JPH06304742A - Method for detecting slag in molten steel flow and method for controlling molten steel flow - Google Patents

Abstract

PURPOSE:To improve the slag detecting ratio, and to suppress the outflow of the slag by integrating the changed value of the voltage to be detected by a slag detector, and defining the integrated value to be the slag outflow when the integrated value exceeds the integration threshold. CONSTITUTION:A detecting coil 5 consists of a primary coil and a secondary coil, and the signal induced in the secondary coil is changed according to the amount of the slag in the molten steel flow. The signal part of the induced voltage is extracted through an insulation amplifier 8 of a receiving amplifier 7, an absolute value detector 9, a filter 10 and a DC amplifier 11. The signal is converted into the digital signal by an A/D converter 12, and after the running mean calculation by a digital processing part 13, the digital integration is executed. The integrated value is compared with the threshold by a sequencer 14, and if it is discriminated as the slag outflow, the signal is transmitted to an opening adjusting device 15 to adjust the opening of a sliding nozzle 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically detecting slag in a molten steel flow, and a molten steel flow control method using the detection result.

[0002]

2. Description of the Related Art Detecting the timing of the start of slag outflow in a molten steel flow flowing out of a ladle is important in collecting the metal until the end.

For example, in Japanese Patent Laid-Open No. 64-27768, the amount of time change of the amplitude component of the voltage signal output from the slag detection coil provided at the bottom of the ladle is extracted, and the amount of drift signal included in this amount of time change is extracted. After the removal of, the time point at which the obtained amplitude component exceeds a certain threshold value is regarded as slag discrimination.

Regarding the drift signal amount removing method, in Japanese Patent Laid-Open No. 64-27768, the drift signal amount removing method is provided by providing a reference coil in addition to the slag detecting coil.
As another method, the signal is removed by using a signal processing means of taking a temporal moving average of the signal with the receiving coil and monitoring it every moment.

[0005]

When performing slag determination with the threshold value of the amplitude component as in the prior art, the slag determination can be performed with a certain degree of accuracy when the outflow amount of the slag is large, but the outflow amount of the slag is When the amount is small, the change in the signal is small, so the threshold value for slag determination is not exceeded, and detection is not performed. Further, if the threshold value is lowered so that it can be detected even in such an outflow situation, a noise signal will be caught, resulting in erroneous detection. Therefore, when the voltage change at the time of outflow of the slag is small, the S / N (signal / noise) is low and cannot be detected.

The problem to be solved by the present invention is to accurately determine slag outflow even when the slag outflow is small.

[0007]

In order to solve the above-mentioned problems, a method for detecting slag in a molten steel flow according to the present invention detects a slag detector when the amount of residual hot water in a ladle becomes equal to or less than a preset amount. The voltage change value excluding the drift component of the voltage change amount is integrated, and when the integrated threshold value is exceeded, the slag outflow is determined.

Further, in the molten steel flow control method of the present invention, a predictive threshold value smaller than the cumulative threshold value is further provided, and when the predictive threshold value is exceeded, the sliding nozzle is automatically closed until the sliding nozzle opening degree becomes a small opening. Alternatively, after the sliding nozzle opening is made small, the slag outflow is suppressed, the sliding nozzle is further opened, and this is repeated.

[0009]

The present inventor has found that when the residual amount of molten steel in the ladle reaches a certain amount, for example, about 10 t or less, relatively intermittent slag outflow occurs. Therefore, even when the outflow amount of the slag is small, the voltage change amount is small but continues to be a value of 0 or more. Therefore, this is determined by the integrated value. A high detection rate can be obtained by performing the slag detection either when the integrated value of the slight outflow amount reaches a certain value or when the threshold value of the amplitude component is exceeded.

Further, at the beginning of slag outflow, once the sliding nozzle is tightened to a small opening and then opened again, the vortex flow and the intermittent flow may stop. Make sure you can get the bullion.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples. FIG. 1 is a block diagram showing a structural example of an apparatus for carrying out the method of the present invention. In the figure, 1 is a ladle, 2 is a long nozzle, 3 is a sliding nozzle, 4 is a tundish, and 5 is a slag detection coil provided at the bottom of the ladle. The detection coil 5 is composed of a primary coil and a secondary coil, and an alternating current is supplied from the transmission amplifier 6 to the primary coil. The signal induced in the secondary coil changes depending on the amount of slag in the molten steel flow, and the induced voltage is extracted as a signal component through the insulation amplifier 8, the absolute value detector 9, the filter 10, and the DC amplifier 11 of the reception amplifier 7. It The signal is A
The signal is converted into a digital signal by the / D converter 12, and the digital processing unit (integrator circuit) 13 performs a moving average operation and digitally integrates it. The integrated value is compared with a threshold value by the sequencer 14, and when it is determined that the slag has flown out, a signal is sent to the opening adjustment device 15 to adjust the opening of the sliding nozzle 3.

As shown in FIG. 2A, the slag outflow is continuous,
In the case of a simple outflow that is uniform and the area occupancy rate is about 50% or more, the amount of voltage change exceeds the amplitude threshold value as shown in FIG. 6B, so that slag detection is possible with the conventional amplitude threshold value.

As shown in FIG. 3A, even in a simple outflow, when the area occupancy rate is about 50% or less, the voltage change is small as shown in FIG. It is possible.

As shown in FIGS. 4 (a) and 5 (a), the case where the slag outflow is discontinuous or uneven such as intermittent outflow or vortex outflow is also shown in FIGS. 4 (b) and 5 (b). As described above, since the detected amplitude does not exceed the amplitude threshold value, slag detection is impossible.

Therefore, as shown in FIG. 6, first, the voltage value caused by the temperature drift is first reset to 0 when the ladle remaining hot water amount is about 10 t, and the drift component voltage generated after about 10 t is canceled by the moving average. , The amount of voltage change from the time of outflow of slag is accumulated, the sliding nozzle automatic opening / closing operation is repeated with the prediction threshold value, and the slag detection signal is output with the integration threshold value. As a result of the experiment, a favorable result was obtained when the prediction threshold was about 30% of the cumulative threshold.

By providing all of these amplitude threshold value, prediction threshold value, and integration threshold value, slag outflow can be suppressed to a minimum.

[0017]

As described above, according to the present invention, since the total amount of outflow is detected by integrating the outflow amount of slag, intermittent or minute continuous slag outflow that cannot be detected by the amplitude threshold value. Can be detected, the current slag detection rate of about 90% is improved to 100%, and the quality is greatly improved by suppressing the outflow amount of slag to the minimum.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of an apparatus for carrying out the method of the present invention.

FIG. 2 is a diagram showing a slag outflow mode and a detected voltage change amount in a molten steel flow, and an explanatory diagram showing a case where outflow is continuous and an area occupancy rate of the slag is about 50% or more.

FIG. 3 is a diagram showing an outflow mode and a detected voltage change amount of slag in a molten steel flow, and an explanatory diagram showing a case where outflow is continuous and an area occupancy rate of the slag is about 50% or less.

FIG. 4 is a diagram showing an outflow mode and a detected voltage change amount of slag in the molten steel flow, and an explanatory diagram showing a case where the outflow is discontinuous.

FIG. 5 is a diagram showing an outflow mode and a detected voltage change amount of slag in the molten steel flow, and an explanatory diagram showing a case where the outflow is a vortex flow.

FIG. 6 is an explanatory diagram of an integrated threshold value and a prediction threshold value for slag detection according to the present invention.

[Explanation of symbols]

1 ladle, 2 long nozzle, 3 sliding nozzle, 4 tundish, 5 slag detection coil, 6
Transmission amplifier, 7 Reception amplifier, 8 Isolation amplifier, 9 Absolute detector, 10 filter, 11 DC amplifier, 12
A / D converter, 13 Digital processing unit (integrating circuit), 14 Sequencer, 15 Opening adjustment device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Oki 1-1, Toibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka New Nippon Steel Corporation Yawata Works

Claims (2)

[Claims] 1. When the amount of remaining hot water in the ladle becomes less than or equal to a preset amount, the voltage change value excluding the drift component of the voltage change amount detected by the slag detector is integrated, and the integrated threshold value is calculated as follows: A method for detecting slag in a molten steel flow, in which slag outflow occurs when the slag is exceeded. 2. A predictive threshold value smaller than the cumulative threshold value according to claim 1 is provided, and when the predictive threshold value is exceeded, the sliding nozzle is automatically closed until the sliding nozzle opening degree becomes a small opening, or the sliding nozzle opening is performed. A molten steel flow control method in which the slag outflow is suppressed, the sliding nozzle is further opened, and this is repeated after the opening degree is made small.