KR100990130B1 - Apparatus for directionally solidified casting products and Manufacturing method of directionally solidified casting products using the same - Google Patents

Abstract

An apparatus for manufacturing a cast product using one-way solidification to manufacture a high quality cast product having a uniform directionality in the longitudinal direction without defects by controlling the position of the solid-liquid interface to be at a reference position, and a manufacturing method using the same. The apparatus and method calculate the reference position in real time by statistical processing using the shape of the interface detected by the detection sensor for detecting the shape of the interface between the solid phase and the liquid phase, and set the reference position calculated in real time in advance. It includes a control unit for controlling the withdrawal speed of the mold by the elevator compared to the reference position.

Unidirectional solidification, solid-liquid interface, reference position, withdrawal speed

Description

Apparatus for directionally solidified casting products and Manufacturing method of directionally solidified casting products using the same}

The present invention relates to an apparatus for manufacturing a cast product and a method thereof, and more particularly, to an apparatus for manufacturing a cast product using unidirectional solidification and a manufacturing method using the apparatus.

A general one-way solidification method is a solidification technique that extends the life of a product by eliminating the transverse grain boundary, ie, the starting point of the crack, which acts perpendicular to the stress when using an existing equiaxed superheat resistant alloy turbine blade casting. Recently, according to the tendency to increase the combustion temperature to improve the efficiency of the gas turbine, it is necessary to manufacture a super heat-resistant alloy turbine blade having excellent high temperature characteristics suitable for this. To this end, the direction of the grains is gradually converted to a single crystal casting grown in the longitudinal direction by selecting only one grain in one-way solidified casting is arranged parallel to the stress axis. Single crystal castings also use a one-way solidification method and are typically manufactured using a Brigman vacuum furnace.

The preferred one-way solidification casting condition is that the solid metal is grown while the interface between the solid phase and the liquid phase (hereinafter, the liquid-liquid interface) remains flat in the direction perpendicular to the growth direction of the solid metal. The position where the solid-liquid interface maintains a flat shape perpendicular to the growth direction of the solid metal is called a reference position. At this time, the reference position is determined by the speed with which the mold is drawn out from the mold heating portion to the outside of the cooling chamber.

When the position of the solid-liquid interface is located in the lower part of the insulation between the mold heating part and the cooling chamber, away from the reference position when the position of the solid liquid is flat, the molten metal located on the mold surface side rather than inside the molten metal by radiant heat transfer of the cold surface and the mold surface of the cooling chamber. The temperature of the decreases. As a result, the shape of the solid-liquid interface is convex downward. On the other hand, if the location of the solid-liquid interface is in the upper part of the heat insulating material, that is, inside the mold heating part, the mold surface has a higher temperature than the inside of the molten metal due to the radiant heat transfer of the hot mold heating part. As a result, the shape of the solid-liquid interface is convex upward.

The shape of the solid-liquid interface has a direct influence on the generation of pores or oriented defects. If the solid-liquid interface that grows in one-way solidification where the cross-sectional area of the casting occurs is convex downward, there is a supercooled place at the end of the part where the cross-sectional area of the part is increased. In the supercooled area, new grains are nucleated and grown from here, ultimately producing uneven grain boundaries and breaking one-way solidification. On the other hand, when the solid-liquid interface has a convex shape, solidification progresses at the end of the portion having the increased cross-sectional area, so that the molten metal of the liquid is trapped, thereby forming pores.

As described above, maintaining the solid-liquid interface at the reference position showing a flat shape in one-way solidification is a very important factor in the quality and yield of the casting.

However, the conventional one-way solidification method of the bridge only proceeds to maintain a constant value simply without controlling the extraction speed in order to match the position of the solid-liquid interface to the reference position. Since the withdrawal speed is maintained at a constant value during the solidification process, if the shape of the casting is complicated and the size of the cross-sectional area is changed in the longitudinal direction, the heat transfer direction may change every moment, so that the position of the solid-liquid interface is flat. Can move away from the reference position. Accordingly, since the shape and position of the solid-liquid interface continuously change with the shape of the casting in the longitudinal direction of the casting or the cross-sectional area of the casting, not only the quality is not uniform, but also pores, non-directional defects occur frequently.

Therefore, in the manufacture of castings using unidirectional solidification, it is important for related companies such as precision casting companies and gas turbine operators to remove porosity or non-directional defects to maximize the yield of high quality castings and not to reduce productivity. Has been one of.

Therefore, the technical problem to be achieved by the present invention is to control the position of the solid-liquid interface where the solidification proceeds to the reference position to provide an apparatus for manufacturing a cast product using one-way solidification to manufacture a high-quality casting of uniform directionality in the longitudinal direction without a defect. There is. In addition, another technical problem to be achieved by the present invention is to provide a method for producing a casting by one-way solidification using the manufacturing apparatus.

The apparatus for producing a cast product using the one-way solidification of the present invention for achieving the above technical problem includes an elevator for extracting a mold containing a mold metal having an interface between a solid phase and a liquid phase in real time. In addition, it is disposed below the elevator, and includes a detection sensor for detecting the shape of the interface between the solid phase and the liquid phase. Using the shape of the interface detected by the detection sensor, the reference position is calculated in real time by statistical processing, and the reference position calculated in real time is compared with a preset reference position to draw out the mold by the elevator. It includes a control unit for controlling the speed.

In a preferred embodiment of the present invention, the reference position is determined by the flatness of the interface set in advance, and the reference position is the position of the interface where the solid metal grows vertically at the interface. In addition, the reference position can be determined through numerical analysis and preliminary experiments.

In the present invention, between the control unit and the elevator may further include an electronic motor for driving the elevator, it is preferable that the detection sensor uses a transverse ultrasonic wave.

The method of manufacturing a cast product using one-way solidification of the present invention for achieving the above another technical problem first sets a reference position having a flatness in which the solid metal grows vertically at a solid-liquid interface of a given one-way solidification. Thereafter, the shape is detected in real time by a solid-liquid interface detection sensor so as to grasp the shape of the solid-liquid interface. The detected data is recognized by distinguishing an area that maintains flatness and an area that deviates from flatness by a predetermined deviation by statistical processing. The flatness of the solid-liquid interface in real time is calculated on the basis of the discriminated and recognized data. If the flatness of the solid-liquid interface in real time is greater than or equal to the flatness determining the reference position, the withdrawal speed of the mold for the one-way solidification is maintained in the current state, and the flatness of the solid-liquid interface in real time maintains the reference position. If less than the determined flatness, the extraction speed is changed to adjust the solid-liquid interface to a reference position.

In a preferred manufacturing method of the present invention, the flatness set in advance and the flatness detected in real time are compared by a controller.

According to the apparatus and method for producing a cast product using the one-way solidification of the present invention, the reference position when the solid-liquid interface is the most flat shape is kept constant, so that a high-quality cast product having a uniform directionality in the longitudinal direction can be manufactured. do. In addition, it is manufactured while adjusting the reference position of the solid-liquid interface in real time, it is possible to produce a casting stably without lowering the productivity.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

Hereinafter, an apparatus for manufacturing a cast product using unidirectional solidification for producing a high quality cast product having no defects and having a uniform directionality in the longitudinal direction, and a method of manufacturing the same will be presented with reference to the reference position. Specifically, the reference position applied when manufacturing the actual casting will be described, and the process of detecting the reference position and applying it to one-way solidification will be described. Of course, the reference position in the scope to which the present invention is applied can be applied in various ways, here only the characteristics thereof will be described by way of example.

Since there is little convection when solidifying in one direction in a vacuum, cooling is mainly achieved by thermal conduction through a cooling section, such as a water-cooled copper plate, and radiant heat transfer between the mold surface and the cooling chamber outside the mold heating section. The ideal unidirectional solidification casting condition is that the solid-liquid interface grows while maintaining a flat shape perpendicular to the solid metal growth direction. The position where the solid-liquid interface maintains a flat shape perpendicular to the growth direction of the solid metal is called a reference position.

If the solid-liquid interface is solidified in one direction while maintaining the reference position, the temperature gradient exists only in the up and down directions regardless of the shape of the component to be manufactured and the solidified position. As a result, all dendrites grow in a precisely aligned direction, so that a complete one-way solidification or single crystal part can be produced. Such a flat solid-liquid interface can be realized when present in a specific reference position, and therefore, it is important to maintain the reference position when the solid-liquid interface is in a flat shape.

Figure 1a is a view for explaining the flatness of the reference position and the solid-liquid interface according to an embodiment of the present invention, Figure 1b is an enlarged view of a portion of Figure 1a.

Referring to FIGS. 1A and 1B, a mold 40 containing a shape of a cast product is placed on the cooling unit 10. The molten metal is injected into the mold 40 through the molten metal inlet 50 and is transformed into a mold metal 20 for manufacturing a casting. The casting metal 20 is separated into the liquid metal 21 near the molten metal inlet 50 around the solid-liquid interface 30, and the solid metal 22 around the cooling unit 10.

 As described above, the shape of the solid-liquid interface 30 may vary depending on the withdrawal speed. In particular, the solid state 22 is maintained at a flat state so that the solid metal 22 grows vertically at a reference position. At this time, the degree of flatness has a relationship between L2 which is the width of the region to maintain flatness and L2 / (L1 + L2 + L3) at L1 and L3 which are the widths of the region deviating from the flatness on both sides of L2. Therefore, when the flatness is large, the size of L1 and L3 is small, the size of L2 is relatively large. The sizes of L1, L2, and L3 may be represented by distances or widths, respectively. The withdrawal speed is a change in the distance d between the solid-liquid interface 30 and the surface where the cooling unit 10 and the solid metal 22 contact each other, per unit time. In FIG. 1B, Δ is a statistical deviation for setting the reference position.

The method of securing the reference position in real time can be variously applied within the scope of the present invention. 2 is a flowchart illustrating a method of securing a reference position in real time according to an embodiment of the present invention. In this case, the one-way solidification method will be described with reference to FIGS. 1A and 1B.

According to FIG. 2, first, a reference position having a flatness in which the solid metal 22 grows vertically at the solid-liquid interface 30 of one-way solidification is set in advance (S10). For example, if the flatness is 0.9, L2 is 0.9 when (L1 + L2 + L3) is assumed to be 1. In this case, since the flatness may vary depending on the conditions of the solidification in one direction such as the type of the alloy and the form of the mold, it may be set through numerical analysis or preliminary experiment. If necessary, the set reference value may be look-up tabled and used continuously in the future. When the flatness is set, the shape of the solid-liquid interface 30 is grasped by the apparatus for detecting the solid-liquid interface 30 (S20). Specifically, data may be secured by checking several points of the solid-liquid interface 30 in various places, or the shape of the solid-liquid interface 30 may be received as an image and converted into digital data through quantization.

By statistical processing, each data is recognized as L2, which is an area that maintains flatness if it falls within the range of a predetermined deviation (△), and L1, L3, which is an area that deviates from flatness, when it falls outside the range of deviation (△). Recognize as (S30). The flatness is calculated using the recognized L1, L2, and L3 values (S40). If the calculated value is greater than a preset value, for example, 0.9, it is determined that the solid-liquid interface 30 is at the reference position (S50). . If the solid-liquid interface 30 is at the reference position, the withdrawal speed currently applied is maintained (S60). If the solid-liquid interface 30 deviates from the reference position, the extraction speed currently being applied is changed to adjust the solid-liquid interface 30 to the reference position (S70).

Figure 3 is a schematic diagram showing a one-way solidification apparatus for producing a high quality cast product by a one-way solidification method according to an embodiment of the present invention.

Referring to FIG. 3, the one-way coagulation apparatus includes a furnace 100 in which a cover is formed of an insulation and a baffle. Inside the furnace 100, a molten metal injection hole 112 for injecting molten metal and an investment mold 110 containing a shape of a cast product are installed. Outside the precision casting mold 110, inside the furnace 100, the mold heating unit 102 composed of a graphite heat source for maintaining above the melting temperature of the alloy, and the precision casting mold is located on the top The cooling part (chill part 120) for solidifying the liquid molten metal inside the bath mold (110), the heat insulating material 104 for effective radiation shielding between the mold heating part and the outside is disposed. In addition, the precision casting mold 110 and the cooling unit 120 are drawn out of the outside of the mold heating unit 102 by an elevator 150 mounted inside the furnace 100.

The molten metal is injected into the mold 110 through the molten metal inlet 112 and is transformed into a mold metal 142 for manufacturing a casting. The mold metal 142 is separated into the liquid metal 141 near the molten metal inlet 112 around the solid-liquid interface 140 and the solid metal 143 around the cooling unit 120. The cooling unit 120 may use cooling water circulating, and may utilize a liquid metal.

A detection sensor 130 for detecting the position of the solid-liquid interface 140 is mounted below the elevator 150 under the cooling unit 120. The detection sensor 130 may be variously applied within the scope of the present invention. Preferably, a method using an ultrasonic wave may be suitable. The electromagnetic ultrasonic wave sensor 130 uses the property that the transverse ultrasonic wave transmits only the solid phase and does not transmit the liquid phase, and the longitudinal ultrasonic wave transmits the uncoagulated layer (molten metal). Accordingly, the shape (or location) of the solid-liquid interface 140 may be continuously calculated in real time by receiving the transverse ultrasonic signal reflected from the solid-liquid interface 140.

Outside the furnace 100, a controller 160 electrically connected to the electromagnetic ultrasonic wave sensor 130 is disposed. The controller 160 amplifies the signal sent from the detection sensor 130 to calculate the reference position by calculating the shape (flatness, Δ) of the solid-liquid interface 140 in real time. The method of calculating the reference position has been described in detail with reference to FIGS. 1A and 1B.

When the control unit 160 calculates the reference position, the control unit 160 controls the drawing speed by sending a signal to the electronic motor 152 to maintain the position of the solid-liquid interface 140 at the reference position. Specifically, when the solid-liquid interface 140 is in the reference position, the withdrawal speed that is currently applied is maintained, and when the solid-liquid interface 140 is out of the reference position, the withdrawal speed that is currently applied is changed to change the solid-liquid interface 140. Adjust to the reference position.

According to an embodiment of the present invention, a process of manufacturing a high quality casting by the one-way solidification system of the present invention is as follows. First, the reference position when the solid-liquid interface 140 is most flat is determined through numerical analysis and preliminary experiments. However, if the cross-sectional area of the casting is different depending on the position, it is possible to determine the position (or flatness, Δ) where the solid-liquid interface is flat at the largest cross-sectional area. Thereafter, the reference position is back-calculated as a signal of the electromagnetic ultrasonic sensor 130 and input to the controller 160 as a reference position or a command position. If necessary, database the reference position by creating a lookup table.

Subsequently, the molten metal is injected into the molten metal injection hole 112 provided in the furnace 100, and the molten metal is flowed into the precision casting mold 110. The molten metal in the precision casting mold 110 flows downward, and heats the precision casting mold 110 with heat generated from the mold heating unit 102 to maintain the flowing molten metal in a liquid state. The heated precision casting mold 110 is positioned above the cooling unit 120 to start the one-way solidification while moving the cooling unit 120 at a predetermined drawing speed in the downward direction.

At this time, the solid metal 143 is grown in one direction by the temperature gradient from the cooling unit 120, the electron ultrasonic detection sensor 130 is continuously (or flatness, △) of the solid-liquid interface 140 Is detected in real time. Based on the detected signal, the controller 160 relatively compares the preset reference position with the current interface position (or flatness, Δ). Based on the interfacial position compared, the controller 160 provides feedback to control the withdrawal speed required for the electronic motor 152.

According to the embodiment of the present invention, the position of the solid-liquid interface 140 maintains the reference position when the flattened shape is constant, thereby making it possible to manufacture a high-quality cast product having a uniform directionality in the longitudinal direction. In addition, it is manufactured while adjusting the reference position of the solid-liquid interface 140 in real time, it is possible to produce a cast product stably without lowering the productivity.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but many variations and modifications may be made without departing from the scope of the present invention. It is possible.

Figure 1a is a view for explaining the flatness of the reference position and the solid-liquid interface according to the present invention, Figure 1b is an enlarged view of a portion of Figure 1a.

2 is a flowchart illustrating a method of securing a reference position in real time according to the present invention.

3 is a schematic view showing a one-way solidification apparatus for producing a high quality cast product by the one-way solidification method according to the present invention.

* Description of the symbols for the main parts of the drawings *

100; To 110; template

112; Molten metal inlet 120; Cooling section

130; Detection sensor 140; A solid-liquid interface

141; Liquid metal 143; Solid metal

150; Elevator 152; Electronic motor

160; Control

Claims (8)

An elevator 150 for extracting the mold 110 containing the mold metal 142 on which the interface 140 between the solid and liquid phases is formed in real time; A detection sensor 130 disposed below the elevator 150 to detect a shape of the interface 140 between the solid and liquid phases; And The reference position is calculated in real time by statistical processing using the shape of the interface 140 detected by the detection sensor 130, and the reference position calculated in real time is compared with a preset reference position. It includes a control unit 160 for controlling the withdrawal speed of the mold by the elevator 150, The reference position is a device for producing a casting using one-way solidification, characterized in that determined by the flatness of the interface 140 is set in advance. delete The apparatus of claim 1, wherein the reference position is a position of an interface at which the solid metal grows vertically at the interface (140). The apparatus of claim 1, wherein the reference position is determined through numerical analysis and preliminary experiments. The apparatus of claim 1, further comprising an electronic motor (152) for driving the elevator (150) between the controller (160) and the elevator (150). The apparatus of claim 1, wherein the detection sensor (130) uses transverse ultrasonic waves. Presetting a reference position having a flatness in which the solid metal grows vertically at a given solid-liquid interface of one-way solidification; Detecting the shape in real time by a solid-liquid interface detection sensor to grasp the shape of the solid-liquid interface; Discriminating and recognizing the detected data by distinguishing a region from which the flatness is kept flat and a region which is out of the flatness by a predetermined deviation by a statistical process; Calculating flatness of the solid-liquid interface in real time based on the discriminated and recognized data; And If the flatness of the solid-liquid interface in real time is greater than or equal to the flatness determining the reference position, the withdrawal speed of the mold for the one-way solidification is maintained in the current state, and the flatness of the solid-liquid interface in real time maintains the reference position. If less than the flatness to determine the manufacturing method of the cast using one-way solidification comprising the step of changing the withdrawal speed to adjust the solid-liquid interface to a reference position. The method of claim 7, wherein the previously set flatness and the flatness detected in real time are compared by a control unit.

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