Preparation method and application of aluminum alloy welding wire

Abstract

The invention is suitable for the technical field of metal material processing, and provides a preparation method and application of an aluminum alloy welding wire, and the method comprises the following steps: step 1, preparing an aluminum magnesium alloy melt, adding a nucleating agent with a twin crystal structure, and casting into an aluminum magnesium alloy cast ingot; and 2, the prepared cast ingot is subjected to hot extrusion, a wire blank is prepared, and the aluminum alloy welding wire is prepared by adopting multi-pass drawing and gradual fine drawing. The method specially aims at grain boundary regulation and control of the welding joint, and a new thought is provided for preparing the high-strength corrosion-resistant aluminum alloy welding wire. The aluminum alloy welding wire using the method is used for fusion welding of aluminum alloy, and the grain structure of a welded joint contains high-density twin boundaries. Compared with a conventional welding joint, the joint containing the high-density twin boundaries not only has higher hardness, but also can keep good intergranular corrosion resistance in the long-term service process.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material processing, and particularly relates to a preparation method and application of an aluminum alloy welding wire. Background Art

[0002] Aluminum-magnesium alloy filler wire is a commonly used material in laser welding of light structural parts. However, there are two key problems when using it for filler laser welding. One is that during the laser welding process, due to the large local heat input of the laser, magnesium elements will volatilize violently, which leads to a loss of the hardness of the welded joint. The other is that when the joint welded with aluminum-magnesium welding wire is in service at medium and high temperatures for a long time, a large amount of continuous β(Al3Mg2) phases will precipitate at the grain boundaries. When encountering a corrosive environment, this β phase and the aluminum matrix will form a primary battery, resulting in serious intergranular corrosion. The softening behavior and intergranular corrosion behavior at the welded joint are the main factors leading to low service life. Therefore, developing welding filler wires with high strength and intergranular corrosion resistance will be of great significance for further improving the service life of structural parts.

[0003] In recent years, researchers have found that the precipitation of the β phase has a great relationship with the type of grain boundaries. They believe that twin boundaries with low energy and low diffusion coefficient rarely or do not precipitate the β phase. However, due to the high stacking fault energy of aluminum alloys, it is difficult to introduce twin boundaries into aluminum alloys by conventional annealing or deformation processes. Although it has been reported that techniques such as low-temperature plastic deformation and magnetron sputtering can be used to introduce twin boundaries into aluminum alloys, obviously these methods are not applicable to welded joints. Therefore, there is currently a lack of a method to introduce twin boundaries at the welded joint to improve the strength and corrosion resistance of the welded joint. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a preparation method and application of an aluminum alloy welding wire, aiming to solve the problems raised in the above background art.

[0005] The embodiments of the present invention are implemented as follows. A preparation method of an aluminum alloy welding wire includes the following steps:

[0006] Including the following steps:

[0007] Step 1: Prepare an aluminum-magnesium alloy melt, add a nucleating agent with a twin structure, and cast it into an aluminum-magnesium alloy ingot;

[0008] Step 2: Obtain a wire blank from the prepared aluminum-magnesium alloy ingot by hot extrusion, and gradually draw it thinner by multi-pass drawing to obtain an aluminum-magnesium alloy welding wire;

[0009] Among them, the mass percentage of the components of the aluminum alloy welding wire is: magnesium: 3.8 - 5.0%, and the balance is aluminum.

[0010] A further technical solution is that the nucleating agent is TiC, Ti or Cr.

[0011] A further technical solution is that the addition amount of TiC is 0.2-1.0% of the mass of the aluminum-magnesium alloy melt.

[0012] A further technical solution is that it can also be applied to the preparation of aluminum-copper alloy welding wires; the mass percentages of the components of the aluminum alloy welding wire are as follows: copper: 5.0%, and the balance is aluminum; the addition amount of TiC particles is 0.5% of the mass of the aluminum-copper alloy melt.

[0013] Another object of the embodiments of the present invention is an application of an aluminum alloy welding wire. Based on the aluminum alloy welding wire prepared by the above method, the aluminum alloy welding wire is applied to laser welding or argon arc welding of aluminum alloys.

[0014] A further technical solution is that the laser welding process parameters are: welding power is 1.0-3.0 kW, welding speed is 1-20 mm / s, wire feeding speed is 1-30 mm / s, and argon gas flow rate is 15 L / min.

[0015] The present invention provides a method for preparing an aluminum alloy welding wire and its application. The present invention proposes a method for specifically regulating the grain boundaries of welding joints, providing a new idea for preparing high-strength and corrosion-resistant aluminum alloy welding wires. The aluminum alloy welding wire prepared by this method is used for fusion welding of aluminum alloys, and high-density twin boundaries are contained in the grain structure of the welding joint. Compared with conventional welding joints, such joints containing high-density twin boundaries not only have higher hardness but also can maintain good intergranular corrosion resistance during long-term service. Description of the Drawings

[0016] Figure 1 It is an EBSD diagram of the surface of the welding joint of the welding wire prepared in Example 1;

[0017] Figure 2 It is a polarized light metallographic photo of the surface of the welding joint of the welding wire prepared in Example 4;

[0018] Figure 3 It is a polarized light metallographic photo of the surface of the welding joint of the welding wire prepared in Example 5;

[0019] Figure 4 It is an EBSD diagram of the surface of the welding joint of the welding wire prepared in Comparative Example 3;

[0020] Figure 5 It is a hardness distribution diagram of the welding joints of the welding wires prepared in Example 1 and Comparative Example 3;

[0021] Figure 6 It is an SEM diagram of the longitudinal section and surface of the welding joint of the welding wire prepared in Example 1 after immersion corrosion;

[0022] Figure 7 SEM images of the longitudinal section and surface of the welded joint of the welding wire prepared in Comparative Example 3 after immersion corrosion. Detailed implementation manners

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention 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 only used to explain the present invention and are not used to limit the present invention.

[0024] The following describes the specific implementation of the present invention in detail with reference to specific embodiments.

[0025] A method for preparing an aluminum alloy welding wire provided by an embodiment of the present invention includes the following steps:

[0026] Step 1: Prepare an aluminum-magnesium alloy melt, add a nucleating agent with a twin structure, specifically TiC particles, and cast it into an aluminum-magnesium alloy ingot;

[0027] Step 2: Obtain a wire blank by hot extruding the prepared aluminum-magnesium alloy ingot, and gradually draw it thinner by multi-pass drawing to obtain an aluminum-magnesium alloy welding wire.

[0028] As a preferred embodiment of the present invention, the mass percentages of the components of the aluminum alloy welding wire are: magnesium: 3.8-5.0%, and the balance is aluminum; the addition amount of TiC particles is 0.3-1.0% of the mass of the aluminum-magnesium alloy melt.

[0029] In the embodiment of the present invention, TiC contains a twin structure, and it can also be replaced by other nucleating particles containing a twin structure or a quasicrystal, such as carbides, borides or oxides containing a twin structure, quasicrystal intermetallic compounds, such as Ti, Cr. The prepared welding wire can be applied to laser welding and argon arc welding of aluminum alloys.

[0030] As a preferred embodiment of the present invention, the specific steps of the step 1 include:

[0031] Step 1.1: Prepare materials according to the content of each alloy component and place them in a resistance melting furnace, raise the temperature to 720-750 °C to obtain a molten aluminum-magnesium alloy liquid, and then keep it warm for 10-20 minutes;

[0032] Step 1.2: Add an aluminum-based master alloy with a twin structure TiC to the molten aluminum-magnesium alloy liquid, mechanically stir for 2-3 minutes and then perform ultrasonic treatment;

[0033] Step 1.3: Adjust the melt temperature to 695 - 705 °C, keep it static and heat-insulated for 3 - 5 minutes, then add a slag removal agent to the melt, stir for 2 - 3 minutes and then skim the slag. Subsequently, pour the melt into a steel mold and cool it to room temperature to obtain an aluminum-magnesium alloy ingot containing twin TiC particles.

[0034] Among them, the mass fraction of TiC particles in the aluminum-based master alloy is 20 - 40%, and by controlling the mass of the aluminum-based master alloy, the mass fraction of the TiC particles is 0.2 - 1.0%.

[0035] As a preferred embodiment of the present invention, in the step 1.2, the preparation of the aluminum-based master alloy with twin-structured TiC includes the following steps:

[0036] Step a: Weigh aluminum powder, titanium powder and carbon powder in proportion and mix and ball-mill them for 24 - 48 h; among them, the mass ratio of the aluminum powder:titanium powder:carbon powder is equal to 70:24:6.

[0037] Step b: Make the mixed alloy powder into a cylindrical compact, place it in a graphite mold, heat it to 850 - 950 °C in a vacuum environment, keep it warm for 10 minutes and then cool it to room temperature to obtain the aluminum-based master alloy with twin-structured TiC.

[0038] In the embodiment of the present invention, the particle diameter of TiC in the aluminum-based master alloy with twin-structured TiC is 100 - 200 nm.

[0039] As a preferred embodiment of the present invention, the step 2 includes the following specific steps:

[0040] Step 2.1: Hot extrusion treatment;

[0041] Heat the prepared ingot to 350 - 450 °C, and then perform hot extrusion to obtain a wire blank with a diameter of 9 - 10 mm.

[0042] Step 2.2: Cold drawing;

[0043] Adopt the existing cold drawing process to draw the wire blank in multiple passes (drawing - annealing - drawing) to gradually thin it, and obtain a welding wire with a diameter of 1.17 - 1.18 mm through precision scraping.

[0044] In the embodiment of the present invention, another embodiment of the present invention provides an application of an aluminum alloy welding wire. Based on the aluminum alloy welding wire prepared by the above method, apply the aluminum alloy welding wire to aluminum alloy laser welding;

[0045] The laser welding process parameters are: welding power is 1.0 - 3.0 kW, welding speed is 1 - 20 mm / s, wire feeding speed is 1 - 30 mm / s, and argon gas flow rate is 15 L / min.

[0046] The following are several specific embodiments to verify the effectiveness of the present method:

[0047] Embodiment 1: A joint welded with an aluminum - magnesium alloy welding wire added with 0.5% TiC particles. The mass percentages of the components of the aluminum - alloy welding wire are as follows: magnesium: 4.0%, and the balance is aluminum; the addition amount of TiC particles is 0.5% of the mass of the aluminum - magnesium alloy melt. The preparation method includes the following steps:

[0048] Step 1: Prepare an aluminum - magnesium alloy melt, add a TiC particle master alloy with a twin structure, and cast it into an aluminum - magnesium alloy ingot;

[0049] Step 2: Obtain a wire blank by hot - extruding the prepared aluminum - magnesium alloy ingot, and gradually draw it thinner by multi - pass drawing to obtain an aluminum - magnesium alloy welding wire.

[0050] The laser welding process parameters are: welding power is 1.5 kW, welding speed is 10 mm / s, wire feeding speed is 15 mm / s, and argon gas flow rate is 15 L / min.

[0051] The EBSD map of the molten pool surface after welding with an aluminum - magnesium welding wire added with TiC particles having a twin structure is as Figure 1 shown. There are high - density twin boundaries distributed in the molten pool, as shown by the thick black lines in the figure. The overall width of the twin structure is about 550 μm. And the high - magnification EBSD map shows that the width of the twin boundary is about 3 μm. The hardness at the center of the welded joint is 66 HV0.1, as Figure 5 shown. While the hardness at the center of the joint of Comparative Example 3 without TiC is 59 HV0.1. It is proved that adding 0.5% TiC changes the microstructure of the welded joint, forms a large number of twin boundaries, and improves the hardness and corrosion resistance.

[0052] The intergranular corrosion test of the welded joint is carried out according to GB / T 7998 - 2023. Before the test, a heat treatment at 150 °C for 7 days is carried out. This heat treatment process is a common process to simulate the performance change during long - term service, and the purpose is to evaluate the intergranular corrosion sensitivity of the joint after long - term service. The joint does not show intergranular corrosion marks, only pitting corrosion pits with a maximum corrosion depth of 3.2 μm appear, as Figure 6 shown. The above test results prove that the present method can greatly improve the hardness and corrosion resistance of the joint.

[0053] Embodiment 2: A joint welded with an aluminum - magnesium alloy welding wire added with 0.2% TiC particles. The mass percentages of the components of the aluminum - alloy welding wire are as follows: magnesium is 4.7%, and the balance is aluminum; the addition amount of TiC particles is 0.2% of the mass of the aluminum - magnesium alloy melt. It is proved that adding 0.2% TiC can produce twin boundaries, indicating the lower limit of the TiC content at which twins can appear.

[0054] The laser welding process parameters are as follows: the welding power is 1.7 kW, the welding speed is 13 mm / s, the wire feeding speed is 12 mm / s, and the argon gas flow rate is 15 L / min.

[0055] After welding with an aluminum-magnesium alloy welding wire added with 0.2% TiC particles, a large amount of twin structures also appear on the surface of the molten pool. The hardness at the center of the welded joint is 65 HV0.1. After the same heat treatment and corrosion test as in Example 1, no obvious intergranular corrosion traces are shown, and only pitting corrosion pits with a maximum corrosion depth of 4 μm appear.

[0056] Example 3: A joint welded with an aluminum-magnesium alloy welding wire added with 1% TiC particles, and the mass percentages of the components of the aluminum alloy welding wire are as follows: magnesium: 5.0%, and the balance is aluminum; the addition amount of TiC particles is 1% of the mass of the aluminum-magnesium alloy melt.

[0057] The laser welding process parameters are as follows: the welding power is 1.6 kW, the welding speed is 14 mm / s, the wire feeding speed is 14 mm / s, and the argon gas flow rate is 15 L / min.

[0058] After welding with an aluminum-magnesium alloy welding wire added with 1% TiC particles, a large amount of twin structures also appear on the surface of the molten pool. The hardness at the center of the welded joint is 69 HV0.1. After the same heat treatment and corrosion test as in Example 1, no obvious intergranular corrosion traces are shown, and only pitting corrosion pits with a maximum corrosion depth of 4.3 μm appear.

[0059] Example 4: A joint welded with an aluminum-magnesium alloy welding wire added with a nucleating agent with other twin structures, specifically it can be Ti element, and the mass percentages of the components of the aluminum alloy welding wire are as follows: magnesium: 4.8%, and the balance is aluminum; the addition amount of Ti is 1.0% of the mass of the aluminum-magnesium alloy melt. During the melting process, pure titanium or an aluminum-titanium master alloy can be added, and twin boundaries can also be introduced in the same way.

[0060] The laser welding process parameters are as follows: the welding power is 1.6 kW, the welding speed is 14 mm / s, the wire feeding speed is 17 mm / s, and the argon gas flow rate is 15 L / min.

[0061] After welding with an aluminum-magnesium alloy welding wire added with nucleating agent particles with other twin structures, a large amount of twin structures also appear on the surface of the molten pool, as Figure 2 shown. The hardness at the center of the welded joint is 68 HV0.1. After the same heat treatment and corrosion test as in Example 1, no obvious intergranular corrosion is shown, and only pitting corrosion pits with a maximum corrosion depth of 3.9 μm appear.

[0062] Example 5: The joint after welding with an Al-Cu alloy welding wire added with 0.5% TiC particles. The mass percentages of the components of the aluminum alloy welding wire are as follows: copper: 5.0%, and the balance is aluminum; the addition amount of TiC particles is 0.5% of the mass of the Al-Cu alloy melt. It is proved that adding 0.5% TiC can also introduce twin boundaries in the welding wire with other components.

[0063] The laser welding process parameters are as follows: the welding power is 1.2 kW, the welding speed is 11 mm / s, the wire feeding speed is 13 mm / s, and the argon gas flow rate is 15 L / min.

[0064] The surface of the molten pool after welding with an Al-Cu alloy welding wire added with 0.5% TiC particles also shows a large amount of twin structures, as Figure 3 shown. The corrosion performance was not measured because the alloy compositions are different and cannot be compared with the Al-Mg alloy.

[0065] Comparative Example 1: The joint after welding with an Al-Mg alloy welding wire added with 0.1% TiC particles. The mass percentages of the components of the aluminum alloy welding wire are as follows: magnesium: 3.9%, and the balance is aluminum; the addition amount of TiC particles is 0.1% of the mass of the Al-Mg alloy melt. It is proved that adding 0.1% TiC does not show twin boundaries, indicating that when the TiC content is less than the lower limit, twin boundaries do not appear, and only columnar crystals with epitaxial growth are present.

[0066] The laser welding process parameters are as follows: the welding power is 1.3 kW, the welding speed is 15 mm / s, the wire feeding speed is 14 mm / s, and the argon gas flow rate is 15 L / min.

[0067] The surface of the molten pool after welding with an Al-Mg welding wire added with 0.1% TiC particles does not show twin boundaries, and only columnar crystals with epitaxial growth are present. The hardness at the center of the welded joint is 54 HV0.1. After the same heat treatment and corrosion test as in Example 1, obvious intergranular corrosion appears, and the maximum corrosion depth is 17.2 μm.

[0068] Comparative Example 2: The joint after welding with an Al-Mg alloy welding wire added with 2% TiC particles. The mass percentages of the components of the aluminum alloy welding wire are as follows: magnesium: 4.5%, and the balance is aluminum; the addition amount of TiC particles is 2% of the mass of the Al-Mg alloy melt. It is proved that adding 2% TiC does not show twin boundaries, indicating that when the TiC content is greater than the upper limit, twin boundaries do not appear, and only refined equiaxed grains are present.

[0069] The laser welding process parameters are as follows: the welding power is 1.5 kW, the welding speed is 15 mm / s, the wire feeding speed is 14 mm / s, and the argon gas flow rate is 15 L / min.

[0070] After welding with an aluminum-magnesium welding wire added with 2% TiC particles, a large number of equiaxed grains appear on the surface of the molten pool, and no twin structure appears. The hardness at the center of the welded joint is 60 HV0.1. The same heat treatment and corrosion test as in Example 1 are carried out, showing obvious intergranular corrosion, and the maximum corrosion depth is 18.2 μm.

[0071] Comparative Example 3: The joint welded with an aluminum-magnesium alloy welding wire without adding TiC particles, and the mass percentage of the components of the aluminum alloy welding wire is: magnesium: 4.8%, and the balance is aluminum. It is proved that there is no twin boundary in the joint welded with the aluminum-magnesium alloy welding wire without adding TiC particles.

[0072] The laser welding process parameters are: welding power is 1.7 kW, welding speed is 17 mm / s, wire feeding speed is 14 mm / s, and argon gas flow rate is 15 L / min.

[0073] The EBSD map of the surface of the molten pool after welding with an aluminum-magnesium welding wire without adding TiC particles is as Figure 4 shown. After welding, only columnar grains with epitaxial growth are in the molten pool. And most of the distributed are large-angle grain boundaries. The hardness at the center of the welded joint is 58.3 HV0.1, as Figure 5 shown. The same heat treatment and corrosion test as in Example 1 are carried out, showing obvious intergranular corrosion, and the maximum corrosion depth is 23 μm, as Figure 7 shown.

[0074] In summary, when using the aluminum alloy welding wire of the present invention for fusion welding of aluminum alloys, a high density of twin boundaries is contained in the grain structure of the welded joint. Compared with conventional welded joints, this joint containing a high density of twin boundaries not only has higher hardness, but also can maintain good intergranular corrosion resistance during long-term service.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an aluminum alloy welding wire, characterized in that, It includes the following steps: Step 1: Prepare an aluminum-magnesium alloy melt, add a nucleating agent with a twin crystal structure, and cast it into an aluminum-magnesium alloy ingot; Step 2: Obtain a wire blank from the prepared aluminum-magnesium alloy ingot through hot extrusion, and gradually draw it thinner by multi-pass drawing to obtain an aluminum-magnesium alloy welding wire; Among them, the mass percentages of the components of the aluminum alloy welding wire are: magnesium: 3.8 - 5.0%, and the balance is aluminum.

2. The preparation method of the aluminum alloy welding wire according to claim 1, characterized in that, In Step 1, the nucleating agent is TiC, Ti or Cr.

3. The preparation method of the aluminum alloy welding wire according to claim 2, characterized in that, The addition amount of TiC is 0.2 - 1.0% of the mass of the aluminum-magnesium alloy melt.

4. The preparation method of the aluminum alloy welding wire according to claim 2, wherein, It can also be applied to the preparation of aluminum-copper alloy welding wires; the mass percentages of the components of the aluminum alloy welding wire are: copper: 5.0%, and the balance is aluminum; the addition amount of TiC particles is 0.5% of the mass of the aluminum-copper alloy melt.

5. Application of an aluminum alloy welding wire, the aluminum alloy welding wire prepared by the preparation method of the aluminum alloy welding wire according to any one of the above claims 1-3, characterized in that, Apply the aluminum alloy welding wire to aluminum alloy laser welding or argon arc welding.

6. The application of the aluminum alloy welding wire according to claim 5, characterized in that, The laser welding process parameters are: welding power is 1.0 - 3.0 kW, welding speed is 1 - 20 mm / s, wire feeding speed is 1 - 30 mm / s, and argon gas flow rate is 15 L / min.

Images