JPS62166071A - Method for measuring heat storage quantity of refractories - Google Patents

Abstract

PURPOSE:To improve the reliability of the measurement of heat storage quantity by inputting square wave pulses to cable sensors embedded into the inside surface of a ladle, determining the average temp. of the refractories in the embedded parts and determining the heat storage quantity from the average temp., average thickness and specific heat of the refractories. CONSTITUTION:The cable sensors 10a, 10e are embedded into the refractories on the inside surface of the ladle 40 and the square wave pulses are selectively impressed from a pulse generator 12 via a coaxial cable 18 to said sensors. The synthesized waves of the input pulses and the reflected pulses from the respective parts of the sensors are observed in an oscilloscope 14. The lengths and temps. in the parts where the sensors 10a-10e are embedded are inputted to respective arithmetic processing circuits which display the average thickness D and average temp. T of the refractories on display devices 32, 34. An arithmetic circuit 36 for the heat storage quantity determines the heat storage quantity Q as Qinfinity D.c.T from the average temp. T, average thickness D, and specific heat C of the refractories. The reliability in measuring the heat storage quantity of the ladle is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring the amount of heat stored in a refractory that constitutes the inner surface of a ladle in a steel factory.

[Conventional technology]

It is important that the temperature of molten steel in the steelmaking process ultimately maintains the specified value for the casting temperature in ingot making or continuous casting. The tapping temperature in the converter is controlled so that the above casting temperature is achieved in consideration of the temperature drop.

[Problem that the invention seeks to solve]

Currently, the amount of temperature drop in the ladle is generally calculated using a model based on the number of times the ladle is used, the time elapsed since the last pouring, etc. However, this method has large variations in estimated values, often resulting in poor accuracy in casting temperature.

Therefore, the temperature of the refractory ladle may be measured and determined.
In this case, it is necessary to measure the temperature of the refractory not only at one point but at multiple points in the thickness direction and circumferential direction of the refractory.

Conventionally, thermoelectric methods have been widely used as a high temperature measurement method, but to measure high temperatures at multiple points, it is necessary to use as many thermocouples as there are multiple points, making installation and measurement complicated. This was unavoidable, and a corresponding decline in measurement accuracy was inevitable.

To calculate the temperature drop in the ladle, it is necessary to know the heat capacity of the ladle, and for this it is necessary to find the mass m of the ladle refractory. Since this mass m is proportional to the average thickness D of the refractory, D may be used instead of m, and since the thickness of the refractory changes due to melting loss, estimation or actual measurement is required.

The TDR method using a cable sensor is effective for actually measuring the thickness of refractories. And TD using this cable sensor
With the R method, it is also possible to measure the temperature of the implanted site.

The present invention focuses on this point, and aims to simply and reliably measure the amount of heat stored in a refractory using a cable sensor.

[Failure to solve the problem]

The present invention embeds a cable sensor in a refractory that constitutes the inner surface of a ladle, inputs a rectangular wave pulse from one end of the cable sensor protruding from the refractory, and generates a composite wave of the input pulse and reflected pulses from various parts of the cable sensor. The average temperature of the refractories in the buried part of the cable sensor is determined from the reflected pulses in the composite wave, and the average thickness of the refractories is determined by actual measurement or estimation, and the average temperature T and average thickness of these refractories are determined. This method is characterized in that the refractory heat storage amount Q is determined as Q DcT from D and the refractory specific heat C.

[Effect]

According to this method, the amount of heat stored in the ladle can be determined by a relatively simple means, and the temperature drop in the converter can be determined by accurately knowing the temperature drop in the ladle. Defects can be avoided.

〔Example〕

To explain with reference to Fig. 1, 40 is a ladle, which is made up of an outer iron shell and an inner refractory, and a cable sensor is placed inside this refractory.
0a to 10e are buried. The cable sensor is specifically a coaxial cable-like sensor (although a parallel-conductor cable may also be used), consisting of a nickel-chromium center conductor, an Inconel outer conductor, and magnesium oxide between these conductors.

The cable sensors 10a and 10b are laid over a part of the circumferential direction of the body of the ladle refractory, and the cable sensors 10a and 10b are
c, 10d are laid over a part of the body in the vertical direction,
The cable sensor lOe is laid in the thickness direction of the ladle refractory. The sensors 10.11 and 10b and 10c and 10d have different positions in the thickness direction. These cable sensors use regular (signal transmission) coaxial cables 18
is connected to the changeover switch 22 via the pulse generator 1
2 square wave pulses are selectively applied (only one at a time).

When a square wave pulse is applied to one end of the cable sensor chain, the pulse propagates through the cable sensor and reaches the other end, where it is reflected and returns to the sending end. Therefore, when the sending end potential is observed, the potential of the sending pulse is initially When the reflected pulse returns, the combined potential of the transmitted pulse and the reflected pulse is observed, and when the transmitted pulse disappears, only the reflected pulse potential is observed (the transmitted pulse width is chosen to be this long). Since the time from pulse sending to the return of the reflected pulse is proportional to the cable sensor length, the cable sensor length can be calculated by knowing the time from sending end potential observation to the return of the reflected pulse.

The inner surface of the ladle-resistant refractory comes into contact with molten steel, so it is eroded and the thickness of the refractory changes. Therefore, if the cable sensor 10e is buried in the thickness direction of the refractory and the tip is exposed to the molten steel, the part of the cable sensor that has entered the molten steel will melt, and the end of the cable sensor will be separated from the inner surface of the refractory. Therefore, by measuring the cable sensor length as described above, the refractory thickness and weld tit can be measured.

FIG. 2(a) does not show an example of the waveform observed at the sending end.

A portion Ca of the curve C corresponds to the coaxial cable 18, a portion Cb corresponds to the cable sensor 10, and a portion Cc corresponds to the reflected wave from the tip of the cable sensor 10.

As shown by the broken line, when the tip of the cable sensor is eroded, the tip reflected wave portion Cc of the curve C also recedes from the dotted line as shown by the solid line, and the amount of erosion can be determined from this time change Δt.

That is, if the amount of erosion is ΔL, the pulse speed is C/l (here, C is the speed of light, and ε is the dielectric constant), so ΔL=Δt−C
/'lk. The thickness of the refractory can be determined by subtracting the amount of erosion ΔL from the initial thickness, or by calculating the total length of the cable from the time from origin O (rectangular wave sending timing) to section Cc, and subtracting the length of cable 18, etc. You can also ask for it as a thing.

The reflected wave portion Cc from the cable sensor end is related to the state of the sensor end. That is, if the sensor end is in an open state, it will rise, and if the sensor end is in a short-circuited state, it will be a fall. It is also related to temperature; the higher the temperature, the gentler the slope of the rise.
Eventually, the slope turns to a downward slope, and the slope becomes steeper.
Figure (b) shows this state. Therefore, the temperature can be determined from the slope of this tip. The position of the tip is obtained by subtracting the dark value level as shown by the chain line and finding the intersection of the curve C and the dark value level. However, if the tip slope changes, the intersection point becomes PI.
, P2. ..., and the tip deviates from the true tip position. If the dark value level is brought closer to the curve C, this deviation will be reduced, but since the curve C is not actually a straight line, if it is brought too close, an intersection will occur in the middle, causing an error. Therefore, the above-mentioned deviation is unavoidable, but this can be corrected by determining the slope of the slope, preparing a correction value corresponding to the slope, and subtracting it.

If you further trace the tip of the curve C in Figure 2 (bl), it will eventually settle down to a certain level. Figure 2 (C1) shows this state. If the rising slope is gentle, it will settle down to a low level, and the falling side will also follow this.Therefore, the temperature can be measured at this settled level, and there is no need to measure the slope. It's easy.

Reflected waves are generated not only from the ends of the cable sensor, but also from any temperature abnormalities. Cd in FIG. 2(C) shows an example of this, and if there is a high temperature part in this part of the cable sensor IO, a depression Cd appears in the waveform C. This dent C
The depth and size of d) also correspond to temperature. Therefore, the temperature of the high temperature area can be determined from this depth. Such a high-temperature area appears when the refractory has a locally large loss of '/g and molten steel approaches the cable sensor. In addition, if you prepare a table with the depth and temperature of the dent in advance,
Temperature calculation is easy.

The oscilloscope 14 of FIG. 1 displays curve C of FIG. That is, the rectangular wave pulse generated by the pulse generator 12 passes through the sampling unit 16 and the changeover switch 22, and is input to one cable sensor selected by the switch 22, and its sending end potential is observed with an oscilloscope.

The square wave pulses are generated periodically and are detected by the oscilloscope 14.
Since the sweep is performed in synchronization with the rectangular wave transmission, the waveform displayed on the oscilloscope screen is a static waveform.

When the changeover switch 22 is operated to switch the cable sensor to which the rectangular wave pulse is applied, the stationary waveform for the switched cable sensor is displayed. The operator may perform the above-described processing on this stationary waveform to determine the thickness and temperature distribution of the refractory. It may also be determined by a processing circuit or computer.

Length measurement signal processing circuit 26, temperature measurement signal processing circuit 24
is a circuit that performs length and temperature measurements.

In the case of computer processing, the waveform C is sampled at a minute sampling period, each sample is converted into a digital value by A/D conversion, and then the tip detection, length calculation, tip level and depression depth derivation, Calculate the temperature by drawing a table.

The obtained temperatures of each part are averaged, stored, and displayed on the refractory average temperature display 34. The obtained refractory thickness is also stored and displayed on the refractory thickness display 32. Since the thickness of the refractory material is expected to be different in each part, the cable sensors 10e inserted in the thickness direction are inserted at a plurality of locations to obtain an average thickness. The heat storage amount calculation circuit 36 is
The average refractory thickness D and the average refractory temperature T obtained in this way
, Calculate the refractory heat storage amount Q as -Dc-T to Q= using the refractory specific heat C1 constant K from the constant setting device 38,
This is displayed on the display 3o. In addition, display device 30.32.
34 may be one display, or may be a permanent display means such as a printer instead of a volatile display such as a CRT display.

If the amount of heat M is known, the temperature drop in the ladle can be calculated from the following equation.

ΔT=αW-To-cM-βQ ΔT: Temperature drop W: Molten steel weight To: Molten steel temperature CM: Molten steel specific heat α, β: Constant The erosion condition of the ladle refractory is complex, so it is difficult to accurately calculate the average thickness of the refractory. To calculate this, it is necessary to install a large number of thickness direction cable sensors 10e. Therefore, this part (thickness measurement) can be performed using a value estimated from the number of times the ladle is used, or an optical or contact type thickness needle for an empty ladle. It may also be a value measured by .

〔Effect of the invention〕

As explained above, according to the present invention, the amount of heat stored in the ladle can be determined by a relatively simple means, the temperature drop in the ladle can be accurately known, and the temperature for tapping steel in the converter can be determined, and the It is possible to avoid problems such as failure due to overheating.

[Brief explanation of drawings]

FIG. 1 is a detailed explanatory diagram of the present invention, and FIG. 2 is an explanatory diagram of the procedure for measuring thickness and temperature. In the drawing, 40 is a ladle, 10 is a cable sensor, 12 is a square wave pulse generator, and 14 is an oscilloscope. Applicant Nippon Steel Corporation Patent Attorney Minoru Aoyagi Figure 1 Figure 2

Claims (3)

[Claims] (1) A cable sensor is embedded in the refractory that makes up the inner surface of the ladle, a rectangular wave pulse is input from one end of the cable sensor protruding from the refractory, and a composite wave of the input pulse and reflected pulses from various parts of the cable sensor is generated. Observe and determine the average temperature of the refractories in the buried part of the cable sensor from the reflected pulses in the composite wave. Also, determine the average thickness of the refractories by actual measurement or estimation, and calculate the average temperature T and average thickness of the refractories. A method for measuring the amount of heat stored in a ladle refractory, characterized by determining the amount of heat stored in the refractory Q as Q∝DcT from D and the specific heat c of the refractory. (2) The refractory heat storage amount measuring method according to claim 1, wherein the cable sensors are buried at different positions in the thickness direction of the refractory. (3) The method for measuring the amount of heat stored in a refractory according to claim 1, wherein the average thickness of the refractory is actually measured as the length of a cable sensor embedded in the thickness direction of the refractory.