Method for laser-brazing-pressure multiple composite preparation of dissimilar metal composite plate

Abstract

The application discloses a laser-brazing-pressure multi-combination preparation method of dissimilar metal composite plates, and first, the surface to be combined of the dissimilar metal plates is cleaned; then, a preset brazing filler layer is formed on the surface of one of the plates through cold spraying; next, the back surface of the surface to be combined of the two metal plates is precisely preheated to a preset temperature by adopting a laser beam; the two metal plates after preheating are conveyed to the first group of rollers to be rolled for the first time, so that the melting and wetting of the brazing filler are realized, and brazing connection is formed; then, the composite plate is placed in an insulation chamber to be subjected to insulation treatment, so that the interface metallurgical reaction is further promoted; finally, the composite plate after insulation is rolled for the second time, and pressure welding connection is completed. Through the synergistic effect of laser-assisted brazing and laser preheating pressure welding, the application realizes the combination of metallurgical bonding and plastic bonding between the dissimilar metal plates, significantly improves the interface bonding strength, and simultaneously reduces the required rolling pressure, and is particularly suitable for the efficient and high-quality combination of copper / aluminum, steel / aluminum and other thin plates.

Description

Technical Field

[0001] This invention relates to the field of composite metal processing technology, specifically to a method for preparing dissimilar metal composite plates using laser-assisted heating combined with brazing and pressure welding. Background Technology

[0002] Dissimilar metal composite panels combine the performance advantages of different metals to achieve performance requirements that a single metal cannot meet. This saves resources and reduces costs without compromising performance, making them widely used in industrial manufacturing and construction. For example, by combining a metal with high electrical and thermal conductivity (such as copper alloys) with a low-cost metal (such as aluminum alloys), the combination of copper's electrical and thermal conductivity and aluminum alloys' low cost and lightweight advantages is achieved. Similarly, by combining high-strength, low-cost carbon steel with low-strength, corrosion-resistant aluminum alloys, a combination of high strength, low cost, high corrosion resistance, and lightweight properties is achieved.

[0003] Currently, all metal composite plate manufacturing technologies have certain limitations. Explosive bonding utilizes the energy of explosive detonation to achieve solid-state metallurgical bonding of metals. Its core advantage lies in its ability to combine dissimilar metals with vastly different melting points and strengths, creating plastic deformation and wave-like characteristics at the interface, thus avoiding the formation of brittle metal compounds. However, explosive bonding requires harsh environmental conditions and is generally conducted outdoors, and is unsuitable for thin plates. Hot rolling bonding requires high temperatures during the rolling process, but the surfaces to be bonded are prone to oxidation during high-temperature heating, affecting the quality of the interface bonding. Cold rolling bonding requires strong downward pressure, which can cause excessive deformation and make the plate too thin for applications requiring lower-hardness metals such as aluminum alloys.

[0004] To address these issues, researchers have proposed brazing or liquid-phase diffusion bonding methods that introduce an intermediate layer. For example, patent application CN120169868A discloses a method for preparing copper-aluminum layered composite plates using laser-introduced intermediate layers. These intermediate layers soften the material, promote plastic deformation, improve strength and toughness, and reduce the difference in deformation resistance between dissimilar metals. However, the introduction of this intermediate layer has limited effect on improving the bonding strength of the composite plate because the intermediate layer is immediately bitten into the rolling mill rolls after being heated to a slightly molten state. This prevents the intermediate layer from fully diffusing and spreading. Furthermore, the composition of the intermediate layer differs from the brazing filler metal used for bonding dissimilar metals, resulting in a significant difference in metallurgical bonding effectiveness. Patent application CN102407404A discloses a method for flux-free laser powder-filled welding of aluminum-steel dissimilar metal joints. In essence, it is a method of laser fusion brazing of dissimilar metals. Under the premise of ensuring that the galvanized steel sheet does not melt, the molten aluminum alloy and the filler metal are spread on the surface of the galvanized steel sheet to form a brazed joint. However, this method requires heating to a high temperature to melt the aluminum alloy, which results in large welding deformation of the joint. In particular, excessive welding deformation of thin plates may cause scrapping. In addition, the mechanical properties of this pure brazed joint are low, which greatly limits its practical application. Patent application CN102581573B proposes a method for preparing composite plates by hot rolling with pre-placed brazing filler metal after thermal spraying. The method involves first applying pre-placed brazing filler metal through thermal spraying, and then preparing the composite plate by hot rolling. However, when using arc thermal spraying, the brazing filler metal layer may suffer from severe oxidation and excessive deformation of the substrate due to excessively high spraying temperature. Similarly, the hot rolling temperature must ensure both the melting of the brazing filler metal and the hot rolling process. Excessively high temperatures may also cause oxidation and excessive deformation of the two metal units, which will directly affect the welding quality.

[0005] Therefore, developing a method for preparing dissimilar metal composite plates that can balance high interfacial bonding strength, low rolling pressure, small deformation, and is suitable for thin plates is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention provides a laser-brazing-pressure multi-composite preparation method for dissimilar metal composite plates. It combines low-temperature brazing and pressure welding with laser precise preheating assistance, and utilizes the synergistic effect of the two to significantly improve the interfacial bonding strength and effectively reduce the load required for pressure welding, thereby improving the composite forming quality and efficiency of thin metal plates.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention provides a method for preparing a laser-brazing-pressure multi-composite composite plate of dissimilar metals, comprising the following steps:

[0009] S1. Clean the surfaces of the first and second metal plates of different materials to be laminated. Specifically, remove the oxide film on the surface by means of scraping or pickling, and then clean the surface with anhydrous ethanol to remove surface moisture, impurities, etc.

[0010] S2. Using a cold spraying process, the brazing powder is uniformly sprayed onto the surface of the first metal plate or the second metal plate to be laminated, forming a pre-placed brazing layer.

[0011] S3. Two laser beams are used to simultaneously irradiate and preheat the back sides of the first metal plate and the second metal plate, respectively, and the temperature of the two metal plates to be composited is monitored in real time to make them reach the preset brazing temperature.

[0012] The preset brazing temperature is lower than the melting point of the two metal plates, but higher than the melting point of the brazing filler metal.

[0013] S4. The two preheated metal plates are respectively conveyed to the first set of rollers for the first rolling composite, and then enter the heat preservation equipment for heat preservation treatment to complete the low-temperature brazing of the two metal plates.

[0014] S5. The heat-insulated composite metal slab is fed into the second set of rollers for a second roll-forming composite process, and pressure welding is completed to obtain a dissimilar metal composite plate.

[0015] The downward pressure applied during the second rolling compounding is greater than the downward pressure applied during the first rolling compounding.

[0016] Furthermore, the first metal plate and the second metal plate are dissimilar metal combinations of copper alloy and aluminum alloy, or steel and aluminum alloy; wherein the thickness of the aluminum alloy plate is 2-4 mm, and the thickness of the copper alloy plate or steel plate is 0.5-1.5 mm.

[0017] Further, in step S2, the brazing filler powder is an alloy powder selected according to the metal combination to be composited:

[0018] For copper-aluminum composite plates, the chemical composition of the brazing filler metal, by mass percentage, is: 92% chemically pure zinc, 4.7%–4.9% chemically pure aluminum, and 3.1%–3.3% chemically pure copper.

[0019] For steel-aluminum composite plates, the chemical composition of the brazing filler metal by mass percentage is: 95% chemically pure zinc and 5% chemically pure lead.

[0020] The brazing filler metal powder is a sprayable alloy powder obtained by mechanically mixing elemental powders with each component comprising more than 99.8% of the total content. The particle size of the brazing filler metal powder is 20–45 µm. If the particle size is too small, the fine powder is easily dispersed and has weak melt-leveling ability, resulting in waste and reduced spraying efficiency. If the particle size is too large, it will lead to difficulties in spraying leveling, and the brazing filler metal powder cannot be fully spread during melting, affecting the subsequent brazing effect. In the cold spraying process, nitrogen is used as the powder feeding gas, and the spraying pressure and gas temperature are set to 3–4 MPa and 300–400℃, respectively. During the spraying process, the spraying distance is 15–25 mm, the spraying angle is 90°, and the thickness of the pre-applied brazing filler metal layer is 0.4–0.8 mm. If the pre-applied brazing filler metal layer is too thin, it will not be able to completely fill the joint gap, affecting the brazing effect. If the pre-applied brazing filler metal layer is too thick, it will increase the residual stress of the joint and affect the flowability of the brazing filler metal, leading to a poorer brazing effect.

[0021] Furthermore, in step S3, both laser beams have a wavelength of 440nm and use rectangular light spots with uniform energy distribution. The length of the rectangular light spot matches the width of the metal plate to be composited, which is 5-30mm, and the width of the rectangular light spot is 2-3mm. The laser power during the preheating of the metal plate is 1000-1500W.

[0022] Further, in step S3, an infrared thermometer is used to measure the temperature of the two metal plates to be laminated. For copper-aluminum metal plates, the preset brazing temperature to be reached by the two laser beams is 400-420℃. For steel-aluminum metal plates, the preset brazing temperature to be reached by the two laser beams is 420-440℃.

[0023] If the preheating temperature is too high, it will cause excessive oxidation and thermal deformation of the metal surface, affecting the composite quality, and may even melt the aluminum alloy, making pressure welding impossible; if the preheating temperature is too low, it will not achieve the purpose of melting the brazing filler metal, making brazing impossible.

[0024] Further, in step S4, the width of the first set of rollers matches the width of the metal plate to be laminated, ranging from 5 to 30 mm, ensuring that the applied pressure can evenly cover the entire width of the metal plate. The downward pressure applied during the first rolling laminate is 500 to 800 N. The temperature of the first and second metal plates is used to heat the brazing filler powder, causing it to melt and become liquid. The liquid brazing filler wets, capillarily flows, fills, spreads, and interacts with the metal plates in the gap or on the surface of the first and second metal plates, thereby achieving a metallurgical bond between the two metal plates.

[0025] If the roller pressure is too low during the first rolling, it will not be able to clamp the two metal plates tightly, which will affect the brazing quality. If the roller pressure is too high, it will squeeze the molten brazing filler metal, and may even squeeze out part of the molten brazing filler metal layer from the surface of the metal to be bonded, so that the molten brazing filler metal layer cannot be evenly covered on the surface of the metal to be bonded, which will affect the brazing quality.

[0026] Furthermore, in step S4, the insulation temperature corresponds to the preset brazing temperature in step S3: for copper-aluminum composite plates, the insulation temperature is 400–420℃; for steel-aluminum composite plates, the insulation temperature is 420–440℃; and the insulation time is 5–15 minutes. Then, insulation is performed in a tunnel insulation chamber to fully wet and fill the liquid brazing filler metal, allowing it to fully react with the base material and achieve a metallurgical bond between dissimilar metals, resulting in a better brazing effect.

[0027] Furthermore, in step S5, the width of the second set of rollers matches the width of the metal plate to be laminated, with a roller width of 5–30 mm. This ensures that the applied pressure can evenly cover the entire width of the metal plate. The applied downward pressure during the second roll lamination is 8000–10000 N, completing the pressure welding of the dissimilar metal plates. This roll lamination utilizes the increased plasticity of the metal after laser preheating, causing plastic deformation of the two metal plate substrates under pressure, achieving direct interatomic bonding (pressure welding). Simultaneously, it breaks down any brittle compound layers that may exist at the interface and disperses them, ultimately resulting in a high-performance dissimilar metal composite plate.

[0028] If the roller pressure is too low during the second rolling process, the composite pressure of dissimilar metals will be insufficient, affecting the composite quality. If the roller pressure is too high, it will place higher demands on equipment requirements, product quality control, and operational safety risks. It will also cause problems such as large extrusion deformation and excessively thinning, affecting the composite quality.

[0029] This invention achieves synergy between "low-temperature (soft) brazing" and "pressure welding" through ingenious process design:

[0030] First, laser preheating not only provides a precise heat source for brazing, but also creates favorable plastic deformation conditions for the second pressure welding of rolling, avoiding the drawbacks of overall heating.

[0031] Secondly, the first low-pressure rolling brazing improved the density of the dissimilar metal bond, achieving the goal of metallurgical bonding and improving the quality of low-temperature brazing.

[0032] Finally, the second high-pressure rolling process, building upon the previous metallurgical bonding, achieves a stronger ductile bond, significantly improving the overall strength of the interface. This multi-layered composite path of "metallurgical bonding first, followed by ductile strengthening" produces a synergistic effect of "1+1>2".

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) This invention combines laser-assisted heating brazing with laser preheating pressure welding, achieving a synergistic effect of metallurgical bonding and plastic bonding between dissimilar metals. Compared with single brazing or single pressure welding of dissimilar metal plates, the interfacial bonding strength of the dissimilar metal composite plate is significantly improved, which can meet more stringent service conditions.

[0035] (2) Because soft soldering is used, the heating temperature is lower. Compared with hard soldering or fusion soldering, the lower temperature can prevent the metal from oxidizing and causing excessive deformation.

[0036] (3) By heating the two metal plates instead of directly heating the brazing filler metal, the heated metal plates are used to melt the brazing filler metal. At the same time, a certain pressure is applied and heat preservation is also carried out, so that the liquid brazing filler metal is fully wetted, filled and spread between the metal plates, which greatly enhances the brazing effect.

[0037] (3) Since laser preheating significantly reduces the deformation resistance of metal, the pressure required for the second pressure welding is much lower than that required for conventional cold pressure welding. This not only reduces the requirements for the rolling mill equipment capacity, saves equipment investment and energy consumption, but also reduces roll wear.

[0038] (4) Using laser as a localized and rapid heat source avoids problems such as thermal deformation, oxidation, and coarsening of soft metal grains caused by overall heating. The cold spraying of the pre-applied brazing filler layer is also a low-temperature process, ensuring the purity of the brazing filler composition. The introduction of the heat preservation step ensures the full progress of the metallurgical reaction, resulting in a product with good plate shape, dense interface bonding, and no overheating defects, making it particularly suitable for thin plate composites with high requirements for plate shape and performance.

[0039] (5) Through the initial brazing connection, the dissimilar metal plates have achieved metallurgical bonding. Then, the preheated pressure welding is used for connection. Compared with cold pressure welding or hot pressure welding alone, it can not only make the dissimilar metal composite plates more firmly bonded, but also significantly reduce pressure and save costs. It will greatly reduce the requirements for equipment, product quality control and operational safety risks. At the same time, it will avoid the problem of excessive pressure causing excessive extrusion deformation and pressing the relatively low-hardness metal too thin, which can improve the bonding efficiency and quality of the composite plate. Attached Figure Description

[0040] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0041] Figure 1 This is a flow chart of the laser-brazing-pressure multi-composite preparation process of the dissimilar metal composite plate in this invention;

[0042] The specific reference numerals in the attached figures are as follows:

[0043] 1. First infrared thermometer 2. Second infrared thermometer 3. Cold spraying device 3. Brazing layer 4. First metal plate 5. Second metal plate 6. First laser beam 7. Second laser beam 8. First set of rollers 9. Insulated tunnel chamber 10. Second set of rollers 11. Dissimilar metal composite plate 12. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] This invention provides a laser-brazing-pressure multi-composite method for preparing dissimilar metal composite plates, the specific preparation process of which is as follows: Figure 1 As shown:

[0046] First, the oxide film on the surfaces of the first metal plate 5 and the second metal plate 6 to be laminated is removed by means of scraping or pickling, and then the surfaces are cleaned with anhydrous ethanol.

[0047] Then, using a cold spraying device 3, brazing filler powder is sprayed onto the second metal plate 6 to form a pre-placed brazing filler layer 4. For the composite of copper and aluminum metal plates, copper-aluminum brazing filler powder is selected, with a chemical composition of 92% chemically pure zinc, 4.7%–4.9% chemically pure aluminum, and 3.1%–3.3% chemically pure copper. For the composite of steel and aluminum metal plates, aluminum-based brazing filler powder is selected, with a chemical composition of 95% chemically pure zinc and 5% chemically pure lead. The brazing filler powder is obtained by mechanically mixing elemental powders with each component content exceeding 99.8%. The powder particle size is 20–45 µm. Nitrogen is used as the powder feeding gas, and the spraying pressure and gas temperature are set to 3–4 MPa and 300–400 °C, respectively. During the spraying process, the spraying distance is 20 mm and the spraying angle is 90°.

[0048] The back surfaces of the surfaces to be composited on the first metal plate 5 and the second metal plate 6 are preheated using the first laser beam 7 and the second laser beam 8, respectively. The wavelengths of the two laser beams are both 440 mm. The laser power during the preheating of the metal plates is 1000-1500 W. A rectangular spot with uniform energy distribution is used to irradiate and preheat the back surfaces of the dissimilar metal plates. The length of the rectangular spot ranges from 5 to 30 mm, and the width is the same as that of the two dissimilar metal plates to be composited. The width of the rectangular spot ranges from 2 to 3 mm. Infrared thermometers are used to measure the temperature of the surfaces to be laminated on the first metal plate 5 and the second metal plate 6. The first infrared thermometer 1 measures the temperature of the surface to be laminated on the first metal plate 5, and the second infrared thermometer 2 measures the temperature of the surface to be laminated on the second metal plate 6 to ensure preheating to a certain temperature. For copper-aluminum metal plates, the two laser beams need to preheat the surface to be laminated to 400-420℃, a temperature range below the melting point of copper and aluminum but above the melting point of the brazing filler metal. For steel-aluminum metal plates, the two laser beams need to preheat the surface to be laminated to 420-440℃, a temperature range below the melting point of steel and aluminum but above the melting point of the brazing filler metal. Then, the first metal plate 5 and the second metal plate 6 are quickly conveyed to the first roller 9 for the first rolling process. The width of the roller is 5-30mm. The metal plates are of the same width to ensure that the applied pressure can evenly cover the entire width of the metal plates. The applied roller pressure is 500N to 800N. The temperature of the first metal plate 5 and the second metal plate 6 is used to heat the brazing filler powder, causing the brazing filler powder to melt into a liquid state. The liquid brazing filler wets, capillarily flows, fills, spreads, and interacts with the metal plates in the gap or on the surface of the first metal plate 5 and the second metal plate 6, thereby achieving a metallurgical bond between the two metal plates. Then, it is kept warm in the tunnel insulation chamber 10. For copper and aluminum metal plates, the insulation temperature range is 400 to 420℃, and for steel and aluminum metal plates, the insulation temperature range is 420 to 440℃, and the insulation time is 5 to 15 minutes. This allows the liquid brazing filler to fully wet and fill, and the brazing filler to fully react with the base material, achieving a metallurgical bond between dissimilar metals and resulting in a better brazing effect.

[0049] Next, the first metal plate 5 and the second metal plate 6 are immediately rolled a second time using the second set of rollers 11. The width of the rollers is 5 to 30 mm, which is the same as the width of the two dissimilar metal plates to be laminated, to ensure that the applied pressure can evenly cover the entire width of the metal plates. The applied roller pressure is 8000 N to 10000 N, and the pressure welding of the dissimilar metal plates is completed to obtain the dissimilar metal composite plate 12.

[0050] Example 1

[0051] This embodiment provides a method for preparing a copper-aluminum metal composite plate, wherein the first metal plate is aluminum alloy 1070 and the second metal plate is copper alloy T2.

[0052] First, the oxide film on the surfaces of the first and second metal plates to be laminated is removed by means of scraping or pickling, and then the surfaces are cleaned with anhydrous ethanol.

[0053] A cold spraying device is used to spray brazing powder onto the second metal plate. The pre-set brazing layer thickness is 0.4 mm. The chemical composition of the brazing powder is 92% chemically pure zinc, 4.8% chemically pure aluminum, and 3.2% chemically pure copper. The brazing powder is produced by processing and mixing. The particle size of the powder is 20-45 µm. Nitrogen is used as the powder feeding gas. The spraying pressure and gas temperature are set to 3.5 MPa and 300 °C, respectively. The spraying distance is 20 mm and the spraying angle is 90 °.

[0054] The back surfaces of the first and second metal plates to be laminated are preheated using a first laser beam and a second laser beam, respectively. Both laser beams have a wavelength of 440 nm, with the first laser beam having a power of 1400 W and the second laser beam having a power of 1100 W. The laser spot is a rectangular spot with uniform energy distribution, the length of which is 20 mm, exactly the same as the width of the first and second metal plates to be laminated, and the width of the rectangular spot is 2 mm. Infrared thermometers are used to measure the temperature of the lamination surfaces of the first and second metal plates. The first infrared thermometer measures the temperature of the lamination surface of the first metal plate, and the second infrared thermometer measures the temperature of the lamination surface of the second metal plate. When the first infrared thermometer... When the temperatures measured by the first and second infrared thermometers both reach approximately 400℃, the first and second metal plates are quickly transported to the first set of rollers for the first rolling process. The rollers are 20mm wide, the same width as the two dissimilar metal plates to be laminated, ensuring that the applied pressure evenly covers the entire width of the metal plates. The applied roller pressure is 800N. The temperature of the first and second metal plates is used to heat the brazing filler powder, causing it to melt and become liquid. Under the pressure of 800N, the liquid brazing filler wets, capillarily flows, fills, spreads, and interacts with the base material in the gap or on the surface of the first and second metal plates, thereby achieving a metallurgical bond between the first and second metal plates.

[0055] Next, the brazed composite metal plates are insulated in a metal tunnel insulated chamber at a temperature of about 400°C for 10 minutes. This allows the liquid brazing filler metal to fully wet and fill the plates, and the filler metal to fully react with the base metal, achieving a metallurgical bond between dissimilar metals and resulting in a better brazing effect.

[0056] Next, the two metal composite plates after heat preservation are rolled a second time under the action of the second set of rollers. The width of the rollers is 20mm, which is the same as the width of the brazed metal composite plates, to ensure that the applied pressure can evenly cover the entire width of the metal composite plates. The applied roller pressure is 9000N, and the pressure welding of the two metal plates is completed.

[0057] Example 2

[0058] This embodiment provides a method for preparing a steel-aluminum metal composite plate, wherein the first metal plate is aluminum alloy 1070 and the second metal plate is Q235.

[0059] First, the oxide film and rust on the surfaces of the first and second metal plates to be laminated are removed by scraping or pickling. Then, the surfaces are cleaned with anhydrous ethanol. A cold spraying device is used to spray brazing filler metal powder onto the second metal plate. The pre-set brazing filler metal layer thickness is 0.6 mm. The chemical composition of the filler metal is 95% chemically pure zinc and 5% chemically pure lead. The brazing filler metal powder is a mixture with a particle size of 20–45 µm. Nitrogen is used as the powder feeding gas. The spraying pressure and gas temperature are set to 3.6 MPa and 350 °C, respectively. The spraying distance is 20 mm and the spraying angle is 90°.

[0060] The back surfaces of the first and second metal plates to be laminated are preheated using a first laser beam and a second laser beam, respectively. Both laser beams have a wavelength of 440 nm, with the first laser beam having a power of 1000 W and the second laser beam having a power of 1300 W. The laser spot is a rectangular spot with uniform energy distribution, the length of which is 20 mm, exactly the same as the width of the first and second metal plates to be laminated, and the width of the rectangular spot is 2 mm. Infrared thermometers are used to measure the temperature of the surfaces of the first and second metal plates to be laminated. The first infrared thermometer measures the temperature of the surface of the first metal plate to be laminated, and the second infrared thermometer measures the temperature of the surface of the second metal plate to be laminated. When the temperatures measured by the first and second infrared thermometers both reach approximately 420℃, the first and second metal plates are quickly transported to the first set of rollers for the first rolling process. The rollers are 20mm wide, the same width as the two dissimilar metal plates to be laminated, ensuring that the applied pressure evenly covers the entire width of the metal plates. The applied roller pressure is 800N. The temperature of the first and second metal plates is used to heat the brazing filler powder, causing it to melt and become liquid. Under the pressure of 800N, the liquid brazing filler wets, capillarily flows, fills, spreads, and interacts with the base material in the gap or on the surface of the first and second metal plates, thereby achieving a metallurgical bond between the first and second metal plates.

[0061] Next, the brazed composite plates of the two metals are kept in a metal tunnel insulation chamber at a temperature of about 420°C for 10 minutes. This allows the liquid brazing filler metal to fully wet and fill the plates, and the filler metal to fully react with the base metal, achieving a metallurgical bond between dissimilar metals and resulting in a better brazing effect.

[0062] Next, the two metal composite plates after heat preservation are rolled a second time under the action of the second set of rollers. The width of the rollers is 20mm, which is the same as the width of the brazed metal composite plates, to ensure that the applied pressure can evenly cover the entire width of the metal composite plates. The applied roller pressure is 10000N, and the pressure welding of the two metal plates is completed.

[0063] Example 3

[0064] This embodiment provides a method for preparing a copper-aluminum metal composite plate, wherein the first metal plate is aluminum alloy 1070 and the second metal plate is copper alloy T2.

[0065] First, the oxide film on the surfaces of the first and second metal plates to be laminated is removed by scraping or pickling, and then the surfaces are cleaned with anhydrous ethanol. Then, a cold spraying device is used to spray brazing filler metal powder onto the second metal plate. The pre-set brazing filler metal layer thickness is 0.5 mm. The chemical composition of the filler metal is 92% chemically pure zinc, 4.8% chemically pure aluminum, and 3.2% chemically pure copper. The filler metal powder is a processed mixture with a particle size of 20–45 µm. Nitrogen is used as the powder feeding gas, and the spraying pressure and gas temperature are set to 3.5 MPa and 300 °C, respectively. The spraying distance is 20 mm, and the spraying angle is 90°.

[0066] The back surfaces of the first and second metal plates to be laminated are preheated using a first laser beam and a second laser beam, respectively. Both laser beams have a wavelength of 440 nm, with the first laser beam having a power of 1450 W and the second laser beam having a power of 1150 W. The laser spot is a rectangular spot with uniform energy distribution, the length of which is 20 mm, exactly the same as the width of the first and second metal plates to be laminated, and the width of the rectangular spot is 2 mm. Infrared thermometers are used to measure the temperature of the surfaces of the first and second metal plates to be laminated. The first infrared thermometer measures the temperature of the surface of the first metal plate to be laminated, and the second infrared thermometer measures the temperature of the surface of the second metal plate to be laminated. When the temperatures measured by the first and second infrared thermometers both reach approximately 410℃, the first and second metal plates are quickly transported to the first set of rollers for the first rolling process. The rollers are 20mm wide, the same width as the two dissimilar metal plates to be laminated, ensuring that the applied pressure evenly covers the entire width of the metal plates. The applied roller pressure is 700N. The temperature of the first and second metal plates is used to heat the brazing filler powder, causing it to melt and become liquid. Under the pressure of 700N, the liquid brazing filler wets, capillarily flows, fills, spreads, and interacts with the base material in the gap or on the surface of the first and second metal plates, thereby achieving a metallurgical bond between the first and second metal plates.

[0067] Next, the brazed composite metal plates are insulated in a metal tunnel insulated room at a temperature of about 410℃ for 10 minutes to allow the liquid brazing filler metal to fully wet and fill the plates, and to allow the brazing filler metal to fully react with the base metal, thus achieving a metallurgical bond between dissimilar metals and resulting in a better brazing effect.

[0068] Next, the two metal composite plates after heat preservation are rolled a second time under the action of the second set of rollers. The width of the rollers is 20mm, which is the same as the width of the brazed metal composite plates, to ensure that the applied pressure can evenly cover the entire width of the metal composite plates. The applied roller pressure is 8500N, thus completing the pressure welding of the two metal plates.

[0069] Example 4

[0070] This embodiment provides a method for preparing a copper-aluminum metal composite plate, wherein the first metal plate is aluminum alloy 1070 and the second metal plate is copper alloy T2.

[0071] First, the oxide film on the surfaces of the first and second metal plates to be laminated is removed by scraping or pickling, and then the surfaces are cleaned with anhydrous ethanol. Then, a cold spraying device is used to spray brazing filler metal powder onto the second metal plate. The pre-set brazing filler metal layer thickness is 0.6 mm. The chemical composition of the filler metal is 92% chemically pure zinc, 4.7%–4.9% chemically pure aluminum, and 3.1%–3.3% chemically pure copper. The brazing filler metal powder is a mixture with a particle size of 20–45 µm. Nitrogen is used as the powder feeding gas, and the spraying pressure and gas temperature are set to 3.5 MPa and 300 °C, respectively. The spraying distance is 20 mm, and the spraying angle is 90°.

[0072] The back surfaces of the first and second metal plates to be laminated are preheated using a first laser beam and a second laser beam, respectively. Both laser beams have a wavelength of 440 nm, with the first laser beam having a power of 1500 W and the second laser beam having a power of 1200 W. The laser spot is a rectangular spot with uniform energy distribution, the length of which is 20 mm, exactly the same as the width of the first and second metal plates to be laminated, and the width of the rectangular spot is 2 mm. Infrared thermometers are used to measure the temperature of the laminated surfaces of the first and second metal plates. The first infrared thermometer measures the temperature of the laminated surface of the first metal plate, and the second infrared thermometer measures the temperature of the laminated surface of the second metal plate. When the temperatures measured by the first and second infrared thermometers both reach approximately 420℃, the first and second metal plates are quickly transported to the first set of rollers for the first rolling process. The rollers are 20mm wide, the same width as the two dissimilar metal plates to be laminated, ensuring that the applied pressure evenly covers the entire width of the metal plates. The applied roller pressure is 600N. The temperature of the first and second metal plates is used to heat the brazing filler powder, causing it to melt and become liquid. Under the pressure of 600N, the liquid brazing filler wets, capillarily flows, fills, spreads, and interacts with the base material in the gap or on the surface of the first and second metal plates, thereby achieving a metallurgical bond between the first and second metal plates.

[0073] Next, the brazed composite plates of the two metals are kept in a metal tunnel insulation chamber at a temperature of about 420°C for 10 minutes. This allows the liquid brazing filler metal to fully wet and fill the plates, and the filler metal to fully react with the base metal, achieving a metallurgical bond between dissimilar metals and resulting in a better brazing effect.

[0074] Next, the two metal composite plates after heat insulation are rolled a second time under the action of the second set of rollers. The width of the rollers is 20mm, which is the same as the width of the brazed metal composite plates, to ensure that the applied pressure can evenly cover the entire width of the metal composite plates. The applied roller pressure is 8000N, thus completing the pressure welding of the two metal plates.

[0075] Example 5

[0076] This embodiment provides a method for preparing a steel-aluminum metal composite plate, wherein the first metal plate is aluminum alloy 1070 and the second metal plate is Q235.

[0077] First, the oxide film and rust on the surfaces of the first and second metal plates to be laminated are removed by scraping or pickling. Then, the surfaces are cleaned with anhydrous ethanol. A cold spraying device is used to spray brazing filler metal powder onto the second metal plate. The pre-set brazing filler metal layer thickness is 0.7 mm. The chemical composition of the filler metal is 95% chemically pure zinc and 5% chemically pure lead. The brazing filler metal powder is a mixture with a particle size of 20–45 µm. Nitrogen is used as the powder feeding gas. The spraying pressure and gas temperature are set to 3.6 MPa and 350 °C, respectively. The spraying distance is 20 mm and the spraying angle is 90°.

[0078] The back surfaces of the first and second metal plates to be laminated are preheated using a first laser beam and a second laser beam, respectively. Both laser beams have a wavelength of 440 nm, with the first laser beam having a power of 1100 W and the second laser beam having a power of 1350 W. The laser spot is a rectangular spot with uniform energy distribution, the length of which is 20 mm, exactly the same as the width of the first and second metal plates to be laminated, and the width of the rectangular spot is 2 mm. Infrared thermometers are used to measure the temperature of the lamination surfaces of the first and second metal plates. The first infrared thermometer measures the temperature of the lamination surface of the first metal plate, and the second infrared thermometer measures the temperature of the lamination surface of the second metal plate. When the first infrared thermometer... When the temperatures measured by the instrument and the second infrared thermometer both reach approximately 430℃, the first and second metal plates are then quickly transported to the first rollers for the first rolling process. The width of the rollers is 20mm, the same as the width of the two dissimilar metal plates to be laminated, ensuring that the applied pressure can evenly cover the entire width of the metal plates. The applied roller pressure is 700N. The temperature of the first and second metal plates is used to heat the brazing filler powder, causing it to melt and become liquid. Under the action of 700N pressure, the liquid brazing filler wets, capillarily flows, fills, spreads, and interacts with the base material in the gap or on the surface of the first and second metal plates, thereby achieving a metallurgical bond between the first and second metal plates.

[0079] Next, the brazed composite metal plates are insulated in a metal tunnel insulated chamber at a temperature of about 430°C for 10 minutes. This allows the liquid brazing filler metal to fully wet and fill the plates, and the filler metal to fully react with the base metal, achieving a metallurgical bond between dissimilar metals and resulting in a better brazing effect.

[0080] Next, the two metal composite plates after heat preservation are rolled a second time under the action of the second set of rollers. The width of the rollers is 20mm, which is the same as the width of the brazed metal composite plates, to ensure that the applied pressure can evenly cover the entire width of the metal composite plates. The applied roller pressure is 9000N, and the pressure welding of the two metal plates is completed.

[0081] Example 6

[0082] This embodiment provides a method for preparing a steel-aluminum metal composite plate, wherein the first metal plate is aluminum alloy 1070 and the second metal plate is Q235.

[0083] First, the oxide film and rust on the surfaces of the first and second metal plates to be laminated are removed by scraping or pickling. Then, the surfaces are cleaned with anhydrous ethanol. Next, brazing filler metal powder is sprayed onto the second metal plate using a cold spraying device. The pre-set brazing filler metal layer thickness is 0.8 mm. The chemical composition of the brazing filler metal is 95% chemically pure zinc and 5% chemically pure lead. The brazing filler metal powder is a mixture produced by processing, and its particle size is 20–45 µm. Nitrogen is used as the powder feeding gas, and the spraying pressure and gas temperature are set to 3°C. The spraying process was carried out at 6MPa and 350℃, with a spraying distance of 20mm and a spraying angle of 90°. The back surfaces of the first and second metal plates to be laminated were preheated using a first laser beam and a second laser beam, respectively. Both laser beams had a wavelength of 440mm, with the first laser beam having a power of 1200W and the second laser beam having a power of 1300W. The laser spot was a rectangular spot with uniform energy distribution, and the length of the rectangular spot was 20mm, exactly matching the width of the first and second metal plates to be laminated. Similarly, the width of the rectangular light spot is 2mm. Infrared thermometers are used to measure the temperature of the surfaces of the first and second metal plates to be laminated. The first infrared thermometer measures the temperature of the surface of the first metal plate to be laminated, and the second infrared thermometer measures the temperature of the surface of the second metal plate to be laminated. When the temperatures measured by both the first and second infrared thermometers reach approximately 440℃, the first and second metal plates are quickly transported to the first roller 9 for the first rolling. The width of the roller is 20mm, the same as the width of the two dissimilar metal plates to be laminated, ensuring that the applied pressure evenly covers the entire width of the metal plates. The applied roller pressure is 600N. The temperature of the first and second metal plates heats the brazing filler powder, causing it to melt into a liquid state. Under the action of 600N pressure, the liquid brazing filler wets, capillarily flows, fills, spreads, and interacts with the base material in the gap or on the surface of the first and second metal plates, thereby achieving a metallurgical bond between the first and second metal plates.

[0084] Next, the brazed dissimilar metal composite plate 12 is kept at a temperature of about 440°C for 10 minutes in a metal tunnel insulation chamber 10. This allows the liquid brazing filler metal to fully wet and fill the substrate, and the filler metal to fully react with the substrate, achieving a metallurgical bond between the dissimilar metals and resulting in a better brazing effect.

[0085] Next, the heat-insulated dissimilar metal composite plate 12 is rolled a second time under the action of the second set of rollers 11. The width of the rollers is 20mm, which is the same as the width of the brazed dissimilar metal composite plate 12, to ensure that the applied pressure can evenly cover the entire width of the metal composite plate. The applied roller pressure is 8000N, thus completing the pressure welding of the two metal plates.

[0086] Comparative Example 1

[0087] Comparative Example 1 is a comparative test example of Example 1, and its difference from Example 1 is as follows:

[0088] Only brazing, first rolling, and heat preservation were performed on the two metal plates; no second rolling was performed.

[0089] The other steps and parameter settings are the same as in Example 1.

[0090] Comparative Example 2

[0091] Comparative Example 2 is a comparative test example of Example 1, and its difference from Example 1 is as follows:

[0092] The two metal plates were cold-pressed, meaning that after cleaning, the metal plates were directly rolled using the second set of rollers without brazing, first rolling, or heat preservation.

[0093] The other steps and parameter settings are the same as in Example 1.

[0094] Comparative Example 3

[0095] Comparative Example 3 is a comparative test example of Example 1, and its difference from Example 1 is as follows:

[0096] Only the two metal plates were insulated and rolled with a second set of rollers; brazing and the first rolling were not performed.

[0097] The other steps and parameter settings are the same as in Example 1.

[0098] Comparative Example 4

[0099] Comparative Example 4 is a comparative test example of Example 1, and its difference from Example 1 is:

[0100] High-pressure cold welding was performed on the two metal plates, that is, only the two metal plates were rolled by the second set of rollers and the rolling pressure was changed to 18000N. Brazing, the first rolling and heat preservation were not performed.

[0101] The other steps and parameter settings are the same as in Example 1.

[0102] Comparative Example 5

[0103] Comparative Example 5 is a comparative test example of Example 1, and its difference from Example 1 is:

[0104] Only the two metal plates were insulated and rolled with the second set of rollers, and the rolling pressure was changed to 15000N. Brazing and the first rolling were not performed.

[0105] The other steps and parameter settings are the same as in Example 1.

[0106] Comparative Example 6

[0107] Comparative Example 6 is a comparative test example of Example 2, and its difference from Example 2 is as follows:

[0108] Only brazing, first rolling, and heat preservation were performed on the two metal plates; no second rolling was performed.

[0109] The other steps and parameter settings are the same as in Example 2.

[0110] Comparative Example 7

[0111] Comparative Example 7 is a comparative test example of Example 2, and its difference from Example 2 is as follows:

[0112] The two metal plates were cold-pressed, meaning that after cleaning, the metal plates were directly rolled using the second set of rollers without brazing, first rolling, or heat preservation.

[0113] The other steps and parameter settings are the same as in Example 2.

[0114] Comparative Example 8

[0115] Comparative Example 8 is a comparative test example of Example 2, and its difference from Example 2 is as follows:

[0116] Only the two metal plates were insulated and rolled with a second set of rollers; brazing and the first rolling were not performed.

[0117] The other steps and parameter settings are the same as in Example 2.

[0118] Comparative Example 9

[0119] Comparative Example 9 is a comparative test example of Example 2, and its difference from Example 2 is as follows:

[0120] High-pressure cold welding was performed on the two metal plates, that is, only the two metal plates were rolled by the second set of rollers and the rolling pressure was changed to 18000N. Brazing, the first rolling and heat preservation were not performed.

[0121] The other steps and parameter settings are the same as in Example 2.

[0122] Comparative Example 10

[0123] Comparative Example 10 is a comparative test example of Example 2, and its difference from Example 2 is as follows:

[0124] Only the two metal plates were insulated and rolled with the second set of rollers, and the rolling pressure was changed to 15000N. Brazing and the first rolling were not performed.

[0125] The other steps and parameter settings are the same as in Example 2.

[0126] Comparative Example 11

[0127] Comparative Example 11 is a comparative test example of Example 3, and its difference from Example 3 is as follows:

[0128] The thickness of the pre-set solder layer is reduced to 0.3 mm.

[0129] The other steps and parameter settings are the same as in Example 3.

[0130] Comparative Example 12

[0131] Comparative Example 12 is a comparative test example of Example 3, and its difference from Example 3 is as follows:

[0132] The thickness of the pre-set solder layer is increased to 1.0 mm.

[0133] The other steps and parameter settings are the same as in Example 3.

[0134] Comparative Example 13

[0135] Comparative Example 13 is a comparative test example of Example 3, and its difference from Example 3 is as follows:

[0136] The preheating temperature of the two metal plates was reduced to 380°C.

[0137] The other steps and parameter settings are the same as in Example 3.

[0138] Comparative Example 14

[0139] Comparative Example 14 is a comparative test example of Example 3, and its difference from Example 3 is as follows:

[0140] The preheating temperature of the two metal plates was increased to 430°C.

[0141] The other steps and parameter settings are the same as in Example 3.

[0142] Comparative Example 15

[0143] Comparative Example 15 is a comparative test example of Example 3, and its difference from Example 3 is as follows:

[0144] The initial rolling pressure of the two metal plates is 400N.

[0145] The other steps and parameter settings are the same as in Example 3.

[0146] Comparative Example 16

[0147] Comparative Example 16 is a comparative test example of Example 3, and its difference from Example 3 is as follows:

[0148] The initial rolling pressure of the two metal plates is 900N.

[0149] The other steps and parameter settings are the same as in Example 3.

[0150] Comparative Example 17

[0151] Comparative Example 17 is a comparative test example of Example 3, and its difference from Example 3 is as follows:

[0152] The second rolling pressure on the two metal plates is 7000N.

[0153] The other steps and parameter settings are the same as in Example 3.

[0154] Comparative Example 18

[0155] Comparative Example 18 is a comparative test example of Example 3, and its difference from Example 3 is as follows:

[0156] The second rolling pressure on the two metal plates is 11000N.

[0157] The other steps and parameter settings are the same as in Example 3.

[0158] Experimental performance testing

[0159] Shear tests were conducted on the metal composite plates in Examples 1-6 and Comparative Examples 1-18 to obtain the interfacial bonding strength of each metal composite plate, as shown in Table 1.

[0160] Table 1

[0161]

[0162] As can be seen from the mechanical property test results in Table 1, Examples 1 to 6 were obtained by laser-assisted brazing and laser pressure welding, achieving the effect of metallurgical and plastic composite bonding. Compared with the comparative examples, the interface bonding strength is the highest.

[0163] Comparative Examples 1 and 6 are equivalent to only undergoing soft soldering, resulting in low interfacial bonding strength.

[0164] Comparative Example 2 and Comparative Example 7 are equivalent to only undergoing cold pressure welding. Due to the low pressure, the plastic bonding effect is limited, resulting in low interfacial bonding strength.

[0165] Comparative Examples 3 and 8 are equivalent to hot-press welding. Since the metal plates are preheated, the deformation resistance is reduced, which is conducive to pressure welding. Therefore, the interfacial bonding strength is improved. However, since the pressure is still low, the plastic bonding effect is limited, so the improvement in interfacial bonding strength is limited.

[0166] Comparative Examples 4 and 9 are equivalent to only performing cold pressure welding, but the applied pressure is increased, the plastic bonding effect is increased, and thus the interfacial bonding strength is increased.

[0167] Comparative Examples 5 and 10 are equivalent to thermocompression welding, which increases pressure compared to the examples, resulting in increased plastic bonding and thus increased interfacial bonding strength.

[0168] In Comparative Example 11, the pre-set brazing filler layer was too thin, which prevented the filler layer from completely filling the joint gap, affecting the brazing effect, weakening the metallurgical bond, and reducing the interfacial bond strength. In Comparative Example 12, the pre-set brazing filler layer was too thick, which increased the residual stress in the joint and affected the flowability of the filler metal, resulting in a poorer brazing effect.

[0169] Comparative Example 13: The preheating temperature of the two metal plates was too low, resulting in the brazing filler layer not melting or melting insufficiently, which affected the brazing effect. Comparative Example 14: The preheating temperature of the two metal plates was too high, resulting in excessive oxidation of the metal surface and excessive heat deformation, which also affected the brazing effect.

[0170] In Comparative Example 15, the initial rolling pressure on the two metal plates was too low, resulting in the inability to clamp the two metal plates tightly, which affected the brazing quality. In Comparative Example 16, the initial rolling pressure on the two metal plates was too high, causing excessive compression of the molten brazing filler metal layer. This caused some of the molten brazing filler metal layer to be squeezed out of the metal surface to be laminated, resulting in the molten brazing filler metal layer not being able to evenly cover the metal surface to be laminated, which affected the brazing quality.

[0171] In Comparative Example 17, the second rolling pressure on the two metal plates was too low, which resulted in insufficient pressure for the composite of dissimilar metals and affected the composite quality. In Comparative Example 18, the second rolling pressure on the two metal plates was too high, which caused large extrusion deformation and excessive thinning, thus affecting the composite quality.

[0172] In summary, this invention employs a multi-composite method of laser-assisted brazing and pressure welding to prepare dissimilar metal composite plates. This method achieves a combination of laser-assisted brazing and laser pressure welding, resulting in a metallurgical and plastic composite effect. Compared to brazing, fusion brazing, cold pressure welding / cold rolling, or hot pressure welding / hot rolling alone, this method can obtain dissimilar metal composite plates with higher interfacial bonding strength under relatively lower pressure.

[0173] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing dissimilar metal composite plates using laser-brazing-pressure multi-composite processes, characterized in that, Includes the following steps: S1. Clean the surfaces of the first and second metal plates of different materials to be laminated. S2. Using a cold spraying process, the brazing powder is uniformly sprayed onto the surface of the first metal plate or the second metal plate to be laminated, forming a pre-placed brazing layer. S3. Two laser beams are used to simultaneously irradiate and preheat the back sides of the first metal plate and the second metal plate, respectively, and the temperature of the two metal plates to be composited is monitored in real time to make them reach the preset brazing temperature. The preset brazing temperature is lower than the melting point of the two metal plates, but higher than the melting point of the brazing filler metal. S4. The two preheated metal plates are respectively conveyed to the first set of rollers for the first rolling composite, and then enter the heat preservation equipment for heat preservation treatment to complete the low-temperature brazing of the two metal plates. S5. The heat-insulated composite metal slab is fed into the second set of rollers for a second roll-forming composite process, and pressure welding is completed to obtain a dissimilar metal composite plate. The downward pressure applied during the second rolling compounding is greater than the downward pressure applied during the first rolling compounding.

2. The method for preparing multiple composites according to claim 1, characterized in that, The first metal plate and the second metal plate are dissimilar metal combinations of copper alloy and aluminum alloy, or steel and aluminum alloy; wherein the thickness of the aluminum alloy plate is 2-4 mm, and the thickness of the copper alloy plate or steel plate is 0.5-1.5 mm.

3. The method for preparing multiple composite materials according to claim 2, characterized in that, In step S2, the brazing filler powder is an alloy powder selected according to the metal combination to be composited: For copper-aluminum composite plates, the chemical composition of the brazing filler metal, by mass percentage, is: 92% chemically pure zinc, 4.7%–4.9% chemically pure aluminum, and 3.1%–3.3% chemically pure copper. For steel-aluminum composite plates, the chemical composition of the brazing filler metal, by mass percentage, is: 95% chemically pure zinc and 5% chemically pure lead. The particle size of the solder powder is 20–45 µm; the thickness of the pre-applied solder layer after spraying is 0.4–0.8 mm.

4. The method for preparing multiple composites according to claim 1, characterized in that, In step S3, both laser beams use rectangular spots with uniform energy distribution. The length of the rectangular spot matches the width of the metal plate to be composited, which is 5-30 mm, and the width of the rectangular spot is 2-3 mm. The laser power during the preheating of the metal plate is 1000-1500 W.

5. The method for preparing multiple composites according to claim 4, characterized in that, In step S3, an infrared thermometer is used to measure the temperature of the two metal plates to be laminated. For copper-aluminum metal plates, the preset brazing temperature to be reached by the two laser beams is 400-420℃. For steel-aluminum metal plates, the preset brazing temperature to be reached by the two laser beams is 420-440℃.

6. The method for preparing multiple composites according to claim 5, characterized in that, In step S4, the width of the first set of rollers matches the width of the metal plate to be laminated, and the downward pressure applied during the first rolling laminate is 500-800N.

7. The method for preparing multiple composites according to claim 6, characterized in that, In step S4, the heat preservation temperature corresponds to the preset brazing temperature in step S3: for copper-aluminum composite plates, the heat preservation temperature is 400-420℃; for steel-aluminum composite plates, the heat preservation temperature is 420-440℃; and the heat preservation time is 5-15 minutes.

8. The method for preparing multiple composites according to claim 7, characterized in that, In step S5, the width of the second set of rollers matches the width of the metal plate to be laminated, and the downward pressure applied during the second rolling lamination is 8000~10000N.

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