Aluminum alloy composite material suitable for brazing surface structure containing fine grain area and brazing method and welding finished product of aluminum alloy composite material

Abstract

The invention provides an aluminum alloy composite material suitable for brazing a surface structure containing a fine grain area, a brazing method of the aluminum alloy composite material and a welding finished product. The brazing method comprises the steps that the section of a first component makes contact with the surface of a brazing filler metal layer of a second component to form a to-be-welded assembly; the second part comprises a core layer and a brazing composite layer, the side, close to the core layer, of the brazing composite layer is an embedded brazing flux layer, and the side, away from the core layer, of the brazing composite layer is a brazing filler metal layer; the pre-embedded brazing flux layer comprises a base material alloy and a brazing flux, the solidus temperature T1 of the brazing filler metal layer is smaller than the solidus temperature T2 of the base material alloy of the pre-embedded layer, and the difference value is at least 2 DEG C; in the brazing process, the temperature of a brazing window in the initial stage is T1-T2 and does not contain T2; in the initial brazing window, a ZnSi-rich area and a low-ZnSi area are formed on the brazing filler metal layer, and the solidus temperature T3 of the low-ZnSi area is larger than T2; the temperature of the middle-stage brazing window is T2-T3, and the middle-stage brazing window does not contain T3; the temperature of the final-stage brazing window is not less than T3. According to the method, corrosion and material climbing can be reduced, and the brazing quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy brazing, in particular to an aluminum alloy composite material suitable for brazing a surface structure containing a fine grain area, a brazing method thereof, and a welded product. Background Art

[0002] With the continuous growth in production and sales of new energy vehicles, especially pure electric vehicles, manufacturers are placing increasing demands on thermal management design. Automotive heat pump systems, as a highly efficient technology for automotive thermal management, achieve heat transfer by absorbing heat and evaporating the refrigerant in the evaporator. This refrigerant is then compressed into a high-temperature, high-pressure gas by a compressor, releasing heat and returning to the evaporator through a condenser. The refrigerant is then throttled and depressurized by an expansion valve before returning to the evaporator, repeating this cycle. With the development of electric vehicles, heat pump systems are becoming increasingly widely used in these vehicles. For example, some models from brands like Tesla and BYD utilize heat pump technology to improve vehicle range and thermal management performance. The manifold is a key component connecting the various components in a heat pump system. It distributes refrigerant or coolant to the components requiring heat dissipation or heating, ensuring that each component receives the appropriate amount of fluid for effective heat exchange. The manifold design optimizes fluid flow within the system, reducing resistance and pressure loss, and improving fluid uniformity and flow rate, thereby enhancing the efficiency of the heat pump system. For example, the Tesla Super Manifold V2 simulates the capillary distribution of a hummingbird's wing, with 18 sets of guide fins within the microchannels. This improves refrigerant flow uniformity by 52% and reduces pressure drop by 31%. Due to the manifold's unique and complex structure, casting is undoubtedly one of the best ways to produce it while balancing production efficiency, dimensional accuracy, and surface quality.

[0003] However, when assembling and brazing the die-cast manifold with other radiator components, such as the condenser and evaporator, problems such as incomplete welds and low weldability are often observed between the manifold and the radiator baseplate. Developing a radiator baseplate material that welds well to the manifold is a key factor in expanding the application of heat pump systems in electric vehicles.

[0004] CN118046135A discloses an aluminum alloy, solder, and preparation method for brazing integrated heat pump substrates for new energy vehicles. This method adds appropriate amounts of Mn and Ti to the Mg-containing aluminum-silicon brazing process to address defects such as solder flowing and creeping along the casting walls during vacuum brazing of new energy heat pump integrated substrates due to the loose structure of the die-cast substrate, resulting in cold welds, incomplete fillet filling, and low weldability.

[0005] New energy heat pump manifolds adopt a highly integrated design, which places high demands on the heat dissipation of the material. To ensure high cleanliness in the flow channel, vacuum brazing technology was previously commonly used. However, due to the shortcomings of vacuum brazing (VB) such as large investment in equipment, low brazing efficiency, and high maintenance costs, heat pump manufacturers are eager to adopt controlled atmosphere brazing (CAB) to replace vacuum brazing.

[0006] The inventors of this patent found through experiments that even if the heat pump base plate manufacturer adjusts the die-casting process to improve the degassing and slag removal efficiency and obtains a non-organized and loose die-cast part with good cast structure, the brazing defects mentioned above will still occur when the part is assembled with brazing materials and vacuum brazing or controlled atmosphere brazing is performed. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an aluminum alloy composite material suitable for brazing a surface structure containing a fine grain area, a brazing method thereof, and a welded product, that is, to provide an aluminum die-casting and a brazing method thereof, an aluminum alloy composite material for brazing, and a welded finished aluminum alloy composite material, which can obtain a brazed part with a full weld joint and no obvious material creeping 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 of the outer wall is greater than the cooling rate of the core during the cooling process, and a chill layer is gradually generated on the outer wall. The grain size of the chill layer is smaller than the core size. Figure 1 The presence of this fine-grained layer is the main reason why the first component suffers from ① solder creeping along the wall and melting, and ② poor weld seam when brazing with conventional solder.

[0009] To achieve this object, the present invention adopts the following technical solutions:

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

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

[0012] The edge area of the cross section of the first component is a fine grain area, the thickness of the fine grain area is not less than 20 μm, and the average grain size of the fine grain area 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 brazing flux layer and a brazing filler metal layer, wherein the layer closer to the core layer is the pre-embedded brazing flux layer, and the layer farther from the core layer is the brazing filler metal layer. The pre-embedded brazing 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.

[0014] (2) brazing the components to be welded in step (1) under a brazing process, wherein the brazing process includes an initial brazing window, a mid-term brazing window, and a final brazing window performed in sequence.

[0015] The temperature of the initial brazing window is between T1 and T2, excluding T2. In the initial brazing window, the brazing material layer forms a ZnSi-rich region and a low-ZnSi region, and the solidus temperature of the low-ZnSi region is T3>T2. The temperature of the mid-term brazing window is between T2 and T3, excluding T3.

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

[0017] Due to the processing characteristics of die-casting, die-cast parts typically have a chilled fine-grain layer on the surface and a coarse-grained layer within. The average grain size of this chilled fine-grain layer is ≤7μm, and the thickness of this fine-grain layer is at least 20μm. The fine-grained region in a cross-section of the first component, taken parallel to the second component, represents this chilled fine-grain layer. During brazing, the weld foot forms at the edge of the second component, forming on the surface of the chilled fine-grain layer. The presence of this chilled fine-grain layer is responsible for solder erosion and wall creep when brazing die-cast parts with conventional brazing materials.

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

[0019] The present invention provides a fast channel for the migration of the flux in the pre-embedded layer to the material surface by forming a molten liquid phase approximately perpendicular to the surface of the solder layer during the initial melting process of the AlSiZn solder alloy, so that the early molten AlSiZn liquid phase can form a small amount of precursor weld. At the same time, the present invention utilizes the dynamic melting point difference between the solder layer with some residual Si and Zn elements and the pre-embedded layer (at this time, the melting point of the solder layer is greater than the melting point of the pre-embedded layer) to avoid the premature flow of a large amount of molten liquid phase of the pre-embedded solder layer to the weld joint after it is formed, thereby improving the premature accumulation of the weld liquid phase and reducing the erosion of the fine grain wall of the aluminum die casting caused by the long-term retention of the molten liquid phase at a large number of welds. Thus, without the need to process the manifold casting, a brazed part with a full weld joint and no obvious creeping of material along the casting wall is obtained.

[0020] Specifically, the present invention introduces a brazing flux pre-embedded layer between the brazing alloy and the core material layer, and simultaneously improves the traditional 4XXX series brazing alloy into an Al-Si alloy containing the Zn element, thereby reducing the initial melting temperature of the entire Al-Si-Zn series brazing alloy to 552-570°C (solidus temperature). During the brazing heating process, as the temperature rises to the solidus temperature of the Al-Si-Zn series brazing layer, the brazing flux in the pre-embedded brazing flux layer begins to melt, but does not reach the initial melting temperature of the base alloy in the pre-embedded brazing flux layer. At this time, the liquid brazing flux aggregates, grows, and spheroidizes. The solidus temperature of the base alloy is selected to be at least 2°C higher than the solidus temperature of the brazing alloy. When the solidus temperature difference is less than 2°C, that is, the pre-embedded brazing flux layer base alloy and the brazing layer begin to melt at approximately the same time, there is too much molten liquid phase filling the weld, which will aggravate the problem of corrosion.

[0021] When the temperature reaches the solidus temperature of the AlSiZn solder alloy and 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 the Si particles and the α(Al) matrix. Si atoms diffuse from the α(Al) matrix to the liquid phase (because the liquid phase can accommodate more Si), while Al atoms diffuse in the opposite direction more slowly, resulting in a rapid increase in the Si concentration in the liquid phase. Similarly, the Zn element content in the liquid phase is also greater than that in the unmelted matrix. Since the generated AlSiZn liquid phase is preferentially enriched at the grain boundaries, Zn and Si-rich regions are formed at the grain boundaries, while low Zn and Si regions are formed within the crystals. At the grain boundaries, AlSiZn liquid phase gradually forms an AlSiZn liquid phase channel that is approximately perpendicular to the surface of the brazing material. At the same time, the spheroidized brazing flux quickly migrates to the interface between the AlSiZn brazing material layer and the embedded layer, and migrates to the surface of the brazing material layer along the AlSiZn liquid phase channel along with the AlSiZn liquid phase, and removes the oxide film on the surface of the brazing material and the adjacent manifold casting to be welded, thereby improving the wettability of the parts to be welded. At this time, due to the relatively low temperature, only part of the AlSiZn molten brazing material in the brazing material layer fills the weld, and the base material in the embedded brazing material layer has not yet reached the solidus temperature, and no liquid phase is generated at the grain boundaries for the weld to be filled, which avoids the premature melting of the weld and the casting wall by a large amount of molten brazing material. Because the relatively high-Si and high-Zn AlSiZn liquid phase generated in the brazing filler metal layer is used to form the initial weld under the action of the brazing flux, the unmelted solid phase in this layer is a relatively high-melting-point region with low Si and low Zn. The time of the initial brazing window is controlled so that the solidus temperature T3 of the low-ZnSi region is greater than T2. Preferably, T3 is at least 2°C higher than T2, for example, 2°C, 3°C, 5°C, 6°C, 8°C, 9°C, 10°C, 12°C, 15°C, 18°C, or 20°C.

[0022] As the brazing temperature is further increased 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. Although there are differences in the liquid phase Si element in this melting process, the presence of the upper layer of high melting point AlSiZn hinders the migration speed of the high Si liquid phase, allowing more Si elements to be retained in the embedded flux layer. Therefore, the Si content of the embedded layer remains relatively stable and no obvious low-silicon area is formed. This means that when the base material of the embedded flux layer is completely melted, the low-silicon and low-zinc high melting point areas of the brazing layer do not reach a complete liquid phase. In this temperature range, the unmelted solid phase in the brazing layer located outside the embedded layer hinders the liquid phase formed by the embedded layer base from filling the weld and the casting wall in large quantities.

[0023] After the temperature reaches the liquidus temperature of the entire brazing filler layer, the molten liquid phase begins a secondary filling process. However, because the liquid phase in the present invention only reaches the liquidus temperature of the entire brazing filler layer before it significantly fills the weld and casting walls, under the same brazing process and with the same amount of liquid phase, the later-generated liquid phase in the present invention spends less time in the high-temperature zone, resulting in less alloying elements from the brazing plate core material and the aluminum die casting diffusing into the liquid phase, significantly reducing erosion of the weld and manifold casting walls.

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

[0025] Specifically, 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, for example, it can be 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C, 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C or 25°C, etc.

[0026] Preferably, the time of the initial brazing window 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.

[0027] During the initial brazing window, sufficient time is required for the Si and Zn elements in the brazing material layer to flow to the surface along with the molten brazing flux, forming Zn and Si-rich regions at the grain boundaries of the brazing material layer and low Zn and Si regions within the grains. This allows the Zn and Si-rich liquid phase at the grain boundaries of the brazing material layer to form the initial weld foot at the weld. If the initial brazing window is insufficient, it is easy to make it difficult to form the low Zn and Si regions within the grains, or the Zn and Si content in the low Zn and Si regions is still high, and the solidus temperature of the low Zn and Si regions formed is lower than the solidus temperature of the base alloy. As a result, the low Zn and Si regions are unable to prevent the migration of a large amount of high Si liquid phase in the pre-embedded brazing flux layer, resulting in a large amount of filling into the weld and casting wall, resulting in severe erosion of the weld and manifold casting wall. If the initial brazing window is too long, there is a problem of intensified diffusion of the molten liquid phase at the weld foot and the base alloy elements around the weld foot, which increases the erosion problem.

[0028] Preferably, the time of the mid-term 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] During the actual brazing process, it takes time for the brazing filler metal to fully melt. If the brazing filler metal matching the core material fails to melt in time, poor filler liquid will result. Therefore, we want to ensure that a large amount of liquid fills the brazing zone and that the liquid phase remains in the high-temperature zone as short a time as possible. During the mid-term brazing window, timing control is primarily focused on ensuring that the pre-embedded flux layer fully transforms into the liquid phase, thereby shortening 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 present invention achieves excellent brazing results with a short final brazing window. However, if the final brazing window is too long, the prolonged high-temperature period causes increased diffusion of alloying elements from the brazing plate core material and manifold casting into the liquid phase, which in turn increases corrosion of the weld and manifold casting walls. Furthermore, if the final brazing window is too short, the low-Zn and Si regions of the brazing filler metal layer may not transform into the liquid phase, resulting in poor solder filling.

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

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

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

[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, the low melting point liquid phase formed in the solder layer stays at the solder foot for too long, increasing the corrosion of the base alloy.

[0036] Preferably, the solder layer comprises the following mass fractions of alloy elements Si: 6-13%, Zn: 1-13%. Among them, 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: 1-13%, for example, 1%, 3%, 4%, 5%, 7%, 8%, 9%, 11%, 12% or 13%, etc.

[0038] Compared to AlSi alloys, the Zn element in the AlSiZn alloy in the solder layer can significantly lower the solidus temperature. After reaching the solidus temperature, the AlSiZn alloy will form Zn-rich and Si-rich regions at the grain boundaries, while low Zn and Si regions will form within the grains. Controlling the presence of at least a solidus temperature difference between the base alloy and the solder layer ensures the formation of sufficient Zn-rich and Si-rich regions and low Zn and Si regions at this stage, ensuring sufficient liquid phase ratio to obtain the initial solder leg, and a low Zn and Si region matrix with lower Zn and Si concentrations (high solidus). At least a solidus temperature difference is ensured to obtain a good initial solder leg and a low Zn and Si region matrix with a high solidus.

[0039] If the Si content is too low, insufficient AlSi molten brazing filler metal will form, making it difficult to form an effective weld foot. If the Si content is too high, the liquidus temperature will rise, and the brazing filler metal will not be completely melted at the brazing temperature, resulting in insufficient weld filling.

[0040] If the Zn content is too low, it cannot effectively lower the melting point. If the Zn content is too high, it will lead to an excessively large solid-liquid phase region (the difference between the liquidus temperature and the solidus temperature), increasing the melting corrosion.

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

[0042] Preferably, in the initial brazing window, the proportion of the liquid phase formed by the brazing filler metal layer to the total liquid phase of the base alloy in the brazing filler metal layer and the pre-embedded layer is 8.74% to 49.84%, for example, 8.74%, 13.31%, 17.88%, 22.44%, 27.01%, 30%, 31%, 31.58%, 36.14%, 40.71%, 45.28%, or 49.84%, but is not limited to the values listed above, and other values not listed within this range are also applicable. More preferably, the proportion of the liquid phase formed by the brazing filler metal layer to the total liquid phase of the base alloy in the brazing filler metal layer and the pre-embedded layer is ≤30%.

[0043] A dynamic solidus temperature difference exists between the pre-embedded flux layer and the brazing material layer. Within the initial brazing window, after the brazing temperature reaches above the flux melting point, a brazing temperature range exists, referred to as the initial brazing temperature. This initial brazing temperature reaches the solidus temperature of the brazing alloy of the pre-embedded flux layer in the second component, but is higher than the solidus temperature of the brazing material layer. At this initial brazing temperature, the Si and Zn elements in the brazing material layer flow toward the surface along with the molten flux, forming Zn- and Si-rich regions at the grain boundaries of the brazing material layer and low-Zn- and Si-rich regions within the grains. This allows the Zn- and Si-rich liquid phase at the grain boundaries of the brazing material layer to form an initial weld foot at the weld. The liquidus fraction of the brazing material layer formed at this stage is 4.76-9.87%, and the remaining low-Zn- and Si-rich regions of the brazing material layer remain unmelted, and do not melt within the mid-term brazing window. When the liquid phase ratio of the solder layer formed at this stage (accounting for the sum of the liquid phase amount of the base alloy in the solder layer and the embedded layer) is too high, corrosion is more likely to occur. When the liquid phase ratio of the solder layer formed at this stage is too low (accounting for the sum of the liquid phase amount of the base alloy in the solder layer and the embedded layer), there is a problem that the molten liquid phase cannot form sufficient effective filler to fill the weld.

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

[0045] More preferably, in the initial soldering window, the proportion of the liquid phase formed in the solder layer to the liquid phase of the solder layer is 31.2 to 68.3%.

[0046] The higher the proportion of the liquid phase formed in the solder layer to the total liquid phase theoretically formed in the solder layer, the shorter the final brazing window time is, 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 includes the following alloy components in percentage by mass: 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, it can be 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% or 1.6%; Mg≤0.3%, for example, it can be 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%; Zn≤4%, for example, it can be 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 includes the following alloy components in percentage by mass: 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, 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.; Mg: 0.4~0.9%, for example, it can be 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.9%, etc.; Ti: 0.01~0.03%, for example, it can be 0.01%, 0.015%, 0.02%, 0.025% or 0.03%.

[0050] Preferably, in terms of mass fraction, Fe in the substrate alloy is ≤ 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 is ≤ 0.2%, for example, 0.2%, 0.18%, 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, in terms of mass fraction, the alloying elements in the solder layer include 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.; Cu≤0.2%, for example, 0.2%, 0.18%, 0.15%, 0.12%, 0.10%, 0.09%, 0.08%, 0.05% or 0.01%, etc.; Mg≤0.1%, for example, 0.1%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04%, 0.03%, 0.02% or 0.01%, etc.

[0052] Preferably, the thickness of the brazing composite layer accounts for 5-15% of the total thickness of the second component, for example, 5%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%.

[0053] Preferably, the content of the flux in the second component is 0.84 to 14.7 g / m 2 , for example, it can be 0.84g / 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 etc., but not limited to the listed values.

[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 used in the brazing method for brazing the first component having a surface structure containing a fine grain region as described in the first aspect.

[0056] In a third aspect, the present invention provides a welded product obtained by brazing using the brazing method for brazing a first component having a surface structure containing a fine grain area as described in the second aspect.

[0057] In a fourth aspect, the present invention provides a welded product, which is a heat pump manifold. The heat pump manifold comprises 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 is suitable for brazing a first component with a surface structure containing a fine crystal area. The molten liquid phase formed during the initial melting process is approximately perpendicular to the surface of the brazing material layer, which provides a fast channel for the migration of the brazing flux in the pre-embedded layer to the material surface, so that the early molten AlSiZn liquid phase can form a partial precursor weld.

[0060] (2) The brazing method provided by the present invention is suitable for brazing a first component with a surface structure containing a fine grain area. The method utilizes the dynamic melting point difference between the brazing material layer containing the remaining Si and Zn elements and the pre-buried layer (at this time, the melting point of the brazing material layer is greater than the melting point of the pre-buried layer) to avoid the premature formation of a large amount of molten liquid phase, thereby improving the premature accumulation of the liquid phase in the weld and reducing the erosion of the fine grain wall of the manifold casting caused by the long-term retention of the molten liquid phase in a large amount of welds. In this way, a brazed component with a full weld joint and no obvious creeping of material along the casting wall is obtained without the need to treat the manifold casting. Specifically, when brazing the first component with a height of 18 mm, the erosion depth is within 250 μm, and the creeping height of the first component is within 14 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is an assembly diagram of the component to be welded provided by the present invention.

[0062] Figure 2 is an EBSDIPF+GB diagram of the cross section of the first component in a specific embodiment.

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

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

[0065] In the figure: 1, first component; 11 - quenched fine-grained area; 12 - intermediate coarse-grained area; 2 - second component; 21 - core layer; 22 - brazing composite layer; 221 - embedded brazing flux layer; 222 - brazing material layer. DETAILED DESCRIPTION

[0066] For the convenience of understanding the present invention, the present invention is given below with examples. It should be understood by those skilled in the art that the examples are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0067] It should be understood that when the weld target, i.e., the edge region of the cross-section of the first component, is a fine-grained region (average grain size ≤ 7 μm), and the thickness of the fine-grained region is not less than 20 μm, this can cause material creep after ablation. Therefore, the weld target of the present invention is a first component having a fine-grained region, and the problem of material creep caused by ablation during welding is solved. When the weld target does not have a fine-grained region, material creep generally does not occur or is not significant. These weld targets are not discussed in the specific embodiments of the present invention.

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

[0069] Test Method

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

[0071] 2. Solidus Temperature: During the material preparation process, 15-20 mg of the material layer was cut and placed in an alumina ceramic crucible. The sample was heated using a German NETZSCH STA 449F5 synchronous thermal analyzer in the temperature range of 25°C to 700°C. The heating rate was 10°C / min, and high-purity argon was used as the shielding gas. After the test, the DSC curve was analyzed using the built-in software to obtain the solidus temperature of the material.

[0072] 3. Liquidus fraction: The chemical composition of the material was analyzed using a Gangyan Nano-plasma 2000 Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The chemical composition was input into the JMatPro software to obtain the liquidus fraction of the material at a specific temperature.

[0073] 4. Melting depth and creeping height: according to Figure 1 In the structure shown, a first component measuring 20 mm in length, 4 mm in width, and 18 mm in height, respectively, was placed on a second component measuring 30 mm by 30 mm (1 mm thick) and secured with 0.8 mm diameter steel wire. The secured first and second components were brazed in a nitrogen-protected OTF-1200X tube furnace to produce a brazed sample. A sample was cut from the middle of the weld formed between the first and second components and subjected to conventional metallographic sample preparation procedures, followed by coarse grinding, fine grinding, coarse polishing, and fine polishing, to obtain the metallographic sample to be observed. After immersing the surface of the metallographic sample in a 0.5% HF solution for 25 seconds, the weld cross-section was observed using a Zeiss LSM900 laser confocal microscope. The distance from the weld liquid parallel to the surface of the second component to the maximum depth of penetration into the second component was measured using the accompanying software. This value was the ablation depth. The maximum height of the weld liquid parallel to the surface of the second component reaching the outer surface of the first component was measured using the accompanying software to obtain the material 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] Brazing material layer

[0078] Solder layer Q1: includes the following alloy components in percentage by mass: Si: 13%, Zn: 1%, Cu: 0.3%, Fe: 0.2%, Mg: 0.01%; solidus temperature is 570°C.

[0079] Solder layer Q2: includes the following alloy components in percentage by mass: Si: 10%, Zn: 6%, Cu: 0.1%, Fe: 0.1%, Mg: 0.05%; solidus temperature is 568°C.

[0080] Solder layer Q3: includes the following alloy components in percentage by mass: Si: 6%, Zn: 13%; Cu: 0.5%; Fe: 0.1%; Mg: 0.1%; solidus temperature is 552°C.

[0081] Solder layer Q4: includes the following alloy components in percentage by mass: Si: 10%, Zn: 15%; Cu: 0.1%; Fe: 0.1%; Mg: 0.05%; solidus temperature is 547°C.

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

[0083] Base alloy

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

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

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

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

[0088] Pre-embedded flux layer

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

[0090] The pre-embedded brazing flux layer Y2 includes a brazing flux (Nocolok potassium fluoroaluminate brazing flux) and a base alloy J2, wherein the base alloy J2 accounts for 95% by mass.

[0091] The embedded brazing flux layer Y3 includes a brazing flux (Nocolok potassium fluoroaluminate brazing flux) and a base alloy J3, wherein the base alloy J3 accounts for 98% by mass.

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

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

[0094] The pre-embedded brazing flux layer Y6 includes a brazing flux (Nocolok potassium fluoroaluminate brazing flux) and a base alloy J4, wherein the base alloy J4 accounts for 92% by mass.

[0095] The second component is aluminum alloy composite material

[0096] Aluminum alloy composite material F1: includes: a core layer (X2) and a brazing composite layer, wherein the brazing composite layer is provided on at least one side of the core layer; the brazing composite layer includes a pre-embedded brazing flux layer (Y2) and a brazing material layer (Q2), wherein the layer close to the core layer is the pre-embedded brazing flux layer, and the layer away from the core layer is the brazing material layer. The temperature difference between the solidus temperature T1 (568°C) of the brazing material layer and the solidus temperature T2 (575°C) of the base alloy is 7°C. The proportion of the brazing composite layer is 10%; the thickness ratio of the pre-embedded brazing flux layer to the brazing material layer is 0.4286. The brazing flux content in the aluminum alloy composite material is 4.2g / m 2 .

[0097] Aluminum alloy composite material F2: includes: a core layer (X1) and a brazing composite layer, wherein the brazing composite layer is provided on at least one side of the core layer; the brazing composite layer includes a pre-embedded brazing flux layer (Y1) and a brazing material layer (Q3), wherein the layer close to the core layer is the pre-embedded brazing flux layer, and the layer away from the core layer is the brazing material layer. The temperature difference between the solidus temperature T1 (552°C) of the brazing material layer and the solidus temperature T2 (563°C) of the base alloy is 11°C. The proportion of the brazing composite layer is 5%; the thickness ratio of the pre-embedded brazing flux layer to the brazing material layer is 0.1111. The brazing flux content in the aluminum alloy composite material is 0.84g / m 2 .

[0098] Aluminum alloy composite material F3: includes: a core layer (X1) and a brazing composite layer, wherein the brazing composite layer is provided on at least one side of the core layer; the brazing composite layer includes a pre-embedded brazing flux layer (Y3) and a brazing material layer (Q1), wherein the layer close to the core layer is the pre-embedded brazing flux layer, and the layer away from the core layer is the brazing material layer. The temperature difference between the solidus temperature T1 (570°C) of the brazing material layer and the solidus temperature T2 (573°C) of the base alloy is 3°C. The proportion of the brazing composite layer is 15%; the thickness ratio of the pre-embedded brazing flux layer to the brazing material layer is 2.3333. The brazing flux content in the aluminum alloy composite material is 14.7g / m 2 .

[0099] Aluminum alloy composite material F4: includes: a core layer (X2) and a brazing composite layer, wherein the brazing composite layer is provided on at least one side of the core layer; the brazing composite layer includes a pre-embedded brazing flux layer (Y6) and a brazing material layer (Q3), wherein the layer close to the core layer is the pre-embedded brazing flux layer, and the layer away from the core layer is the brazing material layer. The temperature difference between the solidus temperature T1 (552°C) of the brazing material layer and the solidus temperature T2 (577°C) of the base alloy is 25°C. The proportion of the brazing composite layer is 8%; the thickness ratio of the pre-embedded brazing flux layer to the brazing material layer is 0.5. The brazing flux content in the aluminum alloy composite material is 8.96g / m 2 .

[0100] Aluminum alloy composite material F5: The only difference from aluminum alloy composite material F1 is that the brazing filler metal layer is the brazing filler metal layer Q4, that is, the temperature difference between the solidus temperature T1 (547°C) of the brazing filler metal layer and the solidus temperature T2 (575°C) of the base alloy is 28°C. The rest is the same as the aluminum alloy composite material F1 and will not be repeated here.

[0101] Aluminum Alloy Composite Material F6: This material differs from aluminum alloy composite material F1 only in that the thickness ratio of the pre-embedded flux layer to the filler metal layer is 0.087. Furthermore, 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 in aluminum alloy composite material F1. All other details are the same as for aluminum alloy composite material F1 and are not further elaborated here.

[0102] Aluminum Alloy Composite Material F7: This material differs from aluminum alloy composite material F1 only in that the thickness ratio of the pre-embedded flux layer to the filler metal layer is 2.57. Furthermore, 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 in aluminum alloy composite material F1. All other details are the same as for aluminum alloy composite material F1 and are not further elaborated here.

[0103] Aluminum alloy composite material DF1 differs from aluminum alloy composite material F1 only in that the filler metal layer is DQ1, meaning that the temperature difference between the solidus temperature T1 (574°C) of the filler metal layer and the solidus temperature T2 (575°C) of the base alloy is only 1°C. All other aspects are the same as those of aluminum alloy composite material F1 and are not further described here.

[0104] Example 1

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

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

[0107] (2) brazing the assembly to be welded in step (1) under a brazing process, wherein the brazing process includes an initial brazing window, a mid-term brazing window, and a final brazing window performed in sequence;

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

[0109] The temperature of the mid-term brazing window is T2-T3, excluding T3, that is, 575-598°C, excluding 598°C; the time of the mid-term brazing window is controlled to 62s;

[0110] The temperature of the final brazing window is ≥ T3 = 598° C., and the time required to complete brazing in the final brazing window is 177 seconds.

[0111] Example 2

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

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

[0114] (2) brazing the assembly to be welded in step (1) under a brazing process, wherein the brazing process includes an initial brazing window, a mid-term brazing window, and a final brazing window performed in sequence;

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

[0116] The temperature of the mid-term brazing window is T2-T3, excluding T3, that is, 563-594° C., excluding 594° C.; the time of the mid-term brazing window is controlled to 48 seconds;

[0117] The temperature of the final brazing window is ≥ T3 = 594° C., and the time required to complete brazing in the final brazing window is 112 seconds.

[0118] Example 3

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

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

[0121] (2) brazing the assembly to be welded in step (1) under a brazing process, wherein the brazing process includes an initial brazing window, a mid-term brazing window, and a final brazing window performed in sequence;

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

[0123] The temperature of the mid-term brazing window is T2-T3, excluding T3, that is, 573-597° C., excluding 597° C.; the time of the mid-term brazing window is controlled to be 216s;

[0124] The temperature of the final brazing window is ≥ T3 = 597° C., and the time required to complete the brazing in the final brazing window is 55 seconds.

[0125] Example 4

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

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

[0128] (2) brazing the assembly to be welded in step (1) under a brazing process, wherein the brazing process includes an initial brazing window, a mid-term brazing window, and a final brazing window performed in sequence;

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

[0130] The temperature of the mid-term brazing window is T2-T3, excluding T3, that is, 577-597° C., excluding 597° C.; the time of the mid-term brazing window is controlled to be 152s;

[0131] The temperature of the final brazing window is ≥ T3 = 597° C., and the time required to complete the brazing in the final brazing window is 59 seconds.

[0132] Example 5

[0133] This embodiment provides a brazing method suitable for brazing a first component having a surface structure containing a fine-grained region. The only difference from Example 1 is that the initial brazing window is controlled to 10 seconds. In the initial brazing window, the liquid phase formed by the brazing layer accounts for 8.75% of the total liquid phase of the brazing layer and the base alloy, and the liquid phase formed by the brazing layer accounts for 12.5% of the total liquid phase of the brazing layer. Under the same mid-term brazing window time, the final brazing window time needs to reach 254 seconds to complete the brazing. The rest is the same as Example 1 and will not be repeated here.

[0134] Example 6

[0135] This embodiment provides a brazing method suitable for brazing a first component having a surface structure with a fine-grained region. The only difference from Example 1 is that the second component is an aluminum alloy composite material F5, thereby adaptively adjusting the temperature of the initial brazing window to a range of T1 to T2 (excluding T2), that is, 547°C to 575°C (excluding 575°C). Within the initial brazing window, the brazing material 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 between the two. Within the initial brazing window, the liquid phase formed in the brazing material layer accounts for 49.84% of the total liquid phase of the brazing material layer and the base alloy, and the liquid phase formed in the brazing material layer accounts for 71.2% of the total liquid phase of the brazing material layer. The duration of the initial and intermediate brazing windows is the same as in Example 1, and the final brazing window required to complete the brazing is 72 seconds.

[0136] Example 7

[0137] This embodiment provides a brazing method suitable for brazing a first component having a surface structure containing a fine-grained region. The only difference from Example 1 is that the second component is made of an aluminum alloy composite material F6, and the initial brazing window is adaptively adjusted to 24 seconds so that the liquid phase formed in the brazing layer accounts for 31% of the total liquid phase of the brazing layer (maintaining substantially the same level as Example 1). As a result, in the initial brazing window, the liquid phase formed in the brazing layer accounts for 28.7% of the total liquid phase of the brazing layer and the base alloy. Furthermore, in order to ensure that the embedded flux layer is completely converted to the liquid phase during the mid-brazing window, the mid-brazing window is adaptively adjusted to 44 seconds, resulting in a final brazing window of 286 seconds required to complete the brazing.

[0138] Example 8

[0139] This embodiment provides a brazing method suitable for brazing a first component having a surface structure containing a fine-grained region. The only difference from Example 1 is that the second component is made of an aluminum alloy composite material F7, and the initial brazing window is adaptively adjusted to 15 seconds so that the liquid phase formed in the brazing layer accounts for 31.3% of the total liquid phase of the brazing layer (maintaining substantially the same level as Example 1). As a result, in the initial brazing window, the liquid phase formed in the brazing layer accounts for 8.74% of the total liquid phase of the brazing layer and the base alloy. Furthermore, in order to fully convert the embedded flux layer into the liquid phase during the mid-brazing window, the mid-brazing window is adaptively adjusted to 240 seconds, resulting in a final brazing window of 69 seconds required to complete the brazing.

[0140] Comparative Example 1

[0141] This comparative example provides a brazing method suitable for brazing a first component having a surface structure containing a fine-grained area. The only difference from Example 1 is that the second component is an aluminum alloy composite material DF1, and the brazing process is adaptively adjusted to start melting from the solidus temperature T1 (574°C) of the brazing alloy and raise the temperature to 603°C until it is completely melted. The total brazing time required is 356s.

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

[0143] Table 1

[0144] Ablation depth Climbing height 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] From Table 1 we can see the following points:

[0146] (1) Based on Examples 1 to 8, it can be seen that the aluminum alloy composite material suitable for brazing a surface structure containing a fine grain region and the brazing method thereof provided by the present invention can reduce brazing defects when welding a first component containing a surface structure containing a fine grain region, and the ablation depth is within 250 μm, and the creep height of the first component is within 14 mm;

[0147] (2) Influence of the solidus temperature difference

[0148] Comparing Example 1 and Example 6, it can be seen that 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 in Example 6 is 28°C, that is, the temperature difference is too large. There is a problem that the low-melting-point liquid phase formed first in the solder layer stays at the solder foot for too long, increasing the corrosion of the base alloy. The corrosion depth is deeper than that in Example 1, and the creep height is increased.

[0149] Comparing Example 1 with Comparative Example 1, it can be seen that the temperature difference between the solidus temperature T1 (547°C) of the brazing material layer and the solidus temperature T2 (575°C) of the base alloy in Comparative Example 1 is only 1°C, that is, the temperature difference is too small, resulting in the simultaneous melting of the brazing material layer and the embedded flux layer, and flowing to the welding surface, without forming a high melting point low ZnSi zone, significantly deepening the ablation of the first component surface, and significantly increasing the material creep height. Among them, the cross-sectional metallographic photograph of the brazing joint provided in Example 1 is shown in FIG. Figure 3 As shown, the cross-sectional metallographic photograph of the brazed joint provided in Comparative Example 1 is shown in FIG. Figure 4 As shown, from Figures 3-4 It can be seen that the corrosion and material creep of Comparative Example 1 are obviously serious.

[0150] (3) Influence of initial brazing window duration

[0151] By comparing Example 1 and Example 5, it can be seen that the initial brazing window in Example 5 is shorter, so that when the solidus temperature T2 of the base alloy is reached, the brazing material layer that should have melted does not melt, resulting in too little initial liquid phase and too long time required for final brazing, that is, the time of high liquid phase is extended, and finally the melting of the finished weld is deepened and the creep height is increased.

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

[0153] By comparing Example 1 with Examples 7 to 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 solder layer is too high, resulting in too much material that needs to be melted at the end, and the time of the final brazing window takes longer to complete brazing, resulting in deeper corrosion 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 solder layer is too low, and there is too little remaining material on the surface, which makes it difficult to block the internal liquid phase in the mid-term brazing window, and ultimately leads to the high-temperature liquid phase residence time covering the time of the mid-term brazing window and the time of the final brazing window, the high-temperature liquid phase residence time is prolonged, and the corrosion and material creep phenomena are aggravated.

[0154] The present invention uses the above-described embodiments to illustrate the detailed features of the present invention. However, the present invention is not limited to the above-described detailed features, which does not mean that the present invention must rely on the above-described detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for the selected technical features of the present invention, additions to auxiliary technical features, and selections of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A brazing method for brazing a first component having a surface structure containing a fine grain area, characterized in that: The brazing method comprises the following steps: (1) assembling a first component and a second component to form a component to be welded, wherein a cross section of the first component and a surface of a solder layer of the second component are in contact with each other; The edge area of the cross section of the first component is a fine grain area, the thickness of the fine grain area is not less than 20 μm, and the average grain size of the fine grain area is ≤7 μm; The second component comprises: a core layer and a brazing composite layer, wherein the brazing composite layer is provided on at least one side of the core layer; the brazing composite layer comprises a pre-embedded brazing flux layer and a brazing filler metal layer, wherein the layer close to the core layer is the pre-embedded brazing flux layer, and the layer away from the core layer is the brazing filler metal layer; the pre-embedded brazing flux layer comprises 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; (2) brazing the assembly to be welded in step (1) under a brazing process, wherein the brazing process includes an initial brazing window, a mid-term brazing window, and a final brazing window performed in sequence; The temperature of the initial brazing window is T1-T2, excluding T2. In the initial brazing window, the brazing material layer forms a ZnSi-rich region and a low ZnSi region, and the solidus temperature of the low ZnSi region is T3>T2. The temperature of the mid-term brazing window is T2-T3, excluding T3. The temperature of the final brazing window is ≥ T3.

2. The brazing method according to claim 1, wherein: The time of the initial brazing window is controlled to be 10 to 51 seconds; Preferably, the time of the mid-term brazing window is controlled to be 44 to 240 seconds; Preferably, the time of the final brazing window is controlled to be 55 to 286 seconds.

3. The brazing method according to claim 1 or 2, characterized in that: The solidus temperature T2 of the base alloy is at most 25° C. higher than the solidus temperature T1 of the brazing material layer; Preferably, the solidus temperature of the solder alloy is 547-570°C; Preferably, the solidus temperature of the substrate alloy is 563-577°C.

4. The brazing method according to any one of claims 1 to 3, characterized in that: The solder layer includes the following mass fractions of alloy elements Si: 6-13%, Zn: 1-13%.

5. The brazing method according to any one of claims 1 to 4, characterized in that: The thickness ratio of the pre-embedded flux layer to the solder layer is 0.11 to 2.33; the mass proportion of the base alloy in the pre-embedded flux layer is 85 to 98%; In the initial brazing window, the liquid phase formed by the brazing material layer accounts for 8.74 to 49.84% of the total liquid phase of the base alloy in the brazing material layer and the embedded layer; more preferably, the liquid phase formed by the brazing material layer accounts for ≤30% of the total liquid phase of the base alloy in the brazing material layer and the embedded layer.

6. The brazing method according to any one of claims 1 to 5, characterized in that: In the initial brazing window, the proportion of the liquid phase formed in the brazing layer to the liquid phase of the brazing layer is ≥12%; More preferably, in the initial soldering window, the proportion of the liquid phase formed in the solder layer to the liquid phase of the solder layer is 31.2 to 68.3%.

7. The brazing method according to any one of claims 1 to 6, characterized in that: The first component is an aluminum die casting.

8. An aluminum alloy composite material, characterized in that: The aluminum alloy composite material is the second component used in the brazing method for brazing a first component having a surface structure containing a fine grain area as described in any one of claims 1 to 7.

9. A welding product, characterized in that: The welded product is obtained by brazing using the brazing method according to any one of claims 1 to 6, which is suitable for brazing a first component having a surface structure with a fine grain area.

10. A welding product, which is a heat pump manifold, characterized in that: The heat pump manifold comprises an aluminum die casting and the aluminum alloy composite material according to claim 8.

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