Aluminum alloy composite material suitable for brazing with fine grain zone surface structure, brazing method thereof and brazed product

Abstract

The application provides a brazing method and a brazed product for an aluminum alloy composite material containing a fine-grain zone surface structure, and the brazing method comprises the following steps: a cross section of a first component and a filler layer surface of a second component are in contact with each other to form a to-be-brazed assembly; the second component comprises a core layer and a brazing composite layer, the brazing composite layer is provided with a pre-embedded brazing flux layer on a side close to the core layer and a filler layer on a side away from the core layer; the pre-embedded brazing flux layer comprises a base alloy and a brazing flux; a solidus temperature T1 of the filler layer is less than a solidus temperature T2 of the base alloy of the pre-embedded layer, and the difference is at least 2 DEG C; in the brazing process, a temperature of an initial brazing window is T1-T2 and does not contain T2; in the initial brazing window, the filler layer forms a ZnSi-rich zone and a low-ZnSi zone, and a solidus temperature T3 of the low-ZnSi zone is greater than T2; a temperature of a middle brazing window is T2-T3 and does not contain T3; and a temperature of a final brazing window is greater than or equal to T3. The application can reduce corrosion and climbing of the filler, and improve brazing quality.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy brazing technology, and in particular to an aluminum alloy composite material suitable for brazing a surface structure containing a fine grain region, a brazing method thereof, and the finished welded product. Background Technology

[0002] With the continuous increase in the production and sales of new energy vehicles, especially pure electric vehicles, manufacturers are constantly raising their design requirements for vehicle thermal management. Automotive heat pump systems, as a highly efficient technology for automotive thermal management, work by having the refrigerant absorb heat and evaporate in the evaporator, then compress it into a high-temperature, high-pressure gas in the compressor, release heat and condense into a liquid in the condenser, and finally return to the evaporator after being throttled and depressurized by the expansion valve. This cycle repeats continuously, achieving heat transfer. With the development of electric vehicles, heat pump systems are being used more and more widely in electric vehicles. For example, some models from brands like Tesla and BYD have adopted heat pump technology to improve vehicle range and thermal management performance. The manifold is a key component in the heat pump system, connecting different parts. It distributes refrigerant or coolant to various components that require heat dissipation or heating, ensuring that each component receives the appropriate amount of fluid for effective heat exchange. The design of the manifold can optimize fluid flow within the system, reduce resistance and pressure loss, and improve fluid uniformity and flow rate, thereby increasing the efficiency of the heat pump system. Taking Tesla's Supermanifold V2 as an example, it mimics the capillary distribution of a hummingbird's wing, setting 18 sets of guide fins in the microchannels, which improves the uniformity of refrigerant flow rate by 52% and reduces pressure drop by 31%. Due to the special and complex structure of the manifold, manufacturing the manifold by casting is undoubtedly one of the best ways to balance production efficiency, dimensional accuracy, and surface quality.

[0003] However, when assembling and brazing die-cast manifolds with other radiator components, such as condensers and evaporators, problems such as incomplete welds and low weld penetration are often found at the weld joint between the manifold and the radiator base plate. Developing a radiator base plate material that can weld well with the manifold is one of the key elements for expanding the application of heat pump systems in electric vehicles.

[0004] CN118046135A discloses an aluminum alloy, solder, and preparation method for gradual brazing of a heat pump integrated substrate for new energy vehicles. This method involves adding appropriate amounts of Mn and Ti elements to the Mg-containing aluminum-silicon brazing process. This addresses defects in vacuum brazing of new energy heat pump integrated substrates caused by the porous structure of the die-cast substrate, leading to solder flow and creep along the casting wall, resulting in incomplete solder joints, insufficient solder fill, and low weld bonding rate.

[0005] Due to the highly integrated design of new energy heat pump manifolds, the heat dissipation requirements of the materials are relatively high. In order to ensure high cleanliness in the flow channel, vacuum brazing process was usually used in the past. However, due to the disadvantages of vacuum brazing (VB) equipment, such as large investment, low brazing efficiency and high maintenance cost, heat pump manufacturers are eager to use controlled atmosphere brazing (CAB) to replace vacuum brazing.

[0006] The inventors of this patent have discovered through experiments that even if heat pump substrate manufacturers adjust the die-casting process to improve degassing and slag removal efficiency and obtain well-structured die-cast parts with loose and unorganized structure, the brazing defects mentioned above will still occur when the parts are assembled with brazing filler material and then vacuum brazed or brazed in a controlled atmosphere. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an aluminum alloy composite material suitable for brazing a surface structure containing a fine grain region, as well as a brazing method and a finished welded product. Specifically, it provides an aluminum die casting and its brazing method, an aluminum alloy composite material for brazing, and a finished welded aluminum alloy composite material, which can obtain a brazed part with a full weld joint and no obvious material creep along the casting wall without processing the manifold casting.

[0008] The inventors of this patent discovered that, due to the certain wall thickness (2-6mm) of the first component to be welded, the cooling rate on the outer side of the wall is greater than that on the core during the cooling process. Gradually, a chilling layer is formed on the outer wall, and the grain size of the chilling layer is smaller than that of the core. Figure 1 As shown. The presence of this fine-grained layer is the main reason why the first component exhibits the following problems when brazed with conventional solder: ① solder creeping and erosion along the wall; ② poor weld joint.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a brazing method suitable for brazing a first component with a surface structure containing a fine grain region, the brazing method comprising the following steps:

[0011] (1) Assemble the first component and the second component to form a component to be soldered, wherein the cross section of the first component and the surface of the solder layer of the second component are in contact with each other;

[0012] The edge region of the first component cross-section is a fine-grained region, the thickness of the fine-grained region is not less than 20 μm, and the average grain size of the fine-grained region is ≤7 μm;

[0013] The second component includes a core layer and a brazing composite layer, with the brazing composite layer disposed on at least one side of the core layer. The brazing composite layer includes a pre-embedded flux layer and a solder layer, wherein the layer closer to the core layer is the pre-embedded flux layer, and the layer farther from the core layer is the solder layer. The pre-embedded flux layer includes a base alloy and a brazing flux, wherein the base alloy contains the alloying element Si but does not contain the element Zn. The solder layer is an AlSiZn-based solder alloy. The solidus temperature T1 of the solder alloy is less than the solidus temperature T2 of the base alloy, and the difference is at least 2°C.

[0014] (2) The components to be welded in step (1) are brazed in a brazing process, which includes an initial brazing window, a middle brazing window and a final brazing window performed sequentially.

[0015] The initial brazing window temperature is T1 to T2, excluding T2. Within the initial brazing window, the solder layer forms a ZnSi-rich region and a low-ZnSi region, with the solidus temperature of the low-ZnSi region being T3 > T2. The intermediate brazing window temperature is T2 to T3, excluding T3.

[0016] The temperature of the final brazing window is ≥T3.

[0017] Due to the processing characteristics of die casting, die castings typically have a chilled fine-grained layer on the surface and a coarse-grained layer inside. The average grain size of the chilled fine-grained layer is ≤7μm, and its thickness is not less than 20μm. The fine-grained region in a cross-section obtained by cutting the first component parallel to the direction of the second component is the chilled fine-grained layer. During brazing, the solder joint forms at the edge of the second component, i.e., on the surface of the chilled fine-grained layer. The presence of the chilled fine-grained layer is the reason why solder erosion and material creep occur when die castings are brazed with conventional brazing fillers.

[0018] Material creep is a phenomenon that occurs under special circumstances. When the grains in the area to be soldered are smaller, that is, when there are more grain boundaries, the molten solder will migrate along the grain boundaries toward the core of the material. The smaller the grains, the more severe the erosion. In particular, when there are different grain layer structures (large grains in the core and small grains on the surface), the molten liquid phase will preferentially erode laterally along the fine grain layer on the surface, thus macroscopically presenting the phenomenon of "material creep" along the wall.

[0019] This invention utilizes the molten liquid phase formed approximately perpendicular to the surface of the solder layer during the initial melting process of the AlSiZn solder alloy. This provides a rapid channel for the migration of flux in the embedded layer to the material surface, allowing the early molten AlSiZn liquid phase to form a small amount of precursor weld. Simultaneously, this invention leverages the dynamic melting point difference between the solder layer (containing residual Si and Zn elements) and the embedded layer (where the solder layer melting point is greater than the embedded layer melting point) to prevent the large amount of molten liquid phase formed in the embedded flux layer from prematurely flowing to the weld joint. This improves the premature accumulation of the weld liquid phase and reduces the erosion of the fine grain walls of the aluminum die casting caused by prolonged retention of molten liquid phase at the weld joint. Thus, without requiring further treatment of the manifold casting, a brazed joint with a full weld joint and no significant material creep along the casting wall can be obtained.

[0020] Specifically, this invention introduces a flux pre-embedded layer between the solder alloy and the core material layer, while simultaneously modifying the traditional 4XXX series solder alloy into an Al-Si alloy containing Zn, thereby reducing the initial melting temperature of the entire Al-Si-Zn solder alloy to 552-570℃ (solidspot temperature). During the brazing heating process, as the temperature rises to the solidspot temperature of the Al-Si-Zn solder layer, the flux in the pre-embedded flux layer begins to melt, but before reaching the initial melting temperature of the base alloy in the pre-embedded flux layer. At this point, the liquid flux aggregates, grows, and spheroidizes. The solidspot temperature of the base alloy is selected to be at least 2℃ higher than that of the solder alloy. When the solidspot temperature difference is less than 2℃, the base alloy of the pre-embedded flux layer and the solder layer begin to melt at approximately the same time, resulting in excessive molten liquid phase filling the weld, which exacerbates the erosion problem.

[0021] When the temperature reaches the solidus temperature of the AlSiZn-based solder alloy but is lower than the solidus temperature of the base alloy in the pre-embedded flux layer, an AlSiZn liquid phase is generated at the interface between Si particles and the α(Al) matrix. Si atoms diffuse from the α(Al) matrix into the liquid phase (because the liquid phase can accommodate more Si), while Al atoms diffuse in the reverse direction more slowly, resulting in a rapid increase in the Si concentration in the liquid phase. Similarly, the Zn content in the liquid phase is also greater than that in the unmelted matrix. Since the generated AlSiZn liquid phase preferentially accumulates at the grain boundaries, Zn- and Si-rich regions are formed at the grain boundaries, while low-Zn- and Si-rich regions are formed within the grains. At the grain boundaries, AlSiZn liquid phase gradually forms AlSiZn liquid phase channels that are approximately perpendicular to the surface of the brazing filler metal. Simultaneously, the spheroidized flux rapidly migrates to the interface between the AlSiZn-based brazing filler metal layer and the pre-embedded layer, and migrates along the AlSiZn liquid phase channels to the surface of the brazing filler metal layer. This removes the oxide film on the surface of the brazing filler metal and the adjacent manifold casting to be welded, improving the wettability of the components to be welded. At this time, due to the relatively low temperature, only a portion of the AlSiZn molten brazing filler metal in the brazing filler metal layer fills the weld, while the substrate in the pre-embedded flux layer has not yet reached the solidus temperature, and no liquid phase has been generated at the grain boundaries for the weld to fill. This avoids premature erosion of the weld and casting wall by a large amount of molten brazing filler metal. Because the relatively high Si and high Zn AlSiZn liquid phase generated in the solder layer is used to form the initial weld under the action of the flux, the unmelted solid phase in this layer is a relatively high melting point region with low Si and low Zn. By controlling the duration of the initial brazing window, the solidus temperature T3 of the low ZnSi region is made greater than T2. ​​Preferably, T3 is at least 2°C higher than T2, for example, it can be 2°C, 3°C, 5°C, 6°C, 8°C, 9°C, 10°C, 12°C, 15°C, 18°C, or 20°C, etc.

[0022] As the brazing temperature further increases to the solidus temperature of the base alloy in the embedded layer, the embedded flux layer gradually melts until it reaches the liquidus temperature of the embedded layer base material. Although there are differences in the liquid phase Si element during this melting process, the presence of the high-melting-point AlSiZn layer on top hinders the migration rate of the high-Si liquid phase, allowing more Si elements to remain in the embedded flux layer. Therefore, the Si content of the embedded layer remains relatively stable and does not form an obvious low-silicon region. This means that when the base material of the embedded flux layer is completely melted, the low-silicon and low-zinc high-melting-point regions of the solder layer do not reach a complete liquid phase. In this temperature range, the unmelted solid phase in the solder layer located on the outside of the embedded layer hinders the large-scale filling of the liquid phase formed by the embedded layer base material into the weld and casting wall.

[0023] Once the temperature reaches the liquidus temperature of the entire brazing filler layer, the molten liquid phase begins secondary filling. However, in this invention, the liquid phase only begins to fill the weld and casting wall in large quantities after the liquidus temperature of the entire brazing filler layer has been reached. Under the same brazing process and with the same amount of liquid phase filling, the later-generated liquid phase in this invention has a shorter residence time in the high-temperature section, and less alloying elements in the brazing core material and aluminum die casting diffuse into the liquid phase, thus greatly reducing the erosion of the weld and manifold casting wall.

[0024] Specifically, the thickness of the fine-grained region at the edge of the first component cross-section is not less than 20 μm, for example, it can be 20 μm, 22 μm, 23 μm, 25 μm, 28 μm, 29 μm, 30 μm, 32 μm, 35 μm, 38 μm or 40 μm, etc.; the average grain size of the fine-grained region is ≤7 μm, for example, it can be 7 μm, 6.8 μm, 6.5 μm, 6.2 μm, 6.0 μm, 5.9 μm, 5.8 μm, 5.4 μm, 5.0 μm, 4.9 μm, 4.8 μm, 4.5 μm or 4.0 μm, etc.

[0025] Specifically, the solidus temperature T1 of the brazing alloy is less than the solidus temperature T2 of the base alloy, and the difference is at least 2℃. For example, it can be 2℃, 3℃, 4℃, 5℃, 6℃, 7℃, 8℃, 9℃, 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, 21℃, 22℃, 23℃, 24℃, or 25℃, etc.

[0026] Preferably, the initial brazing window time is controlled to be 10 to 51 seconds, for example, it can be 10 seconds, 12 seconds, 15 seconds, 18 seconds, 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds or 51 seconds, etc.

[0027] During the initial brazing window, sufficient time is needed for Si and Zn elements in the solder layer to flow to the surface along with the molten flux, forming Zn- and Si-rich regions at the grain boundaries and low-Zn- and Si-rich regions within the grains. This allows the Zn- and Si-rich liquid phase at the grain boundaries to form the initial weld bead at the weld. If the initial brazing window is insufficient, it can lead to difficulty in forming the low-Zn- and Si-rich regions within the grains, or the Zn and Si content in the low-Zn- and Si-rich regions may remain high. The solidus temperature of the formed low-Zn- and Si-rich regions may be lower than that of the base alloy, making it difficult for them to impede the migration of a large amount of high-Si liquid phase from the pre-embedded flux layer. This results in excessive filling into the weld and casting wall, leading to severe erosion of the weld and manifold casting wall. Conversely, if the initial brazing window is too long, the diffusion of the molten liquid phase at the weld bead and the surrounding base alloy elements can be intensified, increasing erosion.

[0028] Preferably, the time of the intermediate brazing window is controlled to be 44 to 240 seconds, for example, it can be 44 seconds, 66 seconds, 88 seconds, 110 seconds, 132 seconds, 153 seconds, 175 seconds, 197 seconds, 219 seconds or 240 seconds.

[0029] In actual brazing, the complete melting of the filler metal takes time. If the filler metal of the matching core material does not melt in time, it will result in poor filler metal filling. Therefore, we want to generate a large amount of liquid phase to fill the brazing zone while also minimizing the time the liquid phase remains in the high-temperature section of the brazing zone. During the intermediate brazing window, time control mainly ensures that the pre-embedded flux layer is fully converted into liquid phase, thereby shortening the time of the subsequent final brazing window.

[0030] Preferably, the time of the final brazing window is controlled to be 55 to 286 seconds, for example, it can be 55 seconds, 81 seconds, 107 seconds, 132 seconds, 158 seconds, 184 seconds, 209 seconds, 235 seconds, 261 seconds or 286 seconds.

[0031] The invention achieves good brazing results with a short final brazing window. However, if the final brazing window is too long, the extended residence time in the high-temperature zone increases the diffusion of alloying elements from the core material of the brazing board and the manifold casting into the liquid phase, thereby increasing erosion of the weld and the manifold casting wall. Conversely, if the final brazing window is too short, the low Zn and Si regions of the brazing filler metal layer may not be converted into the liquid phase, resulting in poor filler metal.

[0032] Preferably, the solidus temperature T2 of the substrate alloy is at most 25°C higher than the solidus temperature T1 of the solder layer.

[0033] Preferably, the solidus temperature of the brazing alloy is 547-570℃, for example, it can be 547℃, 550℃, 552℃, 554℃, 556℃, 558℃, 560℃, 562℃, 564℃, 566℃, 568℃ or 570℃, etc.

[0034] Preferably, the solidus temperature of the substrate alloy is 563-577℃, for example, it can be 563℃, 565℃, 567℃, 568℃, 570℃, 571℃, 573℃, 574℃, 576℃ or 577℃, etc.

[0035] When the difference between the solidus temperature of the base alloy and the solidus temperature of the solder layer is higher than 25°C, there is a problem that the low-melting-point liquid phase formed first in the solder layer stays at the solder joint for too long, increasing the corrosion of the base material.

[0036] Preferably, the solder layer comprises the following alloying elements by mass fraction: Si: 6-13%, Zn: 1-13%. Wherein, Si: 6-13%, for example, can be 6%, 6.8%, 7.6%, 8.4%, 9.2%, ...

[0037] 9.9%, 10.7%, 11.5%, 12.3% or 13%, etc. Zn: 1 to 13%, for example, it can be 1%, 3%, 4%, 5%, 7%, 8%, 9%, 11%, 12% or 13%, etc.

[0038] Compared to AlSi alloys, the Zn element in AlSiZn alloys in the solder layer significantly lowers the solidus temperature. Furthermore, after reaching the solidus temperature, AlSiZn alloys form Zn-rich and Si-rich regions at the grain boundaries, while low-Zn- and Si-rich regions form within the grains. Maintaining a minimum solidus temperature difference between the base alloy and the solder layer ensures the formation of sufficiently rich and low-Zn- and Si-rich regions during this stage. This guarantees a sufficient liquidus ratio for initial solder joints and a low-Zn- and Si-rich matrix with lower Zn and Si concentrations (high solidus temperature). Ensuring at least a solidus temperature difference is crucial for achieving good initial solder joints and a low-Zn- and Si-rich matrix with a high solidus temperature.

[0039] If the Si content is too low, sufficient AlSi molten solder cannot be formed, making it difficult to form an effective solder joint. If it is too high, the liquidus temperature will increase accordingly, and the solder will not be able to completely melt at the brazing temperature, resulting in insufficient solder filler.

[0040] Too low a Zn content will not effectively lower the melting point, while too high a content will result in an excessively large solid-liquid phase region (the difference between the liquidus temperature and the solidus temperature), increasing erosion.

[0041] Preferably, the thickness ratio of the pre-embedded flux layer to the solder layer is 0.11 to 2.33, for example, it can be 0.11, 0.36, 0.61, 0.85, 1.1, 1.35, 1.59, 1.84, 2.09, or 2.33. The mass percentage of the base alloy in the pre-embedded flux layer is 85% to 98%, for example, it can be 85%, 87%, 88%, 90%, 91%, 93%, 94%, 96%, 97%, or 98%.

[0042] Preferably, during the initial brazing window, the proportion of the liquid phase formed in the solder layer to the sum of the liquid phase of the base alloy in the solder layer and the embedded layer is 8.74% to 49.84%, for example, it can be 8.74%, 13.31%, 17.88%, 22.44%, 27.01%, 30%, 31%, 31.58%, 36.14%, 40.71%, 45.28%, or 49.84%, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable. More preferably, the proportion of the liquid phase formed in the solder layer to the sum of the liquid phase of the base alloy in the solder layer and the embedded layer is ≤30%.

[0043] There is a dynamic solidus temperature difference between the pre-embedded flux layer and the solder layer. During the initial brazing window, after the brazing temperature reaches above the flux melting point, there exists a brazing temperature range called the initial brazing temperature. This initial brazing temperature reaches the solidus temperature of the solder alloy in the pre-embedded flux layer of the second component, but is higher than the solidus temperature of the solder layer. This allows Si and Zn elements in the solder layer to flow to the surface along with the molten flux at this initial brazing temperature, forming Zn-rich and Si-rich regions at the grain boundaries and low-Zn and Si-rich regions within the grains. This allows the Zn-rich and Si-rich liquid phase at the grain boundaries to form the initial weld bead at the weld joint. The liquid phase ratio formed in this stage is 4.76-9.87%. The remaining low-Zn and Si-rich regions of the solder layer do not melt and do not melt during the intermediate brazing window. When the liquid phase ratio formed in the brazing filler layer at this stage (which is the sum of the liquid phase of the base alloy in the brazing filler layer and the embedded layer) is too high, it is more likely to erode. When the liquid phase ratio formed in the brazing filler layer at this stage is too low (which is the sum of the liquid phase of the base alloy in the brazing filler layer and the embedded layer), there is a problem that the molten liquid phase cannot form a sufficient effective filler to fill the weld.

[0044] Preferably, during the initial brazing window, the proportion of liquid phase formed in the brazing filler layer to the amount of liquid phase in the brazing filler layer is ≥12%, for example, it can be 12%, 19%, 26%, 33%, 40%, 47%, 54%, 61%, 68%, or 75%, etc.

[0045] More preferably, during the initial brazing window, the proportion of the liquid phase formed in the brazing filler layer to the amount of liquid phase in the brazing filler layer is 31.2% to 68.3%.

[0046] The higher the proportion of the liquid phase formed in the brazing filler layer to the total theoretical liquid phase formed in the brazing filler layer, the shorter the brazing window time in the final stage, and the less likely it is to be eroded.

[0047] Preferably, the core material is a 3xxx series Al-Mn alloy or a 6xxx series Al-Mg-Si alloy.

[0048] Preferably, when the core material is a 3xxx series Al-Mn alloy, it comprises the following alloy components by mass percentage: Si ≤ 1.0%, for example, 1.0%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1%; Fe ≤ 0.8%, for example, 0.8%, 0.7%, 0.65%, 0.6%, 0.55%, 0.5%, 0.45%, 0.4%, 0.3%, 0.2%, or 0.1%; Cu ≤ 0.4%, for example, 0.4%, 0.35%, 0.3%, 0.25%, 0.2%, 0.15%, or 0.1%; Mn 0.8%–1.6%, for example, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, or 1.6%, etc.; Mg ≤ 0.3%, for example, 0.3%, 0.28%, 0.27%, 0.26%, 0.25%, 0.24%, 0.23%, 0.22%, 0.20%, 0.19%, 0.18%, 0.15%, 0.12%, 0.10%, 0.09%, or 0.08%, etc.; Zn ≤ 4%, for example, 1%, 1.4%, 1.7%, 2%, 2.4%, 2.7%, 3%, 3.4%, 3.7%, or 4%, etc.; Ti ≤ 0.2%, for example, it can be 0.01%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, or 0.2%, etc.; Zr ≤ 0.2%, for example, it can be 0.01%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, or 0.2%, etc.

[0049] Preferably, when the core material is a 6xxx series Al-Mg-Si alloy, it comprises the following alloy components by mass percentage: Si: 0.2-0.8%, for example, 0.2%, 0.3%, 0.45%, 0.49%, 0.54%, 0.58%, 0.63%, 0.67%, 0.72%, 0.76%, or 0.8%; Fe: 0.1-0.5%, for example, 0.1%, 0.22%, 0.3%, 0.39%, 0.47%, or 0.5%; Cu ≤ 0.1%, for example, […]. 0.02%, 0.05%, or 0.1%, etc.; Mn ≤ 0.2%, for example, 0.01%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, or 0.2%, etc.; Mg: 0.4–0.9%, for example, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or 0.9%, etc.; Ti: 0.01–0.03%, for example, 0.01%, 0.015%, 0.02%, 0.025%, or 0.03%.

[0050] Preferably, based on mass fraction, the base alloy contains Fe ≤ 0.5%, for example, 0.5%, 0.45%, 0.42%, 0.40%, 0.39%, 0.38%, 0.35%, 0.32%, 0.3%, 0.28%, 0.25%, 0.2%, 0.15%, or 0.1%, etc.; and Cu ≤ 0.2%, for example, 0.2%, 0.18%, etc. 0.15%, 0.12%, 0.10%, 0.09%, 0.08%, 0.05%, or 0.01%, etc.; Mg≤0.5%, for example, it can be 0.5%, 0.45%, 0.42%, 0.40%, 0.39%, 0.38%, 0.35%, 0.32%, 0.3%, 0.28%, 0.25%, 0.2%, 0.15%, or 0.1%, etc.

[0051] Preferably, based on mass fraction, the alloy elements in the solder layer contain Fe ≤ 0.5%, for example, 0.5%, 0.45%, 0.42%, 0.40%, 0.39%, 0.38%, 0.35%, 0.32%, 0.3%, 0.28%, 0.25%, 0.2%, 0.15%, or 0.1%, Cu ≤ 0.2%, for example, 0.2%, 0.18%, 0.15%, 0.12%, 0.10%, 0.09%, 0.08%, 0.05%, or 0.01%, and Mg ≤ 0.1%, for example, 0.1%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04%, 0.03%, 0.02%, or 0.01%.

[0052] Preferably, the thickness of the brazed composite layer accounts for 5% to 15% of the total thickness of the second component, for example, it can be 5%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, etc.

[0053] Preferably, the flux content in the second component is 0.84–14.7 g / m 2 For example, it could be 0.84 g / m 2 2.38g / m 2 3.92g / m 2 5.46g / m 2 7g / m 2 8.54g / m 2 10.08g / m 2 11.62g / m 2 13.16g / m 2 Or 14.7g / m 2 And, but not limited to, the values ​​listed.

[0054] Preferably, the first component is an aluminum die-casting.

[0055] In a second aspect, the present invention provides an aluminum alloy composite material, which is a second component for a brazing method described in the first aspect, applicable to brazing a first component containing a fine-grained surface structure.

[0056] Thirdly, the present invention provides a welded finished product, which is obtained by brazing using the brazing method described in the second aspect, which is suitable for brazing a first component containing a fine-grained surface structure.

[0057] Fourthly, the present invention provides a welded finished product, the welded finished product being a heat pump manifold, the heat pump manifold comprising an aluminum die casting and the aluminum alloy composite material described in the second aspect.

[0058] Compared with the prior art, the present invention has at least the following beneficial effects:

[0059] (1) The brazing method provided by the present invention for brazing a first component with a surface structure containing a fine grain region forms a molten liquid phase that is approximately perpendicular to the surface of the brazing filler layer during the initial melting process. This provides a fast channel for the flux in the pre-embedded layer to migrate to the material surface, enabling the early molten AlSiZn liquid phase to form a partial precursor weld.

[0060] (2) The brazing method provided by the present invention for brazing a first component with a surface structure containing a fine grain region utilizes the dynamic melting point difference between the brazing filler layer with residual Si and Zn elements and the pre-embedded layer (at this time, the melting point of the brazing filler layer is greater than that of the pre-embedded layer) to avoid the premature formation of a large amount of molten liquid phase, thereby improving the premature accumulation of the weld liquid phase and reducing the corrosion of the fine grain wall of the manifold casting caused by the long-term retention of a large amount of molten liquid phase at the weld. Thus, without the need to process the manifold casting, a brazed part with a full weld joint and no obvious material crawling along the casting wall can be obtained. Specifically, when brazing a first component with a height of 18mm, its erosion depth is within 250μm and the material crawling height of the first component is within 14mm. Attached Figure Description

[0061] Figure 1 This is an assembly diagram of the components to be soldered provided by the present invention.

[0062] Figure 2 This is the EBSDIPF+GB diagram of the cross-section of the first component in the specific implementation method.

[0063] Figure 3 This is a metallographic photograph of the cross-section of the brazed joint provided in Embodiment 1 of the present invention.

[0064] Figure 4 This is a metallographic photograph of the cross-section of the brazed joint provided in Comparative Example 1 of the present invention.

[0065] In the figure: 1, First component; 11, Cooling fine grain region; 12, Intermediate coarse grain region; 2, Second component; 21, Core layer; 22, Brazing composite layer; 221, Pre-embedded flux layer; 222, Brazing filler metal layer. Detailed Implementation

[0066] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0067] It should be understood that when the edge region of the cross-section of the first component being welded is a fine-grained region (average grain size ≤ 7 μm) and the thickness of the fine-grained region is not less than 20 μm, it is the cause of material creep after erosion. Therefore, the welding object of the present invention is a first component with a fine-grained region, and solves the problem of erosion and material creep during the welding process. When the welding object does not have a fine-grained region, there is usually no material creep or it is not significant. These welding objects are not discussed in the specific embodiments of the present invention.

[0068] As an example, this embodiment uses the same first component as the object to be welded, such as... Figure 2 As shown, the surface of the first component has a fine-grained region with an average grain size of 4 μm and a thickness of 37 μm.

[0069] Test methods

[0070] 1. Average grain size and thickness of the fine-grained region: The sample was observed using a German Zeiss Sigma300 field emission scanning electron microscope and its matching Oxford C Nano EBSD. The images were processed using the built-in AZTEC software to obtain the equivalent circle diameter of the selected fine-grained region, which is the average grain size. The thickness of the fine-grained region can be directly measured in the software to obtain the thickness value of the fine-grained region.

[0071] 2. Solidus Temperature: During material preparation, 15-20 mg of the material layer was taken and placed in an alumina ceramic crucible. A Netzsch STA 449F5 synchronous thermal analyzer (Germany) was used to perform temperature testing within the range of 25℃-700℃. The heating rate was 10℃ / min, and high-purity argon was used as the protective gas. After the test, the DSC curve was analyzed using the built-in software to obtain the solidus temperature of the material.

[0072] 3. Liquid phase ratio: The chemical composition of the material was analyzed using a NACK Plasma 2000 inductively coupled plasma optical emission spectrometer (ICP-OES). The chemical composition was then input into JMatPro software to obtain the liquid phase ratio of the material at a specific temperature.

[0073] 4. Erosion depth and material climbing height: according to Figure 1 The structure shown involves placing a first component (20mm long, 4mm wide, and 18mm high) on top of a second component (30mm x 30mm, 1mm thick) and securing it with 0.8mm diameter steel wire. The secured first and second components are then brazed in a nitrogen-protected OTF-1200X tube furnace to obtain a brazed sample. A sample is cut along the midpoint of the weld between the first and second components and subjected to conventional metallographic sample preparation methods, including rough grinding, fine grinding, rough polishing, and fine polishing, to obtain the metallographic sample to be observed. The surface of the metallographic sample to be observed is immersed in a 0.5% HF solution for 25 seconds. The weld cross-section is observed using a Zeiss LSM900 laser confocal microscope. The accompanying software is used to measure the distance between the weld molten metal at the weld joint, parallel to the surface of the second component, and the maximum depth into the second component; this value is the erosion depth. The accompanying software is also used to measure the maximum height of the weld molten metal at the weld joint, from parallel to the surface of the second component to the outer surface of the first component; this value is the creep height.

[0074] Core layer

[0075] Core material layer X1: 3xxx series Al-Mn alloy 3003.

[0076] Core material layer X2: 6xxx series Al-Mg-Si alloy 6063.

[0077] solder layer

[0078] The solder layer Q1 comprises the following alloy components by mass percentage: Si: 13%, Zn: 1%, Cu: 0.3%, Fe: 0.2%, Mg: 0.01%, and a solidus temperature of 570℃.

[0079] The solder layer Q2 comprises the following alloy components by mass percentage: Si: 10%, Zn: 6%, Cu: 0.1%, Fe: 0.1%, Mg: 0.05%, and a solidus temperature of 568℃.

[0080] The solder layer Q3, by mass percentage, includes the following alloy components: Si: 6%, Zn: 13%, Cu: 0.5%, Fe: 0.1%, Mg: 0.1%, and a solidus temperature of 552℃.

[0081] The solder layer Q4, by mass percentage, comprises the following alloy components: Si: 10%, Zn: 15%, Cu: 0.1%, Fe: 0.1%, Mg: 0.05%, with a solidus temperature of 547℃.

[0082] The solder layer DQ1 comprises the following alloy components by mass percentage: Si: 13%, Zn: 0.5%, Cu: 0.3%, Fe: 0.2%, Mg: 0.01%, and a solidus temperature of 574℃.

[0083] Base alloy

[0084] Base alloy J1: by mass percentage, it includes the following alloy components: Si: 10%; Fe: 0.2%; Cu: 0.1%; Mg: 0.5%; solidus temperature is 563℃.

[0085] Base alloy J2: by mass percentage, it includes the following alloy components: Si: 10%; Fe: 0.5%; Cu: 0.2%; Mg: 0.05%; solidus temperature is 575℃.

[0086] Base alloy J3: by mass percentage, it includes the following alloy components: Si: 10%; Fe: 0.1%; Cu: 0.05%; Mg: 0.2%; solidus temperature is 573℃.

[0087] Base alloy J4: by mass percentage, it includes the following alloy components: Si: 8%; Fe: 0.1%; solidus temperature is 577℃.

[0088] Pre-embedded flux layer

[0089] Pre-embedded flux layer Y1: includes brazing flux (Nocolok potassium fluoroaluminate flux) and base alloy J1, wherein the base alloy J1 accounts for 85% of the mass.

[0090] Pre-embedded flux layer Y2: includes brazing flux (Nocolok potassium fluoroaluminate flux) and substrate alloy J2, wherein the substrate alloy J2 accounts for 95% of the mass.

[0091] Pre-embedded flux layer Y3: includes brazing flux (Nocolok potassium fluoroaluminate flux) and substrate alloy J3, wherein the substrate alloy J3 accounts for 98% of the mass.

[0092] Pre-embedded flux layer Y4: includes brazing flux (Nocolok potassium fluoroaluminate flux) and substrate alloy J2, wherein the mass percentage of substrate alloy J2 is 80.91%.

[0093] Pre-embedded flux layer Y5: includes brazing flux (Nocolok potassium fluoroaluminate flux) and substrate alloy J2, wherein the mass percentage of substrate alloy J2 is 97.91%.

[0094] Pre-embedded flux layer Y6: includes soldering flux (Nocolok potassium fluoroaluminate flux) and base alloy J4, wherein the base alloy J4 accounts for 92% of the mass.

[0095] The second component is an aluminum alloy composite material.

[0096] Aluminum alloy composite material F1 comprises: a core layer (X2) and a brazing composite layer, wherein a brazing composite layer is disposed on at least one side of the core layer; the brazing composite layer comprises a pre-embedded flux layer (Y2) and a brazing filler metal layer (Q2), wherein the layer closer to the core layer is the pre-embedded flux layer, and the layer farther from the core layer is the brazing filler metal layer. The temperature difference between the solidus temperature T1 (568℃) of the brazing filler metal layer and the solidus temperature T2 (575℃) of the base alloy is 7℃. The brazing composite layer accounts for 10% of the total composition; the thickness ratio of the pre-embedded flux layer to the brazing filler metal layer is 0.4286. The flux content in the aluminum alloy composite material is 4.2 g / m³. 2 .

[0097] Aluminum alloy composite material F2 comprises: a core layer (X1) and a brazing composite layer, wherein the brazing composite layer is disposed on at least one side of the core layer; the brazing composite layer comprises a pre-embedded flux layer (Y1) and a brazing filler metal layer (Q3), wherein the layer closer to the core layer is the pre-embedded flux layer, and the layer farther from the core layer is the brazing filler metal layer. The temperature difference between the solidus temperature T1 (552℃) of the brazing filler metal layer and the solidus temperature T2 (563℃) of the base alloy is 11℃. The brazing composite layer accounts for 5% of the total composition; the thickness ratio of the pre-embedded flux layer to the brazing filler metal layer is 0.1111. The flux content in the aluminum alloy composite material is 0.84 g / m³. 2 .

[0098] Aluminum alloy composite material F3 comprises: a core layer (X1) and a brazing composite layer, wherein the brazing composite layer is disposed on at least one side of the core layer; the brazing composite layer comprises a pre-embedded flux layer (Y3) and a brazing filler metal layer (Q1), wherein the layer closer to the core layer is the pre-embedded flux layer, and the layer farther from the core layer is the brazing filler metal layer. The temperature difference between the solidus temperature T1 (570℃) of the brazing filler metal layer and the solidus temperature T2 (573℃) of the base alloy is 3℃. The brazing composite layer accounts for 15% of the total composition; the thickness ratio of the pre-embedded flux layer to the brazing filler metal layer is 2.3333. The flux content in the aluminum alloy composite material is 14.7 g / m³. 2 .

[0099] Aluminum alloy composite material F4 comprises: a core layer (X2) and a brazing composite layer, wherein the brazing composite layer is disposed on at least one side of the core layer; the brazing composite layer comprises a pre-embedded flux layer (Y6) and a brazing filler metal layer (Q3), wherein the layer closer to the core layer is the pre-embedded flux layer, and the layer farther from the core layer is the brazing filler metal layer. The temperature difference between the solidus temperature T1 (552℃) of the brazing filler metal layer and the solidus temperature T2 (577℃) of the base alloy is 25℃. The brazing composite layer accounts for 8% of the total composition; the thickness ratio of the pre-embedded flux layer to the brazing filler metal layer is 0.5. The flux content in the aluminum alloy composite material is 8.96 g / m³. 2 .

[0100] Aluminum alloy composite material F5: The only difference between F5 and F1 is that the solder layer is Q4, that is, the temperature difference between the solidus temperature T1 (547℃) of the solder layer and the solidus temperature T2 (575℃) of the base alloy is 28℃. All other aspects are the same as F1, and will not be repeated here.

[0101] Aluminum alloy composite material F6 differs from aluminum alloy composite material F1 only in that the thickness ratio of the pre-embedded flux layer to the solder layer is 0.087. Simultaneously, the proportion of the base alloy in the pre-embedded flux layer is adaptively adjusted (i.e., the pre-embedded flux layer uses pre-embedded flux layer Y4) to ensure that the flux content in the aluminum alloy composite material is consistent with that of aluminum alloy composite material F1. All other aspects are the same as aluminum alloy composite material F1 and will not be repeated here.

[0102] Aluminum alloy composite material F7 differs from aluminum alloy composite material F1 only in that the thickness ratio of the pre-embedded flux layer to the solder layer is 2.57, and the proportion of the base alloy in the pre-embedded flux layer is adaptively adjusted (i.e., the pre-embedded flux layer uses pre-embedded flux layer Y5) to ensure that the flux content in the aluminum alloy composite material is consistent with that of aluminum alloy composite material F1. All other aspects are the same as aluminum alloy composite material F1 and will not be repeated here.

[0103] Aluminum alloy composite material DF1: The only difference between it and aluminum alloy composite material F1 is that the solder layer is solder layer DQ1, meaning the temperature difference between the solidus temperature T1 (574℃) of the solder layer and the solidus temperature T2 (575℃) of the base alloy is only 1℃. Everything else is the same as aluminum alloy composite material F1, and will not be repeated here.

[0104] Example 1

[0105] This embodiment provides a brazing method suitable for brazing a first component with a surface structure containing a fine grain region. The brazing method includes the following steps:

[0106] (1) Assemble the first component and the second component to form a component to be soldered, wherein the cross section of the first component and the surface of the solder layer of the second component are in contact with each other; the second component is an aluminum alloy composite material F1;

[0107] (2) The components to be welded in step (1) are brazed in a brazing process, wherein the brazing process includes an initial brazing window, a middle brazing window and a final brazing window performed sequentially.

[0108] The initial brazing window temperature is T1 to T2 excluding T2, i.e., 568 to 575°C excluding 575°C, and the initial brazing window time is controlled at 18 seconds. During the initial brazing window, the solder layer forms a ZnSi-rich region and a low ZnSi region. The solidus temperature of the low ZnSi region is T3 = 598°C > T2 = 575°C, and the difference between the two is 23°C. During the initial brazing window, the proportion of the liquid phase formed in the solder layer to the sum of the liquid phase of the solder layer and the base alloy is 21.84%, and the proportion of the liquid phase formed in the solder layer to the liquid phase of the solder layer is 31.2%.

[0109] The temperature of the intermediate brazing window is T2 to T3, excluding T3, i.e., 575 to 598°C, excluding 598°C; the time of the intermediate brazing window is controlled at 62 seconds.

[0110] The temperature of the final brazing window is ≥T3=598℃, and the time required for the final brazing window to complete the brazing is 177s.

[0111] Example 2

[0112] This embodiment provides a brazing method suitable for brazing a first component with a surface structure containing a fine grain region. The brazing method includes the following steps:

[0113] (1) The first component and the second component are assembled to form a component to be soldered, wherein the cross section of the first component and the surface of the solder layer of the second component are in contact with each other; the second component is an aluminum alloy composite material F2;

[0114] (2) The components to be welded in step (1) are brazed in a brazing process, wherein the brazing process includes an initial brazing window, a middle brazing window and a final brazing window performed sequentially.

[0115] The initial brazing window temperature is T1 to T2 excluding T2, i.e., 552 to 563°C excluding 563°C, and the initial brazing window time is controlled at 27 seconds. During the initial brazing window, the solder layer forms a ZnSi-rich region and a low ZnSi region. The solidus temperature of the low ZnSi region is T3 = 594°C > T2 = 563°C, and the difference between the two is 31°C. During the initial brazing window, the proportion of the liquid phase formed in the solder layer to the sum of the liquid phase of the solder layer and the base alloy is 26.87%, and the proportion of the liquid phase formed in the solder layer to the liquid phase of the solder layer is 59.7%.

[0116] The temperature of the intermediate brazing window is T2 to T3, excluding T3, i.e., 563 to 594°C, excluding 594°C; the time of the intermediate brazing window is controlled at 48 seconds.

[0117] The temperature of the final brazing window is ≥T3=594℃, and the time required for the final brazing window to complete the brazing is 112s.

[0118] Example 3

[0119] This embodiment provides a brazing method suitable for brazing a first component with a surface structure containing a fine grain region. The brazing method includes the following steps:

[0120] (1) Assemble the first component and the second component to form a component to be soldered, wherein the cross section of the first component and the surface of the solder layer of the second component are in contact with each other; the second component is an aluminum alloy composite material F3;

[0121] (2) The components to be welded in step (1) are brazed in a brazing process, wherein the brazing process includes an initial brazing window, a middle brazing window and a final brazing window performed sequentially.

[0122] The initial brazing window temperature is T1 to T2 excluding T2, i.e., 570 to 573°C excluding 573°C, and the initial brazing window time is controlled at 51 seconds. During the initial brazing window, the solder layer forms a ZnSi-rich region and a low ZnSi region. The solidus temperature of the low ZnSi region is T3 = 597°C > T2 = 573°C, and the difference between the two is 24°C. During the initial brazing window, the proportion of the liquid phase formed in the solder layer to the sum of the liquid phase of the solder layer and the base alloy is 22.95%, and the proportion of the liquid phase formed in the solder layer to the liquid phase of the solder layer is 51.0%.

[0123] The temperature of the intermediate brazing window is T2 to T3, excluding T3, i.e., 573 to 597°C, excluding 597°C; the time of the intermediate brazing window is controlled at 216 seconds.

[0124] The temperature of the final brazing window is ≥T3=597℃, and the time required for the final brazing window to complete the brazing is 55s.

[0125] Example 4

[0126] This embodiment provides a brazing method suitable for brazing a first component with a surface structure containing a fine grain region. The brazing method includes the following steps:

[0127] (1) Assemble the first component and the second component to form a component to be soldered, wherein the cross section of the first component and the surface of the solder layer of the second component are in contact with each other; the second component is an aluminum alloy composite material F4;

[0128] (2) The components to be welded in step (1) are brazed in a brazing process, wherein the brazing process includes an initial brazing window, a middle brazing window and a final brazing window performed sequentially.

[0129] The initial brazing window temperature is T1 to T2 excluding T2, i.e., 552 to 577°C excluding 577°C, and the initial brazing window time is controlled at 30 seconds. During the initial brazing window, the solder layer forms a ZnSi-rich region and a low ZnSi region. The solidus temperature of the low ZnSi region is T3 = 597°C > T2 = 577°C, and the difference between the two is 20°C. During the initial brazing window, the proportion of the liquid phase formed in the solder layer to the sum of the liquid phase of the solder layer and the base alloy is 27.32%, and the proportion of the liquid phase formed in the solder layer to the liquid phase of the solder layer is 68.3%.

[0130] The temperature of the intermediate brazing window is T2 to T3, excluding T3, i.e., 577 to 597°C, excluding 597°C; the time of the intermediate brazing window is controlled at 152 seconds.

[0131] The temperature of the final brazing window is ≥T3=597℃, and the time required for the final brazing window to complete the brazing is 59s.

[0132] Example 5

[0133] This embodiment provides a brazing method suitable for brazing a first component with a surface structure containing a fine-grained region. The only difference from Embodiment 1 is that the initial brazing window time is controlled at 10 seconds. During the initial brazing window, the proportion of the liquid phase formed in the solder layer to the sum of the liquid phase in the solder layer and the base alloy is 8.75%, and the proportion of the liquid phase formed in the solder layer to the liquid phase in the solder layer is 12.5%. Under the same intermediate brazing window time, the final brazing window time needs to reach 254 seconds to complete the brazing. All other aspects are the same as in Embodiment 1 and will not be repeated here.

[0134] Example 6

[0135] This embodiment provides a brazing method suitable for brazing a first component with a fine-grained surface structure. The only difference from Embodiment 1 is that the second component is an aluminum alloy composite material F5, thus adaptably setting the initial brazing window temperature to T1-T2 (excluding T2), i.e., 547-575°C (excluding 575°C). During the initial brazing window, the solder layer forms a ZnSi-rich region and a low-ZnSi region. The solidus temperature of the low-ZnSi region is T3 = 593°C > T2 = 575°C, with a difference of 18°C. During the initial brazing window, the liquid phase formed in the solder layer accounts for 49.84% of the sum of the liquid phase in the solder layer and the base alloy, and 71.2% of the liquid phase in the solder layer. The duration of the initial and intermediate brazing windows is the same as in Embodiment 1, and the final brazing window time required to complete the brazing is 72 seconds.

[0136] Example 7

[0137] This embodiment provides a brazing method suitable for brazing a first component with a fine-grained surface structure. The only difference from Embodiment 1 is that the second component is an aluminum alloy composite material F6, and the initial brazing window time is adaptively adjusted to 24s so that the proportion of liquid phase formed in the solder layer accounts for 31% of the total liquid phase in the solder layer (maintaining a value substantially equivalent to that in Embodiment 1). This results in the proportion of liquid phase formed in the solder layer to the sum of the liquid phase in the solder layer and the base alloy in the initial brazing window being 28.7%. Furthermore, in order to ensure that the pre-embedded flux layer is completely converted into liquid phase in the intermediate brazing window, the intermediate brazing window time is adaptively adjusted to 44s, and the final brazing window time required to complete the brazing is 286s.

[0138] Example 8

[0139] This embodiment provides a brazing method for a first component suitable for brazing a surface structure containing a fine-grained region. The only difference from Embodiment 1 is that the second component is an aluminum alloy composite material F7, and the initial brazing window time is adaptively adjusted to 15s so that the proportion of liquid phase formed in the solder layer accounts for 31.3% of the total liquid phase in the solder layer (maintaining a value substantially equivalent to that in Embodiment 1). This results in the proportion of liquid phase formed in the solder layer to the sum of the liquid phase in the solder layer and the base alloy in the initial brazing window being 8.74%. Furthermore, in order to ensure that the pre-embedded flux layer is completely converted into liquid phase in the intermediate brazing window, the intermediate brazing window time is adaptively adjusted to 240s, and the final brazing window time required to complete the brazing is 69s.

[0140] Comparative Example 1

[0141] This comparative example provides a brazing method for a first component suitable for brazing a surface structure containing a fine grain region. The only difference from Example 1 is that the second component is an aluminum alloy composite material DF1, and the brazing process is adapted to start melting from the solidus temperature T1 (574°C) of the brazing filler alloy and then heating up to 603°C until it is completely melted. The total brazing time is 356s.

[0142] The erosion depth of the welded finished products obtained in the above embodiments and comparative examples, as well as the material climbing height of the first component (wherein the height of the first component is 18 mm), are shown in Table 1.

[0143] Table 1

[0144] Example 1 152μm 4mm Example 2 74μm 2.5mm Example 3 61μm 2mm Example 4 65μm 2.2mm Example 5 203μm 10mm Example 6 161μm 8mm Example 7 225μm 11mm Example 8 243μm 13mm Comparative Example 1 327μm 15mm

[0145] The following points can be observed from Table 1:

[0146] (1) As can be seen from the comprehensive examples 1 to 8, the aluminum alloy composite material and its brazing method provided by the present invention, which are suitable for brazing the surface structure containing fine grain regions, can reduce the brazing defects when the first component containing the surface structure containing fine grain regions is welded, and its erosion depth is within 250 μm and the material climbing height of the first component is within 14 mm.

[0147] (2) Effect of solidus temperature difference

[0148] Comparing Examples 1 and 6, it can be seen that in Example 6, the temperature difference between the solidus temperature T1 (547°C) of the solder layer and the solidus temperature T2 (575°C) of the base alloy is 28°C, which is too large. This results in the low-melting-point liquid phase formed first in the solder layer staying at the solder joint for too long, increasing the erosion of the base material. The erosion depth is deeper than in Example 1, and the climbing height is increased.

[0149] Comparing Example 1 and Comparative Example 1, it can be seen that in Comparative Example 1, the temperature difference between the solidus temperature T1 (547°C) of the solder layer and the solidus temperature T2 (575°C) of the base alloy is only 1°C, which is too small. This causes the solder layer and the pre-embedded flux layer to melt simultaneously and rush to the welding surface, failing to form a high-melting-point low-ZnSi region. This significantly deepens the erosion on the surface of the first component and significantly increases the creep height. The metallographic photograph of the brazed joint cross-section provided in Example 1 is shown below. Figure 3 As shown, the metallographic photograph of the brazed joint cross-section provided in Comparative Example 1 is as follows: Figure 4 As shown, from Figures 3-4 It can be seen that the erosion and material creep in Comparative Example 1 are significantly more severe.

[0150] (3) The influence of the initial brazing window duration

[0151] Comparing Examples 1 and 5, it can be seen that the initial brazing window time in Example 5 is shorter, so the brazing filler layer that should have melted when it reaches the solidus temperature T2 of the base alloy does not melt. This results in too little liquid phase in the initial stage and too long time required for final brazing, i.e., the time for high liquid phase is extended, and the erosion of the final welded product is deeper and the climbing height is increased.

[0152] (4) The influence of the proportion of pre-embedded flux layer

[0153] Comparing Examples 1 and 7-8, it can be seen that when the proportion of the pre-embedded flux layer in Example 7 is too low, it means that the proportion of the brazing filler metal layer is too high, resulting in too much material to be melted at the end. The brazing window at the end requires a longer time to complete the brazing, leading to deeper erosion and material creep. When the proportion of the pre-embedded flux layer in Example 8 is too high, it means that the proportion of the brazing filler metal layer is too low, and there is too little material remaining on the surface. It is difficult to block the internal liquid phase at the intermediate brazing window, which ultimately results in the high-temperature liquid phase residence time covering both the intermediate and final brazing windows. The longer the high-temperature liquid phase residence time, the more severe the erosion and material creep phenomena become.

[0154] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A brazing method suitable for brazing a first component with a surface structure containing a fine-grained region, characterized in that, The brazing method includes the following steps: (1) Assemble the first component and the second component to form a component to be soldered, wherein the cross section of the first component and the surface of the solder layer of the second component are in contact with each other; The edge region of the first component cross-section is a fine-grained region, the thickness of the fine-grained region is not less than 20 μm, and the average grain size of the fine-grained region is ≤7 μm; The second component includes: a core layer and a brazing composite layer, wherein the brazing composite layer is disposed on at least one side of the core layer; the brazing composite layer includes a pre-embedded flux layer and a brazing filler metal layer, wherein the layer closer to the core layer is the pre-embedded flux layer, and the layer farther from the core layer is the brazing filler metal layer; the pre-embedded flux layer includes a base alloy and a brazing flux, wherein the base alloy contains the alloying element Si and does not contain the element Zn; the brazing filler metal layer is an AlSiZn-based brazing filler metal alloy; the solidus temperature T1 of the brazing filler metal alloy is less than the solidus temperature T2 of the base alloy, and the difference is at least 2°C; the brazing composite layer is disposed close to the first component; (2) The components to be welded in step (1) are brazed in a brazing process, wherein the brazing process includes an initial brazing window, a middle brazing window and a final brazing window performed sequentially; The initial brazing window temperature is T1~T2, excluding T2; within the initial brazing window, the solder layer forms a ZnSi-rich region and a low ZnSi region, with the solidus temperature of the low ZnSi region being T3 > T2; the intermediate brazing window temperature is T2~T3, excluding T3. The temperature of the final brazing window is ≥T3; The first component is an aluminum die casting. The core layer is made of 3xxx series Al-Mn alloy or 6xxx series Al-Mg-Si alloy. The brazing filler layer includes the following alloying elements by mass fraction: Si: 6~13%, Zn: 1~13%.

2. The brazing method according to claim 1, characterized in that, The initial brazing window time is controlled to be 10~51s.

3. The brazing method according to claim 1, characterized in that, The time control of the intermediate brazing window is 44~240s.

4. The brazing method according to claim 1, characterized in that, The duration of the final brazing window is controlled to be 55~286s.

5. The brazing method according to claim 1, characterized in that, The solidus temperature T2 of the base alloy is at most 25°C higher than the solidus temperature T1 of the solder layer.

6. The brazing method according to claim 5, characterized in that, The solidus temperature of the brazing alloy is 547-570℃.

7. The brazing method according to claim 5, characterized in that, The solidus temperature of the base alloy is 563-577℃.

8. The brazing method according to any one of claims 1 to 7, characterized in that, The thickness ratio of the pre-embedded flux layer to the solder layer is 0.11~2.33; the mass percentage of the base alloy in the pre-embedded flux layer is 85~98%. During the initial brazing window, the proportion of the liquid phase formed in the brazing filler layer to the sum of the liquid phase in the base alloy of the brazing filler layer and the embedded layer is 8.74~49.84%.

9. The brazing method according to claim 8, characterized in that, The proportion of the liquid phase formed in the solder layer to the sum of the liquid phase of the base alloy in the solder layer and the embedded layer is ≤30%.

10. The brazing method according to any one of claims 1 to 7, characterized in that, During the initial brazing window, the proportion of liquid phase formed in the brazing filler layer to the total liquid phase of the brazing filler layer is ≥12%.

11. The brazing method according to claim 10, characterized in that, During the initial brazing window, the proportion of liquid phase formed in the brazing filler layer to the total liquid phase of the brazing filler layer is 31.2% to 68.3%.

12. An aluminum alloy composite material, characterized in that, The aluminum alloy composite material is a second component for a brazing method according to any one of claims 1 to 11, which is suitable for brazing a first component with a surface structure containing a fine grain region.

13. A welded finished product, characterized in that, The welded product is obtained by brazing using the brazing method described in any one of claims 1-11, which is suitable for brazing a first component with a surface structure containing a fine grain region.

14. A welded finished product, said welded finished product being a heat pump manifold, characterized in that, The heat pump manifold comprises an aluminum die-cast part and the aluminum alloy composite material as described in claim 12.

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