Method for preparing high-toughness al-zn-mg-cu series aluminum alloy flat ingot and application thereof

Abstract

The application provides a preparation method of an Al-Zn-Mg-Cu system aluminum alloy flat ingot, raw materials are melted in a melting furnace to obtain an alloy melt, the alloy melt is refined by argon in the furnace, and then is subjected to online degassing and online filtration to obtain a purified melt; AlTi5C0.15 wires are added for online grain refinement, and then semi-continuous direct cooling casting is carried out to obtain an ingot, and then two-stage homogenization annealing treatment is carried out to obtain an aluminum alloy flat ingot; in addition to controlling the content of main elements (Cu, Mg, Zn and Zr), the Zn / Mg ratio also needs to be controlled in the range of 2.9-4.75. The application develops a new Al-Zn-Mg-Cu system aluminum alloy through forward design and fine control of the components of each group, and successfully realizes the industrialized stable production of the aluminum alloy ingot with high strength, high toughness, high corrosion resistance and excellent fatigue performance through optimization of the casting process and adoption of a two-stage homogenization heat treatment process.

Description

Technical Field

[0001] This invention belongs to the field of Al-Zn-Mg-Cu aluminum alloy preparation technology, and relates to a method for preparing Al-Zn-Mg-Cu aluminum alloy flat ingots and its application, particularly a method for preparing high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy flat ingots and its application. Background Technology

[0002] With the continuous development of the aerospace field, the industry's demand for and performance requirements of aluminum alloys, the main material for aircraft, are also constantly increasing. As the main aluminum alloy series, aluminum-zinc-magnesium-copper alloys (7xxx series aluminum alloys, aluminum-zinc wrought aluminum alloys) have received widespread attention in the industry.

[0003] Aluminum-zinc-magnesium-copper alloys are primarily used in fields with stringent performance requirements. They are commonly used in aircraft fuselage structures, mobile equipment, and other high-strength components. They are also key materials in the structures of aerospace equipment such as aircraft, rockets, and spacecraft, where their ultra-high strength significantly reduces structural weight, achieving lightweighting. Furthermore, research on these alloys is further geared towards meeting the demands of high-tech developments in aircraft, ships, automobiles, and large-capacity power grids.

[0004] To meet the increasing design demands for aircraft in terms of damage resistance and high fatigue strength, more stringent requirements have been placed on aluminum alloy materials in terms of strength, fatigue life, and durability. Therefore, continuous research and development and technological breakthroughs are being made in the 7xxx series aluminum alloys, and research on third- and fourth-generation 7xxx series aluminum alloys has become one of the focal points of industry research.

[0005] However, due to the enhanced properties of these new 7xxx series aluminum alloys, the content of each component in Al-Zn-Mg-Cu alloys gradually increases, which easily leads to a wider solidification range and causes compound segregation, resulting in poor formability of the alloy during casting and a significant tendency for hot cracking and porosity.

[0006] Therefore, finding a more suitable method to solve the aforementioned technical problems of existing 7xxx series aluminum alloys has become one of the urgent problems to be solved by many front-line researchers in the industry. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing Al-Zn-Mg-Cu aluminum alloy flat ingots and their applications, particularly a method for preparing high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy flat ingots. Based on the traditional Al-Zn-Mg-Cu alloy system, the present invention develops a new Al-Zn-Mg-Cu aluminum alloy by precisely controlling the composition of each component through forward design. Furthermore, through optimization of the casting process and the adoption of a two-stage homogenization heat treatment process, the industrial-scale stable production of aluminum alloy ingots possessing high strength, high toughness, high corrosion resistance, and excellent fatigue performance has been successfully achieved. Moreover, the method is simple, the conditions are mild, the controllability is good, and the stability is high, making it more suitable for promotion and application in industrial production.

[0008] This invention provides a method for preparing Al-Zn-Mg-Cu series aluminum alloy flat casting ingots, comprising the following steps: 1) The raw materials of Al-Zn-Mg-Cu aluminum alloy are melted in a smelting furnace to obtain the alloy melt; 2) The alloy melt obtained in the above steps is refined with argon gas in a furnace, and then degassed and filtered online to obtain a purified melt; 3) After adding AlTi5C0.15 wire to the purified melt obtained in the above steps for online grain refinement, semi-continuous direct cooling casting is carried out to obtain a flat ingot. Finally, the ingot is subjected to a two-stage homogenization heat treatment to obtain a "homogeneous" flat ingot of Al-Zn-Mg-Cu aluminum alloy with more uniform composition, more stable structure and better process plasticity. In the Al-Zn-Mg-Cu series aluminum alloy flat casting ingot, according to element quality control, there is an additional requirement that 2.9≤Zn / Mg≤4.75.

[0009] Preferably, the Al-Zn-Mg-Cu series aluminum alloy flat ingot, based on elemental mass content, comprises: Si≤0.03%, Fe≤0.05%, Cu: 1.8%~2.2%, Mn≤0.01%, Mg: 1.75%~2.15%, Cr≤0.01%, Zn: 7.8%~8.3%, Ti≤0.06%, Zr: 0.05%~0.15%, Ca≤0.001%, and Al; The Al-Zn-Mg-Cu series aluminum alloy flat ingot is an aluminum alloy flat ingot used to prepare aluminum alloy plates.

[0010] Preferably, the raw materials include AlZr4 master alloy, pure Mg ingot and AlBe3; The raw materials are added by raising the melting temperature to 740~760℃, adding AlZr4 master alloy and Mg ingot with a purity of 99.99%, and the reaction time is ≥20min.

[0011] Preferably, the raw materials are added in the following ways: AlBe3 is added through a backflow channel, and the remaining raw materials are added with the furnace. The melting temperature is 740~760℃.

[0012] Preferably, the in-furnace argon refining method is combined with in-furnace refining by spraying refining powder; The refined powder includes NaCl and KCl.

[0013] Preferably, the online degassing method is to use argon gas for online degassing; After online degassing, the hydrogen content of the melt is less than or equal to 0.12 ml / 100 g Al.

[0014] Preferably, the amount of AlTi5C0.15 wire used is 2.5~3.5 kg / t; The temperature for the semi-continuous direct cooling casting is 725~750℃.

[0015] Preferably, the semi-continuous direct cooling casting speed is 35~65 mm / min; The temperature of the molten aluminum at the end of the flow plate in the semi-continuous direct cooling casting is 690~715℃; The water flow rate in the crystallizer for the semi-continuous direct cooling casting is 25~45m³. 3 / h / root; The water inlet temperature of the crystallizer in the semi-continuous direct cooling casting is 22~30℃.

[0016] Preferably, the first-stage holding temperature of the two-stage homogenization annealing is 395~425℃; The first-stage holding time for the two-stage homogenization annealing is 12~20h; The secondary holding temperature of the two-stage homogenization annealing is 465~480℃; The secondary holding time for the two-stage homogenization annealing is 48~55h.

[0017] The present invention also provides the application of Al-Zn-Mg-Cu aluminum alloy flat castings prepared by any of the above-described technical solutions in the preparation of aerospace aluminum alloy plates.

[0018] This invention provides a method for preparing Al-Zn-Mg-Cu aluminum alloy flat ingots, comprising the following steps: First, the raw materials of Al-Zn-Mg-Cu aluminum alloy are melted in a melting furnace to obtain an alloy melt; then, the alloy melt obtained in the above step is refined by argon gas in the furnace, followed by online degassing and online filtration to obtain a purified melt; finally, AlTi5C0.15 wire is added to the purified melt obtained in the above step for online grain refinement, followed by semi-continuous direct cooling casting to obtain an ingot; finally, the ingot is subjected to a two-stage homogenization annealing treatment to obtain an Al-Zn-Mg-Cu aluminum alloy flat ingot; in the Al-Zn-Mg-Cu aluminum alloy flat ingot, according to element mass control, an additional requirement is 2.9≤Zn / Mg≤4.75. Compared with existing technologies, this invention argues that the high content of each component in the new Al-Zn-Mg-Cu alloy results in poor formability during casting, exhibiting a significant tendency for hot cracking and porosity. Furthermore, current casting processes are prone to causing casting cracks in practical applications and suffer from component segregation. These factors severely restrict the industrial production of Al-Zn-Mg-Cu alloy plates with high strength, high toughness, high corrosion resistance, and excellent fatigue performance. Therefore, this invention optimizes the chemical composition of the Al-Zn-Mg-Cu alloy and further incorporates superior casting process control and an optimized heat treatment regime.

[0019] Based on this, the present invention creatively designs a method for preparing Al-Zn-Mg-Cu aluminum alloy flat ingots with specific component ratios and controlled parameters. Based on the traditional Al-Zn-Mg-Cu alloy system, the present invention develops a new Al-Zn-Mg-Cu aluminum alloy by precisely controlling the composition of each component through forward design. Furthermore, through optimization of the casting process and the adoption of a two-stage homogenization heat treatment process, the industrial-scale stable production of aluminum alloy ingots possessing high strength, high toughness, high corrosion resistance, and excellent fatigue performance has been successfully achieved.

[0020] This invention improves the overall mechanical properties, corrosion resistance, and fatigue strength of the product through optimized chemical composition design; it also ensures fine original grains in the ingot by optimizing the grain refinement process; furthermore, it enhances supercooling strength and melt feeding ability by optimizing casting process parameters, thereby improving ingot forming rate and metallurgical quality; simultaneously, this invention further employs a two-stage homogenization heat treatment method, resulting in ingots with minimal segregation, fewer residual coarse second phases, dispersed compound distribution, and a uniform and fine microstructure. The novel method for preparing high-strength and tough Al-Zn-Mg-Cu aluminum alloy flat ingots and the accompanying homogenization heat treatment process provided by this invention aim to significantly improve ingot forming quality and ensure that the final product possesses excellent mechanical properties and fatigue resistance. Attached Figure Description

[0021] Figure 1 This invention relates to a cracked and scrapped ingot prepared before the optimization of the casting process during production. Figure 2 This refers to a qualified ingot prepared after optimization of the casting process during the production of this invention. Figure 3 Microscopic porosity diagram of the ingot prepared before the optimization of the casting process in the production process according to this invention; Figure 4 This is a microscopic porosity image of an ingot prepared after optimization of the casting process during the production of this invention. Figure 5 Scanned images of fracture surface samples of substandard fatigue plate products prepared from ingots produced using existing processes. Figure 6 Scanning images of qualified fatigue plate fracture samples from the ingots prepared according to this invention. Detailed Implementation

[0022] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0023] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0024] There are no particular restrictions on the purity of any raw materials used in this invention. However, this invention preferably uses industrially pure materials or materials with the purity requirements commonly used in the preparation of Al-Zn-Mg-Cu aluminum alloys.

[0025] All raw materials of this invention are conventional in the field, and each brand name and abbreviation is clear and distinct in its relevant application. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the brand name, abbreviation and corresponding application.

[0026] The processes used in this invention are all commonly referred to in the field. The specific steps and conventional parameters of each abbreviation are clear and well-defined in their respective fields. Those skilled in the art can implement them using conventional methods based on the abbreviations.

[0027] This invention provides a method for preparing Al-Zn-Mg-Cu series aluminum alloy flat casting ingots, comprising the following steps: 1) The raw materials of Al-Zn-Mg-Cu aluminum alloy are melted in a smelting furnace to obtain the alloy melt; 2) The alloy melt obtained in the above steps is refined with argon gas in a furnace, and then degassed and filtered online to obtain a purified melt; 3) After adding AlTi5C0.15 wire to the purified melt obtained in the above steps for online grain refinement, semi-continuous direct cooling casting is carried out to obtain an ingot. Finally, the ingot is subjected to a two-stage homogenization annealing treatment to obtain an Al-Zn-Mg-Cu aluminum alloy flat ingot. In the Al-Zn-Mg-Cu series aluminum alloy flat ingot, the element mass is 2.9≤Zn / Mg≤4.75.

[0028] The present invention first melts the raw material of Al-Zn-Mg-Cu aluminum alloy in a melting furnace to obtain an alloy melt.

[0029] In this invention, the Al-Zn-Mg-Cu aluminum alloy flat ingot, based on elemental mass content, may include: Si≤0.03%, Fe≤0.05%, Cu: 1.8%~2.2%, Mn≤0.01%, Mg: 1.75%~2.15%, Cr≤0.01%, Zn: 7.8%~8.3%, Ti≤0.06%, Zr: 0.05%~0.15%, Ca≤0.001%, and Al, which may be Si≤0.025%, Fe≤0.045%, Cu: 1.85%~2.15%, Mn≤0. 0.008%, Mg: 1.8%~2.1%, Cr≤0.008%, Zn: 7.9%~8.2%, Ti≤0.05%, Zr: 0.07%~0.13%, Ca≤0.0008% and Al, which can be Si≤0.02%, Fe≤0.04%, Cu: 1.9%~2.1%, Mn≤0.006%, Mg: 1.9%~2.0%, Cr≤0.006%, Zn: 8.0%~8.1%, Ti≤0.04%, Zr: 0.09%~0.11%, Ca≤0.0005% and Al.

[0030] In this invention, the Zn / Mg ratio can be ≥2.9, ≥3.5, or ≥4.0.

[0031] In this invention, the Al-Zn-Mg-Cu aluminum alloy flat ingot is preferably an aluminum alloy flat ingot used for preparing aluminum alloy plates.

[0032] In this invention, the raw materials preferably include AlZr4 master alloy, pure Mg ingot and AlBe3.

[0033] In this invention, the raw materials are added in the following ways: the melting temperature can be raised to 740~760℃, 744~756℃, or 748~752℃; AlZr4 master alloy and Mg ingot with a purity of 99.99% are added; and the reaction time can be ≥20min, ≥25min, or ≥30min.

[0034] In this invention, the preferred method of adding the raw materials includes adding AlBe3 through a backflow trough, while the remaining raw materials are added with the furnace.

[0035] In this invention, the melting temperature can be 740~760℃, 744~756℃, or 748~752℃.

[0036] In this invention, the preferred method of in-furnace argon refining includes in-furnace refining combined with spraying refining powder.

[0037] In this invention, the refined powder preferably includes NaCl and KCl. Specifically, the refined powder is a commercially available product with a formula of NaCl + KCl and a brand name of MK4357B.

[0038] The present invention further refines the alloy melt obtained in the above steps with argon gas in a furnace, and then degasses and filters it online to obtain a purified melt.

[0039] In this invention, the in-furnace argon refining method preferably includes refining by spraying refining powder.

[0040] In this invention, the preferred method for online degassing is to use argon gas for online degassing.

[0041] In this invention, after online degassing, the hydrogen content of the melt can be less than or equal to 0.12 ml / 100 g Al, less than or equal to 0.11 ml / 100 g Al, or less than or equal to 0.10 ml / 100 g Al.

[0042] In the end, AlTi5C0.15 wire is added to the purified melt obtained in the above steps for online grain refinement, and then semi-continuous direct cooling casting is performed to obtain an ingot. Finally, the ingot is subjected to a two-stage homogenization annealing treatment to obtain an Al-Zn-Mg-Cu aluminum alloy flat ingot. In the Al-Zn-Mg-Cu series aluminum alloy flat ingot, the element mass is 2.9≤Zn / Mg≤4.75.

[0043] In this invention, the Al-Zn-Mg-Cu series aluminum alloy flat ingot, based on element mass, can be 2.9≤Zn / Mg≤4.7, 3.2≤Zn / Mg≤4.6, or 3.6≤Zn / Mg≤4.5.

[0044] In this invention, the amount of AlTi5C0.15 wire used can be 2.5~3.5 kg / t, 2.7~3.3 kg / t, or 2.9~3.1 kg / t.

[0045] In this invention, the temperature of the semi-continuous direct cooling casting can be 725~750℃, 730~745℃, or 735~740℃.

[0046] In this invention, the speed of the semi-continuous direct cooling casting can be 35~65mm / min, 40~60mm / min, or 45~55mm / min.

[0047] In this invention, the temperature of the molten aluminum at the end of the flow plate in the semi-continuous direct cooling casting can be 690~715℃, 695~710℃, or 700~705℃.

[0048] In this invention, the crystallizer water flow rate for the semi-continuous direct cooling casting can be 25~45m³. 3 / h / root, which can be 29~41m 3 / h / root, can be 34~37m 3 / h / root.

[0049] In this invention, the inlet water temperature of the crystallizer in the semi-continuous direct cooling casting can be 22~30℃, 23.5~28.5℃, or 25~27℃.

[0050] In this invention, the first-stage holding temperature of the two-stage homogenization annealing can be 395~425℃, 400~420℃, 405~415℃, or 410~415℃.

[0051] In this invention, the first-stage holding time of the two-stage homogenization annealing can be 12~20h, 12~17h, or 12~13h, specifically 12h.

[0052] In this invention, the secondary holding temperature of the two-stage homogenization annealing can be 465~480℃, 468~476℃, or 471~473℃.

[0053] In this invention, the secondary holding time for the two-stage homogenization annealing can be 48~55h, 48~52h, or 48~49h, specifically 48h.

[0054] This invention provides the application of Al-Zn-Mg-Cu aluminum alloy flat castings prepared by any of the above-described technical solutions in the preparation of aerospace aluminum alloy plates.

[0055] This invention aims to complete and refine the overall technical solution, better ensure the microstructure and elemental composition of Al-Zn-Mg-Cu aluminum alloy flat ingots, and further improve the performance of Al-Zn-Mg-Cu aluminum alloy flat ingots. The aforementioned method for preparing Al-Zn-Mg-Cu aluminum alloy flat ingots and its applications may specifically include the following: The method for preparing high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy flat casting ingots provided by this invention includes the following eight aspects: (1) Chemical composition: Si≤0.03%, Fe≤0.05%, Cu 1.8%~2.2%, Mn≤0.01%, Mg 1.75%~2.15%, Cr≤0.01%, Zn 7.8%~8.3%, Ti≤0.06%, Zr 0.05%~0.15%, Ca≤0.001%, balance Al.

[0056] This invention requires reasonable control of the content of Cu, Mg, and Zn elements.

[0057] Al-Zn-Mg alloys have poor corrosion resistance. When 0.6% to 1.2% Cu is added, their stress corrosion resistance is greatly improved, and tensile strength is also increased. At the same time, within a certain range of Mg and Zn content, adding Cu can maintain high strength while improving the alloy's plasticity. Zn and Mg are the main strengthening elements, and the main strengthening phases produced are MgZn2 and Mg3Zn3Al2. Increasing the Zn and Mg content can significantly improve strength and hardness, but it will reduce plasticity, stress corrosion resistance, and fracture toughness. Therefore, the addition of Zn and Mg will optimize the alloy properties, but the Zn / Mg ratio must be controlled within a specific range to achieve this effect.

[0058] This invention specifically controls the following elements: Cu 1.8%~2.2%, Mg 1.75%~2.15%, Zn 7.8%~8.3%, and Zn / Mg ≥ 2.9. Among these, the reasonable control of Si and Fe content is crucial: Si reacts with Mg to form the Mg2Si phase, reducing the amount of the main strengthening phases MgZn2 and Mg3Zn3Al2 in the alloy, thus lowering its strength; Fe, to some extent, affects corrosion resistance; and the Si and Fe content also increases the tendency for casting cracks.

[0059] This invention specifically controls Si ≤ 0.03% and Fe ≤ 0.05%. Reasonable control of Zr and Be element content is also crucial: adding a certain amount of Zr can effectively refine the grains, promote the precipitation of strengthening phases, and further improve the strength and hardness of the aluminum alloy; Zr should be controlled within the range of 0.05~0.15%. Adding trace amounts of Be-containing alloys can significantly improve the strength and hardness of the aluminum alloy, while also contributing to grain refinement; the addition amount is 0.2~0.3 kg / t.

[0060] In conjunction with the above-mentioned component control, this invention also provides a corresponding method for preparing aluminum alloy flat castings: (1) Method of adding intermediate alloy: When the melt temperature rises to 740~760℃, add AlZr4 intermediate alloy and Mg ingot with a purity of 99.99%, react for ≥20min, and add the rest with the furnace. Add AlBe3 in the reverse flow tank.

[0061] (2) Melt purification: In-furnace refining first adopts powder spraying refining or a process with the same refining effect, and then argon refining is adopted; online degassing adopts argon refining to reduce the hydrogen content of the melt to less than 0.12ml / 100gAl; after degassing, the melt is filtered online using plate filters.

[0062] (3) Grain refinement: In order to refine the grain structure, the present invention uses AlTi5C0.15 wire for online grain refinement, with a dosage of 2.5~3.5kg / t.

[0063] (4) Casting process: The casting speed of this invention is 35~65mm / min, and the water flow rate is 25~45m³ / min. 3 / h / root, aluminum liquid temperature at the end of the flow plate 690~715℃, water temperature 22~30℃.

[0064] (5) Homogenization process: After the melt is cast, an ingot is obtained. In order to eliminate the ingot stress, reduce the ingot segregation and obtain a dispersed compound, and meet the requirements of high strength, toughness and good fatigue resistance of plate structure, the ingot needs to be subjected to high temperature homogenization annealing. The ingot of this invention adopts two-stage homogenization annealing, with furnace heating and holding time of 12h. The secondary holding temperature is 465~480℃ and the secondary holding time is 48h.

[0065] By implementing the above process parameters, the casting of ingots can be guaranteed and the product quality requirements can be met.

[0066] See Table 1, which shows the composition of the ingots prepared according to the present invention.

[0067] Table 1

[0068] See Table 2, which shows the casting parameters of the ingots prepared according to the present invention.

[0069] Table 2

[0070] See Figure 1 , Figure 1 This invention relates to the preparation of cracked and scrapped ingots before the optimization of the casting process during production.

[0071] See Figure 2 , Figure 2This refers to a qualified ingot prepared after optimizing the casting process during the production of this invention.

[0072] See Figure 3 , Figure 3 The image shows the microstructure of the ingot before the optimization of the casting process in the production process.

[0073] See Figure 4 , Figure 4 This is a microscopic porosity image of the ingot prepared after optimization of the casting process during the production process of this invention.

[0074] See Figure 5 , Figure 5 Scanned images of fracture surfaces of substandard fatigue plate samples prepared from ingots produced using existing processes.

[0075] See Figure 6 , Figure 6 Scanning images of qualified fatigue plate fracture samples from the ingots prepared according to this invention.

[0076] The present invention provides a method for preparing high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy flat ingots and their applications. Based on the traditional Al-Zn-Mg-Cu alloy system, this invention develops a new Al-Zn-Mg-Cu aluminum alloy by precisely controlling the composition of each component through forward design. Furthermore, through optimization of the casting process and the adoption of a two-stage homogenization heat treatment process, the industrial-scale stable production of aluminum alloy ingots possessing high strength, high toughness, high corrosion resistance, and excellent fatigue performance has been successfully achieved.

[0077] This invention improves the overall mechanical properties, corrosion resistance, and fatigue strength of the product through optimized chemical composition design; it also ensures fine original grains in the ingot by optimizing the grain refinement process; furthermore, it enhances supercooling strength and melt feeding ability by optimizing casting process parameters, thereby improving ingot forming rate and metallurgical quality; simultaneously, this invention further employs a two-stage homogenization heat treatment method, resulting in ingots with minimal segregation, fewer residual coarse second phases, dispersed compound distribution, and a uniform and fine microstructure. The novel method for preparing high-strength and tough Al-Zn-Mg-Cu aluminum alloy flat ingots and the accompanying homogenization heat treatment process provided by this invention aim to significantly improve ingot forming quality and ensure that the final product possesses excellent mechanical properties and fatigue resistance.

[0078] To further illustrate the present invention, the following detailed description of the preparation method and application of an Al-Zn-Mg-Cu aluminum alloy flat ingot provided by the present invention is provided in conjunction with embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given only to further illustrate the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0079] Example 1

[0080] Chemical composition: Si 0.03%, Fe 0.05%, Cu 2.0%, Mn 0.01%, Mg 2.1%, Cr 0.01%, Zn 8.0%, Ti 0.06%, Zr 0.10%, Ca 0.0008%, balance Al.

[0081] Ingredients and smelting: This invention uses primary aluminum ingots with an Al content of 99.95% or higher, master alloys, pure metals, and additives. Cu, Mg, and Zn are added using pure metals, while Zr is added using a master alloy. The primary aluminum ingots and Cu are added to a melting furnace and melted. Once the melt temperature reaches 740-760°C, Mg ingots with a purity of 99.99% and AlZr4 master alloy are added. The reaction time is ≥20 minutes, yielding an alloy aluminum liquid conforming to the elements of this invention.

[0082] Melt purification: The smelting furnace performs powder spraying refining on the molten aluminum alloy for 15-20 minutes. Particle refining agent is blown into the bottom of the melt using powder spraying equipment to achieve degassing and slag removal. Online degassing is performed on the molten aluminum alloy passing through the furnace at a certain rate using a dual-rotor rotary degassing system with an argon flow rate of 3-4 m³ / h. 3 The process yielded an alloy aluminum liquid with a liquid hydrogen content of 0.091 ml / 100 g Al at a flow rate of [per hour]. After degassing, it was filtered using a 40+50 PPI ceramic filter plate.

[0083] Grain refinement: The present invention uses AlTi5C0.15 wire for online grain refinement at a dosage of 2.5~3.5 kg / t, with a dosage of 3.0 kg / t, resulting in ingot grain grade 1.

[0084] Casting: Ingot specifications: 400mm thickness, 3 ingots cast, casting temperature 733℃, casting speed 35~65mm / min, water flow rate 25~45m³ / min. 3 / h, the temperature of the molten aluminum at the end of the flow tray is 690~715℃, and the cooling water temperature is 24℃. Even heating: The ingots produced in this invention undergo a two-stage homogenization annealing treatment. The ingots are heated in the furnace, with the first-stage holding temperature at 410℃ for 12 hours and the second-stage holding temperature at 472℃ for 48 hours. Mechanical properties after rolling: The ingot has a first-class grain size, with fine grains and fine, dispersed compounds. After rolling, it has a tensile strength of 475~495MPa, a yield strength of 400~445MPa, and a fatigue life of over 100,000 cycles.

[0085] Example 2

[0086] Chemical composition: Si 0.03%, Fe 0.05%, Cu 1.9%, Mn 0.01%, Mg 2.0%, Cr 0.01%, Zn 8.15%, Ti 0.06%, Zr 0.10%, Ca 0.0008%, balance Al.

[0087] Ingredients and smelting: This invention uses primary aluminum ingots with an Al content of 99.95% or higher, master alloys, pure metals, and additives. Cu, Mg, and Zn are added using pure metals, while Zr is added using a master alloy. The primary aluminum ingots and Cu are added to a melting furnace and melted. Once the melt temperature reaches 740-760°C, Mg ingots with a purity of 99.99% and AlZr4 master alloy are added. The reaction time is ≥20 minutes, yielding an alloy aluminum liquid conforming to the elements of this invention.

[0088] Melt purification: The smelting furnace performs powder spraying refining on the molten aluminum alloy for 15-20 minutes. Particle refining agent is blown into the bottom of the melt using powder spraying equipment to achieve degassing and slag removal. Online degassing is performed on the molten aluminum alloy passing through the furnace at a certain rate using a dual-rotor rotary degassing system with an argon flow rate of 3-4 m³ / h. 3 The process yielded an alloy aluminum liquid with a liquid hydrogen content of 0.089 ml / 100 g Al at a flow rate of [per hour]. After degassing, it was filtered using a 40+50 PPI ceramic filter plate.

[0089] Grain refinement: The present invention uses AlTi5C0.15 wire for online grain refinement at a dosage of 2.5~3.5 kg / t, with a dosage of 3.0 kg / t, resulting in ingot grain grade 1.

[0090] Casting: Ingot specifications: 400mm thickness, 3 ingots cast, casting temperature 727℃, casting speed 35~65mm / min, water flow rate 25~45m³ / min. 3 / h, the temperature of the molten aluminum at the end of the flow tray is 690~715℃, and the cooling water temperature is 24℃. Even heating: The ingots produced in this invention undergo a two-stage homogenization annealing treatment. The ingots are heated in the furnace, with the first-stage holding temperature at 410℃ for 12 hours and the second-stage holding temperature at 472℃ for 48 hours. Mechanical properties after rolling: The ingot has a first-class grain size, with fine grains and fine, dispersed compounds. After rolling, it has a tensile strength of 500~530MPa, a yield strength of 450~490MPa, and an average fatigue life of over 120,000 cycles.

[0091] The present invention provides a detailed description of a method for preparing high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy flat casting ingots and its applications. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those skilled in the art, several improvements and modifications can be made to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the wording of the claims, or if they include equivalent structural elements that are not substantially different from the wording of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing an Al-Zn-Mg-Cu series aluminum alloy flat casting ingot, characterized in that, Includes the following steps: 1) The raw materials of Al-Zn-Mg-Cu aluminum alloy are melted in a smelting furnace to obtain the alloy melt; 2) The alloy melt obtained in the above steps is refined with argon gas in a furnace, and then degassed and filtered online to obtain a purified melt; 3) After adding AlTi5C0.15 wire to the purified melt obtained in the above steps for online grain refinement, semi-continuous direct cooling casting is carried out to obtain an ingot. Finally, the ingot is subjected to a two-stage homogenization annealing treatment to obtain an Al-Zn-Mg-Cu aluminum alloy flat ingot. In the Al-Zn-Mg-Cu series aluminum alloy flat ingot, the element mass is 2.9≤Zn / Mg≤4.

75.

2. The preparation method according to claim 1, characterized in that, The Al-Zn-Mg-Cu series aluminum alloy flat casting ingot, based on elemental mass content, includes: Si≤0.03%, Fe≤0.05%, Cu: 1.8%~2.2%, Mn≤0.01%, Mg: 1.75%~2.15%, Cr≤0.01%, Zn: 7.8%~8.3%, Ti≤0.06%, Zr: 0.05%~0.15%, Ca≤0.001%, and Al; The Al-Zn-Mg-Cu series aluminum alloy flat ingot is an aluminum alloy flat ingot used to prepare aluminum alloy plates.

3. The preparation method according to claim 1, characterized in that, The raw materials include AlZr4 master alloy, pure Mg ingot and AlBe3; The raw materials are added by raising the melting temperature to 740~760℃, adding AlZr4 master alloy and Mg ingot with a purity of 99.99%, and the reaction time is ≥20min.

4. The preparation method according to claim 1, characterized in that, The raw materials are added in the following ways: AlBe3 is added through a backflow channel, and the remaining raw materials are added with the furnace. The melting temperature is 740~760℃.

5. The preparation method according to claim 1, characterized in that, The furnace argon refining method is to combine furnace refining with the injection of refining powder. The refined powder includes NaCl and KCl.

6. The preparation method according to claim 1, characterized in that, The online degassing method is to use argon gas for online degassing; After online degassing, the hydrogen content of the melt is less than or equal to 0.12 ml / 100 g Al.

7. The preparation method according to claim 1, characterized in that, The amount of AlTi5C0.15 wire used is 2.5~3.5 kg / t; The temperature for the semi-continuous direct cooling casting is 725~750℃.

8. The preparation method according to claim 1, characterized in that, The semi-continuous direct cooling casting speed is 35~65mm / min; The temperature of the molten aluminum at the end of the flow plate in the semi-continuous direct cooling casting is 690~715℃; The water flow rate in the crystallizer for the semi-continuous direct cooling casting is 25~45m³. 3 / h / root; The water inlet temperature of the crystallizer in the semi-continuous direct cooling casting is 22~30℃.

9. The preparation method according to claim 1, characterized in that, The first-stage holding temperature of the two-stage homogenization annealing is 395~425℃; The first-stage holding time for the two-stage homogenization annealing is 12~20h; The secondary holding temperature of the two-stage homogenization annealing is 465~480℃; The secondary holding time for the two-stage homogenization annealing is 48~55h.

10. The application of the Al-Zn-Mg-Cu aluminum alloy flat casting ingot prepared by the preparation method according to any one of claims 1 to 9 in the preparation of aerospace aluminum alloy plates.

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