A method for suppressing pores in arc additively manufactured aluminum / magnesium alloy components

Abstract

The present invention relates to the technical field of arc additive manufacturing of aluminum / magnesium alloy components, and in particular to a method for suppressing pores in arc additive manufacturing of aluminum / magnesium alloy components. The protective atmosphere of the method of the present invention is a multi-component mixed protective atmosphere; the multi-component mixed protective atmosphere is a mixed atmosphere of argon, nitrogen, helium and carbon dioxide. The method of the present invention does not require reducing the additive current, reducing the wire feeding speed and the additive speed ratio, nor does it require increasing the complexity of the mechanical structure and the equipment cost. The present invention adjusts the mixing ratio of the multi-component protective atmosphere, maintains high additive efficiency and low equipment cost, and changes the convection pattern inside the molten pool to reduce the nucleation points of pores, thereby significantly improving the defect problem of pores in aluminum / magnesium alloy components, which is conducive to large-scale promotion and application.

Description

Technical Field

[0001] The present invention relates to the technical field of arc additive manufacturing of aluminum / magnesium alloy components, and in particular to a method for suppressing pores in arc additive manufacturing of aluminum / magnesium alloy components. Background Art

[0002] Aluminum / magnesium alloys have become a common high-quality material used in arc additive manufacturing due to their low density, high specific strength, and strong corrosion resistance. In recent years, they have been widely used in aerospace, shipbuilding, pressure vessels and other fields. Arc additive manufacturing uses a welding arc as a heat source to melt the metal wire, and then deposits it layer by layer on the substrate according to a preset path until the metal part is formed. It is characterized by a periodic multi-interface heterogeneous structure formed by the stacking of multiple molten pools. The unique stacking processing characteristics and ultra-fast melting / solidification rates of the arc additive manufacturing process easily form defects such as pores. Porosity reduces the load-bearing area of ​​aluminum / magnesium alloy components, resulting in a decrease in the mechanical properties of aluminum / magnesium alloy components.

[0003] At present, the main methods to solve this problem at home and abroad are: (1) reducing the heat input of the arc additive manufacturing process, such as reducing the additive current and reducing the ratio of wire feed speed to additive speed. Although this method can effectively reduce pores, it also reduces the additive efficiency; (2) changing the arc mode and using the variable polarity composite pulse CMT process to additively manufacture aluminum alloys can significantly reduce pores; (3) using interlayer processing technology, such as interlayer rolling, can effectively reduce the pore content of aluminum alloy components, but at the same time increase the complexity of the mechanical structure and equipment cost. Therefore, it is necessary to propose a new method to reduce the problem of pore defects in traditional arc additive manufacturing of aluminum / magnesium alloy components while maintaining high additive efficiency and low equipment cost. Summary of the Invention

[0004] Based on the above content, the present invention provides a method for suppressing pores in aluminum / magnesium alloy components produced by arc additive manufacturing, which reduces the problem of pore defects in aluminum / magnesium alloy components produced by traditional arc additive manufacturing while maintaining high additive efficiency and low equipment cost.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is a method for suppressing pores in aluminum / magnesium alloy components manufactured by arc additive manufacturing, wherein the protective atmosphere is a multi-component mixed protective atmosphere; the multi-component mixed protective atmosphere is a mixed atmosphere of argon, nitrogen, helium and carbon dioxide.

[0007] The purity of the argon, nitrogen, helium and carbon dioxide is not less than 99.99%.

[0008] Furthermore, in terms of volume percentage, the content of argon in the mixed atmosphere is 80% to 100%, the content of nitrogen is 0% to 5%, the content of helium is 0% to 10%, and the content of carbon dioxide is 0% to 5%, wherein the contents of nitrogen, helium and carbon dioxide are not 0, and the content of argon is not 100%.

[0009] Furthermore, in terms of volume percentage, the content of argon in the mixed atmosphere is 80% to 95%, the content of nitrogen is 0% to 5%, the content of helium is 0% to 10%, and the content of carbon dioxide is 0% to 5%; wherein the contents of nitrogen, helium and carbon dioxide are not zero.

[0010] Further, the following steps are included:

[0011] Based on the 3D model of the aluminum / magnesium alloy component, slice the components in layers along the height direction of the 3D model, determine the additive path for each layer, and set the process parameters for arc additive manufacturing;

[0012] Move the welding gun to the starting point of the additive path, strike an arc on the substrate, and complete the first layer of additive manufacturing along the planned path; after cooling, move the welding gun to the starting point of the next layer of the path; repeat the steps of adding material along the planned path until the aluminum / magnesium alloy component is formed.

[0013] Furthermore, the process parameters include: additive current 90A-120A, shielding gas flow 25L / min, additive speed 0.6-1.0m / min, pulse number EP / EN value 3.0, and interlayer cooling time 45-75 seconds.

[0014] Furthermore, before starting arc additive manufacturing, the welding wire and the substrate also include the steps of removing surface oil stains with alcohol and acetone, and then drying.

[0015] Furthermore, the thickness of the layered slices is 2.5 to 3.0 mm, the distance between the welding gun and the substrate is 8 to 15 mm, and the welding gun is moved to the arc extinguishing point of the previous layer of additive before proceeding to the next layer of additive.

[0016] Furthermore, the welding wire is an aluminum alloy welding wire or a magnesium alloy welding wire, and the substrate is an aluminum alloy substrate or a magnesium alloy substrate.

[0017] Technical concept of the present invention:

[0018] The present invention adjusts the protective atmosphere of the arc additive manufacturing aluminum / magnesium alloy components to a multi-component mixed protective atmosphere (argon, nitrogen, helium and carbon dioxide), wherein argon performs macro-protection to isolate external impurities such as oxygen and water vapor, helium adjusts the convection mode of the arc additive aluminum alloy molten pool, increases the outward escape velocity of the pores, nitrogen is used to enhance the ionization potential energy of the multi-component mixed protective gas, and the addition of carbon dioxide makes it easier to obtain a relatively stable droplet transfer velocity and a relatively high short-circuit transition frequency during the additive process, making the additive process more stable and improving the forming quality of the aluminum / magnesium alloy components, thereby effectively reducing the porosity defects of the aluminum / magnesium alloy as a whole.

[0019] The present invention discloses the following technical effects:

[0020] The method of the present invention does not require reducing the additive current, wire feed speed, or additive speed ratio, nor does it increase the complexity of the mechanical structure or equipment cost. By adjusting the mixing ratio of the multi-component protective atmosphere, the present invention significantly improves the problem of pore nucleation points in aluminum / magnesium alloy components by changing the convection pattern within the molten pool while maintaining high additive efficiency and low equipment cost, facilitating widespread application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 Schematic diagram of multi-element mixed shielding gas arc additive manufacturing according to the present invention;

[0023] Figure 2 This is the metallographic image of the aluminum alloy produced by arc-assisted machining under 100% argon protection in Comparative Example 1;

[0024] Figure 3 This is the metallographic image of 2319 aluminum alloy produced by additive manufacturing using a multi-component mixed arc with 80% argon + 10% helium + 5% nitrogen + 5% carbon dioxide in Example 1;

[0025] Figure 4 This is the metallographic diagram of AZ31 magnesium alloy produced by multi-component mixed arc additive manufacturing using 85% argon + 7.5% helium + 5% nitrogen + 2.5% carbon dioxide in Example 2;

[0026] Figure 5 This is the metallographic diagram of 5356 aluminum alloy manufactured by multi-component mixed arc additive manufacturing using 90% argon + 5% helium + 2.5% nitrogen + 2.5% carbon dioxide in Example 3. DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0029] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0030] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0031] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0032] The present invention provides a method for suppressing pores in aluminum / magnesium alloy components manufactured by arc additive manufacturing, comprising the following steps:

[0033] Step 1: Under the pressure protection of the pressure controller, four gases with a purity of 99.999% argon, helium, nitrogen, and carbon dioxide are connected to the back end of the multi-gas mixing proportioner. The gas proportion control valves at the front end of the proportioner are used to adjust the argon component ratio η1, helium component ratio η2, nitrogen component ratio η3, and carbon dioxide component ratio η4 in the mixed protective gas. The four protective gases are mixed in the internal filter device and diffuser to output the required proportion of additive protective gas. The mixing accuracy reaches 0.1%. The value range of the argon component ratio η1 is 80% to 100%, the value range of the helium component ratio η2 is 0% to 10%, the value range of the nitrogen component ratio η3 is 0% to 5%, and the value range of the carbon dioxide component ratio η4 is 0% to 5%. The pressure control range of the output additive protective gas with the required proportion is 0.4 to 0.6 MPa.

[0034] In the present invention, preferably, the argon component ratio η1 ranges from 80% to 95%, the helium component ratio η2 ranges from 0% to 10%, the nitrogen component ratio η3 ranges from 0% to 5%, and the carbon dioxide component ratio η4 ranges from 0% to 5%.

[0035] The present invention aims to reduce the porosity of aluminum / magnesium alloys at a low cost. Therefore, argon protection is still the main method. Helium is added to adjust the convection mode of the aluminum / magnesium alloy melt pool, converting the original pure argon protection inner convection mode of the melt pool to an outer convection mode, which is more conducive to the escape of pores. The addition of nitrogen increases the ionization potential of the shielding gas, improving the forming quality of the additive component to a certain extent. The addition of carbon dioxide makes it easier to obtain a relatively stable droplet transfer speed and a relatively high short-circuit transition frequency during the additive process, making the additive process more stable. However, the ratio of nitrogen to carbon dioxide should not be too high because nitrogen reacts with aluminum / magnesium alloy to form flaky nitrides, which affect the tensile properties of aluminum / magnesium alloy components to a certain extent, while too much carbon dioxide will cause splashing.

[0036] Step 2: Based on the 3D model of the aluminum / magnesium alloy component, slice the component in layers along the height direction of the 3D model, determine the additive path of each layer, and set the arc additive manufacturing process parameters. The process parameters include: additive current I, shielding gas flow L, additive speed V, pulse number EP / EN value N, and interlayer cooling time T. Among them, the additive current I ranges from 90A to 120A; the additive speed V ranges from 0.6 to 1.0m / min, the shielding gas flow L is 25L / min, the pulse number EP / EN value N is 3.0, and the interlayer cooling time T is 45 to 75 seconds. Degrease the surface of the welding wire and substrate with alcohol and acetone, and then dry them.

[0037] The value range of I is 90A~120A because if I is too small, the molten droplet is not easy to spread on the substrate and the aluminum / magnesium alloy component cannot be formed. If I is too large, the molten pool is easy to flow, resulting in poor forming quality of the aluminum / magnesium alloy component. Therefore, in the present invention, the value of I is 90~120A.

[0038] The interlayer cooling time T is controlled at 45 to 75 seconds because as the number of additive layers increases, the heat accumulation in the aluminum / magnesium alloy component becomes more serious. In order to ensure that the temperature before each additive layer is roughly the same, the cooling time required for the later additive layers is longer than that for the earlier additive layers.

[0039] Step 3: Move the CMT welding gun to the starting point of the additive path, pre-flow the multi-element mixed shielding gas for 1.5 to 2.0 seconds, strike the arc on the substrate, and complete the first layer of additive manufacturing along the planned path;

[0040] Step 4: Wait 45 to 75 seconds for the previous deposited layer to cool, and move the welding gun to the starting point of the next layer path;

[0041] Step 5: Repeat steps 3 and 4 until the aluminum / magnesium alloy component is formed.

[0042] Unless otherwise specified, the "%" in the present invention is calculated as volume percentage.

[0043] The schematic diagram of multi-element mixed shielding gas arc additive manufacturing of the present invention is as follows Figure 1 shown.

[0044] Example 1

[0045] In this embodiment, aluminum alloy single-wall wall components are additively manufactured using a multi-component mixed arc with 80% argon + 10% helium + 5% nitrogen + 5% carbon dioxide, and the aluminum alloy welding wire is ER2319.

[0046] Adjust the multi-gas mixing ratio instrument to adjust the argon ratio η1, helium ratio η2, nitrogen ratio η3, and carbon dioxide ratio η4 to 80%, 10%, 5%, and 5%, respectively. Adjust the output pressure of the mixed shielding gas to 0.5 MPa.

[0047] A 3D model of a single-wall aluminum alloy component was created in SolidWorks. The model was sliced ​​vertically at 2.5mm thickness. A path was planned for each layer. Once the path was appropriate, it was imported into the arc additive manufacturing software. The following process parameters were set on the Fronius welder's control panel: additive current I = 100A, shielding gas flow L = 25L / min, additive speed V = 1.0m / min, pulse count EP / EN value N = 3.0, and inter-pass cooling time T = 45s. An ER2319 welding wire with a diameter of 1.2mm and a 6061 aluminum alloy substrate were selected. The wire and substrate were cleaned with alcohol and acetone, then dried.

[0048] Move the CMT welding gun to the starting point of the additive path, pass the above-mentioned multi-component mixed shielding gas for 1.5 seconds in advance, strike the arc on the substrate, and complete the first layer of additive manufacturing along the planned path; wait 45 seconds for the previous deposited layer to cool, and move the welding gun to the starting point of the next layer path until the single-wall aluminum alloy component is formed.

[0049] The single-wall aluminum alloy components completed by additive manufacturing were subjected to wire cutting to prepare metallographic specimens and tensile specimens. After sanding and polishing, metallographic images were taken using an Olympus optical microscope. Figure 3 As shown, the porosity statistics were performed using Image J software, and the results are shown in Table 1. After the tensile specimen was stretched by an MTS testing machine, the tensile data were obtained, as shown in Table 2.

[0050] Example 2

[0051] In this embodiment, magnesium alloy single-wall wall components are additively manufactured using a multi-component mixed arc with 85% argon + 7.5% helium + 5% nitrogen + 2.5% carbon dioxide, and the grade of the magnesium alloy welding wire is AZ31.

[0052] Adjust the multi-gas mixing instrument to adjust the argon ratio η1, helium ratio η2, nitrogen ratio η3, and carbon dioxide ratio η4 to 85%, 7.5%, 5%, and 2.5%, respectively. Adjust the output pressure of the mixed shielding gas to 0.5 MPa.

[0053] A 3D model of a single-wall magnesium alloy component was created in SolidWorks. The model was sliced ​​into layers with a thickness of 2.8 mm along the height direction. A path was planned for each layer. Once the path planning was appropriate, it was imported into the arc additive manufacturing software. The following process parameters were set on the Fronius welder control panel: additive current I = 90 A, shielding gas flow L = 25 L / min, additive speed V = 0.6 m / min, pulse number EP / EN value N = 3.0, and interlayer cooling time T = 60 s. An AZ31 magnesium alloy welding wire with a diameter of 1.2 mm and an AZ31 magnesium alloy substrate were selected. The wire and substrate were cleaned with alcohol and acetone, then dried.

[0054] Move the CMT welding gun to the starting point of the additive path, pass the multi-component mixed shielding gas for 1.8 seconds in advance, strike the arc on the substrate, and complete the first layer of additive manufacturing along the planned path; wait 60 seconds for the previous deposited layer to cool, and move the welding gun to the starting point of the next layer path until the single-wall magnesium alloy component is formed.

[0055] The single-wall magnesium alloy component after additive manufacturing was subjected to wire cutting to prepare metallographic specimens and tensile specimens. After sandpaper grinding and polishing, metallographic images were taken using an Olympus optical microscope. Figure 4As shown, the porosity statistics were performed using Image J software, and the results are shown in Table 1. After the tensile specimen was stretched by an MTS testing machine, the tensile data were obtained, as shown in Table 2.

[0056] Example 3

[0057] In this embodiment, aluminum alloy single-wall wall components are additively manufactured using a multi-component mixed arc with 90% argon + 5% helium + 2.5% nitrogen + 2.5% carbon dioxide, and the aluminum alloy welding wire is ER5356.

[0058] Adjust the multi-gas mixing instrument to adjust the argon ratio η1, helium ratio η2, nitrogen ratio η3, and carbon dioxide ratio η4 to 90%, 5%, 2.5%, and 2.5%, respectively. Adjust the output pressure of the mixed shielding gas to 0.5 MPa.

[0059] A 3D model of a single-wall aluminum alloy component was created in SolidWorks. The model was sliced ​​into 3mm thick layers along the height direction, and a path was planned for each layer. Once the path planning was appropriate, it was imported into the arc additive manufacturing software. The process parameters were set on the Fronius welder's control panel: additive current I = 120A, shielding gas flow L = 25L / min, additive speed V = 0.8m / min, pulse number EP / EN value N = 3.0, and interpass cooling time T = 75s. An ER5356 welding wire with a diameter of 1.2mm and a 6061 aluminum alloy substrate were selected. The wire and substrate were cleaned with alcohol and acetone, then dried.

[0060] Move the CMT welding gun to the starting point of the additive path, pre-flow the multi-component mixed shielding gas for 2.0 seconds, strike the arc on the substrate, and complete the first layer of additive manufacturing along the planned path; wait 75 seconds for the previous deposited layer to cool, and move the welding gun to the starting point of the next layer path until the single-wall aluminum alloy component is formed.

[0061] The single-wall aluminum alloy components completed by additive manufacturing were subjected to wire cutting to prepare metallographic specimens and tensile specimens. After sanding and polishing, metallographic images were taken using an Olympus optical microscope. Figure 5 As shown, the porosity statistics were performed using Image J software, and the results are shown in Table 1. After the tensile specimen was stretched by an MTS testing machine, the tensile data were obtained, as shown in Table 2.

[0062] Comparative Example 1

[0063] The only difference from Example 3 is that the multi-component mixed gas of 90% argon + 5% helium + 2.5% nitrogen + 2.5% carbon dioxide is replaced by 100% argon.

[0064] The single-wall aluminum alloy components completed by additive manufacturing were subjected to wire cutting and tensile testing to prepare metallographic samples. After grinding and polishing with sandpaper, metallographic images were taken using an Olympus optical microscope, as shown in Figure 2. Figure 2 As shown, the porosity statistics were performed using Image J software, and the results are shown in Table 1. After the tensile specimen was stretched by an MTS testing machine, the tensile data were obtained, as shown in Table 2.

[0065] The protective gas ratios and performance index parameters used in Examples 1-3 and Comparative Example 1 are shown in Table 1.

[0066] The protective gas ratios and tensile properties data used in Examples 1-3 and Comparative Example 1 are shown in Table 2.

[0067] Table 1

[0068]

[0069] Table 2

[0070]

[0071] Compared with the comparative example, the porosity and pore diameter of Examples 1, 2, and 3 are significantly reduced. The pore distribution of the 2319 aluminum alloy component in Example 1 is as follows: Figure 3 As shown in the figure, the porosity and pore diameter decreased by 73.52% and 53.71% respectively. The pore distribution of the AZ31 magnesium alloy component in Example 2 is shown in the figure. Figure 4 As shown in the table, the porosity and pore diameter decreased by 57.84% and 49.73% respectively; the pore distribution of the 5356 aluminum alloy component in Example 3 is shown in the table. Figure 5 As shown in the figure, according to statistics, the porosity and pore diameter decreased by 50.89% and 38.67% respectively.

[0072] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for suppressing pores in arc additively manufactured aluminum / magnesium alloy components, characterized in that: The protective atmosphere is a multi-component mixed protective atmosphere; the multi-component mixed protective atmosphere is a mixed atmosphere of argon, nitrogen, helium and carbon dioxide; In terms of volume percentage, the content of argon in the mixed atmosphere is 80% to 95%, the content of nitrogen is 2.5% to 5%, the content of helium is 0% to 10%, and the content of carbon dioxide is 0% to 5%; wherein the content of helium and carbon dioxide is not 0; The method comprises the following steps: Based on the 3D model of the aluminum / magnesium alloy component, slice the components in layers along the height direction of the 3D model, determine the additive path for each layer, and set the process parameters for arc additive manufacturing; Move the welding gun to the starting point of the additive path, strike an arc on the substrate, and complete the first layer of additive manufacturing along the planned path. After cooling, move the welding gun to the starting point of the next layer of path. Repeat the steps of adding material along the planned path until the aluminum / magnesium alloy component is formed. The process parameters include: additive current 90A-120A, shielding gas flow 25L / min, additive speed 0.6-1.0m / min, pulse number EP / EN value 3.0, interlayer cooling time 45-75 seconds; The thickness of the layered slices is 2.5-3.0 mm, and the distance between the welding gun and the substrate is 8-15 mm.

2. The method for suppressing pores in arc additively manufactured aluminum / magnesium alloy components according to claim 1, characterized in that: Before starting arc additive manufacturing, the welding wire and substrate also include the steps of degreasing the surface with alcohol and acetone, and then drying.

3. The method for suppressing pores in arc additively manufactured aluminum / magnesium alloy components according to claim 2, characterized in that: The welding wire is an aluminum alloy welding wire or a magnesium alloy welding wire, and the substrate is an aluminum alloy substrate or a magnesium alloy substrate.

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