JPH06330136A - Slag-cutting method at the time of tapping steel from converter - Google Patents

Abstract

PURPOSE:To reduce the flow-out of slag into a ladle at the time of tapping molten steel from a converter and to prevent steel from remaining in the furnace caused by early slag-cut. CONSTITUTION:Magnetic filed is formed in a steel tapping port 2 of the converter 1 and electromotive force at the time when the molten steel passes, is measured by using a sensor 6 for measuring the electromotive force and the slag is recognized at the point of time when this detected electromotive force changes. In the method for cutting the slag by blowing off the slag 16 flowed out of a steel tapping port 2 with high pressure gas jetting out of a center nozzle 14 in a stopper 11, the setting value of the electromotive force, by which the slag is recognized, is set at 70-80% of the electromotive force to 100% of the slag till 20-30secs before the assumed completing time of the steel tapping. Thereafter, the setting value of the electromotive force is continued to reduce and the value is set at 40-50% of the electromotive force till completion of the steel tapping from 0-10 secs before the assumed completing time of the steel tapping. By this method, the slag-cutting caused by a temporarily flowing out of the slag can be restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of cutting out slag from flowing out to a ladle when tapping steel from a converter.

[0002]

2. Description of the Related Art When molten steel is tapped into a ladle after it is blown in a converter, if slag floating on the molten steel in the converter flows out into the ladle, Re-phosphorization occurs and the refractory lining of the ladle is eroded. Therefore, conventionally, in order to reduce the amount of slag flowing out of the converter to the ladle as much as possible, the following method is known as a method of detecting the outflow of slag and cutting the slag.

(1) An operator visually recognizes the flow of tapping steel and perceives the outflow of slag from the brightness and color, and at the same time when the slag begins to flow out, the converter is tilted to cut out the slag outflow from the tapping port. Method. (2) The slag outflow is determined by measuring the temperature change and emissivity of the tapped steel flow, the converter is immediately tilted, and the slag flowing out from the tapped steel outlet is blown off with a high-pressure fluid or the like to cut the slag. how to.

(3) A method of separating molten steel and slag by cutting a slag by providing a partition weir of a refractory under the tap hole in the converter. (4) A magnetic field is formed in the tap hole, the electromotive force when molten steel passes through the magnetic field is detected, and the slag is recognized when the electromotive force reaches a certain level (see JP-A-1-309767). ) Do. Then, the slag flowing out from the tap hole is blown off with a high-pressure gas or the like (see Japanese Patent Laid-Open No. 58-31021) to cut the slag.

However, in the method (1) in which the operator visually observes, there is a problem in that there are individual variations in the determination and considerable variations occur, so that the outflow of slag cannot necessarily be prevented. In addition, in the method (2) of measuring temperature change and emissivity of tap steel flow, there are cases in which temperature change and emissivity cannot be measured accurately due to disturbances such as smoke and splash in the ladle during tapping, and the slag There was a problem that it was difficult to reliably cut the outflow.

In the method (3) of cutting a slag by providing a partition weir in the converter, not only the structure becomes complicated and the cost of refractory increases, but also the life is short and the slag can be cut stably for a long time. There was a problem that it was difficult.

[0007]

By the way, in the method (4) of forming a magnetic field in the tap hole and recognizing the slag at the change point of the electromotive force when the molten steel passes through the magnetic field in the tap hole, the slag cutting method is used. There was a case where a large amount of residual steel was left in the converter. Fig. 3 shows a change in electromotive force when a molten steel passes through the tap hole due to tilting of the converter by forming a magnetic field in the tap hole of the converter. As shown in FIG. 3, due to the temporary slag inclusion at the end of tapping, a peak as shown by the value (b) of the electromotive force detection level may occur about 20 to 30 seconds before the tapping ends. This peak (b) value is slag
The electromotive force at 100% fluctuates within the range of 20 to 70%.

Therefore, assuming that the set value of the slag detection level for performing slag cutting is (a) value, when (a) value <(b) value, slag cutting is performed at the stage where residual steel exists in the furnace. Will be done. For this reason, the false detection rate becomes large as shown by the solid line in the conventional method in FIG. But,
For safety, if the value (a) is set excessively, the timing of slag detection is delayed, so that there is a problem that the amount of slag flowing from the converter to the ladle increases.

The present invention has been made in view of the above-described circumstances, and a magnetic field is formed in the tap hole of a converter, and slag detection is performed when molten steel passes through the magnetic field in the tap hole. (EN) A slag cutting method at the time of tapping a converter that can reduce the amount of slag flowing out of the converter into a ladle and prevent residual steel in the furnace by setting the power level to an appropriate value. That is the purpose.

[0010]

Means for Solving the Problems The present invention for achieving the above object is to form a magnetic field in a tap hole of a converter and detect an electromotive force when molten steel passes through the magnetic field in the tap hole. Recognizing slag at the time when this detected electromotive force changes, and slag that flows out of the tapping hole is blown off with high-pressure gas to prevent the slag in the converter from entering the ladle. The set value of the electromotive force to be set is set to 70 to 80% of the electromotive force value for 100% of the slag until 20 to 30 seconds before the estimated tapping end time, and then the set value of the electromotive force is reduced to make the estimated output. This is a slag cutting method when tapping the converter, which is characterized by setting the electromotive value to 40% to 100% of slag from 0 to 10 seconds before the end of steel to the end of tapping.

[0011]

1 shows the structure of a tap hole 2 provided in a converter 1 used in the present invention and a slag stopper device 3 for preventing slag from flowing out from the tap hole 2. As shown in FIG. 1, an electromotive force sensor block 5 is embedded outside the nozzle refractory 4 of the tap hole 2, and the starting force sensor block 5
Is provided with an electromotive force measuring sensor 6. The electromotive force measuring sensor 6 has a transmitting coil 7 and a receiving coil 8 as shown in FIG. 2, and a coil caused by the slag 16 being mixed in the central portion of the molten steel 15 flowing in the tap hole 2 The change in electromotive force due to the current flowing through the sensor is detected.

The slag stopper device 3 installed near the tap hole 2 has a bearing 9 fixed to the iron shell 1a of the converter 1.
The arm 10 is rotatably supported by the arm 10, a cast iron stopper 11 attached to the tip of the arm 10, and a cylinder 12 connected in the middle of the arm 10. By expanding and contracting the cylinder 12, the steel tap 2
You can open and close the exit.

Further, the arm 10 is provided with a nitrogen gas supply passage 13, and the nitrogen gas supplied from a nitrogen gas supply source (not shown) through the nitrogen gas supply passage 13 is tapped from the central nozzle 14 of the stopper 11. It is designed to eject into the mouth 2. In the present invention, the tapping required time is estimated from the tapping start from the tapping port 2 from the molten iron component, the charging amount, the blowing condition and the furnace body profile of the converter 1, and the estimated tapping end time is 20 to
Until 30 seconds before, the slag detection level by the electromotive force measurement sensor 6 is 70 to 80% of the electromotive force value corresponding to 100% slag.
After that, the slag detection level will be lowered with time, and 0 to 10 seconds before the estimated tapping end time, the slag detection level will be set to 40 to 50% of the electromotive force value corresponding to 100% slag.
%, The residual steel in the furnace due to the slag cut at the peak of the detection level of electromotive force that is seen when the slag 16 is temporarily entrained in the molten steel flow 15 flowing out from the tap hole 2 at the end of tapping is set. To prevent. Then, during the actual slag cutting by continuous slag discharge, the detection level of the electromotive force value is lowered to an appropriate set value as described above, and the slag cutting work at this time is performed as follows.

That is, the arm is actuated by the operation of the cylinder 12.
10 is rotated to close the outlet of the tap hole 2 by the stopper 11, and the slag in the tap port 2 is blown off by the nitrogen gas ejected from the central nozzle 14 of the stopper 11 to cut the slag. At this time, since the detection level set value of the electromotive force measured by the electromotive force measuring sensor 6 is lowered to the appropriate value as described above, the amount of slag flowing out from the converter to the ladle and its variation should be reduced. You can

[0015]

Embodiments of the present invention will be described below with reference to the drawings. After blowing the converter 1 as shown in FIG. 1, when tilting the converter 1 for tapping, the stopper 11 attached to the tip of the arm 10 is retracted as shown by the chain line. Therefore, only the molten steel initially flows out from the tap hole 2. Therefore, the electromotive force value measured by the electromotive force measuring sensor 6 embedded in the tap hole 2 changes to a low level as shown in FIG.

That is, from the start of tapping through the tapping port 2 to 30 seconds before the estimated tapping end time, the electromotive force level for slag detection by the sensor 6 is set to the electromotive force value for 100% of slag.
The B level is 70%, and thereafter, the level of the electromotive force value for slag detection is lowered with time. Then, 10 seconds before the estimated end time of tapping, the level is set to A level, which is 40% of the electromotive force value for 100% of slag, and is fixed to the A level thereafter.

In this way, when the electromotive force value measured by the sensor 6 reaches the A level, the cylinder 12 is operated to rotate the stopper 11 at the retracted position via the arm 10 and to supply the nitrogen gas supply path. Nitrogen gas is supplied from 13 and nitrogen gas is ejected from the central nozzle 14 of the stopper 11. When the outlet of the tap hole 2 is closed with the stopper 11, the central nozzle 14
The slag in the tap hole 2 is blown off by the high-pressure nitrogen gas ejected from the slag, and the slag is cut. Therefore, FIG.
As shown in, the method of the present invention can reduce the false detection rate of slag outflow as compared with the conventional method.

On the other hand, for example, when the stopper 11 closes the outlet of the tapping hole 2 at the time when the electromotive force level shown in B in FIG. 6 is reached, the central nozzle 14 blows off the high-pressure nitrogen gas. Is compared with the case of the present invention,
The blow-off timing is delayed. In this case, as shown in FIG. 5, the level of the electromotive force value is high, so that the amount of slag flowing into the ladle increases.

Further, when the level of the electromotive force value shown by A in FIG. 6 is reached, the slag 16 flowing out from the tap hole 2 is stopped.
When blown off with high-pressure nitrogen gas ejected from the central nozzle 14 of 11, if the electromotive force value at that time is due to temporary entrainment in molten steel 15 at the end of tapping, it is placed in converter 1. The remaining steel will be left behind, which will reduce the yield of the steel.

In the present invention, as described above, the electromotive force value level of slag detection by the electromotive force measuring sensor 6 is changed with time, and the electromotive force value due to the temporary inclusion of the slag 16 in the molten steel 15 is changed. In this range, the electromotive force level for slag detection is set high, so that residual steel in the furnace can be prevented and the amount of slag flowing from the converter to the ladle can be reduced.

[0021]

As described above, in the present invention, the set value of the electromotive force for recognizing the slag when the steel is tapped from the tap tap having a magnetic field is estimated to be 20 to 30 seconds which is the tapping end time. Set it to 70-80% of the electromotive force value for 100% of slag, and then reduce the electromotive force setting value to 0% of the estimated end time.
From 10 seconds before tapping to completion, set to 40 to 50% of electromotive force value for 100% slag. Therefore, it is possible to reduce the amount of slag flowing from the converter to the ladle and prevent the residual steel in the converter.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a converter tap hole and a slag stopper device used in the method of the present invention.

FIG. 2 is an explanatory diagram showing the principle of an electromotive force measurement sensor used in the method of the present invention.

FIG. 3 is a diagram showing a transition of electromotive force from the start of tapping to the end of tapping.

FIG. 4 is a diagram showing the relationship between the electromotive force and erroneous detection rate at the time of slag detection in comparison between the method of the present invention and the conventional method.

FIG. 5 is a diagram showing a relationship between an electromotive force at the time of slag detection and a ladle outflow slag.

FIG. 6 is a diagram showing changes in electromotive force between an example of the method of the present invention and a conventional example.

[Explanation of symbols]

 1 Converter 2 Steel tap 3 Slag stopper device 4 Nozzle refractory 5 Electromotive force sensor block 6 Electromotive force measuring sensor 7 Transmitting coil 8 Receiver coil 9 Bearing 10 Arm 11 Stopper 12 Cylinder 13 Nitrogen gas supply channel 14 Center nozzle 15 Molten Steel 16 Slag

Claims (1)

[Claims] 1. A magnetic field is formed in a tap hole of a converter, an electromotive force when molten steel passes through the magnetic field in the tap port is detected, and slag is recognized at the time when the detected electromotive force changes, By blowing off the slag flowing out of the steel mouth with high-pressure gas, in the method of cutting the slag in the converter from entering the ladle, the set value of the electromotive force that recognizes the slag and the estimated tapping end time of 20 ~ Until 30 seconds, set the electromotive force value to 70% to 80% for 100% slag, and then reduce the electromotive force setting value. From 0 to 10 seconds before the estimated tapping end time to tapping end A method for cutting slag when tapping a converter, which is characterized by setting the electromotive force value to 40 to 50% for 100% slag.