Method for reducing feather-like crystals generated by high-purity aluminum-silicon alloy

Abstract

The invention provides a method for reducing feather-like crystals generated by a high-purity aluminum-silicon alloy, which comprises the following steps: (1) mixing high-purity aluminum and an aluminum-silicon intermediate alloy, and smelting to obtain an aluminum-silicon alloy liquid; the smelting temperature ranges from 700 DEG C to 720 DEG C; (2) the aluminum-silicon alloy liquid obtained in the step (1) is sequentially subjected to online filtering and casting, and the high-purity aluminum-silicon alloy is obtained; and after online filtration, the temperature of the aluminum-silicon alloy liquid is reduced by 20-30 DEG C. According to the method, under the condition that casting parameters are not changed, the probability that the obtained high-purity aluminum-silicon alloy generates feather-like crystals can be remarkably reduced by controlling the temperature drop between the smelting process and the casting process and combining the smelting temperature reduction, the finished product rate of products is increased, and the requirement for preparing semiconductor products can be met.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy melting and casting, and relates to a method for reducing the generation of feathery crystals in high-purity aluminum-silicon alloy. Background Art

[0002] At present, sputtering targets are more and more widely used. Sputtering is to use an ion beam with high kinetic energy to bombard the surface of a solid, so that the atoms on the surface of the solid leave the solid and deposit on the surface of the substrate to prepare a thin film material. The solid being bombarded is called a sputtering target. For example, there are different types of targets for different usage scenarios. For example, an aluminum-silicon alloy target is used for sputtering in the production of semiconductor integrated circuits.

[0003] CN109628897A provides a high-purity aluminum-silicon alloy sputtering target blank and a preparation method thereof, including the following steps: (1) Vacuum melting ultra-pure aluminum and high-purity silicon to obtain an intermediate alloy melt; (2) Casting the intermediate alloy melt into an intermediate alloy; (3) Vacuum melting ultra-pure aluminum and the intermediate alloy at 730-745 °C to obtain a high-purity aluminum-silicon alloy melt; (4) Online refining the high-purity aluminum-silicon alloy melt to obtain a refined high-purity aluminum-silicon alloy melt; (5) Online filtering the refined high-purity aluminum-silicon alloy melt to obtain aluminum liquid; (6) Casting the aluminum liquid into a bar blank to obtain a high-purity aluminum-silicon alloy sputtering target blank. However, there is a high probability of feathery crystals in the macroscopic structure of the obtained aluminum-silicon alloy. Because the feathery crystals have thick and straight crystal axes and the mechanical properties are strongly anisotropic, cracks often occur along the twin plane during the rolling and forging of the ingot.

[0004] At present, in the production of aluminum alloys, the measures to reduce the appearance of feathery crystals in aluminum alloys mainly include: (1) Lowering the melting temperature to relatively increase the number of spontaneous nucleation particles in the melt; (2) Lowering the casting temperature to reduce the temperature gradient at the crystallization front; (3) Using a grain refiner; (4) Lowering the cooling intensity to reduce the solidification rate of the melt.

[0005] The aluminum base purity requirement for high-purity aluminum alloys for semiconductors is above 5N (99.999 wt%). During the alloy casting process, a grain refiner cannot be used to control the structure. Therefore, usually, the generation of feathery crystals is reduced by controlling the casting process parameters. It is found through production practice that reducing the casting cooling intensity can effectively reduce the appearance probability of feathery crystals. However, with the reduction of the casting intensity, it will lead to the problem of Si element aggregation, and further lead to easy cracking of the high-purity aluminum-silicon target blank during the processing.

[0006] In summary, without changing the casting parameters, providing a method and device system for reducing the generation of feathery crystals in high-purity aluminum-silicon alloy is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0007] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a method for reducing the generation of feathery crystals in high-purity aluminum-silicon alloys. Without changing the casting parameters, by controlling the temperature drop between the melting and casting processes and combining with reducing the melting temperature, the probability of generating feathery crystals in the obtained high-purity aluminum-silicon alloy can be significantly reduced, and the yield of the product is improved.

[0008] To achieve the purpose of this invention, the following technical solutions are adopted in the present invention:

[0009] The present invention provides a method for reducing the generation of feathery crystals in high-purity aluminum-silicon alloys, and the method comprises the following steps:

[0010] (1) Mix high-purity aluminum and aluminum-silicon master alloy, and conduct melting to obtain aluminum-silicon alloy liquid;

[0011] The temperature of the melting is 700 - 720 °C. For example, it can be 702 °C, 704 °C, 705 °C, 706 °C, 708 °C, 710 °C, 712 °C, 714 °C, 715 °C, 716 °C, 718 °C or 719 °C, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable;

[0012] (2) Sequentially subject the aluminum-silicon alloy liquid obtained in step (1) to online filtration and casting to obtain high-purity aluminum-silicon alloy;

[0013] After the online filtration, the temperature of the aluminum-silicon alloy liquid drops by 20 - 30 °C. For example, it can be 21 °C, 22 °C, 23 °C, 24 °C, 25 °C, 26 °C, 27 °C, 28 °C or 29 °C, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0014] In the present invention, the silicon content in the aluminum-silicon master alloy is 5 wt% - 20 wt%. The preparation process of the aluminum-silicon master alloy is a conventional method, and those skilled in the art can design it according to actual needs, or can also refer to the method provided in CN117778788A for preparation.

[0015] The method provided by the present invention, without changing the casting parameters, by controlling the temperature drop between the melting and casting processes and combining with reducing the melting temperature, can significantly reduce the probability of generating feathery crystals in the obtained high-purity aluminum-silicon alloy, improve the yield of the product, and significantly improve the product quality, meeting the requirements for preparing semiconductor products.

[0016] It should be noted that, compared with the traditional method of reducing the formation of feathery crystals in the aluminum alloy matrix by improving the casting parameters, the method of the present invention has a wider scope of application and does not have the problem that the regulation of casting parameters in the former method easily causes cracking of the aluminum-silicon target blank during the processing. By controlling the temperature drop between melting and casting processes within 20 - 30 °C, a reasonable temperature drop can keep the solidification interface at a relatively constant temperature, promote the uniform nucleation and growth of grains, and also help refine the grain structure of the alloy, thereby effectively reducing the formation probability of feathery crystals; combined with controlling the melting temperature of high-purity aluminum and aluminum-silicon master alloy to 700 - 720 °C, the number of nucleation sites relatively increases. These nucleation sites can serve as crystal nuclei during the subsequent solidification process, promoting the uniform nucleation of grains, thereby reducing the formation probability of feathery crystals, and thus improving the yield of the aluminum-silicon alloy.

[0017] As a preferred technical solution of the present invention, the purity of the high-purity aluminum in step (1) is ≥ 5N, for example, it can be 5N1, 5N2, 5N3, 5N4, 5N5, 5N6, 5N7, 5N8 or 5N9, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0018] As a preferred technical solution of the present invention, when exiting the melting furnace, the temperature of the aluminum-silicon alloy liquid in step (1) is 700 - 720 °C, for example, it can be 702 °C, 704 °C, 705 °C, 706 °C, 708 °C, 710 °C, 712 °C, 714 °C, 715 °C, 716 °C, 718 °C or 719 °C, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0019] In the present invention, the aluminum-silicon alloy liquid obtained after melting does not stay in the furnace for too long and is immediately taken out of the furnace for online filtration operation. Therefore, the temperature during melting can be kept the same as the temperature of the alloy liquid when it exits the furnace.

[0020] As a preferred technical solution of the present invention, after the online filtration in step (2), the temperature of the aluminum-silicon alloy liquid is 680 - 700 °C, for example, it can be 682 °C, 684 °C, 685 °C, 686 °C, 688 °C, 690 °C, 692 °C, 694 °C, 695 °C, 696 °C, 698 °C or 699 °C, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0021] It should be noted that the present invention uses a specific device system for online filtration, which can effectively reduce the heat loss of the aluminum-silicon alloy liquid during the flow process, and further can reduce the melting temperature of the aluminum-silicon alloy.

[0022] As a preferred technical solution of the present invention, the method of online filtration includes: after the aluminum-silicon alloy liquid exiting the melting furnace successively enters the first flow channel, the filtration device and the second flow channel, it is transported to the casting machine.

[0023] A heating cover plate is provided above the first flow channel, the filtering device and the second flow channel; heating wires are arranged inside the bottoms of the first flow channel, the filtering device and the second flow channel.

[0024] In the present invention, a specific device system is provided between the smelting and casting processes in the high-purity aluminum-silicon alloy process. By providing a heating cover plate above the flow channel and the filtering device, not only does it have a heating effect, but it can also prevent impurity particles in the environment from entering the flow channel and contaminating the aluminum-silicon alloy liquid. Combined with the heating wires arranged inside the bottoms of the flow channel and the filtering device, the flow channel and the filtering device can be effectively heated. Through the dual heating effect, the heat loss of the aluminum-silicon alloy liquid during the flowing process can be effectively reduced. In addition, a filtering device is arranged between the flow channels, which can filter out impurities in the high-purity aluminum-silicon liquid and prevent abnormal material purity.

[0025] As a preferred technical solution of the present invention, the cross-sectional area of the heating wire is 70 - 80 mm 2 , for example, it can be 71 mm 2 , 72 mm 2 , 73 mm 2 , 74 mm 2 , 75 mm 2 , 76 mm 2 , 77 mm 2 , 78 mm 2 or 79 mm 2 etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0026] In the present invention, a heating wire with a smaller cross-sectional size is used to replace the heating tube to heat the flow channel and the filtering device. The heating wire is directly arranged inside the bottoms of the flow channel and the filtering device, which can effectively heat the flow channel and the filtering device and save space at the same time.

[0027] Preferably, the heating temperature of the heating cover plate is 800 - 840 °C, for example, it can be 805 °C, 810 °C, 815 °C, 820 °C, 825 °C, 830 °C or 835 °C etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0028] Preferably, the heating temperature of the heating wire is 800 - 840 °C, for example, it can be 805 °C, 810 °C, 815 °C, 820 °C, 825 °C, 830 °C or 835 °C etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0029] As a preferred technical solution of the present invention, the filtering device includes a filtering box.

[0030] Preferably, a baffle and a filter plate are arranged in the filter box.

[0031] Preferably, the height of the filter plate from the bottom of the filter box is 10 - 30 cm. For example, it can be 12 cm, 15 cm, 16 cm, 18 cm, 20 cm, 22 cm, 25 cm, 26 cm or 28 cm, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0032] Preferably, one end of the filter plate is connected to the baffle, and the other end is connected to the side wall of the filter box.

[0033] As a preferred technical solution of the present invention, the temperature of the casting in step (2) is 680 - 700 °C. For example, it can be 682 °C, 684 °C, 685 °C, 686 °C, 688 °C, 690 °C, 692 °C, 694 °C, 695 °C, 696 °C, 698 °C or 699 °C, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0034] Preferably, the speed of the casting in step (2) is 100 - 120 mm / min. For example, it can be 102 mm / min, 105 mm / min, 106 mm / min, 108 mm / min, 110 mm / min, 112 mm / min, 115 mm / min, 116 mm / min or 118 mm / min, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0035] Preferably, cooling is carried out during the casting in step (2).

[0036] Preferably, the temperature of the cooling medium used for cooling during the casting in step (2) is 10 - 20 °C. For example, it can be 11 °C, 12 °C, 13 °C, 14 °C, 15 °C, 16 °C, 17 °C, 18 °C or 19 °C, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0037] Preferably, the flow rate of the cooling medium used for cooling during the casting in step (2) is 200 - 550 L / min. For example, it can be 250 L / min, 300 L / min, 350 L / min, 400 L / min, 450 L / min or 500 L / min, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0038] In the present invention, the cooling medium includes water; the casting parameters are all within the numerical ranges commonly used in the art.

[0039] As a preferred technical solution of the present invention, the purity of the high-purity aluminum-silicon alloy in step (2) is ≥5N, for example, it can be 5N1, 5N2, 5N3, 5N4, 5N5, 5N6, 5N7, 5N8 or 5N9, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0040] Preferably, the generation rate of feather-shaped crystals in the high-purity aluminum-silicon alloy in step (2) is <5%, for example, it can be 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5% or 0, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0041] Preferably, the silicon content in the high-purity aluminum-silicon alloy in step (2) is 0.5wt%-2wt%, for example, it can be 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.2wt%, 1.5wt%, 1.8wt% or 2.0wt%, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0042] As a preferred technical solution of the present invention, the method includes the following steps:

[0043] (1) Mix high-purity aluminum with a purity ≥5N and an aluminum-silicon master alloy, and carry out melting at a temperature of 700-720°C to obtain an aluminum-silicon alloy liquid;

[0044] When discharging from the melting furnace, the temperature of the aluminum-silicon alloy liquid is 700-720°C;

[0045] (2) Carry out online filtration on the aluminum-silicon alloy liquid obtained in step (1), control the temperature of the aluminum-silicon alloy liquid to decrease by 20-30°C, and then carry out casting at a temperature of 680-700°C and a speed of 100-120mm / min to obtain an aluminum-silicon alloy with a purity ≥5N;

[0046] The method of the online filtration includes: after the aluminum-silicon alloy liquid discharged from the melting furnace enters the first flow channel, the filtration device and the second flow channel in sequence, it is transported to the casting machine; a heating cover plate is arranged above the first flow channel, the filtration device and the second flow channel; heating wires are arranged inside the bottoms of the first flow channel, the filtration device and the second flow channel;

[0047] The cross-sectional area of the heating wire is 70-80mm 2 ; the heating temperature of the heating cover plate is 800-840°C; the heating temperature of the heating wire is 800-840°C;

[0048] The filtering device includes a filtering box; a baffle and a filter plate are arranged inside the filtering box; the height of the filter plate from the bottom of the filtering box is 10-30 cm; one end of the filter plate is connected to the baffle, and the other end is connected to the side wall of the filtering box;

[0049] After online filtering, the temperature of the aluminum-silicon alloy liquid is 680-700 °C;

[0050] Cooling is carried out during the casting; the temperature of the cooling medium used for cooling during the casting is 10-20 °C and the flow rate is 200-550 L / min;

[0051] The generation rate of feathery crystals in the high-purity aluminum-silicon alloy is <5%.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] The method provided by the present invention, without changing the casting parameters, by controlling the temperature drop between the melting and casting processes and combining with reducing the melting temperature, can significantly reduce the probability of generating feathery crystals in the obtained high-purity aluminum-silicon alloy, improve the product yield, and significantly improve the product quality, meeting the requirements for preparing semiconductor products; among them, the generation rate of feathery crystals in the obtained high-purity aluminum-silicon alloy is <5%. Description of the Drawings

[0054] Figure 1 is a schematic structural diagram of the device system for reducing feathery crystals in high-purity aluminum-silicon alloy provided by the present invention;

[0055] Among them, 1-melting furnace, 2-first runner, 3-filtering device, 4-second runner, 5-casting machine, 6-heating cover plate, 7-heating wire, 8-baffle, 9-filter plate; the arrow indicates the flow direction of the aluminum-silicon alloy liquid;

[0056] Figure 2 is a photograph of the as-cast structure of the aluminum-silicon alloy prepared in Example 1;

[0057] Figure 3 is a photograph of the as-cast structure of the aluminum-silicon alloy prepared in Comparative Example 3. Detailed Embodiments

[0058] It should be understood that in the description of the present invention, the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0059] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "set", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0060] The technical solution of the present invention will be further described below with reference to the drawings and through specific embodiments.

[0061] The specific embodiment of the present invention provides a device system for reducing the appearance of feather-shaped crystals in high-purity aluminum-silicon alloy. The device system (as Figure 1 shown) includes a melting furnace 1, a first runner 2, a filtering device 3, a second runner 4, and a casting machine 5 connected in sequence;

[0062] A heating cover plate 6 is arranged above the first runner 2, the filtering device 3, and the second runner 4;

[0063] Heating wires 7 are arranged inside the bottoms of the first runner 2, the filtering device 3, and the second runner 4; the cross-sectional area of the heating wire 7 is 78.5 mm 2 ;

[0064] The filtering device includes a filtering box; a baffle 8 and a filter plate 9 are arranged inside the filtering box; the height of the filter plate 9 from the bottom of the filtering box is 20 cm; one end of the filter plate 9 is connected to the baffle 8, and the other end is connected to the side wall of the filtering box.

[0065] Example 1

[0066] This embodiment provides a method for reducing the appearance of feathery crystals in high-purity aluminum-silicon alloy. The method uses the device system described above and specifically includes the following steps:

[0067] (1) Mix high-purity aluminum with a purity of 5N2 and aluminum-silicon master alloy, and melt them at a temperature of 710 °C to obtain aluminum-silicon alloy liquid;

[0068] The silicon content in the aluminum-silicon master alloy is 10 wt%;

[0069] When the aluminum-silicon alloy liquid comes out of the melting furnace, its temperature is 710 °C;

[0070] (2) Subject the aluminum-silicon alloy liquid obtained in step (1) to online filtration, control the temperature of the aluminum-silicon alloy liquid to decrease by 20 °C, and then cast it at a temperature of 690 °C and a speed of 110 mm / min to obtain an aluminum-silicon alloy with a purity of 5N1 and a silicon content of 1 wt%;

[0071] The method of the online filtration includes: after the aluminum-silicon alloy liquid coming out of the melting furnace enters the first flow channel, the filtration device and the second flow channel in sequence, it is transported to the casting machine; the heating temperature of the heating cover plate is 820 °C; the heating temperature of the heating wire is 820 °C;

[0072] After online filtration, the temperature of the aluminum-silicon alloy liquid is 690 °C;

[0073] Cooling is carried out during the casting; the temperature of the water used for cooling during the casting is 15 °C and the flow rate is 400 L / min.

[0074] The as-cast microstructure photograph of the high-purity aluminum-silicon alloy obtained in this embodiment is as Figure 2 shown. It can be seen from Figure 2 that the obtained high-purity aluminum-silicon alloy does not have a feathery crystal structure and can be used for the preparation of semiconductor products.

[0075] Example 2

[0076] This embodiment provides a method for reducing the appearance of feathery crystals in high-purity aluminum-silicon alloy. The method uses the device system described above and specifically includes the following steps:

[0077] (1) Mix high-purity aluminum with a purity of 5N and aluminum-silicon master alloy, and melt them at a temperature of 720 °C to obtain aluminum-silicon alloy liquid;

[0078] The silicon content in the aluminum-silicon master alloy is 5 wt%;

[0079] When the aluminum-silicon alloy liquid comes out of the melting furnace, its temperature is 718 °C;

[0080] (2) Filter the aluminum-silicon alloy liquid obtained in step (1) online, control the temperature of the aluminum-silicon alloy liquid to decrease by 25 °C, and then carry out casting at a temperature of 693 °C and a speed of 100 mm / min to obtain an aluminum-silicon alloy with a purity of 5N and a silicon content of 0.5 wt%.

[0081] The method of the online filtration includes: after the aluminum-silicon alloy liquid out of the melting furnace enters the first runner, the filtering device and the second runner in sequence, it is transported to the casting machine; the heating temperature of the heating cover plate is 800 °C; the heating temperature of the heating wire is 800 °C;

[0082] After online filtration, the temperature of the aluminum-silicon alloy liquid is 693 °C;

[0083] Cooling is carried out during the casting; the temperature of the water used for cooling during the casting is 10 °C and the flow rate is 550 L / min.

[0084] Example 3

[0085] This example provides a method for reducing the appearance of feather-shaped crystals in high-purity aluminum-silicon alloy. The method uses the device system as described above, and specifically includes the following steps:

[0086] (1) Mix high-purity aluminum with a purity of 5N3 and an aluminum-silicon master alloy, and carry out melting at a temperature of 705 °C to obtain an aluminum-silicon alloy liquid;

[0087] The silicon content in the aluminum-silicon master alloy is 15 wt%;

[0088] When the aluminum-silicon alloy liquid comes out of the melting furnace, its temperature is 704 °C;

[0089] (2) Filter the aluminum-silicon alloy liquid obtained in step (1) online, control the temperature of the aluminum-silicon alloy liquid to decrease by 20 °C, and then carry out casting at a temperature of 684 °C and a speed of 120 mm / min to obtain an aluminum-silicon alloy with a purity of 5N2 and a silicon content of 1.2 wt%;

[0090] The method of the online filtration includes: after the aluminum-silicon alloy liquid out of the melting furnace enters the first runner, the filtering device and the second runner in sequence, it is transported to the casting machine; the heating temperature of the heating cover plate is 820 °C; the heating temperature of the heating wire is 820 °C;

[0091] After online filtration, the temperature of the aluminum-silicon alloy liquid is 684 °C;

[0092] Cooling is carried out during the casting; the temperature of the water used for cooling during the casting is 20 °C and the flow rate is 200 L / min.

[0093] Example 4

[0094] This embodiment provides a method for reducing the occurrence of feathery crystals in high-purity aluminum-silicon alloy. Except that the heating temperatures of the heating cover plate and the heating wire are both 785°C, other conditions are the same as those in Embodiment 1.

[0095] Embodiment 5

[0096] This embodiment provides a method for reducing the occurrence of feathery crystals in high-purity aluminum-silicon alloy. Except that the heating temperatures of the heating cover plate and the heating wire are both 860°C, other conditions are the same as those in Embodiment 1.

[0097] Embodiment 6

[0098] This embodiment provides a method for reducing the occurrence of feathery crystals in high-purity aluminum-silicon alloy. Except that in the utilized device system, heating wires are not provided at the bottoms of the first flow channel, the filtering device, and the second flow channel, that is, after the online filtration, the temperature of the aluminum-silicon alloy liquid drops by 55°C, other conditions are the same as those in Embodiment 1.

[0099] Comparative Example 1

[0100] This comparative example provides a method for reducing the occurrence of feathery crystals in high-purity aluminum-silicon alloy. Except that the melting temperature is 690°C and the temperature of the aluminum-silicon alloy liquid is also 690°C when it exits the melting furnace, other conditions are the same as those in Embodiment 1.

[0101] Comparative Example 2

[0102] This comparative example provides a method for reducing the occurrence of feathery crystals in high-purity aluminum-silicon alloy. Except that the melting temperature is 740°C and the temperature of the aluminum-silicon alloy liquid is also 740°C when it exits the melting furnace, other conditions are the same as those in Embodiment 1.

[0103] Comparative Example 3

[0104] This comparative example provides a method for high-purity aluminum-silicon alloy, and the method includes the following steps:

[0105] (1) Mix high-purity aluminum with a purity of 5N2 and an aluminum-silicon master alloy, and conduct melting at a temperature of 745°C to obtain an aluminum-silicon alloy liquid;

[0106] The silicon content in the aluminum-silicon master alloy is 10 wt%;

[0107] When exiting the melting furnace, the temperature of the aluminum-silicon alloy liquid is 745°C;

[0108] (2) Perform online filtration on the aluminum-silicon alloy liquid obtained in step (1), control the temperature of the aluminum-silicon alloy liquid to drop by 55°C, and then conduct casting at a temperature of 690°C and a speed of 120 mm / min to obtain an aluminum-silicon alloy with a purity of 5N1 and a silicon content of 1 wt%;

[0109] The method of online filtration includes: after the aluminum-silicon alloy liquid discharged from the smelting furnace enters the first runner, the filtration device and the second runner in sequence, it is transported to the casting machine; a heating cover plate is arranged above the first runner, the filtration device and the second runner; the heating temperature of the heating cover plate is 820 °C;

[0110] The filtration device includes a filtration box; a baffle and a filter plate are arranged in the filtration box; the height of the filter plate from the bottom of the filtration box is 20 cm; one end of the filter plate is connected to the baffle, and the other end is connected to the side wall of the filtration box;

[0111] After online filtration, the temperature of the aluminum-silicon alloy liquid is 690 °C;

[0112] Cooling is carried out during the casting; the temperature of the water used for cooling during the casting is 20 °C and the flow rate is 200 L / min.

[0113] The as-cast microstructure photos of the high-purity aluminum-silicon alloy obtained in this comparative example are as Figure 3 shown, and it can be seen from Figure 3 that the obtained high-purity aluminum-silicon alloy has a feathery crystal structure, which causes cracks to often occur along the twin plane during subsequent rolling and forging processes.

[0114] For the methods provided in the above embodiments and comparative examples, 100 high-purity aluminum-silicon alloys were prepared respectively, and a microscope was used to observe whether there were feathery crystals in the tissue morphology. If there were feathery crystals, the high-purity aluminum-silicon alloy was recorded as unqualified, and if there were no feathery crystals, the high-purity aluminum-silicon alloy was recorded as qualified, and the yield was calculated (yield = number of qualified products / total input). The results are shown in Table 1 and Figure 2-3 shown.

[0115] Table 1

[0116]

[0117]

[0118] It can be seen from Table 1 that:

[0119] (1) For the methods provided in Embodiments 1-3 of the present invention, without changing the casting parameters, by controlling the temperature drop between the smelting and casting processes and combining with reducing the smelting temperature, the probability of the formation of feathery crystals in the obtained high-purity aluminum-silicon alloy can be significantly reduced, and the product quality is significantly improved; among them, the generation rate of feathery crystals in the high-purity aluminum-silicon alloy < 5%;

[0120] (2) By comparing Example 1 with Examples 4 - 5 comprehensively, it can be seen that when the heating temperatures of the heating cover plate and the heating wire are too low, the temperature drop of the aluminum-silicon alloy liquid is large and fast during the online filtration process, resulting in a relatively low temperature of the aluminum liquid in the casting machine. Cold shuts are likely to form on the surface of the ingot, affecting the performance of the aluminum-silicon alloy ingot. When the heating temperatures of the heating cover plate and the heating wire are too high, the heating wire may be damaged. Additionally, due to the too low temperature drop between the melting and casting processes, the casting temperature is further increased, resulting in too large a temperature gradient in the liquid at the crystallization front of the aluminum-silicon alloy and a very narrow undercooled zone, making it easy to form feathery crystals.

[0121] (3) By comparing Example 1 with Example 6 comprehensively, it can be seen that when no heating wire is provided at the bottom of the first flow channel, the filtering device, and the second flow channel, the heat loss of the aluminum-silicon alloy liquid is large during the online filtration process, resulting in too low a temperature of the aluminum liquid in the casting machine and casting failure.

[0122] (4) By comparing Example 1 with Comparative Examples 1 - 3 comprehensively, it can be seen that when the melting temperature is too low, since the aluminum liquid will lose a part of heat after passing through the flow channel and the filtering device, the temperature of the aluminum liquid in the casting machine is relatively low, and cold shuts are likely to form on the surface of the ingot, affecting the performance of the aluminum-silicon alloy ingot. When the melting temperature is too high, the composition and structure inside the melt change, increasing the tendency to form feathery crystals during solidification. When the melting temperature is too high and no heating wire is provided at the bottom of the first flow channel, the filtering device, and the second flow channel, due to the too high temperature of the melt after melting and the too fast temperature drop before casting, the aluminum-silicon alloy is more likely to form feathery crystals.

[0123] The applicant declares that the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for reducing the generation of feather crystals in high-purity aluminum-silicon alloys, characterized in that: The method comprises the following steps: (1) mixing high-purity aluminum and aluminum-silicon master alloy, and smelting them to obtain aluminum-silicon alloy liquid; The smelting temperature is 700-720°C; (2) filtering and casting the aluminum-silicon alloy liquid obtained in step (1) in sequence online to obtain a high-purity aluminum-silicon alloy; After the online filtration, the temperature of the aluminum-silicon alloy liquid is reduced by 20-30°C.

2. The method according to claim 1, characterized in that The purity of the high-purity aluminum in step (1) is ≥5N.

3. The method according to claim 1 or 2, characterized in that: When leaving the smelting furnace, the temperature of the aluminum-silicon alloy liquid in step (1) is 700-720°C.

4. The method according to any one of claims 1 to 3, characterized in that: After the online filtration in step (2), the temperature of the aluminum-silicon alloy liquid is 680-700°C.

5. The method according to any one of claims 1 to 4, characterized in that: The online filtering method in step (2) comprises: conveying the aluminum-silicon alloy liquid out of the smelting furnace into a first flow channel, a filtering device and a second flow channel in sequence, and then conveying the liquid to a casting machine; A heating cover plate is arranged above the first flow channel, the filter device and the second flow channel; a heating wire is arranged at the bottom of the first flow channel, the filter device and the second flow channel.

6. The method according to claim 5, characterized in that The cross-sectional area of ​​the heating wire is 70-80 mm 2 ; Preferably, the heating temperature of the heating cover plate is 800-840°C; Preferably, the heating temperature of the heating wire is 800-840°C.

7. The method according to claim 5 or 6, characterized in that: The filtering device comprises a filtering box; Preferably, a baffle and a filter plate are provided in the filter box; Preferably, the height of the filter plate from the bottom of the filter box is 10-30 cm; Preferably, one end of the filter plate is connected to the baffle, and the other end is connected to the side wall of the filter box.

8. The method according to any one of claims 1 to 7, characterized in that: The casting temperature in step (2) is 680-700° C. Preferably, the casting speed in step (2) is 100-120 mm / min; Preferably, cooling is performed during the casting in step (2); Preferably, the temperature of the cooling medium used for cooling in the casting in step (2) is 10-20°C; Preferably, the flow rate of the cooling medium used for cooling in the casting in step (2) is 200-550 L / min.

9. The method according to any one of claims 1 to 8, characterized in that: The purity of the high-purity aluminum-silicon alloy in step (2) is ≥5N; Preferably, the generation rate of feather-like crystals in the high-purity aluminum-silicon alloy in step (2) is less than 5%; Preferably, the silicon content in the high-purity aluminum-silicon alloy in step (2) is 0.5wt%-2wt%.

10. The method according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: (1) mixing high-purity aluminum with a purity of ≥5N and an aluminum-silicon master alloy, and smelting them at a temperature of 700-720° C. to obtain an aluminum-silicon alloy liquid; When leaving the smelting furnace, the temperature of the aluminum-silicon alloy liquid is 700-720°C; (2) filtering the aluminum-silicon alloy liquid obtained in step (1) online, controlling the temperature of the aluminum-silicon alloy liquid to decrease by 20-30° C., and then casting at a temperature of 680-700° C. and a speed of 100-120 mm / min to obtain an aluminum-silicon alloy with a purity of ≥5N; The online filtering method comprises: after the aluminum-silicon alloy liquid from the smelting furnace enters the first flow channel, the filtering device and the second flow channel in sequence, it is transported to the casting machine; a heating cover plate is arranged above the first flow channel, the filtering device and the second flow channel; a heating wire is arranged at the bottom of the first flow channel, the filtering device and the second flow channel; The cross-sectional area of ​​the heating wire is 70-80 mm 2 ; The heating temperature of the heating cover is 800-840°C; The heating temperature of the heating wire is 800-840°C; The filtering device comprises a filtering box; a baffle and a filtering plate are arranged in the filtering box; the height of the filtering plate from the bottom of the filtering box is 10-30 cm; one end of the filtering plate is connected to the baffle, and the other end is connected to the side wall of the filtering box; The temperature of the aluminum-silicon alloy liquid after online filtration is 680-700°C; Cooling is performed during the casting; the temperature of the cooling medium used for cooling during the casting is 10-20°C and the flow rate is 200-550L / min; The generation rate of feather-like crystals in the high-purity aluminum-silicon alloy is less than 5%.

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