Aluminum alloy composite plate and method for manufacturing the same

Abstract

The application provides an aluminum alloy composite plate and a preparation method thereof. The aluminum alloy composite plate comprises a core material layer and skin material layers which are stacked on two opposite surfaces of the core material layer; the core material layer comprises the following elements in percentage by mass: 0.2-0.6% of Si, 0.3-0.6% of Cu, 0.1-0.3% of Mg, 0.2-0.6% of Fe and 1.4-1.8% of Mn, the sum of the mass contents of Ti and Zr is 0.15-0.4%, and the balance is Al; each skin material layer comprises the following elements: 9.5-12.0% of Si, 0.6-1.0% of Fe, 1.4-1.8% of Mg, 0.05-0.25% of Zn and 0.08-0.2% of Bi, and the balance is Al; the aluminum alloy composite plate has good mechanical properties, anti-sagging and corrosion resistance, thereby better meeting the requirements of long-term operation of offshore wind turbines.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and more specifically, to an aluminum alloy composite plate and its preparation method. Background Technology

[0002] Aluminum alloys have been widely used in the field of heat exchangers due to their high specific strength, excellent heat transfer performance, abundant reserves and low cost. The all-aluminum trend in heat exchangers has become an inevitable trend in their development.

[0003] In recent years, the wind power market has maintained a steady growth trend, and the heat exchangers for wind power generation are mainly made of vacuum brazed aluminum. Offshore wind turbines operate in marine climate environments with long service lives. During operation, they face harsh environmental conditions and complex stress changes, thus placing higher demands on the mechanical properties and corrosion resistance of brazed composite materials.

[0004] Currently, adjusting the proportion of aluminum alloy components is the main way to improve the strength of aluminum alloy composite materials for brazing. However, while the addition of alloying elements improves the strength, it also has a certain impact on the corrosion resistance of brazed composite materials.

[0005] Chinese patent application CN110947762B discloses a core alloy composition and preparation method for a 308 aluminum alloy three-layer composite plate for vacuum brazing. It employs hot rolling, cold rolling, and finished product annealing processes to address the low strength and compressive strength of conventional 3003 aluminum alloy composite plates before and after brazing. However, this patent has a wide range of element content (Si, Fe, Cu, Mn, Mg, Zn, Ti, (Mn+Fe),) and the low Mn content results in a weak dispersion strengthening effect, while the high Mg content easily causes grain boundary corrosion.

[0006] Chinese patent application CN115771311A discloses an aluminum alloy composite material for brazing and its manufacturing method. The core alloy contains a wide range of elements, including Si, Cu, Mn, Mg, Fe, Sr, Zn, Ti, Zr, and Cr, with a particularly high Si content. This high Si content increases the risk of melting and collapse during brazing, and also tends to accumulate at grain boundaries, creating low-Si concentration zones near these boundaries, which can easily lead to intergranular corrosion.

[0007] Therefore, there is an urgent need to develop an aluminum alloy composite material with good mechanical properties, anti-sagging properties, and corrosion resistance to meet the performance requirements of brazed composite materials under stress changes and environmental conditions during the operation of offshore wind turbines. Summary of the Invention

[0008] The main objective of this invention is to provide an aluminum alloy composite plate and its preparation method, so as to solve the problem that the mechanical properties, anti-sagging properties and corrosion resistance of aluminum alloy composite materials for brazing in the prior art are difficult to meet the long-term operation requirements of offshore wind turbines.

[0009] To achieve the above objectives, according to one aspect of the present invention, an aluminum alloy composite plate is provided, comprising a core layer and a skin layer stacked on two opposing surfaces of the core layer; the core layer comprises, by mass percentage, the following elements: 0.2–0.6% Si, 0.3–0.6% Cu, 0.1–0.3% Mg, 0.2–0.6% Fe, and 1.4–1.8% Mn; the sum of the mass contents of Ti and Zr is 0.15–0.4%; the total content of unavoidable impurities is ≤0.15%; the content of a single impurity is <0.05%; and the balance is Al. Each skin layer comprises the following elements: 9.5–12.0% Si, 0.6–1.0% Fe, 1.4–1.8% Mg, 0.05–0.25% Zn, and 0.08–0.2% Bi. The total content of unavoidable impurities is ≤0.15%, the content of a single impurity is <0.05%, and the balance is Al. The potential difference between the diffusion layer and the skin layer formed after brazing the aluminum alloy composite plate is ≥450mV. Before brazing, the tensile strength of the aluminum alloy composite plate is ≥220MPa, the yield strength is ≥195MPa, and the elongation is ≥5.5%. After brazing, the yield strength of the aluminum alloy composite plate is ≥64.7MPa, and the sag resistance is ≤4mm.

[0010] Further, by mass percentage, the core layer comprises the following elements: 0.3–0.5% Si, 0.4–0.6% Cu, 0.15–0.25% Mg, 0.2–0.4% Fe, and 1.5–1.7% Mn; the sum of the mass contents of Ti and Zr is 0.2–0.3%; the total content of unavoidable impurities is ≤0.15%; the content of a single impurity is <0.05%; and the balance is Al. By mass percentage, each of the above-mentioned skin layers comprises the following elements: 10–11.5% Si, 0.6–0.8% Fe, 1.45–1.65% Mg, 0.1–0.2% Zn, and 0.1–0.15% Bi; the total content of unavoidable impurities is ≤0.15%; the content of a single impurity is <0.05%; and the balance is Al.

[0011] Furthermore, in the core layer, the mass ratio of Mn to Fe is 4–6:1, and / or the mass ratio of Mg to Si is 3–8:10.

[0012] Furthermore, the size of the AlMnSi dispersed phase in the core layer is 100–200 nm; the size of the Fe-containing second phase in the core layer is controlled to be 1–10 μm, and the area ratio of the Fe-containing second phase in the core layer is 1.6–2.58%.

[0013] According to another aspect of the present invention, a method for preparing the above-mentioned aluminum alloy composite plate is provided, the method comprising: step S1, independently heating and rolling a first skin ingot, a core ingot, and a second skin ingot sequentially to obtain a first skin ingot layer, a core ingot layer, and a second skin ingot layer; stacking the first skin ingot layer, the core ingot layer, and the second skin ingot layer sequentially and then performing a composite rolling process to obtain a composite billet; step S2, sequentially preheating the composite billet, hot rough rolling, and hot finish rolling to obtain a hot-rolled billet; and step S3, sequentially performing a first cold rolling, intermediate annealing, and a second cold rolling on the hot-rolled billet. The aluminum alloy composite plate is obtained by cold rolling. The preheating process includes heating the composite billet to 460-490℃ at a rate of 30-80℃ / h and holding it for 1-6h. The intermediate annealing is either direct annealing or continuous intermediate annealing of the billet after the first cold rolling. The direct annealing process includes heating the billet to 380-460℃ at a rate of 20-90℃ / h and holding it for 0.5-3h. The continuous intermediate annealing process includes heating the billet to 400-480℃ at a rate of 30-120℃ / s and holding it for 60-240s, followed by cooling it to below 100℃ at a rate of 50-250℃ / s.

[0014] Furthermore, the preheating process includes: heating the composite blank to 460-490℃ at a rate of 40-60℃ / h and then holding it at that temperature for 2-4 hours.

[0015] Furthermore, the direct annealing process includes: heating the cold-rolled billet to 400-460°C at a rate of 50-80°C / h and holding it at that temperature for 0.5-3h; and / or, the continuous intermediate annealing process includes: heating the cold-rolled billet to 440-480°C at a rate of 40-100°C / s and holding it at that temperature for 60-240s, followed by cooling it to below 100°C at a rate of 100-200°C / s.

[0016] Furthermore, the total processing rate of a single cold rolling operation is 80-90%, and / or the total processing rate of a two-stage cold rolling operation is 10-25%.

[0017] Furthermore, step S1 above also includes: independently and sequentially melting, casting, sawing, and milling the skin alloy and the core alloy to obtain skin ingots and core ingots respectively; wherein, during the melting and casting process, antimony is used to modify the skin alloy; and / or, the single-sided milling amount is 15-20 mm, and the difference between the longitudinal and transverse milling amounts is ≤2 mm.

[0018] Further, in step S1 above, a steel strip is used to fix the stacked structure after the first skin ingot layer, the core ingot layer, and the second skin ingot layer are stacked sequentially for composite rolling treatment; the thickness ratio of the first skin ingot layer, the core ingot layer, and the second skin ingot layer is 1:8 to 10:1; and / or, the width of the first skin ingot layer and the second skin ingot layer are each independently greater than the width of the core ingot layer, and the tolerance of the difference between the width of the first skin ingot layer and the width of the second skin ingot layer and the width of the core ingot layer is 10 to 40 mm.

[0019] Applying the technical solution of this invention, the aluminum alloy composite plate of this application includes a core layer and a skin layer stacked on both sides of the core layer. This structural design can optimize the overall performance of the aluminum alloy composite plate. In the core layer: the added Si, Fe, and Mn elements can form AlFeMnSi compounds, thereby playing a role in dispersion strengthening. Simultaneously, the solid solution strengthening of Si, Fe, and Mn elements in the matrix can improve the strength of the aluminum alloy composite plate. Controlling the Si content within the aforementioned range not only improves the strengthening effect but also avoids problems such as melting and collapse, as well as intergranular corrosion, during the brazing process. Adding Mn and Fe elements can improve the formability and strength of the aluminum alloy composite plate. Simultaneously, controlling the Fe content within the aforementioned range can improve the formability and corrosion resistance of the aluminum alloy composite plate. Adding Mg, Si, and Cu elements helps the aluminum alloy composite plate to undergo natural aging after rapid cooling and placement at room temperature after brazing, thereby producing fine, dispersed Mg2Si and Al2CuMg phases, etc., as second phases. Simultaneously, the synergistic effect of solid solution strengthening and dispersion strengthening can yield aluminum alloy composite plates with higher strength. The solid solution strengthening effect of adding Ti and Zr elements can improve the alloy's strength and promote the formation of fine, dispersed Al3Ti and Al3Zr precipitates, further enhancing the alloy's strength. Furthermore, adding Ti and Zr elements can promote the formation of coarse, elongated grains during brazing of the aluminum alloy composite plate, thereby improving its anti-sagging properties. Controlling the Ti content within the above range can alter the alloy's corrosion potential, thus improving the corrosion resistance of the aluminum alloy composite plate. In each skin layer: the added Bi element not only increases the wettability of the Si liquid phase on the aluminum alloy surface but also promotes the fluidity of the Si liquid phase, thereby improving the welding performance of the aluminum alloy composite plate. Too low a Bi content will not achieve the aforementioned performance of the aluminum alloy composite plate, while too high a Bi content not only has limited effect on further improvement but also increases costs. Therefore, controlling the Bi content within the above range can balance effectiveness and cost. Controlling the Zn content within the above range can reduce the corrosion potential of each skin layer, resulting in a potential difference ≥450mV between the diffusion layer and the skin layer after brazing of the aluminum alloy composite plate. Furthermore, the potential distribution of the diffusion layer is uniform, and the driving force of galvanic corrosion is reduced, thereby improving the corrosion resistance of the aluminum alloy composite plate. The diffusion layer is a structural layer formed by the interdiffusion of alloying elements under the influence of a concentration gradient during the brazing process between the skin and core materials. Through coordinated optimization of the above elements in the core layer and each skin layer, the mechanical properties, anti-sagging properties, and corrosion resistance of the aluminum alloy composite plate can be comprehensively improved, thus better meeting the requirements of long-term operation of offshore wind turbines. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 The image shows the morphology of the Fe-containing second phase in the core layer of the aluminum alloy composite plate in Embodiment 1 of this application;

[0022] Figure 2 The image shows the morphology of the AlMnSi phase in the aluminum alloy composite plate of Embodiment 1 of this application;

[0023] Figure 3 The image shows the grain morphology of the aluminum alloy composite plate after brazing in Embodiment 1 of this application;

[0024] Figure 4 The image shows the morphology of the Fe-containing second phase in the core layer of the aluminum alloy composite plate in Comparative Example 1 of this application;

[0025] Figure 5 The morphology diagram of the AlMnSi phase in the aluminum alloy composite plate of Comparative Example 1 of this application is shown.

[0026] Figure 6 The image shows the grain morphology of the aluminum alloy composite plate after brazing in Comparative Example 1 of this application. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] As analyzed in the background section of this application, the existing technology has the problem that the mechanical properties, anti-sagging properties and corrosion resistance of aluminum alloy composite materials for brazing are difficult to meet the long-term operation requirements of offshore wind turbines. In order to solve the above problems, this application provides an aluminum alloy composite plate and its preparation method.

[0029] In a typical embodiment of this application, an aluminum alloy composite plate is provided, comprising a core layer and skin layers stacked on two opposing surfaces of the core layer; the core layer comprises, by mass percentage, the following elements: 0.2–0.6% Si, 0.3–0.6% Cu, 0.1–0.3% Mg, 0.2–0.6% Fe, and 1.4–1.8% Mn; the sum of the mass contents of Ti and Zr is 0.15–0.4%; the total content of unavoidable impurities is ≤0.15%; the content of a single impurity is <0.05%; and the balance is Al; the skin layer comprises, by mass percentage, the following elements: The material layer comprises the following elements: 9.5–12.0% Si, 0.6–1.0% Fe, 1.4–1.8% Mg, 0.05–0.25% Zn, and 0.08–0.2% Bi. The total content of unavoidable impurities is ≤0.15%, the content of a single impurity is <0.05%, and the balance is Al. The potential difference between the diffusion layer and the skin layer formed after brazing the aluminum alloy composite plate is ≥450mV. Before brazing, the tensile strength of the aluminum alloy composite plate is ≥220MPa, the yield strength is ≥195MPa, and the elongation is ≥5.5%. After brazing, the yield strength of the aluminum alloy composite plate is ≥64.7MPa, and the sag resistance is ≤4mm.

[0030] The aluminum alloy composite plate of this application includes a core layer and skin layers stacked on both sides of the core layer. This structural design optimizes the overall performance of the aluminum alloy composite plate. In the core layer, the added Si, Fe, and Mn elements form AlFeMnSi compounds, thereby providing dispersion strengthening. Simultaneously, the solid solution strengthening of Si, Fe, and Mn elements in the matrix enhances the strength of the aluminum alloy composite plate. Controlling the Si content within the aforementioned range not only improves the strengthening effect but also prevents melting, collapse, and intergranular corrosion during brazing. The addition of Mn and Fe elements improves the formability and strength of the aluminum alloy composite plate. Furthermore, controlling the Fe content within the aforementioned range improves its formability and corrosion resistance. The addition of Mg, Si, and Cu elements facilitates natural aging after rapid cooling and placement at room temperature following brazing, resulting in the formation of fine, dispersed Mg2Si and Al2CuMg phases, among other second phases. Simultaneously, the synergistic effect of solid solution strengthening and dispersion strengthening can yield aluminum alloy composite plates with higher strength. The solid solution strengthening effect of adding Ti and Zr elements can improve the alloy's strength and promote the formation of fine, dispersed Al3Ti and Al3Zr precipitates, further enhancing the alloy's strength. Furthermore, adding Ti and Zr elements can promote the formation of coarse, elongated grains during brazing of the aluminum alloy composite plate, thereby improving its anti-sagging properties. Controlling the Ti content within the above range can alter the alloy's corrosion potential, thus improving the corrosion resistance of the aluminum alloy composite plate. In each skin layer: the added Bi element not only increases the wettability of the Si liquid phase on the aluminum alloy surface but also promotes the fluidity of the Si liquid phase, thereby improving the welding performance of the aluminum alloy composite plate. Too low a Bi content will not achieve the aforementioned performance of the aluminum alloy composite plate, while too high a Bi content not only has limited effect on further improvement but also increases costs. Therefore, controlling the Bi content within the above range can balance effectiveness and cost. Controlling the Zn content within the above range can reduce the corrosion potential of each skin layer, resulting in a potential difference ≥450mV between the diffusion layer and the skin layer after brazing of the aluminum alloy composite plate. Furthermore, the potential distribution of the diffusion layer is uniform, and the driving force of galvanic corrosion is reduced, thereby improving the corrosion resistance of the aluminum alloy composite plate. The diffusion layer is a structural layer formed by the interdiffusion of alloying elements under the influence of a concentration gradient during the brazing process between the skin and core materials. Through coordinated optimization of the above elements in the core layer and each skin layer, the mechanical properties, anti-sagging properties, and corrosion resistance of the aluminum alloy composite plate can be comprehensively improved, thus better meeting the requirements of long-term operation of offshore wind turbines.

[0031] To further improve the synergistic effect between the core layer and each skin layer, thereby optimizing the mechanical properties, anti-sagging properties, and corrosion resistance of the aluminum alloy composite plate, in one embodiment of this application, to further enhance the synergistic effect between the elements, the core layer preferably includes the following elements by mass percentage: 0.3–0.5% Si, 0.4–0.6% Cu, 0.15–0.25% Mg, 0.2–0.4% Fe, and 1.5–1.7% Mn, Ti, and Zr. The total mass content is 0.2-0.3%, the total content of unavoidable impurities is ≤0.15%, the content of a single impurity is <0.05%, and the balance is Al element; by mass percentage, each leather layer includes the following elements: 10-11.5% Si element, 0.6-0.8% Fe element, 1.45-1.65% Mg element, 0.1-0.2% Zn element and 0.1-0.15% Bi element, the total content of unavoidable impurities is ≤0.15%, the content of a single impurity is <0.05%, and the balance is Al element.

[0032] In one embodiment of this application, the mass ratio of Mn to Fe in the core layer is 4 to 6:1, and / or the mass ratio of Mg to Si is 3 to 8:10.

[0033] In the core layer, it is preferable to control the mass ratio of Mn to Fe within the aforementioned range. This helps to enhance the synergistic effect of Mn and Fe, thereby further regulating the content of AlFeMnSi compounds formed by Mn, Fe, and Si, reducing the formation of coarse Fe-containing phases, and thus improving the corrosion resistance of the aluminum alloy composite plate. It is also preferable to control the mass ratio of Mg to Si within the aforementioned range. This helps to enhance the synergistic effect of Mg and Si, thereby promoting the formation of fine Mg2Si phases, and further contributing to improving the strength of the aluminum alloy composite.

[0034] In one embodiment of this application, the size of the AlMnSi phase in the core layer is 100-200 nm; the size of the Fe-containing second phase in the core layer is 1-10 μm, and the area ratio of the Fe-containing second phase in the core layer is 1.6-2.58%.

[0035] Preferably controlling the size of the AlMnSi phase in the core layer within the above-mentioned range helps to improve the mechanical properties and anti-sagging properties of the aluminum alloy composite plate before and after brazing. Preferably controlling the size and area ratio of the Fe-containing second phase in the core layer within the above-mentioned range helps to further improve the formability and corrosion resistance of the aluminum alloy composite plate.

[0036] In another typical embodiment of this application, a method for preparing the above-mentioned aluminum alloy composite plate is provided. The method includes: step S1, heating and rolling a first skin ingot, a core ingot, and a second skin ingot independently and sequentially to obtain a first skin ingot layer, a core ingot layer, and a second skin ingot layer; stacking the first skin ingot layer, the core ingot layer, and the second skin ingot layer sequentially and then performing composite rolling to obtain a composite billet; step S2, preheating the composite billet sequentially, performing hot rough rolling and hot finish rolling to obtain a hot-rolled billet; and step S3, performing a cold rolling and intermediate annealing sequentially on the hot-rolled billet. The aluminum alloy composite plate is obtained by hot rolling and secondary cold rolling. The preheating process includes: heating the composite billet to 460-490℃ at 30-80℃ / h and holding it for 1-6h; the intermediate annealing is either direct annealing or continuous intermediate annealing of the billet after the first cold rolling; the direct annealing process includes: heating the billet after the first cold rolling to 380-460℃ at 20-90℃ / h and holding it for 0.5-3h; the continuous intermediate annealing process includes: heating the billet after the first cold rolling to 400-480℃ at 30-120℃ / s and holding it for 60-240s, and then cooling it to below 100℃ at 50-250℃ / s.

[0037] This application employs a rapid heating process followed by short-time high-temperature or long-time medium-high-temperature preheating and intermediate annealing. This process maximizes the precipitation of fine AlMnSi dispersed phases, thereby improving the mechanical properties and anti-sagging performance of the aluminum alloy composite plate before and after brazing. Compared to existing technologies, this can increase the yield strength of the aluminum alloy composite plate after brazing by more than 20 MPa. Step S1 yields the aforementioned three-layer composite billet, which facilitates subsequent preheating treatment. The preheating treatment controls the size and number density of the AlMnSi dispersed phases, thereby improving the strength of the aluminum alloy composite plate and laying a good microstructure foundation for obtaining elongated large grains during subsequent brazing. Hot roughing and hot finishing processes yield hot-rolled billets with more precise thickness and better plate shape. Single and double cold rolling helps to control grain size and distribution, thereby improving the brazing performance and anti-sagging performance of the aluminum alloy composite plate. The direct annealing described above promotes the precipitation of AlTiZr and AlMnSi dispersed phases, thereby improving the tensile properties, anti-sagging properties, and corrosion resistance of the aluminum alloy composite plate. The continuous intermediate annealing described above controls the precipitation and growth of the AlTiZr and AlMnSi dispersed phases, thus meeting the basic requirements for the final microstructure of the finished aluminum alloy composite plate. Therefore, through the synergistic optimization of alloy composition and processing technology, this invention produces a high-strength, corrosion-resistant aluminum alloy composite plate with excellent mechanical properties, anti-sagging properties, and corrosion resistance.

[0038] In order to further control the size and number density of the AlMnSi dispersed phase and obtain the desired target microstructure of long strip-shaped large grains, in one embodiment of this application, the preheating process preferably includes: heating the composite billet to 460-490°C at a rate of 40-60°C / h and then holding it at that temperature for 2-4 hours.

[0039] To further control the precipitation of AlTiZr and AlMnSi dispersed phases and improve the tensile properties, anti-sagging properties, and corrosion resistance of aluminum alloy composite plates, in one embodiment of this application, the preferred direct annealing process includes: heating the cold-rolled billet to 400-460°C at a rate of 50-80°C / h and holding it at that temperature for 0.5-3h; and / or, the continuous intermediate annealing process includes: heating the cold-rolled billet to 440-480°C at a rate of 40-100°C / s and holding it at that temperature for 60-240s, followed by cooling it to below 100°C at a rate of 100-200°C / s.

[0040] In one embodiment of this application, the total processing rate of the first cold rolling is 80-90%, and / or the total processing rate of the second cold rolling is 10-25%.

[0041] Preferably controlling the total processing rate of the first cold rolling within the aforementioned range not only helps to promote the breakage of coarse compounds, thereby improving the ductility of the aluminum alloy composite plate, but also helps to promote the uniform distribution of the eutectic silicon phase in the skin layer, which in turn helps to promote the uniform distribution of the subsequent brazing liquid phase, thus improving the brazing quality of the aluminum alloy composite plate. Preferably controlling the total processing rate of the second cold rolling within the aforementioned range helps to regulate deformation energy storage. Combined with the control of the second phase distribution, this is beneficial for the formation of elongated grains with appropriate aspect ratios during the brazing process of the aluminum alloy composite plate, thereby giving the aluminum alloy composite plate good brazing performance and anti-sagging properties.

[0042] In one embodiment of this application, step S1 further includes: independently and sequentially melting, casting, sawing, and milling the skin alloy and the core alloy to obtain skin ingots and core ingots respectively; wherein, during the melting and casting process, antimony is used to modify the skin alloy; and / or, the single-sided milling amount is 15-20 mm, and the difference between the longitudinal and transverse milling amounts is ≤2 mm.

[0043] By performing the above-mentioned treatments on the skin alloy and core alloy, and controlling the single-sided milling amount and the difference in longitudinal and transverse thickness of the milled surface within the aforementioned ranges, it is beneficial to perform better composite rolling on the skin ingot and core ingot subsequently. Using antimony for modification treatment not only helps to refine the dimensions of the eutectic silicon but also helps to reduce the formation of welding defects in the aluminum alloy composite plate during high-temperature brazing, thereby improving the corrosion resistance of the composite plate.

[0044] In one embodiment of this application, in step S1 above, a steel strip is used to fix the stacked structure after the first skin ingot layer, the core ingot layer, and the second skin ingot layer are stacked sequentially for composite rolling processing. The thickness ratio of the first skin ingot layer, the core ingot layer, and the second skin ingot layer is 1:8 to 10:1; and / or, the width of the first skin ingot layer and the second skin ingot layer are each independently greater than the width of the core ingot layer, and the tolerance between the width of the first skin ingot layer and the width of the second skin ingot layer and the width of the core ingot layer is 10 to 40 mm.

[0045] Before composite rolling, heating and rolling the skin ingot and core ingot independently helps to control the tolerance of the difference between the width of the first skin ingot layer and the width of the core ingot layer within the above-mentioned range, which facilitates subsequent composite rolling. Using steel strip to fix the laminated structure for composite rolling, and preferably controlling the thickness ratio of the first skin ingot layer, core ingot layer and second skin ingot layer within the above-mentioned range, helps to improve the stability of the composite structure of each layer of the composite billet.

[0046] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0047] Example 1

[0048] The raw materials of the core alloy, by mass percentage, include the following elements: 0.35% Si, 0.3% Cu, 0.15% Mg, 0.3% Fe, 1.55% Mn, and the sum of Ti and Zr is 0.2%, with the balance being Al.

[0049] By mass percentage, the raw materials of the leather alloy include the following elements: 10.5% Si, 0.8% Fe, 1.5% Mg, 0.15% Zn, 0.1% Bi, with the balance being Al.

[0050] The above-mentioned leather alloy and core alloy are independently and sequentially melted, cast, sawed, and milled to obtain a first leather ingot, a second leather ingot, and a core ingot, respectively. These are then independently heated and rolled to obtain a first leather ingot layer, a core ingot layer, and a second leather ingot layer. These layers are then stacked sequentially to obtain a laminated structural component. The laminated structural component is fixed with steel strips for composite rolling to obtain a composite billet. The leather alloy undergoes antimony modification treatment during melting and casting. The single-sided milling margin is 15mm, and the difference between the longitudinal and transverse milling margins is 2mm. The widths of the first and second leather ingot layers are each independently greater than the width of the core ingot layer, and the tolerance between the widths of the first and second leather ingot layers and the width of the core ingot layer is 10mm. The thickness ratio of the first leather ingot layer, the core material ingot layer, and the second leather ingot layer is 1:10:1.

[0051] The composite billet was preheated to 460℃ at a rate of 40℃ / h and held at that temperature for 2h. Then, it was subjected to hot roughing and hot finishing rolling. The rolling rate of hot roughing was 90% and the rolling rate of hot finishing was 83%, resulting in a hot-rolled billet with a thickness of 6mm.

[0052] The hot-rolled billet is subjected to a first cold rolling, with a total processing rate of 80%. Then, the billet after the first cold rolling is heated to 400℃ at a rate of 60℃ / h and held at that temperature for 1.5h for intermediate annealing. Finally, it is subjected to a second cold rolling, with a total processing rate of 15%, to obtain an aluminum alloy composite plate with a thickness of 0.6mm.

[0053] Example 2

[0054] The raw materials of the core alloy, by mass percentage, include the following elements: 0.5% Si, 0.4% Cu, 0.2% Mg, 0.4% Fe, 1.65% Mn, and the sum of Ti and Zr is 0.25%, with the balance being Al.

[0055] By mass percentage, the raw materials of the leather alloy include the following elements: 11% Si, 0.8% Fe, 1.6% Mg, 0.18% Zn, 0.12% Bi, with the balance being Al.

[0056] The above-mentioned leather alloy and core alloy are independently and sequentially melted, cast, sawed, and milled to obtain a first leather ingot, a second leather ingot, and a core ingot, respectively. These are then independently heated and rolled to obtain a first leather ingot layer, a core ingot layer, and a second leather ingot layer. These layers are then stacked sequentially to obtain a laminated structural component. The laminated structural component is fixed with steel strips for composite rolling to obtain a composite billet. The leather alloy undergoes antimony modification treatment during melting and casting. The single-sided milling margin is 18mm, and the difference between the longitudinal and transverse milling margins is 1.5mm. The widths of the first and second leather ingot layers are each independently greater than the width of the core ingot layer, and the tolerance between the widths of the first and second leather ingot layers and the width of the core ingot layer is 25mm. The thickness ratio of the first leather ingot layer, the core material ingot layer, and the second leather ingot layer is 1:10:1.

[0057] The composite billet was preheated to 470℃ at a rate of 50℃ / h and held at that temperature for 3h. Then, it was subjected to hot roughing and hot finishing rolling. The rolling rate of hot roughing was 90% and the rolling rate of hot finishing was 83%, resulting in a hot-rolled billet with a thickness of 6mm.

[0058] The hot-rolled billet is cold-rolled once, with a total processing rate of 85%. Then, the billet after the first cold rolling is heated to 420℃ at a rate of 60℃ / h and held for 1.5h for intermediate annealing. Finally, it is cold-rolled a second time, with a total processing rate of 18%, to obtain an aluminum alloy composite plate with a thickness of 0.6mm.

[0059] Example 3

[0060] The raw materials of the core alloy, by mass percentage, include the following elements: 0.5% Si, 0.5% Cu, 0.25% Mg, 0.5% Fe, 1.65% Mn, and the sum of Ti and Zr is 0.25%, with the balance being Al.

[0061] By mass percentage, the raw materials of the leather alloy include the following elements: 11% Si, 0.8% Fe, 1.6% Mg, 0.2% Zn, 0.14% Bi, with the balance being Al.

[0062] The above-mentioned leather alloy and core alloy are independently and sequentially melted, cast, sawed, and milled to obtain a first leather ingot, a second leather ingot, and a core ingot, respectively. These are then independently heated and rolled to obtain a first leather ingot layer, a core ingot layer, and a second leather ingot layer. These layers are then stacked sequentially to obtain a laminated structural component. The laminated structural component is fixed with steel strips for composite rolling to obtain a composite billet. The leather alloy undergoes antimony modification treatment during melting and casting. The milled surface thickness is 20 mm, and the difference between the longitudinal and transverse milled surface thickness is 1 mm. The widths of the first and second leather ingot layers are each independently greater than the width of the core ingot layer, and the tolerance between the widths of the first and second leather ingot layers and the width of the core ingot layer is 40 mm. The thickness ratio of the first leather ingot layer, the core material ingot layer, and the second leather ingot layer is 1:10:1.

[0063] The composite billet was preheated to 480℃ at a rate of 50℃ / h and held at that temperature for 3h. Then, it was subjected to hot roughing and hot finishing rolling. The rolling rate of hot roughing was 90% and the rolling rate of hot finishing was 83%, resulting in a hot-rolled billet with a thickness of 6mm.

[0064] The hot-rolled billet is subjected to a first cold rolling process with a total processing rate of 85%. The billet after the first cold rolling is then heated to 460°C at a rate of 60°C / s and held for 180s. It is then cooled to below 100°C at a rate of 150°C / s for intermediate annealing. Finally, it is subjected to a second cold rolling process with a total processing rate of 15%, resulting in an aluminum alloy composite plate with a thickness of 0.6mm.

[0065] Example 4

[0066] The difference from Example 1 is that the total mass content of Mn and Fe elements in the core layer is 1.85%, and the mass ratio of Mn to Fe elements is 3:1, ultimately resulting in an aluminum alloy composite plate.

[0067] Example 5

[0068] The difference from Example 1 is that the total mass content of Mn and Fe elements in the core layer is 1.85%, and the mass ratio of Mn to Fe elements is 4:1, ultimately resulting in an aluminum alloy composite plate.

[0069] Example 6

[0070] The difference from Example 1 is that the total mass content of Mn and Fe elements in the core layer is 1.85%, and the mass ratio of Mn to Fe elements is 8:1, ultimately resulting in an aluminum alloy composite plate.

[0071] Example 7

[0072] The difference from Example 1 is that the total mass content of Mg and Si elements in the core layer is 0.5%, and the mass ratio of Mg to Si elements is 3:10, resulting in an aluminum alloy composite plate.

[0073] Example 8

[0074] The difference from Example 1 is that the total mass content of Mg and Si elements in the core layer is 0.5%, and the mass ratio of Mg to Si elements is 8:10, resulting in an aluminum alloy composite plate.

[0075] Example 9

[0076] The difference from Example 1 is that the total mass content of Mg and Si elements in the core layer is 0.5%, and the mass ratio of Mg to Si elements is 6:5, resulting in an aluminum alloy composite plate.

[0077] Example 10

[0078] The difference from Example 1 is that the preheating process includes: heating the composite billet to 490°C at 30°C / h and holding it at that temperature for 1 hour to finally obtain an aluminum alloy composite plate.

[0079] Example 11

[0080] The difference from Example 1 is that the preheating process includes: heating the composite billet to 460°C at 80°C / h and holding it at that temperature for 6 hours to finally obtain an aluminum alloy composite plate.

[0081] Example 12

[0082] The difference from Example 1 is that the billet after one cold rolling is heated to 380°C at a rate of 20°C / h and then held at that temperature for 3 hours for intermediate annealing, and finally an aluminum alloy composite plate is obtained.

[0083] Example 13

[0084] The difference from Example 1 is that the billet after one cold rolling is heated to 460°C at a rate of 90°C / h and then held at that temperature for 0.5h for intermediate annealing, and finally an aluminum alloy composite plate is obtained.

[0085] Example 14

[0086] The difference from Example 1 is that the billet after one cold rolling is heated to 400°C at 30°C / s and held for 240s, and then cooled to below 100°C at 50°C / s for intermediate annealing, and finally aluminum alloy composite plate is obtained.

[0087] Example 15

[0088] The difference from Example 1 is that the billet after one cold rolling is heated to 480°C at 120°C / s and held for 60s, and then cooled to below 100°C at 250°C / s for intermediate annealing, and finally aluminum alloy composite plate is obtained.

[0089] Example 16

[0090] The difference from Example 1 is that the total processing rate of one cold rolling is 90%, and the final product is an aluminum alloy composite plate.

[0091] Example 17

[0092] The difference from Example 1 is that the total processing rate of one cold rolling is 70%, and the final product is an aluminum alloy composite plate.

[0093] Example 18

[0094] The difference from Example 1 is that the total processing rate of the second cold rolling is 25%, and the final product is an aluminum alloy composite plate.

[0095] Example 19

[0096] The difference from Example 1 is that the total processing rate of the second cold rolling is 35%, and the final product is an aluminum alloy composite plate.

[0097] Comparative Example 1

[0098] The raw materials of the core alloy, by mass percentage, include the following elements: 0.15% Si, 0.65% Fe, 1.35% Mn, and the sum of Ti and Zr is 0.1%, with the balance being Al.

[0099] By mass percentage, the leather alloy comprises the following elements: 11% Si, 0.8% Fe, 0.8% Mg, with the balance being Al.

[0100] The above-mentioned leather alloy and core alloy are independently and sequentially melted, cast, sawed, and milled to obtain a first leather ingot, a second leather ingot, and a core ingot, respectively. These are then independently heated and rolled to obtain a first leather ingot layer, a core ingot layer, and a second leather ingot layer. These layers are then stacked sequentially to obtain a laminated structural component. The laminated structural component is fixed with steel strips for composite rolling to obtain a composite billet. The leather alloy undergoes antimony modification treatment during melting and casting. The single-sided milling margin is 15mm, and the difference between the longitudinal and transverse milling margins is 2mm. The widths of the first and second leather ingot layers are each independently greater than the width of the core ingot layer, and the tolerance between the widths of the first and second leather ingot layers and the width of the core ingot layer is 10mm. The thickness ratio of the first leather ingot layer, the core material ingot layer, and the second leather ingot layer is 1:10:1.

[0101] The composite billet was preheated to 430℃ at a rate of 50℃ / h and held at that temperature for 3h. Then, it was subjected to hot roughing and hot finishing rolling. The rolling rate of hot roughing was 90% and the rolling rate of hot finishing was 83%, resulting in a hot-rolled billet with a thickness of 6mm.

[0102] The hot-rolled billet is subjected to a first cold rolling process with a total processing rate of 75%. The billet after the first cold rolling is then heated to 460°C at a rate of 60°C / s and held for 180s. It is then cooled to below 100°C at a rate of 150°C / s for intermediate annealing. Finally, a second cold rolling process is performed with a total processing rate of 20%, resulting in an aluminum alloy composite plate with a thickness of 0.6mm.

[0103] Comparative Example 2

[0104] The difference from Example 1 is that the preheating process includes: heating the composite billet to 520°C at 90°C / h and holding it at that temperature for 7h to finally obtain an aluminum alloy composite plate.

[0105] Comparative Example 3

[0106] The difference from Example 1 is that the billet after one cold rolling is heated to 480°C at 100°C / h and held for 4 hours for intermediate annealing, and finally aluminum alloy composite plate is obtained.

[0107] Comparative Example 4

[0108] The difference from Example 1 is that the billet after one cold rolling is heated to 380°C at 25°C / s and held for 30s, and then cooled to below 100°C at 40°C / s for intermediate annealing, and finally aluminum alloy composite plate is obtained.

[0109] Test methods

[0110] Yield strength, tensile strength and elongation tests: conducted in accordance with GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0111] Sagging resistance test: The air furnace is heated to the brazing temperature of 610℃, the sample (15mm wide and 50mm long at the free end) is placed in the furnace, and the furnace temperature is kept at the brazing temperature for 10 minutes. The sample is then removed from the furnace and air-cooled, and the sagging value is calculated.

[0112] The size of the AlMnSi phase in the core material layer, the size of the Fe-containing second phase in the core material layer, and the area ratio of the Fe-containing second phase were tested: After the sample was polished, it was observed and photographed using a metallographic microscope without etching. Then, the area ratio of the second phase and the dispersed phase in the core material was calculated using IPP (Image-Pro-Plus) software.

[0113] Potential difference test: The potential difference between the diffusion layer and the skin layer formed after brazing of the aluminum alloy composite plate was tested for 1680h using the seawater acid cyclic corrosion test (SWAAT) according to ASTM G85-02 A3 standard.

[0114] The aluminum alloy composite plates of the above embodiments and comparative examples were subjected to microstructure characterization and performance testing. The test results are shown in Table 1 and Table 2.

[0115] Table 1

[0116]

[0117]

[0118] Table 2

[0119]

[0120]

[0121] in, Figure 1 This is a morphology diagram of the Fe-containing second phase in the core layer of the aluminum alloy composite plate in Example 1. Figure 1 As can be seen, the AlFeMnSi phase has a uniform size distribution. Therefore, by controlling the amount of compounds formed by Mn, Fe and Si, the aluminum alloy composite plate can have high strength and corrosion resistance.

[0122] Figure 2 This is a morphology diagram of the AlMnSi phase in the aluminum alloy composite plate of Example 1. Figure 2As can be seen, the AlMnSi phase is small in size and has a high number density. Therefore, by using rapid heating, high temperature for short time or medium-high temperature for long time preheating treatment and intermediate annealing process, more fine AlMnSi phases can be precipitated to the maximum extent, thereby improving the mechanical properties and anti-sagging properties of aluminum alloy composite plates before and after brazing.

[0123] Figure 3 This is a grain morphology image of the aluminum alloy composite plate after brazing in Example 1. Figure 3 As can be seen, after brazing, the core material of the aluminum alloy composite plate has a long strip-shaped large grain structure, which gives it good high-temperature mechanical properties and brazing anti-sagging properties.

[0124] Figure 4 This is a morphology diagram of the Fe-containing second phase in the core layer of the aluminum alloy composite plate in Comparative Example 1. Figure 4 As can be seen, the size distribution of the AlFeMnSi phase is not uniform.

[0125] Figure 5 This is a morphology diagram of the AlMnSi phase in the aluminum alloy composite plate of Comparative Example 1. Figure 5 As can be seen, the AlMnSi phase has a large size and a low number density.

[0126] Figure 6 The image shows the grain morphology of the aluminum alloy composite plate after brazing in Comparative Example 1. Figure 6 As can be seen, the core material of the aluminum alloy composite plate has fine grains after brazing, therefore, the anti-sagging performance of the aluminum alloy composite plate after brazing is poor.

[0127] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0128] The aluminum alloy composite plate of this application includes a core layer and skin layers stacked on both sides of the core layer. This structural design optimizes the overall performance of the aluminum alloy composite plate. In the core layer, the added Si, Fe, and Mn elements form AlFeMnSi compounds, thereby providing dispersion strengthening. Simultaneously, the solid solution strengthening of Si, Fe, and Mn elements in the matrix enhances the strength of the aluminum alloy composite plate. Controlling the Si content within the aforementioned range not only improves the strengthening effect but also prevents melting, collapse, and intergranular corrosion during brazing. The addition of Mn and Fe elements improves the formability and strength of the aluminum alloy composite plate. Furthermore, controlling the Fe content within the aforementioned range improves its formability and corrosion resistance. The addition of Mg, Si, and Cu elements facilitates natural aging after rapid cooling and placement at room temperature following brazing, resulting in the formation of fine, dispersed Mg2Si and Al2CuMg phases, among other second phases. Simultaneously, the synergistic effect of solid solution strengthening and dispersion strengthening can yield aluminum alloy composite plates with higher strength. The solid solution strengthening effect of adding Ti and Zr elements can improve the alloy's strength and promote the formation of fine, dispersed Al3Ti and Al3Zr precipitates, further enhancing the alloy's strength. Furthermore, adding Ti and Zr elements can promote the formation of coarse, elongated grains during brazing of the aluminum alloy composite plate, thereby improving its anti-sagging properties. Controlling the Ti content within the above range can alter the alloy's corrosion potential, thus improving the corrosion resistance of the aluminum alloy composite plate. In each skin layer: the added Bi element not only increases the wettability of the Si liquid phase on the aluminum alloy surface but also promotes the fluidity of the Si liquid phase, thereby improving the welding performance of the aluminum alloy composite plate. Too low a Bi content will not achieve the aforementioned performance of the aluminum alloy composite plate, while too high a Bi content not only has limited effect on further improvement but also increases costs. Therefore, controlling the Bi content within the above range can balance effectiveness and cost. Controlling the Zn content within the above range can reduce the corrosion potential of each skin layer, resulting in a potential difference ≥450mV between the diffusion layer and the skin layer after brazing of the aluminum alloy composite plate. Furthermore, the potential distribution of the diffusion layer is uniform, and the driving force of galvanic corrosion is reduced, thereby improving the corrosion resistance of the aluminum alloy composite plate. The diffusion layer is a structural layer formed by the interdiffusion of alloying elements under the influence of a concentration gradient during the brazing process between the skin and core materials. Through coordinated optimization of the above elements in the core layer and each skin layer, the mechanical properties, anti-sagging properties, and corrosion resistance of the aluminum alloy composite plate can be comprehensively improved, thus better meeting the requirements of long-term operation of offshore wind turbines.

[0129] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An aluminum alloy composite plate, characterized in that, The aluminum alloy composite plate includes a core layer and a skin layer stacked on two opposite surfaces of the core layer; The core layer comprises the following elements by weight percentage: The elements are: 0.2-0.6% Si, 0.3-0.6% Cu, 0.1-0.3% Mg, 0.2-0.6% Fe, 1.4-1.8% Mn, and the sum of the mass contents of Ti and Zr is 0.15-0.4%. The total content of unavoidable impurities is ≤0.15%, the content of a single impurity is <0.05%, and the balance is Al. By mass percentage, each of the aforementioned leather layers comprises the following elements: 9.5~12.0% Si, 0.6~1.0% Fe, 1.4~1.8% Mg, 0.05~0.25% Zn, 0.08~0.2% Bi, with a total unavoidable impurity content ≤0.15%, a single impurity content <0.05%, and the balance being Al. The potential difference between the diffusion layer formed after brazing the aluminum alloy composite plate and the skin layer is ≥450mV; Before brazing, the aluminum alloy composite plate has a tensile strength ≥220MPa, a yield strength ≥195MPa, and an elongation ≥5.5%. After brazing, the aluminum alloy composite plate has a yield strength ≥64.7MPa and a sagging resistance ≤4mm. The preparation method of the aluminum alloy composite plate includes preheating treatment and intermediate annealing; The preheating process includes: heating the composite blank to 460-490℃ at a rate of 30-80℃ / h and then holding it at that temperature for 1-6 hours; The intermediate annealing refers to direct annealing of the billet after one cold rolling or continuous intermediate annealing. The direct annealing process includes: heating the billet after the first cold rolling at 20~90℃ / h to 380~460℃ and holding it at that temperature for 0.5~3h; The continuous intermediate annealing process includes: heating the billet after the first cold rolling at 30~120℃ / s to 400~480℃ and holding it at that temperature for 60~240s, and then cooling it at 50~250℃ / s to below 100℃.

2. The aluminum alloy composite plate according to claim 1, characterized in that, The core layer comprises the following elements by weight percentage: The elements are: 0.3-0.5% Si, 0.4-0.6% Cu, 0.15-0.25% Mg, 0.2-0.4% Fe, 1.5-1.7% Mn, and the sum of Ti and Zr is 0.2-0.3% by mass. The total content of unavoidable impurities is ≤0.15%, the content of a single impurity is <0.05%, and the balance is Al. By mass percentage, each of the aforementioned leather layers comprises the following elements: 10-11.5% Si, 0.6-0.8% Fe, 1.45-1.65% Mg, 0.1-0.2% Zn, 0.1-0.15% Bi, with a total unavoidable impurity content ≤0.15%, a single impurity content <0.05%, and the balance being Al.

3. The aluminum alloy composite plate according to claim 1 or 2, characterized in that, In the core material layer, the mass ratio of Mn to Fe is 4~6:1, and / or the mass ratio of Mg to Si is 3~8:

10.

4. The aluminum alloy composite plate according to claim 1 or 2, characterized in that, The size of the AlMnSi dispersed phase in the core material layer is 100~200nm; the size of the Fe-containing second phase in the core material layer is controlled to be 1~10μm, and the area ratio of the Fe-containing second phase in the core material layer is 1.6~2.58%.

5. A method for preparing an aluminum alloy composite plate according to any one of claims 1 to 4, characterized in that, The preparation method includes: Step S1: The first leather ingot, the core ingot, and the second leather ingot are heated and rolled independently in sequence to obtain the first leather ingot layer, the core ingot layer, and the second leather ingot layer. The first leather ingot layer, the core ingot layer, and the second leather ingot layer are stacked in sequence and then subjected to composite rolling to obtain a composite billet. Step S2 involves sequentially preheating, hot roughing, and hot finishing of the composite billet to obtain a hot-rolled billet; and Step S3: The hot-rolled billet is subjected to a first cold rolling, intermediate annealing and a second cold rolling in sequence to obtain the aluminum alloy composite plate; The preheating process includes: heating the composite blank to 460-490°C at a rate of 30-80°C / h and then holding it at that temperature for 1-6 hours; The intermediate annealing refers to direct annealing of the billet after one cold rolling or continuous intermediate annealing. The direct annealing process includes: heating the billet after the first cold rolling at 20~90℃ / h to 380~460℃ and holding it at that temperature for 0.5~3h; The continuous intermediate annealing process includes: heating the billet after the first cold rolling at 30~120℃ / s to 400~480℃ and holding it at that temperature for 60~240s, and then cooling it at 50~250℃ / s to below 100℃.

6. The preparation method according to claim 5, characterized in that, The preheating process includes: heating the composite blank to 460-490℃ at a rate of 40-60℃ / h and then holding it at that temperature for 2-4 hours.

7. The preparation method according to claim 5 or 6, characterized in that, The direct annealing process includes: heating the cold-rolled billet to 400-460°C at a rate of 50-80°C / h and holding it at that temperature for 0.5-3h; and / or, the continuous intermediate annealing process includes: heating the cold-rolled billet to 440-480°C at a rate of 40-100°C / s and holding it at that temperature for 60-240s, followed by cooling it to below 100°C at a rate of 100-200°C / s.

8. The preparation method according to claim 5 or 6, characterized in that, The total processing rate of the first cold rolling is 80-90%, and / or the total processing rate of the second cold rolling is 10-25%.

9. The preparation method according to claim 5 or 6, characterized in that, Step S1 further includes: melting, casting, sawing and milling the skin alloy and the core alloy independently and sequentially to obtain skin ingots and core ingots respectively; In the casting process, antimony is used to modify the leather alloy. And / or, the single-sided milling amount of the milled surface is 15~20mm, and the difference between the longitudinal and transverse milling amounts of the milled surface is ≤2mm.

10. The preparation method according to claim 5 or 6, characterized in that, In step S1, steel strips are used to fix the stacked structure after the first skin ingot layer, the core material ingot layer and the second skin ingot layer are stacked in sequence for the composite rolling process. The thickness ratio of the first leather ingot layer, the core material ingot layer and the second leather ingot layer is 1:8 to 10:1; And / or, the widths of the first leather ingot layer and the second leather ingot layer are each independently greater than the width of the core material ingot layer, and the tolerance between the widths of the first leather ingot layer and the second leather ingot layer and the width of the core material ingot layer is 10~40mm.

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