Patent Application
20150196952
1. Field of the Invention
The invention relates to an up-drawing continuous casting apparatus and an up-drawing continuous casting method.
2. Description of Related Art
In Japanese Patent Application Publication No. 2012-61518 (JP 2012-61518 A), the inventors propose a free casting method as a groundbreaking continuous casting method that does not require a mold. As described in JP 2012-61518 A, a starter is first immersed into the surface of molten metal (a molten metal surface), and then when the starter is drawn up, molten metal is also drawn out following the starter by surface tension and the surface film of the molten metal. Here, a casting that, has a desired sectional shape is able to be continuously cast by drawing out the molten metal via a shape determining member arranged near the molten metal surface, and cooling it (i.e., the drawn out molten metal).
With a normal continuous casting method, the sectional shape and the shape in the longitudinal direction are both determined by a mold. In particular, the solidified metal (i.e., the casting) must pass through the mold, so the cast casting takes on a shape that extends linearly in the longitudinal direction. In contrast, the shape determining member in the free casting method determines only the sectional shape of the casting, the shape in the longitudinal direction is not determined. Also, the shape determining member is able to move in a direction parallel to the molten metal surface (i.e., horizontally), so castings of various shapes in the longitudinal direction are able to be obtained. For example, JP 2012-61518 A describes a hollow casting (i.e., a pipe) formed in a zigzag shape or a helical shape, not a linear shape in the longitudinal direction.
The inventors discovered that with the free casting method described in JP 2012-61518 A, the molten metal drawn out via the shape determining member is cooled by only cooling gas, so the casting speed is slow, which is problematic in terms of productivity.
The invention thus provides an up-drawing continuous casting apparatus and an up-drawing continuous casting method that increases casting speed, and thus offers excellent productivity.
A first aspect of the invention relates to an up-drawing continuous casting apparatus. This up-drawing continuous casting apparatus includes a holding furnace that holds molten metal; a shape determining member that is arranged near a molten metal surface of the molten metal held in the holding furnace, and that determines a sectional shape of a casting by the molten metal passing through the shape determining member; a cooling portion that cools and solidifies the molten metal that has passed through the shape determining member; and a molten metal cooling portion that lowers a temperature of the molten metal held in the holding furnace.
According to this first aspect, casting speed is able to be increased, so productivity is able to be improved.
In the first aspect described above, the molten metal cooling portion may be provided directly below the shape determining member.
With this structure, the temperature of the molten metal positioned directly below the shape determining member is able to be lowered in a short period of time, so the casting speed is able to be increased.
The up-drawing continuous casting apparatus of the first aspect described above may also include an actuator that moves the molten metal cooling portion in a top-bottom direction inside the holding furnace.
In the first aspect described above, cooling gas may pass through an inside of the molten metal cooling portion.
In the first aspect described above, the molten metal cooling portion may be made of ceramic.
The up-drawing continuous casting apparatus of the first aspect described above may also include a partition wall that surrounds the molten metal, and an ambient temperature regulating portion that regulates a temperature of an atmosphere surrounded by the partition wall.
According to the first aspect described above, the quality of a casting is able to be made stable.
A second aspect of the invention relates to an up-drawing continuous casting method that uses a casting apparatus having a shape determining member that determines a sectional shape of a casting, a holding furnace that holds a molten metal, and a molten metal cooling portion provided in the holding furnace. The up-drawing continuous casting method includes arranging the shape determining member near a molten metal surface of the molten metal held in the holding furnace; lowering a temperature of the molten metal held in the holding furnace, with the molten metal cooling portion; passing the molten metal that has been lowered in temperature through the shape determining member and drawing up the molten metal; and cooling the molten metal that has passed through the shape determining member and been drawn up.
According to this second aspect, casting speed is able to be increased, so productivity is able to be improved.
In the second aspect described above, the molten metal cooling portion may be provided directly below the shape determining member.
With this structure, the temperature of the molten metal positioned directly below the shape determining member is able to be lowered in a short period of time, so the casting speed is able to be increased.
The up-drawing continuous casting method of the second aspect described above may also include moving the molten metal cooling portion in a top-bottom direction inside the holding furnace.
In the second aspect described above, lowering the temperature of the molten metal may be done by leading cooling gas into the molten metal cooling portion.
In the second aspect described above, the molten metal cooling portion may be made of ceramic.
The up-drawing continuous casting method of the second aspect described above may also include surrounding the molten metal with a partition wall, and regulating a temperature of an atmosphere surrounded by the partition wall.
According to the second aspect described above, the quality of a casting is able to be made stable.
A third aspect of the invention relates to an up-drawing continuous casting apparatus. This up-drawing continuous casting apparatus includes a holding furnace that holds molten metal; a shape determining member that is arranged near a molten metal surface of the molten metal held in the holding furnace, and that determines a sectional shape of a casting by the molten metal passing through the shape determining member; and a cooling portion that cools and solidifies the molten metal that has passed through the shape determining member with a starter. The starter has a cooling mechanism that is integrated with the starter.
According to this third aspect, casting speed is able to be increased, so productivity is able to be improved.
In the third aspect described above, the cooling mechanism may include a pipe that is attached to the starter and into which coolant is introduced.
In the third aspect described above, the cooling mechanism may be the starter itself that is formed by a pipe into which coolant is introduced.
A fourth aspect of the invention relates to an up-drawing continuous casting method that uses a casting apparatus having a shape determining member that determines a sectional shape of a casting, a holding furnace that holds a molten metal, a starter, and a cooling mechanism that is integrated with the starter. The up-drawing continuous casting method includes arranging the shape determining member near a molten metal surface of the molten metal held in the holding furnace; passing the molten metal through the shape determining member and drawing up the molten metal with the starter; cooling and solidifying the molten metal that has passed through the shape determining member and been drawn up; and cooling the starter with the cooling mechanism.
According to this fourth aspect, casting speed is able to be increased, so productivity is able to be improved.
In the fourth aspect described above, the cooling mechanism may be formed by attaching a pipe to the starter and introducing coolant into the pipe.
In the fourth aspect described above, the cooling mechanism may be formed by introducing coolant into the starter itself that is formed by a pipe.
According to the, first to the fourth aspects of the invention, it is possible to provide an up-drawing continuous casting apparatus and an up-drawing continuous casting method that increases casting speed, and thus offers excellent 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:
Hereinafter, specific example embodiments to which the invention has been applied will be described in detail with reference to the accompanying drawings. However, the invention is not limited to these example embodiments. Also, the description and the drawings are simplified as appropriate to clarify the invention. Terms such as “top-bottom direction” and “left-right direction” and the like match the top-bottom and left-right directions in the drawings.
First, a free casting apparatus (up-drawing continuous casting apparatus) according to a first example embodiment of the invention will be described with reference to
The molten metal holding furnace 101 holds molten metal M1 such as aluminum or an aluminum alloy, for example, and keeps it at a predetermined temperature.
In the example in
The inner shape determining member 102a and the outer shape determining member 102b are made of ceramic or stainless steel, for example, and are arranged near the molten metal surface. In the example shown in
Moreover, the inner shape determining member 102a determines the inner shape of a casting M3, and the outer shape determining member 102b determines the outer shape of the casting M3. The casting M3 shown in
As shown in
The support rod 103 supports the inner shape determining member 102a and the support rod 104 supports the outer shape determining member 102b. The positional relationship between the inner shape determining member 102a and the outer shape determining member 102b is able to be maintained by these support rods 103 and 104. Here, having the support rod 103 be a pipe structure, flowing cooling gas through the support rod 103, and moreover, providing blow holes in the inner shape determining member 102a, enables the casting M3 to be cooled from the inside as well.
The support rods 103 and 104 are both connected to the actuator 105. This actuator 105 enables the support rods 103 and 104 to move in the top-bottom direction (the perpendicular direction) and the left-right direction, while maintaining the positional relationship between the inner shape determining member 102a and the outer shape determining member 102b. According to this kind of structure, the inner shape determining member 102a and the outer shape determining member 102b are able to be moved downward as the molten metal level drops as casting progresses. Also, the inner shape determining member 102a and the outer shape determining member 102b are able to be moved in the left-right direction, so the shape of the casting M3 in the longitudinal direction is able to be changed freely.
A cooling gas nozzle (a cooling portion) 106 is used to spray cooling gas (e.g., air, nitrogen, argon, or the like) at the casting M3 to cool the casting M3. The casting M3 is cooled by the cooling gas while being drawn up by a drawer, not shown, that is connected to a starter ST. Accordingly, the retained molten metal M2 near the solidification interface solidifies sequentially, thus forming the casting M3. Here, in order to increase the heat removal from the casting M3 and thus increase the casting speed, the temperature of the cooling gas is preferably made as low as possible. For example, an extremely low temperature gas such as cooling gas that has been cooled by liquefied, gas or cooling gas of liquefied gas (e.g., liquid nitrogen or liquid argon) has been vaporized may be used.
The molten metal cooler (a molten metal cooling portion) 107 is designed to lower the temperature of the molten metal M1 positioned directly below the inner shape determining member 102a and the outer shape determining member 102b. Coolant is circulated through the molten metal cooler 107 only when the temperature of the molten metal M1 is to be lowered. The provision of the molten metal cooler 107 is one characteristic of the free casting apparatus according to this example embodiment.
The coolant conduit 108 introduces the coolant into the molten metal cooler 107, circulates the coolant through the molten metal cooler 107, and leads the coolant that has removed the heat from the molten metal M1 out of the molten metal cooler 107. Also, the coolant conduit 108 supports the molten metal cooler 107. The coolant is not particularly limited, but from the viewpoint of safety, cooling gas (e.g., air, nitrogen, argon, or the like) is preferable. Also, as a method for circulating the coolant, a suction-type method is more preferable than a pressure-type method from the viewpoint of safety.
The material of the molten metal cooler 107 and the coolant conduit 108 is not particularly limited. For example, the material may be ceramic or stainless steel. Also, when stainless steel is used, it is preferable to prepare against molten metal loss, e.g., to wrap heat-resistant tape around the portion that contacts the molten metal M1.
The coolant conduit 108 is connected to the actuator 109. As shown in
When the temperature of the molten metal M1 positioned directly below the inner shape determining member 102a and the outer shape determining member 102b is to be lowered, coolant may be circulated inside the molten metal cooler 107, and the molten metal cooler 107 may be raised so that it moves closer to the inner shape determining member 102a and the outer shape determining member 102b. On the other hand, in any other case, circulation of the coolant in the molten metal cooler 107 may be stopped, and the molten metal cooler 107 may be lowered so that it moves away from the inner shape determining member 102a and the outer shape determining member 102b.
Next, the effects of the molten metal cooler 107 will be described in detail. The temperature of the molten metal M1 is always maintained at a predetermined appropriate temperature by the molten metal holding furnace 101. Here, the appropriate temperature is a temperature for keeping the solidification interface at an appropriate height. The height of the solidification interface is maintained by a balance between heat removal from the casting M3 and up-drawing speed. For example, when the thickness of the casting M3 is thick during casting, the heat capacity of the retained molten metal M2 increases, so the balance becomes off, the position of the solidification interface rises, and the desired shape becomes difficult to obtain. That is, moldability deteriorates.
At this time, in order to return the position of the solidification interface to the original appropriate height, if the heat removal from the casting M3 is unable to be increased, the casting speed must be slowed or the temperature of the molten metal M1 must be lowered. In order to lower the temperature of the molten metal M1, all that need be done is to lower the set temperature of the molten metal holding furnace 101. However, it takes time for all of the molten metal M1 to actually drop to the set temperature. With the free casting apparatuses until now, the casting speed had to be slowed until the temperature of all of the molten metal M1 dropped to the set temperature.
In contrast, the free casting apparatus according to this example embodiment is provided with the molten metal cooler 107, so the temperature of the molten metal M1 can be lowered in a short period of time. In particular, the molten metal cooler 107 is positioned directly below the inner shape determining member 102a and the outer shape determining member 102b, so the temperature of only the molten metal M1 near the inner shape determining member 102a and the outer shape determining member 102b (or more specifically, directly below the inner shape determining member 102a and the outer shape determining member 102b) is able to be lowered in a short period of time. Therefore, the casting speed does not need to be slowed, so the casting speed can be faster than it is with the free casting apparatuses until now. As a result, the casting time is shorter, so productivity is improved.
Next, the free casting method according to the first example embodiment will be described with reference to
Next, the starter ST starts to be drawn up at a predetermined speed. Here, when the starter ST separates from the molten metal surface, the retained molten metal M2 that follows the starter ST and is drawn up from the molten metal surface by the surface film and surface tension is formed. As shown in
Next, the starter ST is cooled by cooling gas blown from the cooling gas nozzle 106, so the retained molten metal M2 solidifies sequentially from the upper side toward the lower side, thus forming the casting M3. In this way, the casting M3 is able to be continuously cast.
Next, a free casting apparatus according to a second example embodiment of the invention will be described with reference to
As shown in
According to this kind of structure, the temperature in the space partitioned off by the partition wall 110 is maintained at a predetermined temperature (such as 25° C. for example) by the ambient temperature regulating portion 111. Because the temperature of the atmosphere of the molten metal M1 and the casting M3 is kept constant, the quality of the casting M3 is able to be more stable than it is with the free casting apparatus according to the first example embodiment. Also, by keeping the temperature of the atmosphere at 25° C., for example, the temperature of the atmosphere drops farther than it does when the temperature of the atmosphere is not controlled, so the casting speed is able to be faster than is with the free casting apparatus according to the first example embodiment. The location where the ambient temperature regulating portion 111 is arranged is not particularly limited. Also, as shown in
Next, a free casting apparatus according to a third example embodiment of the invention will be described with reference to
As shown in
Of course, the casting speed may be increased even more by combining the first example embodiment with the third example embodiment, or the second example embodiment with the third example embodiment.
Next, a free casting apparatus according to a fourth example embodiment of the invention will be described with reference to
As shown in
With the free casting apparatus according to the fourth example embodiment, the starter ST itself is the coolant conduit, so the starter ST is cooled. The coolant is not particularly limited, but cooling gas (e.g., air, nitrogen, argon, or the like) may be used, for example. Also, the flow rate of the coolant may be controlled at the start of casting and during casting. More specifically, the flow rate of the coolant may be lower at the start of casting than it is during casting. Furthermore, during casting (i.e., after casting has progressed to some extent), cooling water may also be used. Also, cooling gas may be used at the start of casting, and cooling water may be used during casting.
With the free casting apparatus according to the fourth example embodiment, cooling the starter ST enables heat removal from the casting M3 to be increased and casting speed to be faster, just like the third example embodiment. Also, because the starter ST is cooled, material with a lower melting point than the molten metal temperature may be used as the starter ST. Furthermore, the coolant temperature on the inlet side and the coolant temperature on the outlet side may be monitored and fed back to the casting control. After casting, heat treatment for texture control may be performed by circulating heat treating oil instead of coolant through the starter ST.
Also, a normal starter ST is removed after casting, but the starter ST according to the fourth example embodiment is able to be used as it is as a product. For example, pipe for a heat exchanger may be used as the normal starter ST. Furthermore, an even more complicated cooling circuit may also be used as the starter ST. Also, a casting that includes a pipe therein can also be formed by immersing the starter ST in the molten metal.
Of course, the casting speed may be increased even more by combining the first example embodiment with the fourth example embodiment, or the second example embodiment with the fourth example embodiment.
The invention is not limited to the example embodiments described above, and may be modified as appropriate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-204463 | Sep 2012 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2013/002129 | 9/13/2013 | WO | 00 |
