Method for manufacturing a stirrer and an aluminum alloy ingot

Abstract

In the process of manufacturing an ingot, by mechanically oscillating the molten metal, the crystal grain size is refined to suppress the generation of abnormal structures, reduce the macrosegregation of solute elements, and suppress casting cracks. 【Solution means】A method for manufacturing an aluminum alloy ingot, comprising a casting process in which a stirrer 3 is rotated in a molten aluminum alloy and the molten metal is solidified while being oscillated. In the casting process, the stirrer is rotated with a flow straightening plate 32 having a protrusion provided at its lower edge positioned between the surface of the molten metal and the rotating blades.

Description

Technical Field

[0001] The present invention relates to a stirrer and a method for manufacturing an aluminum alloy ingot. Specifically, in the ingot manufacturing process, by mechanically oscillating the molten metal, the macro segregation of solute elements is reduced, the crystal grain size is refined to suppress the generation of abnormal structures, and the occurrence of ingot cracking can be suppressed. The present invention relates to a stirrer and a method for manufacturing an aluminum alloy ingot.

Background Art

[0002] For example, a sputtering target is required to have few contained impurities in its chemical composition, not contain foreign substances such as non-metallic inclusions, have a low defect occupancy rate including voids, and have a uniform and fine crystal grain size over the entire sputtering surface. Similar characteristics are also required for the ingot that is the raw material.

[0003] When manufacturing a sputtering target, first, the target metal is melted, the components are adjusted to purify the molten metal, and then it is cast to obtain an ingot as the raw material. Further, by performing predetermined plastic working and heat treatment on this ingot, a sputtering target is obtained.

[0004] Also, the crystal grains of the sputtering target are controlled in the processes of plastic working and heat treatment. However, the finer the crystal grain size of the ingot, the easier the control, and cost reduction can also be achieved by simplifying the plastic working and heat treatment processes.

[0005] Note that the ingot, which is the raw material for the sputtering target, has few contained impurities in its chemical composition and a low generation frequency of solidification nuclei during the solidification process. Therefore, the crystal grain size tends to be coarse, and the occurrence frequency of abnormal structures such as feathery crystals is also high. Furthermore, there are strict regulations on the contained components, and the addition of metals and their compounds called grain refinement materials, which are often used in general alloy ingots, is not allowed.

[0006] However, the fact that the crystal grain size of the ingot, which is the material for the sputtering target, is coarse or the presence of abnormal structures has adverse effects such as poor deformation and non-uniform structures in the plastic working process of the sputtering target, and also in the solidification process of the ingot, it is known that it concentrates solidification stress and causes ingot cracking. In order to improve the quality of the sputtering target, it is necessary to suppress the generation of abnormal structures and refine the crystal grain size.

[0007] In casting, when solidifying the molten metal containing solute elements, solute redistribution occurs, resulting in microscopic and macroscopic segregation of solute components. Among these, in particular, macroscopic segregation of solute components not only deteriorates the characteristics of the sputtering target but may also cause ingot cracking. By reducing the macroscopic segregation of solute elements, the success rate of the casting process can be increased.

[0008] It is already known that the above problems can be improved by mechanically oscillating the molten metal near the solidification interface in the casting process. As one such method, for example, the technique described in Patent Document 1 has been proposed.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] However, even if the molten metal is oscillated by the technique described in Patent Document 1, in actuality, feathery crystals may occur, and the effect of refining the crystal grain size to suppress the generation of abnormal structures and the effect of reducing macroscopic segregation of solute elements to suppress casting cracking are not sufficient, and sufficient quality of the ingot could not be stably obtained.

[0011] The present invention has been devised in view of the above points, and aims to provide a manufacturing method for a stirrer and an aluminum alloy ingot that can reduce the macroscopic segregation of solute elements, refine the crystal grain size, suppress the occurrence of abnormal structures, and suppress casting cracks. [Means for solving the problem]

[0012] In order to achieve the above-mentioned object, the present invention provides a stirrer for stirring molten aluminum or aluminum alloy, comprising a designated rotating shaft, a rotating blade that rotates in conjunction with the rotation of the rotating shaft, a baffle plate located above the rotating blade, and a protrusion provided on the lower edge of the baffle plate.

[0013] Here, the stirrer is provided with a protrusion on the lower edge of the straightening plate, so that the horizontal discharge flow generated by the rotation can be directed downward (towards the solidification interface). This makes it possible to obtain a sufficient vertical flow to the solidification interface, and suppresses grain growth and the growth of abnormal structures that cause the crystal grains to become coarse.

[0014] The baffle plate may be integral with the "rotating shaft and rotor blades" or may be separate therefrom. However, if the "rotating shaft and rotor blades" and the "blowback plate" are separate bodies, the rotating shaft and the blowback plate will come into contact and rub against each other, shortening the lifespan of the rotating shaft and the blowback plate, and there is also a risk that slag produced by the rub will be mixed into the ingot. Therefore, from the viewpoint of preventing the inclusion of slag due to the rub, it is preferable that the blowback plate be formed integrally with the rotating shaft.

[0015] Furthermore, when the protrusions are positioned outboard of the rotating blades in a plan view, the horizontal discharge flow generated by rotation can be directed downward (towards the solidification interface) even more effectively.

[0016] In addition, when a plurality of protrusions are provided on the rectifying plate and the distance between the protrusions is 8 mm or less, the flow velocity in the horizontal direction can be suppressed, so that the rotational speed of the rotating shaft can be increased. By increasing the rotational speed, a more sufficient vertical flow with respect to the solidification interface can be obtained.

[0017] In addition, in order to achieve the above object, the present invention rotates a predetermined stirrer having a predetermined rotating shaft and rotating blades that rotate as the rotating shaft rotates in a molten metal of aluminum or an aluminum alloy, and solidifies the molten metal while oscillating it. A method for manufacturing an aluminum alloy ingot including a casting step, wherein in the casting step, the stirrer is rotated with a rectifying plate having protrusions provided at its lower edge portion positioned between the molten metal surface and the rotating blades.

[0018] According to the method for manufacturing an aluminum alloy ingot of the present invention, the oscillation of the molten metal promotes the generation of crystal grains, thereby suppressing grain growth that causes coarsening of the crystal grain size and the growth of abnormal structures.

[0019] That is, in the present invention, since a predetermined stirrer is rotated in a molten metal of aluminum or an aluminum alloy and the molten metal is solidified while being oscillated, the solidification interface receives a predetermined pressure by the flowing fluid due to the oscillating molten metal. As described above, grain growth that causes coarsening of the crystal grain size and the growth of abnormal structures are suppressed.

[0020] Here, in the casting step, by rotating the stirrer with a rectifying plate having protrusions provided at its lower edge portion positioned between the molten metal surface and the rotating blades, the horizontal discharge flow generated by the rotation can be directed downward (toward the solidification interface). As a result, the oscillation of the molten metal becomes a flow including a vector perpendicular to the solidification interface, rather than a flow consisting only of vectors parallel to the solidification interface such as a swirling flow.

[0021] When the velocity of this flow is decomposed into a "vector perpendicular to the solidification interface" and "other vectors", when the "vector perpendicular to the solidification interface" is equal to or greater than a predetermined value (for example, 0.1 m / sec or more), the problem of macrosegregation of solute elements caused by the stirring effect of the flow can also be solved together.

[0022] In addition, such fluctuations of the molten metal are effective in refining the crystal grain size, and the crystal grain size can be refined without adding a refining agent (for example, titanium, boron, etc.).

[0023] Thus, the present invention mechanically oscillates the molten metal, reduces macrosegregation of solute elements, and applies a pressure including a vector perpendicular to the solidification interface to the molten metal, thereby refining the crystal grain size, suppressing the generation of abnormal structures, and suppressing casting cracks.

[0024] In addition, since the present invention positions a predetermined flow rectifying plate between the molten metal surface and the rotating blades, it is possible to suppress the depression of the molten metal surface by suppressing the drawing-in of the molten metal from above the stirrer. Furthermore, the flow of the molten metal generated by the stirrer can be concentrated between the stirrer and the solidification interface, and the stirring efficiency near the solidification interface can be improved.

[0025] When a swirling flow is generated by the rotation of the stirrer, the flow is transmitted in the molten metal surface direction (upward direction) due to the friction of the molten metal, and the drawing-in of the molten metal surface by the vortex occurs. When "depression of the molten metal surface" occurs due to the drawing-in of the molten metal surface, foreign substances such as oxides floating on the molten metal surface are mixed into the ingot, and the quality of the ingot deteriorates. That is, in order to prevent foreign substances from entering the ingot, the rotation speed of the stirrer is naturally limited.

[0026] However, when a flow rectifying plate is positioned between the molten metal surface and the rotating blades, it is possible to prevent the generation of a drawing-in flow of the molten metal from above the stirrer. In addition, since the transmission of the swirling flow generated by the rotation of the stirrer in the molten metal surface direction is inhibited, an effect of suppressing the generation of vortices near the molten metal surface can also be expected. That is, by suppressing the generation of "depressions on the surface of the molten metal" with the flow rectifying plate, the rotational speed of the stirrer can be increased, and large fluctuations can be imparted to the molten metal.

[0027] From these facts, it can be considered that when the flow rectifying plate is positioned between the surface of the molten metal and the rotating blades, the influence of the stirring above the stirrer becomes smaller. That is, it is also possible to expect the effect that most of the energy used for stirring acts below the stirrer (near the solidification interface), thereby increasing the stirring efficiency.

[0028] Moreover, in the method for manufacturing an aluminum alloy ingot of the present invention, the purity of the aluminum alloy can be 99.99 wt% or more.

[0029] In the case of a high-purity aluminum alloy with a purity of 99.99 wt% or more, although it is difficult to add a grain refinement material (for example, titanium or boron), in the present invention, the grain refinement of the high-purity aluminum alloy is possible because the grain size can be refined without adding a grain refinement material.

Advantages of the Invention

[0030] In the stirrer and the method for manufacturing an aluminum alloy ingot of the present invention, the grain size of the ingot can be refined to suppress the generation of abnormal structures, reduce the macrosegregation of solute elements, and suppress casting cracks.

Brief Description of the Drawings

[0031]

Figure 1

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Figure 13

Mode for Carrying Out the Invention

[0032] Hereinafter, a mode for carrying out the invention (hereinafter referred to as "embodiment") will be described. Here, the case of manufacturing an aluminum alloy ingot, which is a material for a sputtering target, by applying the HOTTOP casting method will be taken as an example for explanation.

[0033] FIG. 1 is a schematic diagram for explaining the structure of an ingot manufacturing apparatus M used in the method for manufacturing an aluminum alloy ingot of the present invention. The ingot manufacturing apparatus M shown in FIG. 1 has a vertical mold 1 with a jacket structure, and on the mold 1, a molten metal receiving container 2 having a molten metal reservoir 20 made of heat-insulating refractory and having a diameter smaller than that of the mold 1 is placed. In addition, a runner 21 for injecting the molten aluminum alloy into the molten metal reservoir 20 is connected to the molten metal receiving container 2.

[0034] While forming the solidification interface S on the upper surface portion of the ingot during casting, the aluminum alloy is sequentially poured into the molten metal receiving vessel 2 through the runner 21 and into the molten metal reservoir 20 until the molten metal reservoir 20 is filled to a molten metal level 90 of a predetermined height.

[0035] In addition, a stirrer 3 is disposed inside the molten metal reservoir 20. The stirrer 3 has a rotating shaft 30, a rotating blade 31c attached to the tip of the rotating shaft 30, and a rectifying plate 32 attached above the rotating blade 31c. The rotating shaft 30, the rotating blade 31c, and the rectifying plate 32 are formed of carbon or ceramics.

[0036] Here, in the present embodiment, in order to oscillate the molten metal near the solidification interface, it is necessary to insert the stirrer 3 into the upper molten metal reservoir or the mold and rotate the stirrer. Therefore, the rotating shaft 30 is provided so as to be rotatable forward and backward by a motor (not shown), and the cycle of forward and backward rotation is set to 5 seconds.

[0037] Note that the cycle of forward and backward rotation does not necessarily have to be 5 seconds as long as the entire exposure of the solidification interface S is realized.

[0038] Furthermore, as shown in FIG. 2 (the illustration of the rectifying plate 32 is omitted in FIGS. 2 and 3), the inclination angle of the rotating blade with respect to the rotation plane perpendicular to the rotating shaft 30 is appropriately set, and there are several variations.

[0039] For example, the rotating blade 31a shown in FIG. 2(a) (90° with respect to the rotation plane), the rotating blade 31b shown in FIG. 2(b) (60° with respect to the rotation plane), the rotating blade 31c shown in FIG. 2(c) (45° with respect to the rotation plane), the rotating blade 31d shown in FIG. 2(d) (30° with respect to the rotation plane), and the rotating blade 31e shown in FIG. 2(e) (0° with respect to the rotation plane) can be mentioned. However, even if there is a difference in the stirring efficiency, it is possible to stir with a setting of 70° to 20° in practical use.

[0040] When tests were conducted using the rotating blades 31a to 31e shown in Fig. 2, the rotating blade 31c inclined at 45° with respect to the rotation plane perpendicular to the rotation axis 30 had the best balance between the area receiving the molten metal and the ratio of discharging and flowing the molten metal downward during forward rotation, and was the most efficient rotating blade.

[0041] On the other hand, in the case of the rotating blade 31b inclined at 60° (see Fig. 3(a)), although the area receiving the molten metal (the area indicated by reference numeral 3A) is large, the "ratio of discharging the molten metal in the horizontal direction" indicated by reference numeral 3B is large, so the "ratio of discharging and flowing the molten metal downward" indicated by reference numeral 3C becomes small. Note that the reference numeral R in Fig. 3(a) indicates the rotation direction of the rotation axis 30.

[0042] Also, in the case of the rotating blade 31d inclined at 30° (see Fig. 3(b)), since the "ratio of discharging the molten metal in the horizontal direction" indicated by reference numeral 3E is small, the "ratio of discharging and flowing the molten metal downward" indicated by reference numeral 3F is large, but the area receiving the molten metal (the area indicated by reference numeral 3D) becomes small. Note that the reference numeral R in Fig. 3(b) indicates the rotation direction of the rotation axis 30.

[0043] And it was confirmed that at the same rotational speed, the rotating blade 31c at 45° had the highest "downward flow velocity of the molten metal". In addition, even if there was an influence due to the difference in the angle of the rotating blade, it was also confirmed that by adjusting the stirring speed, a sufficient vertical flow with respect to the solidification interface could be obtained even when the inclination angle was between 70° and 20°.

[0044] Also, in the case of the rotating blade 31a inclined at 90° (see Fig. 2(a)), a normal structure was obtained only directly below the stirrer 3, and feathery crystals were generated around it. This is considered to be because a drawing flow (vertical flow) occurred only directly below the stirrer 3 and had an effect. And this indicates that the casting structure is improved not only by the "pressure generated by the flow toward the solidification interface S" but also by the "pressure (negative pressure) generated by the flow away from the solidification interface".

[0045] In the case of the rotating blade 31a inclined at 90°, although there is a flow parallel to the solidification interface S, it was confirmed that tissue abnormalities occurred. Therefore, it was determined that the effect of the flow parallel to the solidification interface S is absent or almost absent.

[0046] Furthermore, in the case of the rotating blade 31e inclined at 0° (see Fig. 2(e)), the area for receiving the molten metal was extremely small, and it was difficult to generate an up-and-down flow.

[0047] Here, the shape of the rotating blade may be in the form of curved plates with the same angle (45°) with respect to each other as in the present embodiment, or curved plates with different angles with respect to each other. The shape of the rotating blade is not particularly limited, and it may be a plate body, a straight plate in a circular or elliptical shape, etc.

[0048] Moreover, between the rotating blade 31c of the stirrer 3 of the ingot manufacturing apparatus M and the molten metal surface 90, a rectifying plate 32 for blocking or disturbing the flow of the molten metal is provided. The rectifying plate 32 is, for example, fixedly arranged on the rotating blade 31c (see A to D in Fig. 4). Note that the rectifying plate 32 may be arranged separately from the rotating shaft 30 or the rotating blade 31c and fixed from the outside (see E in Fig. 4).

[0049] In the variations of Fig. 4, when viewed from above or below, each rectifying plate 32 has a disk shape.

[0050] Here, when a swirling flow is generated by the rotation of the stirrer 3, the flow is transmitted in the molten metal surface direction (upward direction) due to the friction of the molten metal, and the drawing-in of the molten metal surface by the vortex occurs. When the rectifying plate 32 is attached to the stirrer 3 (in the case of Fig. 5), the generation of the drawing-in flow from above the stirrer 3 can be prevented. In addition, since the transmission of the swirling flow generated by the rotation of the stirrer 3 in the molten metal surface direction is inhibited, an effect of suppressing the generation of the vortex can also be expected.

[0051] From these points, it is considered that the rectifying plate 32 can reduce the influence of stirring above the stirrer 3 (the region indicated by reference numeral 5A in Fig. 5). That is, it is also possible to expect the effect of causing most of the energy used for stirring to act below the stirrer 3 (the region indicated by reference numeral 5B in Fig. 5, near the solidification interface S) (see Fig. 5). Note that reference numeral 5C in Fig. 5 represents the "drawing-in flow from below".

[0052] On the other hand, when there is no rectifying plate 32 (in the case of Fig. 6), the influence of stirring will reach the entire molten metal (in other words, it means that the influence of stirring cannot effectively reach the solidification interface S). Note that although reference numeral 6A in Fig. 6 represents the "drawing-in flow from above", the stirrer 3 discharges and flows the molten metal downward, and sucks in that much molten metal from above.

[0053] As the rectifying plate 32, not only the rectifying plate A in Fig. 4 but also the rectifying plates B to E may be used. For A, a guide (an example of a protrusion) 33 is provided at the lower surface peripheral portion in order to direct the horizontal discharge flow toward the solidification interface S, and the inner surface of the guide 33 is formed in a straight line. For B as well, a guide 33 is provided at the lower surface peripheral portion in order to direct the horizontal discharge flow toward the solidification interface S, and for B, the inner surface of the guide 33 is formed in a curved shape.

[0054] C and D are positioned at a distance from the rotating blade 31c (a guide 33 identical to that of the rectifying plate A is provided, and the rectifying plate C is positioned vertically above the rectifying plate A. A guide 33 identical to that of the rectifying plate B is provided, and the rectifying plate D is positioned vertically above the rectifying plate B).

[0055] E is fixed from the outside independently of the rotating shaft 30 or the rotating blade 31c. Note that it may be fixedly arranged on the inner surface (reference numeral omitted) facing the molten metal reservoir 20 of the molten metal receiving container 2.

[0056] Incidentally, depending on the structure of the ingot manufacturing apparatus M and the position of the stirrer 3, increasing the rotational speed of the stirrer 3 may increase the discharge flow rate in the horizontal direction, which may cause inconvenience.

[0057] For example, in the HOTTOP casting method, in order to improve the appearance of the ingot, a method of pressurizing the molten metal with gas (gas pressurized HOTTOP casting method) may be applied. And when using a rectifying plate without a guide, if the position of the rectifying plate (position in the Z-axis direction) coincides with the gas pressurizing part (gas pressurizing the molten metal), in order to avoid the destruction of the gas pressurizing part due to the increase in the discharge flow rate in the horizontal direction, an increase in the rotational speed may be restricted.

[0058] In such a case (when using a rectifying plate without a guide and the increase in the rotational speed is restricted), in the case of the rectifying plates A to D, even if the rotational speed increases, the discharge flow rate in the horizontal direction does not increase, so the rotational speed can be increased. Also, the rectifying plate E (externally fixed type) can increase the rotational speed because although it is in the molten metal, it is offset from the gas pressurizing part in the Z-axis direction.

[0059] (Example) Hereinafter, examples will be described. In the example, for the rotating blade 31c, the height in the front view (see Fig. 7(a)) is 20 mm, the length in the direction of the inclination angle of 45° in the side view (see Fig. 7(b)) is about 25.3 mm, the thickness is 3 mm, the length in the short side direction in the bottom view (see Fig. 7(c)) is 20 mm, and the length in the long side direction is 40 mm, and a stirrer 3 with a rotating shaft diameter of 15 mm (see Fig. 7(c)) was used.

[0060] Also, in the examples (except for Example 4), as the rectifying plate 32, one with a diameter (outer diameter) of 57 mm and a diameter up to the guide start point of 45 mm was used (see Fig. 8(a)). On the other hand, in Example 4, a rectifying plate 32 having an outer diameter as described later was used. Hereinafter, the height of the guide indicated by reference sign A in Fig. 8(b) will be defined as the "guide height", and the width of the guide indicated by reference sign B in Fig. 8(b) will be defined as the "guide width" for explanation purposes.

[0061] In addition, in the examples (except for Example 3), an integral rectifying plate 32 was used. On the other hand, in Example 3, a separate rectifying plate 32 as described later was also used. Furthermore, in the examples (except for Example 5), a guide 33 without a notch was used. On the other hand, in Example 5, a guide 33 with a notch as described later was also used.

[0062] In the examples, the rotational speed of the stirrer 3 was 450 rpm (250 rpm only in Example 6), the rotational direction was forward and reverse rotation, with a cycle of 5 seconds of forward rotation, 1 second of stop, 5 seconds of reverse rotation, and 1 second of stop. The installation height of the stirrer 3 was 122 mm from the upper surface of the molten metal receiving vessel 2 to the upper part of the rotating blade 3c of the stirrer 3.

[0063] Furthermore, in the water test, the stirrer 3 was rotated in water at 10°C containing beads (whose viscosity can be evaluated as equivalent to that of aluminum molten metal at 700°C), and the maximum value of the velocity component in the horizontal direction (the direction perpendicular to the rotation axis 30) was confirmed by calculating the moving distance of the beads per unit time. Also, in Examples 1 to 4, the maximum value of the velocity component in the direction perpendicular to the solidification interface S was also confirmed.

[0064] ■ Example 1 (see Fig. 9) In Example 1, when no guide was provided, water tests were conducted for six patterns where the "guide height" was 2.5 mm (see Fig. 9(a)), 5.0 mm (see Fig. 9(b)), 7.5 mm (see Fig. 9(c)), 10 mm (see Fig. 9(d)), 15 mm (see Fig. 9(e)) (the "diameter to the guide start point" was fixed at 45 mm, and the "guide width" was fixed at 5 mm).

[0065] Note that the angle formed by the "lower surface (horizontal plane) of the rectifying plate 32" and the "inner surface (inclined plane) of the guide 33" is 153.4° in Fig. 9(a), 135°C in Fig. 9(b), 123.6° in Fig. 9(c), 116.5° in Fig. 9(d), and 108.4° in Fig. 9(e).

[0066] Table 1 shows the "horizontal flow velocity (maximum value)" and the "vertical flow velocity (maximum value)".

[0067] [Table 1] TIFF0007712464000002.tif42169

[0068] From Table 1, it can be seen that when comparing with the case where the guide 33 is not provided, when the guide 33 is provided (when the guide height is 2.5 mm to 15 mm), the horizontal flow velocity (maximum value) is smaller in all cases.

[0069] Also, from Table 1, it can be seen that when comparing with the case where the guide 33 is not provided, the vertical flow velocity is larger when the guide height is "2.5 mm", "5 mm", or "7.5 mm".

[0070] Note that when the guide height is "10 mm" or "15 mm", although the vertical flow velocity is smaller, the horizontal flow velocity is small enough, and the rotation speed can be increased. And by increasing the rotation speed, the vertical flow velocity can be increased.

[0071] ■Example 2 (see Fig. 10) In Example 2, water tests were conducted for 6 patterns: when no guide was provided, when the "guide width" was 5 mm (see Fig. 10(a)), 4 mm (see Fig. 10(b)), 3 mm (see Fig. 10(c)), 2 mm (see Fig. 10(d)), and 1 mm (see Fig. 10(e)) (the "guide height" was fixed at 5 mm).

[0072] Note that the angle formed by the "lower surface (horizontal plane) of the straightening plate 32" and the "inner surface (inclined plane) of the guide 33" is 135° in Fig. 10(a), 128.6° in Fig. 10(b), 120.9° in Fig. 10(c), 111.8° in Fig. 10(d), and 101.3° in Fig. 10(e).

[0073] In addition, the "diameter to the guide starting point" is 45 mm in Fig. 10(a), 47 mm in Fig. 10(b), 49 mm in Fig. 10(c), 51 mm in Fig. 10(d), and 53 mm in Fig. 10(e).

[0074] Table 2 shows the "flow velocity in the horizontal direction (maximum value)" and the "flow velocity in the vertical direction (maximum value)".

[0075] [Table 2] TIFF0007712464000003.tif42170

[0076] From Table 2, it can be seen that when comparing with the case where the guide 33 is not provided, in the case where the guide is provided (when the guide width is 1 mm to 5 mm), the flow velocity in the horizontal direction (maximum value) is smaller in all cases.

[0077] Also, from Table 2, it can be seen that when comparing with the case where the guide 33 is not provided, in the case where the guide 33 is provided (when the guide width is 1 mm to 5 mm), the flow velocity in the vertical direction (maximum value) is larger in all cases.

[0078] ■Example 3 (see Fig. 11) In Example 3, water tests were conducted for the case where no guide is provided, the case of the integrated flow straightening plate 32 (the type A flow straightening plate in Fig. 4, see Fig. 11(a)), and the case of the separate flow straightening plate 32 supported by the support rod 11 (the type E flow straightening plate in Fig. 4, see Fig. 11(b)) (the "diameter to the guide starting point" of the integrated flow straightening plate 32 and the separate flow straightening plate 32 was fixed at 45 mm, the "guide width" was 5 mm, and the "guide height" was 5 mm).

[0079] Furthermore, water tests were conducted for the separate flow straightening plate 32 with three patterns of "inner diameter of the opening" being 20 mm (see Fig. 11(c)), 30 mm (see Fig. 11(d)), and 40 mm (see Fig. 11(e)).

[0080] Note that the clearances (the clearances indicated by the symbol W in Fig. 11(b)) with the rotation axis 30 (the diameter of the rotation axis is 15 mm) are 2.5 mm in Fig. 11(c), 7.5 mm in Fig. 11(d), and 12.5 mm in Fig. 11(e).

[0081] Table 3 (Tables 3-1 to 3-3) shows the "horizontal flow velocity (maximum value)" and the "vertical flow velocity (maximum value).

[0082] [Table 3-1]: When no guide is provided TIFF0007712464000004.tif18170

[0083] [Table 3-2]: In the case of an integrated flow straightening plate TIFF0007712464000005.tif18170

[0084] [Table 3-3]: In the case of a separate flow straightening plate TIFF0007712464000006.tif27170

[0085] From Table 3, it can be seen that when compared with the case where the guide 33 is not provided, in the case where the guide 33 is provided (in the case of an integrated flow straightening plate and in the case of a separate flow straightening plate), the horizontal flow velocity (maximum value) is smaller in both cases.

[0086] Also, from Table 3, it can be seen that when compared with the case where the guide portion 33 is not provided, in the case where the guide 33 is provided (in the case of an integrated flow straightening plate and in the case of a separate flow straightening plate with an opening inner diameter of 20 mm and 30 mm), the vertical flow velocity (maximum value) is larger in both cases.

[0087] Note that in the case of a separate flow straightening plate, when the opening inner diameter becomes 40 mm, the maximum value of the "vertical flow velocity" tends to decrease (when the opening inner diameter of the flow straightening plate 32 becomes 40 mm, a deteriorating tendency is observed).

[0088] ■Example 4 In Example 4, water tests were conducted for 16 patterns in the case where the outer diameter of the rectifying plate 32 was "57 mm", "70 mm", "80 mm", or "100 mm" without providing a guide, and in the case where the "guide height" was 5 mm, 7.5 mm, or 10 mm (the "guide width" was fixed at 5 mm).

[0089] Note that the "diameter to the guide starting point" is 45 mm when the outer diameter of the rectifying plate 32 is 57 mm, 58 mm when the outer diameter of the rectifying plate 32 is 70 mm, 68 mm when the outer diameter of the rectifying plate 32 is 80 mm, and 88 mm when the outer diameter of the rectifying plate 32 is 100 mm.

[0090] Table 4 shows the "horizontal flow velocity (maximum value)" and the "vertical flow velocity (maximum value)".

[0091] [Table 4] TIFF0007712464000007.tif91169

[0092] From Table 4, it can be seen that when comparing with the case where the guide 33 is not provided, in the case where the guide 33 is provided (when the outer diameter of the rectifying plate is 57 mm to 100 mm), the "horizontal flow velocity (maximum value)" is smaller in all cases.

[0093] Also, from Table 4, it can be seen that when comparing with the case where the guide 33 is not provided, in the case where the guide 33 is provided (when the outer diameter of the rectifying plate is 57 mm to 100 mm), the "vertical flow velocity (maximum value)" is larger in all cases.

[0094] Note that as the outer diameter of the rectifying plate 32 increases, the suppression effect of the "horizontal flow velocity" by the guide 33 becomes smaller. When the outer diameter of the rectifying plate 32 is 57 mm to 70 mm, there is almost no change in the maximum value of the "horizontal flow velocity", but when the outer diameter of the rectifying plate 32 exceeds 80 mm, the maximum value of the "horizontal flow velocity" tends to increase (when the outer diameter of the rectifying plate 32 exceeds 80 mm, there is a tendency to deteriorate).

[0095] Also, the larger the outer diameter of the rectifying plate 32, the more the effect of improving the "vertical flow velocity" by the guide 33 can be obtained. However, the increase rate of the "vertical flow velocity" levels off when the outer diameter of the rectifying plate 32 reaches 70 mm.

[0096] ■Example 5 (see Fig. 12) In Example 5, a water test was conducted for the cases where the guide 33 was not provided, where the missing part (the gap between the guides 33) of the guide 33 was not provided, and where the missing part of the guide 33 was provided (the "diameter up to the guide start point" was fixed at 45 mm, the "guide width" was fixed at 5 mm, and the "guide height" was fixed at 5 mm).

[0097] Furthermore, for the case of "where the missing part of the guide is provided", with the circumferential length taken as 100%, a water test was conducted for 5 patterns where the guide was divided into 4 parts (see Fig. 12(a)), 8 parts (see Fig. 12(b)), 16 parts (see Fig. 12(c)), 32 parts (see Fig. 12(d)), and 64 parts (see Fig. 12(e)) so that the total of the missing parts would be 20%.

[0098] Note that the missing parts of the guide are provided evenly, and the width of the missing part (missing width) is 7.04 mm in Fig. 12(a), 3.53 mm in Fig. 12(b), 1.77 mm in Fig. 12(c), 0.88 mm in Fig. 12(d), and 0.44 mm in Fig. 12(e).

[0099] Table 5-1 shows the "horizontal flow velocity (maximum value)". Also, Table 5-2 shows the relationship between the "missing width" and the "horizontal flow velocity (maximum value)".

[0100] [Table 5-1] TIFF0007712464000008.tif43170

[0101] [Table 5-2] JPEG0007712464000009.jpg56170

[0102] From Table 5-1, it can be seen that when compared with the case where the guide 33 is not provided, in the case where the guide 33 is provided (when the notch width is 0 to 7.04), the horizontal flow velocity (maximum value) is smaller in all cases.

[0103] Also, from the approximate straight line in Table 5-2, it can be seen that the notch width at which it is comparable to the case without a guide (when the maximum value of the horizontal flow velocity is 109 mm / sec) is 8.04 mm. Therefore, it can be seen that when the notch width is smaller than 8.04 mm (for example, when it is 8 mm or less), the effect of suppressing the maximum value of the horizontal flow velocity by the guide 33 can be obtained.

[0104] ■Example 6 (see Fig. 13) In Example 6, aluminum alloy ingots were produced in two patterns: when no guide was provided and when a guide was provided (the "diameter to the guide start point" was 45 mm, the "guide height" was 5 mm, and the "guide width" was 5 mm).

[0105] Here, with reference to the radius of the aluminum alloy ingot, in the region corresponding to approximately 70 to 95% from the center (the region indicated by symbol A in Fig. 13(a)), since dendritic crystals are generated when the refinement of crystal grains is insufficient, it is necessary to focus on this region. Note that the region corresponding to approximately 95 to 100% from the center (the region indicated by symbol B in Fig. 13(a), which is called the "primary (initial) solidification layer") is a structure formed by rapid cooling due to contact with the mold and has no direct relationship with the refinement of crystal grains.

[0106] Fig. 13(b) shows the cross-sectional structure of the aluminum alloy ingot "when no guide is provided", and Fig. 13(c) shows the cross-sectional structure of the aluminum alloy ingot "when a guide is provided".

[0107] As shown in Fig. 13(b), when no guide is provided (that is, when the velocity component in the direction perpendicular to the solidification interface S is small), a region where dendritic crystals 5 are generated around the relatively fine-grained central part could be confirmed.

[0108] On the other hand, as shown in Fig. 13(c), when a guide is provided (i.e., when the velocity component in the direction perpendicular to the solidification interface S is large), the crystal grains on almost the entire surface are fine, there is no abnormal structure, and no feathery crystals are generated. Also, the macrosegregation of solute elements is reduced, and there is no casting crack.

Explanation of Signs

[0109] M Ingot Manufacturing Apparatus 1 Mold 11 Support Rod 2 Molten Metal Receiver 20 Ladle 21 Runner 3 Stirrer 30 Rotating Shaft 31a, 31b, 31c, 31d, 31e Rotating Blades 32 Rectifying Plate 5 Feathery Crystal 9 Molten Metal 90 Molten Metal Surface S Solidification Interface

Claims

1. A stirrer for stirring a molten aluminum or aluminum alloy, comprising: a predetermined rotating shaft; rotating blades that rotate as the rotating shaft rotates; a rectifying plate positioned above the rotating blades; and protrusions provided at the lower edge of the rectifying plate for directing the horizontally discharged flow generated by rotation toward the solidification interface. The stirrer.

2. The rectifying plate is integrally formed with the rotating shaft. The stirrer according to Claim 1.

3. In a plan view, the protrusions are positioned outside the rotating blades. The stirrer according to Claim 1.

4. A plurality of the protrusions are provided on the rectifying plate, and the distance between the protrusions is 8 mm or less. The stirrer according to Claim 1.

5. A method for manufacturing an aluminum alloy ingot, comprising a casting step of rotating a predetermined stirrer having a predetermined rotating shaft and rotating blades that rotate as the rotating shaft rotates in a molten aluminum or aluminum alloy, and solidifying the molten metal while oscillating it, wherein the casting step comprises: rotating the stirrer with a rectifying plate having protrusions provided at its lower edge positioned between the molten metal surface and the rotating blades, so that the protrusions direct the horizontally discharged flow toward the solidification interface. The method for manufacturing an aluminum alloy ingot.

6. Rotating the stirrer together with the rectifying plate. The method for manufacturing an aluminum alloy ingot according to Claim 5.

7. The rectifying plate is supported independently of the stirrer, and the stirrer is rotated without being interlocked with the rectifying plate. The method for manufacturing an aluminum alloy ingot according to Claim 5.

8. The purity of the aluminum alloy is 99.99 wt% or more. The method for manufacturing an aluminum alloy ingot according to Claim 5.

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