JPH03120309A - Method for detecting flowing-out of slag from steel tapping hole in converter - Google Patents

Abstract

PURPOSE:To prevent involution of molten slag eddy into molten steel and to accurately detect flowing-out of the molten slag by floating refractory on the molten steel surface just above the steel tapping hole at the time of detecting flowing-out of the molten slag mixed in the molten steel from the steel tapping hole in a converter by utilizing difference of magnetic permeability between the molten steel and the molten slag. CONSTITUTION:At the time of tapping the molten steel 3 from a steel tapping hole 20 by tilting the converter after completing converter operation, as countermeasure to the flowing-out of mixed molten slag 4 in a molten steel passage 21 of the steel tapping hole 20 at the end stage of steel tapping, a primary coil 5 and secondary coil 6 are arranged to the steel tapping hole, and AC current is conducted to the primary coil 5 to measure voltage V induced to the secondary coil 6 through the molten steel flow 3. When the molten slag starts to mix in the molten steel, as the induced voltage V' in the secondary coil 6 is varied with ratio of the magnetic permeabilities of molten steel flow 3 to molten slag flow 4, the mixture of molten slag 4 is detected and steel tapping is stopped. The molten steel passage 21 becomes larger as the number of the steel tappings increases, and then, in order to prevent the deterioration of detecting accuracy with the secondary coil 6 by involving the molten slag 4 into the molten steel flow in the eddy state, the refractory 1 is floated just above the tapping hole to prevent the involution of molten slag 4 and the mixture of molten slag is accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for detecting slag outflow from a tapping port during tapping in a converter.

[Conventional technology]

One method for detecting slag outflow at the end of steel tapping in a converter in a steelmaking factory is to utilize the difference in magnetic permeability between molten steel and slag. That is, as shown in FIGS. 3(a) and (b),
A primary coil (5) and a secondary coil (6) are provided at the tap port of the converter, and the design is such that molten steel (3) can pass through the center of the primary coil (5) and secondary coil (6).

When an alternating current ■ is supplied to this primary coil (5), the following formula ■
A magnetic field H is generated.

R: Primary coil radius When the magnetic field H is generated, an induced voltage V is generated in the secondary coil (6) according to the following equation (2).

Φ: Magnetic flux: Constant μ: Magnetic permeability As shown in Figure 3 (a), when the tap hole is filled only with molten steel (3), the magnetic permeability μ is approximately constant, so the induced voltage V is 0. The value is close to . However, when the slag (4) enters the tapping hole as shown in FIG. 2(b), the magnetic permeability μ changes and the induced voltage ■ increases, so that the slag (4) can be detected.

Therefore, at the end of tapping, the change in the magnetic permeability μ is detected as a change in the induced voltage V in this way, and the tapping is ended when the voltage reaches a certain value.

[Problem that the invention seeks to solve]

FIG. 4 is an oscillographic diagram showing a typical detection signal waveform during tapping when such a slag outflow detection method is used. The number of times the steel is tapped is 1 to 50 times.

In this case, the induced voltage V is approximately constant during tapping (molten steel level), but when slag (4) begins to flow out at the end of tapping, the signal level begins to rise, and when it reaches the set level, a slag alarm occurs ( For example, in the same figure, if the alarm setting level is 2V, an alarm will occur at the O mark)
.

However, as the number of tapping holes increases, the diameter of the tapping hole increases due to melting, and a vortex is generated toward the tapping hole and slag (4) is drawn in, so the induced voltage V increases even during tapping. Figure 5 is an oscillographic diagram showing the signal waveform of 96 taps, and the molten steel level fluctuates rapidly during tapping, making it difficult to distinguish from the true completion of tapping. It can be seen that the decision to end steel is very difficult.

As a way to solve this problem, there is a method of increasing the induced voltage value used to determine the end of tapping, but this is not practical because the detection of slag outflow is delayed and the slag thickness increases.

The present invention was devised in view of the above-mentioned problems of the prior art, and is intended to prevent slag from being entrained by vortices during tapping, and to accurately detect slab outflow.

[Means for solving problems]

Therefore, in implementing a method for detecting slag outflow at the time of tapping a converter using the difference in magnetic permeability between molten steel and a slab, the present invention has developed a method in which refractories are suspended on the surface of the molten metal just above the tapping port during tapping. This is what I did. As a result, even if the diameter of the tap hole increases due to melting and a vortex is generated toward the tap hole, the refractory floating on the hot water surface directly above the tap hole effectively prevents the entrainment of slag. To prevent. Therefore, it is possible to accurately determine the end of steel tapping with less slag outflow.

〔Example〕

Specific examples of the method of the present invention will be described in detail below.

The present inventors used the following converter equipment to perform slab extraction detection according to the method of the present invention during steel tapping, and determined whether steel tapping had been completed.

First, to explain the above converter equipment, as shown in Fig. 1, the converter (2) has a trunnion ring (7) provided on the outer periphery of the furnace body connected to the rotating shaft of a tilting device (not shown). It is supported by itself and can tilt 360'. A tapping port (20) is provided on the upper side wall of the converter (2), and the converter self-molten steel (3) can flow out through the molten steel passageway (21) of the tapping port (20) when the furnace body is tilted. It looks like this. In the drawing, the top of the converter self-melting steel (3) is covered with a slab (4). On the other hand, a ladle (8) is provided below the converter equipment, and is capable of receiving tapped molten steel (3).

The ladle (8) is placed on a trolley (not shown),
Once the molten steel (3) is charged, it will be transported from the converter equipment to the casting equipment.

In such a converter equipment, after the converter refining is completed, in-furnace melting 1! When (3) was tapped into the ladle (8), slab outflow detection was performed using the method of the present invention, which will be described in detail below.

That is, after the blowing is completed, the furnace body is tilted toward the tapping port (20), and when the tilt angle reaches 80°, the tilting is stopped. With this tilting, tapping begins, and at that time, as shown in FIG. 1, a refractory for preventing slag entrainment (1) was suspended on the hot water surface directly above the tapping port (20). The refractory (1)
may be made of any material as long as it can withstand the temperature of molten steel, and may have any shape as long as it can entrain slag. This refractory (1) prevents the slag (4) from being drawn into the molten steel (3) even if a vortex is generated toward the tapping port (20).

During this tapping process, the above-mentioned method of detecting slab outflow using the difference in magnetic permeability between molten #4 (3) and slag (4) was carried out, and the passage of slag (4) was detected. By the way, tapping was stopped, the furnace body was stood upright, and the ladle (8) was pulled out.

Figure 2 shows the voltage peak value during tapping when the above slag detection method was implemented.
The axis shows the voltage peak value during tapping and is graphed.

In the figure, white circles represent results obtained by the conventional method, and triangles represent results obtained by the present invention.

As is clear from the figure, according to the method of the present invention, even if the number of taps exceeds 50, the voltage peak value during tapping can be stably suppressed to 3 V or less, and the slag outflow can be controlled accurately and This made it possible to make early decisions. As a result, the thickness of the slag was stably kept at a low level, and unexpected slag removal work could be reduced.

〔Effect of the invention〕

According to the method of the present invention described in detail above, it is possible to prevent slag entrainment due to the generation of vortices during lectures, and therefore accurate and early judgment of slag outflow is possible until the end of the number of taps. This makes it possible to stably keep the slag thickness low.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing equipment for implementing an embodiment of the present invention, and Fig. 2 is a graph showing the relationship between the number of taps and the peak voltage during tapping when the present invention method and the conventional method are implemented. Figure, Figure 3 (
a) and (b) are explanatory diagrams showing the principle of a method for detecting slab outflow during tapping from a converter using the difference in magnetic permeability between molten steel and slag. An oscillographic diagram showing an example of the detection signal waveform in the range, Figure 5 shows the number of tapping points 9
It is an oscillographic diagram showing six detection signal waveforms. In the figure, (1) is refractory, (2) is converter, and (3) is molten steel. (4) shows the slag, (5) shows the primary coil, (6) shows the secondary coil, (7) shows the trunnion ring, and (8) shows the ladle. Fig. 1 Fig. 2 Number of steel taps (dan) 1, Hei electromotive force Lt (V)

Claims (1)

[Claims] Converter tapping is characterized by suspending refractories on the surface of the hot water directly above the tap during tapping, in order to detect the outflow of slag during tapping in the converter using the difference in magnetic permeability between molten steel and slag. Mouth slag outflow detection method.