UP-DRAWING CONTINUOUS CASTING METHOD, UP-DRAWING CONTINUOUS CASTING APPARATUS, AND CONTINUOUS CASTING
An up-drawing continuous casting method according to the present invention is an up-drawing continuous casting method for forming a casting having a predetermined shape by drawing up molten metal held in a holding furnace, and includes: a step of introducing, into the molten metal, a hollow member configured to draw up the molten metal; and a step of flowing inert gas into the hollow member so as to pour the inert gas into the molten metal. The casting is formed by drawing up the molten metal with the hollow member after stopping the flowing of the inert gas into the molten metal.
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1. Field of the Invention
The present invention relates to an up-drawing continuous casting method, an up-drawing continuous casting apparatus, and a continuous casting.
2. Description of Related Art
Japanese Patent Application Publication No. 2012-61518 (JP 2012-61518 A) describes a technique related to a free casting method (an up-drawing continuous casting method) that does not require a mold. In the free casting method described in JP 2012-61518 A, a starter is immersed into a surface of molten metal (that is, a molten metal surface), and then the starter is drawn up to lead out the molten metal. At this time, a casting having a desired sectional shape is continuously casted by leading out the molten metal via a shape determining member placed near the molten metal surface, and then cooling the molten metal thus led out.
With a normal continuous casting method, the sectional shape and the shape in a longitudinal direction are both determined by a mold. Particularly, in the continuous casting method, solidified metal (i.e., a casting) should pass through the mold, so that a casting casted hereby has a shape that extends linearly in the longitudinal direction. In contrast, in the free casting method described in JP 2012-61518 A, the shape of the casting is determined by the shape determining member movable in a direction parallel (i.e., a horizontal direction) to the molten metal surface, so that castings having various shapes in the longitudinal direction can be formed. For example, JP 2012-61518 A describes a casting formed in a zigzag shape or a helical shape in the longitudinal direction.
In the free casting method described in JP 2012-61518 A, the molten metal led out by drawing up the starter is cooled by use of coolant gas. At this time, as a flow rate of the coolant gas is increased more, a cooling rate of the molten metal is improved, thereby making it possible to raising a casting speed. However, the flow rate of the coolant gas has a limit, so there is a limit to improvement of the productivity (that is, the casting speed) by increasing the flow rate of the coolant gas in the free casting method of the related art.
SUMMARY OF THE INVENTIONThe present invention provides an up-drawing continuous casting method and an up-drawing continuous casting apparatus each of which is able to improve the productivity.
An up-drawing continuous casting method according to the present invention is an up-drawing continuous casting method for forming a casting having a predetermined shape by drawing up molten metal held in a holding furnace, and includes: introducing a hollow member into the molten metal, the hollow member configured to draw up the molten metal; and flowing inert gas into the hollow member so as to pour the inert gas into the molten metal.
An up-drawing continuous casting apparatus according to the present invention is an up-drawing continuous casting apparatus for forming a casting having a predetermined shape by drawing up molten metal, and includes: a holding furnace configured to hold the molten metal; a hollow member configured to draw up the molten metal; a driving portion configured to draw up the hollow member so as to draw up the molten metal with the hollow member; and a gas supply portion configured to supply inert gas into the hollow member.
In the up-drawing continuous casting method and the up-drawing continuous casting apparatus according to the present invention, the hollow member is used as a member to draw up the molten metal. Further, the inert gas is flowed through the hollow member before the hollow member is drawn up from the molten metal, so that the hollow member is cooled off. Because of this, heat of the molten metal drawn up with the hollow member is moved to the hollow member. Accordingly, the cooling of the molten metal thus drawn up is promoted, thereby making it possible to increase a draw-up speed to draw up the hollow member and to improve the productivity of the casting.
According to the present invention, it is possible to provide an up-drawing continuous casting method and an up-drawing continuous casting apparatus each of which is able to improve the productivity.
Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
With reference to drawings, the following describes embodiments of the present invention.
The holding furnace 10 holds molten metal M1. The molten metal M1 is molten metal of aluminum or aluminum alloy, for example. The holding furnace 10 holds the molten metal M1 at a temperature of a melting point or more of a material constituting the molten metal M1. In the example in
The hollow member 11 is used to draw up the molten metal M1 held in the holding furnace 10. That is, the hollow member 11 is immersed into the molten metal M1 when a casting is formed. At the time when the hollow member 11 thus immersed is drawn up, molten metal M2 (hereinafter, molten metal drawn up from the molten metal surface is referred to as the molten metal M2) is drawn up with the hollow member 11. The molten metal M2 is drawn up with the hollow member 11 due to surface film of the molten metal M2, surface tension of the molten metal M2, wettability between the molten metal M2 and the hollow member 11, and the like. After that, the molten metal M2 thus drawn up is cooled off, so that a casting M3 is formed. There is a solidification interface SIF in a boundary between the molten metal M2 and the casting M3.
The hollow member 11 includes a hollow portion 12, and inert gas supplied to the hollow member 11 flows through the hollow portion 12. The hollow member 11 is further used to pour the inert gas into the molten metal M1. A tube 17 is connected to the hollow member 11 via a joint 18. The tube 17 is connected to the gas supply portion 16. The inert gas supplied from the gas supply portion 16 is supplied into the molten metal M1 via the tube 17, the joint 18, and the hollow member 11 (the hollow portion 12). At this time, the hollow member 11 immersed in the molten metal M1 is cooled by the inert gas flowing therethrough.
A shape of the hollow member 11 can be determined according to a shape of a casting to be formed. That is, the hollow member 11 is not limited to a bar-shaped member, and may be a member having a curved portion. Further, the number of hollow members 11 may be one or more (a case where a plurality of hollow members is used will be described more specifically in Embodiment 3). In a case where a plurality of hollow members is provided, the inert gas may be poured into the molten metal M1 via at least one of the plurality of hollow members.
The hollow member 11 can be made of the same material as the material used for the molten metal M1. For example, in a case where the molten metal M1 is molten metal of aluminum or its alloy aluminum or its alloy can be used for the hollow member 11. Alternatively, the hollow member 11 may be made of a material different from the material used for the molten metal M1. In this case, in order to prevent the hollow member 11 made of a material different from the molten metal M1 from being melted into the molten metal M1, it is preferable that a melting point of the material constituting the hollow member 11 be higher than the melting point of the material used for the molten metal M1. For example, in a case where aluminum is used for the molten metal M1, the hollow member 11 can be made by use of stainless.
The driving portion 13 moves the hollow member 11 in a given direction according to a shape of the casting M3 to be formed. That is, the driving portion 13 is configured to be able to move the hollow member 11 in an up-down direction (a direction perpendicular to the molten metal surface of the molten metal M1), and in a direction (a horizontal direction) parallel to the molten metal surface of the molten metal M1. Further, the driving portion 13 may move the hollow member 11 in a diagonal direction to the molten metal surface of the molten metal M1.
When the driving portion 13 draws up the hollow member 11, the molten metal M2 is also drawn up with the hollow member 11. Then, the molten metal M2 is cooled off, so the casting M3 is formed. That is, when the driving portion 13 draws up the hollow member 11 continuously, the casting M3 is formed continuously. When a draw-up speed to draw up the hollow member 11 by the driving portion 13 is increased, a position of the solidification interface SIF can be raised. When the draw-up speed is decreased, the position of the solidification interface SIF can be lowered. At this time, the driving portion 13 may control the draw-up speed to draw up the hollow member 11 according to the shape of the casting M3 to be formed.
The cooling portion (a cooling nozzle) 15 is cooling device configured to cool off the casting M3 by spraying, on the casting M3, the coolant gas (air, nitrogen, argon, or the like) supplied from a coolant gas supply portion (not shown). When a flow rate of the coolant gas is increased, the position of the solidification interface SIF is lowered, and when the flow rate of the coolant gas is decreased, the position of the solidification interface SIF is raised. Here, since the molten metal M2 does not solidify, if the coolant gas is directly sprayed on the molten metal M2, the coolant gas undulates the molten metal M2, thereby resulting in that dimension accuracy and surface quality of the casting are decreased. In view of this, the cooling portion 15 sprays the coolant gas on the casting M3 shortly after solidifying, so as to cool the molten metal M2 indirectly. Note that the position of the cooling portion 15 can be moved to a given position in the horizontal direction or the up-down direction.
The gas supply portion 16 is connected to the hollow member 11 (the hollow portion 12) via the tube 17 and the joint 18. The gas supply portion 16 supplies inert gas at a predetermined flow rate to the hollow member 11. For example, the gas supply portion 16 is configured to be able to adjust an amount of the inert gas to supply. Since the hollow member 11 is cooled by the inert gas flowing therethrough, it is possible to control a temperature of the hollow member 11 (particularly, a temperature of the hollow member 11 at the time when the hollow member 11 is immersed into the molten metal M1) by adjusting the flow rate of the inert gas. At this time, the gas supply portion 16 may control the flow rate of the inert gas to flow through the hollow member 11, according to the shape of the casting to be formed. For example, nitrogen (N2), argon (Ar), or the like can be used as the inert gas.
An operation of the driving portion 13, the flow rate of the coolant gas discharged from the cooling portion 15, and the flow rate of the inert gas supplied from the gas supply portion 16 are controlled by use of a control device (not shown). That is, the up-drawing continuous casting apparatus can form a casting having a given shape by controlling these parameters.
Next will be described an up-drawing continuous casting method according to the present embodiment with reference to
After that, as illustrated in
At this time, the molten metal M2 is indirectly cooled off via the casting M3. That is, the coolant gas from the cooling portion 15 is sprayed on the casting M3 shortly after solidifying, so as to cool off the casting M3, so that heat of the molten metal M2 is moved to the casting M3 thus cooled off. Hereby, the molten metal M2 is cooled off. Further, in the up-drawing continuous casting method according to the present embodiment, the inert gas 21 is flowed through the hollow member 11 before the hollow member 11 is drawn up from the molten metal M1 (see
That is, when the cooling of the molten metal M2 is promoted, the position of the solidification interface SIF, which is a boundary between the molten metal M2 and the casting M3, is lowered. Since the position of the solidification interface SIF is lowered, the driving portion 13 can increase the draw-up speed to draw up the hollow member 11 in accordance with the amount of dropping of the position of the solidification interface SIF, thereby making it possible to increase the casting speed.
After that, the hollow member 11 is kept drawn up, and when a tip end 19 of the hollow member 11 reaches near the molten metal surface (may be on the molten metal surface) of the molten metal M1 as illustrated in
Note that the up-drawing continuous casting method described above is an example, and the up-drawing continuous casting method according to the present embodiment is not limited to the example described above. For example, before the hollow member 11 is immersed into the molten metal M1 (see
Further, in
Further, the up-drawing continuous casting method described above deals with a case where the hollow portion 12 remains after the casting is formed. However, in the up-drawing continuous casting method according to the present embodiment, the hollow portion 12 may disappear after the casting is formed. For example, in the step illustrated in
In the up-drawing continuous casting method according to the present embodiment, even in a case where the same hollow member 11 is used, the casting speed and the shape of the casting vary depending on time for holding the hollow member 11 in the molten metal M1, the heat capacity of the molten metal M1, the flow rate (coolability) of the inert gas to flow through the hollow member 11, or the like. For example, as the time for holding the hollow member 11 in the molten metal M1 is shorter, or as the heat capacity of the molten metal M1 is smaller, or as the flow rate of the inert gas to flow through the hollow member 11 is higher, the temperature of the hollow member 11 decreases and the casting speed improves.
Further, in the up-drawing continuous casting method according to the present embodiment, when the hollow member 11 reaches near the molten metal surface (may be on the molten metal surface) of the molten metal M1 (see
In the free casting method described in JP 2012-61518 A, the molten metal led out by drawing up the starter is cooled by use of coolant gas. At this time, as a flow rate of the coolant gas is increased more, a cooling rate of the molten metal is improved, thereby making it possible to raising a casting speed. However, the flow rate of the coolant gas has a limit, so there is a limit to improvement of the productivity (that is, the casting speed) by increasing the flow rate of the coolant gas in the free casting method of the related art.
In view of this, in the present embodiment, the hollow member 11 is used as a member to draw up the molten metal M1. Further, the inert gas is flowed through the hollow member 11 before the hollow member 11 is drawn up from the molten metal M1, so that the hollow member 11 is cooled off. Because of this, the heat of the molten metal M2 drawn up with the hollow member 11 is moved to the casting M3 and to the hollow member 11. Accordingly, the cooling of the molten metal M2 is promoted, thereby making it possible to increase the draw-up speed to draw up the hollow member 11 and to improve the productivity of the casting.
Moreover, in the present embodiment, the inert gas is poured into the molten metal M1 via the hollow member 11 before the hollow member 11 is drawn up from the molten metal M1. Hereby, impurities (hydrogen or the like) included in the molten metal M1, the impurities causing defects (blowhole) of a casting, can be removed, and thus, the molten metal M1 can be cleaned. This makes it possible to improve the quality of the casting to be formed.
Embodiment 2Next will be described Embodiment 2 of the present invention.
The shape determining member 25 is a member configured to determine a shape (a sectional shape) of a casting M3 by applying, to molten metal M1, an external force (that is, a force that acts on the molten metal M1 at the time when the molten metal M1 passes through a molten metal passage portion 26), when the molten metal M1 is drawn up with a hollow member 11 to form the casting M3. The shape determining member 25 is made of ceramics or stainless, for example, and is placed near a molten metal surface. In an example illustrated in
As illustrated in
Note that the shape determining member 25 illustrated in
As illustrated in
Since the length w, t of each side of the molten metal passage portion 28 can be changed in the shape determining member 25′ illustrated in
As described above, in the up-drawing continuous casting method according to the present embodiment, since an external force is applied to the molten metal M1 by use of the shape determining member, the sectional shape of the casting M3 can be determined to a given shape. That is, in Embodiment 1, the shape (the sectional shape) of the casting to be formed is determined by the shape of the hollow member 11 and the flow rate of the inert gas to flow through the hollow member 11 (that is, a cooling degree of the hollow member 11). In contrast, in the up-drawing continuous casting method according to the present embodiment, the sectional shape of the casting can be determined by use of the shape determining member in addition to the shape of the hollow member 11 and the flow rate of the inert gas to flow through the hollow member 11. Accordingly, it is possible to form the casting with accuracy.
Further, in the present embodiment, the hollow member 11 is also used to draw up the molten metal M1, similarly to Embodiment 1, so it is possible to improve the productivity of the casting. Moreover, the inert gas is poured into the molten metal M1 via the hollow member 11 before the hollow member 11 is drawn up from the molten metal M1. This makes it possible to clean the molten metal M1 and to improve the quality of the casting to be formed.
Embodiment 3Next will be described Embodiment 3 of the present invention. Embodiments 1, 2 deal with a case where a casting is formed by use of one hollow member. Embodiment 3 deals with a case where a casting is formed by use of a plurality of hollow members. Note that the following exemplary castings are merely examples, and castings having other various shapes can be formed in an up-drawing continuous casting method according to the present invention. Note that an up-drawing continuous casting apparatus for use in the present embodiment is the same as the up-drawing continuous casting apparatus as described in Embodiments 1, 2, so duplicate-description is omitted.
At the time of forming a casting, the tube 17 to supply inert gas is first fixed to the hollow members 41_1, 41_2, and further, the hollow members 41_1, 41_2 are fixed to the driving portion 13 (see
After that, the discharge of the inert gas from the hollow members 41_1, 41_2 is stopped (see
In the case illustrated in
In the case illustrated in
In a case where the two hollow members 41_1, 41_2 are placed so as to separate from each other as such, the molten metal M2 can be retained in a space between the hollow member 41_1 and the hollow member 412, so that it is possible to form a casting having a large volume while reducing the number of hollow members.
In the case illustrated in
In the case illustrated in
Further, when the draw-up speed to draw up the hollow members 51 is slowed down in the middle of the draw-up, it is possible to form a casting in which the hollow portions 52 in lower half of a casting 55 are closed as illustrated
Further, in the present embodiment, the inert gas may be flowed through at least one of the plurality of hollow members. That is, it is not necessary to flow the inert gas through all the hollow members. For example, as illustrated in
In the case illustrated in
In the case illustrated in
In the case illustrated in
In the case illustrated in
Meanwhile, in a region 84, one hollow member 81_2 projects from a tip end, on a lower side, of the hollow members 81_1 placed in an annular shape. Accordingly, the sectional shape of the molten metal M2 retained by the hollow members 81_1, 81_2 in the region 84 is a circular shape that is reduced in diameter from an upper side toward a lower side in the region 84. Because of this, that part of the casting 85 which corresponds to the region 84 has a generally circular cone shape 87 (that is, a tapered shape).
Note that each of the placements of the hollow members described above is just an example, and the placement of the hollow members can be determined according to a shape of a casting to be formed in the up-drawing continuous casting method according to the present invention. Further, the exemplary placements described above can be combined appropriately. For example, a plurality of hollow members may be different in thickness and further different in length from each other.
Embodiment 4Next will be described Embodiment 4 of the present invention. Embodiment 4 deals with a case where a mold release agent is provided in at least part of a hollow member. Note that an up-drawing continuous casting apparatus for use in the present embodiment is the same as the up-drawing continuous casting apparatus as described in Embodiments 1, 2, so duplicate description is omitted.
At the time of forming a casting, the tube 17 to supply inert gas is first fixed to the hollow member 101_1, 101_2, and further, the hollow members 101_1, 101_2 are fixed to the driving portion 13 (see
After that, the discharge of the inert gas from the hollow members 101_1, 101_2 is stopped (see
In the case illustrated in
By providing the mold release agent in part of the hollow member as such, the shape of the casting to be formed can be determined. Further, by providing the mold release agent in part of the hollow member, melting of the hollow member can be restrained. Further, in a case where the material of the hollow member is different from the material of the molten metal, electrolytic corrosion of the hollow member can be restrained by providing the mold release agent in the hollow member.
When a casting is formed by use of the hollow members 111_1, 111_2 illustrated on the upper-left side of
Accordingly, as illustrated on the lower side of
By providing the mold release agents in the hollow member as such, castings having various shapes can be formed. Particularly, by combining the present embodiment with Embodiment 3 (the embodiment in which a plurality of hollow members is placed), it is possible to form castings having various shapes.
A casting formed by use of the up-drawing continuous casting method described in Embodiments 1 to 4 includes a matrix having a unidirectional solidified structure extended in a longitudinal direction and a hollow member extended in the longitudinal direction as a dualphase. On that account, the casting has excellent longitudinal strength. At this time, a plurality of hollow members may be included therein as the hollow member. Further, the hollow member may be made of the same material as a material constituting the matrix. Further, the hollow member may be made of a material different from the material constituting the matrix. In this case, a melting point of the material constituting the hollow member is higher than a melting point of the material constituting the matrix.
The present invention has been described in line with the above embodiments, but the present invention is not limited to the configurations of the above embodiments, and includes various alterations, modifications, and combinations that would be made by a person skilled in the art within the scope of the invention according to Claims.
Claims
1: An up-drawing continuous casting method for forming a casting having a predetermined shape by drawing up molten metal held in a holding furnace, the up-drawing continuous casting method comprising:
- introducing a hollow member into the molten metal, the hollow member configured to draw up the molten metal; and
- flowing inert gas into the hollow member so as to pour the inert gas into the molten metal.
2: The up-drawing continuous casting method according to claim 1, further comprising:
- forming the casting by drawing up the molten metal with the hollow member after stopping the flowing of the inert gas into the molten metal.
3: The up-drawing continuous casting method according to claim 1, further comprising:
- introducing a plurality of hollow members into the molten metal; and
- flowing the inert gas into at least one of the plurality of hollow members so as to pour the inert gas into the molten metal.
4: The up-drawing continuous casting method according to claim 1, wherein:
- a mold release agent is provided in at least part of the hollow member.
5: The up-drawing continuous casting method according to claim 4, further comprising:
- separating the part of the hollow member from the casting formed by the molten metal solidifying, the part of the hollow member being provided with the mold release agent.
6: The up-drawing continuous casting method according to claim 1, further comprising:
- spraying coolant gas on the molten metal drawn up with the hollow member, when the hollow member is drawn up.
7: The up-drawing continuous casting method according to claim 1, wherein:
- the hollow member is immersed in the molten metal,
- the molten metal is drawn up with the hollow member at the time of drawing up the hollow member immersed, the molten metal being drawn up with the hollow member due to a surface film of the molten metal, a surface tension of the molten metal, and wettability between the molten metal and the hollow member, and,
- the molten metal drawn up is cooled off to form the casting.
8: An up-drawing continuous casting apparatus for forming a casting having a predetermined shape by drawing up molten metal, the up-drawing continuous casting apparatus comprising:
- a holding furnace configured to hold the molten metal;
- a hollow member configured to draw up the molten metal;
- a driving portion configured to draw up the hollow member so as to draw up the molten metal with the hollow member; and
- a gas supply portion configured to supply inert gas into the hollow member.
9: The up-drawing continuous casting apparatus according to claim 8, wherein:
- the driving portion draws up the molten metal with the hollow member after stopping flowing of the inert gas into the molten metal.
10: The up-drawing continuous casting apparatus according to claim 8, wherein:
- a plurality of hollow members is provided; and
- the gas supply portion flows the inert gas into at least one of the plurality of hollow members so as to pour the inert gas into the molten metal.
11: The up-drawing continuous casting apparatus according to claim 8, wherein:
- a mold release agent is provided in at least part of the hollow member.
12: The up-drawing continuous casting apparatus according to claim 8, further comprising:
- a cooling portion configured to spray coolant gas on the molten metal drawn up with the hollow member, when the hollow member is drawn up.
13: The up-drawing continuous casting apparatus according to claim 8, wherein:
- the molten metal is drawn up with the hollow member at the time of drawing up the hollow member immersed, the molten metal being drawn up with the hollow member due to a surface film of the molten metal, a surface tension of the molten metal, and wettability between the molten metal and the hollow member, and
- the molten metal drawn up is cooled off to form the casting.
14: A continuous casting comprising:
- a matrix having a unidirectional solidified structure extended in a longitudinal direction; and
- a dualphase extended in the longitudinal direction, wherein:
- the dualphase is constituted by a hollow member.
15: The continuous casting according to claim 14, wherein:
- a plurality of hollow members is provided.
16: The continuous casting according to claim 14, wherein:
- the hollow member is immersed into molten metal,
- the molten metal is drawn up with the hollow member at the time of drawing up the hollow member immersed, the molten metal being drawn up with the hollow member due to a surface film of the molten metal, a surface tension of the molten metal, and wettability between the molten metal and the hollow member, and
- the molten metal drawn up is cooled off to form the continuous casting.
Type: Application
Filed: Dec 10, 2014
Publication Date: Nov 17, 2016
Applicant: TOYOTA JIDOSHA KABUSHIKI KAISHA (Toyota-shi)
Inventors: Yuichi FURUKAWA (Toyota-shi), Keiichi MORITA (Toyota-shi)
Application Number: 15/105,660