Large-size aluminum alloy thin-wall hollow round cast ingot and production method thereof

Abstract

The invention discloses a large-size aluminum alloy thin-wall hollow round cast ingot and a production method thereof, belongs to the technical field of aluminum alloy casting, and aims to solve the problem that the thin-wall hollow round cast ingot lacks related production processes which are mature in technology and controllable in cost. The method comprises the steps of burdening; and smelting, refining and casting. High-temperature raw aluminum liquid produced by the aluminum electrolysis cell is directly utilized, large-specification aluminum alloy hollow and solid round cast ingots are produced, meanwhile, the production line can also produce aluminum alloy flat cast ingots and aluminum alloy round cast ingots in a compatible mode, product types can be increased for enterprises, economic benefits can be improved, and energy conservation and consumption reduction can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy casting, and particularly relates to a large-size aluminum alloy thin-wall hollow round ingot and a production method thereof. Background Art

[0002] Large-sized aluminum alloy hollow round ingots have good forming and processing performance, corrosion resistance, and strong weldability. They are widely used in equipment manufacturing fields such as ships, automobiles, and aircraft welding parts, pressure vessels, and refrigeration equipment. The existing domestic production of aluminum alloy hollow round ingots mainly produces hollow round ingots by cold material dissolution. This method not only has a slow smelting speed, but also has a low casting output due to the limitations of the furnace body and the water tray itself. The filtering device during the casting process is simple, and it is difficult to improve the product quality. It is impossible to cast thin-walled hollow round ingots. New products such as large-sized thin-walled aluminum alloy hollow round ingots such as 6061 (Φ600mm / Φ400mm) are currently blank in domestic production; there are also solid round ingots that are processed into hollow round ingots through car skins and boring, but their production costs are high and production efficiency is low.

[0003] During the research and development process, it was found that the continuous casting process of aluminum alloy hollow round ingots is very different from that of solid ingots. A water-cooled core (core rod) is usually placed at the center of the ingot to establish the conditions for the melt to enter the crystallizer, basically forming one or two main liquid flows into the annular liquid cavity of the ingot. In this case, a "plum blossom" type of local uneven structure is easily formed during the solidification of the ingot. The change in casting conditions causes a large range of liquid level fluctuations in the crystallizer, which will lead to uneven and anisotropic longitudinal structures of the ingot. In particular, large-sized hollow round ingots have large diameters and thin tube walls, which have high requirements on the temperature of the aluminum liquid and the flow and temperature ratio of the water during casting. There are many uncontrollable factors, especially for direct casting of electrolytic aluminum liquid. There is no successful experience in China to learn from. The main technical difficulties are: first, the flow channel is long and the temperature of the aluminum liquid drops quickly; second, it is difficult to match the temperature and water volume of the surface cooling water and the core water; third, the center geometric point is calculated by physical measurement, and a common water tray is designed, and the adjustable range of the designed water tray becomes smaller, making the technical implementation difficult; fourth, the water temperature in the casting well is high, the drainage pump is easily damaged, and the maximum water level control value required for hollow ingot casting is difficult to achieve; fifth, the process control and operation requirements are high.

[0004] Based on the problems in the above-mentioned background technology, researchers have proposed a large-sized aluminum alloy thin-walled hollow round ingot and a production method thereof. Summary of the invention

[0005] The purpose of the present invention is to provide a large-size aluminum alloy thin-wall hollow round ingot and a production method thereof, so as to solve the problem that thin-wall hollow round ingots lack relevant production processes with mature technology and controllable costs.

[0006] In order to solve the above problems, the technical solution of the present invention is: A large-size aluminum alloy thin-wall hollow round ingot and a production method thereof, the method comprises the following steps: S1, ingredients; Directly use the high-temperature original aluminum liquid produced by the aluminum electrolytic cell for batching; S2, smelting; The prepared aluminum liquid is melted and stirred, during which the slag is removed, samples are taken for analysis, and additional materials are added and stirred when necessary, and secondary sampling and analysis are performed until the composition meets the requirements; S3, refining; The molten aluminum is allowed to stand after smelting, then filtered through a filter box, degassed in a degassing chamber, and then deep-bed filtered to ensure that the melt meets casting specifications; S4, casting; S4.1 Aluminum water enters the casting well; The main well + auxiliary well mode is adopted. The main well and the auxiliary well are sealed and connected through a culvert. At the same time, an overflow pipe is installed in the middle of the auxiliary well mouth. A float liquid level control system and a submersible pump are placed in the auxiliary well. S4.2 Casting temperature control; The temperature loss needs to be controlled from the outlet of the melting furnace to the inlet chute of the casting machine, and the temperature fluctuation range needs to be controlled between 0-10℃; The hollow ingot crystallizer platform adopts the method of aluminum liquid being fed at both ends for flow supply. The switching of casting between different furnace groups is completed by switching the position of the mobile transition chute. The water tray residual material at the end of casting is discharged by the method of head-in and tail-out. S4.3 Ingot cooling crystallization; When casting hollow round ingots, cooling water is placed inside and outside the ingot to help the ingot crystallize. After reaching thermal equilibrium, the ingot is separated from the crystallizer while cooling until it is cast to the corresponding length. S4.4 Clean up the accumulated slag; After the hollow rod casting is completed, the slag accumulated in the equipment should be cleaned in time and the corresponding damaged areas should be repaired.

[0007] Furthermore, the auxiliary shaft described in S4.1 is located 2 meters away from the main shaft, with a specification of 2500mm×3000mm. A 1700mm×700mm×2500mm steel rectangular culvert is sealed between the main shaft and the auxiliary shaft, and a Φ400 overflow pipe is installed in the middle position 1500mm downward from the auxiliary shaft opening.

[0008] Furthermore, in S4.3, the temperature fluctuation range of the molten aluminum from the outlet of the smelting furnace to the inlet launder of the casting machine is controlled to be between 0-10°C.

[0009] The beneficial effects of the present invention are as follows: (1) Based on the production of primary aluminum liquid by our company, the present invention directly uses electrolytic aluminum liquid to mix cold materials for smelting, which reduces the melting and casting process, greatly reduces the burning loss, shortens the smelting time, increases product output, improves the internal quality of aluminum alloy products, and can reduce the number of forging times and the amount of mechanical processing, saving costs and reducing expenses.

[0010] The refining process uses multi-stage filtration technology to achieve melt purification. The filter box and degassing chamber can degas and remove slag, and the deep bed filtration can effectively reduce slag inclusion waste. The whole process can control the hydrogen content of hollow and solid round ingots to between (0.080-0.105ml / 100gAl), meeting the technical standard of 0.120ml / 100gAl required by the order. At the same time, the refining process of the project uses industrial chlorine and argon mixed gas to effectively remove melt impurities and harmful gases while taking into account the melt temperature maintenance function.

[0011] The ingot casting process ensures production safety and product quality from aspects such as the adjustment of the aluminum liquid inlet method, the setting of the main and auxiliary wells, temperature control, and cold zone crystallization. In particular, the process of the ingot being cooled and separated from the crystallizer overcomes the pulling force of the high viscosity of the aluminum liquid on the mold core, solves the problem of the core sticking when casting thin-walled hollow ingots, and achieves stable and high-quality casting surface quality, laying a good foundation for continuous production.

[0012] (2) Based on our company's existing 70,000-ton flat ingot casting production line, the present invention can realize the production of large-size aluminum alloy thin-walled hollow round ingots by adding auxiliary shafts and hollow round ingot core cooling water systems. Compared with the construction of a new production line, the capital investment scale can be almost ignored; on this basis, if there is renovation funds, the crystallizer platform for cleaning slag accumulation can also be updated to enable it to tilt 90° for easy cleaning; the electronic control system and cooling water drainage system can be updated to enable it to match the switching between the production of four types of products: hollow round ingots, solid round ingots, flat ingots, and round ingots. Even these overall upgrade investments are negligible compared to the construction of a new production line. However, this compatible and switchable casting production line formed by the additional installation and renovation can realize the production of hollow round ingots, solid round ingots, flat ingots, and round ingots.

[0013] (3) The present invention directly utilizes the high-temperature raw aluminum liquid produced by the aluminum electrolytic cell to produce large-sized aluminum alloy hollow and solid round ingots. At the same time, the production line can also be compatible with the production of aluminum alloy flat ingots and round ingots, which can increase the product variety for the enterprise, improve economic benefits, and save energy and reduce consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a process flow chart of the smelting and casting process of a large-sized aluminum alloy thin-walled hollow round ingot and its production method; Figure 2 The cast structure characteristics of the product in Example 1; Figure 3 This is the homogenized structure of the product in Example 1. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed but is merely representative of selected embodiments of the present invention.

[0017] Example 1 - Production of thin-walled hollow round ingots with specifications of Ф546×Ф335 and thickness of 105.5 mm; like Figure 1 As shown, a large-size aluminum alloy thin-wall hollow round ingot and a production method thereof, the method is divided into the following steps: S1, ingredients; Utilize the high-temperature original aluminum liquid produced by our aluminum electrolytic cell and directly add aluminum liquid for batching.

[0018] S2, smelting; The prepared aluminum liquid is melted and stirred, during which the slag is removed, samples are taken for analysis, and additional material is added and stirred when necessary, and secondary sampling and analysis are performed until the composition meets the manufacturer's requirements.

[0019] S3, refining; The molten aluminum after smelting is allowed to stand, then filtered through a filter box, degassed in a degassing chamber, and then deep-bed filtered to ensure that the melt meets casting specifications.

[0020] In this embodiment, two 40-ton mixed smelting furnaces are equipped. Each smelting furnace corresponds to a launder line for conveying aluminum liquid. Each line is equipped with a filter box, a degassing chamber, a wire feeder, a deep bed, and a cantilever crane. They share a hanging basket type wire rope casting machine. The furnace group and casting machine are configured in a "2+1" configuration. Specifically: The filter box uses a ceramic foam filter, which has the dual functions of filtering metal and controlling the metal temperature at the set temperature; The degassing chamber uses graphite double rotors for degassing, which mainly removes hydrogen and also has the function of heating to keep the melt temperature constant. The online deep bed filtration equipment uses alumina balls and alumina gravel for filtration, which can effectively remove fine impurities in the melt that the filter box cannot remove, and has a heating and heat preservation function to maintain the melt temperature to meet the requirements of the casting process.

[0021] S4, casting; S4.1 Aluminum water enters the casting well; The casting machine of our company's existing aluminum alloy flat ingot production line is only equipped with a casting well. The casting water temperature is high, and the drainage pump is easily damaged, so it mainly relies on overflow drainage. The hollow ingot is hollow, and circulating water is also required for internal cooling during production. A large amount of water vapor is produced during casting. In order to prevent a large amount of water vapor in the core from failing to be discharged from the bottom of the ingot in time, resulting in aluminum liquid bubbling, leakage and explosion, dry well casting must be used.

[0022] In order to ensure safe casting, the single well used for casting in the original production line was changed to a main well + auxiliary well. The main well of the original production line remained unchanged, and a 2500mm×3000mm auxiliary well was made 2 meters away from the main well. A 1700mm×700mm×2500mm steel rectangular culvert was sealed between the main well and the auxiliary well. At the same time, a Φ400 overflow pipe was installed in the middle position 1500mm downward from the auxiliary well mouth.

[0023] A float liquid level control system and a submersible pump are placed in the auxiliary well. The submersible pump adopts frequency conversion control, one for use and one for backup).

[0024] S4.2 Casting temperature control; The perfect filtering configuration in the refining process is conducive to improving the quality of casting alloys, but it also leads to a long flow channel from the outlet of the melting furnace to the inlet of the casting machine, resulting in large temperature losses. Limited by the objective factors of the production line, the temperature range fluctuation is reduced to 0-10℃ by installing natural gas spray guns, adding chute insulation covers, increasing the deep bed heating power for temperature compensation, and coordinating with movable chute mobile torch heating devices and other technical means to control temperature drop, thereby improving the internal product quality of hollow ingots, reducing scrap rates, and improving economic benefits.

[0025] According to the characteristics of the plane layout of the furnace group and the casting machine (2 + 1), in line with the purpose of improving equipment utilization and efficiency, the hollow ingot crystallizer platform in this embodiment adopts the method of aluminum liquid being fed at both ends for flow supply, and the switching of the casting of the two furnace groups is completed by switching the installation position of the mobile transition flow channel; the water tray residual material at the end of casting is discharged by the method of head-in and tail-out (the head and tail follow the conversion during the switching of the furnace group, and are distinguished by the flow direction of aluminum liquid) to ensure safe casting.

[0026] S4.3 Ingot cooling crystallization; When casting hollow round ingots, cooling water is needed both inside and outside the ingot to help the ingot crystallize. After reaching thermal equilibrium, the ingot is separated from the crystallizer while cooling until it is cast to the corresponding length.

[0027] The ingot produced in this embodiment has a specification of Ф546×Ф335 and a thickness of only 105.5mm, which is a thin-walled hollow ingot. Therefore, the uniform distribution and stable supply of cooling water are very important. To achieve this goal, the cooling water of the core crystallizer and the outer ring crystallizer must be a separate waterway, and the water volume control can be changed at any time according to the process parameter requirements. The water flow of the core crystallizer and the external crystallizer is PID-regulated by the electric actuator on the pipeline.

[0028] S4.4 Clean up the accumulated slag; After the hollow rod casting is completed, there will be a lot of aluminum slag and gaps in the insulation cap, adapter plate, and graphite ring. To ensure that the next casting can start smoothly, these accumulated slag must be cleaned up in time and the corresponding damaged areas must be repaired.

[0029] In this embodiment, in order to facilitate maintenance, the modified crystallizer platform can be tilted 90°. Because its disk is much heavier than the original disk, the original hydraulic station cannot flip up the new disk. According to the lifting weight of the new disk, the motor power of the hydraulic station is increased to 5.5KW, the flow rate is increased to 30L / min, the system pressure is increased to 11MPa, and the cylinder diameter is increased from 90mm to 125mm. At the same time, in order to ensure that the tilting arms on both sides can move at the same time, a balancing valve is installed in the oil circuit.

[0030] The φ546 aluminum alloy hollow round ingot produced in this embodiment is sliced ​​and tested for macrostructure. Its cast structure characteristics are as follows: Figure 2 As shown, the homogenized tissue characteristics are Figure 3 As shown in the figure, there is no defect. The grain size is first-class under high magnification detection, the chemical composition is uniform, and all indicators meet customer needs. Customers give good feedback after use.

[0031] Example 2 - Production of aluminum alloy slab ingots; The difference from Example 1 is that: In the S4 casting process, only the casting mold needs to be replaced.

[0032] Example 3 - Production of solid round ingots of aluminum alloy; The difference from Example 1 is that: In the S4 casting process, only the casting mold needs to be replaced. It can be seen that the present invention not only casts large-sized aluminum alloy thin-walled hollow round ingots, but also the production process method is a technical improvement based on the original aluminum alloy flat ingot production line, which can greatly save the cost investment of newly built production lines. On this basis, it can also realize the production of aluminum alloy flat ingots, aluminum alloy hollow round ingots, and aluminum alloy solid round ingots in the same shaft, and products can be switched according to market and customer needs, which broadens the product variety of the production line, increases product added value, and enhances the company's market competitiveness.

Claims

1. A large-size aluminum alloy thin-wall hollow round ingot and a production method thereof, characterized in that: The method consists of the following steps: S1, ingredients; Directly use the high-temperature original aluminum liquid produced by the aluminum electrolytic cell for batching; S2, smelting; The prepared aluminum liquid is melted and stirred, during which the slag is removed, samples are taken for analysis, and additional materials are added and stirred when necessary, and secondary sampling and analysis are performed until the composition meets the requirements; S3, refining; The molten aluminum is allowed to stand after smelting, then filtered through a filter box, degassed in a degassing chamber, and then deep-bed filtered to ensure that the melt meets casting specifications; S4, casting; S4.1 Aluminum water enters the casting well; The main well + auxiliary well mode is adopted. The main well and the auxiliary well are sealed and connected through a culvert. At the same time, an overflow pipe is installed in the middle of the auxiliary well mouth. A float liquid level control system and a submersible pump are placed in the auxiliary well. S4.2 Casting temperature control; The temperature loss needs to be controlled from the outlet of the melting furnace to the inlet chute of the casting machine, and the temperature fluctuation range needs to be controlled between 0-10℃; The hollow ingot crystallizer platform adopts the method of aluminum liquid being fed at both ends for flow supply. The switching of casting between different furnace groups is completed by switching the position of the mobile transition chute. The water tray residual material at the end of casting is discharged by the method of head-in and tail-out. S4.3 Ingot cooling crystallization; When casting hollow round ingots, cooling water is placed inside and outside the ingot to help the ingot crystallize. After reaching thermal equilibrium, the ingot is separated from the crystallizer while cooling until it is cast to the corresponding length. S4.4 Clean up the accumulated slag; After the hollow rod casting is completed, the slag accumulated in the equipment should be cleaned in time and the corresponding damaged areas should be repaired.

2. A large-size aluminum alloy thin-wall hollow round ingot and a production method thereof as claimed in claim 1, characterized in that: The auxiliary shaft described in S4.1 is located 2 meters away from the main shaft, with a specification of 2500mm×3000mm. A 1700mm×700mm×2500mm steel rectangular culvert is sealed between the main shaft and the auxiliary shaft. At the same time, a Φ400 overflow pipe is installed in the middle position 1500mm downward from the auxiliary shaft opening.

3. A large-size aluminum alloy thin-wall hollow round ingot and a production method thereof as claimed in claim 1, characterized in that: In S4.3, the temperature fluctuation range of the molten aluminum from the outlet of the smelting furnace to the inlet launder of the casting machine is controlled between 0-10°C.

Images