JP2011177724A - Eddy-current-type molten metal level detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable eddy current type molten metal level detector.
SOLUTION: A support tube 12 for holding a probe part 8 is constituted by a member having heat resistance, corrosion resistance, oxidation resistance, and aluminum resistance, and the probe part 8 is made of alumina fiber or silica fiber alone or both materials. As a configuration to be coated with mixed fibers containing woven fabric or woven fabric 15, impact resistance is improved. Further, the probe portion 8 is configured by being sandwiched and held by a nut 13 attached to the screw portion 12a of the support tube while the flange portion 12b of the support tube and the flange portion 12b of the support tube are locked. The parts are configured not to fall on the molten metal.
[Selection] Figure 2

Description

  The present invention relates to a molten metal level detector for detecting a surface position of a molten metal in a mold of a molten metal furnace or a casting machine.

  Conventionally, an eddy current type molten metal level detector for detecting a surface position of a molten metal in a molten metal furnace (for example, aluminum) or a mold of a casting machine is known in Patent Document 1 and Patent Document 2. Yes.

  A conventional eddy current type molten metal level detector has a high-frequency current supplied to a coil embedded in a probe unit to generate an alternating magnetic field from the coil, and when the probe unit approaches the molten metal surface, the molten metal has conductivity. An eddy current is induced near the surface of the metal to generate an alternating magnetic field. Then, the alternating magnetic field near the molten metal surface interferes with the alternating magnetic field of the coil and attenuates the alternating magnetic field of the coil. At this time, the attenuation amount of the alternating magnetic field has a strong correlation with the distance between the probe portion and the molten metal surface. Therefore, it is possible to accurately measure the position of the molten metal surface from the probe portion by measuring the attenuation amount of the alternating magnetic field of the coil.

  As another method for detecting the position of the molten metal surface of the molten metal furnace, the method disclosed in Patent Document 3 is known. As for what is shown by patent document 3, the sensor which has a rod-shaped conduction | electrical_connection part contacts a molten metal, detects conduction | electrical_connection, and detects a molten metal surface position.

JP 60-158952 A Japanese Patent Application Laid-Open No. 08-068683 JP 2005-189504 A

  In the apparatus disclosed in Patent Document 1, a tetrafluoroethylene resin cap is attached to the lower end surface of the support tube in order to protect the measurement coil of the probe unit from the heat of the molten metal. If the cap is removed during measurement, the measuring coil may fall on the molten metal. In addition, it is difficult for the tetrafluoroethylene resin to withstand the heat from the molten metal for a long time. Furthermore, in order to protect the measuring coil in the cap from heat, a gas such as air is sent into the cap to prevent a temperature rise. For this reason, an air source is separately required, and it is necessary to provide a plurality of air passages in the support tube, resulting in an increase in cost. Since the coil material is accelerated by high temperature and fresh air, the volume of the coil material is reduced during long-term use, which affects the accuracy and life of the detector.

  Moreover, in the apparatus shown by patent document 2, the coil of a probe part and the outer cylinder for high temperature interruption | blocking are attached with screws. For this reason, when screws etc. come off, a coil and the outer cylinder for high temperature interruption | blocking will fall on a molten metal. Further, since the coil is surrounded by a ceramic high temperature shut-off outer cylinder, it has a weak point that it is easily damaged by an impact force due to a collision or the like. Further, in order to protect the coil in the high temperature cutoff outer cylinder from heat, air is sent into the high temperature cutoff outer cylinder to prevent the temperature from rising. Therefore, an air source is required, and an air passage is provided in the support arm. It is necessary, and a cooling air duct is also required. In addition, since the coil material is accelerated by high temperature and fresh air, the volume of the coil material is reduced and the accuracy and life of the detector are affected.

  In the apparatus shown in Patent Document 3, since a sensor having a rod-like conduction part is in direct contact with the molten metal, icicles due to solidification of the molten metal are likely to occur. In order to prevent this, it is necessary to provide an impact applying member that applies an impact to the sensor body. However, with this method, icicles due to solidification of the molten metal cannot be completely removed, and the impact on the sensor affects the accuracy and life of the detector.

  Therefore, the present invention has been made in view of the conventional problems, and an object of the present invention is to provide an eddy current type molten metal level detector that is more reliable than the conventional one.

   Technical measures taken in order to solve the above technical problems include an eddy current type molten metal that uses eddy currents to detect the height of the molten metal in the mold of a molten metal furnace or casting machine from the surface of the molten metal. In the level detector, a bobbin made of ceramics, a coil wound around the bobbin, and applying a voltage to the coil to generate an eddy current on the molten metal surface, and supporting the probe unit The support tube made of a heat-resistant material and the probe portion are configured to include fiber reinforced ceramics covering the periphery while being supported by the support tube.

   In this case, the bobbin made of ceramics hardly reacts with the molten metal, and a material having a melting point higher than that of the molten metal, for example, zirconia, silica, magnesia, magnesium phosphate, boron nitride, silicon nitride, silicon carbide alone Or a ceramic containing two or more components among them.

   The metal material constituting the support tube is a material that is difficult to react with the molten metal, has a melting point higher than the molten metal temperature, and has corrosion resistance and oxidation resistance, such as an alloy containing nickel, chromium, and iron. Alternatively, the alloy is used as a base material and the alloy contains at least one of molybdenum, aluminum, niobium, and tantalum.

   Further, the surface of the probe part is preferably made of fiber reinforced ceramic, which is hard to react with the molten metal and is coated with a ceramic material having a melting point higher than the molten metal temperature. The fibers may be alumina fibers or silica fibers alone or a mixed fiber woven fabric containing both materials.

  In the above configuration, the support tube may have a flange at an end, and the probe unit may be positioned with respect to the support tube in a state where the bobbin is locked by the flange.

  Further, it is preferable that a nut is interposed between the support tube and the bobbin in the fiber reinforced ceramic and positioned by the nut. Accordingly, it is preferable that the probe portion is sandwiched and held by the nut attached to the screw portion of the support tube in a state where the flange portion of the bobbin and the flange portion of the support tube are locked.

  According to the present invention, the surface height of the high-temperature molten metal is covered with the fiber reinforced ceramics around the probe part that generates eddy current and the support tube that supports the probe part, thereby providing heat resistance, corrosion resistance, and acid resistance. It is possible to give it. As a result, deformation of the probe portion does not occur, and it is possible to withstand mechanical use for a long time. By reinforcing the outermost skin of the probe portion with fiber reinforced ceramics, it is possible to improve impact resistance. Moreover, it can protect from a high temperature by coating the coil in a probe part with a ceramic material. In addition, even when the temperature becomes high, the coil wire does not come into contact with corrosive gas or air, so the coil wire can maintain the initial electrical characteristics for a long time without causing a short circuit or volume reduction, and the surface position of the molten metal is high. It becomes possible to measure with accuracy. Furthermore, according to the present invention, the nut is loosened by holding the probe portion with the nut attached to the screw portion of the support tube while being held by the flange of the bobbin and the flange of the support tube. Even in this case, since the periphery is covered with fiber reinforced ceramics, the components constituting the probe portion are prevented from falling on the molten metal, and the reliability is improved.

  From the above, since the position of the molten metal surface in the crucible can be measured with high accuracy, the amount of molten metal pumped by the ladle at the time of casting is correctly stabilized without variation, and the occurrence of defects in production can be reduced.

It is a block diagram at the time of applying the eddy current type molten metal level detector in Embodiment 1 of this invention to a metal molten metal furnace or a holding furnace. It is sectional drawing showing the structure of the eddy current type molten metal level detector shown in FIG. It is sectional drawing at the time of applying the eddy current type molten metal level detector in Embodiment 2 of this invention in the casting_mold | template of a casting machine.

  Embodiments of an eddy current type molten metal level detector (hereinafter referred to as a level detector) according to the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram when a level detector is applied to a molten metal metal furnace or a holding furnace. In FIG. 1, a furnace such as die casting or gravity casting includes a crucible 2 surrounded by a furnace body outer wall 1 and a combustion part 3, and when a predetermined amount of molten metal (for example, aluminum) 4 is pumped by a ladle 6 that pumps molten metal. In addition, a level detector 7 is provided for determining the position where the ladle 6 is stopped from being pumped. The level detector 7 is supported in the vicinity of the ladle 6 by a support member 30 attached to the tip of the robot arm 5 together with the ladle 6 via the rod 31. The level detector 7 detects the surface position 4 a of the molten metal 4 in the crucible 2 with the level detector 7, and is detected by a measuring unit 17 electrically connected to the level detector 7. The measuring unit 17 controls the robot arm 5 in the vertical direction shown in FIG. 1 and is electrically connected via a cable 21 to a control device 20 that automatically rotates the ladle 6 with respect to the rod 31. The control device 20 receives information from the measuring unit 17 and issues an instruction to the robot arm 5 through the cable 22 to move the robot arm 5 in the vertical direction and rotate the ladle 6 around the connection point of the rod 31. As a result, the molten metal can be assembled or the molten metal in the ladle 6 can be poured out.

  When the surface position 4a of the molten metal 4 reaches a predetermined value (for example, 20 to 40 cm) by the level detector 7, the control device 20 is pumped by the ladle 6 supported by the robot arm 5 and is carried to a mold (not shown). It is the composition which issues the instruction.

  Next, the configuration of the level detector 7 of the present invention will be described with reference to FIG.

  In FIG. 2, the probe part 8 which detects the surface position 4a of the molten metal 4 in the level detector 7 has a cylindrical shape. The probe portion 8 has a bobbin 9 made of a donut-shaped ceramic formed with a hole penetrating in the center in the radial direction, and a helical recess formed in the outer peripheral surface of the bobbin 9, and a coil wire rod is formed in the recess. (Coil) 10 is embedded. The bobbin 9 in which the coil is embedded has a cylindrical peripheral surface coated with a ceramic coating material 11 so as to be surely protected from heat, corrosive gas, and an external environment causing oxidation.

  The probe portion 8 and the pipe-shaped support tube 12 having a distal end having a flange in the radial direction are locked in the axial direction by a flange 9 a protruding in the inner diameter direction of the bobbin 9 and a flange 12 b protruding in the outer diameter direction of the support tube 12. Has been. A threaded portion 12 a is formed at a predetermined position that is a part of the outer periphery of the pipe-shaped support tube 12. The position of the bobbin 9 with respect to the support tube 12 is positioned by a nut 13 attached to the screw portion 12a of the support tube 12, and the bobbin 9 is sandwiched and held at a predetermined position by the nut 13 and the flange 12b. A space 14 formed on the inner diameter side of the bobbin 9 and stepped by the flange 9a is filled with a ceramic mold material so as to fill the gap. The outermost skin of the probe portion 8 is coated with alumina fiber and silica fiber mixed fibers, and then the surface is coated with ceramics to form fiber reinforced ceramics 15 to ensure impact resistance. In this configuration, both ends of the coil wire 10 are soldered and electrically connected to two wires 10a and 10b (for example, a signal wire and a ground wire) that propagate signals through the high-frequency cable 16. The surface of the high-frequency cable 16 passing through the support tube 12 is covered with a ceramic insulator 19 having good heat resistance and insulation. The high-frequency cable 16 in the support tube 12 is preferably held so as not to move by the ceramic mold material 18 filled in the space 14.

  The other end of the high-frequency cable 16 that is electrically connected to the coil wire 10 is electrically connected to a measurement unit 17 that includes a high-frequency transmitter 17a, an amplifier 17b that amplifies the signal, and an arithmetic / display unit 17c. It is the composition which is.

  The high-frequency cable 16 has a first conductor in the center, a heat-resistant insulator is provided outside the first conductor, a second conductor is provided on the outer periphery of the heat-resistant insulator, and a glass fiber insulator is provided on the outermost skin. Is used. In this case, it is preferable to reduce the thickness of the heat resistant insulator to such a thickness that the first and second conductors do not short-circuit each other. Thereby, since the conductance of the high frequency cable 16 can be kept as low as possible, the detection capability of the probe unit 8 can be improved.

  In the level detector 7 having such a configuration, a predetermined voltage is applied to the coil wire 10 at a high frequency via the high-frequency cable 16 according to an instruction from the measurement unit 17. When a high frequency is applied and the probe portion 8 approaches the surface of the molten metal 4, an eddy current is induced near the surface of the molten metal 4 having conductivity, and an alternating magnetic field is generated. The AC magnetic field in the vicinity of the surface of the molten metal 4 interferes with the AC magnetic field of the coil and attenuates the AC magnetic field of the coil, thereby measuring the attenuation amount of the AC magnetic field of the coil. Can be detected with high accuracy. Here, since the detection method of the eddy current type molten metal height is known in the above-described prior art and the like, detailed description thereof will be omitted.

  With the above-described configuration, the support tube 7 that supports the probe portion 8 is covered with fiber reinforced ceramics to have heat resistance, corrosion resistance, oxidation resistance, aluminum resistance, and the like. be able to. As a result, it is possible to withstand long-term mechanical use without deformation of the probe portion 8. By reinforcing the outermost skin of the probe portion 8 with fiber reinforced ceramics, it is possible to improve impact resistance. Furthermore, even when the temperature becomes high, the coil wire 10 can maintain the initial electrical characteristics for a long time without causing a short circuit or volume reduction because it does not come into contact with corrosive gas or air, and the surface position of the molten metal can be maintained. It becomes possible to measure with high accuracy.

  With the above configuration, the probe unit 8 is sandwiched and held by the nut 13 attached to the threaded portion of the support tube 12 in a state in which the probe unit 8 is locked by the flange of the bobbin 9 and the flange 12b of the support tube 12. The components to be configured are prevented from falling on the molten metal 4 and the reliability is improved as compared with the conventional configuration.

(Embodiment 2)
FIG. 3 is a cross-sectional view when the level detector 7 is applied in a casting machine mold. Constituent elements similar to those of the first embodiment are given the same reference numerals. Here, the detailed description is omitted, and mainly the configuration different from the first embodiment will be mainly described.

  The level detector 7 having the above-described configuration is used for detecting the height of the molten metal surface filled in the cavity 27 of the mold 25 such as a movable type or a fixed type (upper die, lower die). It is also possible. In this case, the probe portion 8 of the level detector 7 is provided with an installation hole 23 formed in a part of the mold 25 and is inserted from the installation hole 23 so as to be seated on a pedestal 26 provided below the installation hole 23. So that For example, the molten metal is poured downward from above the supply port 24 provided in parallel with the installation hole 23, and the cavity 27 is filled with the molten metal. It is possible to detect the molten metal level of the molten metal by the level detector 7 and adjust the amount of molten metal supplied so as to be a predetermined liquid level. Due to the heating of the mold 25 and the inflow of molten metal into the cavity 27, the mold 25 expands at a high temperature. As a result, the probe part and the installation hole are distorted and stressed, but the probe part is not damaged because the outermost skin of the probe part is reinforced with ceramic fibers.

DESCRIPTION OF SYMBOLS 1 Furnace outer wall 2 Crucible 3 Combustion part 4 Molten metal 5 Robot arm 6 Ladle 7 Level detector 8 Probe part 9 Bobbin 10 Coil wire 11 Ceramic coating material 12 Pipe-shaped support pipe 13 Nut 14 Space 15 Fiber reinforced ceramic 16 High frequency cable 17 Electronic measurement unit 18 Ceramic mold material 19 Ceramic insulator 20 Control device 21 Cable 22 Cable 23 Installation hole 24 Supply port 25 Mold 26 Base 27 Cavity 30 Support member 31 Rod

Claims (3)

In an eddy current type molten metal level detector that detects the height from the molten metal surface in the mold of a molten metal furnace or casting machine using eddy currents,
Bobbins made of ceramics,
A probe is wound around the bobbin and generates an eddy current to the molten metal surface by applying a voltage to the coil;
A support tube made of a heat-resistant material for supporting the probe part;
An eddy current type molten metal level detector, wherein the probe unit is provided with a fiber reinforced ceramic covering the periphery while being supported by the support tube. In the eddy current type molten metal level detector according to claim 1,
The support tube has a flange at an end portion, and the probe portion is positioned with respect to the support tube in a state where the bobbin is locked by the flange. Detector. In the eddy current type molten metal level detector according to claim 2,
An eddy current type molten metal level detector, wherein a nut is interposed between the support tube and the bobbin in the fiber reinforced ceramic, and is positioned by the nut.

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