Zn-Al series brazing material for aluminum-copper welding and preparation method and application of Zn-Al series brazing material

Abstract

The invention discloses a Zn-Al series brazing material for aluminum-copper welding and a preparation method and application of the Zn-Al series brazing material, and belongs to the technical field of brazing materials. The brazing material comprises the following chemical components in percentage by weight: 9%-25% of Al, 1%-5% of Ag, 1%-4% of Cu, 1%-4.5% of Si, 0.003%-1% of Mg, 0.05%-1% of Sr, 0.05%-1% of Ti, 0.05%-1.5% of Ni, 0.02%-0.15% of Sc and the balance of Zn. The Zn-Al series brazing material is used for brazing welding of Al and Cu, and a welded joint with high shear strength and high corrosion resistance can be obtained. The preparation method comprises the steps that raw materials prepared according to the preset chemical composition of the brazing material are subjected to vacuum melting and pouring, and an alloy ingot is obtained; and the alloy cast ingot is subjected to double-roller rapid solidification. The method is simple, easy to operate and suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of brazing materials, and in particular to a Zn-Al series brazing material for aluminum-copper welding, and a preparation method and application thereof. Background Art

[0002] Copper and aluminum, due to their excellent electrical and thermal conductivity, are widely used in fields such as electricity transmission, heat exchange, and daily necessities. However, aluminum's electrical and thermal conductivity are inferior to copper's. Furthermore, in terms of production cost, aluminum's market price is one-third that of copper, and its density is also only one-third. Without considering mechanical and electrical properties, the material cost of an aluminum component is one-ninth that of an equivalent copper component. Consequently, many industries are adopting the "aluminum-to-copper" technique to reduce production costs. Furthermore, this technique helps alleviate the scarcity of copper resources. However, this technique presents challenges with aluminum / copper connections. Due to the need for electrical and thermal conductivity, as well as sealing, welding is often used to achieve reliable aluminum / copper connections. Fusion welding is known to produce brittle aluminum / copper joints, exhibiting low strength and prone to cracking. Pressure welding, which includes cold pressure welding, friction welding, explosion welding, and flash butt welding, offers high strength and excellent performance, leading to its widespread application. Brazing, under strict control of the filler metal composition and brazing process, can also produce excellent aluminum / copper joints. Compared to pressure welding, brazing offers lower production costs, greater adaptability to complex workpieces, and the ability to produce parts online, which pressure welding lacks. Therefore, brazing is a promising aluminum / copper joining technology.

[0003] Filler metal selection is a key issue in aluminum / copper brazing technology. Currently, commonly used filler metals for aluminum / copper brazing include Al-Si, Zn-Sn, Zn-Al, and Sn-Zn. Al-Si filler metals have low joint strength for aluminum / copper brazing and a high melting point, requiring welding temperatures as high as 590°C to 610°C. The aluminum base metal is prone to overburning during high-frequency brazing or flame brazing. Zn-Sn filler metals also have low joint strength, are not corrosion-resistant, and are prone to pore formation in reactive fluxes. Sn-Zn filler metals have attracted widespread attention from researchers due to their low eutectic temperature, high strength, and excellent wettability for aluminum and copper. Sn-Zn-based filler metals can achieve shear strengths exceeding 40 MPa when used for aluminum / copper soft soldering, but they can flake off after immersion in water or salt water for 1 to 4 weeks, and their poor corrosion resistance also limits their practical application. Compared to Sn-Zn-based brazing filler metals, Zn-Al-based brazing filler metals offer significantly better corrosion resistance and a significantly lower melting point than Al-Si-based filler metals, making them suitable for the most common brazing methods used in the refrigeration industry. However, the current problem with various Zn-Al-based brazing filler metals on the market is their low brazing strength, with joint shear strengths of only around 40MPa to 50MPa, hindering joint reliability.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The object of the present invention is to provide a Zn-Al brazing material for aluminum-copper welding and a preparation method and application thereof, so as to solve or improve the above-mentioned technical problems.

[0006] The present invention can be achieved like this:

[0007] In a first aspect, the present invention provides a Zn-Al brazing material for aluminum-copper welding. The chemical composition of the Zn-Al brazing material includes, by weight percentage, 9% to 25% Al, 1% to 5% Ag, 1% to 4% Cu, 1% to 4.5% Si, 0.003% to 1% Mg, 0.05% to 1% Sr, 0.05% to 1% Ti, 0.05% to 1.5% Ni and 0.02% to 0.15% Sc, with the balance being Zn.

[0008] In an optional embodiment, the chemical composition includes 10% to 20% Al, 2.0% to 4.0% Ag, 2.0% to 3.5% Cu, 2.0% to 3.5% Si, 0.01% to 0.05% Mg, 0.1% to 0.5% Sr, 0.1% to 0.5% Ti, 0.1% to 1.0% Ni and 0.03% to 0.1% Sc, with the balance being Zn.

[0009] In an optional embodiment, the Zn—Al brazing material for aluminum-copper welding is in the form of a thin strip.

[0010] In an optional embodiment, the Zn—Al brazing material for aluminum-copper welding has a thickness of 80 μm to 400 μm and a width of 5 mm to 50 mm.

[0011] In an optional embodiment, the Zn—Al brazing material for aluminum-copper welding has a thickness of 100 μm to 200 μm and a width of 10 mm to 30 mm.

[0012] In a second aspect, the present invention provides a method for preparing a Zn-Al brazing material for aluminum-copper welding as described in any of the aforementioned embodiments, comprising the following steps: vacuum melting and pouring raw materials prepared according to a preset chemical composition of the Zn-Al brazing material for aluminum-copper welding to obtain an alloy ingot; and subjecting the alloy ingot to double-roll rapid solidification.

[0013] In an optional embodiment, vacuum melting and pouring includes: -3 Pa~8×10 -3 The vacuum melting furnace is filled with inert gas for protection and heated to 550°C to 600°C. The raw materials are heated to a molten state and kept warm for 20min to 30min, and then poured to obtain alloy ingots.

[0014] In an optional embodiment, the twin-roll rapid solidification includes: remelting the alloy ingot and keeping it warm to obtain a remelt; spraying the remelt through a nozzle under the action of inert gas pressure into the gap between two spaced-apart and relatively rotating rollers, so that the remelt begins to cool and solidify rapidly from the roller surface to form a stable solidified shell; under the action of the friction force of the roller surface of the continuously rotating roller, the solidified shell moves downward to the minimum gap to form a thin strip.

[0015] In an optional embodiment, the alloy ingot is further cut and polished before the twin-roll rapid solidification is performed.

[0016] In an optional embodiment, the holding time after remelting is 5 min to 10 min; the injection pressure of the inert gas is 0.02 MPa to 0.07 MPa, the diameter of the nozzle is 1 mm to 2 mm, and the roller speed is 200 r / min to 600 r / min.

[0017] In a third aspect, the present invention provides use of the Zn—Al based brazing material for aluminum-copper welding according to any one of the aforementioned embodiments in aluminum-copper brazing.

[0018] In a fourth aspect, the present invention provides an aluminum-copper joint, which is obtained by brazing an aluminum alloy and a copper material, and the solder used in the brazing process is the Zn-Al series brazing material for aluminum-copper welding according to any of the aforementioned embodiments.

[0019] In an optional embodiment, the brazing is performed by high-frequency induction brazing, the brazing flux is CsF-AlF3 brazing flux, the welding current is 25A to 40A, the brazing time is 25s to 35s, and the brazing gap is 0.1mm to 0.3mm.

[0020] The beneficial effects of the present invention include:

[0021] The Zn-Al brazing material for aluminum-copper welding provided by the present invention utilizes a specific raw material combination and is suitable for welding various types of aluminum alloys and copper. Its welding performance surpasses the bonding strength of widely used ZnAl, ZnSn, ZnSi, and SnZn brazing filler metals on the market, resulting in welded joints with high shear strength and corrosion resistance, satisfying its industrial application. The Zn-Al brazing material is simple to prepare, easy to operate, and suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a schematic diagram of the welding assembly of aluminum alloy and copper in the application example;

[0024] Figure 2 This is a microstructure photograph of the weldment joint after welding the weldment using the Zn-Al brazing material provided in Example 1 in the application example;

[0025] Figure 3 This is a microstructure photograph of the weldment joint after welding the weldment using the Zn-Al brazing material provided in Example 2 in the application example;

[0026] Figure 4 This is a microstructure photograph of the weldment joint after welding the weldment using the Zn-Al brazing material provided in Example 3 in the application example;

[0027] Figure 5 The microstructure photograph of the weld joint after welding the weldment using the Zn-Al series brazing material provided in Example 4 in the application example. DETAILED DESCRIPTION

[0028] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0029] The following is a detailed description of a Zn-Al brazing material provided by the present invention, its preparation method and application.

[0030] The present invention provides a Zn-Al series brazing material for aluminum-copper welding. Calculated by weight percentage, the chemical composition of the Zn-Al series brazing material includes 9% to 25% of Al, 1% to 5% of Ag, 1% to 4% of Cu, 1% to 4.5% of Si, 0.003% to 1% of Mg, 0.05% to 1% of Sr, 0.05% to 1% of Ti, 0.05% to 1.5% of Ni and 0.02% to 0.15% of Sc, with the balance being Zn.

[0031] Among them, the Al content can be 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24% or 25%, etc., or it can be other values ​​within the range of 9% to 25%.

[0032] The Ag content may be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, or other values ​​within the range of 1% to 5%.

[0033] The Cu content may be 1%, 1.5%, 2%, 2.5%, 3%, 3.5% or 4%, or other values ​​within the range of 1% to 4%.

[0034] The Si content may be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, or other values ​​within the range of 1% to 4.5%.

[0035] The Mg content may be 0.003%, 0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8% or 1%, or other values ​​within the range of 0.003% to 1%.

[0036] The Sr content may be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, etc., or other values ​​within the range of 0.05% to 1%.

[0037] The Ti content may be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, etc., or other values ​​within the range of 0.05% to 1%.

[0038] The Ni content can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%, etc., or other values ​​within the range of 0.05% to 1.5%.

[0039] The Sc content may be 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14% or 0.15%, etc., or other values ​​within the range of 0.02% to 0.15%.

[0040] In some preferred embodiments, the chemical composition of the Zn-Al brazing material includes 10% to 20% Al, 2.0% to 4.0% Ag, 2.0% to 3.5% Cu, 2.0% to 3.5% Si, 0.01% to 0.05% Mg, 0.1% to 0.5% Sr, 0.1% to 0.5% Ti, 0.1% to 1.0% Ni and 0.03% to 0.1% Sc, with the balance being Zn.

[0041] It should be noted that the inventors added Cu, Si, Ag, Mg, Ni, Ti, Sr and rare earth element Sc to the commercial Zn-Al solder to form a new type of ZnAl solder, which improves the spreadability and brazing strength in aluminum-copper brazing and ensures the corrosion resistance of the joint.

[0042] The Cu element contained in the Zn-Al brazing material can increase the wettability of the brazing filler metal on the Al substrate. The addition of the Cu element can also improve the mechanical properties of the aluminum-copper brazed joint. The addition of the Ag element can reduce the size of the CuAl phase in the weld of the aluminum-copper brazed joint, thereby improving the mechanical properties of the brazed joint. The addition of the Sc element can precipitate the Al3Sc dispersed phase during the brazing process, which can effectively prevent recrystallization. The Al3Sc itself is smaller and more uniform in size, which can effectively refine the grains. In addition, Sc can also improve the corrosion resistance of the joint. The Si element can promote the precipitation of Al in the weld when the brazing filler metal condenses, thereby reducing the formation and growth of brittle compounds of CuAl2 and Cu3Al2, and reducing the thickness of the brittle compound layer at the interface between the weld and copper. The Ti element, as a grain refiner for zinc-aluminum alloys, can refine the grains of the weld and interface structure, thereby improving the mechanical properties of the joint. The addition of a small amount of Mg can not only reduce the melting temperature of the brazing filler metal, but also form fine CuMgAl2 and Mg2Si intermetallic compounds in the brazing filler metal structure, so that the joint has higher tensile strength. The addition of trace amounts of Sr can increase the electrode potential of the solder and improve its corrosion resistance. The addition of Ni improves the solder's oxidation resistance and corrosion resistance.

[0043] As mentioned above, the Zn-Al brazing material provided by the present invention has a relatively low melting temperature (about 480°C, which is nearly 100°C lower than the melting point of the Al-Si eutectic brazing material). When used in conjunction with the low-melting-point, non-corrosive CsF-AlF3 brazing flux (melting point of about 471°C) for brazing low-melting-point aluminum alloys, the joints can obtain very high brazing strength and good corrosion resistance after welding.

[0044] In some optional embodiments, the Zn-Al brazing material for aluminum-copper welding is in the form of a thin strip. The thin strip alloy material has a better welding effect during welding.

[0045] The thickness of the Zn-Al brazing material for aluminum-copper welding can be 80 μm to 400 μm, such as 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 250 μm, 280 μm, 300 μm, 320 μm, 350 μm, 380 μm, or 400 μm, or other values ​​within the range of 80 μm to 400 μm. In some preferred embodiments, the thickness of the Zn-Al brazing material for aluminum-copper welding can be 100 μm to 200 μm.

[0046] The width of the Zn-Al brazing material for aluminum-copper welding can be 5 mm to 50 mm, such as 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, or 50 mm, or other values ​​within the range of 5 mm to 50 mm. In some preferred embodiments, the width of the Zn-Al brazing material for aluminum-copper welding can be 10 mm to 30 mm.

[0047] Accordingly, the present invention provides a method for preparing the above-mentioned Zn-Al brazing material for aluminum-copper welding, comprising the following steps: vacuum melting and pouring raw materials prepared according to a preset chemical composition of the Zn-Al brazing material for aluminum-copper welding to obtain an alloy ingot; and subjecting the alloy ingot to double-roll rapid solidification.

[0048] In some optional embodiments, prior to vacuum melting and pouring, the raw materials may be sequentially subjected to acid washing for 25 to 35 seconds, alkaline washing for 25 to 35 seconds, and water washing for 10 to 15 seconds. Acid washing removes oxides and dirt from the raw material surface, alkaline washing removes grease from the raw material surface, and water washing removes insoluble impurities and dirt from the raw material surface.

[0049] In the present invention, vacuum melting and pouring can be carried out in a vacuum melting furnace to ensure that the composition of the prepared alloy ingot is uniform.

[0050] In some optional embodiments, vacuum melting and pouring includes: -3 Pa~8×10 -3 The vacuum melting furnace is filled with inert gas for protection and heated to 550°C to 600°C. The raw materials are heated to a molten state and kept warm for 20min to 30min, and then poured to obtain alloy ingots.

[0051] For example, the vacuum degree of the smelting furnace can be 4×10 -3 Pa, 4.5×10 -3 Pa, 5×10 -3 Pa, 5.5×10 - 3 Pa, 6×10-3 Pa, 6.5×10 -3 Pa, 7×10 -3 Pa, 7.5×10 -3 Pa or 8×10 -3 Pa, etc., can also be 4×10 -3 Pa~8×10 -3 Other values ​​within the range.

[0052] Filling with inert gas protection can prevent the molten liquid from splashing during the smelting process.

[0053] The heating temperature may be 550°C, 555°C, 560°C, 565°C, 570°C, 575°C, 580°C, 585°C, 590°C, 595°C or 600°C, or other values ​​within the range of 550°C to 600°C.

[0054] The holding time in the molten state can be 20 min, 22 min, 24 min, 26 min, 28 min or 30 min, etc., or other values ​​within the range of 20 min to 30 min.

[0055] In some optional embodiments, the twin-roll rapid solidification includes: remelting the alloy ingot and keeping it warm to obtain a remelt; spraying the remelt through a nozzle under the action of inert gas pressure into the gap between two spaced-apart and relatively rotating rollers to establish a molten pool, and the remelt begins to cool and solidify rapidly from the roller surface to form a stable solidified shell; under the action of the friction force of the roller surface of the continuously rotating roller, the two solidified shells move downward to the minimum gap and meet to form a thin strip.

[0056] Illustratively, the holding time after remelting may be 5 min to 10 min, such as 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, or may be other values ​​within the range of 5 min to 10 min.

[0057] The injection pressure of the inert gas can be 0.02 MPa to 0.07 MPa, such as 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, 0.06 MPa or 0.07 MPa, or other values ​​within the range of 0.02 MPa to 0.07 MPa. In some preferred embodiments, the injection pressure of the inert gas can be 0.04 MPa to 0.06 MPa.

[0058] The diameter of the nozzle may be 1 mm to 2 mm, such as 1 mm, 1.5 mm or 2 mm, or other values ​​within the range of 1 mm to 2 mm. In some preferred embodiments, the diameter of the nozzle may be 1.5 mm to 2 mm.

[0059] The roller speed may be 200 r / min to 600 r / min, such as 200 r / min, 250 r / min, 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, 550 r / min or 600 r / min, or other values ​​within the range of 200 r / min to 600 r / min. In some preferred embodiments, the roller speed may be 300 r / min to 400 r / min.

[0060] In some optional embodiments, the alloy ingot may be cut and ground before being subjected to twin-roll rapid solidification.

[0061] Cutting primarily involves shaping the alloy ingot into bars of appropriate size. The bars are then sandblasted to remove surface oil and dirt. Ultrasonic cleaning with alcohol and acetone is then performed to remove surface oil and dirt. The cleaned bars are then processed through a twin-roll rapid solidification process to form the bars. This treatment leaves the bars free of oxides, residue, and other impurities, enabling rapid melting in the subsequent twin-roll rapid solidification process.

[0062] In addition, the present invention also provides the application of the above-mentioned Zn-Al series brazing material for aluminum-copper brazing in aluminum-copper brazing.

[0063] Correspondingly, the present invention also provides an aluminum-copper joint, which is obtained by brazing an aluminum alloy and a copper material, and the solder used in the brazing process is the above-mentioned Zn-Al series brazing material for aluminum-copper welding.

[0064] In some optional embodiments, brazing is performed using high-frequency induction brazing, with a CsF-AlF3 brazing flux, a welding current of 25A to 40A (e.g., 25A, 30A, 35A, or 40A), a brazing time of 25s to 35s (e.g., 25s, 28s, 30s, 32s, or 35s), and a brazing gap of 0.1mm to 0.3mm (e.g., 0.1mm, 0.15mm, 0.2mm, 0.25mm, or 0.3mm). Air cooling is performed after welding.

[0065] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0066] Example 1

[0067] This embodiment provides a Zn-Al brazing material for aluminum-copper welding, and the preparation method thereof includes:

[0068] S1: The raw material is prepared by weight percentage according to Al 20%, Ag 3.0%, Cu 3.0%, Si 2.0%, Mg 0.03%, Sr 0.1%, Ti 0.2%, Ni 0.5%, Sc 0.1%, and the balance is Zn.

[0069] Among them, Si element is added in the form of Al-Si alloy, Cu element is added in the form of Zn-Cu alloy, Sr element is added in the form of Al-Sr alloy, Ti element is added in the form of Al-Ti alloy, and Al, Zn, Mg, Ni, Ag and Sc are added in the form of single substances.

[0070] S2: The raw materials are acid-washed for 30 seconds, alkaline-washed for 30 seconds, and water-washed for 10 seconds to remove surface oxide film and impurities.

[0071] S3: Place the cleaned raw materials in an induction vacuum melting furnace and evacuate the furnace to a vacuum of 5×10 -3 After Pa, N2 gas is filled in for atmosphere protection, and then heated to 600℃. After all the raw materials are melted, the temperature is kept for 20min, and then poured into the melting furnace to obtain alloy ingots.

[0072] S4: The alloy ingot is mechanically cut, the surface oxide scale and residue are polished, and then placed into the melt container of the double-roller belt spinning machine.

[0073] S5: The alloy ingot is remelted in a N2 gas protective atmosphere. After the alloy is completely melted, it is kept warm for 6 minutes to obtain a remelt; then a strip is spun in the following manner: the remelt is sprayed through a nozzle under the action of inert gas pressure into the gap between two spaced and relatively rotating rollers, so that the remelt begins to cool and solidify rapidly from the roller surface to form a stable solidified shell; under the action of the friction force of the roller surface of the continuously rotating roller, the solidified shell moves downward to the smallest gap to form a thin strip, thereby obtaining a Zn-Al brazing material for aluminum-copper welding.

[0074] When the strip is spun, the roller speed is set to 400 r / min, the initial roller gap is 0.06 mm, the diameter of the nozzle (single hole) is 1.5 mm, and the injection pressure of the N2 gas for spraying the melt is 0.06 MPa.

[0075] Example 2

[0076] The difference between this embodiment and embodiment 1 is that the chemical composition of the Zn-Al brazing material for aluminum-copper welding includes 15% Al, 2.5% Ag, 3% Cu, 2.5% Si, 0.08% Mg, 0.2% Sr, 0.2% Ti, 0.1% Ni and 0.15% Sc, with the balance being Zn.

[0077] Example 3

[0078] The difference between this embodiment and embodiment 1 is that the chemical composition of the Zn-Al brazing material for aluminum-copper welding includes 10% Al, 3% Ag, 3% Cu, 3% Si, 0.1% Mg, 0.3% Sr, 0.4% Ti, 0.5% Ni and 0.12% Sc, with the balance being Zn.

[0079] Example 4

[0080] The difference between this embodiment and embodiment 1 is that the chemical composition of the Zn-Al brazing material for aluminum-copper welding includes 15% Al, 3.5% Ag, 3% Cu, 2% Si, 0.08% Mg, 0.1% Sr, 0.2% Ti, 0.2% Ni and 0.1% Sc, with the balance being Zn.

[0081] Example 5

[0082] The difference between this embodiment and embodiment 1 is that the chemical composition of the Zn-Al brazing material for aluminum-copper welding includes 15% Al, 1.0% Ag, 3% Cu, 1.0% Si, 0.08% Mg, 0.08% Sr, 0.2% Ti, 0.1% Ni and 0.15% Sc, with the balance being Zn.

[0083] Example 6

[0084] The difference between this embodiment and embodiment 1 is that the chemical composition of the Zn-Al brazing material for aluminum-copper welding includes 15% Al, 5.0% Ag, 1.0% Cu, 4.5% Si, 1.0% Mg, 0.08% Sr, 0.2% Ti, 0.1% Ni and 0.15% Sc, with the balance being Zn.

[0085] Comparative Example 1

[0086] The difference between this comparative example and Example 1 is that the chemical composition of the Zn-Al brazing material for aluminum-copper welding includes 20% Al, 3% Cu, 3% Si, 0.03% Mg, 0.1% Sr, 0.2% Ti, 0.5% Ni and 0.06% Sc, with the balance being Zn.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 1 is that the chemical composition of the Zn-Al brazing material for aluminum-copper welding includes 15% Al, 2.5% Ag, 3% Si, 0.08% Mg, 0.2% Sr, 0.2% Ti, 0.1% Ni and 0.06% Sc, with the balance being Zn.

[0089] Comparative Example 3

[0090] The difference between this comparative example and Example 1 is that the chemical composition of the Zn-Al brazing material for aluminum-copper welding includes 10% Al, 2.5% Ag, 2.5% Cu, 2.5% Si, 0.1% Mg, 0.3% Sr, 0.4% Ti and 0.5% Ni, with the balance being Zn.

[0091] Comparative Example 4

[0092] The difference between this comparative example and Example 1 is that the chemical composition of the Zn-Al brazing material for aluminum-copper welding includes 10% Al, 2.5% Ag, 0.1% Mg, 0.3% Sr, 0.1% Sc, and the balance is Zn.

[0093] Comparative Example 5

[0094] The difference between this comparative example and Example 1 is that the chemical composition of the Zn-Al brazing material for aluminum-copper welding includes 15% Al and 3.3% Ag, with the balance being Zn.

[0095] Comparative Example 6

[0096] The difference between this comparative example and Example 1 is that the chemical composition of the brazing material for aluminum-copper welding includes 12% Si and the balance is Al.

[0097] Application Examples

[0098] The following schematic diagrams of the welding assembly of aluminum alloy and copper are as follows: Figure 1 shown.

[0099] The brazing materials prepared in Examples 1 to 3, Examples 5 to 6, and Comparative Examples 1 to 5 were all applied to aluminum-copper welding in the following manner: the prepared thin strip Zn-Al brazing material was applied to high-frequency induction brazing of 1060 aluminum alloy and T2 copper, and the welding process parameters were set as follows: the brazing flux was CsF-AlF3 brazing flux, the welding current was 30 A, the brazing time was 15 s, the brazing gap was 0.15 mm, and air cooling was performed after welding.

[0100] The brazing material prepared in Example 4 was applied to aluminum-copper welding in the following manner: it was used for high-frequency induction brazing of 6061 aluminum alloy and T2 copper, and the welding process parameters were set as follows: the brazing flux was CsF-AlF3 brazing flux, the welding current was 30A, the brazing time was 15s, the brazing gap was 0.15mm, and air cooling was performed after welding.

[0101] The brazing material prepared in Comparative Example 6 was applied to aluminum-copper welding in the following manner: it was used for high-frequency induction brazing of 6061 aluminum alloy and T2 copper, and the welding process parameters were set as follows: the brazing flux was KF-AlF3 brazing flux, the welding current was 35A, the brazing time was 15s, the brazing gap was 0.15mm, and air cooling was performed after welding.

[0102] The brazed welds of Examples 1-6 and Comparative Examples 1-6 were subjected to joint strength tests before and after corrosion. The joint corrosion test was conducted by immersing the welds in artificial seawater for 30 days. The artificial seawater consisted of water containing 2.7 wt% NaCl, 0.1 wt% KCl, 0.1 wt% CaCl2, and 0.6 wt% MgCl2 at a temperature of 20°C ± 3°C.

[0103] The mechanical properties of the joints before and after corrosion were tested on a universal tensile machine with a tensile rate of 1 mm / min. The instrument used was CMT5105 from MTS SYSTEMS, USA. The test method was based on GB T 11363-2008, a test method for brazing joint strength.

[0104] The comparison results are shown in Table 1. In addition, the microstructure photos of the welded joints corresponding to Examples 1 to 4 are shown in Table 1. Figures 2 to 5 shown.

[0105] Table 1 Performance comparison results

[0106]

[0107]

[0108] Table 1 shows that when brazing aluminum and copper using the thin strip Zn-Al brazing materials provided by the embodiments of the present invention, the shear strength of the resulting welded joints, both before and after corrosion, is higher in Example 1 than in Examples 2-5. This demonstrates that the brazing material with the corresponding chemical composition of Example 1 can produce welded joints with higher shear strength and corrosion resistance. The welded joint in Example 1 exhibited a high shear strength of 68.3 MPa at room temperature, and even after corrosion, the shear strength remained as high as 56.9 MPa. This demonstrates that the resulting welded joint exhibits high shear strength both before and after corrosion.

[0109] As shown in Table 1, when brazing aluminum and copper using the thin strip Zn-Al brazing material provided by the present invention, the shear strength of the resulting welded joints before and after corrosion in Comparative Examples 1-4 was significantly lower than that in Examples 1-4, and similar to that in Comparative Example 5, but higher than that in Comparative Example 6. It can be seen that if the brazing filler metal lacks any of the alloying strengthening elements (Ag, Cu, Sc, etc.), the resulting welded joint strength is significantly lower than that obtained using a composition ratio within the protective range. Compared to Example 1, the shear strength of the welded joints prepared in Comparative Examples 1-5 before corrosion was reduced by approximately 27.7% to 30.4%, and the shear strength after corrosion was reduced by approximately 28.8% to 36.6%.

[0110] The shear strength of Examples 1 to 3 is significantly better than that of the existing Zn-Al-based and Al-Si-based brazing filler metals provided in Comparative Examples 5 and 6. The brazing material provided by the present invention can obtain a weld joint with higher strength than the currently commonly used brazing materials.

[0111] In summary, the Zn-Al brazing material for welding provided by the present invention utilizes an optimal raw material combination to produce a thin-strip Zn-Al brazing material for welding. This solution utilizes a simple preparation process, and when applied to the brazing of aluminum and copper, the Zn-Al brazing material exhibits excellent welding performance, resulting in high shear strength of the welded joints before and after corrosion. This Zn-Al brazing material is suitable for welding various types of aluminum alloys to copper, and its welding performance surpasses the bonding strength of commercially available ZnAl, ZnSn, ZnSi, and SnZn brazing filler metals, meeting the requirements of industrial applications.

[0112] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A Zn-Al brazing material for aluminum-copper welding, characterized in that: Measured in percentage by weight, the chemical composition of the Zn-Al brazing material includes 9% to 25% Al, 1% to 5% Ag, 1% to 4% Cu, 1% to 4.5% Si, 0.003% to 1% Mg, 0.05% to 1% Sr, 0.05% to 1% Ti, 0.05% to 1.5% Ni and 0.02% to 0.15% Sc, with the balance being Zn.

2. The Zn-Al brazing material for aluminum-copper welding according to claim 1, characterized in that: The chemical composition includes 10% to 20% Al, 2.0% to 4.0% Ag, 2.0% to 3.5% Cu, 2.0% to 3.5% Si, 0.01% to 0.05% Mg, 0.1% to 0.5% Sr, 0.1% to 0.5% Ti, 0.1% to 1.0% Ni and 0.03% to 0.1% Sc, and the balance is Zn.

3. The Zn-Al brazing material for aluminum-copper welding according to claim 1 or 2, characterized in that: The Zn-Al brazing material for aluminum-copper welding is in the form of a thin strip; Preferably, the Zn-Al brazing material for aluminum-copper welding has a thickness of 80 μm to 400 μm and a width of 5 mm to 50 mm; More preferably, the Zn—Al brazing material for aluminum-copper welding has a thickness of 100 μm to 200 μm and a width of 10 mm to 30 mm.

4. The method for preparing a Zn-Al brazing material for aluminum-copper welding according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: vacuum melting and pouring raw materials prepared according to the preset chemical composition of the Zn-Al series brazing material for aluminum-copper welding to obtain an alloy ingot; and double-roller rapid solidification of the alloy ingot.

5. The preparation method according to claim 4, characterized in that: Vacuum melting and pouring includes: -3 Pa~8×10 -3 The vacuum melting furnace is filled with inert gas for protection and heated to 550°C to 600°C. After the raw materials are heated to a molten state, the temperature is kept constant for 20min to 30min, and then casting is performed to obtain an alloy ingot.

6. The preparation method according to claim 5, characterized in that: The double-roller rapid solidification comprises: remelting the alloy ingot and keeping it warm to obtain a remelt; spraying the remelt through a nozzle under the action of inert gas pressure to the gap between two rolls that are spaced apart and rotate relatively, so that the remelt starts to cool and solidify rapidly from the roll surface to form a stable solidified shell; under the action of the friction force of the roll surface of the continuously rotating roll, the solidified shell moves downward to the smallest gap to form a thin strip; Preferably, before the twin-roll rapid solidification, the alloy ingot is also cut and polished.

7. The preparation method according to claim 6, characterized in that: The holding time after remelting is 5 min to 10 min; the injection pressure of the inert gas is 0.02 MPa to 0.07 MPa, the diameter of the nozzle is 1 mm to 2 mm, and the roller speed is 200 r / min to 600 r / min.

8. Use of the Zn-Al brazing material for aluminum-copper welding according to any one of claims 1 to 3 in aluminum-copper brazing.

9. An aluminum-copper joint, characterized in that: The aluminum-copper joint is obtained by brazing an aluminum alloy and a copper material, and the solder used in the brazing process is the Zn-Al series brazing material for aluminum-copper welding as described in any one of claims 1 to 3.

10. The aluminum-copper joint according to claim 9, characterized in that: The brazing is carried out by high-frequency induction brazing, the brazing flux is CsF-AlF3 brazing flux, the welding current is 25A-40A, the brazing time is 25s-35s, and the brazing gap is 0.1mm-0.3mm.

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