Method for manufacturing aluminum alloy hollow ingot under assistance of ultrasonic waves

Abstract

The invention relates to the technical field of aluminum alloy hollow ingot casting, and discloses a method for manufacturing an aluminum alloy hollow ingot under the assistance of ultrasonic waves, and after metal melt is injected into a crystallizer through a launder, the melt at the upper part is kept in a liquid state under the action of a hot top heat preservation device. And along with continuous injection of the melt, under the forced cooling action of a double water cooling system of the outer wall and the inner core of the crystallizer, the mold tray descends at a constant speed according to a preset casting speed, so that the metal melt is gradually solidified and formed from a liquid state, ultrasonic oscillation is introduced in the casting process, and finally the hollow cast ingot structure is obtained. According to the method, ultrasonic-assisted casting is introduced into casting of the large-specification aluminum-copper alloy hollow cast ingot, ultrasonic vibration is adopted for intervention in a degassing box and a hot top crystallizer, meanwhile, ultrasonic vibration is introduced in the casting process in different distribution and control modes of an ultrasonic radiation rod, and finally the high-quality large-specification aluminum alloy hollow cast ingot is obtained. Casting cost is reduced, process steps are reduced, and light weight of equipment is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy hollow ingot casting, and in particular to a method for manufacturing aluminum alloy hollow ingots with the assistance of ultrasound. Background Art

[0002] In modern industry, demand for aluminum alloys is trending towards greater diversification and performance. Aluminum alloys, with their numerous advantages, including low density, high specific strength, and excellent corrosion resistance, are widely used in key industries such as aerospace, transportation, and energy. Aluminum alloy hollow ingots, in particular, are gaining increasing prominence as a key raw material for products such as pipes, gas cylinders, tanks, and hollow industrial profiles.

[0003] Aluminum alloy hollow ingots are typically cast using centrifugal casting and spray deposition techniques. Centrifugal casting involves continuously injecting molten metal into a high-speed rotating centrifuge. Under the influence of centrifugal force, the melt adheres evenly to the inner wall of the mold, cooling and solidifying to form a hollow tube. The disadvantages of centrifugal casting for hollow ingots are as follows: 1. High equipment precision is required. Vibrations generated by the centrifuge during casting can affect the dimensional accuracy of the ingot, necessitating a dedicated centrifuge and precision control system. 2. Controlling process parameters such as rotational speed, casting temperature, and cooling rate is difficult. 3. Centrifugal casting is suitable for small and medium-sized castings, but has limitations in casting large hollow ingots.

[0004] The process of spray deposition technology is similar to layer-by-layer deposition. Specifically, the molten metal is broken into fine droplets by an atomizer and then sprayed at high speed onto the surface of a rotating tube mold. The droplets solidify rapidly during the deposition process, and through the cumulative effect of multiple layers of deposition, a hollow tube ingot with a certain wall thickness is ultimately formed. Process parameters such as the injection velocity, temperature, and deposition rate in spray deposition casting require precise control, making it difficult to produce ingots with high-precision dimensions and controlling the size of the deposited layers. Furthermore, high-speed spraying consumes a lot of energy, requires a sophisticated control system, and results in high equipment and maintenance costs.

[0005] Therefore, there is an urgent need for a preparation method that can obtain high-quality, large-scale aluminum alloy hollow ingots, reduce casting costs, reduce process steps, and achieve lightweight equipment. Summary of the Invention

[0006] The present invention provides a method for manufacturing hollow aluminum alloy ingots using ultrasound to assist the casting. Ultrasonic assisted casting is introduced into the casting of large-scale aluminum-copper alloy hollow ingots. Ultrasonic vibration is used to intervene in a degassing box and a hot top crystallizer. At the same time, different arrangements of ultrasonic radiation rods are used to introduce ultrasonic oscillations during the casting process. Ultimately, high-quality large-scale hollow aluminum alloy ingots are obtained, which reduces casting costs, reduces process steps, and achieves lightweight equipment.

[0007] The present invention provides a method for manufacturing aluminum alloy hollow ingots using ultrasound-assisted methods, based on an ultrasound-assisted hot-top semi-continuous casting process device consisting of an aluminum melting furnace, a guide trough, a degassing box, a filter box, an ultrasonic device, a hot-top crystallizer, a cooling water system, and an ingot starter device. The method specifically includes:

[0008] S1. Preheat the aluminum melting furnace to 800°C and start feeding. First, add aluminum blocks for melting. Control the temperature at 750-770°C. Evenly disperse and add other master alloys of Cu, Mn, Si, Mg, and Ti elements one by one. The resulting melt enters the degassing box and filter box through the guide trough.

[0009] S2, degassing and filtering the melt in the degassing box and the filter box using an online purification process to ensure that the hydrogen content of the melt is controlled at 0.11 ml / 100 g Al, and the degassed and filtered melt enters the hot top crystallizer through the guide groove;

[0010] S3. After the melt stabilizes in the guide trough, 1 to 4 sets of ultrasonic vibration systems are applied in the guide trough using an ultrasonic device, and the depth of the ultrasonic vibration system is 10 to 30 mm. When the melt enters the hot top crystallizer and stabilizes and the ingot begins to be drawn down, 1 to 5 sets of ultrasonic vibration systems are applied in the hot top crystallizer using an ultrasonic device, and the depth of the ultrasonic vibration system is 20 to 100 mm. The liquid level of the hot top crystallizer is kept stable during the immersion process. The ultrasonic vibration system of the ultrasonic device is controlled by 2, 3, and 4 ultrasonic radiation rods, forming a symmetrical distribution.

[0011] S4. Starting and regulating the ultrasonic power supply of the ultrasonic equipment so that the ultrasonic vibration system is in a resonant working state, the ultrasonic power supply frequency is 10-30 kHz, ensuring that the power in the guide trough is 0.8-1 kW, and the ultrasonic power of the hot top crystallizer is 0.8-1 kW; during the entire process of ultrasonic vibration treatment of the aluminum alloy melt, the stability of the ultrasonic parameters is ensured by automatic tracking and adjustment of the ultrasonic power supply;

[0012] S5. When the remaining casting length is 100mm, turn off the ultrasonic power supply, start the lifting platform to slowly lift the ultrasonic vibration system, and move it to a safe area. The movement must be smooth to avoid the fluctuation of aluminum liquid and the involvement of oxide film. The removed ultrasonic vibration system continues to be ventilated and cooled, and the surface of its ultrasonic radiation rod is cleaned in time.

[0013] S6. During the ultrasonic vibration process and the downward pulling process of the ingot guide device, the aluminum ingot is cooled and solidified by the cooling water system.

[0014] Furthermore, in the ultrasonic-assisted hot-top semi-continuous casting process device, the aluminum melting furnace is connected to the hot-top crystallizer through a guide groove, and the degassing box and the filter box are arranged on the guide groove to degas and filter the melt;

[0015] The hot top crystallizer includes a hot top insulation cap, a core and a graphite crystallization ring. The hot top insulation cap is annular in shape and is arranged on the ingot starting device. The graphite crystallization ring is located below the hot top insulation cap. The core is arranged on the inner ring of the hot top insulation cap.

[0016] The cooling water system includes internal cooling water and external cooling water, wherein the internal cooling water is located below the core and the external cooling water is located below the graphite crystallization ring;

[0017] The ultrasonic equipment includes an ultrasonic power supply, an ultrasonic vibration system and a positioning tool. The ultrasonic vibration system includes a plurality of ultrasonic radiation rods. The ultrasonic radiation rods extend into the melt in the hot top insulation cap. The positioning tool is used to move the ultrasonic radiation rods. The ultrasonic power supply is electrically connected to the ultrasonic radiation rods.

[0018] Furthermore, the process of casting an aluminum alloy hollow ingot using the ultrasonic-assisted hot-top semi-continuous casting process device is as follows:

[0019] Liquid aluminum flows out of the aluminum melting furnace, passes through the degassing box and the filter box for refinement and purification, and then flows into the hot top crystallizer through the guide groove. Finally, it is initially cooled and solidified into a shell by the cooling water system in the graphite crystallization ring and the core. As the ingot starter device is pulled downward, the solidified shell moves downward and is directly sprayed with cooling water for secondary cooling and further solidification.

[0020] Multiple ultrasonic vibration systems are added to the guide trough and hot top crystallizer. The ultrasonic energy field is introduced to assist in the manufacture of hollow aluminum alloy ingots. On this basis, the entire process flow and process parameters are coordinated and optimized.

[0021] Furthermore, the step S1 further includes:

[0022] During the smelting process, the melt is stirred manually for multiple times, with each stirring time not less than 5 minutes and the time interval between manual stirring being 30 to 40 minutes. During the stirring process, the melt temperature is controlled to be not less than 750°C, and the aluminum slag is removed in time to avoid being drawn into the melt during stirring.

[0023] Furthermore, in step S1,

[0024] The content of the main alloying element copper is controlled below the middle value of its nominal content range;

[0025] Aluminum raw materials are selected from ordinary aluminum raw materials with a content of not less than 99.85%, and the weight of first-grade recycled materials accounts for ≤30% of the total weight. For products with special quality requirements, high-purity aluminum with a content of more than 99.999% is selected, and recycled materials are not used;

[0026] The addition state of the materials: Mg is added in the form of pure magnesium, Cu is added in the form of a homemade master alloy, Ti is added in the form of a master alloy and aluminum titanium boron wire, and other elements are added in the form of master alloys.

[0027] Furthermore, after step S1, the following steps are further included:

[0028] After the melt is completely melted, stirred and slag-skimmed, sampling and analysis are carried out; the sampling position is at 1 / 2 depth near the center of the aluminum melting furnace, and the spectral analysis method is used to detect whether the melt composition content meets the design requirements. If it does not meet the requirements, the material is added to adjust the composition. After the added metal is fully melted and stirred, a second sampling is carried out to determine whether the composition is qualified. If it does not meet the requirements, continue to follow this step until the requirements are met.

[0029] Furthermore, in step S2, the online purification process specifically includes:

[0030] A single stirring rotor is used for degassing, the preheating temperature of the degassing box is not less than 800°C, the purity of the argon gas introduced is not less than 99.999%, the pressure is 0.3-0.5MPa, the rotor speed is 450-500 rpm, and ultrasound and aluminum titanium boron wire refining agent are simultaneously applied in the degassing box to treat the melt; the preheating temperature of the filter box is not less than 800°C.

[0031] Furthermore, in step S2,

[0032] The degassing box adopts the rotating nozzle inert gas flotation method. Argon is passed into the rotating nozzle in the heated and heat-insulated degassing box and then sprayed into the melt. The high-speed rotation of the nozzle disperses the argon into tiny bubbles, stirring the melt to degas and remove slag.

[0033] The filter box adopts foam ceramic filtration method, and the sponge-like ceramic filter sheet is made of aluminum oxide and chromium oxide materials.

[0034] Furthermore, before step S3, the method further includes:

[0035] The ultrasonic radiation rod of the ultrasonic equipment is surface cleaned and preheated, with the preheating temperature being no less than 350° C. At the same time, the ultrasonic vibration system of the ultrasonic equipment is debugged at no load to ensure that the effective output amplitude at no load is no less than 15 μm.

[0036] The beneficial effects of the present invention are:

[0037] It is difficult to prepare high-quality hollow aluminum-copper alloy ingots using conventional processes. However, the present invention injects the molten metal into the hot-top crystallizer through a guide groove, and keeps the upper melt in a liquid state under the action of the hot-top insulation cap. As the melt continues to be injected, under the forced cooling action of the dual water cooling system of the outer wall and the internal core of the hot-top crystallizer, the mold tray descends at a uniform speed according to the preset casting speed, so that the molten metal is gradually solidified and formed from the liquid state. Different control methods of ultrasonic radiation rods are used (the number of ultrasonic radiation rods is 1-6 rods, and they are symmetrically distributed) to introduce ultrasonic oscillations in the casting process of the hollow aluminum-copper alloy ingot, and finally obtains a hollow ingot structure, greatly refines the grains, reduces element segregation, and makes the eutectic phase more dispersed, thereby obtaining large-scale, high-quality aluminum alloy hollow ingots. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a structural schematic diagram of the ultrasonic assisted hot top semi-continuous casting process device in the present invention.

[0039] Figure 2 Schematic diagram of the ultrasonic molten pool in the present invention.

[0040] Figure 3 This is a schematic diagram of the casting of the Ф800 / Ф400mm aluminum alloy hollow ingot in Experiment 1 of the present invention.

[0041] Figure 4 This is the cross-sectional radial metallographic structure diagram of Experiment 1 in the present invention.

[0042] Figure 5 This is the velocity cloud diagram of different control methods of ultrasonic radiation rods in Experiment 2 of the present invention.

[0043] In the accompanying drawings, there are an aluminum melting furnace 1, a guide trough 2, an aluminum melt 3, a degassing box 4, a filter box 5, a hot top insulation cap 6, an ultrasonic radiation rod 7, a core 8, internal cooling water 9, an aluminum ingot 10, a graphite crystallization ring 11, an external cooling water 12, and an ingot guide device 13.

[0044] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0045] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0046] The present invention provides a method for manufacturing aluminum alloy hollow ingots using ultrasound-assisted hot top semi-continuous casting process device, such as Figure 1As shown, the device includes an aluminum melting furnace 1, a guide trough 2, a degassing box 4, a filter box 5, ultrasonic equipment (including an ultrasonic power supply, an ultrasonic vibration system, and a positioning tool), a hot top mold, a cooling water system, an ingot starter device 13, and other auxiliary tools or equipment. During the casting process, the ultrasonic vibration system is applied in the guide trough 2 near the hot top mold mouth to assist in treating the aluminum melt 3. Ultrasonic vibration is applied in the hot top mold molten pool to assist in the melt solidification process.

[0047] The specific structure of the device is as follows: the aluminum melting furnace 1 is connected to the hot top crystallizer through a guide groove 2, and the degassing box 4 and the filter box 5 are arranged on the guide groove 2 to degas and filter the melt; the hot top crystallizer includes a hot top insulation cap 6, a core 8 and a graphite crystallization ring 11, the hot top insulation cap 6 is annular in shape and is arranged on the ingot guide device 13, the graphite crystallization ring 11 is located below the hot top insulation cap 6, and the core 8 is arranged on the inner ring of the hot top insulation cap 6; the cooling water system includes internal cooling water 9 and external cooling water 12, the internal cooling water 9 is located below the core 8, and the external cooling water 12 is located below the graphite crystallization ring 11; the ultrasonic equipment includes an ultrasonic power supply, an ultrasonic vibration system and a positioning tool, the ultrasonic vibration system includes a plurality of ultrasonic radiation rods, the ultrasonic radiation rod 7 extends into the melt in the hot top insulation cap 6, the positioning tool is used to move the ultrasonic radiation rod 7, and the ultrasonic power supply is electrically connected to the ultrasonic radiation rod 7.

[0048] The process of casting aluminum alloy hollow ingots using the ultrasonic-assisted hot-top semi-continuous casting process device is as follows:

[0049] Liquid aluminum, or aluminum melt 3, flows from the aluminum melting furnace 1, is refined and purified by a degassing box 4 and a filtration device, then flows through a guide trough 2 into a hot-top crystallizer. Finally, it undergoes initial cooling and solidification into a shell through the cooling water system in the hot-top crystallizer and core 8. As the ingot starter 13 pulls the solidified shell downward, it is directly sprayed with cooling water for secondary cooling and further solidification, forming an aluminum ingot 10. The present invention incorporates multiple ultrasonic vibration systems in the guide trough 2 and the hot-top crystallizer, introducing an ultrasonic energy field to assist in the manufacture of hollow aluminum alloy ingots. On this basis, the entire process flow and process parameters are collaboratively optimized.

[0050] The present invention provides a method for manufacturing an aluminum alloy hollow ingot using ultrasound assistance, which specifically includes:

[0051] S1. Melting and composition adjustment

[0052] (1) Melting

[0053] The aluminum melting furnace 1 is preheated to 800°C and the feeding is started. First, aluminum blocks are added for melting. The temperature is controlled at 750-770°C. Other intermediate alloys of elements such as Cu, Mn, Si, Mg, and Ti are evenly dispersed and added one by one to obtain a melt that enters the degassing box 4 and the filter box 5 through the guide groove 2. To ensure complete melting of the alloy and uniformity of the composition, the melt is stirred manually during the smelting process. Each stirring time is not less than 5 minutes, and the time interval of manual stirring is 30-40 minutes. During the stirring process, care must be taken to control the melt temperature to not less than 750°C, and aluminum slag must be cleaned in time to avoid being drawn into the melt during stirring.

[0054] Aluminum alloys are formulated in accordance with the basic principle of the specified range of alloy grade nominal composition, with special attention to: ① In order to control the size and quantity of the crystalline phase in the ingot, the content of the main alloying element copper is controlled below the middle value of its nominal content range; ② Aluminum raw materials are generally selected with a content of not less than 99.85% ordinary aluminum raw materials, and the weight of first-level recycled materials accounts for ≤30% of the total weight. For products with special quality requirements, high-purity aluminum of more than 99.999% is selected, and recycled materials shall not be used; ③ Material addition status: Mg is added in the form of pure magnesium, Cu is added in the form of a self-made master alloy (another invention patent is applied for separately), Ti is added in the form of a master alloy and aluminum-titanium-boron wire, and other elements are added in the form of master alloys.

[0055] (2) Ingredient adjustment

[0056] After the melt is fully melted, stirred, and slag-skimmed, sampling and analysis are performed. The sampling position is 1 / 2 the depth of the center of the furnace. Spectral analysis is used to detect whether the melt composition content meets the design requirements. If not, it is necessary to add material to adjust the composition. After the added metal is fully melted and stirred, a second sampling is performed to determine whether the composition is qualified. If not, continue to follow this step until the requirements are met.

[0057] S2. Melt purification

[0058] The melt is degassed efficiently using an online purification process to ensure that the hydrogen content of the melt is controlled at 0.11 ml / 100 gAl. After degassing and filtration, the melt enters the hot top crystallizer through the guide groove 2. The online purification process is as follows:

[0059] ① Use a single stirring rotor for degassing, the preheating temperature of the degassing box is not less than 800℃, the purity of the argon introduced is not less than 99.999%, the pressure is 0.3-0.5MPa, and the rotor speed is 450-500 rpm.

[0060] ②The preheating temperature of the filter box body shall not be lower than 800℃.

[0061] ③ Simultaneously apply ultrasound and aluminum titanium boron wire refiner to treat the melt in the degassing box.

[0062] The degassing adopts the rotating nozzle inert gas flotation method (SNIF melt purification method for short). This method mainly passes argon into a rotating nozzle in a heated and insulated degassing box and then sprays it into the aluminum melt. Through the high-speed rotation of the nozzle, the argon is dispersed into tiny bubbles, stirring the aluminum liquid, enhancing mass transfer and heat transfer, and can play a role in degassing and slag removal during the flotation process.

[0063] The filtration and slag removal adopts the foam ceramic filtration method. This sponge-like ceramic filter is mainly made of materials such as aluminum oxide and chromium oxide. The foam ceramic filtration and purification principle belongs to the deep filtration mechanism with large filtration capacity. It is suitable for filtration and purification in continuous casting and casting and rolling production.

[0064] S3. Ultrasonic preliminary preparation for ultrasonic assisted casting

[0065] (1) Ultrasonic radiation rod treatment

[0066] The ultrasonic radiation rod of the ultrasonic equipment is surface cleaned and preheated, with the preheating temperature being no less than 350° C. At the same time, the ultrasonic vibration system of the ultrasonic equipment is debugged at no load to ensure that the effective output amplitude at no load is no less than 15 μm.

[0067] (2) Ultrasonic vibration system control

[0068] After the molten aluminum flows through the diversion trough and stabilizes, one to four ultrasonic vibration systems are applied to the diversion trough, immersed in the molten aluminum to a depth of 10 to 30 mm. After the molten aluminum stabilizes in the hot top mold and the ingot begins to be pulled down, one to five ultrasonic vibration systems are applied to the hot top mold, immersed in the molten aluminum to a depth of 20 to 100 mm. The liquid level in the hot top mold must be kept stable during the immersion process. The ultrasonic vibration systems are arranged in symmetrical patterns of two, three, or four rods.

[0069] S4. Ultrasonic start-up and control of ultrasonic assisted casting

[0070] Start and control the ultrasonic power supply system to ensure that the ultrasonic vibration system is in a resonant operating state. The ultrasonic power supply frequency is 10-30 kHz, ensuring that the power in the diversion trough is 0.8-1 kW, and the ultrasonic power in the hot top mold is 0.8-1 kW. Throughout the ultrasonic vibration treatment of the aluminum alloy melt, the automatic tracking and adjustment function of the ultrasonic power supply system ensures the stability of the ultrasonic parameters. The ultrasonic vibration system must not be disturbed during operation to avoid disturbances in the ultrasonic parameters and fluctuations in the aluminum liquid.

[0071] S5. Remove the ultrasonic vibration system

[0072] When the remaining casting length is approximately 100mm, turn off the ultrasonic power supply, start the lifting platform, and slowly raise the ultrasonic vibration system to a safe area. Move it smoothly to avoid causing fluctuations in the aluminum liquid and the involvement of the oxide film. The removed ultrasonic vibration system should continue to be ventilated and cooled, and the surface of its radiation rod should be cleaned promptly.

[0073] S6. During the ultrasonic vibration process and the downward pulling process of the ingot guide device, the aluminum ingot is cooled and solidified by the cooling water system.

[0074] It is difficult to prepare high-quality hollow aluminum-copper alloy ingots using conventional processes. However, the present invention injects the molten metal into the hot-top crystallizer through a guide groove, and keeps the upper melt in a liquid state under the action of the hot-top insulation cap. As the melt continues to be injected, under the forced cooling action of the dual water cooling system of the outer wall and the internal core of the hot-top crystallizer, the mold tray descends at a uniform speed according to the preset casting speed, so that the molten metal is gradually solidified and formed from the liquid state. Different control methods of ultrasonic radiation rods are used (the number of ultrasonic radiation rods is 1-6 rods, and they are symmetrically distributed) to introduce ultrasonic oscillations in the casting process of the hollow aluminum-copper alloy ingot, and finally obtains a hollow ingot structure, greatly refines the grains, reduces element segregation, and makes the eutectic phase more dispersed, thereby obtaining large-scale, high-quality aluminum alloy hollow ingots.

[0075] Experiment 1

[0076] Three process parameters were used to cast Ф800 / Ф400mm aluminum alloy hollow ingots respectively. The specific processes are as follows:

[0077] (1) Ingot I is an ordinary ingot, cast in a conventional manner;

[0078] (2) Ingot II adds ultrasonic vibration, using two ultrasonic radiation rods vertically inserted into the melt to perform ultrasonic vibration, with an ultrasonic power of 300W, an ultrasonic frequency of 20kHz, and an insertion depth of 30mm;

[0079] (3) Ingot III adds ultrasonic vibration, using two ultrasonic radiation rods tilted 45 degrees symmetrically to the center to perform ultrasonic vibration on the melt, with an ultrasonic power of 350W, an ultrasonic frequency of 20kHz, and an insertion depth of 80mm;

[0080] 1. Casting process

[0081] 1) Debugging and preparation before casting

[0082] Inspect the casting equipment to ensure that ① the heating device, electromagnetic stirring device, and tilting furnace power device of the furnace are normal; ② the guide trough and online degassing and impurity removal parts mainly check whether the heating device is normal, whether the rotary nozzle is normal and available, whether the filter plate is seriously damaged, whether the refiner wire feeder is operating normally, and ensure that the guide trough is clean and free of aluminum slag, etc.; ③ the hot top crystallizer part: whether the hot top cap and graphite crystallization ring are seriously damaged and need to be replaced, whether the ingot guide device is normal, and ensure that the oil and gas lubrication system and cooling water system are normal.

[0083] 2) Alloy ratio and smelting

[0084] The smelting process requires strict control of smelting time and chemical composition. While ensuring complete melting of the alloy, the working hours should be shortened as much as possible to reduce burnout. The specific operation is to first place a pure aluminum ingot into the furnace, turn on the heating equipment to raise the furnace temperature to 750°C and keep it warm for a certain period of time to ensure complete melting of the aluminum ingot. Then, other metals are gradually added in batches. Once all are melted, slag is skimmed and stirred. After manual stirring, samples are taken for composition measurement. Based on the composition test results, additional materials or dilution are selected. After refining is completed, the ingot is allowed to stand for a period of time before being removed from the furnace. The alloy composition range is shown in Table 4.

[0085] Table 4 Aluminum alloy composition (wt%)

[0086]

[0087] 3) Online degassing and impurity removal of molten aluminum

[0088] An online degassing and filtration device is installed in the flow guidance system between the smelting furnace and the hot-top crystallizer. Degassing utilizes the rotating nozzle inert gas flotation method (SNIF melt purification method). This method primarily involves passing argon gas through a rotating nozzle in a heatable and insulated degassing chamber and then spraying it into the molten aluminum. The high-speed rotation of the nozzle disperses the argon gas into tiny bubbles, stirring the molten aluminum and enhancing mass and heat transfer. The flotation process also degasses and removes slag. Filtration and slag removal utilizes ceramic foam filtration. This sponge-like ceramic filter is primarily made of materials such as aluminum oxide and chromium oxide. The ceramic foam filtration purification principle is a deep-seated filtration mechanism with high filtration capacity, making it suitable for filtration and purification in continuous casting and roll-casting production.

[0089] 4) Casting parameters

[0090] The main casting process parameters during the casting process are: casting temperature 705℃, casting speed 35mm / min, peripheral cooling water flow 12m 3 / h, core cooling water flow rate 6m 3 / h.

[0091] 5) Ultrasonic casting

[0092] Preheat the guide groove, the inner wall of the hot top crystallizer and the ultrasonic radiation rod. After the temperature stabilizes, open the furnace mouth and tilt the furnace for pouring. Figure 2 , open the hot top crystallizer and core cooling water, wait for the aluminum liquid to flow into the hot top crystallizer to a certain height, start the ingot dummy device, and open the secondary cooling water spray system at the same time. At this time, the dummy plate moves down to drive the ingot to be pulled down, and semi-continuous casting begins. The specific casting process diagram is shown in Figure 3 , Figure 3 (a) shows a conventional casting scene; (b) shows an ultrasonic casting scene for group 1; (c) shows an ultrasonic casting scene for group 2; and (d) shows a finished aluminum alloy hollow ingot. When using conventional hot-top casting to cast an ingot 120 mm long, two approximately symmetrically distributed ultrasonic vibration systems are added vertically and obliquely above the hot-top mold and vibrate. The ultrasonic radiating rods are immersed in the molten aluminum to depths of approximately 30 and 90 mm until the casting is complete.

[0093] 2. Organizational Analysis

[0094] like Figure 4 As shown, Figure 4 Among them, (A) no ultrasound group; (B) ultrasound group 1; (C) ultrasound group 2. Figure 4 It can be seen from the figure that the structure of the ultrasonic ingot is obviously refined. The average grain size of the outer ring, 1 / 2 radius and inner ring area of ​​the ultrasonic group 1 is reduced from about 223μm, 285μm and 206μm to 208μm, 263μm and 192μm respectively; the average grain size of the outer ring, 1 / 2 radius and inner ring area of ​​the ultrasonic group 2 is reduced from about 223μm, 285μm and 206μm to 110μm, 122μm and 102μm respectively.

[0095] In summary, by continuously optimizing the casting process, the quality of the ingots is continuously improved, and the ingot quality obtained by the casting process of the present invention is the best.

[0096] Experiment 2

[0097] The actual casting process of Ф800 / Ф400mm aluminum alloy hollow ingots was numerically simulated using process parameters under different ultrasonic radiation rod control methods. The specific results are as follows:

[0098] like Figure 5 is the cross-sectional velocity cloud diagram, Figure 5 Among them, (a) conventional casting; (b) single-source ultrasound; (c) two-source ultrasound; (d) four-source ultrasound. Figure 5As can be seen in the figure, without ultrasound, the maximum velocity occurs at the entrance of the first diversion channel, and the velocity distribution in the molten pool is relatively uneven. When single-source ultrasound is applied, the velocity is higher near the ultrasonic radiation rod, and the velocity distribution in the molten pool near the ultrasonic radiation rod begins to uniformize. The velocity away from the ultrasonic region remains unchanged. With four-source ultrasound, velocity uniformity in the molten pool is significantly improved, and solute gradually begins to flow near the outer and inner rings.

[0099] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, apparatus, article, or method comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, apparatus, article, or method. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, apparatus, article, or method comprising the element.

[0100] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for manufacturing aluminum alloy hollow ingots using ultrasound, characterized in that: Based on an ultrasonic-assisted hot-top semi-continuous casting process device consisting of an aluminum melting furnace, a guide trough, a degassing box, a filter box, an ultrasonic device, a hot-top crystallizer, a cooling water system, and an ingot starter device, the method specifically includes: S1. Preheat the aluminum melting furnace to 800°C and start feeding. First, add aluminum blocks for melting. Control the temperature at 750-770°C. Evenly disperse and add other master alloys of Cu, Mn, Si, Mg, and Ti elements one by one. The resulting melt enters the degassing box and filter box through the guide trough. S2, degassing and filtering the melt in the degassing box and the filter box using an online purification process to ensure that the hydrogen content of the melt is controlled at 0.11 ml / 100 g Al, and the degassed and filtered melt enters the hot top crystallizer through the guide groove; S3. After the melt stabilizes in the guide trough, 1 to 4 sets of ultrasonic vibration systems are applied in the guide trough using an ultrasonic device, and the depth of the ultrasonic vibration system is 10 to 30 mm. When the melt enters the hot top crystallizer and stabilizes and the ingot begins to be drawn down, 1 to 5 sets of ultrasonic vibration systems are applied in the hot top crystallizer using an ultrasonic device, and the depth of the ultrasonic vibration system is 20 to 100 mm. The liquid level of the hot top crystallizer is kept stable during the immersion process. The ultrasonic vibration system of the ultrasonic device is controlled by 2, 3, and 4 ultrasonic radiation rods, forming a symmetrical distribution. S4. Starting and regulating the ultrasonic power supply of the ultrasonic equipment so that the ultrasonic vibration system is in a resonant working state, the ultrasonic power supply frequency is 10-30 kHz, ensuring that the power in the guide trough is 0.8-1 kW, and the ultrasonic power of the hot top crystallizer is 0.8-1 kW; during the entire process of ultrasonic vibration treatment of the aluminum alloy melt, the stability of the ultrasonic parameters is ensured by automatic tracking and adjustment of the ultrasonic power supply; S5. When the remaining casting length is 100mm, turn off the ultrasonic power supply, start the lifting platform to slowly lift the ultrasonic vibration system, and move it to a safe area. The movement must be smooth to avoid the fluctuation of aluminum liquid and the involvement of oxide film. The removed ultrasonic vibration system continues to be ventilated and cooled, and the surface of its ultrasonic radiation rod is cleaned in time. S6. During the ultrasonic vibration process and the downward pulling process of the ingot guide device, the aluminum ingot is cooled and solidified by the cooling water system.

2. The method for manufacturing aluminum alloy hollow ingots using ultrasound-assisted methods according to claim 1, wherein: In the ultrasonic-assisted hot-top semi-continuous casting process device, the aluminum melting furnace is connected to the hot-top crystallizer through a guide groove, and the degassing box and the filter box are arranged on the guide groove to degas and filter the melt; The hot top crystallizer includes a hot top insulation cap, a core and a graphite crystallization ring. The hot top insulation cap is annular in shape and is arranged on the ingot starting device. The graphite crystallization ring is located below the hot top insulation cap. The core is arranged on the inner ring of the hot top insulation cap. The cooling water system includes internal cooling water and external cooling water, wherein the internal cooling water is located below the core and the external cooling water is located below the graphite crystallization ring; The ultrasonic equipment includes an ultrasonic power supply, an ultrasonic vibration system and a positioning tool. The ultrasonic vibration system includes a plurality of ultrasonic radiation rods. The ultrasonic radiation rods extend into the melt in the hot top insulation cap. The positioning tool is used to move the ultrasonic radiation rods. The ultrasonic power supply is electrically connected to the ultrasonic radiation rods.

3. The method for manufacturing aluminum alloy hollow ingots using ultrasound-assisted method according to claim 2, characterized in that: The process of casting aluminum alloy hollow ingots using the ultrasonic-assisted hot-top semi-continuous casting process device is as follows: Liquid aluminum flows out of the aluminum melting furnace, passes through the degassing box and the filter box for refinement and purification, and then flows into the hot top crystallizer through the guide groove. Finally, it is initially cooled and solidified into a shell by the cooling water system in the graphite crystallization ring and the core. As the ingot starter device is pulled downward, the solidified shell moves downward and is directly sprayed with cooling water for secondary cooling and further solidification. Multiple ultrasonic vibration systems are added to the guide trough and hot top crystallizer. The ultrasonic energy field is introduced to assist in the manufacture of hollow aluminum alloy ingots. On this basis, the entire process flow and process parameters are coordinated and optimized.

4. The method for manufacturing aluminum alloy hollow ingots using ultrasound-assisted method according to claim 1, characterized in that: The step S1 further includes: During the smelting process, the melt is stirred manually for multiple times, with each stirring time not less than 5 minutes and the time interval between manual stirring being 30 to 40 minutes. During the stirring process, the melt temperature is controlled to be not less than 750°C, and the aluminum slag is removed in time to avoid being drawn into the melt during stirring.

5. The method for manufacturing aluminum alloy hollow ingots using ultrasound-assisted method according to claim 4, characterized in that: In the step S1, The content of the main alloying element copper is controlled below the middle value of its nominal content range; Aluminum raw materials are selected from ordinary aluminum raw materials with a content of not less than 99.85%, and the weight of first-grade recycled materials accounts for ≤30% of the total weight. For products with special quality requirements, high-purity aluminum with a content of more than 99.999% is selected, and recycled materials are not used; The addition state of the materials: Mg is added in the form of pure magnesium, Cu is added in the form of a homemade master alloy, Ti is added in the form of a master alloy and aluminum titanium boron wire, and other elements are added in the form of master alloys.

6. The method for manufacturing aluminum alloy hollow ingots using ultrasound-assisted methods according to claim 4, characterized in that: After step S1, the following steps are also included: After the melt is completely melted, stirred and slag-skimmed, sampling and analysis are carried out; the sampling position is at 1 / 2 depth near the center of the aluminum melting furnace, and the spectral analysis method is used to detect whether the melt composition content meets the design requirements. If it does not meet the requirements, the material is added to adjust the composition. After the added metal is fully melted and stirred, a second sampling is carried out to determine whether the composition is qualified. If it does not meet the requirements, continue to follow this step until the requirements are met.

7. The method for manufacturing aluminum alloy hollow ingots using ultrasound-assisted methods according to claim 1, wherein: In step S2, the online purification process specifically includes: A single stirring rotor is used for degassing, the preheating temperature of the degassing box is not less than 800°C, the purity of the argon gas introduced is not less than 99.999%, the pressure is 0.3-0.5MPa, the rotor speed is 450-500 rpm, and ultrasound and aluminum titanium boron wire refining agent are simultaneously applied in the degassing box to treat the melt; the preheating temperature of the filter box is not less than 800°C.

8. The method for manufacturing aluminum alloy hollow ingots using ultrasound-assisted methods according to claim 7, characterized in that: In the step S2, The degassing box adopts the rotating nozzle inert gas flotation method. Argon is passed into the rotating nozzle in the heated and heat-insulated degassing box and then sprayed into the melt. The high-speed rotation of the nozzle disperses the argon into tiny bubbles, stirring the melt to degas and remove slag. The filter box adopts foam ceramic filtration method, and the sponge-like ceramic filter sheet is made of aluminum oxide and chromium oxide materials.

9. The method for manufacturing aluminum alloy hollow ingots using ultrasound-assisted methods according to claim 1, characterized in that: Before step S3, the method further includes: The ultrasonic radiation rod of the ultrasonic equipment is surface cleaned and preheated, with the preheating temperature being no less than 350° C. At the same time, the ultrasonic vibration system of the ultrasonic equipment is debugged at no load to ensure that the effective output amplitude at no load is no less than 15 μm.

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