JPS5847548A - Level gage for molten steel in mold for electromagnetic agitation - Google Patents

Abstract

PURPOSE:To make the accurate level measurement possible by providing a dummy coil which detects only the magnetic field for electromagnetic agitation to a level gage of a magnetic flux balance type fluxmeter and constituting a circuit in such a way that said coil is made differential with a level detecting coil. CONSTITUTION:A dummy coil 14 is provided to the level gage of a magnetic flux balance type fluxmeter 3 in order to eliminate the influence of a magnetic field for electromagnetic agitation of the case when electromagnets 18 are provided on both long sides of a mold 1. The output signal and amplitude value of an existing amplifier 8 are made coincident by an amplifier 15. Further, a phase difference from the signal of the amplifier 8 is regulated with a phase regulator 16. Therefore the detection signals for the magnetic field for electromagnetic agitation of the detecting coils synchronize exactly in phase and amplitude with the detection signal of the coil 14. When the signals of the amplifier 8 and the regulators 16 are inputted to a differential amplifier 17, the magnetic field signals for elecromagnetic agitation are made zero and only the signals for energized magnetic fields are detected in the fluxmeter 3, whereby the level of molten steel 2 is measured accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bell needle for electromagnetic stirring in a continuous casting machine.

Controlling the level of the molten metal in the °C mold at a constant level during continuous casting is an important operation in order to keep the surface and internal properties of the cast product fresh and to stabilize the operation. Accurately detecting the level of molten steel in a steel plate is a necessary condition, and methods currently in practical use include ■ Radiation ■ The dead plate temperature method, but recently, the
No. 41859 proposed a level needle using a magnetic flux-balanced magnetic processor, and Japanese Patent Application Laid-open No. 76926/1983 proposed an eddy current method.
These are non-contact methods and have been put into practical use in large numbers due to their detection accuracy and response time4.

On the other hand, the continuous casting method has conventionally been able to cast only deoxidized steel, but in order to continuously cast non-oxidized steel, a method has been put into practical use in which molten steel is stirred and cast using magnetic force in a °C mold. For the sake of safety, the molten steel level needle that uses the lid magnetic field cannot accurately measure the level and cannot perform molten steel level control.As an example of this, a magnetic flux balanced type magnetic flux needle is This section describes in detail the case in which the molten steel level needle used in this study is applied to an electromagnetic stirrer.

Figure 1 shows the configuration of the above system, where l is 7-wire, 2 is molten steel, and 3 is a magnetic flux balancing type magnetic flux needle. The magnetometer 3 consists of three coils 4, 5, 6, The coils 7 and 6 are configured so that the directions of the magnetic fields generated are opposite to each other, and the excitation current is supplied from the power source 7. When the molten steel 2 approaches the magnetometer 3, a deviation occurs between the magnetic fields of the coils 4 and 6.

The deviation of this magnetic field is detected by a coil 5, amplified by 8, and converted into a DC signal by 9. The level of this DC signal has the characteristics shown in FIG. 2 depending on the distance between the molten steel 2 and the magnetometer 3.

Therefore, the magnetometer 3 is driven vertically by a servo mechanism so that the output from the detection coil remains constant even if the molten steel level fluctuates. This drive amount is the level fluctuation value. That is, the target value for keeping the distance between the magnetometer 3 and the molten steel 2 constant is set using lO, the signal is compared with the signal from 9, the deviation signal is amplified by 11, the servo motor from 12 is driven, and the servo motor from 12 is driven. The driving amount is detected by 13 pulse generators.

The level of the molten steel in the mold having such a table structure was measured using a lead plate having the same electrical characteristics as the molten steel. An example of the results is shown in FIG. In the absence of a magnetic field, it is possible to measure the level at ±0°, but by generating an electromagnetic stirring magnetic field, a hushing phenomenon of ±7.01 occurs. As the level of the steel that generated the electromagnetic stirring magnetic field compared with this □ output signal fluctuates, large amplitude fluctuations are generated ◎Figure 4 (a) shows the case without a magnetic field. The DC signal 9 in Figure 1 is also exactly the same, that is, 1
This is generated because the magnetometer 3 in Fig. 1 detects the excitation magnetic field (approximately 1.6 kHz) and the magnetic field for electromagnetic stirring (approximately -Hz), and it detects the signal of the magnetic field for electromagnetic stirring. 1 is not removed, accurate level measurement is impossible.

The present invention includes a tummy coil for detecting only the magnetic field for electromagnetic stirring, and has a differential circuit structure with the level detection coil to detect only the excitation magnetic field signal, that is, the level detection signal. This enables accurate level measurement.

Since the actual distribution of the magnetic field within an electromagnetic stirring held changes depending on the width and thickness directions of the heir, the detection signal can be completely matched in both phase and amplitude depending on the arrangement of the detection coil and tummy coil. It is impossible to make the electrical characteristics of two coils that do not match completely the same.Therefore, it is impossible to create a circuit that adjusts the phase and output in the tummy coil or detection coil. is necessary.

Examples will be described below. FIG. 5 shows the level needle of the magnetic flux balanced type magnetic flux needle shown in FIG. A coil 14 is attached, the amplitude value is matched with the output signal of the existing suspension device 18 using an amplifier 15, and the phase is further adjusted.

Adjust the phase difference with the signal from the amplifier 8 using the adjuster l.6.
Therefore, the electromagnetic stirring coil and the tummy coil detection signals have exactly the same phase and amplitude. By manually inputting the difference between the signal of the amplifier 8 and the signal of the phase adjuster 16 to the dynamic amplifier 17, the magnetic field signal for electromagnetic stirring becomes rOJ. Only the excitation magnetic field signal is detected by the level detector 3. This will be accurate.

With the level needle of this circuit configuration, level measurement is performed using a lead plate as a pseudo-molten steel in an electromagnetic stirring t-rud. As a result, no scorching phenomenon occurs at all, and the output signal waveform of the differential amplifier 17 is shown in Fig. 6 (c). ), there is no difference in the presence or absence of an electromagnetic stirring magnetic field, and accurate level measurement is possible.
With this circuit configuration, the level of molten steel in the electromagnetic stirrer was controlled to be stable within ±5.0 as shown in FIG. 7. Figure 6 (a) shows the case with a conventional coil without a magnetic field, (b) shows the case with a conventional coil and a magnetic field 0 Figure 7 (a) shows the case without electromagnetic stirring, and (b) shows the case with electromagnetic stirring .

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of a molten steel leveling needle using a magnetic flux balance type magnetic flux needle, Figure 2 is a diagram showing the relationship between the cessiser output and the cessiser weld distance in the same level meter, and Figure 3 is a diagram showing the relationship between the Diagram a411 showing the relationship between the external magnetic field and the molten steel level in
(a) A diagram showing the amplitude of the measurement results when there is no magnetic field, (b) shows the amplitude fluctuation when a magnetic field is applied, and Fig. 5 is an explanatory diagram of the molten steel level needle according to the embodiment of the present invention. 1. Figure 6 (IL
) is a diagram showing the amplitude when there is no magnetic field with a conventional coil;
b) is a diagram showing the amplitude when there is a magnetic field with a conventional coil, (c) is a diagram showing the amplitude when there is a magnetic field with a differential coil type according to the embodiment of the present invention, and Fig. 7 is a diagram showing the amplitude when a magnetic field is present in the embodiment of the present invention. Figures illustrating the results of controlling the level of molten steel in an electromagnetic stirrer in an example, (a) is a diagram without electromagnetic stirring, and (b) is a diagram showing level fluctuations during electromagnetic stirring. 1...℃-old 2...molten steel 3...magnetic flux balanced type magnetic flux needle 4, m, s...coil 7...power supply
8...Amplifier 9...Signal converter 1
0... Target value setter 11... Amplifier 12.
...Servo motor 13...Pulse generator 14...
・Tummy coil 15...Amplifier 16...Phase adjuster 17...Differential amplifier 18...Electromagnetic stirrer x)! IF3 Figure 4E

Claims (1)

[Claims] In a magnetic level needle for molten steel in a seven-hole for electromagnetic stirring,
A magnetic t-shicer for detecting a magnetic field for electromagnetic stirring is attached to a magnetic secessor for detecting the level of molten steel, and a composite signal of a level signal obtained from the level detection secessor and an electromagnetic stirring magnetic field signal, and a signal obtained from the magnetic field detection secessor for electromagnetic stirring are obtained. For electromagnetic stirring ゛Inside the electromagnetic stirring circuit, which consists of a circuit that changes the phase and gain of the magnetic field signal and subtracts the magnetic field for electromagnetic stirring (No. 1) from the above composite signal, so as to obtain only the level signal. Molten steel bell needle.