Aluminum alloy composite material for automobile heat exchange system and preparation process thereof

Abstract

The present application belongs to the technical field of aluminum alloy, and particularly relates to an aluminum alloy composite material for an automobile heat exchange system and a preparation process thereof. The present application comprises the following steps: preparation of aluminum alloy fins; preparation of semi-foam foil-shaped filler metal; turbulence strengthening of the surface of the aluminum alloy fins; and composite brazing of the material. The semi-foam foil-shaped filler metal is prepared by a NaCl salt template method. The foam-shaped filler metal alloy layer has highly connected open pores and compressible elasticity. The semi-foam foil-shaped filler metal can not only quickly and uniformly wet the entire interface to be connected by capillary driving force, prevent the segregation phenomenon caused by a long melting range, but also absorb and temporarily lock a certain amount of molten filler metal, prevent the molten filler metal from flowing to a non-target area, and better adapt to the irregular fin surface due to the compressible elasticity, thereby enhancing the mechanical engagement with the fins, strengthening the brazing stability and compactness of the micro-uneven interface, and forming a stable welded joint.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy technology, and particularly relates to an aluminum alloy composite material for automotive heat exchange systems and its preparation process. Background Technology

[0002] As global manufacturing shifts towards lightweighting, low pollution, and energy efficiency, the automotive and construction machinery sectors are placing higher demands on heat exchange systems. Traditional aluminum-copper heat exchangers, limited by rising raw material costs and bottlenecks in heat dissipation efficiency, are no longer sufficient to meet the cooling needs of high-power engines. Aluminum alloys, due to their superior comprehensive properties (density of only 2.7 g / cm³), offer a more competitive alternative. 3 Materials with thermal conductivity ≥180W / (m·K) and excellent corrosion resistance have become the mainstream materials for heat exchangers.

[0003] Most commercially available aluminum alloy heat exchangers are complex, all-aluminum integral welded structures. They use multi-layered complex fins connected to the base plate and pipes to form a unit, which is then welded to the manifold to form a heat exchanger. Such complex structures are particularly difficult to connect using ordinary welding methods, and brazing is considered the most suitable process for connecting complex and precision components.

[0004] In the brazing process of aluminum alloy materials, Al-based filler metals are required. The melting point of the filler metal should be at least 15°C lower than that of the base metal. The filler metal is required to spread and wet the surface of the base metal completely, so that the weld is fully filled and the composition is uniform. Commonly used filler metals include cast filler metals, foil filler metals and powder filler metals. When the surface of the base metal to be brazed has an irregular microstructure, the above-mentioned filler metals cannot quickly wet the base metal, resulting in a longer brazing time. This not only consumes more energy, but also easily leads to melting and precipitation, which affects the brazing effect. Summary of the Invention

[0005] To address the aforementioned technical deficiencies, this invention presents a preparation process for aluminum alloy composite materials used in automotive heat exchange systems. The resulting aluminum alloy composite material exhibits high strength, excellent heat exchange capacity, and good brazed joint performance and stability.

[0006] A process for preparing an aluminum alloy composite material for automotive heat exchange systems includes the following steps:

[0007] S1: Preparation of aluminum alloy fins

[0008] Take 1.2-1.45wt% Si, 0.63-1.1wt% Fe, 0.85-1.32wt% Mn, 1.4-2wt% Mg, 0.4-0.8wt% Cu, 0.02-0.08wt% Ti and 0.08-0.11wt% Pr, with the remainder being Al and unavoidable impurity elements. Mix and melt the mixture, then refine and cast it. Cut it into alloy core sheets with a thickness of 10-15mm, then cold roll it to a thickness of 5-7mm and anneal it. Then cold roll it to a thickness of 0.8-1mm and anneal it. Finally, cold roll it to a thickness of 0.1-0.2mm and roll it into a corrugated fin to obtain aluminum alloy fins.

[0009] S2: Preparation of semi-foamed foil solder

[0010] Al, Si, Ni, Cu, Y and Zr elements are mixed, melted and cast into ingots to obtain a brazing alloy. NaCl salts of different particle sizes and aluminum powder are mixed evenly and then added to a mold for compression to obtain a granular salt template. Then, the molten brazing alloy is melted and pressed into the granular salt template. Molten brazing alloy is then added again. After cooling and demolding, the NaCl particles are dissolved to obtain a semi-foam foil brazing alloy containing a foam layer and a solid layer.

[0011] S3: Turbulence enhancement on the surface of aluminum alloy fins

[0012] Aluminum isopropoxide was dispersed in anhydrous ethanol, and acetylacetone and nitric acid solution were added to obtain a seed crystal precursor sol. Aluminum alloy fins were immersed in the seed crystal precursor sol for extraction and drying, and then immersed in a growth solution prepared by mixing sodium aluminate aqueous solution and urea. A hydrothermal reaction was carried out in a reactor, and after drying and calcination, turbulence-strengthened aluminum alloy fins were obtained.

[0013] S4: Composite brazing of materials

[0014] Turbulence-enhanced aluminum alloy fins and 6063 aluminum alloy tubing are brazed together using semi-foamed foil brazing filler metal to obtain an aluminum alloy composite material.

[0015] Furthermore, the preparation of the aluminum alloy fins in step S1 specifically includes the following steps:

[0016] S1.1: Take 1.2-1.45wt% Si, 0.63-1.1wt% Fe, 0.85-1.32wt% Mn, 1.4-2wt% Mg, 0.4-0.8wt% Cu, 0.02-0.08wt% Ti and 0.08-0.11wt% Pr, with the remainder being Al and unavoidable impurity elements. Mix them evenly and melt them, then transfer them to a holding furnace. Refine and degas them at 745-770℃ for 20-30 minutes. After holding at this temperature for 10-15 minutes, cast and roll them to obtain a cast and rolled alloy ingot. Then, cut off the head, tail and end face in sequence, and cut it into 10-15mm thick alloy core sheets using a flat saw.

[0017] S1.2: The alloy core sheet is cold-rolled to a thickness of 5-7mm, then subjected to a first annealing process. The first annealing process involves heating to 415-465℃ and holding for 2-3 hours. Then, it is cold-rolled to a thickness of 0.8-1mm, followed by a second annealing process at 350-385℃. Finally, it is cold-rolled to a thickness of 0.1-0.2mm to obtain an aluminum alloy sheet. This sheet is then rolled by a roller cutter into corrugated fins with a width of 35-45mm to obtain aluminum alloy fins.

[0018] Furthermore, in step S1.1 during the casting and rolling process, the roll diameter is 800-850mm, the front box temperature is 715-740℃, and the casting and rolling speed is 600-650mm / min.

[0019] Furthermore, the melting point of the aluminum alloy fins in step S1.2 is 650-665℃.

[0020] Furthermore, the preparation of the semi-foamed foil solder in step S2 specifically includes the following steps:

[0021] S2.1: Take 5-5.5wt% Si, 2-2.5wt% Ni, 0.4-0.5wt% Cu, 0.2-0.3wt% Y and 0.05-0.15wt% Zr, with the remainder being Al and unavoidable impurity elements, mix them, melt and cast them into an ingot to obtain a brazing filler alloy.

[0022] S2.2: Add NaCl particles with a diameter of 5-6μm and NaCl particles with a diameter of 12-15μm into a container at a volume ratio of 1:(3-3.5), then add aluminum powder accounting for 4-6% of the volume of NaCl particles, stir and mix evenly to obtain fibrous salt powder.

[0023] S2.3: Place the fiber salt powder in a percolation mold, and then compress it to 1 / 3-1 / 2 of its original volume using a press to obtain a granular salt template with a thickness of 0.1 mm. Place the percolation mold containing the granular salt template in a pit-type resistance furnace. Place the brazing alloy in another pit-type resistance furnace and heat it to 550-560℃ to melt it, obtaining a molten brazing alloy. Pour the molten brazing alloy into the percolation mold containing the granular salt template. Apply a pressure of 1-1.5 MPa at 610-650℃ to allow the molten brazing alloy to percolate into the granular salt template. When the granular salt template is full of molten brazing alloy, stop pressurizing and continue adding molten brazing alloy until it is 0.1 mm above the granular salt template. Stop heating and air-cool the mold before demolding to obtain a mixed salt-alloy double-layer brazing alloy. Then, dissolve the NaCl particles in water to obtain a semi-foam foil-like brazing alloy containing a foam layer and a solid layer.

[0024] Furthermore, the melting point of the brazing alloy in step S2.1 is 530-540℃.

[0025] Furthermore, the aluminum powder particle size in step S2.2 is 6-8 μm.

[0026] Furthermore, the turbulence enhancement of the aluminum alloy fin surface in step S3 specifically includes the following steps:

[0027] S3.1: Place 2-3 parts by weight of aluminum isopropoxide in a beaker, add 80-100 parts by weight of anhydrous ethanol, and stir at 300-400 rpm for 10-15 minutes on a magnetic stirrer to form a uniform dispersion. Add 0.5-0.8 parts by weight of acetylacetone dropwise to the uniform dispersion, then heat to 72-75℃ and stir in a water bath for 30-35 minutes. Add 0.1-0.2 parts by weight of 65-70% nitric acid solution and continue stirring at 250-300 rpm at room temperature for 1-1.5 hours to obtain the seed crystal precursor sol.

[0028] S3.2: Immerse the aluminum alloy fins in the seed crystal precursor sol, let stand for 25-30 seconds, then pull them out, and then dry and cure them in hot air at 120-125℃ for 12-15 minutes. Repeat the immersion-pulling-drying cycle 3-4 times, and then transfer them to a tube furnace and keep them at 420-450℃ for 1-1.5 hours to obtain fins loaded with alumina seed crystals.

[0029] S3.3: Dissolve 1-2 parts by weight of sodium aluminate in 50-75 parts by weight of deionized water, add 0.5-0.7 parts by weight of urea, and then add 65-70% nitric acid solution to adjust the pH to 9.5-10. Stir at 200-250 rpm for 4-6 hours to obtain the growth solution. Then, place the fins loaded with alumina seed crystals into a polytetrafluoroethylene reactor, lean it against the reactor wall, and pour in the growth solution to immerse the fins loaded with alumina seed crystals. Seal the polytetrafluoroethylene reactor and heat it to 120-125℃ at a heating rate of 3-4℃ / min. After holding at this temperature for 3-4 hours, cool it down to room temperature with the reactor. Take it out and rinse it with deionized water. Vacuum dry it at 60-65℃ to constant weight. Then place it in a muffle furnace and hold it at 450-470℃ for 2-2.5 hours. After cooling with the furnace, you will obtain turbulence-strengthened aluminum alloy fins.

[0030] Furthermore, in step S3.2, the immersion speed of the aluminum alloy is 100-120 mm / min, and the pulling speed is 50-60 mm / min.

[0031] Furthermore, the composite brazing of the materials in step S4 specifically includes the following steps:

[0032] The semi-foam foil brazing filler metal is cut to a width of 0.2-0.3 mm. The solid layer of the semi-foam foil brazing filler metal is then fixed to the surface of a 6063 aluminum alloy tube. Turbulence-reinforced aluminum alloy fins are then fixed to the foam layer of the semi-foam foil brazing filler metal and brazed together. The brazing temperature is 565-575℃ and the brazing time is 20 minutes. The turbulence-reinforced aluminum alloy fins are spirally distributed on the tube with a spacing of 0.8-1 cm, thus obtaining an aluminum alloy composite material.

[0033] An aluminum alloy composite material for automotive heat exchange systems is prepared by the aforementioned preparation process of an aluminum alloy composite material for automotive heat exchange systems.

[0034] The beneficial effects are as follows: 1. This invention prepares a semi-foam foil-shaped brazing alloy using the NaCl salt template method. Its structure consists of two layers: a foam-like brazing alloy layer and a solid brazing alloy layer. The foam-like brazing alloy layer has highly interconnected open pores and compressible elasticity. It can not only actively draw in the molten brazing alloy through capillary driving force and distribute it evenly within the foam skeleton during the brazing heating process, quickly and evenly wetting the entire interface to be joined and preventing melting and precipitation due to excessive melting range, but also absorb and temporarily lock in a certain amount of molten brazing alloy, preventing it from accidentally flowing out of the joint to non-target areas due to gravity or excessive flow. At the same time, its compressible elasticity can better adapt to the irregular fin surface, enhance the mechanical engagement with the fins, thereby enhancing the brazing stability and density of the micro-uneven interface and forming a stable welded joint.

[0035] 2. This invention prepares a seed crystal precursor sol, in which aluminum alloy fins are immersed and dried to load alumina seed crystals onto the fin surface. A growth solution is then prepared by mixing sodium aluminate with urea. The fins loaded with alumina seed crystals are immersed in the growth solution in polytetrafluoroethylene (PTFE) to carry out a hydrothermal reaction, thereby further constructing a micro-array structure on the fin surface. When heat exchange air passes through the fins, the turbulence effect is enhanced, and the air velocity on the fin surface increases, thereby enabling better heat dissipation and improving the heat exchange efficiency of the heat exchange system.

[0036] 3. This invention involves mixing, melting, refining, and casting Al, Si, Fe, Mn, Mg, Cu, Ti, and Pr metal elements in appropriate proportions to obtain a cast-rolled alloy ingot. This ingot is then cut into alloy core sheets with a thickness of 10-15 mm, and the thickness of the alloy core sheets is gradually reduced by sequentially performing cold rolling-annealing-cold rolling-annealing-cold rolling processes, thereby obtaining high-strength single-layer aluminum alloy fins. Attached Figure Description

[0037] Figure 1 This is a process flow diagram of the preparation process of aluminum alloy composite materials for automotive heat exchange systems used in embodiments of the present invention. Detailed Implementation

[0038] 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.

[0039] Example 1

[0040] A preparation process for aluminum alloy composite materials used in automotive heat exchange systems, such as... Figure 1 As shown, the specific steps include:

[0041] S1: Preparation of aluminum alloy fins

[0042] S1.1: Take 1.2wt% Si, 0.63wt% Fe, 0.85wt% Mn, 1.4wt% Mg, 0.4wt% Cu, 0.02wt% Ti and 0.08wt% Pr, with the remainder being Al and unavoidable impurity elements. Mix them evenly and melt them, then transfer them to a holding furnace. Refine and degas them at 745℃ for 20 minutes. After holding at this temperature for 10 minutes, cast and roll them to obtain a cast and rolled alloy ingot. Then, cut off the head, tail and end face in sequence, and cut it into 10mm thick alloy core material sheets using a flat saw.

[0043] S1.2: The alloy core sheet is cold-rolled to a thickness of 5mm, then subjected to a first annealing process. The first annealing process involves heating to 415℃ and holding for 2 hours. The sheet is then cold-rolled to a thickness of 0.8mm, followed by a second annealing process at 350℃. Finally, the sheet is cold-rolled to a thickness of 0.1mm to obtain an aluminum alloy sheet. This sheet is then rolled by a roller cutter into a corrugated fin with a width of 35mm to obtain an aluminum alloy fin.

[0044] S2: Preparation of semi-foamed foil solder

[0045] S2.1: Take 5wt% Si, 2wt% Ni, 0.4wt% Cu, 0.2wt% Y and 0.05wt% Zr, with the remainder being Al and unavoidable impurity elements, mix them, melt and cast them into an ingot to obtain a brazing alloy.

[0046] S2.2: Add NaCl particles with a diameter of 5μm and NaCl particles with a diameter of 12μm to a container at a volume ratio of 1:3, then add aluminum powder with a diameter of 6μm, which accounts for 4% of the volume of NaCl particles, and stir to mix evenly to obtain fibrous salt powder.

[0047] S2.3: Place the fiber salt powder in a percolation mold, and then compress it to 1 / 3 of its original volume using a press to obtain a granular salt template with a thickness of 0.1 mm. Place the percolation mold containing the granular salt template in a pit-type resistance furnace. Place the brazing alloy in another pit-type resistance furnace and heat it to 550°C to melt it, obtaining a molten brazing alloy. Pour the molten brazing alloy into the percolation mold containing the granular salt template. Apply a pressure of 1 MPa at 610°C to allow the molten brazing alloy to percolate into the granular salt template. When the granular salt template is full of molten brazing alloy, stop pressurizing and continue adding molten brazing alloy until it is 0.1 mm above the granular salt template. Stop heating and air-cool the mold to demold it, obtaining a mixed salt-alloy double-layer brazing alloy. Then, dissolve the NaCl particles in water to obtain a semi-foam foil-like brazing alloy containing a foam layer and a solid layer.

[0048] S3: Turbulence enhancement on the surface of aluminum alloy fins

[0049] S3.1: Place 2 parts by weight of aluminum isopropoxide in a beaker, add 80 parts by weight of anhydrous ethanol, stir at 300 rpm for 10 minutes on a magnetic stirrer to form a uniform dispersion, add 0.5 parts by weight of acetylacetone dropwise to the uniform dispersion, then heat to 72°C and stir in a water bath for 30 minutes, then add 0.1 parts by weight of 65% nitric acid solution, and continue stirring at 250 rpm at room temperature for 1 hour to obtain the seed crystal precursor sol.

[0050] S3.2: Immerse the aluminum alloy fins in the seed crystal precursor sol, let stand for 25 seconds and then pull them out. The immersion speed is 100 mm / min and the pulling speed is 50 mm / min. Then place them under 120℃ hot air to dry and cure for 12 minutes. Repeat the immersion-pulling-drying cycle 3 times. Then transfer them to a tube furnace and keep them at 420℃ for 1 hour to obtain fins loaded with alumina seed crystals.

[0051] S3.3: Dissolve 1 part by weight of sodium aluminate in 50 parts by weight of deionized water, add 0.5 parts by weight of urea, and then add 65% nitric acid solution to adjust the pH to 9.5. Stir at 200 rpm for 4 hours to obtain the growth solution. Then, place the fins loaded with alumina seed crystals into a polytetrafluoroethylene reactor, lean it against the reactor wall, and pour in the growth solution to immerse the fins loaded with alumina seed crystals. Seal the polytetrafluoroethylene reactor and heat it to 120°C at a heating rate of 3°C / min. After holding at this temperature for 3 hours, cool it down to room temperature with the reactor. Take it out and rinse it with deionized water. Vacuum dry it at 60°C to constant weight. Then place it in a muffle furnace and hold it at 450°C for 2 hours. After cooling with the furnace, turbulence-strengthened aluminum alloy fins are obtained.

[0052] S4: Composite brazing of materials

[0053] S4: Cut the semi-foam foil brazing filler metal to a width of 0.2 mm, then fix the solid layer of the semi-foam foil brazing filler metal to the surface of the 6063 aluminum alloy tube. Fix the turbulence-reinforced aluminum alloy fins to the foam layer of the semi-foam foil brazing filler metal and braze them together. The brazing temperature is 565℃ and the brazing time is 20 minutes. The turbulence-reinforced aluminum alloy fins are spirally distributed on the tube with a spacing of 0.8 cm to obtain the aluminum alloy composite material.

[0054] Example 2

[0055] A preparation process for aluminum alloy composite materials used in automotive heat exchange systems, such as... Figure 1 As shown, the specific steps include:

[0056] S1: Preparation of aluminum alloy fins

[0057] S1.1: Take 1.45wt% Si, 1.1wt% Fe, 1.32wt% Mn, 2wt% Mg, 0.8wt% Cu, 0.08wt% Ti and 0.11wt% Pr, the remainder being Al and unavoidable impurity elements, mix them evenly and melt them, then transfer them to a holding furnace, refine and degas them at 745℃ for 20 minutes, hold them at the temperature for 10 minutes and then cast and roll them to obtain cast and rolled alloy ingots. Then, cut off the head, tail and end face in sequence, and cut them into 10mm thick alloy core sheets using a flat saw.

[0058] S1.2: The alloy core sheet is cold-rolled to a thickness of 5mm, then subjected to a first annealing process. The first annealing process involves heating to 415℃ and holding for 2 hours. The sheet is then cold-rolled to a thickness of 0.8mm, followed by a second annealing process at 350℃. Finally, the sheet is cold-rolled to a thickness of 0.1mm to obtain an aluminum alloy sheet. This sheet is then rolled by a roller cutter into a corrugated fin with a width of 35mm to obtain an aluminum alloy fin.

[0059] S2: Preparation of semi-foamed foil solder

[0060] S2.1: Take 5.5wt% Si, 2.5wt% Ni, 0.5wt% Cu, 0.3wt% Y and 0.15wt% Zr, with the remainder being Al and unavoidable impurity elements, mix them, melt and cast them into an ingot to obtain a brazing alloy.

[0061] S2.2: Add NaCl particles with a diameter of 5μm and NaCl particles with a diameter of 12μm to a container at a volume ratio of 1:3.5, then add aluminum powder with a diameter of 6μm, which accounts for 6% of the volume of NaCl particles, and stir to mix evenly to obtain fibrous salt powder.

[0062] S2.3: Place the fiber salt powder in a percolation mold, and then compress it to 1 / 3 of its original volume using a press to obtain a granular salt template with a thickness of 0.1 mm. Place the percolation mold containing the granular salt template in a pit-type resistance furnace. Place the brazing alloy in another pit-type resistance furnace and heat it to 550°C to melt it, obtaining a molten brazing alloy. Pour the molten brazing alloy into the percolation mold containing the granular salt template. Apply a pressure of 1 MPa at 610°C to allow the molten brazing alloy to percolate into the granular salt template. When the granular salt template is full of molten brazing alloy, stop pressurizing and continue adding molten brazing alloy until it is 0.1 mm above the granular salt template. Stop heating and air-cool the mold to demold it, obtaining a mixed salt-alloy double-layer brazing alloy. Then, dissolve the NaCl particles in water to obtain a semi-foam foil-like brazing alloy containing a foam layer and a solid layer.

[0063] S3: Turbulence enhancement on the surface of aluminum alloy fins

[0064] S3.1: Place 3 parts by weight of aluminum isopropoxide in a beaker, add 100 parts by weight of anhydrous ethanol, stir at 300 rpm for 10 minutes on a magnetic stirrer to form a uniform dispersion, add 0.8 parts by weight of acetylacetone dropwise to the uniform dispersion, then heat to 72°C and stir in a water bath for 30 minutes, then add 0.2 parts by weight of 65% nitric acid solution, and continue stirring at 250 rpm at room temperature for 1 hour to obtain the seed crystal precursor sol;

[0065] S3.2: Immerse the aluminum alloy fins in the seed crystal precursor sol, let stand for 25 seconds and then pull them out. The immersion speed is 100 mm / min and the pulling speed is 50 mm / min. Then place them under 120℃ hot air to dry and cure for 12 minutes. Repeat the immersion-pulling-drying cycle 3 times. Then transfer them to a tube furnace and keep them at 420℃ for 1 hour to obtain fins loaded with alumina seed crystals.

[0066] S3.3: Dissolve 2 parts by weight of sodium aluminate in 70 parts by weight of deionized water, add 0.7 parts by weight of urea, and then add 65% nitric acid solution to adjust the pH to 9.5. Stir at 200 rpm for 4 hours to obtain the growth solution. Then, place the fins loaded with alumina seed crystals into a polytetrafluoroethylene reactor, lean it against the reactor wall, and pour in the growth solution to immerse the fins loaded with alumina seed crystals. Seal the polytetrafluoroethylene reactor and heat it to 120°C at a heating rate of 3°C / min. After holding at this temperature for 3 hours, cool it down to room temperature with the reactor. Take it out and rinse it with deionized water. Vacuum dry it at 60°C to constant weight. Then place it in a muffle furnace and hold it at 450°C for 2 hours. After cooling with the furnace, turbulence-strengthened aluminum alloy fins are obtained.

[0067] S4: Composite brazing of materials

[0068] S4: Cut the semi-foam foil brazing filler metal to a width of 0.2 mm, then fix the solid layer of the semi-foam foil brazing filler metal to the surface of the 6063 aluminum alloy tube. Fix the turbulence-reinforced aluminum alloy fins to the foam layer of the semi-foam foil brazing filler metal and braze them together. The brazing temperature is 565℃ and the brazing time is 20 minutes. The turbulence-reinforced aluminum alloy fins are spirally distributed on the tube with a spacing of 0.8 cm to obtain the aluminum alloy composite material.

[0069] Example 3

[0070] A preparation process for aluminum alloy composite materials used in automotive heat exchange systems, such as... Figure 1 As shown, the specific steps include:

[0071] S1: Preparation of aluminum alloy fins

[0072] S1.1: Take 1.2wt% Si, 0.63wt% Fe, 0.85wt% Mn, 1.4wt% Mg, 0.4wt% Cu, 0.02wt% Ti and 0.08wt% Pr, with the remainder being Al and unavoidable impurity elements. Mix them evenly and melt them, then transfer them to a holding furnace. Refine and degas them at 770℃ for 30 minutes. After holding at this temperature for 15 minutes, cast and roll them to obtain a cast and rolled alloy ingot. Then, cut off the head, tail and end face in sequence, and cut it into 15mm thick alloy core material sheets using a flat saw.

[0073] S1.2: The alloy core sheet is cold-rolled to a thickness of 7mm, then subjected to a first annealing process, which involves heating to 465℃ and holding for 3 hours. After that, it is cold-rolled to a thickness of 1mm, and then subjected to a second annealing process, which involves annealing at 385℃. Finally, it is cold-rolled to a thickness of 0.2mm to obtain an aluminum alloy sheet. This sheet is then rolled by a roller cutter into a corrugated fin with a width of 45mm to obtain an aluminum alloy fin.

[0074] S2: Preparation of semi-foamed foil solder

[0075] S2.1: Take 5wt% Si, 2wt% Ni, 0.4wt% Cu, 0.2wt% Y and 0.05wt% Zr, with the remainder being Al and unavoidable impurity elements, mix them, melt and cast them into an ingot to obtain a brazing alloy.

[0076] S2.2: Add NaCl particles with a diameter of 6μm and NaCl particles with a diameter of 15μm to a container at a volume ratio of 1:3, then add aluminum powder with a diameter of 8μm, which accounts for 4% of the volume of NaCl particles, and stir to mix evenly to obtain fibrous salt powder.

[0077] S2.3: Place the fiber salt powder in a percolation mold, and then compress it to 1 / 2 of its original volume using a press to obtain a granular salt template with a thickness of 0.1 mm. Place the percolation mold containing the granular salt template in a pit-type resistance furnace. Place the brazing alloy in another pit-type resistance furnace and heat it to 560°C to melt it, obtaining a molten brazing alloy. Pour the molten brazing alloy into the percolation mold containing the granular salt template. Apply a pressure of 1.5 MPa at 650°C to allow the molten brazing alloy to percolate into the granular salt template. When the granular salt template is full of molten brazing alloy, stop pressurizing and continue adding molten brazing alloy until it is 0.1 mm above the granular salt template. Stop heating and air-cool the mold to demold it, obtaining a mixed salt-alloy double-layer brazing alloy. Then, dissolve the NaCl particles in water to obtain a semi-foam foil-like brazing alloy containing a foam layer and a solid layer.

[0078] S3: Turbulence enhancement on the surface of aluminum alloy fins

[0079] S3.1: Place 2 parts by weight of aluminum isopropoxide in a beaker, add 80 parts by weight of anhydrous ethanol, and stir at 400 rpm for 15 minutes on a magnetic stirrer to form a uniform dispersion. Add 0.5 parts by weight of acetylacetone dropwise to the uniform dispersion, then heat to 75°C and stir in a water bath for 35 minutes. Add 0.1 parts by weight of 65% nitric acid solution and continue stirring at 300 rpm at room temperature for 1.5 hours to obtain the seed crystal precursor sol.

[0080] S3.2: Immerse the aluminum alloy fins in the seed crystal precursor sol, let stand for 30 seconds and then pull them out. The immersion speed is 120 mm / min and the pulling speed is 60 mm / min. Then place them under 125℃ hot air to dry and cure for 15 minutes. Repeat the immersion-pulling-drying cycle 4 times. Then transfer them to a tube furnace and keep them at 450℃ for 1.5 hours to obtain fins loaded with alumina seed crystals.

[0081] S3.3: Dissolve 1 part by weight of sodium aluminate in 50 parts by weight of deionized water, add 0.5 parts by weight of urea, and then add 65% nitric acid solution to adjust the pH to 10. Stir at 250 rpm for 6 hours to obtain the growth solution. Then, place the fins loaded with alumina seed crystals into a polytetrafluoroethylene reactor, lean it against the reactor wall, and pour in the growth solution to immerse the fins loaded with alumina seed crystals. Seal the polytetrafluoroethylene reactor and heat it to 125°C at a heating rate of 4°C / min. After holding at this temperature for 4 hours, cool it down to room temperature with the reactor. Take it out and rinse it with deionized water. Vacuum dry it at 65°C to constant weight. Then place it in a muffle furnace and hold it at 470°C for 2.5 hours. After cooling with the furnace, turbulence-strengthened aluminum alloy fins are obtained.

[0082] S4: Composite brazing of materials

[0083] The semi-foam foil brazing filler metal was cut to a width of 0.3 mm. The solid layer of the semi-foam foil brazing filler metal was then fixed to the surface of a 6063 aluminum alloy tube. Turbulence-reinforced aluminum alloy fins were then fixed to the foam layer of the semi-foam foil brazing filler metal and brazed together. The brazing temperature was 575℃ and the brazing time was 20 minutes. The turbulence-reinforced aluminum alloy fins were spirally distributed on the tube with a spacing of 1 cm, resulting in an aluminum alloy composite material.

[0084] Comparative Example 1

[0085] The difference from Example 1 is that Comparative Example 1 omits steps S2.2 and 2.3, directly forms a solid foil-like solder with a solder alloy of 0.2 mm thickness, and replaces the semi-foamed foil-like solder in step S4 with a solid foil-like solder. The rest of the implementation is the same as Example 1.

[0086] Comparative Example 2

[0087] The difference from Example 1 is that Comparative Example 2 omits steps S3.1-S3.3 and replaces the turbulence-enhanced aluminum alloy fins in S4 with the aluminum alloy fins in S1.2. The implementation methods are the same as those in Example 1.

[0088] Brazing performance test:

[0089] Shear strength: The aluminum alloy composite materials prepared in Examples 1-3 and Comparative Example 1 were placed on a universal electronic testing machine for shear testing. The temperature was room temperature, the test force was 20 kN, and the loading rate was 0.1 mm / min. The shear strength was calculated as F / S (where F is the maximum shear force (N) and S is the effective interface area (mm²)). 2 ));

[0090] Air tightness: First, a circular through hole with a diameter of 0.05 mm is opened at the weld joint of the 6063 aluminum alloy tube. Then, brazing is performed using the processes of Examples 1-3 and Comparative Example 1 to obtain an air tightness test sample. Both ends of the tube of the air tightness test sample are sealed, with an air tightness hole opened at one end. Helium gas is continuously introduced into the tube through the air tightness hole using a spray gun to pressurize the inside of the tube. A helium leakage mass spectrometer is set at the brazing joint on the outside to test whether there is helium leakage and the leakage rate is recorded. After standing for one week, the test is repeated and the leakage rate after one week is recorded.

[0091] All the above tests were conducted in three parallel trials, and the average value of the test results was taken, as shown in Table 1.

[0092] Table 1: Shear strength and airtightness of brazed joints

[0093]

[0094] As can be seen from the data in Table 1 of Examples 1-3, the brazed joints of the aluminum alloy composite material prepared in this application have excellent shear strength and air tightness. However, in Comparative Example 1, which did not use the semi-foam foil brazing filler metal of this application for brazing, both its shear strength and air tightness decreased. This proves that preparing semi-foam foil brazing filler metal for brazing can enhance the brazing stability and density of the micro-uneven interface and form a stable welded joint.

[0095] Heat exchange efficiency test: The aluminum alloy composite materials prepared in Examples 1-3 and Comparative Example 2 were filled with 1L of clean water at a temperature of 75°C in the tubes of the aluminum alloy composite materials. They were placed in the same ventilated environment at a temperature of 20°C and an airflow rate of 5m / s. The cooling time when the water temperature dropped to 25°C was recorded. The test results are shown in Table 2.

[0096] Table 2: Efficiency of aluminum alloy composite materials in cooling water at 75°C

[0097]

[0098] As can be seen from the data in Examples 1-3 and Comparative Example 2 in Table 2, the heat exchange efficiency of the aluminum alloy composite material decreases when the aluminum alloy fins are not subjected to turbulence enhancement. This proves that by constructing a micro-array structure on the surface of the aluminum alloy fins, this application can enhance the turbulence effect, increase the air velocity on the fin surface, and thus better dissipate heat.

[0099] Mechanical property testing: Turbulence-strengthened aluminum alloy fins prepared in Examples 1-3 and commercially available 0.1mm heat exchanger fin steel strips were used as control groups. Three weight samples of tensile test were prepared according to GB / T228.1-2010 standard, with a gauge length of 50mm. Tensile tests were then conducted at room temperature with a tensile speed of 20mm / min to test the yield strength and tensile strength. The average values ​​of the three samples were taken, as shown in Table 3.

[0100] Table 3: Tensile strength of turbulence-enhanced aluminum alloy fins and control group

[0101]

[0102] As can be seen from the data of Examples 1-3 and the control group in Table 3, the present invention can produce high-strength single-layer aluminum alloy fins that meet industrial requirements by mixing, melting, refining and casting the metal elements Al, Si, Fe, Mn, Mg, Cu, Ti and Pr in appropriate proportions, melting, refining and casting the cast-rolled alloy ingots, cutting them into alloy core sheets with a thickness of 10-15 mm, and then performing cold rolling-annealing-cold rolling-annealing-cold rolling processes in sequence.

[0103] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A preparation process for an aluminum alloy composite material used in an automotive heat exchange system, characterized in that, Includes the following steps: S1: Preparation of aluminum alloy fins Take 1.2-1.45wt% Si, 0.63-1.1wt% Fe, 0.85-1.32wt% Mn, 1.4-2wt% Mg, 0.4-0.8wt% Cu, 0.02-0.08wt% Ti and 0.08-0.11wt% Pr, with the remainder being Al and unavoidable impurity elements. Mix and melt the mixture, then refine and cast it. Cut it into alloy core sheets with a thickness of 10-15mm, then cold roll it to a thickness of 5-7mm and anneal it. Then cold roll it to a thickness of 0.8-1mm and anneal it. Finally, cold roll it to a thickness of 0.1-0.2mm and roll it into a corrugated fin to obtain aluminum alloy fins. S2: Preparation of semi-foamed foil solder Al, Si, Ni, Cu, Y and Zr elements are mixed, melted and cast into ingots to obtain a brazing alloy. NaCl salts of different particle sizes and aluminum powder are mixed evenly and then added to a mold for compression to obtain a granular salt template. Then, the molten brazing alloy is melted and pressed into the granular salt template. Molten brazing alloy is then added again. After cooling and demolding, the NaCl particles are dissolved to obtain a semi-foam foil brazing alloy containing a foam layer and a solid layer. S3: Turbulence enhancement on the surface of aluminum alloy fins Aluminum isopropoxide was dispersed in anhydrous ethanol, and acetylacetone and nitric acid solution were added to obtain a seed crystal precursor sol. Aluminum alloy fins were immersed in the seed crystal precursor sol for extraction and drying, and then immersed in a growth solution prepared by mixing sodium aluminate aqueous solution and urea. A hydrothermal reaction was carried out in a reactor, and after drying and calcination, turbulence-strengthened aluminum alloy fins were obtained. S4: Composite brazing of materials Turbulence-enhanced aluminum alloy fins and 6063 aluminum alloy tubing are brazed together using semi-foamed foil brazing filler metal to obtain an aluminum alloy composite material.

2. The preparation process of an aluminum alloy composite material for an automotive heat exchange system according to claim 1, characterized in that, Step S1, the preparation of aluminum alloy fins, specifically includes the following steps: S1.1: Take 1.2-1.45wt% Si, 0.63-1.1wt% Fe, 0.85-1.32wt% Mn, 1.4-2wt% Mg, 0.4-0.8wt% Cu, 0.02-0.08wt% Ti and 0.08-0.11wt% Pr, with the remainder being Al and unavoidable impurity elements. Mix them evenly and melt them, then transfer them to a holding furnace. Refine and degas them at 745-770℃ for 20-30 minutes. After holding at this temperature for 10-15 minutes, cast and roll them to obtain a cast and rolled alloy ingot. Then, cut off the head, tail and end face in sequence, and cut it into 10-15mm thick alloy core sheets using a flat saw. S1.2: The alloy core sheet is cold-rolled to a thickness of 5-7mm, then subjected to a first annealing process. The first annealing process involves heating to 415-465℃ and holding for 2-3 hours. Then, it is cold-rolled to a thickness of 0.8-1mm, followed by a second annealing process at 350-385℃. Finally, it is cold-rolled to a thickness of 0.1-0.2mm to obtain an aluminum alloy sheet. This sheet is then rolled by a roller cutter into corrugated fins with a width of 35-45mm to obtain aluminum alloy fins.

3. The preparation process of an aluminum alloy composite material for an automotive heat exchange system according to claim 2, characterized in that, The melting point of the aluminum alloy fins in step S1.2 is 650-665℃.

4. The preparation process of an aluminum alloy composite material for an automotive heat exchange system according to claim 1, characterized in that, Step S2, the preparation of the semi-foamed foil solder, specifically includes the following steps: S2.1: Take 5-5.5wt% Si, 2-2.5wt% Ni, 0.4-0.5wt% Cu, 0.2-0.3wt% Y and 0.05-0.15wt% Zr, with the remainder being Al and unavoidable impurity elements, mix them, melt and cast them into an ingot to obtain a brazing filler alloy. S2.2: Add NaCl particles with a diameter of 5-6μm and NaCl particles with a diameter of 12-15μm into a container at a volume ratio of 1:(3-3.5), then add aluminum powder accounting for 4-6% of the volume of NaCl particles, stir and mix evenly to obtain fibrous salt powder. S2.3: Place the fiber salt powder in a percolation mold, and then compress it to 1 / 3-1 / 2 of its original volume using a press to obtain a granular salt template with a thickness of 0.1 mm. Place the percolation mold containing the granular salt template in a pit-type resistance furnace. Place the brazing alloy in another pit-type resistance furnace and heat it to 550-560℃ to melt it, obtaining a molten brazing alloy. Pour the molten brazing alloy into the percolation mold containing the granular salt template. Apply a pressure of 1-1.5 MPa at 610-650℃ to allow the molten brazing alloy to percolate into the granular salt template. When the granular salt template is full of molten brazing alloy, stop pressurizing and continue adding molten brazing alloy until it is 0.1 mm above the granular salt template. Stop heating and air-cool the mold before demolding to obtain a mixed salt-alloy double-layer brazing alloy. Then, dissolve the NaCl particles in water to obtain a semi-foam foil-like brazing alloy containing a foam layer and a solid layer.

5. The preparation process of an aluminum alloy composite material for an automotive heat exchange system according to claim 4, characterized in that, The melting point of the brazing alloy in step S2.1 is 530-540℃.

6. The preparation process of an aluminum alloy composite material for an automotive heat exchange system according to claim 4, characterized in that, The aluminum powder in step S2.2 has a particle size of 6-8 μm.

7. The preparation process of an aluminum alloy composite material for an automotive heat exchange system according to claim 1, characterized in that, Step S3, turbulence enhancement of the aluminum alloy fin surface, specifically includes the following steps: S3.1: Place 2-3 parts by weight of aluminum isopropoxide in a beaker, add 80-100 parts by weight of anhydrous ethanol, and stir at 300-400 rpm for 10-15 minutes on a magnetic stirrer to form a uniform dispersion. Add 0.5-0.8 parts by weight of acetylacetone dropwise to the uniform dispersion, then heat to 72-75℃ and stir in a water bath for 30-35 minutes. Add 0.1-0.2 parts by weight of 65-70% nitric acid solution and continue stirring at 250-300 rpm at room temperature for 1-1.5 hours to obtain the seed crystal precursor sol. S3.2: Immerse the aluminum alloy fins in the seed crystal precursor sol, let stand for 25-30 seconds, then pull them out, and then dry and cure them in hot air at 120-125℃ for 12-15 minutes. Repeat the immersion-pulling-drying cycle 3-4 times, and then transfer them to a tube furnace and keep them at 420-450℃ for 1-1.5 hours to obtain fins loaded with alumina seed crystals. S3.3: Dissolve 1-2 parts by weight of sodium aluminate in 50-75 parts by weight of deionized water, add 0.5-0.7 parts by weight of urea, and then add 65-70% nitric acid solution to adjust the pH to 9.5-10. Stir at 200-250 rpm for 4-6 hours to obtain the growth solution. Then, place the fins loaded with alumina seed crystals into a polytetrafluoroethylene reactor, lean it against the reactor wall, and pour in the growth solution to immerse the fins loaded with alumina seed crystals. Seal the polytetrafluoroethylene reactor and heat it to 120-125℃ at a heating rate of 3-4℃ / min. After holding at this temperature for 3-4 hours, cool it down to room temperature with the reactor. Take it out and rinse it with deionized water. Vacuum dry it at 60-65℃ to constant weight. Then place it in a muffle furnace and hold it at 450-470℃ for 2-2.5 hours. After cooling with the furnace, you will obtain turbulence-strengthened aluminum alloy fins.

8. The preparation process of an aluminum alloy composite material for an automotive heat exchange system according to claim 7, characterized in that, In step S3.2, the immersion speed of the aluminum alloy is 100-120 mm / min, and the pulling speed is 50-60 mm / min.

9. The preparation process of an aluminum alloy composite material for an automotive heat exchange system according to claim 1, characterized in that, The composite brazing of materials in step S4 specifically includes the following steps: The semi-foam foil brazing filler metal is cut to a width of 0.2-0.3 mm. The solid layer of the semi-foam foil brazing filler metal is then fixed to the surface of a 6063 aluminum alloy tube. Turbulence-reinforced aluminum alloy fins are then fixed to the foam layer of the semi-foam foil brazing filler metal and brazed together. The brazing temperature is 565-575℃ and the brazing time is 20 minutes. The turbulence-reinforced aluminum alloy fins are spirally distributed on the tube with a spacing of 0.8-1 cm, thus obtaining an aluminum alloy composite material.

10. An aluminum alloy composite material for automotive heat exchange systems, characterized in that, It is prepared by the preparation process of an aluminum alloy composite material for an automotive heat exchange system as described in any one of claims 1-9.

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