Preparation method of superhard Al-Zn-Mg-Cu aluminum alloy large-size flat cast ingot

Abstract

The invention relates to a preparation method of a superhard Al-Zn-Mg-Cu aluminum alloy large-size flat cast ingot, in particular to a preparation method of a superhard Al-Zn-Mg-Cu aluminum alloy large-size flat cast ingot. The invention aims to solve the problem that crack waste products are easy to generate when the Al-Zn-Mg-Cu aluminum alloy flat cast ingot is produced by adopting an existing traditional casting tool. The method comprises the following steps: 1, preparing a double-row cold graphite crystallizer; 2, weighing the materials; 3, smelting; and 4, casting. The graphite crystallizer is adopted, the scientific proportion of raw materials and reasonable adjustment of technological parameters are combined, the crack defect of the cast ingot is reduced, and the forming rate of the cast ingot reaches 93% or above.

Description

Technical Field

[0001] The invention specifically relates to a method for preparing a large-size flat ingot of superhard Al-Zn-Mg-Cu aluminum alloy. Background Art

[0002] In today's era of rapid technological development, aluminum alloys have been widely used in aerospace, transportation and many other fields that have strict requirements on material properties due to their outstanding characteristics such as low density, high strength, good corrosion resistance and excellent processing performance. In the production and manufacturing process of aluminum alloys, the casting process is one of the key links, which directly determines the quality and performance of aluminum alloy ingots, and thus affects the subsequent processing and use.

[0003] The traditional DC casting (direct water-cooled semi-continuous casting) method exposes a series of serious problems when casting Al-Zn-Mg-Cu aluminum alloy flat ingots with a small solid-liquid zone. First, at the beginning of casting, the bottom of the ingot often warps, and the degree of warping is large. This warping phenomenon will cause uneven stress distribution inside the ingot. When the stress exceeds the ultimate strength of the material, it is very easy to cause tensile cracks and cracks. These cracks not only destroy the integrity of the ingot, but also in the subsequent processing process, the cracks may further expand, seriously reducing the quality and reliability of aluminum alloy products, and even causing the product to be scrapped.

[0004] Secondly, during the entire casting process, the lubricating effect of the lubricating oil has a crucial impact on the quality of the ingot. Since it is difficult to achieve uniform lubrication of the lubricating oil in the traditional casting process, the friction force on the ingot during the solidification and drawing process is uneven. Excessive local friction will hinder the normal contraction and movement of the ingot, thereby generating additional stress concentration inside the ingot, and eventually causing the ingot to crack. These cracking and cracking problems caused by bottom warping and uneven lubrication have kept the yield of the ingot at a low level, greatly increased production costs, and limited the production efficiency and market competitiveness of aluminum alloy products.

[0005] With the rapid development of industries such as aerospace and transportation, the demand for high-quality aluminum alloy ingots is growing. These defects of traditional casting processes have become increasingly prominent and can no longer meet the industry's requirements for high quality and high yield of aluminum alloy ingots. Therefore, it is urgent to develop a new casting technology and equipment to solve these problems. Summary of the invention

[0006] The present invention aims to solve the problem that crack waste is easily generated when producing Al-Zn-Mg-Cu aluminum alloy flat ingots using existing traditional casting tools, and to provide a method for preparing large-size superhard Al-Zn-Mg-Cu aluminum alloy flat ingots.

[0007] A method for preparing a large-size flat ingot of superhard Al-Zn-Mg-Cu aluminum alloy is completed by the following steps:

[0008] 1. Weighing: According to the mass percentage of Si less than 0.5%, Fe less than 1.0%, Cu: 1.8% to 3.0%, Mn less than 0.5%, Mg: 1.8% to 3.0%, Cr less than 0.3%, Ni less than 0.3%, Zn: 5.0% to 8.2%, Zr: 0.05% to 0.5%, Ti: 0.02% to 0.2% and the balance is Al, weigh aluminum ingots, pure Cu plates, pure Mg ingots, pure Zn ingots, Al-Zr master alloys and Al-Ti master alloys as smelting raw materials;

[0009] 2. Melting: Add the weighed aluminum ingot, pure Cu plate, pure Zn ingot and Al-Zr master alloy into a natural gas melting furnace, add pure Mg ingot and Al-Ti master alloy at a temperature of 700-720°C, use electromagnetic stirring for 25-35 minutes when the temperature reaches 720°C, take samples and analyze the chemical composition, and obtain aluminum alloy melt when the chemical composition is qualified;

[0010] 3. Casting: The aluminum alloy melt is introduced into a holding furnace, refined with Ar gas at a temperature of 720-780°C for 30-40 minutes, and then allowed to stand at a temperature of 720-780°C for 30-40 minutes to obtain a casting melt, and then the melt first flows into an online degassing device, into which Ar gas is introduced, the purity of Ar gas is required to be 99.996% and above, and the working pressure of the argon gas pipeline is 0.3MPa-1.0MPa; then it flows into a filtering device, and then through a flow plate, the melt is injected into a double-row line-cooled graphite crystallizer under the conditions of a casting speed of 40-55mm / min, a casting temperature of 685-710°C, a cooling water flow of 75-145T / h, a cooling water temperature of 15-28°C and online seeding of Al-Ti-B wire to form a large-size flat ingot of superhard Al-Zn-Mg-Cu aluminum alloy.

[0011] Beneficial effects of the present invention:

[0012] The present invention adopts a double-row cooling water impact zone located in the area where the surface conductivity of the ingot is the smallest and the temperature rebounds, thereby ensuring the cooling effect of the ingot and eliminating the sputtering of cooling water to avoid the generation of interference fountains; second, the design of inlaying graphite plates in the inner cavity of the crystallizer does not require lubricating oil for production and casting due to the self-lubricating property of graphite, which not only improves the surface quality, but also avoids water pollution and saves production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the structure of a double-layer water-cooled graphite crystallizer;

[0014] Figure 2It is a schematic diagram of the structural decomposition of a double-layer water-cooled graphite crystallizer;

[0015] Figure 3 This is a partial enlarged view of a double-row water-cooled graphite crystallizer;

[0016] Figure 4 It is a structural schematic diagram of the water inlet filter;

[0017] Figure 5 It is a structural schematic diagram of the pneumatic control valve. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0019] Specific implementation method 1: In this implementation method, a method for preparing a large-size flat ingot of superhard Al-Zn-Mg-Cu aluminum alloy is completed by the following steps:

[0020] 1. Weighing: According to the mass percentage of Si less than 0.5%, Fe less than 1.0%, Cu: 1.8% to 3.0%, Mn less than 0.5%, Mg: 1.8% to 3.0%, Cr less than 0.3%, Ni less than 0.3%, Zn: 5.0% to 8.2%, Zr: 0.05% to 0.5%, Ti: 0.02% to 0.2% and the balance is Al, weigh aluminum ingots, pure Cu plates, pure Mg ingots, pure Zn ingots, Al-Zr master alloys and Al-Ti master alloys as smelting raw materials;

[0021] 2. Melting: Add the weighed aluminum ingot, pure Cu plate, pure Zn ingot and Al-Zr master alloy into a natural gas melting furnace, add pure Mg ingot and Al-Ti master alloy at a temperature of 700-720°C, use electromagnetic stirring for 25-35 minutes when the temperature reaches 720°C, take samples and analyze the chemical composition, and obtain aluminum alloy melt when the chemical composition is qualified;

[0022] 3. Casting: The aluminum alloy melt is introduced into a holding furnace, refined with Ar gas at a temperature of 720-780°C for 30-40 minutes, and then allowed to stand at a temperature of 720-780°C for 30-40 minutes to obtain a casting melt, and then the melt first flows into an online degassing device, into which Ar gas is introduced, the purity of Ar gas is required to be 99.996% and above, and the working pressure of the argon gas pipeline is 0.3MPa-1.0MPa; then it flows into a filtering device, and then through a flow plate, the melt is injected into a double-row line-cooled graphite crystallizer under the conditions of a casting speed of 40-55mm / min, a casting temperature of 685-710°C, a cooling water flow of 75-145T / h, a cooling water temperature of 15-28°C and online seeding of Al-Ti-B wire to form a large-size flat ingot of superhard Al-Zn-Mg-Cu aluminum alloy.

[0023] Specific embodiment 2: This embodiment is different from the specific embodiment 1 in that: the double-sided row cooling graphite crystallizer is composed of a large-surface box body 8, a small-surface box body 4, a large-surface lower pressure cover 1, a small-surface lower pressure cover 3, a large-surface upper pressure cover 9 and a small-surface upper pressure cover 6; the large-surface box body 8, the large-surface lower pressure cover 1, and the large-surface upper pressure cover 9 form a large-surface assembly, and the small-surface box body 4, the small-surface lower pressure cover 3, and the small-surface upper pressure cover 6 form a small-surface assembly; two large-surface assemblies and two small-surface assemblies form the inner cavity of the crystallizer. The rest is the same as the specific embodiment 1.

[0024] The double-row water-cooled graphite crystallizer is water-cooled once through heat conduction on the graphite plate surface. The crystallizer cavity is forged from 2A50 aluminum alloy and manufactured through a CNC machining center.

[0025] This embodiment determines the inner cavity size of the crystallizer by measuring the shrinkage coefficient of the aluminum alloy and the cross-sectional dimensions of ingots of different specifications of the same alloy; selects a suitable tool material according to the characteristics of the crystallizer; designs the crystallizer into an inner oblong casting tool with a certain inclination according to the inherent characteristics of the aluminum alloy and some product defects that have occurred on site; the inner cavity of the hard aluminum alloy crystallizer is a combined box body, which is composed of two large-surface boxes and two small-surface boxes overlapped and fixed with bolts; the crystallizer is a double drainage design, the first drainage hole is designed to be ￠3.8mm in size, and the angle is 44° to the vertical direction, and the second drainage hole is ￠3.8mm in size, and the angle is 44° to the vertical direction. The size of the drainage hole is designed to be 3.2mm, with an angle of 26° to the vertical direction, and it can be adjusted by a pneumatic control valve and can be freely switched according to the hard aluminum alloy casting process; in the design process of the hard alloy double-drain cooling graphite crystallizer, the upstream heat conduction area of ​​the ingot is moved upward through the design of the cooling water hole, and the width of the stagnant area of ​​the ingot cooling is increased, thereby avoiding surface defects, cracks, cracks and aluminum liquid leakage during the process; in the design process of the graphite crystallizer, the casting friction is effectively reduced, the surface quality is improved, the surface segregation is reduced, and the milling surface geometric scrap is reduced by inlaying graphite plates in the inner cavity of the crystallizer. Matching process parameters, the single drainage and double drainage alternating cooling methods are used at the beginning to reduce the tendency of cracks at the beginning of casting and improve the ingot forming rate.

[0026] Specific implementation method three: This implementation method is different from specific implementation method two in that: the inner sides of the small face box body 4 and the large face box body 8 are processed with grooves for embedding graphite plates, and the graphite plates are fixed to the inner side of the box body by the small face pressure cover 6 and the large face pressure cover 9; after the small face of the crystallizer is assembled, the extended parts on both sides of the small face pressure cover 6 are overlapped on the large face assembly, and the part of the large face pressure cover 9 that overlaps with the small face assembly is processed with threads for locking and fixing the small face assembly and the large face assembly, and the surface of the graphite plate is used as the crystallization working surface. Others are the same as specific implementation method two.

[0027] In this embodiment, the high-purity graphite plates embedded on the inner sides of the large surface and the small surface increase the lubrication of the ingot and the inner side of the crystallizer during casting, reduce the tendency of the ingot to crack, and improve the ingot forming rate.

[0028] Specific embodiment 4: This embodiment is different from specific embodiment 2 in that the inclination angle of the inner cavity working surface of the graphite plate in the small face assembly and the large face assembly is 0.68°. The rest is the same as specific embodiment 2.

[0029] Specific implementation mode 5: This implementation mode is different from specific implementation mode 2 in that: the large face box body 8 and the small face box body 4 are processed to construct a partition structure at the upper and lower parts thereof, forming an upper cavity and a lower cavity as a water chamber for cooling water; the pneumatic control valve 5 is located inside the lower cavity, the water inlet quick connector 2 is installed in the lower cavity, and its interface part is exposed outside the cavity and connected to the external water supply pipeline; the water inlet filter screen 7 is tightly installed on the water inlet quick connector 2 and passes through the upper and lower cavities, and the water inlet filter screen 7 and the lower cavity are a watertight isolation structure; the upper cavity is provided with a lower drain hole, the diameter of the lower drain hole is Φ3.2mm, the angle is 26° with the vertical direction, the lower drain hole is connected with the internal space of the upper cavity, and the water in the upper cavity can be discharged into the inner cavity of the crystallizer; the lower cavity is provided with an upper drain hole, the diameter of the upper drain hole is Φ3.8mm, the angle is 44° with the vertical direction, the upper drain hole is connected with the internal space of the lower cavity, and the water in the lower cavity can be discharged into the inner cavity of the crystallizer. The rest is the same as specific implementation mode 2.

[0030] The function of the pneumatic control valve is to control the water flow channel between the lower cavity and the upper cavity. When it is in the closed state, it prevents the water flow in the upper cavity from entering the lower cavity; when it is opened, it allows the water flow to flow from the upper cavity into the lower cavity through a specific gap, thereby achieving precise control of the water flow path.

[0031] The through-type design allows the water to first be filtered through the water inlet filter after entering the box through the water inlet quick connector to remove impurity particles in the water and prevent them from clogging or damaging the internal structure of the box and subsequent water flow channels. A sealed connection method is used between the water inlet filter and the water inlet quick connector, such as a rubber sealing ring or other sealing parts, to ensure that the water can only enter the box through the filter and will not leak from the connection between the connector and the filter or bypass the filter to directly enter the box.

[0032] Specific embodiment 6: This embodiment is different from the specific embodiment 2 in that the large surface upper pressure cover 9, the large surface lower pressure cover 1, the small surface pressure cover 6, and the small surface lower pressure cover 3 are processed with an annular groove near the inner side of the water chamber, and an "O"-shaped sealing silicone strip is installed in the groove. The rest is the same as the specific embodiment 2.

[0033] The double-ring "O"-shaped sealing silicone strip used in this embodiment is used to prevent cooling water leakage in the mold cavity after the crystallizer box is assembled.

[0034] Specific embodiment 7: This embodiment is different from specific embodiments 2 and 5 in that the large-surface box 8, small-surface box 4, water inlet filter 7, water inlet quick connector 2, pneumatic control valve 5, large-surface lower gland 1, small-surface lower gland 3, large-surface upper gland 9 and small-surface upper gland 6 are fastened and connected by adjusting screw rods and nuts. Others are the same as specific embodiments 2 and 5.

[0035] Specific embodiment 8: This embodiment is different from the specific embodiment 1 in that the Zr content in the Al-Zr master alloy is 5%; the Ti content in the Al-Ti master alloy is 5%. Other aspects are the same as the specific embodiment 1.

[0036] Specific embodiment 9: This embodiment is different from the specific embodiment 1 in that the filtering device uses a double-stage ceramic filter sheet for filtering, and the double-stage ceramic filter sheet is imported 30ppi+60ppi. Others are the same as the specific embodiment 1.

[0037] Specific embodiment 10: This embodiment is different from the specific embodiment 1 in that the cooling water is firstly treated with a single row of pulse water 75-80m 3 / h for cooling, until the casting length is 150mm, cooling water is 80~100m 3 / h for double row cooling, until the casting length is 500mm, the cooling water is double-drained for 90 to 120m 3 / h for cooling, 800mm cooling water is discharged in a single stream of 130~145m 3 / h for cooling. Other aspects are the same as those in the first embodiment.

[0038] Specific embodiment 11: This embodiment differs from the specific embodiment 1 in that the cross-sectional dimensions of the large-sized flat ingot of superhard Al-Zn-Mg-Cu aluminum alloy are 520×1680 mm. The rest is the same as the specific embodiment 1.

[0039] The following examples are used to verify the beneficial effects of the present invention:

[0040] Embodiment 1: A method for preparing a large-sized flat ingot of superhard Al-Zn-Mg-Cu aluminum alloy is completed by the following steps:

[0041] 1. Weighing: According to the proportion of mass fraction Si less than 0.5%, Fe less than 1.0%, Cu: 2.5%, Mn less than 0.5%, Mg: 2.6%, Cr less than 0.3%, Ni less than 0.3%, Zn: 6.2%, Zr: 0.2%, Ti: 0.026% and the balance is Al, weigh aluminum ingots, pure Cu plates, pure Mg ingots, pure Zn ingots, Al-Zr master alloys and Al-Ti master alloys as smelting raw materials;

[0042] 2. Melting: Add the weighed aluminum ingot, pure Cu plate, pure Zn ingot and Al-Zr master alloy into a natural gas melting furnace, add pure Mg ingot and Al-Ti master alloy at a temperature of 700°C, use electromagnetic stirring for 30 minutes when the temperature reaches 720°C, take samples and analyze the chemical composition, and obtain aluminum alloy melt when the chemical composition is qualified;

[0043] 3. Casting: The aluminum alloy melt is introduced into a holding furnace, refined at 740°C with Ar gas for 30 minutes, and then allowed to stand at 735°C for 60 minutes to obtain a casting melt. The melt first flows into an online degassing device, into which Ar gas is introduced. The purity of Ar gas is required to be 99.996% or above, and the working pressure of the argon gas pipeline is 0.3MPa to 1.0MPa; then it flows into a filtering device, and then through a flow plate at a casting speed of 50mm / min, a casting temperature of 705°C, and a cooling water flow rate of 80m3 / s for a single discharge. 3 / h for cooling, until the casting length is 150mm, cooling water is 90m 3 / h for double row cooling, until the casting length is 500mm, the cooling water is double drained for 90m 3 / h~120m 3 / h for cooling, 800mm cooling water is discharged in a single line of 130m 3 / h~145m 3 / h, and the melt under the conditions of cooling water temperature of 23°C and online seeding of Al-Ti-B wire was injected into a double-layer line-cooled graphite crystallizer to produce large-sized flat ingots of superhard Al-Zn-Mg-Cu aluminum alloy.

[0044] The double-sided row-cooled graphite crystallizer is composed of a large-surface box body 8, a small-surface box body 4, a large-surface lower pressure cover 1, a small-surface lower pressure cover 3, a large-surface upper pressure cover 9 and a small-surface upper pressure cover 6; the large-surface box body 8, the large-surface lower pressure cover 1 and the large-surface upper pressure cover 9 form a large-surface assembly, and the small-surface box body 4, the small-surface lower pressure cover 3 and the small-surface upper pressure cover 6 form a small-surface assembly; two large-surface assemblies and two small-surface assemblies form an inner cavity of the crystallizer;

[0045] The inner sides of the small face box body 4 and the large face box body 8 are processed with grooves for embedding graphite plates, and the graphite plates are fixed to the inner side of the box body by the small face pressure cover 6 and the large face pressure cover 9; after the small face of the crystallizer is assembled, the extended parts on both sides of the small face pressure cover 6 are overlapped on the large face assembly, and the parts of the large face pressure cover 9 that overlap with the small face assembly are processed with threads for locking and fixing the small face assembly and the large face assembly, and the surface of the graphite plate is used as the crystallization working surface;

[0046] The inclination angle of the inner cavity working surface of the graphite plate in the small face assembly and the large face assembly is 0.68°;

[0047] The large-surface box body 8 and the small-surface box body 4 are processed to construct a partition structure at the upper and lower parts thereof, forming an upper cavity and a lower cavity as a water chamber for cooling water; the pneumatic control valve 5 is located inside the lower cavity, and the water inlet quick connector 2 is installed in the lower cavity, and its interface part is exposed outside the cavity and connected to the external water supply pipeline; the water inlet filter screen 7 is tightly installed on the water inlet quick connector 2 and passes through the upper and lower cavities, and the water inlet filter screen 7 and the lower cavity are a watertight isolation structure; the upper cavity is provided with a lower drainage hole, the diameter of the lower drainage hole is Φ3.2mm, the angle is 26° with the vertical direction, and the lower drainage hole is connected to the internal space of the upper cavity, so that the water in the upper cavity can be drained. Discharged into the inner cavity of the crystallizer; the lower cavity is provided with an upper drainage hole, the diameter of the upper drainage hole is Φ3.8mm, the angle is 44° with the vertical direction, the upper drainage hole is connected with the internal space of the lower cavity, and the water in the lower cavity can be discharged into the inner cavity of the crystallizer; the large surface pressure cover 9, the large surface lower pressure cover 1, the small surface pressure cover 6, and the small surface lower pressure cover 3 are processed with an annular groove near the inner side of the water chamber, and an "O"-shaped sealing silicone strip is installed in the groove; the large surface box body 8, the small surface box body 4, the water inlet filter 7, the water inlet quick connector 2, the pneumatic control valve 5, the large surface lower pressure cover 1, the small surface lower pressure cover 3, the large surface pressure cover 9 and the small surface pressure cover 6 are fastened and connected by adjusting the screw rod and the nut;

[0048] The Zr content of the Al-Zr master alloy is 5%; the Ti content of the Al-Ti master alloy is 5%; the filtering device adopts a double-stage ceramic filter plate for filtering, and the double-stage ceramic filter plate is an imported 30ppi+60ppi; the cross-sectional size of the large-size flat ingot of superhard Al-Zn-Mg-Cu aluminum alloy is 520×1680mm.

[0049] The superhard Al-Zn-Mg-Cu aluminum alloy flat ingot with a specification of 520×1680 mm obtained in this embodiment has qualified chemical composition, no defects such as cracks and slag inclusions on the surface, and a forming rate of 100%.

Claims

1. A method for preparing a large-sized flat ingot of superhard Al-Zn-Mg-Cu aluminum alloy, characterized in that The preparation method of superhard Al-Zn-Mg-Cu aluminum alloy large size flat ingot is completed according to the following steps:

1. Weighing: According to the mass percentage of Si less than 0.5%, Fe less than 1.0%, Cu: 1.8% to 3.0%, Mn less than 0.5%, Mg: 1.8% to 3.0%, Cr less than 0.3%, Ni less than 0.3%, Zn: 5.0% to 8.2%, Zr: 0.05% to 0.5%, Ti: 0.02% to 0.2% and the balance is Al, weigh aluminum ingots, pure Cu plates, pure Mg ingots, pure Zn ingots, Al-Zr master alloys and Al-Ti master alloys as smelting raw materials; 2. Melting: Add the weighed aluminum ingot, pure Cu plate, pure Zn ingot and Al-Zr master alloy into a natural gas melting furnace, add pure Mg ingot and Al-Ti master alloy at a temperature of 700-720°C, use electromagnetic stirring for 25-35 minutes when the temperature reaches 720°C, take samples and analyze the chemical composition, and obtain aluminum alloy melt when the chemical composition is qualified; 3. Casting: The aluminum alloy melt is introduced into a holding furnace, refined with Ar gas at a temperature of 720-780°C for 30-40 minutes, and then allowed to stand at a temperature of 720-780°C for 30-40 minutes to obtain a casting melt, and then the melt first flows into an online degassing device, into which Ar gas is introduced, the purity of Ar gas is required to be 99.996% and above, and the working pressure of the argon gas pipeline is 0.3MPa-1.0MPa; then it flows into a filtering device, and then through a flow plate, the melt is injected into a double-row line-cooled graphite crystallizer under the conditions of a casting speed of 40-55mm / min, a casting temperature of 685-710°C, a cooling water flow of 75-145T / h, a cooling water temperature of 15-28°C and online seeding of Al-Ti-B wire to form a large-size flat ingot of superhard Al-Zn-Mg-Cu aluminum alloy.

2. The method for preparing a large-sized superhard Al-Zn-Mg-Cu aluminum alloy flat ingot according to claim 1, characterized in that The double-surface upper row cooling graphite crystallizer is composed of a large-surface box body (8), a small-surface box body (4), a large-surface lower pressure cover (1), a small-surface lower pressure cover (3), a large-surface upper pressure cover (9) and a small-surface upper pressure cover (6); the large-surface box body (8), the large-surface lower pressure cover (1) and the large-surface upper pressure cover (9) form a large-surface assembly, and the small-surface box body (4), the small-surface lower pressure cover (3) and the small-surface upper pressure cover (6) form a small-surface assembly; two large-surface assemblies and two small-surface assemblies form an inner cavity of the crystallizer.

3. The method for preparing a large-sized superhard Al-Zn-Mg-Cu aluminum alloy flat ingot according to claim 2, characterized in that The inner sides of the small face box (4) and the large face box (8) are both machined with grooves for embedding graphite plates, and the graphite plates are fixed to the inner sides of the boxes by means of a pressure cover (6) on the small face and a pressure cover (9) on the large face. After the small face of the crystallizer is assembled, the extended parts on both sides of the pressure cover (6) on the small face are overlapped on the large face assembly, and threads are machined on the parts of the pressure cover (9) on the large face that overlap with the small face assembly, which are used for locking and fixing the small face assembly and the large face assembly, and the surface of the graphite plate is used as the crystallization working surface.

4. The method for preparing a large-sized superhard Al-Zn-Mg-Cu aluminum alloy flat ingot according to claim 2, characterized in that The inclination angle of the inner cavity working surface of the graphite plate in the small-surface assembly and the large-surface assembly is 0.68°.

5. The method for preparing a large-sized superhard Al-Zn-Mg-Cu aluminum alloy flat ingot according to claim 2, characterized in that The large-surface box body (8) and the small-surface box body (4) are processed to construct a partition structure at the upper and lower parts thereof, so as to form an upper cavity and a lower cavity as a water chamber for cooling water; the pneumatic control valve (5) is located inside the lower cavity, and the water inlet quick connector (2) is installed in the lower cavity, and its interface part is exposed outside the cavity and connected to the external water supply pipeline; the water inlet filter screen (7) is tightly installed on the water inlet quick connector (2) and passes through the upper and lower cavities, and the water inlet filter screen (7) and the lower cavity are a watertight isolation structure; the upper cavity is provided with a lower drainage hole, the diameter of the lower drainage hole is Φ3.2mm, the angle is 26° with the vertical direction, the lower drainage hole is connected with the internal space of the upper cavity, and the water in the upper cavity can be discharged into the inner cavity of the crystallizer; the lower cavity is provided with an upper drainage hole, the diameter of the upper drainage hole is Φ3.8mm, the angle is 44° with the vertical direction, the upper drainage hole is connected with the internal space of the lower cavity, and the water in the lower cavity can be discharged into the inner cavity of the crystallizer.

6. The method for preparing a large-sized superhard Al-Zn-Mg-Cu aluminum alloy flat ingot according to claim 2, characterized in that The large surface upper pressure cover (9), the large surface lower pressure cover (1), the small surface pressure cover (6) and the small surface lower pressure cover (3) are machined with annular grooves near the inner side of the water chamber, and "O"-shaped sealing silicone strips are installed in the grooves.

7. A method for preparing a large-sized superhard Al-Zn-Mg-Cu aluminum alloy flat ingot according to claims 2 and 5, characterized in that The large-surface box body (8), the small-surface box body (4), the water inlet filter (7), the water inlet quick connector (2), the pneumatic control valve (5), the large-surface lower pressure cover (1), the small-surface lower pressure cover (3), the large-surface upper pressure cover (9) and the small-surface upper pressure cover (6) are fastened and connected via adjusting screw rods and nuts.

8. The method for preparing a large-sized superhard Al-Zn-Mg-Cu aluminum alloy flat ingot according to claim 1, characterized in that The Zr content in the Al-Zr master alloy is 5%; the Ti content in the Al-Ti master alloy is 5%.

9. The method for preparing a large-sized superhard Al-Zn-Mg-Cu aluminum alloy flat ingot according to claim 1, characterized in that The filtering device adopts a double-stage ceramic filter plate for filtering, and the double-stage ceramic filter plate is imported 30ppi+60ppi.

10. The method for preparing a large-sized superhard Al-Zn-Mg-Cu aluminum alloy flat ingot according to claim 1, characterized in that The cooling water is firstly treated with single-row pulse water 75-80m 3 / h for cooling, until the casting length is 150mm, cooling water is 80~100m 3 / h for double row cooling, until the casting length is 500mm, the cooling water is double-drained for 90 to 120m 3 / h for cooling, 800mm cooling water is discharged in a single stream of 130~145m 3 / h for cooling.

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