A high-strength rare earth aluminum alloy large-size ingot and a preparation method thereof

Abstract

The application relates to a high-strength rare earth aluminum alloy large-size ingot and a preparation method thereof, and belongs to the field of high-strength rare earth aluminum alloy large-size ingots and preparation methods thereof. The application aims to solve the problems of difficult forming of the high-strength aluminum alloy ingot, coarse structure and low product yield of the ingot under industrial conditions. The method comprises the following steps: ingredient preparation, smelting, casting and homogenizing annealing. The high-strength rare earth aluminum alloy large-size ingot prepared by the application has the advantages of uniform and fine equiaxed crystal structure, solid hydrogen content less than 0.18 mu g / mg, no metallurgical defects and the like, and the product yield of the ingot can be increased from 30% to 100%. The application is used for preparing the high-strength rare earth aluminum alloy large-size ingot.

Description

Technical Field

[0001] This invention relates to the field of large-scale casting of high-strength rare earth aluminum alloy and its preparation method. Background Technology

[0002] With the progress of the times, industries such as aerospace, shipbuilding, and rail transportation are developing rapidly. The construction of spacecraft, large aircraft, and large ships not only increases the requirements for the comprehensive performance of materials, but also requires larger material dimensions. Therefore, it is imperative to develop and optimize large-size ingots required for the manufacturing of large-size structural components. In addition, the expansion of ingot dimensions is also beneficial to improving the production efficiency and reducing energy consumption in the material preparation process.

[0003] High-strength aluminum alloys have been widely used in load-bearing structural components in aerospace, shipbuilding, and other fields due to their excellent comprehensive properties. However, the preparation of high-strength aluminum alloy ingots is often difficult due to the high alloying composition, which easily leads to casting defects such as ingot cracking and metallurgical defects. In addition, the addition of the rare earth element scandium to further improve the comprehensive properties of the alloy makes the melting, casting, and microstructure control of the ingot even more challenging.

[0004] Currently, large-size high-strength rare-earth aluminum alloy ingots face challenges in semi-continuous casting due to their high alloying degree, strong cracking tendency, and difficult casting process. During solidification, the large ingots exhibit significant differences in cooling rates between different regions, easily leading to heterogeneous issues such as inhomogeneous microstructure, macroscopic segregation, shrinkage cavities / porosity, hot cracking, and impurity enrichment. These heterogeneous problems are difficult to eliminate in subsequent processing and can even result in product scrap. Adding the heavy rare-earth element scandium to aluminum alloys further complicates the control of melt elemental homogeneity. Furthermore, the large ingot dimensions, reaching thicknesses of 420mm and widths of 1620mm, result in significant differences in cooling rates between the edges and the core during casting, greatly increasing the risk of ingot cracking. Simultaneously, the slower cooling rate in the ingot core makes it difficult to avoid coarse primary Sc-containing phases and fully utilize the positive effects of Sc-containing phases, posing a significant challenge. Summary of the Invention

[0005] The present invention aims to solve the problems of difficult forming of high-strength aluminum alloy ingots and coarse microstructure under industrial conditions, resulting in low ingot yield, and provides a large-size high-strength rare earth aluminum alloy ingot and its preparation method.

[0006] A high-strength rare-earth aluminum alloy large-size ingot, wherein the mass percentage of each element in the high-strength rare-earth aluminum alloy large-size ingot is composed of Zn: 4.5%–7.0%, Mg: 1.5%–3.0%, Mn: 0.10%–0.40%, Sc: 0.10%–0.35%, Zr: 0.11%–0.15%, Ti: 0.02%–0.10%, and the balance Al; the impurities in the large-size ingot are Si≤0.18% and Fe≤0.18%.

[0007] The method for preparing a large-scale high-strength rare-earth aluminum alloy ingot is specifically carried out according to the following steps:

[0008] I. Batching: Weigh out pure aluminum ingots, pure zinc ingots, pure magnesium ingots, aluminum-manganese master alloy, aluminum-scandium master alloy, aluminum-zirconium master alloy, and aluminum-titanium master alloy according to the following mass percentages of each element in the large-size high-strength rare earth aluminum alloy ingot: Zn: 4.5-7.0%, Mg: 1.5-3.0%, Mn: 0.10-0.40%, Sc: 0.10-0.35%, Zr: 0.11-0.15%, Ti: 0.02-0.10%, with the balance Al.

[0009] II. Smelting: A. Smelt the pure aluminum ingots, pure zinc ingots, and aluminum-manganese master alloy weighed in step one into a molten liquid. When the temperature of the molten liquid reaches 800℃, add the aluminum-scandium master alloy, then perform electromagnetic stirring, heat to a temperature not lower than 800℃ and hold for 15 minutes, then perform electromagnetic stirring for another 10 minutes and stop stirring, heat to a temperature that rises back to 800℃ and hold for 15 minutes, then perform electromagnetic stirring for another 10 minutes and stop stirring, heat to a temperature not lower than 800℃ and hold for 15 minutes, then add the aluminum-zirconium master alloy and perform electromagnetic stirring for 10 minutes to obtain a melt; B. Cool the melt obtained in step A. When the temperature of the melt drops to 760℃, add pure magnesium ingots and aluminum-titanium master alloy, stir, then refine with Ar-Cl2 mixed gas, and let stand for 30 minutes to obtain an aluminum alloy molten liquid;

[0010] III. Casting: At the beginning of casting, the aluminum-titanium-boron wire grain refiner is uniformly melted into the aluminum alloy melt obtained in step two in the casting channel. Then, casting is carried out under the conditions of temperature 720℃~740℃, water pressure 0.03MPa~0.05MPa, and speed 40mm / min~45mm / min to obtain an alloy ingot with a thickness of 420mm, a width of 1620mm, and a length of 5000mm~6000mm.

[0011] IV. Homogenization Annealing: The alloy ingot obtained in step 3 is loaded into the furnace at room temperature. The ingot temperature is monitored by a piezoelectric couple. When the alloy ingot temperature reaches 345-355℃, it is held for 8 hours. Then, the temperature is turned to a constant 480℃. When the alloy ingot temperature reaches 465-475℃, it is held for 24 hours to obtain a large-size high-strength rare earth aluminum alloy ingot.

[0012] The impurity elements in the large-size high-strength rare earth aluminum alloy ingots of this invention are derived from aluminum ingots. The impurities are Si≤0.18%, Fe≤0.18%, and other individual impurities≤0.05%, with a total impurity of ≤0.15%. Impurities within this range have no impact on the forming and quality of large-size ingots.

[0013] Beneficial effects of this invention:

[0014] This invention provides a novel technology and method for preparing large-scale high-strength rare-earth aluminum alloy ingots. The ingot yield is significantly improved, filling a gap in domestic technology. This invention completely solves the problems of low ingot yield caused by difficulties in forming high-strength aluminum alloy ingots and coarse microstructure under industrial conditions. The prepared large-scale high-strength rare-earth aluminum alloy ingots have a uniform and fine equiaxed grain structure; the solid hydrogen content of the ingot is less than 0.18 μg / mg; and there are no metallurgical defects, increasing the ingot yield from 30% to 100%.

[0015] This invention is used to prepare large-size ingots of high-strength rare earth aluminum alloy. Attached Figure Description

[0016] Figure 1 Metallographic diagram of the large-scale high-strength rare-earth aluminum alloy ingot prepared in this embodiment;

[0017] Figure 2 The metallographic structure of the large-scale high-strength rare earth aluminum alloy ingot prepared in this embodiment is enlarged. Detailed Implementation

[0018] Specific Implementation Method 1: This implementation method describes a large-scale high-strength rare-earth aluminum alloy ingot. The mass percentage of each element in the large-scale high-strength rare-earth aluminum alloy ingot is composed of Zn: 4.5-7.0%, Mg: 1.5%-3.0%, Mn: 0.10%-0.40%, Sc: 0.10%-0.35%, Zr: 0.11%-0.15%, Ti: 0.02%-0.10%, and the balance Al. The impurities in the large-scale ingot are Si≤0.18% and Fe≤0.18%.

[0019] Specific Implementation Method Two: This implementation method provides a method for preparing large-scale high-strength rare-earth aluminum alloy ingots, specifically following these steps:

[0020] I. Batching: Weigh out pure aluminum ingots, pure zinc ingots, pure magnesium ingots, aluminum-manganese master alloy, aluminum-scandium master alloy, aluminum-zirconium master alloy, and aluminum-titanium master alloy according to the following mass percentages of each element in the large-size high-strength rare earth aluminum alloy ingot: Zn: 4.5-7.0%, Mg: 1.5-3.0%, Mn: 0.10-0.40%, Sc: 0.10-0.35%, Zr: 0.11-0.15%, Ti: 0.02-0.10%, with the balance Al.

[0021] II. Smelting: A. Smelt the pure aluminum ingots, pure zinc ingots, and aluminum-manganese master alloy weighed in step one into a molten liquid. When the temperature of the molten liquid reaches 800℃, add the aluminum-scandium master alloy, then perform electromagnetic stirring, heat to a temperature not lower than 800℃ and hold for 15 minutes, then perform electromagnetic stirring for another 10 minutes and stop stirring, heat to a temperature that rises back to 800℃ and hold for 15 minutes, then perform electromagnetic stirring for another 10 minutes and stop stirring, heat to a temperature not lower than 800℃ and hold for 15 minutes, then add the aluminum-zirconium master alloy and perform electromagnetic stirring for 10 minutes to obtain a melt; B. Cool the melt obtained in step A. When the temperature of the melt drops to 760℃, add pure magnesium ingots and aluminum-titanium master alloy, stir, then refine with Ar-Cl2 mixed gas, and let stand for 30 minutes to obtain an aluminum alloy molten liquid;

[0022] III. Casting: At the beginning of casting, the aluminum-titanium-boron wire grain refiner is uniformly melted into the aluminum alloy melt obtained in step two in the casting channel. Then, casting is carried out under the conditions of temperature 720℃~740℃, water pressure 0.03MPa~0.05MPa, and speed 40mm / min~45mm / min to obtain an alloy ingot with a thickness of 420mm, a width of 1620mm, and a length of 5000mm~6000mm.

[0023] IV. Homogenization Annealing: The alloy ingot obtained in step 3 is loaded into the furnace at room temperature. The ingot temperature is monitored by a piezoelectric couple. When the alloy ingot temperature reaches 345-355℃, it is held for 8 hours. Then, the temperature is turned to a constant 480℃. When the alloy ingot temperature reaches 465-475℃, it is held for 24 hours to obtain a large-size high-strength rare earth aluminum alloy ingot.

[0024] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method Two in that: Step One involves preparing the materials according to the following mass percentages of each element in a large-scale high-strength rare earth aluminum alloy ingot: Zn: 5.4%, Mg: 2.0%, Mn: 0.3%, Sc: 0.15%, Zr: 0.13%, Ti: 0.03%, with the balance being Al. Everything else is the same as in Specific Implementation Method Two.

[0025] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Two or Three in that the scandium content in the aluminum-scandium master alloy in step one is 1.8% to 2.2% by mass. Everything else is the same as in Specific Implementation Method Two or Three.

[0026] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods Two to Four in that: in step two, the aluminum alloy melt is refined until the hydrogen content is ≤0.15mL per 100g. Everything else is the same as in Specific Implementation Methods Two to Four.

[0027] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods Two to Five in that: after adding pure magnesium ingots and aluminum-titanium master alloy in step two, stir for 3 minutes. Everything else is the same as in Specific Implementation Methods Two to Five.

[0028] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods Two to Six in that the volume ratio of Ar to Cl2 in the Ar-Cl2 mixed gas described in step two is (31-33.5):1. Everything else is the same as in Specific Implementation Methods Two to Six.

[0029] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods Two to Seven in that the melting rate of the aluminum-titanium-boron wire grain refiner in step three is 400 mm / min to 500 mm / min. Everything else is the same as in Specific Implementation Methods Two to Seven.

[0030] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods Two to Eight in that step three employs a two-stage ceramic filter. The ceramic filter in the first-stage filtration furnace has a mesh size of 30 ppi, and the ceramic filter in the second-stage filtration furnace has a mesh size of 50 ppi. Everything else is the same as in Specific Implementation Methods Two to Eight.

[0031] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods Two to Nine in that step three is carried out under the conditions of a temperature of 720℃, a water pressure of 0.04MPa, and a speed of 42mm / min. Everything else is the same as in Specific Implementation Methods Two to Nine.

[0032] The scope of this invention is not limited to the above-described embodiments; a combination of one or more specific embodiments can also achieve the purpose of the invention.

[0033] Example:

[0034] A method for preparing large-size high-strength rare-earth aluminum alloy ingots, specifically comprising the following steps:

[0035] I. Batching: Weigh out pure aluminum ingots, pure zinc ingots, pure magnesium ingots, aluminum-manganese master alloy, aluminum-scandium master alloy, aluminum-zirconium master alloy, and aluminum-titanium master alloy according to the mass percentage of each element in the large-size high-strength rare earth aluminum alloy ingot: Zn: 5.4%, Mg: 2.0%, Mn: 0.3%, Sc: 0.15%, Zr: 0.13%, Ti: 0.03%, and the balance Al.

[0036] II. Smelting: A. Smelt the pure aluminum ingots, pure zinc ingots, and aluminum-manganese master alloy weighed in step one into a molten liquid. When the temperature of the molten liquid reaches 800℃, add the aluminum-scandium master alloy, then perform electromagnetic stirring. Heat to a temperature not lower than 800℃ and hold for 15 minutes, then perform electromagnetic stirring for another 10 minutes and stop stirring. Heat to a temperature that rises back to 800℃ and hold for 15 minutes, then perform electromagnetic stirring for another 10 minutes and stop stirring. Heat to a temperature not lower than 800℃ and hold for 15 minutes, then add the aluminum-zirconium master alloy and perform electromagnetic stirring for 10 minutes to obtain a melt; B. Cool the melt obtained in step A. When the temperature of the melt drops to 760℃, add pure magnesium ingots and aluminum-titanium master alloy, stir for 3 minutes, then refine with Ar-Cl2 mixed gas until the hydrogen content in 100 grams of melt is ≤0.15 mL, let stand for 30 minutes to obtain an aluminum alloy molten liquid; the volume ratio of Ar to Cl2 in the Ar-Cl2 mixed gas is (31~33.5):1;

[0037] III. Casting: Clean the crystallizer and place the aluminum-titanium-boron wire grain refiner in the flow channel at the outlet of the filter box. The flow channel uses a two-stage ceramic filter (the ceramic filter in the first-stage filter furnace has a mesh size of 30ppi, and the ceramic filter in the second-stage filter furnace has a mesh size of 50ppi). While casting, insert two aluminum-titanium-boron wires into the flow channel to ensure that the elements in the aluminum-titanium-boron grain refiner are uniformly melted into the aluminum alloy melt. The feed rate of the aluminum-titanium-boron wire grain refiner is 450mm / min. Then, turn on the Alpur dual-rotor online degassing device and cast under the conditions of temperature 720℃, water pressure 0.04MPa, and speed 42mm / min to obtain an alloy ingot with a thickness of 420mm, a width of 1620mm, and a length of 6000mm.

[0038] IV. Homogenization Annealing: The alloy ingot obtained in step 3 is loaded into the furnace at room temperature. The ingot temperature is monitored by a piezoelectric couple. When the alloy ingot temperature reaches 350℃±5℃, it is held for 8 hours. Then, the temperature is turned to a constant 480℃. When the alloy ingot temperature reaches 470℃±5℃, it is held for 24 hours to obtain a large-size high-strength rare earth aluminum alloy ingot.

[0039] Figure 1 Metallographic diagram of the large-scale high-strength rare-earth aluminum alloy ingot prepared in this embodiment;

[0040] Figure 2 The metallographic structure of the large-scale high-strength rare earth aluminum alloy ingot prepared in this embodiment is enlarged.

[0041] The high-strength rare earth aluminum alloy large-size ingot prepared in this embodiment has a uniform and fine equiaxed crystal structure; the solid hydrogen content of the ingot is less than 0.18 μg / mg; and there are no metallurgical defects.

Claims

1. A method for preparing large-scale high-strength rare-earth aluminum alloy ingots, characterized in that... This method is specifically carried out in the following steps: I. Batching: Weigh out pure aluminum ingots, pure zinc ingots, pure magnesium ingots, aluminum-manganese master alloy, aluminum-scandium master alloy, aluminum-zirconium master alloy, and aluminum-titanium master alloy according to the mass percentage of each element in the large-size high-strength rare earth aluminum alloy ingot: Zn: 5.4%, Mg: 2.0%, Mn: 0.3%, Sc: 0.15%, Zr: 0.13%, Ti: 0.03%, and the balance Al. II. Smelting: A. Smelt the pure aluminum ingots, pure zinc ingots, and aluminum-manganese master alloy weighed in step one into a molten liquid. When the temperature of the molten liquid reaches 800℃, add the aluminum-scandium master alloy, then perform electromagnetic stirring, heat to a temperature not lower than 800℃ and hold for 15 minutes, then perform electromagnetic stirring for another 10 minutes and stop stirring, heat to a temperature that rises back to 800℃ and hold for 15 minutes, then perform electromagnetic stirring for another 10 minutes and stop stirring, heat to a temperature not lower than 800℃ and hold for 15 minutes, then add the aluminum-zirconium master alloy and perform electromagnetic stirring for 10 minutes to obtain a melt; B. Cool the melt obtained in step A. When the temperature of the melt drops to 760℃, add pure magnesium ingots and aluminum-titanium master alloy, stir, then refine with Ar-Cl2 mixed gas, and let stand for 30 minutes to obtain an aluminum alloy molten liquid; III. Casting: At the beginning of casting, the aluminum-titanium-boron wire grain refiner is uniformly melted into the aluminum alloy melt obtained in step two in the casting channel. Then, casting is carried out under the conditions of temperature 720℃~740℃, water pressure 0.03MPa~0.05MPa, and speed 40mm / min~45mm / min to obtain an alloy ingot with a thickness of 420mm, a width of 1620mm, and a length of 5000mm~6000mm. IV. Homogenization Annealing: The alloy ingot obtained in step 3 is loaded into the furnace at room temperature. The ingot temperature is monitored by a piezoelectric couple. When the alloy ingot temperature reaches 345-355℃, it is held for 8 hours. Then, the temperature is turned to a constant 480℃. When the alloy ingot temperature reaches 465-475℃, it is held for 24 hours to obtain a large-size high-strength rare earth aluminum alloy ingot. Step 3 employs a two-stage ceramic filter system, with the ceramic filter in the first-stage filtration furnace having a mesh size of 30ppi and the ceramic filter in the second-stage filtration furnace having a mesh size of 50ppi.

2. The method for preparing a large-scale high-strength rare-earth aluminum alloy ingot according to claim 1, characterized in that... In step one, the scandium content in the aluminum-scandium master alloy is 1.8% to 2.2% by mass.

3. The method for preparing a large-scale high-strength rare-earth aluminum alloy ingot according to claim 1, characterized in that... Step 2: Refine until the hydrogen content in every 100 grams of aluminum alloy melt is ≤0.15 mL.

4. The method for preparing a large-scale high-strength rare-earth aluminum alloy ingot according to claim 1, characterized in that... After adding pure magnesium ingots and aluminum-titanium master alloy in step two, stir for 3 minutes.

5. The method for preparing a large-scale high-strength rare-earth aluminum alloy ingot according to claim 1, characterized in that... In step two, the volume ratio of Ar to Cl2 in the Ar-Cl2 mixed gas is (31-33.5):

1.

6. The method for preparing a large-scale high-strength rare-earth aluminum alloy ingot according to claim 1, characterized in that... Step 3: The melting rate of the aluminum-titanium-boron wire grain refiner is 400 mm / min to 500 mm / min.

7. The method for preparing a large-scale high-strength rare-earth aluminum alloy ingot according to claim 1, characterized in that... Step 3 involves casting at a temperature of 720℃, a water pressure of 0.04MPa, and a speed of 42mm / min.

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