Heat treatment method for preparing high-strength aluminum alloy strip and aluminum alloy strip

Abstract

The invention relates to the technical field of aluminum alloy, in particular to a heat treatment method for preparing a high-strength aluminum alloy strip and the aluminum alloy strip, the aluminum alloy strip comprises an aluminum alloy matrix and a reinforcing agent, and the reinforcing agent comprises lanthanum oxide powder, nickel powder and cobalt powder; the heat treatment method for preparing the high-strength aluminum alloy strip comprises the steps of smelting, ingot casting, tempering, surface milling, hot rolling, cold rolling, intermediate annealing treatment, finish rolling, rough finished product annealing and slitting. The step of annealing the crude finished product comprises the following steps: primary annealing: uniformly heating the crude finished product to 170-190 DEG C, preserving heat for 1.5-2.5 hours, then heating to 200-230 DEG C, preserving heat for 1.4-2.5 hours, then heating to 240-270 DEG C, preserving heat for 7-11 hours, and cooling along with a furnace; secondary annealing: heating the annealed crude finished product to 350-450 DEG C, preserving heat for 4-6 hours, and cooling along with the furnace; the method has the advantage of simultaneously improving the strength and toughness of the aluminum alloy.

Description

Technical Field

[0001] This application relates to the technical field of aluminum alloys, and in particular to a heat treatment method for preparing high-strength aluminum alloy strips and the aluminum alloy strips themselves. Background Technology

[0002] Cables are characterized by being labor-intensive, capital-intensive, and low in technology. Metal shielding tape is an essential structure for medium and low-voltage power cables, providing electromagnetic pulse shielding. High-voltage cables primarily use corrugated aluminum sheaths, while medium and low-voltage cables mainly use copper tape. China's copper reserves are relatively low, making it difficult to meet domestic production needs. In stark contrast, China has abundant aluminum reserves. Using aluminum to produce shielding tapes to replace existing copper products can significantly reduce copper consumption, lower costs, and promote sustainable development in the industry.

[0003] Pure aluminum has advantages such as low density, low melting point, high plasticity, good corrosion resistance, and good electrical conductivity. However, its strength is relatively low, making it unsuitable for direct use in manufacturing shielding strips. To ensure the required tensile strength, elongation, and conductivity in practical applications, alloying methods are necessary to improve its properties. In related technologies, methods to increase the strength of aluminum alloys include adjusting the chemical composition or adding rare earth metals to reduce grain fineness. While these methods can improve strength, their toughness still needs improvement. Summary of the Invention

[0004] In order to simultaneously improve the strength and toughness of aluminum alloys, this application provides a heat treatment method for preparing high-strength aluminum alloy strips and the aluminum alloy strips themselves.

[0005] In a first aspect, this application provides a heat treatment method for preparing high-strength aluminum alloy strip, employing the following technical solution: A heat treatment method for preparing high-strength aluminum alloy strip, characterized in that: the aluminum alloy strip comprises an aluminum alloy matrix and a reinforcing agent, the reinforcing agent comprising lanthanum oxide powder, nickel powder and cobalt powder, the mass ratio of lanthanum oxide powder, nickel powder and cobalt powder being (0.5-1.5):(1-3):(0.5-1.5), and the mass percentage of the reinforcing agent added being 0.7-0.9 wt%; the heat treatment method for preparing high-strength aluminum alloy strip comprises melting, ingot casting, tempering, milling, hot rolling, cold rolling, intermediate annealing, finish rolling, rough finished product annealing and slitting; The tempering process is as follows: the ingot is heated to 350-430℃ and then cooled in the furnace; The intermediate annealing process is as follows: the intermediate annealing thickness is 0.8-1.2 mm. The cold-rolled rough product is heated to 180-220℃ and held for 1.5-2.5 h. The temperature is then uniformly increased to 450-520℃ and held for 2-4 h. The product is then cooled in the furnace to 380-450℃ and held for 6-10 h. The steps for annealing the crude product are as follows: First annealing: The crude product is uniformly heated to 170-190℃ and held for 1.5-2.5h, then heated to 200-230℃ and held for 1.4-2.5h, then heated to 240-270℃ and held for 7-11h, and then cooled in the furnace. Secondary annealing: The annealed crude product is heated to 350-450℃, held for 4-6 hours, and then cooled in the furnace.

[0006] By adopting the above technical solution and adding lanthanum oxide, nickel powder, and cobalt powder to the aluminum alloy matrix, it was found that lanthanum oxide can refine grains and significantly improve the reduction of microcracks, the promotion of crack deflection, and the delay of crack propagation. However, residual stress and weak bonding exist at the interface between lanthanum oxide and the aluminum alloy matrix, resulting in uneven dispersion and difficulty in achieving the grain-refining effect. The addition of nickel and cobalt powder can improve the wettability and bonding force of lanthanum oxide to the aluminum alloy matrix, allowing it to participate in the surface reaction of lanthanum oxide and form a stable lanthanum-nickel / cobalt oxide layer (such as LaNiO3, LaCoO3), enhancing the interfacial bonding between lanthanum oxide and the matrix, reducing interfacial defects. The synergistic effect of nickel and cobalt can improve the dispersion of lanthanum oxide, forming a composite strengthening network structure within the matrix, improving the strength and toughness of the aluminum alloy strip. It can also form nanoscale intermetallic compounds (such as Al3Ni, Al2O3 ... Lanthanum oxide (L3Co) acts as a reinforcing phase in the matrix through solid solution strengthening and precipitation strengthening, further enhancing strength. From a heat treatment perspective, tempering eliminates residual stress in the ingot and improves microstructure uniformity. During intermediate annealing, the low-temperature stage alleviates energy storage from cold rolling deformation and prevents premature recrystallization; the high-temperature stage promotes dynamic recovery and recrystallization, synergistically refining the grains with lanthanum oxide; the slow cooling stage reduces thermal stress and prevents interfacial cracking. During rough annealing, stepped heating gradually releases internal stress and stabilizes the microstructure. Secondary annealing eliminates residual stress and acts on lanthanum oxide, further alleviating or eliminating internal cracks in the matrix, thus improving the toughness and strength of the aluminum alloy strip. Furthermore, furnace cooling prevents lanthanum oxide from reacting with excessive carbon dioxide and water in the air at high temperatures to form lanthanum carbonate, which could cause interfacial cracking and affect the strength and toughness of the aluminum alloy strip.

[0007] Preferably, the average particle size of the lanthanum oxide powder is in the range of 2-10 μm.

[0008] By adopting the above technical solution, 2-10μm lanthanum oxide particles are conducive to their dispersion in the matrix and subsequent heat treatment process, achieving uniform distribution and avoiding the high preparation cost of nanoparticles. As heterogeneous nucleation sites, they can effectively inhibit the growth of α-Al dendrites during the solidification of aluminum alloys and play an excellent role in refining grains.

[0009] Preferably, the lanthanum oxide powder has graphene oxide loaded on its surface.

[0010] By adopting the above technical solutions, the dispersibility of lanthanum oxide can be improved, and graphene oxide (GO) can form chemical bonds with the Al alloy matrix (such as Al-OC), enhancing the interfacial bonding force and reducing interfacial debonding; it can also delay the penetration of hot corrosive media and improve corrosion resistance.

[0011] Preferably, the lanthanum oxide powder is treated with an aqueous solution of a cationic surfactant, then reacted with an aqueous dispersion of graphene oxide, and then vacuum dried to obtain lanthanum oxide powder with graphene oxide loaded on its surface; both the aqueous solution of the cationic surfactant and the aqueous dispersion of graphene oxide are ≤10℃.

[0012] By adopting the above technical solution, the preparation method is simple and uses water as a solvent, which is relatively environmentally friendly. In addition, lanthanum oxide has slight solubility in water, and using water as a solvent can also improve the defects on the surface of lanthanum oxide and enhance the interfacial bonding force between it and the aluminum alloy matrix. By controlling the water temperature, the solubility of lanthanum oxide in water can be reduced.

[0013] Preferably, the lanthanum oxide powder has an average particle size of 6 μm.

[0014] By adopting the above technical solution, the 6μm particle size is easy to disperse uniformly during the melting process, and its effect on refining grains is also better. Compared with finer particle sizes, it can also save costs.

[0015] Preferably, the nickel powder has an average particle size of 80 nm, and the cobalt powder has an average particle size of 50 nm.

[0016] By adopting the above technical solution, nano-sized particles can be partially dissolved in the aluminum alloy matrix, hindering dislocation movement and improving the solid solution strengthening effect. During the aging process, the nano-particles form Al3Ni / Al3Co dispersed distribution, producing a precipitation strengthening effect. They can also serve as heterogeneous nucleation cores to promote grain refinement.

[0017] Preferably, in the annealing step of the rough product, the temperature of the secondary annealing is 400°C.

[0018] By adopting the above technical solution, residual stress can be eliminated, excessive grain growth can be avoided, and the size of nanoscale precipitates can be maintained.

[0019] Secondly, this application provides an aluminum alloy strip, which adopts the following technical solution: An aluminum alloy strip, wherein the aluminum alloy strip is prepared by the heat treatment method for preparing high-strength aluminum alloy strip.

[0020] By adopting the above technical solution, the aluminum alloy strip prepared by the preparation method of this application has the advantages of high strength, high toughness and corrosion resistance, which can meet the requirements of high-end industries.

[0021] In summary, this application includes at least one of the following beneficial technical effects: 1. By adding lanthanum oxide, nickel powder, and cobalt powder to the aluminum alloy matrix, it was found that lanthanum oxide can refine grains and significantly improve the reduction of microcracks, promote crack deflection, and delay crack propagation. The addition of nickel and cobalt powder can improve the wettability and bonding force of lanthanum oxide to the aluminum alloy matrix, participate in the surface reaction of lanthanum oxide to form a stable lanthanum-nickel / cobalt oxide layer (such as LaNiO3, LaCoO3), enhance the interfacial bonding between lanthanum oxide and the matrix, reduce interfacial defects, and the synergistic effect of nickel and cobalt can improve the dispersion of lanthanum oxide, forming a composite strengthening network structure in the matrix, thereby improving the strength and toughness of the aluminum alloy strip. From the perspective of heat treatment process, during the annealing of the rough product, the internal stress can be gradually released and the microstructure stabilized by step heating. Then, the secondary annealing can eliminate residual stress and act on lanthanum oxide, further alleviating or eliminating cracks inside the matrix and improving the toughness and strength of the aluminum alloy strip. 2. The aluminum alloy strip prepared by the preparation method of this application has excellent tensile strength and elongation at break. Its tensile strength is 281-355 MPa, its elongation at break is 19.2-21.1%, and its conductivity is 62.1-63.2% IACS. Detailed Implementation

[0022] The following provides a more detailed description of this application in conjunction with specific details.

[0023] raw material The raw materials used in the embodiments of this application are all commercially available products. The refining agent was purchased from Jiangxi Century Xing New Material Co., Ltd., and the model is SJ-JLJ. The graphene oxide has a thickness of 1-2 nm and a sheet diameter range of 1-5 μm. The cationic surfactant is hexadecyltrimethylammonium chloride.

[0024] Example 1 A heat treatment method for preparing high-strength aluminum alloy strip, wherein the aluminum alloy strip comprises an aluminum alloy substrate and a reinforcing agent, the aluminum alloy substrate being aluminum alloy 8030, which, upon measurement, has a tensile strength of 180 MPa and an elongation at break of 15.8%; Its preparation method is as follows: S1. Melting: Set the furnace temperature to 850℃, add the aluminum alloy substrate, and stir until completely melted. Then add the reinforcing agent, which includes lanthanum oxide powder, nickel powder, and cobalt powder in a mass ratio of 1:2:1. The amount of reinforcing agent added is 0.78wt%. The particle size of the nickel powder is 80nm, the particle size of the cobalt powder is 50nm, and the average particle size of the lanthanum oxide powder is 10μm. After stirring for 30 minutes, hold at 760℃ and use high-purity argon to blow in the refining agent for refining and slag removal for at least 15 minutes, ensuring uniformity and avoiding tumbling of the aluminum liquid. After refining for 60 minutes, control the furnace temperature at 725℃, let it stand for 15 minutes, and then remove the slag. S2. Ingot casting: The ingot dimensions are 360*1200*5000 mm. The ingot is homogenized in a heating furnace at a temperature of 585℃ for 13 hours, and then air-cooled. S3. Tempering: The ingot is heated uniformly in a heating furnace to 400°C at a heating rate of 50°C / h, and then cooled in the furnace to obtain an aluminum alloy. S4. Milling: Machining aluminum alloy. Milling parameters: lowest point 6-8mm / single side, tool mark depth ≤0.1mm. The surface after milling is smooth, without cracks or slag inclusions, ensuring the removal of the ingot head and tail. S5. Hot rolling: The milled ingot is heated uniformly to 490℃ in a uniformly heated annealing furnace and held for 13 hours. Then it is put into a hot rolling mill for hot rolling. The initial rolling temperature is 480-490℃ and the final rolling temperature is 260-290℃. The rolling process is shown in Table 1. The hot rolling mill is a four-roll reversible single-stand double-coil hot rolling mill with a working roll diameter of φ630 mm, a support roll diameter of 1200 mm, a maximum rolling force of 2500 kN, and a roll width of 1320 mm. Table 1 Hot rolling process of Example 1

[0025] S6. Cold rolling: The cold rolling process parameters are shown in Table 2. Table 2 Cold rolling process parameters of Example 1

[0026] S7. Intermediate annealing treatment: The intermediate annealing thickness is 1.0 mm. The cold-rolled rough product is uniformly heated to 200℃ at a heating rate of 50℃ / h and held for 2 hours. Then, it is uniformly heated to 500℃ and held for 3 hours. Finally, it is furnace cooled to 420℃ and held for 8 hours. S8. Finishing Rolling: The finishing mill specifications are φ230 / 550 × 1350mm four-high irreversible mill, thickness tolerance: ±2%, plate shape tolerance: ±20I, rolling speed: 1200 mm / min, rolling force: 4000 KN / maximum; the finishing mill produces rough finished products, and the number of rolling passes is shown in Table 3. Table 3 Finishing Rolling Passes

[0027] S9. Annealing of the crude product: First annealing: The crude product is uniformly heated to 180℃ and held for 2 hours, then heated to 220℃ and held for 2 hours, then heated to 255℃ and held for 10 hours, and then cooled with the furnace. The uniform heating rate is 40℃ / h. Secondary annealing: The annealed crude product is uniformly heated to 400℃, held for 5 hours, and then cooled in the furnace; 50℃ / h; S10. Slitting: The annealed rough product is slit to obtain aluminum alloy strip. The width of the aluminum alloy strip is 35mm, and the width tolerance is ±0.2mm.

[0028] Example 2 A heat treatment method for preparing high-strength aluminum alloy strip differs from Example 1 in that the average particle size of lanthanum oxide powder in S1 is 6 μm, while the remaining steps are the same as in Example 1.

[0029] Example 3 A heat treatment method for preparing high-strength aluminum alloy strip differs from Example 1 in that the average particle size of lanthanum oxide powder in S1 is 2 μm, while the remaining steps are the same as in Example 1.

[0030] Example 4 A heat treatment method for preparing high-strength aluminum alloy strip differs from Example 2 in that the lanthanum oxide powder in S1 is loaded with graphene oxide. The specific preparation method is as follows: 2g of lanthanum oxide was dispersed in 200mL of a 1g / mL cationic surfactant aqueous solution, then filtered, washed, and then dispersed in 100mL of a 0.1g / L graphene oxide aqueous dispersion. The mixture was stirred for 20min, filtered, and vacuum dried to obtain lanthanum oxide-supported graphene oxide. The temperatures of both the cationic surfactant aqueous solution and the graphene oxide aqueous dispersion were ≤10℃.

[0031] Example 5 A heat treatment method for preparing high-strength aluminum alloy strip differs from Example 1 in that, in the S9 secondary annealing, the temperature of the rough finished product is uniformly raised to 350°C, held for 5 hours, and then cooled in the furnace. The remaining steps are the same as in Example 1.

[0032] Example 6 A heat treatment method for preparing high-strength aluminum alloy strip differs from Example 1 in that, in the S9 secondary annealing, the temperature of the rough finished product is uniformly raised to 450°C, held for 5 hours, and then cooled in the furnace. The remaining steps are the same as in Example 1.

[0033] Comparative Example 1 A heat treatment method for preparing high-strength aluminum alloy strip differs from Example 1 in that lanthanum oxide powder is not added in step S1, while the remaining steps are the same as in Example 1.

[0034] Comparative Example 2 A heat treatment method for preparing high-strength aluminum alloy strip differs from Example 1 in that nickel powder and cobalt powder are not added in step S1, while the remaining steps are the same as in Example 1.

[0035] Comparative Example 3 A heat treatment method for preparing high-strength aluminum alloy strip differs from Example 1 in that the added nickel powder in S1 is replaced with an equal mass of cobalt powder, while the remaining steps are the same as in Example 1.

[0036] Comparative Example 4 A heat treatment method for preparing high-strength aluminum alloy strip differs from Example 1 in that the cobalt powder added in step S1 is replaced with an equal mass of nickel powder, while the remaining steps are the same as in Example 1.

[0037] Comparative Example 5 A heat treatment method for preparing high-strength aluminum alloy strip differs from Example 1 in that the secondary annealing temperature in S9 is 300°C, while the remaining steps are the same as in Example 1.

[0038] Performance testing Detection methods / test methods High-strength aluminum alloy strips were prepared according to the methods in Examples 1-6 and Comparative Examples 1-5, and then tested according to the following testing methods. The test results are shown in Table 4.

[0039] Tensile strength and elongation at break shall be tested according to the test methods in GB / T228.1-2010; Conductivity: Tested according to the test method in GB / T351-2019.

[0040] Table 4. Detection results of Examples 1-6 and Comparative Examples 1-5

[0041] As can be seen from Examples 1-6, Comparative Examples 1-5, and the test data in Table 4, the aluminum alloy strips prepared by the preparation method of this application have excellent tensile strength and elongation at break. Their tensile strength is 281-355 MPa, their elongation at break is 19.2-21.1%, and their electrical conductivity is 62.1-63.2% IACS.

[0042] By adding lanthanum oxide, nickel powder, and cobalt powder to an aluminum alloy matrix, it was found that lanthanum oxide can refine grain size and significantly improve the reduction of microcracks, promotion of crack deflection, and delay of crack propagation. However, residual stress and weak bonding exist at the interface between lanthanum oxide and the aluminum alloy matrix, leading to uneven dispersion and hindering the grain-refining effect. The addition of nickel and cobalt powder can improve the wettability and bonding force of lanthanum oxide to the aluminum alloy matrix, allowing them to participate in the surface reaction of lanthanum oxide and form a stable lanthanum-nickel / cobalt oxide layer (such as LaNiO3 and LaCoO3). This enhances the interfacial bonding between lanthanum oxide and the matrix, reduces interfacial defects, and the synergistic effect of nickel and cobalt can improve the dispersion of lanthanum oxide, forming a composite strengthening network structure within the matrix, thus improving the strength and toughness of the aluminum alloy strip. Furthermore, it can form nanoscale intermetallic compounds (such as Al3Ni and Al3Co), which, through solid solution strengthening and precipitation strengthening, act as reinforcing phases distributed in the matrix, further enhancing strength. This is verified by the test data from Example 1 and Comparative Examples 1-4. Building upon this, and referring to Examples 2-3, as the particle size of lanthanum oxide powder decreased, the tensile strength and elongation at break of the aluminum alloy strip both improved, but the increase was very small at 2 μm. This is presumably due to uneven dispersion. Referring to Example 4, by loading graphene oxide onto the surface of lanthanum oxide powder, the dispersibility of lanthanum oxide can be improved, and graphene oxide (GO) forms chemical bonds with the Al alloy matrix (e.g., Al-OC), enhancing interfacial adhesion and reducing interfacial debonding; thereby further improving the strength and toughness of the aluminum alloy strip.

[0043] From a heat treatment perspective, secondary annealing can eliminate residual stress and act on lanthanum oxide, further alleviating or eliminating internal cracks in the matrix and improving the toughness and strength of the aluminum alloy strip. Furthermore, furnace cooling prevents lanthanum oxide from reacting with excessive carbon dioxide and water in the air at high temperatures to form lanthanum carbonate, which would cause interfacial cracking and affect the strength and toughness of the aluminum alloy strip. By controlling the temperature of the secondary annealing, a better annealing effect can be achieved. This is verified by the test data from Examples 1, 5-6, and Comparative Example 5.

[0044] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A heat treatment method for preparing high-strength aluminum alloy strip, characterized in that: The aluminum alloy strip comprises an aluminum alloy matrix and a reinforcing agent. The reinforcing agent comprises lanthanum oxide powder, nickel powder, and cobalt powder, with a mass ratio of lanthanum oxide powder, nickel powder, and cobalt powder of (0.5-1.5):(1-3):(0.5-1.5). The mass percentage of the reinforcing agent added is 0.7-0.9 wt%. The heat treatment method for preparing the high-strength aluminum alloy strip includes smelting, ingot casting, tempering, milling, hot rolling, cold rolling, intermediate annealing, finish rolling, rough finished product annealing, and slitting. The tempering process is as follows: the ingot is heated to 350-430℃ and then cooled in the furnace; The intermediate annealing process is as follows: the intermediate annealing thickness is 0.8-1.2 mm. The cold-rolled rough product is heated to 180-220℃ and held for 1.5-2.5 h. The temperature is then uniformly increased to 450-520℃ and held for 2-4 h. The product is then cooled in the furnace to 380-450℃ and held for 6-10 h. The steps for annealing the crude product are as follows: First annealing: The crude product is uniformly heated to 170-190℃ and held for 1.5-2.5h, then heated to 200-230℃ and held for 1.4-2.5h, then heated to 240-270℃ and held for 7-11h, and then cooled in the furnace. Secondary annealing: The annealed crude product is heated to 350-450℃, held for 4-6 hours, and then cooled in the furnace.

2. The heat treatment method for preparing high-strength aluminum alloy strip according to claim 1, characterized in that: The average particle size of the lanthanum oxide powder ranges from 2 to 10 μm.

3. The heat treatment method for preparing high-strength aluminum alloy strip according to claim 1, characterized in that: The lanthanum oxide powder has graphene oxide loaded on its surface.

4. The heat treatment method for preparing high-strength aluminum alloy strip according to claim 3, characterized in that: The lanthanum oxide powder is treated with an aqueous solution of a cationic surfactant, then reacted with an aqueous dispersion of graphene oxide, and then vacuum dried to obtain lanthanum oxide powder with graphene oxide loaded on its surface; both the aqueous solution of the cationic surfactant and the aqueous dispersion of graphene oxide are ≤10℃.

5. The heat treatment method for preparing high-strength aluminum alloy strip according to claim 1, characterized in that: The average particle size of the lanthanum oxide powder is 6 μm.

6. The heat treatment method for preparing high-strength aluminum alloy strip according to claim 1, characterized in that: The average particle size of the nickel powder is 80 nm, and the average particle size of the cobalt powder is 50 nm.

7. The heat treatment method for preparing high-strength aluminum alloy strip according to claim 1, characterized in that: In the annealing step of the crude product, the temperature of the secondary annealing is 400℃.

8. An aluminum alloy strip, characterized in that, The aluminum alloy strip is prepared by any one of the heat treatment methods for preparing high-strength aluminum alloy strips according to claims 1-7.

Images