JP2010247179A - Method of manufacturing aluminum alloy ingot, and the aluminum alloy ingot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing aluminum alloy ingot having a fine and uniform solidification structure, in large quantities and stably without adding a micronizing agent. <P>SOLUTION: The tip part of an ultrasonic horn 28 is immersed in molten metal 12 in a casting mold 10. Simultaneously, in a state that the ultrasonic horn 28 is inclined so as to be extended toward the center side of a solidification shell 36 with an inclination angle &theta; of &le;45&deg;, the ultrasonic horn 28 is arranged in such a manner that the center &cir; of the tip face of the ultrasonic horn 28 is located away from the inner wall face 38 of the casting mold 10 by &ge;15 mm and at the depth of &le;15 mm from the molten metal surface 40. Then, in this state, while applying ultrasonic vibration to the molten metal 12 with the ultrasonic horn 28, semi-continuous casting is performed to manufacture the aluminum alloy ingot 32. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for producing an aluminum alloy ingot and an aluminum alloy ingot, and in particular, performs semi-continuous casting while applying ultrasonic vibration to a molten aluminum alloy poured into a mold. The present invention relates to a method for producing an alloy ingot and an aluminum alloy ingot obtained by such a method.

  Conventionally, so-called aluminum alloy ingots such as aluminum alloy slabs and billets are mostly produced by a semi-continuous casting method (DC casting method) using a vertical semi-continuous casting apparatus having a stationary mold. ing. Also, when carrying out this semi-continuous casting method, generally, the molten metal is poured into the mold via a refractory header without using a float or an open mold method in which a float is used for pouring the molten metal into the mold. A casting method such as a hot top method in which water is poured horizontally is adopted.

  By the way, when an aluminum alloy ingot is manufactured by semi-continuous casting, cracking of the ingot at the time of casting is prevented, and workability such as rolling and extrusion performed using the manufactured aluminum alloy ingot is improved. From the viewpoint of enhancing, it is desirable to uniformly refine the solidification structure of the aluminum alloy ingot. For this reason, conventionally, when manufacturing an aluminum alloy ingot, a method for refining a solidified structure by adding a refining agent such as an Al-Ti-B alloy to an aluminum alloy is generally used. It has been adopted. However, when such a solidification structure refinement method is adopted, the refiner itself is mixed as an impurity into the ingot, thereby reducing the quality of the manufactured aluminum alloy ingot. there's a possibility that.

  Therefore, semi-continuous casting is performed while applying ultrasonic vibrations to the molten metal poured into the mold as a technique for refining the solidification structure without adding any micronizing agent to the aluminum alloy. Techniques have been proposed, for example, in Patent Documents 1 and 2 below.

  In such a proposed method, an ultrasonic horn is used, which is immersed in the molten metal poured into the mold and oscillated, thereby applying ultrasonic vibration to the molten metal in the mold. It is like that. When ultrasonic vibration is applied to the molten aluminum alloy in the mold, the impact force generated when the cavitation generated by the ultrasonic vibration is crushed, and the part immersed in the molten metal near the inner wall of the mold or the ultrasonic horn The dendrite generated in the vicinity of is finely divided, and they are dispersed around by the acoustic flow generated by the ultrasonic vibration. The fine dendrite thus dispersed becomes a new nucleation site for the solidified shell, thereby increasing the nucleation site. As a result, a fine grain structure is formed.

  However, according to the researches of the present inventors, the proposed technique disclosed in Patent Documents 1 and 2 described below, which merely applies ultrasonic vibration to the molten metal in the mold, makes the solidification structure of the aluminum alloy ingot fine. It was found difficult to realize the stabilization stably.

  That is, in order to uniformly refine the solidified structure by a technique using ultrasonic vibration, it is possible to form a melt flow in which finely divided dendrites are uniformly dispersed in the melt in the mold. It becomes extremely important. However, Patent Documents 1 and 2 below exemplify those in which an ultrasonic horn is immersed in the molten metal poured into the crucible and ultrasonic vibration is applied to the molten metal in the crucible. I was just there. In other words, these documents merely disclosed an example in which a method for refining a solidified structure using ultrasonic vibration was applied to a method for manufacturing a small ingot at a laboratory level. . Therefore, as a matter of course, in the manufacturing method of such a small ingot at the laboratory level, a finely divided dendrite is not used when manufacturing an aluminum alloy ingot by a general semi-continuous casting at the industrial level. It was completely unknown how to uniformly disperse the molten metal in the mold. Therefore, simply adopting such a conventional method as it is, it was impossible to produce an aluminum alloy ingot having a solidified microstructure uniformly refined in a large quantity and stably at an industrial level. is there.

Japanese Examined Patent Publication No. 7-84626 JP 2004-209487 A

  Here, the present invention has been made in the background as described above, and the problem to be solved is to make an aluminum alloy ingot having a fine and uniform solidification structure as a refiner. An object of the present invention is to provide a method for producing an aluminum alloy ingot which can be produced in a large amount and stably at an industrial level without addition. Another object of the present invention is to provide an aluminum alloy ingot that has a uniformly refined solidified structure and can be stably mass-produced.

  The present inventors conducted various experiments and studies in order to solve the above problems. As a result, it has been found that the position and orientation of the immersed portion of the ultrasonic horn immersed in the molten metal poured into the mold has a great influence on the molten metal flow during the molten metal. Based on this fact, the present inventors have conducted further diligent research, and as a result, the ultrasonic horn is tilted at a specific angle and placed at a predetermined position in the mold, thereby finely dividing. It has been found that the molten dendrites can form a molten metal stream that is uniformly dispersed in the molten metal in the mold.

  The present invention has been completed based on such knowledge, and the gist thereof is that an ultrasonic horn is immersed in a molten aluminum alloy poured into a mold, A method of producing an aluminum alloy ingot by performing semi-continuous casting while applying ultrasonic vibration to the ultrasonic horn, wherein the tip of the ultrasonic horn is immersed in the molten metal, The state in which the ultrasonic horn is inclined so that the angle formed by the extension line of the central axis and the contact surface of the solidified shell with the molten metal is 45 ° or less and extends toward the center of the solidified shell Then, the center part (tip center) of the tip surface of the immersion part of the ultrasonic horn in the molten metal is separated by 15 mm or more from the inner wall surface of the mold located in the immediate vicinity of the immersion part, and The center portion of the tip surface is in the mold The ultrasonic horn is oscillated in a state where the ultrasonic horn is disposed so as to be located at a depth within 15 mm from the surface of the hot water, and ultrasonic vibration is applied to the molten metal. The method is for producing an aluminum alloy ingot. In the present specification, the solidified shell refers to the entire surface layer portion including the contact surface (solidified interface) with the molten aluminum alloy ingot produced by semi-continuous casting.

  In the method for producing an aluminum alloy ingot according to the present invention, a configuration in which the immersed portion of the ultrasonic horn is oscillated with an amplitude of ± 10 μm or more is preferably employed.

  Furthermore, in the method for producing an aluminum alloy ingot according to the present invention, a configuration in which ultrasonic vibration is continuously applied to the molten metal in the mold while semi-continuous casting is performed is advantageously employed.

  In the present invention, an aluminum alloy ingot produced by the above-described method for producing an aluminum alloy ingot is also the gist thereof.

  That is, in the method for producing an aluminum alloy ingot according to the present invention, the immersed portion of the ultrasonic horn in the molten metal poured into the mold is spaced apart from the inner wall surface of the mold by a sufficient distance, and the molten metal It is arranged in a relatively shallow area. Therefore, the flow of the molten metal between the immersed part of the ultrasonic horn and the inner wall surface of the mold is stagnant, and the flow in the shallow area near the molten metal surface and the flow in the deep area of the molten metal are not uniform. Can advantageously be prevented. Moreover, since the portion of the ultrasonic horn immersed in the molten metal is inclined at an angle within a specific range so as to extend toward the center side of the solidified shell, the molten metal in a substantially constant direction throughout the mold. Can produce a flow. Therefore, according to the method of the present invention, it is possible to form a molten metal flow in which finely divided dendrites are uniformly dispersed in the molten metal in the mold, and in a substantially constant direction throughout the mold. By the molten metal flow, the temperature distribution of the molten metal in the entire mold can be made as uniform as possible.

  Therefore, according to the method for producing an aluminum alloy ingot according to the present invention as described above, an aluminum alloy ingot having a fine and uniform solidification structure can be obtained without adding any micronizing agent to the aluminum alloy. By continuous casting, it can be manufactured in large quantities and stably on an industrial level. As a result, not only the quality of aluminum alloy ingots manufactured at an industrial level is improved, but also improvement of workability such as rolling and extrusion performed using such aluminum alloy casting is realized extremely advantageously. Can be done.

  In addition, the aluminum alloy ingot according to the present invention is manufactured by the characteristic manufacturing method as described above, so that it has a uniformly refined solidified structure and can be stably mass-produced. It has become. And, when carrying out rolling, extrusion, etc., excellent workability can be exhibited.

It is explanatory drawing which shows an example of the process which manufactures an aluminum alloy ingot by the hot-top type semi-continuous casting according to this invention method. It is a figure corresponding to FIG. 1 which shows the example of a process which manufactures an aluminum alloy ingot by the method different from this invention by semi-continuous casting of a hot top system. It is a figure corresponding to FIG. 1 which shows an example of the process of manufacturing an aluminum alloy ingot by the open mold type semi-continuous casting according to the method of the present invention. It is a microscope picture of the solidification structure of the aluminum alloy ingot manufactured by the hot top type semi-continuous casting according to the method of the present invention. It is the microscope picture of the solidification structure | tissue of the aluminum alloy ingot manufactured by semi-continuous casting of a hot top system, after adding a micronizing agent to the aluminum alloy according to the conventional method. It is a microscope picture of the solidification structure | tissue of the aluminum alloy ingot manufactured by the open mold system semi-continuous casting according to this invention method. It is a microscope picture of the solidification structure | tissue of the aluminum alloy ingot manufactured by the semi-continuous casting of an open mold system, after adding a micronizing agent to the aluminum alloy according to the conventional method.

  Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

  First, FIG. 1 schematically shows an example of a process for producing an aluminum alloy ingot by hot-top semi-continuous casting according to the method of the present invention. As is apparent from FIG. 1, in this embodiment, a hot top casting apparatus having a structure similar to the conventional one used at the industrial level is used in producing the ingot of the target aluminum alloy.

  That is, the hot top casting apparatus used here has a graphite mold 10 that is open up and down. Above the mold 10, a molten metal flow path 14 is provided which extends from a tundish (not shown) and into which the molten aluminum 12 of aluminum alloy flows. The molten metal flow path 14 has a bottom wall portion, a side wall portion, and a top plate portion that are made of a current plate 16, and the inside in which the molten metal 12 is flowed is a closed space. Further, the molten metal flow path 14 covers the upper opening of the mold 10 with a part of the rectifying plate 16 constituting the bottom wall portion. A large-diameter outlet 18 is formed in the rectifying plate 16 that covers the upper opening of the mold 10.

  Thus, the molten metal 12 supplied from the tundish flows in the molten metal flow path 14 and is poured into the mold 10 through the outlet 18. Further, the molten metal 12 is prevented from being exposed to the surrounding atmosphere even when flowing in the molten metal flow path 14 or after being poured into the mold 10. Furthermore, the upper opening of the mold 10 is covered with the rectifying plate 16 so that the temperature of the molten metal 12 in the mold 10 is made uniform.

  On the other hand, a bottom block (not shown) capable of covering the lower opening of the mold 10 is disposed below the mold 10 so as to be movable up and down, and an injection port 19 for injecting cooling water is provided. A water jacket 20 is provided at a fixed position.

  Such a hot top casting apparatus has an ultrasonic oscillator 22 for applying ultrasonic vibration to the molten metal 12 of the mold 10. This ultrasonic oscillator 22 also has a structure similar to that of the prior art, and includes an ultrasonic oscillator 24, an amplifier 26, and an ultrasonic horn 28. The ultrasonic generator 22 is configured such that the ultrasonic horn 28 having a cylindrical shape can be ultrasonically vibrated with an amplitude of ± 10 μm or more at the tip portion by the oscillation of the ultrasonic oscillator 24. Then, such an ultrasonic horn 28 is inserted into the insertion hole 30 formed in the top plate portion located at a position corresponding to the outlet 18 of the molten metal flow path 14, and is inserted into the mold 10. The tip of the ultrasonic horn 28 that has entered the mold 10 is immersed in the molten metal 12 poured into the mold 10.

  By the way, in general, the ultrasonic horn of the ultrasonic oscillator is designed to have a length of about ¼ of the wavelength at which the tip portion shows the maximum amplitude. Therefore, the higher the frequency of the ultrasonic wave used, the shorter the ultrasonic horn and the smaller the obtained amplitude. In other words, the length of the ultrasonic horn can be increased by setting the amplitude at the tip of the ultrasonic horn large. As described above, the ultrasonic horn 28 used in the present embodiment is ultrasonically vibrated with an amplitude of ± 10 μm or more. Therefore, the length of the ultrasonic horn 28 is set to a relatively long length, specifically 200 mm or more.

  Thus, in the ultrasonic generator 22 having such an ultrasonic horn 28, the amplifier 26 and the ultrasonic oscillator 24 are operated at a high temperature in a state where the tip of the ultrasonic horn 28 is immersed in the molten metal 12. It is kept away from 12 as much as possible, and is less susceptible to damage from radiant heat from the molten metal 12 and heat transfer through the ultrasonic horn 28. Thus, in the ultrasonic generator 22, stable ultrasonic vibration is generated for a long time by the ultrasonic horn 28 without applying special measures for heat insulation to the amplifier 26 and the ultrasonic oscillator 24. To get.

  At present, semi-continuous casting of an aluminum alloy at an industrial level is usually performed over a period of several tens of minutes to one hour or more. The molten aluminum alloy 12 generally reaches a high temperature of 660 ° C. or higher. For this reason, in order to continuously and stably apply ultrasonic vibration to the molten metal 12 of such an aluminum alloy, the ultrasonic horn 28 immersed in the molten metal 12 has strength and heat resistance that do not break even at high temperatures. It is desired to be made of a material that has impact properties and is not eroded by the molten metal 12. Examples of the material for forming the ultrasonic horn 28 that satisfies such requirements include refractory metal materials such as Nb and various ceramic materials. In the present embodiment, among these materials, a silicon nitride ceramic material that is not only high in strength at high temperatures but also lightweight and does not react with the molten metal 12 is used as a material for forming the ultrasonic horn 28. In the ultrasonic horn 28 made of silicon nitride ceramics, an amplitude of ± 10 μm or more is obtained by the ultrasonic oscillator 24 that can obtain an output of about 1 kW at a frequency of 15 to 20 kHz due to the characteristics of the silicon nitride ceramic material. The ultrasonic vibration can be obtained relatively easily.

  When producing an aluminum alloy ingot using the hot top casting apparatus having such a structure, as shown in FIG. 1, the molten metal 12 is passed through the molten metal flow path 14 according to the same procedure as in the prior art. While the molten metal 12 is poured into the mold 10, the molten metal 12 is cooled and solidified on the bottom block (not shown) by the cooling water sprayed from the spray port 19 of the water jacket 20 at the lower part of the mold 10, thereby casting the aluminum alloy. A mass 32 is produced. Then, the bottom block is lowered, and the manufactured ingot 32 is gradually drawn downward. In the ingot 32, the entire surface layer portion including the contact surface 34 (solidification interface) with the molten metal 12 is a solidified shell 36.

  Further, in such a casting process of the ingot 32, the ultrasonic generator 22 is continuously operated from the start of the pouring of the molten metal 12 into the mold 10 until the end of the casting of the aluminum alloy ingot 32. Then, ultrasonic vibration having an amplitude of ± 10 μm or more is continuously applied to the molten metal 12 by the ultrasonic horn 28 immersed in the molten metal 12 in the mold 10. In this way, during the semi-continuous casting of the aluminum alloy ingot 32, the impact generated when the cavitation generated by the ultrasonic vibration is crushed by continuously applying the ultrasonic vibration to the molten metal 12. By force, the dendrite generated in the molten metal 12 is more finely divided, and the finely divided dendrite is dispersed in the acoustic flow generated by the ultrasonic vibration. A nucleation site. As a result, a fine solidified structure is formed in the ingot 32 to be manufactured.

  Here, in particular, in order to make the solidified structure inside the ingot 32 finer and uniform, the ultrasonic horn 28 is arranged at a predetermined position in a specific direction. That is, the tip portion of the ultrasonic horn 28 is closer to the inner wall surface 38 of the mold 10 disposed on the front side in the flow direction of the molten metal 12 in the molten metal flow path 14 than the central axis T of the mold 10. At the position, it is inserted into the mold 10 and immersed in the molten metal 12 in the mold 10.

  At this time, the center of the tip surface of the portion of the ultrasonic horn 28 immersed in the molten metal 12 is O, and the molten metal surface 40 of the molten metal 12 in the mold 10 (in the case of using a hot top casting apparatus, the upper opening of the mold 10). The distance D between the bottom surface of the current plate 16 covering the portion and the contact surface of the molten metal 12 corresponds to D within 15 mm. That is, the center O of the tip surface of the immersed portion of the ultrasonic horn 28 needs to be disposed at a relatively shallow depth within 15 mm from the molten metal surface 40 of the molten metal 12 in the mold 10. This is because when the distance D exceeds 15 mm, the acoustic flow velocity of the molten metal 12 near the molten metal surface 40 shallower than the tip of the ultrasonic horn 28 is deeper than the tip of the ultrasonic horn 28. In addition to the fact that the dendrite finely divided by the ultrasonic vibration is inevitably smaller than the flow velocity of the acoustic flow of the molten metal 12 in FIG. A temperature difference occurs between the deep region and the growth rate of the solidified tissue varies. This is because the solidification structure formed inside the ingot 32 is not sufficiently refined, and the refined solidification structure is not uniform.

  In addition, the distance L between the center of the tip surface of the immersed portion of the ultrasonic horn 28 in the molten metal 12: O and the inner wall surface 38 of the mold 10 positioned in the vicinity thereof must be 15 mm or more. . That is, it is necessary that the center O of the tip surface of the immersion portion of the ultrasonic horn 28 is spaced 15 mm or more from the inner wall surface portion 38 of the mold 10 located in the immediate vicinity of the immersion portion. This is because when the distance L is less than 15 mm, the flow of the molten metal 12 between the immersed portion of the ultrasonic horn 28 and the inner wall surface portion 38 of the mold 10 becomes stagnant. Even in such a case, the dendrite finely divided by the ultrasonic vibration is not sufficiently dispersed throughout the molten metal 12, and the temperature distribution in the molten metal 12 is not uniform. As a result, the solidification structure formed inside the ingot 32 is not sufficiently refined, and the refined solidification structure is not uniform.

  Furthermore, the ultrasonic horn 28 is inclined so as to extend toward the central part: a side of the solidified shell 36 of the ingot 32 at the above position, and the central axis of the ultrasonic horn 28: an extension line of P: Q. And the contact point 34 of the solidified shell 36 of the ingot 32 with the contact surface 34 with the molten metal 12 are arranged in the immediate vicinity of the central portion a of the solidified shell 36 and the portion of the ultrasonic horn 28 immersed in the molten metal 12. (Here, arranged in the flow direction of the molten metal 12 in the molten metal flow path 14) so as to be positioned between the contact portion: b of the solidified shell 36 that contacts the inner wall surface portion 38 of the mold 10, Be placed. At this time, the inclination angle of the ultrasonic horn 28: θ, specifically, the central axis of the ultrasonic horn 28: an extension line of P: Q and the angle formed between the contact surface 34 of the solidified shell 36 with the molten metal 12; The angle formed by the contact portion: b side of the solidified shell 36 in contact with the inner wall surface portion 38: θ needs to be 45 ° or less.

  When the angle formed by the angle: θ exceeds 45 °, the acoustic flow generated by the ultrasonic vibrations in the mold 10 is caused by the solidified shell in the mold 10 as indicated by the solid line arrow in FIG. The contact surface 34 with the molten metal 12 collides at an angle closer to a right angle. Therefore, such an acoustic flow does not flow over the entire molten metal 12, and the mold 10. It becomes a partial flow inside. As a result, a flow having a small flow velocity separate from the acoustic flow is generated in the molten metal 12 as indicated by a broken arrow in FIG. Also in this manner, in addition to insufficient dispersion of the dendrites finely divided by the ultrasonic vibration throughout the molten metal 12, the temperature between the regions where flows having different flow velocities occur in the molten metal 12 There will be a clear difference in distribution. As a result, the refinement of the solidified structure formed inside the ingot 32 becomes insufficient, and the refined solidified structure becomes non-uniform.

  On the other hand, when the angle formed by the above-mentioned angle: θ is 45 ° or less, as shown by the solid line arrow in FIG. Therefore, the acoustic flow becomes a flow in a certain direction so as to spread over substantially the entire molten metal 12. Thereby, the dendrite finely divided by the ultrasonic vibration is sufficiently dispersed so as to be swept away by the acoustic flow so as to spread over the entire molten metal 12, and it is advantageous to make the temperature of the molten metal 12 uniform. Is envisioned. Therefore, by setting the inclination angle θ of the ultrasonic horn 28 to 45 ° or less, both the refinement and homogenization of the solidified structure formed in the ingot 32 can be advantageously achieved. It is.

  Thus, in the method of the present embodiment, the ultrasonic horn 28 is inclined at an inclination angle of 45 ° or less, and the center portion O of the tip surface of the immersion portion of the molten metal 12 is defined as the inner wall surface portion of the mold 10. The tip of the ultrasonic horn 28 is immersed in the molten metal 12 in a state where it is separated from the surface 38 by 15 mm or more and disposed at a depth within 15 mm from the molten metal surface 40. The semi-continuous casting proceeds while applying ultrasonic vibration to the molten metal 12. As a result, the finely divided dendrites can be uniformly dispersed in the molten metal 12 in the mold 10, and a flow of the molten metal 12 that can make the temperature of the molten metal 12 uniform can be formed in the mold 10. .

  Therefore, according to the method of the present embodiment as described above, an ingot 32 of an aluminum alloy having a fine and uniform solidification structure can be obtained by semi-continuous casting without adding any micronizing agent to the aluminum alloy. It can be manufactured in large quantities and stably on an industrial level. As a result, not only the quality of the aluminum alloy ingot 32 to be mass-produced is improved, but also the workability such as rolling and extrusion performed using such an aluminum alloy ingot 32 is extremely improved. This can be realized advantageously.

  Further, in this embodiment method, ultrasonic vibration is continuously applied to the molten metal 12 by the ultrasonic horn 28 while the aluminum alloy ingot 32 is manufactured by semi-continuous casting. Accordingly, uniform refinement of the solidified structure of the ingot 32 can be further sufficiently advanced.

  Furthermore, in this embodiment method, since the ultrasonic horn 28 having a sufficiently long length that can generate ultrasonic vibration having an amplitude of ± 10 μm or more is used, the ultrasonic horn 28 A stable ultrasonic vibration can be applied to the molten metal 12 in the mold 10 for a long time. This also enables stable mass production of the aluminum alloy ingot 32 having a fine and uniform solidification structure.

  And the ingot 32 of the aluminum alloy manufactured by such a method of this embodiment can be stably mass-produced with excellent quality having a fine and uniform solidified structure. Further, excellent workability can be exhibited when performing rolling or extrusion.

  Next, FIG. 3 schematically shows an example of a process for manufacturing an aluminum alloy ingot 32 by open mold semi-continuous casting according to the method of the present invention. As apparent from FIG. 3, in this embodiment, an open mold casting apparatus having a structure similar to that of the prior art, which is used at an industrial level, is used in manufacturing the ingot 32 of the target aluminum alloy. . Note that the open mold casting apparatus shown in FIG. 3 is the same as that in FIG. 1 with respect to the members and parts having the same structure as the hot top casting apparatus shown in FIG. The detailed description is omitted by attaching the reference numeral.

  That is, the open mold casting apparatus used here has a water-cooled mold 42 opened up and down. The water cooling mold 42 is provided with a water chamber 44 in which cooling water is accommodated, and an injection port 46 for injecting the cooling water in the water chamber 44 at a lower end portion. Further, a pouring nozzle 48 extending from a tundish (not shown) is plunged into the water-cooled mold 42, and the molten metal 12 is poured into the water-cooled mold 42 through the pouring nozzle 48. ing. Furthermore, the float 50 is floated on the molten metal surface 40 of the molten metal 12 poured into the water-cooled mold 42 so as to be positioned below the molten metal nozzle 48. The float 50 is moved up and down as the molten metal surface 40 is raised and lowered to open and close the lower end opening of the pouring nozzle 48, or the lower end opening of the pouring nozzle 48 and the upper surface of the float 50. The level of the hot water surface 40 in the water-cooled mold 10 can be kept constant by increasing or decreasing the size of the gap between them.

  The open mold casting apparatus has an ultrasonic oscillator 22 for applying ultrasonic vibration to the molten metal 12 in the water-cooled mold 42. The ultrasonic oscillator 22 has the same structure as that provided in the hot top casting apparatus used in the first embodiment, and includes an ultrasonic oscillator 24, an amplifier 26, and an ultrasonic horn 28. It is configured to include.

  Thus, when the aluminum alloy ingot 32 is manufactured using such an open mold casting apparatus, the molten metal surface 40 is held at a certain level by the float 50 according to the same procedure as in the prior art. As described above, semi-continuous casting is performed while the molten metal 12 is poured into the water-cooled mold 42. Further, during the execution of such semi-continuous casting, the ultrasonic horn 28 of the ultrasonic generator 22 is immersed in the molten metal 12, and from the start of pouring of the molten metal 12 into the water-cooled mold 42 until the end of casting, With this ultrasonic horn 28, ultrasonic vibration is continuously applied to the molten metal 12.

  And even in the present embodiment method, the ultrasonic horn 28 immersed in the molten metal 12 is immersed in a state where the ultrasonic horn 28 is inclined at an inclination angle of 45 ° or less: θ, as in the above-described embodiment method. The central portion O of the front end surface of the portion is spaced 15 mm or more from the inner wall surface portion 38 of the water-cooling mold 42 closest thereto, and is disposed at a depth position within 15 mm from the molten metal surface 40.

  Therefore, the flow of the molten metal 12 that can evenly disperse the finely divided dendrites in the molten metal 12 in the water-cooled mold 42 and uniformize the temperature of the entire molten metal 12 by the technique of this embodiment as described above, It can be formed in the water-cooled mold 42. As a result, the aluminum alloy ingot 32 having a fine and uniform solidification structure can be stably produced in large quantities at an industrial level by semi-continuous casting without adding any finer to the aluminum alloy. Can be manufactured. As a result, the quality of the aluminum alloy ingot 32 to be mass-produced is improved, as well as the improvement of workability such as rolling and extrusion performed using such an aluminum alloy ingot 32. This can be realized advantageously.

  Even in the aluminum alloy ingot 32 manufactured by the method of the present embodiment, the excellent features exhibited in the aluminum alloy ingot 32 manufactured by the method of the first embodiment are sufficiently Can be secured.

  The specific configuration of the present invention has been described in detail above. However, this is merely an example, and the present invention is not limited by the above description.

  For example, in the first embodiment, the ultrasonic horn 28 is disposed on the inner wall surface portion of the mold 10 disposed on the front side in the flow direction of the molten metal 12 in the molten metal flow path 14 with respect to the central axis T of the mold 10. At a position close to 38, it was plunged into the mold 10 and immersed in the molten metal 12 in the mold 10. However, the ultrasonic horn 28 has a solidified shell 36 such that the angle θ between the central axis: extension line P: Q and the angle 34 between the solidified shell 36 and the contact surface 34 with the molten metal 12 is 45 ° or less. Center portion of the mold 10, which is inclined so as to extend toward the a side, the center portion O of the tip surface of the immersed portion in the molten metal 12 is the inner wall surface portion 38 of the mold 10 positioned in the immediate vicinity of the immersed portion. It should just be arrange | positioned so that it may be 15 mm or more away from, and may be located in the depth within 15 mm from the molten metal surface 40. Accordingly, the ultrasonic horn 28 is located at a position closer to the inner wall surface of the mold 10 arranged on the rear side or the side side in the flow direction of the molten metal 12 in the molten metal flow path 14 than the central axis T of the mold 10. It is also possible to squeeze into the mold 10 and soak in the molten metal 12 in the mold 10.

  Further, as shown in the second embodiment, even when the target aluminum alloy ingot 32 is manufactured using an open mold casting apparatus, the ultrasonic horn 28 enters the water-cooled mold 42. The entry position is not limited as long as the immersion position and the inclination angle in the molten metal 12 are satisfied.

  Further, in the first embodiment, the upper opening of the mold 10 is partially covered with the rectifying plate 16 constituting the bottom wall portion of the molten metal flow path 14. Even if the rectifying plate 16 portion covering the opening is omitted, there is no problem.

  Furthermore, the structure of the ultrasonic generator 22 used in manufacturing the target aluminum alloy ingot 32 is not particularly limited to the illustrated one, and any known one can be used. is there.

  In addition to the cylindrical horn 28, a known horn having a conical shape, for example, can be used as appropriate.

  Furthermore, the oscillation of the ultrasonic horn 28 is generally started simultaneously with the start of pouring, but the timing of starting the oscillation of the ultrasonic horn 28 is not limited to that. For example, the timing of the oscillation start of the ultrasonic horn 28 is set before the molten metal 12 is first filled in the molds 10, 42, or in the molten metal 12 poured into the molds 10, 42. It is also possible that the tip of the metal is immersed, or that the molten metal 12 is first filled in the molds 10 and 42 at the same time.

  Furthermore, it is preferable that the ultrasonic vibration is continuously applied to the molten metal 12 during the casting of the ingot 32, but the molten metal 12 is intermittently applied by ultrasonic waves. You can also make it vibrate.

  In addition, the present invention can be advantageously applied to any of various methods for producing an aluminum alloy ingot without questioning the type or form of billets or slabs. It is.

  In addition, although not enumerated one by one, the present invention can be carried out in a mode to which various changes, modifications, improvements, etc. are added based on the knowledge of those skilled in the art. It goes without saying that all are included in the scope of the present invention without departing from the spirit of the present invention.

  Hereinafter, examples of the present invention will be shown to clarify the present invention more specifically. Needless to say, the present invention is not limited by the description of such embodiments. is there.

<Example 1>
First, a predetermined amount of molten Al-Zn-Cu aluminum alloy was prepared as a molten aluminum alloy. Moreover, a hot top casting apparatus provided with an ultrasonic generator as shown in FIG. 1 was prepared. Note that. As an ultrasonic generator equipped in this hot top casting apparatus, an apparatus having an ultrasonic horn made of silicon nitride ceramics having a round bar shape with a diameter of 20 mm and a length of 260 mm was used.

  Then, the tip of the ultrasonic horn of the ultrasonic generator in the prepared hot-top casting apparatus is immersed in the molten metal in the mold, and the ultrasonic horn is tilted at the angle of inclination (super The angle formed by the extension line of the central axis of the acoustic horn and the contact surface of the solidified shell with the molten metal is 45 °, and the distance indicated by L in FIG. The distance to the inner wall surface of the mold located in the immediate vicinity thereof is 40 mm, and the distance indicated by D in FIG. 1 (the distance from the molten metal surface to the central portion of the tip surface of the ultrasonic horn: O) is 15 mm. Arranged. In this state, semi-continuous casting was performed according to a known technique while continuously applying ultrasonic vibration to the molten metal from the start of pouring to the end of casting. As a result, an Al—Zn—Cu-based aluminum alloy ingot having a diameter of about 250 mm was produced without adding any micronizing agent to the aluminum alloy. The aluminum alloy ingot thus obtained was designated as Test Example 1. In the semi-continuous casting for producing the aluminum alloy ingot of Test Example 1, the frequency of the ultrasonic wave emitted from the ultrasonic horn was set to 19 kHz and the amplitude was set to ± 17 μm. The casting speed was 45 mm / min.

  In addition, water is filled in an acrylic resin container having the same dimensions as the mold used to manufacture the aluminum alloy ingot of Test Example 1, and an ultrasonic horn is placed in this water under the same conditions as described above. A water model test was conducted to observe the flow of water under the above conditions. As a result, as shown by the arrows in FIG. 1, it was confirmed that a flow of water in a certain direction extending throughout the container was generated in the container. Also, the angle θ between the extension line of the central axis of the ultrasonic horn and the contact surface of the solidified shell with the molten metal is determined during the production of the aluminum alloy ingot of Test Example 1 (during casting). Tin was mixed in to clarify the contact surface of the solidified shell with the molten metal, and this was confirmed by macro observation after the ingot production.

  For comparison, a hot top casting apparatus having the same structure as that used to manufacture the aluminum alloy ingot of Test Example 1 except that no ultrasonic apparatus is provided, an Al-Ti-B alloy, etc. A semi-continuous casting by a conventionally known hot-top method is performed using a molten Al-Zn-Cu aluminum alloy to which a micronizing agent is added, and an Al-Zn-Cu type having a diameter of about 250 mm An aluminum alloy ingot was produced. The aluminum alloy ingot thus obtained was used as Comparative Example 1. In the production of the aluminum alloy ingot of Comparative Example 1, the casting speed was 45 mm / min.

  And the solidification structure of each center axis | shaft vicinity of the aluminum alloy ingot of the test example 1 manufactured as mentioned above and the aluminum alloy ingot of the comparative example 1 was observed using the optical electron microscope. The results are shown in FIGS. As is clear from these figures, it was found that the solidification structure of the aluminum alloy ingot of Test Example 1 was clearly made finer than the solidification structure of the aluminum alloy ingot of Comparative Example 1. . It should be understood that FIGS. 4 and 5 and FIGS. 6 and 7 to be described later are all micrographs of the same magnification and are shown on the same scale.

  Further, the average crystal grain sizes of the aluminum alloy ingot of Test Example 1 and the aluminum alloy ingot of Comparative Example 1 were evaluated based on the quadrature method (ASTM Designation E 112-82) defined by ASTM. As a result, the average crystal grain size of the aluminum alloy ingot of Comparative Example 1 was about 200 μm, whereas the average crystal grain size of the aluminum alloy ingot of Test Example 1 was about 50 μm. The size was about 1/4 of the average crystal grain size of the alloy ingot.

  Furthermore, using each of the aluminum alloy ingot of Test Example 1 and the aluminum alloy ingot of Comparative Example 1, after homogenizing the two types of aluminum alloy ingots under the same conditions, Using various mass production facilities, extrusion molding was performed under the same conditions to form tubes having an outer diameter of 60 mm and an inner diameter of 45 mm from each aluminum alloy ingot. As a result, when the aluminum alloy ingot of Test Example 1 is used, extrusion molding is performed at an extrusion speed equal to or higher than that when the aluminum alloy ingot of Comparative Example 1 is used without causing cracks. Was made.

  From these results, by carrying out the hot-top semi-continuous casting according to the method of the present invention, an aluminum alloy ingot having a more uniform refined solidification structure is produced compared to the case of performing the conventional method. It can be clearly recognized that this is possible. It can also be confirmed that the aluminum alloy ingot produced by the method of the present invention can ensure the machinability equivalent to or better than the aluminum alloy ingot produced by the conventional method.

<Example 2>
First, a predetermined amount of molten Al-Zn-Cu aluminum alloy was prepared as a molten aluminum alloy. Further, an open mold casting apparatus provided with an ultrasonic generator as shown in FIG. 3 was prepared. Note that. As an ultrasonic generator equipped in this open mold casting apparatus, an ultrasonic generator having an ultrasonic horn made of silicon nitride ceramics having a round bar shape with a diameter of 20 mm and a length of 260 mm was used.

  Then, the tip of the ultrasonic horn of the ultrasonic generator in the prepared open mold casting apparatus is immersed in the molten metal in the mold, and the ultrasonic horn is tilted at an inclination angle (super The angle between the extension line of the central axis of the acoustic horn and the contact surface of the solidified shell with the molten metal is 32 °, and the distance indicated by L in FIG. The distance to the inner wall surface of the mold located in the immediate vicinity thereof is 20 mm, and the distance indicated by D in FIG. 3 (the distance from the molten metal surface to the central portion of the tip surface of the ultrasonic horn: O) is 15 mm. Arranged. In this state, semi-continuous casting was performed according to a known technique while continuously applying ultrasonic vibration to the molten metal from the start of pouring to the end of casting. As a result, an Al—Zn—Cu-based aluminum alloy ingot having a diameter of about 250 mm was produced without adding any micronizing agent to the aluminum alloy. The aluminum alloy ingot thus obtained was used as Test Example 2. In the semi-continuous casting for producing the aluminum alloy ingot of Test Example 2, the frequency of the ultrasonic wave emitted from the ultrasonic horn was set to 19 kHz and the amplitude was set to ± 17 μm. The casting speed was 50 mm / min. The angle formed by the extension line of the central axis of the ultrasonic horn and the contact surface of the solidified shell with the molten metal: θ is the same method as the method confirmed when manufacturing the aluminum alloy ingot of Test Example 1 Confirmed with.

  For comparison, an open mold casting apparatus having the same structure as that used to manufacture the aluminum alloy ingot of Test Example 2 except that no ultrasonic apparatus is provided, an Al-Ti-B alloy, etc. Al-Zn-Cu-based aluminum having a diameter of about 250 mm is obtained by performing a semi-continuous casting by a conventionally known open mold method using a molten Al-Zn-Cu-based aluminum alloy to which a micronizing agent is added. An alloy ingot was produced. The aluminum alloy ingot thus obtained was used as Comparative Example 2. In the production of the aluminum alloy ingot of Comparative Example 2, the casting speed was 50 mm / min.

  And the solidification structure of each center axis | shaft vicinity of the aluminum alloy ingot of the test example 2 manufactured as mentioned above and the aluminum alloy ingot of the comparative example 2 was observed using the optical electron microscope. The results are shown in FIGS. As is clear from these figures, it was confirmed that the solidified structure of the aluminum alloy ingot of Test Example 2 was clearly made finer than the solidified structure of the aluminum alloy ingot of Comparative Example 2. .

  Further, the average crystal grain sizes of the aluminum alloy ingot of Test Example 2 and the aluminum alloy ingot of Comparative Example 2 were evaluated based on the quadrature method (ASTM Designation E 112-82) defined by ASTM. As a result, the average crystal grain size of the aluminum alloy ingot of Comparative Example 2 was about 220 μm, whereas the average crystal grain size of the aluminum alloy ingot of Test Example 2 was about 40 μm. The average crystal grain size of the alloy ingot was 1/5 or less.

  Furthermore, using each of the aluminum alloy ingot of Test Example 2 and the aluminum alloy ingot of Comparative Example 2, after homogenizing the two types of aluminum alloy ingots under the same conditions, Using various mass production facilities, extrusion molding was performed under the same conditions to form tubes having an outer diameter of 60 mm and an inner diameter of 45 mm from each aluminum alloy ingot. As a result, even when any of the aluminum alloy ingot of Test Example 2 and the aluminum alloy ingot of Comparative Example 2 was used, extrusion molding was possible at the same extrusion speed without causing cracks.

  From these results, by performing semi-continuous casting of the open mold method according to the method of the present invention, an aluminum alloy ingot having a more uniform refined solidification structure is produced compared to the case of performing the conventional method. What can be done can be clearly recognized. It can also be confirmed that the aluminum alloy ingot produced by the method of the present invention can ensure the same machinability as the aluminum alloy ingot produced by the conventional method.

DESCRIPTION OF SYMBOLS 10 Mold 12 Molten metal 14 Molten flow path 22 Ultrasonic generator 28 Ultrasonic horn 32 Ingot 34 Contact surface 36 Solidified shell 40 Hot surface 42 Water-cooled mold 48 Pouring nozzle 50 Float

Claims (4)

In a method of manufacturing an aluminum alloy ingot by immersing an ultrasonic horn in a molten aluminum alloy poured into a mold and applying ultrasonic vibration to the molten metal while performing semi-continuous casting. There,
While the tip of the ultrasonic horn is immersed in the molten metal, the angle between the extension line of the central axis of the ultrasonic horn and the contact surface of the solidified shell with the molten metal is 45 ° or less, and the In the state where the ultrasonic horn is inclined so as to extend toward the center side of the solidified shell, the central portion of the tip surface of the immersed portion of the ultrasonic horn in the molten metal is positioned in the immediate vicinity of the immersed portion. The ultrasonic horn so that it is at least 15 mm away from the inner wall surface of the mold and the center of the tip surface of the immersion part is located at a depth within 15 mm from the molten metal surface in the mold. A method for producing an aluminum alloy ingot, wherein the ultrasonic horn is oscillated and ultrasonic vibration is applied to the molten metal in an arranged state.   The method for producing an aluminum alloy ingot according to claim 1, wherein the immersed portion of the ultrasonic horn is oscillated with an amplitude of ± 10 μm or more.   The method for producing an aluminum alloy ingot according to claim 1 or 2, wherein ultrasonic vibration is continuously applied to the molten metal in the mold during the semi-continuous casting. An aluminum alloy ingot produced by the method for producing an aluminum alloy ingot according to any one of claims 1 to 3.

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