Manufacturing method of thin-wall aluminum-copper metallurgical composite pipe

Abstract

The invention discloses a manufacturing method of a thin-wall aluminum-copper metallurgical composite pipe, which is characterized in that the composite pipe comprises a bottom-layer aluminum pipe, a metallurgical alloy layer positioned outside the aluminum pipe, an outer-layer copper layer positioned outside the metallurgical alloy layer and a surface layer, and the metallurgical alloy layer is formed by heating the surface of the aluminum pipe through laser to enable the aluminum surface to reach a molten state. Meanwhile, the copper material is heated to be in a molten state and then sprayed to the surface of the aluminum, so that the copper and the aluminum form a micron-sized alloy layer; and the outer copper layer is formed by laser cladding. The outer copper layer enables the bottom layer aluminum pipe to be in complete contact with the outside, the service life is long, the heat conduction effect is close to that of the copper pipe, the micron-sized metallurgical alloy layer enables the aluminum-copper shear strength to be greatly improved, copper-aluminum potential corrosion is eradicated, and the surface macromolecule modified silane nano composite layer improves the corrosion resistance; and the wall thickness can be controlled between 0.6 mm and 0.8 mm.

Description

Technical Field

[0001] This invention relates to the field of metal composite material processing technology, specifically a method for manufacturing thin-walled aluminum-copper metallurgical composite tubes, which is particularly suitable for industrial applications requiring high thermal conductivity, corrosion resistance, and lightweight heat exchangers, refrigeration pipelines, etc. Background Technology

[0002] In existing technologies, some air conditioning refrigeration systems and components are made entirely of copper tubing. The manufacturing process involves: cathode electrolysis of copper → remelting → casting → descaling → continuous rolling → triple drawing → coil drawing → coiling → testing → annealing → packaging. The disadvantages of this type of product are high cost, the weight of copper components increases the risk of the outdoor unit falling, and the lack of a protective layer on the surface makes it prone to oxidation.

[0003] Traditional aluminum-copper composite pipes are mostly manufactured using mechanical pressing or brazing, which suffers from problems such as low interfacial bonding strength, high thermal resistance, and susceptibility to corrosion. For example, patent publication number CN101737565B describes a method for manufacturing copper-aluminum composite pipes, including preparing an inner tube and a covering tape, cleaning the surfaces of the inner tube and the covering tape, wrapping the cleaned covering tape around the cleaned inner tube, and then performing longitudinal covering welding to obtain a copper-aluminum composite pipe blank. The blank is then linearly drawn and wound without tension, annealed, and finally wound to obtain the finished product. This method claims to achieve a strong metallurgical bond between copper and aluminum, but in reality, it is still a mechanical pressing process. For example, patent publication number CN102418813A describes a copper-aluminum composite pipe comprising a copper layer and an aluminum layer, with the copper layer on the inside and the aluminum layer on the outside. An intermediate interlayer is provided between the copper and aluminum layers, and this intermediate interlayer can be any one of a manganese layer, a nickel layer, or a chromium layer. A first metallurgical bonding layer exists between the copper layer and the intermediate interlayer, and a second metallurgical bonding layer exists between the intermediate interlayer and the aluminum layer. These products all aim to achieve a metallurgical bonding layer, but none disclose a technical solution that can achieve this. These conventional methods, in reality, cannot obtain a truly meaningful metallurgical bonding layer.

[0004] Although laser cladding technology can be used to bond dissimilar metals, aluminum and copper are prone to cracks and pores due to the large difference in their coefficients of thermal expansion. These existing technical problems have also hindered the application of laser cladding technology in this field.

[0005] In addition, existing composite pipe surface protection mostly uses a single coating, which has insufficient weather resistance and adhesion. Summary of the Invention

[0006] The purpose of this invention is to solve the above problems and provide a method for manufacturing thin-walled aluminum-copper metallurgical composite pipes, which have the characteristics of being lightweight, having a long service life, having thermal conductivity close to that of copper pipes, eliminating copper-aluminum potential corrosion, having a nano-composite protective film on the surface, and having a wall thickness of up to 0.6-0.8 mm.

[0007] The above-mentioned technical problems of the present invention are mainly solved by the following technical solution: a method for manufacturing a thin-walled aluminum-copper metallurgical composite pipe, characterized in that the composite pipe includes a bottom aluminum pipe, a metallurgical alloy layer located outside the aluminum pipe, an outer copper layer located outside the metallurgical alloy layer, and a surface layer. The metallurgical alloy layer is formed by heating the surface of the aluminum pipe with a laser to make the aluminum surface reach a molten state, while simultaneously heating the copper material to a molten state, and then spraying it onto the aluminum surface to form a micron-level alloy layer of copper and aluminum; the outer copper layer is formed by laser cladding.

[0008] In the aforementioned method for manufacturing thin-walled aluminum-copper metallurgical composite pipes, the bottom aluminum pipe is obtained from aluminum material through continuous extrusion, and the metallurgical alloy layer and outer copper layer are applied during the forming of the aluminum pipe, forming a continuous process.

[0009] In the aforementioned method for manufacturing thin-walled aluminum-copper metallurgical composite pipes, the surface layer is a polymer-modified silane nanocomposite layer, which comprises the following components by weight: 10-12 parts of organosilicon-modified acrylate, 2-3 parts of fluorosilicone resin, 2 parts of polyolefin emulsion, 2-2.5 parts of benzotriazole, 1-2 parts of modified nano-silica, 1-3 parts of modified organosilicon, 0.5-1 parts of a mixture of polysiloxane and hydrophobic particles, 0.2 parts of leveling agent, 0.2 parts of wetting agent, 5-12 parts of ethanol, and the remainder being water.

[0010] In the aforementioned method for manufacturing thin-walled aluminum-copper metallurgical composite pipes, the thickness of the metallurgical alloy layer is 0.005–0.012 mm; the aluminum pipe wall thickness is 0.6–0.8 mm; and the copper layer thickness is 0.04–0.11 mm.

[0011] In the aforementioned method for manufacturing thin-walled aluminum-copper metallurgical composite pipes, the outer copper layer is a toothed surface or a smooth surface. The toothed surface is formed by the aluminum pipe rotating during laser cladding, causing the outer surface of the copper layer to form concentric toothed surfaces. The smooth surface is obtained by grinding and polishing after laser cladding.

[0012] In the aforementioned method for manufacturing thin-walled aluminum-copper metallurgical composite pipes, during the forming process of the metallurgical alloy layer on the outside of the aluminum pipe, nitrogen gas of 0.02 to 0.06 MPa is introduced into the aluminum pipe for cooling, so that the aluminum pipe substrate remains solid.

[0013] In the aforementioned method for manufacturing thin-walled aluminum-copper metallurgical composite tubes, during the laser heating and laser cladding process, the laser defocusing distance is controlled, wherein the molten pool depth is controlled to be 0.008–0.02 mm, the alloy layer thickness is controlled to be 0.003–0.008 mm, the laser power is 800–1200 W, and the scanning speed is 8–25 mm / s.

[0014] In the aforementioned method for manufacturing thin-walled aluminum-copper metallurgical composite pipes, the metallurgical alloy layer and the copper layer are supplied with copper powder material by a coaxial powder feeding system. The copper powder has a purity of ≥99.5% and a particle size of 15–45 μm.

[0015] In the aforementioned method for manufacturing thin-walled aluminum-copper metallurgical composite pipes, the protective atmosphere during laser heating and laser cladding is a mixture of nitrogen and hydrogen gas, wherein the hydrogen is controlled at 1-3% and the flow rate is 15-25 L / min, forming a double gas curtain to protect the molten pool.

[0016] The composite tube obtained by this method has a four-layer structure: a bottom aluminum tube, continuously extruded using existing technology, with a wall thickness of 0.6–0.8 mm; an outer layer of micron-sized Cu-Al diffusion layer, i.e., a metallurgical alloy layer; an outer copper layer clad by laser; and finally, a nano-composite coating, i.e., a sealing layer. Metallurgical bonding is achieved through coaxial powder feeding and synchronous laser cladding, with the alloy layer thickness accurate to 0.003–0.008 mm. During the cladding process, the aluminum tube is cooled by nitrogen to prevent the substrate from melting.

[0017] This method, through strict control of various process parameters and the setting of a double-air curtain to protect the molten pool, enables the metallurgical alloy layer to meet the true technical requirements.

[0018] This technical solution uses organosilicon-modified acrylate, fluorosilicone resin, and polyolefin emulsion as the main film-forming substances, which can form a complete protective film on the copper surface. Copper corrosion inhibitors (benzotriazole or mercaptobenzothiazole), modified nano-silica, etc. are used as auxiliary film-forming substances, which work synergistically with the main film-forming substances to improve the protective performance of the film, improve the scratch resistance of the protective film, and also play a certain repair role in the case of film damage. Polysiloxane and hydrophobic particle mixture, leveling agent, wetting agent, etc. are used as auxiliary additives to improve the construction performance of the sealing liquid, ensure good contact with the copper surface, make the sealing layer uniformly and densely spread on the copper surface, improve the bonding force between the sealing liquid and copper, and improve the density.

[0019] Compared with the prior art, the beneficial effects of the present invention are: lightweight, 2 / 3 lighter than copper tubes, and low cost of continuous process forming; the outer copper layer allows the bottom aluminum tube to be in complete contact with the outside world, resulting in a long service life; the thermal conductivity is close to that of copper tubes; the micron-level metallurgical alloy layer greatly improves the shear strength of aluminum and copper and eliminates copper-aluminum potential corrosion; the surface polymer modified silane nanocomposite layer improves corrosion resistance; and the wall thickness can be controlled between 0.6-0.8 mm. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a composite pipe cross-section structure according to the present invention.

[0021] Figure 2 This is a schematic diagram of an embodiment of the outer copper layer of the tooth-shaped surface according to the present invention.

[0022] Figure 3 This is a process flow diagram of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0024] This embodiment discloses a method for manufacturing a thin-walled aluminum-copper metallurgical composite pipe, the composition of which is as follows: Figure 1 As shown, it includes a bottom aluminum tube 1, a metallurgical alloy layer 2 located outside the aluminum tube 1, an outer copper layer 3 located outside the metallurgical alloy layer 2, and a polymer-modified silane nanocomposite layer - surface layer 4.

[0025] The aluminum tube 1 has a wall thickness of 0.6 to 0.8 mm. The metallurgical alloy layer 2 is formed by heating the surface of the aluminum tube 1 with a laser to make the surface of the aluminum tube 1 reach a molten state, while simultaneously heating the copper material to a molten state, and then spraying it onto the surface of the aluminum tube to form a micron-level alloy layer of copper and aluminum. The thickness of the metallurgical alloy layer 2 is 0.005 to 0.012 mm.

[0026] The outer copper layer 3 is formed by laser cladding, and the thickness of the copper layer 3 is 0.04 to 0.11 mm.

[0027] In this method, the bottom aluminum tube 1 is obtained by continuous extrusion of aluminum material. During the forming of the aluminum tube 1, the metallurgical alloy layer 2 and the outer copper layer 3 are applied to form a continuous process.

[0028] The specific process is as follows: See Figure 3 The raw material aluminum rod is first descaled, then extruded and cold-drawn into aluminum tube 1 of the set size in the extrusion equipment. After cooling, it is coiled, then straightened and cut to length according to product specifications, and then enters the metallurgical alloy layer 2 production stage.

[0029] This method of aluminum-copper cladding metallurgy includes the formation of a metallurgical alloy layer 2 and an outer copper layer 3. High-speed laser heating combined with copper powder metallurgy is used on an aluminum tube blank 1. The aluminum tube 1 is mounted on a machine tool and rotates simultaneously with laser cladding. During laser cladding, the surface temperature of the aluminum tube 1 reaches its melting point. Due to its thin wall, it is easily melted through, making copper cladding impossible. Therefore, during the formation of the metallurgical alloy layer 2, nitrogen gas (0.02–0.06 MPa) is introduced into the aluminum tube 1 for cooling, keeping the aluminum tube substrate solid. The aluminum tube 1 is a pre-formed product with open ends; during nitrogen filling, an internal pressure of less than or equal to 0.06 MPa prevents deformation of the aluminum tube 1.

[0030] During laser heating and laser cladding, the laser defocusing distance is controlled, with the molten pool depth controlled at 0.008–0.02 mm and the alloy layer thickness controlled at 0.003–0.008 mm.

[0031] Process parameters: Laser power is 800-1200W, scanning speed is 8-25mm / s; powder feeding rate is 2-4g / min, precisely controlling the cladding layer thickness; overlap rate is 30-40%, ensuring a continuous, groove-free surface; fiber laser (wavelength 1070nm, power 2-4kW), dynamic focusing system controls the spot diameter to 0.5-1.5mm; both processes are supplied with copper powder by a coaxial powder feeding system, the copper powder purity is ≥99.5%, and the particle size is 15-45μm.

[0032] Nitrogen flow rate inside aluminum tube: 5-15 L / min.

[0033] Protective atmosphere: Nitrogen and hydrogen are mixed and vaporized, with hydrogen controlled at 1-3% and a flow rate of 15-25 L / min, forming a double gas curtain to protect the molten pool.

[0034] After laser cladding of the outer copper layer 3, there are two process options: one is to form a series of toothed surfaces on the outer surface of the copper layer 3, such as... Figure 2 As shown, the toothed surface is achieved by mounting the aluminum tube on a machine tool and rotating it during laser cladding, creating concentric toothed surfaces on the outer surface of the copper layer. Secondly, depending on customer needs, a grinding machine can be used for polishing to achieve a smooth surface, similar to the surface effect of extruded pure copper tubes.

[0035] The outer layer 4 is a layer of polymer-modified silane nanocomposite coated on the outer surface of the copper layer 3 as a sealing layer. The sealing layer comprises the following components by weight: 10-12 parts of organosilicon-modified acrylate, 2-3 parts of fluorosilicone resin, 2 parts of polyolefin emulsion, 2-2.5 parts of benzotriazole, 1-2 parts of modified nano-silica, 1-3 parts of modified organosilicon, 0.5-1 parts of a mixture of polysiloxane and hydrophobic particles, 0.2 parts of leveling agent, 0.2 parts of wetting agent, 5-12 parts of ethanol, and the remainder is water.

[0036] Experiments showed that the thin-walled aluminum-copper metallurgical composite pipe obtained through this embodiment, due to the effect of the nano-scale metallurgical alloy layer, achieved an aluminum-copper shear strength ≥80MPa, which is more than 30% higher than that of traditional brazing. Salt spray testing of the nano-composite surface showed no blistering after ≥1000 hours.

[0037] After the surface layer of the four polymer-modified silane nanocomposite layers is completed, the nozzle is deburred, then inspected, and then packaged.

[0038] The above embodiments are illustrative of the present invention and not intended to limit the invention. The described embodiments are merely some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art inspired by the present invention without creative effort are within the scope of protection of the present invention.

Claims

1. A method for manufacturing a thin-walled aluminum-copper metallurgical composite pipe, characterized in that, The composite tube includes a bottom aluminum tube (1), a metallurgical alloy layer (2) located outside the aluminum tube, an outer copper layer (3) located outside the metallurgical alloy layer, and a surface layer (4). The metallurgical alloy layer is formed by heating the surface of the aluminum tube with a laser to make the aluminum surface reach a molten state, while heating the copper material to a molten state, and then spraying it onto the aluminum surface to form a micron-level alloy layer of copper and aluminum. The outer copper layer (3) is formed by laser cladding.

2. The method for manufacturing thin-walled aluminum-copper metallurgical composite pipe according to claim 1, characterized in that, The bottom aluminum tube (1) is obtained by continuous extrusion of aluminum material. During the forming of the aluminum tube, the metallurgical alloy layer (2) and the outer copper layer (3) are formed to form a continuous process.

3. The method for manufacturing thin-walled aluminum-copper metallurgical composite pipe according to claim 1, characterized in that, The surface layer (4) is a polymer-modified silane nanocomposite layer, which includes the following components by weight: 10-12 parts of organosilicon-modified acrylate, 2-3 parts of fluorosilicone resin, 2 parts of polyolefin emulsion, 2-2.5 parts of benzotriazole, 1-2 parts of modified nano silica, 1-3 parts of modified organosilicon, 0.5-1 parts of a mixture of polysiloxane and hydrophobic particles, 0.2 parts of leveling agent, 0.2 parts of wetting agent, 5-12 parts of ethanol, and the remainder is water.

4. The method for manufacturing thin-walled aluminum-copper metallurgical composite pipe according to claim 1, characterized in that, The metallurgical alloy layer (2) has a thickness of 0.005 to 0.012 mm; the aluminum tube (1) has a wall thickness of 0.6 to 0.8 mm; and the copper layer (3) has a thickness of 0.04 to 0.11 mm.

5. The method for manufacturing thin-walled aluminum-copper metallurgical composite pipe according to claim 1, characterized in that, The outer copper layer (3) is a toothed surface or a smooth surface. The toothed surface is formed by the aluminum tube (1) rotating during laser cladding, so that the outer surface of the copper layer forms a series of toothed surfaces. The smooth surface is obtained by grinding and polishing after laser cladding.

6. The method for manufacturing thin-walled aluminum-copper metallurgical composite pipe according to claim 1, characterized in that, in During the forming process of the metallurgical alloy layer (2) on the outside of the aluminum tube, nitrogen gas of 0.02 to 0.06 MPa is introduced into the aluminum tube (1) for cooling, so that the aluminum tube substrate remains solid.

7. The method for manufacturing thin-walled aluminum-copper metallurgical composite pipe according to claim 1, characterized in that, During laser heating and laser cladding, the laser defocusing distance is controlled, with the molten pool depth controlled at 0.008–0.02 mm and the alloy layer thickness controlled at 0.003–0.008 mm; the laser power is 800–1200 W and the scanning speed is 8–25 mm / s.

8. The method for manufacturing thin-walled aluminum-copper metallurgical composite pipe according to claim 1, characterized in that, The metallurgical alloy layer (2) and the copper layer (3) are supplied with copper powder by a coaxial powder feeding system. The copper powder has a purity of ≥99.5% and a particle size of 15~45μm.

9. The method for manufacturing thin-walled aluminum-copper metallurgical composite pipe according to claim 1, characterized in that, The protective atmosphere during laser heating and laser cladding is a mixture of nitrogen and hydrogen, with hydrogen controlled at 1-3% and a flow rate of 15-25 L / min, forming a double gas curtain to protect the molten pool.

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