Round cast ingot for ultrahigh-strength aluminum rare earth alloy profile and preparation method of round cast ingot

Abstract

The invention relates to a circular cast ingot for an ultrahigh-strength aluminum rare earth alloy profile and a preparation method of the circular cast ingot, in particular to the circular cast ingot for the ultrahigh-strength aluminum rare earth alloy profile and the preparation method of the circular cast ingot. The problem that a traditional aluminum alloy material cannot meet the comprehensive performance requirements of ultrahigh strength (750MPa and above), light weight, corrosion resistance and low cost at the same time is solved. The aluminum alloy comprises, by mass, less than or equal to 0.20% of Si, less than or equal to 0.20% of Fe, 10.00%-11.50% of Zn, 2.50%-3.50% of Mg, 1.10%-1.80% of Cu, 0.08%-0.15% of Zr, 0.03%-0.35% of Yb, less than or equal to 0.10% of single impurities, less than or equal to 0.20% of total impurities and the balance Al. The method comprises the following steps: 1, burdening; 2, smelting; and 3, casting. The material selection range of aluminum profiles for aerospace, ships and other equipment can be widened.

Description

Technical Field

[0001] This invention specifically relates to a round ingot for ultra-high strength aluminum rare earth alloy profiles and its preparation method. Background Technology

[0002] In modern industry, the development of high-end equipment such as aerospace and ships has placed increasingly stringent demands on material performance. During their service, these equipment not only require materials with ultra-high strength to withstand complex loads and stresses, but also need to meet lightweight requirements to improve operational efficiency and reduce energy consumption. At the same time, excellent corrosion resistance is key to ensuring the long-term stable operation of the equipment in harsh environments such as the ocean and high altitudes, while low cost is an important prerequisite for realizing the large-scale application of materials and promoting the industrialization of equipment.

[0003] Aluminum alloys, with their low density, high specific strength, and good machinability, have long held an important position in aerospace, shipbuilding, and other fields. However, as equipment develops towards higher speeds, larger sizes, and greater precision, traditional aluminum alloys are gradually showing performance bottlenecks. Existing aluminum alloy materials struggle to simultaneously meet the comprehensive requirements of ultra-high strength (such as 750 MPa and above), lightweight, corrosion resistance, and low cost. Under extreme operating conditions, their mechanical and corrosion resistance properties often fail to meet the design standards of next-generation equipment, which to some extent limits further improvements in equipment performance.

[0004] my country is a major rare earth resource country, possessing abundant and unique rare earth reserves, which provides a unique advantage for developing new high-performance materials. Due to their special electronic structure and chemical properties, rare earth elements can play a significant modifying role in aluminum alloys, such as refining grains, inhibiting precipitate growth, and improving the strength and corrosion resistance of alloys. Therefore, fully utilizing this resource advantage and independently developing novel rare earth aluminum alloys with original characteristics has become an important way to break through the limitations of traditional material performance and improve the overall performance of materials.

[0005] Against this backdrop, the development of 750MPa-grade ultra-high strength rare-earth aluminum alloy profiles is of great significance for broadening the selection range of aluminum profiles used in my country's aerospace, shipbuilding, and other equipment. As the basic raw material for preparing high-performance aluminum profiles, the quality of round ingots directly affects subsequent rolling, extrusion, and other processing processes, as well as the performance of the final profile. Therefore, researching and developing round ingots suitable for 750MPa ultra-high strength rare-earth aluminum alloy profiles and their preparation methods is a key link in realizing the industrial application of this type of high-performance material and meeting the material needs of high-end equipment. This has significant practical and strategic value for promoting the development of my country's high-end equipment manufacturing industry. Summary of the Invention

[0006] The present invention aims to solve the problem that traditional aluminum alloy materials cannot simultaneously meet the comprehensive performance requirements of ultra-high strength (750MPa and above), lightweight, corrosion resistance and low cost, and provides a round casting ingot for ultra-high strength aluminum rare earth alloy profiles and its preparation method.

[0007] The ultra-high strength aluminum rare earth alloy profile round casting of the present invention contains the following by mass percentage: Si≤0.20%, Fe≤0.20%, Zn: 10.00%~11.50%, Mg: 2.50%~3.50%, Cu: 1.10%~1.80%, Zr: 0.08%~0.15%, Yb: 0.03%~0.35%, individual impurities≤0.10%, total impurities≤0.20%, and the remainder is Al.

[0008] The preparation method of the ultra-high strength aluminum rare earth alloy profile round ingot of the present invention is completed according to the following steps:

[0009] I. Raw Materials: By mass percentage: Si≤0.20%, Fe≤0.20%, Zn: 10.00%~11.50%, Mg: 2.50%~3.50%, Cu: 1.10%~1.80%, Zr: 0.08%~0.15%, Yb: 0.03%~0.35%, individual impurities≤0.10%, total impurities≤0.20%, the remainder being Al. Weigh out aluminum ingots, magnesium ingots, zinc ingots, copper plates, aluminum-zirconium master alloys, and aluminum-ytterbium master alloys for remelting as smelting raw materials.

[0010] II. Melting: Under conditions of 740~780℃, weighed aluminum ingots, zinc ingots, copper plates, and aluminum-zirconium master alloys for remelting are added to the melting furnace; after the melt is completely melted, the temperature is raised to 780℃, aluminum-ytterbium master alloys are added, ensuring they are completely immersed in the melt; after the aluminum-ytterbium master alloys melt, the melt is heated to 780℃ again; the temperature is held at 780℃ for 20 minutes, followed by the first stirring; after stirring, the temperature is maintained at 780℃, and the temperature is held for another 20 minutes, followed by the second stirring; when the melt temperature is not lower than 740℃, magnesium ingots are added, and the melt is stirred thoroughly until it is homogeneous, then refined; after refining, the melt is transferred to a settling furnace and settling for at least 30 minutes to obtain ultra-high strength aluminum rare earth profile aluminum alloy melt;

[0011] III. Casting: The aluminum alloy melt for ultra-high strength aluminum rare earth profiles is filtered, and the filtered melt is uniformly injected into the crystallizer using a separatory funnel for casting to obtain aluminum alloy round ingots; the aluminum alloy round ingots are subjected to homogenization annealing treatment to obtain homogenized annealed aluminum alloy round ingots; the round ingots are sawed to the finished length, and the surface oxide scale is machined to obtain finished ingots.

[0012] Beneficial effects of this invention:

[0013] The ultra-high strength aluminum rare earth alloy profile prepared by the round casting of this invention has a tensile strength of ≥750MPa in the T6 state, which is 150MPa~180MPa higher than the tensile strength of the commonly used 7075-T6 alloy. Moreover, its exfoliation corrosion is EA grade, which takes into account the requirements of low cost, high strength and good corrosion resistance, and can broaden the selection range of aluminum profiles for aerospace, shipbuilding and other equipment. Detailed Implementation

[0014] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0015] Specific Implementation Method 1: The round ingots used for ultra-high strength aluminum rare earth alloy profiles in this implementation method are as follows by mass percentage: Si≤0.20%, Fe≤0.20%, Zn: 10.00%~11.50%, Mg: 2.50%~3.50%, Cu: 1.10%~1.80%, Zr: 0.08%~0.15%, Yb: 0.03%~0.35%, individual impurities≤0.10%, total impurities≤0.20%, and the remainder is Al.

[0016] Zn and Mg are the main strengthening elements in 7xxx series aluminum alloys. When Zn and Mg coexist in an alloy, they form the MgZn2 phase and the T-Al2Mg3Zn3 phase. When the Zn / Mg ratio is greater than 3%, the MgZn2 strengthening phase can precipitate in large quantities and be uniformly distributed in the matrix. This high ratio maximizes the precipitation density of the strengthening phase, significantly improving the alloy strength through dispersion strengthening and precipitation strengthening effects, laying the foundation for achieving tensile strengths above 750 MPa. Simultaneously, the combined addition of Zn and Mg avoids the increased brittleness caused by excessive amounts of a single element, ensuring the alloy's basic plasticity while strengthening it.

[0017] Cu can work synergistically with Zn and Mg to improve the specific strength and tensile strength of the alloy. However, as the Cu content increases, the corrosion resistance of the alloy decreases. Therefore, when designing the alloy composition, it is necessary to balance the strengthening effect of Cu with its impact on corrosion resistance. Cu (1.10%~1.80%) further enhances the precipitation strengthening effect by forming multi-element alloy phases (such as Al2CuMg phase) with Zn and Mg, synergistically improving the tensile strength and specific strength of the alloy. In addition, Cu can refine the precipitation size of the MgZn2 phase, making the distribution of the strengthening phase more uniform and reducing stress concentration points. However, this application strictly limits the upper limit of Cu content to avoid the formation of continuous Cu-rich phases at grain boundaries due to excessive Cu, thus balancing the contradiction between strength improvement and corrosion resistance. It utilizes the strengthening effect of Cu while preventing its excessive damage to corrosion resistance, ensuring that the alloy maintains EA-level exfoliation corrosion resistance.

[0018] As a rare earth element, Yb can improve the mechanical properties of alloys by refining ingot grains and inhibiting recrystallization. Simultaneously, Yb can form an Al3(Zr,Yb) dispersed phase with Zr. This phase not only pins grain boundaries and hinders dislocation movement to enhance strength but also isolates harmful phases at grain boundaries (such as Zn-rich phases), reducing intergranular corrosion susceptibility and thus synergistically improving corrosion resistance. Furthermore, the addition of Yb can reduce the amount of high-valence elements used in traditional alloys, controlling costs while maintaining performance. The presence of Zr stabilizes the dispersion strengthening effect of Yb, preventing coarsening of the strengthening phase during high-temperature processing and ensuring the alloy maintains ultra-high strength during subsequent heat treatments (such as the T6 state).

[0019] Specific Implementation Method Two: The preparation method of a round ingot for ultra-high strength aluminum rare earth alloy profiles in this implementation method is completed according to the following steps:

[0020] I. Raw Materials: By mass percentage: Si≤0.20%, Fe≤0.20%, Zn: 10.00%~11.50%, Mg: 2.50%~3.50%, Cu: 1.10%~1.80%, Zr: 0.08%~0.15%, Yb: 0.03%~0.35%, individual impurities≤0.10%, total impurities≤0.20%, the remainder being Al. Weigh out aluminum ingots, magnesium ingots, zinc ingots, copper plates, aluminum-zirconium master alloys, and aluminum-ytterbium master alloys for remelting as smelting raw materials.

[0021] II. Melting: Under conditions of 740~780℃, weighed aluminum ingots, zinc ingots, copper plates, and aluminum-zirconium master alloys for remelting are added to the melting furnace; after the melt is completely melted, the temperature is raised to 780℃, aluminum-ytterbium master alloys are added, ensuring they are completely immersed in the melt; after the aluminum-ytterbium master alloys melt, the melt is heated to 780℃ again; the temperature is held at 780℃ for 20 minutes, followed by the first stirring; after stirring, the temperature is maintained at 780℃, and the temperature is held for another 20 minutes, followed by the second stirring; when the melt temperature is not lower than 740℃, magnesium ingots are added, and the melt is stirred thoroughly until it is homogeneous, then refined; after refining, the melt is transferred to a settling furnace and settling for at least 30 minutes to obtain ultra-high strength aluminum rare earth profile aluminum alloy melt;

[0022] III. Casting: The aluminum alloy melt for ultra-high strength aluminum rare earth profiles is filtered, and the filtered melt is uniformly injected into the crystallizer using a separatory funnel for casting to obtain aluminum alloy round ingots; the aluminum alloy round ingots are subjected to homogenization annealing treatment to obtain homogenized annealed aluminum alloy round ingots; the round ingots are sawed to the finished length, and the surface oxide scale is machined to obtain finished ingots.

[0023] In step two of this embodiment, adding an aluminum-ytterbium master alloy at 780°C ensures that trace alloying elements are fully dissolved in the molten aluminum, prevents alloying elements from settling to the bottom of the furnace, reduces component segregation, and shortens the melting time to obtain a melt with uniform composition.

[0024] This implementation reduces the loss of precious elements such as magnesium and rare earths by step-by-step temperature control (e.g., increasing the recovery rate of magnesium by 10%~15%), and reduces the cost of using pure rare earths by using aluminum-rare earth intermediate alloys (e.g., Al-10Yb).

[0025] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the aluminum-ytterbium master alloy mentioned in step one is Al-10Yb. Other steps and parameters are the same as in Specific Implementation Method 2.

[0026] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Two in that the ratio of Zn to Mg elements in step one is greater than 3. Other steps and parameters are the same as in Specific Implementation Method Two.

[0027] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Two in that the refining in step two is carried out at 720~740℃ using an Ar-Cl2 mixed gas until the hydrogen content in 100 grams of melt is ≤0.20 mL. Other steps and parameters are the same as in Specific Implementation Method Two.

[0028] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Two in that the duration of the first stirring in step two is controlled to be 3-5 minutes. Other steps and parameters are the same as in Specific Implementation Method Two.

[0029] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Two in that the duration of the second stirring in step two is controlled to be 3-5 minutes. Other steps and parameters are the same as in Specific Implementation Method Two.

[0030] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Two in that the filtration in step three uses a double-layer ceramic filter. Other steps and parameters are the same as in Specific Implementation Method Two.

[0031] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Two in that the casting process parameters in step three are: casting temperature of 720℃~740℃, casting speed of 30mm / min~60mm / min, and casting water flow rate of 30m³ / min. 3 / h~60m 3 / h. Other steps and parameters are the same as in Specific Implementation Method Two.

[0032] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Two in that the homogenization annealing process parameters in step three are: 440℃ / 12h + 470℃ / 36h. Other steps and parameters are the same as in Specific Implementation Method Two.

[0033] This embodiment employs a two-stage homogenization annealing low-temperature pretreatment to promote the precipitation of Al3(Yb,Zr) dispersed phases and refine their size, reducing the area without precipitation of second-phase particles. The second-stage annealing at 470℃ allows for the full dissolution of low-melting-point eutectic phases, improving ingot purity. The high-temperature stage promotes the dissolution of low-melting-point eutectic phases (such as Al-Cu-Mg phases), preserving the dispersion strengthening effect of the reinforcing phases while eliminating brittle grain boundary phases (which are easily retained in traditional processes), thereby improving both strength and corrosion resistance. This synergistic effect of the annealing process and rare earth elements avoids the contradiction of "coarsening of the reinforcing phase" or "decreased corrosion resistance" in traditional single-stage annealing.

[0034] The beneficial effects of the present invention are verified using the following embodiments:

[0035] Example 1: A method for preparing a round ingot for ultra-high strength aluminum rare earth alloy profiles is completed according to the following steps:

[0036] I. Raw Materials: By mass percentage: Si≤0.20%, Fe≤0.20%, Zn: 10.00%~11.50%, Mg: 2.50%~3.50%, Cu: 1.10%~1.80%, Zr: 0.08%~0.15%, Yb: 0.03%~0.35%, individual impurities ≤0.10%, total impurities ≤0.20%, the remainder being Al. Weigh out aluminum ingots, magnesium ingots, zinc ingots, copper plates, aluminum-zirconium master alloy, and aluminum-ytterbium master alloy for remelting as smelting raw materials; the aluminum-ytterbium master alloy is Al-10Yb; the ratio of Zn to Mg is greater than 3.

[0037] II. Melting: At a temperature of 740-780℃, weighed aluminum ingots, zinc ingots, copper plates, and aluminum-zirconium master alloy are added to the melting furnace. After the melt is completely melted, the temperature is raised to 780℃, and the aluminum-ytterbium master alloy is added, ensuring it is completely immersed in the melt. After the aluminum-ytterbium master alloy melts, the melt temperature is raised again to 780℃. The melt is held at 780℃ for 20 minutes, followed by the first stirring, lasting 3-5 minutes. After stirring, heating continues to raise the melt temperature. Maintain the temperature at 780℃ and hold for another 20 minutes, then stir a second time for 3-5 minutes. When the melt temperature is not lower than 740℃, add magnesium ingots and stir thoroughly until the melt is homogeneous. Then refine the melt and transfer it to a settling furnace for at least 30 minutes to obtain ultra-high strength aluminum rare earth profile aluminum alloy melt. The refining process is carried out at 720-740℃ using Ar-Cl2 mixed gas until the hydrogen content in 100 grams of melt is ≤0.20 mL.

[0038] III. Casting: The molten aluminum alloy for ultra-high strength aluminum rare earth profiles is filtered using a double-layer ceramic filter. The filtered melt is then uniformly injected into a crystallizer using a separating funnel for casting, yielding aluminum alloy round ingots. These ingots undergo homogenization annealing to obtain homogenized annealed aluminum alloy round ingots. The round ingots are then sawn to the desired length, and the surface oxide scale is removed to obtain φ157mm×540mm round ingots. The casting process parameters are: casting temperature 720℃~740℃, casting speed 30mm / min, and casting water flow rate 50m³ / min. 3 / h; The homogenization annealing process parameters are: 440℃ / 12h + 470℃ / 36h.

[0039] The ultra-high strength aluminum rare earth alloy profiles prepared using the round ingots obtained in this embodiment have a tensile strength of ≥750MPa in the T6 state, which is 150MPa~180MPa higher than the tensile strength of the commonly used 7075-T6 alloy. Moreover, the exfoliation corrosion is at the EA level, which takes into account the requirements of low cost, high strength and good corrosion resistance.

Claims

1. A round ingot for ultra-high strength aluminum rare earth alloy profiles, characterized in that... The round ingots for ultra-high strength aluminum rare earth alloy profiles are composed of the following percentages by mass: Si≤0.20%, Fe≤0.20%, Zn: 10.00%~11.50%, Mg: 2.50%~3.50%, Cu: 1.10%~1.80%, Zr: 0.08%~0.15%, Yb: 0.03%~0.35%, with individual impurities ≤0.10% and total impurities ≤0.20%, the remainder being Al.

2. A method for preparing a round ingot for ultra-high strength aluminum rare earth alloy profiles, characterized in that... The preparation method of round ingots for ultra-high strength aluminum rare earth alloy profiles is completed according to the following steps: I. Raw Materials: By mass percentage: Si≤0.20%, Fe≤0.20%, Zn: 10.00%~11.50%, Mg: 2.50%~3.50%, Cu: 1.10%~1.80%, Zr: 0.08%~0.15%, Yb: 0.03%~0.35%, individual impurities≤0.10%, total impurities≤0.20%, the remainder being Al. Weigh out aluminum ingots, magnesium ingots, zinc ingots, copper plates, aluminum-zirconium master alloys, and aluminum-ytterbium master alloys for remelting as smelting raw materials. II. Melting: Under conditions of 740~780℃, weighed aluminum ingots, zinc ingots, copper plates, and aluminum-zirconium master alloys for remelting are added to the melting furnace; after the melt is completely melted, the temperature is raised to 780℃, aluminum-ytterbium master alloys are added, ensuring they are completely immersed in the melt; after the aluminum-ytterbium master alloys melt, the melt is heated to 780℃ again; the temperature is held at 780℃ for 20 minutes, followed by the first stirring; after stirring, the temperature is maintained at 780℃, and the temperature is held for another 20 minutes, followed by the second stirring; when the melt temperature is not lower than 740℃, magnesium ingots are added, and the melt is stirred thoroughly until it is homogeneous, then refined; after refining, the melt is transferred to a settling furnace and settling for at least 30 minutes to obtain ultra-high strength aluminum rare earth profile aluminum alloy melt; III. Casting: The aluminum alloy melt for ultra-high strength aluminum rare earth profiles is filtered, and the filtered melt is uniformly injected into the crystallizer using a separatory funnel for casting to obtain aluminum alloy round ingots; the aluminum alloy round ingots are subjected to homogenization annealing treatment to obtain homogenized annealed aluminum alloy round ingots; the round ingots are sawed to the finished length, and the surface oxide scale is machined to obtain finished ingots.

3. The method for preparing a round ingot for ultra-high strength aluminum rare earth alloy profiles according to claim 2, characterized in that... The aluminum-ytterbium master alloy mentioned in step one is Al-10Yb.

4. The method for preparing a round ingot for ultra-high strength aluminum rare earth alloy profiles according to claim 2, characterized in that... The ratio of Zn to Mg in step one is greater than 3.

5. The method for preparing a round ingot for ultra-high strength aluminum rare earth alloy profiles according to claim 2, characterized in that... The refining process described in step two involves refining the melt at 720~740℃ using an Ar-Cl2 mixed gas until the hydrogen content in every 100 grams of melt is ≤0.20 mL.

6. The method for preparing a round ingot for ultra-high strength aluminum rare earth alloy profiles according to claim 2, characterized in that... The duration of the first stirring in step two should be controlled at 3-5 minutes.

7. The method for preparing a round ingot for ultra-high strength aluminum rare earth alloy profiles according to claim 2, characterized in that... The duration of the second stirring in step two should be controlled at 3-5 minutes.

8. The method for preparing a round ingot for ultra-high strength aluminum rare earth alloy profiles according to claim 2, characterized in that... The filtration process described in step three uses a double-layer ceramic filter.

9. The method for preparing a round ingot for ultra-high strength aluminum rare earth alloy profiles according to claim 2, characterized in that... The casting process parameters described in step three are as follows: casting temperature 720℃~740℃, casting speed 30mm / min~60mm / min, and casting water flow rate 30m³ / min. 3 / h~60m 3 / h.

10. The method for preparing a round ingot for ultra-high strength aluminum rare earth alloy profiles according to claim 2, characterized in that... The homogenization annealing process parameters in step three are: 440℃ / 12h + 470℃ / 36h.