The disclosure of Japanese Patent Application No. 2014-046047 filed on Mar. 10, 2014 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to an up-drawing continuous casting method.
2. Description of Related Art
Japanese Patent Application Publication No. 2012-61518 (JP 2012-61518 A) proposes a free casting method as a groundbreaking up-drawing continuous casting method that does not require a mold. As described in JP 2012-61518 A, a starter is first dipped into the surface of molten metal (a molten metal surface), and then when the starter is drawn up, molten metal is also drawn up 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 up the molten metal through a shape determining member arranged near the molten metal surface, and cooling the drawn up 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, with a continuous casting method, 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. Therefore, castings of various shapes in the longitudinal direction are able to be obtained by drawing the starter up while moving the starter (or the shape determining member) in a horizontal direction. 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 the problem described below. With the free casting method described in JP 2012-61518 A, the molten metal drawn up through the shape determining member is cooled and solidified by cooling gas, so a solidification interface is positioned above the shape determining member. Therefore, when forming a bent shape in the casting by changing the up-drawing direction of the molten metal, the molten metal solidifies after the change in the up-drawing direction. Therefore, the molten metal drawn up before the change in the up-drawing direction ends up being drawn to the molten metal drawn up after the change in the up-drawing direction, and as a result, the bent shape ends up becoming rounded. As a result, a bent shape having a predetermined bending angle is unable to be formed in the casting, which is problematic.
In view of this, the invention aims to provide an up-drawing continuous casting method capable of forming a bent shape having a predetermined angle in a cast casting.
One aspect of the invention relates to an up-drawing continuous casting method for forming a bent shape in a cast casting by forming the casting in a first direction and then changing an up-drawing direction to a second direction and forming the casting in the second direction, the casting being formed by drawing up molten metal held in a holding furnace from a molten metal surface of the molten metal, passing the molten metal through a molten metal passage portion of a shape determining member that determines a sectional shape of the casting, and solidifying the molten metal. This up-drawing continuous casting method includes a step of drawing up the molten metal in the first direction; and a step of changing the up-drawing direction to a third direction in which an angle between the third direction and the first direction is greater than an angle between the second direction and the first direction, from after a portion that will have the bent shape passes through the molten metal passage portion until the portion that will have the bent shape reaches a solidification interface, and then drawing up the molten metal. The up-drawing continuous casting method according to this aspect of the invention changes the up-drawing direction of the molten metal after the portion that will have the bent shape moves close to the solidification interface. Therefore, the majority of the molten metal drawn up before the portion that will have the bent shape is already solidified when the up-drawing direction of the molten metal changes, so a constant shape is able to be maintained without being affected by the molten metal drawn up after the change in the up-drawing direction. As a result, rounding of the bent shape is able to be suppressed. Also, the up-drawing direction is changed to the third direction in which the angle between the third direction and the first direction is greater than the angle between the second direction and the first direction, and then the molten metal is drawn up. Accordingly, the extending direction of the retained molten metal is able to be aligned with the second direction in a short period of time from after the up-drawing direction of the molten metal is changed until the portion that will have the bent shape reaches the solidification interface. As a result, a bent shape having a predetermined bending angle is able to be formed in the casting.
The invention thus makes it possible to provide an up-drawing continuous casting method capable of forming a bent shape having a predetermined angle in a cast casting.
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 description.
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 at which the molten metal M1 has fluidity. In the example in
The shape determining member 102 is made of ceramic or stainless steel, for example, and is arranged above the molten metal M1. The shape determining member 102 determines the sectional shape of a cast casting M3. The casting M3 shown in
In the example in
As shown in
The support rod 104 supports the shape determining member 102. The support rod 104 is connected to the actuator 105. The shape determining member 102 is able to move up and down (i.e., in the vertical direction; the z-axis direction) via the support rod 104, by the actuator 105. According to this kind of structure, the shape determining member 102 is able to be moved downward as the molten metal surface level drops as casting proceeds.
A cooling gas nozzle (a cooling portion) 106 is cooling means for spraying cooling gas (e.g., air, nitrogen, argon, or the like) supplied from the cooling gas supplying portion 107 at the casting M3 to cool the casting M3. The position of the solidification interface SIF is able to be lowered by increasing the flow rate of the cooling gas, and raised by reducing the flow rate of the cooling gas. The cooling gas nozzle 106 is also able to be moved up and down (i.e., in the vertical direction; in the z-axis direction) and horizontally (i.e., in the x-axis direction and the y-axis direction). Therefore, for example, the cooling gas nozzle 106 can be moved downward, in concert with the movement of the shape determining member 102, as the molten metal surface level drops as casting proceeds.
Alternatively, the cooling gas nozzle 106 can be moved horizontally, in concert with horizontal movement of the up-drawing machine 108.
The casting M3 is formed by the retained molten metal M2 near the solidification interface SIF progressively solidifying from the upper side (i.e., the plus side in the z-axis direction) toward lower side (i.e., the minus side in the z-axis direction), by cooling the starter ST and the casting M3 with the cooling gas, while drawing the casting M3 up with the up-drawing machine 108 that is connected to the starter ST. The position of the solidification interface SIF is able to be raised by increasing the up-drawing speed with the up-drawing machine 108, and lowered by reducing the up-drawing speed. Also, the retained molten metal M2 is able to be drawn up diagonally by drawing the casting M3 up while moving the up-drawing machine 108 horizontally (in the x-axis direction and the y-axis direction). Therefore, the longitudinal shape of the casting M3 is able to be freely changed. The longitudinal shape of the casting M3 may also be freely changed by moving the shape determining member 102 horizontally, instead of by moving the up-drawing machine 108 horizontally.
Continuing on, a free casting method according to the example embodiment will be described with reference to
First, the starter ST is lowered by the up-drawing machine 108 so that it passes through the molten metal passage portion 103 of the shape determining member 102, and the tip end portion of the starter ST is dipped into the molten metal M1.
Next, the starter ST starts to be drawn up at a predetermined speed. Here, even if the starter ST separates from the molten metal surface, the molten metal M1 follows the starter ST and is drawn up from the molten metal surface by the surface film and surface tension, and forms the retained molten metal M2. As shown in
Next, the starter ST (or the casting M3 formed by the retained molten metal M2 solidifying) is cooled by cooling gas blown from the cooling gas nozzle 106. As a result, the retained molten metal M2 is indirectly cooled and solidifies progressively 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.
Here, a bent shape is able to be formed in the casting M3 by changing the up-drawing direction of the molten metal M1. This will be described in detail below.
With the molded component of the casting M3 shown in
First, the retained molten metal M2 (1 and 2 in the drawing; hereinafter, also referred to as retained molten metals M2_1 and M2_2) that extends in the first direction is progressively formed by continuously drawing up the molten metal M1 in the first direction (time t0 to t2).
Then, by drawing up the molten metal M1 in the first direction, a retained molten metal M2_3 (3 in the drawing) that extends in the first direction is formed after the retained molten metals M2_1 and M2_2 are formed (time t2 to t3). At this time, the retained molten metal M2_1 reaches the solidification interface and thus solidifies, forming the casting M3_1 that extends in the first direction (time t2 to t3). At time t2 to t3, the up-drawing direction of the retained molten metal M2_3 remains the first direction, just like the retained molten metals M2_1 and M2_2. That is, at time t2 to t3, a portion that will have the bent shape (near the boundary between the retained molten metals M2_2 and M2_3) does not have the bent shape. Therefore, the retained molten metal M2_1 is able to solidify without being drawing by the retained molten metals M2_2 and M2_3 and changing shape.
Then, as the portion that will have the bent shape moves close to the solidification interface, the up-drawing direction is changed to a direction (hereinafter, referred to as a “third direction”) inclined toward the x-axis direction plus side by an angle θ2 (θ2>θ1) with respect to the first direction, and the molten metal M1 starts to be drawn up (time t3). In the example in
Also, at this time, the retained molten metal M2_2 reaches the solidification interface, so it solidifies, forming the casting M3_2 that extends in the first direction (time t3 to t4). Here, as described above, the up-drawing direction of the molten metal M1 is changed after the portion that will have the bent shape moves close to the solidification interface, so the casting M3_1 will of course not be drawn by the retained molten metal M2 and thus will not change shape. What is more, the retained molten metal M2_2 will also solidify either before being drawn by the retained molten metals M2_3 and M2_4 and changing shape, or while that effect is still small. As a result, the desired casting M3_2 that extends in the first direction is able to be formed.
After the portion that will have the bent shape has reached the solidification interface, the up-drawing direction is changed to the second direction, which is the forming direction of the castings M3_3 and M3_4, and the molten metal M1 is drawn up (time t4 to t6). At this time, the retained molten metals M2_3 and M2_4 reach the solidification interface, so they solidifies while maintaining a shape that extends in the second direction, thus forming the castings M3_3 and M3_4.
As a result, a molded component of the casting M3 is able to be formed, the molded component of the casting M3 is formed by the castings M3_1 and M3_2 that extend in the first direction, and the castings M3_3 and M3_4 that extend in the second direction, and molded component of the casting M3 has a bent shape of a predetermined bending angle α.
In contrast, with the up-drawing continuous casting method according to this example embodiment shown in
With the molded component of the casting M3 shown in
In this way, with the free casting method according to this example embodiment, the up-drawing direction of the molten metal M1 is changed after the portion that will have the bent shape moves close to solidification interface. As a result, the majority of the molten metal M1 drawn up before the portion that will have the bent shape is already solidified when the up-drawing direction of the molten metal M1 changes, so a constant shape is able to be maintained without being affected by the molten metal M1 drawn up after the change in the up-drawing direction. As a result, rounding of the bent shape is able to be suppressed. Also, the up-drawing direction is changed to the third direction in which the angle between the third direction and the first direction is greater than the angle between the second direction and the first direction, and then the molten metal M1 is drawn up. Accordingly, the extending direction of the retained molten metal M2 is able to be aligned with the second direction (i.e., the molding direction of the casting M3) in a short period of time from after the up-drawing direction of the molten metal M1 is changed until the portion that will have the bent shape reaches the solidification interface. As a result, a bent shape having a predetermined bending angle is able to be formed in the casting M3.
In this example embodiment, a case in which the up-drawing direction of the molten metal M1 is changed when the portion that will have the bent shape is positioned midway between the molten metal passage portion 103 and the solidification interface has been described, but the example embodiment is not limited to this. The timing at which the up-drawing direction of the molten metal M1 is changed may any time from after the portion that will have the bent shape passes through the molten metal passage portion 103 until it reaches the solidification interface. However, the value of the angle θ2 must be adjusted such that the direction in which the portion that will have the bent shape heads toward the solidification interface from the molten metal passage portion 103, when the portion that will have the bent shape reaches the solidification interface, comes to match the second direction. For example, a bent shape is able to be made in the casting M3 more accurately the closer the timing at which the up-drawing direction of the molten metal M1 changes is to when the portion that will have the bent shape is near the solidification interface. On the other hand, the change in the up-drawing direction of the molten metal M1 becomes smaller the closer the timing at which the up-drawing direction of the molten metal M1 changes is to when the portion that will have the bent shape is near the molten metal passage portion 103, so the retained molten metal M2 is able to be prevented from being torn or the like by the change in the up-drawing direction. The up-drawing direction of the molten metal M1 is preferably changed when the portion that will have the bent shape is midway between the molten metal passage portion 103 and the solidification interface, or closer to the solidification interface than midway between the molten metal passage portion 103 and the solidification interface.
Also, in this example embodiment, an example in which the up-drawing direction of the molten metal M1 is changed only once to form one bent shape in the casting M3 is described, but the example embodiment is not limited to this. The up-drawing direction of the molten metal M1 may also be changed two or more times to form one bent shape in the casting M3.
Next, a free casting apparatus according to a second example embodiment of the invention will be described with reference to
The shape determining member 102 according to the first example embodiment shown in
As shown in
Also, as shown in
Next, the drive mechanism of the shape determining plate 202a will be described with reference to
As shown in
Also, as shown in
With the free casting method according to the second example embodiment, effects similar to those of the first example embodiment are able to be displayed. In addition, the thickness t1 and width w1 of the molten metal passage portion 203 of the shape determining member 202 are able to be changed. Therefore, the dimensions (the thickness t and the width w) of the casting are able to be freely changed.
The invention is not limited to the example embodiments described above, and may be modified as appropriate without departing from the spirit of the invention.
Number | Date | Country | Kind |
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2014-046047 | Mar 2014 | JP | national |