The present invention relates to a casting device that produces a casting through directional solidification, and in particular to a casting device high in cooling performance for the directional solidification.
For example, in a turbine blade and other components, the suppression of creep deformation and the improvement of fatigue strength have been sought by using precision casting by means of directional solidification to make the crystal structure columnar crystalline or single crystalline. The casting device sequentially cools a mold poured with a molten metal from one end part toward the other end, normally from a lower end part toward an upper end part, thereby achieving the directional solidification. The casting device includes a heating chamber and a cooling chamber that are adjacent to each other, and the mold poured with the molten metal in the heating chamber is moved, from the lower end part, to the cooling chamber at a slow speed.
As described above, to achieve the directional solidification, the mold is moved to the cooling chamber at a slow speed and solidification advances while maintaining a state where temperature gradient at a solidification interface of the molten metal is large. To reduce casting defect and to obtain a sound columnar crystal or a sound single crystal, it is important to increase the temperature gradient to accelerate solidification (or cooling).
As means to accelerate the solidification, cooling gas containing inert gas is blown to the mold in the cooling chamber, for example, as disclosed in Patent Literature 1.
An object of the present invention is to stably achieve high cooling performance in the casting device in which cooling gas is blown to the mold in the cooling chamber.
A casting device according to the present invention includes a heating chamber in which a molten metal is poured into a mold, and a cooling chamber that is provided adjacently to the heating chamber and in which directional solidification is effected while the mold poured with the molten metal is moved.
The cooling chamber according to the present invention includes a gas cooling portion that includes one or more gas supply nozzles each blowing cooling gas toward the mold, and positions of discharge ends discharging the cooling gas of the respective gas supply nozzles are adjusted in response to movement of the mold.
In the casting device according to the present invention, the positions of the discharge ends discharging the cooling gas of the respective gas supply nozzles are adjusted in response to movement of the mold. This makes it possible to keep a distance between each of the discharge ends and the mold constant, and to accordingly stably achieve high cooling performance by blowing of the cooling gas. Alternatively, the distance is adjustable to an appropriate distance irrespective of whether the distance between each of the discharge ends and the mold is kept constant. This makes it possible to further stably achieve high cooling performance by blowing of the cooling gas.
The one or more gas supply nozzles according to the present invention may be moved to adjust the positions of the respective discharge ends. As one mode, the one or more gas supply nozzles may be advanced or retreated to adjust the positions of the respective discharge ends. In addition, in the present invention, the one or more gas supply nozzles may be expanded or contracted at fixed positions to adjust the positions of the respective discharge ends.
In the present invention, the plurality of gas supply nozzles are preferably radially provided in a horizontal direction to surround the mold.
In the present invention, the gas supply nozzles may each include a slit-like nozzle opening extending in a horizontal direction.
In the present invention, the discharge ends of the gas supply nozzles may be directed downward.
The cooling chamber according to the present invention preferably includes a radiation cooling portion configured to cool the mold by radiation.
The radiation cooling portion according to the present invention is preferably arranged, below the gas cooling portion that is provided directly below a heat shielding body partitioning the heating chamber and the cooling chamber, in series to the gas cooling portion in a vertical direction.
The radiation cooling portion preferably includes a cylindrical water-cooling jacket that surrounds the mold below the gas cooling portion and through which cooling water circulates.
In the present invention, in a case where casting is performed in a plurality of molds at the same time, one or more gas supply nozzles associated with the molds are provided. In this case, the positions of the discharge ends of the one or more gas supply nozzles are adjustable in response to movement of the molds.
In the casting device, the one or more gas supply nozzles may be rotated in a horizontal direction to adjust the positions of the respective discharge ends.
According to the casting device of the present invention, the positions of the discharge ends discharging the cooling gas of the respective gas supply nozzles are adjusted in response to movement of the mold. This makes it possible to stably achieve high mold cooling performance by blowing of the cooling gas.
A casting device 1 according to an embodiment of the present invention is described below with reference to accompanying drawings.
The casting device 1 fabricates, for example, gas turbine components such as a rotor blade and a vane that are required to have mechanical strength at high temperature, through precision casting to which directional solidification is applied. In particular, the casting device 1 is designed to maximize mold cooling performance by cooling gas.
As illustrated in
Further,
The mold M is made of a refractory material, and includes therein a cavity that is a space corresponding to an outer shape of, for example, a rotor blade or a vane to be cast, as illustrated in
The cavity of the mold M includes an upper opening MA at the upper end and a lower opening MB at the lower end, and penetrates through the mold M in a vertical direction. In addition, the cavity of the mold M can be filled with an alloy A in a molten state from the upper opening MA. In addition, the lower opening MB is closed by the cooling table 9 from below, and the cooling table 9 constitutes a bottom wall of the mold M.
In
In the pouring, in the pouring chamber 3, the alloy A in the molten state stored in an unillustrated molten metal ladle, is poured into the mold M through a pouring nozzle 11. The pouring nozzle 11 is supported by the heat shielding body 6 that is the boundary between the pouring chamber 3 and the heating chamber 4. The unillustrated molten metal ladle is introduced into the pouring chamber 3 from outside before the vacuum chamber 2 is evacuated. Thereafter, after the vacuum chamber 2 is depressurized to vacuum, the alloy A in the molten state is poured from the molten metal ladle.
In the casting, the heating chamber 4 maintains the mold M poured with the alloy A in the molten state, at temperature higher than a melting point of the alloy A. To do so, as illustrated in
The heat shielding body 7 partitions the heating chamber 4 and the cooling chamber 5, and suppresses heat transfer therebetween.
As illustrated in
Next, the cooling chamber 5 is described.
The cooling chamber 5 is a region to solidify the poured alloy A in the molten state, and is maintained at temperature lower than the melting point of the alloy A poured in the mold M and includes a cooling mechanism 20 to forcibly cool the alloy A in the molten state.
The mold M that has received the alloy A in the molten state in the heating chamber 4 is moved to the cooling chamber 5. An upstream and a downstream are defined based on a direction in which the mold M is moved.
As illustrated in
The gas cooling portion 21 includes a plurality of gas supply nozzles 22 each jetting cooling gas CG (
The gas supply nozzles 22 are provided directly below the heat shielding body 7 as illustrated in
Each of the actuators 23 advances and retreats the corresponding gas supply nozzle 22 so as to keep a distance between the discharge end 221 of the corresponding gas supply nozzle 22 and the mold M constant while avoiding interference between the gas supply nozzle 22 and the mold M. In other words, advancing and retreating of the gas supply nozzles 22 are performed depending on the width dimension of the mold M. The gas supply nozzles 22 are advanced with respect to a part of the mold M having a small width dimension, and are retreated with respect to a part of the mold M having a large width dimension. The actuators 23 are provided corresponding to the plurality of gas supply nozzles 22, and the gas supply nozzles 22 are independently advanced and retreated. Accordingly, even in a case of the mold M including a deformed planar shape, it is possible to keep a distance from each of the gas supply nozzles 22 to the mold M constant, or to adjust the distance to an appropriate distance.
Next, the radiation cooling portion 25 effects radiation cooling of the mold M. In this case, radiation indicates a phenomenon that energy is transferred from a high-temperature object to a low-temperature object. In a case of the casting device 1, the high-temperature object is the mold M and the low-temperature object is the radiation cooling portion 25.
The radiation cooling portion 25 includes a structure in which a cooling medium such as cooling water CW circulates through, for example, a path provided inside a cylindrical water-cooling jacket 26 that is made of copper, a copper alloy, aluminum, an aluminum alloy, or the like with high thermal conductivity. The radiation cooling portion 25 surrounds the mold M to perform radiation cooling of the high-temperature mold M that passes through a hollow part.
The radiation cooling portion 25 is adjacently provided directly below the gas supply nozzles 22 of the gas cooling portion 21, and the gas supply nozzles 22 and the radiation cooling portion 25 are arranged in series to one another in the vertical direction.
The driving rod 8 elevates and lowers the mold M through the cooling table 9.
As illustrated in
As illustrated in
Next, casting operation by the casting device 1 including the above-described configuration is described.
As illustrated in
Since the heating chamber 4 is maintained at the temperature higher than the melting point of the alloy A, the alloy A in the molten state poured in the mold M is not solidified. On the other hand, the bottom of the poured alloy A in the mold M is solidified earlier by coming into contact with the cooling table 9, and a solidification interface that is a thin solidified part is formed.
In the pouring step, each of the discharge ends 221 of the respective gas supply nozzles 22 stands by at an advanced position that is closest to a center axis of the casting device 1. In the pouring step, the cooling gas CG may be discharged from the gas supply nozzles 22, or the cooling water CW may circulate through the water-cooling jacket 26.
After a necessary amount of alloy A is poured, the driving rod 8 is lowered to move the mold M into the cooling chamber 5 through the mold path 7A of the heat shielding body 7 at a slow speed as illustrated in
Since the inside of the cooling chamber 5 is maintained at the temperature lower than the melting point of the alloy A inside the mold M, the solidification interface is gradually moved upward according to the movement of the mold M into the cooling chamber 5, and directional solidification is accordingly effected.
The cooling gas CG is blown toward the mold M from the gas supply nozzles 22 and the cooling water CW circulates through the water-cooling jacket 26 while the mold M is lowered. This allows the cooling mechanism 20 to cool the mold M directly below the heat shielding body 7. The actuators 23 are operated in conjunction with the lowering operation of the driving rod 8 to retreat the gas supply nozzles 22. As a result, the distance from each of the gas supply nozzles 22 to the mold M is kept constant.
During the process of lowering the mold M, the gas supply nozzles 22 each reach the most retreated position when the part of the mold M including the largest width dimension passes through the mold path 7A of the heat shielding body 7, as illustrated in
After the mold M is lowered in position at a slow speed, the cooling step ends. Thereafter, the mold M is taken out from the cooling chamber 5 and is dismantled to obtain a directionally-solidified casting.
The casting device 1 according to the present embodiment achieves the following effects.
In the casting device 1, the cooling gas CG is blown from the gas supply nozzles 22 to perform cooling and the radiation cooling is effected by the radiation cooling portion 25 in association with lowering of the mold M in the cooling chamber 5. As a result, cooling is effected on the mold M from the lower end toward the upper end. Therefore, according to the present embodiment, the directional solidification is performable while improving the temperature gradient and the solidification speed by increasing the speed to cool the mold M. This makes it possible to manufacture a casting increased in mechanical strength, while suppressing casting defect.
In particular, in the present embodiment, the gas supply nozzles 22 that are advanceable and retreatable are used to perform cooling while the distance between each of the discharge ends 221 of the respective gas supply nozzles 22 and the mold M is kept constant. Accordingly, it is possible to constantly maintain high cooling performance even for molds M that have different width dimensions.
At this time, in place of advancing and retreating of the gas supply nozzles 22, a supply amount of the cooling gas CG may be increased and decreased. In this case, however, a large amount of cooling gas CG is necessary. In contrast, in the present embodiment, the supply of cooling gas CG can be suppressed at a certain minimum amount, which makes it possible to suppress a manufacturing cost of a casting. In addition, the mechanism to advance and retreat the gas supply nozzles 22 is advantageously simple. However, it is not intended to eliminate the increase and decrease of the supply amount of cooling gas CG in addition to the present invention.
In the casting device 1, the gas cooling portion 21 and the radiation cooling portion 25 constituting the cooling mechanism 20 are arranged in series to each other in the vertical direction. Therefore, they can fully exert cooling performance without inhibiting cooling functions each other. In addition, since the radiation cooling portion 25 allows the radiation cooling to be acted also on the gas supply nozzles 22 and the cooling gas CG that is discharged, the cooling effect on the mold M is maximized by the gas cooling portion 21.
In particular, in the cooling mechanism 20, the gas cooling portion 21 and the radiation cooling portion 25 are disposed in order from above. The mold M that is being lowered is cooled by the cooling gas CG blown from the gas supply nozzles 22, and is then subjected to the radiation cooling by the radiation cooling portion 25. Therefore, according to the present embodiment, as compared with a case where the arrangement of the gas cooling portion 21 and the radiation cooling portion 25 is inverse in the vertical direction, the cooling gas CG is supplied to a region immediately next to the heating chamber 4 in which the temperature of the mold M itself is high. This makes it possible to maximize the cooling performance by the gas cooling portion 21.
Although the preferred embodiment of the present invention has been described above, the configurations described in the above-described embodiment may be selected or appropriately modified without departing from the scope of the present invention.
For example, as illustrated in
In the case of the casting device 1, the gas supply nozzles 22 may be advanced or retreated as illustrated in
Further, the gas cooling portion 21 includes the plurality of independent gas supply nozzles 22. Alternatively, as illustrated in
When the gas supply nozzles 22 each including the slit-like nozzle opening 222 are used, discharge flow velocity of the cooling gas CG becomes uniform, which makes it possible to uniformly cool the surface of the mold M.
Further, the above-described gas supply nozzles 22 correspond to an example in which the cooling gas CG is discharged in the horizontal direction; however, the present invention is not limited thereto. For example, as illustrated in
Further, the above-described gas cooling portion 21 can keep the distance between each of the gas supply nozzles 22 and the mold M constant or can adjust the distance to an appropriate distance by advancing or retreating the gas supply nozzles 22. The present invention, however, is not limited thereto. As illustrated in
Further, in the above-described embodiment, each of the gas supply nozzles 22 is advanced and retreated; however, movement of the gas supply nozzles 22 according to the present invention is not limited thereto. For example, the gas supply nozzles 22 may be parallelly moved in the horizontal direction as a group. More specifically, as illustrated in
Further, each of the plurality of gas supply nozzles 22 may be rotated in the horizontal direction. More specifically, as illustrated in
Movement of the gas supply nozzles 22 is not limited to the movement exemplified in
Further, as a mode of the movement, the gas supply nozzles 22 may be moved in the vertical direction without being limited to the movement in the horizontal direction. For example, a rotation axis may be set in the horizontal direction, and the gas supply nozzles 22 may be swung around the rotation axis.
Moreover, in the present invention, means to control the movement of the gas supply nozzles 22 are optional. For example, data relating to the dimensions and the shape of the mold M used in the casting is held, and the advanced and retreated positions of the gas supply nozzles 22 may be adjusted based on the data. Alternatively, a range sensor that measures the distance from each of the discharge ends 221 of the respective gas supply nozzles 22 to the surface of the mold M may be provided, and the advanced and retreated positions of the gas supply nozzles 22 may be adjusted based on the distance to the surface of the mold M measured by the range sensor.
Number | Date | Country | Kind |
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2016-047733 | Mar 2016 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2017/009475 | 3/9/2017 | WO | 00 |