A welding wire applied to 5 series recycled aluminum alloy and a preparation method thereof

Abstract

This invention belongs to the field of aluminum alloy welding wire technology, specifically a welding wire for use in 5-series recycled aluminum alloys and its preparation method. The welding wire is composed of the following weight percentage components: Mg, 4.5%~5%; Fe, 0.2%~0.4%; Mn, 0.8%~0.9%; aluminum-titanium-boron master alloy, 4%~5%; and the remainder being Al. The preparation method includes the following steps: all raw materials are ground, cleaned with alcohol, and dried; then the alloy components are proportioned and batched sequentially; electromagnetic stirring-assisted ultrasonic melting is performed; followed by rolling and drawing. This invention solves the problem of coarse grains or second phases that may result from the addition of Mn alone.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy welding wire technology, specifically a welding wire for use in 5-series recycled aluminum alloys and its preparation method. Background Technology

[0002] Reasonable microalloyed welding wire materials can effectively reduce the harm caused by high Fe content in recycled aluminum alloys. Compared with traditional welding wires, the welding wire composition can be reasonably designed according to the impurity elements and contents in recycled aluminum to give full play to its performance advantages.

[0003] In the existing technology, the commercially available welding wires commonly used for aluminum alloy welding mainly include ER4043, ER5356 and ER5183. However, they all have certain technical limitations when applied to welding recycled aluminum alloys with high impurity (especially Fe) content.

[0004] ER4043 welding wire primarily contains silicon (Si). Silicon significantly reduces the solidification temperature range of molten aluminum alloys, improves fluidity, and promotes interdendritic liquid feeding, thereby effectively reducing the susceptibility to welding hot cracking. This is crucial for recycled aluminum alloys with high impurity (especially Fe) content and high solidification cracking susceptibility. Furthermore, silicon forms Al-Fe-Si ternary phases (such as α-AlFeSi) with iron. Compared to the coarse acicular β-AlFe phase, these phases are generally less harmful. However, for recycled aluminum alloys with high iron content, the Si element in ER4043 has limited effect on improving the iron-rich phase and cannot fundamentally eliminate the harmful effects of Fe. Moreover, introducing excessive Si can easily lead to brittle formation when welding 5-series (Al-Mg) recycled aluminum. The high Fe / Si ratio in recycled aluminum increases the risk of forming coarse, brittle phases, reduces plasticity, and significantly increases the weld's susceptibility to hot cracking, resulting in poor process adaptability of this welding wire in recycled aluminum welding. The main components of ER5356 welding wire are still Mg and Mn, with a higher Mn content, unlike ER5356. However, its advantage lies in the higher Mn content, which allows it to form Al2O3 with Fe and Si in recycled aluminum sheets. 6( The Fe,Mn) or Alx(Fe,Mn)Si phase is used to reduce the harmful effects of Fe and Si elements. However, the Mn content can reach up to 1.0%. It is unavoidable that when some plates with low Fe content are welded using ER5183 welding wire, the excessive Mn content will lead to the formation of coarse Al-Fe-Mn meso phases, which will cut the matrix and reduce the mechanical properties of the joint.

[0005] Disadvantages of existing technology:

[0006] 1. Common welding wire microalloying is costly, for example, by adding Sc, La and some rare earth elements.

[0007] 2. Its effect on harmful Fe and Si phases in recycled aluminum alloys is limited. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a welding wire for use in 5-series recycled aluminum alloys and its preparation method, innovatively introducing Mn and Al-Ti-B refining agents into the welding wire. Through the dual mechanisms of "substitution solid solution" of Mn and "heterogeneous nucleation" of Al-Ti-B, the "harmful iron-rich phase" is transformed into a "dispersed strengthening phase".

[0009] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0010] A welding wire for use with 5-series recycled aluminum alloys comprises the following components by weight percentage: Mg, 4.5%~5%; Fe, 0.2%~0.4%; Mn, 0.8%~0.9%; aluminum-titanium-boron master alloy, 4%~5%; and the remainder being Al. The recycled aluminum alloy is a 5-series recycled aluminum alloy, and the aluminum-titanium-boron master alloy is Al-5Ti-B.

[0011] A method for preparing welding wire for use in 5-series recycled aluminum alloys includes the following steps:

[0012] Step 1, Smelting

[0013] First, prepare all raw materials according to the above component categories. All raw materials are polished, cleaned and dried with alcohol. Mg is added in the form of pure Mg, and Mn, Fe and Al-Ti-B are added in the form of intermediate alloys of Al-10Mn, Al-10Fe and Al-5Ti-B, respectively. Then, all raw materials are subjected to electromagnetic stirring-assisted ultrasonic melting.

[0014] Step 2, rolling

[0015] The smelted ingots are milled to obtain cylindrical ingots with a diameter of 8mm. These ingots are then heated at 420℃~450℃ for 90 minutes. After heat treatment, the ingots are placed in a two-roll mill for multi-pass rolling. The rolling process uses a "square-square" pass, utilizing pre-set square grooves with decreasing dimensions on the rolls. Through repeated rolling, the ingot cross-section is transformed from circular to square, with the cross-sectional size decreasing with each pass. Specific process parameters are as follows: a total of 12 rolling passes are performed. During rolling, after each pass, the wire rod is rotated 90 degrees axially before being fed into the next pass to ensure uniform deformation. Annealing is required between each pass, ultimately producing a square intermediate wire rod with a side length of 2.0mm.

[0016] Step 3, Adjustment of pre-drawing section

[0017] To avoid corner folding or surface cracking caused by stress concentration when rectangular wire blanks enter circular drawing dies, a "rectangular-circular" transition shaping process is introduced before precision drawing. This process uses a small-deformation round die to compress the diagonal dimension of the rectangular wire blank to match the diameter of the target drawing die, obtaining a smooth-surfaced circular pre-formed wire blank, providing experimental conditions for subsequent multi-pass drawing.

[0018] Step 4, Pulling

[0019] Before drawing, the rolled wire blank was annealed at 460℃ for 12 hours. The rolled welding wire ingot was drawn in 5 passes with the diameter reduction dies being 2.0mm-1.8mm-1.6mm-1.4mm-1.2mm respectively, and the drawing speed was controlled at 22mm / s.

[0020] Furthermore, in step 1, during smelting, the covering agent is KCl+NaCl, and the degassing agent is C2Cl6.

[0021] Furthermore, in step 2, the intermediate annealing parameters are 420℃~450℃ for 90 minutes.

[0022] Furthermore, in step 4, vacuum pump oil is used for drawing lubrication.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention effectively solves the technical problem of easy agglomeration of TiB2 particles during the smelting process by using the synergistic assistance of ultrasonic treatment and electromagnetic stirring, ensuring that the refined particles are dispersed in the welding wire matrix, thereby providing key microstructure protection for the refinement of the weld joint structure and the improvement of its performance.

[0025] 2. Unlike the traditional approach of simply increasing Mg content to compensate for burn-off, this invention addresses the high-Fe base material characteristics of 5-series recycled aluminum alloys by introducing a specific proportion of Mn and Al-Ti-B refining agents into the welding wire. Through the dual mechanisms of "substitutional solid solution" by Mn and "heterogeneous nucleation" by Al-Ti-B, the "harmful iron-rich phase" is transformed into a "dispersed strengthening phase," a design concept not found in traditional general-purpose welding wires such as ER5356.

[0026] 3. This invention utilizes the coupling effect of Mn and Al-Ti-B: Mn preferentially combines with Fe to change the crystal structure and morphology of the precipitated phase (from needle-like to Chinese character-like or spherical), while the TiB2 particles introduced by Al-Ti-B act as a core to refine the matrix grain size. This combination of a grain refiner and the iron-rich phase solves the problem of coarse grains or second phases that may result from the addition of Mn alone, and also overcomes the drawback of not being able to eliminate coarse and brittle iron phases when adding a grain refiner alone.

[0027] 4. This invention overcomes the limitation of Fe content in 5-series recycled aluminum alloys on welding quality. The welding wire described in this invention can tolerate high Fe content (e.g., >0.4wt%) in the 5-series recycled aluminum alloy base material, enabling low-cost, high-Fe-content 5-series recycled aluminum alloy sheets to maintain excellent mechanical and processing properties after welding. This greatly broadens the range of raw material selection for 5-series aluminum alloys and the reuse pathways for recycled materials.

[0028] 5. The cost of Al-10Mn alloy and Al-Ti-B alloy added through micro-alloying is significantly lower than that of Sc, La and rare earth elements, thus offering excellent economic benefits. Attached Figure Description

[0029] Figure 1 Here is a summary diagram of the mechanical properties of welded joints using different welding wires in the embodiments of this invention;

[0030] Figure 2 The following are anodic coating images of different welding wire welds in the embodiments of the present invention: (a) 0.6%Mn; (b) 0.8%Mn; (c) 1.0%Mn; (d) 0.8%Mn+Al-Ti-B;

[0031] Figure 3 Here are the statistical diagrams of the second phase distribution in the weld zone of different welding wires in the embodiments of the present invention: (a) 0.6%Mn; (b) 0.8%Mn; (c) 1.0%Mn; (d) 0.8%Mn+Al-Ti-B;

[0032] Figure 4 Here is a statistical diagram of the phase dimensions of the weld zone for different welding wire joints in this embodiment of the invention;

[0033] Figure 5 For example: SEM images of joints of high Fe content plates welded with different welding wires in the embodiments of the present invention: (a) 0.6%Mn; (b) 0.8%Mn; (c) 1.0%Mn; (d) 0.8%Mn+Al-Ti-B;

[0034] Figure 6 XRD patterns of joints formed by welding high-Fe content plates with different welding wires in embodiments of the present invention. Detailed Implementation

[0035] To illustrate the technical content, objectives, and effects of the present invention in detail, the following description is provided in conjunction with embodiments and accompanying drawings.

[0036] Example 1

[0037] In this embodiment, a welding wire for use with 5-series recycled aluminum alloys is composed of the following components by weight percentage: Mg, 5%; Fe, 0.2%; Mn, 0.8%; aluminum-titanium-boron master alloy, 5%; and the remainder is Al.

[0038] The method for preparing welding wire for 5-series recycled aluminum alloys in this embodiment is as follows:

[0039] Step 1, Smelting

[0040] First, prepare all raw materials according to the above component categories. All raw materials are polished, cleaned with alcohol, and dried. Mg is added in the form of pure Mg, and Mn, Fe, and Al-Ti-B are added in the form of Al-10Mn, Al-10Fe, and Al-5Ti-B intermediate alloys, respectively. Then, all raw materials are subjected to electromagnetic stirring-assisted ultrasonic melting. During melting, KCl+NaCl is used as the covering agent and C2Cl6 is used as the degassing agent.

[0041] Step 2, rolling

[0042] The smelted ingots are milled to obtain cylindrical ingots with a diameter of 8 mm. These ingots are then heated to 450℃ for 90 minutes. The heat-treated ingots are then placed in a two-roll mill for multi-pass rolling. The rolling process uses a "square-square" pass, utilizing pre-set square grooves with decreasing dimensions on the rolls. Through repeated rolling, the ingot cross-section is transformed from circular to square, with the cross-sectional size decreasing with each pass. Specific process parameters are as follows: a total of 12 rolling passes are performed. During rolling, after each pass, the wire rod is rotated 90 degrees axially before being fed into the next pass to ensure uniform deformation. Annealing is required between each pass, ultimately producing a square intermediate wire rod with a side length of 2.0 mm. The intermediate annealing parameters are heating at 420℃ for 90 minutes.

[0043] Step 3, Adjustment of pre-drawing section

[0044] To avoid corner folding or surface cracking caused by stress concentration when rectangular wire blanks enter circular drawing dies, a "rectangular-circular" transition shaping process is introduced before precision drawing. This process uses a small-deformation round die to compress the diagonal dimension of the rectangular wire blank to match the diameter of the target drawing die, obtaining a smooth-surfaced circular pre-formed wire blank, providing experimental conditions for subsequent multi-pass drawing.

[0045] Step 4, Pulling

[0046] Before drawing, the rolled wire blank was annealed at 460℃ for 12 hours. The rolled welding wire ingot was then drawn in 5 passes, with the drawing dies successively reducing the diameter to 2.0mm-1.8mm-1.6mm-1.4mm-1.2mm, and the drawing speed was controlled at 22mm / s. Vacuum pump oil was used for drawing lubrication.

[0047] Example 2

[0048] In this embodiment, a welding wire for use with 5-series recycled aluminum alloys is composed of the following components by weight percentage: Mg, 4.5%; Fe, 0.4%; Mn, 0.9%; aluminum-titanium-boron master alloy, 4%; and the remainder is Al.

[0049] The method for preparing welding wire for 5-series recycled aluminum alloys in this embodiment is as follows:

[0050] Step 1, Smelting

[0051] First, prepare all raw materials according to the above component categories. All raw materials are polished, cleaned with alcohol, and dried. Mg is added in the form of pure Mg, and Mn, Fe, and Al-Ti-B are added in the form of Al-10Mn, Al-10Fe, and Al-5Ti-B intermediate alloys, respectively. Then, all raw materials are subjected to electromagnetic stirring-assisted ultrasonic melting. During melting, KCl+NaCl is used as the covering agent and C2Cl6 is used as the degassing agent.

[0052] Step 2, rolling

[0053] The smelted ingots are milled to obtain cylindrical ingots with a diameter of 8 mm. These ingots are then heated to 420℃ for 90 minutes. The heat-treated ingots are then placed in a two-roll mill for multi-pass rolling. The rolling process uses a "square-square" pass, utilizing pre-set square grooves with decreasing dimensions on the rolls. Through repeated rolling, the ingot cross-section is transformed from circular to square, with the cross-sectional size decreasing with each pass. Specific process parameters are as follows: a total of 12 rolling passes are performed. During rolling, after each pass, the wire rod is rotated 90 degrees axially before being fed into the next pass to ensure uniform deformation. Annealing is required between each pass, ultimately producing a square intermediate wire rod with a side length of 2.0 mm. The intermediate annealing parameters are heating at 450℃ for 90 minutes.

[0054] Step 3, Adjustment of pre-drawing section

[0055] To avoid corner folding or surface cracking caused by stress concentration when rectangular wire blanks enter circular drawing dies, a "rectangular-circular" transition shaping process is introduced before precision drawing. This process uses a small-deformation round die to compress the diagonal dimension of the rectangular wire blank to match the diameter of the target drawing die, obtaining a smooth-surfaced circular pre-formed wire blank, providing experimental conditions for subsequent multi-pass drawing.

[0056] Step 4, Pulling

[0057] Before drawing, the rolled wire blank was annealed at 460℃ for 12 hours. The rolled welding wire ingot was then drawn in 5 passes, with the drawing dies successively reducing the diameter to 2.0mm-1.8mm-1.6mm-1.4mm-1.2mm, and the drawing speed was controlled at 22mm / s. Vacuum pump oil was used for drawing lubrication.

[0058] Comparative Example 1

[0059] The welding wire used in this comparative example for 5-series aluminum alloys is composed of the following components by weight percentage: Mg, 5%; Fe, 0.2%; Mn, 0.6%; and the remainder is Al.

[0060] The preparation method of the welding wire used in this comparative example for 5-series aluminum alloys is as follows:

[0061] Step 1, Smelting

[0062] First, prepare all raw materials according to the above component categories. All raw materials are polished, cleaned with alcohol, and dried. Mg is added in the form of pure Mg, and Mn and Fe are added in the form of Al-10Mn and Al-10Fe intermediate alloys. Then, all raw materials are subjected to electromagnetic stirring-assisted ultrasonic melting. During melting, KCl+NaCl is used as the covering agent and C2Cl6 is used as the degassing agent.

[0063] Step 2, rolling

[0064] The smelted ingots are milled to obtain cylindrical ingots with a diameter of 8 mm. These ingots are then heated to 420℃ for 90 minutes. The heat-treated ingots are then placed in a two-roll mill for multi-pass rolling. The rolling process uses a "square-square" pass, utilizing pre-set square grooves with decreasing dimensions on the rolls. Through repeated rolling, the ingot cross-section is transformed from circular to square, with the cross-sectional size decreasing with each pass. Specific process parameters are as follows: a total of 12 rolling passes are performed. During rolling, after each pass, the wire rod is rotated 90 degrees axially before being fed into the next pass to ensure uniform deformation. Annealing is required between each pass, ultimately producing a square intermediate wire rod with a side length of 2.0 mm. The intermediate annealing parameters are heating at 420℃ for 90 minutes.

[0065] Step 3, Adjustment of pre-drawing section

[0066] To avoid corner folding or surface cracking caused by stress concentration when rectangular wire blanks enter circular drawing dies, a "rectangular-circular" transition shaping process is introduced before precision drawing. This process uses a small-deformation round die to compress the diagonal dimension of the rectangular wire blank to match the diameter of the target drawing die, obtaining a smooth-surfaced circular pre-formed wire blank, providing experimental conditions for subsequent multi-pass drawing.

[0067] Step 4, Pulling

[0068] Before drawing, the rolled wire blank was annealed at 460℃ for 12 hours. The rolled welding wire ingot was then drawn in 5 passes, with the drawing dies successively reducing the diameter to 2.0mm-1.8mm-1.6mm-1.4mm-1.2mm, and the drawing speed was controlled at 22mm / s. Vacuum pump oil was used for drawing lubrication.

[0069] Comparative Example 2

[0070] The welding wire used in this comparative example for 5-series aluminum alloys is composed of the following components by weight percentage: Mg, 4.5%; Fe, 0.4%; Mn, 0.8%; with the remainder being Al.

[0071] The preparation method of the welding wire used in this comparative example for 5-series aluminum alloys is as follows:

[0072] Step 1, Smelting

[0073] First, prepare all raw materials according to the above component categories. All raw materials are polished, cleaned with alcohol, and dried. Mg is added in the form of pure Mg, and Mn and Fe are added in the form of Al-10Mn and Al-10Fe intermediate alloys. Then, all raw materials are subjected to electromagnetic stirring-assisted ultrasonic melting. During melting, KCl+NaCl is used as the covering agent and C2Cl6 is used as the degassing agent.

[0074] Step 2, rolling

[0075] The smelted ingots are milled to obtain cylindrical ingots with a diameter of 8 mm. These ingots are then heated to 420℃ for 90 minutes. The heat-treated ingots are then placed in a two-roll mill for multi-pass rolling. The rolling process uses a "square-square" pass, utilizing pre-set square grooves with decreasing dimensions on the rolls. Through repeated rolling, the ingot cross-section is transformed from circular to square, with the cross-sectional size decreasing with each pass. Specific process parameters are as follows: a total of 12 rolling passes are performed. During rolling, after each pass, the wire rod is rotated 90 degrees axially before being fed into the next pass to ensure uniform deformation. Annealing is required between each pass, ultimately producing a square intermediate wire rod with a side length of 2.0 mm. The intermediate annealing parameters are heating at 450℃ for 90 minutes.

[0076] Step 3, Adjustment of pre-drawing section

[0077] To avoid corner folding or surface cracking caused by stress concentration when rectangular wire blanks enter circular drawing dies, a "rectangular-circular" transition shaping process is introduced before precision drawing. This process uses a small-deformation round die to compress the diagonal dimension of the rectangular wire blank to match the diameter of the target drawing die, obtaining a smooth-surfaced circular pre-formed wire blank, providing experimental conditions for subsequent multi-pass drawing.

[0078] Step 4, Pulling

[0079] Before drawing, the rolled wire blank was annealed at 460℃ for 12 hours. The rolled welding wire ingot was then drawn in 5 passes, with the drawing dies successively reducing the diameter to 2.0mm-1.8mm-1.6mm-1.4mm-1.2mm, and the drawing speed was controlled at 22mm / s. Vacuum pump oil was used for drawing lubrication.

[0080] Comparative Example 3

[0081] The welding wire used in this comparative example for 5-series aluminum alloys is composed of the following components by weight percentage: Mg, 4.5%; Fe, 0.4%; Mn, 1.0%; with the remainder being Al.

[0082] The preparation method of the welding wire used in this comparative example for 5-series aluminum alloys is as follows:

[0083] Step 1, Smelting

[0084] First, prepare all raw materials according to the above component categories. All raw materials are polished, cleaned with alcohol, and dried. Mg is added in the form of pure Mg, and Mn and Fe are added in the form of Al-10Mn and Al-10Fe intermediate alloys. Then, all raw materials are subjected to electromagnetic stirring-assisted ultrasonic melting. During melting, KCl+NaCl is used as the covering agent and C2Cl6 is used as the degassing agent.

[0085] Step 2, rolling

[0086] The smelted ingots are milled to obtain cylindrical ingots with a diameter of 8 mm. These ingots are then heated to 420℃ for 90 minutes. The heat-treated ingots are then placed in a two-roll mill for multi-pass rolling. The rolling process uses a "square-square" pass, utilizing pre-set square grooves with decreasing dimensions on the rolls. Through repeated rolling, the ingot cross-section is transformed from circular to square, with the cross-sectional size decreasing with each pass. Specific process parameters are as follows: a total of 12 rolling passes are performed. During rolling, after each pass, the wire rod is rotated 90 degrees axially before being fed into the next pass to ensure uniform deformation. Annealing is required between each pass, ultimately producing a square intermediate wire rod with a side length of 2.0 mm. The intermediate annealing parameters are heating at 420℃ for 90 minutes.

[0087] Step 3, Adjustment of pre-drawing section

[0088] To avoid corner folding or surface cracking caused by stress concentration when rectangular wire blanks enter circular drawing dies, a "rectangular-circular" transition shaping process is introduced before precision drawing. This process uses a small-deformation round die to compress the diagonal dimension of the rectangular wire blank to match the diameter of the target drawing die, obtaining a smooth-surfaced circular pre-formed wire blank, providing experimental conditions for subsequent multi-pass drawing.

[0089] Step 4, Pulling

[0090] Before drawing, the rolled wire blank was annealed at 460℃ for 12 hours. The rolled welding wire ingot was then drawn in 5 passes, with the drawing dies successively reducing the diameter to 2.0mm-1.8mm-1.6mm-1.4mm-1.2mm, and the drawing speed was controlled at 22mm / s. Vacuum pump oil was used for drawing lubrication.

[0091] The welding wires prepared in Examples 1-2 and Comparative Examples 1-3 were applied to the welding of 5-series recycled aluminum alloys. The welding parameters are shown in Table 1.

[0092] Table 1. Welding Equipment and Parameters

[0093]

[0094] Table 2 summarizes the mechanical properties of welded joints using different welding wires in Examples 1-2 and Comparative Examples 1-3.

[0095] Table 2. Summary of Mechanical Properties of Welded Joints with Different Welding Wires

[0096]

[0097] The weld joints of the four sets of welding wires in Example 1 and Comparative Examples 1-3 were scanned by SEM and the phase element content was marked as follows: Figure 5 As shown in the figure, the gray area represents the α-Al matrix, and the white area represents the Al-Fe-Mn intermediate phase. The specific elemental percentages at each point are shown in Table 3.

[0098] Table 3. Specific elemental content of EDS (unit: weight percentage)

[0099]

[0100] The welded joints of the four sets of welding wires in Example 1 and Comparative Examples 1-3 were subjected to tensile testing at room temperature. The tensile results are as follows: Figure 1 As shown in the figure, among the three groups of Mn-containing welding wires in the comparative example, the welding wire containing 0.8% Mn had the highest joint tensile strength, which was 266 MPa. With the addition of Al-Ti-B grain refiner to the welding wire, the joint strength was significantly improved, and the tensile strength reached 323 MPa, which is closer to that of the base material, which was a 5-series recycled aluminum alloy.

[0101] After anodic coating was applied to the weld joints of the four types of welding wires, the macroscopic grain size change was not significant. The grain distribution of the metallographic structure of each weld joint was as follows: Figure 2 As shown in the figure. Further statistical calculations yielded the average grain size of the weld, as shown in the figure. It can be seen that with the increase of Mn content in the welding wire, the grain size of the weld becomes correspondingly refined, decreasing from an average grain size of 100 μm to 70 μm. The effect is more pronounced after adding Al-Ti-B, with the average grain size decreasing to 60 μm.

[0102] pass Figure 3 , Figure 4 In summary, with changes in the welding wire, the morphology and size of the phases in the weld zone undergo significant changes. Figure 2 The statistics show that the trend of phase size change is consistent with that of grain size change.

[0103] Second-phase analysis was performed on the weld zone of joints using different welding wires, using SEM, etc. Figure 5As shown, in the joints of welding wires with different Mn contents, white second-phase particles are dispersed on a dark gray α-Al matrix. EDS data indicates that Fe and Mn elements segregate, forming white needle-like and plate-like Al-Fe-Mn type second phases with Al elements, distributed in the α-Al matrix. The differences in the second phase in joints of different welding wires are mainly reflected in the phase morphology and size. Comparison revealed that at the grain boundaries of the α-Al matrix, obvious long needle-like bright white phases were observed in the joints of 0.6% Mn welding wire. These phases have sharp edges and are relatively long, cutting through the matrix like blades. Spot analysis of the needle-like phases indicates that their composition is rich in Al, Fe, and Mn. For base materials with high Fe content, 0.6% Mn welding wire typically results in an Mn / Fe ratio <1.0 in the molten pool; in the joints of 0.8% Mn welding wire, the needle-like phase is significantly reduced or disappears. Instead, second phases resembling Chinese characters, skeletons, or polygonal blocks are present. Compared to the 0.6%Mn group, the edges of the second phase became rounded; in the joint of the 1.0%Mn welding wire, although the Fe phase was still blocky, the number of phases was significantly increased, and some were larger in size; in the joint of the 0.8%Mn+Al-Ti-B welding wire, the iron-rich phase not only maintained a harmless blocky shape, but also had a smaller size and a more diffuse distribution.

[0104] XRD diffraction analysis was performed on the weld zones of the four joints, and the results are as follows: Figure 6 As shown in the figure, α-Al and Al6(Fe, Mn) phases were detected in all four joints. The characteristic diffraction peak intensity of α-Al was higher, while that of Al6(Fe, Mn) was lower. This is because the alloy is mostly composed of α-Al matrix, while the content of the second phase is relatively low.

[0105] In summary, this invention utilizes the coupling effect of Mn and Al-Ti-B: Mn preferentially combines with Fe to alter the crystal structure and morphology of the precipitated phase (changing from needle-like to Chinese character-like or spherical), while the TiB2 particles introduced by Al-Ti-B act as a core to refine the matrix grain size. This combination of a grain refiner and the iron-rich phase solves the problem of coarse grains or second phases that may result from the addition of Mn alone, and also overcomes the drawback of the inability to eliminate coarse and brittle iron phases when adding a grain refiner alone. Through the dual mechanism of "substitutional solid solution" of Mn and "heterogeneous nucleation" of Al-Ti-B, the "harmful iron-rich phase" is transformed into a "dispersed strengthening phase." The welding wire described in this invention can tolerate high Fe content in the base material (e.g., >0.4wt%), allowing low-cost, high-Fe-content Al-Mg plates to maintain excellent mechanical and processing properties after welding, greatly expanding the range of raw material selection for 5-series aluminum alloys and the reuse pathways for recycled materials.

[0106] Although the present invention has been described in detail above with specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing welding wire for use in 5-series recycled aluminum alloys, characterized in that, The welding wire is composed of the following components by weight percentage: Mg, 4.5%~5%; Fe, 0.2%~0.4%; Mn, 0.8%~0.9%; aluminum-titanium-boron master alloy, 4%~5%; and the remainder is Al. The recycled aluminum alloy is a 5-series recycled aluminum alloy, and the aluminum-titanium-boron master alloy is Al-5Ti-B. The preparation method includes the following steps: Step 1, Smelting First, prepare all raw materials according to the weight percentages. All raw materials are polished, cleaned with alcohol, and dried. Mg is added in the form of pure Mg, and Mn, Fe and Al-Ti-B are added in the form of intermediate alloys of Al-10Mn, Al-10Fe and Al-5Ti-B, respectively. Then, all raw materials are subjected to electromagnetic stirring-assisted ultrasonic melting. Step 2, rolling The smelted ingots are milled to obtain cylindrical ingots with a diameter of 8mm. They are heated at 420℃~450℃ for 90 minutes. The heat-treated ingots are then rolled in 12 passes. During the rolling process, after each pass, the wire blank is rotated 90 degrees axially before being fed into the next pass. Intermediate annealing is performed in the middle of each pass, and finally, a square intermediate wire blank with a side length of 2.0mm is obtained. Step 3, Adjustment of pre-drawing section Using a small-deformation round die, the diagonal dimension of the rectangular wire blank is compressed to match the diameter of the target drawing die, thus obtaining a circular pre-made wire blank; Step 4, Pulling Before drawing, the rolled wire blank was annealed at 460℃ for 12 hours. The rolled welding wire ingot was drawn in 5 passes with the diameter reduction dies being 2.0mm-1.8mm-1.6mm-1.4mm-1.2mm respectively, and the drawing speed was controlled at 22mm / s.

2. The method for preparing welding wire for 5-series recycled aluminum alloys according to claim 1, characterized in that: In step 1, during smelting, the covering agent is KCl+NaCl, and the degassing agent is C2Cl6.

3. The method for preparing welding wire for 5-series recycled aluminum alloys according to claim 1, characterized in that: In step 2, the intermediate annealing parameters are 420℃~450℃ for 90 minutes.

4. The method for preparing welding wire for 5-series recycled aluminum alloys according to claim 1, characterized in that: In step 4, vacuum pump oil is used for drawing lubrication.

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