Preparation method of 7-series aluminum alloy

Abstract

According to the preparation method of the 7-series aluminum alloy, an extrusion die is optimized, an inlet of a working tape of the die is inclined downwards by 10-15 degrees, and technological parameters of extrusion treatment are optimized, so that the problems of dragging and cracking of a 7-series aluminum alloy profile can be solved, and the production quality is guaranteed. Besides, by optimizing the components and the proportion of the 7-series aluminum alloy, especially adding Er which is subjected to solid solution in an aluminum matrix, a certain refining effect on crystal grains is achieved, the Er interacts with Sc, an original net-shaped structure phase in the 7-series aluminum alloy is gradually converted into a skeleton-shaped and rod-shaped structure, Zr, V and Al3Zr dispersed phases are added to supply to an Al matrix, grain boundary pinning force and an A12lV2 dispersed phase are generated, recrystallization is hindered, and therefore the anti-corrosion performance of the 7-series aluminum alloy is improved. And the high-temperature strength and the crack propagation resistance of the 7-series aluminum alloy are improved, the overall mechanical property can be improved by combining with process optimization, and then the cracking problem can be reduced.

Description

Technical Field

[0001] The present invention relates to the field of preparation of aluminum alloy materials, and more particularly to a method for preparing a 7-series aluminum alloy. Background Art

[0002] As a lightweight material, aluminum alloy has a wide range of applications in the fields of aerospace, military, and civilian due to its high strength, high modulus, good electrical and thermal conductivity, low density, good plasticity and processing performance, etc. However, during the casting process, there is a high segregation tendency, and the thermal stress during solidification is very large, making it easy to generate thermal cracks, which poses very high requirements for the entire melting and casting device and process.

[0003] In actual production, in order to ensure that the 7-series aluminum alloy structural parts meet performance indicators such as high strength and toughness, high damage tolerance, and high fatigue life, it is necessary to significantly reduce the contents of Fe and Si elements, and also strictly control the composition segregation, hydrogen content, slag content, and grain size. The requirement for a large diameter of the ingot in the production of large-section profiles will increase the depth of the liquid cavity, significantly increasing the difficulty of controlling the composition segregation and grain size, and increasing the risk of casting cracking of the ingot. The reduction of the contents of Fe and Si elements is likely to cause the coarsening of the ingot grains and further increase the difficulty of casting forming. The control of the hydrogen content and slag content of the ingot has always been a difficult problem in aluminum alloy melting and casting.

[0004] In recent years, new alloy composition design, optimization of existing heat treatment process parameters, development of new heat treatment processes, and research on related mechanisms have especially become important directions in the research and development of 7-series aluminum alloys. However, there are few improvements to the mold. For example, for 7075 alloy profiles, when produced according to the conventional mold working belt design, obvious problems such as dragging and cracking will occur, which will affect the product quality. Therefore, in the existing technology, when optimizing the preparation process of 7-series aluminum alloys to improve the performance of one or several preparations, there are few systematic overall improvements to the process and the mold. The performance of 7-series aluminum alloy structural parts has not been comprehensively improved, and there are still problems such as dragging and cracking in the prepared plates or bars. Summary of the Invention

[0005] Based on this, in order to solve one of the above problems, the present invention provides a method for preparing a 7-series aluminum alloy, and the specific technical solution is as follows:

[0006] A method for preparing a 7-series aluminum alloy, the preparation method comprising the following steps:

[0007] Weigh the raw materials according to the composition of the 7-series aluminum alloy, then add the aluminum ingots to the melting furnace. After heating until all the aluminum ingots are melted, use an electromagnetic stirring device to stir for 15 min to 20 min, then add the remaining raw materials, control the melting temperature, continue the electromagnetic stirring treatment until the raw materials are completely melted, and after slag skimming treatment, obtain the melt;

[0008] Refine the melt, and during the refining process, the dross needs to be cleaned up in a timely manner. After the refining process is completed, through filtration, casting, solution treatment, extrusion treatment, annealing, and aging treatment, a 7-series aluminum alloy is obtained.

[0009] Among them, the temperature of the casting rod in the extrusion treatment is 460°C to 470°C, the extrusion speed is 0.8 mm / s to 1.0 mm / s, and the starting pressure speed is 0.2 mm / s; and the working belt inlet of the mold used in the extrusion treatment is inclined downward by 10° to 15°.

[0010] Furthermore, the 7-series aluminum alloy includes the following components by mass percentage:

[0011] Zn 3.2% - 4.0%, Mg 0.5% - 2.2%, Cu 1.2% - 2.2%, Zr 0.1% - 0.3%, Sc 0.01% - 0.02%, Er 0.01% - 0.02%, Ti 0.01% - 0.12%, V 0.01% - 0.05%, Si ≤ 0.2%, Mn ≤ 0.1%, other single elements ≤ 0.05%, the total amount of other impurity elements ≤ 0.15%, with the balance being Al.

[0012] Furthermore, the melting temperature is 720°C to 750°C.

[0013] Furthermore, the refining treatment includes the first refining treatment and the second refining treatment. The rotor speed of the first refining treatment is 250 RPM to 300 RPM, and a mixed gas of argon and chlorine is introduced. The argon flow rate is 8 m 3 / h to 12 m 3 / h, the chlorine flow rate is 1 m 3 / h to 2 m 3 / h, the temperature is controlled at 720°C to 740°C, and the time is 5 min to 15 min; in the second refining treatment, a refining agent is added, and the single-rotor argon flow rate is 8 m 3 / h to 10 m 3 / h, the temperature is 700°C to 720°C, and the time is 5 min to 10 min.

[0014] Furthermore, the refining agent is one or more of CaF, Na3AlF6, and NaCl.

[0015] Furthermore, the filtration is carried out in a double-layer filtration box. The porosity of the first-stage filter plate is 30 ppi, and the porosity of the second-stage filter plate is 50 ppi.

[0016] Further, the casting temperature is 700°C to 720°C, the initial casting speed is 16 mm / min to 20 mm / min. When the length to be cast reaches 100 mm, the casting speed is adjusted to 30 mm / min to 35 mm / min. When the length to be cast exceeds 500 mm, the casting speed is adjusted to 18 mm / min to 22 mm / min.

[0017] Further, the solution treatment is to heat up to 300°C to 350°C within 1 h, hold for 1 h to 3 h at 300°C to 350°C, then continue to heat up to 400°C to 420°C within 10 min, and hold for 10 h to 24 h at 400°C to 420°C.

[0018] Further, the annealing temperature is 300°C to 400°C, the time is 3 h to 5 h, and then air-cooled.

[0019] Further, the aging treatment temperature is 150°C to 200°C, and the time is 10 h to 20 h.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] 1. By optimizing the extrusion die, with the working belt inlet of the die inclined downward by 10° to 15°, and optimizing the process parameters of the extrusion treatment, the present invention can solve the problems of dragging and cracking of 7-series aluminum alloy profiles and ensure the production quality.

[0022] 2. By optimizing the composition and ratio of the 7-series aluminum alloy, especially by adding Er, which is dissolved in the aluminum matrix and plays a certain role in refining the grains. Interacting with Sc, the original reticular structure phase in the 7-series aluminum alloy gradually transforms into a skeletal and rod-like structure, which is beneficial to improving the hardness and mechanical properties of the 7-series aluminum alloy. Adding Zr and V, the Al3Zr dispersion phase is lattice-matched with the Al matrix, generating a grain boundary pinning force, and the dispersion phase of A1 2l V2 hinders recrystallization and improves the high-temperature strength and crack propagation resistance of the 7-series aluminum alloy.

[0023] 3. By optimizing the casting parameters and the parameters of the solution treatment, the uniformity of the structure and composition of the 7-series aluminum alloy can be improved, thereby providing thermoplasticity, reducing internal stress, helping to improve its plasticity and fatigue fracture resistance, and further helping to reduce the problem of cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a partial schematic diagram of the optimized die in Embodiment 3 of the present invention;

[0025] Figure 2 It is a schematic diagram of the sample prepared in Embodiment 3;

[0026] Figure 3 Schematic diagram of the comparative sample in Comparative Example 1. Detailed implementation manners

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation manners described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific implementation manners and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0029] A preparation method of a 7xxx series aluminum alloy in an embodiment of the present invention, the preparation method includes the following steps:

[0030] Weigh raw materials according to the composition of the 7xxx series aluminum alloy, then add aluminum ingots to a melting furnace, heat until all the aluminum ingots are melted, use an electromagnetic stirring device to stir for 15 min to 20 min, then add the remaining raw materials, control the melting temperature, continue electromagnetic stirring treatment until the raw materials are completely melted, and after slag skimming treatment, obtain a melt;

[0031] Refine the melt, and it is necessary to clean the floating slag in time during the refining process. After the refining process is completed, after filtration, casting, solution treatment, extrusion treatment, annealing and aging treatment, a 7xxx series aluminum alloy is obtained;

[0032] Among them, the temperature of the cast rod in the extrusion treatment is 460 °C to 470 °C, the extrusion speed is 0.8 mm / s to 1.0 mm / s, and the starting pressure speed is 0.2 mm / s; and the working belt inlet of the die used in the extrusion treatment is inclined downward by 10° to 15°.

[0033] In one embodiment, the 7xxx series aluminum alloy includes the following components by mass percentage:

[0034] Zn 3.2% to 4.0%, Mg 0.5% to 2.2%, Cu 1.2% to 2.2%, Zr 0.1% to 0.3%, Sc 0.01% to 0.02%, Er 0.01% to 0.02%, Ti 0.01% to 0.12%, V 0.01% to 0.05%, Si ≤ 0.2%, Mn ≤ 0.1%, other single elements ≤ 0.05%, the total amount of other impurity elements ≤ 0.15%, and the balance is Al.

[0035] In one embodiment, the smelting temperature is 720°C to 750°C.

[0036] In one embodiment, the refining treatment includes a first refining treatment and a second refining treatment. The rotor speed of the first refining treatment is 250 RPM to 300 RPM, and a mixed gas of argon and chlorine is introduced. The argon flow rate is 8 m 3 / h to 12 m 3 / h, the chlorine flow rate is 1 m 3 / h to 2 m 3 / h, the temperature is controlled at 720°C to 740°C, and the time is 5 min to 15 min. In the second refining treatment, a refining agent is added, and the single-rotor argon flow rate is 8 m 3 / h to 10 m 3 / h, the temperature is 700°C to 720°C, and the time is 5 min to 10 min.

[0037] In one embodiment, the refining agent is one or more of CaF, Na3AlF6, and NaCl.

[0038] In one embodiment, the filtration is carried out in a double-layer filtration box. The porosity of the first-stage filter plate is 30 ppi, and the porosity of the second-stage filter plate is 50 ppi.

[0039] In one embodiment, the casting temperature is 700°C to 720°C, the starting casting speed is 16 mm / min to 20 mm / min. When the casting length reaches 100 mm, the casting speed is adjusted to 30 mm / min to 35 mm / min. When the casting length exceeds 500 mm, the casting speed is adjusted to 18 mm / min to 22 mm / min.

[0040] In one embodiment, the solution treatment is to raise the temperature to 300°C to 350°C within 1 h, hold at 300°C to 350°C for 1 h to 3 h, then continue to raise the temperature to 400°C to 420°C within 10 min, and hold at 400°C to 420°C for 10 h to 24 h.

[0041] In one embodiment, the annealing temperature is 300°C to 400°C, the time is 3 h to 5 h, and then air-cooled.

[0042] In one embodiment, the aging treatment temperature is 150°C to 200°C, and the time is 10 h to 20 h.

[0043] In the above solution, by optimizing the composition and composition ratio of the 7-series aluminum alloy, the process parameters and the extrusion die, the problems of dragging and cracking of the 7-series aluminum alloy profiles can be solved, and the production quality can be guaranteed.

[0044] The embodiments of the present invention will be described in detail below in conjunction with specific embodiments.

[0045] Example 1:

[0046] The 7xxx series aluminum alloy comprises the following components by mass percentage:

[0047] Zn 3.6%, Mg 1.8%, Cu 1.7%, Zr 0.3%, Sc 0.02%, Er 0.02%, Ti 0.01% - 0.12%, V 0.01% - 0.05%, Si ≤ 0.2%, Mn ≤ 0.1%, other single elements ≤ 0.05%, total amount of other impurity elements ≤ 0.15%, and the balance is Al;

[0048] The preparation method of the 7xxx series aluminum alloy comprises the following steps:

[0049] Weigh the raw materials according to the components of the 7xxx series aluminum alloy, then add the aluminum ingots into the melting furnace. After heating until all the aluminum ingots are melted, use an electromagnetic stirring device to stir for 20 min, then add the remaining raw materials, control the melting temperature at 740 °C, continue the electromagnetic stirring treatment until all the raw materials are melted, and after skimming, obtain the melt;

[0050] Perform the first refining treatment and the second refining treatment on the melt. The rotor speed of the first refining treatment is 250 RPM, and a mixed gas of argon and chlorine is introduced. The argon flow rate is 8 m 3 / h, the chlorine flow rate is 1 m 3 / h, the temperature is controlled at 720 °C, and the time is 10 min; In the second refining treatment, add Na3AlF6, and the single-rotor argon flow rate is 10 m 3 / h, the temperature is 700 °C, and the time is 5 min. During the first refining treatment and the second refining treatment, the floating slag needs to be cleaned in time. After the refining treatment is completed, filter through a double-layer filter box. The porosity of the first-stage filter plate is 30 ppi, and the porosity of the second-stage filter plate is 50 ppi;

[0051] Cast, and the casting temperature is 720 °C, the initial casting speed is 16 mm / min. When the casting length reaches 100 mm, the casting speed is adjusted to 30 mm / min. When the casting length exceeds 500 mm, the casting speed is adjusted to 18 mm / min;

[0052] Perform solution treatment, and the solution treatment is to raise the temperature to 350 °C within 1 h and hold at 350 °C for 2 h, then continue to raise the temperature to 400 °C within 10 min and hold at 400 °C for 16 h;

[0053] Extrusion treatment, with the temperature of the casting rod during the extrusion treatment being 460 °C, the extrusion speed being 0.8 mm / s, the starting pressure speed being 0.2 mm / s, and the working belt inlet of the die used during the extrusion treatment being inclined downward by 15°. Then, it is heat-preserved at 300 °C for 5 h and air-cooled;

[0054] Aging treatment, with the temperature of the aging treatment being 200 °C and the time being 15 h, to obtain a 7-series aluminum alloy.

[0055] Example 2:

[0056] The 7-series aluminum alloy comprises the following components by mass percentage:

[0057] Zn 3.5%, Mg 1.8%, Cu 1.7%, Zr 0.1%, Sc 0.01%, Er 0.01%, Ti 0.05%, V 0.04%, Si 0.06%, Mn 0.05%, other single elements ≤ 0.05%, total amount of other impurity elements ≤ 0.15%, and the balance is Al;

[0058] A preparation method of the 7-series aluminum alloy, comprising the following steps:

[0059] Weigh the raw materials according to the components of the 7-series aluminum alloy, then add the aluminum ingots to the melting furnace. After heating until all the aluminum ingots are melted, use an electromagnetic stirring device to stir for 20 min, then add the remaining raw materials, control the melting temperature at 740 °C, continue the electromagnetic stirring treatment until the raw materials are completely melted, and after slag skimming treatment, obtain a melt;

[0060] Perform the first refining treatment and the second refining treatment on the melt. The rotor speed of the first refining treatment is 280 RPM, and a mixed gas of argon and chlorine is introduced. The argon flow rate is 10 m 3 / h, and the chlorine flow rate is 2 m 3 / h. The temperature is controlled at 740 °C and the time is 15 min. In the second refining treatment, Na3AlF6 is added, and the single-rotor argon flow rate is 10 m 3 / h, the temperature is 720 °C, and the time is 10 min. During the first refining treatment and the second refining treatment processes, the floating slag needs to be cleaned in a timely manner. After the refining treatment is completed, it is filtered through a double-layer filter box. The porosity of the first-stage filter plate is 30 ppi, and the porosity of the second-stage filter plate is 50 ppi;

[0061] Casting, with the temperature of the casting being 720 °C, the starting casting speed being 18 mm / min. When the casting length reaches 100 mm, the casting speed is adjusted to 35 mm / min. When the casting length exceeds 500 mm, the casting speed is adjusted to 20 mm / min;

[0062] Solution treatment, and the solution treatment is to heat up to 320 °C within 1 h, hold at 320 °C for 3 h, then continue to heat up to 420 °C within 10 min, and hold at 420 °C for 18 h;

[0063] Extrusion treatment, and the temperature of the casting rod in the extrusion treatment is 470 °C, the extrusion speed is 1.0 mm / s, the starting pressure speed is 0.2 mm / s, and the working belt inlet of the die used in the extrusion treatment is inclined downward by 15°, and then hold at 350 °C for 4 h and air-cool;

[0064] Aging treatment, and the temperature of the aging treatment is 180 °C and the time is 18 h to obtain a 7-series aluminum alloy.

[0065] Example 3:

[0066] The 7-series aluminum alloy comprises the following components by mass percentage:

[0067] Zn 3.8%, Mg 1.2%, Cu 2.0%, Zr 0.2%, Sc 0.01%, Er 0.02%, Ti 0.04%, V 0.03%, Si 0.05%, Mn 0.08%, other single elements ≤ 0.05%, total amount of other impurity elements ≤ 0.15%, and the balance is Al;

[0068] A preparation method of a 7-series aluminum alloy, comprising the following steps:

[0069] Weigh raw materials according to the components of the 7-series aluminum alloy, then add aluminum ingots to a melting furnace, heat until all the aluminum ingots are melted, use an electromagnetic stirring device to stir for 20 min, then add the remaining raw materials, control the melting temperature at 740 °C, continue electromagnetic stirring treatment until the raw materials are completely melted, and after slag skimming treatment, obtain a melt;

[0070] Perform the first refining treatment and the second refining treatment on the melt, and the rotor speed of the first refining treatment is 300 RPM, and a mixed gas of argon and chlorine is introduced, the argon flow rate is 12 m 3 / h, the chlorine flow rate is 2 m 3 / h, the temperature is controlled at 740 °C, and the time is 10 min; in the second refining treatment, Na3AlF6 is added, and the single-rotor argon flow rate is 10 m 3 / h, the temperature is 720 °C, and the time is 10 min, and the floating slag needs to be cleaned up in time during the first refining treatment and the second refining treatment. After the refining treatment is completed, filter through a double-layer filter box, the porosity of the first-stage filter plate is 30 ppi, and the porosity of the second-stage filter plate is 50 ppi;

[0071] Cast, and the casting temperature is 720 °C, the initial casting speed is 20 mm / min. When the casting length reaches 100 mm, the casting speed is adjusted to 35 mm / min. When the casting length exceeds 500 mm, the casting speed is adjusted to 20 mm / min;

[0072] Solution treatment, and the solution treatment is to heat up to 350 °C within 1 h, hold at 350 °C for 2 h, then continue to heat up to 400 °C within 10 min, and hold at 400 °C for 20 h;

[0073] Extrusion treatment, and the temperature of the cast rod in the extrusion treatment is 470 °C, the extrusion speed is 1.0 mm / s, the starting pressure speed is 0.2 mm / s, and the inlet of the working belt of the die used in the extrusion treatment is inclined downward by 15°. Then hold at 400 °C for 3 h and air-cool;

[0074] Aging treatment, and the temperature of the aging treatment is 200 °C and the time is 16 h to obtain a 7-series aluminum alloy.

[0075] Comparative Example 1:

[0076] Compared with Example 3, in Comparative Example 1, a conventional extrusion die is used, as Figure 2 shown, that is, the inlet of the working belt of the die used is not inclined downward by 15°, and the others are the same as in Example 3.

[0077] Comparative Example 2:

[0078] Compared with Example 3, the extrusion speed in Comparative Example 2 is 1.5 mm / s, and the others are the same as in Example 3.

[0079] Comparative Example 3:

[0080] Compared with Example 3, the composition of the 7-series aluminum alloy in Comparative Example 3 does not include Zr, and the others are the same as in Example 3.

[0081] Comparative Example 4:

[0082] Compared with Example 3, the composition of the 7-series aluminum alloy in Comparative Example 4 does not include Sc, and the others are the same as in Example 3.

[0083] Comparative Example 5:

[0084] Compared with Example 3, the composition of the 7-series aluminum alloy in Comparative Example 5 does not include Er, and the others are the same as in Example 3.

[0085] Comparative Example 6:

[0086] Compared with Example 3, the composition of the 7-series aluminum alloy in Comparative Example 6 does not include V, and the others are the same as in Example 3.

[0087] Comparative Example 7:

[0088] Compared with Example 3, the casting speed in Comparative Example 7 was 30 mm / min, and the others were the same as in Example 3.

[0089] Comparative Example 8:

[0090] Compared with Example 3, the solution treatment temperature in Comparative Example 8 was 450 °C and the time was 10 h, and the others were the same as in Example 3.

[0091] The 7xxx series aluminum alloy samples prepared in Examples 1 to 3 and the 7xxx series aluminum alloy comparative samples prepared in Comparative Examples 1 to 8 were tested for mechanical properties at 200 °C with reference to the standard of GB / T 433-2006 "Test Method for High Temperature Tensile Properties of Metallic Materials". And the forming rate after extrusion treatment was recorded, and the results are shown in Table 1 below.

[0092] Table 1: Performance test results

[0093]

[0094] It can be seen from the data analysis in Table 1 that through the optimization of the extrusion process and the extrusion die in this application, a higher forming rate can be obtained. Combining Figure 1 analysis, Figure 1 is a partial schematic diagram of the optimized die in the extrusion treatment of Example 3 of the present invention. Figure 1 At position 1 of, the inlet of the die working belt is inclined downward by 15°. After optimization, combined with the optimization of the extrusion parameters, the problems of dragging and cracking of 7xxx series aluminum alloy profiles can be solved, and the production quality can be guaranteed. In addition, by optimizing the composition and process of the 7xxx series aluminum alloy, the mechanical properties of the 7xxx series aluminum alloy are ensured to be excellent, it is not easy to crack and deform during stamping, which helps to improve the forming of the 7xxx series aluminum alloy.

[0095] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0096] The above-described embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A preparation method of 7xxx series aluminum alloy, characterized in that The preparation method includes the following steps: Weigh the raw materials according to the composition of the 7-series aluminum alloy, then add the aluminum ingots into the melting furnace. After heating until all the aluminum ingots are melted, use the electromagnetic stirring equipment to stir for 15 min to 20 min, then add the remaining raw materials, control the melting temperature, continue the electromagnetic stirring treatment until the raw materials are completely melted, and after slag skimming treatment, obtain the melt; Refine the obtained melt, and during the refining process, it is necessary to timely clean the floating slag. After the refining treatment is completed, after filtration, casting, solution treatment, extrusion treatment, annealing, and aging treatment, obtain the 7-series aluminum alloy; Among them, the temperature of the casting rod in the extrusion treatment is 460°C to 470°C, the extrusion speed is 0.8 mm / s to 1.0 mm / s, and the starting pressure speed is 0.2 mm / s; and the working belt inlet of the mold used in the extrusion treatment inclines downward by 10° to 15°.

2. The preparation method according to claim 1, characterized in that, The 7-series aluminum alloy includes the following components by mass percentage: Zn 3.2% to 4.0%, Mg 0.5% to 2.2%, Cu 1.2% to 2.2%, Zr 0.1% to 0.3%, Sc 0.01% to 0.02%, Er 0.01% to 0.02%, Ti 0.01% to 0.12%, V 0.01% to 0.05%, Si ≤ 0.2%, Mn ≤ 0.1%, other single elements ≤ 0.05%, the total amount of other impurity elements ≤ 0.15%, and the balance is Al.

3. The preparation method according to claim 1, wherein The melting temperature is 720°C to 750°C.

4. The preparation method according to claim 1, characterized in that, The refining treatment includes a first refining treatment and a second refining treatment. The rotational speed of the rotor in the first refining treatment is 250 RPM to 300 RPM, and a mixed gas of argon and chlorine is introduced. The argon flow rate is 8 m 3 / h to 12 m 3 / h, the chlorine flow rate is 1 m 3 / h to 2 m 3 / h, the temperature is controlled at 720 °C to 740 °C, and the time is 5 min to 15 min; in the second refining treatment, a refining agent is added, and the single-rotor argon flow rate is 8 m 3 / h to 10 m 3 / h, the temperature is 700 °C to 720 °C, and the time is 5 min to 10 min.

5. The preparation method according to claim 4, characterized in that, The refining agent is one or more of CaF, Na3AlF6, and NaCl.

6. The preparation method according to claim 1, characterized in that, The filtration is carried out in a double-layer filtration box. The porosity of the first-stage filter plate is 30 ppi, and the porosity of the second-stage filter plate is 50 ppi.

7. The preparation method according to claim 1, characterized in that, The temperature of the casting is 700°C to 720°C, the starting casting speed is 16 mm / min to 20 mm / min. When the casting length reaches 100 mm, the casting speed is adjusted to 30 mm / min to 35 mm / min. When the casting length exceeds 500 mm, the casting speed is adjusted to 18 mm / min to 22 mm / min.

8. The preparation method according to claim 1, characterized in that, The solution treatment is to raise the temperature to 300°C to 350°C within 1 h, and keep it at 300°C to 350°C for 1 h to 3 h, then continue to raise the temperature to 400°C to 420°C within 10 min, and keep it at 400°C to 420°C for 10 h to 24 h.

9. The preparation method according to claim 1, characterized in that, The annealing temperature is 300°C to 400°C, the time is 3 h to 5 h, and then air-cooled.

10. The preparation method according to claim 1, characterized in that, The aging treatment temperature is 150°C to 200°C, and the time is 10 h to 20 h.

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