JPH06235014A - Method for predicting slopping in refining vessel and instrument therefor - Google Patents

Abstract

PURPOSE:To directly predict the slopping without the delay of time by measuring conducting current value or electric resistant value in between an electrode arranged at the inner wall of refractory in a refining vessel and an electrode arranged through an insulating layer. CONSTITUTION:Molten steel 2, supplied into a converter body 1 is refined by blow through molten slag 3. The electrodes 4-1, 4-2 surrounded with the insulating refractory are arranged at the intermediate part and the uppermost end part in the side wall of this converter body 1 and also the electrode 4-3 as a base is arranged at the lower part in the side wall, and the electric conduction is held with the molten steel 2 through the MgO-C brick, etc. A circuit providing constant voltage generators 6-1, 6-2 is formed in between this electrode 4-3 and the electrodes 4-1, 4-2, respectively. A level of the molten slag 3 during refining is ascended and at the time of reaching to the electrode 4-1 or 4-2, by detecting the current I1 or I2 with an ammeter 5-1 or 5-2, the development of the slopping is predicted, and by trying the necessary treatment, the yield of the steel tapping quantity, the stability of blowing, the recovery ratio of OG gas, etc., can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for predicting or detecting a so-called sloping phenomenon in which slag foams in a refining vessel and escapes outside the furnace when refining molten metal.

[0002]

2. Description of the Related Art When refining molten metal using a refining vessel, for example, when refining molten steel in a converter, a lance is vertically inserted from the furnace opening of the converter to produce pure oxygen gas from the lance. Blowing is performed while decarburizing while spraying molten steel. At this time, depending on various conditions such as the composition of the molten slag, the acid feeding rate, and the temperature, CO gas generated during decarburization causes the slag to foam abnormally, so-called sloping occurs. When sloping occurs, it affects molten steel composition, total steel yield, etc., and causes various problems such as lower work efficiency, lower OG recovery rate, worsening work environment such as red smoke, and damage to equipment. To do.

Therefore, it is necessary to promptly predict the situation in the refining vessel and to carry out an appropriate operation to prevent the occurrence of sloping, and various methods as shown below have been conventionally proposed. Estimate the amount of slag in the furnace based on the exhaust gas information during blowing. The slag level is estimated from changes in the frequency and intensity of the sound generated in the furnace (JP-A-54-33790).

A slag level or a slag state is estimated from a change in vibration of a lance or a furnace body during blowing (Japanese Patent Laid-Open No. 54-114414). Occurrence of sloping is predicted from changes in the surface temperature of the furnace body (Japanese Patent Laid-Open No. 58-48615) and changes in the temperature inside the furnace by a temperature sensor provided on the side wall (Japanese Patent Laid-Open No. 1-215918).

Microwaves are projected onto the slag surface or the inner wall surface in the furnace, and the slag level is estimated from the intensity and frequency of the reflected wave (Japanese Patent Laid-Open No. 227709/1988, Japanese Patent Laid-Open No. Hei 1 (1998) -187709).
No. 191734). Change in color signal obtained by a photodetector installed in a through hole provided in the side wall of the furnace body (Japanese Patent Laid-Open No. 60-228928).
Change in the visual field area of an image obtained by a photodetector installed at the tip of the sublance (Japanese Patent Laid-Open No. 63-176).
411), the occurrence of sloping is detected.

The slag level is detected by inserting a thin tube from the side wall of the furnace body, injecting an inert gas into the furnace and measuring the back pressure change thereof (Japanese Patent Laid-Open No. 61-210114). A rotating body is inserted into the furnace, and sloping is detected from the change in the rotation resistance (Japanese Patent Laid-Open No. 63-235417).

[0007]

However, in the method of estimating the amount of slag in the furnace based on the exhaust gas information during blowing, the analysis of the exhaust gas causes a time delay and the occurrence of sloping. Does not depend only on the amount of slag, so there are problems such as low prediction accuracy. In addition, in the method of estimating the slag level from changes in the frequency and intensity of the sound generated from the furnace, it is not possible to quantitatively grasp the slag level and the state of the slag due to the indirect measurement method, and only the foaming condition of the slag. In addition, since the sound changes even if the internal pressure changes due to a change in the amount of fed acid, there is a problem that the prediction accuracy is low. The method of detecting changes in vibration of the lance and the furnace body, the method of measuring temperature changes, and the method of measuring the back pressure of the gas ejected into the furnace have a large influence of disturbance, and the prediction accuracy There is a problem that is low. In addition, the method of projecting microwaves from the upper part of the furnace mouth onto the slag surface and the inner wall surface and measuring the intensity and frequency of the reflected waves causes large disturbance, and since there is a sensor at the upper part of the furnace mouth, the dust frame For example, severe damage to the tip of the sensor is a problem. In the method of inserting the rotating body into the furnace to measure the rotation resistance, equipment for rotating the rotating body is required, and there are problems that the cost is high and the rotating body is worn out severely. In the method using the photodetector, the color signal changes depending on the operating temperature and the prediction accuracy of sloping decreases, and when installed at the tip of the sublance, it is difficult to measure for a long time to avoid wear. That is a problem.

The present invention has been made in view of the above circumstances, and it is possible to solve the above-mentioned problems and to make a prediction without delay with respect to sloping and to obtain a total yield of steel. It is intended to improve, stabilize blowing, and improve the OG gas recovery rate.

[0009]

According to the present invention, during refining a molten metal using a refining vessel, an electrode provided on the refractory inner wall of the refining vessel and a lower side of the refractory inner wall of the electrode through an insulating layer are provided. Alternatively, the electrodes provided on the body of the refining vessel measure the conduction current value or electric resistance value with the molten metal interposed between both electrodes, and detect the increase of the conduction current value or the decrease of the electric resistance value and sloping. The gist is a method for predicting sloping in a refining container, which is characterized by predicting the occurrence of

Further, according to the present invention, at least one electrode is provided on the inner wall of the refractory material of the metal refining vessel, and an electrode is provided on the lower side of the inner wall of the refractory material of the electrode or the refining vessel body through an insulating layer. Is equipped with a means for measuring a current value or an electric resistance value between both electrodes, specifically, an ammeter or an ohmmeter, and a predetermined intensity change is observed in the measured current value or electric resistance value. In this case, the gist is a sloping prediction device in a refining vessel, which is provided with a means for issuing a prediction signal of sloping occurrence. Note that the predetermined intensity change means a large change exceeding the steady error variation range.

A feature of the present invention is that one of the electrodes is installed at a position where it directly contacts the molten metal, or the molten metal is electrically connected to the molten metal through a conductor refractory such as MgO-C. Installed on the refractory wall of the refining vessel through the insulating layer, the molten slag of the conductor foams, increasing the current value when it contacts the latter electrode or By measuring the decrease in the electrical resistance value, the slag level can be detected directly and with high accuracy with little disturbance. If the latter electrode is installed on the top of the furnace body, it can be detected when the slag foams up to the furnace mouth.If the electrode is installed on the furnace wall between the top of the furnace body and the molten steel surface, the slag will be located at that electrode position. Can be detected when bubbles occur.

That is, since the slag level can be directly measured without a time delay and the occurrence of sloping can be accurately predicted, the measures for avoiding sloping by lowering the blowing acid velocity, adding a slag foaming sedative, etc. should be taken promptly. Is possible. 1 and 2 show an embodiment of the present invention, FIG. 1 is an overall explanatory view thereof, and FIG. 2 is an enlarged view of a portion of FIG. 1A.

In the present invention, an electrode 4-2 is provided on the side wall of the refining vessel, for example, the uppermost end of the converter body 1. Further, an electrode 4-1 is provided on the side wall between the furnace opening and the surface of the molten steel. The reference electrode 4-3 is installed in the furnace body 1 which is electrically connected to the molten steel 2 through a MgO-C brick or the like. Electrodes 4-1 and 4
-2 has a circuit formed with the reference electrode 4-3,
A constant voltage is applied between the electrodes by a constant voltage generator 6. The electrodes 4-1 and 4-2 are surrounded by an insulative refractory 7 as shown in FIG. 2 and are disconnected from the reference electrode, but are electrically connected to each other via the slag in the furnace. Current flows in the circuit only when there is
It is measured by 1, 5-2.

The electrode material is a carbon electrode or air cooled
For steel, conductive refractory, etc. that are difficult to react with molten slag 3
Can be Insulating refractory 7 has MgO brick, MgO-
Cr ₂O₃Brick is used.

[0015]

When the molten steel 2 starts to be blown and the slag 3 is melted, the amount of CO gas generated from the slag-molten steel interface increases and the slag 3 becomes large and the slag 3 becomes large.
Comes into contact with the electrode 4-1 and the molten slag 3 has electric conductivity, so that a current flows in the circuit and the current value I ₁ is measured by the ammeter 5-1. At this point, if measures such as a decrease in the acid transfer rate and the addition of a slag foaming sedative are taken, the foaming of the slag can be suppressed.
-2, a current flows through the circuit, and the current value I ₂ is measured by the ammeter 5-2.

[0016]

EXAMPLE FIG. 3 shows the changes over time in the current value in each circuit when the occurrence of sloping is predicted when blowing molten steel by applying the present invention. A constant voltage of 5 V was applied to each circuit. About 4 minutes after the start of blowing, a rapid increase in the current value I ₁ was recognized, indicating that the slag foamed up to the level of the electrode 4-1. Then, about 7 minutes after the start of blowing, the current value I ₂ also rapidly increased. If you continue blowing as it is, severe sloping occurs. Since the slopping subsided, the current value I ₂ again rapidly increased when the blowing was continued. Therefore, when the blowing acid rate was immediately reduced, the sloping did not occur this time. Therefore, according to the present invention, sloping can be predicted with high accuracy,
It was confirmed that sloping could be avoided if slag foaming suppression measures were taken immediately after the increase of the current value I ₂ .

As described above, according to the present invention, while predicting the occurrence of sloping, the slopping frequency and the average when the slag foaming suppression measure is immediately taken upon detecting the increase in the current value I ₂ as described above. Of molten steel yield,
The results are shown in Table 1 in comparison with the case where sloping is predicted by the conventional method (the above method).

[0018]

[Table 1]

According to the present invention, sloping can be predicted with high accuracy, and rapid slag foaming suppression measures can be taken, whereby the frequency of slopping occurrence can be greatly reduced and the molten steel yield can be improved.

[0020]

According to the slopping prediction method of the present invention, the slag level can be detected with high accuracy directly and without time delay by utilizing the electrical conductivity of the slag. And accurately predict and respond
It has extremely great value in operation such as stabilization of molten metal refining and improvement of yield.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of a portion A of FIG.

FIG. 3 is a change with time of a current value between electrodes when the present invention is carried out.

[Explanation of symbols]

 1 Converter Main Body 2 Molten Steel 3 Molten Slag 4 Electrode 5 Ammeter 6 Constant Voltage Generator 7 Insulating Refractory 8 Conductor

Claims (2)

[Claims] 1. While refining molten metal using a refining vessel,
An electrode provided on the refractory inner wall of the refining vessel and an electrode provided on the lower side of the refractory inner wall of the electrode or on the refining vessel main body through an insulating layer, and a conduction current value with the molten metal interposed between the electrodes. Alternatively, a method of predicting sloping in a refining vessel, which comprises measuring an electric resistance value and detecting an increase in a conduction current value or a decrease in an electric resistance value to predict occurrence of sloping. 2. A metal refining vessel having at least one electrode on an inner wall of the refractory, and an electrode provided on the lower side of the refractory inner wall of the electrode or on the body of the refining vessel through an insulating layer. Equipped with a means for measuring the current value or electric resistance value between both electrodes, when a predetermined intensity change is observed in the measured current value or electric resistance value, a means for issuing a prediction signal of sloping occurrence is provided. A sloping prediction device in a refining container, which is characterized by being attached.