A grain refinement method for large-size zirconium-containing aluminum-lithium alloy ingot

Abstract

The application belongs to the technical field of non-ferrous metallurgy, and particularly relates to a grain refinement method for large-size zirconium-containing aluminum-lithium alloy ingot, wherein the casting of the large-size zirconium-containing aluminum-lithium alloy ingot is semi-continuous casting, and the casting steps are as follows: zirconium-containing aluminum-lithium alloy raw material smelting, melt degassing, filtration, and casting to obtain an ingot; titanium strips and grain refiners are intermittently added into the melt before the filtration after the degassing; when the grain refiners are added, the part of the melt is controlled to have melted titanium, and the melted titanium exists in the melt for no more than 5s before meeting the grain refiners; the time from the addition of the grain refiners to the start of the casting is controlled to be 5-15min; and the ratio of the weight of the titanium strips to the weight of the zirconium is 0.5-1:1. The application aims to solve the problem of refinement poisoning caused by Zr and Li elements in large-size aluminum-lithium alloy, and effectively reduce the grain size.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-ferrous metallurgy, and particularly relates to a grain refinement method for large-size zirconium-containing aluminum-lithium alloy ingot. BACKGROUND

[0002] Aluminum-lithium alloy is widely used in aerospace structural parts due to low density, high specific strength and excellent stiffness. With the development of the third and fourth generation aluminum-lithium alloy, Zr and Li elements are introduced together to form Al3Zr and Al3Li dispersed phases, realizing the dual effects of precipitation strengthening and inhibition of recrystallization. However, during the casting and solidification stage, the presence of Zr and Li significantly weakens the effect of traditional Al-Ti-B and Al-Ti-C grain refiners, resulting in the so-called "refinement poisoning" phenomenon. The reasons are as follows: on the one hand, Zr is enriched at the solid / liquid interface front, which is easy to form a continuous or semi-continuous Ti2Zr coating layer on the surface of TiB2 particles, hindering TiB2 from becoming an effective nucleation substrate; on the other hand, Li increases the activity of the melt, and its presence further exacerbates the poisoning effect of Zr. At the same time, due to the presence of Li, the thermal conductivity of the alloy is reduced, and when the size of the ingot reaches a certain extent, the cooling conduction becomes low, and the refinement ability is even worse. As a result, the grains of the cast blank are coarse and the structure is uneven, and cracks are easily produced during subsequent hot working and the mechanical properties are reduced.

[0003] The prior art attempts to weaken the poisoning effect by increasing the addition amount of Al-Ti-B, using Al-Ti-C refiner or applying external field methods such as ultrasound and electromagnetic stirring, but all have obvious deficiencies, which are as follows: excessive grain refiner increases the manufacturing cost and reduces the purity of the alloy; the use of Al-Ti-C refiner also has the risk of poisoning for Zr-containing aluminum-lithium alloy system; the external field equipment is complex and has high energy consumption, and it is difficult to be stably applied in large-size ingot production. Therefore, how to retain the advantages of Zr and Li micro-alloying while inhibiting the refinement poisoning and obtaining fine equiaxed grains has become a key technical problem to be solved in the field of large-size aluminum-lithium alloy preparation. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a grain refinement method for large-size zirconium-containing aluminum-lithium alloy ingot, which effectively reduces the grain size. The purpose is to solve the industry problem of coarse grains caused by "poisoning effect" of Zr and Li elements during the melting and casting process of large-size Zr-containing aluminum-lithium alloy ingot.

[0005] The embodiment of the present application provides a grain refinement method for large-size zirconium-containing aluminum-lithium alloy ingot. The casting of the large-size zirconium-containing aluminum-lithium alloy ingot is semi-continuous casting. The steps of the casting are as follows: zirconium-containing aluminum-lithium alloy raw material melting, melt degassing, filtration and casting in sequence to obtain a zirconium-containing aluminum-lithium alloy ingot.

[0006] The titanium strip and the grain refiner are added to the melt at intervals after the degassing and before the filtering, the melt is controlled to contain melted titanium when the grain refiner is added, and the melted titanium is controlled to exist in the melt for no more than 5s before meeting the grain refiner, the time from the addition of the grain refiner to the start of the casting is controlled to be 5-15 min, and the ratio of the weight of the titanium strip to the weight of the zirconium is 0.5-1:1.

[0007] The addition weight of the grain refiner is determined according to the type of the grain refiner and the refinement requirement, and other addition weights can also be adopted, preferably, the addition weight of the grain refiner is 0.2-0.6% of the weight of the zirconium-containing aluminum-lithium alloy.

[0008] The grain refiner can be any suitable grain refiner, preferably, the grain refiner is Al-5Ti-1B, Al-5Ti-1C or Al-5Ti-1B-Re grain refiner.

[0009] Preferably, the titanium strip is an aluminum-titanium alloy, such as Al-10Ti intermediate alloy, and the thickness of the titanium strip is 2-5 mm.

[0010] The zirconium-containing aluminum-lithium alloy does not have special requirements for the contents of Zr and Li, and any Zr and Li that can meet the performance requirements are acceptable, preferably, in the zirconium-containing aluminum-lithium alloy, the content of Zr is 0.05-0.20 wt%, preferably 0.05-0.10 wt%, and the content of Li is 0.5-2.2 wt%.

[0011] Preferably, in the flow direction of the melt, the adding positions of the titanium strip and the grain refiner are 15-30 cm apart, the titanium strip is upstream of the melt, the grain refiner is downstream of the melt, and the titanium strip and the grain refiner are added to the melt at the same time. The titanium is upstream of the melt in the flow direction, and the titanium is melted in a short time after being added. After the melt containing the melted titanium flows for a certain distance, the grain refiner is added to the melt, the titanium and the grain refiner contact, the Ti element is instantaneously dissolved to provide a Ti-rich environment for the grain refiner, block the poisoning reaction, and ensure the activity of the grain refiner. At the same time, the excess Ti provides a growth inhibitor to inhibit the grain growth and further refine the grains.

[0012] When the grain refiner is added, the temperature of the melt is suitable for the casting, and is preferably 720-730℃.

[0013] Preferably, the diameter of the zirconium-containing aluminum-lithium alloy ingot is more than 400 mm.

[0014] The average grain size of the zirconium-containing aluminum-lithium alloy ingot obtained by the method is ≤120 μm.

[0015] The beneficial effects of the present application are that the present application realizes the stable refinement of the grain size of large-size aluminum-lithium alloy ingots to ≤120 μm by the composite addition of titanium bars and grain refiners, control of the addition amount, addition time and casting time of titanium elements and grain refiners, no change of existing casting equipment, no introduction of expensive alloy elements, wide process window, good repeatability and suitability for industrialization.

[0016] The present application provides a Ti-rich environment for TiB2 particles through the instantaneous melting of titanium, thereby blocking the poisoning effect of Zr elements on TiB2 particles and restoring the nucleation ability thereof. Meanwhile, the excess titanium elements act as grain growth inhibitors to inhibit further grain growth. After implementation, the average grain size of large-size ingots such as Ø400 mm and Ø600 mm is ≤120 μm, the equiaxed crystal ratio is ≥90%, the process window is wide and the addition amount is low.

[0017] The present application controls the existing time of titanium and grain refiners before meeting in the melt, and titanium is added in a spaced manner with grain refiners, so that titanium is melted first to form a titanium-rich environment, but the existing time of titanium in the melt is controlled, because long time is easy to react with Zr. The present application controls the existing time of grain refiners in the melt to avoid Zr poisoning and refinement failure.

[0018] The present application controls the weight ratio of titanium bars and zirconium in the melt. The main role of Zr is to introduce Al3Zr dispersion phase, the size of Al3Zr phase ranges from 0.05 to 0.5 μm, mainly plays a role in inhibiting recrystallization and grain growth after deformation, and excessive Zr elements will lead to the overgrowth of its phase and lose its original role. The present application adds titanium bars to form a titanium-rich environment, protects the nucleation particles in the grain refiner from being modified by Zr elements, maintains the stable nucleation of the grain refiner, provides part of the small and dispersed Al3Ti nucleation particles and inhibits grain growth, and excessive titanium will lead to the formation of coarse and hard impurities and hard and brittle phase, which can cause cracking in the deformation process as a crack source. Therefore, the weight ratio of titanium bars and zirconium is controlled to be 0.5-1:1; when the Ti element is less than 0.5 times of the Zr element, the improvement of Zr poisoning auxiliary refinement effect will be weakened.

[0019] The present application fundamentally solves the double poisoning problem of Zr and Li on the refiner in Zr-containing aluminum-lithium alloy through the composite refinement strategy of "grain refiner + titanium bar", and provides a reliable and economic grain refinement solution for the popularization and application of high-performance aluminum-lithium alloy in aerospace large-size structural parts. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The present application is added to the position of grain refiner and thin titanium bar in the process.

[0021] Figure 2This is an EBSD grain morphology diagram of the ingot of Embodiment 1 of the present invention.

[0022] Figure 3 These are low-magnification and high-magnification grain morphology images of Example 2 of the present invention. (a) is a low-magnification grain morphology image, and (b) is a high-magnification grain morphology image.

[0023] Figure 4 These are low-magnification and high-magnification grain morphology images of Example 3 of the present invention. (a) is a low-magnification grain morphology image, and (b) is a high-magnification grain morphology image.

[0024] Figure 5 This is a low-magnification grain morphology image of Comparative Example 1 of the present invention.

[0025] Figure 6 This is a high-magnification grain morphology image of Comparative Example 2 of the present invention.

[0026] Figure 7 This is a high-magnification grain morphology image of Comparative Example 3 of the present invention.

[0027] Figure 8 This is a high-magnification grain morphology image of Comparative Example 4 of the present invention.

[0028] Figure 9 This is a high-magnification grain morphology image of Comparative Example 5 of the present invention. Detailed Implementation Example 1

[0029] This embodiment describes the semi-continuous casting of a Ø400mm ingot, with a target alloy of Al-1.15Li-0.1Zr (wt%). 0.05wt% Ti (0.05wt% of the target alloy) and 0.3wt% AlTiB wire (0.3wt% of the target alloy) are added online, with the Ti (thin Ti strip) / Zr mass fraction ratio controlled at 0.5.

[0030] The specific steps of casting are as follows:

[0031] First, add pure aluminum ingots and aluminum-zirconium master alloy, heat to 720 ℃, and stir evenly after melting. You can first use a direct-reading spectrometer to detect the composition. If the composition is accurate, add high-purity Li. After 10 minutes, wait for it to melt, stir evenly with a graphite rod, and then use a direct-reading spectrometer to detect the Li element composition again. If the composition is accurate, you can start degassing.

[0032] Argon gas was injected and degassed by rotating a graphite rotor for 15 minutes, and then the slag was removed.

[0033] After slagging, the smelting furnace can be drained, at which time the thin Ti strip and the AlTiB wire are fed into the flow channel between the degassing tank and the filter tank at a certain speed, while maintaining a 20 cm interval between the thin Ti strip and the AlTiB wire, that is, the thin Ti strip is melted before the AlTiB wire, providing a Ti-rich environment. See Figure 1

[0034] The grain refiner self-mixes in the flow channel and the filter tank, and is then introduced into the Ø400 mm crystallizer for semi-continuous casting at a pulling speed of 30 mm / min. The grain refiner is added to the casting in the crystallizer within 15 min.

[0035] Ingot sampling analysis statistics: the grain structure is equiaxed crystal, and the average grain size is about 96 μm, as shown in Figure 2 Example 2

[0036] This example is semi-continuous casting of a Ø400 mm ingot, and the target alloy for smelting is a 2195 aluminum-lithium alloy: Al-1.15Li-4.15Cu-0.4Mg-0.4Ag-0.1Zr (wt%), with 0.05wt% Ti and 0.3wt% AlTiB wire added online, and the mass fraction ratio of Ti (thin Ti strip) to Zr is controlled at 0.5.

[0037] The specific steps of casting are as follows:

[0038] First, add pure aluminum ingot, electrolytic copper, pure magnesium, pure silver powder, and aluminum-zirconium intermediate alloy, and heat to 720 ℃. After melting, stir evenly, and first detect the composition with a direct-reading spectrometer. After 10 minutes, add high-purity Li after melting, stir evenly with a graphite rod, and then detect the Li element composition with a direct-reading spectrometer. When the composition is accurate, start degassing.

[0039] Degassing for 15 min by rotating and blowing argon with a graphite rotor, and slagging.

[0040] After slagging, the smelting furnace can be drained, at which time the thin Ti strip and the AlTiB wire are fed into the flow channel between the degassing tank and the filter tank at a certain speed, while maintaining a 20 cm interval between the thin Ti strip and the AlTiB wire, that is, the thin Ti strip is melted before the AlTiB wire, providing a Ti-rich environment.

[0041] The grain refiner and the Ti element self-mix in the flow channel and the filter tank, and are then introduced into the Ø400 mm crystallizer for semi-continuous casting at a pulling speed of 30 mm / min. The grain refiner is added to the casting in the crystallizer within 15 min.

[0042] ​​Statistical analysis of ingot sampling: average grain size 108 μm, substantially all equiaxed grains, no columnar grains. Repeat three heats, grain size fluctuation <± 7 μm, process stable, as shown in Figure 3 Example 3

[0043] This example is a semi-continuous casting of a Ø600 mm ingot, and the target alloy to be smelted is a 2195 aluminum-lithium alloy: Al-1.15Li-4.15Cu-0.4Mg-0.4Ag-0.1Zr (wt%), with 0.1wt% Ti and 0.5wt% AlTiB wire added on-line, and the mass fraction ratio of Ti (thin Ti strip) / Zr controlled at 1.

[0044] The specific steps of casting are as follows:

[0045] First, add pure aluminum ingot, electrolytic copper, pure magnesium, pure silver powder, and aluminum-zirconium master alloy, and heat to 720°C. After melting, stir uniformly, and first detect the composition with a direct-reading spectrometer. If the composition is accurate, add high-purity Li. After 10 minutes, melt, stir uniformly with a graphite rod, and then detect the Li element composition with a direct-reading spectrometer. If the composition is accurate, start degassing.

[0046] Degassing for 15 minutes by rotating and blowing argon with a graphite rotor, and remove slag.

[0047] After removing slag, the smelting furnace can be watered. At this time, the AlTiB wire and thin Ti strip are fed into the flow channel between the degassing tank and the filter tank at a certain speed through the mechanism, while maintaining a 20 cm interval between the thin Ti strip and the AlTiB wire. That is, the thin Ti strip melts first, providing a Ti-rich environment.

[0048] The grain refiner and Ti element self-mix in the flow channel and filter tank, and are then introduced into a Ø600 mm crystallizer for semi-continuous casting at a pulling speed of 25 mm / min. The grain refiner is added to the crystallizer within 15 minutes of casting.

[0049] Statistical analysis of ingot sampling: average grain size 108 μm, substantially all equiaxed grains, no columnar grains. Repeat three heats, grain size fluctuation <± 7 μm, process stable, as shown in Figure 4 Comparative Example 1

[0050] Comparative Example 1 is a semi-continuous casting of a Ø400 mm ingot, and the target alloy to be smelted is Al-1.15Li-0.1Zr (wt%), with only 0.3wt% AlTiB wire added.

[0051] The specific steps of casting are as follows:

[0052] ​​Firstly, add pure aluminum ingot, aluminum-zirconium intermediate alloy, and heat to 720 ℃. After melting, stir evenly, and then detect the composition by a direct-reading spectrometer. If the composition is accurate, add high-purity Li. After 10 minutes, melt, stir evenly with a graphite rod, and then detect the Li element composition by a direct-reading spectrometer. If the composition is accurate, start degassing.

[0053] Degassing for 15 minutes by spraying argon through a rotating graphite rotor, and remove slag.

[0054] After removing slag, the smelting furnace can be watered. At this time, feed AlTiB wires into the flow channel between the smelting furnace and the filter box at a certain speed.

[0055] The grain refiner self-mixes in the flow channel and the filter box, and then is introduced into a Ø400 mm crystallizer for semi-continuous casting at a pulling speed of 30 mm / min. The grain refiner is added to the casting in the crystallizer within 15 minutes.

[0056] Casting ingot sampling analysis statistics: the grain structure is columnar crystal, and the average grain size is about 2 mm, as shown in Figure 5 . Comparative Example 2

[0057] Comparative Example 2 is a Ø400 mm ingot semi-continuous casting. The target alloy for smelting is 2195 aluminum-lithium alloy: Al-1.15Li-4.15Cu-0.4Mg-0.4Ag-0.1Zr (wt%), and only 0.3 wt% AlTiB wires are added.

[0058] The specific steps for casting are as follows:

[0059] Firstly, add pure aluminum ingot, electrolytic copper, pure magnesium, pure silver powder, and aluminum-zirconium intermediate alloy, and heat to 720 ℃. After melting, stir evenly, and then detect the composition by a direct-reading spectrometer. If the composition is accurate, add high-purity Li. After 10 minutes, melt, stir evenly with a graphite rod, and then detect the Li element composition by a direct-reading spectrometer. If the composition is accurate, start degassing.

[0060] Degassing for 15 minutes by spraying argon through a rotating graphite rotor, and remove slag.

[0061] After removing slag, the smelting furnace can be watered. At this time, feed AlTiB wires into the flow channel between the smelting furnace and the filter box at a certain speed.

[0062] The grain refiner self-mixes in the flow channel and the filter box, and then is introduced into a Ø400 mm crystallizer for semi-continuous casting at a pulling speed of 30 mm / min. The grain refiner is added to the casting in the crystallizer within 15 minutes.

[0063] Casting ingot sampling analysis statistics: the grain structure is coarse dendrite, and the size is about 610 μm, as shown inFigure 6 As shown in FIG. 1. Comparative Example 3

[0064] Comparative Example 3 is a Ø400 mm ingot semi-continuous casting, and the target alloy to be smelted is a 2195 aluminum-lithium alloy: Al-1.15Li-4.15Cu-0.4Mg-0.4Ag-0.1Zr (wt%), with 0.05wt% Ti and 0.3wt% AlTiB wire being added, and the mass fraction ratio of Ti (thin Ti strip) / Zr is controlled at 0.5, but the thin Ti strip is directly added into the smelting furnace.

[0065] The specific steps of the casting are as follows:

[0066] First, pure aluminum ingots, electrolytic copper, pure magnesium, pure silver powder, and aluminum-zirconium intermediate alloy are added, and the temperature is raised to 720°C. After the smelting is complete, the composition is detected by a direct-reading spectrometer. After the composition is accurate, high-purity Li is added. After 10 minutes, the Li element composition is detected again by a direct-reading spectrometer after the smelting is complete. After the composition is accurate, 0.05wt% thin Ti strip is added, and the smelting is complete.

[0067] The smelting furnace is cooled by water after the slag is removed. At this time, the AlTiB wire is fed into the flow channel between the smelting furnace and the filter box at a certain speed through a mechanism. The grain refiner is added to the casting within 15 minutes, but the Ti element is added to the guide crystallizer for more than 30 minutes.

[0068] The smelting furnace is cooled by water after the slag is removed. At this time, the AlTiB wire is fed into the flow channel between the smelting furnace and the filter box at a certain speed through a mechanism. The grain refiner is added to the casting within 15 minutes, but the Ti element is added to the guide crystallizer for more than 30 minutes.

[0069] The smelting furnace is cooled by water after the slag is removed. At this time, the AlTiB wire is fed into the flow channel between the smelting furnace and the filter box at a certain speed through a mechanism. The grain refiner is added to the casting within 15 minutes, but the Ti element is added to the guide crystallizer for more than 30 minutes.

[0070] The ingot sampling analysis statistics show that the grain structure is coarse dendrite, with a size of about 590μm, as shown in FIG. 2. Figure 7 As shown in FIG. 1. Comparative Example 4

[0071] This example is a Ø400 mm ingot semi-continuous casting, and the target alloy to be smelted is a 2195 aluminum-lithium alloy: Al-1.15Li-4.15Cu-0.4Mg-0.4Ag-0.1Zr (wt%), with 0.05wt% Ti and 0.3wt% AlTiB wire being added, and the mass fraction ratio of Ti (thin Ti strip) / Zr is controlled at 0.5, but the thin Ti strip and the grain refiner are directly added into the smelting furnace.

[0072] The specific steps of the casting are as follows:

[0073] Firstly, add pure aluminum ingot, electrolytic copper, pure magnesium, pure silver powder, aluminum zirconium intermediate alloy, and heat to 720 °C. After melting, stir evenly and detect the composition with a direct-reading spectrometer. If the composition is accurate, add high-purity Li. After 10 minutes, melt and stir evenly with a graphite rod. Then detect the Li element composition with a direct-reading spectrometer. If the composition is accurate, add 0.05wt% thin Ti strip and 0.3wt% AlTiB wire. After melting, start degassing.

[0074] Degassing and stirring for 15 minutes by rotating graphite rotor and blowing argon. Remove slag.

[0075] After removing slag, the smelting furnace can be drained. The melt is introduced into a Ø400mm crystallizer through a degassing tank and a filtering tank, and semi-continuous casting is performed at a pulling speed of 30mm / min. The Ti strip and grain refiner are added to the melt before it is introduced into the crystallizer, and the time from addition to casting is greater than 30 minutes.

[0076] Statistical analysis of ingot samples: the grain structure is coarse dendrite with a size of about 675μm, as shown in Figure 8 . Comparative Example 5

[0077] This example is semi-continuous casting of a Ø400mm ingot. The target alloy for smelting is 2195 aluminum-lithium alloy: Al-1.15Li-4.15Cu-0.4Mg-0.4Ag-0.1Zr (wt%). Online composite addition of 0.02wt% Ti and 0.3wt% AlTiB wire is performed. The mass fraction ratio of Ti (thin Ti strip) to Zr is controlled at 0.2.

[0078] The specific steps of casting are as follows:

[0079] Firstly, add pure aluminum ingot, electrolytic copper, pure magnesium, pure silver powder, aluminum zirconium intermediate alloy, and heat to 720 °C. After melting, stir evenly and detect the composition with a direct-reading spectrometer. If the composition is accurate, add high-purity Li. After 10 minutes, melt and stir evenly with a graphite rod. Then detect the Li element composition with a direct-reading spectrometer. If the composition is accurate, start degassing.

[0080] Degassing for 15 minutes by rotating graphite rotor and blowing argon. Remove slag.

[0081] After removing slag, the smelting furnace can be drained. At this time, AlTiB wire and thin Ti strip are fed into the flow channel between the degassing tank and the filtering tank at a certain speed, while maintaining a 20cm interval between the thin Ti strip and the AlTiB wire. That is, the thin Ti strip is melted before the AlTiB wire.

[0082] The grain refiner and Ti element self-mix in the flow channel and filter box, and then are introduced into a Ø400mm crystallizer for semi-continuous casting at a casting speed of 30mm / min. The time for adding the grain refiner into the crystallizer and casting is within 15 minutes.

[0083] Ingot sampling analysis and statistics: The average grain size is 312μm, almost entirely equiaxed crystals, with no columnar crystals. Three repeated furnace runs showed grain size fluctuations of <±7μm, indicating stable process performance. Figure 9 As shown.

[0084] The grain size of the aluminum alloy ingots in each embodiment and comparative example was measured, and the grain size results are shown in Table 1.

[0085] Table 1. Grain size results for the three sets of examples and comparative examples.

[0086]

[0087] As shown in Table 1, the grain refinement effect of Examples 1 to 3 of the present invention is significantly better than that of the comparative examples. Example 1 is a ternary Al-Li-Zr alloy. Although there are grain refinement poisoning elements, its grain size is refined to 96 μm under the method of the present invention.

[0088] Example 2 is a mature alloy grade. Due to the relatively large number of elements, there is some interference, so it is refined to 108μm.

[0089] In Example 3, the ingot diameter was increased to 600 mm. For aluminum-lithium alloys, due to the low thermal conductivity caused by Li, the heat conduction is slower and more difficult to refine after the size is increased compared to other Li-free alloys. However, it can still be refined to 120 μm using this method.

[0090] Comparative Example 1, with the addition of only a grain refiner, showed severe Zr and Li poisoning, resulting in columnar grains with a size as large as 2 mm.

[0091] In Comparative Example 2, although the presence of multiple elements can pin the grain boundaries and inhibit grain growth, the grain refinement poisoning effect still exists, resulting in grains as large as 610 micrometers.

[0092] In Comparative Example 3, thin Ti strips were directly added to the melting furnace for alloying. However, due to the large amount of molten material in the large-sized ingot and the long duration of the molten material, Ti elements reacted with Zr to form compounds such as Ti2Zr, which consumed Ti elements. As a result, the molten material still had a grain refinement poisoning effect, and the grains were still coarse. Therefore, the time from adding the thin Ti strips and grain refiner to casting should be controlled to 5 to 15 minutes to ensure that they can fully exert their grain refinement effect.

[0093] In Comparative Example 4, thin Ti strips and grain refiners were directly added to the melting furnace. Due to the large-scale semi-continuous casting, the melt volume was excessive. Furthermore, after adding the Ti strips and grain refiners, the melt required in-furnace degassing and stirring, troughing, online degassing, and filtration. The presence time of Ti and the grain refiner in the melt exceeded 30 minutes, far exceeding 15 minutes. During this period, Ti reacted with Zr, causing the nucleation particles of the grain refiner to aggregate and precipitate, significantly weakening the refining effect and resulting in grains as coarse as 675 μm.

[0094] In summary, the method of online composite addition of thin Ti strips and grain refiners using flow channels in large-scale Zr-containing aluminum-lithium alloys is indeed feasible. This invention provides a stable and reliable grain refinement technology solution for large-scale Zr-containing aluminum-lithium alloys. Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and 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 the details for the sake of brevity.

[0095] 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 grain refinement method of a large-size ingot of a Zr-containing Al-Li alloy, wherein the large-size ingot of the Zr-containing Al-Li alloy is cast by semi-continuous casting, and the casting is performed by melting a Zr-containing Al-Li alloy raw material, degassing the melt, filtering the melt, and casting the melt to obtain the ingot of the Zr-containing Al-Li alloy, wherein, after the degassing and before the filtering, a titanium bar and a grain refiner are intermittently added to the melt, the melt is controlled so that the melt contains molten titanium when the grain refiner is added, the molten titanium is controlled so that the molten titanium is present in the melt for not more than 5 seconds before the molten titanium meets the grain refiner, the time from the addition of the grain refiner to the start of the casting is controlled to be 5 to 15 minutes, and the ratio of the weight of the titanium bar to the weight of Zr is 0.5 to 1:

1. The grain refiner is added in an amount of 0.2 to 0.6% by weight of the Zr-containing Al-Li alloy.

2. The grain refining method of claim 1, wherein the step of applying the electromagnetic field is performed after the step of applying the mechanical vibration. The grain refiner is Al-5Ti-1B, Al-5Ti-1C, or Al-5Ti-1B-Re. ​ 3. The grain refining method of claim 1 wherein the step of applying the fluxing agent is performed by spraying the fluxing agent onto the molten metal. The titanium bar is an Al-10Ti intermediate alloy, and the thickness of the titanium bar is 2 to 5 mm. ​ 4. The grain refining method of claim 1 wherein the step of applying the fluxing agent is performed by spraying the fluxing agent onto the molten metal. The Zr-containing Al-Li alloy contains Zr in an amount of 0.05 to 0.20% by weight and Li in an amount of 0.5 to 2.2% by weight. ​ 5. The grain refining method of claim 1 wherein the step of applying the fluxing agent is performed by spraying the fluxing agent onto the molten metal. In the flow direction of the melt, the titanium bar and the grain refiner are spaced apart by 15 to 30 cm, the titanium bar is upstream of the melt, the grain refiner is downstream of the melt, and the titanium bar and the grain refiner are simultaneously added to the melt. ​ 6. The grain refinement method of claim 1, wherein the step of adding the refining agent is performed after the step of melting the base metal. The temperature of the melt at the time of the addition of the grain refiner is 720 to 730°C.

7. The grain refinement method as described in claim 6, characterized in that, The diameter of the ingot of the Zr-containing Al-Li alloy is 400 mm or more.

8. The grain refining method of claim 1 wherein the step of applying the fluxing agent is performed by spraying the fluxing agent onto the molten metal. ​ ​

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