Level meter, molding device, and molding device operating method

Abstract

To accurately measure a liquid surface over 400 mm from the bottom of a casting mold to the liquid surface when measuring the liquid surface level of high-temperature liquid such as molten steel.SOLUTION: A level meter 1 comprises: a cylindrical guide pipe 10 that is disposed in parallel to a liquid surface 101 of high-temperature liquid 100 and propagates microwaves or millimeter waves in its internal space; an antenna 20 that is disposed opposite to one opening 10a of the guide pipe 10; transmission and reception means 30 for microwaves or millimeter waves that is connected with the antenna 20; and a reflecting plate 40 that is disposed opposite to the other opening 10b of the guide pipe 10, reflects the microwaves or millimeter waves transmitted from the antenna 20 toward the high-temperature liquid 100, and guides the reflected microwaves or reflected millimeter waves to the guide pipe 10. The pipe length L of the guide pipe 10 is adjusted to a length at which phase constants in a TE mode and a TM mode of the microwaves or millimeter waves match each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a level meter for detecting the level of a high-temperature liquid such as a metal melt, and also to a molding apparatus equipped with the level meter and a method for operating the same. [Background technology]

[0002] For example, in a casting machine, molten steel is poured into a mold, solidified, and an iron molded body is produced by pulling it downward from the mold. In this process, the level of the molten steel is detected using a level meter to control the amount of molten steel poured into the mold. Conventionally, a "vortex level meter" has been commonly used as the level meter, and is described in, for example, Patent Documents 1 and 2.

[0003] Furthermore, vortex current level meters are installed close to the surface of the molten steel because, in principle, they have a short measurement distance. Molten steel is a high-temperature liquid, so vortex current level meters are required to have high heat resistance. Therefore, in Patent Document 2, a vortex current level meter is provided with an inner case made of alumina that houses the sensor coil and an outer case made of silicon nitride that encases the inner case, and the heat resistance is improved by cooling the inside of the case with air or the like. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-286887 [Patent Document 2] Japanese Utility Model Application Publication No. 5-49156 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, in principle, vortex level meters can only measure up to about 150 mm above the liquid surface. Therefore, in order to perform an auto-start at the start of casting, which automatically controls the rise of molten steel poured into the mold to the control level, they must be used in conjunction with other level meters, such as thermocouple level meters, which have lower accuracy but a wider measurement range. This has created the problem of not being able to measure the level over a height of approximately 400 mm, from the bottom of the mold to the control level of the liquid surface.

[0006] Therefore, the present invention aims to solve the above problem by measuring over a height of approximately 400 mm from the bottom of the mold to the liquid surface control level. [Means for solving the problem]

[0007] In order to solve the above problems, a microwave or millimeter wave level meter having a long measurement range is used instead of an eddy current level meter. The present invention provides the following level meter, molding device, and method of operating the molding device.

[0008] (1) A level meter that transmits microwaves or millimeter waves from an antenna toward high-temperature liquid stored in a storage container, receives the reflected microwaves or millimeter waves reflected by the surface of the high-temperature liquid with the antenna, and measures the distance to the surface of the high-temperature liquid, a cylindrical guide pipe with both ends open, which is disposed parallel to or obliquely to the liquid surface of the high-temperature liquid and through which microwaves or millimeter waves propagate in its internal space; the antenna disposed opposite one opening of the guide pipe; a transmitting / receiving means connected to the antenna for transmitting and receiving the microwave or millimeter wave; a reflector disposed opposite the other opening of the guide pipe, for reflecting the microwaves or millimeter waves transmitted from the antenna and propagating through the guide pipe toward the high-temperature liquid, and for guiding the reflected microwaves or millimeter waves to the guide pipe; The distance from the opening surface of the antenna to the other opening end of the guide pipe is determined based on the positions of the TE mode and TM mode of the microwave or millimeter wave propagating through the internal space of the guide pipe. Phase A level meter characterized by having matching lengths. (2) A level gauge as described in (1), characterized in that it is provided with a ceramic cover body that surrounds the reflector and the other opening of the guide pipe and is attached so as to be freely rotatable around the axis of the guide pipe. (3) The level meter according to (2), wherein the cover body has an inclined portion that gradually narrows from the other opening of the guide pipe toward the reflector. (4) A level meter as described in (2) or (3), characterized in that a threaded portion formed on the outer surface of the guide pipe and a threaded portion formed on the inner surface of the cover body are threadedly engaged with each other. (5) The level meter according to any one of (1) to (4), characterized in that it has a background cancellation function and determines the cancellation range. (6) The level meter according to any one of (1) to (5), wherein the inside of the guide pipe is purged. (7) A cylindrical body having open end faces and erected with its axis perpendicular to the liquid surface of the high-temperature liquid, The level meter according to any one of (1) to (6), characterized in that the microwave or millimeter wave is sent from one end face of the cylindrical body to the liquid surface of the high-temperature liquid that has flowed in from the other end face, and the reflected microwave or millimeter wave from the liquid surface of the high-temperature liquid is detected. (8) The cylindrical body has an inner diameter, where f is the frequency of the microwave or millimeter wave and C is the speed of light. The level meter according to (7) is a cylinder that satisfies the condition "inner diameter > (C × 1.841184) / (π × f)". (9) A level meter according to (7) or (8), characterized in that the other end face of the cylindrical body is closed with a ceramic plate that transmits the microwaves or millimeter waves. (10) A cylindrical body having open end faces and erected with its axis perpendicular to the liquid surface of the high-temperature liquid, The microwave or millimeter wave is transmitted from one end face of the cylindrical body to the liquid surface of the high-temperature liquid that has flowed in from the other end face, and the microwave or millimeter wave reflected from the liquid surface of the high-temperature liquid is detected, A level meter as described in any one of (2) to (4), characterized in that the other end face of the cylindrical body is connected and integrated with the part of the cover body that faces the storage container of the reflector. (11) The cylindrical body has an inner diameter, where f is the frequency of the microwave or the millimeter wave and C is the speed of light. The level meter according to (10) is a cylinder that satisfies the condition "inner diameter > (C × 1.841184) / (π × f)." (12) A level meter according to (10) or (11), characterized in that the other end face of the cylindrical body is closed with a ceramic plate that transmits the microwaves or millimeter waves. (13) The level meter according to any one of (7) to (12), wherein the cylindrical body is made of a heat-resistant material containing carbon in an amount of 10% by mass or more of the total amount. (14) The level meter according to any one of (7) to (13), wherein the peripheral wall on one end face side of the cylindrical body has one or more notches. (15) A level meter described in any one of (7) to (14), characterized in that when a heat insulating material for keeping the high-temperature liquid warm is floating on the liquid surface, one end face of the cylindrical body is located below the boundary between the heat insulating material and the high-temperature liquid. (16) A molding apparatus for producing a metal molded body by injecting a molten metal from a storage container of the molten metal into a mold and solidifying the molten metal injected into the mold, A molding apparatus characterized in that the level meter according to any one of (1) to (15) is disposed in the space between the storage container and the mold. (17) A molding apparatus according to (16), characterized in that an inclined plate is attached to the periphery of the mold opposite the level gauge, which rises from the outside toward the periphery or descends toward the periphery. (18) A method for operating a molding apparatus according to (16) or (17), comprising: A method for operating a molding apparatus, characterized in that a rise in the liquid level of the molten metal supplied to the mold is continuously detected from a state in which the mold is empty, and the liquid level is controlled. [Effects of the Invention]

[0009] The level meter of the present invention is an alternative to a vortex-current level meter, but it can measure the height of approximately 400 mm from the bottom of the mold to the liquid level, which was not possible with a vortex-current level meter. By using an appropriate guide pipe length, the liquid level can be measured with high accuracy.

[0010] Furthermore, the molding apparatus of the present invention replaces or uses the above-mentioned level meter in addition to a vortex-type level meter in a molding apparatus equipped with a vortex-type level meter, allowing the molding apparatus equipped with a vortex-type level meter to be used as is. Furthermore, the liquid level can be measured with high accuracy over a height of approximately 400 mm from the bottom of the mold to the liquid level, which could not be measured with a vortex-type level meter. As mentioned above, a vortex-type level meter may also be used in combination with a thermocouple-type level meter, but the vortex-type level meter can provide more accurate measurements than a thermocouple-type level meter.

[0011] Furthermore, since such a level meter is provided, the liquid level can be controlled by continuously measuring with high accuracy from the bottom of the mold. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view showing an example of an embodiment of a level meter according to the present invention. [Figure 2] FIG. 2 is a schematic diagram showing a test device used to determine the relationship between the pipe length of the guide pipe and the received power. [Figure 3] FIG. 3 is a graph showing the relationship between the pipe length of the guide pipe and the received power. [Figure 4] FIG. 4 is a graph showing the directivity of millimeter waves radiated from the conical horn antenna used in the test device of FIG. [Figure 5] FIG. 5 is a graph showing the directivity of millimeter waves radiated from the antenna device when a guide pipe with a pipe length of 360 mm is used. [Figure 6] FIG. 6 is a graph showing the directivity of millimeter waves radiated from the antenna device when a guide pipe with a pipe length of 215 mm is used. [Figure 7] FIG. 7 is an enlarged view showing the manner in which the cover body and the guide pipe are attached. [Figure 8] FIG. 8 is a cross-sectional view showing another example of the cover body. [Figure 9] FIG. 9 is a cross-sectional view showing the structure of a device for barging a guide pipe. [Figure 10] FIG. 10 is a cross-sectional view showing a level meter also using a cylindrical body. [Figure 11] FIG. 11 is an enlarged view showing the cylindrical body. [Figure 12] FIG. 12 is a side view showing another example of an embodiment of the cylindrical body. [Figure 13] FIG. 13 is a cross-sectional view showing another example of a level meter also using a cylindrical body. [Figure 14] FIG. 14 is a cross-sectional view showing an example of an embodiment of the molding device of the present invention. [Figure 15] FIG. 15 is a cross-sectional view showing another example of an embodiment of the molding apparatus of the present invention. [Figure 16A] FIG. 16A is an FFT spectrum diagram without the background cancellation function. [Figure 16B] FIG. 16B is an FFT spectrum diagram when the background cancellation function is provided. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited to the embodiments described below.

[0014] [Level meter] 1 is a cross-sectional view showing one embodiment of a level meter of the present invention. As shown in the figure, the level meter 1 includes a guide pipe 10 that propagates microwaves or millimeter waves within its internal space. The guide pipe 10 is a cylindrical body made of a metal such as iron or stainless steel.

[0015] An antenna 20 is disposed opposite one opening 10a of the guide pipe 10. The antenna 20 is connected to a transmitting / receiving means 30 that transmits, receives, and controls microwaves and millimeter waves outside the guide pipe 10. There are no restrictions on the type of antenna 20; in addition to the horn antenna shown in the figure, it may also be an antenna with a dielectric lens attached to the opening surface to increase directivity. It may also be a patch antenna. The transmitting / receiving means 30 is connected to a control means (not shown) to control transmission and reception.

[0016] As will be described later, the level meter 1 is suitable for use in a molding device for molten steel, but it must be able to withstand high temperatures of approximately 1500°C. Furthermore, the transmitting and receiving means 30 is an electronic circuit, so it must be kept at room temperature. Therefore, by using the guide pipe 10, the transmitting and receiving means 30 can be kept at room temperature.

[0017] A reflector 40 is disposed opposite the other opening 10b of the guide pipe 10. The reflector 40 faces both the antenna 20 and the high-temperature liquid 100.

[0018] 1, microwaves and millimeter waves transmitted from the transmitting / receiving means 30 through the antenna 20 are reflected by the reflector 40 and sent to the high-temperature liquid 100, where they are reflected by the liquid surface 101 of the high-temperature liquid 100. The microwaves and millimeter waves reflected by the liquid surface 101 reach the reflector 40, are reflected by the reflector 40, and are received by the transmitting / receiving means 30 through the antenna 20. In this way, the distance from the antenna 20 to the liquid surface 101 of the high-temperature liquid 100 is measured, and the liquid level of the high-temperature liquid 100 stored in the container 110 can be determined.

[0019] As described above, the present invention uses a guide pipe 10. However, it is also possible to place the antenna 20 near the reflector 40 instead of the guide pipe 10 and connect the antenna 20 and the transmitting / receiving means 30 with a waveguide. However, attenuation in the waveguide increases at high frequencies, and the manufacturing cost of the waveguide becomes quite high. Therefore, the distance from the opening surface 20a of the antenna 20 to the other opening 10b of the guide pipe 10 (hereinafter referred to as the "pipe length") is optimized.

[0020] Specifically, the pipe length is adjusted to the position of the TE mode and TM mode of microwaves and millimeter waves. Phase When a guide pipe 10 is used, a higher-order mode (TM mode) is generated when microwaves or millimeter waves from the antenna 20 propagate while being reflected by the inner wall of the guide pipe 10, and the directivity of the microwaves or millimeter waves emitted from the other opening 10b of the guide pipe 10 deteriorates. Therefore, by focusing on the fact that the propagation speeds of the TE mode of microwaves or millimeter waves and the TM mode, which is a higher-order mode generated inside the guide pipe 10, are different, the position of the TE mode and the TM mode is determined. Phase It specifies the pipe length to match.

[0021] FIG. 2 is a schematic diagram showing a test device used to determine the relationship between the pipe length L of the guide pipe 10 and the received power. The antenna 20 is accommodated on the side opposite to the other opening 10b of the guide pipe 10, and a reflector 80 is installed opposite the other opening 10b. The transmitting / receiving means 30 is connected to the antenna 20, and millimeter waves from the antenna 20 propagate through the internal space of the guide pipe 10 and are radiated from the other opening 10b toward the reflector 80 (transmitted wave M O ) will be done.

[0022] Transmission wave M O is reflected by the reflector 80, and the reflected wave M R is incident on the guide pipe 10, propagates through the internal space of the guide pipe 10, is received by the antenna 20, and its reception strength is measured by the transmitting / receiving means 30. The guide pipe 10 and the reflector 80 are fixed, and the antenna 20 moves continuously inside the guide pipe 10 as shown by the symbol F in FIG. 2, so that the pipe length L changes continuously.

[0023] In the above test equipment, the antenna 20 is a conical horn antenna with an aperture surface 20a having a diameter of 18 mm, and the guide pipe 10 is a cylinder with an inner diameter of 34.7 mm. While radiating a millimeter wave with a frequency of 79 GHz from the other aperture 10b of the guide pipe 10, the antenna 20 is continuously moved toward the other aperture 10b, and the reflected wave M from the reflector 80 is measured. R The received power was measured.

[0024] The measurement results are shown in Figure 3. The maximum and minimum received power repeatedly occur periodically, with peaks of received power appearing at intervals of approximately 260 mm along the pipe length L.

[0025] We also investigated the directivity of the conical horn antenna used. Figure 4 shows the directivity of the conical horn antenna itself when the pipe length L is 0 mm, i.e., when there is no guide pipe. The horizontal axis represents the directivity angle, and the vertical axis represents the transmission power.

[0026] In contrast, when a guide pipe with a pipe length L of 360 mm is attached when the received power shown in Figure 3 reaches its peak, the beam angle narrows and the directivity increases, as shown in Figure 5.

[0027] On the other hand, when a guide pipe with a pipe length L of 215 mm is attached, which minimizes the received power as shown in Figure 3, there is no difference in the beam angle compared to when there is no guide pipe as shown in Figure 4, as shown in Figure 6.

[0028] From Figures 3 to 6, it can be seen that there is a correlation between the pipe length L of the guide pipe 10 and the received power, and at the pipe length L at which the received power reaches its peak, the directivity angle of the millimeter waves emitted from the other opening 10b of the guide pipe 10 narrows and the directivity increases.

[0029] The above test results show that by setting the pipe length L of the guide pipe 10 to an appropriate length, it is possible to improve the directivity of the electromagnetic waves from the antenna 20 for transmission and reception. This means that the phases of the TE mode and TM mode of the electromagnetic waves coincide when they propagate through the internal space of the guide pipe 10, which results in the wavefronts of the E / H plane being aligned and the directivity becoming sharper.

[0030] When the guide pipe 10 is a cylinder, the propagation constants of the TE mode and TM mode of the electromagnetic waves generated in the internal space can be found by solving Maxwell's equations in a cylindrical coordinate system. phase γTE, TM mode position Phase γ TM is expressed by the following equations, where ω is the angular velocity of the electromagnetic wave propagating through the guide pipe, ε0 is the permittivity, μ0 is the magnetic permeability, and a is the inner diameter of the guide pipe.

[0031]

number

[0032]

number

[0033] Furthermore, χ m,n and χ´ m,n In the above, m and n are the root numbers of the Bessel function.

[0034] From equations (1) and (2), the distance d at which the phases of the TE mode and the TM mode coincide is given by equation (3).

[0035]

number

[0036] Therefore, by making the pipe length L of the guide pipe 10 equal to the distance d, the directivity of the millimeter wave radiated from the other opening 10b of the guide pipe 10 is increased.

[0037] However, equations (1) and (2) are theoretical equations, and in practice the value obtained by equation (3) is multiplied by a coefficient.

[0038] Note that microwaves and millimeter waves radiated from the other opening 10b of the guide pipe 10 propagate through the air, and therefore do not generate higher-order modes as would occur when propagating through the internal space of the guide pipe 10. Therefore, the distance from the other opening 10b of the guide pipe 10 to the reflector 40 and the distance from the reflector 40 to the liquid surface 101 of the high-temperature liquid 100 does not cause the problem of attenuation due to higher-order modes of microwaves and millimeter waves during transmission and reception. Therefore, as shown in FIG. 1, the reflector 40 may be attached so as to abut against the end face of the other opening 10b of the guide pipe 10, or it may be attached away from the other opening 10b.

[0039] Although microwaves or millimeter waves can be used as detection waves, the use of higher frequency millimeter waves (79 GHz band) allows the guide pipe 10 to be made thinner, which also contributes to the miniaturization of the level meter 1.

[0040] However, it is desirable to surround the other opening 10b of the guide pipe 10 and the reflector 40 with a ceramic cover body 50, as shown in Fig. 1 etc. The cover body 50 is a cylindrical body with a bottom, as shown in the figure, and by covering the other opening 10b of the guide pipe 10 together with the reflector 40 with the cover body 50, splashes from the high-temperature liquid 100 will not enter the inside of the guide pipe 10. Therefore, the closer the reflector 40 is to the other opening 10b of the guide pipe 10, the shorter the cover body 50 will be, and therefore it is preferable to attach the reflector 40 so that it abuts against the end face of the other opening 10b of the guide pipe 10.

[0041] The cover body 50 is made of ceramics, and does not interfere with transmission or reception of microwaves or millimeter waves. Furthermore, the ceramics that form the cover body 50 are heat-resistant and can adequately withstand the heat from the high-temperature liquid 100, so the level meter 1 can be disposed close to the liquid surface 101 of the high-temperature liquid 100 (see FIG. 10).

[0042] It is preferable that the ceramic has poor wettability with the high-temperature liquid 100. Droplets from the high-temperature liquid 100 will adhere to the cover body 50, but if the wettability is poor, they will fall as droplets and will not easily adhere to the cover body 50. The wettability depends on the combination of the type of ceramic that is the cover body 50 and the type of high-temperature liquid 100, but for example, if the high-temperature liquid 100 is iron or an iron alloy, it is preferable that the cover body 50 be made of boron nitride.

[0043] 1, the cover body 50 is rotatable about the axis C of the guide pipe 10. Therefore, even if droplets from the high-temperature liquid 100 adhere to the cover body 50, simply rotating it by 180°, for example, will bring the surface free of droplets facing the high-temperature liquid 100, thereby restoring good measurement accuracy.

[0044] 7, the guide pipe 10 and the cover body 50 may be connected by threading a threaded portion (male thread) 18 formed on the outer peripheral surface of the guide pipe 10 with a threaded portion (female thread) 58 formed on the inner peripheral surface of the cover body 50. By threading the two threaded portions 18, 58 together, the cover body 50 is prevented from coming off and can be rotatably attached to the guide pipe 10. The cover body 50 may also be fixed at any angle with a nut 60.

[0045] 8, the cover body 50 may be formed to have an inclined portion 55 that gradually narrows from the other opening 10b of the guide pipe 10 toward the reflector 40. The microwaves and millimeter waves from the other opening 10b of the guide pipe 10 are reflected by the reflector 40 and propagate downward in the figure, but are also reflected by the inner circumferential surface of the bottom of the cover body 50 and received by the transmitting / receiving means 30. In this case, if the cover body 50 is a cylinder of the same diameter as shown in FIG. 7, the microwaves and millimeter waves are incident perpendicularly on the inner circumferential surface of the bottom of the cover body 50, and the received intensity is also increased. 8, when an inclined portion 55 is formed on the cover body 50, microwaves and millimeter waves are incident on the inclined portion 55, and the received strength from the cover body 50 is reduced compared to when the waves are incident perpendicularly. By reducing the reflection strength from the cover body 50, better transmission and reception is possible.

[0046] Since the level meter 1 is installed near the liquid surface 101 of the high-temperature liquid 100, it is preferable to cool it. As a cooling method, for example, as shown in Fig. 9, the internal space of the guide pipe 10 is purged with a purge gas such as air or nitrogen gas. That is, the entire antenna 20 is surrounded by the guide pipe 10, and purge gas is supplied from a purge gas supply hole 70a and discharged from a purge gas discharge hole 70b.

[0047] As shown in Figure 10, in a casting machine, molten steel 220 as high-temperature liquid 100 is poured into a tundish 210 as a vessel 110. When the molten steel 220 reaches a certain level, heat-insulating materials 225 such as rice husks or tundish powder are poured in to keep the molten steel 220 warm. These heat-insulating materials 225 have a lower specific gravity than steel, so they do not penetrate into the molten steel 220 but spread to cover the liquid surface of the molten steel 220. Therefore, in order to remove the heat-insulating materials 225 and more accurately detect the liquid surface of the molten steel 220, a cylindrical body 150 is used as shown in the figure.

[0048] As shown in the figure, the cylindrical body 150 is open at both end faces and is erected inside the tundish 210 so that its axis is perpendicular to the liquid surface of the molten steel 220. One end face 151 of the cylindrical body 150 is spaced a predetermined distance H from the bottom face 211 of the tundish 210.

[0049] Then, molten steel 220 is poured into the tundish 210 while the cylindrical body 150 is in an upright position, and when the pouring amount exceeds the end face 151 of the cylindrical body 150, the molten steel 220 starts to flow into the cylindrical body 150. As shown enlarged in FIG. 11 , a notch 160 may be formed in the peripheral wall of the end face 151 of the cylindrical body 150 to facilitate the inflow of the molten steel 220. Furthermore, the cylindrical body 150 is formed of a heat-resistant material containing 10% or more by mass of carbon so that it can withstand the high temperature of the molten steel 220.

[0050] Meanwhile, the other end surface 152 of the cylindrical body 150 faces the reflector plate 40 of the level meter 1, and microwaves or millimeter waves are incident thereon. The incident microwaves or millimeter waves are then propagated through the internal space of the cylindrical body 150 and sent to the surface of the molten steel 220. Because only the molten steel 220 flows into the interior of the cylindrical body 150 and no heat insulating material 225 flows therein due to the specific gravity relationship as described above, the microwaves or millimeter waves are reflected by the surface of the molten steel 220. The reflected microwaves or millimeter waves are then propagated through the internal space of the cylindrical body 150 and emitted from the end surface 152, and are detected by the level meter 1.

[0051] In order to improve the propagation of microwaves or millimeter waves in the internal space of cylindrical body 150, it is preferable that the inner diameter D of cylindrical body 150 satisfies the following equation (4), where f is the frequency of the microwaves or millimeter waves and C is the speed of light.

[0052]

number

[0053] 12, it is also preferable that the end surface 152 of the cylindrical body 150 is covered with a ceramic plate 170 that is transparent to microwaves or millimeter waves. The interior is then preferably purged with an inert gas and then evacuated. To cover the end surface 152 with the ceramic plate 170, the ceramic plate 170 is attached to a flange 153 provided on the end surface 152. Furthermore, an intake port 180 and an exhaust port 181 are provided near the end surface 152 of the cylindrical body 150 so as to be positioned above the liquid level of the molten steel 220 at the maximum pouring time, and the interior of the cylindrical body 150 is purged with an inert gas.

[0054] Furthermore, when microwaves or millimeter waves are incident on end face 152 of cylindrical body 150, they are reflected by ceramic plate 170, and it is preferable to make end face 152 an inclined surface as shown in the figure so that the reflected waves are not received. This prevents the waves reflected from ceramic plate 170 from heading toward reflector 40.

[0055] 13, a mounting portion 51 may be provided to protrude from the cover body 50 of the level gauge 1 directly below the reflector 40, i.e., in a portion facing the high-temperature liquid 100, and the cylindrical body 150 may be connected to the mounting portion 51 for integration. Possible connection methods include forming a screw groove on the inner wall of the mounting portion 51 of the cover body 50, forming a screw thread on the outer peripheral surface of the periphery of the end face 152 of the cylindrical body 150, and screwing the cylindrical body 150 into the mounting portion 51 of the cover body 50.

[0056] Furthermore, the overall length of the cylindrical body 150 may be adjusted so that the end face 151 is immersed in the molten steel 220, for example, so that the end face 151 is positioned a few centimeters closer to the molten steel than the bottom surface of the heat insulating material 225.

[0057] In this way, by providing the cylindrical body 150, even if floating objects such as heat insulating material 225 are present on the surface of the high-temperature liquid 100, the liquid level of the high-temperature liquid 100 can be accurately detected without being affected by the floating objects.

[0058] [Molding equipment] The present invention also relates to a molding apparatus equipped with the above-described level meter 1. An example of an embodiment of the molding apparatus is shown in Fig. 14, and here a casting apparatus is exemplified.

[0059] In the casting device 200, molten steel 220, which is a high-temperature liquid, is stored in a tundish 210, which is a storage container, and the molten steel 220 is supplied to a mold 230 from the bottom of the tundish 210. The level of a liquid surface 221 of the molten steel 220 poured into the mold 230 is detected.

[0060] Conventionally, a vortex level meter is disposed in the space between the tundish 210 and the mold 230 to measure the level 221 of the molten steel 220. Therefore, in the present invention, the guide pipe 10 of the level meter 1 of the present invention described above is inserted parallel to or obliquely from the level 221 of the molten steel 220 into the space between the tundish 210 and the mold 230 so that the casting apparatus 200 can be used as is. As described above, the vortex level meter is located close to the level 221 of the molten steel 220 to improve measurement accuracy. However, the level meter 1 of the present invention may be located away from the level 221 of the molten steel 220 because it uses microwaves or millimeter waves as detection waves. Specifically, while a vortex level meter cannot be disposed more than 150 to 200 mm above the level 221, the level meter 1 of the present invention can be disposed closer to the tundish 210, for example, up to about 400 mm away from the level 221 of the molten steel 220. Therefore, in addition to being superior in heat resistance, the scattering distance of droplets from the molten steel 220 is increased, and adhesion of the droplets can be further suppressed.

[0061] Furthermore, since distance measurement is possible regardless of the distance to the object to be measured, distance measurement is possible down to the bottom of the mold 230, and the amount of molten steel 220 poured can be detected continuously even when the mold 230 is empty.

[0062] Furthermore, the pipe length L of the guide pipe 10 is set to an optimum length for transmission and reception, but this is unrelated to the diameter of the guide pipe 10, and a thin guide pipe 10 can be used, and it can be fully adapted even if the gap between the tundish 210 and the mold 230 is narrow.

[0063] Furthermore, since droplets mainly adhere to the outer peripheral surface of the cover body 50, even if droplets adhere, if the cover body is rotated, for example, by 180°, the surface without the adhesion will face the liquid surface 221 of the molten steel 220, and the initial transmission and reception strength without the adhesion of droplets will be obtained.

[0064] Furthermore, as shown in the figure, an inclined plate 240 may be attached to the periphery 230a of the mold 230 facing the level gauge 1, rising from the outside toward the periphery 230a. Alternatively, although not shown, the inclined plate 240 may descend toward the periphery 230a. Microwaves and millimeter waves are transmitted through the cover body 50, but are transmitted with a certain degree of spread. Therefore, in addition to the liquid surface 221 of the molten steel 220, microwaves and millimeter waves are also reflected not only by the liquid surface 221 of the molten steel 220 but also by the periphery of the periphery 230a on the upper surface of the mold 230 and the inner wall 230b of the mold 230, and the reflected waves from these are received. In particular, the periphery of the periphery 230a on the upper surface of the mold 230 is closest to the level gauge 1, so the received strength of the reflected waves is high. Therefore, the inclined plate 240 reflects the transmitted microwave or millimeter wave in a direction other than the reflector plate 40, and only the reflected wave from the liquid surface 221 of the molten steel 220 is sent to the reflector plate 40, thereby reducing noise.

[0065] 13, the guide pipe 10 is arranged so that the level meter 1 is horizontal to the liquid surface 221 of the molten steel 220. Microwaves and millimeter waves are also reflected from the inner circumferential surface of the bottom of the cover body 50, so when the guide pipe 10 is horizontal to the liquid surface 221 of the molten steel 220, the microwaves and millimeter waves from the reflector 40 are incident perpendicularly on the inner circumferential surface of the bottom of the cover body 50, and the reflection intensity is also high.

[0066] Therefore, the guide pipe 10 can be tilted downward or upward (not shown) toward the liquid surface 221 of the molten steel 220, as shown in Fig. 15. By tilting the guide pipe 10, the incident angle of the microwaves and millimeter waves from the reflector 40 to the inner circumferential surface of the bottom of the cover body 50 is no longer perpendicular, and the reflection intensity by the cover body 50 is reduced.

[0067] Furthermore, there is no limitation on the inclination angle of the guide pipe 10, i.e., the angle θ between the axis of the guide pipe 10 and the liquid surface 221 of the molten steel 220, and it can be set appropriately depending on the size of the gap between the mold 230 and the tundish 210 and the pipe diameter of the guide pipe 10, and may be, for example, about 5 to 30°.

[0068] Furthermore, a background cancellation function may be added to suppress the effects of reflected waves from the inner circumferential surface of the bottom of the cover body 50. The background cancellation function is a function that adds a signal that offsets the amount of unwanted reflection in the FFT spectrum of the FMCW rangefinder to the spectrum before background cancellation, thereby eliminating unwanted reflections. To make background cancellation more effective, it is desirable to add a phase-locked loop (PLL) to further stabilize the sweep frequency. The range of the background cancellation function may be, for example, from the periphery 230a of the mold 230 to the aperture surface 20a of the antenna 20.

[0069] 16A shows the FET spectra without the background cancellation function, and FIG. 16B shows the spectra with the background cancellation function. It can be seen that with the background cancellation function, there is no reflection from the inner circumferential surface of the bottom of the cover body 50.

[0070] Furthermore, adding a background cancellation function is particularly effective when the distance to the liquid surface 221 of the molten steel 220 is short, for example, 200 mm. Using a filter is also possible, but because the measurement distance is short, the signal level of the liquid surface 221 may be affected by the filter and become smaller, or the position of the signal level may move. The background cancellation function can prevent these problems.

[0071] Furthermore, by periodically updating the background cancellation function, it is possible to reduce fluctuations in the background cancellation function due to adhesions or temperature.

[0072] In this way, the molding apparatus of the present invention can use a molding apparatus equipped with a vortex-type level meter as is, can detect the liquid level with high measurement accuracy, and allows for stable operation. [Explanation of symbols]

[0073] 1 Level meter 10 Guide pipe 18 Threaded part 20 Antenna 30 Transmission and Reception Means 40 Reflector 50 Cover body 55 Slope 58 Threaded part 60 nuts 70a Purge gas supply hole 70b Purge gas discharge hole 80 Reflector 100 Hot Liquids 101 Liquid level 150 cylinder 160 notch 170 Ceramic Plate 180 Air Intake 181 Exhaust port 200 Casting equipment (mold equipment) 210 Tundish 220 Molten Steel 221 Liquid level 225 Heat insulation material 230 Mold 230a Periphery 230b Interior wall 240 Inclined plate

Claims

1. A level meter that transmits microwaves or millimeter waves from an antenna toward high-temperature liquid stored in a storage container, and receives the microwaves or millimeter waves reflected by the surface of the high-temperature liquid with the antenna to measure the distance to the surface of the high-temperature liquid, a cylindrical guide pipe with both ends open, which is disposed parallel to or obliquely to the liquid surface of the high-temperature liquid and through which microwaves or millimeter waves propagate in its internal space; the antenna disposed opposite one opening of the guide pipe; a transmitting / receiving means connected to the antenna for transmitting and receiving the microwave or millimeter wave; a reflector disposed opposite the other opening of the guide pipe, for reflecting the microwaves or millimeter waves transmitted from the antenna and propagating through the guide pipe toward the high-temperature liquid, and for guiding the reflected microwaves or millimeter waves to the guide pipe; A level meter characterized in that the distance from the opening surface of the antenna to the other opening end of the guide pipe is a length such that the phases of the TE mode and TM mode of the microwaves or millimeter waves propagating through the internal space of the guide pipe are in agreement.

2. 2. The level meter according to claim 1, further comprising a ceramic cover body that surrounds the reflector and the other opening of the guide pipe and is attached so as to be rotatable about the axis of the guide pipe.

3. 3. The level meter according to claim 2, wherein the cover body has an inclined portion that gradually narrows from the other opening of the guide pipe toward the reflector.

4. 4. The level meter according to claim 2, wherein a threaded portion formed on an outer peripheral surface of the guide pipe and a threaded portion formed on an inner peripheral surface of the cover body are threadedly engaged with each other.

5. a cylindrical body having open end faces and an axis perpendicular to the liquid surface of the high-temperature liquid; The level meter according to any one of claims 1 to 4, characterized in that the microwaves or millimeter waves are sent from one end face of the cylindrical body to the surface of the high-temperature liquid that has flowed in from the other end face, and the reflected microwaves or millimeter waves from the surface of the high-temperature liquid are detected.

6. 6. The level meter according to claim 5, wherein the other end face of the cylindrical body is closed with a ceramic plate that transmits the microwaves or millimeter waves.

7. a cylindrical body having open end faces and an axis perpendicular to the liquid surface of the high-temperature liquid; The microwave or millimeter wave is transmitted from one end face of the cylindrical body to the liquid surface of the high-temperature liquid that has flowed in from the other end face, and the microwave or millimeter wave reflected from the liquid surface of the high-temperature liquid is detected, A level gauge as described in any one of claims 2 to 4, characterized in that the other end face of the cylindrical body is connected and integrated with the part of the cover body that faces the storage container of the reflector.

8. 8. The level meter according to claim 7, wherein the other end face of the cylindrical body is closed with a ceramic plate that transmits the microwaves or millimeter waves.

9. 9. The level meter according to claim 5, wherein the peripheral wall on one end face side of the cylindrical body is provided with one or more notches.

10. A level meter according to any one of claims 5 to 9, characterized in that, when a heat insulating material for keeping the high-temperature liquid warm is floating on the liquid surface, one end face of the cylindrical body is positioned below the boundary between the heat insulating material and the high-temperature liquid.

11. 1. A molding apparatus for producing a metal molded body by injecting a molten metal from a storage container of the molten metal into a mold and solidifying the molten metal injected into the mold, A molding apparatus, characterized in that the level meter according to any one of claims 1 to 10 is disposed in a space between the storage container and the mold.

12. 12. The molding apparatus according to claim 11, wherein an inclined plate is attached to the peripheral edge of the mold opposite the level gauge, the inclined plate rising from the outside toward the peripheral edge or descending toward the peripheral edge.

13. 13. A method for operating a molding apparatus according to claim 11 or 12, comprising: A method for operating a molding apparatus, characterized in that a rise in the liquid level of the molten metal supplied to the mold is continuously detected from a state in which the mold is empty, and the liquid level is controlled.

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