A composite brazing sheet and a method of manufacturing the same, a brazed body

Abstract

The application provides a composite brazing sheet, a preparation method thereof and a brazing body. The composite brazing sheet comprises a core material, a brazing material layer arranged on at least one side surface of the core material, and an intermediate layer arranged between the core material and the brazing material layer. The intermediate layer comprises a low-melting-point phase, and the melting point of the low-melting-point phase is not higher than 600 DEG C. The low-melting-point phase comprises magnesium and at least one element selected from bismuth and tin. The composite brazing sheet provided by the application is provided with an intermediate layer, and the intermediate layer forms a specific low-melting-point phase, so that the breaking of the oxide film and the improvement of the uniformity of wetting are realized, the formation of an effective weld is more favorable, the use of a brazing agent in the CAB brazing process is avoided, the problem of brazing agent residue is completely avoided, and good brazing effect is ensured.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy brazing plate technology, and particularly relates to a composite brazing plate and its preparation method, as well as the brazing body. Background Technology

[0002] Aluminum alloys, with their excellent lightweight, high thermal conductivity, corrosion resistance, and cost control advantages, have become the core material for manufacturing heat exchange devices such as automotive radiators and intercoolers. In this field, brazing is a key process for achieving reliable connections in complex flow channel structures. Currently, the mainstream aluminum alloy brazing processes include vacuum brazing and inert gas shielded brazing (CAB). CAB typically uses a composite brazing plate as the base material, with a 4xxx series aluminum-silicon filler metal layer (such as 4343 or 4045 alloy) coated on the surface of the aluminum alloy core. During brazing, the filler metal layer melts and fills the connection interface under capillary action, thereby achieving overall welding of the components. To ensure that the filler metal can effectively wet the base material and spread smoothly, this process often relies on applying a non-corrosive flux to the surface of the brazing plate to break down the dense alumina film during heating.

[0003] However, flux residues can accumulate in narrow cooling channels, causing physical blockages and affecting heat dissipation and fluid flow. Furthermore, they pose a potential source of corrosion during long-term service, compromising product reliability and lifespan. Especially with the increasingly stringent requirements for material cleanliness and ion emission standards in high-end sectors such as new energy vehicles, the risk of ion contamination from residual components in the flux (such as potassium ions) presents a significant compliance challenge for products manufactured using traditional CAB processes.

[0004] Therefore, developing a novel composite brazing board suitable for inert gas protection environments and capable of achieving high-quality connections without relying on flux has become an urgent need in this field to solve the aforementioned series of technical problems. Summary of the Invention

[0005] This invention provides a composite brazing plate that can completely avoid the problem of flux residue during the brazing process and promote the wetting of the brazing filler metal. When the brazed body is prepared from the composite brazing plate, no flux needs to be applied during the CAB brazing process, and it has a good brazing effect.

[0006] This invention provides a method for preparing a composite brazing plate. The composite brazing plate prepared by this method can completely avoid the problem of flux residue during the brazing process and promote the wetting of the brazing filler metal. When preparing the brazing body from the composite brazing plate, no flux needs to be applied during the CAB brazing process, and it has a good brazing effect.

[0007] The present invention also provides a brazing body that does not require flux during CAB brazing and has good brazing performance.

[0008] The first aspect of the present invention provides a composite brazing board, comprising a core material and a solder layer disposed on at least one surface of the core material, wherein an intermediate layer is disposed between the core material and the solder layer; the intermediate layer comprises a low-melting-point phase, the melting point of the low-melting-point phase being not higher than 600°C; the low-melting-point phase comprises magnesium and at least one element selected from bismuth and tin.

[0009] In the composite brazing board described above, the low-melting-point phase includes a tin-containing phase and a bismuth-containing phase, the tin-containing phase includes a Mg2Sn phase, and the bismuth-containing phase includes a Mg3Bi2 phase and a Mg2Bi phase.

[0010] In the composite brazing plate described above, the number of low-melting-point phases is not less than 50 per mm under a scanning electron microscope. 2 .

[0011] The composite brazing board as described above, wherein, under a scanning electron microscope, the ratio of the amount of the tin-containing phase to the amount of the bismuth-containing phase is (4-20):1; and / or, the length of the low-melting-point phase is 1-20 μm.

[0012] The composite brazing plate described above, wherein, by mass percentage, the intermediate layer comprises 0.1-2.4% Mg, 0.1-1.0% Sn, 0.1-0.5% Bi, 7.5-12% Si, ≤0.2% Fe, ≤0.1% Cu, ≤0.1% Mn, ≤0.1% Zn, ≤0.1% Ti, with unavoidable total impurities ≤0.2%, each impurity ≤0.05%, and the balance being aluminum.

[0013] In the composite brazing board described above, the thickness of the intermediate layer is 1-15% of the thickness of the composite brazing board; and / or, the thickness of the solder layer is 1-10% of the thickness of the composite brazing board.

[0014] The composite brazing plate as described above, wherein, by mass percentage, the intermediate layer comprises 0.2-2.2% Mg, 0.8-1.0% Sn, and 0.1-0.3% Bi.

[0015] The composite brazing board as described above, wherein, by mass percentage, the core material comprises Si≤0.6%, Fe≤0.7%, Cu 0.01-0.8%, Mn 1.0-1.5%, Zn≤0.1%, refining agent element≤0.1%, total unavoidable impurities≤0.2%, each impurity≤0.05%, and the balance being aluminum; and / or,

[0016] The solder layer comprises, by mass percentage: Si 1-6%, Fe ≤ 0.2%, Cu ≤ 0.1%, Mn ≤ 0.1%, Zn ≤ 0.1%, Ti ≤ 0.1%, Bi ≤ 0.2%, unavoidable total impurities ≤ 0.2%, each impurity ≤ 0.05%, and the balance being aluminum.

[0017] A second aspect of the present invention provides a method for preparing the composite brazing plate, comprising the following steps:

[0018] An intermediate ingot is placed on at least one side of the core material ingot, and a solder layer ingot is placed on the surface of the intermediate ingot opposite to the core material ingot to obtain a multilayer material.

[0019] The multilayer material is subjected to hot rolling, cold rolling and annealing in sequence to obtain the composite brazing plate; wherein, the composite brazing plate includes a core material, a brazing filler layer on at least one surface of the core material, and an intermediate layer located between the core material and the brazing filler layer; the intermediate layer includes a low-melting-point phase, the melting point of the low-melting-point phase is not higher than 600°C, and the low-melting-point phase includes magnesium and at least one element selected from bismuth and tin.

[0020] The preparation method described above, wherein the hot-rolled billet is obtained after the hot rolling treatment, and the temperature of the hot rolling treatment is ≤500℃; and / or,

[0021] The casting speed of the intermediate ingot is 60-80 mm / min.

[0022] A third aspect of the present invention provides a brazing body, which is brazed from the composite brazing plate described in the first aspect above, or brazed from the composite brazing plate prepared by the preparation method described in the second aspect above.

[0023] The composite brazing plate provided by this invention has an intermediate layer, and the intermediate layer forms a specific low-melting-point phase, which realizes the removal of oxide film and the improvement of wetting uniformity, thereby avoiding the use of flux in the CAB brazing process, completely avoiding the problem of flux residue, and ensuring good brazing effect. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] Figure 1 This is a schematic diagram of the composite brazing plate provided in Embodiment 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of the composite brazing plate provided in Embodiment 7 of the present invention;

[0027] Figure 3This is a SEM image of the composite brazing plate provided in Embodiment 1 of the present invention;

[0028] Figure 4 This is a schematic diagram of the joint after brazing of the composite brazing plate provided in Embodiment 1 of the present invention.

[0029] Figure label:

[0030] 1-Core material; 2-Intermediate layer; 3-Solder metal layer.

[0031] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] To address the flux residue problem in CAB brazing, existing technologies employ two methods: core material element control and flux pre-embedding composite method. The core material element control method involves adding elements such as Mg and Bi to the core material, utilizing their evaporation or diffusion characteristics at high temperatures to break down the oxide film and promote solder wetting. However, Mg in this method tends to evaporate prematurely or form an MgO oxide film at high temperatures, which exacerbates oxide film instability and hinders solder flow. The flux pre-embedding composite method involves mixing flux powder with aluminum-silicon alloy powder and pre-embedding it between the core material and the solder layer using methods such as hot isostatic pressing to form a composite plate. However, the pre-embedded flux may migrate or distribute unevenly at high temperatures, affecting brazing uniformity. Relying solely on localized flux release makes it difficult to achieve synergistic optimization of oxide film removal and wetting.

[0034] Based on this, the inventors proposed the composite brazing plate of the present invention with the goal of ensuring brazing quality, removing oxide film and wettability.

[0035] The first aspect of the present invention provides a composite brazing board, comprising: a core material, and a brazing filler layer disposed on at least one surface of the core material, wherein an intermediate layer is disposed between the core material and the brazing filler layer; the intermediate layer comprises a low-melting-point phase, the melting point of the low-melting-point phase being not higher than 600°C; the low-melting-point phase comprises magnesium and at least one element selected from bismuth and tin.

[0036] For example, the melting point of the low melting point phase is 600°C, 590°C, 580°C, 570°C, 560°C, 550°C, 540°C, 530°C or below, or a range of any two of these values.

[0037] The composite brazing plate provided by this invention can completely avoid the problem of flux residue during the brazing process and promote solder wetting. When preparing the brazed body from this composite brazing plate, no additional flux is required during CAB brazing, and good brazing results can still be obtained. This is because the low-melting-point phase formed in the intermediate layer preferentially melts during the brazing heating stage, wetting the solder layer through capillary action. Magnesium elements in the low-melting-point phase migrate to the oxide film through the phase interface, effectively and continuously breaking down the oxide film and promoting solder flow, avoiding failure caused by premature oxidation due to the diffusion and migration of magnesium elements in traditional brazing methods. Simultaneously, the molten low-melting-point phase promotes the wetting and flow of the solder layer, replacing external flux, thereby completely eliminating flux residue and avoiding the risk of pipe blockage and corrosion. Therefore, this composite brazing plate, through the aforementioned intermediate layer, can completely replace traditional flux, significantly reducing post-brazing residue while ensuring good brazing results.

[0038] To further control the wetting of the brazing filler metal and thus improve the uniformity and reliability of brazing, the specific types of low-melting-point phases can be limited.

[0039] In one specific embodiment, the low-melting-point phase includes a tin-containing phase and a bismuth-containing phase. The tin-containing phase includes the Mg₂Sn phase, and the bismuth-containing phase includes the Mg₃Bi₂ phase and the Mg₂Bi phase. The Mg₂Sn phase plays a wetting role in the initial stage of brazing, while the Mg₃Bi₂ and Mg₂Bi phases continue to play a role in the middle and later stages of brazing, extending the wetting time window. The coexistence of these phases allows the solder layer to continuously obtain wetting ability within the range of 550-600℃, which is more conducive to the formation of a longer effective weld, thereby improving the brazing effect.

[0040] In one specific embodiment, the number of low-melting-point phases under a scanning electron microscope is not less than 50 per mm. 2 The dense distribution of low-melting-point phases ensures the continuous release of Mg during brazing, promoting capillary flow and interfacial wetting of the brazing filler metal, thereby ensuring the complete removal of the oxide film at the brazing interface and significantly reducing weld defects.

[0041] For example, the number of low-melting-point phases is 50 / mm. 2 55 pieces / mm 2 60 pieces / mm 2 65 pieces / mm 2 70 pieces / mm 2 75 pieces / mm 2 80 pieces / mm 2 85 pieces / mm 2Or more, or a range consisting of any two of these values.

[0042] The method for testing the quantity of the low-melting-point phase in this invention is as follows: Under a scanning electron microscope, select an observation area of ​​400mm×400mm, and manually calculate the quantity of the low-melting-point phase within the observation area.

[0043] In one specific embodiment, under a scanning electron microscope, the ratio of the amount of tin-containing phase to the amount of bismuth-containing phase is (4-20):1. Within this range, the wetting rate and duration during brazing are further adjusted, allowing the Mg2Sn phase to act rapidly in the initial stage of brazing, while the bismuth-containing phase maintains its wetting effect in subsequent stages, thus improving brazing uniformity. The preferred ratio of tin-containing phase to bismuth-containing phase is (6-8):1. Within this preferred range, it is more conducive to balancing the wetting rate and duration during brazing, resulting in a better brazing effect.

[0044] For example, the ratio of the amount of tin phase to the amount of bismuth phase is 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1 or 20:1, or a range of any two of these values.

[0045] The methods for testing the amount of tin-containing phase and bismuth-containing phase in this invention are the same as those for testing the amount of low-melting-point phase described above, and will not be repeated here.

[0046] In one specific embodiment, the length of the low-melting-point phase is 1-20 μm. The length of the low-melting-point phase within this range further enhances its fluidity in the molten state and improves wetting uniformity.

[0047] For example, the length of the low-melting-point phase is 1 μm, 2 μm, 4 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 14 μm, 16 μm, 18 μm or 20 μm, or a range of any two of these values.

[0048] Under a scanning electron microscope, the low-melting-point phase can be observed to be in the form of short rods.

[0049] In one specific embodiment, the intermediate layer, by mass percentage, comprises 0.1-2.4% Mg, 0.1-1.0% Sn, 0.1-0.5% Bi, 7.5-12% Si, ≤0.2% Fe, ≤0.1% Cu, ≤0.1% Mn, ≤0.1% Zn, and ≤0.1% Ti. The total unavoidable impurities are ≤0.2%, with each impurity ≤0.05%, and the balance being aluminum. The elements and their contents within this range in the intermediate layer are more conducive to the formation of the aforementioned low-melting-point phase network, improving the uniform distribution of the low-melting-point phase while suppressing the formation of impurities.

[0050] For example, the Mg content in the intermediate layer is 0.1%, 0.4%, 1.0%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, or 2.4% by mass percentage, or a range of any two of these values.

[0051] For example, the Sn content in the intermediate layer is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0% by mass percentage, or a range of any two of these values.

[0052] For example, the Bi content in the intermediate layer is 0.1%, 0.2%, 0.3%, 0.4%, or 0.5% by mass percentage, or a range of any two of these values.

[0053] For example, the Si content in the intermediate layer is 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, or 12% by mass percentage, or a range of any two of these values.

[0054] For example, the Fe content in the intermediate layer is 0.2%, 0.19%, 0.18%, 0.17%, 0.16%, 0.15%, 0.14%, 0.13%, 0.12% or less by mass percentage, or a range of any two of these values.

[0055] For example, the Cu content in the intermediate layer is 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05% or less by mass percentage, or a range of any two of these values.

[0056] For example, the Mn content in the intermediate layer is 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05% or less by mass percentage, or a range of any two of these values.

[0057] For example, the Zn content in the intermediate layer is 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05% or less by mass percentage, or a range of any two of these values.

[0058] For example, the Ti content in the intermediate layer is 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05% or less by mass percentage, or a range of any two of these values.

[0059] For example, the total unavoidable impurities in the intermediate layer, by mass percentage, are 0.2%, 0.19%, 0.18%, 0.17%, 0.16%, 0.15%, 0.14%, 0.13%, 0.12% or less, or a range of any two of these values.

[0060] For example, the content of each impurity in the intermediate layer is 0.05%, 0.04%, 0.03%, 0.02%, 0.01% or less by mass percentage, or a range of any two of these values.

[0061] In one specific embodiment, the thickness of the intermediate layer is 1-15% of the thickness of the composite brazing board. The fact that the thickness of the intermediate layer is within this range ensures both sufficient formation of the low-melting-point phase and close bonding with the core material and the brazing filler layer, thereby guaranteeing good brazing results.

[0062] For example, the thickness of the intermediate layer is 1%, 3%, 5%, 7%, 9%, 11%, 13%, or 15% of the thickness of the composite brazing board, or a range of any two of these values.

[0063] In one specific embodiment, the thickness of the solder layer is 1-10% of the thickness of the composite brazing board. Maintaining the solder layer thickness as a percentage of the composite brazing board thickness within this range ensures both the melt flowability of the solder and material cost.

[0064] For example, the thickness of the solder layer is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% of the thickness of the composite brazing board, or a range of any two of these values.

[0065] This invention does not impose specific limitations on the thickness of the intermediate layer, core material, and solder layer, and these thicknesses can be adjusted according to actual needs. In one embodiment, the thickness of the intermediate layer is 15-200 μm, the thickness of the core material is 1-3 mm, and the thickness of the solder layer is 50-200 μm.

[0066] In one specific embodiment, the intermediate layer comprises, by mass percentage, 0.2-2.2% Mg, 0.8-1.0% Sn, and 0.1-0.3% Bi. The content of magnesium, tin, and bismuth in the intermediate layer falls within this range, and the elements work synergistically to promote a better distribution of the low-melting-point phases. During brazing, these low-melting-point phases can melt and form a continuous and stable wetting network, thereby significantly improving the spreadability and filling capacity of the brazing filler metal and achieving optimal brazed joint performance.

[0067] In one specific embodiment, the core material, by mass percentage, comprises Si ≤ 0.6%, Fe ≤ 0.7%, Cu 0.01-0.8%, Mn 1.0-1.5%, Zn ≤ 0.1%, refining agent element ≤ 0.1%, unavoidable total impurities ≤ 0.2%, each impurity ≤ 0.05%, and the balance being aluminum. When the content and composition of each element in the core material are within this range, the resulting composite brazing plate exhibits excellent strength and corrosion resistance.

[0068] For example, the Si content in the core material is 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1% or less by mass percentage, or a range of any two of these values.

[0069] For example, the Fe content in the core material is 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1% or less by mass percentage, or a range of any two of these values.

[0070] For example, the Cu content in the core material is 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, or 0.8% by mass, or a range of any two of these values.

[0071] For example, the Mn content in the core material is 1.0%, 1.2%, 1.3%, 1.4% or 1.5% by mass percentage, or a range of any two of these values.

[0072] For example, the Zn content in the core material is 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05% or less by weight, or a range of any two of these values.

[0073] For example, the content of refining agent element in the core material is 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05% or less by mass percentage, or a range of any two of these values.

[0074] For example, the total unavoidable impurities in the core material, by mass percentage, are 0.2%, 0.19%, 0.18%, 0.17%, 0.16%, 0.15% or less, or a range of any two of these values.

[0075] For example, the content of each impurity in the core material is 0.05%, 0.04%, 0.03%, 0.01%, 0.01% or less by mass percentage, or a range of any two of these values.

[0076] The present invention does not specifically limit the refining agent element, but includes, but is not limited to, at least one of titanium, boron and zirconium.

[0077] In one specific embodiment, the solder layer, by mass percentage, comprises: Si 1-6%, Fe ≤ 0.2%, Cu ≤ 0.1%, Mn ≤ 0.1%, Zn ≤ 0.1%, Ti ≤ 0.1%, Bi ≤ 0.2%, unavoidable total impurities ≤ 0.2%, each impurity ≤ 0.05%, and the balance being aluminum. The content and composition of each element in the solder layer are within this range. The melting point of the solder layer, combined with the low melting point of the intermediate layer, synergistically optimizes the overall brazing temperature window to 550-600℃, thereby reducing the impact of thermal stress on the composite brazed plate.

[0078] For example, the Si content in the solder layer is 6%, 5%, 4%, 3%, 2% or 1% by mass percentage, or a range of any two of these values.

[0079] For example, the Fe content in the solder layer is 0.2%, 0.19%, 0.18%, 0.17%, 0.16%, 0.15%, 0.14% or less by mass percentage, or a range of any two of these values.

[0080] For example, the Cu content in the solder layer is 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04% or less by mass percentage, or a range of any two of these values.

[0081] For example, the Mn content in the solder layer is 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04% or less by mass percentage, or a range of any two of these values.

[0082] For example, the Zn content in the solder layer is 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04% or less by mass percentage, or a range of any two of these values.

[0083] For example, the Ti content in the solder layer is 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04% or less by mass percentage, or a range of any two of these values.

[0084] For example, the Bi content in the solder layer is 0.2%, 0.19%, 0.18%, 0.17%, 0.16%, 0.15%, 0.14% or less by mass percentage, or a range of any two of these values.

[0085] For example, the total unavoidable impurities in the solder layer, by mass percentage, are 0.2%, 0.19%, 0.18%, 0.17%, 0.16%, 0.15% or less, or a range of any two of these values.

[0086] For example, the content of each impurity in the solder layer is 0.05%, 0.04%, 0.03%, 0.01%, 0.01% or less by mass percentage, or a range of any two of these values.

[0087] A second aspect of the present invention provides a method for preparing a composite brazing plate, comprising:

[0088] The intermediate ingot is placed on at least one side of the core material ingot, and the solder layer ingot is placed on the surface of the intermediate ingot away from the core material ingot to obtain a multilayer material.

[0089] A composite brazing plate is obtained by sequentially hot rolling, cold rolling and annealing of multi-layer material; wherein the composite brazing plate includes a core material, a brazing filler layer on at least one surface of the core material, and an intermediate layer located between the core material and the brazing filler layer; the intermediate layer includes a low-melting-point phase, the melting point of the low-melting-point phase is not higher than 600°C, and the low-melting-point phase includes magnesium and at least one element selected from bismuth and tin.

[0090] The preparation method of this invention forms a specific low-melting-point phase in the intermediate layer. These phases preferentially melt and migrate to the oxide film interface during the brazing heating stage. The oxide film is broken down and the brazing filler metal is uniformly wetted through the controlled release of Mg. Compared with the prior art, this process does not require external flux, avoiding flux residue problems. At the same time, the low-melting-point phases formed improve the uniformity and reliability of brazing.

[0091] To further remove impurities, the surfaces of the intermediate ingot, core material ingot, and brazing filler layer ingot were polished to prepare a multi-layer material.

[0092] The present invention does not specifically limit the temperature of cold rolling and annealing. In one embodiment, the temperature of cold rolling is 25°C; in another embodiment, the temperature of annealing is 300-350°C.

[0093] This invention does not specifically limit the types and contents of elements in the intermediate ingot, as long as it can form a low-melting-point phase including the above-mentioned characteristics.

[0094] This invention does not specifically limit the types and contents of elements in the core material ingot and the brazing filler layer ingot. For example, the core material ingot includes, but is not limited to, 3003 aluminum alloy, and the brazing filler layer ingot includes, but is not limited to, 4xxx series aluminum-silicon alloys (such as 4343).

[0095] In one specific embodiment, a hot-rolled billet is obtained after hot rolling treatment at a temperature ≤500°C. Controlling the heat treatment temperature within this range helps to suppress the premature decomposition of the low-melting-point phase and prevent it from failing during subsequent brazing.

[0096] For example, the hot rolling temperature is 500°C, 495°C, 490°C, 485°C, 480°C, 475°C, 470°C or below, or a range of any two of these values.

[0097] The present invention does not specifically limit the thickness of the hot-rolled billet obtained after hot rolling. In one specific embodiment, the thickness of the hot-rolled billet is 5-12 mm.

[0098] The present invention does not specifically limit the thickness of the cold-rolled billet obtained after cold rolling. In one embodiment, the thickness of the cold-rolled billet is 0.4-3 mm.

[0099] In one specific embodiment, the casting speed of the intermediate ingot is 60-80 mm / min. Within this casting speed range, the segregation of Sn and Bi elements in the low-melting-point phase of the intermediate layer is suppressed, thereby improving the wetting uniformity of the brazing process and ultimately enhancing the brazing effect.

[0100] Furthermore, the core material ingot is subjected to high-temperature annealing to prepare a multilayer material. This invention does not specifically limit the conditions for high-temperature annealing; conventional conditions in the art can be used. In one embodiment, the high-temperature annealing temperature is 600-615℃, and the holding time is 8-20 hours.

[0101] A third aspect of the present invention provides a brazing body, which is brazed from the composite brazing plate of the first aspect described above, or brazed from the composite brazing plate prepared by the method of the second aspect described above. This brazing body does not require additional application of Noclock flux during CAB brazing and still exhibits good brazing performance.

[0102] The present invention will be further described below through specific embodiments.

[0103] Example 1

[0104] (1) By mass percentage, the core material of this embodiment includes Si 0.12%, Fe 0.35%, Cu 0.01%, Mn 1.0%, Zn 0.009%, Ti 0.01%, the total amount of unavoidable impurities ≤0.05%, each impurity ≤0.05%, and the balance is aluminum.

[0105] By mass percentage, the intermediate layer of this embodiment includes 0.1% Mg, 0.1% Sn, 0.1% Bi, 7.5% Si, 0.15% Fe, 0.004% Cu, 0.02% Mn, 0.009% Zn, and 0.01% Ti. The total amount of unavoidable impurities is ≤0.05%, each impurity is ≤0.05%, and the balance is aluminum.

[0106] By mass percentage, the solder layer of this embodiment includes: Si 1%, Fe 0.15%, Cu 0.004%, Mn 0.02%, Zn 0.004%, Ti 0.01%, Bi 0.12%, unavoidable total impurities ≤0.05%, each impurity ≤0.05%, and the balance is aluminum.

[0107] (2) The method for preparing the composite brazing plate in this embodiment includes:

[0108] 1) According to the above-mentioned brazing filler layer, intermediate layer and core material composition design ratio, the core material ingot, intermediate ingot and brazing filler layer ingot are cast by aluminum alloy semi-continuous casting method, and the ends are sawn 250mm and the surface is milled.

[0109] 2) The core material ingot is subjected to high-temperature annealing to obtain a homogenized core material ingot; the high-temperature annealing conditions are 600℃ for 8 hours. The casting speed of the intermediate ingot is 80 mm / min.

[0110] 3) Press Figure 1 As shown, after grinding the surfaces of the homogenized core material ingot, intermediate ingot, and brazing filler layer ingot, they are stacked to obtain a multi-layer material.

[0111] 4) The multi-layer material is preheated to 480℃, and then rolled into hot-rolled coils using a hot rolling mill. The thickness of the hot-rolled coils is 12mm, and the temperature of the hot rolling mill is 500℃.

[0112] 5) Using hot-rolled coils as cold-rolled blanks, cold-rolling them to 0.4mm at 25℃, and then annealing them at 320℃ for 10h, a composite brazed plate is obtained.

[0113] Example 2

[0114] (1) By mass percentage, the core material of this embodiment includes Si 0.4%, Fe 0.5%, Cu 0.4%, Mn 1.3%, Zn 0.05%, Ti 0.08%, unavoidable total impurities 0.2%, each impurity 0.05%, and the balance is aluminum.

[0115] By mass percentage, the intermediate layer of this embodiment comprises 1.2% Mg, 0.5% Sn, 0.3% Bi, 10% Si, 0.2% Fe, 0.1% Cu, 0.1% Mn, 0.1% Zn, 0.1% Ti, 0.2% unavoidable total impurities, 0.05% for each impurity, and the balance being aluminum.

[0116] By mass percentage, the solder layer of this embodiment includes: Si 3%, Fe 0.1%, Cu 0.08%, Mn 0.09%, Zn 0.09%, Ti 0.1%, Bi 0.2%, unavoidable total impurities 0.2%, each impurity 0.05%, and the balance being aluminum.

[0117] (2) The method for preparing the composite brazing plate in this embodiment includes:

[0118] 1) According to the above-mentioned brazing filler layer, intermediate layer and core material composition design ratio, the core material ingot, intermediate ingot and brazing filler layer ingot are cast by aluminum alloy semi-continuous casting method, and the ends are sawn 250mm and the surface is milled.

[0119] 2) The core material ingot is subjected to high-temperature annealing to obtain a homogenized core material ingot; the high-temperature annealing conditions are 608℃ for 14 hours. The casting speed of the intermediate ingot is 70 mm / min.

[0120] 3) Press Figure 1 As shown, after grinding the surfaces of the homogenized core material ingot, intermediate ingot, and brazing filler layer ingot, they are stacked to obtain a multi-layer material.

[0121] 4) The multi-layer material is preheated to 480℃, and then rolled into hot-rolled coils using a hot rolling mill. The thickness of the hot-rolled coils is 9mm, and the temperature of the hot rolling mill is 500℃.

[0122] 5) Using hot-rolled coils as cold-rolled blanks, cold-rolling them to 1.2mm at 25℃, and then annealing them at 300℃ for 8 hours, a composite brazed plate is obtained.

[0123] Example 3

[0124] (1) By mass percentage, the core material of this embodiment includes 0.6% Si, 0.7% Fe, 0.8% Cu, 1.5% Mn, 0.1% Zn, 0.1% Zr, 0.2% unavoidable impurities, 0.05% of each impurity, and the balance is aluminum.

[0125] By mass percentage, the intermediate layer of this embodiment comprises 2.4% Mg, 1.0% Sn, 0.5% Bi, 12% Si, 0.2% Fe, 0.1% Cu, 0.1% Mn, 0.1% Zn, 0.1% Ti, 0.2% unavoidable total impurities, 0.05% of each impurity, and the balance being aluminum.

[0126] By mass percentage, the solder layer of this embodiment includes: Si 6%, Fe 0.2%, Cu 0.1%, Mn 0.1%, Zn 0.1%, Ti 0.1%, Bi 0.2%, unavoidable total impurities 0.2%, each impurity 0.05%, and the balance being aluminum.

[0127] (2) The method for preparing the composite brazing plate in this embodiment includes:

[0128] 1) According to the above-mentioned brazing filler layer, intermediate layer and core material composition design ratio, the core material ingot, intermediate ingot and brazing filler layer ingot are cast by aluminum alloy semi-continuous casting method, and the ends are sawn 250mm and the surface is milled.

[0129] 2) The core material ingot is subjected to high-temperature annealing to obtain a homogenized core material ingot; the high-temperature annealing conditions are 615℃ for 20 hours. The casting speed of the intermediate ingot is 60 mm / min.

[0130] 3) Press Figure 1 As shown, after grinding the surfaces of the homogenized core material ingot, intermediate ingot, and brazing filler layer ingot, they are stacked to obtain a multi-layer material.

[0131] 4) The multi-layer material is preheated to 480℃, and after preheating, it is rolled into a hot rolling mill into a hot rolled coil. The thickness of the hot rolled coil is 12mm, and the temperature of the hot rolling mill is 500℃.

[0132] 5) Using hot-rolled coils as cold-rolled blanks, cold-rolling them to 2mm at 25℃, and then annealing them at 350℃ for 10h, a composite brazed plate is obtained.

[0133] Example 4

[0134] This embodiment is basically the same as Embodiment 1, except that:

[0135] (1) By mass percentage, the intermediate layer of this embodiment includes 1.6% Mg, 0.8% Sn, 0.1% Bi, 12% Si, 0.2% Fe, 0.1% Cu, 0.1% Mn, 0.1% Zn, 0.1% Ti, 0.2% unavoidable total impurities, 0.05% of each impurity, and the balance being aluminum.

[0136] Example 5

[0137] This embodiment is basically the same as Embodiment 1, except that:

[0138] (1) By mass percentage, the intermediate layer of this embodiment includes 2.0% Mg, 0.9% Sn, 0.15% Bi, 12% Si, 0.2% Fe, 0.1% Cu, 0.1% Mn, 0.1% Zn, 0.1% Ti, 0.2% unavoidable total impurities, 0.05% of each impurity, and the balance being aluminum.

[0139] Example 6

[0140] This embodiment is basically the same as Embodiment 1, except that:

[0141] (1) By mass percentage, the intermediate layer of this embodiment includes 2.3% Mg, 1.0% Sn, 0.3% Bi, 12% Si, 0.2% Fe, 0.1% Cu, 0.1% Mn, 0.1% Zn, 0.1% Ti, 0.2% unavoidable total impurities, 0.05% of each impurity, and the balance being aluminum.

[0142] Example 7

[0143] This embodiment is basically the same as Embodiment 1, except that:

[0144] (2) 3) according to Figure 2 As shown, core material ingots, intermediate ingots, and brazing filler layer ingots are stacked to obtain multi-layered materials.

[0145] Example 8

[0146] This embodiment is basically the same as Embodiment 1, except that:

[0147] (1) By mass percentage, the intermediate layer of this embodiment includes 0.2% Mg, 0.8% Sn, 0.1% Bi, 7.5% Si, 0.15% Fe, 0.004% Cu, 0.02% Mn, 0.009% Zn, 0.01% Ti, with an unavoidable total amount of impurities ≤0.05%, each impurity ≤0.05%, and the balance being aluminum.

[0148] Example 9

[0149] This embodiment is basically the same as Embodiment 1, except that:

[0150] (1) By mass percentage, the intermediate layer of this embodiment includes 2.2% Mg, 1.0% Sn, 0.3% Bi, 7.5% Si, 0.15% Fe, 0.004% Cu, 0.02% Mn, 0.009% Zn, 0.01% Ti, with an unavoidable total amount of impurities ≤0.05%, each impurity ≤0.05%, and the balance being aluminum.

[0151] Comparative Example 1

[0152] This comparative example is basically the same as Example 1, except that:

[0153] (1) By mass percentage, the core material of this embodiment includes 2.8% Mg, 0.35% Bi, 0.6% Si, 0.4% Fe, 0.01% Cu, 1.0% Mn, 0.009% Zn, 0.01% Ti, with an unavoidable total impurity amount of <0.2%, each impurity amount of <0.05%, and the balance being aluminum.

[0154] No intermediate layer is set.

[0155] Comparative Example 2

[0156] This comparative example is basically the same as Example 1, except that:

[0157] By mass percentage, the core material of this embodiment includes 2.8% Mg, 0.35% Sn, 0.6% Si, 0.4% Fe, 0.01% Cu, 1.0% Mn, 0.009% Zn, and 0.01% Ti. The total amount of unavoidable impurities is <0.2%, each impurity is <0.05%, and the balance is aluminum.

[0158] No intermediate layer is set.

[0159] Experimental Example 1

[0160] 1. The number of low-melting-point phases, the thickness of the intermediate layer, and the thickness of the brazing filler layer of the composite brazing plates of the examples and comparative examples were tested, and the results are shown in Table 1.

[0161] Table 1

[0162]

[0163] Note: The element content, tin phase quantity, bismuth phase quantity, ratio of tin phase to bismuth phase quantity, intermediate layer thickness, and solder layer thickness in the intermediate layer of the examples and comparative examples in Table 1 are all results of single-sided testing, that is, only the intermediate layer and solder layer on one side of the core material surface are tested.

[0164] 2. Testing Methods

[0165] 1) Test method for the number of low-melting-point phases

[0166] The distribution and morphology of the low-melting-point phase were observed using scanning electron microscopy (SEM). The SEM image of the intermediate layer of the composite brazing board in Example 1 is shown below. Figure 3 . Figure 3 Point 1# is a bismuth-containing phase and point 2# is a tin-containing phase. The atomic percentage and weight percentage of some elements in point 1# are shown in Table 2, and the atomic percentage and weight percentage of some elements in point 2# are shown in Table 3.

[0167] Table 2

[0168]

[0169] Table 3

[0170]

[0171] 2) Test methods for intermediate layer thickness and solder layer thickness

[0172] Metallurgical microscope test.

[0173] Experimental Example 2

[0174] 1. The composite brazing plates of the examples and comparative examples were prepared into brazing bodies respectively. The oxygen content in the brazing furnace was controlled within 50 ppm, the brazing temperature was 610℃ and the holding time was 10 min, and the brazing performance was tested. The results are shown in Table 4.

[0175] 2. Testing Methods

[0176] 1) Brazing performance

[0177] This invention is based on the width of the joint formed after brazing of the composite brazing plate (e.g. Figure 4 (As shown) Evaluate brazing performance.

[0178] Table 4

[0179]

[0180] Note: Brazing performance evaluation in Table 4: Excellent > Good > Fairly Good > No weld.

[0181] As shown in Table 4, compared with the comparative example, the composite brazing plate of the present invention has excellent brazing effect.

[0182] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A composite brazing plate, characterized in that, The device includes a core material and a solder layer disposed on at least one surface of the core material, with an intermediate layer disposed between the core material and the solder layer; the intermediate layer includes a low-melting-point phase, the melting point of which is not higher than 600°C. The low-melting-point phase includes a tin-containing phase and a bismuth-containing phase. The tin-containing phase includes the Mg2Sn phase, and the bismuth-containing phase includes the Mg3Bi2 phase and the Mg2Bi phase. Under a scanning electron microscope, the ratio of the number of the tin-containing phase to the number of the bismuth-containing phase is (4-20):

1.

2. The composite brazing plate according to claim 1, characterized in that, Under a scanning electron microscope, the number of the low-melting-point phase is not less than 50 per mm. 2 .

3. The composite brazing plate according to claim 1, characterized in that, The length of the low-melting-point phase is 1-20 μm.

4. The composite brazing plate according to claim 1, characterized in that, The intermediate layer comprises, by mass percentage, 0.1-2.4% Mg, 0.1-1.0% Sn, 0.1-0.5% Bi, 7.5-12% Si, ≤0.2% Fe, ≤0.1% Cu, ≤0.1% Mn, ≤0.1% Zn, ≤0.1% Ti, with unavoidable total impurities ≤0.2%, each impurity ≤0.05%, and the balance being aluminum.

5. The composite brazing plate according to claim 1, characterized in that, The thickness of the intermediate layer is 1-15% of the thickness of the composite brazing board; and / or, the thickness of the solder layer is 1-10% of the thickness of the composite brazing board.

6. The composite brazing plate according to claim 4, characterized in that, The intermediate layer comprises, by mass percentage, 0.2-2.2% Mg, 0.8-1.0% Sn, and 0.1-0.3% Bi.

7. The composite brazing plate according to claim 1, characterized in that, By weight percentage, the core material comprises Si ≤ 0.6%, Fe ≤ 0.7%, Cu 0.01-0.8%, Mn 1.0-1.5%, Zn ≤ 0.1%, refining agent element ≤ 0.1%, total unavoidable impurities ≤ 0.2%, each impurity ≤ 0.05%, and the balance being aluminum; and / or, The solder layer comprises, by mass percentage: Si 1-6%, Fe≤0.2%, Cu≤0.1%, Mn≤0.1%, Zn≤0.1%, Ti≤0.1%, Bi≤0.2%, unavoidable total impurities ≤0.2%, each impurity ≤0.05%, and the balance being aluminum.

8. A method for preparing a composite brazing plate according to any one of claims 1-7, characterized in that, Includes the following steps: An intermediate ingot is placed on at least one side of the core material ingot, and a solder layer ingot is placed on the surface of the intermediate ingot opposite to the core material ingot to obtain a multilayer material. The multilayer material is subjected to hot rolling, cold rolling and annealing in sequence to obtain the composite brazing plate; wherein, the composite brazing plate includes a core material, a brazing filler layer on at least one surface of the core material, and an intermediate layer located between the core material and the brazing filler layer; the intermediate layer includes a low melting point phase, the melting point of the low melting point phase is not higher than 600℃, the low melting point phase includes a tin-containing phase and a bismuth-containing phase, the tin-containing phase includes a Mg2Sn phase, and the bismuth-containing phase includes a Mg3Bi2 phase and a Mg2Bi phase; under a scanning electron microscope, the ratio of the amount of the tin-containing phase to the amount of the bismuth-containing phase is (4-20):

1.

9. The preparation method according to claim 8, characterized in that, The hot-rolled billet is obtained after the hot rolling treatment, wherein the hot rolling treatment temperature is ≤500℃; and / or, The casting speed of the intermediate ingot is 60-80 mm / min.

10. A brazing body, characterized in that, It is brazed from the composite brazing plate described in any one of claims 1-7, or brazed from the composite brazing plate prepared by the preparation method described in claim 8 or 9.

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