Aluminum-based brazing filler metal and preparation method thereof

Abstract

The invention relates to aluminum-based brazing filler metal and a preparation method thereof, and relates to the technical field of brazing materials, and the brazing filler metal is prepared from the following raw materials in percentage by mass: 6.8-9.7% of Si, 10.5-14.9% of Cu, 5.8-7.3% of Zn, 1.0-3.0% of Sn and the balance of Al. The preparation method comprises the following steps that S1, raw materials are prepared, specifically, Si, Cu, Zn, Sn and Al raw materials are weighed according to the material proportion; s2, primary smelting is conducted, specifically, after molten salt is scattered into a graphite crucible and heated to be molten, Si and Al raw materials are put into the graphite crucible to be smelted into Al-Si intermediate alloy liquid; s3, secondary smelting is conducted, specifically, Cu, Zn and Sn raw materials are sequentially added into the Al-Si intermediate alloy liquid, the time interval is 10-15 min, heat preservation is conducted for 20-30 min at the temperature of 900-1000 DEG C, stirring is conducted, and brazing filler metal alloy liquid is obtained; and S4, machining and forming are conducted, specifically, the brazing filler metal alloy liquid is poured into an ingot, and the aluminum-based brazing filler metal is prepared after rolling and drawing. According to the raw material ratio, the prepared aluminum-based brazing filler metal has the advantages of being low in melting point, low in cost, good in processability and high in brazing structural strength.

Description

Technical Field

[0001] The present application relates to the technical field of brazing materials, and in particular to an aluminum-based brazing filler metal and a preparation method thereof. Background Art

[0002] Aluminum and aluminum alloys have the advantages of low density, high specific strength, good corrosion resistance, good processing performance, good electrical and thermal conductivity, low cost, and easy recycling. They are widely used in the main structures and some lightweight components in the fields of aviation, aerospace, automobiles, electronics, high-speed trains, etc. In recent years, with the increasing demand for aluminum and aluminum alloys, the related manufacturing processes have attracted much attention. Brazing is one of the most important methods for manufacturing aluminum alloy products due to its small product deformation, high dimensional accuracy and strong structural adaptability. Brazing materials, as the key to aluminum alloy brazing, have become the focus of research at home and abroad.

[0003] At present, aluminum alloy brazing materials are mainly Al-Si alloys. The disadvantage of Al-Si alloy brazing filler metal is that the melting point is relatively high (577℃). The required welding temperature is generally above 600℃, which is very close to the melting point of aluminum alloy. During brazing, defects such as overburning, dissolution, and coarse grains of the base material are very likely to occur. Therefore, it is imperative to reduce the melting temperature of Al-Si alloy brazing filler metal. On the basis of Al-Si alloy brazing filler metal, adding melting-reducing elements such as Cu, Ge, and Zn to form a low melting point alloy is the mainstream direction of aluminum alloy hard brazing filler metal optimization. The aluminum alloy low melting point alloy brazing filler metals that have been developed are mainly divided into two categories: ternary and quaternary.

[0004] However, for existing ternary alloy brazing materials, achieving a low melting point always requires sacrificing the performance of the brazing material or the brazing joint, and the cost is relatively high, so it is greatly limited in practical applications. For existing quaternary alloy brazing materials, although the processing performance of the brazing material and the mechanical properties of the brazing joint have been improved, in order to ensure a lower melting temperature, the content of the main melting-reducing elements such as Cu and Ge in the brazing material is still high, and the cost problem is still significant.

[0005] In short, with the development of aerospace, automobile manufacturing, electronic equipment, high-speed trains and other fields, the application scope of aluminum and aluminum alloys has been continuously expanded, and the brazing manufacturing industry of aluminum alloys has also developed rapidly. At present, the traditional aluminum and aluminum alloy brazing materials have problems such as high melting point, high cost, and poor joint performance. It is extremely necessary to research and develop an aluminum alloy brazing material with low melting point, low cost, good processing performance and high brazing joint strength. Summary of the invention

[0006] The present application provides an aluminum-based brazing filler metal and a preparation method thereof, which has the advantages of low melting point, low cost, good processing performance and high brazing structure strength.

[0007] In the first aspect, the present application provides an aluminum-based brazing filler metal, which adopts the following technical solution: An aluminum-based brazing filler metal, the brazing filler metal being made of the following raw materials in percentage by mass: Si 6.8~9.7%, Cu 10.5~14.9%, Zn 5.8~7.3%, Sn 1.0~3.0%, The balance is Al.

[0008] By adopting the above technical solution, Si is an effective melting point depressant element, which can significantly reduce the liquidus temperature of the solder, and the addition of Si can improve the fluidity of the solder, making it easier to fill the weld during the brazing process. At the same time, Si can also enhance the spreadability of the solder, and improve the strength and toughness of the solder, so that the brazed joint has better mechanical properties.

[0009] Cu can significantly reduce the melting point of the solder and significantly improve the shear strength of the solder joint. Cu also has good wettability, which can improve the wettability of the solder to the base material, thereby improving the quality of the brazed joint. In addition, Cu can form solid solutions or eutectics with Zn and Sn elements, and the formation of these structures helps to improve the mechanical properties of the solder.

[0010] Zn is also an element that can effectively reduce the melting point of the solder. An appropriate amount of Zn can improve the fluidity and wettability of the solder, making it easier to fill the weld during the brazing process and form a uniform weld structure. In addition, Zn itself has a certain corrosion resistance. After being added to the solder, it can improve the corrosion resistance of the brazed joint. By adding an appropriate amount of Zn, the mechanical properties of the brazed joint can be adjusted to a certain extent. Zn can also promote the interface reaction between the solder and the base material to form a more stable bonding interface. In the action mechanism of Sn-Zn eutectic solder and aluminum, Zn will penetrate into the aluminum grain boundary and form Al-Zn solid solution at the edge of the grain; at the same time, aluminum will also stab into the Sn-Zn alloy at certain interface points and grow into needle-shaped Al-Sn-Zn solid solution whiskers, thereby further strengthening the bonding between the solder and the base material.

[0011] Sn is a low melting point element. When it forms an alloy with Zn, Cu, etc., it can significantly reduce the melting point of the solder. Sn also has good fluidity, wettability and corrosion resistance.

[0012] Through the above ratio, the prepared aluminum-based brazing filler metal has the advantages of low melting point, low cost, good processing performance and high brazing structure strength.

[0013] Optionally, the solder is made of the following raw materials in the following mass percentages: Si 7.8%, Cu 14.52%, Zn 6.76%, Sn 3%, and the balance is Al.

[0014] By adopting the above technical solution and under the above ratio, the prepared aluminum-based solder has the best comprehensive performance.

[0015] Optionally, the melting point of the solder is 420.00-530.46°C.

[0016] Optionally, the shear strength of the brazed lap joint is 73.3-81.8 MPa.

[0017] In a second aspect, the present application provides a method for preparing an aluminum-based solder, using the following technical solution: A method for preparing an aluminum-based solder comprises the following steps: S1. Raw material preparation: Weigh Si, Cu, Zn, Sn and Al raw materials respectively according to the material ratio; S2, primary smelting: sprinkle molten salt into a graphite crucible and heat it to melt, then add Si and Al raw materials to smelt Al-Si master alloy liquid; S3, secondary smelting: Cu, Zn, Sn raw materials are added to the Al-Si master alloy liquid in sequence, with a time interval of 10 to 15 minutes, and kept at 900 to 1000°C for 20 to 30 minutes with stirring to obtain solder alloy liquid; S4. Processing and forming: The solder alloy liquid is poured into an ingot, which is then rolled and drawn to form an aluminum-based solder.

[0018] By adopting the above technical solution, it is possible to avoid the aggregation of particles and the inclusion of air. After all the solids are completely melted, they are fully stirred with a glass rod, which can effectively reduce the segregation of alloy elements to obtain a solder alloy with uniform composition.

[0019] Optionally, the molten salt includes NaCl and KCl in a mass ratio of 1:1.

[0020] By adopting the above technical solution, NaCl and KCl are used as molten salt media, which can significantly reduce the synthesis temperature of the solder, thereby reducing energy consumption and improving production efficiency.

[0021] The brazing filler metal prepared using a mixed molten salt of NaCl and KCl usually has a smaller particle size, high purity, and controllable structure. These properties are essential for improving the performance of brazed joints, such as enhancing the strength, toughness, and corrosion resistance of the joints.

[0022] Optionally, the volume of the molten salt after melting is 2 to 3 times the volume of the Al-Si master alloy liquid.

[0023] By adopting the above technical solution, the above amount of molten salt is used as a reaction medium, which can provide a stable reaction environment and help control the properties of the solder, such as the melting point, fluidity and spreadability.

[0024] In summary, the present application includes at least one of the following beneficial technical effects: 1. The melting point of the brazing material is 420.00~530.46℃, which can braze aluminum alloys with a minimum solidus temperature of more than 550℃, and has a wide range of applications; 2. The solder of the present application combined with AlF3-KF-KCl-CsF flux has a much larger spreading area than the solder of 4045 combined with NOCOLOK flux at the same brazing temperature, showing good wettability; 3. This application achieves low melting point and high joint strength by reasonably adjusting the proportion of each component, while significantly reducing the production cost of the solder. DETAILED DESCRIPTION Example

[0025] Example 1 A method for preparing an aluminum-based solder comprises the following steps: S1. Raw material configuration: Weigh Si, Cu, Zn, Sn and Al raw materials respectively according to the material ratio, and the material ratio is shown in Table 1; S2, primary smelting: sprinkle NaCl and KCl molten salts with a mass ratio of 1:1 into a graphite crucible, and heat to 900°C by high-frequency induction for 20 minutes to make the molten salt completely melted, and add Si and Al raw materials into the molten salt to melt Al-Si master alloy liquid. The volume of the molten salt after melting is twice that of the Al-Si master alloy liquid; S3, secondary smelting: Cu, Zn, Sn raw materials are added to the Al-Si master alloy liquid in sequence, with a time interval of 10 minutes, and kept at 900°C for 30 minutes with stirring to obtain solder alloy liquid; S4. Processing and forming: The solder alloy liquid is poured into an ingot, which is then rolled and drawn to form an aluminum-based solder.

[0026] Example 2 A method for preparing an aluminum-based solder comprises the following steps: S1. Raw material configuration: Weigh Si, Cu, Zn, Sn and Al raw materials respectively according to the material ratio, and the material ratio is shown in Table 1; S2, primary smelting: sprinkle NaCl and KCl molten salts with a mass ratio of 1:1 into a graphite crucible, heat to 1000°C by high-frequency induction for 10 minutes to completely melt the molten salt, add Si and Al raw materials into the molten salt to melt Al-Si master alloy liquid, and the volume of the molten salt after melting is 3 times that of the Al-Si master alloy liquid; S3, secondary smelting: Cu, Zn, Sn raw materials are added to the Al-Si master alloy liquid in sequence, with a time interval of 15 minutes, and kept at 1000°C for 20 minutes with stirring to obtain solder alloy liquid; S4. Processing and forming: The solder alloy liquid is poured into an ingot, which is then rolled and drawn to form an aluminum-based solder.

[0027] Example 3 A method for preparing an aluminum-based solder, which differs from Example 1 in that the material ratio of the raw materials is as shown in Table 1.

[0028] Example 4 A method for preparing an aluminum-based solder, which differs from Example 1 in that the material ratio of the raw materials is as shown in Table 1.

[0029] Example 5 A method for preparing an aluminum-based solder, which differs from Example 1 in that the material ratio of the raw materials is as shown in Table 1.

[0030] Table 1, the amount of each raw material added in Examples 1-5 Si Cu Zn Sn Al Example 1 6.8% 10.5% 5.8% 1.0% margin Example 2 9.7% 14.9% 7.3% 3.0% margin Example 3 7.8% 14.52% 6.76% 3.0% margin Example 4 7.8% 11.5% 5.89% 2.5% margin Example 5 7.8% 14.9% 7.3% 2.0% margin

[0031] Test conditions: The brazing materials of each embodiment were combined with AlF3-KF-KCl-CsF flux, and 3003 aluminum alloy was brazed in an argon protection furnace at a brazing temperature of 540°C and a holding time of 2 minutes.

[0032] Melting point test: Differential scanning calorimetry (DSC) was used to test the solidus temperature and liquidus temperature of the samples in each embodiment. The test results are shown in Table 2.

[0033] Wettability test: The wettability of the solder was tested according to the national standard GB / T 11364-2008 “Test method for wettability of solder”. The test results are shown in Table 2.

[0034] Joint strength test: Referring to the national standard GB / T 11363-2008 “Brazing joint strength test method”, the shear strength test of the brazed lap joint was carried out. The test results are shown in Table 2.

[0035] Corrosion resistance test: Referring to the national standard GB / T 16545-2015 “Corrosion of metals and alloys - Removal of corrosion products on corrosion specimens”, the solder alloy was subjected to a weight loss corrosion test in a 3% NaCl solution at 50°C for 96 hours. The test results are shown in Table 2.

[0036] Table 2. Test results Solidus temperature Liquidus temperature Spread area Shear Strength Corrosion weight loss Example 1 492.93℃ 529.76℃ <![CDATA[171.63mm 2 ]]> 81.8MPa ＜2% Example 2 494.56℃ 530.46℃ <![CDATA[200.04 mm 2 ]]> 73.3 MPa ＜2% Example 3 490.41℃ 529.39℃ <![CDATA[192.54 mm 2 ]]> 76.2MPa ＜2% Example 4 420.00℃ 521.83℃ <![CDATA[183.21 mm 2 ]]> 79.3MPa ＜2% Example 5 430.00℃ 504.52℃ <![CDATA[198.56 mm 2 ]]> 73.21MPa ＜2% 4045 solder 574.00℃ 599.00℃ <![CDATA[78.48 mm 2 ]]> 60.33MPa ＜2% By comparing Examples 1-5 with the 4045 solder in the prior art (the 3003 aluminum alloy plate purchased from Shanghai Huafeng Aluminum Co., Ltd., which comes with 4045 solder), it can be found that the melting point, wettability and joint strength of each embodiment of the present application are better than those of 4045 solder, which significantly reduces the production cost of the solder while achieving a low melting point and high joint strength.

[0037] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. An aluminum-based brazing filler metal, characterized in that: The solder is made of the following raw materials in percentage by mass: Si 6.8~9.7%, Cu 10.5~14.9%, Zn 5.8~7.3%, Sn 1.0~3.0%, The balance is Al.

2. The aluminum-based brazing filler metal according to claim 1, characterized in that: The solder is made of the following raw materials in mass percentage: Si 7.8%, Cu 14.52%, Zn 6.76%, Sn 3%, and the balance is Al.

3. The aluminum-based brazing filler metal according to claim 1, characterized in that: The melting point of the solder is 420.00-530.46°C.

4. The aluminum-based brazing filler metal according to claim 1, characterized in that: The shear strength of the brazed lap joint is 73.21-81.8 MPa.

5. The method for preparing an aluminum-based solder according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Raw material preparation: Weigh Si, Cu, Zn, Sn and Al raw materials according to the material ratio; S2, primary smelting: sprinkle molten salt into the graphite crucible and heat it to melt, then add Si and Al raw materials to smelt Al-Si master alloy liquid; S3, secondary smelting: Cu, Zn, and Sn raw materials are added to the Al-Si master alloy liquid in sequence at intervals of 10 to 15 minutes, and kept at 900 to 1000°C for 20 to 30 minutes while stirring to obtain the solder alloy liquid; S4. Processing and forming: The solder alloy liquid is poured into an ingot, which is then rolled and drawn to form an aluminum-based solder.

6. The method for preparing an aluminum-based solder according to claim 5, characterized in that: The molten salt includes NaCl and KCl in a mass ratio of 1:

1.

7. The method for preparing an aluminum-based solder according to claim 6, characterized in that: The volume of the molten salt after melting is 2 to 3 times the volume of the Al-Si master alloy liquid.