Aluminum alloy welding method

Abstract

The invention relates to an aluminum alloy welding method, and belongs to the technical field of metal welding. The aluminum alloy welding method comprises the steps that a groove is formed in an aluminum alloy to be welded, the surface of the groove and the surface of the truncated edge of the groove are coated with coating liquid, laser-MIG hybrid welding is conducted, the coating step and the welding step are repeated till a welding seam is filled, and welding is completed; the coating liquid comprises a coating agent and an organic solvent, and the mass of the coating agent accounts for 10-40% of the mass of the organic solvent in percentage by mass; the coating agent comprises potassium tetrafluoroaluminate and nanoparticles, and the nanoparticles are at least one of TiC, TiB2, AlN and TiCN. By the adoption of the welding method, the problem of hot cracking in the fusion welding process of 2xxx, 6xxx and 7xxx aging strengthening type high-strength aluminum alloy can be solved, meanwhile, the width of a heat affected zone can be reduced, and a high-performance high-strength aluminum alloy fusion welding joint is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of metal welding, and in particular to an aluminum alloy welding method. Background Art

[0002] 2xxx, 6xxx and 7xxx are aging-hardened high-strength aluminum alloys with high specific strength and specific stiffness, and are widely used in aerospace, rail transit and automotive fields. However, due to its wide solidification range, hot cracks are easily formed during the solidification process. At present, high-strength aluminum alloy fusion welding often uses welding wires with high Mg (such as ER5356) or high Si (ER4043) content for welding. High Mg or high Si welding wires increase the Mg or Si elements in the molten pool, reduce the solidification range of the weld pool, promote the fluidity of the molten pool, and reduce hot cracking during welding; Patents CN202111047715.9 and CN202110641042.3 use welding wires containing nanoparticles to melt weld high-strength aluminum alloys. The introduced nanoparticles have a refining effect on the molten pool grains, promote the transformation of columnar crystals to equiaxed crystals in the molten pool, and inhibit the formation of hot cracks.

[0003] When welding with high Mg or high Si (ER4043) content welding wire, the original parent metal alloy elements in the molten pool are diluted, which often causes the weld strength to be much lower than the parent metal. Even after heat treatment, the corresponding alloy elements are diluted due to the formation of precipitation, resulting in a decrease in the number of nano-precipitated phases, and the strength is still much lower than the parent metal. When using nanoparticles to weld high-strength aluminum alloys, it is necessary to first prepare aluminum alloy welding wire containing nanoparticles. The preparation process of aluminum welding wire includes ingot preparation, ingot extrusion, drawing, annealing and other processes. Nanoparticles are introduced during the ingot preparation process. Since nanoparticles have a high specific surface area, they are very easy to agglomerate in the aluminum alloy melt. Therefore, the nanoparticles added to the ingot will reduce the elongation of the ingot, resulting in wire breakage during the preparation process of the welding wire, and the welding wire yield is relatively low.

[0004] Therefore, it is urgent to develop a new type of aluminum alloy welding method to simplify the welding process, solve the thermal cracking problem of aging-hardened high-strength aluminum alloy fusion welding process, and prepare high-performance and high-strength aluminum alloy fusion welding joints, which has high practical value. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an aluminum alloy welding method, which solves the problem of thermal cracking during the fusion welding of aging-hardened high-strength aluminum alloys in the prior art, can prepare high-performance and high-strength aluminum alloy fusion welding joints, and has high practical value.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention provides an aluminum alloy welding method, comprising the following steps:

[0008] A groove is formed on the aluminum alloy to be welded, a coating liquid is coated on the groove and the surface of the blunt edge of the groove, laser-MIG composite welding is performed, and the coating and welding steps are repeated until the weld is filled, thereby completing the welding of the aluminum alloy to be welded;

[0009] The coating liquid comprises a coating agent and an organic solvent, and in terms of mass percentage, the mass of the coating agent is 10-40% of the mass of the organic solvent;

[0010] The coating agent comprises potassium tetrafluoroaluminate and nanoparticles, and the nanoparticles are at least one of TiC, TiB2, AlN and TiCN.

[0011] In order to solve the problems in the prior art that the weld strength is much lower than that of the base material and hot cracking is prone to occur, the present invention provides an aluminum alloy welding method: a coating liquid composed of a coating agent and an organic solvent is coated on the welding groove and the blunt edge surface by a coating method, and the high-strength aluminum alloy is welded by a low heat input laser-MIG composite welding technology.

[0012] The coating agent includes potassium tetrafluoroaluminate and specific types of nanoparticles. During the welding process, the coating agent melts and dissolves the oxides on the surface of specific nanoparticles, thereby improving the wettability of the aluminum melt and the nanoparticles in the molten pool, and can prompt the nanoparticles to quickly enter the molten pool and achieve uniform dispersion, ultimately solving the thermal cracking problem during the high-strength aluminum alloy fusion welding process.

[0013] At the same time, under a specific coating liquid ratio, specific nanoparticles can more significantly improve the tensile strength of the weld and solve the problem of low weld strength after welding in the prior art. If the selected nanoparticles are not suitable or the organic solvent ratio in the coating liquid is not suitable, the nanoparticles may not work well during the welding process, agglomerate, or produce thermal cracks, welding failure, or the tensile strength of the joint is significantly reduced, and the strength difference with the parent alloy is too large.

[0014] The aluminum alloy welding method provided by the present invention avoids the complicated process of adding nanoparticles to the ingot and dispersing the nanoparticles in the melt; in addition, the laser-MIG composite welding has low heat input and reduces the width of the heat-affected zone; the present invention can comprehensively realize the hot crack-free, high-performance welding of high-strength aluminum alloys that are prone to hot cracking and aging hardening.

[0015] Preferably, the content of nanoparticles in the coating agent is 10-40% by mass.

[0016] Further preferably, in terms of mass percentage, the content of nanoparticles in the coating agent is 30-40%; and the coating agent accounts for 30-40% of the organic solvent.

[0017] Under the preferred ratio, the tensile strength of the joint after welding using the aluminum alloy welding method of the present invention is further improved.

[0018] Preferably, the organic solvent is at least one of acetone and ethanol.

[0019] Preferably, the coating liquid is prepared by placing the coating agent in an organic solvent for ultrasonic treatment, wherein the ultrasonic treatment time is 10-60 min.

[0020] Preferably, the particle size of the nanoparticles is 5-500 nm.

[0021] Preferably, the nanoparticles are at least one of TiC, AlN and TiCN.

[0022] Preferably, the aluminum alloy has a thickness of 3-10 mm.

[0023] Preferably, the coating liquid is mechanically stirred before each coating, the stirring rate is 30-200 rpm, and the stirring time is 3-30 min.

[0024] Preferably, after each coating, welding is performed after the organic solvent has completely evaporated.

[0025] Preferably, the angle of the groove is 10-45°, and the height of the groove is 1-5 mm.

[0026] Preferably, in the laser-MIG hybrid welding, the composition of the welding wire is the same as the composition of the aluminum alloy to be welded.

[0027] The welding wire used in the present invention has the same composition as the base material, which can avoid the softening problem caused by element dilution.

[0028] Further preferably, the conditions of the laser-MIG hybrid welding are: welding power is 2-10 kW, welding speed is 0.002-0.1 m / min, wire feeding speed is 5-10 m / min, and laser incident inclination angle is 5-15°.

[0029] As a preferred embodiment of the present invention, the conditions of the laser-MIG hybrid welding are: the welding power is 5 kW, the welding speed is 0.1 m / s, the wire feeding speed is 9 m / min, and the laser incident inclination angle is 10°.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] In order to solve the problem of thermal cracking of aging-hardened high-strength aluminum alloys in fusion welding and prepare high-strength aluminum alloy high-performance fusion welding joints, the present invention provides a new aluminum alloy welding method: by combining low-heat input laser-MIG composite welding technology with coating technology, and by optimizing the type of nanoparticles and the ratio of coating agents, the efficient introduction and good dispersion of nanoparticles in the molten pool can be guaranteed, and the complex processes such as the introduction of nanoparticles into ingots and the dispersion of nanoparticles as well as the problems of poor plasticity and wire making difficulties caused by nanoparticles are avoided. The method is simple and easy to operate, with high operability, and can significantly improve the tensile strength of the joint while solving the problem of welding thermal cracking, and has high practical value. DETAILED DESCRIPTION

[0032] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below in conjunction with specific examples. The test methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0033] Example 1

[0034] An embodiment of the aluminum alloy welding method of the present invention comprises the following steps:

[0035] S1. preparing a coating agent: the selected nanoparticles are TiC, the diameter of the nanoparticles is 50 nm, and the nanoparticles are mixed with potassium tetrafluoroaluminate to obtain a coating agent; in terms of mass percentage, the content of the nanoparticles in the coating agent is 40%, and the rest is potassium tetrafluoroaluminate;

[0036] S2. Prepare coating liquid: mix the coating agent with ethanol and perform ultrasonication for 30 minutes; in terms of mass percentage, the mass of the coating agent is 30% of that of the ethanol;

[0037] S3. Pretreatment of the base material: groove the 8mm thick 7075 aluminum alloy plate to be welded, with a groove height of 3mm and a groove angle of 30°; grind the base material and the groove surface, and wipe it clean with alcohol; use a brush to evenly apply the coating agent after ultrasonic treatment on the groove and the blunt edge of the groove;

[0038] S4, welding: after the organic solvent is completely volatilized, multi-layer and multi-pass laser-MIG composite welding is performed on the plate to be welded, and surface treatment and coating liquid are applied before each welding until the weld is filled, thereby completing the welding of the aluminum alloy plate;

[0039] The welding process parameters are as follows: welding power is 5 kW, welding speed is 0.1 m / s, wire feeding speed is 9 m / min, and laser incident angle is 10°.

[0040] Example 2

[0041] An embodiment of the aluminum alloy welding method of the present invention is different from Embodiment 1 only in that the nanoparticles are replaced with TiCN, and the diameter of the nanoparticles is 50 nm.

[0042] Example 3

[0043] An embodiment of the aluminum alloy welding method of the present invention comprises the following steps:

[0044] S1. preparing a coating agent: the selected nanoparticles are AlN, the diameter of the nanoparticles is 50 nm, and the nanoparticles are mixed with potassium tetrafluoroaluminate to obtain a coating agent; in terms of mass percentage, the content of the nanoparticles in the coating agent is 40%, and the rest is potassium tetrafluoroaluminate;

[0045] S2. Prepare coating liquid: mix the coating agent with ethanol and perform ultrasonication for 30 minutes; in terms of mass percentage, the mass of the coating agent is 40% of that of the ethanol;

[0046] The processing method of steps S3-S4 is the same as that of Example 1, and the welding of the aluminum alloy plates is completed.

[0047] Example 4

[0048] An embodiment of the aluminum alloy welding method of the present invention comprises the following steps:

[0049] S1. preparing a coating agent: the selected nanoparticles are AlN, the diameter of the nanoparticles is 50 nm, and the nanoparticles are mixed with potassium tetrafluoroaluminate to obtain a coating agent; in terms of mass percentage, the content of the nanoparticles in the coating agent is 25%, and the rest is potassium tetrafluoroaluminate;

[0050] S2. Prepare coating liquid: mix the coating agent with ethanol and perform ultrasonication for 30 minutes; in terms of mass percentage, the mass of the coating agent is 30% of that of the ethanol;

[0051] The processing method of steps S3-S4 is the same as that of Example 1, and the welding of the aluminum alloy plates is completed.

[0052] Example 5

[0053] An embodiment of the aluminum alloy welding method of the present invention comprises the following steps:

[0054] S1. preparing a coating agent: the selected nanoparticles are AlN, the diameter of the nanoparticles is 50 nm, and the nanoparticles are mixed with potassium tetrafluoroaluminate to obtain a coating agent; in terms of mass percentage, the content of the nanoparticles in the coating agent is 40%, and the rest is potassium tetrafluoroaluminate;

[0055] S2. Prepare coating liquid: mix the coating agent with ethanol and perform ultrasonication for 30 minutes; in terms of mass percentage, the mass of the coating agent is 25% of that of the ethanol;

[0056] The processing method of steps S3-S4 is the same as that of Example 1, and the welding of the aluminum alloy plates is completed.

[0057] Example 6

[0058] An embodiment of the aluminum alloy welding method of the present invention is different from Embodiment 3 only in that: in step S2, the mass of the coating agent is 30% of the ethanol in terms of mass percentage.

[0059] Comparative Example 1

[0060] The aluminum alloy welding method in Comparative Example 1 comprises the following steps:

[0061] S1. Prepare a coating agent: select B4C nanoparticles with a diameter of 50 nm, mix the nanoparticles with potassium tetrafluoroaluminate to obtain a coating agent; in terms of mass percentage, the content of the nanoparticles in the coating agent is 30%, and the rest is potassium tetrafluoroaluminate;

[0062] S2. Prepare coating liquid: mix the coating agent with ethanol and perform ultrasonication for 30 minutes; in terms of mass percentage, the mass of the coating agent is 10% of the mass of the ethanol;

[0063] The processing method of steps S3-S4 is the same as that of embodiment 1.

[0064] Comparative Example 2

[0065] The aluminum alloy welding method in Comparative Example 2 comprises the following steps:

[0066] S1. preparing a coating agent: the selected nanoparticles are AlN, the diameter of the nanoparticles is 50 nm, and the nanoparticles are mixed with potassium tetrafluoroaluminate to obtain a coating agent; in terms of mass percentage, the content of the nanoparticles in the coating agent is 0.2%, and the rest is potassium tetrafluoroaluminate;

[0067] S2. Prepare coating liquid: mix the coating agent with ethanol and perform ultrasonication for 30 minutes; in terms of mass percentage, the mass of the coating agent is 5% of the ethanol;

[0068] The processing method of steps S3-S4 is the same as that of embodiment 1.

[0069] Comparative Example 3

[0070] The aluminum alloy welding method in Comparative Example 3 comprises the following steps:

[0071] S1. preparing a coating agent: the selected nanoparticles are WC, the diameter of the nanoparticles is 50 nm, and the nanoparticles are mixed with potassium tetrafluoroaluminate to obtain a coating agent; in terms of mass percentage, the content of the nanoparticles in the coating agent is 40%, and the rest is potassium tetrafluoroaluminate;

[0072] S2. Prepare coating liquid: mix the coating agent with ethanol and perform ultrasonication for 30 minutes; in terms of mass percentage, the mass of the coating agent is 50% of that of the ethanol;

[0073] The processing method of steps S3-S4 is the same as that of embodiment 1.

[0074] Comparative Example 4

[0075] The aluminum alloy welding method in Comparative Example 4 comprises the following steps:

[0076] S1. preparing a coating agent: the selected nanoparticles are AlN, the diameter of the nanoparticles is 50 nm, and the nanoparticles are mixed with potassium hexafluoroaluminate to obtain a coating agent; in terms of mass percentage, the content of the nanoparticles in the coating agent is 40%, and the rest is potassium tetrafluoroaluminate;

[0077] S2. Prepare coating liquid: mix the coating agent with ethanol and perform ultrasonication for 30 minutes; in terms of mass percentage, the mass of the coating agent is 30% of that of the ethanol;

[0078] The processing method of steps S3-S4 is the same as that of embodiment 1.

[0079] Effect example

[0080] In order to explore the welding effect of the aluminum alloy welding method provided by the present invention, the tensile strength of the welding joints of the embodiment and the comparative example was tested, and the state of the weld after welding was observed. The results are shown in Table 1.

[0081] Table 1 Welding effect of aluminum alloy welding method of embodiment and comparative example

[0082]

[0083] It can be seen from Table 1 that the aluminum alloy welding method defined in the present invention in the embodiments achieves successful welding of the 7075 high-strength aluminum alloy that is prone to thermal cracking, and the joint has no thermal cracks, and the tensile strength of the obtained joint is above 380MPa. In terms of mass percentage, when the content of nanoparticles in the coating agent is 30-40%, and the coating agent accounts for 30-40% of the organic solvent, the tensile strength of the joint is higher, and can stably reach more than 400MPa, and the comprehensive performance after welding is better; when the nanoparticles used are AlN, the tensile strength of the joint after welding can reach the highest.

[0084] In Comparative Examples 1 and 3, nanoparticles outside the scope of the present invention are used to prepare the coating agent. Even if the proportion of nanoparticles and the ratio of coating agent to organic solvent are appropriate, it may cause nanoparticle agglomeration and significantly reduce the tensile strength of the joint, resulting in poor overall effect.

[0085] It can be seen from the comparison between Comparative Example 2 and the Example that when the nanoparticles defined in the present invention are used, when the proportion of the nanoparticles and the ratio of the coating agent to the organic solvent are outside the defined range of the present invention, welding failure and thermal cracking will occur.

[0086] In Comparative Example 4, potassium tetrafluoroaluminate in the coating agent was replaced with potassium hexafluoroaluminate. Although successful welding without thermal cracks could be achieved, the tensile strength of the joint decreased.

[0087] In summary, the aluminum alloy welding method provided by the present invention is simple to operate and has high feasibility. It is suitable for laser-MIG composite additive manufacturing of high-strength aluminum alloys, solves the problem of thermal cracking in the fusion welding process of aging-hardened high-strength aluminum alloys in the prior art, and reduces the width of the heat-affected zone. It can prepare high-performance and high-strength aluminum alloy fusion welding joints and has high practical value.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for welding aluminum alloy, characterized in that: The following steps are involved: A groove is formed on the aluminum alloy to be welded, a coating liquid is coated on the groove and the surface of the blunt edge of the groove, laser-MIG composite welding is performed, and the coating and welding steps are repeated until the weld is filled, thereby completing the welding of the aluminum alloy to be welded; The coating liquid comprises a coating agent and an organic solvent, and in terms of mass percentage, the mass of the coating agent is 10-40% of the mass of the organic solvent; The coating agent comprises potassium tetrafluoroaluminate and nanoparticles, and the nanoparticles are at least one of TiC, TiB2, AlN and TiCN.

2. The aluminum alloy welding method according to claim 1, characterized in that: In terms of mass percentage, the content of nanoparticles in the coating agent is 10-40%.

3. The aluminum alloy welding method according to claim 1, characterized in that: The organic solvent is at least one of acetone and ethanol.

4. The aluminum alloy welding method according to claim 1, characterized in that: The coating liquid is prepared by placing the coating agent in an organic solvent for ultrasonic treatment, wherein the ultrasonic treatment time is 10-60 minutes.

5. The aluminum alloy welding method according to claim 1, characterized in that: The particle size of the nanoparticles is 5-500 nm.

6. The aluminum alloy welding method according to claim 1, characterized in that: The nanoparticles are at least one of TiC, AlN and TiCN.

7. The aluminum alloy welding method according to claim 1, characterized in that: The coating liquid is mechanically stirred before each coating, the stirring rate is 30-200 rpm, and the stirring time is 3-30 min.

8. The aluminum alloy welding method according to claim 1, characterized in that: The angle of the groove is 10-45°, and the height of the groove is 1-5 mm.

9. The aluminum alloy welding method according to claim 1, characterized in that: In the laser-MIG hybrid welding, the composition of the welding wire is the same as the composition of the aluminum alloy to be welded.

10. The aluminum alloy welding method according to claim 9, characterized in that: The conditions of the laser-MIG hybrid welding are: welding power of 2-10 kW, welding speed of 0.002-0.1 m / min, wire feeding speed of 5-10 m / min, and laser incident inclination angle of 5-15°.

Images