Preparation method of aluminum / steel composite plate

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a preparation method of an aluminum / steel composite plate, which mainly comprises the following steps: (1) pretreatment of a steel substrate: cleaning the steel substrate with absolute ethyl alcohol to remove dirt, and then carrying out sand blasting treatment on the surface of the steel substrate; (2) cold spraying: performing cold spraying of aluminum powder on the surface of the steel substrate pretreated in the step (1) to obtain an original aluminum / steel / aluminum composite plate; (3) hot pressing is conducted, specifically, the aluminum / steel / aluminum composite plate obtained in the step (2) is subjected to hot pressing in the argon atmosphere; (4) hot rolling forming is conducted, specifically, the aluminum / steel / aluminum composite plate obtained in the step (3) is subjected to hot rolling forming; and (5) annealing is conducted, specifically, the aluminum / steel / aluminum composite plate obtained after the steps are completed is subjected to annealing treatment. The prepared aluminum / steel composite plate is high in performance and high in comprehensive mechanical property.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material preparation, and in particular relates to a method for preparing an aluminum / steel composite plate. Background Art

[0002] There are many preparation technologies for aluminum / steel composite plates, among which the most common ones are rolling method, explosive composite method, and cast-rolling composite method. Among them, the rolling method can be divided into hot rolling, cold rolling, and two-step rolling method. Cold rolling method: The cold rolling method first uses corrugated rollers to achieve a strong meshing between steel and aluminum, and then uses hot rolling flat rollers to flatten the composite plate and further coordinate the deformation of the metal. However, due to the lack of high temperature and high pressure in the cold rolling process, the diffusion and bonding between metal atoms are subject to certain restrictions, so the bonding strength of the prepared composite plate is not high. Hot rolling method: The aluminum plate and the steel plate are heated to a certain temperature and then pressed together to form a composite plate. This method can ensure a good bond between the aluminum and steel matrix, but the plate shape is difficult to control during the hot rolling process. Cold rolling method: The aluminum plate and the steel plate are rolled together by a rolling mill at room temperature to form a composite plate. This method can produce a thinner composite plate, but requires higher pressure and processing accuracy to ensure a tight bond between the aluminum and steel matrix. Explosive composite method: explosives are set between the steel matrix and aluminum to explode in an instant, generating extremely high temperature and pressure, so that the two metals are quickly fused together. The aluminum / steel composite plate prepared by this method has high interface bonding performance, but requires high precision and technology, and the explosives and their byproducts make this method face great safety issues. Two-step rolling method: first, the two metal sheets are assembled and fixed, then hot rolled, annealed and straightened, and then cold rolled. This method has problems such as difficulty in quality control and weak interface bonding. Casting and rolling composite method: two steel plates are superimposed, the inner layer is coated with a stripping agent, and the surroundings are welded and placed in a mold containing molten metal. After the liquid metal solidifies, the initial rolling is carried out, and finally the welded edges are cut off to obtain a composite plate. This method has a simple process, low cost, and can be used for mass production. However, it should be noted that due to the high composite temperature, the surface of the composite substrate is prone to oxidation, and the melting point of the composite metal and the matrix metal is different, and melting loss is prone to occur at the bonding site. In summary, the currently commonly used composite board preparation methods have their inevitable defects, so it is particularly important to propose a preparation method that is more convenient and efficient than the traditional preparation process.

[0003] Cold spraying is a new type of additive manufacturing technology that uses a special spraying device to spray powdered coating materials onto the surface of the substrate through a high-speed gas flow. Its working principle is to introduce high-pressure gas (He, N2, air or their mixed gases) into a specially designed Laval nozzle, and use high-pressure gas to accelerate micron-sized particles at a relatively low temperature (lower than the melting point of the spraying material), so that they hit the substrate at a high speed in the solid state, and the particles undergo severe plastic deformation and are deposited on the surface of the substrate to form a coating. The characteristics of cold spraying technology include: there is no need to melt the sprayed metal particles, the temperature generated on the substrate surface is generally not too high, and it can achieve fast, efficient, and environmentally friendly coating preparation on the surface of metal, glass, and ceramic workpieces. It can be used to prepare coatings with various structures such as multi-layer coatings and sandwich coatings. If the coating is defective or damaged, it can be repaired by cold spraying technology. Summary of the invention

[0004] The present invention provides a method for preparing an aluminum / steel composite plate. The preparation method is simple to operate and can be stably produced in large quantities. Cold spraying is to accelerate the movement of micron-sized metal aluminum particles through high-speed airflow, and then use the plastic deformation generated by the collision of high-speed particles with the substrate to achieve the firm welding of metal aluminum particles and carbon steel substrates. At the same time, the composite plate prepared by this special spraying process can form an interlocking or interlocking structure between aluminum powder and steel substrate, which has strong adhesion and is not easy to fall off. However, the influence of high-speed micron-sized metal aluminum particles in the cold spraying process usually causes uneven plastic deformation of particles in the deposited layer, thereby producing a hardening effect, resulting in brittleness, poor mechanical properties and anisotropy of the deposit. For this reason, the aluminum / steel / aluminum composite plate obtained by preliminary cold spraying is hot pressed. The hot pressing treatment causes diffusion between interface elements, thereby improving its bonding performance. At the same time, the aluminum layer structure can be made denser, the porosity is reduced, the strength is improved, and the elongation is greatly improved. In order to further improve the bonding performance between the aluminum layer and the steel matrix and the mechanical properties of the aluminum layer, the hot-pressed aluminum / steel composite plate needs to be hot-rolled and deformed. After hot rolling, the bonding interface between the steel matrix and the aluminum layer presents a serrated shape under a microscopic state, and the aluminum layer is embedded in the steel matrix to form an embedded structure; the final annealing treatment can eliminate residual stress to a large extent, and there is an obvious diffusion layer at the interface.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing an aluminum / steel composite plate comprises the following steps:

[0007] (1) Pretreatment of the steel substrate: The steel substrate is cleaned and decontaminated with anhydrous ethanol, and then the surface of the steel substrate is sandblasted;

[0008] (2) Cold spraying: cold spraying aluminum powder on the surface of the steel substrate pretreated in step (1) to obtain an original aluminum / steel / aluminum composite plate;

[0009] (3) hot pressing: hot pressing the aluminum / steel / aluminum composite plate obtained in step (2) in an argon atmosphere;

[0010] (4) hot rolling forming: hot rolling forming the aluminum / steel / aluminum composite plate obtained in step (3);

[0011] (5) Annealing: The aluminum / steel / aluminum composite plate that has completed the above steps is annealed.

[0012] In the present invention, it is further described that in step (2), the average particle size of the cold-sprayed aluminum powder is 10-50 μm; the cold spraying uses a Laval-type spray gun to obtain the original aluminum / steel / aluminum composite plate.

[0013] In the present invention, it is further described that in step (2), the specific operation of the cold spraying is: before spraying, the pretreated steel substrate is first fixed on the fixture to ensure that the plane of the steel substrate is located directly in front of the nozzle and remains perpendicular to the spraying direction, and then the aluminum powder is poured into the powder feeding tank and sealed, and after adjusting the parameters, cold spraying is started on both sides of the steel substrate at the same time. During spraying, the nozzle is connected to the robot arm to automatically spray back and forth, and finally the original aluminum / steel / aluminum composite plate is obtained.

[0014] In the present invention, it is further described that in step (3), the hot pressing temperature is 300-550°C, the pressure is 10-50 MPa, the holding time is 10-50 min, and the heating rate is 2-10°C / min.

[0015] In the present invention, it is further described that in step (4), the hot rolling temperature is 300-500°C, the holding time is 5-20min, the reduction rate is 20%-60%, and the rolling speed is 150mm / s.

[0016] In the present invention, it is further described that in step (5), the annealing temperature is 200-500° C., the time is 1-5 hours, and the annealing environment is pure argon or vacuum state.

[0017] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0018] 1. The present invention adopts cold spraying technology to spray aluminum powder onto a steel substrate, and the maximum coating thickness can reach 10 mm, which is suitable for the preparation of aluminum / steel / aluminum composite plates with an aluminum layer thickness of less than 10 mm. During spraying, the temperature of the substrate surface is lower than 150°C, and no internal stress will be generated, there is no phase change, the bonding strength is high, and the deposition speed is fast; the hot pressing and hot rolling processes are used to further optimize the interface bonding performance and the aluminum layer performance. Due to hot rolling, the plastic deformation of the aluminum particles in the aluminum layer is increased, the density is improved, and the porosity is reduced, thereby improving the mechanical properties of the aluminum layer. Compared with a single hot pressing or a single hot rolling process, the combination of hot pressing and hot rolling has a more obvious effect on enhancing the bonding performance and the performance of the aluminum layer.

[0019] 2. Annealing in argon or vacuum in the present invention can significantly eliminate the residual stress in the aluminum layer, promote atomic diffusion at the interface, and avoid oxidation of aluminum during the heating process.

[0020] 3. At present, the price of ordinary cold spray equipment is between 100,000 and 200,000 yuan. The purchase cost is low, the equipment is small in size, easy to place, and has little site restrictions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Process flow chart of preparing aluminum / steel composite plate according to the present invention.

[0022] Figure 2 The XRD spectrum of the aluminum layer in the aluminum / steel composite plate prepared by the present invention.

[0023] Figure 3 The present invention prepares an SEM scanning diagram of the interface of an aluminum / steel composite plate. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0026] Experimental Example 1

[0027] A method for preparing an aluminum / steel composite plate comprises the following steps:

[0028] Prepare the substrate plate: select Q235 steel with a thickness of 1.5 mm and a length and width of 150 mm and 100 mm respectively as the substrate plate (hereinafter referred to as the steel substrate) and clean its surface with anhydrous ethanol until the surface is clean and free of oil stains, then sandblast the surfaces on both sides of the steel substrate to complete the preparation of the steel substrate.

[0029] Prepare the spraying raw materials: put the pure aluminum powder with an average particle size of 20μm into the powder feeder of the spraying equipment.

[0030] Cold spraying: The propulsion gas used for cold spraying is natural air without water or oil. After adjusting the spraying equipment parameters (compressed air working temperature: 400℃; powder delivery flow rate is 50g / min), the nozzle is fixed on the mechanical arm, and the mechanical arm automatically sprays both sides of the steel substrate. The spraying direction is along the length direction. During the spraying process, the nozzle is always kept perpendicular to the steel substrate. The spraying thickness is 1mm. At this point, the spraying work is completed, and a preliminary aluminum / steel / aluminum composite plate is obtained, with a thickness ratio of 2:3:2 for each layer.

[0031] Hot pressing: To prevent the aluminum layer of the aluminum / steel / aluminum composite plate from oxidizing when in contact with oxygen at high temperatures, we perform hot pressing in an argon atmosphere with a hot pressing temperature of 300°C, a holding time of 10 minutes, a pressure of 30MPa, and a heating rate of 20°C / min.

[0032] Adjust rolling parameters: before starting rolling, adjust the rolling speed to 150 mm / s and the reduction rate to 20%.

[0033] Hot rolling: After hot pressing, the aluminum / steel / aluminum composite plate is placed in a heating furnace and kept at 400°C for 10 minutes, then taken out and immediately put into a rolling mill for rolling. During operation, the time interval between taking the sample out of the heating furnace and putting it into the rolling mill shall not exceed 2s.

[0034] Annealing: The aluminum / steel / aluminum composite plate after rolling is placed in a tubular annealing furnace with a heating rate of 7°C / min, kept at 400°C in an argon atmosphere for 2 hours, and then cooled to room temperature with the furnace.

[0035] The preparation of the aluminum / steel / aluminum composite plate was completed and named FHB-1.

[0036] Example 2

[0037] Compared with case 1, the reduction ratio in case 2 was changed to 40%, and the remaining operation steps were the same.

[0038] Prepare the substrate plate: select Q235 steel with a thickness of 1.5 mm and a length and width of 150 mm and 100 mm respectively as the substrate plate (hereinafter referred to as the steel substrate) and clean its surface with anhydrous ethanol until the surface is clean and free of oil stains, then sandblast the surfaces on both sides of the steel substrate to complete the preparation of the steel substrate.

[0039] Prepare the spraying raw materials: put the pure aluminum powder with an average particle size of 20μm into the powder feeder of the spraying equipment.

[0040] Cold spraying: The propulsion gas used for cold spraying is natural air without water or oil. After adjusting the spraying equipment parameters (compressed air working temperature: 400℃; powder delivery flow rate is 50g / min), the nozzle is fixed on the mechanical arm, and the mechanical arm automatically sprays both sides of the steel substrate. The spraying direction is along the length direction. During the spraying process, the nozzle is always kept perpendicular to the steel substrate. The spraying thickness is 1mm. At this point, the spraying work is completed, and a preliminary aluminum / steel / aluminum composite plate is obtained, with a thickness ratio of 2:3:2 for each layer.

[0041] Hot pressing: To prevent the aluminum layer of the aluminum / steel / aluminum composite plate from oxidizing when in contact with oxygen at high temperatures, we perform hot pressing in an argon atmosphere with a hot pressing temperature of 300°C, a holding time of 10 minutes, a pressure of 30MPa, and a heating rate of 20°C / min.

[0042] Adjust rolling parameters: before starting rolling, adjust the rolling speed to 150 mm / s and the reduction rate to 40%.

[0043] Hot rolling: After hot pressing, the aluminum / steel / aluminum composite plate is placed in a heating furnace and kept at 400°C for 10 minutes, then taken out and immediately put into a rolling mill for rolling. During operation, the time interval between taking the sample out of the heating furnace and putting it into the rolling mill shall not exceed 2s.

[0044] Annealing: The rolled aluminum / steel / aluminum composite plate is placed in a tubular annealing furnace with a heating rate of 7°C / min, kept at 400°C for 2h in an argon atmosphere, and cooled to room temperature along with the furnace.

[0045] The preparation of the aluminum / steel / aluminum composite plate was completed and named FHB-2.

[0046] Example 3

[0047] Comparing Case 1 and Case 2, the downward pressure in Case 3 is changed to 60%, and the remaining operation steps are the same.

[0048] Prepare the substrate plate: select Q235 steel with a thickness of 1.5 mm and a length and width of 150 mm and 100 mm respectively as the substrate plate (hereinafter referred to as the steel substrate) and clean its surface with anhydrous ethanol until the surface is clean and free of oil stains, then sandblast the surfaces on both sides of the steel substrate to complete the preparation of the steel substrate.

[0049] Prepare the spraying raw materials: put the pure aluminum powder with an average particle size of 20μm into the powder feeder of the spraying equipment.

[0050] Cold spraying: The propulsion gas used for cold spraying is natural air without water or oil. After adjusting the spraying equipment parameters (compressed air working temperature: 400℃; powder delivery flow rate is 50g / min), the nozzle is fixed on the mechanical arm, and the mechanical arm automatically sprays both sides of the steel substrate. The spraying direction is along the length direction. During the spraying process, the nozzle is always kept perpendicular to the steel substrate. The spraying thickness is 1mm. At this point, the spraying work is completed, and a preliminary aluminum / steel / aluminum composite plate is obtained, with a thickness ratio of 2:3:2 for each layer.

[0051] Hot pressing: To prevent the aluminum layer of the aluminum / steel / aluminum composite plate from oxidizing when in contact with oxygen at high temperatures, we perform hot pressing in an argon atmosphere with a hot pressing temperature of 300°C, a holding time of 10 minutes, a pressure of 30MPa, and a heating rate of 20°C / min.

[0052] Adjust rolling parameters: before starting rolling, adjust the rolling speed to 150mm / s

[0053] After keeping the sample at 400°C for 10 minutes in a hot furnace, take it out and immediately put it into a rolling mill for rolling. During operation, the time interval between taking the sample out of the heating furnace and putting it into the rolling mill for rolling shall not exceed 2 seconds.

[0054] Annealing: The rolled aluminum / steel / aluminum composite plate is placed in a tubular annealing furnace with a heating rate of 7°C / min, kept at 400°C for 2h in an argon atmosphere, and cooled to room temperature along with the furnace.

[0055] The preparation of the aluminum / steel / aluminum composite plate was completed and named FHB-3.

[0056] The aluminum layer density, tensile strength and shear strength of the samples prepared in Example 1, Example 2 and Example 3 were tested and the results are shown in Table 1.

[0057] Table 1

[0058] sample Shear strength / MPa Aluminum layer tensile strength / MPa <![CDATA[Density of aluminum layer g / cm 3 > FHB-1 83.76 93.14 3.2307 FHB-2 123.67 121.71 3.0639 FHB-3 >80.37 160.74 2.9926

[0059] Note: Due to the 60% downward pressure, the thickness of the aluminum deposition layer is too thin, resulting in fracture at the aluminum deposition layer during the shearing process, and shearing cannot be successful. Therefore, it can be inferred from the maximum force at fracture that its tensile strength should be greater than 80.37MPa.

[0060] By comparing the three composite plate samples prepared in the examples, it can be seen that when the pressing rate is between 20% and 60%, as the pressing rate increases, the inter-plate bonding performance of the prepared aluminum / steel / aluminum composite plate becomes better, and the tensile strength of the aluminum deposition layer becomes greater, but the density of the aluminum deposition layer shows a decreasing trend. When the pressing rate is greater than 60%, the density is reduced to below 3.00g / cm3.

[0061] The SEM microscopic morphology of the bonding surface of sample FHB-1 is shown in the following figure: Figure 3 shown.

[0062] It can be seen from the SEM image that the aluminum / steel bonding interface is serrated, and there is obvious mechanical interlocking between the two metal layers on the surface. That is, during the hot rolling process, brittle fracture occurs on the surface of the aluminum deposited layer under the action of the rolling force, and then the exposed new aluminum is squeezed to the steel side to form a metallurgical bond. This is one of the main reasons why the composite plate has high bonding strength. From the perspective of this field, the more obvious the serrations, the better the bonding performance.

[0063] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications completed under the technical concept suggested by the present invention should fall within the scope of the patent covered by the present invention.

Claims

1. A method for preparing an aluminum / steel composite plate, characterized in that: The following steps are involved: (1) Pretreatment of the steel substrate: The steel substrate is cleaned and decontaminated with anhydrous ethanol, and then the surface of the steel substrate is sandblasted; (2) Cold spraying: cold spraying aluminum powder on the surface of the steel substrate pretreated in step (1) to obtain an original aluminum / steel / aluminum composite plate; (3) hot pressing: hot pressing the aluminum / steel / aluminum composite plate obtained in step (2) in an argon atmosphere; (4) hot rolling forming: hot rolling forming the aluminum / steel / aluminum composite plate obtained in step (3); (5) Annealing: The aluminum / steel / aluminum composite plate that has completed the above steps is annealed.

2. The method for preparing the aluminum / steel composite plate according to claim 1, characterized in that: In step (2), the average particle size of the cold-sprayed aluminum powder is 10-50 μm; the cold spraying uses a Laval-type spray gun to obtain the original aluminum / steel / aluminum composite plate.

3. The method for preparing the aluminum / steel composite plate according to claim 1, characterized in that: In step (2), the specific operation of the cold spraying is as follows: before spraying, the pretreated steel substrate is first fixed on the fixture to ensure that the plane of the steel substrate is located directly in front of the nozzle and remains perpendicular to the spraying direction, and then the aluminum powder is poured into the powder feeding tank and sealed. After adjusting the parameters, cold spraying is started on both sides of the steel substrate at the same time. During spraying, the nozzle is connected to the robot arm to automatically spray back and forth, and finally the original aluminum / steel / aluminum composite plate is obtained.

4. The method for preparing the aluminum / steel composite plate according to claim 1, characterized in that: In step (3), the hot pressing temperature is 300-550°C, the pressure is 10-50 MPa, the holding time is 10-50 min, and the heating rate is 2-10°C / min.

5. The method for preparing the aluminum / steel composite plate according to claim 1, characterized in that: In step (4), the hot rolling temperature is 300-500° C., the holding time is 5-20 min, the reduction rate is 20%-60%, and the rolling speed is 150 mm / s.

6. The method for preparing the aluminum / steel composite plate according to claim 1, characterized in that: In step (5), the annealing temperature is 200-500° C., the time is 1-5 hours, and the annealing environment is pure argon or vacuum state.

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