Brazing filler metal and preparation method and application thereof

Abstract

The invention relates to the technical field of brazing materials, in particular to brazing filler metal and a preparation method and application thereof. The solid state of the brazing filler metal is in a sandwich foil shape, the brazing filler metal comprises a foil-shaped brazing filler metal core and an aluminum foil layer wrapping the peripheral side of the brazing filler metal core, and the brazing filler metal core contains Sr and foamed aluminum particles. The preparation method comprises the following steps: S1, melting a required amount of aluminum foil layer raw material into molten metal, and casting to obtain a hollow plate-shaped aluminum frame body with openings at two ends; s2, a required amount of brazing filler metal metal core raw material is heated to prepare a metal suspension containing solid foamed aluminum particles, the metal suspension is injected into the aluminum frame body, and a composite metal plate is obtained after cooling; and S3, the composite metal plate is subjected to multi-pass rough rolling and finish rolling, and the sandwich foil-shaped brazing filler metal is obtained. The brazing filler metal structure and the formula components are optimized and improved, brazing filler metal loss and brazing filler metal liquid turbulence during brazing can be restrained, and the shear strength of a brazed joint is improved.

Description

Technical Field

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

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

[0003] However, since the rare earth modified die-cast aluminum alloy material contains a high content of rare earth elements such as Ce and La, the content of Ce and La rare earth elements is as high as more than 10%, the rare earth elements are relatively active and have a strong affinity with the Si element in the conventional aluminum silicon brazing filler metal, resulting in a large amount of loss of aluminum silicon eutectic brazing filler metal liquid during the brazing process, which not only leads to a loose brazing seam, but also serious turbulence of the brazing filler metal liquid, which flows into the radiator flow channel in large quantities and blocks the flow channel, seriously deteriorating the radiator performance.

[0004] In order to solve the above-mentioned shortcomings, it is urgent to develop a low-flow characteristic brazing filler metal that can be used for brazing of rare earth modified die-cast aluminum alloys to achieve high-reliability brazing of rare earth modified die-cast aluminum alloys.

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

[0006] The first purpose of the present invention is to provide a brazing filler metal to solve the technical problems of large loss of brazing filler metal, loose brazing seams, and severe turbulence of brazing filler metal when brazing rare earth modified die-cast aluminum alloys. The present invention can suppress the loss of brazing filler metal and turbulence of brazing filler metal during brazing by optimizing and improving the brazing filler metal structure and formula components, thereby improving the shear strength of the brazed joint.

[0007] The second object of the present invention is to provide a method for preparing the solder as described above, which is simple to operate and easy to implement.

[0008] The third object of the present invention is to provide an application of the brazing filler metal as described above in the brazing of rare earth modified die-cast aluminum alloy.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

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

[0011] Preferably, the solder metal core comprises the following components in parts by mass:

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

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

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

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

[0016] Preferably, the single-side thickness of the aluminum foil layer is 1 / 5-1 / 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 solder in the form of a sandwich foil is 0.1-0.5 mm.

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

[0019] S1. The required amount of raw material of the aluminum foil layer is melted into molten metal, and a hollow plate-shaped aluminum frame with openings at both ends is obtained by casting;

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

[0021] S3. The composite metal plate is subjected to multiple rough rolling and finish rolling to obtain a sandwich foil-shaped solder.

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

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

[0024] Preferably, in step S2, before injecting the metal suspension, the following steps are also included:

[0025] The inner surface of the aluminum frame is cleaned and evenly coated with a layer of aluminum brazing flux.

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

[0027] Application of the brazing filler metal according to any one of the aforementioned embodiments or the brazing filler metal prepared by the method for preparing the brazing filler metal according to any one of the aforementioned embodiments in brazing of rare earth modified die-cast aluminum alloys.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

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

[0030] (2) The solder metal core of the present invention contains a relatively high content of alkaline earth metal element Sr, which can be oxidized into strontium peroxide with a relatively large specific gravity and evenly distributed in the solder liquid to increase the viscosity of the solder liquid, causing the solder liquid to become pasty at high temperatures and reducing the flow of the solder liquid.

[0031] (3) The solder metal core of the present invention contains foamed aluminum particles. A large number of micro- and nano-pores evenly distributed inside the foamed aluminum particles can absorb a portion of the solder liquid, thereby reducing the turbulence of the solder liquid.

[0032] (4) The method of the present invention is simple in process and easy to implement. When the brazing material prepared by the method of the present invention is used to braze rare earth modified die-cast aluminum alloy, the brazing material is not easy to lose or flow turbulently, and the shear strength of the joint after brazing is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic diagram of a solder preparation process provided by an embodiment of the present invention;

[0035] Figure 2 The macroscopic picture of the turbulent flow of the solder on the surface of the die-cast aluminum alloy brazed by the solder in each embodiment and each comparative example;

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

[0037] Reference numerals:

[0038] 1- solder metal core; 2- aluminum foil layer. DETAILED DESCRIPTION

[0039] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, 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 the solder is a sandwich foil, including a foil-shaped solder metal core 1 and an aluminum foil layer 2 wrapped around the outer peripheral side of the solder metal core 1, and the solder metal core 1 contains Sr and foam aluminum particles.

[0041] The solid form of the solder of the present invention is a sandwich foil formed by an aluminum foil and a solder metal core, with both ends open and an end surface in a U-shaped shape. The molten state is a paste. By utilizing the barrier effect of the external aluminum foil, the aluminum foil reacts with the solder liquid first during brazing, reducing the flow rate of the solder liquid and the intensity of the reaction between the solder liquid and the die-cast aluminum alloy base material, and can inhibit the turbulence of the solder liquid to a certain extent. The solder metal core contains a highly active alkaline earth element Sr, which is used to make the solder liquid paste-like. Sr can react with trace oxygen and is easily oxidized to form strontium oxide (density 4.56g / cm 3 ), the specific gravity is greater than the density of the solder liquid (density is about 2.7g / cm 3 ), will be evenly distributed in the solder liquid in large quantities, thereby increasing the viscosity of the solder liquid; the foamed aluminum particles in the component also play a role in pasting. The foamed aluminum particles are evenly distributed in the solder liquid, and can fully absorb the solder liquid by utilizing a large number of micro- and nano-scale pores evenly distributed inside themselves, and block the flow of the solder liquid, thereby suppressing the turbulence of the solder liquid; at the same time, the foamed aluminum particles in the solder liquid 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 brazing metal core 1 is an aluminum-silicon based brazing material.

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

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

[0045] In the above-mentioned aluminum-silicon based solder, the role of the foamed aluminum particles and Sr is to suppress the turbulence of the solder liquid, and the role of B is to purify the grain boundary of the solder joint, refine the solder joint structure, and improve the brazing strength; among them, if the amount of Sr and foamed aluminum particles is too small, they will not have a pasting effect and the effect of suppressing the turbulence of the solder is not good; if the amount is too much, the solder viscosity is too high, which will lead to poor solder fluidity and affect the brazing effect. Therefore, controlling it within the above range can not only suppress the turbulence of the solder, but also have a better brazing effect.

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

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

[0048] When the porosity of foamed aluminum is between 40% and 60%, it can absorb turbulent solder liquid and hinder the flow of solder liquid; when the porosity is too small, the ability to absorb solder liquid is not strong, and the effect of suppressing turbulence is not good; when the porosity is too large, the adsorption capacity is too strong, most of the solder liquid is absorbed into the foamed aluminum, and there is not enough solder liquid to flow into the surface of the base material to be welded.

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

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

[0051] In some specific embodiments of the present invention, the single-side thickness of the aluminum foil layer 2 is 1 / 5-1 / 4 of the total thickness of the solder, for example, it can be any point value among 1 / 5, 1 / 4.8, 1 / 4.5, 1 / 4.2, and 1 / 4, or a range value composed of any two point values; the role of the aluminum foil is to react with the solder liquid first, the solder metal core melts and reacts with the aluminum foil layer of a certain thickness, the aluminum dissolves in the solder liquid, the viscosity of the solder liquid is increased, and the turbulence of the solder liquid is slowed down or suppressed; the thickness of the aluminum foil layer is just enough to completely react, and if the thickness of the aluminum foil is too thick, the reaction will not be complete, and the residual aluminum foil will affect the welding effect; if the aluminum foil is too thin, it will dissolve into the solder liquid instantly and will not play a buffering role, and the viscosity of the solder liquid will not increase significantly, and the effect of suppressing the turbulence of the solder liquid will not be obvious; therefore, the thickness ratio of the aluminum foil layer and the foil solder needs to be reasonably controlled.

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

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

[0054] S1. The required amount of raw material of the aluminum foil layer is melted into molten metal, and a hollow plate-shaped aluminum frame with openings at both ends is obtained by casting;

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

[0056] S3. The composite metal plate is subjected to multiple rough rolling and finish rolling to obtain a sandwich foil-shaped solder.

[0057] The amounts of the raw materials for the aluminum foil layer and the raw materials for the brazing metal core in the present invention are calculated based on the size specifications of the final sandwich foil brazing material and the ratio of the single-side thickness of the aluminum foil layer to the total thickness of the entire sandwich foil brazing material. The hollow plate-shaped aluminum frame prepared in step S1 is used to form the aluminum foil layer; the foamed aluminum particles in the metal suspension in step S2 are in a solid form, and the remaining components are in a metal liquid form. The brazing metal core can be obtained by mixing and heating all the raw materials to a certain temperature, or by first mixing and heating the components except the foamed aluminum particles to melt into a metal liquid, and then adding the foamed aluminum particles to the metal liquid and mixing evenly. The heating temperature is lower than the melting point of the foamed aluminum. The purpose of making the foamed aluminum exist in a solid form is to retain its porous structure. During brazing, a large number of micro- and nano-polar pores inside the foamed aluminum are used to fully absorb the brazing liquid, block the flow of the brazing liquid, and thus suppress the turbulence of the brazing liquid. The method of the present 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 of the aluminum foil layer is at least one of a pure aluminum metal block, a 3003 alloy, and a 6063 alloy.

[0059] In some specific embodiments of the present invention, in step S2, the raw materials of the brazing metal core include Al-20Si, Al-20Sr, foamed aluminum particles, Al-5B and Al. Al-20Si is selected as the master alloy because the alloy has a high Si content and can be used to prepare a brazing alloy with a high Si content and multiple elements, and the melting temperature of the alloy is 600-680°C, which is close to the melting temperature of the brazing material and can be melted better; Al-5B is a refiner, and B dissolves less in aluminum, so it is added in the form of 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 after melting into molten metal, Al-20Sr and Al-5B wrapped in aluminum foil are added; this is because Al-20Sr and Al-5B are modifiers and refiners, and need to be added last to achieve a 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 point value among 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, or a range value consisting of any two point values.

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

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

[0064] In some specific embodiments of the present invention, in step S2, before injecting the metal suspension, the following steps are also included:

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

[0066] The purpose of coating the brazing flux on 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 brazing flux plays a role in removing the film and aiding the flow.

[0067] In some specific embodiments of the present invention, the aluminum brazing 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 brazing flux used is 18-22:1:6-10, for example, it can be any point value among 18:1:6, 18:1:8, 18:1:10, 20:1:6, 20:1:8, 20:1:10, 22:1:6, 22:1:8, 22:1:10, or a range value consisting of any two point values, preferably 20:1:8.

[0069] The third aspect of the present invention provides an application of a solder described in any one of the aforementioned embodiments or a solder prepared by the method for preparing a solder described in any one of the aforementioned embodiments in the brazing of rare earth modified die-cast aluminum alloys, which can solve the problem of solder loss caused by the violent reaction between the rare earth modified die-cast aluminum alloy base material and the solder, and can also avoid turbulence of the solder liquid.

[0070] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0071] Example 1

[0072] This embodiment provides a solder, which is in a sandwich foil structure in solid state and in a paste state in molten state, and is composed of a metal aluminum foil layer and a solder metal core wrapped in the aluminum foil layer; the ratio of the single-side thickness 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: 10 parts of Si, 2.5 parts of Sr, 0.3 parts of foamed aluminum particles, 0.08 parts of B, and 87.12 parts of Al.

[0074] A sandwich foil solder having a size specification of 0.2 mm thick, 100 mm wide and 10 m long is prepared, and the preparation method comprises the following steps:

[0075] S1. According to the size specifications of solder foil, the ratio of the thickness of the aluminum foil layer on one side to the total thickness of the solder foil is 1:5, based on the density of pure aluminum of 2.7g / cm 3 The density of the solder is 2.65g / cm 3 , the required aluminum foil weight is calculated to be 216g, and the required solder metal core weight is 318g;

[0076] 216g of aluminum block is melted into molten metal and injected into a specific graphite mold cavity, and after cooling and demoulding, 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 brazing flux, which is a mixture of potassium fluoroaluminate, cesium fluoroaluminate and alcohol in a mass ratio of 20:1:8;

[0078] The raw materials of the brazing metal core, Al-20Si, Al-20Sr, foamed aluminum particles, Al-5B and Al, are weighed by mass, wherein the foamed aluminum particles have a particle size of 20 μm, a porosity of 40%, and an average pore size of 0.2 nm; the raw materials are mixed and heated to 650° C. to obtain a metal suspension, the metal suspension is injected into an aluminum frame coated with an aluminum brazing agent layer, and the composite metal plate is obtained by cooling, wherein the ratio of the single-side thickness of the aluminum frame to the total thickness of the composite metal plate is 1 / 5;

[0079] S3. The composite metal plate is subjected to multiple rough rolling and finish rolling to obtain a sandwich foil solder of required specifications and dimensions.

[0080] Example 2

[0081] This embodiment provides a solder, which is in a sandwich foil structure in solid state and in a paste state in molten state, and is composed of a metal aluminum foil layer and a solder metal core wrapped in the aluminum foil layer; the ratio of the single-side thickness 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: 9 parts of Si, 3.0 parts of Sr, 0.2 parts of foamed aluminum particles, 0.06 parts of B, and 87.74 parts of Al.

[0083] A sandwich foil solder having a size of 0.16 mm thick, 100 mm wide and 10 m long was prepared. The preparation method was similar to that of Example 1, except for the following differences:

[0084] In step S1, according to the size specification and thickness ratio of the solder foil, it is calculated that the required aluminum foil metal weight is 216g and the required solder metal core weight is 212g;

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

[0086] The remaining process conditions are the same as those in Example 1.

[0087] Example 3

[0088] This embodiment provides a solder, which is in a sandwich foil structure in solid state and in a paste state in molten state, and is composed of a metal aluminum foil layer and a solder metal core wrapped in the aluminum foil layer; the ratio of the single-side thickness 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: 9.5 parts of Si, 3.5 parts of Sr, 0.1 parts of foamed aluminum particles, 0.07 parts of B, and 86.83 parts of Al.

[0090] A sandwich foil solder having a size of 0.3 mm thick, 100 mm wide and 10 m long was prepared. The preparation method was similar to that of Example 1, except that:

[0091] In step S1, according to the size specification and thickness ratio of the solder foil, it is calculated that the required aluminum foil metal weight is 324g and the required solder metal core weight is 477g.

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

[0093] The remaining process conditions are the same as those in Example 1.

[0094] Example 4

[0095] This embodiment provides a solder, which is in a sandwich foil structure in solid state and in a paste state in molten state, and is composed of a metal aluminum foil layer and a solder metal core wrapped in the aluminum foil layer; the ratio of the single-side thickness 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: 8.5 parts of Si, 4.0 parts of Sr, 0.3 parts of foamed aluminum particles, 0.05 parts of B, and 87.15 parts of Al.

[0097] A sandwich foil solder having a size of 0.4 mm thick, 100 mm wide and 10 m long was prepared. The preparation method was similar to that of Example 1, except that:

[0098] In step S1, according to the size specification and thickness ratio of the solder foil, it is calculated that the required aluminum foil metal weight is 540g and the required solder metal core weight is 530g;

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

[0100] The remaining process conditions are the same as those in Example 1.

[0101] Example 5

[0102] This embodiment provides a solder, which is in a sandwich foil structure in solid state and in a paste state in molten state, and is composed of a metal aluminum foil layer and a solder metal core wrapped in the aluminum foil layer; the ratio of the single-side thickness 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: 8.0 parts of Si, 4.5 parts of Sr, 0.2 parts of foamed aluminum particles, 0.08 parts of B, and 87.22 parts of Al.

[0104] A sandwich foil solder having a size of 0.5 mm thick, 100 mm wide and 10 m long was prepared. The preparation method was similar to that of Example 1, except for the following differences:

[0105] In step S1, the required aluminum foil weight is calculated to be 540 g and the required brazing metal core weight is 795 g according to the brazing foil size specification and thickness ratio;

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

[0107] The remaining process conditions are the same as those in Example 1.

[0108] Comparative Example 1

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

[0110] Comparative Example 2

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

[0112] Comparative Example 3

[0113] Comparative Example 3 is similar to Example 1, except that the solder metal core does not contain foamed aluminum particles, and the other conditions are the same as those of 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 the other conditions are the same as those of 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 the other conditions are the same as those of Example 1.

[0118] Comparative Example 6

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

[0120] Comparative Example 7

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

[0122] Comparative Example 8

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

[0124] Comparative Example 9

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

[0126] Comparative Example 10

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

[0128] Test Example 1

[0129] In order to investigate and compare the turbulence characteristics of the brazing joints of the brazing fillers in Examples 1-5 of the present invention and the brazing fillers in Comparative Examples 1-10, the rare earth modified die-casting aluminum alloy and the 3003 aluminum alloy were brazed in a furnace (furnace temperature 590°C, holding time 10 min) using the brazing fillers in each embodiment and each comparative example, 5 samples were welded with each brazing filler, and the degree of brazing filler turbulence on the surface of the die-casting aluminum alloy was analyzed (from bad to good, it was divided into severe, general, slight, and none). The test results are shown in Tables 1 and Figure 2 .

[0130] Table 1

[0131]

[0132]

[0133] Depend on Figure 2 As can be seen from the data in Table 1, the solders in the embodiments of the present invention did not experience turbulence during brazing; in Comparative Examples 1-3, Comparative Example 1 did not wrap the aluminum foil layer on the outside of the solder metal core, lacking the barrier of the aluminum foil, Comparative Example 2 did not contain the gelatinized component Sr, and Comparative Example 3 did not contain the gelatinized component foamed aluminum, and the solders all experienced general turbulence; in Comparative Examples 4 and 6, the content of the gelatinized component Sr or foamed aluminum particles in the solder metal core was relatively low, and slight turbulence also occurred, indicating that the content of metal Sr and foamed aluminum particles must reach a certain level to better suppress the turbulence of the solder. Effect; The porosity of the foamed aluminum particles in Comparative Example 8 is low, the effect of suppressing the disorder of the solder is not good, and a slight overflow phenomenon also occurs; the Sr content of the paste component in Comparative Example 5 is high, the foamed aluminum content of the paste component in Comparative Example 7 is relatively high, and the porosity of the foamed aluminum particles in Comparative Example 9 is relatively high. Comparative Examples 5, 7, and 9 all result in less flowing solder liquid. Although there is no overflow phenomenon, the strength of the brazed joint is relatively low; in Comparative Example 10, traditional 4045 solder is used for brazing, and the solder liquid has serious turbulence; It shows that the method of the present invention can solve the technical problem of solder turbulence during brazing of rare earth modified die-casting aluminum alloys.

[0134] Test Example 2

[0135] In order to investigate and compare the brazing joint strength of the brazing fillers in Examples 1-5 of the present invention and the brazing fillers in Comparative Examples 1-10, the rare earth modified die-casting aluminum alloy and the 3003 aluminum alloy were brazed in a furnace (furnace temperature 590°C, holding time 10 min) using the brazing fillers in each embodiment and each comparative example. Five samples were brazed with each brazing filler. The shear strength of the joint was tested according to the GB / T 11363-2008 method, and the average value was taken. The test results are shown in Table 2. The joint morphology is shown in Table 2. Figure 3 As shown, the 5 joints on the left figure are the joints of Example 1 to Example 5 from left to right, and the 8 joints on the right figure are the joints of Comparative Example 1 to Comparative Example 8 from left to right.

[0136] Table 2

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

[0138] It can be seen from the data in Table 2 that the joint strength of the solder brazing in the embodiments is much higher than that of the solder brazing in the comparative examples. The joint strength after solder brazing in the embodiments is all above 60 MPa, especially in Example 5, whose shear strength is as high as 70.4 MPa, which is 100% higher than the shear strength of 35.2 MPa of the conventional solder brazing joint in Comparative Example 10.

[0139] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A solder, characterized in that: The solid form of the solder is in the form of a sandwich foil, including a foil-shaped solder metal core and an aluminum foil layer wrapped around the outer circumference of the solder metal core. The solder metal core contains Sr and foamed aluminum particles.

2. The solder according to claim 1, characterized in that The brazing filler metal core comprises the following components by mass: Si 8.0-10 parts, Sr 2.5-4.5 parts, foamed aluminum particles 0.1-0.3 parts, B 0.05-0.08 parts, Al 85-90 parts.

3. The solder according to claim 2, characterized in that The porosity of the foamed aluminum particles is 40%-60%, and the average pore size is 0.2-0.8nm; And / or, the particle size of the foamed aluminum particles is 20-50 μm.

4. The solder according to claim 1, characterized in that Contains at least one of the following characteristics: (1) The composition of the aluminum foil layer includes any one of Al, 3003 alloy, and 6063 alloy; (2) The thickness of the aluminum foil layer on one side accounts for 1 / 5-1 / 4 of the total thickness of the solder; (3) The thickness of the aluminum foil layer on one side is 0.04-0.1 mm, and the total thickness of the solder in the form of a sandwich foil is 0.1-0.5 mm.

5. The method for preparing the solder according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. The required amount of raw material of the aluminum foil layer is melted into molten metal, and a hollow plate-shaped aluminum frame with openings at both ends is obtained by casting; S2. The required amount of brazing metal core raw material is heated to form a metal suspension containing solid aluminum foam particles, and the metal suspension is injected into the aluminum frame, and the composite metal plate is obtained after cooling; S3. The composite metal plate is subjected to multiple rough rolling and finish rolling to obtain a sandwich foil-shaped solder.

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

7. The method for preparing the solder according to claim 5, characterized in that: In step S2, the heating temperature for preparing the metal suspension is 650-720°C.

8. The method for preparing the solder according to claim 5, characterized in that: In step S2, before injecting the metal suspension, the following steps are also included: The inner surface of the aluminum frame is cleaned and evenly coated with a layer of aluminum brazing flux.

9. The method for preparing the solder according to claim 8, characterized in that: The aluminum brazing flux comprises potassium fluoroaluminate, cesium fluoroaluminate and alcohol.

10. Use of the brazing filler metal according to any one of claims 1 to 4 or the brazing filler metal prepared by the method for preparing the brazing filler metal according to any one of claims 5 to 9 in brazing of rare earth modified die-casting aluminum alloy.

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