JP2009039775A - Abnormality diagnosis method in electromagnetic field generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormality diagnosis method where the abnormality of an electromagnetic coil in an electromagnetic field generator installed in a continuous casting machine can be diagnosed before the reduction in the insulation of the electromagnetic coil and interphase short circuit are generated. <P>SOLUTION: Regarding the abnormality diagnosis method in an electromagnetic field generator, when an electromagnetic field with a prescribed intensity is applied from an electromagnetic coil in an electromagnetic field generator 10 installed in a continuous casting machine, and a molten steel 7 is continuously cast, the electric power fed to the electromagnetic coil is measured, and, based on the time series change of the measured fed electric power, the abnormality of the electromagnetic coil is diagnosed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of diagnosing an abnormality in an electromagnetic field generator for applying an electromagnetic field to a molten steel which is an unsolidified portion of a slab, which is disposed on a back surface of a continuous casting mold or a secondary cooling zone of a continuous casting machine. It is.

  In continuous casting of steel, non-metallic inclusions and gas bubbles contained in the molten steel injected into the mold are positively levitated and removed on the molten steel surface in the mold, and these are excellent in cleanliness. In order to obtain slabs, there are a wide variety of AC electromagnetic field generators that stir the moving steel in the mold by applying a moving magnetic field, and DC type electromagnetic field generators that reduce the flow velocity of the molten steel by applying a static magnetic field to the molten steel in the mold. It is used. In addition, since the dendritic solidified structure is melted by moving the moving magnetic field and the solidified structure is refined, and the center segregation of the slab is improved accordingly, an AC electromagnetic field for generating the moving magnetic field is generated in the secondary cooling zone. Installation of generators is also done. The AC electromagnetic field generator is also called an electromagnetic stirring device because of its function.

  This electromagnetic field generator is an electromagnetic formed by an iron core (also referred to as a “yoke”) and a coil around which the iron core is wound, whether it is an AC type for generating a moving magnetic field or a DC type for generating a static magnetic field. It is constituted by a coil. Since it is necessary to flow a large current, the coil is formed by a water-cooled copper pipe through which cooling water flows (see, for example, Patent Document 1), and the coil is generally used for power supply. A coil lead-out portion for connection to the bus bar and the water supply pipe is provided.

  The electromagnetic field generator configured in this way is a very harsh electrically used environment in which a large current continues to flow during casting. In addition, the electromagnetic coil generator is caused to vibrate by the vibration of the electromagnetic coil. Stress concentrates and cracks etc. are likely to occur in the coil lead-out part and the surrounding copper pipe, resulting in equipment abnormalities such as loss of insulation of the water-cooled copper pipe due to water leakage etc. Every time an equipment abnormality occurred, the electromagnetic coil had to be replaced.

Under such circumstances, Patent Document 2 discloses an electromagnetic coil in which at least a part of the coil lead-out portion is made of a flexible conductor in order to prevent cracking / damage of the coil lead-out portion and its periphery. However, the damage of the electromagnetic coil is not limited to the coil lead-out portion, and although the occurrence of equipment abnormality has been reduced by Patent Document 2, the equipment abnormality has not yet disappeared, and the electromagnetic coil must be replaced every time equipment abnormality occurs. Have been forced to.
JP 2006-110598 A JP-A-2005-254291

  Thus, in a continuous casting machine with an electromagnetic field generator installed, the electromagnetic coil suddenly needs to be replaced suddenly due to the disappearance of insulation of the electromagnetic coil or a short circuit between phases, resulting in a decrease in the operating rate of the continuous casting machine. It was.

  If the abnormality can be detected and determined before the insulation loss of the electromagnetic coil or the short circuit between the phases is reached, the electromagnetic coil can be replaced before the short circuit between the phases that cannot be recovered, and the electromagnetic coil can be reused. In addition, since it is possible to replace it systematically, it is possible to schedule replacement of the electromagnetic field generator in accordance with other repairs. In this case, the decrease in the operating rate of the continuous casting machine is minimized. You can also

  The present invention has been made in view of such circumstances, and the object of the present invention is that the abnormality of the electromagnetic coil of the electromagnetic field generator installed in the continuous casting machine leads to the disappearance of insulation of the electromagnetic coil and the short circuit between phases. It is to provide an abnormality diagnosis method that can be diagnosed before.

  The inventors of the present invention have intensively studied to solve the above problems. As a result, the following knowledge was obtained.

  That is, a predetermined amount of electric power is supplied to the electromagnetic coil of the electromagnetic field generator in order to apply a desired electromagnetic field. For example, in a direct current type electromagnetic field generator, the current value of the power source to be supplied is set according to the electromagnetic field intensity to be applied. When a predetermined current value is supplied to generate a static magnetic field, the voltage generated by the circuit passing through the electromagnetic coil includes the resistance of the water-cooled copper tube of the electromagnetic coil and the resistance of the electrical wiring from the power supply device of the electrical room to the electromagnetic field generator. Is the sum of the current multiplied by the current. Therefore, when the insulation tape of the water-cooled copper tube deteriorates and leakage current or the like starts to occur, the resistance of the water-cooled copper tube of the electromagnetic coil decreases, and the voltage generated in the circuit passing through the electromagnetic coil decreases.

  That is, in the electric room, the power value supplied to the electromagnetic field generator to obtain an electromagnetic field having a desired intensity is measured, and deterioration of the electromagnetic coil can be diagnosed by monitoring the time series change of the measured power value. And the knowledge was obtained.

  The present invention has been made based on the above knowledge, and the electromagnetic field generator abnormality diagnosis method according to the first aspect of the present invention provides an electromagnetic field having a predetermined strength from an electromagnetic coil of an electromagnetic field generator installed in a continuous casting machine. The power supplied to the electromagnetic coil is measured when the molten steel is continuously cast by applying, and abnormality of the electromagnetic coil is diagnosed based on the time series change of the measured supply power. is there.

  An abnormality diagnosis method for an electromagnetic field generator according to a second invention is the DC power supply in which the electric power supplied to the electromagnetic coil has a constant current value in the first invention, and the voltage of the supplied DC power supply is normal. It is characterized by diagnosing that an abnormality has occurred in the electromagnetic coil when it has decreased by 10% or more compared to the time.

  According to the present invention, the electromagnetic field generator installed in the continuous casting machine is abnormal, that is, the insulating tape of the water-cooled copper pipe constituting the electromagnetic coil of the electromagnetic field generator is deteriorated or the water-cooled copper pipe is cracked and the cooling water oozes out. It is possible to diagnose abnormalities such as leakage currents that occur due to the occurrence of electromagnetic leakage before the insulation loss of the electromagnetic coil or short-circuit between the phases is reached. Can be avoided, thereby minimizing the reduction in availability of continuous casters. In addition, since the electromagnetic coil can be replaced before it reaches a short circuit between phases that cannot be recovered, the electromagnetic coil can be reused.

  The present invention will be specifically described below.

  In the present invention, an electromagnetic field of a predetermined strength is applied to the molten steel in the mold and the unsolidified phase in the slab of the secondary cooling zone from the electromagnetic coil of the electromagnetic field generator installed in the mold of the continuous casting machine or the secondary cooling zone. Then, when steel is continuously cast, the power supplied to the electromagnetic coil is measured, the time series change of the measured power supply is monitored, and the resistance of the electromagnetic coil is reduced due to coil deterioration. The abnormality of the electromagnetic coil is diagnosed from the change in the supplied power that occurs.

  Electromagnetic field generators used in continuous casting machines include AC-type electromagnetic field generators that apply a moving magnetic field to stir the unsolidified phase of molten steel and slabs in molds, and for braking the flow of molten steel. Although a DC type electromagnetic field generator that applies a static magnetic field is used, the present invention can be applied to either an AC type electromagnetic field generator or a DC type electromagnetic field generator.

  Hereinafter, a DC electromagnetic field generator installed on the back of the long side of the mold of a slab continuous casting machine will be described as an example with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a side cross-section of a slab continuous casting machine mold portion in which a DC type electromagnetic field generator is arranged.

  In FIG. 1, a mold 1 of a slab continuous casting machine includes a pair of opposed long mold copper plates 2 and a pair of opposed short mold copper plates (not shown) sandwiched between the long mold copper plates 2. A plurality of slits 3 cut in the vertical direction are carved at predetermined intervals on the back surface of the long-side copper plate 2 of the mold. A back plate 4 is attached to the back surface of the mold long side copper plate 2 by a bolt (not shown) embedded in the mold long side copper plate 2 so as to cover the slit 3. It becomes the flow path of the cooling water for cooling. Further, the long side water box 5 and the long side water box 5 </ b> A having the same length as the width of the mold long side copper plate 2 are disposed at the upper and lower end portions of the back side of the mold long side copper plate 2. The cooling water supplied to the long-side water box 5A from a water supply pipe (not shown) connected to the long-side water box 5A is distributed to each slit 3 by the long-side water box 5A. After cooling the long side copper plate 2 through the mold, it is collected in the long side water box 5 and flows out from a drain pipe (not shown) connected to the long side water box 5. The mold short side copper plate has the same structure.

  On the back surface of the back plate 4, two electromagnetic field generators 10 are installed facing each other with the long-side copper plate 2 interposed therebetween. The outer shell of the electromagnetic field generator 10 is a metal case sealed so that water does not enter inside, and an electromagnetic coil (not shown) comprising an iron core and a coil made of water-cooled copper pipe is installed in the case. Has been. The electromagnetic field generator 10 covers the entire width direction of the long-side copper plate 2 of the mold, and an electromagnetic field is applied to the entire width of the cast piece 9 to be cast. The electromagnetic field generator 10 is connected to a power supply device 11, and the power supply device 11 is connected to a control device 12 for controlling the intensity of the electromagnetic field and the application timing. In this case, the electromagnetic field applied by the electromagnetic field generator 10 is a static magnetic field, and the two electromagnetic field generators are applied so that the static magnetic field is applied from one of the opposing electromagnetic field generators 10 to the other electromagnetic field generator 10. 10 and 10 and the power supply device 11 are connected. Although not shown, a cooling water pipe is also installed to flow through the coil made of water-cooled copper pipe. Usually, the power supply device 11 and the control device 12 are arranged in an electric chamber away from the continuous casting machine.

  In FIG. 1, the electromagnetic field generator 10 is installed at a position lower than the discharge hole 6A of the immersion nozzle 6 in the casting direction. However, the electromagnetic field generator 10 may be located at a position equivalent to the discharge hole 6A or from the discharge hole 6A. May also be above. Furthermore, you may install the electromagnetic field generator 10 in the upper and lower two steps. What is necessary is just to arrange | position the electromagnetic field generator 10 according to the objective.

  The present invention is carried out as follows in a slab continuous casting machine provided with the electromagnetic field generator 10 having such a configuration in the mold 1.

  From a tundish (not shown) installed above the mold 1, molten steel 7 is poured into the mold 1 through an immersion nozzle 6 installed at the bottom of the tundish. The molten steel 7 is cooled by the mold 1 to form a solidified shell 8. And the slab 9 which makes the solidified shell 8 an outer shell and the inside is the unsolidified molten steel 7 is continuously drawn out below the mold 1, and the molten steel 7 is continuously cast. In that case, the static magnetic field which permeate | transmits the casting_mold | template 1 from the electromagnetic field generator 10 is applied according to casting conditions. Specifically, for example, the control device 12 performs control so that a constant magnetic field strength is applied according to the width of the slab 9 and the casting speed.

  In the case of a static magnetic field, since a static magnetic field having a constant strength can be obtained by flowing a constant DC current through the electromagnetic coil of the electromagnetic field generator 10, a constant DC current is generated from the power supply device 11 according to the casting conditions. It is supplied to the electromagnetic coil of the generator 10. The voltage generated in the circuit of the electromagnetic field generator 10 is measured by the power supply device 11 when a constant direct current according to the casting conditions is supplied. The voltage measured by the power supply device 11 is obtained by multiplying the sum of the resistance of the water-cooled copper tube constituting the electromagnetic coil of the electromagnetic field generator 10 and the resistance of the electrical wiring from the power supply device 11 to the electromagnetic coil by the supplied current. Therefore, when the insulation tape of the water-cooled copper tube deteriorates and leakage current or the like starts to occur, the resistance of the water-cooled copper tube constituting the electromagnetic coil decreases, and the generated voltage decreases. That is, the power supplied to the electromagnetic coil of the electromagnetic field generator 10 is reduced. This is because the resistance of the electrical wiring from the power supply device 11 to the electromagnetic coil is constant, and the change in resistance is considered to be caused by the electromagnetic coil.

  The measured voltage is stored in a recorder (not shown) or the like, and the time series change of the voltage is monitored. Of course, the comparison is made with the voltage measured under the same application condition. If the measured voltage is lowered, it is diagnosed that the deterioration of the electromagnetic coil is proceeding. If the deterioration of the electromagnetic coil is allowed to proceed, the electromagnetic coil reaches a phase-to-phase short circuit and cannot be reused. Therefore, the electromagnetic field generator 10 is replaced when the deterioration has progressed to some extent. In the continuous casting facility, periodic repairs are provided, for example, in accordance with furnace repairs at the converter factory. Therefore, the electromagnetic field generator 10 is replaced in accordance with these periodic repairs.

  A guideline for replacement of the electromagnetic field generator 10 may be a case where the voltage value is decreased by 10% or more from the voltage at the time when the maintained electromagnetic field generator 10 is placed on the long-side copper plate 2 of the mold. . That is, when the voltage value is reduced by 10% or more with respect to the reference voltage value, it is determined that there is an abnormality, and the electromagnetic field generator 10 may be replaced for the shortest regular repair from the time when the voltage value drops by 10% or more.

The above description is an example of a DC type electromagnetic field generator in which the electromagnetic field generator 10 applies a static magnetic field. However, even if it is an AC type electromagnetic field generator in which a linear moving magnetic field is applied, the DC type electromagnetic field generator is basically used. The deterioration of the electromagnetic coil is diagnosed from the time series change of the power value of the power supply to be supplied. However, in the case of a linear moving magnetic field, the electromagnetic force is proportional to the value obtained by multiplying the square of the magnetic flux density and the frequency (F = 2τσfB ² [F: electromagnetic force, τ: pole pitch of the electromagnetic coil, σ is the molten steel Electrical conductivity, f: frequency, B: magnetic flux density]), the frequency must also be managed, and since the voltage changes periodically, only the voltage value is monitored as in a DC electromagnetic field generator. Therefore, it is preferable to convert the three-phase AC power applied from the cycloconverter to the electromagnetic coil into DC and monitor the voltage of the converted DC current.

  As described above, according to the present invention, an abnormality of the electromagnetic field generator 10 installed in the continuous casting machine can be diagnosed before the insulation loss of the electromagnetic coil or the short circuit between the phases is reached. The generator 10 can be replaced, so that sudden replacement can be avoided, thereby minimizing the reduction in the operation rate of the continuous casting machine. In addition, since the electromagnetic coil can be replaced before it reaches a short circuit between phases that cannot be recovered, the electromagnetic coil can be reused.

  An example in which the present invention is applied to a DC magnetic field generator for generating a static magnetic field installed on the back surface of the long-side copper plate as shown in FIG. 1 will be described. A mold with a rectified DC electromagnetic field generator installed was installed in a continuous casting machine, and thereafter, the voltage generated in the circuit of the electromagnetic field generator was measured for each casting. In addition, the two electromagnetic field generators facing each other with the mold sandwiched are connected in series with the DC power source.

  FIG. 2 shows a time-series change in the resistance value (voltage / current) of the circuit of the electromagnetic field generator measured under an applied condition where the applied current is 1000 amperes or more. The horizontal axis in FIG. 2 represents the number of days that have elapsed since the day when the maintained DC type electromagnetic field generator was placed. In FIG. 2, the average value of the voltage measurement values for one day is displayed at one point. As shown in FIG. 2, the resistance value, which was about 0.33 ohms at the beginning of the placement, began to gradually decrease from the 10th day onward, and then decreased to about 0.3 ohms around the 18th day, and the 20th day. The eyes dropped to 0.27 ohm, which is 10% or more lower than the reference value (0.33 ohm).

  Therefore, it was decided to replace the mold together with the mold on the 26th day which is the shortest repair date. Although the resistance value continued to decrease after the 20th day, a static magnetic field with a predetermined strength could be applied until the replacement day on the 26th day, and the electromagnetic coil could not be recovered and could not be recovered. Was possible. As a result of inspection after removal, it was found that the reason why the resistance value decreased was due to water leakage inside one of the electromagnetic field generators. The other electromagnetic field generator was normal.

It is the schematic of the side surface cross section of the slab continuous casting machine casting | molding part by which the direct current | flow type electromagnetic field generator is arrange | positioned. It is a figure which shows the time-sequential change of the resistance value of the circuit of an electromagnetic field generator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold 2 Mold long side copper plate 3 Slit 4 Back plate 5 Long side water box 6 Immersion nozzle 7 Molten steel 8 Solidified shell 9 Cast slab 10 Electromagnetic field generator 11 Power supply device 12 Control device

Claims (2)

  When the molten steel is continuously cast by applying an electromagnetic field of a predetermined strength from the electromagnetic coil of the electromagnetic field generator installed in the continuous casting machine, the power supplied to the electromagnetic coil is measured, and the measured supply power An abnormality diagnosis method for an electromagnetic field generator, characterized by diagnosing an abnormality of an electromagnetic coil based on a time series change.   The power supplied to the electromagnetic coil is a direct current power supply with a constant current value, and diagnosis is made that an abnormality has occurred in the electromagnetic coil when the voltage of the direct current power supply to be supplied is reduced by 10% or more compared to the normal state. The abnormality diagnosis method for an electromagnetic field generator according to claim 1, wherein:

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