7-series large-specification aluminum alloy ingot blank and preparation method thereof

Abstract

The invention relates to the field of aluminum alloy material processing, in particular to a 7-series large-specification aluminum alloy ingot blank, which comprises the following components in percentage by weight: 4.45-4.55% of Zn, 0.35-0.35% of Al, 0.35-0.35% of Ti, 0.35-0.35% of Ti, 0.35-0.35% The content of Mg is 1.15 to 1.25 percent; the content of Mn is 0.3 to 0.4 percent; the content of Cr is 0.1 to 0.25 percent; the content of Zr is 0.1 to 0.15 percent; the content of Ti is less than or equal to 0.05%; the content of Si is less than or equal to 0.1%; the content of Fe is less than or equal to 0.1%; the content of Cu is 0.1 to 0.15 percent; the content of V is less than or equal to 0.1%; the total content of other impurity elements is less than or equal to 0.05%; and the balance of Al. According to the preparation method of the aluminum alloy ingot blank, the crystallizer structure is optimized. The aluminum alloy ingot blank is uniform in structure, not thick in grain, and free of cracks, inclusions and segregation during casting.

Description

Technical Field

[0001] The invention relates to the field of aluminum alloy material processing, and in particular to a 7 series large-size aluminum alloy ingot and a preparation method thereof. Background Art

[0002] With the rapid advancement of lightweighting of rail transit and road freight vehicles around the world, improving the overall performance of the vehicle has become an inevitable trend of development. Increasing the width of aluminum profiles and reducing the number of welds in rail transit and road freight vehicles is a necessary means to achieve this goal. In addition, the market increasingly needs ultra-thin and ultra-wide high-performance aluminum profiles suitable for the next generation of rail transit and road freight vehicles to replace existing profiles. Ultra-large-sized fine-grained, homogeneous high-quality aluminum alloy ingots are the prerequisite for the production of ultra-thin and ultra-wide high-performance aluminum profiles. At present, there are difficulties in the melting and casting process of large-sized aluminum alloy round ingots, such as segregation leakage, uneven structure, casting cracks, and coarse grains.

[0003] Therefore, there is an urgent need for a 7 series large-size aluminum alloy ingot with uniform structure, not coarse grains, and no cracks, inclusions, or segregation during casting, and a preparation method thereof. Summary of the invention

[0004] The present invention aims to solve the problems of segregation leakage, uneven structure, casting cracks and coarse grains in 7 series large-size aluminum alloy ingots.

[0005] In order to achieve the above object, the first aspect of the present invention provides a 7 series large-size aluminum alloy ingot, wherein the components and their weight percentages in the aluminum alloy ingot are:

[0006] Zn content is 4.45-4.55%;

[0007] Mg content is 1.15-1.25%;

[0008] Mn content is 0.3-0.4%;

[0009] Cr content is 0.1-0.25%;

[0010] Zr content is 0.1-0.12%;

[0011] Ti content is ≤0.05%;

[0012] Si content is ≤0.1%;

[0013] Fe content is ≤0.1%;

[0014] Cu content is 0.1-0.15%;

[0015] V content is ≤0.1%;

[0016] The total content of other impurity elements is ≤0.05%;

[0017] The balance is Al.

[0018] A second aspect of the present invention provides a method for preparing the above-mentioned 7 series large-size aluminum alloy ingot, wherein the preparation method comprises:

[0019] Melting, refining, slagging, heat preservation and standing, online refinement, online degassing, filtering, casting, homogenization treatment;

[0020] In the casting, the height of the crystallizer used is 110.0-117.0 mm, the height of the graphite ring is 20.0-21.0 mm, and the inner diameter of the crystallizer where the graphite ring is installed is 814.0-815.0 mm;

[0021] In the casting, aluminum chips are placed at the bottom of the crystallizer before casting, and aluminum liquid is added until the aluminum chips are in a semi-solidified state, and then casting begins;

[0022] When the flow is stopped and the distance between the end of the cast rod and the crystallizer is 7-12cm, the machine is stopped and the water supply is stopped, and the cast rod is tempered.

[0023] The third aspect of the present invention provides a 7 series large-size aluminum alloy ingot produced by the above-mentioned preparation method.

[0024] The beneficial effects of the present invention are:

[0025] By controlling alloy composition, optimizing mold structure, cooling water hole distribution and quantity, water spray angle, cooling water volume, and specific casting process, the 7 series large-size aluminum alloy ingot provided by the present invention has uniform structure, not coarse grains, and is free of cracks, inclusions, and segregation during casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a photo of the 7 series large-size aluminum alloy ingot of Example 1;

[0027] Figure 2 This is a photo of the 7 series large-size aluminum alloy ingot of Example 2;

[0028] Figure 3 This is a photo of the 7 series large-size aluminum alloy ingot of Comparative Example 1. DETAILED DESCRIPTION

[0029] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0030] In the 7 series large-size aluminum alloy ingot referred to in the present invention, large-size means a diameter of 520 mm or more.

[0031] When the existing technology is used to produce 7 series large-size aluminum alloy ingots, segregation leakage, uneven structure, casting cracks and coarse grains occur during the preparation process.

[0032] In the present invention, the inventors found that by controlling the alloy composition and adjusting the preparation process, the 7 series large-scale aluminum alloy ingot can have a uniform structure, not coarse grains, and no cracks, inclusions, or segregation during casting.

[0033] To achieve this goal, the inventors tried to optimize the component composition and preparation process of 7 series large-size aluminum alloy ingots. The inventors found that the above objectives can be achieved by controlling the alloy composition and optimizing the crystallizer structure. Furthermore, the distribution and number of cooling water holes, water spray angle, cooling water volume, and specific casting process make the performance of aluminum alloy even better.

[0034] The first aspect of the present invention provides a 7 series large-size aluminum alloy ingot, wherein the components and their weight percentages in the aluminum alloy ingot are:

[0035] Zn content is 4.45-4.55%;

[0036] Mg content is 1.15-1.25%;

[0037] Mn content is 0.3-0.4%;

[0038] Cr content is 0.1-0.25%;

[0039] Zr content is 0.1-0.12%;

[0040] Ti content is ≤0.05%;

[0041] Si content is ≤0.1%;

[0042] Fe content is ≤0.1%;

[0043] Cu content is 0.1-0.15%;

[0044] V content is ≤0.1%;

[0045] The total content of other impurity elements is ≤0.05%;

[0046] The balance is Al.

[0047] In the present invention, the inventors found that the above alloy formula forms A12Mg3Zn3 (T phase), which has the best comprehensive performance. The T phase is a quasi-crystal-like phase in Al-Cu-Mn alloys and has a very complex structure.

[0048] The second aspect of the present invention provides a method for preparing the above-mentioned 7 series large-size aluminum alloy ingot, wherein the preparation method comprises:

[0049] Melting, refining, slagging, heat preservation and standing, online refinement, online degassing, filtering, casting, homogenization treatment;

[0050] In the casting, the height of the crystallizer used is 110.0-117.0 mm, the height of the graphite ring is 20.0-21.0 mm, and the inner diameter of the crystallizer where the graphite ring is installed is 814.0-815.0 mm;

[0051] In the casting, aluminum chips are placed at the bottom of the crystallizer before casting, and aluminum liquid is added until the aluminum chips are in a semi-solidified state, and then casting begins;

[0052] When the flow is stopped and the distance between the end of the cast rod and the crystallizer is 7-12cm, the machine is stopped and the water supply is stopped, and the cast rod is tempered.

[0053] In the present invention, as the height of the crystallizer decreases, the effective crystallization zone is short during casting, the cooling rate is fast, the solute elements have no time to diffuse, there are many active particles, and the internal structure of the grains is fine. The upper melt temperature is high and the fluidity is good, which is conducive to the floating of gas and non-metallic inclusions and has a small loose tendency; as the effective crystallization zone shortens, the grains are fine, which is conducive to improving the average mechanical properties of the ingot. When using the above-mentioned specific optimized crystallizer, the thickness of the solidified shell and the depth of the liquid cavity during casting are reduced, low melting point segregation and cold shut are avoided, the surface of the ingot is smooth, the degree of reverse segregation and reverse segregation depth around the ingot are small, there is no secondary remelting phenomenon of the solidified shell, and the formation of segregation nodules is suppressed, thereby obtaining a uniform and fine solidification structure and good surface quality, and ultimately improving the comprehensive performance of the extruded profile.

[0054] In the present invention, since the 7 series super-hard alloy has a low solidification point and a very high tendency to cold and hot cracks, cracks are easily formed at the head and tail during the casting process. Therefore, the aluminum chip preforming and parking tempering technology are integrated. The surface quality of the cast rods obtained by the above process is good, and the generation of bottom cracks is effectively controlled. The specific cast rod tempering conditions can improve the plasticity of the pouring gate, reduce stress, and prevent cracks from occurring at the ingot pouring gate.

[0055] According to the present invention, in the casting, the number of cooling water holes is 300-400, the cross-sectional diameter of the cooling water holes is 2.5-3.5 mm, the water outlet angle of the cooling water holes is 10-15 degrees, and the cooling water volume is 1690-1720 m 3 / min.

[0056] In the present invention, the specific size and spacing of the water outlet holes can ensure uniform cooling and sufficient cooling water along the periphery of the ingot. When the total area and water pressure of the water outlet holes are constant, reducing the cross section of the water outlet holes and making the distance between the holes small is conducive to uniform cooling, but too small water outlet holes will increase the possibility of being blocked by dirt during the casting process. In order to ensure sufficient cooling water during casting, the cooling water pressure should not be less than 0.15MPa-0.20MPa.

[0057] In the present invention, the water outlet angle of the cooling water hole is the inclination angle of the water outlet hole to the center line of the ingot. The water outlet angle of the cooling water hole determines the water-seeing position of the ingot. If the angle is too small, the ingot will see water late, resulting in reduced cooling intensity; if the angle is too large, the cooling water will splash and cannot flow evenly along the ingot, reducing the cooling effect. At the same time, it is possible to force water into the liquid surface in the crystallizer and cause an accident.

[0058] According to the present invention, the smelting conditions include: a smelting temperature of 730-750° C., a stirring number of 2-4 times, a stirring time of 8-12 minutes, and a stirring interval of 10-15 minutes.

[0059] According to the present invention, the refining conditions include: the amount of refining agent is 1-1.5 kg / t, the refining temperature is 745-750° C., and the refining time is 15-30 min.

[0060] According to the present invention, the conditions for slagging include: a slagging temperature of 730-745°C.

[0061] According to the present invention, the heat preservation and standing conditions include: the heat preservation and standing temperature is 740-754° C., and the heat preservation and standing time is 20-30 minutes.

[0062] According to the present invention, the conditions for online thinning include: a wire feeding speed of 80-160 cm / min.

[0063] According to the present invention, the online degassing conditions include: using powder spray degassing and online three-rotor degassing, and the graphite rotor speed is 300-350r / min.

[0064] In the present invention, the online three-rotor degassing can reduce the average hydrogen content in the melt to 0.08 ml / 100 gAl.

[0065] According to the present invention, the filtering conditions include: using foam ceramic filtration and deep bed filtration, the foam ceramic filtration is a CFF type foam ceramic filter plate, the filter plate preheating time is 25-30 minutes, and then the aluminum liquid is deeply filtered through a DBF type deep bed filter.

[0066] In the present invention, the specific filtering method effectively improves the surface and internal quality of the ingot.

[0067] According to the present invention, the casting conditions include: a casting temperature of 680-695° C., a casting speed of 22-28 mm / min, and a hydrogen content of ≤0.08 ml / 100 gAl.

[0068] In the present invention, according to the different stages of casting, a pulsed distributed electromagnetic field is applied by low-frequency electromagnetic casting to effectively control the temperature gradient of the molten pool in the initial stage of large-size ingot casting, control the temperature gradient, maintain the casting temperature between 680-695°C, and reduce the tendency of the ingot to form columnar crystals and feather crystals.

[0069] According to the present invention, the homogenization treatment is (535-545)°C×(12-14)h.

[0070] The third aspect of the present invention provides a 7 series large-size aluminum alloy ingot produced by the above-mentioned preparation method.

[0071] Test Method

[0072] The test method for the composition of aluminum alloy profiles is in accordance with GB / T7999-2015 "Photoelectric Direct Reading Emission Spectroscopy Analysis Method for Aluminum and Aluminum Alloys", and the test equipment is ARL-3460 direct reading spectrometer.

[0073] The tensile strength test method is in accordance with GB / T16865-2013 "Specimens and methods for tensile testing of deformed aluminum, magnesium and their alloy products", and the test equipment is AG-X 100KN electronic universal testing machine.

[0074] The yield strength test method is in accordance with GB / T16865-2013 "Specimens and methods for tensile testing of deformed aluminum, magnesium and their alloy products", and the test equipment is AG-X 100KN electronic universal testing machine.

[0075] The elongation test method is in accordance with GB / T16865-2013 "Specimens and methods for tensile testing of deformed aluminum, magnesium and their alloy products", and the test equipment is AG-X 100KN electronic universal testing machine.

[0076] The technical scheme of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the embodiments described herein are only some embodiments of the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments implemented by ordinary technicians in this field without making creative improvements belong to the protection scope of the present invention.

[0077] Example 1

[0078] The aluminum alloy ingot contains the following chemical components calculated by mass fraction: Zn 4.45%; Mg 1.25%; Mn 0.3%; Cr 0.13%; Zr 0.12%; Ti 0.05%; Si 0.1%; Fe 0.1%; Cu 0.11%; and Al balance.

[0079] The raw materials other than magnesium ingot are added into the furnace for smelting at a melting temperature of 735°C. After the magnesium ingot is completely melted and refined, the slag is removed and then added. An electromagnetic stirrer is used for stirring. The stirring frequency is once every 10 minutes, 10 minutes each time, and 3 times per furnace. High-purity argon is used as a carrier to carry the granular sodium-free refining agent for refining. The amount of refining agent is 1.5kg / t based on the mass ratio of refining agent to melt. The refining temperature is 745°C and the refining time is 20min. Remove scum on the surface of the melt, the slag removal temperature is 730℃; transfer the melt to the insulation furnace for insulation and static, control the insulation temperature to 740℃, the time is 25min; use Al-5Ti-1B double titanium boron wire for online refinement, the wire feeding speed is 150cm / min; transfer the heat-insulated melt to the degassing box, and use argon to remove impurity gases in the melt, adjust the rotor speed according to the workshop environment humidity, the graphite rotor speed is 320r / min; the filtration process includes foam ceramic filtration and deep bed filtration, CFF type foam ceramic filter plate, the filter plate preheating time is 25min, after the ceramic filter plate, the aluminum liquid is deep filtered through the DBF type deep bed filter;

[0080] Before casting, aluminum chips were placed at the bottom of the crystallizer. When the aluminum chips were semi-solidified, casting began. The filtered melt was injected into the mold to obtain aluminum alloy castings. The casting temperature was 685°C, the casting speed was 25mm / min, the height of the crystallizer used was 113mm, the height of the graphite ring was 20.6mm, the inner diameter of the crystallizer where the graphite ring was installed was 814.8mm, the number of cooling water holes was 360, the cross-sectional diameter of the cooling water holes was 3mm, the water outlet angle of the cooling water holes was 13 degrees, and the cooling water flow rate was 1700m 3 / min, hydrogen content ≤0.08ml / 100gAl, when the flow is stopped and the distance between the end of the cast rod and the crystallizer is 10cm, the car is stopped and the water supply is stopped, and the cast rod is tempered.

[0081] The ingot round rods were placed in a homogenizing furnace and a single-stage homogenization system was adopted at 540℃×12h.

[0082] A 7 series large-size aluminum alloy ingot A1 was produced.

[0083] Example 2

[0084] The aluminum alloy ingot contains the following chemical components calculated by mass fraction: Zn 4.55%; Mg 1.15%; Mn 0.33%; Cr 0.14%; Zr 0.15%; Ti 0.05%; Si 0.1%; Fe 0.1%; Cu 0.12%; and Al balance.

[0085] The raw materials other than magnesium ingot are added into the furnace for smelting at a melting temperature of 745°C. After the magnesium ingot is completely melted and refined and slag is removed, the magnesium ingot is added. An electromagnetic stirrer is used for stirring, and the stirring frequency is once every 10 minutes, 10 minutes each time, and 3 times per furnace. High-purity argon is used as a carrier to carry a granular sodium-free refining agent for refining. The amount of refining agent is 1.5kg / t based on the mass ratio of refining agent to melt. The refining temperature is 750°C and the refining time is 20min. Remove scum on the surface of the melt, and the slag removal temperature is 744℃; transfer the melt to a holding furnace for holding and keeping at a temperature of 745℃ for 25min; use Al-5Ti-1B double titanium boron wire for online refinement, and the wire feeding speed is 150cm / min; transfer the heat-treated melt to a degassing box, and use argon to remove impurity gases in the melt. Adjust the rotor speed according to the workshop ambient humidity, and the graphite rotor speed is 350r / min; the filtration process includes foam ceramic filtration and deep bed filtration, CFF type foam ceramic filter plate, the filter plate preheating time is 30min, and after the ceramic filter plate, the aluminum liquid is deeply filtered through a DBF type deep bed filter;

[0086] Before casting, aluminum chips are placed at the bottom of the crystallizer. When the aluminum chips are semi-solidified, the casting begins. The filtered melt is injected into the mold to obtain an aluminum alloy casting. The casting temperature is 690°C, the casting speed is 24mm / min, the height of the crystallizer used is 115mm, the height of the graphite ring is 20.8mm, the inner diameter of the crystallizer where the graphite ring is installed is 814.9mm, the number of cooling water holes is 360, the cross-sectional diameter of the cooling water holes is 3.5mm, the water outlet angle of the cooling water holes is 15 degrees, and the cooling water flow rate is 1720m 3 / min, hydrogen content ≤0.08ml / 100gAl, when the flow is stopped and the distance between the end of the cast rod and the crystallizer is 8mm, the car is stopped and the water supply is stopped, and the cast rod is tempered.

[0087] The ingot round rods were placed in a homogenizing furnace and a single-stage homogenization system was adopted at 540℃×12h.

[0088] A 7 series large-size aluminum alloy ingot A2 was produced.

[0089] Example 3

[0090] A 7 series large-size aluminum alloy ingot was prepared according to the preparation method of Example 1, except that the height of the crystallizer used was 117 mm, the height of the graphite ring was 21 mm, and the inner diameter of the crystallizer where the graphite ring was installed was 815.0 mm.

[0091] A 7 series large-size aluminum alloy ingot A3 was produced.

[0092] Example 4

[0093] A 7 series large-size aluminum alloy ingot was prepared according to the preparation method of Example 1, except that the height of the crystallizer used was 110.0 mm, the height of the graphite ring was 20.0 mm, and the inner diameter of the crystallizer where the graphite ring was installed was 814.0 mm.

[0094] A 7 series large-size aluminum alloy ingot A4 was produced.

[0095] Example 5

[0096] A 7 series large-size aluminum alloy ingot was prepared according to the preparation method of Example 1, except that the number of cooling water holes was 400, the cross-sectional diameter of the cooling water holes was 3.5 mm, the outlet angle of the cooling water holes was 15 degrees, and the cooling water flow rate was 1720 m 3 / min.

[0097] A 7 series large-size aluminum alloy ingot A5 was produced.

[0098] Example 6

[0099] A 7 series large-size aluminum alloy ingot was prepared according to the preparation method of Example 1, except that the number of cooling water holes was 300, the cross-sectional diameter of the cooling water holes was 2.5 mm, the outlet angle of the cooling water holes was 10 degrees, and the cooling water flow rate was 1690 m 3 / min.

[0100] A 7 series large-size aluminum alloy ingot A6 was produced.

[0101] Example 7

[0102] A 7 series large-size aluminum alloy ingot was prepared according to the preparation method of Example 1, except that the number of cooling water holes was 290, the cross-sectional diameter of the cooling water holes was 2.3 mm, the outlet angle of the cooling water holes was 9 degrees, and the cooling water flow rate was 1650 m 3 / min.

[0103] A 7 series large-size aluminum alloy ingot A7 was produced.

[0104] Comparative Example 1

[0105] A 7 series large-size aluminum alloy ingot was prepared according to the preparation method of Example 1, except that no aluminum chips were placed at the bottom of the crystallizer before casting, and the system was stopped and water was stopped according to conventional processes.

[0106] A 7 series large-size aluminum alloy ingot DA1 was produced.

[0107] Comparative Example 2

[0108] A 7 series large-size aluminum alloy ingot was prepared according to the preparation method of Example 1, except that the height of the crystallizer used was 118.0 mm, the height of the graphite ring was 21.5 mm, and the inner diameter of the crystallizer where the graphite ring was installed was 815.5 mm.

[0109] 7 series large-size aluminum alloy ingot DA2 was produced.

[0110] A1-A7 and DA1-DA2 were subjected to the same conventional extrusion and heat treatment to obtain aluminum alloy profiles B1-B8 and DB1-DB2, and performance tests were performed, as shown in Table 1.

[0111] Table 1

[0112]

[0113] It can be seen from Table 1 above that the aluminum alloy profiles obtained by the aluminum alloy ingot provided by the present invention after the same extrusion and heat treatment process have excellent performance, which is better than the performance of the aluminum alloy ingot DA1 integrated with the aluminum chip-free preforming and parking tempering technology and the aluminum alloy ingot DA2 made by the conventional crystallizer structure.

[0114] Figure 1 and Figure 2 The photos of 7 series large-size aluminum alloy ingots are respectively Example 1 and Example 2. The aluminum alloys prepared in Example 1 and Example 2 basically have no defects of casting cracks; the chemical composition segregation of the obtained rods is very low, and there is almost no deviation of Zn from the edge to the core along the diameter direction; the thickness of the coarse grain layer is much lower than the thickness of the traditional casting method, and there are no defects such as looseness, pores, and slag inclusions inside the cast rods. Figure 3 This is a photo of the 7 series large-size aluminum alloy ingot of comparative example 1. The preforming and parking tempering technology without aluminum chips are integrated, and cracks appear on the surface of the ingot.

[0115] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A 7 series large-size aluminum alloy ingot, characterized in that: The components and their weight percentages in the aluminum alloy ingot are: Zn content is 4.45-4.55%; Mg content is 1.15-1.25%; Mn content is 0.3-0.4%; Cr content is 0.1-0.25%; Zr content is 0.1-0.15%; Ti content is ≤0.05%; Si content is ≤0.1%; Fe content is ≤0.1%; Cu content is 0.1-0.15%; V content is ≤0.1%; The total content of other impurity elements is ≤0.05%; The balance is Al.

2. A method for preparing the 7 series large-size aluminum alloy ingot according to claim 1, characterized in that: The preparation method comprises: Melting, refining, slagging, heat preservation and standing, online refinement, online degassing, filtering, casting, homogenization treatment; In the casting, the height of the crystallizer used is 110.0-117.0 mm, the height of the graphite ring is 20.0-21.0 mm, and the inner diameter of the crystallizer where the graphite ring is installed is 814.0-815.0 mm; In the casting, aluminum chips are placed at the bottom of the crystallizer before casting, and aluminum liquid is added until the aluminum chips are in a semi-solidified state, and then casting begins; When the flow is stopped and the distance between the end of the cast rod and the crystallizer is 7-12cm, the machine is stopped and the water supply is stopped, and the cast rod is tempered.

3. The preparation method according to claim 2, characterized in that: In the casting, the number of cooling water holes is 300-400, the cross-sectional diameter of the cooling water holes is 2.5-3.5 mm, the water outlet angle of the cooling water holes is 10-15 degrees, and the cooling water volume is 1690-1720 m 3 / min.

4. The preparation method according to claim 2, wherein the smelting conditions include: The melting temperature is 730-750℃, the stirring times are 2-4 times, the stirring time is 8-12min, and the stirring interval time is 10-15min; The refining conditions include: the amount of refining agent is 1-1.5 kg / t, the refining temperature is 745-750° C., and the refining time is 15-30 min; The conditions for slagging include: the slagging temperature is 730-745°C; The heat preservation and standing conditions include: the heat preservation and standing temperature is 740-754° C., and the heat preservation and standing time is 20-30 minutes; The conditions for the online thinning include: a wire feeding speed of 80-160 cm / min; The online degassing conditions include: using powder spray degassing and online three-rotor degassing, and the graphite rotor speed is 300-350r / min.

5. The preparation method according to claim 2, characterized in that: The filtering conditions include: using foam ceramic filtration and deep bed filtration, the foam ceramic filtration is a CFF type foam ceramic filter plate, the filter plate preheating time is 25-30 minutes, and then the aluminum liquid is deeply filtered through a DBF type deep bed filter.

6. The preparation method according to claim 2, characterized in that: The casting conditions include: a casting temperature of 680-695° C., a casting speed of 22-28 mm / min, and a hydrogen content of ≤0.08 ml / 100 gAl; The homogenization treatment is (535-545)°C×(12-14)h.

7. A 7 series large-size aluminum alloy ingot produced by the preparation method described in any one of claims 2 to 6.

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