A brazing clad plate and a preparation method and application thereof

Abstract

The present application relates to the technical field of brazing material, in particular to a brazing composite plate and a preparation method and application thereof. The brazing composite plate comprises a core material layer and brazing material layers located on both sides of the core material layer. The contact surface of the core material layer and the brazing material layer is in a concave circular arc shape with a thin center and thick edges. The side of the brazing material layer close to the core material layer is in a convex circular arc shape with a thick center and thin edges. The convex circular arc on the brazing material layer is matched with the concave circular arc on the core material layer. The brazing material layer contains 1.5-3% of La by mass percentage. The core material layer and the brazing material layer of the brazing composite plate provided by the present application are in a structure of concave and convex circular arcs inlaid with each other, achieving the design effect of thick center brazing material layer and thin edge brazing material layer. In the furnace brazing process, the thick center brazing material layer melts slowly, which can inhibit or reduce the loss of brazing material liquid at the center position of the workpiece, improving the brazing quality. The addition of the paste component La in the brazing material layer can inhibit the flooding of the brazing material liquid in the furnace brazing process.

Description

Technical Field

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

[0002] Brazed composite boards consist of a core substrate and a surface brazing layer. They are commonly used for furnace welding of various sizes of radiators or sealed shielding boxes, as well as complete assemblies.

[0003] Currently, in radiator brazing, the brazing plate used consists of a base material substrate coated with a conventional filler metal, either single-sided or double-sided. After the base material is cut, processed, and assembled into a complete workpiece, flux is sprayed onto the surface of the brazing plate, and after drying, it can be placed in the furnace for brazing. However, due to the large size of large base station radiators (over 1 meter in length and over 0.6 meters in width), the workpiece has a high edge temperature and a low center temperature during furnace welding. This causes a large amount of filler metal on the surface of the composite plate to flow away towards the edges, resulting in less or no filler metal in the center of the workpiece, affecting the brazing quality of the radiator. In addition, the filler metal on the surface of existing brazed composite plates usually has good fluidity. For example, the aluminum-silicon filler metal on the surface of aluminum brazed composite plates flows severely during brazing, easily clogging the flow channels. Furthermore, the joint strength after brazing of existing brazed composite plates is relatively low, and a layer of flux needs to be sprayed before brazing, which not only increases the number of steps and affects the brazing efficiency, but also makes the sprayed flux layer easy to be knocked off during subsequent manual assembly, affecting the stability of the weld quality.

[0004] To address the aforementioned shortcomings, there is an urgent need to develop a brazing composite plate for radiators and its preparation method to achieve highly reliable brazing of radiators.

[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 composite plate to address the technical problem of insufficient or absent brazing flux in the center of large workpieces when brazing existing brazing composite plates, resulting in severe flux overflow. This invention improves the structure of the brazing composite plate by increasing the amount of brazing flux in the center and by adding a gelling agent (La) to the flux layer to suppress flux overflow.

[0007] The second objective of this invention is to provide a method for preparing the brazed composite plate as described above. The preparation process of this invention is simple and easy to operate.

[0008] A third objective of this invention is to provide an application of the brazed composite plate as described above, or the brazed composite plate prepared by the method described above, in the brazing of radiators.

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

[0010] A brazed composite board includes a core layer and solder layers located on both sides of the core layer. The contact surface between the core layer and the solder layer is a concave arc shape with a thin center and a thick edge. The side of the solder layer adjacent to the core layer is a convex arc shape with a thick center and a thin edge. The convex arc on the solder layer matches the concave arc on the core layer. The solder layer contains 1.5%-3% La by mass percentage.

[0011] A method for preparing the brazed composite plate as described above includes the following steps:

[0012] S1. Take a core material substrate and a solder metal plate of the required size and specifications. Process concave arcs on both sides of the core material substrate. The solder metal plate contains La. Process a convex arc on one side of the solder metal plate to match the concave arcs.

[0013] S2. Two processed brazing metal plates and one processed core substrate are stacked together, with the core substrate located between the two brazing metal plates, and the convex arc on the brazing metal plate is embedded in the concave arc on the core substrate. They are then fixed together by spot welding to obtain a metal composite block.

[0014] S3. The metal composite block is hot rolled and cut in multiple passes to obtain a brazed composite plate.

[0015] Application of the brazed composite plate as described above, or the brazed composite plate prepared by the method described above, in the brazing of radiators.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) The core material layer and the brazing filler layer of the brazing composite plate provided by the present invention are in a structure of concave and convex arcs interlocking with each other, which realizes the design effect of thick center brazing filler layer and thin edge brazing filler layer. During the furnace welding process, the thicker center brazing filler layer melts slowly and has a large amount of material, which can suppress or reduce the loss of brazing filler liquid at the center of the workpiece to a certain extent and improve the brazing quality.

[0018] (2) The solder layer of the present invention contains a highly active element La, which readily forms lanthanum oxide with a high specific gravity and is dispersed in the solder liquid, thereby increasing the viscosity of the solder liquid and inhibiting the overflow of the solder liquid. Attached Figure Description

[0019] 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.

[0020] Figure 1 This is a schematic diagram of the structure of the brazed composite plate provided in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram illustrating the processing of concave and convex circular arcs according to an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the final rolling process of the brazed composite plate provided in an embodiment of the present invention;

[0023] Figure 4 These are comparative images of the sampling morphology at the center position of the brazed composite plate in different embodiments and comparative examples of the present invention. Among them, A is sample 3 of comparative example, B is sample 1 of example, and C is sample 5 of comparative example.

[0024] Figure 5 This is a diagram showing the brazing filler metal flow morphology on the surface of the die-cast aluminum alloy used for brazing the brazed composite plate in Comparative Example 2 of this invention.

[0025] Figure 6 This is a surface morphology diagram of the die-cast aluminum alloy used for brazing the brazed composite plate in Comparative Example 4 of the present invention.

[0026] Figure label:

[0027] 1-Soldering metal layer; 2-Core material layer; 3-Fluoride layer; 4-Concave arc brush; 5-Handle; 6-Convex arc scraper; 7-Motor. Detailed Implementation

[0028] 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.

[0029] like Figure 1As shown, the first aspect of the present invention provides a brazed composite board, including a core layer 2 and a solder layer 1 located on both sides of the core layer 2. The contact surface between the core layer 2 and the solder layer 1 is a concave arc shape with a thin center and a thick edge. The side of the solder layer 1 adjacent to the core layer 2 is a convex arc shape with a thick center and a thin edge. The convex arc on the solder layer 1 is adapted to the concave arc on the core layer 2. The solder layer 1 contains 1.5%-3% La by mass percentage.

[0030] This invention designs the core layer 2 and the brazing filler layer 1 of the brazed composite plate into a complex structure with interlocking concave and convex arcs. This achieves a design effect where the center brazing filler layer is thicker and the edge brazing filler layer is thinner. During furnace welding, the thicker center brazing filler layer requires more molten heat. Even if the brazing filler melt is lost, some filler melt will be retained, which can inhibit or reduce the loss of brazing filler melt at the center of the workpiece to a certain extent, thus improving the brazing quality. This invention also adds the highly reactive rare earth element La to the brazing filler layer. Its function is to make the brazing filler melt into a paste. La is easily oxidized to form lanthanum oxide (density 6.51 g / cm³). 3 Its density is much greater than that of the solder (approximately 2.7 g / cm³). 3 It will be dispersed in the solder fluid in large quantities, thereby increasing the viscosity of the solder fluid, inhibiting the overflow of the solder fluid, reducing the loss of solder fluid, and avoiding the blockage of the flow channel.

[0031] If the La content in the solder layer is too low, the effect of suppressing flow will be poor. If the La content is too high, the viscosity of the solder will be too high and the flowability of the solder will be too poor, which will affect the brazing effect. Therefore, it is necessary to reasonably control the La content in the solder layer. In some embodiments, typically but not limitingly, for example, the mass percentage of La in the solder layer can be any one value or a range of any two values ​​from 1.5%, 2%, 2.5%, to 3%.

[0032] In some specific embodiments of the present invention, the thickness at the center of the single-sided solder layer 1 accounts for 10%-12% of the total thickness of the brazed composite plate. For example, it can be any one value or a range of any two values ​​among 10%, 10.5%, 11%, 11.5%, and 12%. The thickness at the edge of the single-sided solder layer 1 accounts for 5%-8% of the total thickness of the brazed composite plate. For example, it can be any one value or a range of any two values ​​among 5%, 6%, 7%, and 8%. And there is a rounded transition between the edge and the center.

[0033] Controlling the convex arc dimension of the solder layer within the above range can achieve better brazing results. If the center thickness is too small and the edge thickness is too large, it will be difficult to suppress the loss of solder in the center. Conversely, if the center thickness is too large and the edge thickness is too small, there will be too much solder in the center, resulting in weld beads. Moreover, after the concave arc of the core material layer is filled with solder, the excess solder will flow to the periphery, causing severe overflow and affecting the brazing effect.

[0034] In some specific embodiments of the present invention, the brazing filler layer 1 further contains 1%-2% Zr by mass percentage. For example, the mass percentage of Zr can be any one of 1%, 1.2%, 1.5%, 1.8%, or 2%, or a range of any two of these values. Zr can form a large amount of Al3Zr and ZrSi phases in the alloy, which are dispersed in the matrix, playing a role in solid solution strengthening and age-hardening, thereby improving the strength of the brazed joint in the brazed composite plate. If the Zr content is too low, the strengthening effect is poor; if the Zr content is too high, the material will become more brittle and the processing performance will decrease.

[0035] In some specific embodiments of the present invention, the core layer 2 is an aluminum alloy core, such as any one of alloy 3003, alloy 6061, or alloy 6063; the brazing filler layer 1 contains the following components by mass: 8.0-10 parts Si, 1.5-3.0 parts La, 1.0-2.0 parts Zr, and 80-90 parts Al. An aluminum-silicon based brazing filler suitable for aluminum alloy brazing is selected for the aluminum alloy core, and the addition of the paste-forming element La and the strengthening element Zr suppresses the overflow of the brazing filler during furnace welding and improves the strength of the brazed joint. This brazing plate is suitable for brazing die-cast aluminum alloy heat sinks. In other embodiments, depending on the material of the workpiece being brazed, other core and brazing filler materials can be selected. For example, for stainless steel heat sinks, a stainless steel core can be used.

[0036] In some implementations, typically but not limitingly, for example, in solder layer 1, the mass fraction of Si can be any one of 8.0 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, or a range of any two of these values; the mass fraction of La can be any one of 1.5 parts, 2.0 parts, 2.5 parts, 3.0 parts, or a range of any two of these values; the mass fraction of Zr can be any one of 1.0 parts, 1.2 parts, 1.5 parts, 1.8 parts, 2.0 parts, or a range of any two of these values; and the mass fraction of Al can be any one of 80 parts, 82.5 parts, 85 parts, 87.5 parts, 90 parts, or a range of any two of these values.

[0037] In some specific embodiments of the present invention, a flux layer 3 is provided on the side of the brazing filler layer 1 away from the core material layer 2. The flux layer is integrally bonded with the composite board, making it less likely to be knocked off. This eliminates the need for the flux spraying process during furnace welding, thus improving brazing efficiency.

[0038] In some specific embodiments of the present invention, the flux layer used comprises potassium fluoroaluminate, cesium fluoroaluminate, and potassium fluoroborate.

[0039] In some specific embodiments of the present invention, the mass ratio of potassium fluoroaluminate, cesium fluoroaluminate, and potassium fluoroborate in the flux layer is 10:1-3:0.5-1. For example, it can be any one value or a range of any two values ​​from 10:1:0.5, 10:1:0.8, 10:1:1, 10:2:0.5, 10:2:0.8, 10:2:1, 10:3:0.5, 10:3:0.8, and 10:3:1.

[0040] In some specific embodiments of the present invention, the surface of the solder layer 1 away from the core layer 2 is evenly distributed with multiple grooves, and the flux forming the flux layer 3 is located in the grooves. The purpose of setting the grooves is twofold: first, to accommodate the flux, and second, to roughen the surface of the solder layer 1, increase the contact area between the solder layer 1 and the flux, increase the bonding force between the solder layer 1 and the flux layer 3, and prevent the flux layer 3 from falling off.

[0041] In some specific embodiments of the present invention, the groove depth on the surface of the solder layer 1 is 30-50 μm, for example, it can be any one value or a range of any two values ​​among 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm; the spacing between two adjacent grooves is 3-8 mm, for example, it can be any one value or a range of any two values ​​among 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, and 8 mm.

[0042] A second aspect of the present invention provides a method for preparing the brazed composite plate as described above, comprising the following steps:

[0043] S1. Take the core substrate and the solder metal plate of the required size and specifications. Process concave arcs on both sides of the core substrate. The solder metal plate contains La. Process a convex arc on one side of the solder metal plate that matches the concave arc on the core substrate.

[0044] S2. Stack two processed brazing metal plates and one processed core substrate together in the order of "brazing metal plate-core substrate-brazing metal plate", so that the core substrate is located between the two brazing metal plates, and the convex arc on the brazing metal plate is embedded in the concave arc on the core substrate, and fix them together by spot welding to obtain a metal composite block.

[0045] S3. The metal composite block obtained in step S2 is subjected to multiple hot rolling and cutting processes to obtain a brazed composite plate.

[0046] The method of this invention is simple to prepare and easy to operate. It involves machining concave arcs on both sides of the core substrate and machining a convex arc on one side of the solder metal plate to match the concave arcs. During assembly, the convex arc on the solder metal plate is fitted into the concave arc of the core substrate. After hot rolling, a brazing composite plate with a thick core solder layer and a thin edge solder layer can be obtained. This structure can suppress or reduce the loss of solder fluid at the center of the workpiece. The solder metal plate used contains a paste-like component La, which can increase the viscosity of the solder fluid and suppress its overflow. The two work together to improve the brazing quality of the workpiece.

[0047] In some specific embodiments of the present invention, the thickness at the center of any solder metal plate with a convex arc accounts for 10%-12% of the total thickness of the metal composite block. For example, it can be any one value or a range of any two values ​​among 10%, 10.5%, 11%, 11.5%, and 12%. The thickness at the edge of any solder metal plate with a convex arc accounts for 5%-8% of the total thickness of the metal composite block. For example, it can be any one value or a range of any two values ​​among 5%, 6%, 7%, and 8%. Furthermore, the edge of the convex arc of the solder metal plate has a circular arc transition with the center.

[0048] In some specific embodiments of the present invention, the brazing metal plate used in step S1 can be obtained by purchase or by processing. In some embodiments, the processing method of the brazing metal plate includes: weighing raw materials according to mass fractions, obtaining brazing metal foil of the required initial thickness through melting, casting, and rolling, and cutting it into brazing metal plates with the same length and width as the core substrate. The initial thickness of the brazing metal plate can be calculated based on the dimensions of the core substrate and the proportion of the core thickness and edge thickness of the brazing layer to the total thickness of the entire brazed composite plate.

[0049] In some specific embodiments of the present invention, the core material substrate is selected from aluminum alloy plates, such as any one of 3003 alloy plates, 6061 alloy plates or 6063 alloy plates; the raw materials of the brazing metal plate include Al-20Si, Al-10La, Al-5Zr and Al.

[0050] like Figure 3 As shown, in some specific embodiments of the present invention, step S3 further includes the following step:

[0051] Before the final hot rolling, the brazed composite plate is roughened by upper and lower wire brush rollers to create uniform grooves on its surface. The roughened composite plate then passes through a semi-molten flux solution.

[0052] The purpose of roughening the surface of the composite board to form grooves is to increase the contact area between the solder layer and the flux liquid on the surface of the composite board, and to increase the adhesion between the solder layer and the flux liquid. The purpose of controlling the flux liquid to be in a semi-molten state is to increase the viscosity of the flux liquid, further increasing the adhesion between the flux liquid and the solder layer. Furthermore, the flux liquid fills the grooves on the surface of the solder layer, making it less likely to fall off during the final hot rolling.

[0053] In some specific embodiments of the present invention, the speed at which the composite plate passes through the flux solution is 5-10 mm / s. For example, it can be any one value or a range of any two values ​​among 5 mm / s, 6 mm / s, 7 mm / s, 8 mm / s, 9 mm / s, and 10 mm / s.

[0054] In some specific embodiments of the present invention, the flux used includes potassium fluoroaluminate, cesium fluoroaluminate, and potassium fluoroborate, and the temperature of the flux is 480-520°C. For example, it can be any single value or a range of any two values ​​from 480°C, 490°C, 500°C, 510°C, and 520°C. The purpose of controlling this temperature is to keep the flux in a semi-molten state. In other embodiments, other fluxes may be selected, and the temperature at which they are kept in the semi-molten state varies depending on the flux.

[0055] like Figure 2 As shown, in some specific embodiments of the present invention, the concave arc on the core substrate is machined by a convex arc scraper 6, which matches the concave arc on the core substrate. Specific steps include: mounting the convex arc scraper 6 on a planer, starting the motor 7 to rotate the convex arc scraper 6, and machining concave arcs on both the upper and lower surfaces of the core substrate.

[0056] In some specific embodiments of the present invention, the method for preparing the convex arc on the brazing filler metal plate includes the following steps:

[0057] The solder metal plate is fixed on the platform. A concave arc brush 4 is dipped in etching solution and placed on the surface of the solder metal plate. The handle 5 is rotated to repeatedly brush and etch the solder metal plate until it meets the size requirements. After washing, a solder metal plate with a convex arc on one side is obtained. The concave arc brush 4 is matched with the convex arc on the solder metal plate. The washing includes at least one of acid washing, water washing, and alcohol washing.

[0058] In some specific embodiments of the present invention, the etching solution used includes at least one of an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, or an aqueous solution of sodium bicarbonate.

[0059] In some specific embodiments of the present invention, the mass concentration of the etching solution used is 3%-10%, for example, it can be any one value or a range of any two values ​​from 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.

[0060] A third aspect of the present invention provides the application of a brazed composite plate as described in any of the foregoing embodiments, or a brazed composite plate prepared by the method described in any of the foregoing embodiments, in the brazing of a radiator. For example, an aluminum brazed composite plate can be used for brazing die-cast aluminum alloy radiators.

[0061] 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.

[0062] Example 1

[0063] This embodiment provides a brazing composite plate, which has a five-layer plate structure, including a core material layer, brazing filler metal layers located on both sides of the core material layer, and a flux layer located on the outside of the brazing filler metal layer; the core material layer is 3003 alloy;

[0064] The core material layer is thick at the edges and thin at the center, with concave arcs on both the top and bottom surfaces. The solder layer is thick at the center and thin at the edges on the side adjacent to the core material layer, with a convex arc shape. The convex arc of the solder layer and the concave arc of the core material layer are completely fitted together.

[0065] The flux layer is composed of potassium fluoroaluminate, cesium fluoroaluminate, and potassium fluoroborate, with a mass ratio of 10:1:0.5.

[0066] The mass fractions of each element in the solder layer are as follows: Al 89.5 parts, Si 8.0 parts, La 1.5 parts, Zr 1.0 parts;

[0067] The thickness of the center of the single-sided solder layer accounts for 10% of the total thickness of the brazed composite plate; the thickness of the outermost edge of the single-sided solder layer accounts for 5% of the total thickness of the brazed composite plate, and there is a rounded transition between the edge and the center.

[0068] The preparation method includes the following steps:

[0069] S1. Given a 3003 alloy plate with dimensions of 400×400×20mm, and assuming the thickness of the solder layer edge on one side accounts for 5% of the total composite plate thickness, the required thickness at the edge of the solder metal plate is calculated to be 1.11mm. Based on the assumption that the thickness of the solder layer center on one side accounts for 10% of the composite plate thickness, the required thickness of the solder metal plate core is calculated to be 1.11mm + 1.11mm = 2.22mm (i.e., the initial thickness of the solder plate). Solder raw materials Al-20Si, Al-10La, Al-5Zr, and Al are weighed according to their mass fractions. Through smelting, casting, and rolling, a solder foil with a thickness of 2.22mm is obtained and cut into solder metal plates of 400×400×2.22mm.

[0070] Take a 3003 alloy plate of a given size, fix it on the worktable, install the convex arc scraper on the planer, and machine concave arc surfaces on the upper and lower sides of the 3003 alloy plate respectively, so that the thickness of the 3003 alloy plate at the center is 20-1.11×2=17.78mm.

[0071] Two cut solder metal plates were fixed on the platform. A concave arc coarse brush was used to dip into a 5% NaOH aqueous solution and repeatedly rotated to brush and etch the solder metal plates until the thickness of the outermost edge of the solder metal plates was 1.11 mm. After acid washing, water washing and alcohol cleaning, two solder metal plates with convex arcs were obtained.

[0072] S2. The two brazing metal plates processed in step S1 are stacked together with the 3003 alloy plate in the order of "brazing metal plate-3003 alloy plate-brazing metal plate", and the convex arc of the brazing metal plate is embedded in the concave arc of the 3003 alloy plate. They are then spot welded together to form a metal composite block.

[0073] S3. The metal composite block obtained in step S2 is subjected to multiple hot rolling passes. Before the last rolling pass, it is roughened by upper and lower wire brush rollers to process uniform grooves with a depth of about 30 μm and a spacing of about 3 mm. The roughened composite plate is passed through a semi-molten flux liquid (480°C) at a speed of 5 mm / s. After the last hot rolling and cutting, a brazed composite plate with a five-layer structure is obtained.

[0074] Example 2

[0075] This embodiment provides a brazing composite plate, which has a five-layer plate structure, including a core material layer, brazing filler metal layers located on both sides of the core material layer, and a flux layer located on the outside of the brazing filler metal layer; the core material layer is 3003 alloy;

[0076] The core material layer is thick at the edges and thin at the center, with concave arcs on both the top and bottom surfaces. The solder layer is thick at the center and thin at the edges on the side adjacent to the core material layer, with a convex arc shape. The convex arc of the solder layer and the concave arc of the core material layer are completely fitted together.

[0077] The flux layer is composed of potassium fluoroaluminate, cesium fluoroaluminate, and potassium fluoroborate, with a mass ratio of 10:2:0.8.

[0078] The mass fractions of each element in the solder layer are as follows: Al 88.5 parts, Si 8.5 parts, La 1.8 parts, Zr 1.2 parts;

[0079] The thickness of the center of the single-sided solder layer accounts for 12% of the total thickness of the brazed composite plate; the thickness of the outermost edge of the single-sided solder layer accounts for 8% of the total thickness of the brazed composite plate, and there is a rounded transition between the edge and the center.

[0080] The preparation method is similar to that in Example 1, with the following differences:

[0081] In step S1, given the dimensions of the 3003 alloy plate as 400×400×20mm, and assuming that the thickness of the edge of the solder layer on one side accounts for 8% of the total thickness of the composite plate, the required thickness at the edge of the solder metal plate is calculated to be 1.9mm. Based on the assumption that the thickness of the center of the solder layer on one side accounts for 12% of the total thickness of the composite plate, the required thickness of the core of the solder metal plate is calculated to be 2.856mm (i.e., the initial thickness of the solder plate); the initial dimensions of the solder metal plate are 400×400×2.856mm.

[0082] The thickness at the center of the 3003 alloy plate after machining a concave arc is 20 - 0.956 × 2 = 18.088 mm;

[0083] The thickness of the outermost edge of the brazing filler metal plate after machining a convex arc is 1.9 mm;

[0084] In step S3, the roughened grooves are approximately 40 μm deep and 5 mm apart; the roughened composite board passes through the flux solution at a speed of 8 mm / s; and the flux solution temperature is 500 °C.

[0085] The remaining process conditions are the same as in Example 1.

[0086] Example 3

[0087] This embodiment provides a brazing composite plate, which has a five-layer plate structure, including a core material layer, brazing filler metal layers located on both sides of the core material layer, and a flux layer located on the outside of the brazing filler metal layer; the core material layer is 3003 alloy;

[0088] The core material layer is thick at the edges and thin at the center, with concave arcs on both the top and bottom surfaces. The solder layer is thick at the center and thin at the edges on the side adjacent to the core material layer, with a convex arc shape. The convex arc of the solder layer and the concave arc of the core material layer are completely fitted together.

[0089] The flux layer is composed of potassium fluoroaluminate, cesium fluoroaluminate and potassium fluoroborate, with a mass ratio of potassium fluoroaluminate, cesium fluoroaluminate and potassium fluoroborate of 10:3:1;

[0090] The mass fractions of each element in the solder layer are as follows: Al 87.5 parts, Si 9 parts, La 2.0 parts, Zr 1.5 parts.

[0091] The thickness of the center of the single-sided solder layer accounts for 10% of the total thickness of the brazed composite plate; the thickness of the outermost edge of the single-sided solder layer accounts for 5% of the total thickness of the brazed composite plate, and there is a rounded transition between the edge and the center.

[0092] The preparation method is similar to that in Example 1, with the following differences:

[0093] In step S3, the roughened grooves are approximately 50 μm deep and 8 mm apart; the roughened composite board passes through the flux solution at a speed of 10 mm / s; and the flux solution temperature is 520 °C.

[0094] The remaining process conditions are the same as in Example 1.

[0095] Example 4

[0096] This embodiment provides a brazing composite plate, which has a five-layer plate structure, including a core material layer, brazing filler metal layers located on both sides of the core material layer, and a flux layer located on the outside of the brazing filler metal layer; the core material layer is 3003 alloy;

[0097] The core material layer is thick at the edges and thin at the center, with concave arcs on both the top and bottom surfaces. The solder layer is thick at the center and thin at the edges on the side adjacent to the core material layer, with a convex arc shape. The convex arc of the solder layer and the concave arc of the core material layer are completely fitted together.

[0098] The flux layer is composed of potassium fluoroaluminate, cesium fluoroaluminate, and potassium fluoroborate, with a mass ratio of 10:1:0.5.

[0099] The mass fractions of each element in the solder layer are as follows: Al 85 parts, Si 10 parts, La 3.0 parts, Zr 2.0 parts.

[0100] The thickness of the center of the single-sided solder layer accounts for 10% of the total thickness of the brazed composite plate; the thickness of the outermost edge of the single-sided solder layer accounts for 5% of the total thickness of the brazed composite plate, and there is a rounded transition between the edge and the center.

[0101] The preparation method is similar to that in Example 1, with the following differences:

[0102] In step S3, the roughened grooves are approximately 50 μm deep and 8 mm apart; the roughened composite board passes through the flux solution at a speed of 10 mm / s; and the flux solution temperature is 520 °C.

[0103] The remaining process conditions are the same as in Example 1.

[0104] Example 5

[0105] This embodiment provides a brazing composite plate, which has a five-layer plate structure, including a core material layer, brazing filler metal layers located on both sides of the core material layer, and a flux layer located on the outside of the brazing filler metal layer; the core material layer is 3003 alloy;

[0106] The core material layer is thick at the edges and thin at the center, with concave arcs on both the top and bottom surfaces. The solder layer is thick at the center and thin at the edges on the side adjacent to the core material layer, with a convex arc shape. The convex arc of the solder layer and the concave arc of the core material layer are completely fitted together.

[0107] The flux layer is composed of potassium fluoroaluminate, cesium fluoroaluminate, and potassium fluoroborate, with a mass ratio of 10:2:0.8.

[0108] The mass fractions of each element in the solder layer are as follows: Al 85 parts, Si 10 parts, La 3.0 parts, Zr 2.0 parts.

[0109] The thickness of the center of the single-sided solder layer accounts for 10% of the total thickness of the brazed composite plate; the thickness of the outermost edge of the single-sided solder layer accounts for 5% of the total thickness of the brazed composite plate, and there is a rounded transition between the edge and the center.

[0110] The preparation method is similar to that in Example 1, with the following differences:

[0111] In step S3, the roughened grooves are approximately 50 μm deep and 8 mm apart; the roughened composite board passes through the flux solution at a speed of 10 mm / s; and the flux solution temperature is 520 °C.

[0112] The remaining process conditions are the same as in Example 1.

[0113] Example 6

[0114] Example 6 is similar to Example 1, except that the solder layer does not contain Zr, and all other conditions are the same as in Example 1.

[0115] Example 7

[0116] Example 7 is similar to Example 1, except that it does not contain a flux layer, and all other conditions are the same as in Example 1.

[0117] Comparative Example 1

[0118] Comparative Example 1 is similar to Example 1, except that the mass percentage of La in the solder layer is 1%, and all other conditions are the same as in Example 1.

[0119] Comparative Example 2

[0120] Comparative Example 2 is similar to Example 1, except that the solder layer does not contain La, and all other conditions are the same as in Example 1.

[0121] Comparative Example 3

[0122] Comparative Example 3 is similar to Example 1, except that the core material layer and the solder layer are not interlocking with a concave-convex arc structure, but a conventional planar structure. The thickness of the solder layer accounts for 10% of the total thickness of the composite board. The other conditions are the same as in Example 1.

[0123] Comparative Example 4

[0124] Comparative Example 4 is similar to Example 1, except that the core material layer and the solder layer are embedded in a convex-concave arc structure. That is, the two sides of the core material layer are set with convex arcs, and the side of the solder layer adjacent to the core material layer is set with concave arcs. The center of the solder layer is thin (the thickness on one side is 5% of the total thickness of the composite board) and the edge is thick (the thickness on one side is 10% of the total thickness of the composite board). All other conditions are the same as in Example 1.

[0125] Comparative Example 5

[0126] Comparative Example 5 is similar to Example 1, except that the thickness of the center of the single-sided solder layer accounts for 15% of the total thickness of the composite board, and the thickness of the outermost edge of the single-sided solder layer accounts for 3% of the total thickness of the composite board. The other conditions are the same as in Example 1.

[0127] Test case

[0128] To examine and compare the joint strength and flow characteristics of the brazed heat sinks using brazed composite plates in various embodiments and comparative examples of the present invention (tunnel furnace brazing, brazing furnace temperature 615℃, chain speed 300mm / min), brazed composite plates from each embodiment and comparative example were used for furnace brazing of die-cast aluminum alloy heat sinks. One sample was welded for each composite plate. The joint shear strength was tested according to the method of standard GB / T11363-2008, and the degree of brazing filler flow on the surface of the die-cast aluminum alloy and the presence of brazing filler at the center of the heat sink were observed. The results are shown in Table 1.

[0129] Table 1

[0130]

[0131]

[0132] As shown in Table 1, when brazing the composite plate of the present invention into the die-cast aluminum alloy heat exchanger, the brazing filler metal did not overflow, and there was filler metal in the center of the workpiece. The brazing strength was high and the brazing quality was good. As can be seen from the comparative examples of Example 1 and Example 6, adding Zr to the filler metal layer can improve the shear strength of the joint. In Comparative Example 2, there was no la, the filler metal overflowed severely, there was filler metal in the center, but the amount of filler metal was small, and the shear strength of the joint was low. In Comparative Example 1, the content of la was low, there was slight overflow, and the joint strength was higher than that of Comparative Example 2, but lower than that of Example 3. In Comparative Example 4, the core material layer and the brazing filler layer are flat. Compared with the previous example, there is less brazing filler in the center, and some areas in the center will be without brazing filler after brazing, which will reduce the brazing quality. In Comparative Example 5, the core material layer and the brazing filler layer have a convex and concave arc inlay structure. There is even less brazing filler in the center, and the convex arc on the core material layer makes it easier for the brazing filler to flow to the edge, resulting in most of the center of the workpiece being without brazing filler. In Comparative Example 5, the concave arc on the core material layer is too deep, and the center of the brazing filler layer is too thick, resulting in too much brazing filler in the center, with weld beads. Moreover, due to the excessive brazing filler, after the concave arc in the core is filled, the excess brazing filler will flow to the edge, causing serious overflow.

[0133] During the brazing process, since the brazed composite plates in Examples 1-6 contain a flux layer, there is no need to spray flux; they can be directly used for assembly and welding. In Example 7, the brazed composite plate requires pre-spraying a uniform layer of flux and drying before assembly and welding. Compared to Example 7, the composite plates in Examples 1-6 containing a flux layer eliminate the flux spraying and drying processes, saving 20-30 minutes of brazing time per workpiece. The flux layer on the brazed composite plate also improves brazing efficiency.

[0134] like Figure 4 As shown, the surface of the central sample B in Example 1 has a layer of solder (bright metal), that is, there is solder in the center; the surface of the central sample A in Comparative Example 3 is relatively smooth (at the red arrow), and is still the original color of die-cast aluminum, with almost no solder layer; the surface of the central sample C in Comparative Example 5 has serious solder buildup, forming weld beads, which affects the welding effect.

[0135] like Figure 5 As shown in Comparative Example 2, the brazing filler metal on the die-cast aluminum surface of the brazed composite plate was severely overflowing, with rivers of overflowing filler metal forming around each boss.

[0136] like Figure 6 As shown, in Comparative Example 4, most of the die-cast aluminum surface at the center of the brazed composite plate sample had no brazing filler metal.

[0137] 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 brazed composite plate, characterized in that, The brazing composite board comprises a core layer and solder layers on both sides of the core layer. The contact surface between the core layer and the solder layer is a concave arc shape with a thin center and a thick edge. The side of the solder layer adjacent to the core layer is a convex arc shape with a thick center and a thin edge. The convex arc on the solder layer matches the concave arc on the core layer. The thickness at the center of the solder layer on one side accounts for 10%-12% of the total thickness of the brazed composite board, and the edge thickness of the solder layer on one side accounts for 5%-8% of the total thickness of the brazed composite board, with a rounded transition between the edge and the center. The solder layer contains 1.5%-3% La by mass percentage.

2. The brazed composite plate according to claim 1, characterized in that, It meets at least one of the following characteristics: (1) The solder layer also contains 1%-2% Zr by mass percentage; (2) The core material layer is an aluminum alloy core material, and the solder layer contains the following components by mass: 8.0-10 parts Si, 1.5-3.0 parts La, 1.0-2.0 parts Zr, and 80-90 parts Al.

3. The brazed composite plate according to claim 1, characterized in that, The solder layer has a flux layer on the side away from the core material layer.

4. The brazed composite plate according to claim 3, characterized in that, The solder layer has multiple grooves evenly distributed on the side surface away from the core material layer, and the flux forming the flux layer is located in the grooves.

5. The method for preparing the brazed composite plate according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Take a core material substrate and a solder metal plate of the required size and specifications. Process concave arcs on both sides of the core material substrate. The solder metal plate contains La. Process a convex arc on one side of the solder metal plate to match the concave arcs. S2. Two processed brazing metal plates and one processed core substrate are stacked together, with the core substrate located between the two brazing metal plates, and the convex arc on the brazing metal plate is embedded in the concave arc on the core substrate. They are then fixed together by spot welding to obtain a metal composite block. S3. The metal composite block is subjected to multiple hot rolling and cutting processes to obtain a brazed composite plate.

6. The method for preparing the brazed composite plate according to claim 5, characterized in that, Step S3 also includes the following steps: Before the final hot rolling, the brazed composite plate is roughened by machining uniform grooves on its surface. The composite plate after the roughening treatment passes through the semi-molten flux liquid.

7. The method for preparing the brazed composite plate according to claim 6, characterized in that, The composite plate passes through the flux solution at a speed of 5-10 mm / s; And / or, the flux solution includes potassium fluoroaluminate, cesium fluoroaluminate, and potassium fluoroborate, and the temperature of the flux solution is 480-520°C.

8. The method for preparing the brazed composite plate according to claim 6, characterized in that, The method for preparing the convex arc on the brazing metal plate includes the following steps: The brazing metal plate is fixed, and the brazing metal plate is repeatedly brushed with etching solution using a concave arc brush until it meets the size requirements. After washing, the product is obtained.

9. The method for preparing the brazed composite plate according to claim 8, characterized in that, The etching solution includes at least one of an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, or an aqueous solution of sodium bicarbonate. And / or, the mass concentration of the etching solution is 3%-10%.

10. The application of the brazed composite plate according to any one of claims 1-4 or the brazed composite plate prepared by the method of brazed composite plate according to any one of claims 5-9 in the brazing of radiators.

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