A solder, its preparation method and application

Abstract

This invention relates to the field of brazing materials technology, specifically to a brazing filler metal, its preparation method, and its application. The solid form of the brazing filler metal is a sandwich foil, comprising a foil-shaped brazing filler metal core and an aluminum foil layer surrounding the outer periphery of the core. The core contains Sr and aluminum foam particles. The preparation method includes the following steps: S1. Melting the required amount of aluminum foil layer raw material into a molten metal, and casting it to obtain a hollow plate-shaped aluminum frame with openings at both ends; S2. Heating the required amount of brazing filler metal core raw material to form a metal suspension containing solid aluminum foam particles, injecting the metal suspension into the aluminum frame, and cooling to obtain a composite metal plate; S3. Performing multiple passes of rough rolling and finish rolling on the composite metal plate to obtain the sandwich foil-shaped brazing filler metal. This invention, through optimization and improvement of the brazing filler metal structure and formulation, can suppress filler metal loss and turbulence during brazing, thereby improving the shear strength of the brazed joint.

Description

Technical Field

[0001] This invention relates to the field of brazing materials technology, and more specifically, to a brazing filler metal, its preparation method, and its application. Background Technology

[0002] Rare earth modified die-cast aluminum alloys are widely used in the manufacture of die-cast aluminum alloy heat sinks for 5G base stations due to their high thermal conductivity, good corrosion resistance and excellent die-casting filling ability.

[0003] However, rare earth modified die-cast aluminum alloys contain high levels of rare earth elements such as Ce and La, with Ce and La content exceeding 10%. These rare earth elements are highly reactive and have a strong affinity for Si in conventional aluminum-silicon brazing filler metals. This results in a significant loss of molten aluminum-silicon eutectic brazing filler metal during the brazing process. Consequently, the brazing seam becomes loose, and the filler metal turbulence becomes severe, flowing into the radiator channels and clogging them, thus seriously degrading the radiator's performance.

[0004] To address the aforementioned shortcomings, there is an urgent need to develop a low-flow brazing filler metal that can be used for brazing rare-earth modified die-cast aluminum alloys, thereby achieving highly reliable brazing of rare-earth modified die-cast aluminum alloys.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The primary objective of this invention is to provide a brazing filler metal that addresses the technical problems of excessive filler metal loss, non-dense weld joints, and severe turbulence in brazing rare-earth modified die-cast aluminum alloys using conventional aluminum-silicon brazing filler metals. This invention, through optimization and improvement of the filler metal's structure and formulation, can suppress filler metal loss and turbulence during brazing, thereby increasing the shear strength of the brazed joint.

[0007] The second objective of this invention is to provide a method for preparing the solder as described above. This method is simple to operate and easy to implement.

[0008] A third objective of this invention is to provide an application of the brazing filler metal described above in the brazing of rare earth modified die-cast aluminum alloys.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0010] A solder, wherein the solid form of the solder is a sandwich foil, comprising a foil-shaped solder metal core and an aluminum foil layer wrapped around the outer periphery of the solder metal core, wherein the solder metal core contains Sr and aluminum foam particles.

[0011] Preferably, the brazing filler metal core comprises the following components by weight:

[0012] Si 8.0-10 parts, Sr 2.5-4.5 parts, aluminum foam particles 0.1-0.3 parts, B 0.05-0.08 parts, Al 85-90 parts.

[0013] Preferably, the porosity of the aluminum foam particles is 40%-60%, and the average pore size is 0.2-0.8 nm;

[0014] And / or, the particle size of the aluminum foam particles is 20-50 μm.

[0015] Preferably, the aluminum foil layer comprises any one of Al, 3003 alloy, and 6063 alloy.

[0016] Preferably, the thickness of one side of the aluminum foil layer is 1 / 5 to 1 / 4 of the total thickness of the solder.

[0017] Preferably, the thickness of one side of the aluminum foil layer is 0.04-0.1 mm, and the total thickness of the brazing filler metal, which is sandwiched in the shape of a foil, is 0.1-0.5 mm.

[0018] The method for preparing the solder according to any one of the foregoing embodiments includes the following steps:

[0019] S1. Melt the required amount of aluminum foil raw material into a liquid metal, and obtain a hollow plate-shaped aluminum frame with open ends by casting;

[0020] S2. The required amount of brazing filler metal core raw material is heated to form a metal suspension containing solid foamed aluminum particles, and the metal suspension is injected into the aluminum frame. After cooling, a composite metal plate is obtained.

[0021] S3. The composite metal plate is subjected to multiple passes of rough rolling and fine rolling to obtain sandwich foil-shaped brazing filler metal.

[0022] Preferably, in step S2, the raw materials of the brazing filler metal core include Al-20Si, Al-20Sr, aluminum foam particles, Al-5B, and Al.

[0023] Preferably, in step S2, the heating temperature for preparing the metal suspension is 650-720℃.

[0024] Preferably, in step S2, before injecting the metal suspension, the following step is further included:

[0025] Clean the inner surface of the aluminum frame and coat it evenly with a layer of aluminum flux.

[0026] Preferably, the aluminum flux includes potassium fluoroaluminate, cesium fluoroaluminate, and alcohol.

[0027] Application of the brazing filler metal as described in any of the foregoing embodiments, or the brazing filler metal prepared by the method described in any of the foregoing embodiments, in brazing rare earth modified die-cast aluminum alloys.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) The present invention designs the brazing filler metal into a sandwich foil structure, that is, the brazing filler metal core is wrapped with aluminum foil. The purpose is to use the aluminum foil to reduce the flow rate of the molten brazing filler metal and reduce the intensity of the reaction between the molten brazing filler metal and the die-cast aluminum alloy base material, thereby suppressing the turbulence of the brazing filler metal.

[0030] (2) The brazing filler metal core of the present invention contains a high content of alkaline earth metal element Sr, which can be oxidized into strontium peroxide with a large specific gravity and evenly distributed in the brazing filler liquid, thereby increasing the viscosity of the brazing filler liquid, making the brazing filler liquid paste at high temperature, and reducing the flow of the brazing filler liquid.

[0031] (3) The brazing metal core of the present invention contains aluminum foam particles. The numerous micro and nano pores evenly distributed inside the aluminum foam particles can absorb a portion of the brazing fluid, thereby reducing the turbulence of the brazing fluid.

[0032] (4) The method of the present invention is simple and easy to implement. When brazing rare earth modified die-cast aluminum alloys, the brazing filler metal prepared by the method of the present invention is not easy to lose or flow, and the joint after brazing has high shear strength. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the solder preparation process provided in an embodiment of the present invention;

[0035] Figure 2 Macroscopic diagrams of brazing filler metal turbulence on the surface of die-cast aluminum alloys in each embodiment and comparative example;

[0036] Figure 3 The images show the morphology of the die-cast aluminum alloy and 3003 joints brazed with brazing filler metal in Examples 1-5 and Comparative Examples 1-8.

[0037] Figure label:

[0038] 1- Brazing metal core; 2- Aluminum foil layer. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0040] like Figure 1 As shown, the first aspect of the present invention provides a solder, the solid form of which is a sandwich foil, comprising a foil-shaped solder metal core 1 and an aluminum foil layer 2 wrapped around the outer periphery of the solder metal core 1, wherein the solder metal core 1 contains Sr and aluminum foam particles.

[0041] The solid form of the solder in this invention is a sandwich foil consisting of an aluminum foil and a solder core, open at both ends with a U-shaped end face. In its molten state, it is a paste. Utilizing the barrier effect of the outer aluminum foil, the aluminum foil reacts with the solder slurry first during brazing, reducing the flow rate of the solder slurry and mitigating the intensity of the reaction between the solder slurry and the die-cast aluminum alloy base material, thus suppressing turbulence to a certain extent. The solder core contains the highly reactive alkaline earth element Sr, which helps to paste the solder slurry. Sr reacts with trace amounts of oxygen and is easily oxidized to form strontium oxide (density 4.56 g / cm³). 3 Its specific gravity is greater than the density of the solder (approximately 2.7 g / cm³). 3 The aluminum foam particles in the solder will be evenly distributed in large quantities in the solder, thereby increasing the viscosity of the solder. The aluminum foam particles in the component also play a paste-like role. The aluminum foam particles are evenly distributed in the solder and can fully absorb the solder by utilizing the large number of micro and nano-sized pores evenly distributed inside them, thereby inhibiting the turbulence of the solder. At the same time, the aluminum foam particles in the solder are evenly distributed in the brazing seam, which can also enhance the bonding strength of the joint.

[0042] In some specific embodiments of the present invention, the solder core 1 is an aluminum-silicon based solder.

[0043] In some specific embodiments of the present invention, the brazing filler metal core 1 comprises the following components by mass parts:

[0044] Si 8.0-10 parts, Sr 2.5-4.5 parts, aluminum foam particles 0.1-0.3 parts, B 0.05-0.08 parts, Al 85-90 parts.

[0045] In the aforementioned aluminum-silicon based brazing filler metal, the role of aluminum foam particles and Sr is to suppress turbulent flow of the brazing filler metal, while the role of B is to purify the grain boundaries of the brazing seam, refine the brazing seam structure, and improve the brazing strength. However, if the amount of Sr and aluminum foam particles is too small, they will not achieve the desired paste-like effect, resulting in poor suppression of brazing filler metal turbulence. Conversely, if the amount is too large, the viscosity of the brazing filler metal will be too high, leading to poor flowability and affecting the brazing effect. Therefore, controlling the amounts within the aforementioned range is necessary to both suppress turbulent flow and achieve a good brazing effect.

[0046] In some embodiments, typically but not limitingly, for example, in the solder core 1, the mass fraction of Si can be any one of 8.0 parts, 8.5 parts, 9.0 parts, 9.5 parts, or 10 parts, or a range of any two of these values; the mass fraction of Sr can be any one of 2.5 parts, 3 parts, 3.5 parts, 4 parts, or 4.5 parts, or a range of any two of these values; the mass fraction of aluminum foam particles can be any one of 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, or 0.3 parts, or a range of any two of these values; the mass fraction of B can be any one of 0.05 parts, 0.06 parts, 0.07 parts, or 0.08 parts, or a range of any two of these values; and the mass fraction of Al can be any one of 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, or 90 parts, or a range of any two of these values.

[0047] In some specific embodiments of the present invention, the porosity of the aluminum foam particles used is 40%-60%, for example, it can be any one value or a range of any two values ​​among 40%, 45%, 50%, 55%, and 60%; the average pore size is 0.2-0.8 nm, for example, it can be any one value or a range of any two values ​​among 0.2 nm, 0.4 nm, 0.6 nm, and 0.8 nm.

[0048] When the porosity of aluminum foam is between 40% and 60%, it can adsorb turbulent solder and hinder its flow. If the porosity is too small, the ability to adsorb solder is weak, and the effect of suppressing turbulence is not good. If the porosity is too large, the adsorption capacity is too strong, and most of the solder is adsorbed into the aluminum foam, and there is not enough solder to flow into the surface of the base material to be soldered.

[0049] In some specific embodiments of the present invention, the particle size of the aluminum foam particles is 20-50 μm. For example, it can be any single value or a range of any two values ​​among 20 μm, 30 μm, 40 μm, and 50 μm. If the particles are too small, they absorb a large amount of heat and are easily dissolved in the solder. If the particles are too large, the specific surface area decreases, and the adsorption effect of the solder decreases.

[0050] In some specific embodiments of the present invention, the aluminum foil layer 2 comprises any one of Al, 3003 alloy, and 6063 alloy.

[0051] In some specific embodiments of the present invention, the thickness of one side of the aluminum foil layer 2 is 1 / 5 to 1 / 4 of the total thickness of the solder. For example, it can be any one value or a range of any two values ​​from 1 / 5, 1 / 4.8, 1 / 4.5, 1 / 4.2, and 1 / 4. The role of the aluminum foil is to react with the solder in one step. The solder metal core melts and reacts with the aluminum foil layer of a certain thickness. The aluminum dissolves in the solder, increasing the viscosity of the solder and slowing down or suppressing the turbulence of the solder. It is best if the thickness of the aluminum foil layer is just enough to completely react. If the aluminum foil is too thick, the reaction will be incomplete, and the residual aluminum foil will affect the welding effect. If the aluminum foil is too thin, it will dissolve into the solder instantly and will not play a buffering role. Moreover, the increase in the viscosity of the solder will not be significant, and the effect of suppressing the turbulence of the solder will not be significant. Therefore, it is necessary to reasonably control the thickness ratio of the aluminum foil layer to the foil-shaped solder.

[0052] In some specific embodiments of the present invention, the thickness of one side of the aluminum foil layer is 0.04-0.1 mm, for example, it can be any one value or a range of any two values ​​among 0.04 mm, 0.06 mm, 0.08 mm, and 0.1 mm; the total thickness of the sandwich foil-shaped brazing filler metal is 0.1-0.5 mm, for example, it can be any one value or a range of any two values ​​among 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm.

[0053] like Figure 1 As shown, a second aspect of the present invention provides a method for preparing the solder according to any one of the foregoing embodiments, comprising the following steps:

[0054] S1. Melt the required amount of aluminum foil raw material into a liquid metal, and obtain a hollow plate-shaped aluminum frame with open ends by casting;

[0055] S2. The required amount of brazing filler metal core raw material is heated to make a metal suspension containing solid foamed aluminum particles, and the metal suspension is injected into the aluminum frame. After cooling, a composite metal plate is obtained.

[0056] S3. The composite metal plate is subjected to multiple passes of rough rolling and fine rolling to obtain sandwich foil-shaped brazing filler metal.

[0057] In this invention, the amounts of raw materials for the aluminum foil layer and the brazing metal core are calculated based on the final size specifications of the sandwich foil-shaped brazing metal and the ratio of the thickness of one side of the aluminum foil layer to the total thickness of the entire sandwich foil-shaped brazing metal. The hollow plate-shaped aluminum frame prepared in step S1 is used to form the aluminum foil layer. In step S2, the foamed aluminum particles in the metal suspension exist in a solid form, while the remaining components exist in the form of liquid metal. This can be achieved by mixing all the raw materials for the brazing metal core and heating them to a certain temperature, or by first mixing and melting the components other than the foamed aluminum particles into a liquid metal, and then adding the foamed aluminum particles to the liquid metal and mixing them evenly. The heating temperature is lower than the melting point of the foamed aluminum. The purpose of keeping the foamed aluminum in a solid form is to preserve its porous structure. During brazing, it can fully absorb the brazing metal using its numerous micro and nano-sized pores, blocking the flow of the brazing metal and thus suppressing turbulence. The method of this invention is simple to operate, easy to implement, and convenient for mass production.

[0058] In some specific embodiments of the present invention, the raw material for the aluminum foil layer is at least one of pure aluminum metal block, 3003 alloy, and 6063 alloy.

[0059] In some specific embodiments of the present invention, in step S2, the raw materials for the brazing filler metal core include Al-20Si, Al-20Sr, aluminum foam particles, Al-5B, and Al. Al-20Si is chosen as the intermediate alloy because it has a high Si content, which allows for the formulation of brazing filler alloys with high Si content and multiple elements. Furthermore, the melting temperature of this alloy, 600-680℃, is close to the melting temperature of the brazing filler metal, resulting in better melting. Al-5B is a refining agent; since B has a low solubility in aluminum, it is added in the form of an Al-5B alloy.

[0060] In some specific embodiments of the present invention, when preparing a mixed molten metal of Al-20Si, Al-20Sr, Al-5B and Al, Al and Al-20Si are added first and melted into a molten metal before Al-20Sr and Al-5B wrapped in aluminum foil are added; this is because Al-20Sr and Al-5B are modifiers and refiners, and must be added last to achieve the modifier effect.

[0061] In some specific embodiments of the present invention, in step S2, the heating temperature for preparing the metal suspension is 650-720°C, for example, it can be any one value or a range of any two values ​​among 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, and 720°C.

[0062] In some specific embodiments of the present invention, the particle size of the aluminum foam particles used in step S2 is 20-50 μm. For example, it can be any one value or a range of any two values ​​among 20 μm, 30 μm, 40 μm, and 50 μm.

[0063] In some specific embodiments of the present invention, the thickness of one side of the aluminum frame of the composite metal plate prepared in step S2 is 1 / 5 to 1 / 4 of the total thickness of the entire composite metal plate. For example, it can be any one value or a range of any two values ​​among 1 / 5, 1 / 4.8, 1 / 4.5, 1 / 4.2, and 1 / 4.

[0064] In some specific embodiments of the present invention, step S2 further includes the following steps before injecting the metal suspension:

[0065] Clean the inner surface of the aluminum frame and apply a layer of aluminum flux evenly.

[0066] The purpose of applying flux to the inner surface of the aluminum frame is to form a metallurgical reaction layer at the interface between the injected molten metal and the aluminum frame. The flux acts as a film remover and flow aid.

[0067] In some specific embodiments of the present invention, the aluminum flux includes potassium fluoroaluminate, cesium fluoroaluminate, and alcohol.

[0068] In some specific embodiments of the present invention, the mass ratio of potassium fluoroaluminate, cesium fluoroaluminate, and alcohol in the aluminum flux is 18-22:1:6-10. For example, it can be any one value or a range of any two values ​​from 18:1:6, 18:1:8, 18:1:10, 20:1:6, 20:1:8, 20:1:10, 22:1:6, 22:1:8, and 22:1:10, preferably 20:1:8.

[0069] The third aspect of the present invention provides the application of the brazing filler metal as described in any of the foregoing embodiments or the brazing filler metal prepared by the preparation method of the brazing filler metal as described in any of the foregoing embodiments in the brazing of rare earth modified die-cast aluminum alloys. This can solve the problem of brazing filler metal loss caused by the violent reaction between the rare earth modified die-cast aluminum alloy base material and the brazing filler metal, and can also avoid turbulence of the brazing filler metal liquid.

[0070] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0071] Example 1

[0072] This embodiment provides a solder that has a sandwich foil structure in the solid state and a paste-like state in the molten state. It consists of an aluminum foil layer and a solder metal core wrapped inside the aluminum foil layer. The ratio of the thickness of one side of the aluminum foil layer to the thickness of the entire sandwich foil solder is 1 / 5.

[0073] The mass fractions of each element in the brazing filler metal core are as follows: Si 10 parts, Sr 2.5 parts, aluminum foam particles 0.3 parts, B 0.08 parts, and Al 87.12 parts.

[0074] The preparation method for a sandwich foil-shaped brazing filler metal with dimensions of 0.2 mm thickness, 100 mm width, and 10 meters length includes the following steps:

[0075] S1. Based on the solder foil size specifications, the ratio of the single-sided thickness of the aluminum foil layer to the total thickness of the solder foil is 1:5, and the density of pure aluminum is 2.7 g / cm³. 3 The density of the brazing filler metal is 2.65 g / cm³. 3 The required aluminum foil weight is calculated to be 216g, and the required solder core weight is 318g.

[0076] 216g of aluminum block is melted into molten metal and injected into a specific graphite mold cavity. After cooling and demolding, a hollow plate-shaped aluminum frame with openings at both ends is obtained.

[0077] S2. Clean the inner surface of the aluminum frame and evenly coat it with a layer of aluminum flux. The aluminum flux is a mixture of potassium fluoroaluminate, cesium fluoroaluminate and alcohol in a mass ratio of 20:1:8.

[0078] Weigh out the raw materials Al-20Si, Al-20Sr, aluminum foam particles, Al-5B, and Al according to the mass fractions, wherein the aluminum foam particles have a particle size of 20μm, a porosity of 40%, and an average pore size of 0.2nm; mix the raw materials and heat to 650℃ to obtain a metal suspension; inject the metal suspension into an aluminum frame coated with an aluminum flux layer; cool to obtain a composite metal plate; the ratio of the thickness of one side of the aluminum frame to the total thickness of the composite metal plate is 1 / 5;

[0079] S3. Perform multiple passes of rough rolling and finish rolling on the composite metal plate to obtain the sandwich foil brazing filler metal of the required specifications and dimensions.

[0080] Example 2

[0081] This embodiment provides a solder that has a sandwich foil structure in the solid state and a paste-like state in the molten state. It consists of an aluminum foil layer and a solder metal core wrapped inside the aluminum foil layer. The ratio of the thickness of one side of the aluminum foil layer to the thickness of the entire sandwich foil solder is 1 / 4.

[0082] The mass fractions of each element in the brazing filler metal core are as follows: Si 9 parts, Sr 3.0 parts, aluminum foam particles 0.2 parts, B 0.06 parts, and Al 87.74 parts.

[0083] A sandwich foil-shaped brazing filler metal with dimensions of 0.16 mm thick, 100 mm wide, and 10 meters long was prepared. The preparation method was similar to that in Example 1, with the following differences:

[0084] In step S1, based on the size and thickness ratio of the solder foil, the required aluminum foil metal weight is calculated to be 216g and the required solder metal core weight is 212g.

[0085] In step S2, the average pore size of the aluminum foam particles used is 0.3 nm and the porosity is 45%. The temperature for preparing the metal suspension is 680 °C. The ratio of the thickness of one side of the aluminum frame to the total thickness of the composite metal plate is 1 / 4.

[0086] All other process conditions are the same as in Example 1.

[0087] Example 3

[0088] This embodiment provides a solder that has a sandwich foil structure in the solid state and a paste-like state in the molten state. It consists of an aluminum foil layer and a solder metal core wrapped inside the aluminum foil layer. The ratio of the thickness of one side of the aluminum foil layer to the thickness of the entire sandwich foil solder is 1 / 5.

[0089] The mass fractions of each element in the brazing filler metal core are as follows: Si 9.5 parts, Sr 3.5 parts, aluminum foam particles 0.1 parts, B 0.07 parts, and Al 86.83 parts.

[0090] A sandwich foil-shaped brazing filler metal with dimensions of 0.3 mm thickness, 100 mm width, and 10 meters length was prepared. The preparation method was similar to that in Example 1, with the following differences:

[0091] In step S1, based on the size specifications and thickness ratio of the solder foil, the required aluminum foil metal weight is calculated to be 324g and the required solder metal core weight is 477g.

[0092] In step S2, the aluminum foam particles used have a particle size of 40 μm, a porosity of 50%, and an average pore size of 0.5 nm. The temperature for preparing the metal suspension is 700 °C.

[0093] All other process conditions are the same as in Example 1.

[0094] Example 4

[0095] This embodiment provides a solder that has a sandwich foil structure in the solid state and a paste-like state in the molten state. It consists of an aluminum foil layer and a solder metal core wrapped inside the aluminum foil layer. The ratio of the thickness of one side of the aluminum foil layer to the thickness of the entire sandwich foil solder is 1 / 4.

[0096] The mass fractions of each element in the brazing filler metal core are as follows: Si 8.5 parts, Sr 4.0 parts, aluminum foam particles 0.3 parts, B 0.05 parts, and Al 87.15 parts.

[0097] A sandwich foil-shaped brazing filler metal with dimensions of 0.4 mm thickness, 100 mm width, and 10 meters length was prepared. The preparation method was similar to that in Example 1, with the following differences:

[0098] In step S1, based on the size and thickness ratio of the solder foil, the required aluminum foil metal weight is calculated to be 540g and the required solder metal core weight is 530g.

[0099] In step S2, the aluminum foam particles used have a particle size of 50 μm, a porosity of 55%, an average pore size of 0.6 nm, and the temperature for preparing the metal suspension is 710 °C. The ratio of the thickness of one side of the aluminum frame to the total thickness of the composite metal plate is 1 / 4.

[0100] All other process conditions are the same as in Example 1.

[0101] Example 5

[0102] This embodiment provides a solder that has a sandwich foil structure in the solid state and a paste-like state in the molten state. It consists of an aluminum foil layer and a solder metal core wrapped inside the aluminum foil layer. The ratio of the thickness of one side of the aluminum foil layer to the thickness of the entire sandwich foil solder is 1 / 5.

[0103] The mass fractions of each element in the brazing filler metal core are as follows: Si 8.0 parts, Sr 4.5 parts, aluminum foam particles 0.2 parts, B 0.08 parts, and Al 87.22 parts.

[0104] A sandwich foil-shaped brazing filler metal with dimensions of 0.5 mm thick, 100 mm wide, and 10 meters long was prepared. The preparation method was similar to that in Example 1, with the following differences:

[0105] In step S1, the required aluminum foil metal weight is calculated to be 540g and the required brazing metal core weight is 795g based on the brazing foil size specifications and thickness ratio.

[0106] In step S2, the porosity of the aluminum foam particles used is 60% and the average pore size is 0.8 nm, and the temperature for preparing the metal suspension is 720 °C.

[0107] All other process conditions are the same as in Example 1.

[0108] Comparative Example 1

[0109] Comparative Example 1 is similar to Example 1, except that the foil-shaped solder core is not wrapped with an aluminum foil layer, and all other conditions are the same as in Example 1.

[0110] Comparative Example 2

[0111] Comparative Example 2 is similar to Example 1, except that the solder core does not contain Sr metal, and all other conditions are the same as in Example 1.

[0112] Comparative Example 3

[0113] Comparative Example 3 is similar to Example 1, except that the brazing filler metal core does not contain aluminum foam particles, and all other conditions are the same as in Example 1.

[0114] Comparative Example 4

[0115] Comparative Example 4 is similar to Example 1, except that the mass fraction of Sr is 2.0 parts, and all other conditions are the same as in Example 1.

[0116] Comparative Example 5

[0117] Comparative Example 5 is similar to Example 1, except that the mass fraction of Sr is 5.0 parts, and all other conditions are the same as in Example 1.

[0118] Comparative Example 6

[0119] Comparative Example 6 is similar to Example 1, except that the mass fraction of aluminum foam particles is 0.05 parts, and all other conditions are the same as in Example 1.

[0120] Comparative Example 7

[0121] Comparative Example 7 is similar to Example 1, except that the mass fraction of aluminum foam particles is 0.5 parts, and all other conditions are the same as in Example 1.

[0122] Comparative Example 8

[0123] Comparative Example 8 is similar to Example 1, except that the porosity of the aluminum foam particles is 30%, and all other conditions are the same as in Example 1.

[0124] Comparative Example 9

[0125] Comparative Example 9 is similar to Example 1, except that the porosity of the aluminum foam particles is 70%, and all other conditions are the same as in Example 1.

[0126] Comparative Example 10

[0127] The solder in Comparative Example 10 is in the form of a single-layer foil and is composed of conventional 4045 solder, which, by mass percentage, includes 10% Si, 0.3% Cu, 0.1% Zn, and the balance Al.

[0128] Experimental Example 1

[0129] To examine and compare the brazing joint flow characteristics of the brazing filler metals in Examples 1-5 and Comparative Examples 1-10 of this invention, in-furnace brazing of rare earth modified die-cast aluminum alloys and 3003 aluminum alloys was performed using the brazing filler metals from each example and each comparative example (furnace temperature 590℃, holding time 10min). Five samples were welded for each type of brazing filler metal, and the degree of brazing filler metal flow on the surface of the die-cast aluminum alloys was analyzed (from poor to good, classified as severe, moderate, slight, and none). The test results are shown in Table 1 and [Table data would be inserted here]. Figure 2 .

[0130] Table 1

[0131]

[0132]

[0133] Depend on Figure 2 As shown in Table 1, the brazing filler metals in the embodiments of the present invention did not exhibit turbulence during brazing. In Comparative Examples 1-3, Comparative Example 1 lacked an aluminum foil layer wrapped around the outside of the brazing filler metal core, thus lacking the aluminum foil's obstruction; Comparative Example 2 did not contain the gelling component Sr; and Comparative Example 3 did not contain the gelling component aluminum foam. In both examples, general turbulence was observed. In Comparative Examples 4 and 6, the content of gelling component Sr or aluminum foam particles in the brazing filler metal core was relatively low, yet slight turbulence still occurred. This indicates that the content of metallic Sr and aluminum foam particles must reach a certain level to effectively suppress brazing filler metal turbulence. Effects: In Comparative Example 8, the low porosity of the aluminum foam particles resulted in poor suppression of brazing filler metal turbulence and slight overflow. In Comparative Example 5, the high Sr content in the paste component, in Comparative Example 7, the high aluminum foam content in the paste component, and in Comparative Example 9, the high porosity of the aluminum foam particles all resulted in less flowing brazing filler metal in Comparative Examples 5, 7, and 9. Although there was no overflow, the brazed joint strength was low. In Comparative Example 10, traditional 4045 brazing filler metal was used, resulting in severe brazing filler metal turbulence. This demonstrates that the method of the present invention can solve the technical problem of brazing filler metal turbulence during the brazing of rare earth modified die-cast aluminum alloys.

[0134] Experimental Example 2

[0135] To examine and compare the brazed joint strength of the brazing filler metals in Examples 1-5 and Comparative Examples 1-10 of this invention, furnace brazing of rare earth modified die-cast aluminum alloy and 3003 aluminum alloy was performed using the brazing filler metals from each example and each comparative example (furnace temperature 590℃, holding time 10min). Five samples were welded for each type of brazing filler metal. The shear strength of the joint was tested according to GB / T 11363-2008, and the average value was taken. The test results are shown in Table 2. The joint morphology is as follows. Figure 3 As shown, the five connectors in the left figure are, from left to right, connectors of Example 1 to Example 5, and the eight connectors in the right figure are, from left to right, connectors of Comparative Example 1 to Comparative Example 8.

[0136] Table 2

[0137] Types of brazing filler metal Average shear strength of joint / MPa Example 1: Brazing filler metal 60.5 Example 2 Brazing filler metal 63.8 Example 3 Brazing filler metal 65.2 Example 4 Brazing filler metal 68.8 Example 5: Brazing filler metal 70.4 Comparative Example 1: Brazing filler metal 48.8 Comparative Example 2: Brazing filler metal 45.2 Comparative Example 3: Brazing filler metal 42.8 Comparative Example 4: Brazing filler metal 50.2 Comparative Example 5: Brazing filler metal 49.5 Comparative Example 6 Brazing filler metal 43.2 Comparative Example 7: Brazing filler metal 44.5 Comparative Example 8 Brazing filler metal 50.2 Comparative Example 9: Solder 38.6 Comparative Example 10: Brazing filler metal 35.2

[0138] As can be seen from the data in Table 2, the joint strength of the brazed joint in the examples is much higher than that of the brazed joint in the comparative examples. The joint strength of the brazed joint in the examples is all above 60 MPa. In particular, the shear strength of Example 5 is as high as 70.4 MPa, which is 100% higher than the shear strength of 35.2 MPa of the conventional brazed joint in Comparative Example 10.

[0139] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A brazing filler metal, characterized in that, The solid form of the brazing filler metal is sandwich foil, comprising a foil-shaped brazing filler metal core and an aluminum foil layer wrapped around the outer periphery of the brazing filler metal core, wherein the brazing filler metal core contains Sr and aluminum foam particles; The solder core comprises, by weight, the following components: 8.0-10 parts Si, 2.5-4.5 parts Sr, 0.1-0.3 parts aluminum foam particles, 0.05-0.08 parts B, and 85-90 parts Al; the porosity of the aluminum foam particles is 40%-60%, and the average pore size is 0.2-0.8 nm. The thickness of the aluminum foil layer on one side accounts for 1 / 5 to 1 / 4 of the total thickness of the solder; the thickness of the aluminum foil layer on one side is 0.04-0.1 mm, and the total thickness of the solder, which is sandwich foil, is 0.1-0.5 mm.

2. The brazing filler metal according to claim 1, characterized in that, The particle size of the aluminum foam particles is 20-50 μm.

3. The brazing filler metal according to claim 1, characterized in that, The aluminum foil layer comprises any one of Al, 3003 alloy, and 6063 alloy.

4. The method for preparing the solder according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Melt the required amount of aluminum foil raw material into a liquid metal, and obtain a hollow plate-shaped aluminum frame with open ends by casting; S2. Heat the required amount of brazing metal core raw material to 650-720℃ to make a metal suspension containing solid foamed aluminum particles, and inject the metal suspension into the aluminum frame. After cooling, a composite metal plate is obtained. S3. The composite metal plate is subjected to multiple passes of rough rolling and fine rolling to obtain sandwich foil-shaped brazing filler metal.

5. The method for preparing the brazing filler metal according to claim 4, characterized in that, In step S2, the raw materials for the brazing filler metal core include Al-20Si, Al-20Sr, aluminum foam particles, Al-5B, and Al.

6. The method for preparing the brazing filler metal according to claim 4, characterized in that, In step S2, before injecting the metal suspension, the following steps are also included: Clean the inner surface of the aluminum frame and coat it evenly with a layer of aluminum flux.

7. The method for preparing the brazing filler metal according to claim 6, characterized in that, The aluminum flux includes potassium fluoroaluminate, cesium fluoroaluminate, and alcohol.

8. The application of the brazing filler metal according to any one of claims 1-3 or the brazing filler metal prepared by the preparation method of any one of claims 4-7 in the brazing of rare earth modified die-cast aluminum alloys.

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