Patent Application
20150034269
This application is based upon and claims the benefit of priority from Japanese patent application No. 2013-158204, filed on Jul. 30, 2013, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a pulling-up-type continuous casting apparatus and a pulling-up-type continuous casting method.
2. Description of Related Art
The inventors of the present application have proposed, in Japanese Unexamined Patent Application Publication No. 2012-61518, a free casting method as a revolutionary continuous casting method that does not requires any mold. As shown in Japanese Unexamined Patent Application Publication No. 2012-61518, after a starter is submerged into the surface of a melted metal (molten metal) (i.e., molten-metal surface), the starter is pulled up, so that some of the molten metal follows the starter and is drawn by the starter by the surface film of the molten metal and/or the surface tension. Note that it is possible to continuously cast a cast-metal article having a desired cross-sectional shape by drawing the molten metal and cooling the drawn molten metal through a shape defining member disposed in the vicinity of the molten-metal surface.
In the ordinary continuous casting method, the shape in the longitudinal direction as well as the shape in cross section is defined by the mold. In the continuous casting method, in particular, since the solidified metal (i.e., cast-metal article) needs to pass through inside of the mold, the cast-metal article has such a shape that it extends in a straight-line shape in the longitudinal direction. In contrast to this, the shape defining member used in the free casting method defines only the cross-sectional shape of the cast-metal article, while it does not define the shape in the longitudinal direction. Further, since the shape defining member can be moved in the direction parallel to the molten-metal surface (i.e., in the horizontal direction), cast-metal articles having various shapes in the longitudinal direction can be produced. For example, Japanese Unexamined Patent Application Publication No. 2012-61518 discloses a hollow cast-metal article (i.e., a pipe) having a zigzag shape or a helical shape in the longitudinal direction rather than the straight-line shape.
However, the present inventors have found the following problem.
In the free casting method disclosed in Japanese Unexamined Patent Application Publication No. 2012-61518, the cross-sectional shape of a cast-metal article is defined by bringing a shape defining member into contact with the molten metal (held molten metal), which has followed the pulled-up starter and been pulled up from the molten-metal surface but has not solidified yet, thereby applying an external force to the molten metal (held molten metal). As a result, a local load is exerted on the held molten metal. Therefore, there has been a problem in the free casting method disclosed in Japanese Unexamined Patent Application Publication No. 2012-61518 that the starter needs to be pulled up slowly in order to prevent the held molten metal from being torn off due to the local load.
The present invention has been made in view of the above-described problem, and an object thereof is to provide a pulling-up-type continuous casting apparatus and a pulling-up-type continuous casting method that can make it possible to improve the pulling-up speed of the starter by applying an external force to the held molten metal without using the contact-type shape defining member and thereby reducing the local load exerted on the held molten metal.
A first exemplary aspect of the present invention is a pulling-up-type continuous casting apparatus that lets molten metal solidify while pulling up a drawing section for drawing the molten metal from a molten-metal surface of the molten metal held in a holding furnace, and thereby shapes the molten metal, including means for applying a non-contact force to held molten metal, the held molten metal being molten metal that has been drawn from the molten-metal surface by the drawing section but has not solidified yet. As a result, since the external force can be applied without using the shape defining member, the local load exerted on the held molten metal is reduced and the pulling-up speed of the starter is thereby improved.
It is preferable to apply an electromagnetic force to the held molten metal.
The electromagnetic force applied to the held molten metal is preferably applied in a direction perpendicular to a pulling-up direction of the held molten metal.
The electromagnetic force applied to the held molten metal is preferably applied in the same direction as a pulling-up direction of the held molten metal.
The pulling-up-type continuous casting apparatus preferably includes an electromagnetic force applying unit that defines a cross-sectional shape of a cast-metal article to be cast by applying the electromagnetic force to the held molten metal, and the electromagnetic force applying unit preferably includes a current output unit that feeds an electric current to the held molten metal and a magnetic field applying unit that applies a magnetic field to the held molten metal.
The magnetic field applying unit preferably generates the magnetic field in a direction perpendicular to a pulling-up direction of the held molten metal and applies the generated magnetic field to the held molten metal.
An N-pole and an S-pole of the magnetic field applying unit are preferably arranged so as to be opposed to each other with the held molten metal interposed therebetween.
The magnetic field applying unit is preferably a permanent magnet.
The magnetic field applying unit is preferably an electromagnet.
The current output unit preferably makes an electric current flow from the drawing section toward the molten metal held in the holding furnace through the held molten metal, or from the molten metal held in the holding furnace to the drawing section through the held molten metal.
The pulling-up-type continuous casting apparatus preferably includes an electromagnetic force applying unit that defines a cross-sectional shape of a cast-metal article to be cast by applying the electromagnetic force to the held molten metal, and the electromagnetic force applying unit preferably applies a magnetic field in a first direction perpendicular to a pulling-up direction of the held molten metal and a magnetic field in an opposite direction, to the held molten metal to be pulled up in an alternate manner.
The electromagnetic force applying unit preferably includes at least a pair of rotors disposed so as to be opposed to each other with the held molten metal interposed therebetween and configured to rotate in a pulling-up direction of the held molten metal, and a pair of magnets disposed so as to surround peripheral surfaces of the pair of rotors. Further, the pair of magnets preferably have magnetic poles of different polarities respectively in an alternate manner along a circumferential direction of the pair of rotors.
The pair of magnets are preferably permanent magnets.
The electromagnetic force applying unit preferably changes a cross-sectional shape of a cast-metal article to be cast by changing at least one of the number of revolutions of the pair of rotors, a strength of the magnetic field, and a direction of the magnetic field.
The electromagnetic force applying unit preferably includes a plurality of pairs of electromagnets disposed so as to be opposed to each other with the held molten metal interposed therebetween along a pulling-up direction of the held molten metal. Further, each of the plurality of pairs of electromagnets preferably generates an alternate magnetic field of a different direction from that of an adjacent pair of electromagnets and applies the generated magnetic field to the held molten metal.
The electromagnetic force applying unit preferably generates the alternate magnetic field by periodically changing a direction of an electric current flowing through a plurality of pairs of coils, each of the plurality of pairs of coils forming a respective one of the plurality of pairs of electromagnets.
The electromagnetic force applying unit preferably changes a cross-sectional shape of a cast-metal article to be cast by changing a magnitude of an electric current flowing through the plurality of pairs of coils each forming a respective one of the plurality of pairs of electromagnets.
The pulling-up-type continuous casting apparatus preferably further includes a shape defining member disposed in the vicinity of the molten-metal surface, the shape defining member being configured to define a cross-sectional shape of a cast-metal article to be cast by applying an external force to the held molten metal.
Another exemplary aspect of the present invention is a pulling-up-type continuous casting method for letting molten metal solidify while pulling up a drawing section for drawing the molten metal from a molten-metal surface of the molten metal held in a holding furnace, and thereby shaping the molten metal, including applying an electromagnetic force to held molten metal and thereby defining a cross-sectional shape of a cast-metal article to be cast, the held molten metal being molten metal that has been drawn from the molten-metal surface by the drawing section but has not solidified yet. As a result, since the external force can be applied without using the shape defining member, the local load exerted on the held molten metal is reduced and the pulling-up speed of the starter is thereby improved.
It is preferable to apply an electromagnetic force to the held molten metal by feeding an electric current to the held molten metal and applying a magnetic field to the held molten metal.
It is preferable to apply a magnetic field to the held molten metal in a direction perpendicular to a pulling-up direction of the held molten metal.
It is preferable to generate the magnetic field by disposing an N-pole and an S-pole of a magnet so as to be opposed to each other with the held molten metal interposed therebetween.
The magnet that generates the magnetic field is preferably a permanent magnet.
The magnet that generates the magnetic field is preferably an electromagnet.
It is preferable to make an electric current flow from the drawing section toward the molten metal held in the holding furnace through the held molten metal, or from the molten metal held in the holding furnace to the drawing section through the held molten metal.
It is preferable to apply a magnetic field in a first direction perpendicular to a pulling-up direction of the held molten metal and a magnetic field in an opposite direction, to the held molten metal to be pulled up in an alternate manner.
It is preferable to provide at least a pair of rotors disposed so as to be opposed to each other with the held molten metal interposed therebetween and configured to rotate in a pulling-up direction of the held molten metal, and a pair of magnets disposed so as to surround peripheral surfaces of the pair of rotors. Further, the pair of magnets preferably have magnetic poles of different polarities respectively in an alternate manner along a circumferential direction of the pair of rotors.
The pair of magnets are preferably permanent magnets.
It is preferable to change a cross-sectional shape of a cast-metal article to be cast by changing at least one of the number of revolutions of the pair of rotors, a strength of the magnetic field, and a direction of the magnetic field.
It is preferable to provide a plurality of pairs of electromagnets disposed so as to be opposed to each other with the held molten metal interposed therebetween along a pulling-up direction of the held molten metal. Further, each of the plurality of pairs of electromagnets preferably generates an alternate magnetic field of a different direction from that of an adjacent pair of electromagnets and applies the generated magnetic field to the held molten metal.
It is preferable to generate the alternate magnetic field by periodically changing a direction of an electric current flowing through a plurality of pairs of coils, each of the plurality of pairs of coils forming a respective one of the plurality of pairs of electromagnets.
It is preferable to change a cross-sectional shape of a cast-metal article to be cast by changing a magnitude of an electric current flowing through the plurality of pairs of coils each forming a respective one of the plurality of pairs of electromagnets.
It is preferable to further dispose a shape defining member in the vicinity of the molten-metal surface of the molten metal held by the holding furnace, the shape defining member being configured to define a cross-sectional shape of a cast-metal article to be cast by applying an external force to the held molten metal.
According to the present invention, since the external force can be applied without using the contact-type shape defining member, the local load exerted on the held molten metal can be reduced and the pulling-up speed of the starter can be thereby improved.
The above and other objects, features and advantages of the present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Specific exemplary embodiments to which the present invention is applied are explained hereinafter in detail with reference to the drawings. However, the present invention is not limited to exemplary embodiments shown below. Further, the following descriptions and the drawings are simplified as appropriate for clarifying the explanation.
Firstly, a free casting apparatus (pulling-up-type continuous casting apparatus) according to a first exemplary embodiment is explained with reference to
The molten-metal holding furnace 101 contains molten metal M1 such as aluminum or its alloy, and maintains the molten metal at a predetermined temperature. In the example shown in
The drawing section 106 includes a starter (thawing member) ST that is submerged into the molten metal M1, and a pulling-up machine PL that drives the starter ST, for example, in the vertical direction.
As shown in
The starter ST is made of, for example, ceramics or stainless steel. Note that the surface of the starter ST may be covered with a protection film (not shown) such as a salt crystal film. In this way, the melt bonding between the starter ST and the molten metal M1 is suppressed, thereby improving the removal property between the starter ST and the cast metal M3. As a result, the starter ST can be reused. Further, the starter ST may have unevenness on its surface. This facilitates the adhesion (precipitation) of a protection film on the surface of the starter ST, thus improving the removal property between the starter ST and the cast metal M3 even further. At the same time, the bonding force between the starter ST and the molten metal M1 in the pulling-up direction at the time when the molten metal is drawn can also be improved.
The magnetic-field applying unit 102 applies a magnetic field to the held molten metal M2. For example, the magnetic-field applying unit 102 generates a magnetic field(s) in a direction (horizontal direction) perpendicular to the pulling-up direction of the held molten metal M2 (vertical direction) and applies the generated magnetic field(s) to the held molten metal M2.
More specifically, the magnetic-field applying unit 102 includes a magnet(s) such as a permanent magnet(s) and an electromagnet(s), and is disposed in the vicinity of the molten-metal surface. In this exemplary embodiment, an example in which the magnetic-field applying unit 102 includes a pair of cylindrical permanent magnets and the N-pole of one of the magnets is disposed so as to be opposed to the S-pole of the other magnet with the held molten metal M2 interposed therebetween is explained. As a result, a magnetic field oriented in a direction perpendicular to the pulling-up direction of the held molten metal M2 is applied to the held molten metal M2.
The current output unit 107 is electrically connected, for example, between the drawing section 106 and the molten-metal holding furnace 101, and feeds an electric current to the held molten metal M2. More specifically, the current output unit 107 makes an electric current flow from the drawing section 106 toward the molten-metal holding furnace 101 through the cast metal M3, the held molten metal M2, and the molten metal Ml, or makes an electric current flow from the molten-metal holding furnace 101 toward the drawing section 106 through the molten metal M1, the held molten metal M2, and the cast metal M3.
Note that an electromagnetic force is applied to the held molten metal M2 by applying a magnetic field to the held molten metal M2 by using the magnetic-field applying unit 102 and by feeding an electric current to the held molten metal M2 by using the current output unit 107. In other words, the electromagnetic-force applying unit 110, which includes the magnetic-field applying unit 102 and the current output unit 107, applies an electromagnetic force to the held molten metal M2 by applying a magnetic field and feeding an electric current to the held molten metal M2. A more detailed explanation is given hereinafter with reference to
Further, in the example shown in
In this state, an electromagnetic force is applied in the positive direction on the Y-axis according to Fleming's left-hand rule in the held molten metal M2. As a result, the held molten metal M2 is deformed, for example, toward the positive direction on the Y-axis. More specifically, the cross-sectional shape in the horizontal direction of the held molten metal M2 (hereinafter referred to as “horizontal cross section”) is deformed toward the positive direction on the Y-axis.
That is, the electromagnetic-force applying unit 110 defines the outside shape of the cast metal M3 to be cast (more specifically, the outside diameter of the horizontal cross section of the cast metal M3 to be cast) by applying an electromagnetic force to the held molten metal M2.
Note that the electromagnetic-force applying unit 110 can shape the held molten metal M2 into an arbitrary shape by adjusting the strength and/or the direction of the electromagnetic force applied to the held molten metal M2 by changing the strength and/or the direction of the magnetic field applied to the held molten metal M2 and the magnitude and/or the direction of the electric current fed to the held molten metal M2. In this way, the electromagnetic-force applying unit 110 can freely define the cross-sectional shape of the cast metal M3. For example, the electromagnetic-force applying unit 110 can cast a cast metal M3 having a circular horizontal cross-sectional shape as shown in
Note that although the example shown in
Referring to
The actuator 104 has a function of moving the magnetic-field applying unit 102 in the up/down direction (vertical direction) and in the horizontal direction through the support rod 103. In this manner, it is possible to move the magnetic-field applying unit 102 downward as the molten-metal surface is lowered due to the advance of the casting process. Further, since the magnetic-field applying unit 102 can be moved in the horizontal direction, the shape in the longitudinal direction of the cast metal M3 can be freely changed.
The cooling nozzle (cooling unit) 105 sprays a cooling gas (such as oxygen, nitrogen, and argon) on the starter ST and/or the cast metal M3, and thereby cools the starter ST and/or the cast metal M3. By cooling the starter ST and/or the cast metal M3 by the cooling gas while pulling up the cast metal M3 by using the pulling-up machine PL connected to the starter ST, the held molten metal M2 located in the vicinity of the solidification interface is successively solidified and the cast metal M3 is continuously formed.
Next, a free casting method according to this exemplary embodiment is explained with reference to
Firstly, the starter ST is lowered and submerged into the molten metal M1.
Next, the starter ST starts to be pulled up at a predetermined speed. Note that even when the starter ST is pulled away from the molten-metal surface, the molten metal M1 follows the starter ST and is pulled up (drawn) from the molten-metal surface by the surface film and/or the surface tension. The pulled-up molten metal M1 forms the held molten metal M2. As shown in
Next, the starter ST and the cast metal M3 are cooled by a cooling gas sprayed from the cooling nozzle 105. As a result, the held molten metal M2 is successively solidified from the upper side toward the lower side, so that the cast metal M3 grows. In this manner, the cast metal M3 can be continuously cast.
As described above, the free casting apparatus according to this exemplary embodiment defines the cross-sectional shape of the cast metal M3 to be cast by applying an electromagnetic force to the held molten metal M2. In this way, since the free casting apparatus according to this exemplary embodiment can apply an external force to the held molten metal without using any shape defining member, the local load exerted on the held molten metal can be reduced and the pulling-up speed of the starter can be thereby improved.
(Difference from Related Art)
Differences between the free casting apparatus according to this exemplary embodiment and the related art are explained hereinafter in detail by referring to
Firstly, in the related art shown in
In contrast to this, in the free casting apparatus according to this exemplary embodiment, the held molten metal M2 is shaped into a given shape by applying an electromagnetic force to the held molten metal M2 without using the related-art contact-type shape defining member, i.e., without bringing any object into contact with the held molten metal M2. As a result, the local load is less likely to be exerted on the held molten metal M2, thus making the held molten metal M2 less prone to be torn off Therefore, the pulling-up speed of the starter ST can be improved.
Note that as shown in
Next, a modified example of the free casting apparatus according to this exemplary embodiment is explained hereinafter with reference to
The outside-shape defining member 108a is made of, for example, ceramics or stainless steel, and is disposed in the vicinity of the molten-metal surface. In the example shown in
Similarly to the electromagnetic-force applying unit 110, the outside-shape defining member 108a defines the outside shape of the cast metal M3 to be cast (more specifically, the outside diameter of the horizontal cross section of the cast metal M3 to be cast).
Referring to
As described above, the free casting apparatus shown in
Note that in the example shown in
The electromagnetic-force applying unit 201 applies a magnetic field in a first direction perpendicular to the pulling-up direction of the held molten metal M2 and a magnetic field in the opposite direction, to the held molten metal M2 to be pulled up in an alternate manner. A detailed explanation of this is given hereinafter.
In the example shown in
As described above, the free casting apparatus according to this exemplary embodiment can produce advantageous effects equivalent to those of the first exemplary embodiment. Further, the free casting apparatus according to this exemplary embodiment can cancel out the gravity for the held molten metal M2 that is being pulled up, by applying a vertically-upward electromagnetic force to the held molten metal M2. Therefore, the free casting apparatus according to this exemplary embodiment can make the held molten metal M2 less prone to be torn off.
In the example shown in
With the above-described configuration, similarly to the electromagnetic-force applying unit 201, the electromagnetic-force applying unit 202 can apply a magnetic field in a first direction perpendicular to the pulling-up direction of the held molten metal M2 and a magnetic field in the opposite direction, to the held molten metal M2 in an alternate manner while moving the magnetic fields in the pulling-up direction of the held molten metal M2. As a result, similarly to the electromagnetic-force applying unit 201, the electromagnetic-force applying unit 202 can apply a vertically-upward electromagnetic force to the held molten metal M2.
Note that as shown in
The free casting apparatus shown in
Note that in the example shown in
As described above, the above-described free casting apparatuses according to the first and second exemplary embodiments define the cross-sectional shape of the cast metal M3 to be cast by applying an electromagnetic force to the held molten metal M2. In this way, since the above-described free casting apparatuses according to the first and second exemplary embodiments can apply an external force to the held molten metal without using the shape defining member, the local load exerted on the held molten metal can be reduced and the pulling-up speed of the starter can be thereby improved.
Although examples in which a cast-metal article having a circular cross-sectional shape is cast are explained in the above-described exemplary embodiments, the present invention is not limited to such examples. The present invention can also be applied to cases where a cast-metal article having a cross-sectional shape other than the circular shape, such as a prismatic shape, is cast.
Note that the present invention is not limited to the above-described exemplary embodiments, and various modifications can be made without departing the spirit and scope of the present invention. For example, the above-described configuration examples may be combined and used at the same time.
From the invention thus described, it will be obvious that the embodiments of the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-158204 | Jul 2013 | JP | national |
