Crack-free aluminum alloy flux-cored wire and preparation method and application thereof

Abstract

The present application belongs to the technical field of welding material, and discloses a crack-free aluminum alloy flux-cored wire and a preparation method and application thereof.The wire includes a tube and a powder filled in the tube, and the powder includes the following components in mass fraction: 4-6.8 parts of Cu, 0.8-1.2 parts of Mg, 0.1-0.6 parts of Mn, 0.05-0.4 parts of Cr, 0.2-0.5 parts of Ti, 0.1-0.25 parts of Zr, 2-4 parts of a composite material, more than 0 parts and less than 0.1 part of Si, more than 0 parts and less than 0.1 part of Fe, 1-2 parts of TiC, and the balance of Al powder; wherein the composite material is a mixture of zirconium oxide and carbon nanotubes.The present application adds heterogeneous nucleation particles and reinforcing phases into an alpha-Al aluminum matrix to form an aluminum-based composite material, so that the weld metal grain is refined, and the weld metal has high thermal cracking resistance, hardness and tensile strength.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of welding materials, and more particularly relates to a crack-free aluminum alloy flux-cored wire and a preparation method and application thereof. BACKGROUND

[0002] 2 series high-strength aluminum alloy has high specific strength, specific stiffness, good stress corrosion resistance, high fracture toughness and excellent processing performance, and is widely used in the fields of aerospace, weapon equipment and transportation, especially occupies a very important position in the field of aerospace, and is one of the most important structural materials in the field. Although this kind of high-strength aluminum alloy has high specific strength, its welding performance is poor, and solidification cracks are prone to occur during fusion welding, which seriously damages its mechanical properties and limits its industrial application. As a solid-phase welding technology, friction stir welding technology does not produce coarse grain structure and solidification crack defects because the base material is not melted during welding, and the joint strength generally reaches more than 75% of the base material strength, which has been successfully applied to weld this kind of high-strength aluminum alloy. However, friction stir welding requires relatively large upset pressure and forward driving force, and the equipment is relatively complex and heavy, especially for complex welds, which is difficult to set, thereby hindering its wide application in this kind of high-strength aluminum alloy. Therefore, fusion welding is still the main welding method for this kind of high-strength aluminum alloy, but how to realize the suppression of solidification crack defects faces severe challenges.

[0003] Adding welding materials to change the chemical composition of the weld is a common method to solve the solidification crack defects of high-strength aluminum alloy. The 2 series aluminum alloy welding wires currently used mainly include ER2319 (Al-Cu) welding wire and ER4043 (Al-Si) welding wire. Although the joint strength of ER2319 welding wire is high, it has a tendency to crack, which cannot meet the use requirements in the field of aerospace. ER4043 welding wire has good casting performance and easy wire production process, and a large amount of low-melting eutectic is easily formed during welding, which reduces the tendency of solidification cracks by using its "healing effect", so it is widely used in actual production process, but the joint strength obtained is not high, which is difficult to meet the use demand of the field with high performance requirements. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the present application provides a crack-free aluminum alloy flux-cored wire and a preparation method and application thereof. By adding heterogeneous nucleation particles and reinforcing phases to the alpha-Al aluminum matrix, an aluminum matrix composite is formed, so that the weld metal grain is refined, and has high thermal cracking resistance, hardness and tensile strength.

[0005] To achieve the above object, according to one aspect of the present application, a crack-free aluminum alloy flux-cored wire is provided, which comprises a tube and a flux powder filled in the tube, the flux powder comprising the following components in mass fraction: 4-6.8 parts of Cu, 0.8-1.2 parts of Mg, 0.1-0.6 parts of Mn, 0.05-0.4 parts of Cr, 0.2-0.5 parts of Ti, 0.1-0.25 parts of Zr, 2-4 parts of a composite material, more than 0 parts and less than 0.1 parts of Si, more than 0 parts and less than 0.1 parts of Fe, 1-2 parts of TiC, and the balance of Al powder; wherein the composite material is a mixture of zirconium oxide and carbon nanotubes.

[0006] Further, the mass ratio of the zirconium oxide to the carbon nanotubes is (3-5):2.

[0007] Further, the zirconium oxide is yttrium stabilized zirconium oxide powder, the specific surface area is 5m 2 / g, the density is 6g / cm 3 , the purity is greater than 99.9%, and the particle size is 30-50μm.

[0008] Further, the carbon nanotubes are multi-walled carbon nanotubes, the outer diameter is 30-50nm, the inner diameter is 5-12nm, the length is 10-15μm, the specific surface area is 250m 2 / g, the density is 0.01g / cm 3 , the purity is greater than 99%, and the particle size is less than 25μm.

[0009] Further, the flux powder comprises the following components in parts: 6.8 parts of Cu, 1 part of Mg, 0.4 parts of Mn, 0.2 parts of Cr, 0.4 parts of Ti, 0.2 parts of Zr, 3 parts of a composite material, more than 0 parts and less than 0.1 parts of Si, more than 0 parts and less than 0.1 parts of Fe, 2 parts of nano-TiC, and the balance of Al powder.

[0010] Further, the tube is made of a 1060 pure aluminum strip with a wall thickness of 0.5-0.8mm and a width of 14-16mm.

[0011] Further, the filling rate of the wire is 45%-60%, and the filling rate is the ratio of the mass of the flux powder to the sum of the mass of the flux powder and the aluminum strip.

[0012] Further, the particle sizes of copper, magnesium, chromium, manganese, titanium and zirconium are all 50-125μm, and the average particle size of nano-titanium carbide is 40nm.

[0013] The present application also provides a preparation method of the crack-free aluminum alloy flux-cored wire.

[0014] The application further provides application of the crack-free aluminum alloy flux-cored wire in welding.

[0015] Compared with the prior art, the crack-free aluminum alloy flux-cored wire and the preparation method and application thereof provided by the application have the following beneficial effects:

[0016] 1. The welding wire provided by the application is alloyed in situ by flexibly adding flux powder, and yttrium-stabilized zirconium and nano-titanium carbide are added as nucleation cores to promote the generation of fine equiaxed crystals of α-Al, since the fine equiaxed grains are more likely to coordinate the deformation between the grains and thus inhibit solidification cracks, and the fine equiaxed crystal structure has high strength; in addition, the carbon nanotubes help to reduce the porosity in the 2XXX aluminum alloy weld by an order of magnitude, promote the precipitation of phases, increase the dislocation density, and provide a basis for dislocation strengthening, and the carbon nanotubes can be closely combined with the surrounding aluminum matrix to improve the load transfer process, and the addition of multi-walled carbon nanotubes and the dispersion distribution thereof can further improve the corresponding joint strength.

[0017] 2. The application solves the problems of thermal cracks, joint softening and low joint strength of 2-series high-strength aluminum alloys, and the thermal stability and weld strength of the weld are significantly improved when the 2-series aluminum alloys are welded by using the welding wire, and the joint strength of some welds can approach the joint strength obtained by solid-phase friction stir welding.

[0018] 3. The welding wire can be made into a diameter of 1.2 mm and used for gas shielded welding or laser-arc hybrid welding, or made into a diameter of 3.6 mm and suitable for large-current welding, and the production efficiency is further improved.

[0019] 4. The welding wire can be of any length and can be wound into a disc, and is suitable for continuous automatic welding, and can be used for laser wire filling welding, laser-arc hybrid welding and other welding methods in addition to gas shielded welding.

[0020] 5. The welding wire provides a new idea for welding of other difficult-to-weld material systems, such as nickel-based high-temperature alloys and dissimilar metal welding, and is expected to improve the welding between different materials and can be used for additive manufacturing to prepare large and complex components. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a scanning electron microscope microstructure diagram of the deposited metal provided by Example 1 of the application;

[0022] Figure 2 is a scanning electron microscope microstructure diagram of the deposited metal provided by Comparative Example 1 of the application;

[0023] Figure 3 is a scanning electron microscope microstructure diagram of the deposited metal provided by Comparative Example 2 of the application. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely intended to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0025] The present application provides a crack-free aluminum alloy flux-cored wire, which comprises a tube and a flux powder filled in the tube, the flux powder comprising the following components in mass fraction: 4-6.8 parts of Cu, 0.8-1.2 parts of Mg, 0.1-0.6 parts of Mn, 0.05-0.4 parts of Cr, 0.2-0.5 parts of Ti, 0.1-0.25 parts of Zr, 2-4 parts of a composite material, more than 0 parts and less than 0.1 parts of Si, more than 0 parts and less than 0.1 parts of Fe, 1-2 parts of TiC, and the balance being Al powder; wherein the composite material is a mixture of zirconium oxide and carbon nanotubes.

[0026] In the present embodiment, the mass ratio of the zirconium oxide to the carbon nanotubes is (3-5):2, and the ball milling method is used for preparation. The zirconium oxide is yttrium stabilized zirconium oxide powder, the specific surface area is 5 m 2 / g, the density is 6 g / cm 3 , the purity is greater than 99.9%, and the particle size is 30-50 μm.

[0027] The carbon nanotubes are multi-walled carbon nanotubes, the outer diameter is 30-50 nm, the inner diameter is 5-12 nm, the length is 10-15 μm, the specific surface area is 250 m 2 / g, the density is 0.01 g / cm 3 , the purity is greater than 99%, and the particle size is less than 25 μm.

[0028] The ball milling conditions of the composite material are as follows: the dry milling process is used, the milling balls are zirconium dioxide (homogeneous with the milled material to avoid impurities), the ball-to-material ratio is 6:1-8:1, the ball milling time is 2-3 hours, and the rotation speed is 800-1000 rpm; the ball-to-material ratio, the ball milling time and the rotation speed are controlled so that the multi-walled carbon nanotubes are firmly adhered to the surface of the yttrium stabilized zirconium oxide ceramic particles after ball milling, and the particle size of the material after ball milling is 5-8 μm.

[0029] In one embodiment, the flux powder comprises the following components in parts: 6.8 parts of Cu, 1 part of Mg, 0.4 parts of Mn, 0.2 parts of Cr, 0.4 parts of Ti, 0.2 parts of Zr, 3 parts of a composite material, more than 0 parts and less than 0.1 parts of Si, more than 0 parts and less than 0.1 parts of Fe, 2 parts of nano-TiC, and the balance being Al powder.

[0030] The 1060 pure aluminum strip with a wall thickness of 0.5mm-0.8mm and a width of 14mm-16mm is used to prepare the pipe.

[0031] The Cu content of the copper powder is not less than 99.9% by mass percentage, the Mg content of the magnesium powder is not less than 99.9% by mass percentage, the Cr content of the chromium powder is not less than 99.5% by mass percentage, the Mn content of the manganese powder is not less than 99.8% by mass percentage, the Ti content of the titanium powder is not less than 99.6% by mass percentage, the Zr content of the zirconium powder is not less than 99.9% by mass percentage, the component of the yttrium stabilized zirconium oxide is not less than 99.9% by mass percentage, the ZrO2 content is not less than 99.9%, the component of the multi-walled carbon nanotube is not less than 99% by mass percentage, and the TiC content of the nano-titanium carbide is not less than 99.9% by mass percentage.

[0032] In terms of the alloy powder of the embodiment, the particle size of the copper powder, the magnesium powder, the metallic chromium powder, the manganese powder, the titanium powder, and the zirconium powder is preferably 50μm-125μm, the particle size of the yttrium stabilized zirconium oxide is 30μm-50μm, the particle size of the multi-walled carbon nanotube is less than 25μm, and the average particle size of the nano-titanium carbide is 40nm.

[0033] The application also provides a preparation method of the crack-free aluminum alloy flux-cored wire, which comprises the following steps:

[0034] S1, the yttrium stabilized zirconium oxide and the multi-walled carbon nanotube are weighed according to the powder formula and then dry ball-milled to obtain a composite material; the components are weighed according to the ratio of the powder formula and then mixed after being added to the composite material to obtain the powder. The powder is obtained by mixing the powder for 30 minutes-60 minutes using a powder mixer.

[0035] The powder comprises the following components in mass fraction: 4-6.8 parts of Cu, 0.8-1.2 parts of Mg, 0.1-0.6 parts of Mn, 0.05-0.4 parts of Cr, 0.2-0.5 parts of Ti, 0.1-0.25 parts of Zr, 2-4 parts of a composite material, more than 0 parts and less than 0.1 part of Si, more than 0 parts and less than 0.1 part of Fe, 1-2 parts of TiC, and the balance of Al powder; wherein the composite material is a mixture of zirconium oxide and carbon nanotubes, the mass ratio of the two is 3-5:2, the particle size of the yttrium stabilized zirconium oxide is 30μm-50μm, the particle size of the multi-walled carbon nanotube is less than 25μm, the average particle size of the nano-titanium carbide is 40nm, and the particle size of other powders is 50μm-125μm.

[0036] S2, the 1060 pure aluminum strip with width of 14mm-16mm and thickness of 0.5mm-0.8mm is cleaned of the upper surface oxide film by a doctor blade, then cleaned by an ultrasonic cleaning device, and then the aluminum strip is rolled into a U shape by using the existing flux-cored wire production equipment, and the flux powder prepared in step S1 is added into the U-shaped groove, and the filling rate (the ratio of the mass of the flux powder to the mass of the flux-cored wire) is 45%-60%.

[0037] S3, the U-shaped groove is closed to wrap the flux powder therein, and the closed part is connected in a lap joint manner (the width of the lap joint part is 1mm-2mm, which is ensured by the forming roller of the existing flux-cored wire production equipment); the diameter is reduced by 15-25 passes of drawing, and each pass is annealed at 250°C-400°C for 30 minutes, and finally the diameter reaches 0.8mm-2.4mm.

[0038] S4, the obtained flux-cored wire layer is wound into a coil, and a new type of crack-free high-strength aluminum alloy flux-cored wire is obtained.

[0039] When the above-described flux-cored wire is used for welding, it is recommended to use a laser oscillation-arc hybrid welding process, and the specific welding process is as follows: the laser power is 5000W-10000W, the welding speed is 20mm / s-40mm / s, the amplitude is 1.5mm-2.5mm, the oscillation frequency is 150Hz-250Hz, the defocusing amount is 0mm, the light-wire distance is 4mm-6mm, the dry extension of the flux-cored wire is 14mm-22mm, the welding current is 175A-300A, the voltage is 24V-38V, the gas flow rate is 15L / min-25L / min, and the dry extension of the flux-cored wire is 16mm. The process performance of the flux-cored wire is good, the arc is stable, the spatter is less, and the crack resistance is good.

[0040] The following will be further described in detail by means of several specific embodiments. In the following embodiments, the preparation method of the composite material is as follows: yttrium-stabilized zirconium oxide and multi-walled carbon nanotubes are used as raw materials, a dry grinding process is adopted, zirconium dioxide is used as the grinding ball, the ball-to-material ratio is 8:1-10:1, the ball milling time is 2 hours-3 hours, the rotation speed is 800 revolutions / minute-1000 revolutions / minute, and the particle size of the material after ball milling is 5μm-8μm.

[0041] Example 1

[0042] The crack-free aluminum alloy flux-cored wire provided in the embodiment 1 of the present application mainly includes the following steps:

[0043] S1: The following components are mixed according to the powder formula: 6.8 parts of Cu, 1.0 parts of Mg, 0.4 parts of Mn, 0.2 parts of Cr, 0.4 parts of Ti, 0.2 parts of Zr, 3 parts of composite material, more than 0 parts and less than 0.1 parts of Si, more than 0 parts and less than 0.1 parts of Fe, 2 parts of nano-TiC, and the balance of Al powder; 3 mol of Y2O3 is used to stabilize zirconia, the particle size is 30-50 μm, the particle size of multi-walled carbon nanotubes is less than 25 μm, the average particle size of nano-titanium carbide powder is 40 nm, and the particle size of other powders is 50-125 μm.

[0044] S2: The upper surface of a 15 mm wide and 0.5 mm thick 1060 pure aluminum strip is cleaned of the oxide film by a doctor blade, and then cleaned by an ultrasonic cleaning device. The aluminum strip is then rolled into a U shape by using an existing flux-cored wire production device, and the powder prepared in step S1 is added to the U-shaped groove, with a filling rate (ratio of the mass of the powder to the mass of the flux-cored wire) of 60%.

[0045] S3: The U-shaped groove is closed to wrap the powder therein, and the closed part is connected by lap joint (the width of the lap joint part is 1.5 mm, which is ensured by the forming roller of the existing flux-cored wire production device); the diameter is reduced by 20 passes of drawing, and each pass is annealed at 250-400°C for 30 minutes, and finally the diameter is reduced to 1.2 mm.

[0046] S4: The flux-cored wire obtained in step S3 is wound into a coil to obtain the new high-strength aluminum alloy flux-cored wire product without cracks.

[0047] The new high-strength aluminum alloy flux-cored wire is used in a laser oscillation-arc hybrid welding process, and the base material is 8 mm thick 2024-T4 aluminum alloy. The specific welding process is as follows: laser power is 5000 W, welding speed is 20 mm / s, amplitude is 2.5 mm, oscillation frequency is 250 Hz, spot diameter is 0.1 mm, defocusing amount is 0 mm, light-wire distance is 4 mm, wire dry extension is 16 mm, welding current is 175 A, voltage is 24 V, gas flow is 20 L / min, and wire dry extension is 16 mm. The process performance of the wire is good, the arc is stable, the spatter is less, and there is no solidification crack after welding, as shown in FIG. 1. The microhardness of the weld is 155 HV, the tensile strength of the joint is 364 MPa, and the joint strength coefficient is 81%, which is comparable to the joint strength obtained by friction stir welding. Figure 1

[0048] Comparative Example 1

[0049] ​A commercially available ER2319 aluminum-copper welding wire is used as filler metal, which includes the following components by mass fraction: 5.8-6.8 parts of Cu, 0.2-0.6 parts of Mn, 0.2 parts of Si, 0.3 parts of Fe, 0.02 parts of Mg, 0.1 parts of Zn, 0.05-0.15 parts of V, 0.1-0.2 parts of Ti, and 0.1-0.25 parts of Zr. The diameter of the welding wire is 1.2 mm.

[0050] A laser oscillation-arc hybrid welding process is used to weld a 2024-T4 aluminum alloy base material with a thickness of 8 mm. The specific welding process is as follows: the laser power is 5000 W, the welding speed is 20 mm / s, the amplitude is 2.5 mm, the oscillation frequency is 250 Hz, the defocusing amount is 0 mm, the light-wire distance is 4 mm, the wire dry extension is 16 mm, the welding current is 175 A, the voltage is 24 V, the gas flow rate is 20 L / min, and the wire dry extension is 16 mm. The welding wire has good process performance, the arc is stable, and the spatter is small. After welding, no solidification cracks occur, as shown in FIG. 2. The microhardness of the weld is 135 HV, the tensile strength of the joint is 320 MPa, and the joint strength coefficient is 71%. Figure 2

[0051] Compared with the comparative example, the new crack-free high-strength aluminum alloy flux-cored wire can inhibit the solidification cracking of the 2024 high-strength aluminum alloy during welding, and the joint strength is increased by 14% compared with the joint strength obtained by using the ER2319.

[0052] Comparative Example 2

[0053] A commercially available ER4043 aluminum-silicon welding wire is used as filler metal, which includes the following components by mass fraction: 4.5-6.0 parts of Si, 0.8 parts of Fe, 0.3 parts of Cu, 0.05 parts of Mn, 0.05 parts of Mg, 0.1 parts of Zn, and 0.2 parts of Ti. The diameter of the welding wire is 1.2 mm.

[0054] A laser oscillation-arc hybrid welding process is used to weld a 2024-T4 aluminum alloy base material with a thickness of 8 mm. The specific welding process is as follows: the laser power is 5000 W, the welding speed is 20 mm / s, the amplitude is 2.5 mm, the oscillation frequency is 250 Hz, the defocusing amount is 0 mm, the light-wire distance is 4 mm, the wire dry extension is 16 mm, the welding current is 175 A, the voltage is 24 V, the gas flow rate is 20 L / min, and the wire dry extension is 16 mm. The welding wire has good process performance, the arc is stable, and the spatter is small. After welding, no solidification cracks occur, as shown in FIG. 2. The microhardness of the weld is 135 HV, the tensile strength of the joint is 320 MPa, and the joint strength coefficient is 71%. Figure 3

[0055] ​​Example 1 compared to the comparative example, a new type of crack-free high-strength aluminum alloy flux-cored wire obtained joint strength is improved by 22% compared with the joint strength obtained by ER4043.

[0056] The application further provides a welding wire as described above in the welding, and can be used in the welding of aerospace devices.

[0057] Those skilled in the art will easily understand that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A crack-free aluminum alloy flux-cored welding wire, characterized in that: The welding wire comprises a tube and a flux powder filled within the tube. The flux powder comprises the following components in parts by weight: 4-6.8 parts Cu, 0.8-1.2 parts Mg, 0.1-0.6 parts Mn, 0.05-0.4 parts Cr, 0.2-0.5 parts Ti, 0.1-0.25 parts Zr, 2-4 parts composite material, greater than 0 parts and less than 0.1 parts Si, greater than 0 parts and less than 0.1 parts Fe, 1-2 parts TiC, and the balance being Al powder; wherein the composite material is a mixture of zirconium oxide and carbon nanotubes. The zirconium oxide is yttrium-stabilized zirconium oxide powder; the carbon nanotubes are multi-walled carbon nanotubes. The mass ratio of zirconium oxide to carbon nanotubes is (3~5):2; The specific surface area of ​​the zirconium oxide is 5 m². 2 / g, density is 6g / cm³ 3 The purity is greater than 99.9%, and the particle size is 30μm ~ 50μm; The carbon nanotubes have an outer diameter of 30 nm to 50 nm, an inner diameter of 5 nm to 12 nm, a length of 10 μm to 15 μm, and a specific surface area of ​​250 m². 2 / g, density is 0.01g / cm³ 3 The purity is greater than 99% and the particle size is less than 25μm.

2. The crack-free aluminum alloy flux-cored welding wire as described in claim 1, characterized in that: The powder comprises the following components in parts: 6.8 parts Cu, 1 part Mg, 0.4 parts Mn, 0.2 parts Cr, 0.4 parts Ti, 0.2 parts Zr, 3 parts composite material, more than 0 parts and less than 0.1 parts Si, more than 0 parts and less than 0.1 parts Fe, 2 parts nano TiC, and the balance being Al powder.

3. The crack-free aluminum alloy flux-cored welding wire as described in any one of claims 1-2, characterized in that: The tube is made of 1060 pure aluminum strip with a wall thickness of 0.5 mm to 0.8 mm and a width of 14 mm to 16 mm.

4. The crack-free aluminum alloy flux-cored welding wire as described in any one of claims 1-2, characterized in that: The filling rate of the welding wire is 45% to 60%, which is the ratio of the mass of the flux to the sum of the masses of the flux and the aluminum strip.

5. The crack-free aluminum alloy flux-cored welding wire as described in any one of claims 1-2, characterized in that: The particle sizes of copper, magnesium, chromium, manganese, titanium, and zirconium are all 50 μm to 125 μm, while the average particle size of nano-titanium carbide is 40 nm.

6. A method for preparing a crack-free aluminum alloy flux-cored welding wire, characterized in that: The preparation method is used to prepare the crack-free aluminum alloy flux-cored welding wire according to any one of claims 1-5.

7. The application of the crack-free aluminum alloy flux-cored welding wire according to any one of claims 1-5 in welding.

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