Brazing alloy and preparation method and application thereof

Abstract

The invention belongs to the technical field of welding, and particularly relates to a brazing alloy and a preparation method and application thereof. The brazing alloy is prepared from the following components in percentage by mass: 10 to 12.5 weight percent of Si, 1 to 3 weight percent of Mg, 0.2 to 2 weight percent of Zn, 0.1 to 1 weight percent of Cu, 0.1 to 1 weight percent of Ni, 0.05 to 0.2 weight percent of Ti, 0.05 to 0.15 weight percent of Fe and the balance of Al and inevitable impurities. The brazing alloy solid-liquid line is controlled to be 530-560 DEG C through component optimization, 20-40 DEG C heat input is reduced compared with traditional Al-Si brazing filler metal, and thermal deformation and grain coarsening of 6-series aluminum alloy precision components are effectively avoided; meanwhile, according to the brazing alloy, through the synergistic effect of all the elements, a brazed aluminum alloy joint is excellent in corrosion resistance, high in shear strength and free of brittle fracture tendency.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, specifically relating to a brazing alloy, its preparation method, and its application. Background Technology

[0002] With the rapid development of high-end manufacturing fields such as aerospace and electronic equipment towards lightweighting and high integration, the reliability of precision component connections has become a key factor restricting product performance. Brazing technology, as the core process for achieving efficient connections of precision components, relies heavily on the performance of its key material—the brazing alloy—which directly determines the structural stability, environmental corrosion resistance, and service life of the components. Among these, 6-series aluminum alloys, due to their high strength, low density, and excellent machinability, are widely used in precision components such as thin-walled heat sinks, radar and electronic equipment housings, and aerospace honeycomb panels. However, these alloys have a relatively low melting point (approximately 580℃~650℃) and are extremely sensitive to heat input during the brazing process.

[0003] In existing technologies, Al-Si brazing alloys (such as 4343 and 4045) have become the mainstream materials for aluminum alloy brazing due to their low cost and mature processes. However, their melting point temperature is usually as high as 575℃ to 590℃, requiring high-temperature processes close to the melting point of 6-series aluminum alloy substrates during brazing. This can easily lead to irreversible damage to the substrate, such as grain coarsening and thermal deformation, which seriously affects the dimensional accuracy and mechanical properties of thin-walled and complex structural components. At the same time, the corrosion resistance of traditional Al-Si brazing alloys is poor, and they are prone to pitting corrosion and intergranular corrosion in harsh environments such as coastal high-humidity salt spray and aviation kerosene, significantly reducing the service life of components.

[0004] To address the substrate damage caused by high-temperature brazing, the industry has attempted to develop low-melting-point brazing alloys, such as Al-Cu-Si (melting point 520℃~560℃) and Al-Zn-Si (melting point 480℃~540℃). However, these alloys require the addition of large amounts of Cu and Zn elements to lower the melting point, leading to the following new problems: (1) Cu and Zn elements easily form brittle intermetallic compounds (such as Al2Cu and AlZnMg) with the Al matrix, significantly reducing the plasticity of the brazing filler metal and making it difficult to prepare precision brazing forms such as thin strips and powders; (2) Excessive alloying elements increase the brittleness of the brazed joint, reduce its shear strength, and easily form a micro-battery effect in corrosive environments, accelerating joint failure. Therefore, existing low-melting-point brazing fillers still cannot meet the dual requirements of "low-damage brazing + high-reliability joints" for precision 6-series aluminum alloy components.

[0005] In summary, traditional Al-Si brazing alloys suffer from drawbacks such as high melting points leading to thermal damage to the substrate and insufficient corrosion resistance. Existing low-melting-point brazing alloys, on the other hand, are limited by poor machinability and brittle joints, making them unsuitable for the stringent connection requirements of 6-series aluminum alloy precision components in aerospace and electronic equipment applications. Therefore, developing a medium-temperature brazing alloy with a moderate melting point, excellent machinability, high brazed joint strength, and superior corrosion resistance is crucial to overcoming existing technological bottlenecks. Summary of the Invention

[0006] Based on this, the present invention provides a medium-temperature brazing alloy with a solid-liquid line of 530℃-560℃ by optimizing the alloy composition, based on existing Al-Si brazing alloys. This can reduce the brazing temperature of 6-series aluminum alloys to reduce thermal damage to the substrate, while improving the corrosion resistance and weld strength of the brazed joint.

[0007] To achieve the above objectives, the present invention can adopt the following technical solutions:

[0008] In one aspect, the present invention provides a brazing alloy, which, by mass fraction, comprises Si 10wt% to 12.5wt%, Mg 1wt% to 3wt%, Zn 0.2wt% to 2wt%, Cu 0.1wt% to 1wt%, Ni 0.1wt% to 1wt%, Ti 0.05wt% to 0.2wt%, Fe 0.05wt% to 0.15wt%, with the balance being Al and unavoidable impurities.

[0009] Preferably, the brazing alloy is selected from any one of the following:

[0010] (a1) The brazing alloy, by mass fraction, includes 12wt% Si, 2.5wt% Mg, 1wt% Zn, 0.1wt% Cu, 0.5wt% Ni, 0.1wt% Ti, and 0.1wt% Fe, with the balance being Al and unavoidable impurities;

[0011] (b1) The brazing alloy, by mass fraction, comprises 12.5 wt% Si, 2 wt% Mg, 1.5 wt% Zn, 1 wt% Cu, 0.1 wt% Ni, 0.05 wt% Ti, and 0.1 wt% Fe, with the balance being Al and unavoidable impurities;

[0012] (c1) The brazing alloy, by mass fraction, includes 12wt% Si, 1wt% Mg, 2wt% Zn, 0.1wt% Cu, 0.5wt% Ni, 0.1wt% Ti, and 0.1wt% Fe, with the balance being Al and unavoidable impurities;

[0013] (d1) The brazing alloy, by mass fraction, includes 12.5 wt% Si, 1 wt% Mg, 0.2 wt% Zn, 1 wt% Cu, 0.5 wt% Ni, 0.1 wt% Ti, and 0.1 wt% Fe, with the balance being Al and unavoidable impurities;

[0014] (e1) The brazing alloy, by mass fraction, includes 10wt% Si, 3wt% Mg, 1wt% Zn, 0.5wt% Cu, 0.5wt% Ni, 0.05wt% Ti, 0.1wt% Fe, with the balance being Al and unavoidable impurities.

[0015] Preferably, the solid-liquid line of the above-mentioned brazing alloy is 530°C to 560°C.

[0016] Preferably, the brazing alloy is a foil with a thickness of 0.05 mm to 0.5 mm.

[0017] In another aspect, the present invention provides a method for preparing the above-mentioned brazing alloy, comprising the following steps:

[0018] (1) The metal raw materials are smelted, refined and cast in sequence to obtain ingots;

[0019] (2) The ingot is subjected to homogenization annealing, hot rolling, cold rolling and finished product annealing in sequence to obtain brazing alloy.

[0020] Preferably, the above preparation method satisfies one or more of the following conditions:

[0021] (a2) The smelting temperature is 700℃~750℃;

[0022] (b2) The casting temperature is 700℃~730℃, and / or the casting speed is 70mm / min~120mm / min;

[0023] (c2) The homogenization annealing temperature is 450℃~520℃, and / or the homogenization annealing heating rate is 100℃ / h~150℃ / h, and / or the homogenization annealing holding time is 5h~10h.

[0024] (d2) The hot rolling temperature is 400℃~480℃;

[0025] (e2) The annealing temperature of the finished product is 250℃~320℃, and / or the holding time of the finished product annealing is 1h~3h.

[0026] Preferably, the above preparation method satisfies one or more of the following conditions:

[0027] (a3) Electromagnetic stirring is carried out during the smelting process. The electromagnetic stirring frequency is 5Hz to 50Hz and the stirring time is 1min to 10min.

[0028] (b3) The total processing rate of hot rolling is 90% to 95%, and / or the total processing rate of cold rolling is 70% to 99%;

[0029] (c3) Intermediate annealing is performed every two passes during cold rolling. The intermediate annealing temperature is 400℃-480℃, and / or the intermediate annealing time is 0.5h to 3h.

[0030] Preferably, in the above preparation method, air cooling is selected as the cooling method for homogenization annealing or finished product annealing.

[0031] In another aspect, the present invention provides the application of the above-mentioned brazing alloy as a solder for 6-series aluminum alloys.

[0032] Preferably, the above-mentioned 6-series aluminum alloy is selected from aluminum alloy 6A02 and / or aluminum alloy 6061.

[0033] The beneficial effects of this invention include: by optimizing the composition, the solid-liquid line of the brazing alloy is controlled at 530℃~560℃, reducing heat input by 20-40℃ compared to traditional Al-Si brazing filler metals, effectively avoiding thermal deformation and grain coarsening of 6-series aluminum alloy precision components; simultaneously, through the synergistic effect of various elements, the brazing alloy of this invention results in excellent corrosion resistance, high shear strength, and no tendency for brittle fracture in the brazed aluminum alloy joint. Furthermore, the composition design of the brazing alloy provided by this invention is compatible with conventional casting-rolling processes, requiring no special equipment and possessing industrial mass production potential. Detailed Implementation

[0034] The illustrated embodiments are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the illustrated embodiments. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description of the invention still fall within the protection scope of the present invention.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. Singular expressions include plural expressions unless they have a distinct meaning in the context. As used herein, it should be understood that terms such as “comprising,” “having,” “including,” are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials, or combinations thereof. The terminology of the invention is disclosed in the specification and is not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials, or combinations thereof may be present or added. As used herein, “ / ” may be interpreted as “and” or “or,” depending on the context.

[0036] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.

[0037] In a first aspect, embodiments of the present invention provide a brazing alloy, which, by mass fraction, comprises 10wt% to 12.5wt% Si, 1wt% to 3wt% Mg, 0.2wt% to 2wt% Zn, 0.1wt% to 1wt% Cu, 0.1wt% to 1wt% Ni, 0.05wt% to 0.2wt% Ti, and 0.05wt% to 0.15wt% Fe, with the balance being Al and unavoidable impurities.

[0038] It should be noted that this invention controls the solid-liquid line of the brazing alloy to 530℃-560℃ through composition optimization, reducing heat input by 20℃-40℃ compared to traditional Al-Si brazing filler metals, effectively avoiding thermal deformation and grain coarsening of 6-series aluminum alloy precision components. Simultaneously, the brazing alloy of this invention, through the synergistic effect of various elements, results in excellent corrosion resistance, high shear strength, and no tendency for brittle fracture in the brazed aluminum alloy joint. Specifically, in this invention, Mg and Si elements can lower the liquidus line, as can Cu and Zn elements. However, too little content leads to a high solid-liquid line, while excessive content results in a low solid-liquid line and poor joint performance; therefore, optimization is necessary to achieve a reasonable range. Furthermore, the addition of Ti and Ni elements can reduce pitting corrosion at the joint, thereby promoting uniform corrosion and improving the joint's corrosion resistance; however, excessive content can negatively impact joint performance. In addition, strict control of the Fe content in this invention effectively controls the Fe-containing second phase, improving brazing performance and corrosion resistance.

[0039] In some specific examples, the brazing alloys mentioned above are selected from any of the following:

[0040] (a1) The brazing alloy, by mass fraction, includes 12wt% Si, 2.5wt% Mg, 1wt% Zn, 0.1wt% Cu, 0.5wt% Ni, 0.1wt% Ti, and 0.1wt% Fe, with the balance being Al and unavoidable impurities;

[0041] (b1) The brazing alloy, by mass fraction, comprises 12.5 wt% Si, 2 wt% Mg, 1.5 wt% Zn, 1 wt% Cu, 0.1 wt% Ni, 0.05 wt% Ti, and 0.1 wt% Fe, with the balance being Al and unavoidable impurities;

[0042] (c1) The brazing alloy, by mass fraction, includes 12wt% Si, 1wt% Mg, 2wt% Zn, 0.1wt% Cu, 0.5wt% Ni, 0.1wt% Ti, and 0.1wt% Fe, with the balance being Al and unavoidable impurities;

[0043] (d1) The brazing alloy, by mass fraction, includes 12.5 wt% Si, 1 wt% Mg, 0.2 wt% Zn, 1 wt% Cu, 0.5 wt% Ni, 0.1 wt% Ti, and 0.1 wt% Fe, with the balance being Al and unavoidable impurities;

[0044] (e1) The brazing alloy, by mass fraction, includes 10wt% Si, 3wt% Mg, 1wt% Zn, 0.5wt% Cu, 0.5wt% Ni, 0.05wt% Ti, 0.1wt% Fe, with the balance being Al and unavoidable impurities.

[0045] It should be noted that the brazing alloys in this invention can preferably be the brazing alloys listed above. The brazing alloys listed above can achieve a joint welding rate of 97.4% or higher when welding 6-series aluminum alloys, a weld shear strength of 67.5 MPa or higher, and a weight loss of less than 1.8% after 20 days of SWAAT salt spray corrosion.

[0046] In some specific examples, the solid-liquid line of the above-mentioned brazing alloy is 530℃~560℃.

[0047] It should be noted that, as mentioned above, the solid-liquid line of the brazing alloy in this invention can be controlled at 530℃~560℃ through composition optimization, making it more suitable for welding 6-series aluminum alloys.

[0048] In some specific examples, the aforementioned brazing alloy is a foil with a thickness of 0.05 mm to 0.5 mm.

[0049] It should be noted that, in order to meet the needs of precision welding, efficient production and specific process scenarios, the brazing alloy in this invention can be prepared into foil, and the thickness of the foil can be 0.05mm to 0.5mm, such as 0.1mm, 0.2mm, 0.3mm or 0.4mm.

[0050] Secondly, embodiments of the present invention provide a method for preparing the above-mentioned brazing alloy, comprising the following steps:

[0051] (1) The metal raw materials are smelted, refined and cast in sequence to obtain ingots;

[0052] (2) The ingot is subjected to homogenization annealing, hot rolling, cold rolling and finished product annealing in sequence to obtain brazing alloy.

[0053] It should be noted that the composition design of the brazing alloy in this invention is compatible with conventional casting-rolling processes, and its preparation method is well known in the art. Furthermore, based on this, the brazing alloy in this invention requires no special equipment and has the potential for industrial-scale mass production.

[0054] In some specific examples, the above preparation method satisfies one or more of the following conditions:

[0055] (a2) The melting temperature is 700℃~750℃; specifically, the melting temperature in the above preparation method can be 700℃~750℃, for example 710℃, 720℃, 730℃ or 740℃, etc.

[0056] (b2) The casting temperature is 700℃~730℃, and / or the casting speed is 70mm / min~120mm / min; specifically, the casting temperature in the above preparation method can be 700℃~730℃, for example 705℃, 710℃, 715℃, 720℃ or 725℃, etc.; in addition, the casting speed can be 70mm / min~120mm / min, for example 80mm / min, 90mm / min, 100mm / min or 110mm / min, etc.

[0057] (c2) The homogenization annealing temperature is 450℃~520℃, and / or the homogenization annealing heating rate is 100~150℃ / h, and / or the homogenization annealing holding time is 5h~10h; specifically, the homogenization annealing temperature in the above preparation method can be 450℃~520℃, for example 460℃, 470℃, 480℃, 490℃, 500℃ or 510℃, etc.; the holding time can be 5h~10h, for example 6h, 7h, 8h or 9h, etc.;

[0058] (d2) The hot rolling temperature is 400℃~480℃; specifically, the hot rolling temperature in the above preparation method can be 400℃~480℃, such as 410℃, 420℃, 430℃, 440℃, 450℃, 460℃ or 470℃, etc.

[0059] (e2) The annealing temperature of the finished product is 250℃~320℃, and / or the holding time of the finished product annealing is 1h~3h; specifically, the annealing temperature of the finished product in the above preparation method can be 250℃~320℃, such as 260℃, 270℃, 280℃, 290℃, 300℃ or 310℃, etc.; the holding time can be 1h~3h, such as 1.5h, 2h or 2.5h, etc.

[0060] It should be noted that the above preparation method can satisfy any one of the above conditions (a2) to (e2), and preferably all of the above conditions are satisfied at the same time.

[0061] In some specific examples, the above preparation method satisfies one or more of the following conditions:

[0062] (a3) Electromagnetic stirring is performed during the melting process. The electromagnetic stirring frequency is 5Hz to 50Hz, and the stirring time is 1min to 10min. Specifically, in the above preparation method, electromagnetic stirring can be performed during the melting process to refine the grains and the second phase. The electromagnetic stirring frequency can be 5Hz to 50Hz, such as 10Hz, 15Hz, 20Hz, 25Hz, 30Hz, 35Hz, 40Hz, or 45Hz, etc.; the stirring time can be 1min to 10min, 3min, 5min, or 7min, etc.

[0063] (b3) The total processing rate of hot rolling is 90% to 95%, and / or the total processing rate of cold rolling is 70% to 99%; specifically, the total processing rate of hot rolling and the total processing rate of cold rolling in the above preparation method can be rolled according to the above ratio, wherein the total processing rate (also known as the deformation rate) is the core indicator for measuring the degree of plastic deformation of metal materials during rolling, and is usually expressed as a percentage of thickness change. The calculation formula is: total processing rate (%) = [(original thickness - thickness after rolling) / original thickness] × 100%;

[0064] (c3) Intermediate annealing is performed every two passes during cold rolling. The intermediate annealing temperature is 400℃-480℃, and / or the intermediate annealing time is 0.5h-3h. Specifically, intermediate annealing is performed every two passes during cold rolling to eliminate the work hardening state of the material and improve its processing performance. The intermediate annealing temperature can be 400℃-480℃, such as 420℃, 450℃ or 470℃, and the holding time can be 0.5h-3h, such as 1h, 1.5h, 2h or 2.5h.

[0065] It should be noted that the above preparation method can satisfy any one of the above conditions (a3) ​​to (c3), preferably satisfying all of the above conditions simultaneously. More preferably, it satisfies the above conditions (a2) to (e2) and (a3) ​​to (c3) simultaneously.

[0066] In some specific examples, air cooling is chosen as the cooling method for homogenization annealing or finished product annealing in the above preparation methods.

[0067] It should be noted that the cooling methods for homogenization annealing or finished product annealing in the preparation method of the present invention are well known in the art, and air cooling is preferred.

[0068] Thirdly, embodiments of the present invention provide an application of the above-mentioned brazing alloy as a solder for 6-series aluminum alloys.

[0069] It should be noted that, as described above, this invention controls the solid-liquid line of the brazing alloy to 530℃~560℃ through composition optimization, reducing heat input by 20℃~40℃ compared to traditional Al-Si brazing filler metals, effectively avoiding thermal deformation and grain coarsening of precision 6-series aluminum alloy components; therefore, the brazing alloy in this invention is particularly suitable as a solder for 6-series aluminum alloys. Verification shows that joints of 6-series aluminum alloys welded using this brazing alloy exhibit excellent corrosion resistance, high shear strength, and no tendency for brittle fracture.

[0070] In some specific examples, the aforementioned 6-series aluminum alloys are selected from aluminum alloy 6A02 and / or aluminum alloy 6061.

[0071] It should be noted that the 6-series aluminum alloys used in this invention are well known in the art, such as aluminum alloy 6A02 and / or aluminum alloy 6061.

[0072] Preparation Examples

[0073] Example 1

[0074] (1) Material preparation: Aluminum ingots (purity ≥99.7%), silicon (industrial silicon, purity ≥99.9%), magnesium, zinc, copper, nickel and iron are added in pure metal form, and titanium is added in Al-Ti-B wire form; the mass percentage of each raw material is shown in Table 1 below;

[0075] (2) Smelting: Aluminum ingots and other raw materials are placed into the smelting furnace in sequence. The temperature of the molten aluminum is controlled at 750℃, the casting speed is 120mm / min, the electromagnetic stirring frequency is 50Hz and the stirring time is 10min. Then, the aluminum is passed through a converter and refined with Ar gas at 720℃ for 30min. Then, it is left to stand for 30min.

[0076] (3) Casting: The refined aluminum liquid is cast into an ingot with a thickness of 80mm at 730℃;

[0077] (4) Homogenization annealing: The ingot is heated to 520℃ at 150℃ / h and held for 10 hours, followed by air cooling;

[0078] (5) Hot rolling: The annealed ingot is heated to 480°C and rolled into a 6mm thick plate through multiple passes, with a final rolling temperature ≥300°C.

[0079] (6) Cold rolling: The hot-rolled sheet is rolled to 0.5mm foil through multiple passes at room temperature; intermediate annealing is carried out every two passes during cold rolling, with an intermediate annealing temperature of 420℃ and a time of 1h;

[0080] (7) Finished product annealing: The cold-rolled foil is kept at 320°C for 3 hours and then air-cooled to obtain a brazing alloy with a thickness of 0.1 mm.

[0081] Table 1. Components and mass percentages of each raw material in Example 1

[0082] Components mass percentage Si 12wt% Mg 2.5wt% Zn 1wt% Cu 0.1wt% Ni 0.5wt% Ti 0.1wt% Fe 0.1wt% Al Balance Al

[0083] Example 2

[0084] Example 2 is largely the same as Example 1, except that the mass percentages of each raw material are different. Otherwise, it is the same as Example 1, and a brazing alloy (thickness of 0.1 mm) is prepared. The components and mass percentages of each raw material in Example 2 are shown in Table 2 below.

[0085] Table 2. Components and mass percentages of raw materials in Example 2

[0086] Components mass percentage Si 12.5wt% Mg 2wt% Zn 1.5wt% Cu 1wt% Ni 0.1wt% Ti 0.05wt% Fe 0.1wt% Al Balance Al

[0087] Example 3

[0088] Example 3 is largely the same as Example 1, except that the mass percentages of each raw material are different. Otherwise, it is the same as Example 1, and a brazing alloy (thickness of 0.1 mm) is prepared. The components and mass percentages of each raw material in Example 3 are shown in Table 3 below.

[0089] Table 3. Components and mass percentages of each raw material in Example 3

[0090] Components mass percentage Si 12wt% Mg 1wt% Zn 2wt% Cu 0.1wt% Ni 0.5wt% Ti 0.1wt% Fe 0.1wt% Al Balance Al

[0091] Example 4

[0092] Example 4 is largely the same as Example 1, except that the mass percentages of each raw material are different. Otherwise, it is the same as Example 1, and a brazing alloy (thickness of 0.1 mm) is prepared. The components and mass percentages of each raw material in Example 4 are shown in Table 4 below.

[0093] Table 4. Components and mass percentages of raw materials in Example 4

[0094] Components mass percentage Si 12.5wt% Mg 1wt% Zn 0.2wt% Cu 1wt% Ni 0.5wt% Ti 0.1wt% Fe 0.1wt% Al Balance Al

[0095] Example 5

[0096] Example 5 is largely the same as Example 1, except that the mass percentages of each raw material are different. Otherwise, it is the same as Example 1, and a brazing alloy (thickness of 0.1 mm) is prepared. The components and mass percentages of each raw material in Example 5 are shown in Table 5 below.

[0097] Table 5. Components and mass percentages of each raw material in Example 5

[0098] Components mass percentage Si 10wt% Mg 3wt% Zn 1wt% Cu 0.5wt% Ni 0.5wt% Ti 0.05wt% Fe 0.1wt% Al Balance Al

[0099] Comparative Example 1

[0100] Comparative Example 1 is largely the same as Example 1, except that the mass percentages of each raw material are different. Otherwise, it is the same as Example 1, and a brazing alloy (thickness of 0.1 mm) is prepared. The components and mass percentages of each raw material in Comparative Example 1 are shown in Table 6 below.

[0101] Table 6 shows the components and mass percentages of each raw material in Comparative Example 1.

[0102] Components mass percentage Si 10wt% Mg 2.5wt% Zn 0.1wt% Cu 0.1wt% Ni 0.5wt% Ti 0.1wt% Fe 0.1wt% Al Balance Al

[0103] Comparative Example 2

[0104] Comparative Example 2 is largely the same as Example 2, except that the mass percentages of each raw material are different. Otherwise, it is the same as Example 1, and a brazing alloy (thickness of 0.1 mm) is prepared. The components and mass percentages of each raw material in Comparative Example 2 are shown in Table 7 below.

[0105] Table 7 shows the components and mass percentages of each raw material in Comparative Example 2.

[0106] Components mass percentage Si 12.5wt% Mg 0.5wt% Zn 1.5wt% Cu 0.05wt% Ni 0.1wt% Ti 0.05wt% Fe 0.1wt% Al Balance Al

[0107] Comparative Example 3

[0108] Comparative Example 3 is largely the same as Example 2, except that the mass percentages of each raw material are different. Otherwise, it is the same as Example 1, and a brazing alloy (thickness of 0.1 mm) is prepared. The components and mass percentages of each raw material in Comparative Example 3 are shown in Table 8 below.

[0109] Table 8 shows the components and mass percentages of each raw material in Comparative Example 3.

[0110] Components mass percentage Si 12.5wt% Mg 2wt% Zn 1.5wt% Cu 1wt% Ni 0.01wt% Ti 0.01wt% Fe 0.1wt% Al Balance Al

[0111] Performance testing

[0112] In the following tests, the mass percentage of the base material 6A02 was 1wt% Si, 0.6wt% Mg, 0.1wt% Zn, 0.3wt% Cu, 0.2wt% Mn, 0.05wt% Ti, and 0.1wt% Fe, with the balance being Al and unavoidable impurities.

[0113] The solidus and liquidus temperatures of the brazing alloys obtained in the examples and comparative examples were tested using differential scanning calorimetry. The base material 6A02 was then welded using the brazing alloys obtained in the examples and comparative examples (brazing parameters are shown in Table 9 below). The weld ratio and weld shear strength of the welded joints were tested using a metallographic microscope and a tensile testing machine, respectively. The weight loss of the welded joints after 20 days of SWAAT salt spray corrosion was tested using a salt spray testing machine (JYWX-016B).

[0114] The test results are shown in Table 9 below.

[0115] Table 9. Welding performance of the brazing alloy base material 6A02 obtained in the examples and comparative examples.

[0116]

[0117] From Table 9 above, we can see that:

[0118] Firstly, the solid-liquid phase line of the brazing alloy obtained in the example is lower than that of the brazing alloys obtained in Comparative Example 1 and Comparative Example 2, by about 20°C-30°C.

[0119] Secondly, the welding rate of the 6A02 aluminum alloy welded joint obtained by using the brazing alloy in the example is basically the same as that of the joints obtained by the brazing alloy in Comparative Examples 1 and 2, but the shear strength of the weld is much higher than that of the joints in Comparative Examples 1 and 2.

[0120] Thirdly, although the solid-liquid phase line of Comparative Example 3 was between 530-560℃, which was not significantly different from the solid-liquid phase line of the brazing alloy obtained in Example 2, the corrosion resistance of the joint was much lower than that of Example 2. This indicates that the content of Ni and Ti was reduced, thereby reducing the corrosion resistance of the joint.

[0121] In addition, the brazing alloy obtained in Example 2 was used as the base material 6061 for welding (brazing parameters are shown in Table 10 below). The weld ratio and weld shear strength of the welded joint were tested using a metallographic microscope and a tensile testing machine, respectively. The weight loss of the welded joint after 20 days of SWAAT salt spray corrosion was tested using a salt spray tester (JYWX-016B type), and compared with the welding results of the base material 6A02. The test results are shown in Table 10 below.

[0122] Table 10 Welding performance of the brazing alloy base material 6A02 obtained in Example 2

[0123]

[0124] As can be seen from Table 10 above, the welding performance of different 6-series aluminum alloy base materials using the brazing alloy obtained in Example 2 is not significantly different, indicating that the brazing alloy in this invention is suitable for 6-series aluminum alloys, especially aluminum alloys 6A02 and 6061.

[0125] As can be seen from the above, the brazing alloy of the present invention can be used to connect at a lower brazing temperature, that is, the brazing temperature of 6-series aluminum alloy is reduced, and the brazed joint has high strength and excellent corrosion resistance, thus achieving higher shear strength and corrosion resistance of 6-series aluminum alloy brazed joints.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A brazing alloy, characterized in that, The brazing alloy, by mass fraction, includes Si 10wt%–12.5wt%, Mg 1wt%–3wt%, Zn 0.2wt%–2wt%, Cu 0.1wt%–1wt%, Ni 0.1wt%–1wt%, Ti 0.05wt%–0.2wt%, Fe 0.05wt%–0.15wt%, with the balance being Al and unavoidable impurities.

2. The brazing alloy according to claim 1, characterized in that, The brazing alloy is selected from any of the following: (a1) The brazing alloy, by mass fraction, includes 12wt% Si, 2.5wt% Mg, 1wt% Zn, 0.1wt% Cu, 0.5wt% Ni, 0.1wt% Ti, and 0.1wt% Fe, with the balance being Al and unavoidable impurities; (b1) The brazing alloy, by mass fraction, comprises 12.5 wt% Si, 2 wt% Mg, 1.5 wt% Zn, 1 wt% Cu, 0.1 wt% Ni, 0.05 wt% Ti, and 0.1 wt% Fe, with the balance being Al and unavoidable impurities; (c1) The brazing alloy, by mass fraction, includes 12wt% Si, 1wt% Mg, 2wt% Zn, 0.1wt% Cu, 0.5wt% Ni, 0.1wt% Ti, and 0.1wt% Fe, with the balance being Al and unavoidable impurities; (d1) The brazing alloy, by mass fraction, includes 12.5wt% Si, 1wt% Mg, 0.2wt% Zn, 1wt% Cu, 0.5wt% Ni, 0.1wt% Ti, and 0.1wt% Fe, with the balance being Al and unavoidable impurities; (e1) The brazing alloy, by mass fraction, includes 10wt% Si, 3wt% Mg, 1wt% Zn, 0.5wt% Cu, 0.5wt% Ni, 0.05wt% Ti, 0.1wt% Fe, with the balance being Al and unavoidable impurities.

3. The brazing alloy according to claim 1 or 2, characterized in that, The solid-liquid line of the brazing alloy is 530℃~560℃.

4. A medium-temperature brazing alloy according to claim 1 or 2, characterized in that, The brazing alloy is a foil with a thickness of 0.05 mm to 0.5 mm.

5. The method for preparing the brazing alloy according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) The metal raw materials are smelted, refined and cast in sequence to obtain ingots; (2) The ingot is subjected to homogenization annealing, hot rolling, cold rolling and finished product annealing in sequence to obtain brazing alloy.

6. The preparation method according to claim 5, characterized in that, The preparation method satisfies one or more of the following conditions: (a2) The smelting temperature is 700℃~750℃; (b2) The casting temperature is 700℃~730℃, and / or the casting speed is 70mm / min~120mm / min; (c2) The homogenization annealing temperature is 450℃~520℃, and / or the homogenization annealing heating rate is 100℃ / h~150℃ / h, and / or the homogenization annealing holding time is 5h~10h. (d2) The hot rolling temperature is 400℃~480℃; (e2) The annealing temperature of the finished product is 250℃~320℃, and / or the holding time of the finished product annealing is 1h~3h.

7. The preparation method according to claim 5 or 6, characterized in that, The preparation method satisfies one or more of the following conditions: (a3) Electromagnetic stirring is carried out during the smelting process. The electromagnetic stirring frequency is 5Hz to 50Hz and the stirring time is 1min to 10min. (b3) The total processing rate of hot rolling is 90% to 95%, and / or the total processing rate of cold rolling is 70% to 99%; (c3) Intermediate annealing is performed every two passes during cold rolling, with an intermediate annealing temperature of 400℃~480℃ and / or an intermediate annealing time of 0.5h~3h.

8. The preparation method according to claim 5 or 6, characterized in that, Air cooling is selected as the cooling method for homogenization annealing or finished product annealing.

9. The use of the brazing alloy according to any one of claims 1 to 4 as a solder for 6-series aluminum alloys.

10. The application according to claim 9, characterized in that, The 6-series aluminum alloys are selected from aluminum alloy 6A02 and / or aluminum alloy 6061.

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