A method of improving the quality of an aluminum alloy melt

Abstract

The application belongs to the technical field of non-ferrous metal material preparation, and particularly relates to a method for improving the quality of aluminum alloy melt, wherein the aluminum alloy is smelted and refined; the temperature of the aluminum alloy melt is controlled to be 720-750 DEG C; Al-Ti-C-B seeds and TCB seeds are sequentially added, the adding amount of the Al-Ti-C-B seeds and the TCB seeds is respectively 0.02-0.05% of the mass of the aluminum alloy melt, the adding time of each time is 1-5 min; the aluminum alloy melt is uniformly stirred, the temperature of the aluminum alloy melt is controlled to be 730-740 DEG C, and the temperature is maintained for 20-30 min; and the method effectively reduces the grain size and improves the grain refinement effect and consistency of the deformed aluminum alloy ingot.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal material preparation technology, specifically relating to a method for improving the quality of aluminum alloy melt. Background Technology

[0002] In the semi-continuous casting production of wrought aluminum alloys (such as 2-series, 6-series, and 7-series aluminum alloys), adding grain refiners to the melt is a key step in refining the ingot grains and improving machinability. Currently, industrial production mainly adopts a combined process of "in-furnace addition of aluminum-titanium master alloy + online addition of aluminum-titanium-boron wire." Medium-frequency furnaces are widely used in wrought aluminum alloy melting due to their advantages such as fast melting speed, uniform composition, and adjustable electromagnetic stirring. However, existing addition processes have the following shortcomings: the master alloy added in the furnace is prone to sedimentation and uneven dispersion; online addition requires equipment such as wire feeders, resulting in high investment costs, and the seed crystals have a short residence time in the melt, making it difficult to fully utilize the long-term benefits of the seed crystals. Furthermore, 7-series aluminum alloys containing Zr also face the problem of "Zr poisoning" failure of conventional grain refiners. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for improving the quality of aluminum alloy melt, effectively reducing grain size, and improving the grain refinement effect and consistency of wrought aluminum alloy ingots.

[0004] This invention provides a method for improving the quality of aluminum alloy melt, wherein the aluminum alloy is smelted and refined; The temperature of the aluminum alloy melt was controlled at 720-750℃. Al-Ti-CB seed crystals and TCB seed crystals were added sequentially. The amount of Al-Ti-CB seed crystals and TCB seed crystals added was 0.02-0.05% of the mass of the aluminum alloy melt, and the time for each addition was 1-5 minutes. Stir evenly, control the temperature of the aluminum alloy melt to 730-740℃, and hold for 20-30 minutes. The holding operation allows the seed crystals to be fully stabilized, forming a diffusely distributed heterogeneous nucleation core.

[0005] Preferably, the aluminum alloy is a 2-series aluminum alloy, a 6-series aluminum alloy, or a 7-series aluminum alloy, and more preferably 7050 aluminum alloy. The 7050 aluminum alloy comprises the following components by weight percentage: Zn 5.7-6.7%, Mg 1.9-2.6%, Cu 2.0-2.6%, Zr 0.08-0.15%, with the balance being Al and unavoidable impurities.

[0006] Preferably, the Al-Ti-CB seed crystal comprises 5wt%Ti, 0.3wt%C and 0.2wt%B, with the balance being aluminum, and the TCB seed crystal comprises 4.5wt%Ti, 0.15wt%C, 0.5wt%B and 1%Re, with the balance being aluminum.

[0007] Preferably, the refining, seed crystal addition, uniform stirring, and heat preservation of the present invention are all completed in an intermediate frequency furnace, and no online grain refiner needs to be added during casting.

[0008] Preferably, the melting temperature is 730-750℃ and the melting time is 1-2 hours; Preferably, the refining temperature is 740-750℃, the refining time is 20-30 minutes, and after refining, the mixture is left to stand and the residue is removed.

[0009] Preferably, the temperature of the aluminum alloy melt is 730-750℃ when Al-Ti-CB seed crystals are added, and 720-740℃ when TCB seed crystals are added. When the aluminum alloy melt is heated to the above target temperature, it is held at that temperature for 3-5 minutes.

[0010] Preferably, the method of uniform stirring is electromagnetic stirring for 8-15 minutes. Electromagnetic stirring generates uniform electromagnetic force in the melt, promoting the formation of an up-and-down circulating flow of the melt.

[0011] Preferably, after heat preservation, casting and homogenization treatment are carried out to obtain aluminum alloy ingots; during casting, the casting end temperature is 680-690℃, and the steady-state casting speed is 50-60mm / min, preferably 52-58mm / min.

[0012] Preferably, during casting, the material passes through an online degassing box and a filter box without the addition of an online grain refiner.

[0013] Preferably, the homogenization treatment temperature is 450-480℃, and more preferably 464-470℃.

[0014] Preferably, the heat preservation time for homogenization treatment is 30-40 hours.

[0015] The beneficial effects of this invention are that it addresses the problems of complex equipment, uneven dispersion, and difficulty in leveraging the anti-fading advantages of the existing two-stage process of "adding intermediate alloy in the furnace + adding refiner online" in the semi-continuous casting production of wrought aluminum alloys. This invention proposes a preparation method that completes the entire process of seed addition, dispersion, and heat preservation stabilization within a medium-frequency furnace. Its core innovation lies in: fully utilizing the electromagnetic stirring function of the medium-frequency furnace, performing electromagnetic stirring immediately after seed addition, using its strong penetrating power to break up seed agglomerates and achieve uniform dispersion; simultaneously, precisely controlling the melt temperature to the optimal addition temperature window for different types of seed (TCB seed 730-750℃, Al-Ti-CB quaternary seed 720-740℃); and adding a heat preservation stabilization process (20-30 min) after seed addition to ensure sufficient nucleation and stabilization of the seed. This invention eliminates the need for additional equipment such as online wire feeders, making the process centralized and controllable, fully leveraging the long-term advantages of anti-fading seed such as TCB, and significantly improving the grain refinement effect and consistency of wrought aluminum alloy ingots. Detailed Implementation

[0016] Example 1 A method for improving the quality of aluminum alloy melt includes the following steps: 1) Melting: According to the target composition of 7050 aluminum alloy (Zn 6.2%, Mg 2.2%, Cu 2.3%, Zr 0.12%, balance Al), put it into an induction furnace, heat it to 740℃ and melt it (50% of rated power, rated power is 300kw), and the melting time is 1.5 hours.

[0017] 2) Refining: After smelting, remove the slag and introduce argon gas for refining and degassing. The refining temperature is 745℃, and the refining time is 25 minutes. During the refining process, maintain medium-frequency low-power heating (15% of rated power). After refining, turn off the medium-frequency power supply, let it stand for 8 minutes, and remove all surface slag.

[0018] 3) Heating: Heat the melt to 745℃ (30% of rated power).

[0019] 4) Adding seed crystals: While maintaining medium-frequency heating and electromagnetic stirring, add Al-Ti-CB seed crystals at 730℃ (the amount of Al-Ti-CB seed crystals added is 0.03% of the mass of the aluminum alloy melt), and then add TCB seed crystals at 740℃ (the amount of TCB seed crystals added is 0.03% of the mass of the aluminum alloy melt). Each addition process should be completed within 3 minutes.

[0020] Al-Ti-CB seed crystals consist of 5wt% Ti, 0.3wt% C, and 0.2wt% B, with the balance being aluminum. TCB seed crystals consist of 4.5wt% Ti, 0.15wt% C, 0.5wt% B, and 1% Re, with the balance being aluminum.

[0021] 5) Electromagnetic stirring: After the seed crystals are added, the melt is stirred by low-frequency heating (15% of rated power) for 12 minutes.

[0022] 6) Heat preservation and stabilization: After the electromagnetic stirring is completed, adjust the temperature of the melt to 735℃ and let it stand for 25 minutes.

[0023] 7) Casting: Semi-continuous casting is carried out after the heat preservation is completed. The casting end temperature is 680-690℃ and the steady-state casting speed is 55mm / min. The material passes through the degassing box and filter box online without adding online grain refiner.

[0024] 8) Homogenization: The ingot is homogenized at a temperature of 467±3℃ for 36 hours.

[0025] Example 2 The difference compared to Example 1 is as follows: The melting temperature in step 1) is 735℃; The addition temperature of Al-Ti-CB and TCB seed crystals in step 4) is 735℃. In step 4), the amount of Al-Ti-CB seed crystals added is 0.05%, and the amount of TCB seed crystals added is 0.02%. The electromagnetic stirring time in step 5) is 15 minutes; The stabilization temperature for step 6) is 730℃, and the static stabilization time is 30 minutes.

[0026] Everything else is the same as in Example 1.

[0027] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is as follows: Step 4) is as follows: While maintaining medium-frequency heating and electromagnetic stirring, add Al-10Ti master alloy at 730℃ (the amount of Al-10Ti master alloy added is 0.1% of the mass of the aluminum alloy melt), and add it for 2 minutes.

[0028] In step 7), during semi-continuous casting, Al-5Ti-1B wire is fed online (the amount added is 0.02wt% of the mass of the aluminum alloy melt based on Ti).

[0029] The rest is the same as in Example 1.

[0030] Comparative Example 2 Compared with Example 1, Comparative Example 2 differs in that: in step 4), only TCB seed crystals are added at 740°C (the amount of TCB seed crystals added is 0.06% of the mass of the aluminum alloy melt), and Al-Ti-CB seed crystals are not added. Everything else is the same as in Example 1.

[0031] Comparative Example 3 Compared with Example 1, Comparative Example 3 differs in that the heat preservation stabilization step 6) is omitted, and the casting step is directly started after the electromagnetic stirring is completed. Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that TCB seed crystals were added at 730°C (the amount of TCB seed crystals added was 0.03% of the mass of the aluminum alloy melt), and then Al-Ti-CB seed crystals were added at 740°C (the amount of Al-Ti-CB seed crystals added was 0.03% of the mass of the aluminum alloy melt). Otherwise, they were the same as Example 1.

[0032] The average grain size of Examples 1-2 and Comparative Examples 1-4 was measured, and the experimental results are shown in Table 1.

[0033] Table 1. Average grain size of Examples 1-2 and Comparative Examples 1-4

[0034] As shown in Table 1, the grain size of Example 1 is only 58 μm, while that of Comparative Example 1 (conventional process) is as high as 110 μm. Compared with the traditional "in-furnace addition of intermediate alloy + online wire feeding" process (Comparative Example 1), the "in-furnace full addition of seed crystals + heat preservation" process of the present invention (Examples 1 and 2) can significantly reduce the average grain size. The method of the present invention has an overwhelming advantage in refining grains, reducing the grain size by approximately 47%. This means that the aluminum alloy ingots produced using the process of the present invention have a denser microstructure, and subsequent processing properties (such as plasticity and strength) will be significantly improved.

[0035] Comparative Example 2, with only TCB seed crystals added, showed a grain size of 98 μm. This demonstrates that the effect of a single seed crystal is far inferior to the "Al-Ti-C-B+TCB" dual seed crystal combination in this invention. The two seed crystals in this invention are complementary in their nucleation mechanisms, and their combined action is necessary to achieve the optimal grain refinement effect.

[0036] Comparative Example 3 eliminated the "20-30 min heat preservation" step, resulting in a grain size of 84 μm. The heat preservation step is crucial for the full dispersion of the seed crystals and the stabilization of the nucleation core. Without this step, the seed crystals cannot fully realize their long-lasting benefits, leading to coarse grains.

[0037] In Comparative Example 4, the addition order was reversed (TCB first, then Al-Ti-CB), and the grain size was 81 μm. It can be seen that the order of seed crystal addition has a significant impact on the final result. The order specified in this invention, "add Al-Ti-CB first, then TCB," is the optimized path; reversing the order will significantly weaken the grain refinement effect.

[0038] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0039] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A method for improving the quality of aluminum alloy melt, characterized in that, The aluminum alloy is smelted and refined; The temperature of the aluminum alloy melt was controlled at 720-750℃. Al-Ti-CB seed crystals and TCB seed crystals were added sequentially. The amount of Al-Ti-CB seed crystals and TCB seed crystals added was 0.02-0.05% of the mass of the aluminum alloy melt, and the time for each addition was 1-5 minutes. Stir well and control the temperature of the aluminum alloy melt at 730-740℃, then hold for 20-30 minutes. The Al-Ti-CB seed crystal consists of 5wt% Ti, 0.3wt% C and 0.2wt% B, with the balance being aluminum. The TCB seed crystal consists of 4.5wt% Ti, 0.15wt% C, 0.5wt% B and 1wt% Re, with the balance being aluminum.

2. The method as described in claim 1, characterized in that, The aluminum alloy is a 2-series aluminum alloy, a 6-series aluminum alloy, or a 7-series aluminum alloy.

3. The method as described in claim 1, characterized in that, The melting temperature is 730-750℃, and the melting time is 1-2 hours.

4. The method as described in claim 1, characterized in that, The refining temperature is 740-750℃, the refining time is 20-30 minutes, and after refining, the mixture is left to stand and the residue is removed.

5. The method as described in claim 1, characterized in that, When Al-Ti-CB seed crystals are added, the temperature of the aluminum alloy melt is 730-750℃; when TCB seed crystals are added, the temperature of the aluminum alloy melt is 720-740℃.

6. The method as described in claim 1, characterized in that, The mixing method is electromagnetic stirring, and the time is 8-15 minutes.

7. The method as described in claim 1, characterized in that, After heat preservation, casting and homogenization treatment are carried out to obtain aluminum alloy ingots; during casting, the casting end temperature is 680-690℃, and the steady-state casting speed is 50-60mm / min.

8. The method of claim 7, characterized in that, During casting, the material passes through an online degassing box and a filter box without the addition of an online grain refiner.

9. The method of claim 7, characterized in that, The homogenization treatment temperature is 450-480℃.

10. The method of claim 7, characterized in that, The heat treatment time for homogenization is 30-40 hours.

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