JP2012145331A - Method and device for detecting molten metal level - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for detecting a molten metal level that cause reduced noise and enable detection of a molten metal level with high sensitivity, and that further has an excellent heat resistance property and is capable of tolerating high temperature, even in a duct conveying high-temperature molten metal.SOLUTION: There is provided a device for detecting a molten metal level, in which a heater 2 is wound for thermal insulation around a duct 1 having heat resistance and corrosion resistance. Further, an AC transmitting primary coil 6 is wound around the duct 1, and AC receiving secondary coils 7a, 7b are wound around the duct 1 adjacent to the primary coil 6. In the device for detecting a molten metal level, a heating power supply is connected to the heater 2, a transmitter is connected to the primary coil 6, and a receiver is connected to the secondary coils 7a, 7b, whilst the heater 2 is a non-inductive sheath heater, and the primary coil 6 and the secondary coils 7a, 7b are inorganic insulation cables.

Description

  The present invention relates to an apparatus and method for detecting the level of molten metal present in a duct, and in particular, an alternating current is transmitted by a transmitter provided in the vicinity of a heat-resistant duct heated by a heater and adjacent to the primary transmitter. The present invention relates to an apparatus and a method for detecting an induced electromotive force induced in a receiver provided in the vicinity of the duct and detecting a level of molten metal existing in the duct.

  There are a low pressure casting method, a differential pressure casting method, a reduced pressure casting method, and the like as a method of casting by filling a molten metal into a cavity using a pressure difference between the molten metal and the cavity. For example, in the low-pressure casting method, a relatively low pressure by a gas such as an inert gas or carbon dioxide is applied to a closed furnace containing molten metal, and the molten metal in the closed furnace is pushed upward through stalk at this pressure. This is a method for producing a cast product by filling molten metal into a mold placed above a closed furnace.

  In such various casting methods, when controlling the filling of molten metal such as molten aluminum into the mold cavity, it is necessary to detect the level of molten metal in a duct such as stalk connected to the cavity of the mold. As a level detection means used to detect the level of molten metal in such a duct, an induction type that detects a change in inductance value due to a change in induced electromotive force by detecting a change in inductance value due to the molten metal in the duct and detects the level. Level detection devices are known. The following Patent Documents 1 to 10 describe these inductive level detection devices.

  An inductive level detector basically has a transmitter that transmits alternating current around and around the duct through which molten metal passes, and induces a secondary current around and around the duct adjacent to this transmitter. A receiver is provided. When an AC power supply is connected to the transmitter and a high frequency is applied and transmitted, a secondary current is induced in the receiver. At this time, if a molten metal such as molten aluminum exists between the transmitter and the receiver in the duct, dielectric loss occurs due to the molten metal as a conductor, and the secondary current induced in the receiver Change occurs. By the change of the secondary current induced in the receiver, the presence of the molten metal in the duct, that is, the liquid level of the molten metal in the duct can be detected and the level can be known.

  A duct such as stalk for supplying molten metal to a mold cavity by a casting apparatus or the like is made of ceramic having heat resistance and corrosion resistance, and is itself an insulator. However, in order to maintain the fluidity of the molten metal in the duct, it is necessary to constantly heat and keep the duct warm. For this heat insulation, an electric heater is generally wound around the duct, and a heating power source is connected to the electric heater to generate heat and keep the duct warm. For this reason, the current flowing through the heater may affect the secondary current induced in the receiver. Moreover, in order to supply molten metal through a duct, an electromagnetic pump is provided in the duct and thrust is given to the molten metal in the duct. In this case, the current flowing through the electromagnetic pump and the generated magnetic field also affect the secondary current induced in the receiver.

JP 2007-152424 A JP 2002-113567 A JP-A-11-188470 Japanese Patent Laid-Open No. 07-88606 JP-A-06-137721 JP 05-31620 A JP 05-138319 A JP 04-258354 A Japanese Patent Laid-Open No. 04-238661 JP-A 64-68623

  In view of the problems in the conventional molten metal level detection device and detection method, the present invention can detect the level of molten metal with high sensitivity and low noise even in a duct that conveys high-temperature molten metal. It aims at obtaining the molten metal level detection apparatus and detection method excellent in heat resistance which can endure.

  In order to achieve the above object, the present invention makes the heater 2 that keeps the heat-resistant and corrosion-resistant duct 1 heat-resistant and non-inductive, and is wound adjacent to the periphery of the duct. The primary coil 6 for alternating current transmission and the secondary coils 7a and 7b for alternating current reception are inorganic insulation cables.

  That is, the molten metal level detecting device according to the present invention winds the heater 2 around the duct 1 having heat resistance and corrosion resistance, and further heats the duct 1 around the duct 1 and winds the primary coil 6 for AC transmission around the duct 1. The secondary coil 7a, 7b for AC reception is wound around the duct 1 adjacent to the primary coil 6, the heating power source is connected to the heater 2, the transmitter is connected to the primary coil 6, and the secondary coil. A receiver is connected to 7a and 7b, the heater 2 is a non-inductive sheathed heater, and the primary coil 6 and the secondary coils 7a and 7b are inorganic insulation cables.

  Using this molten metal level detection device, the duct 1 is heated by the heater 2 and an alternating current is transmitted from the primary coil 6 while maintaining the inside of the duct 1 at a temperature equal to or higher than the melting point of the molten metal. The induced current induced in the coils 7a and 7b is measured, and the level of the molten metal in the duct 1 is detected by the change in the induced current.

  For example, the secondary coils 7a and 7b are connected so that the polarities of the secondary coils 7a and 7b are reversed so that the induced electromotive forces induced in the two upper and lower secondary coils 7a and 7b of the primary coil 6 cancel each other. The other terminals of the secondary coils 7a and 7b are connected to the detector. Thereby, the difference output of these two secondary coils 7a and 7b is detected, and the level of the molten metal in the duct 1 is detected by the fluctuation.

  In this molten metal level detection device, the heater 2 that heats the duct 1 is a non-inductive sheathed heater, so the heater 2 has heat resistance and does not induce noise in the secondary coils 7a and 7b. Further, since the primary coil 6 and the secondary coils 7a and 7b are inorganic insulated cables, these coils 6, 7a and 7b are also heat resistant and do not receive the noise of the heater 2. Thereby, even if it is the duct 1 which conveys a high temperature molten metal, the level of a molten metal can be detected correctly.

  The frequency of the alternating current supplied to the primary coil 6 is about 1 KHz to 30 KHz. Generally, when the frequency is increased, the induced voltage of the secondary coils 7a and 7b is increased. However, in the primary coil 6 and the secondary coils 7a and 7b using the inorganic insulating cable, the eddy current loss generated in the sheath becomes large, the induced electromotive force reaches a peak, and does not increase over several tens of KHz.

  In the molten metal level detection device and detection method according to the present invention, even in a duct that conveys a high-temperature molten metal, noise can be detected with low sensitivity, and the level of the molten metal can be detected with high sensitivity. Excellent in properties. For example, it is optimal for transporting molten aluminum for aluminum casting or the like.

It is principal part sectional drawing of the duct which shows one Example of a molten metal level detection apparatus. It is a connection diagram which shows one Example of a molten metal level detection apparatus. It is a graph which shows the example of the output of the secondary coil of a molten metal level detection apparatus. It is a connection diagram which shows the other connection example of one Example of a molten metal level detection apparatus. It is principal part sectional drawing of the duct which shows the other Example of a molten metal level detection apparatus. It is sectional drawing of the molten metal supply apparatus which shows the example of application of a molten metal level detection apparatus. It is sectional drawing of the molten metal supply apparatus which shows the other application example of a molten metal level detection apparatus.

In the present invention, in order to achieve the object, the heater 2 that keeps the heat-resistant and corrosion-resistant duct 1 is heat-resistant and non-inductive, and AC transmission is wound adjacent to the periphery of the duct. The primary coil 6 for use and the secondary coils 7a and 7b for AC reception were used as inorganic insulation cables.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  As shown in FIG. 1, a thin plate 9 made of stainless steel or the like is wound around a duct 1 for transferring molten metal, and a heater 2 is wound thereon. In order to fix the heater 2, the outer periphery of the heater 2 is fixed. A fixed band 8 is wound. As the duct 1, a ceramic tube such as alumina having heat resistance and corrosion resistance against a molten metal such as molten aluminum is used. As the heater 2, a sheath heater having heat resistance and corrosion resistance to molten metal such as molten aluminum, that is, a heater wire made of Ni-Cr or the like is housed in a sheath such as a stainless thin tube, and magnesia filled in the sheath. Insulated with powder is used. A device using a thin sheath is called a micro heater. As the fixing band 8, a stainless steel long sheet having heat resistance and corrosion resistance against molten metal is used. Further, a heat insulating sheet 10 is wound on the heater 2.

  Further, a primary coil 6 for transmission is wound outside the heat insulating sheet 10, and secondary coils 7a and 7b for reception are wound adjacent to the primary coil 6. In the illustrated example, two secondary coils 7 a and 7 b are provided adjacent to each other in the vertical direction of the primary coil 6. As will be described later, when the difference data of the outputs of the two secondary coils 7a and 7b is not taken, there may be one. Furthermore, two or more secondary coils 7a and 7b can be provided. These primary coil 6 and secondary coils 7a and 7b are wound so as to be horizontal.

  As the coils 6, 7a, 7b, it is preferable to use an inorganic insulated cable (sheath cable) having excellent heat resistance. In this inorganic insulated cable, a conductive wire such as a copper wire is housed in a sheath such as a stainless thin tube, and is insulated with magnesia powder filled in the sheath. Other than the sheath cable, for example, a copper-coated cable that is subjected to nickel plating or the like and is ceramic-coated is not preferable because the ceramic coating is peeled off by vibration or thermal cycle and the insulation is likely to be lowered.

  When an inorganic insulated cable is used as the coils 6, 7 a, 7 b, the frequency of alternating current supplied to the primary coil 6 is about 1 KHz to 30 KHz. Generally, when the frequency of the primary coil 6 is increased, the voltage of the induced electromotive force induced in the secondary coils 7a and 7b is increased. However, in an inorganic insulated cable, loss due to an eddy current generated in a sheath made of a conductor, the fixed band 8 of the heater 2 or the like increases, and the electromotive force induced in the secondary coils 7a and 7b has a frequency of several tens of the primary coil 6. It reaches a peak at about KHz and does not become higher than that.

  In addition, when an induction electromagnetic pump is provided in the duct 1 to convey the molten metal in the duct 1, the magnetic force generated from the inductor of the induction electromagnetic pump does not reach the primary coil 6 and the secondary coils 7a and 7b. The coils 6, 7a and 7b are arranged as far as possible from the induction electromagnetic pump. Alternatively, a magnetic shield is provided between the coils 6, 7a, 7b and the induction electromagnetic pump.

  As shown in FIG. 2, a transmitter is connected to the primary coil 6 through an amplifier, and an alternating current having a frequency of about 1 KHz to 30 KHz is energized. A receiver is connected to the adjacent secondary coils 7a and 7b. The induced electromotive force is induced in the adjacent secondary coils 7a and 7b by the alternating current transmitted from the primary coil 6 by the alternating current, and this is received by the receiver. Further, a heating power source is connected to the heater 2 provided around the duct 1, and then the heater 2 is heated by energizing the heater with heating power, and the inside of the duct 1 is heated to a temperature equal to or higher than the melting point of the molten metal. . In this case, the non-inductively wound heater 2 is energized to reduce noise to the secondary coils 7a and 7b.

  In FIG. 1 and FIG. 2, when the molten metal rises in the duct 1, if the molten metal is present at a position between the primary coil 6 and the secondary coils 7 a and 7 b around the duct 1, it is a conductor. An induced current also flows through the molten metal, and the secondary current induced in the secondary coils 7a and 7b is reduced accordingly. This is shown in FIG. In FIG. 3, the alternate long and short dash line indicates the height of the primary coil 6. When the heights of the two secondary coils 7a and 7b are above and below the primary coil 6, the change in the secondary current induced in the secondary coils 7a and 7b caused by the dielectric loss of the molten metal is It appears differently depending on the positions of the coils 7a and 7b. By receiving this and comparing it with the receiver, the level of the molten metal in the duct 1 can be detected. As shown in FIG. 1, when the diameter of the coils 6, 7a, 7b is D, it is possible to detect the level of molten metal in the range up to about D2 / 3 in the vertical direction.

  In FIG. 4, the secondary coils 7 a and 7 b are connected so that the polarities of the secondary coils 7 a and 7 b are reversed so that the induced electromotive forces induced in the two upper and lower secondary coils 7 a and 7 b of the primary coil 6 cancel each other. Further, the other terminals of the secondary coils 7a and 7b are connected to a detector to detect the induced electromotive force. Thereby, as shown in FIG. 3, the AC output difference of the secondary coils 7a and 7b, that is, the differential output is detected. When the liquid level of the molten metal is at an intermediate position between the secondary coils 7a and 7b, this differential output reaches a peak, so that the liquid level of the molten metal can be detected.

  FIG. 5 shows an embodiment when the duct 1 is inclined. As shown in FIG. 5, when the duct 1 is inclined, the primary coil 6 and the secondary coils 7a and 7b are wound obliquely around the duct 1 in accordance with the inclination of the duct 1, and each coil 6, 7a and 7b are made horizontal. When the coils 6, 7a, 7b are inclined, the change in electromotive force induced in the secondary coils 7a, 7b differs between the molten metal level change, the melt amount change region, and the constant melt amount region. It becomes gradual, and then the change becomes larger, making it difficult to detect the level of molten metal. Dielectric loss is caused by the molten metal, which is a conductor, and a change occurs in the secondary current induced in the receiver.

  FIG. 6 shows an example in which the molten metal level detection device is applied to a molten metal supply device using an electromagnetic pump. In this molten metal supply apparatus, the duct 1 is disposed at an angle of about 45 °, and a two-stage inductor of a hot water supply inductor 14 and a rising inductor 24 is provided at the lower and upper portions of the duct 1. . A thrust is applied to the molten metal in the duct 1 by the inductors 14 and 24, and the molten metal 12 is supplied from the nozzle 21 at the tip of the duct 1 to the molten metal supply destination 20 such as a mold.

  The lower end of the duct 1 is inserted into the liquid level of the molten metal m stored in the molten metal tank. Around the portion of the duct 1 above the liquid surface of the molten metal m, the hot water supply inductor 14 in which a coil 16 is wound around a magnetic yoke 15 is disposed. The yoke 15 is fitted on the outer peripheral side so as to surround a portion above the liquid level of the molten metal m of the pump side duct 1, and a coil 16 constituting a three-phase coil is wound around the yoke 15. Yes.

  A core 12 made of a magnetic cylinder is disposed at a position corresponding to the hot water supply inductor 14 in the duct 1 so that the central axes thereof coincide with each other. The core 12 is housed in a cylindrical protective tube 13 whose both ends are closed, and is not in direct contact with the molten metal m passing through the passage in the duct 1. There is a gap between the duct 1 and the protective tube 13, and this portion becomes a passage of molten metal. The protective tube 13 is made of a heat-resistant and corrosion-resistant material such as ceramic, and a ceramic fiber such as alumina or magnesia or ceramic powder is used as a cushioning material between the core 12 and the protective tube 13 therein. Filler 18 is filled.

  Further, the rising inductor 24 is arranged around a portion of the pump side duct 1 below the inductor 14. The riser inductor 24 is formed by winding a coil 26 around a magnetic yoke 25 fitted on the lower outer periphery of the duct 1, similarly to the hot water inductor 14. The coil 26 of the rising inductor 24 is wound around a heat-resistant inorganic insulating cable. The inorganic insulated cable has a structure in which a conductive wire is housed in a sheath made of a stainless thin tube and the like, and the conductive wire and the sheath are insulated with an inorganic insulating powder such as magnesia powder filled between them. It is called a so-called sheath cable. Such an inorganic insulated cable has high heat resistance and can withstand a temperature of 800 ° C. However, the number of turns of the coil 26 of the startup inductor 24 is smaller than that of the coil 16 of the hot water supply inductor 14.

  A core 22 made of a magnetic cylinder is disposed at a position corresponding to the rising inductor 24 in the duct 1 so that the central axes thereof coincide with each other. The core 22 is housed in a position below the core 12 in the protective tube 13 in which the upper core 12 is housed, and does not come into direct contact with the molten metal m in the duct 1. Yes. Of course, the portion of the protective tube 13 in which the lower core 22 is accommodated is also filled with a filler 18 such as ceramic fiber such as alumina or magnesia or ceramic powder as a cushioning material between the core 22 and the protective tube 13. Has been. The lower end of the protective tube 13 is closed. In addition, you may comprise the upper core 12 and the lower core 22 as a continuous integral core.

  The rising inductor 24 is surrounded by a cylindrical protective case 17 made of heat-resistant ceramic or the like. The upper end opening of the protective case 17 is fixed to the lower end surface of the upper hot water supply inductor 14. The opening at the lower end of the protective case 17 is closely joined to the lower end of the pump-side duct 1, and the inside surrounded by the joint is the introduction of the molten metal m at the lower end of the pump-side duct 1. Mouth.

  The primary coil 6 and the secondary coils 7 a and 7 b described above are wound around the portion near the upper end of the duct 1, whereby the level of the molten metal m in the duct 1 is detected. That is, it is detected by the primary coil 6 and the secondary coils 7a and 7b that the liquid level of the molten metal m exists in a portion near the upper end of the duct 1. When thrust is applied to the molten metal m in the duct 1 from the state of the molten metal m in the duct 1 by the hot water supply inductor 14, the molten metal flows over the upper end of the duct 1 and is supplied from the nozzle 21 to the supply destination 20. Molten metal m is supplied to.

  The embodiment shown in FIG. 7 is an example in which the molten metal m supply device is applied to a low pressure casting device. The duct 1 is provided substantially vertically, and a molten metal supply destination 20 ′ as a mold is connected to the upper end of the duct 1. Molten metal m is pumped from the lower hot water supply port through the duct 1 and supplied to the casting mold, which is the supply destination 20 ′ of the molten metal m, by the inductors 14 and 24 provided above and below the duct 1. Other than this, the configuration is basically the same as that of the embodiment described above with reference to FIG. 6, and the corresponding parts are indicated by the same reference numerals. Detailed description of common corresponding parts is omitted.

  The molten metal level detection device and detection method according to the present invention is used in a casting mold or the like, in the case of controlling the filling of molten metal such as molten aluminum into a mold cavity, in a duct such as stalk connected to the mold cavity. Used to detect the level of some molten metal.

1 Duct 2 Heater 6 Primary coil 7a Secondary coil 7b Secondary coil

Claims (8)

A primary coil 6 for AC transmission is provided in the vicinity of the duct 1, secondary coils 7 a and 7 b for AC reception are provided in the vicinity of the duct 1 adjacent to the primary coil 6, and a transmitter is connected to the primary coil 6. In the molten metal level detection device in which a receiver is connected to the secondary coils 7a and 7b, a heater 2 is provided in a duct 1 having heat resistance and corrosion resistance, a heating power source is connected to the heater 2, and the heater 2 is not used. A molten metal level detecting device characterized in that an induction sheathed heater is used, and the primary coil 6 and the secondary coils 7a and 7b are inorganic insulating cables. The molten metal level detection device according to claim 1, wherein a heater (2) is wound around the duct (1), and a primary coil (6) and secondary coils (7a, 7b) are wound around the duct (1). The molten metal level detection device according to claim 2, wherein the primary coil (6) and the secondary coils (7a, 7b) are wound horizontally around the duct (1). The secondary coils 7a and 7b are connected so that the polarities of the secondary coils 7a and 7b are reversed so that the induced electromotive forces induced in the two upper and lower secondary coils 7a and 7b of the primary coil 6 cancel each other. The other terminal of 7b was connected to the detector, The molten metal level detection apparatus in any one of Claims 1-3 characterized by the above-mentioned. A primary coil 6 for AC transmission is provided in the duct 1, secondary coils 7 a and 7 b for AC reception are provided in the duct 1 adjacent to the primary coil 6, a transmitter is connected to the primary coil 6, and the secondary coil In a method for detecting the level of molten metal in the duct 1 using a molten metal level detecting device having a receiver connected to 7a and 7b, a heater 2 is provided in the duct 1 having heat resistance and corrosion resistance. A heating power source is connected, the heater 2 is a non-inductive sheathed heater, the primary coil 6 and the secondary coils 7a and 7b are inorganic insulating cables, the duct 1 is heated by the heater 2, and the inside of the duct 1 is melted. While maintaining the temperature above the melting point of the metal, alternating current is transmitted from the primary coil 6, the induced current induced in the secondary coils 7a and 7b by this alternating current is measured, and the duct 1 is determined by the change in the induced current. Molten metal level detection method characterized by sensing the level of molten metal. The molten metal level detection method according to claim 5, wherein the heater 2 is wound around the duct 1, and the primary coil 6 and the secondary coils 7 a and 7 b are wound around the duct 1. The secondary coils 7a and 7b are provided adjacent to the upper and lower sides of the primary coil 6, and the level of the molten metal in the duct 1 is detected by fluctuations in the differential output of the two secondary coils 7a and 7b. Item 7. The molten metal level detection method according to Item 5 or 6. The method for detecting a molten metal level according to any one of claims 5 to 7, wherein the frequency of alternating current supplied to the primary coil 6 is 1 KHz to 30 KHz.

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