High-strength rare earth aluminum alloy large-specification cast ingot and preparation method thereof

Abstract

The invention discloses a high-strength rare earth aluminum alloy large-size cast ingot and a preparation method thereof, and relates to the field of high-strength rare earth aluminum alloy large-size cast ingots and preparation methods thereof. The invention aims to solve the problem of low yield of cast ingots caused by difficulty in forming and coarse structure of high-strength aluminum alloy cast ingots under industrial conditions. The method comprises: burdening; smelting is conducted; casting is conducted; and homogenizing and annealing. The high-strength rare earth aluminum alloy large-size cast ingot prepared through the method is uniform in structure and small in equiaxed crystal structure; the solid hydrogen content of the cast ingot is less than 0.18 mu g / mg; and no metallurgical defect exists, and the yield of cast ingots can be increased to 100% from 30%. The method is used for preparing the high-strength rare earth aluminum alloy large-specification cast ingot.

Description

Technical Field

[0001] The invention relates to the field of high-strength rare earth aluminum alloy large-size ingot and a preparation method thereof. Background Art

[0002] With the progress of the times, the aerospace, shipbuilding, rail transportation and other industries are developing rapidly. The construction of spacecraft, large aircraft, large ships, etc., while the requirements for the comprehensive performance of materials are increasing, the size specifications of materials are also increasing. Therefore, it is imperative to develop and optimize the large-size ingots required for the manufacture of large-size structural parts. In addition, the expansion of ingot specifications is also beneficial to improving the production efficiency and reducing energy consumption in the material preparation process.

[0003] High-strength aluminum alloy materials have been widely used in load-bearing structural parts such as aerospace and ships due to their excellent comprehensive performance. However, the preparation of high-strength aluminum alloy ingots is often prone to casting cracks, metallurgical defects and other casting waste due to the high alloying components. In addition, in order to further improve the comprehensive performance of the alloy, the addition of rare earth element scandium makes the smelting, casting and ingot structure control of the ingot more difficult.

[0004] At present, large-scale high-strength rare earth aluminum alloy ingots are difficult to cast in semi-continuous casting due to the high degree of alloying, high crack tendency, and difficulty in casting. During the solidification process of large-scale ingots, due to the large difference in cooling rate between different regions, it is easy to cause non-homogeneous problems such as uneven structure, macro segregation, shrinkage / looseness, hot cracking and impurity enrichment. These non-homogeneous problems are difficult to eliminate in the subsequent processing process and may even lead to product scrapping. Adding heavy rare earth element scandium to aluminum alloy makes it more difficult to control the uniformity of melt elements. In addition, the thickness of large-scale ingots reaches 420mm and the width reaches 1620mm. During the casting process, the cooling rates of the edges and cores of the ingots are very different, which can easily cause the ingots to crack. At the same time, the slow cooling rate of the core of the ingot is very difficult to avoid the coarse primary phase containing Sc and give full play to the positive role of the Sc phase. Summary of the invention

[0005] The present invention aims to solve the problem that high-strength aluminum alloy ingots are difficult to shape and have coarse structures under industrial conditions, resulting in low ingot yield, and to provide a large-size high-strength rare earth aluminum alloy ingot and a preparation method thereof.

[0006] A large-sized ingot of high-strength rare earth aluminum alloy, wherein the mass percentage of each element of the large-sized ingot of high-strength rare earth aluminum alloy is 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 Si in the large-sized ingot are ≤0.18%, and Fe is ≤0.18%.

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

[0008] 1. Ingredients: weigh pure aluminum ingots, pure zinc ingots, pure magnesium ingots, aluminum-manganese master alloys, aluminum-scandium master alloys, aluminum-zirconium master alloys and aluminum-titanium master alloys according to the mass percentage of each element in the high-strength rare earth aluminum alloy large-size 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% and the balance Al;

[0009] 2. Melting: A. Melt the pure aluminum ingot, pure zinc ingot and aluminum-manganese master alloy weighed in step 1 into a melt. When the temperature of the melt reaches 800°C, add the aluminum-scandium master alloy, then perform electromagnetic stirring, heat to a temperature not lower than 800°C and keep warm for 15 minutes, then perform electromagnetic stirring for 10 minutes and stop stirring, heat to a temperature of 800°C, keep warm for 15 minutes, then perform electromagnetic stirring for 10 minutes and stop stirring, heat to a temperature not lower than 800°C, keep warm 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 melt temperature drops to 760°C, add the pure magnesium ingot and the aluminum-titanium master alloy, stir, then refine with Ar-Cl2 mixed gas, and let stand for 30 minutes to obtain an aluminum alloy melt;

[0010] 3. Casting: At the beginning of casting, the aluminum titanium boron wire grain refiner is uniformly melted into the aluminum alloy melt obtained in step 2 in the casting flow trough, and then casting is carried out at a temperature of 720°C to 740°C, a water pressure of 0.03MPa to 0.05MPa, and a speed of 40mm / min to 45mm / min to obtain an alloy ingot with a thickness of 420mm, a width of 1620mm, and a length of 5000mm to 6000mm;

[0011] 4. Homogenization annealing: the alloy ingot obtained in step 3 is charged into a furnace at room temperature, and a piezoelectric couple is used to monitor the temperature of the ingot. The temperature of the alloy ingot reaches 345-355°C, and is kept warm for 8 hours. The temperature is then changed to 480°C, and the temperature of the alloy ingot reaches 465-475°C. The temperature is kept warm for 24 hours to obtain a large-sized ingot of high-strength rare earth aluminum alloy.

[0012] The impurity elements in the large-size high-strength rare earth aluminum alloy ingot of the present invention are derived from the aluminum ingot, the impurities Si≤0.18%, Fe≤0.18%, other single impurities≤0.05%, and the total impurities≤0.15%. The impurities within this range have no effect on the molding and quality of the large-size ingot.

[0013] Beneficial effects of the present invention:

[0014] The high-strength rare earth aluminum alloy large-scale ingot preparation technology of the present invention provides a new large-scale high-strength rare earth aluminum alloy ingot preparation technology and preparation method. The ingot yield rate is greatly improved, filling the domestic gap. The high-strength rare earth aluminum alloy large-scale ingot preparation technology of the present invention thoroughly solves the problems of low ingot yield rate such as difficult molding of high-strength aluminum alloy ingots and coarse structure under industrial conditions. The prepared high-strength rare earth aluminum alloy large-scale ingot has uniform structure and fine equiaxed crystal structure; the ingot solid hydrogen content is less than 0.18μg / mg; there is no metallurgical defect, which can increase the ingot yield rate from 30% to 100%.

[0015] The invention is used for preparing large-size high-strength rare earth aluminum alloy ingots. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The metallographic structure diagram of the large-sized high-strength rare earth aluminum alloy ingot prepared in this embodiment;

[0017] Figure 2 This is the metallographic structure diagram (enlarged) of the large-sized ingot of high-strength rare earth aluminum alloy prepared in this embodiment. DETAILED DESCRIPTION

[0018] Specific implementation method 1: This implementation method is a large-sized ingot of high-strength rare earth aluminum alloy, and the mass percentage of each element in the large-sized ingot of high-strength rare earth aluminum alloy is 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 remainder Al; the impurities Si≤0.18% and Fe≤0.18% in the large-sized ingot.

[0019] Specific implementation method 2: This implementation method is a method for preparing a large-size high-strength rare earth aluminum alloy ingot, which is specifically carried out in the following steps:

[0020] 1. Ingredients: weigh pure aluminum ingots, pure zinc ingots, pure magnesium ingots, aluminum-manganese master alloys, aluminum-scandium master alloys, aluminum-zirconium master alloys and aluminum-titanium master alloys according to the mass percentage of each element in the high-strength rare earth aluminum alloy large-size 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% and the balance Al;

[0021] 2. Melting: A. Melt the pure aluminum ingot, pure zinc ingot and aluminum-manganese master alloy weighed in step 1 into a melt. When the temperature of the melt reaches 800°C, add the aluminum-scandium master alloy, then perform electromagnetic stirring, heat to a temperature not lower than 800°C and keep warm for 15 minutes, then perform electromagnetic stirring for 10 minutes and stop stirring, heat to a temperature of 800°C, keep warm for 15 minutes, then perform electromagnetic stirring for 10 minutes and stop stirring, heat to a temperature not lower than 800°C, keep warm 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 melt temperature drops to 760°C, add the pure magnesium ingot and the aluminum-titanium master alloy, stir, then refine with Ar-Cl2 mixed gas, and let stand for 30 minutes to obtain an aluminum alloy melt;

[0022] 3. Casting: At the beginning of casting, the aluminum titanium boron wire grain refiner is uniformly melted into the aluminum alloy melt obtained in step 2 in the casting flow trough, and then casting is carried out at a temperature of 720°C to 740°C, a water pressure of 0.03MPa to 0.05MPa, and a speed of 40mm / min to 45mm / min to obtain an alloy ingot with a thickness of 420mm, a width of 1620mm, and a length of 5000mm to 6000mm;

[0023] 4. Homogenization annealing: the alloy ingot obtained in step 3 is charged into a furnace at room temperature, and a piezoelectric couple is used to monitor the temperature of the ingot. The temperature of the alloy ingot reaches 345-355°C, and is kept warm for 8 hours. The temperature is then changed to 480°C, and the temperature of the alloy ingot reaches 465-475°C. The temperature is kept warm for 24 hours to obtain a large-sized ingot of high-strength rare earth aluminum alloy.

[0024] Specific implementation method three: This implementation method is different from specific implementation method two in that: Step 1 is to prepare the ingredients according to the mass percentage of each element in the 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% and the balance Al. The rest is the same as specific implementation method two.

[0025] Specific embodiment 4: This embodiment differs from specific embodiment 2 or 3 in that the mass content of scandium in the aluminum-scandium master alloy in step 1 is 1.8% to 2.2%. Other aspects are the same as specific embodiment 2 or 3.

[0026] Specific embodiment 5: This embodiment differs from specific embodiments 2 to 4 in that: step 2 is to refine the aluminum alloy melt to a hydrogen content of ≤ 0.15 mL per 100 g. The rest is the same as specific embodiments 2 to 4.

[0027] Specific implementation example 6: This implementation example is different from specific implementation examples 2 to 5 in that: after adding the pure magnesium ingot and the aluminum-titanium master alloy in step 2, stirring is performed for 3 minutes. The rest is the same as specific implementation examples 2 to 5.

[0028] Specific embodiment 7: This embodiment is different from specific embodiments 2 to 6 in that the volume ratio of Ar to Cl2 in the Ar-Cl2 mixed gas in step 2 is (31-33.5): 1. Other aspects are the same as those of specific embodiments 2 to 6.

[0029] Specific embodiment 8: This embodiment differs from specific embodiments 2 to 7 in that: in step 3, the melting speed of the aluminum titanium boron wire grain refiner is 400 mm / min to 500 mm / min. The rest is the same as specific embodiments 2 to 7.

[0030] Specific embodiment 9: This embodiment is different from specific embodiments 2 to 8 in that: step 3 uses double-stage ceramic sheet filtration, the mesh number of the ceramic filter sheet in the first filter furnace is 30ppi, and the mesh number of the ceramic filter sheet in the second filter furnace is 50ppi. The rest is the same as specific embodiments 2 to 8.

[0031] Specific embodiment 10: This embodiment differs from specific embodiments 2 to 9 in that step 3 is performed under the conditions of a temperature of 720°C, a water pressure of 0.04 MPa, and a speed of 42 mm / min. The rest is the same as specific embodiments 2 to 9.

[0032] The content of the present invention is not limited to the content of the above-mentioned embodiments. The combination of one or several specific embodiments can also achieve the purpose of the invention.

[0033] Example:

[0034] A method for preparing a large-size high-strength rare earth aluminum alloy ingot is specifically carried out according to the following steps:

[0035] 1. Ingredients: weigh pure aluminum ingots, pure zinc ingots, pure magnesium ingots, aluminum-manganese master alloys, aluminum-scandium master alloys, aluminum-zirconium master alloys and aluminum-titanium master alloys according to the mass percentage of each element in the high-strength rare earth aluminum alloy large-size ingot: Zn: 5.4%, Mg: 2.0%, Mn: 0.3%, Sc: 0.15%, Zr: 0.13%, Ti: 0.03% and the balance Al;

[0036] 2. Melting: A. Melt the pure aluminum ingot, pure zinc ingot and aluminum-manganese master alloy weighed in step 1 into a melt. When the temperature of the melt reaches 800°C, add the aluminum-scandium master alloy, then perform electromagnetic stirring, heat to a temperature not lower than 800°C and keep warm for 15 minutes, then perform electromagnetic stirring for 10 minutes and stop stirring, heat to a temperature of 800°C, keep warm for 15 minutes, then perform electromagnetic stirring for 10 minutes and stop stirring, heat to a temperature not lower than 800°C, keep warm 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 melt temperature drops to 760°C, add the pure magnesium ingot and the aluminum-titanium master alloy, stir for 3 minutes, and then refine with Ar-Cl2 mixed gas to a hydrogen content of ≤0.15mL per 100 grams of melt, let stand for 30 minutes to obtain an aluminum alloy melt; the volume ratio of Ar and Cl2 in the Ar-Cl2 mixed gas is (31-33.5):1;

[0037] 3. Casting: Clean the crystallizer and place the aluminum-titanium-boron wire grain refiner in the flow channel at the outlet of the filter box. Use two-stage ceramic sheets for filtration in the flow channel (the mesh number of the ceramic filter sheet in the first-stage filtration furnace is 30ppi, and the mesh number of the ceramic filter sheet in the second-stage filtration furnace is 50ppi). While casting, insert two aluminum-titanium-boron wires into the flow channel at the same time to make the elements in the aluminum-titanium-boron grain refiner evenly melt into the aluminum alloy melt. The feed speed of the aluminum-titanium-boron wire grain refiner is 450mm / min, and then turn on the Alpur double-rotor online degassing device. Casting is carried out under the conditions of temperature of 720°C, water pressure of 0.04MPa, and speed of 42mm / min to obtain an alloy ingot with a thickness of 420mm, a width of 1620mm, and a length of 6000mm.

[0038] 4. Homogenization annealing: the alloy ingot obtained in step 3 is charged into a furnace at room temperature, and a piezoelectric couple is used to monitor the temperature of the ingot. The temperature of the alloy ingot reaches 350°C±5°C, and is kept warm for 8 hours. The temperature is then changed to 480°C, and the temperature of the alloy ingot reaches 470°C±5°C. The temperature is kept warm for 24 hours to obtain a large-sized ingot of high-strength rare earth aluminum alloy.

[0039] Figure 1 The metallographic structure diagram of the large-sized high-strength rare earth aluminum alloy ingot prepared in this embodiment;

[0040] Figure 2 This is the metallographic structure diagram (enlarged) of the large-sized ingot of high-strength rare earth aluminum alloy prepared in this embodiment.

[0041] The large-scale high-strength rare earth aluminum alloy ingot prepared in this embodiment has a uniform structure 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 large-size high-strength rare earth aluminum alloy ingot, characterized in that The mass percentage of each element in the large-sized high-strength rare earth aluminum alloy ingot is Zn: 4.5% to 7.0%, Mg: 1.5% to 3.0%, Mn: 0.10% to 0.40%, Sc: 0.10% to 0.35%, Zr: 0.11% to 0.15%, Ti: 0.02% to 0.10% and the balance Al; the impurities Si in the large-sized ingot are ≤0.18% and Fe ≤0.18%.

2. The method for preparing a large-sized high-strength rare earth aluminum alloy ingot according to claim 1, characterized in that The method is specifically carried out in the following steps:

1. Ingredients: weigh pure aluminum ingots, pure zinc ingots, pure magnesium ingots, aluminum-manganese master alloys, aluminum-scandium master alloys, aluminum-zirconium master alloys and aluminum-titanium master alloys according to the mass percentage of each element in the high-strength rare earth aluminum alloy large-size 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% and the balance Al; 2. Melting: A. Melt the pure aluminum ingot, pure zinc ingot and aluminum-manganese master alloy weighed in step 1 into a melt. When the temperature of the melt reaches 800°C, add the aluminum-scandium master alloy, then perform electromagnetic stirring, heat to a temperature not lower than 800°C and keep warm for 15 minutes, then perform electromagnetic stirring for 10 minutes and stop stirring, heat to a temperature of 800°C, keep warm for 15 minutes, then perform electromagnetic stirring for 10 minutes and stop stirring, heat to a temperature not lower than 800°C, keep warm 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 melt temperature drops to 760°C, add the pure magnesium ingot and the aluminum-titanium master alloy, stir, then refine with Ar-Cl2 mixed gas, and let stand for 30 minutes to obtain an aluminum alloy melt; 3. Casting: At the beginning of casting, the aluminum titanium boron wire grain refiner is uniformly melted into the aluminum alloy melt obtained in step 2 in the casting flow trough, and then casting is carried out at a temperature of 720°C to 740°C, a water pressure of 0.03MPa to 0.05MPa, and a speed of 40mm / min to 45mm / min to obtain an alloy ingot with a thickness of 420mm, a width of 1620mm, and a length of 5000mm to 6000mm; 4. Homogenization annealing: the alloy ingot obtained in step 3 is charged into a furnace at room temperature, and a piezoelectric couple is used to monitor the temperature of the ingot. The temperature of the alloy ingot reaches 345-355°C, and is kept warm for 8 hours. The temperature is then changed to 480°C, and the temperature of the alloy ingot reaches 465-475°C. The temperature is kept warm for 24 hours to obtain a large-sized ingot of high-strength rare earth aluminum alloy.

3. The method for preparing a large-sized high-strength rare earth aluminum alloy ingot according to claim 2, characterized in that Step 1: prepare the ingredients according to the mass percentage of each element in the large-size ingot of high-strength rare earth aluminum alloy: Zn: 5.4%, Mg: 2.0%, Mn: 0.3%, Sc: 0.15%, Zr: 0.13%, Ti: 0.03% and the balance Al.

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

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

6. The method for preparing a large-sized high-strength rare earth aluminum alloy ingot according to claim 2, characterized in that Step 2: Add pure magnesium ingot and aluminum-titanium master alloy and stir for 3 minutes.

7. The method for preparing a large-sized high-strength rare earth aluminum alloy ingot according to claim 2, characterized in that In step 2, the volume ratio of Ar to Cl2 in the Ar-Cl2 mixed gas is (31-33.5):

1.

8. The method for preparing a large-sized high-strength rare earth aluminum alloy ingot according to claim 2, characterized in that Step 3: The melting speed of the aluminum titanium boron wire grain refiner is 400 mm / min to 500 mm / min.

9. The method for preparing a large-sized high-strength rare earth aluminum alloy ingot according to claim 2, characterized in that Step three uses double-stage ceramic filter, the mesh number of the ceramic filter in the first-stage filter furnace is 30ppi, and the mesh number of the ceramic filter in the second-stage filter furnace is 50ppi.

10. The method for preparing a large-sized high-strength rare earth aluminum alloy ingot according to claim 2, characterized in that Step 3: Casting is carried out at a temperature of 720°C, a water pressure of 0.04MPa, and a speed of 42mm / min.

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