Steel-aluminum-steel three-layer composite thin material and preparation method thereof

Abstract

The present invention relates to the technical field of lightweight materials, and more specifically, to a steel-aluminum-steel three-layer composite thin material and a preparation method thereof. The preparation method comprises: texturing and cleaning a first steel, an aluminum, and a second steel online, and then stacking and cold-rolling the composite material in sequence; performing a first online annealing process at a furnace temperature of 350-550°C and a speed of 1-10 m / min; performing a first surface cleaning process; performing cold rolling; performing a second surface cleaning process; performing a second online annealing process at a furnace temperature of 300-550°C and a speed of 1-10 m / min; performing stretch bend leveling; and performing a third surface cleaning process. The preparation method can improve the uniformity and bonding strength of the interface bonding strength of a composite plate of a layered composite material, making it less prone to cracking and delamination problems, and can eliminate internal stress and improve plasticity.

Description

Technical Field

[0001] The present invention relates to the technical field of lightweight materials, and in particular to a steel-aluminum-steel three-layer composite thin material and a preparation method thereof. Background Art

[0002] For new energy vehicles and 3C products (a general term for computers, communications and consumer electronics), the selected metal materials must meet the requirements of lightweight on the one hand and strength on the other.

[0003] Layered metal composites are new materials with broad application prospects that effectively combine the performance advantages of a single material by combining two or more layers of metal, leveraging their strengths and avoiding their weaknesses, being economical and practical, and integrating the performance attributes of two or more materials. Common preparation methods for layered metal composites include casting and rolling composites, explosive composites, rolling composites, and extrusion composites, which combine dissimilar metals to form a new type of layered composite material. Among them, rolling is one of the main preparation methods for metal laminates and has the advantage of stable and continuous production. The rolling method enables the metal sheets to be composited to break the coating on the contact surface of the dissimilar metals under the strong rolling pressure of the rolling mill, and to produce plastic flow in the entire contact surface. The fresh matrix metal squeezed out from the surface cracks comes into close contact and produces microscopic atomic reactions, and finally the contact interface between the metal layers forms a metallurgical bond of a certain strength. Compared with other methods, the rolling method has the advantages of low pollution, stable operation, and good continuity in mass production.

[0004] Layered steel-aluminum composite materials can achieve lightweighting through aluminum and ensure strength requirements through steel. However, the composite plate interface bonding strength of the layered steel-aluminum composite materials obtained by the preparation method provided by the relevant technology is uneven and has low bonding force. It is easy to crack and delaminate, has large internal stress, and has poor plasticity. Especially for ultra-thin steel-aluminum-steel composite materials of 0.1mm-0.5mm, the above problems are more significant. Summary of the Invention

[0005] The purpose of the present invention is to provide a steel-aluminum-steel three-layer composite thin material and a preparation method thereof. The preparation method can improve the uniformity and bonding strength of the interface bonding strength of the composite plate of the layered composite material, especially the ultra-thin steel-aluminum-steel composite material of 0.1mm-0.5mm, is not prone to cracking and delamination problems, and can eliminate internal stress and improve plasticity.

[0006] The present invention is achieved in that:

[0007] In a first aspect, the present invention provides a method for preparing a steel-aluminum-steel three-layer composite thin material, comprising:

[0008] The first steel, aluminum and the second steel are textured and cleaned online, and then stacked and cold-rolled in sequence;

[0009] First online annealing: the furnace temperature of the first online annealing is 350-550°C and the speed is 1-10m / min;

[0010] First surface decontamination;

[0011] cold rolling;

[0012] Second surface decontamination;

[0013] Second online annealing: the furnace temperature of the second online annealing is 300-550°C and the speed is 1-10m / min;

[0014] Bending and straightening;

[0015] The third surface decontamination.

[0016] In an optional embodiment, the furnace temperature of the first online annealing is 350-480° C. and the speed is 1-2 m / min;

[0017] The speed of the second online annealing is 1-2 m / min.

[0018] In an optional embodiment, the furnace temperature of the second online annealing is 451-550° C., and the speed of the second online annealing is at least 0.5 m / min faster than the speed of the first online annealing.

[0019] In an optional embodiment, the cold rolling step adopts a cold rolling method with multiple small deformations, and the reduction rate of a single pass is controlled to be 10-20%.

[0020] In an optional embodiment, annealing is performed when the reduction ratio of a single process reaches 30-50%, and the annealing furnace temperature is 300-550° C. and the speed is 1-10 m / min.

[0021] In an optional embodiment, when the reduction rate of a single process is less than 50%, the reduction rate of a single pass is controlled to be greater than or equal to 15% and less than or equal to 20%;

[0022] When the reduction rate of a single process is greater than 50%, the reduction rate of a single pass is controlled to be greater than or equal to 10% and less than 15%.

[0023] In an optional embodiment, the reduction ratio of the cold rolling composite is 45-65%.

[0024] In an optional embodiment, before cold rolling and cladding, when the thickness of the first steel and the second steel is 1:1 and the thickness ratio of the aluminum to the first steel is less than 1:1, the reduction ratio of the cold rolling and cladding is controlled to be greater than or equal to 45% and less than 50%;

[0025] Before cold rolling and laminating, when the thickness ratio of the first steel, aluminum, and the second steel is 1:(1-2):1, the reduction ratio of the cold rolling and laminating is controlled to be greater than or equal to 50% and less than 55%;

[0026] Before cold rolling and cladding, when the thickness of the first steel and the second steel is 1:1 and the thickness ratio of aluminum to the first steel is greater than 2:1, the reduction rate of cold rolling and cladding is controlled to be greater than or equal to 55% and less than or equal to 65%.

[0027] In an optional embodiment, when the thickness ratio of the first steel, aluminum and second steel in the finished steel-aluminum-steel three-layer composite thin material is 1:2:1, the thickness ratio of the first steel, aluminum and second steel before cold rolling and composite bonding is 1:(2.1-2.6):1.

[0028] In an optional embodiment, the speed of stretching and straightening is 5-40 m / min, the tensioning force is 5% of the yield strength of the steel-aluminum-steel composite material after the second online annealing × the cross-sectional area of ​​the steel-aluminum-steel composite material after the second online annealing ~ 20% of the yield strength of the steel-aluminum-steel composite material after the second online annealing × the cross-sectional area of ​​the steel-aluminum-steel composite material after the second online annealing, and the elongation of stretching and straightening is 0.1-0.8%.

[0029] In a second aspect, the present invention provides a steel-aluminum-steel three-layer composite thin material, which is prepared by the preparation method of the steel-aluminum-steel three-layer composite thin material of any of the aforementioned embodiments.

[0030] The present invention includes the following beneficial effects:

[0031] The preparation method of the steel-aluminum-steel three-layer composite thin material of the present invention includes two online annealings, namely the first online annealing and the second online annealing. Among them, the temperature control of the first online annealing after cold rolling and lamination is crucial to the interface bonding strength. The furnace temperature of the first online annealing is controlled to be 350-550°C and the annealing speed is 1-10m / min. At a higher temperature, online annealing is performed at a slower feeding speed so that the steel and aluminum are not overheated, thereby improving the problem of steel-aluminum-steel overheating and avoiding the problem of increasing the brittle phase at the middle interface of the composite material, thereby improving the interface bonding strength and making the interface between steel and aluminum tightly bonded. Moreover, online annealing refers to the condition that the furnace temperature is constant (for example: the first online annealing temperature is 350-550°C) and the composite material is annealed at a certain speed (for example: the first online annealing speed is 1-10m / mi n) pass through the furnace cavity, and annealing is achieved in the process of the composite material passing through the furnace cavity. Therefore, during the first online annealing, the part of the composite material entering the annealing furnace cavity will transfer heat to the part of the composite material that has not yet entered the furnace cavity, so that the composite material that has not yet entered the furnace cavity is preheated, thereby reducing the thermal shock caused by excessive temperature difference, and improving the interface bonding strength, thereby improving the performance of the composite material. By controlling the speed of the first online annealing, when the composite material leaves the annealing furnace, it is more conducive to achieving rapid, continuous and uniform cooling of the ultra-thin composite material when it leaves the annealing furnace, which can minimize surface oxidation and reduce the unstable performance caused by uneven cooling of the ultra-thin composite material. By adopting the first online annealing and reasonably controlling the temperature and speed, online preheating and rapid and uniform cooling are achieved, thereby improving the interface bonding strength of the ultra-thin composite material, reducing the annealing time and improving efficiency. The second online annealing after cold rolling is carried out at a controlled temperature of 300-550°C and a speed of 1-10m / min. Online annealing at a higher temperature and a slower speed can prevent the steel and aluminum from overheating, thereby ensuring good interface bonding. Through online preheating and continuous and uniform cooling after leaving the furnace, the rolling defects of ultra-thin composite materials can be reduced, the internal stress of the composite materials can be eliminated, the plasticity of the composite materials can be improved, the annealing time can be reduced, and the efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 Schematic diagram of the steel-aluminum-steel three-layer composite thin material prepared in Example 1 of the present invention;

[0034] Figure 2 This is a schematic diagram of the steel-aluminum-steel three-layer composite thin material prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0035] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0036] The present invention provides a method for preparing a steel-aluminum-steel three-layer composite thin material, comprising: roughening and cleaning a first steel, aluminum, and a second steel online, and stacking and cold-rolling the composite material in sequence; first online annealing; first surface decontamination; cold rolling; second surface decontamination; second online annealing; stretching and straightening; and third surface decontamination.

[0037] Optionally, the first steel, aluminum, and second steel may be coils, and their surfaces may be degreased and cleaned before lamination. The first and second steels may be stainless steels such as 304, 316, 316L, and 316Li, and the aluminum may be 1-series, 3-series, 5-series, or 6-series aluminum alloys, without specific limitation.

[0038] The thicknesses of the first steel, the second steel and the aluminum can be selected as needed. The thicknesses of the first steel and the second steel can both be 0.1-0.5 mm, for example, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm. The thickness of the aluminum can be 0.2-2 mm, for example, 0.2 mm, 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, and 2 mm, etc., which are not specifically limited here.

[0039] Due to the different properties of aluminum and steel, the deformation degree of the two is different. Aluminum is more easily deformed than steel. The present invention can select the thickness of the steel and aluminum before cold rolling and compounding according to the thickness of the target finished product, and can prepare a thinner finished steel-aluminum-steel three-layer composite thin material by optimizing the thickness of the steel and aluminum.

[0040] The inventors have discovered that during the cold rolling process, the ratio of the deformation of steel and aluminum is approximately 1:1.05-1.3. In a preferred embodiment, the thickness ratio of the first steel, aluminum, and second steel in the final steel-aluminum-steel three-layer composite thin product can be controlled to be 1:2:1. To meet this thickness ratio, before cold rolling and lamination, the thickness ratio of the first steel, aluminum, and second steel can be controlled to be 1:2×(1.05-1.3):1, for example, 1:2.1:1, 1:2.2:1, 1:2.3:1, 1:2.4:1, 1:2.5:1, 1:2.6:1, etc., without specific limitation herein. Furthermore, this thickness control facilitates the production of finished ultra-thin products with a thickness of 0.1-0.5 mm.

[0041] Optionally, in the preparation method of the present invention, online texturing, cleaning and cold rolling composite are carried out simultaneously, that is, while the first steel, aluminum and second steel are texturing, cleaning and rolling are carried out after texturing, that is, the first steel, aluminum and second steel are texturized in the front process, and the interface after texturing is cleaned in the back process, so that the first steel, aluminum and second steel corresponding to the parts where texturing is completed are immediately cleaned and immediately sent to the rolling mill for cold rolling after cleaning, instead of texturing the first steel, aluminum and second steel separately, cleaning them separately, and then stacking them up and cold rolling them compositely. The entire texturing, cleaning and cold rolling composite process is carried out continuously and synchronously, and the texturing adopts online texturing, and the texturing speed is the same as the cold rolling composite speed. Compared with the process of texturing first, cleaning, and cold rolling composite, the efficiency is fully improved.

[0042] Of course, in other embodiments, the first steel, aluminum, and second steel may be textured separately, cleaned separately, and then stacked and cold-rolled together.

[0043] The texturing process is crucial for interfacial adhesion. Maintaining a certain level of roughness and cleanliness on the textured surface—that is, reducing dirt and debris—helps improve the interfacial adhesion of composite materials. The texturing roughness significantly impacts the performance of the finished thin composite material. Optionally, the texturing roughness can range from Ra1-6 (e.g., 1, 2, 3, 4, 5, 6, etc., not specifically limited here). For ultra-thin materials, minimizing roughness while maintaining interfacial adhesion can mitigate poor interface flatness caused by excessive roughness, thereby reducing adverse effects on the interface quality of the ultra-thin material, improving the inability to precisely control the layer thickness ratio, and addressing performance deviations and unevenness at different locations on the ultra-thin material. Furthermore, it can address issues such as low interfacial adhesion and prone to delamination and cracking.

[0044] In a preferred embodiment, the roughness of the texturing is controlled to be Ra2-4; in this way, good interface bonding strength can be ensured, so that the composite thin material is not prone to delamination and cracking.

[0045] It should be noted that the method of regulating the roughness of the hair texture is similar to that of related technologies, for example, by controlling the thickness of the bristles of the brush, etc., which will not be described in detail here.

[0046] It should also be noted that the texturing process requires texturing four surfaces at the same time, namely the lower surface of the first steel (the surface where the first steel is bonded to the aluminum), the two surfaces of the aluminum (the surfaces where the aluminum is bonded to the first steel and the second steel respectively), and the upper surface of the second steel (the surface where the second steel is bonded to the aluminum).

[0047] Optionally, you can use emery cloth to remove fine grains from the roughened surface, combine this with dust removal in a negative pressure, and install an air knife to blow the roughened surface to ensure a clean surface. Without the air knife, there may be noticeable particles remaining on the roughened surface; with the air knife, there will be no noticeable particles remaining on the roughened surface.

[0048] Optionally, the cold rolling composite process can adopt a four-roll mill for cold rolling, and the reduction rate is crucial to the interface bonding strength; among them, too small a reduction rate will make the material unable to be composited or the bonding strength after composited low, while too large a reduction rate will cause the surface of the material to crack due to the different plasticity of steel and aluminum; the reduction rate of the present invention is controlled to be 45-65%, which can ensure the composite interface bonding strength while avoiding the surface cracking of the material.

[0049] The inventors further discovered that using different reduction ratios for steel and aluminum materials of varying thickness can further ensure the quality of the finished product. Steel is more difficult to deform than aluminum, so when steel and aluminum composites of varying thicknesses are combined, they have varying degrees of difficulty in deformation. The reduction ratio can be controlled based on the thickness of the composite material.

[0050] Before cold rolling and laminating, when the thickness of the first steel and the second steel is 1:1 and the thickness ratio of the aluminum to the first steel is less than 1:1, the reduction ratio of the cold rolling and laminating process is controlled to be greater than or equal to 45% and less than 50%. This cold rolling and laminating process has the following advantages: 1. High dimensional accuracy. The cold rolling and laminating process is carried out at room temperature, and the material expands and contracts with heat. Therefore, the dimensional accuracy of the product is higher. 2. Good surface quality. The temperature of the material and the rollers is low during the cold rolling and laminating process, which is less likely to cause surface quality problems such as roller sticking. 3. Good material properties. The cold rolling and laminating temperature is low (room temperature), so the material can retain its original microstructure, and the mechanical properties of the product are more uniform and stable. 4. Excellent composite properties. The cold rolling and laminating process does not form brittle compounds between the multiple metal layers. The degree of diffusion can be precisely controlled through subsequent diffusion control, resulting in better composite properties. 5. Low equipment requirements. The cold rolling and laminating process does not require a heating device, which reduces equipment investment and maintenance costs, makes process control easier, and improves stability.

[0051] Before cold rolling and cladding, when the thickness ratio of the first steel, aluminum, and second steel is 1:(1-2):1, the reduction rate of cold rolling and cladding is controlled to be greater than or equal to 50 and less than 55%; in this way, it can ensure that the composite material is better bonded and there are no cracks on the surface.

[0052] Before cold rolling and cladding, when the thickness of the first steel and the second steel is 1:1 and the thickness ratio of aluminum to the first steel is greater than 2:1, the reduction rate of the cold rolling and cladding is controlled to be greater than or equal to 55% and less than or equal to 65%; in this way, it can ensure that the composite material is better bonded and there are no cracks on the surface.

[0053] In the present invention, the furnace temperature of the first online annealing is 350-550° C., and the speed is 1-10 m / min; the furnace temperature of the second online annealing is 300-550° C., and the speed is 1-10 m / min.

[0054] The temperature control of the first online annealing after cold rolling and compounding is crucial to the interface bonding strength. The furnace temperature of the first online annealing is controlled to be 350-550℃ and the annealing speed is 1-10m / min. At a higher temperature, online annealing is carried out at a slower speed so that the steel and aluminum are not overheated, which can improve the problem of steel-aluminum overheating and avoid the problem of increasing the brittle phase at the interface between the composite material, thereby improving the interface bonding strength and making the interface between steel and aluminum tightly bonded. Moreover, online annealing refers to the condition that the furnace temperature is constant (for example: the first online annealing temperature is 350-550℃), so that the composite material passes through the furnace cavity at a certain speed (for example: the first online annealing speed is 1-10m / min), and annealing is achieved in the process of the composite material passing through the furnace cavity, that is, the annealing method of the present invention is different from the related technology. After the temperature of the annealing furnace is raised to the target temperature, the composite material is placed in the furnace cavity as a whole and maintained for the set time. Therefore, the present invention, during the first online annealing, the composite material portion entering the annealing furnace cavity will transfer heat to the composite material portion that has not yet entered the furnace cavity, so that the composite material that has not yet entered the furnace cavity is preheated, so as to reduce the thermal shock caused by the excessive temperature difference, and improve the interface bonding strength, improve the performance of the composite material, by controlling the speed of the first online annealing, when the composite material leaves the annealing furnace, it is more conducive to achieving rapid, continuous and uniform cooling of the ultra-thin composite material when it leaves the annealing furnace, which can minimize surface oxidation and reduce the unstable performance caused by uneven cooling of the ultra-thin composite material, by adopting the first online annealing and reasonably controlling the temperature and speed, achieving online preheating, rapid and uniform cooling, and improving the interface bonding strength of the ultra-thin composite material. The second online annealing after cold rolling is controlled at a temperature of 300-550 ° C and a speed of 1-10 m / min. At a higher temperature, annealing at a slower speed online can prevent the steel and aluminum from overheating, thereby ensuring good interface bonding strength. By online preheating and continuous and uniform cooling after leaving the furnace, it is possible to reduce rolling defects of the ultra-thin composite material, eliminate the internal stress of the composite material, and improve the plasticity of the composite material.

[0055] Compared with related technologies that use vacuum or box annealing, online annealing can also make the properties of the composite material more uniform, thereby making the properties of the entire coil uniform; moreover, the online annealing method can shorten the annealing time to improve efficiency and can also monitor the surface quality of the material.

[0056] It should be noted that the temperature of the first online annealing can be 350°C, 380°C, 400°C, 420°C, 450°C, 480°C, 500°C, 530°C, 550°C, etc., and the speed can be 1m / min, 1.2m / min, 1.5m / min, 1.7m / min, 2m / min, 3m / min, 4m / min, 5m / min, 6m / min, 7m / min, 8m / min, 9m / min, 10m / min, etc., and there is no specific limitation here. The temperature of the second online annealing can be 300°C, 320°C, 350°C, 380°C, 400°C, 420°C, 450°C, 470°C, 500°C, 530°C, 550°C, etc., and the speed can be 1m / min, 1.2m / min, 1.5m / min, 1.7m / min, 2m / min, 3m / min, 4m / min, 5m / min, 6m / min, 7m / min, 8m / min, 9m / min, 10m / min, etc., which are not specifically limited here.

[0057] Optionally, the length of the annealing furnace for at least one of the first online annealing and the second online annealing may be 6 m.

[0058] In a preferred embodiment, the first online annealing process is performed at a furnace temperature of 350-480°C and a speed of 1-2 m / min; the second online annealing process is performed at a speed of 1-2 m / min. This can further enhance the bonding strength of the composite material interface and effectively reduce internal stress.

[0059] Furthermore, the furnace temperature for the first online annealing is 350-450°C, and the furnace temperature for the second online annealing is 451-550°C. The second online annealing speed is at least 0.5 m / min faster than the first online annealing speed. This is beneficial for interlayer bonding, effectively improving interfacial bonding strength, and is conducive to efficiently eliminating internal stress and improving plasticity.

[0060] The preparation method of the present invention does not need to clean the material with liquid cleaning agents such as water before performing the first online annealing, so as to prevent liquid cleaning agents such as water from entering the interface of the composite material and causing a decrease in the interfacial bonding strength; cleaning is performed after the first online annealing forms a tight metallurgical bond at the interface of the composite material. However, in order to further improve the interfacial bonding strength and to improve the surface strength of the material after annealing, emery cloth can be added to the annealing furnace mouth to wipe the composite material with emery cloth before the composite material enters the annealing furnace to reduce dirt such as oil. There is no requirement for the roughness of the emery cloth, as long as it can wipe off the oil and other dirt.

[0061] Optionally, a cooling device can be configured downstream of the first online annealing process to cooperate with the online annealing. The cooling device can be a uniform water cooling device so as to uniformly cool the composite material leaving the annealing furnace of the first online annealing in a timely manner, that is, the composite thin material can be cooled to room temperature more quickly and evenly after leaving the furnace, so as to reduce surface oxidation of the composite material and improve the problem of unstable performance caused by uneven cooling.

[0062] Optionally, in some embodiments, the steps of cold rolling, second surface decontamination and second online annealing can be added, that is, after the previous second online annealing step, the steps of cold rolling, second surface decontamination and second online annealing are repeated until the thickness of the steel-aluminum-steel three-layer composite material obtained after cold rolling reaches the target thickness.

[0063] Thin composite materials are prone to surface wrinkling and other issues, making it difficult for existing layered metal composite materials to achieve thicknesses of 0.2-0.5mm. The inventors have discovered that by employing multiple cold rolling processes with small deformations and controlling the reduction rate per pass to 10-20% (e.g., 10%, 12%, 15%, 17%, 20%, etc., without specific limitations), the composite material's elongation can be gradually increased during these multiple cold rolling processes, thereby reducing the quality issue of wrinkling. Furthermore, by employing multiple cold rolling processes with small deformations and controlling the reduction rate per pass to be small, gradually accumulating smaller reduction rates until the composite material reaches the target thickness, followed by in-line annealing, the composite material's plasticity can be maintained.

[0064] Rolling will harden the material, while the annealing process can soften the material. In order to further improve the plasticity of the composite material and increase the elongation, an annealing step can be added during the cold rolling step. During multiple small deformation cold rolling processes, the greater the total reduction rate, the harder the composite material and the lower the elongation. When the reduction rate of a single process reaches 30-50% (for example: 30%, 40%, 50%, etc., not specifically limited here), online annealing is carried out, and the annealing furnace temperature is 300-550℃ (for example: 300℃, 320℃, 350℃, 380℃, 400℃, 420℃, 450℃, 470℃, 500℃, 530℃, 550℃, etc.). , not specifically limited herein), with a speed of 1-10 m / min (for example, 1 m / min, 1.2 m / min, 1.5 m / min, 1.7 m / min, 2 m / min, 3 m / min, 4 m / min, 5 m / min, 6 m / min, 7 m / min, 8 m / min, 9 m / min, 10 m / min, etc., not specifically limited herein), the composite material can be softened, internal stress can be eliminated, and elongation can be increased.

[0065] When the reduction rate of a single process reaches 30-50%, adding an online annealing step not only ensures the elongation, but also ensures the surface quality of the composite material. If the reduction rate of a single process is greater than 50%, the plasticity of the composite material is greatly reduced, and even with annealing, it is difficult to ensure that there will be no fine horizontal lines on the surface of the composite material.

[0066] In some embodiments, multiple online annealing steps can be added to the cold rolling step. For example, each time the single process reduction rate reaches 30-50%, online annealing is performed, and after the annealing is completed, cold rolling is performed again, and the reduction rate is accumulated from the beginning. When the single process reduction rate reaches 30-50% again, online annealing is performed again, and the cold rolling and annealing steps are repeated again after the annealing is completed. This cycle is repeated until the thickness of the composite material reaches the target thickness. The more annealing times during the cold rolling process, the lower the material hardness and the greater the elongation, which is conducive to obtaining a composite thin material with good surface quality.

[0067] It should be noted that the above-mentioned single-process reduction rate is the cumulative deformation of the plate after multiple single-pass rolling. For example, the deformation of the composite plate after three-pass rolling is compared with the deformation before cold rolling.

[0068] Optionally, to obtain high-quality layered composite thin materials, the reduction rate per pass can be controlled in stages during cold rolling; when the reduction rate per pass is less than 50%, the reduction rate per pass is controlled to be greater than or equal to 15% and less than or equal to 20%; when the reduction rate per pass is greater than 50%, the reduction rate per pass is controlled to be greater than or equal to 10% and less than 15%. When the reduction rate per pass is less than 50%, the overall thickness of the composite sheet is relatively large, while when the reduction rate per pass is greater than 50%, the overall thickness of the composite sheet is relatively thin. When the thickness of the composite sheet is relatively thick, a larger reduction rate per pass can improve rolling efficiency. When the composite sheet has been rolled to a relatively thin state, a smaller reduction rate per pass can gradually roll the composite sheet to the target thickness, while ensuring the quality of the composite sheet, reducing cracks, and ensuring that the ultra-thin steel-aluminum-steel three-layer composite sheet has a high elongation.

[0069] The stretching and straightening steps have a great influence on the surface quality of ultra-thin composite sheets. Controlling the process parameters of stretching and straightening can not only ensure the surface flatness of ultra-thin composite sheets, but also ensure the surface quality. Moreover, the yield strength, thickness and elongation of the composite material have a significant impact on the straightening effect. Among them, the greater the yield strength and thickness of the composite material and the smaller the elongation, the greater the required straightening parameters. Therefore, when selecting the process parameters of stretching and straightening, the above factors should be fully considered.

[0070] Optionally, the speed of the stretch bending straightening is 5-40 m / min (for example, 5 m / min, 10 m / min, 15 m / min, 20 m / min, 25 m / min, 30 m / min, 35 m / min, 40 m / min, etc., which are not specifically limited herein), and the tensioning force is 5-20% (for example, 5%, 7%, 9%, 10%, 13%, 15%, 17%, 20%, etc., which are not specifically limited herein) of the yield strength of the steel-aluminum-steel composite material after the second online annealing. The product of the cross-sectional area of ​​the composite material (i.e., tensioning force = 5% of the yield strength of the composite material × the cross-sectional area of ​​the composite material ~ 20% of the yield strength × the cross-sectional area of ​​the composite material), the elongation of the stretch and bend straightening is 0.1-0.8% (for example: 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, etc., not specifically limited here); under the above stretch and bend straightening process parameters, the quality of the ultra-thin composite material after straightening can be ensured, and if the above stretch and bend straightening parameters are too large or too small, the straightening quality of the material will be reduced.

[0071] It should be noted that the cross-sectional area of ​​the above-mentioned composite material refers to the product of the sum of the thicknesses of the first steel, aluminum and second steel (i.e., the thickness of the composite material) and the width of the composite material, wherein the extension direction of the width of the composite material is perpendicular to the direction from the first steel to the second steel.

[0072] Optionally, the first surface decontamination, the second surface decontamination and the third surface decontamination are similar in manner, wherein surface decontamination has a great influence on the surface quality and appearance of the composite material, and it is necessary to control the brushing speed, grinding wheel pressure, grinding wheel replacement frequency and cleaning fluid replacement frequency, etc. Taking the influence of the grinding wheel pressure on the quality of the composite material as an example, when the grinding wheel pressure is large, the composite material surface has obvious scratches and causes discoloration on the composite material surface; when the grinding wheel pressure is small, the decontamination effect is poor and there are residual dirt; when the grinding wheel pressure is moderate, it can be effectively decontaminated and a composite material with good surface quality can be obtained. Any of the above surface decontamination is for decontamination of the entire surface of the composite thin material.

[0073] It should be noted that the specific pressure parameters of the above-mentioned grinding wheel pressure, such as large, small and moderate, are similar to those of the relevant technologies, and in the surface decontamination step, the brushing speed, the frequency of grinding wheel replacement and the frequency of cleaning liquid replacement can also refer to the relevant technologies and will not be repeated here.

[0074] The present invention is described in further detail below with reference to the examples.

[0075] Example 1

[0076] The first steel, aluminum, and second steel were textured and cleaned online, then layered and cold-rolled. The original thickness of the first and second steels was 0.4mm, and the original thickness of the aluminum was 0.88mm. Before cold rolling, the thickness of the three-layer steel-aluminum-steel composite was 1.68mm. The roughness after textured was Ra 4. During post-texturing cleaning, an air knife was used to clean the surface. The cold rolling reduction was 65%, resulting in a thickness of 0.588mm for the three-layer steel-aluminum-steel composite.

[0077] The first online annealing process has a furnace temperature of 450° C. and a speed of 1 m / min.

[0078] First surface decontamination.

[0079] Cold rolling; it is divided into 9 rolling passes, the reduction rate of each of the first 5 rolling passes is 15%, and after the fifth rolling, the deformation of a single process is between 30-50%. After annealing at a furnace temperature of 550°C and a speed of 2m / min, the subsequent 4 rolling passes are carried out, and the reduction rate of each of the subsequent 4 passes is 10%.

[0080] Second surface decontamination.

[0081] The second online annealing process has a furnace temperature of 550° C. and a speed of 1.5 m / min.

[0082] The stretch bending straightening is carried out at a speed of 5 m / min and a tensioning force of 5% of the yield strength of the steel-aluminum-steel composite material after the second online annealing × the cross-sectional area of ​​the steel-aluminum-steel composite material after the second online annealing; the elongation is 0.1%.

[0083] The third surface decontamination.

[0084] The prepared steel-aluminum-steel three-layer composite material has tight interlayer bonding without cracking or delamination problems (such as Figure 1 The hardness of the composite thin material was tested, and the test results are shown in Table 1.

[0085] Table 1

[0086]

[0087] Example 2

[0088] The difference between Example 2 and Example 1 is that: before cold rolling composite, the thickness of the first steel and the second steel is 0.2 mm, and the thickness ratio of aluminum to steel is 1:1; the reduction rate of cold rolling composite is 50%; the roughness after online texturing is Ra 6; the first online annealing, the furnace temperature of the first online annealing is 550°C, and the speed is 10 m / min; the second online annealing, the furnace temperature of the second online annealing is 550°C, and the speed is 10 m / min; during cold rolling, the reduction rate of each pass is 18%; the speed of stretching and straightening is 20 m / min, and the tensioning force is 10% of the yield strength of the steel-aluminum-steel composite material after the second online annealing × the cross-sectional area of ​​the steel-aluminum-steel composite material after the second online annealing; the elongation is 0.5%; please refer to Example 1 for other process parameters.

[0089] The prepared steel-aluminum-steel three-layer composite thin material has tight interlayer bonding and no cracking or delamination problems. The hardness of the composite thin material was tested, and the test results are shown in Table 2. The temperature and speed of the two online annealings in Example 2 are the same, and the single-pass reduction rate during cold rolling is 18% (that is, the single-pass reduction rate is still 18% after the single-process reduction rate reaches 50%), resulting in the hardness and yield strength of the prepared composite material being slightly worse than the composite material in Example 1.

[0090] Table 2

[0091]

[0092] Example 3

[0093] The difference between Example 3 and Example 1 is that before cold rolling and laminating, the thickness of the first steel and the second steel is 2 mm, and the thickness ratio of aluminum to steel is 2:1; the reduction rate of cold rolling and laminating is 54%; the first online annealing, the furnace temperature of the first online annealing is 350°C, and the speed is 5 m / min; the second online annealing, the furnace temperature of the second online annealing is 300°C, and the speed is 4 m / min; please refer to Example 1 for other process parameters.

[0094] The prepared steel-aluminum-steel three-layer composite thin material has tight interlayer bonding, no cracking or delamination problems, and relatively poor internal stress elimination effect, that is, poor plasticity and poor elongation data; the hardness of the composite thin material was tested, and the test results are shown in Table 3; the temperature and speed of the second online annealing are lower than those of the first online annealing, and the elongation of the composite material is somewhat lower than that of Example 1.

[0095] Table 3

[0096]

[0097] Example 4

[0098] The difference between Example 4 and Example 1 is that before cold rolling and bonding, the thickness of the first steel and the second steel is 1 mm, and the thickness ratio of aluminum to steel is 3:1; the reduction rate of cold rolling and bonding is 55%; the first online annealing, the furnace temperature of the first online annealing is 480°C, and the speed is 2 m / min; the second online annealing, the furnace temperature of the second online annealing is 480°C, and the speed is 2 m / min; please refer to Example 1 for other process parameters.

[0099] The prepared steel-aluminum-steel three-layer composite material has tight interlayer bonding and no cracking or delamination. The composite material was subjected to hardness testing, and the test results are shown in Table 4. By optimizing the temperatures of the first online annealing and the second online annealing, the hardness of the composite material is better than that of Example 2. However, since the temperature and speed of the two annealing processes are the same and the initial thickness of the raw materials before cold rolling is relatively large, the finished product performance (i.e., ductility) of the composite material is slightly worse than that of Examples 1 and 2.

[0100] Table 4

[0101]

[0102] Example 5

[0103] The difference between Example 5 and Example 1 lies in the total thickness of the first steel, the second steel and the aluminum (the ratio of the three refers to Example 1), and the cold rolling step.

[0104] The initial total thickness of the first steel, the second steel, and the aluminum is 0.85 mm. The cold rolling in Example 5 is divided into 9 rolling passes, and the thickness (mm) of the composite material changes from 0.85 to 0.75 to 0.65 to 0.58 to 0.47 to 0.41 to 0.33 to 0.27 to 0.23 to 0.2. No annealing is added during the cold rolling process. For other process parameters, please refer to Example 1.

[0105] The prepared steel-aluminum-steel three-layer composite thin material has tight interlayer bonding without cracking or delamination. The hardness of the composite thin material was tested, and the test results are shown in Table 5. There was no annealing during the cold rolling process, and the elongation of the prepared composite material was slightly poor.

[0106] Table 5

[0107]

[0108] Example 6

[0109] The difference between Example 6 and Example 1 lies in the total thickness of the first steel, the second steel and the aluminum (the ratio of the three refers to Example 1), and the cold rolling step.

[0110] The initial total thickness of the first steel, the second steel, and the aluminum is 0.85 mm. The cold rolling in Example 6 is divided into 9 rolling passes, and the thickness (mm) of the composite material changes as follows: 0.85 → 0.75 → 0.65 → 0.58 → 0.47 → 0.41 → adding an annealing step (annealing furnace temperature of 300° C., annealing speed of 5 m / min) → 0.33 → 0.27 → 0.23 → 0.2, and annealing is added during the cold rolling process. For other process parameters, please refer to Example 1.

[0111] The prepared steel-aluminum-steel three-layer composite thin material has tight interlayer bonding without cracking or delamination. The hardness of the composite thin material was tested, and the test results are shown in Table 6. Adding annealing during the cold rolling process can ensure that the hardness and elongation of the composite material are better.

[0112] Table 6

[0113]

[0114] Example 7

[0115] The difference between Example 7 and Example 1 is that before cold rolling and cladding, the thickness of the first steel and the second steel is 1 mm, and the thickness ratio of aluminum to steel is 1:2; the reduction rate of cold rolling and cladding is 45%; other process parameters refer to Example 1.

[0116] The prepared steel-aluminum-steel three-layer composite thin material has tight interlayer bonding without cracking or delamination. The hardness of the composite thin material was tested, and the test results are shown in Table 7.

[0117] Table 7

[0118]

[0119] Comparative Example 1

[0120] The difference between Comparative Example 1 and Example 1 is that the first online annealing and the second online annealing are replaced by box annealing, wherein the furnace temperature of the first box annealing after cold rolling and lamination is 450°C and the holding time is 1 hour; the furnace temperature of the second box annealing after cold rolling is 550°C and the holding time is 1 hour; other process parameters refer to Example 1.

[0121] The prepared steel-aluminum-steel three-layer composite material has poor interlayer bonding and cracks (such as Figure 2 As shown in the figure, there are obvious cracks), delamination (poor bonding strength of the composite material). The composite thin material was tested for hardness, and the test results are shown in Table 8. However, the performance of the prepared composite material was not uniform, that is, some areas of the composite material could not achieve the performance shown in the table below.

[0122] Table 8

[0123]

[0124] Comparative Example 2

[0125] The difference between Comparative Example 2 and Example 1 is that only the first online annealing is performed and the second online annealing is omitted; other process parameters refer to Example 1.

[0126] The prepared steel-aluminum-steel three-layer composite thin material has relatively tight interlayer bonding, but poor ductility and plasticity. The hardness of the composite thin material was tested, and the test results are shown in Table 9.

[0127] Table 9

[0128]

[0129] Comparative Example 3

[0130] The difference between Comparative Example 3 and Example 1 is that only the second online annealing is performed and the first online annealing is omitted; other process parameters refer to Example 1.

[0131] The prepared steel-aluminum-steel three-layer composite thin material cracks when bent and has poor bonding effect.

[0132] The hardness of the composite thin material was tested, and the test results are shown in Table 10.

[0133] Table 10

[0134]

[0135] Comparative Example 4

[0136] The difference between Comparative Example 4 and Example 1 is that the temperature of the first online annealing is 600° C. and the speed is 5 m / min; the temperature of the second online annealing is 600° C. and the speed is 5 m / min; other process parameters refer to Example 1.

[0137] Although the prepared steel-aluminum-steel three-layer composite thin material does not crack when bent, the bonding strength is reduced due to overheating. The hardness of the composite thin material is tested, and the test results are shown in Table 11.

[0138] Table 11

[0139]

[0140] Comparative Example 5

[0141] The difference between Comparative Example 5 and Example 1 is that the temperature of the first online annealing is 200° C. and the speed is 5 m / min; the temperature of the second online annealing is 200° C. and the speed is 5 m / min; other process parameters refer to Example 1.

[0142] Although the prepared steel-aluminum-steel three-layer composite thin material does not crack when bent, its bonding strength is poor, and the hardness of steel and aluminum changes little, and work hardening is obvious. The hardness of the composite thin material was tested, and the test results are shown in Table 12.

[0143] Table 12

[0144]

[0145] Comparative Example 6

[0146] The difference between Comparative Example 6 and Example 1 is that the reduction ratio of the cold-rolled composite is 70%; the other process parameters refer to Example 1.

[0147] The surface of the prepared steel-aluminum-steel three-layer composite thin material has obvious cracks.

[0148] Comparative Example 7

[0149] The difference between Comparative Example 7 and Example 1 is that the reduction ratio of the cold-rolled composite is 40%; the other process parameters refer to Example 1.

[0150] The prepared steel-aluminum-steel three-layer composite thin material has poor bonding and cannot form a stable composite structure.

[0151] Comparative Example 8

[0152] Comparative Example 8 differs from Example 1 in that the prepared three-layer composite material is aluminum-steel-aluminum; other process parameters refer to Example 1. The surface hardness of the aluminum-steel-aluminum three-layer composite material in Comparative Example 8 is 52 HV, which is much lower than the surface hardness of the steel-aluminum-steel material in Example 1.

[0153] In summary, the steel-aluminum-steel three-layer composite thin material and its preparation method of the present invention can improve the uniformity and bonding strength of the composite plate interface of the layered composite material, is less likely to have cracking and delamination problems, and can eliminate internal stress and improve plasticity.

[0154] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a steel-aluminum-steel three-layer composite thin material, characterized in that: Used to prepare 0.1mm-0.5mm ultra-thin steel-aluminum-steel composite materials, the preparation method of the steel-aluminum-steel three-layer composite thin material includes: The first steel, aluminum and the second steel are textured and cleaned online, and then stacked and cold-rolled in sequence; Before the cold rolling and cladding, when the thickness of the first steel and the second steel is 1:1 and the thickness ratio of the aluminum to the first steel is less than 1:1, the reduction ratio of the cold rolling and cladding is controlled to be greater than or equal to 45% and less than 50%; Before the cold rolling and cladding, when the thickness ratio of the first steel, the aluminum, and the second steel is 1:(1-2):1, the reduction rate of the cold rolling and cladding is controlled to be greater than or equal to 50% and less than 55%; Before the cold rolling and cladding, when the thickness of the first steel and the second steel is 1:1 and the thickness ratio of the aluminum to the first steel is greater than 2:1, the reduction ratio of the cold rolling and cladding is controlled to be greater than or equal to 55% and less than or equal to 65%; When the thickness ratio of the first steel, the aluminum, and the second steel in the finished steel-aluminum-steel three-layer composite thin material is 1:2:1, the thickness ratio of the first steel, the aluminum, and the second steel before the cold rolling composite material is 1:(2.1-2.6):1; First online annealing, wherein the furnace temperature of the first online annealing is 350-480° C. and the speed is 1-2 m / min; First surface decontamination; Cold rolling: The cold rolling step adopts a cold rolling method with multiple small deformations, and the reduction rate of a single pass is controlled to be 10-20%; when the reduction rate of a single process is less than 50%, the reduction rate of the single pass is controlled to be greater than or equal to 15% and less than or equal to 20%; when the reduction rate of a single process is greater than 50%, the reduction rate of the single pass is controlled to be greater than or equal to 10% and less than 15%; Second surface decontamination; A second online annealing process, wherein the furnace temperature of the second online annealing process is 451-550° C., the speed is 1-2 m / min, and the speed of the second online annealing process is at least 0.5 m / min faster than the speed of the first online annealing process; Bending and straightening; The third surface decontamination.

2. The method for preparing the steel-aluminum-steel three-layer composite thin material according to claim 1, characterized in that: The speed of the stretching and straightening is 5-40m / min, the tensioning force is 5% of the yield strength of the steel-aluminum-steel composite material after the second online annealing × the cross-sectional area of ​​the steel-aluminum-steel composite material after the second online annealing ~ 20% of the yield strength of the steel-aluminum-steel composite material after the second online annealing × the cross-sectional area of ​​the steel-aluminum-steel composite material after the second online annealing, and the elongation of the stretching and straightening is 0.1-0.8%.

3. A steel-aluminum-steel three-layer composite thin material, characterized in that: The steel-aluminum-steel three-layer composite thin material is prepared by the preparation method of any one of claims 1-2.

Images