A magnesium alloy welding wire and a method of manufacturing the same

Abstract

The application belongs to the technical field of magnesium alloy welding wire, and specifically discloses a magnesium alloy welding wire and a preparation method thereof, the magnesium alloy welding wire comprises the following chemical components in percentage by mass: Al 3.5%-4.5%, Y 2.5%-3.5%, Ca 0.8%-1.2%, Mn 0.2%-0.5%, and the rest is Mg and inevitable impurities. The preparation method is as follows: first, a magnesium alloy casting rod with qualified components is obtained by casting; then, the magnesium alloy casting rod is heated to 440-470 DEG C; and then, extrusion treatment is performed, so that the magnesium alloy welding wire is obtained. The magnesium alloy welding wire is suitable for AZXW4120 magnesium alloy welding, has good corrosion resistance, mechanical strength and flame retardant performance, and can meet the working condition requirements of bearing dynamic load or impact vibration load.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy welding wire technology, specifically relating to a magnesium alloy welding wire and its preparation method. Background Technology

[0002] Magnesium alloys, due to their low density, high specific strength, and good vibration damping performance, have important applications in fields with prominent lightweighting requirements, such as aerospace, military equipment, and new energy vehicles. AZXW4120 magnesium alloy, as a new type of high-strength flame-retardant magnesium alloy, has a tensile strength exceeding 265 MPa and excellent flame-retardant properties, making it a preferred material for key components such as aero-engine casings and missile components. The chemical composition of AZXW4120 magnesium alloy, by mass percentage, is as follows: Al 3.5%-4.5%, Zn 0.5%-1%, Ca 1.8%-2.2%, Mn 0.2%-0.5%, with the remainder being Mg and unavoidable impurities. Welding is a key process in the manufacture of complex structural components, directly impacting applications in high-end equipment.

[0003] Currently, magnesium alloy welding wires such as AZ31 and AZ61 are commonly used for argon arc welding of AZXW4120 magnesium alloy. However, the weld seam has poor corrosion resistance; it is very easy to induce combustion of magnesium alloy when multi-layer welding and with large heat input; the weld joint has low strength and insufficient elongation, which cannot meet the requirements of working conditions that can withstand dynamic loads or impact vibration loads. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a magnesium alloy welding wire and its preparation method. The magnesium alloy welding wire of this invention is suitable for welding AZXW4120 magnesium alloy and has good corrosion resistance, mechanical strength and flame retardant properties, which can meet the working conditions of bearing dynamic loads or impact vibration loads.

[0005] The technical solution of this invention is implemented as follows:

[0006] A magnesium alloy welding wire, by mass percentage, comprises the following chemical composition: Al 3.5%-4.5%, Y 2.5%-3.5%, Ca 0.8%-1.2%, Mn 0.2%-0.5%, with the remainder being Mg and unavoidable impurities.

[0007] Furthermore, by mass percentage, the magnesium alloy welding wire comprises the following chemical composition: Al 3.8%-4.1%, Y 2.8%-3.2%, Ca 0.8%-1.0%, Mn 0.2%-0.3%, with the remainder being Mg and unavoidable impurities.

[0008] Furthermore, by mass percentage, the magnesium alloy welding wire comprises the following chemical composition: Al 4%, Y 3.0%, Ca 1%, Mn 0.2%, with the remainder being Mg and unavoidable impurities.

[0009] Furthermore, the diameter of the magnesium alloy welding wire is 1.0-3.0 mm.

[0010] This invention also provides a method for preparing magnesium alloy welding wire, specifically including the following steps:

[0011] S1: The casting yields a magnesium alloy ingot with qualified composition, which, by mass percentage, comprises the following chemical composition: Al 3.5%-4.5%, Y 2.5%-3.5%, Ca 0.8%-1.2%, Mn 0.2%-0.5%, with the remainder being Mg and unavoidable impurities;

[0012] S2: Heat the magnesium alloy casting rod to 440-470℃ and then extrude it to obtain the magnesium alloy welding wire.

[0013] Further, in step S1, the method for casting magnesium alloy rods is as follows: under gas protection, pure magnesium ingots are heated and melted, and then aluminum ingots, Mg-Y master alloy, Mg-Ca master alloy and Mg-Mn master alloy are added in sequence. After they are completely melted, they are stirred evenly, then heated to remove slag, and then cast to obtain the magnesium alloy rods.

[0014] Furthermore, the gas is a mixture of CO2 and SF6, wherein the volume fraction of CO2 is 99%.

[0015] Furthermore, the temperature for smelting pure magnesium ingots is 700-740℃.

[0016] Furthermore, in step S2, the magnesium alloy casting rod is precision machined before heating to make the diameter of the magnesium alloy casting rod 90-110mm.

[0017] Furthermore, in step S2, the extrusion ratio of the extrusion process is 15-25:1.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The aluminum content of the magnesium alloy welding wire described in this invention is comparable to that of the AZXW4120 magnesium alloy base material, which can significantly reduce the electrochemical potential difference between the weld and the base material from the source, effectively suppressing the tendency of galvanic corrosion induced by compositional inhomogeneity. Simultaneously, the addition of rare earth element Y and alkaline earth element Ca, while purifying the melt, promotes the formation of a denser and more stable composite oxide film on the weld surface, providing a long-lasting corrosion protection barrier for the welded joint, fundamentally solving the problem of poor weld corrosion resistance caused by compositional mismatch in traditional AZ series welding wires.

[0020] 2. This invention introduces Y and Ca as functional flame-retardant elements. At high welding temperatures, Y and Ca preferentially oxidize over magnesium and aluminum. The resulting Y₂O₃ and CaO effectively fill and repair the inherent loose and porous MgO oxide film of magnesium alloys, thereby forming a continuous, dense, strongly adhered, and highly thermally stable composite oxide film (mainly a CaO-Y₂O₃-Al₂O₃ system) in situ on the surface of the molten pool. This composite oxide film can efficiently isolate oxygen, significantly increase the effective ignition point of the welding area, and prevent combustion of the weld joint under the heat accumulation conditions of multi-layer and multi-pass welding. This greatly improves the stability and safety of the welding process and meets the special requirements of high-strength flame-retardant magnesium alloys for welding processes.

[0021] 3. The Y and Ca in the welding wire of this invention are not only powerful grain refiners, capable of transforming coarse columnar grains in the weld into fine equiaxed grains, thus strengthening both strength and plasticity through grain refinement; they are also effective precipitation strengthening phase forming elements, combining with aluminum to form thermally stable intermetallic compounds such as Al2Y and Al2Ca, producing a significant dispersion strengthening effect; simultaneously, they are excellent melt purifiers, capable of adsorbing and fixing harmful impurities such as oxygen and hydrogen, significantly reducing welding defects such as porosity and inclusions, and improving joint density. The synergistic effect of these multiple strengthening mechanisms enables the tensile strength of the welded joint to stably reach more than 70% of the base metal strength, while maintaining good plasticity reserves, achieving an ideal balance between high strength and moderate toughness, fully meeting the requirements for use under dynamic load conditions. Attached Figure Description

[0022] Figure 1 - Macroscopic photograph of magnesium alloy welding wire after welding in Example 1.

[0023] Figure 2 - SEM image of the fusion zone after welding with magnesium alloy welding wire in Example 1.

[0024] Figure 3 -SEM image of AZXW4120 magnesium alloy base material.

[0025] Figure 4 - SEM image of the weld area after welding with magnesium alloy welding wire in Example 1. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0027] When using magnesium alloy welding wires such as AZ31 and AZ61 for argon arc welding of AZXW4120 magnesium alloy, the weld has poor corrosion resistance; it is prone to combustion of magnesium alloy under multi-layer welding and high heat input; the welded joint has low strength and insufficient elongation, which cannot meet the requirements of working conditions that can withstand dynamic loads or impact vibration loads.

[0028] Based on this, the present invention provides a magnesium alloy welding wire, which, by mass percentage, comprises the following chemical composition: Al 3.5%-4.5%, Y 2.5%-3.5%, Ca 0.8%-1.2%, Mn 0.2%-0.5%, with the remainder being Mg and unavoidable impurities.

[0029] The chemical composition of AZXW4120 magnesium alloy, by mass percentage, is as follows: Al 3.5%-4.5%, Y 0.5%-1%, Ca 1.8%-2.2%, Mn 0.2%-0.5%, with the remainder being Mg and unavoidable impurities. Here, the present invention sets the Al content of the welding wire to be comparable to that of the AZXW4120 magnesium alloy. Welding with the magnesium alloy welding wire described in this invention fundamentally reduces the electrochemical difference between the weld and the base material, lowers the driving force for localized corrosion caused by compositional inhomogeneity, and improves the corrosion resistance of the welded joint. Meanwhile, the addition of Y and Ca to the welding wire of this invention results in Y and Ca having a much higher affinity for oxygen than Mg and Al at high welding temperatures, preferentially oxidizing to form Y2O3 and CaO. Y2O3 and CaO can fill the pores of the inherent MgO oxide film of magnesium alloys, and work together with aluminum oxide (Al2O3) to form a continuous, dense, strongly adherent, and thermally stable composite oxide film on the surface of the molten pool and subsequent weld seam. This composite oxide film not only effectively isolates oxygen under the heat accumulation conditions of multi-layer welding, increases the actual ignition point of the alloy, prevents combustion, and improves the flame retardant performance of the weld joint, but also provides an effective physical barrier during service, preventing the entry of corrosive media and improving the corrosion resistance of the weld seam.

[0030] Furthermore, Y and Ca are effective grain refiners. During weld solidification, they promote heterogeneous nucleation and inhibit grain growth, thus significantly refining the as-cast microstructure of the weld and transforming coarse columnar crystals into fine equiaxed crystals, thereby effectively improving the mechanical strength and plasticity of the weld joint. Additionally, Al, Y, and Ca can form thermally stable intermetallic compound phases (Al₂Y and Al₂Ca) in the solid state. These fine precipitates effectively pin dislocations and hinder grain boundary slip during weld cooling and subsequent use. Simultaneously, Y and Ca have a strong adsorption and fixation effect on impurities such as oxygen, hydrogen, and sulfur, purifying the molten pool during melting and welding, reducing welding defects such as porosity and inclusions, and increasing the density of the weld joint, thereby improving its mechanical strength.

[0031] The method for preparing the welding wire specifically includes the following steps:

[0032] S1: Under the protection of a mixed gas of CO2 and SF6, the crucible is preheated to 400℃, and then pure magnesium ingots are added; the temperature is raised to 700-740℃ to melt the pure magnesium ingots; then aluminum ingots, Mg-Y master alloy, Mg-Ca master alloy, and Mg-Mn master alloy are added in sequence. After all the metals have melted, the molten metal is stirred, and then the temperature is raised to 740-760℃ and held for 30 minutes. After degassing, slag removal, and standing for 5 minutes, the metal is poured into a preheated steel mold to obtain magnesium alloy casting rods.

[0033] S2: The magnesium alloy casting rod is precision machined to obtain a magnesium alloy rod with a diameter of 90-110mm; then the magnesium alloy rod is heated to 440-470℃ and extruded at an extrusion ratio of 15-25:1 to obtain the magnesium alloy welding wire.

[0034] Example 1

[0035] A method for preparing magnesium alloy welding wire specifically includes the following steps:

[0036] S1: Under the protection of a mixed gas of CO2 and SF6, the crucible is preheated to 400°C, and then pure magnesium ingots are added; the temperature is raised to 700°C to melt the pure magnesium ingots; then aluminum ingots, Mg-Y master alloy, Mg-Ca master alloy, and Mg-Mn master alloy are added in sequence. After all the metals have melted, the molten metal is stirred, and then the temperature is raised to 740°C and held for 30 minutes. After degassing, slag removal, and standing for 5 minutes, the metal is poured into a preheated steel mold to obtain a magnesium alloy casting rod. The magnesium alloy casting rod contains the following chemical composition by mass percentage: Al 4%, Y 3%, Ca 1%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0037] S2: The magnesium alloy casting rod is precision machined to obtain a magnesium alloy rod with a diameter of 100 mm; then the magnesium alloy rod is heated to 440°C and extruded at an extrusion ratio of 15:1 to obtain the magnesium alloy welding wire.

[0038] Example 2

[0039] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 4%, Y 2.5%, Ca 1%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0040] Example 3

[0041] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 4%, Y 3.5%, Ca 1%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0042] Example 4

[0043] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 3.8%, Y 3.0%, Ca 1%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0044] Example 5

[0045] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 4.2%, Y 3.0%, Ca 1%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0046] Example 6

[0047] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 4%, Y 3.0%, Ca 0.8%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0048] Example 7

[0049] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 4%, Y 3.0%, Ca 1.2%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0050] Comparative Example 1

[0051] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 4%, Y 1.0%, Ca 0.8%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0052] Comparative Example 2

[0053] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 4%, Y 5.0%, Ca 0.8%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0054] Comparative Example 3

[0055] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 2.0%, Y 3.0%, Ca 0.8%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0056] Comparative Example 4

[0057] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 5.0%, Y 3.0%, Ca 0.8%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0058] Comparative Example 5

[0059] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 4%, Y 3.0%, Ca 0.5%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0060] Comparative Example 6

[0061] This embodiment is the same as Embodiment 1, except that, in this embodiment, the magnesium alloy casting rod, by mass percentage, includes the following chemical composition: Al 4%, Y 3.0%, Ca 2.0%, Mn 0.3%, with the remainder being Mg and unavoidable impurities.

[0062] Argon arc welding was performed on AZXW4120 magnesium alloy (base material) using magnesium alloy welding wires from Examples 1-7 and Comparative Examples 1-6. The AZXW4120 magnesium alloy, by mass percentage, comprised the following chemical composition: Al 3.5%, Zn 1.0%, Ca 2.0%, Mn 0.2%, with the remainder being Mg and unavoidable impurities. A macroscopic photograph of the welded material using the magnesium alloy welding wire from Example 1 is shown below. Figure 1 As shown in the figure, neither the weld nor the magnesium alloy base material exhibits macroscopic defects. Simultaneously, microstructural analysis was performed on the welded component. The SEM images of the fusion region, the AZXW4120 magnesium alloy base material, and the weld region are shown below. Figure 2 , Figure 3 and Figure 4 As shown. By Figure 2-4 It is evident that the fusion region exhibits good bonding and a smooth transition in microstructure, indicating that the welding wire and the magnesium alloy base material have good metallurgical compatibility. The weld region contains fine equiaxed crystals, with a dense microstructure and a dispersed distribution of the second phase.

[0063] Tensile tests were conducted on the welded joint area and the AZXW4120 magnesium alloy base material, and the test results are shown in the table below.

[0064] AZXW4120 magnesium alloy base material 265 200 0.23 Example 1 200 149 0.16 Example 2 193 141 0.17 Example 3 202 150 0.15 Example 4 198 142 0.17 Example 5 203 150 0.15 Example 6 202 151 0.17 Example 7 195 143 0.15 Comparative Example 1 165 121 0.18 Comparative Example 2 205 152 0.11 Comparative Example 3 180 139 0.19 Comparative Example 4 205 148 0.13 Comparative Example 5 185 139 0.18 Comparative Example 6 210 154 0.09

[0065] As can be seen from the table above: (1) When the magnesium alloy welding wire described in this invention is used to weld AZXW4120 magnesium alloy, the tensile strength and yield strength at the weld joint reach more than 70% of the base material, and the elongation reaches more than 65% of the base material.

[0066] (2) Comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that as the Y element content increases, the tensile strength and yield strength at the welded joint increase, but the plasticity decreases significantly. When the Y element content is 3%, the welded joint ensures both high strength and good plasticity.

[0067] (3) Comparing Examples 1, 4-5 and Comparative Examples 3-4, it can be seen that as the Al content increases, the tensile strength and yield strength at the welded joint increase, but the plasticity decreases significantly. When the Al content is 4%, the welded joint ensures both high strength and good plasticity.

[0068] (4) Comparing Examples 1, 6-7 and Comparative Examples 5-6, it can be seen that as the Ca content increases, the tensile strength and yield strength of the welded joint increase, but the plasticity decreases significantly. When the Ca content is 1%, the welded joint ensures both high strength and good plasticity.

[0069] Finally, it should be noted that the above embodiments of the present invention are merely illustrative examples and not intended to limit the implementation of the invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A magnesium alloy welding wire, characterized in that, The magnesium alloy welding wire comprises the following chemical composition by mass percentage: Al 3.5%-4.5%, Y 2.5%-3.5%, Ca 0.8%-1.2%, Mn 0.2%-0.5%, with the remainder being Mg and unavoidable impurities.

2. The magnesium alloy welding wire according to claim 1, characterized in that, The magnesium alloy welding wire comprises the following chemical composition by mass percentage: Al 3.8%-4.1%, Y 2.8%-3.2%, Ca 0.8%-1.0%, Mn 0.2%-0.3%, with the remainder being Mg and unavoidable impurities.

3. The magnesium alloy welding wire according to claim 2, characterized in that, The magnesium alloy welding wire comprises the following chemical composition by mass percentage: Al 4%, Y 3.0%, Ca 1%, Mn 0.2%, with the remainder being Mg and unavoidable impurities.

4. A magnesium alloy welding wire according to any one of claims 1-3, characterized in that, The diameter of the magnesium alloy welding wire is 1.0-3.0 mm.

5. A method for preparing magnesium alloy welding wire, characterized in that, Specifically, the following steps are included: S1: The casting yields a magnesium alloy ingot with qualified composition, which, by mass percentage, comprises the following chemical composition: Al 3.5%-4.5%, Y 2.5%-3.5%, Ca 0.8%-1.2%, Mn 0.2%-0.5%, with the remainder being Mg and unavoidable impurities; S2: Heat the magnesium alloy casting rod to 440-470℃ and then extrude it to obtain the magnesium alloy welding wire.

6. The method for preparing a magnesium alloy welding wire according to claim 5, characterized in that, In step S1, the method for casting magnesium alloy rods is as follows: under gas protection, pure magnesium ingots are heated and melted, and then aluminum ingots, Mg-Y master alloy, Mg-Ca master alloy and Mg-Mn master alloy are added in sequence. After they are completely melted, they are stirred evenly, then heated to remove slag, and then cast to obtain the magnesium alloy rods.

7. The method for preparing a magnesium alloy welding wire according to claim 6, characterized in that, The gas is a mixture of CO2 and SF6, wherein the volume fraction of CO2 is 99%.

8. The method for preparing a magnesium alloy welding wire according to claim 6, characterized in that, The temperature for smelting pure magnesium ingots is 700-740℃.

9. The method for preparing a magnesium alloy welding wire according to claim 5, characterized in that, In step S2, the magnesium alloy casting rod is precision machined before heating to make the diameter of the magnesium alloy casting rod 90-110mm.

10. A method for preparing a magnesium alloy welding wire according to claim 5, characterized in that, In step S2, the extrusion ratio of the extrusion process is 15-25:1.

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