakens the fracture toughness and fatigue properties of the weld metal. In addition, in the heat-affected zone (HAZ), welds of Mg-deficient alloys also face the problem of performance degradation in the structural transition zone. Due to the lack of a refinement mechanism to inhibit the expansion of the coarse-grained zone, the grains in the heat-affected zone are coarse and the strengthening phase is sparse, which easily forms a softening zone. As a result, the overall mechanical properties of the joint are distributed in a "weak chain" manner, which seriously restricts its engineering application performance.

[0073] Test Example 2

[0074] The microhardness distribution of the welds prepared by the aluminum alloy welding wires of Example 1 and Comparative Example 1 was tested, and the results are as follows: Figure 2 As shown. Figure 2 It can be seen that the weld prepared by the aluminum alloy welding wire of Example 1 presents a clear "W" shape. The microhardness decreases significantly from BM to HAZ, and then the hardness increases significantly from HAZ to FZ. The lowest hardness occurs at the HAZ / PMZ interface. This hardness performance is comprehensively superior to commercial welding wires. This is because Mg is added to the aluminum alloy welding wire of Example 1, which supplements the evaporation of Mg inside the base material, making the hardness of the weld center higher. The microhardness of the weld center of the weld prepared by the aluminum alloy welding wire of Comparative Example 1 is lower than that of the heat-affected zone. This is a phenomenon attributed to the evaporation of alloying elements such as Mg inside the base material; the loss of magnesium leads to significant softening of the weld center.

[0075] Test Example 3

[0076] The macroscopic and microscopic morphologies of the welds prepared by the aluminum alloy welding wires of Example 1 and Comparative Examples 1-3 are as follows: Figure 3-Figure 4 As shown. Figure 3-Figure 4 It can be seen that the weld structure of Example 1 is dense, with fine grains, uniform morphology, a continuous weld interface, and no obvious pores or cracks. The weld shows excellent mechanical properties and forming quality overall. This is because the aluminum alloy welding wire of Example 1 can form an appropriate amount of Mg2Si second phase, which not only plays a good role in solid solution strengthening and precipitation strengthening, but also avoids weld embrittlement caused by excessive coarse precipitates. In addition, the synergistic effect of Mn and Cr elements helps to convert the brittle β-Al5FeSi phase induced by Fe impurities into massive or spherical α-Al(Fe,Mn,Cr)Si stable intermetallic compounds, thereby reducing the tendency of hot cracking in the weld and enhancing the toughness of the weld.

[0077] Although the weld structure of Comparative Example 1 has fewer apparent pores and no obvious hot cracks, its microstructure has obvious defects: the grains are mainly coarse columnar crystals and some equiaxed crystals, with uneven size distribution; the main precipitate is the harmful brittle β-Al5FeSi phase, and this phase is distributed in flake or needle shapes; in addition, Mn and Cr elements assist in the formation of some α-Al(Fe,Mn,Cr)Si phases, but the overall structure and performance of the weld are still greatly affected. This is because when Mg is not added, the strengthening mechanism of the weld mainly relies on eutectic Si and some intermetallic compounds, but the amount and distribution of these phases are insufficient, resulting in poor tensile strength, yield strength and toughness of the weld. At the same time, a large amount of harmful β-Al5FeSi phase remains. Due to the lack of Mg participation, it cannot promote the transformation and acclimation of the Fe phase. The remaining β phase exists in needle or flake form, becoming a source of brittle fracture, greatly weakening the overall reliability and fatigue life of the weld.

[0078] While the weld structure in Comparative Example 2 exhibits localized grain refinement, the overall structure is uneven, exhibiting a mixed distribution of coarse and fine grains. The increased number of pores reduces weld density. Furthermore, a large amount of Mg2Si phase forms in the weld, some of which is distributed in coarse flakes or agglomerates. However, the production of α-Al(Fe,Mn,Cr)Si phase is limited, suppressed by competing reactions with Mg. This is because Mg has a high oxidizing activity and readily reacts with oxygen and moisture to form MgO and H2 during welding. These gases are unable to fully escape, significantly increasing the probability of porosity defects. Especially under conditions of high heat input or insufficient protection, the volatilization and evaporation of Mg significantly enhances the gas saturation in the molten pool, leading to a high number of diffuse or aggregated pores in the weld. Furthermore, a Mg / Si mass ratio greater than 1.7 increases surface tension fluctuations in the molten pool, increasing its instability and thus affecting weld formation, leading to an irregular fusion interface and even the risk of edge incomplete fusion or collapse. At the same time, an excessively high Mg / Si mass ratio can reduce the fluidity of the molten metal, resulting in poor weld fillability and reduced weld bead smoothness. Excessive Mg can cause secondary phases such as Mg2Si to aggregate and coarsen locally due to insufficient nucleation control, ultimately losing their intended refinement and strengthening effects.

[0079] The weld structure of Comparative Example 3 is slightly improved compared to Comparative Example 1, but the grain size is still coarse, and there are heterogeneous grains in local areas. The amount of precipitation of Mg2Si phase is small, resulting in insufficient strengthening effect. Although the β-Al5FeSi brittle phase has been reduced, it has not been completely converted into the α-Al(Fe, Mn, Cr)Si phase. This is because when the mass ratio of Mg / Si is less than 1.5, the Mg2Si phase is difficult to form effectively, which leads to coarse weld structure and the inability to achieve the refinement and length control of the α-Al matrix grains. The coarse grain structure weakens the bonding force between the grains, and the weld is prone to failure under tensile or impact loads. At the same time, due to the lack of distribution of strengthening phases such as Mg2Si, the mechanical properties of the weld are significantly reduced. In addition, when the mass ratio of Mg / Si is less than 1.5, it is impossible to effectively promote the transformation and acclimation of the Fe phase, resulting in the residual β-Al5FeSi phase existing in the form of needles or flakes, becoming a source of brittle fracture, which greatly weakens the overall reliability and fatigue life of the weld.

[0080] Test Example 4

[0081] The welds prepared from the aluminum alloy welding wires of Example 1 and Comparative Examples 1-5 were tested for yield strength, tensile strength, etc.:

[0082] (1) Tensile strength, yield strength, and elongation after fracture: The samples were cut into dog-bone-shaped specimens with a length of 32 mm, a thickness of 3 mm, and a width of 6 mm. Mechanical properties were tested using a Zwick electric universal testing machine at room temperature with a tensile strain rate of 1×10 -3s -1 ,Each set of conditions was tested three times;

[0083] (2) Average hardness: The average hardness test was performed using a Wilson VH1102 automatic hardness tester with a load of 0.98 N for 10 s. The measurement was performed along a line of the entire weld joint with a spacing of 1 mm between adjacent indentations.

[0084] (3) Welding coefficient: the ratio of the tensile strength of the weld to the tensile strength of the base material;

[0085] Table 1 shows the relevant properties of the weld finally measured:

[0086] Table 1

[0087]

[0088] As can be seen from Table 1, the welds of the examples have excellent mechanical properties, with an average hardness of 95.6 HV, indicating sufficient precipitation strengthening and fine grain strengthening in the weld region. The welding coefficient reaches 78.1%, indicating that the overall mechanical properties of the weld are closest to those of the base material and the microstructure continuity is optimal. This is because the general-purpose aluminum alloy welding wire used in the examples has a moderate Mg content, which is within the optimal range of the Mg2Si strengthening mechanism, forming an appropriate amount of precipitation-strengthening phase Mg2Si, significantly improving tensile strength and hardness without causing excessive porosity. The low Si content reduces the tendency to form a eutectic Si brittle network and improves plasticity and fracture toughness. The Fe content matches the Mn / Cr mass ratio, promoting the transformation of the β-Al5FeSi brittle phase to the α-Al(Fe,Mn,Cr)Si stable phase, reducing crack sources and improving microstructure density.

[0089] Comparing Example 1 with Comparative Example 1 reveals that without Mg addition, the weld's strength, plasticity, and hardness decrease significantly. This is because the absence of Mg leads to a lack of Mg2Si precipitation strengthening, resulting in reduced strength and hardness. Furthermore, the excess Si exists as a coarse eutectic or free phase, reducing plasticity. Furthermore, the slightly higher Fe content (1.5%), but the lack of Mg and a balanced ratio control mechanism, leads to an increase in brittle β phase. Ultimately, a large and coarse β-Al5FeSi and eutectic Si network forms, further compromising plasticity and strength.

[0090] Comparing Example 1 and Comparative Example 2, it can be seen that when the Mg / Si mass ratio is greater than 1.7, the weld strength, plasticity, and hardness are still poor. This is because, although Mg can strengthen the weld, its low boiling point makes it easily evaporate during welding, increasing the tendency to form pores. Furthermore, an excessively high Mg / Si mass ratio can lead to the formation of supersaturated phases and residual stresses, all of which affect the stability of the weld, further destabilizing the weld region's microstructure and reducing the strengthening effect.

[0091] Comparing Example 1 and Comparative Example 3, it can be seen that when the Mg / Si mass ratio is less than 1.5, the weld's strength, ductility, and hardness all decline. This is because the low Mg / Si mass ratio results in insufficient strengthening. The limited amount of Mg2Si phase fails to provide a sufficient strengthening mechanism. While porosity control is acceptable, strength remains slightly low, and the microstructure hardness is less than ideal.

[0092] Comparing Example 1 and Comparative Example 4, it can be seen that when the Mn content is greater than 2.5%, the strength, plasticity and hardness of the weld also decrease overall. This is because when the Mn content is greater than 2.5%, the size of the intermetallic compounds formed by its reaction with Fe and Si increases and the number is too large, making it difficult to disperse evenly, resulting in the agglomeration of the intermetallic phase and becoming a source of microcracks; thereby making the weld tissue brittle, and the impact toughness and ductility significantly reduced. In addition, high Mn elements have a strong tendency to segregate, and will concentrate at the grain boundaries or interdendritic regions at the end of solidification, resulting in chemical inhomogeneity of the tissue. The Mn-rich areas at the grain boundaries are prone to forming low-melting-point composite eutectic structures, thereby reducing the weld's resistance to thermal cracking. At the same time, excessively high Mn content will compete with Mg and Si, inhibiting the precipitation of Mg2Si dispersed phases. Although the Mg content is as high as 3%, the precipitation strengthening effect is weakened due to the limited number of strengthening phases, making it difficult to improve the mechanical properties of the weld.

[0093] Comparing Example 1 and Comparative Example 5, it can be seen that when the Cr content is greater than 1.5%, the strength, plasticity and hardness of the weld still decrease overall. This is because when the Cr content is large, a large amount of brittle phases will be generated. These particles have sharp morphology and poor dispersibility, which can easily become a source of stress concentration, thereby reducing the plasticity and fatigue life of the weld. At the same time, Cr is easily enriched at the grain boundaries and participates in the formation of low-melting-point eutectics or composite phases, especially in welding processes with faster cooling rates. This will significantly increase the thermal crack sensitivity of the weld, especially in high-Mg systems, where brittle grain boundary structures are more likely to form. In addition, high Cr content will also compete with Mg and Si, weakening the dispersion strengthening mechanism of Mg2Si. Since the alloy should be strengthened by Mg, the presence of excessive Cr offsets this strengthening effect.

[0094] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A general-purpose aluminum alloy welding wire, characterized in that: The element composition and mass percentage of the universal aluminum alloy welding wire are as follows: Si 1.5%-3.5%, Fe 1.0%-3.0%, Mg 4.0%-5.0%, Mn 0.5%-2.5%, Cr 0.3%-1.5%, and the balance is Al and other inevitable impurities, each inevitable impurity is less than 0.05%, and the total impurities are less than 0.15%; The mass ratio of Mn / Fe is 0.9-1.1; The mass ratio of Cr / Mn is 0.25-0.4; The mass ratio of Mg / Si is 1.5-1.7; The mass ratio of (Fe+Si) / (Mn+Cr) does not exceed 2.5; The mass ratio of (Mn+Cr) / Fe is not less than 1.

2. The universal aluminum alloy welding wire according to claim 1, characterized in that: The diameter of the universal aluminum alloy welding wire is 1.0 mm to 1.2 mm.

3. The method for preparing a universal aluminum alloy welding wire according to claim 1 or 2, wherein: The following steps are involved: S1. Adding pure aluminum, Al-Si master alloy, Al-Fe master alloy, Al-Mn master alloy, Al-Cr master alloy and pure magnesium into a smelting furnace in proportion, melting and refining, and then standing and casting to obtain an aluminum alloy ingot; the Al-Fe master alloy is recycled aluminum with an Fe content of 1.5%-2.5%; S2. Annealing the aluminum alloy ingot described in S1, and extruding to obtain a first aluminum alloy wire having a diameter of 9 mm to 10 mm; S3. Performing multiple drawing processes on the first aluminum alloy wire described in S2, and performing intermediate annealing after each drawing process to obtain a second aluminum alloy wire having a diameter of 2.0 mm to 2.2 mm; S4. Roughly scraping, drawing, and finely scraping the second aluminum alloy wire described in S3 to obtain a third aluminum alloy wire with a diameter of 1.1 mm to 1.3 mm; S5. Surface cleaning is performed on the third aluminum alloy wire described in S4 to obtain a universal aluminum alloy welding wire.

4. The method for preparing a universal aluminum alloy welding wire according to claim 3, wherein: In S1, the melting temperature is 820°C-840°C, and the rotation speed is 150 rpm-300 rpm; The refining is carried out under an argon atmosphere at a gas flow rate of 1.5 L / min to 2.5 L / min for 8 min to 12 min; The standing time is 5 min-10 min.

5. The method for preparing a universal aluminum alloy welding wire according to claim 3, wherein: In S2, the annealing temperature is 460° C.-480° C., and the annealing time is 6 h-18 h.

6. The method for preparing a universal aluminum alloy welding wire according to claim 3, wherein: In S3, the diameter reduction rate of each drawing process is 6%-8%; The intermediate annealing temperature is 370° C.-390° C., and the time is 1.5 h-2.5 h.

7. The method for preparing a universal aluminum alloy welding wire according to claim 3, wherein: In S4, the speed of the rough scraping is 4.0 m / s-5.5 m / s, and the diameter reduction is 0.15 mm-0.25 mm; The speed of the fine scraping is 3.5m / s-4.0m / s, and the diameter reduction is 0.4mm-0.6mm.

8. The method for preparing a universal aluminum alloy welding wire according to claim 3, wherein: In S5, the cleaning temperature is 45°C-55°C and the cleaning time is 2 min-5 min; The cleaning liquid used in the cleaning is an alkaline solution.

9. Use of the universal aluminum alloy welding wire according to claim 1 or 2 in aluminum alloy welding.

10. The use according to claim 9, characterized in that The aluminum alloy is selected from 4XXX series aluminum alloy and / or 6XXX series aluminum alloy.

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