Method and device for grain refinement of high-purity aluminum flat ingot under strong static magnetic field

Abstract

A method and device for the grain refinement of a high-purity aluminum slab ingot under a strong static magnetic field, which method comprises: S1, heating and melting high-purity aluminum to obtain a melt; S2, pouring the melt into a slab ingot mold (1); S3, placing the slab ingot mold (1) in a horizontal strong static magnetic field; S4, introducing argon to the space above the melt, and introducing a cooling gas to the space below the melt; S5, when the temperature in the space above the melt decreases to 630°C, pouring the melt into the slab ingot mold (1) again; S6, repeating steps S3-S5 until the slab ingot mold (1) is full of the poured melt; and S7, when the temperature in the space above the melt decreases to 630°C or lower, rapidly cooling the melt, so as to obtain an equiaxed-crystal slab ingot.

Description

A method and apparatus for refining the grains of high-purity aluminum flat ingots under strong static magnetic field conditions.

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese patent application No. 202510372870.X, filed on March 27, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of high-purity metal casting technology, and in particular to a method and apparatus for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field. Background Technology

[0004] High-purity aluminum refers to aluminum with an aluminum content of 99.999% (5N) or higher. Compared to ordinary electrolytic aluminum, high-purity aluminum has superior electrical conductivity, thermal conductivity, light reflectivity, ductility, antimagnetism, and corrosion resistance. It is mainly used in the preparation of aluminum sputtering targets for flat panel displays and large-scale integrated circuits. With the development of high-purity aluminum applications, the performance requirements for high-purity aluminum products are also becoming higher, which in turn places new demands on the quality of high-purity aluminum flat ingots. High-purity aluminum flat ingots not only need to meet the requirements for high-purity aluminum purity and impurity element content, but also need to ensure that the grain size of the flat ingots is sufficiently fine and uniform.

[0005] Currently, the known methods for refining the grain size of metal flat ingots involve increasing the number of nuclei, including adding nucleating agents, increasing undercooling, and vibration-promoted nucleation. Adding nucleating agents introduces impurities and reduces purity, making it unsuitable for refining the grain size of high-purity aluminum flat ingots. Increasing undercooling promotes nucleation in the molten metal, but the slow cooling at the center of the melt causes the solidified flat ingot to be divided into fine-grained, columnar, and central equiaxed grain regions, resulting in uneven microstructure. Vibration-promoted nucleation involves applying vibration or stirring to the solidification process of the melt, causing dendrites to break up and become new crystallization nuclei, thus promoting nucleation and proliferation. Applying ultrasonic oscillation to the molten metal can achieve grain refinement, but ultrasonic waves experience significant attenuation within the melt, affecting the uniformity of microstructure refinement. Mechanical and electromagnetic stirring can break and melt dendrites during their growth process, increasing the number of crystals during metal solidification and thus refining the grains. However, for high-purity aluminum, due to the extremely low content of impurity elements, the change in impurity concentration at the solid-liquid interface front caused by segregation during solidification is minimal, resulting in a very small supercooled zone. The solid-liquid interface grows roughly in a planar manner. Only at the end of solidification will the probability of dendrite formation increase due to the continuous enrichment of impurity elements with low partition coefficients in the liquid phase. Therefore, it is difficult to achieve overall grain refinement through vibration. Summary of the Invention

[0006] A method and apparatus for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, utilizing one or more embodiments of the present disclosure, solves the technical problem that high-purity aluminum cannot achieve grain refinement by increasing the number of nuclei through dendrite breakage during solidification.

[0007] In a first aspect, according to some embodiments of this disclosure, a method for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field includes: S1, heating and melting high-purity aluminum to obtain a melt with a first set temperature; S2, injecting the melt into a flat ingot mold with a second set temperature, and controlling the depth of the melt in the flat ingot mold to a set depth; S3, placing the flat ingot mold containing the melt in a horizontal strong static magnetic field; S4, introducing argon gas above the melt in the flat ingot mold at a first set argon gas flow rate to maintain the temperature above the melt (including the upper surface) at 630°C to 642°C, and introducing cooling gas below the melt in the flat ingot mold at a first set gas flow rate to maintain the temperature below the melt (including the lower surface) at 450°C to 550°C. S5. When the temperature above (including the upper surface) of the melt in the flat ingot mold drops to 630°C, remove the horizontal strong static magnetic field and inject the melt with the set depth into the flat ingot mold again; S6. Repeat steps S3 to S5 until the injected melt fills the flat ingot mold; and S7. When the temperature above (including the upper surface) of the melt in the flat ingot mold drops to 630°C, adjust the argon flow rate above the melt to the second set argon flow rate and adjust the cooling gas flow rate below the melt to the second set gas flow rate to quickly cool the melt to the third set temperature to obtain an equiaxed crystal flat ingot; the first set argon flow rate < the second set argon flow rate, and the first set gas flow rate < the second set gas flow rate.

[0008] A method for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, according to some embodiments of this disclosure, includes: S1, heating and melting high-purity aluminum to obtain a melt with a first set temperature; S2, injecting the melt into a flat ingot mold with a second set temperature, and controlling the depth of the melt in the flat ingot mold to a set depth; S3, placing the flat ingot mold containing the melt in a horizontal strong static magnetic field; S4, introducing argon gas above the melt in the flat ingot mold at a first set argon gas flow rate to maintain the temperature above the melt (including the upper surface) at 630°C to 642°C, and introducing cooling gas below the melt in the flat ingot mold at a first set gas flow rate to maintain the temperature below the melt (including the lower surface) at 450°C to 550°C; S5, ... When the temperature above the melt (including the upper surface) in the flat ingot mold drops to 630°C, the horizontal strong static magnetic field is removed, and the melt with the set depth is injected into the flat ingot mold again; S6, Steps S3 to S5 are repeated until the injected melt fills the flat ingot mold; and S7, after the temperature above the melt (including the upper surface) in the flat ingot mold drops below 630°C, the argon flow rate above the melt is adjusted to the second set argon flow rate, and the cooling gas flow rate below the melt is adjusted to the second set gas flow rate, so as to quickly cool the melt to the third set temperature to obtain an equiaxed crystal flat ingot; the first set argon flow rate < the second set argon flow rate, and the first set gas flow rate < the second set gas flow rate.

[0009] Secondly, according to some embodiments of this disclosure, an apparatus for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, the apparatus being adapted to the method described in any one of the first aspects, the apparatus comprising: a flat ingot mold, including a mold cover, a high-temperature resistant alloy steel liner, a heat insulation layer, multiple sets of cooling gas pipes, an argon gas inlet and an argon gas outlet, the multiple sets of cooling gas pipes being laid at the bottom of the flat ingot mold, the argon gas inlet and the argon gas outlet being disposed on the mold cover, the flat ingot mold being used to accommodate the melt and to cool the upper and lower surfaces of the melt; a strong static magnetic field generating component, including magnetic poles, an excitation coil and a magnetic yoke, the strong static magnetic field generating component being symmetrically distributed on both sides of the flat ingot mold for generating a horizontal strong static magnetic field; and a pad block, disposed below the flat ingot mold for supporting the flat ingot mold.

[0010] According to some embodiments of this disclosure, an apparatus for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field is provided. The apparatus is adapted to the method described in any one of the first aspects. The apparatus includes: a flat ingot mold (1) comprising a mold cover (11), a high-temperature alloy steel liner (12), a heat insulation layer (13), multiple sets of cooling gas pipes (14), an argon gas inlet (15), and an argon gas outlet (16). The high-temperature alloy steel liner (12) is disposed within the mold body cavity of the flat ingot mold (1). The heat insulation layer (13) is disposed between the side wall of the high-temperature alloy steel liner (12) and the side wall of the mold outer shell of the flat ingot mold (1). The multiple sets of cooling gas pipes (14) are laid at the bottom of the flat ingot mold (1) and contact the lower surface of the high-temperature alloy steel liner (12). The argon gas inlet (15)... 15) and the argon gas outlet (16) are provided on the mold cover (11). The flat ingot mold (1) is used to accommodate the melt and cool the upper and lower surfaces of the melt. The strong static magnetic field generating component (2) contains a magnetic pole (21), an excitation coil (22) and a magnetic yoke (23). The magnetic yoke (23) is provided around the periphery of the flat ingot mold (1). The magnetic pole (21) is provided inside the magnetic yoke (23) and extends toward the flat ingot mold (1). The excitation coil (22) is fitted around the periphery of the magnetic pole (21). The strong static magnetic field generating component (2) is symmetrically distributed on both sides of the flat ingot mold (1) to generate a horizontal strong static magnetic field. And a pad (3) is provided below the flat ingot mold (1) to support the flat ingot mold (1). Attached Figure Description

[0011] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0012] To more clearly illustrate the technical solutions in the embodiments or related technologies of this disclosure, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0013] Figure 1 shows a schematic flowchart of a method for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, according to some embodiments of the present disclosure.

[0014] Figure 2 shows a schematic diagram of a device for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, according to some embodiments of the present disclosure.

[0015] Figure label:

[0016] 1- Flat ingot mold, 11- Mold cover, 12- High temperature resistant alloy steel liner, 13- Insulation layer, 14- Multiple sets of cooling gas pipes, 15- Argon gas inlet, 16- Argon gas outlet;

[0017] 2-Strong static magnetic field generating component, 21-Magnetic pole, 22-Excitation coil, 23-Magnetic yoke;

[0018] 3-Place block. Embodiments of the present invention

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0020] Various embodiments of this disclosure may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this disclosure; therefore, it should be considered that the range description has specifically disclosed all possible subranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0021] Furthermore, in the description of this disclosure, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships may exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts representation" such as parts by weight or parts by mass indicates the proportional relationship between components. In the proportional relationships discussed in this article, parameters that need to be described by proportion should be understood as the first term of the proportion in the order of description, while the proportion figure should be understood as the second term. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figure in the proportion in the order of description, i.e., the mass of substance A : the mass of substance B : the mass of substance C = 1:2:3.

[0022] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this disclosure are available on the market or can be prepared by existing methods.

[0023] Figure 1 shows a schematic flowchart of a method for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, according to some embodiments of the present disclosure.

[0024] As shown in Figure 1, a method for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, according to some embodiments of this disclosure, involves controlling the heat dissipation direction of the melt in the mold and utilizing the release of latent heat of crystallization to create a negative temperature gradient at the solid-liquid interface, promoting dendrite formation in the high-purity aluminum. Simultaneously, the strong static magnetic field stabilizes the temperature gradient in the melt, and the combined thermo-electromagnetic force generated by the strong static magnetic field and the temperature gradient causes dendrite fracture, achieving the transformation from dendrites to equiaxed crystals and refining the grains of the high-purity aluminum flat ingot. This method for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field includes:

[0025] S1. High-purity aluminum is heated and melted to obtain a melt with a first set temperature;

[0026] S2. Inject the melt into a flat ingot mold with a second set temperature, and control the depth of the melt in the flat ingot mold to a set depth;

[0027] S3. Place the flat ingot mold containing the melt in a horizontal strong static magnetic field;

[0028] S4. Argon gas is introduced into the upper part of the melt in the flat ingot mold at a first set argon gas flow rate to maintain the temperature of the upper part of the melt (including the upper surface) at 630°C to 642°C, and cooling gas is introduced into the lower part of the melt in the flat ingot mold at a first set gas flow rate to maintain the temperature of the lower part of the melt (including the lower surface) at 450°C to 550°C.

[0029] S5. When the temperature above the melt in the flat ingot mold (including the upper surface) drops to 630°C, remove the horizontal strong static magnetic field and inject the same amount of melt as in step S2 into the flat ingot mold again.

[0030] S6. Repeat steps S3 to S5 until the injected melt fills the flat ingot mold.

[0031] S7. When the temperature above the melt (including the upper surface) in the flat ingot mold drops to 630°C, adjust the argon flow rate above the melt to the second set argon flow rate, and adjust the cooling gas flow rate below the melt to the second set gas flow rate, so as to quickly cool the melt to the third set temperature and obtain equiaxed crystal flat ingots; the first set argon flow rate < the second set argon flow rate, and the first set gas flow rate < the second set gas flow rate.

[0032] Understandably, the term "equiaxed flat ingot" in this document refers to a high-purity aluminum flat ingot obtained by the preparation method provided in one or more embodiments of this disclosure.

[0033] In some embodiments, methods for refining the grain size of high-purity aluminum flat ingots under strong static magnetic field conditions include:

[0034] S1. High-purity aluminum is heated and melted to obtain a melt with a first set temperature;

[0035] S2. Inject the melt into a flat ingot mold with a second set temperature, and control the depth of the melt in the flat ingot mold to a set depth;

[0036] S3. Place the flat ingot mold containing the melt in a horizontal strong static magnetic field;

[0037] S4. Argon gas is introduced into the upper part of the melt in the flat ingot mold at a first set argon gas flow rate to maintain the temperature of the upper part of the melt (including the upper surface) at 630°C to 642°C, and cooling gas is introduced into the lower part of the melt in the flat ingot mold at a first set gas flow rate to maintain the temperature of the lower part of the melt (including the upper surface) at 450°C to 550°C.

[0038] S5. After the temperature above the melt in the flat ingot mold (including the upper surface) drops below 630°C, remove the horizontal strong static magnetic field and inject the same amount of melt as in step S2 into the flat ingot mold again.

[0039] S6. Repeat steps S3 to S5 until the injected melt fills the flat ingot mold.

[0040] S7. When the temperature above the melt (including the upper plane) in the flat ingot mold drops below 630°C, adjust the argon flow rate above the melt to the second set argon flow rate, and adjust the cooling gas flow rate below the melt to the second set gas flow rate, so as to quickly cool the melt to the third set temperature and obtain equiaxed crystal flat ingots; the first set argon flow rate < the second set argon flow rate, and the first set gas flow rate < the second set gas flow rate.

[0041] In some implementations, the first set temperature is 660°C to 680°C.

[0042] Aluminum has a melting point of about 660°C. The first set temperature of the melt obtained after heating high-purity aluminum is 660°C to 680°C. This ensures that the high-purity aluminum is completely melted and maintains its liquid fluidity, while avoiding overheating that could lead to grain coarsening or accelerated oxidation.

[0043] For example, the first set temperature of the melt can be 660°C, 662°C, 665°C, 670°C, 675°C, 680°C, etc.

[0044] Understandably, in step S2, the melt is injected into the flat ingot mold for the purpose of solidification of the melt; therefore, the second set temperature must be lower than the first set temperature.

[0045] In some implementations, the second set temperature is 450°C to 500°C.

[0046] The second set temperature of preheating the flat ingot mold to 450℃~500℃ is to evaporate the water vapor inside the flat ingot mold, reduce the thermal shock of the molten liquid to the flat ingot mold, protect the flat ingot mold, and improve the quality of high-purity aluminum flat ingots.

[0047] For example, the second set temperature of the preheated flat ingot mold can be 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, etc.

[0048] In some implementations, the depth is set to 1 / 5 to 1 / 3 of the total depth of the flat ingot mold.

[0049] The high-purity aluminum casting process involves multiple castings. By setting the depth of the molten metal in the flat ingot mold to 1 / 5 to 1 / 3 of the total depth of the mold, the thickness of a single layer of molten metal can be reduced, making it easier to change the direction and magnitude of the temperature gradient in the molten metal through air cooling. Each casting depth of 1 / 5 to 1 / 3 of the total depth of the flat ingot mold can increase the magnitude of the temperature gradient at the solid-liquid interface during solidification.

[0050] It should be noted that the above-mentioned gas cooling refers to the cooling of the melt by the combined action of argon gas above the flat ingot mold and cooling gas below the flat ingot mold.

[0051] For example, the set depth of the melt cast into the flat ingot mold is 1 / 5, 1 / 4, 1 / 3, etc., of the total depth of the flat ingot mold.

[0052] In some embodiments, a boron nitride coating with a thickness of 5 μm to 10 μm can be sprayed onto the inner wall of the high-temperature alloy steel liner before the melt is poured into the flat ingot mold, thereby preventing the high-temperature alloy steel liner from contaminating the aluminum melt.

[0053] In some embodiments, a boron nitride coating with a thickness of 5 μm to 10 μm can be sprayed onto the bottom of the high-temperature alloy steel liner before the melt is poured into the flat ingot mold, thereby preventing the high-temperature alloy steel liner from contaminating the aluminum melt.

[0054] It should be noted that a horizontal strong static magnetic field refers to a horizontally oriented, stable magnetic field generated by excitation coils distributed on both sides of the flat ingot mold and threaded onto the magnetic yoke.

[0055] In some embodiments, the magnetic field direction of the horizontal strong static magnetic field is parallel to the width direction of the flat ingot mold, and the magnetic induction intensity of the horizontal strong static magnetic field is 0.95T to 1.05T.

[0056] Parallelizing the magnetic field direction with the width of the flat ingot mold can suppress convection of the melt in the vertical direction (temperature gradient direction) and stabilize the temperature distribution. The thermo-magnetic force generated by the coupling of the magnetic field and the temperature gradient can cause dendrite fracture and promote the formation of equiaxed crystal nuclei.

[0057] For example, the magnetic induction intensity of a horizontal strong static magnetic field can be 0.95T, 0.97T, 0.99T, 1.01T, 1.03T, 1.05T, etc.

[0058] It should be noted that cooling gas can refer to compressed air. By controlling the flow rate of the cooling gas, the temperature at the bottom of the mold is maintained at 450℃~550℃, thereby maintaining the temperature of the lower surface of the melt at 450℃~550℃.

[0059] In some embodiments, the first set argon flow rate is 1.8 L / min to 2.2 L / min.

[0060] In some embodiments, the first set gas flow rate is 22 L / min to 35 L / min.

[0061] In step S4, cooling gas with a first set flow rate of 22 L / min to 35 L / min is introduced into the cooling gas pipe located at the bottom of the flat ingot mold to maintain the temperature at the bottom of the mold at 450 to 550°C, that is, to maintain the temperature of the lower part of the melt (including the lower plane) at 450 to 550°C, which can cool the bottom of the melt and solidify it from bottom to top. Argon gas is introduced into the mold cover, and the first set flow rate of argon gas is controlled at 1.8 L / min to 2.2 L / min, which can maintain the temperature of the upper part of the melt at 630°C to 642°C, thereby achieving heat dissipation from the upper surface of the melt and preventing excessive supercooling of the upper surface of the melt from solidifying and crystallizing. During the solidification process, the release and accumulation of latent heat of crystallization at the solid-liquid interface causes the temperature at the solid-liquid interface front to gradually decrease towards the liquid phase, forming a negative temperature gradient.

[0062] For example, the first set argon flow rate can be 1.8L / min, 1.9L / min, 2.0L / min, 2.1L / min, 2.2L / min, etc., and the first set gas flow rate can be 22L / min, 25L / min, 27L / min, 30L / min, 32L / min, 35L / min, etc.

[0063] In step S5, when the temperature above the melt (including the upper plane) drops to 630°C, the melt solidification is nearly complete. Each casting in the multiple casting process of the melt is carried out when the melt in the flat ingot mold is nearly complete in solidification. At this time, the newly added melt will dilute the impurity elements segregated in the residual melt in the flat ingot mold, promote the reduction of impurity content in the solidified solid phase, and effectively reduce macroscopic segregation in high-purity aluminum flat ingots.

[0064] In some embodiments, the second set argon flow rate is 24 L / min to 26 L / min.

[0065] In some embodiments, the second set gas flow rate is 75 L / min to 85 L / min.

[0066] In some implementations, the third set temperature is ≤450°C.

[0067] In some implementations, the average grain size of the equiaxed flat ingot is <400 μm.

[0068] Therefore, in the embodiments of this disclosure, high-purity aluminum flat ingots are cast in multiple stages. After each pour of melt into the ingot mold, only the upper and lower planes of the melt are cooled, allowing the melt to gradually decrease in temperature. As the melt temperature decreases, non-uniform nucleation occurs at the contact point between the lower plane of the melt and the bottom of the ingot mold, leading to preferential crystallization. Because the melt dissipates heat simultaneously in both the upper and lower planes, the release of latent heat of crystallization results in the highest temperature at the solid-liquid interface, forming a negative temperature gradient at the interface front. Applying a strong horizontal static magnetic field to the melt causes it to be subjected to electromagnetic forces, inhibiting flow in the vertical direction (temperature gradient direction) and reducing convection, thus maintaining the negative temperature gradient. The negative temperature gradient causes the protruding parts in the crystallization to extend into the cooler liquid phase and continue to grow, forming dendrites. With the release of latent heat of crystallization and the action of thermo-electromagnetic forces generated by the temperature gradient under the magnetic field conditions, the newly formed dendrites break, forming equiaxed crystals at the solid-liquid interface front, resulting in a dendritic-to-equiaxed crystal transformation and promoting compositional homogenization. After high-purity aluminum flat ingots are cast in multiple stages, overall grain refinement is achieved. During the grain refinement process, the melt only comes into contact with the boron nitride coated mold, which avoids secondary contamination. Multiple casting stages effectively prevent shrinkage cavities, reduce macroscopic segregation and internal stress in high-purity aluminum flat ingots, and prevent cracking.

[0069] Figure 2 shows a schematic diagram of a device for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, according to some embodiments of the present disclosure.

[0070] As shown in Figure 2, a device for grain refinement of high-purity aluminum flat ingots under a strong static magnetic field, according to some embodiments of the present disclosure, is adapted to the method described in any of the above embodiments. The device includes:

[0071] The flat ingot mold 1 includes a mold cover 11, a high-temperature resistant alloy steel liner 12, a heat insulation layer 13, multiple sets of cooling gas pipes 14, an argon gas inlet 15, and an argon gas outlet 16. The multiple sets of cooling gas pipes 14 are laid at the bottom of the flat ingot mold 1, and the argon gas inlet 15 and the argon gas outlet 16 are located on the mold cover 11. The flat ingot mold 1 is used to contain the melt and cool the upper and lower surfaces of the melt.

[0072] A strong static magnetic field generating component 2, comprising magnetic poles 21, an excitation coil 22, and a magnetic yoke 23, is symmetrically distributed on both sides of the flat ingot mold and is used to generate a horizontal strong static magnetic field; and

[0073] The pad 3 is located below the flat ingot mold 1 and is used to support the flat ingot mold 1.

[0074] In some embodiments, the flat ingot mold 1 has a taper of 7°, an internal depth of 60 mm, an opening length of 650 mm, an opening width of 100 mm, and a volume of 3 L.

[0075] A flat ingot mold is a casting mold with an outer heat insulation layer 13 on all four sides and a taper of 7°. The bottom is lined with multiple sets of spaced cooling pipes 14. The mold's inner lining is made of high-temperature resistant alloy steel, with an internal depth of 60mm, an opening length of 650mm, an opening width of 100mm, and a volume of 3L. The mold has a mold cover 11 with an argon gas inlet and outlet, allowing argon gas to enter the mold through the inlet. This allows argon gas to be introduced above the melt, cooling the upper surface of the melt and effectively reducing oxidation.

[0076] In some embodiments, the high-temperature alloy steel liner 12 is disposed on the inner wall of the mold body of the flat ingot mold 1, forming a working surface that is in direct contact with the melt. In some embodiments, the outer side of the high-temperature alloy steel liner 12 is covered with a heat insulation layer 13.

[0077] In some embodiments, the heat insulation layer 13 is disposed between the high-temperature alloy steel liner 12 and the mold shell of the flat ingot mold 1, that is, the outer side of the liner 12 is covered with the heat insulation layer 13.

[0078] In some embodiments, multiple sets of cooling air pipes 14 are provided at the bottom of the flat ingot mold 1.

[0079] In some embodiments, the magnetic yoke 23 is disposed around the flat ingot mold 1 to guide magnetic lines of force to form a closed loop.

[0080] In some embodiments, the magnetic pole 21 is disposed inside the magnetic yoke 23 and extends toward the flat ingot mold 1 to concentrate and guide the magnetic field to the flat ingot mold 1.

[0081] In some embodiments, the excitation coil 22 is fitted around the magnetic pole 21. When the excitation coil 22 is energized, a strong static magnetic field is generated in the cavity of the flat ingot mold 1 under the action of the magnetic pole 21 and the magnetic yoke 23.

[0082] In summary, the method and apparatus for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, according to some embodiments of this disclosure, have the following advantages:

[0083] (1) Innovative grain refinement mechanism: By simultaneously cooling the upper and lower planes of the melt (forced heat dissipation at the bottom + argon gas temperature control at the top), a negative temperature gradient is formed at the solid-liquid interface, promoting dendrite growth into the low-temperature liquid phase. At the same time, the horizontal strong static magnetic field can suppress vertical melt convection, thereby stabilizing the negative temperature gradient and causing the newly formed dendrites to fracture through thermo-magnetic force, realizing the transformation of dendrites into equiaxed crystals, and finally obtaining a uniform microstructure with an average grain size of <400μm. In addition, unlike the traditional method of using Al-Ti-B grain refiner (which requires the introduction of impurity elements) for grain refinement, this method uses the coupling effect of magnetic field and temperature gradient to achieve grain refinement, avoiding contamination of high-purity aluminum melt and ensuring material purity.

[0084] (2) Multi-dimensional defect control and microstructure optimization: The melt is injected in stages (each filling depth is 1 / 5 to 1 / 3 of the total depth of the flat ingot mold). The newly injected melt can dilute the impurity elements segregated in the residual liquid phase of the melt in the flat ingot mold, reduce the impurity content in the subsequently generated solid phase, and significantly reduce macroscopic segregation. The layered solidification of the melt can avoid the shrinkage stress concentration of a single casting and inhibit the formation of shrinkage cavities and hot cracks. At the same time, the fragments generated by dendrite fracture serve as the nucleation core for subsequent solidification, and combined with the melt mixing introduced by multiple castings, promote the homogenization of the composition of high-purity aluminum flat ingots and enhance the consistency of material mechanical properties.

[0085] (3) High-efficiency temperature control and protection design: The bottom cooling gas, i.e., the first set gas (22-35 L / min), promotes directional heat dissipation at the bottom of the flat ingot mold, and the top argon gas, i.e., the first set argon gas (2 L / min), maintains the surface temperature (630-642℃) to ensure a stable negative temperature gradient; the final rapid cooling stage (25 L / min of the second set argon gas + 80 L / min of the cooling gas, i.e., the second set gas) achieves rapid cooling of the melt to ≤450℃, suppressing grain coarsening. At the same time, argon gas is introduced above the melt to reduce oxidation and gas inclusions; the inner wall of the mold is sprayed with a boron nitride coating (5-10 μm) to isolate the alloy steel material from the contamination of high-purity aluminum and ensure the purity of the material.

[0086] (4) Optimization of device structure and process adaptability: The flat ingot mold has a taper of 7°, which facilitates the demolding of equiaxed flat ingots; multiple sets of cooling gas pipes are distributed at intervals at the bottom to optimize the uniformity of heat dissipation; the combination of high-temperature alloy steel lining and insulation layer improves the durability of the flat ingot mold and coordinates the heat dissipation direction of the melt; the mold cover integrates argon gas inlet and outlet to realize dynamic temperature control and protection of the upper surface of the melt. At the same time, the excitation coil and magnetic yoke are symmetrically distributed on both sides of the mold to generate a horizontal and constant magnetic field. The direction of the magnetic field is parallel to the width direction of the mold, which maximizes the suppression of vertical disturbance of the melt and has strong process adaptability.

[0087] (5) Comprehensive benefits and industrial application potential: The melt only contacts the boron nitride coating mold, without the intervention of other tools or media, which is suitable for the clean production requirements of high-purity aluminum. At the same time, no complex chemical additives are required, and the process parameters (temperature, flow rate, magnetic field strength) are easy to control, making it suitable for large-scale production.

[0088] Therefore, the method and apparatus for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, according to some embodiments of this disclosure, solves the problem of grain refinement and composition homogenization during the solidification of high-purity aluminum melt by innovatively combining a horizontal strong static magnetic field with bidirectional heat dissipation and temperature control technology. It has the advantages of being pollution-free, highly uniform, and having a low defect rate, and provides an efficient and clean technical solution for the high-performance preparation of high-purity aluminum flat ingots.

[0089] The present disclosure is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the disclosure. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0090] Example 1

[0091] S1, 5N high-purity aluminum is heated and melted in an aluminum melting furnace to obtain a melt, and the melt is kept at 670℃; at the same time, the flat ingot mold with a 5μm boron nitride coating on the inner wall is preheated to 450℃.

[0092] S2, the melt obtained by melting high-purity aluminum is poured into a preheated flat ingot mold, and the casting is stopped when the depth of the melt reaches 1 / 3 of the depth of the flat ingot mold.

[0093] S3, after covering the mold, place the flat ingot mold in the horizontal strong static magnetic field generated by the strong static magnetic field generating component.

[0094] S4. Argon gas is introduced into the mold through the mold cover to cool it down, with the argon gas flow rate controlled at 2L / min, maintaining the temperature of the upper part of the melt (including the upper surface) at 630-642℃. At the same time, cooling gas with a flow rate of 35L / min is introduced into the cooling gas pipe at the bottom of the mold to maintain the temperature of the lower part of the melt (including the lower surface) at 450℃, so that the bottom of the melt cools down and solidifies.

[0095] S5. After the temperature above the melt (including the upper surface) inside the flat ingot mold drops to 630°C, the flat ingot mold is removed from the strong static magnetic field, the cover is opened and melt of the same depth as in step S2 is injected again, and the mold cover is closed and the flat ingot mold is placed in the magnetic field again.

[0096] S6, repeat S3 to S5 until the flat ingot mold is filled with molten high-purity aluminum.

[0097] S7. After the temperature of the melt above (including the upper surface) in the flat ingot mold is lower than 630°C, increase the cooling gas flow rate to 80L / min and the argon flow rate to 25L / min to rapidly cool the high-purity aluminum flat ingot to 450°C. Then open the mold cover and take out the high-purity aluminum flat ingot, allowing it to air-cool to room temperature.

[0098] The cast high-purity aluminum flat ingots have no obvious shrinkage cavities, uniform composition, and equiaxed crystal structure. The grain size is mainly concentrated between 280 and 400 μm, with an average grain size of 330 μm.

[0099] Example 2

[0100] S1, 5N high-purity aluminum is heated and melted in an aluminum melting furnace to obtain a melt, and the melt is kept at 670℃; at the same time, the flat ingot mold with a 5μm boron nitride coating on the inner wall is preheated to 450℃.

[0101] S2, the melt obtained by melting high-purity aluminum is injected into a preheated flat ingot mold, and casting is stopped when the depth of the melt reaches 1 / 3 of the depth of the flat ingot mold.

[0102] S3, after covering the mold, place the flat ingot mold in the horizontal strong static magnetic field generated by the strong static magnetic field generating component.

[0103] S4. Argon gas is introduced into the mold through the mold cover to cool it down, with the argon gas flow rate controlled at 2L / min, maintaining the temperature of the upper part of the melt (including the upper surface) at 630-642℃. At the same time, cooling gas with a flow rate of 22L / min is introduced into the cooling gas pipe at the bottom of the mold to maintain the temperature of the lower part of the melt (including the lower surface) at 550℃, so that the bottom of the melt cools down and solidifies.

[0104] S5. After the temperature above the melt (including the upper surface) inside the flat ingot mold drops to 630°C, the flat ingot mold is removed from the strong static magnetic field, the cover is opened and melt of the same depth as in step S2 is injected again, and the mold cover is closed and the flat ingot mold is placed in the magnetic field again.

[0105] S6, repeat S3 to S5 until the flat ingot mold is filled with molten high-purity aluminum.

[0106] S7. After the temperature of the melt above (including the upper surface) in the flat ingot mold is lower than 630°C, increase the cooling gas flow rate to 80L / min and the argon flow rate to 25L / min to rapidly cool the high-purity aluminum flat ingot to 450°C. Then open the mold cover and take out the high-purity aluminum flat ingot, allowing it to air-cool to room temperature.

[0107] The cast high-purity aluminum flat ingots have no obvious shrinkage cavities, uniform composition, and equiaxed crystal structure. The grain size is mainly concentrated between 300 and 500 μm, with an average grain size of 390 μm.

[0108] Example 3

[0109] S1, 5N high-purity aluminum is heated and melted in an aluminum melting furnace to obtain a melt, and the melt is kept at 670℃; at the same time, the flat ingot mold with a 5μm boron nitride coating on its inner wall is preheated to 450℃.

[0110] S2, the melt obtained by melting high-purity aluminum is poured into a preheated flat ingot mold, and the casting is stopped when the depth of the melt reaches 1 / 5 of the depth of the flat ingot mold.

[0111] S3, after covering the mold, place the flat ingot mold in the horizontal strong static magnetic field generated by the strong static magnetic field generating component.

[0112] S4. Argon gas is introduced into the mold through the mold cover to cool it down, with the argon gas flow rate controlled at 2L / min, maintaining the temperature of the upper part of the melt (including the upper surface) at 630-642℃. At the same time, cooling gas with a flow rate of 35L / min is introduced into the cooling gas pipe at the bottom of the mold to maintain the temperature of the lower part of the melt (including the lower surface) at 450℃, so that the bottom of the melt cools down and solidifies.

[0113] S5. After the temperature above the melt (including the upper surface) inside the flat ingot mold drops to 630°C, the flat ingot mold is removed from the strong static magnetic field, the cover is opened and melt of the same depth as in step S2 is injected again, and the mold cover is closed and the flat ingot mold is placed in the magnetic field again.

[0114] S6, repeat S3 to S5 until the flat ingot mold is filled with molten high-purity aluminum.

[0115] S7. After the temperature of the melt above (including the upper surface) in the flat ingot mold is lower than 630°C, increase the cooling gas flow rate to 80L / min and the argon flow rate to 25L / min to rapidly cool the high-purity aluminum flat ingot to 450°C. Then open the mold cover and take out the high-purity aluminum flat ingot, allowing it to air-cool to room temperature.

[0116] The cast high-purity aluminum flat ingots have no obvious shrinkage cavities, uniform composition, and equiaxed crystal structure. The grain size is mainly concentrated between 270 and 350 μm, with an average grain size of 300 μm.

[0117] Example 4

[0118] S1, 5N high-purity aluminum is heated and melted in an aluminum melting furnace to obtain a melt, and the melt is kept at 670℃; at the same time, the flat ingot mold with a 5μm boron nitride coating on the inner wall is preheated to 450℃.

[0119] S2, the melt obtained by melting high-purity aluminum is poured into a preheated flat ingot mold, and the casting is stopped when the depth of the melt reaches 1 / 5 of the depth of the flat ingot mold.

[0120] S3, after covering the mold, place the flat ingot mold in the horizontal strong static magnetic field generated by the strong static magnetic field generating component.

[0121] S4. Argon gas is introduced into the mold through the mold cover to cool it down, with the argon gas flow rate controlled at 2L / min, maintaining the temperature of the upper part of the melt (including the upper surface) at 630-642℃. At the same time, cooling gas with a flow rate of 22L / min is introduced into the cooling gas pipe at the bottom of the mold to maintain the temperature of the lower part of the melt (including the lower surface) at 550℃, so that the bottom of the melt cools down and solidifies.

[0122] S5. After the temperature above the melt (including the upper surface) inside the flat ingot mold drops to 630°C, the flat ingot mold is removed from the strong static magnetic field, the cover is opened and melt of the same depth as in step S2 is injected again, and the mold cover is closed and the flat ingot mold is placed in the magnetic field again.

[0123] S6, repeat S3 to S5 until the flat ingot mold is filled with molten high-purity aluminum.

[0124] S7. After the temperature of the melt above (including the upper surface) in the flat ingot mold is lower than 630°C, increase the cooling gas flow rate to 80L / min and the argon flow rate to 25L / min to rapidly cool the high-purity aluminum flat ingot to 450°C. Then open the mold cover and remove the high-purity aluminum flat ingot, allowing it to air-cool to room temperature.

[0125] The cast high-purity aluminum flat ingots have no obvious shrinkage cavities, uniform composition, and equiaxed crystal structure. The grain size is mainly concentrated between 300 and 410 μm, with an average grain size of 350 μm.

[0126] Comparative Example 1

[0127] S1, use an aluminum melting furnace to heat and melt 5N high-purity aluminum to obtain a melt, and keep the melt at 670℃; at the same time, preheat the flat ingot mold with a 5μm boron nitride coating on the inner wall to 450±5℃.

[0128] S2, the melt obtained by melting high-purity aluminum is poured into a preheated flat ingot mold. The casting is stopped when the depth of the melt reaches 1 / 3 of the depth of the flat ingot mold, and the mold cover is closed.

[0129] S3. Argon gas is introduced into the mold through the mold cover to cool it down, with the argon gas flow rate controlled at 2L / min, maintaining the temperature of the upper part of the melt (including the upper surface) at 630-642℃. At the same time, cooling gas with a flow rate of 35L / min is introduced into the cooling gas pipe at the bottom of the mold to maintain the temperature of the lower part of the melt (including the lower surface) at 450℃, so that the bottom of the melt cools down and solidifies.

[0130] S4. After the temperature above the melt (including the upper surface) inside the flat ingot mold drops to 630°C, open the lid and re-inject melt to the same depth as in step S2, and then close the mold lid.

[0131] S5, repeat S3 to S5 until the flat ingot mold is filled with molten high-purity aluminum.

[0132] S6. After the temperature of the melt above (including the upper surface) in the flat ingot mold is lower than 630°C, increase the cooling gas flow rate to 80L / min and the argon flow rate to 25L / min to rapidly cool the high-purity aluminum flat ingot to 450°C. Then open the mold cover 4 to remove the high-purity aluminum flat ingot and allow it to air-cool to room temperature.

[0133] The cast high-purity aluminum flat ingots have no obvious shrinkage cavities. Except for the upper and lower surfaces, the rest of the high-purity aluminum flat ingots are mainly composed of columnar crystal structures. A small number of finer equiaxed crystals are distributed between the columnar crystals. The grain size is uneven. The width of the columnar crystals is in the range of 300 to 1500 μm, and the length can reach more than 3000 μm.

[0134] Furthermore, one or more technical solutions in the embodiments of this disclosure have at least the following technical effects or advantages:

[0135] In this embodiment, high-purity aluminum melt is poured into a flat ingot mold in multiple stages, and only the upper and lower planes of the melt are cooled after each pour. By releasing the latent heat of crystallization, a negative temperature gradient is constructed at the solid-liquid interface, which promotes the formation of dendrites in high-purity aluminum. At the same time, a strong static magnetic field is used to stabilize the temperature gradient in the melt, and the thermo-electromagnetic force generated by the magnetic field and the temperature gradient is combined to cause the dendrites to break, thereby realizing the transformation of dendrites into equiaxed crystals. Finally, equiaxed high-purity aluminum flat ingots with an average grain size of less than 400 μm are obtained.

[0136] One or more technical solutions in the embodiments of this disclosure can prevent shrinkage cavities, avoid secondary contact contamination, promote the homogenization of the composition of high-purity aluminum flat ingots, reduce macroscopic segregation and internal stress of high-purity aluminum flat ingots, and prevent cracking.

[0137] The technical solutions provided in this disclosure have the following advantages compared with the prior art:

[0138] This disclosure provides a method for refining the grain size of high-purity aluminum flat ingots under a strong static magnetic field. Through multiple castings and controlling the heat dissipation direction of the melt in the mold, a negative temperature gradient is created at the solid-liquid interface by releasing the latent heat of crystallization, promoting dendrite formation in the high-purity aluminum. The strong horizontal static magnetic field suppresses convection in the direction perpendicular to the temperature gradient, thereby stabilizing the temperature gradient in the melt. The thermo-magnetic force generated by the magnetic field and temperature gradient causes dendrite fracture, achieving a transformation from dendrites to equiaxed crystals, refining the grain size of the high-purity aluminum flat ingot, and obtaining equiaxed high-purity aluminum flat ingots with an average grain size of less than 400 μm. Simultaneously, the nascent dendrite fragments act as nuclei and mix with the later solidified portion, promoting the homogenization of the high-purity aluminum flat ingot composition. During this casting process, apart from the boron nitride-coated mold, the melt does not come into contact with other objects or tools, resulting in no secondary pollution. By casting multiple times, the thickness of the melt is reduced, the negative temperature gradient at the interface front is increased, the thermo-magnetic force is enhanced, and the grains are effectively refined. At the same time, each time a new melt is added, the impurity elements segregated in the residual melt are diluted, resulting in a lower content of solid impurities in the solidified phase, thereby reducing macroscopic segregation. Multiple castings can also avoid the formation of shrinkage cavities, reduce the accumulation of internal stress, and prevent cracking.

[0139] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for refining the grain size of high-purity aluminum flat ingots under a strong static magnetic field, comprising: S1. High-purity aluminum is heated and melted to obtain a melt with a first set temperature; S2. The melt is injected into a flat ingot mold with a second set temperature, and the depth of the melt in the flat ingot mold is controlled to a set depth. S3. Place the flat ingot mold containing the melt in a horizontal strong static magnetic field; S4. Argon gas is introduced into the upper part of the melt in the flat ingot mold at a first set argon gas flow rate to maintain the temperature above the melt at 630°C to 642°C, and cooling gas is introduced into the lower part of the melt in the flat ingot mold at a first set gas flow rate to maintain the temperature below the melt at 450°C to 550°C. S5. When the temperature above the melt in the flat ingot mold drops to 630°C, remove the horizontal strong static magnetic field and inject the melt with the set depth into the flat ingot mold again. S6. Repeat steps S3 to S5 until the injected melt fills the flat ingot mold. as well as, S7. When the temperature above the melt in the flat ingot mold drops to 630°C, adjust the argon flow rate above the melt to the second set argon flow rate, and adjust the cooling gas flow rate below the melt to the second set gas flow rate, so as to quickly cool the melt to the third set temperature and obtain an equiaxed crystal flat ingot; the first set argon flow rate < the second set argon flow rate, and the first set gas flow rate < the second set gas flow rate.

2. The method of claim 1, wherein, The first set temperature is 660℃~680℃.

3. The method of claim 1, wherein, The second set temperature is 450℃~500℃.

4. The method of claim 1, wherein, The third set temperature is ≤450℃.

5. The method of claim 1, wherein, The set depth is 1 / 5 to 1 / 3 of the total depth of the flat ingot mold.

6. The method of claim 1, wherein, The first set argon flow rate is 1.8 L / min to 2.2 L / min, and the second set argon flow rate is 24 L / min to 26 L / min.

7. The method of claim 1, wherein, The first set gas flow rate is 22L / min to 35L / min, and the second set gas flow rate is 75L / min to 85L / min.

8. The method of claim 1, wherein, The direction of the horizontal strong static magnetic field is parallel to the width direction of the flat ingot mold, and the magnetic induction intensity of the horizontal strong static magnetic field is 0.95T to 1.05T.

9. A device for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, the device being adapted to the method described in any one of claims 1 to 8, the device comprising: A flat ingot mold (1) includes a mold cover (11), a high-temperature resistant alloy steel liner (12), a heat insulation layer (13), multiple sets of cooling gas pipes (14), an argon gas inlet (15), and an argon gas outlet (16). The multiple sets of cooling gas pipes (14) are laid at the bottom of the flat ingot mold (1). The argon gas inlet (15) and the argon gas outlet (16) are located on the mold cover (11). The flat ingot mold (1) is used to contain the melt and to cool the upper and lower surfaces of the melt. A strong static magnetic field generating component (2) includes a magnetic pole (21), an excitation coil (22) and a magnetic yoke (23). The strong static magnetic field generating component (2) is symmetrically distributed on both sides of the flat ingot mold (1) and is used to generate a horizontal strong static magnetic field. as well as A pad (3) is provided below the flat ingot mold (1) to support the flat ingot mold (1).

10. The apparatus of claim 9, wherein, The flat ingot mold (1) has a taper of 7°, an internal depth of 60mm, an opening length of 650mm, an opening width of 100mm, and a volume of 3L.

11. A device for refining the grains of high-purity aluminum flat ingots under a strong static magnetic field, the device being adapted to the method described in any one of claims 1 to 8, the device comprising: A flat ingot mold (1) includes a mold cover (11), a high-temperature alloy steel liner (12), a heat insulation layer (13), multiple sets of cooling gas pipes (14), an argon gas inlet (15), and an argon gas outlet (16). The high-temperature alloy steel liner (12) is located on the inner wall of the mold body of the flat ingot mold (1). The heat insulation layer (13) is located between the high-temperature alloy steel liner (12) and the mold shell of the flat ingot mold (1). The multiple sets of cooling gas pipes (14) are laid at the bottom of the flat ingot mold (1) and contact the lower part of the high-temperature alloy steel liner (12). The argon gas inlet (15) and the argon gas outlet (16) are located on the mold cover (11). The flat ingot mold (1) is used to contain the melt and to cool the upper and lower surfaces of the melt. A strong static magnetic field generating component (2) includes a magnetic pole (21), an excitation coil (22), and a magnetic yoke (23). The magnetic yoke (23) is disposed around the periphery of the flat ingot mold (1). The magnetic pole (21) is disposed inside the magnetic yoke (23) and extends toward the flat ingot mold (1). The excitation coil (22) is fitted around the periphery of the magnetic pole (21). The strong static magnetic field generating component (2) is symmetrically distributed on both sides of the flat ingot mold (1) to generate a horizontal strong static magnetic field. as well as A pad (3) is provided below the flat ingot mold (1) to support the flat ingot mold (1).

12. A method for refining the grain size of high-purity aluminum flat ingots under a strong static magnetic field, comprising: S1. High-purity aluminum is heated and melted to obtain a melt with a first set temperature; S2. The melt is injected into a flat ingot mold with a second set temperature, and the depth of the melt in the flat ingot mold is controlled to a set depth. S3. Place the flat ingot mold containing the melt in a horizontal strong static magnetic field; S4. Argon gas is introduced into the upper part of the melt in the flat ingot mold at a first set argon gas flow rate to maintain the temperature above the melt at 630°C to 642°C, and cooling gas is introduced into the lower part of the melt in the flat ingot mold at a first set gas flow rate to maintain the temperature below the melt at 450°C to 550°C. S5. When the temperature above the melt in the flat ingot mold drops to 630°C, remove the horizontal strong static magnetic field and inject the melt with the set depth into the flat ingot mold again. S6. Repeat steps S3 to S5 until the injected melt fills the flat ingot mold. as well as, S7. After the temperature above the melt in the flat ingot mold drops below 630°C, adjust the argon flow rate above the melt to the second set argon flow rate, and adjust the cooling gas flow rate below the melt to the second set gas flow rate, so as to quickly cool the melt to the third set temperature and obtain an equiaxed crystal flat ingot; the first set argon flow rate < the second set argon flow rate, and the first set gas flow rate < the second set gas flow rate.

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