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

Abstract

The invention relates to the technical field of lightweight materials, in particular to a steel-aluminum-steel three-layer composite thin material and a preparation method thereof. The preparation method comprises the steps that first steel, aluminum and second steel are subjected to online roughening and cleaning and are sequentially laminated, cold-rolled and compounded; the furnace temperature of the first online annealing is 350-550 DEG C, and the speed of the first online annealing is 1-10 m / min; carrying out primary surface decontamination; cold rolling; carrying out secondary surface decontamination; the furnace temperature of the second online annealing is 300-550 DEG C, and the speed of the second online annealing is 1-10 m / min; stretch bending and straightening; and performing surface decontamination for the third time. According to the preparation method, the uniformity and binding force of the interface bonding strength of the composite board of the layered composite material can be improved, the problems of cracking and layering are not prone to occurring, internal stress can be eliminated, and plasticity can be improved.

Description

Technical Field

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

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

[0003] The laminated metal composite material combines the performance advantages of single materials effectively through the combination of two or more layers of metals, making the best use of advantages and avoiding disadvantages, being economical and practical, and integrating the performance attributes of two or more materials. It is a new material with broad application prospects. Common preparation methods of laminated metal composite materials include casting-rolling composite, explosive composite, rolling composite, extrusion composite, etc., which combine dissimilar metals to form a new type of laminated composite material. Among them, the rolling method is one of the main preparation methods of metal laminates, with the advantage of stable and continuous production. The rolling method can break the coating film on the contact surface of dissimilar metals under the strong rolling pressure of the rolling mill, and generate plastic flow within the entire contact surface. The fresh matrix metal extruded from the surface cracks comes into close contact and then undergoes microscopic atomic reactions, and finally a metallurgical bond with a certain strength is formed at the metal layer interface. Compared with other methods, the rolling method has the advantages of low pollution, stable operation, and good batch production continuity.

[0004] The laminated steel-aluminum composite material can achieve lightweight through aluminum and ensure the strength requirements through steel. However, the composite plate interface of the laminated steel-aluminum composite material prepared by the preparation methods provided by the related technologies has uneven bonding strength and low bonding force, is prone to cracking and delamination, has large internal stress, and poor plasticity. Especially for the 0.1mm - 0.5mm ultra-thin steel-aluminum-steel composite material, 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 sheet and a preparation method thereof. The preparation method can improve the uniformity and bonding force of the composite plate interface of the laminated composite material, especially the 0.1mm - 0.5mm ultra-thin steel-aluminum-steel composite material, is not prone to cracking and delamination problems, and can eliminate internal stress and improve plasticity.

[0006] The present invention is implemented as follows: In a first aspect, the present invention provides a preparation method of a steel-aluminum-steel three-layer composite thin sheet, including: Subjecting the first steel, aluminum, and the second steel to online surface texturing and cleaning, and then laminating and cold rolling them in sequence for composite; The first online annealing, the furnace temperature of the first online annealing is 350 - 550 °C, and the speed is 1 - 10 m / min; The first surface decontamination; Cold rolling; The second surface decontamination; The second online annealing, the furnace temperature of the second online annealing is 300 - 550 °C, and the speed is 1 - 10 m / min; Tension leveling; The third surface decontamination.

[0007] In an alternative embodiment, the furnace temperature of the first online annealing is 350 - 480 °C, and the speed is 1 - 2 m / min; The speed of the second online annealing is 1 - 2 m / min.

[0008] In an alternative 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.

[0009] In an alternative embodiment, the cold rolling step adopts a cold rolling method with multiple small deformations, and the reduction rate per pass is controlled to be 10 - 20%.

[0010] In an alternative embodiment, when the reduction rate of a single process reaches 30 - 50%, annealing is performed, and the furnace temperature of the annealing is 300 - 550 °C, and the speed is 1 - 10 m / min.

[0011] In an alternative embodiment, when the reduction rate of a single process 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 of a single process is greater than 50%, the reduction rate per pass is controlled to be greater than or equal to 10% and less than 15%.

[0012] In an alternative embodiment, the reduction rate of cold rolling composite is 45 - 65%.

[0013] In an alternative embodiment, before cold rolling composite, when the thickness ratio of the first steel and the second steel is 1:1 and the thickness ratio of aluminum to the first steel is less than 1:1, the reduction rate of cold rolling composite is controlled to be greater than or equal to 45% and less than 50%; Before cold rolling composite, when the thickness ratio of the first steel, aluminum and the second steel is 1:(1 - 2):1, the reduction rate of cold rolling composite is controlled to be greater than or equal to 50% and less than 55%; Before cold rolling composite, when the thickness ratio 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 composite is controlled to be greater than or equal to 55% and less than or equal to 65%.

[0014] In an alternative embodiment, when the thickness ratio of the first steel, aluminum, and the second steel in the finished steel-aluminum-steel three-layer composite sheet is 1:2:1, the thickness ratio of the first steel, aluminum, and the second steel before cold rolling and lamination is 1:(2.1 - 2.6):1.

[0015] In an alternative embodiment, the speed of stretcher-leveling is 5 - 40 m / min, the tension force is 5% × the cross-sectional area of the steel-aluminum-steel composite material after the second online annealing ~ 20% × the cross-sectional area of the steel-aluminum-steel composite material after the second online annealing of the yield strength of the steel-aluminum-steel composite material after the second online annealing, and the elongation of stretcher-leveling is 0.1 - 0.8%.

[0016] In a second aspect, the present invention provides a steel-aluminum-steel three-layer composite sheet, which is prepared by the preparation method of the steel-aluminum-steel three-layer composite sheet according to any one of the foregoing embodiments.

[0017] The present invention has the following beneficial effects: The preparation method of the steel-aluminum-steel three-layer composite thin sheet 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 composite is crucial for the interfacial bonding force. The furnace temperature of the first online annealing is controlled at 350-550°C, and the annealing speed is 1-10 m / min. At a relatively high temperature, annealing online at a slower feeding speed can prevent the steel and aluminum from overheating, thus improving the problem of overheating of the steel-aluminum-steel, avoiding the problem of increased brittle phases at the middle interface of the composite material, and thereby enhancing the interfacial bonding force to make the interface between the steel and aluminum tightly bonded. Moreover, online annealing means that under the condition of a certain furnace temperature (for example, the first online annealing temperature is 350-550°C), the composite material passes through the furnace cavity at a certain speed (for example, the speed of the first online annealing is 1-10 m / min), and annealing is achieved during 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 conduct 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 can be preheated, reducing the thermal shock caused by too large a temperature difference, and enhancing the interfacial bonding force and 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 realizing the rapid, continuous and uniform cooling of the ultra-thin composite material out of the furnace, minimizing surface oxidation and reducing the performance instability 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 realized, improving the interfacial bonding strength of the ultra-thin composite material, reducing the annealing time and enhancing the efficiency. For the second online annealing after cold rolling, the temperature is controlled at 300-550°C and the speed is 1-10 m / min. Annealing online at a relatively high temperature and a slower speed can prevent the steel and aluminum from overheating, thereby ensuring good interfacial bonding force. Through online preheating and continuous and uniform cooling out of the furnace, it is possible to reduce the rolling defects of the ultra-thin composite material, eliminate the internal stress of the composite material, improve the plasticity of the composite material, reduce the annealing time and enhance the efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a schematic diagram of the steel-aluminum-steel three-layer composite thin sheet prepared in Embodiment 1 of the present invention; Figure 2 It is a schematic diagram of the steel-aluminum-steel three-layer composite thin sheet prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not indicated by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0021] The present invention provides a method for preparing a steel-aluminum-steel three-layer composite thin sheet, which includes: online texturing, cleaning of the first steel, aluminum, and the second steel, and sequential cold rolling and lamination; first online annealing; first surface decontamination; cold rolling; second surface decontamination; second online annealing; stretch-bending straightening; third surface decontamination.

[0022] Optionally, the first steel, aluminum, and the second steel can be strip materials, and surface degreasing and decontamination cleaning can be performed before lamination. Among them, the first steel and the second steel can be stainless steels such as 304, 316, 316L, 316Li, etc., and the aluminum can be aluminum alloys of series 1, 3, 5, 6, etc., which are not specifically limited herein.

[0023] The thicknesses of the first steel, the second steel, and the aluminum can be selected according to needs. Among them, 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, 0.5 mm, and 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, 2 mm, etc., which are not specifically limited herein.

[0024] Due to the different properties of aluminum and steel, their deformation degrees are different. Aluminum is more prone to deformation than steel. The present invention can select the thicknesses of the steel and aluminum materials before cold rolling lamination according to the thickness of the target finished product, and can optimize the thicknesses of the steel and aluminum to prepare a finished steel-aluminum-steel three-layer composite thin sheet with a thinner thickness.

[0025] The inventors have found through research that in the cold rolling process, the ratio of the deformation amounts of steel and aluminum is approximately 1:1.05 - 1.3; in a preferred embodiment, the thickness ratio of the first steel, aluminum, and the second steel in the finished product of the final steel-aluminum-steel three-layer composite thin sheet can be controlled to be 1:2:1; in order to meet the above-mentioned thickness ratio of the finished product, before cold rolling lamination, the thickness ratio of the first steel, aluminum, and the 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., which are not specifically limited herein. Moreover, through the above-mentioned thickness control, it is beneficial to produce a finished ultra-thin sheet with a thickness of 0.1 - 0.5 mm.

[0026] Optionally, in the preparation method of the present invention, online texturing, cleaning and cold rolling are carried out simultaneously, that is, while the first steel, aluminum and the second steel are texturing, cleaning and rolling are carried out after texturing, that is, the first steel, aluminum and the 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 the second steel corresponding to the parts where the 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 the second steel separately, cleaning them separately, and then stacking them up for cold rolling. 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.

[0027] 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.

[0028] The roughening process is crucial to the interface bonding strength. Ensuring a certain degree of roughness and cleanliness of the roughened surface, that is, reducing dirt and debris, is conducive to improving the interface bonding strength of the composite material; among them, the roughening roughness has a great impact on the performance of the finished composite thin material. Optionally, the roughening roughness can be Ra1-6 (for example: 1, 2, 3, 4, 5, 6, etc., not specifically limited here); for ultra-thin materials, the roughness can be reduced as much as possible while ensuring the interface bonding strength, which can improve the problem of poor interface flatness caused by excessive roughness, thereby reducing the adverse effects on the interface quality of ultra-thin materials, improving the problem of the inability to accurately control the layer thickness ratio, and improving the deviation and unevenness of the performance of different positions of ultra-thin materials, and improving the problem of low interface bonding strength and easy delamination and cracking.

[0029] In a preferred embodiment, the roughness of the roughening 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.

[0030] It should be noted that the method for regulating the roughness of the hair-forming process is similar to the related art, for example, by controlling the thickness of the bristles of the brush, etc., which will not be elaborated here.

[0031] 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).

[0032] Optionally, the cleaning can be carried out by using abrasive cloth to roughen and break up the surface, combined with dust removal in a negative pressure enclosed space and installing air knives to blow the roughened surface to ensure the cleanliness of the roughened surface. Among them, if the air knives are not added, there may be obvious particle residues on the material roughened surface; if the air knives are added, there will be no obvious particle residues on the material roughened surface.

[0033] Optionally, the cold rolling composite process can use a four-high rolling mill for cold rolling, and the reduction ratio is crucial for the interfacial bonding force; among them, too small a reduction ratio will prevent the materials from being composite or result in low bonding force after composite, while too large a reduction ratio will cause the surface of the material to crack due to the different plasticity of steel and aluminum; the reduction ratio of the present invention is controlled at 45 - 65%, which can ensure the interfacial bonding force of the composite while avoiding cracking on the surface of the material.

[0034] The inventor further studies and finds that for steel and aluminum raw materials with different thicknesses, using different reduction ratios can further ensure the quality of the finished product. Among them, the deformation difficulty of steel is greater than that of aluminum. Therefore, when steel and aluminum with different thicknesses are composite, they have different deformation difficulties, and the reduction ratio can be controlled according to the composite of steel and aluminum materials with different thicknesses.

[0035] Before cold rolling composite, when the thickness ratio of the first steel to the second steel is 1:1 and the thickness ratio of aluminum to the first steel is less than 1:1, control the reduction ratio of cold rolling composite to be greater than or equal to 45 and less than 50%; this cold rolling composite process has the following advantages: 1. High dimensional accuracy, cold rolling composite is rolled at room temperature, and the thermal expansion and contraction of the material are small, so the dimensional accuracy of the product is higher; 2. Good surface quality, under cold rolling composite, the temperature of the material and the rolling mill is low, and it is not easy to have surface quality problems such as sticking rolls; 3. Good material properties, the cold rolling composite temperature is low (room temperature), the material can retain its original organizational structure, and the mechanical properties of the product are more uniform and stable; 4. Excellent composite performance, the cold rolling composite process will not form brittle compounds between multiple layers of metals, and the degree of diffusion can be precisely controlled through subsequent diffusion control, and the composite performance is better; 5. Low equipment requirements, cold rolling composite has no heating device, the investment and maintenance costs of the equipment are low, the process control is relatively easy, and the stability is good.

[0036] Before cold rolling composite, when the thickness ratio of the first steel, aluminum and the second steel is 1:(1 - 2):1, control the reduction ratio of cold rolling composite to be greater than or equal to 50 and less than 55%; in this way, it can ensure better combination of the composite material and there are no cracks on the surface.

[0037] Before cold rolling composite, when the thickness ratio of the first steel to the second steel is 1:1 and the thickness ratio of aluminum to the first steel is greater than 2:1, control the reduction ratio of cold rolling composite to be greater than or equal to 55 and less than or equal to 65%; in this way, it can ensure better combination of the composite material and there are no cracks on the surface.

[0038] 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.

[0039] The temperature control of the first online annealing after cold rolling compounding is crucial for the interfacial bonding force. By controlling the furnace temperature of the first online annealing to be 350 - 550 °C and the annealing speed to be 1 - 10 m / min, annealing online at a slower speed at a relatively high temperature can prevent the steel-aluminum from overheating, thus improving the problem of overheating of the steel-aluminum-steel, avoiding the problem of an increase in brittle phases at the middle interface of the composite material, thereby enhancing the interfacial bonding force and making the interface between the steel and aluminum bond tightly; moreover, online annealing means that under a certain furnace temperature (for example: the first online annealing temperature is 350 - 550 °C), the composite material passes through the furnace cavity at a certain speed (for example: the speed of the first online annealing is 1 - 10 m / min), and annealing is achieved during 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, in which after the temperature of the annealing furnace rises to the target temperature, the entire composite material is then placed into the furnace cavity and annealed for a set time. Therefore, during the first online annealing of the present invention, the part of the composite material entering the annealing furnace cavity will conduct 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 can be preheated, reducing the thermal shock caused by too large a temperature difference, enhancing the interfacial bonding force, and 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 out of the furnace, minimizing surface oxidation as much as possible, and reducing the performance instability 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, improving the interfacial bonding strength of the ultra-thin composite material. For the second online annealing after cold rolling, the temperature is controlled to be 300 - 550 °C, and the speed is 1 - 10 m / min. Annealing online at a slower speed at a relatively high temperature can prevent the steel-aluminum from overheating, thus ensuring good interfacial bonding force. Through online preheating and continuous and uniform cooling out of the furnace, the rolling defects of the ultra-thin composite material can be reduced, and the internal stress of the composite material can be eliminated, improving the plasticity of the composite material.

[0040] Compared with the related technology that uses vacuum or box annealing, online annealing can also make the performance of the composite material more uniform, thus making the performance of the entire coil material uniform; moreover, the online annealing method can shorten the annealing time to improve efficiency and can also monitor the surface quality of the material.

[0041] 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 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., and no specific limitations are made 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 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., and no specific limitations are made here.

[0042] Optionally, the furnace length of the annealing furnace for at least one of the first online annealing and the second online annealing can be 6 m.

[0043] In a preferred embodiment, the furnace temperature of the first online annealing is 350 - 480°C, and the speed is 1 - 2 m / min; the speed of the second online annealing is 1 - 2 m / min. In this way, the bonding strength of the composite material interface can be further improved, and the internal stress can be effectively reduced.

[0044] Furthermore, the furnace temperature of the first online annealing is 350 - 450°C, 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. In this way, it is beneficial to interlayer bonding, that is, it can effectively improve the interface bonding force, and is beneficial to efficiently eliminate internal stress and improve plasticity.

[0045] Before performing the first online annealing in the preparation method of the present invention, it is not necessary to clean the material with a liquid cleaning agent such as water to avoid the entry of a liquid cleaning agent such as water into the interface of the composite material, resulting in a decrease in the interface bonding force; after the first online annealing forms a tight metallurgical bond at the composite material interface, cleaning is performed. However, in order to further improve the interface bonding strength and to improve the surface strength of the material after annealing, abrasive cloth can be added at the furnace mouth of the annealing furnace to wipe the composite material with the abrasive cloth before the composite material enters the annealing furnace to reduce dirt such as oil stains. Among them, there is no requirement for the roughness of the abrasive cloth, as long as it can wipe off oil stains, etc.

[0046] 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 facilitate the timely and uniform cooling of the composite material that exits the annealing furnace of the first online annealing, that is, it can enable the composite thin sheet after leaving the furnace to cool down to room temperature more quickly and uniformly, reduce the oxidation of the surface of the composite material, and improve the problem of unstable performance caused by uneven cooling.

[0047] Optionally, in some embodiments, 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.

[0048] Composite materials with a relatively thin thickness are prone to problems such as surface wrinkles. Therefore, it is difficult for the layered metal composite materials provided by the prior art to reach a thickness of 0.2 - 0.5 mm. The inventors have found that in the cold rolling step, a cold rolling method with multiple small deformations is adopted, and the reduction rate per pass is controlled to be 10 - 20% (for example: 10%, 12%, 15%, 17%, 20%, etc., which are not specifically limited here). Then, during the cold rolling process with multiple small deformations, the elongation rate of the composite material can be gradually increased, thereby reducing the quality problem of wrinkles in the composite material. Moreover, by adopting the cold rolling method with multiple small deformations, controlling the reduction rate per pass to be small, gradually accumulating small reduction rates until the composite material reaches the target thickness, and then performing online annealing, the plasticity of the composite material can also be ensured.

[0049] 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 rate, an annealing step can be added in the cold rolling step. During the cold rolling process with multiple small deformations, the greater the total reduction rate, the harder the composite material and the lower the elongation rate. When the reduction rate per single process reaches 30 - 50% (for example: 30%, 40%, 50%, etc., which are not specifically limited here), online annealing is performed, and the furnace temperature for annealing is 300 - 550 °C (for example: 300 °C, 320 °C, 350 °C, 380 °C, 400 °C, 420 °C, 450 °C, 470 °C, 500 °C, 530 °C, 550 °C, etc., which are not specifically limited here), and the speed is 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., which are not specifically limited here). Then, the composite material can be softened, internal stress can be eliminated, and the elongation rate can be increased.

[0050] When the single - process reduction rate reaches 30 - 50%, adding the step of online annealing not only ensures the elongation rate but also ensures the surface quality of the composite material. If the single - process reduction rate is greater than 50%, the plasticity of the composite material is greatly reduced, and even after annealing, it is difficult to ensure that there are no fine transverse lines on the surface of the composite material.

[0051] In some embodiments, multiple online annealings can be added during the cold - rolling step. For example, each time the single - process reduction rate reaches 30 - 50%, online annealing is carried out. After the annealing is completed, cold - rolling is carried out again, and the accumulated reduction rate is calculated from the beginning. When the single - process reduction rate reaches 30 - 50% again, online annealing is carried out again. After the annealing is completed, the cold - rolling and annealing steps are repeated again, and this cycle continues until the thickness of the composite material reaches the target thickness. The more times of annealing during the cold - rolling process, the lower the hardness of the material and the greater the elongation rate, which is beneficial to obtaining a composite thin sheet with good surface quality.

[0052] It should be noted that the above - mentioned single - process reduction rate is the accumulated deformation amount of the sheet after multiple single - pass rollings. For example, after the composite sheet is rolled three times, compared with the deformation amount when no cold - rolling is carried out.

[0053] Optionally, in order to obtain a high - quality laminated composite thin sheet, the reduction rate of a single pass can be controlled in segments during cold - rolling. Among them, when the single - process reduction rate 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%; when the single - process reduction rate 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%. When the single - process reduction rate is less than 50%, the overall thickness of the composite sheet is relatively large. When the single - process reduction rate is greater than 50%, the overall thickness of the composite sheet is relatively thin. When the thickness of the composite sheet is relatively thick, using a larger reduction rate for a single pass can improve the rolling efficiency. When the composite sheet has been rolled to a relatively thin state, using a smaller reduction rate for a single pass can not only gradually roll the composite sheet to the target thickness but also ensure the quality of the composite sheet, reduce cracks, and ensure that the ultra - thin steel - aluminum - steel three - layer composite sheet has a high elongation rate.

[0054] The tension - leveler step has a great influence on the surface quality of the ultra - thin composite sheet. Controlling the process parameters of the tension - leveler can not only ensure the surface flatness of the ultra - thin composite sheet but also ensure the surface quality. Moreover, the yield strength, thickness, and elongation rate of the composite material have a significant impact on the leveling effect. Among them, the greater the yield strength and thickness of the composite material and the smaller the elongation rate, the greater the required leveling parameters. Therefore, when selecting the process parameters of the tension - leveler, the above - mentioned factors should be fully considered.

[0055] Optionally, the speed of stretcher leveling 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., not specifically limited herein), the tension is the product of 5 - 20% (for example: 5%, 7%, 9%, 10%, 13%, 15%, 17%, 20%, etc., not specifically limited herein) of the yield strength of the steel-aluminum-steel composite material after the second online annealing and the cross-sectional area of the steel-aluminum-steel composite material after the second online annealing (i.e., tension = 5% of the yield strength of the composite material × cross-sectional area of the composite material ~ 20% of the yield strength of the composite material × cross-sectional area of the composite material), and the elongation of stretcher leveling 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 herein); under the above stretcher leveling process parameters, the quality of the ultra-thin composite material after straightening can be ensured. If the above stretcher leveling parameters are too large or too small, the straightening quality of the material will be reduced.

[0056] It should be noted that the cross-sectional area of the above composite material refers to the product of the sum of the thicknesses of the first steel, aluminum, and the second steel (i.e., the thickness of the composite thin sheet) and the width of the composite material, where the extension direction of the width of the composite material is perpendicular to the direction from the first steel to the second steel.

[0057] Optionally, the methods of the first surface decontamination, the second surface decontamination, and the third surface decontamination are similar. Among them, 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, the grinding wheel pressure, the frequency of grinding wheel replacement, and the frequency of cleaning liquid replacement, 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, there are obvious scratches on the surface of the composite material, and it will cause different colors on the surface of the composite material; when the grinding wheel pressure is small, the decontamination effect is poor, and there are residues of dirt; when the grinding wheel pressure is moderate, the decontamination can be effectively carried out, and a composite material with good surface quality can be obtained. Any of the above surface decontaminations is the decontamination of the entire surface of the composite thin sheet.

[0058] It should be noted that the specific pressure parameters of the above large, small, and moderate grinding wheel pressures are similar to the related technologies, and in the surface decontamination step, the brushing speed, the frequency of grinding wheel replacement, and the frequency of cleaning liquid replacement, etc. can also refer to the related technologies, which will not be elaborated herein.

[0059] The present invention will be further described in detail below in conjunction with embodiments.

[0060] Embodiment 1 The first steel, aluminum, and second steel are subjected to in-line texturing, cleaning, and then laminated and cold-rolled in sequence. Among them, the original thickness of the first steel and the second steel is 0.4 mm, and the original thickness of the aluminum is 0.88 mm; before cold rolling, the thickness of the steel-aluminum-steel three-layer composite material is 1.68 mm. The roughness after in-line texturing is Ra = 4. When cleaning after in-line texturing, an air knife is added to clean the surface of the material; the reduction rate of cold rolling is 65%, and the thickness of the steel-aluminum-steel three-layer composite material after cold rolling is 0.588 mm.

[0061] The first in-line annealing is carried out, and the furnace temperature of the first in-line annealing is 450 °C and the speed is 1 m / min.

[0062] The first surface decontamination.

[0063] Cold rolling; among them, it is divided into 9 passes of rolling. The reduction rate of each pass in the first 5 passes of rolling is 15%. After the fifth pass of rolling, the single-process deformation amount is between 30% and 50%. After annealing at a furnace temperature of 550 °C and a speed of 2 m / min, the subsequent 4 passes of rolling are carried out, and the reduction rate of each of the subsequent 4 passes is 10%.

[0064] The second surface decontamination.

[0065] The second in-line annealing is carried out, and the furnace temperature of the second in-line annealing is 550 °C and the speed is 1.5 m / min.

[0066] Stretch-bending straightening is carried out, the speed is 5 m / min, and the tension is 5% of the yield strength of the steel-aluminum-steel composite material after the second in-line annealing × the cross-sectional area of the steel-aluminum-steel composite material after the second in-line annealing; the elongation is 0.1%.

[0067] The third surface decontamination.

[0068] The prepared steel-aluminum-steel three-layer composite thin sheet has a tight interlayer bond and no problems of cracking or delamination (as Figure 1 shown), and the hardness of this composite thin sheet is detected, and the detection results are shown in Table 1.

[0069] Table 1

[0070] Example 2 The differences between Example 2 and Example 1 are as follows: Before cold rolling and compounding, the thicknesses of the first steel and the second steel are 0.2 mm, and the thickness ratio of aluminum to steel is 1:1; the reduction rate of cold rolling and compounding is 50%; the surface roughness after online texturing is Ra = 6; for the first online annealing, the furnace temperature is 550 °C and the speed is 10 m / min; for the second online annealing, the furnace temperature is 550 °C and the speed is 10 m / min; during cold rolling, the reduction rate for each pass is 18%; the speed of stretch-bending straightening is 20 m / min, and the tension 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%; for other process parameters, please refer to Example 1.

[0071] The prepared steel-aluminum-steel three-layer composite thin sheet has a tight interfacial bonding, without problems of cracking and delamination; hardness testing was performed on this composite thin sheet, and the test results are shown in Table 2; the temperatures and speeds of the two online annealings in Example 2 are the same, and the reduction rate for each single pass during cold rolling is 18% (i.e., the reduction rate for each single pass after the reduction rate in a single process reaches 50% is still 18%), resulting in the hardness and yield strength of the prepared composite material being slightly worse than those of the composite material in Example 1.

[0072] Table 2

[0073] Example 3 The differences between Example 3 and Example 1 are as follows: Before cold rolling and compounding, the thicknesses of the first steel and the second steel are 2 mm, and the thickness ratio of aluminum to steel is 2:1; the reduction rate of cold rolling and compounding is 54%; for the first online annealing, the furnace temperature is 350 °C and the speed is 5 m / min; for the second online annealing, the furnace temperature is 300 °C and the speed is 4 m / min; for other process parameters, please refer to Example 1.

[0074] The prepared steel-aluminum-steel three-layer composite thin sheet has a tight interfacial bonding, without problems of cracking and delamination, but the effect of eliminating internal stress is relatively poor, that is, the plasticity is poor and the elongation data is not good; hardness testing was performed on this composite thin sheet, and the test results are shown in Table 3; the temperature and speed of the second online annealing are both lower than those of the first online annealing, and the elongation of the composite material has a certain decrease compared to Example 1.

[0075] Table 3

[0076] Example 4 Example 4 is different from Example 1 in that: before cold rolling and compounding, the thicknesses of the first steel and the second steel are 1 mm, and the thickness ratio of aluminum to steel is 3:1; the reduction rate of cold rolling and compounding is 55%; for the first online annealing, the furnace temperature of the first online annealing is 480 °C and the speed is 2 m / min; for the second online annealing, the furnace temperature of the second online annealing is 480 °C and the speed is 2 m / min; for other process parameters, please refer to Example 1.

[0077] The prepared three-layer steel-aluminum-steel composite thin sheet has tight interfacial bonding and no problems of cracking or delamination. The hardness of this composite thin sheet was detected, 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, due to the same temperature and speed of the two annealings and the relatively large initial thickness of the raw materials before cold rolling, the final product performance (i.e., ductility) of the prepared composite material is slightly worse than that of Examples 1 and 2.

[0078] Table 4

[0079] Example 5 Example 5 is different from Example 1 in the total thickness of the first steel, the second steel, and aluminum (the ratio of the three is referred to Example 1), and the cold rolling steps.

[0080] Among them, the initial total thickness of the first steel, the second steel, and aluminum is 0.85 mm. The cold rolling in Example 5 is divided into 9 passes of rolling, and the thickness (mm) change of the composite material is 0.85 → 0.75 → 0.65 → 0.58 → 0.47 → 0.41 → 0.33 → 0.27 → 0.23 → 0.2. No annealing is added during cold rolling; for other process parameters, please refer to Example 1.

[0081] The prepared three-layer steel-aluminum-steel composite thin sheet has tight interfacial bonding and no problems of cracking or delamination. The hardness of this composite thin sheet was detected, and the test results are shown in Table 5. There is no annealing during cold rolling, and the elongation rate of the prepared composite material is slightly worse.

[0082] Table 5

[0083] Example 6 Example 6 is different from Example 1 in the total thickness of the first steel, the second steel, and aluminum (the ratio of the three is referred to Example 1), and the cold rolling steps.

[0084] Among them, the initial total thickness of the first steel, the second steel and aluminum is 0.85 mm. The cold rolling in Example 6 is divided into 9 passes, and the thickness (mm) of the composite material changes as 0.85 → 0.75 → 0.65 → 0.58 → 0.47 → 0.41 → adding an annealing step (annealing furnace temperature is 300 °C, annealing speed is 5 m / min) → 0.33 → 0.27 → 0.23 → 0.2. Annealing is added during the cold rolling process; for other process parameters, please refer to Example 1.

[0085] The prepared three-layer steel-aluminum-steel composite thin sheet has a tight interfacial bonding, without problems of cracking and delamination. The hardness of the composite thin sheet is detected, and the detection results are shown in Table 6. Adding annealing during the cold rolling process can ensure that both the hardness and elongation of the composite material are better.

[0086] Table 6

[0087] Example 7 The difference between Example 7 and Example 1 lies in that: before cold rolling and compounding, the thicknesses of the first steel and the second steel are 1 mm, and the thickness ratio of aluminum to steel is 1:2; the reduction rate of cold rolling and compounding is 45%; for other process parameters, please refer to Example 1.

[0088] The prepared three-layer steel-aluminum-steel composite thin sheet has a tight interfacial bonding, without problems of cracking and delamination. The hardness of the composite thin sheet is detected, and the detection results are shown in Table 7.

[0089] Table 7

[0090] Comparative Example 1 The difference between Comparative Example 1 and Example 1 lies in that: the first online annealing and the second online annealing are replaced by box annealing. Among them, the furnace temperature of the first box annealing after cold rolling and compounding is 450 °C, and the holding time is 1 h; the furnace temperature of the second box annealing after cold rolling is 550 °C, and the holding time is 1 h; for other process parameters, please refer to Example 1.

[0091] The prepared three-layer steel-aluminum-steel composite thin sheet has a loose interfacial bonding, with problems of cracking (as shown in the figure, there are obvious cracks in the figure) and delamination (the bonding force of the composite material is poor). The hardness of the composite thin sheet is detected, and the detection results are shown in Table 8. However, the performance of the prepared composite material is not uniform, that is, some areas of the composite material cannot reach the performance of the following table. Figure 2 shown, there are obvious cracks in the figure), delamination (the bonding force of the composite material is poor). The hardness of the composite thin sheet is detected, and the detection results are shown in Table 8, but the performance of the prepared composite material is not uniform, that is, some areas of the composite material cannot reach the performance of the following table.

[0092] Table 8

[0093] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that only the first online annealing is carried out and the second online annealing is cancelled; other process parameters refer to Example 1.

[0094] The obtained steel-aluminum-steel three-layer composite thin sheet has relatively tight interfacial bonding, but poor ductility and plasticity. The hardness of this composite thin sheet is detected, and the detection results are shown in Table 9.

[0095] Table 9

[0096] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that only the second online annealing is carried out and the first online annealing is cancelled; other process parameters refer to Example 1.

[0097] The obtained steel-aluminum-steel three-layer composite thin sheet cracks when bent, and the bonding effect is poor.

[0098] The hardness of this composite thin sheet is detected, and the detection results are shown in Table 10.

[0099] Table 10

[0100] Comparative Example 4 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.

[0101] The obtained steel-aluminum-steel three-layer composite thin sheet does not crack when bent, but the bonding force is reduced due to overheating. The hardness of this composite thin sheet is detected, and the detection results are shown in Table 11.

[0102] Table 11

[0103] Comparative Example 5 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.

[0104] The obtained steel-aluminum-steel three-layer composite thin sheet does not crack when bent, but the bonding force is poor, and the hardness change of steel and aluminum is small, and work hardening is obvious. The hardness of this composite thin sheet is detected, and the detection results are shown in Table 12.

[0105] Table 12

[0106] Comparative Example 6 The difference between Comparative Example 6 and Example 1 lies in that the reduction ratio of cold rolling composite is 70%; other process parameters refer to Example 1.

[0107] Obvious cracks appeared on the surface of the prepared steel-aluminum-steel three-layer composite sheet.

[0108] Comparative Example 7 The difference between Comparative Example 7 and Example 1 lies in that the reduction ratio of cold rolling composite is 40%; other process parameters refer to Example 1.

[0109] The bonding of the prepared steel-aluminum-steel three-layer composite sheet is poor and a stable composite structure cannot be formed.

[0110] Comparative Example 8 The difference between Comparative Example 8 and Example 1 is that the prepared three-layer composite sheet is aluminum-steel-aluminum; other process parameters refer to Example 1. The surface hardness of the aluminum-steel-aluminum three-layer composite sheet in Comparative Example 8 is 52 HV, which is much lower than the surface hardness of the steel-aluminum-steel sheet in Example 1.

[0111] In summary, the steel-aluminum-steel three-layer composite sheet and its preparation method of the present invention can improve the uniformity and bonding force of the composite plate interface of the laminated composite material, are not prone to cracking and delamination problems, and can eliminate internal stress and improve plasticity.

[0112] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a steel-aluminum-steel three-layer composite thin material, characterized in that, Including: Online hair-roughening, cleaning of the first steel, aluminum, and the second steel, and laminating and cold rolling them in sequence; First online annealing, with the furnace temperature of the first online annealing being 350 - 550°C and the speed being 1 - 10 m / min; First surface decontamination; Cold rolling; the cold rolling step adopts a cold rolling method with multiple small deformations, and the reduction rate per pass is controlled to be 10 - 20%; when the reduction rate in a single process reaches 30 - 50%, annealing is carried out, and the furnace temperature of the annealing is 300 - 550°C and the speed is 1 - 10 m / min; when the reduction rate in a single process 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 in a single process is greater than 50%, the reduction rate per pass is controlled to be greater than or equal to 10% and less than 15%; Second surface decontamination; Second online annealing, with the furnace temperature of the second online annealing being 300 - 550°C and the speed being 1 - 10 m / min; Stretch-bending straightening; Third surface decontamination.

2. The preparation method of the steel-aluminum-steel three-layer composite thin material according to claim 1, wherein The furnace temperature of the first online annealing is 350 - 480°C and the speed is 1 - 2 m / min; The speed of the second online annealing is 1 - 2 m / min.

3. The preparation method of the steel-aluminum-steel three-layer composite thin sheet according to claim 2, characterized in that, 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.

4. The preparation method of the steel-aluminum-steel three-layer composite thin material according to claim 1, characterized in that, The reduction rate of the cold rolling composite is 45 - 65%.

5. The manufacturing method of the steel-aluminum-steel three-layer composite thin material according to claim 4, characterized in that, Before the cold rolling composite, when the thickness ratio 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 rate of the cold rolling composite is controlled to be greater than or equal to 45% and less than 50%; Before the cold rolling composite, 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 composite is controlled to be greater than or equal to 50% and less than 55%; Before the cold rolling composite, when the thickness ratio 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 rate of the cold rolling composite is controlled to be greater than or equal to 55% and less than or equal to 65%.

6. The preparation method of the steel-aluminum-steel three-layer composite thin sheet according to claim 1, characterized in that, 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 is 1:(2.1 - 2.6):1; The speed of the stretch-bending straightening is 5 - 40 m / min, the tension is 5% × the cross-sectional area of the steel-aluminum-steel composite material after the second online annealing × the yield strength of the steel-aluminum-steel composite material after the second online annealing to 20% × the cross-sectional area of the steel-aluminum-steel composite material after the second online annealing × the yield strength of the steel-aluminum-steel composite material after the second online annealing, and the elongation of the stretch-bending straightening is 0.1 - 0.8%.

7. A steel-aluminum-steel three-layer composite thin sheet, characterized in that, It is prepared by the preparation method of the steel-aluminum-steel three-layer composite thin material according to any one of claims 1 - 6.

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