Low-corrosion and low-crack aluminum alloy, aluminum alloy metal plate and preparation method of aluminum alloy metal plate

Abstract

The invention relates to a low-corrosion and low-crack aluminum alloy, an aluminum alloy metal plate and a preparation method of the aluminum alloy metal plate, the low-corrosion and low-crack aluminum alloy is 6-series aluminum alloy, and the average grain size of the 6-series aluminum alloy in the parallel rolling direction is 115-520 microns; the total proportion of the Cube texture and the R-Cube texture in the grain structure of the 6-series aluminum alloy is smaller than or equal to 50%. By optimizing the composition of the 6-series aluminum alloy and matching with specific preparation procedures and parameters, the grain size and the grain structure of the 6-series aluminum alloy are regulated and controlled, so that the obtained aluminum alloy metal plate has an excellent brazing effect, the proportion of the corrosion depth to the thickness of the plate is as low as 25% or below, the crack depth is as low as 10 microns or below, and the performance of the aluminum alloy metal plate is improved. The corrosion ratio is preferably as low as 20% or below, so that the product yield is improved, and the preparation method is simple in technological process, low in cost and easy for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloys and their preparation technology, and in particular to a low-corrosion, low-cracking aluminum alloy, an aluminum alloy metal plate, and a method for preparing the same. Background Technology

[0002] Vacuum brazing technology primarily relies on the volatility of magnesium (Mg) in the brazing layer during the brazing process. Mg reacts with the oxide film on the base material surface, breaking down the oxide film and allowing for the formation of welded joints between components. Therefore, the brazing process eliminates the need for flux and post-weld cleaning. Furthermore, the excellent wettability and fluidity of the brazing filler metal make it particularly suitable for welding precision and large, complex components, significantly improving product yield. Currently, this technology is widely used in the manufacture of products with high thermal management requirements, such as oil coolers, coolant temperature control units (new energy vehicle battery / electric control thermal management systems), sealed radiators, insulated-gate bipolar transistors, and plate-fin liquid cooling plates.

[0003] Plate-fin liquid cooling plates typically consist of an upper single-sided composite metal plate, fins, a lower single-sided composite metal plate, and large and small sealing strips. These components are assembled and then vacuum brazed to form the liquid cooling plate. The single-sided composite metal plate is usually composed of a brazed layer of 4-series Al-Si-Mg aluminum alloy (AA4104 or AA4004) and a base material of 6XXX aluminum alloy (AA6063). The fins are typically AA3003 or AA3003 MOD single-layer aluminum alloy, and the large and small sealing strips are generally AA3003 extruded profiles. Due to its use of all-aluminum materials, it features high heat transfer efficiency, compact structure, high strength, and high corrosion resistance, making it widely used and in demand in petrochemical, engineering machinery, offshore wind power, energy storage systems, and air separation equipment.

[0004] However, as plate-fin liquid cooling plate structures become increasingly compact, lightweight (thinner), high-strength, and large-sized, and vacuum brazing processes are continuously optimized—for example, to meet these design requirements while maintaining good brazing quality, the high-temperature period needs to be extended during brazing; however, to prevent localized overheating and improve brazing efficiency, the overall brazing time needs to be shortened—existing 6XXX aluminum alloy core materials often exhibit cracking and severe erosion after brazing. This leads to reduced corrosion resistance and structural strength, and may even result in product failure or scrapping.

[0005] For example, CN107598318B discloses a process method and fixture for reducing defects in vacuum brazing of 6061 aluminum alloy. This process method adjusts the heating, holding and cooling process curves during brazing, mainly targeting thick plate structures. For thin-walled parts with lightweight requirements, it is difficult to control the temperature accurately, which can easily lead to local overheating and uneven heating. Moreover, the total holding time reaches more than 5 hours. There is no effective way to deal with the thermal stress accumulation caused by the extended high-temperature holding time and the cracks generated during the cooling stage. In addition, the production cycle of a single piece is too long and the energy consumption is too high, making it difficult to meet the needs of large-size and mass production.

[0006] For example, CN114670509A discloses a high-strength aluminum alloy composite plate for brazing battery liquid cooling plates and its preparation method. The high-strength aluminum alloy composite plate includes three layers: a brazing layer (4-series Al), a barrier layer (3-series / 1-series Al), and a core material (6-series Al). Although the barrier layer can slow down the erosion rate, when the brazing temperature is too high or the holding time is too long, the Si element in the 4-series brazing layer will still penetrate the barrier layer and diffuse into the 6-series core material, forming a low-melting-point eutectic phase, which makes local erosion inevitable.

[0007] Therefore, in order to address the above problems, there is an urgent need to propose a low-corrosion and low-cracking aluminum alloy, aluminum alloy metal plate and its preparation method, which can meet the requirements of low corrosion and low cracking after vacuum brazing, based on a compact and lightweight design, so as to improve the corrosion resistance and structural strength of the product. Summary of the Invention

[0008] To solve the above-mentioned technical problems, the present invention provides a low-corrosion and low-cracking aluminum alloy, an aluminum alloy metal plate and its preparation method. By controlling the grain size and grain structure of the low-corrosion and low-cracking aluminum alloy, the problem of cracking and severe corrosion after vacuum brazing is avoided, thereby improving the corrosion resistance and structural strength of the product.

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

[0010] In a first aspect, the present invention provides a low-erosion, low-cracking aluminum alloy, wherein the low-erosion, low-cracking aluminum alloy is a 6-series aluminum alloy;

[0011] The average grain size of the 6-series aluminum alloy in the parallel rolling direction is 115-520μm, for example, it can be 115μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm or 520μm, etc.

[0012] The total proportion of Cube texture and R-Cube texture in the grain structure of the 6-series aluminum alloy is ≤50%, for example, it can be 50%, 45%, 40%, 35% or 30%, etc.

[0013] This invention provides a low-erosion, low-cracking aluminum alloy with a specific grain size and microstructure, which can be used to prepare low-erosion, low-cracking aluminum alloy metal plates suitable for vacuum brazing.

[0014] Specifically, if the average grain size of the 6-series aluminum alloy in the parallel rolling direction is too small, the number of grain boundaries will increase. During the brazing process, the solder will flow along the grain boundaries, leading to erosion problems after the cold plate is brazed. Severe erosion may even cause failure problems such as perforation and coolant leakage in the cold plate. At the same time, the deepening of the cracks at the grain boundaries will further reduce the corrosion resistance of the material. If the average grain size of the 6-series aluminum alloy in the parallel rolling direction is too large, the large grains will continue to grow abnormally during the brazing process, which will lead to cracks at the grain boundaries. In addition, the corrosion resistance will also be reduced, causing the cold plate to fail prematurely in the service environment due to insufficient corrosion resistance.

[0015] Among them, the Cube texture and R-Cube texture in the grain structure of the 6-series aluminum alloy are soft textures. If the proportion of these textures is too large, the thermal stability of the grain boundaries will be poor. During high-temperature brazing, if the proportion of Cube+R-cube texture exceeds 50%, cracks will appear at the grain boundaries. In addition, the solder flows along the grain boundaries of this type of texture, causing erosion and reducing the corrosion resistance of the material.

[0016] Preferably, the grain aspect ratio of the 6-series aluminum alloy is 2.3-2.6, for example, it can be 2.3, 2.4, 2.5 or 2.6.

[0017] The grain aspect ratio refers to the ratio of the average grain size in the parallel rolling direction to the average grain size in the perpendicular rolling direction.

[0018] The present invention further preferably uses a grain aspect ratio of 2.3-2.6 for the 6-series aluminum alloy, which, combined with the above-mentioned average grain size range in the parallel rolling direction, further improves its corrosion resistance. If the average grain size in the parallel rolling direction of the 6-series aluminum alloy remains basically unchanged, but the grain aspect ratio is small, that is, the grain growth is equiaxed and the grain boundaries are shorter, the corrosion path is also shorter when corrosion occurs, and the corrosion resistance of the material will decrease.

[0019] The 6-series aluminum alloy comprises the following components by weight percentage: Si: 0.5-1.0 wt%, Mg: 0.7-1.0 wt%, Fe: 0.2-0.3 wt%.

[0020] Preferably, the mass ratio of Mg to Si in the 6-series aluminum alloy is 1.5-1.6, for example, it can be 1.5, 1.52, 1.54, 1.56, 1.58, or 1.6. Specifically, in the 6-series aluminum alloy: Si: 0.5-1.0 wt%, for example, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%; Mg: 0.7-1.0 wt%, for example, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%; Fe: 0.2-0.3 wt%, for example, 0.2 wt%, 0.22 wt%, 0.25 wt%, 0.28 wt%, or 0.3 wt%.

[0021] Preferably, the 6-series aluminum alloy does not contain Cu, Mn, or Zn elements.

[0022] This invention optimizes the elemental composition of 6-series aluminum alloys, primarily by redesigning the Si, Fe, and Mg elements. Specifically, the 6-series aluminum alloy is designed to have a Si content of 0.5-1.0 wt%, a Mg content of 0.7-1.0 wt%, and a Mg to Si mass ratio of 1.5-1.6.

[0023] The role of Si is as follows: the maximum solubility of Si in aluminum alloy is 1.65 wt%. Adding 0.5-1.0 wt% Si will solidify in the aluminum alloy, improving the strength of the material. On the other hand, Si and Mg combine to form a sufficient number of dispersed strengthening phases Mg2Si with a size in the range of 1-2 μm. During vacuum high-temperature brazing of the material, the dispersed strengthening phases of Mg2Si pin the grain boundaries and inhibit abnormal grain growth.

[0024] The role of Mg is twofold: firstly, during vacuum brazing, Mg reacts with oxygen and moisture in the brazing furnace, eliminating the influence of oxygen and moisture on brazing and thus obtaining excellent brazing quality; secondly, Mg combines with all Si as much as possible to form a dispersed strengthening and thermally stable phase Mg2Si. Mg2Si inhibits abnormal grain growth during vacuum brazing and improves the high-temperature thermal stability of the material.

[0025] Furthermore, the mass ratio of Mg to Si affects the size of the Mg2Si precipitate. When the mass ratio of Mg to Si is too small, the size of the Mg2Si precipitate is >2μm. The larger size of the precipitate promotes the recrystallization process of the material, resulting in a smaller average grain size. When the mass ratio of Mg to Si is too large, the size of the Mg2Si precipitate is <1μm, resulting in a larger average grain size.

[0026] This invention controls the Fe content in the 6-series aluminum alloy to be 0.2-0.3 wt%, forming a sufficient number of dispersed AlFeSi ternary compounds with a size of 1-2 μm with Al and Si to suppress abnormal grain growth. On the other hand, the Fe-containing phase is generally a high-temperature thermally stable phase, which can suppress the softening and collapse problems of the material at high temperatures. This results in an average grain size of 115-520 μm and a grain aspect ratio of 2.3-2.6 in the parallel rolling direction of the 6-series aluminum alloy, with a flat microstructure, thereby improving the high-temperature resistance (above 600℃) and corrosion resistance of the aluminum alloy metal sheet obtained from it. The Fe content is strictly controlled at 0.2-0.3 wt%. When the Fe content is less than 0.2 wt%, the size of the AlFeSi second phase formed by Fe and Al and Si is >2 μm, which promotes the recrystallization process of the material, resulting in a smaller average grain size and more grain boundaries in the parallel rolling direction. When the Fe content exceeds 0.3 wt%, a large amount of Fe will refine the material grains, which will also lead to a smaller average grain size in the parallel rolling direction.

[0027] The 6-series aluminum alloy described in this invention does not contain Cu. The addition of Cu will, on the one hand, synergistically promote the dynamic recrystallization process of the material with Mg and Si elements, refine the grains, reduce the average grain size, and increase the number of grain boundaries. During the brazing process, the solder flows along the grain boundaries, causing significant erosion and the appearance of cracks at the grain boundaries, which will further reduce the corrosion resistance of the material. On the other hand, the grains become shorter in the parallel rolling direction and longer in the perpendicular rolling direction, resulting in a smaller grain aspect ratio and more severe corrosion resistance.

[0028] The 6-series aluminum alloys described in this invention do not contain Mn. Adding Mn to 6063 aluminum alloy will affect the performance of the material after brazing. Mn has a certain sensitivity to the aging of 6063 aluminum alloy.

[0029] The 6-series aluminum alloy described in this invention does not contain Zn, and the vacuum brazing material does not contain Zn. Because Zn is easily volatilized during vacuum brazing, it will affect the evaporation of Mg and the removal of the oxide film, thus affecting the brazing quality.

[0030] Preferably, the 6-series aluminum alloy contains Ti ≤ 0.05 wt% by mass, for example, 0.05 wt%, 0.04 wt%, 0.03 wt%, 0.02 wt%, or 0.01 wt%.

[0031] The present invention further preferably uses Ti ≤ 0.05 wt% in the 6-series aluminum alloy. On the one hand, this is beneficial because Ti can act as a grain refiner during the smelting of 6063 aluminum alloy ingots, refining the as-cast grains. On the other hand, the addition of trace amounts of Ti allows for a certain degree of segregation during ingot casting, forming a segregated layer. This segregated layer and the substrate create a potential difference, improving the material's corrosion resistance. When the Ti content exceeds 0.05 wt%, for example, 0.15 wt%, Ti's role as a grain refiner becomes ineffective; however, Ti still promotes equiaxed grain growth.

[0032] In a second aspect, the present invention provides an aluminum alloy metal sheet, the aluminum alloy metal sheet comprising a core material and a sheath material; the core material comprises the low-corrosion, low-cracking aluminum alloy described in the first aspect, and the sheath material comprises a 4-series aluminum alloy.

[0033] Preferably, the 4-series aluminum alloy comprises the following components by weight percentage: Si: 9.0-10.5wt%, Mg: 1.0-2.0wt%, Bi: 0.05-0.2wt%, Fe < 0.8wt%, Cu < 0.25wt%, Mn < 0.1wt%, Zn < 0.2wt%.

[0034] The composition of the components is as follows: Si: 9.0-10.5 wt%, for example, 9.0 wt%, 9.2 wt%, 9.5 wt%, 9.8 wt%, 10.0 wt%, 10.2 wt%, or 10.5 wt%; Mg: 1.0-2.0 wt%, for example, 1.0 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, or 2.0 wt%; Bi: 0.05-0.2 wt%, for example, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.18 wt%, or 0.2 wt%; Fe < 0.8 wt%. wt%, for example, can be 0.7wt%, 0.6wt%, 0.5wt%, 0.4wt%, or 0.3wt%, etc.; Cu < 0.25wt%, for example, can be 0.24wt%, 0.20wt%, 0.18wt%, 0.16wt%, 0.14wt%, or 0.12wt%, etc.; Mn < 0.1wt%, for example, can be 0.08wt%, 0.06wt%, 0.04wt%, or 0.02wt%, etc.; Zn < 0.2wt%, for example, can be 0.18wt%, 0.16wt%, 0.14wt%, 0.12wt%, or 0.1wt%, etc.

[0035] This invention prepares a high-temperature resistant, low-erosion, and low-cracking aluminum alloy metal plate for vacuum brazing by combining a low-erosion, low-cracking aluminum alloy with a specific composition, specific grain size, and microstructure as described in the first aspect with a 4-series aluminum alloy.

[0036] The main function of the 4-series aluminum alloy is as a solder. During brazing, it melts and breaks down the oxide film, thus achieving the welding effect. Its high temperature resistance and low cracking are mainly related to the core material, while its corrosion resistance is related to the brazing layer. The Si and Mg content of the brazing layer will affect the fluidity of the solder and the degree of core material corrosion. Generally, the Si and Mg content of the 4-series brazing layer is 10wt% and 1.6wt%, respectively.

[0037] Preferably, the thickness of the core material in the aluminum alloy metal plate accounts for 90-95%, for example, it can be 90%, 91%, 92%, 93%, 94% or 95%, etc.

[0038] The present invention further controls the thickness ratio of the core material within the above-mentioned range, which is beneficial to ensuring the post-weld strength and structural strength of the cold plate finished product. If the thickness ratio of the core material is too low, the post-weld strength and structural strength of the cold plate will be weakened, and may even fail to meet the customer's technical requirements. If the thickness ratio of the core material is too high, the proportion of the solder layer will be reduced, and there will not be enough solder to fill the weld, which may lead to problems such as poor welding and product leakage.

[0039] Preferably, the total thickness of the aluminum alloy sheet is 0.8-1.5 mm, for example, it can be 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm or 1.5 mm, and preferably 0.8-1.0 mm.

[0040] The thickness of the aluminum alloy metal plate described in the second aspect of the present invention can be in the range of 0.8-1.0 mm, which meets the current requirements for compactness and lightweighting of plate-fin liquid cooling plate structures.

[0041] Thirdly, the present invention provides a method for preparing the aluminum alloy metal plate described in the second aspect, the method comprising the following steps:

[0042] (1) The core material raw materials are first melted and cast according to the formula to obtain the core material ingot, and the leather material raw materials are second melted and cast according to the formula to obtain the leather material ingot;

[0043] (2) The core material ingot described in step (1) is subjected to homogenization heat treatment and milling in sequence, and then combined with the skin material ingot described in step (1) to obtain a composite ingot;

[0044] (3) The composite ingot described in step (2) is subjected to hot rolling, cold rolling and annealing in sequence to obtain the aluminum alloy metal plate.

[0045] In the exemplary casting process, the first casting temperature is 750-780℃, for example, it can be 750℃, 755℃, 760℃, 765℃, 770℃, 775℃, or 780℃, etc.; the first casting time is 2-4h, for example, it can be 2h, 2.5h, 3h, 3.5h, or 4h, etc.; the second casting temperature is 720-750℃, for example, it can be 720℃, 725℃, 730℃, 735℃, 740℃, 745℃, or 750℃, etc.; the second casting time is 2-4h, for example, it can be 2h, 2.5h, 3h, 3.5h, or 4h, etc.

[0046] In the exemplary heat homogenization process, the temperature of the heat homogenization treatment is 560-590℃, for example, it can be 560℃, 565℃, 570℃, 575℃, 580℃, 585℃ or 590℃, etc.; the time of the heat homogenization treatment is 9-12h, for example, it can be 9h, 10h, 11h or 12h, etc.

[0047] In the exemplary milling process, the milling amount on one side is 5-10mm, for example, it can be 5mm, 6mm, 7mm, 8mm, 9mm or 10mm, and there are no obvious tool marks on the surface of the core material ingot after milling.

[0048] One exemplary composite process includes bundling composite, or, prior to the composite, preheating and cutting the leather ingot, i.e., hot-rolling the leather ingot to the required thickness according to the design and cutting it into plates, and then physically bundling it together with the core ingot.

[0049] In the exemplary hot rolling process, a preheating treatment is included before the hot rolling process. The preheating temperature is 450-520℃, for example, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, or 520℃; the preheating time is 2-3 hours, for example, 2 hours, 2.2 hours, 2.5 hours, 2.8 hours, or 3 hours; the rolling speed of the hot rolling process is 500-1000 mm / s. For example, the speed can be 500mm / s, 600mm / s, 700mm / s, 800mm / s, 900mm / s, or 1000mm / s; the single-pass reduction of the hot rolling process is 20-30mm, for example, 20mm, 22mm, 24mm, 26mm, 28mm, or 30mm; the final rolling temperature of the hot rolling process is >250℃, for example, 260℃, 270℃, 280℃, 290℃, or 300℃.

[0050] Preferably, the thickness of the hot-rolled sheet is 3-5mm, for example, it can be 3mm, 3.5mm, 4mm, 4.5mm or 5mm.

[0051] In the exemplary cold rolling process, the temperature of the cold rolling treatment is 25-100℃, for example, it can be 25℃, 35℃, 50℃, 75℃ or 100℃, etc.; the rolling speed of the cold rolling treatment is 250-500 mm / s, for example, it can be 250mm / s, 300mm / s, 350mm / s, 400mm / s, 450mm / s or 500mm / s, etc.; the single-pass reduction of the cold rolling treatment is 1-2mm, for example, it can be 1mm, 1.2mm, 1.5mm, 1.8mm or 2mm, etc.

[0052] Preferably, the total processing amount of the cold rolling process in step (3) does not exceed 75%, for example, it can be 75%, 72%, 70%, 68% or 35%, etc.

[0053] The preparation method of the present invention obtains an aluminum alloy metal plate through melting and casting, heat treatment, milling, composite, hot rolling, cold rolling and annealing. The total processing amount of the cold rolling process does not exceed 75%, so that the total proportion of cube texture and R-cube texture in the grain structure of the core material of the aluminum alloy metal plate is ≤50%. As a result, the aluminum alloy metal plate has low erosion and low cracking when used for vacuum brazing, and has excellent high temperature resistance and corrosion resistance.

[0054] Preferably, the thickness of the cold-rolled sheet is 0.8-1.5 mm, for example, it can be 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm or 1.5 mm.

[0055] Preferably, the annealing temperature in step (3) is 350-380℃, for example, it can be 350℃, 355℃, 360℃, 365℃, 370℃ or 380℃.

[0056] The preparation method of the present invention controls the annealing temperature within the above-mentioned range, which on the one hand is conducive to obtaining a fully recrystallized grain structure with uniform grain size, exhibiting a long and flat shape, and the mechanical properties of the finished product meet customer requirements. On the other hand, the elements in the core material are fully diffused during the annealing process, which improves the uniformity of element distribution.

[0057] Preferably, the annealing time in step (3) is 2-3 hours, for example, 2 hours, 2.2 hours, 2.5 hours, 2.8 hours or 3 hours.

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

[0059] The present invention provides a low-corrosion, low-cracking aluminum alloy, aluminum alloy metal plate and its preparation method. By optimizing the core material composition of the aluminum alloy metal plate and combining it with specific preparation processes and parameters, the two work synergistically to optimize the grain size and grain structure of the core material alloy, thereby achieving the advantages of low corrosion and low cracking. This results in excellent brazing performance during the brazing process, with the corrosion depth accounting for less than 25% of the plate thickness, the crack depth less than 10 μm, and the corrosion ratio preferably less than 20%. Detailed Implementation

[0060] The technical solution of the present invention will be further described below with reference to specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0061] It should be understood that the expression "comprising" encompasses both the expressions "consistently composed of" and "composed of". The composition of the elements mentioned above refers to the alloying elements intentionally added to the aluminum alloy to serve the intended function of this invention. In addition, unavoidable impurities exist in the aluminum alloy. Unavoidable impurities refer to other elements that are not intentionally added during the alloy production process but are unavoidably introduced due to reasons such as contact with production equipment. These impurity elements can be divided into specially constrained impurity elements and unconstrained impurity elements. The types and contents of specially constrained impurity elements are specified in the composition, while the types and contents of unconstrained impurity elements are not specified in the composition, and their total amount is generally specified as less than or equal to 0.2 wt%.

[0062] Unless otherwise stated, all percentages of alloying elements are by weight.

[0063] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a preferred upper limit and a preferred lower limit, it should be understood as equivalent to specifically disclosing any range by combining any pair of upper or preferred values ​​with any lower or preferred values, regardless of whether the range is specifically disclosed.

[0064] Test method:

[0065] 1. Precipitated phase size

[0066] A 10mm*10mm sample was taken from an aluminum alloy metal plate and mechanically ground and polished to a mirror finish using sandpaper of different grits (400#, 800#, 1000#, 1200#, and 2000#). The precipitate structure was photographed using a scanning electron microscope (SEM), and the size of the precipitate was measured and analyzed using Image Pro Plus image analysis software from Media Cybernetics.

[0067] 2. Average grain size and grain aspect ratio in the parallel rolling direction

[0068] According to GB / T 3246.1-2024 "Methods for Inspection of Microstructure of Wrought Aluminum and Aluminum Alloy Products - Part 1: Microstructure Inspection Methods", samples of 10mm*10mm thickness were taken from aluminum alloy metal plates in both the parallel and perpendicular rolling directions. The samples were mechanically ground and polished, and then anodized (coating voltage 25V, time 3min, coating solution 400mL H2O + 10mL HBF4). The grain structure of the samples was observed under an Olympus optical microscope. The average grain size in the parallel rolling direction and the average grain size in the perpendicular rolling direction were measured according to GB / T 6394-2017 "Method for Determination of Average Grain Size of Metals". The aspect ratio is the ratio of the average grain size in the parallel rolling direction to the average grain size in the perpendicular rolling direction.

[0069] 3. Texture proportion

[0070] Samples were taken from aluminum alloy metal plates and mechanically ground and electropolished to prepare samples suitable for EBSD analysis. The electrolyte composition was 10% perchloric acid + 90% anhydrous ethanol. The polishing voltage was 20V, the current was 1A, and the polishing time was 60s. The experiment was carried out on a FEI Nova400 field emission scanning electron microscope equipped with an EBSD probe, and the experimental data were analyzed using the HKL channel 5 software package to analyze the texture type and its proportion of the samples.

[0071] 4. Erosion depth

[0072] Samples were taken from the brazed aluminum alloy metal plate according to GB / T 3246.1-2024 Test Methods for Microstructure of Wrought Aluminum and Aluminum Alloy Products Part 1: Test Methods for Microstructure. The samples were mechanically ground and polished, and the morphology of the samples was observed under an Olympus optical microscope. The erosion depth of the three largest erosion locations was measured and the average value was taken.

[0073] 5. Crack depth

[0074] Samples were taken from the brazed metal plate according to GB / T 3246.1-2024 Test Methods for Microstructure of Wrought Aluminum and Aluminum Alloy Products Part 1: Test Methods for Microstructure. The samples were mechanically ground and polished, and the cracks were observed under an Olympus optical microscope. The three largest crack points were measured, and their crack depths were measured and averaged.

[0075] 6. Corrosion resistance (Neutral Salt Spray Test, NSS)

[0076] The brazed aluminum alloy metal plate samples were subjected to NSS corrosion tests according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test" for 700 hours. After the test, the depths of the three deepest corrosion pits were measured, and the average value was taken and divided by the thickness of the material after brazing to calculate the corrosion ratio.

[0077] As a specific embodiment of the present invention, an aluminum alloy metal plate is provided, the aluminum alloy metal plate comprising a core material and a skin material; the core material is a low-corrosion, low-cracking aluminum alloy, and the skin material comprises a 4-series aluminum alloy;

[0078] The low-corrosion, low-cracking aluminum alloy comprises the following components by weight percentage: Si: 0.5-1.0 wt%, Mg: 0.7-1.0 wt%, Fe: 0.2-0.3 wt%, Ti ≤ 0.05 wt%, and contains no Cu, Mn, or Zn;

[0079] The 4-series aluminum alloy comprises the following components by weight percentage: Si: 9.0-10.5wt%, Mg: 1.0-2.0wt%, Bi: 0.05-0.2wt%, Fe < 0.8wt%, Cu < 0.25wt%, Mn < 0.1wt%, Zn < 0.2wt%, and balance Al;

[0080] The thickness of the core material in the aluminum alloy metal plate accounts for 90-95%; the total thickness of the aluminum alloy metal plate is 0.8-1.5 mm.

[0081] As a specific embodiment of the present invention, a method for preparing the above-mentioned aluminum alloy metal plate is also provided, the method comprising the following steps:

[0082] (1) The core material raw material is first melted and cast at 750℃-780℃ for 2-4 hours according to the formula to obtain the core material ingot; the leather material raw material is second melted and cast at 720-750℃ for 2-4 hours according to the formula to obtain the leather material ingot.

[0083] (2) The leather ingot described in step (1) is preheated and rolled to the target thickness, and then the core ingot described in step (1) is subjected to homogenization heat treatment at 560-590℃ for 9-12 hours, and then milled, with a single-sided milling amount of 5-10 mm; then the leather ingot of the target thickness is combined with the core ingot to obtain a composite ingot.

[0084] (3) The composite ingot described in step (2) is preheated at 45-520℃ and held for 2-3 hours. Then it is hot rolled at a rolling speed of 500-1000 mm / s and a single-pass reduction of 20-30 mm. The final rolling temperature is >250℃. The thickness of the composite ingot after hot rolling is 3-5 mm. Then it is cold rolled at 25-100℃ with a single-pass reduction of 1-2 mm and a rolling speed of 250-500 mm / s. The total processing amount of the cold rolling is <75%. The thickness of the composite ingot after cold rolling is 0.8-1.5 mm. Then it is annealed at 350-380℃ for 2-3 hours to obtain the aluminum alloy metal plate.

[0085] As a specific embodiment of the present invention, a brazing method for the above-mentioned aluminum alloy metal plate is also provided. The brazing method includes: brazing the tube sheet material, wherein the maximum brazing temperature is 605-610℃, and the temperature is maintained above 600℃ for 15-30 minutes, and the cooling rate of the brazing is 5-15℃ / min during the cooling process from the maximum temperature to 300-400℃.

[0086] The following detailed description uses specific examples.

[0087] Based on a total mass of 100wt% for the core material or the leather material, the composition and content of the core material and leather material in Examples 1 to 4 below are shown in Table 1.

[0088] Table 1

[0089]

[0090] I. Implementation Examples

[0091] Example 1

[0092] This embodiment provides an aluminum alloy metal plate, which includes a core material and a skin material; the core material is a low-corrosion, low-cracking aluminum alloy, and the skin material includes a 4-series aluminum alloy; the composition and content of the core material and the skin material are as shown in the formulation of Example 1 in Table 1; the thickness of the core material in the aluminum alloy metal plate is 92%, and the total thickness of the aluminum alloy metal plate is 0.8 mm.

[0093] This embodiment also provides a method for preparing the above-mentioned aluminum alloy metal plate, the method comprising the following steps:

[0094] (1) The core material raw material is first melted and cast at 760℃ for 2 hours according to the formula to obtain the core material ingot. The leather material raw material is second melted and cast at 580℃ for 10 hours according to the formula to obtain the leather material ingot.

[0095] (2) The leather ingot described in step (1) is preheated and rolled to the target thickness, and then the core ingot described in step (1) is subjected to homogenization heat treatment at 580°C for 10 hours, and then milled, with a single-sided milling amount of 8 mm; then the leather ingot of the target thickness is combined with the core ingot to obtain a composite ingot.

[0096] (3) The composite ingot described in step (2) is preheated at 480°C and held for 2 hours. Then it is hot rolled at a rolling speed of 800 mm / s and a single-pass reduction of 25 mm. The final rolling temperature is 280°C. The thickness of the plate after hot rolling is 4 mm. Then it is cold rolled at 80°C with a single-pass reduction of 2 mm and a rolling speed of 350 mm / s. The total processing amount of the cold rolling is 70%. The thickness of the composite ingot after cold rolling is 0.8 mm. Then it is annealed at 360°C for 2.5 hours to obtain the aluminum alloy metal plate.

[0097] This embodiment also provides a brazing method for the above-mentioned aluminum alloy metal plate. The brazing method includes brazing the aluminum alloy metal plate, wherein the maximum brazing temperature is 605°C, and the temperature is maintained above 600°C for 20 minutes, and the cooling rate of the brazing is 10°C / min during the cooling process from the maximum temperature to 350°C.

[0098] Example 2

[0099] This embodiment provides an aluminum alloy metal plate, which includes a core material and a sheath material; the core material is a low-corrosion, low-cracking aluminum alloy, and the sheath material includes a 4-series aluminum alloy; the composition and content of the core material and the sheath material are as shown in the formulation of Example 2 in Table 1; the thickness of the core material in the aluminum alloy metal plate is 90%, and the total thickness of the aluminum alloy metal plate is 1.2 mm.

[0100] This embodiment also provides a method for preparing the above-mentioned aluminum alloy metal plate, the method comprising the following steps:

[0101] (1) The core material raw material is melted and cast at 750°C for 3 hours according to the formula to obtain the core material ingot. The leather material raw material is melted and cast at 720°C for 3 hours according to the formula to obtain the leather material ingot.

[0102] (2) The leather ingot described in step (1) is preheated and rolled to the target thickness, and then the core ingot described in step (1) is subjected to homogenization heat treatment at 560°C for 12 hours, and then milled, with a single-sided milling amount of 5 mm; then the leather ingot of the target thickness is combined with the core ingot to obtain a composite ingot.

[0103] (3) The composite ingot described in step (2) is preheated at 450°C and held for 3 hours. Then it is hot rolled at a rolling speed of 500 mm / s and a single-pass reduction of 20 mm. The final rolling temperature is 260°C. The thickness of the plate after hot rolling is 3 mm. Then it is cold rolled at 25°C with a single-pass reduction of 1 mm and a rolling speed of 250 mm / s. The total processing amount of the cold rolling is 66%. The thickness of the composite ingot after cold rolling is 1.2 mm. Then it is annealed at 350°C for 2 hours to obtain the aluminum alloy metal plate.

[0104] This embodiment also provides a brazing method for the above-mentioned aluminum alloy metal plate. The brazing method includes brazing the aluminum alloy metal plate, wherein the maximum brazing temperature is 600°C and is maintained above 600°C for 30 minutes, and the cooling rate of the brazing is 5°C / min during the cooling process from the maximum temperature to 300°C.

[0105] Example 3

[0106] This embodiment provides an aluminum alloy metal plate, which includes a core material and a sheath material; the core material is a low-corrosion, low-cracking aluminum alloy, and the sheath material includes a 4-series aluminum alloy; the composition and content of the core material and the sheath material are as shown in the formulation of Example 3 in Table 1; the thickness of the core material in the aluminum alloy metal plate is 95%, and the total thickness of the aluminum alloy metal plate is 1.5 mm.

[0107] This embodiment also provides a method for preparing the above-mentioned aluminum alloy metal plate, the method comprising the following steps:

[0108] (1) The core material raw material is melted and cast at 780°C for 4 hours according to the formula to obtain the core material ingot. The leather material raw material is melted and cast at 750°C for 4 hours according to the formula to obtain the leather material ingot.

[0109] (2) The leather ingot described in step (1) is preheated and rolled to the target thickness, and then the core ingot described in step (1) is subjected to homogenization heat treatment at 590°C for 9 hours, and then milled, with a single-sided milling amount of 10 mm; then the leather ingot of the target thickness is combined with the core ingot to obtain a composite ingot.

[0110] (3) The composite ingot described in step (2) is preheated at 520°C and held for 3 hours. Then it is hot rolled at a rolling speed of 1000 mm / s and a single-pass reduction of 30 mm. The final rolling temperature is 300°C. The thickness of the plate after hot rolling is 5 mm. Then it is cold rolled at 100°C with a single-pass reduction of 2 mm and a rolling speed of 500 mm / s. The total processing amount of the cold rolling is 73%. The thickness of the composite ingot after cold rolling is 1.5 mm. Then it is annealed at 380°C for 3 hours to obtain the aluminum alloy metal plate.

[0111] This embodiment also provides a brazing method for the above-mentioned aluminum alloy metal plate. The brazing method includes brazing the aluminum alloy metal plate, wherein the maximum brazing temperature is 610°C, and the temperature is maintained above 600°C for 15 minutes, and the cooling rate of the brazing is 15°C / min during the cooling process from the maximum temperature to 320°C.

[0112] Example 4

[0113] This embodiment provides an aluminum alloy metal plate, which includes a core material and a skin material; the core material is a low-corrosion, low-cracking aluminum alloy, and the skin material includes a 4-series aluminum alloy; the composition and content of the core material and the skin material are as shown in the formulation of Example 4 in Table 1; the thickness of the core material in the aluminum alloy metal plate is 93%, and the total thickness of the aluminum alloy metal plate is 1.12 mm.

[0114] This embodiment also provides a method for preparing the above-mentioned aluminum alloy metal plate, the method comprising the following steps:

[0115] (1) The core material raw material is melted and cast at 770°C for 2.5 hours according to the formula to obtain the core material ingot. The leather material raw material is melted and cast at 740°C for 3 hours according to the formula to obtain the leather material ingot.

[0116] (2) The leather ingot described in step (1) is preheated and rolled to the target thickness, and then the core ingot described in step (1) is subjected to homogenization heat treatment at 565°C for 10 hours, and then milled, with a single-sided milling amount of 6 mm; then the leather ingot of the target thickness is combined with the core ingot to obtain a composite ingot.

[0117] (3) The composite ingot described in step (2) is preheated at 460°C and held for 3 hours. Then it is hot rolled at a rolling speed of 600 mm / s and a single-pass reduction of 28 mm. The final rolling temperature is 320°C. The thickness of the plate after hot rolling is 4 mm. Then it is cold rolled at 30°C with a single-pass reduction of 1.5 mm and a rolling speed of 480 mm / s. The total processing amount of the cold rolling is 68%. The thickness of the composite ingot after cold rolling is 1.12 mm. Then it is annealed at 370°C for 2.8 hours to obtain the aluminum alloy metal plate.

[0118] This embodiment also provides a brazing method for the above-mentioned aluminum alloy metal plate. The brazing method includes brazing the aluminum alloy metal plate, wherein the maximum brazing temperature is 610°C, and the temperature is maintained above 608°C for 18 minutes, and the cooling rate of the brazing is 8°C / min during the cooling process from the maximum temperature to 400°C.

[0119] Example 5

[0120] This embodiment provides an aluminum alloy metal plate. Except that the Ti content in the core material is 0.06wt%, and the Al content is reduced accordingly based on the increase in Ti, and the preparation method is adjusted accordingly to adjust the core material raw material formula, the rest of the aluminum alloy metal plate is the same as that in Embodiment 1.

[0121] This embodiment also provides a brazing method for the above-mentioned aluminum alloy metal plate, which is the same as that in Embodiment 1.

[0122] II. Comparative Example

[0123] Comparative Example 1

[0124] This comparative example provides an aluminum alloy metal plate, which is the same as in Example 1 except that the core material has a Si content of 0.59 wt%, a Mg to Si mass ratio of 1.44:1, and the Al content is reduced accordingly based on the increase in Si. The preparation method is adjusted accordingly to adjust the core material raw material formula.

[0125] This comparative example also provides a brazing method for the above-mentioned aluminum alloy metal plate, which is the same as that in Example 1.

[0126] Comparative Example 2

[0127] This comparative example provides an aluminum alloy metal plate, which is the same as in Example 1 except that the core material has a Si content of 0.50 wt%, a Mg to Si mass ratio of 1.7:1, and an Al content that is increased according to the reduction of Si, and the core material raw material formula is adjusted accordingly.

[0128] This comparative example also provides a brazing method for the above-mentioned aluminum alloy metal plate, which is the same as that in Example 1.

[0129] Comparative Example 3

[0130] This comparative example provides an aluminum alloy metal plate, which is the same as in Example 1 except that the Fe content in the core material is 0.1 wt%, and the Al content is increased accordingly based on the reduction of Fe, and the preparation method is adjusted accordingly to adjust the core material raw material formula.

[0131] This comparative example also provides a brazing method for the above-mentioned aluminum alloy metal plate, which is the same as that in Example 1.

[0132] Comparative Example 4

[0133] This comparative example provides an aluminum alloy metal plate, which is the same as in Example 1 except that the Fe content in the core material is 0.4wt%, and the Al content is reduced accordingly based on the increase in Fe, and the preparation method is adjusted accordingly to adjust the core material raw material formula.

[0134] This comparative example also provides a brazing method for the above-mentioned aluminum alloy metal plate, which is the same as that in Example 1.

[0135] Comparative Example 5

[0136] This comparative example provides an aluminum alloy metal plate, which is the same as in Example 1 except that the Cu content in the core material is 0.05wt%, and the Al content is reduced accordingly based on the increase in Cu. The preparation method is adjusted accordingly to adjust the core material raw material formula.

[0137] This comparative example also provides a brazing method for the above-mentioned aluminum alloy metal plate, which is the same as that in Example 1.

[0138] Comparative Example 6

[0139] This comparative example provides a method for preparing an aluminum alloy metal plate. Except for the total processing amount of the cold rolling process in step (3) being 80%, the preparation method is the same as that in Example 1.

[0140] This comparative example also provides a brazing method for the above-mentioned aluminum alloy metal plate, which is the same as that in Example 1.

[0141] III. Tests and Results

[0142] ① The precipitate size, average grain size in the parallel rolling direction, average grain size in the perpendicular rolling direction, grain aspect ratio, and the total proportion of Cube texture and R-Cube texture of the aluminum alloy metal plates described in the above embodiments or comparative examples were tested respectively, and the results are shown in Table 2.

[0143] Table 2

[0144]

[0145] ② The ratio of the erosion depth to the plate thickness, the crack depth, and the corrosion ratio of the aluminum alloy metal plates described in the above embodiments or comparative examples after brazing were tested and calculated respectively. The results are shown in Table 3.

[0146] Table 3

[0147]

[0148] According to the test results:

[0149] (1) As can be seen from the comprehensive examples 1 to 4, the present invention optimizes the composition of the aluminum alloy metal plate core material and combines it with a specific total cold rolling processing amount, so that the precipitated phase size of the aluminum alloy metal plate is in the range of 1-2 μm, the average grain size in the parallel rolling direction is in the range of 115-520 μm, the average grain size in the perpendicular rolling direction is in the range of 50-200 μm, the grain aspect ratio is 2.3-2.6, and the total proportion of Cube texture and R-Cube texture in the grain structure is ≤50%, thereby making the aluminum alloy metal plate have excellent brazing effect, achieving low erosion, low cracking and excellent corrosion resistance, with the erosion depth accounting for less than 25% of the plate thickness, the crack depth less than 10 μm, and the corrosion ratio less than 20%.

[0150] (2) It can be seen from the combined examples 1 and 5 that the Ti content in the core material of the aluminum alloy metal plate described in example 5 is too high. When the Ti content exceeds 0.05wt%, the effect of Ti as a grain refining modifier fails. However, Ti still promotes grain growth to present an equiaxed shape, and the aspect ratio of the grains becomes smaller. It was found that grains with a small aspect ratio have short grain boundaries, and the corrosion path is also short when corrosion occurs. The corrosion resistance of the material is better, and the corrosion ratio is as low as 22%.

[0151] (3) It can be seen from the comprehensive comparison of Example 1 with Comparative Example 1 and Comparative Example 2 that the mass ratio of Mg to Si in the core material of the aluminum alloy metal plate in Comparative Example 1 is too small, resulting in the size of the Mg2Si precipitate phase being >2μm, which promotes the recrystallization process of the material, resulting in a smaller average grain size and more grain boundaries, leading to poor brazing effect, a melting depth to plate thickness ratio as high as 30%, a crack depth as high as 20μm, and a corrosion ratio as high as 40%; the mass ratio of Mg to Si in the core material of the aluminum alloy metal plate in Comparative Example 2 is too large, resulting in the size of the Mg2Si precipitate phase being <1μm, a larger average grain size, leading to poor brazing effect, a melting depth to plate thickness ratio as high as 35%, a crack depth as high as 35μm, and a corrosion ratio as high as 42%.

[0152] (4) It can be seen from the comprehensive comparison of Example 1 with Comparative Example 3 and Comparative Example 4 that the Fe content in the core material of the aluminum alloy metal plate in Comparative Example 3 is less than 0.2wt%, which leads to the increase of the precipitated phase size to 5.0μm and the decrease of the average grain size, resulting in poor brazing effect. The ratio of the erosion depth to the plate thickness is as high as 34%, the crack depth is as high as 35μm, and the corrosion ratio is as high as 35%. In Comparative Example 4, the Fe content in the core material of the aluminum alloy metal plate exceeds 0.3wt%. A large amount of Fe will refine the material grains, resulting in poor brazing effect. The ratio of the erosion depth to the plate thickness is as high as 32%, the crack depth is as high as 28μm, and the corrosion ratio is as high as 25%.

[0153] (5) It can be seen from the combination of Example 1 and Comparative Example 5 that the core material of the aluminum alloy metal plate in Comparative Example 5 contains Cu, which leads to a finer grain size, resulting in poor brazing effect, a melting depth to plate thickness ratio as high as 36%, a crack depth as high as 36 μm, and a corrosion ratio as high as 45%.

[0154] (6) It can be seen from the combined example 1 and comparative example 6 that the total amount of cold rolling in the preparation method of aluminum alloy metal plate described in comparative example 6 is too large, resulting in the proportion of Cube and R-cube texture in the material as high as 80%, which leads to poor brazing effect, the ratio of erosion depth to plate thickness as high as 45%, the crack depth as high as 55 μm, and the corrosion ratio as high as 55%.

[0155] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An aluminum alloy having low erosion and low cracking, characterized in that, The low-erosion and low-crack aluminum alloy is a 6-series aluminum alloy. The 6-series aluminum alloy has an average grain size in the parallel rolling direction of 115-520 μm. The total proportion of Cube texture and R-Cube texture in the grain structure of the 6-series aluminum alloy is ≤50%.

2. The low-erosion, low-cracking aluminum alloy of claim 1, wherein, The 6-series aluminum alloy has a grain aspect ratio of 2.3-2.

6.

3. The low-erosion, low-cracking aluminum alloy of claim 1 or 2, wherein, The 6-series aluminum alloy comprises the following components in mass percentage: Si: 0.5-1.0 wt%, Mg: 0.7-1.0 wt%, Fe: 0.2-0.3 wt%. Preferably, the mass ratio of Mg to Si in the 6-series aluminum alloy is 1.5-1.

6. Preferably, the 6-series aluminum alloy does not contain Cu, Mn and Zn elements.

4. The low erosion, low crack aluminum alloy of any of claims 1-3, wherein, The 6-series aluminum alloy contains ≤0.05 wt% of Ti in mass percentage.

5. An aluminum alloy metal sheet characterized by, The aluminum alloy metal plate comprises a core material and a skin material; the core material comprises the low-erosion and low-crack aluminum alloy according to any one of claims 1-4, and the skin material comprises a 4-series aluminum alloy.

6. The aluminum alloy metal sheet according to claim 5, characterized in that, The 4-series aluminum alloy comprises the following components in mass percentage: Si: 9.0-10.5 wt%, Mg: 1.0-2.0 wt%, Bi: 0.05-0.2 wt%, Fe < 0.8 wt%, Cu < 0.25 wt%, Mn < 0.1 wt%, Zn < 0.2 wt%.

7. The aluminum alloy metal sheet according to claim 5 or 6, characterized in that, The thickness of the core material in the aluminum alloy metal plate accounts for 90-95%. Preferably, the total thickness of the aluminum alloy metal plate is 0.8-1.5 mm, preferably 0.8-1.0 mm.

8. A method of producing an aluminum alloy sheet according to any one of claims 5 to 7, characterized by, The preparation method comprises the following steps: (1) first melting and casting core material raw materials according to the formula to obtain a core material ingot, and second melting and casting skin material raw materials according to the formula to obtain a skin material ingot; (2) sequentially subjecting the core material ingot of step (1) to soaking treatment and face milling, and then combining the skin material ingot of step (1) to obtain a composite ingot; (3) sequentially subjecting the composite ingot of step (2) to hot rolling treatment, cold rolling treatment and annealing treatment to obtain the aluminum alloy metal plate.

9. The method of producing an aluminum alloy sheet according to claim 8, characterized by, The total processing amount of the cold rolling treatment of step (3) is not more than 75%.

10. The method of producing an aluminum alloy sheet according to claim 8 or 9, characterized in that, The annealing treatment of step (3) is performed at a temperature of 350-380℃. Preferably, the annealing treatment of step (3) is performed for 2-3 h.

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