JP5915589B2 - Temperature measurement method for continuous casting mold - Google Patents

Description

  The present invention relates to a temperature measurement method for a continuous casting mold in which a copper plate temperature of a mold is measured by a thermocouple in a continuous casting apparatus provided with electromagnetic stirring means for stirring molten steel in the mold by electromagnetic force.

  As a technique for measuring a mold temperature (copper plate temperature) in a continuous casting apparatus, a method of measuring temperature by embedding a thermocouple in a copper plate constituting a mold is known. The measured temperature of the mold is used for predicting breakout or the like. Breakout is a phenomenon in which unsolidified molten steel is ejected from a defective portion due to insufficient growth of a solidified shell. As a technique for preventing this, Patent Document 1, for example, A method for monitoring temperature changes and predicting breakouts based on the temperature changes is disclosed.

  On the other hand, in recent years, a continuous casting apparatus is generally equipped with an electromagnetic stirring device that stirs molten steel in a mold by electromagnetic force in order to improve the quality of a slab. In a continuous casting apparatus equipped with such an electromagnetic stirrer, when the temperature is measured by the thermocouple embedded in the mold as described above, the electromagnetic stirrer is used as an electromagnetic induction noise source when detecting the thermoelectromotive force of the thermocouple. It is known to be. This is because the electromagnetic stirring coil constituting the electromagnetic stirring device is arranged in the vicinity of the thermocouple in the layout, and the output signal of the thermocouple is affected by the magnetic field generated by the alternating current flowing through the electromagnetic stirring coil. In some cases, electromagnetic induction noise is superimposed on the temperature, and accurate temperature measurement cannot be performed. In particular, when a breakout is predicted using the measured temperature as in the technique of Patent Document 1, a change in the output signal of the thermocouple based on a minute temperature change of the molten steel in the mold is buried in electromagnetic induction noise, In some cases, it was difficult to detect the sign of a breakout.

  Conventionally, various proposals have been made as a method for removing electromagnetic induction noise from an output signal of a thermocouple. For example, Patent Literature 1 describes that a noise signal from an electromagnetic stirrer can be effectively removed from an output signal of a thermocouple by performing a moving average calculation of an output signal from a thermocouple. Further, Patent Document 2 discloses a configuration in which thermocouple wires forming a set are arranged side by side and a circuit unit that connects the base end sides in parallel or in series is provided, and is induced in each thermocouple wire. It is described that electromagnetic induction noise can be effectively removed by canceling the electromotive force. Patent Document 3 discloses a configuration in which wiring for detecting electromagnetic induction, radiation noise, and radiation noise is wired together with a thermocouple, and the electromotive force generated in the detection wiring is offset from the electromotive force of the thermocouple. .

JP 2007-245208 A JP 2009-58403 A Japanese Patent Laid-Open No. 2004-219098

  By the way, the electromagnetic induction noise generated in the output signal of the thermocouple is not necessarily limited to the magnetic field generated by the alternating current flowing in the electromagnetic stirring coil but also the magnetic field generated by the induced current generated in the mold copper plate or molten steel by the alternating magnetic field. In some cases, a sinusoidal waveform may not be obtained, and if it is attempted to detect a minute temperature change of the molten steel in the mold by moving average calculation of the output signal, it may be necessary to perform signal sampling for 5 to 10 cycles. However, when the number of sampling points increases, the time delay of temperature measurement becomes a problem. Moreover, in order to embed a thermocouple for measuring the copper plate temperature in the mold as described in Patent Document 2 and Patent Document 3, a hole is formed in the copper plate constituting the mold to form a thermocouple embedded hole. Need to form. Therefore, when measuring the copper plate temperature by applying the thermocouple disclosed in Patent Document 2 or Patent Document 3 described above, the compensation wire and the detection wire are wired together with the thermocouple wires arranged side by side or with the thermocouple. As a result, the thermocouple-embedded hole has to be formed in a large size, and there is a problem that the cooling function of the molten steel, which is the original purpose of the mold, is lowered. In order to avoid this, measures such as shifting the wiring by changing the depth of the embedded hole can be considered, but when embedding multiple thermocouples, the position of each wiring is different and the size of the electromagnetic induction is Since it differs depending on the wiring position, the influence of electromagnetic induction noise varies, and there is a limit to improving the noise removal rate.

  The present invention has been made to solve the above-described problems, and can accurately measure the copper plate temperature of the mold without being affected by electromagnetic induction noise superimposed on the output signal of the thermocouple. An object of the present invention is to provide a temperature measurement method for a continuous casting mold that can be used.

  In order to solve the above-described problems and achieve the object, a temperature measurement method for a continuous casting mold according to the present invention is a continuous casting apparatus provided with an electromagnetic stirring means for stirring molten steel in a mold by electromagnetic force. A temperature measurement method of a continuous casting mold for measuring a copper plate temperature with a thermocouple, wherein the thermocouple is embedded in the mold together with a detection wiring arranged inside a thermocouple wiring, and an output signal of the thermocouple The electromotive force generated in the detection wiring is simultaneously sampled over a half cycle of the voltage cycle applied to the electromagnetic stirring means, and the sampling time with the smallest electromotive force generated in the detection wiring is selected every half cycle. The temperature of the copper plate of the mold is calculated based on the output signal of the thermocouple at the selected sampling time.

  The temperature measurement method for a continuous casting mold according to the present invention is characterized in that, in the above-mentioned invention, the copper plate temperature is calculated by performing a moving average calculation based on an output signal of the thermocouple at the selected sampling time.

  According to the present invention, the copper plate temperature of the mold can be measured with high accuracy without being affected by electromagnetic induction noise superimposed on the output signal of the thermocouple.

FIG. 1 is a schematic diagram illustrating a schematic configuration example of a continuous casting apparatus. FIG. 2 is a diagram illustrating a schematic configuration of a thermocouple embedded in a mold. FIG. 3 is a diagram for explaining the principle of measuring the copper plate temperature of the mold.

  Hereinafter, with reference to drawings, the form for implementing the temperature measuring method of the continuous casting mold of this invention is demonstrated. Note that the present invention is not limited to the embodiments. Moreover, in description of drawing, the same code | symbol is attached | subjected and shown to the same part.

  FIG. 1 is a schematic diagram illustrating a schematic configuration example of a continuous casting apparatus 1 according to the present embodiment. As shown in FIG. 1, the continuous casting apparatus 1 includes a rectangular copper mold (continuous casting mold) 2 that is open at the top and bottom.

  The mold 2 is composed of a pair of long sides 21 and 21 and a pair of short sides 23 and 23 provided between the long sides 21 and 21, and the long sides 21 and 21 and the short sides from an immersion nozzle (not shown). Molten steel is poured into the internal casting space surrounded by 23 and 23. The molten steel injected into the mold 2 by the immersion nozzle is cooled to form a solidified shell on the side surface, and is drawn out below the mold 2 as a cast piece whose side surface is solidified. This slab is finally cut into an appropriate length to produce a target slab (slab).

  In the mold 2 (for example, the long side 21 on the near side in FIG. 1), a plurality of thermocouples 3 are arranged and embedded in multiple stages. Each thermocouple 3 is embedded at a predetermined depth from the outer surface of the long side 21. The arrangement of the thermocouple 3 is not limited to the illustrated example. Moreover, it is preferable to arrange the thermocouple 3 on the long side 21 and the short sides 23 and 23 on the back side.

  The thermocouple 3 embedded in the mold 2 is for estimating the temperature of the molten steel in the mold 2 by measuring the temperature of the mold 2 (copper plate temperature). Output current signal. Here, as described above, the continuous casting apparatus 1 is generally provided with an electromagnetic stirring device as an electromagnetic stirring means for stirring the molten steel in the mold 2 and controlling the flow of the molten steel. This electromagnetic stirring device (electromagnetic stirring coil) is disposed in the vicinity of the outer surface of the mold 2 although not shown. Therefore, the current signal output by each thermocouple 3 is output as a thermocouple output signal (output signal) on which electromagnetic induction noise is superimposed due to the influence of the magnetic field generated by the alternating current flowing in the electromagnetic stirring coil in the vicinity. The Rukoto.

  FIG. 2 is a diagram showing a schematic configuration example of the thermocouple 3 embedded in the mold 2, and shows a cut surface of the mold 2 including one thermocouple 3. As shown in FIG. 2, the thermocouple 3 is embedded in the mold 2 by forming a thermocouple embedded hole 211 in the copper plate constituting the mold 2 and disposing the thermocouple wiring 31 inside the thermocouple embedded hole 211. The In the present embodiment, a detection wiring 4 for detecting electromagnetic induction is wired inside the thermocouple wiring 31, whereby the thermocouple 3 (thermocouple wiring 31) is mounted on the mold 2 together with the detection wiring 4. Buried. The thermocouple output signal of the thermocouple 3 (thermocouple wiring 31) and the detection wiring signal of the detection wiring 4 are input to the circuit unit 5, and output to the measuring instrument 6 through the circuit unit 5.

  The inventors of the present invention arrange the detection wiring 4 together with the thermocouple wiring 31 inside the thermocouple embedding hole 211 as described above, and the electromotive force generated in the detection wiring 4 and the electromotive force of the thermocouple 3 The behavior was compared and examined. As a result, the inventors of the present invention do not necessarily match the electromagnetic induction noise detected as the electromotive force (detection wiring signal) generated in the detection wiring 4 and the electromagnetic induction noise amount superimposed on the thermocouple output signal. However, it is found that the timing when both of them become “0” is the same, and even if there is a slight deviation between the position of the thermocouple wiring 31 and the position of the detection wiring 4 in the thermocouple embedded hole 211. It was found that the electromotive force (thermocouple output signal) of the thermocouple 3 when the signal value of the detection wiring signal is “0” can be regarded as a value not including electromagnetic induction noise.

FIG. 3 is a diagram for explaining the measurement principle of the copper plate temperature of the mold 2, and shows the time change L ₁₁ of the thermocouple output signal and the time change L ₁₃ of the detection wiring signal side by side. A straight line L ₀ shown in FIG. 3 indicates a signal value level at which the signal value of the detection wiring signal is “0”.

As shown in the time change L ₁₁ and the time change L ₁₃ in FIG. 3, both the thermocouple output signal and the detection wiring signal are affected by the electromagnetic induction by the electromagnetic stirrer and are applied to the electromagnetic stirrer. It repeated periodic fluctuation in each cycle, but the time variation L ₁₃ of the detection wire signal timing T ₁₃ is present which is a signal value of "0" in each half cycle of the voltage period of the above. As described above, for example, when attention is paid to the timing T _13-1 at which the signal value of the detection wiring signal is “0”, the signal value V _11-1 of the thermocouple output signal at the timing T _13-1 is electromagnetic It can be regarded as a value that does not include induced noise. Therefore, measuring instrument 6, by converting this manner the signal value V ₁₁ of the thermocouple output signal at each timing T ₁₃ of the signal value "0" of the detection wire signal to a temperature value, the copper plate temperature of the mold 2 Is calculated.

  In actual processing, the measuring instrument 6 simultaneously samples the thermocouple output signal and the detection wiring signal at predetermined sampling periods. Therefore, the sampling time and the timing at which the signal value of the detection wiring signal becomes “0” do not always coincide. Therefore, the measuring instrument 6 selects the sampling time with the smallest signal value of the detection wiring signal every half cycle of the voltage period, and the copper plate temperature of the mold 2 based on the signal value of the thermocouple output signal at the selected sampling time. Is calculated.

  The continuous casting apparatus 1 configured as described above includes a thermocouple output signal of the thermocouple 3 (thermocouple wiring 31) embedded in the mold 2 and an electromotive force (detection wiring signal) generated in the detection wiring 4. Are sampled at the same time for half or more of the voltage cycle, and the sampling time with the smallest signal value of the detection wiring signal is selected every half cycle, and the template 2 is selected based on the signal value of the thermocouple output signal at the selected sampling time. The temperature measurement method is implemented by calculating the copper plate temperature. By calculating the copper plate temperature in this way, the copper plate temperature of the mold 2 can be measured with high accuracy without being affected by electromagnetic induction noise superimposed on the thermocouple output signal of the thermocouple 3. Further, since the detection wiring 4 is arranged inside the thermocouple wiring 31, it is not necessary to increase the size of the thermocouple embedding hole 211 for embedding the thermocouple 3.

  The obtained copper plate temperature of the mold 2 can be used, for example, for predicting breakout. According to this, since it is possible to prevent the change of the thermocouple output signal of the thermocouple 3 from being buried in the electromagnetic induction noise, it is possible to reliably detect a minute temperature change of the molten steel in the mold 2 and to give an indication of a breakout. Can be captured properly.

(Example)
In the continuous casting apparatus 1 described above, the mold 2 was heated by attaching a heater to the copper plate surface of the mold 2 during non-operation. Then, after sufficient time had passed since heating by the heater was started and the output of the thermocouple 3 was stabilized, the electromagnetic stirring device was operated at a set frequency of 1 [Hz]. In this state, the sampling cycle was set to 20 [msec], and the thermocouple output signal of the thermocouple 3 and the electromotive force (detection wiring signal) generated in the detection wiring 4 were simultaneously sampled and recorded for 2 minutes. Subsequently, the signal value of the recorded detection wiring signal is displayed on the monitor, and the signal value of the detection wiring signal is minimized every 0.5 [sec] which is a half cycle of the voltage cycle applied to the electromagnetic stirring device. 240 sampling times were selected. And the signal value of the thermocouple output signal of the thermocouple 3 in the sampling time of 240 points | pieces selected was converted into the temperature value, and the copper plate temperature of the casting_mold | template 2 was computed. This is referred to as Invention Example 1.

  In addition, the signal value of the thermocouple output signal of the thermocouple 3 at the sampling time of 240 points selected in the invention example 1 is converted into a temperature value, and a moving average calculation is performed at three points that are temporally adjacent to each other to calculate the mold 2 The copper plate temperature was calculated. This is referred to as Invention Example 2.

On the other hand, the same conditions except that the sampling period is set to 500 [msec], the thermocouple output signal of the thermocouple 3 and the electromotive force (detection wiring signal) generated in the detection wiring 4 are simultaneously sampled for 2 minutes. Recorded. And the copper plate temperature of the casting_mold | template 2 was computed by subtracting the signal value of the wiring signal for a detection from the signal value of a thermocouple output signal for every sampling time, and converting the calculated | required value into a temperature value. This is a comparative example. Table 1 shows the average values and standard deviations of the copper plate temperatures calculated in Invention Example 1, Invention Example 2, and Comparative Example.

  As shown in Table 1, it was confirmed that in Invention Examples 1 and 2, the standard deviation was smaller than in the comparative example, and the copper plate temperature could be measured with high accuracy.

DESCRIPTION OF SYMBOLS 1 Continuous casting apparatus 2 Mold 21 Long side 23 Short side 211 Thermocouple embedding hole 3 Thermocouple 31 Thermocouple wiring 4 Detection wiring 5 Circuit part 6 Measuring instrument

Claims (2)

In a continuous casting apparatus provided with an electromagnetic stirring means for stirring molten steel in a mold by electromagnetic force, a temperature measurement method for a continuous casting mold for measuring a copper plate temperature of the mold with a thermocouple,
The thermocouple is embedded in the mold together with the detection wiring wired inside the thermocouple wiring,
The output signal of the thermocouple and the electromotive force generated in the detection wiring under the influence of electromagnetic induction by the electromagnetic stirring means are simultaneously sampled over a half cycle of the voltage cycle applied to the electromagnetic stirring means, and the half A sampling time with the smallest electromotive force generated in the detection wiring for each cycle is selected, and the copper plate temperature of the mold is calculated based on the output signal of the thermocouple at the selected sampling time. Temperature measurement method for casting mold.   The method for measuring a temperature of a continuous casting mold according to claim 1, wherein the copper plate temperature is calculated by performing a moving average calculation based on an output signal of the thermocouple at the selected sampling time.

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