JPS5813455A - Method and device for stopping charging - Google Patents

Abstract

PURPOSE:To prevent the degradation in the quality of an ingot owing to inclusion of slag in the stage of receiving molten metal in a vessel by detecting the oscillations of the vessel which increase temporarily upon inflow of the slag and stopping the charging electrically, automatically and quickly. CONSTITUTION:In the stage of charging the molten metal 3 on which slag 16 is afloat into a tundisch 4 through a ladle nozzle 2 from a ladle 1, the oscillations of the tundish 4 increase temporarily upon inflow of the slag 16 into the tundish 4. The oscillations are detected with an oscillation detector 7 mounted to the tundish 4 and are outputted as a signal. After the output is amplified with an amplifier 8, it is converted to oscillation components with a coverter 9, and further the oscillation components by external factors are removed with a filter circuit 10. The output thereof is passed through a smoothing circuit 11a and an output device 11, and is outputted as the smoothed signal to an operator 12. Here, the signal that receives the oscillation signal output higher than a reference value is outputted to an output device 13 for stopping of charging, by which a charging controller 14 and a machine 15 for opening or closing the ladle nozzle is operated to close the nozzle 2.

Description

[Detailed Description of the Invention] This invention, when pouring molten metal such as molten steel into a predetermined container, accurately stops pouring in order to minimize the amount of slag flowing into the container. The present invention relates to a method for carrying out the method and an apparatus for carrying out the method.

For example, when continuously casting slabs, billets, etc., molten metal such as molten steel is poured from a ladle into a -H tundish, and then supplied from the tundish to the mold. ``When the slag in the ladle flows into the tundish, if it is cast as is, the slag may be mixed in as inclusions in the resulting slab, and the quality of the slab may be significantly impaired. If the slag that has flowed into the tundish comes into contact with the inner wall of the tundish and the contact frequency is high, problems such as adversely affecting the life of the refractory that forms the inner wall of the tundish arise. As a method of stopping the pouring to ensure that the amount of slag is as small as possible, the operator constantly visually observes the flow of molten steel flowing out of the ladle, and the brightness and color of the flow of molten steel as the slag flows out. A method was used to determine whether slag was flowing out based on changes in the slag and stop pouring.

On the other hand, when continuously casting high-grade steel, for example, the molten steel flow from the ladle to the tundish is sealed in a non-oxidizing atmosphere with an inert gas, or non-oxidizing injection is generally performed using a long nozzle. However, in such cases, if the above-mentioned method of visual inspection by the operator is used to stop pouring, changes in the brightness and light color of the molten steel flow cannot be detected accurately or at all. At the end of pouring, when slag begins to flow out of the ladle, it is necessary to temporarily stop sealing the molten steel flow with inert gas, or to raise the long nozzle from the tundish and expose the molten steel flow to air. Oxidation may occur. Furthermore, if the seal is not temporarily stopped using an inert gas or the long nozzle is pulled up, the slag will flow into the tundish and then float on top of the molten steel in the kundish. Since the inflow has to be judged frequently, the amount of slag inflow increases, and in any case, with the conventional method, there is a considerable risk that the quality of the slab will deteriorate. Furthermore, when pouring molten steel in a non-oxidized state as described above, even though the molten steel flow cannot be visually observed, it is necessary to pour the molten steel with some amount of molten steel remaining in the ladle to ensure safety. If the tundish is stopped, slag will not flow into the tundish, but on the other hand, the entire amount of molten steel in the ladle cannot be poured into the tundish, so there is a problem that the yield will be extremely poor.

On the other hand, in continuous casting, C is added to the molten steel flow to prevent inclusions.
In some cases, ferroalloy such as A-81 is poured in. However, if white smoke is generated when the ferroalloy is poured, the flow of molten steel cannot be visually observed, so the conventional method described above does not allow pouring. Either it is not possible to accurately determine the point at which to stop pouring, or it is necessary to stop adding ferroalloy at the end of the pouring process.In either case, there is a problem in maintaining the quality of the slab.

Furthermore, the conventional method in which workers visually observe the flow of molten steel can lead to incorrect judgments and delays in stopping the pouring operation, which also restricts workers and impedes labor-saving and automation. There were problems such as.

Therefore, the inventors of the present invention have already proposed a pouring stop control method that can solve the above-mentioned problems. For example, when pouring molten steel from a ladle into a tundish, the density of molten steel (approximately 7 tons) and the density of slag (2 to 3 t/m
), the vibration state of the kundish is attenuated as the slag begins to flow out. If the value decreases significantly (for example, if the amplitude decreases and the output value decreases) (5
), it is determined that slag has leaked and the pouring is stopped.

Since this pouring stop control method can be performed electrically and automatically, the pouring stop operation can be performed more quickly than the conventional method described above, thereby reducing the amount of slag flowing into containers such as Tandifushi 1. However, in this method, the vibration of the container, which is the basis of the signal to stop pouring, is caused by the fact that slag has already flowed into the container. Therefore, since the above method is based on the premise that slag flows into a container such as a tundish, the amount of slag flowing in should be smaller than in the conventional method. However, it is necessary to allow some slag to flow into the container, and there is still room for improvement in this respect.

In view of the above circumstances, this invention further improves the above-mentioned pouring stop control method that has already been proposed, and stops pouring so as to further reduce the amount of slag flowing into a container such as a tundish (6). The object of the present invention is to provide a method for stopping pouring of molten metal and a device for implementing the method.

This invention will be explained in detail below.

Figure 1 (4) shows the detection of the amplitude of the actual vibration that occurs in the inflow container when molten steel is injected from a container such as a ladle (hereinafter referred to as the outflow container) to a container such as a tundish (hereinafter referred to as the inflow container). It is clear from this diagram that the vibration amplitude of the inflow vessel may temporarily decrease due to disturbance factors such as building vibration even during molten steel injection, so the above-mentioned If the method described above is implemented based on such a detection signal, the slag must be determined to have flowed out after Δ seconds from the time when the slag begins to flow out, that is, when the vibration amplitude begins to stabilize at a predetermined low level. However, there is a slight time delay between the outflow of the slag and the stop of pouring. In order to more accurately stop the pouring using the method described above, the signal was passed through a filter circuit to remove disturbance factors such as vibrations in the building, and the results shown in Figure 1 were obtained. Obtained.

However, with the vibration amplitude shown in Fig. 1 (B), although the degree of vibration reduction that occurs temporarily during molten steel pouring is small, it is difficult to determine whether slag has flowed out or whether to stop pouring based on such a detection signal. As in the case described above, this must be carried out at the point when the amplitude begins to stabilize at a predetermined low level, which is not sufficient for the purpose of accurately stopping pouring. Therefore, the inventors of this invention repeatedly conducted experiments and examined the obtained data in detail, and found that the vibration amplitude of the inflow container temporarily increases at the same time as the slag begins to flow out into the inflow container. I found it. Figure 1 (Q is a diagram showing the result of passing the signal obtained by electrically detecting the amplitude of the vibration of the inflow container through a filter circuit and processing the signal to further smooth it. Q
As shown in , it is clearly seen that the vibration amplitude of the inflow container, ,ll'i, temporarily increases as soon as the slag begins to flow out into the inflow container.

This invention was made based on the above knowledge, and detects the phenomenon in which the vibration of the inflow container temporarily increases when slag starts flowing out, and stops pouring based on the output signal at that point. Therefore, according to the present invention, pouring can be stopped after the slag has flowed out to the inflow container to some extent and before the vibration amplitude of the inflow container stabilizes at a predetermined low level. The amount of slag flowing out can be made smaller than ever before.

Next, embodiments of the invention will be described.

First, a device for carrying out the method of the present invention, that is, an embodiment of the invention described second in the claims, will be described as a second embodiment.
To explain with reference to the drawings, Fig. 2 is a schematic diagram showing one embodiment of the invention, in which a ladle 1 serving as a first container is used to collect molten steel through a ladle nozzle 2 provided at its bottom. is injected into a tundish 4 serving as a second container, and the tundish 4 is configured to supply the molten steel 3 therein into the mold 6 through the immersion nozzle 5.
A vibration detector 7 is attached to the tandish 4 to detect its vibrations. An amplifier 8 and a converter 9 are sequentially connected to the vibration detector 7, and after the signal output from the vibration detector 7 is amplified by the amplifier 8, the signal is transferred to the converter 9. The signal is converted into a displacement component, a vibration velocity component, or a vibration acceleration component, and the signal converted into any of the above components is input to the filter circuit 10 at the next stage. This filter circuit 10 is in a state where disturbance factors such as building vibrations are included in the entire frequency band, so in order to cut out these disturbance factors and extract only the vibrations associated with pouring as much as possible. The frequency band and frequency to be selected by this filter circuit 1o are determined by comparing the power spectrum distribution during molten steel injection and the power spectrum distribution during slag outflow, and select a frequency band in which the power distribution differs. and frequency, and these should be selected depending on the vibration characteristics based on the structure, material, etc. of the tundish 4.

An output device 11 having a smoothing circuit 11m is connected to the filter circuit 1o, and outputs a signal corresponding to the vibration of the frequency selected by the filter circuit 10 among the vibrations of the filter circuit 10. It is designed to smooth and output. The reason why the smoothing circuit 11m was provided here is that minute changes occur in the vibration of Tandisi-4 even during molten steel injection, so if the signal is not particularly smoothed, vibration changes due to slag outflow can be suppressed during molten steel injection. It takes time to distinguish from vibration changes, and there is a risk of a time delay in determining slag outflow.Therefore, the vibration detection signal during molten steel injection is made as stable as possible, and the vibration (signal) at the time of slag outflow is minimized. This is to clarify the temporary increase and thereby eliminate the time delay in determining slag outflow.

A computing unit 12 and a pouring stop output unit 13 are sequentially connected to the output unit 11. This computing unit 12 is
The reference value of the rate of change of the II output value obtained by detecting the vibration of the tundish 4 during pouring of molten steel was determined manually and
and a function to compare and calculate the rate of change of the signal input from the output device 11 with the reference value described in 1'IJ. When the ratio to the rate of change exceeds a certain value, a signal is output to the pouring stop output device 13. The pouring stop output device 13 outputs a pouring stop signal to the pouring control device 14 when a signal is input from the computing device 12, and as a result, the ladle nozzle opening/closing device 15 operates to close the ladle nozzle. 2 is fully closed.

Next, the operation of the apparatus configured as described above, that is, the method of stopping pouring of metal according to the present invention will be explained.

First, the rate of change yI of the vibration detection signal output value obtained during pouring of molten steel is input and set as a reference value in the calculator 12. In this state, the ladle nozzle 2 is opened and the molten steel 3 is
When the liquid is poured from the ladle 1 into the tundish 4, the tundish 4 vibrates, and the vibration is detected by the vibration detector 7. The Ω output signal from the vibration detector 7 is amplified by an amplifier 8, and then converted into a signal with a predetermined vibration component by a gate converter 9. Then, a predetermined frequency band of the output signal is converted into a signal with a predetermined vibration component. A frequency signal is selected by the filter circuit 10, and a signal corresponding to the selected frequency band or frequency oscillation is smoothed from the output device 11 and input to the arithmetic unit 12. Fig. 3 (4) is a diagram showing the output signal of the output device 11 when the frequency band is set to 30 Hz or higher, and Fig. 3 (B) is a diagram showing the rate of change of the output signal during injection of molten steel. The output signal of the output device 11 is almost constant as shown in the range of symbol M in FIG. 3 (4), and its rate of change is at most 10 as shown as the range of symbol M in It is about 1. Therefore, the rate of change of the signal input to the calculator 12 during injection of molten steel is the reference value y!, which is input and set in advance. Since the ratio of these rates of change becomes less than 1, and as a result, the arithmetic unit 12 does not output a signal, the ladle nozzle 2 is particularly unlikely to perform a closing operation.

Then, when the slag 16 in the ladle 1 begins to flow out to the tundish 4, the vibration of the tundish 4 temporarily increases, and the output signal from the output device 11 is accordingly changed to P as shown in FIG. 3 (4). , and at the same time, the rate of change also temporarily increases as shown by the symbol PI in Figure 3 (B) (13), and as a result, the rate of change becomes lower than the reference value. Shi is also dog-like, and since the ratio of these is greater than 1,
The computing unit 12 outputs a signal, and in response, the pouring stop output device 13 outputs a pouring stop signal to the pouring control device 14, and as a result, the ladle nozzle opening/closing device 15 operates to close the ladle nozzle. When the nozzle 2 is fully closed, pouring is stopped. Therefore, since the ladle nozzle 2 is completely closed almost simultaneously with the outflow of the slag, the amount of the slag 16 flowing into the tundish 4 can be suppressed to an extremely small amount.

Note that during pouring, the opening of the ladle nozzle 2 may be increased or decreased, but in such cases, the vibration state of the tundish 4 may change due to changes in the flow rate of molten steel. The output value of the vibration detection signal fluctuates greatly, so in order to distinguish it from the fluctuation of the output value at the time of slag outflow and prevent malfunction, the output value is stabilized when changing the opening degree of the ladle nozzle 2. for a few seconds (2
(on the order of seconds), it is preferable to turn off the vibration detection/calculation system and prevent it from functioning. In addition, in the above device, (14) is the reference value, in addition to the rate of change of the vibration output value during molten steel injection, the rate of change y2 of the output value when slag flows out, and the output when the ladle nozzle is fully closed. It is also possible to adopt the value 2, where the rate of change of the input value to the arithmetic unit 12 and the rate of change of the output value when slag flows out is y! When the ratio of the slag 16 to the molten metal becomes 1 or more, it may be determined that the slag has flowed out and the pouring may be stopped. Alternatively, if the slag 16 has flowed out, the input value to the calculator 12 indicates that the ladle nozzle is fully closed. Therefore, when the input value to the calculator 12 becomes, for example, 1.12 or less, it may be determined that slag has flowed out and the pouring may be stopped.

In any case, according to the present invention, pouring can be quickly stopped at the same time as the slag flows out, or immediately after that. According to experiments conducted by the inventors of the present invention, visual inspection The conventional method also has O, S on average.
It is possible to perform the pouring stop operation about 2 centimeters earlier, and it is still 0% faster on average than the previously proposed method based on vibration amplitude reduction.
．． The pouring operation could be stopped approximately 77 seconds earlier.

In addition, in the above embodiment, from the ladle 1 to the ladle 5-4
Although the case where the molten steel 3 is poured into the container is explained, the present invention is not limited to the above-mentioned embodiment, but can also be applied to the case where molten steel is poured from a suitable container to another container, and the fluid to be injected is the molten steel and the molten steel. Not limited to slag, but also other materials with different specific gravity2
More than one kind of fluid may be mixed, and even in that case, only one fluid can be injected into an appropriate container by controlling as described above. Furthermore, the present invention can be applied to the case where solids such as powders or granules having different densities are dropped and stored in a predetermined container, in which case,
Furthermore, since the vibration of the container changes greatly when the object to be dropped or contained changes, it is sufficient to stop the object from falling at that point, and in this way, the falling or contained objects can be sorted by density or particle size. Can be classified and □.

′::.

As is clear from the above explanation, the method and method for stopping pouring of this invention
According to the device, as soon as slag begins to flow out, it detects a temporary increase in vibration occurring in an inflow container such as a tundish, and stops pouring based on the detected value. , or immediately after that, the pouring can be quickly stopped, and therefore the amount of slag flowing out can be made smaller than ever before. Furthermore, since this invention does not require the operator to visually observe the pouring flow, the pouring flow can be completely sealed in a non-oxidizing atmosphere until the pouring is finished, and at the end of pouring, Ca alloy etc. Therefore, during continuous casting, for example, the amount of slag flowing out is small, and the quality of the slab can be improved.Furthermore, vibration detection and pouring stop operation based on it can be performed electrically. It has the effect of being done quickly and automatically.

[Brief explanation of the drawing]

FIG. 1 (4) is a diagram showing a vibration waveform obtained by detecting the vibration of the tandish, and FIG. 1 (B) is a diagram showing the vibration waveform obtained by detecting the vibration of the tandish and applying the detection signal to a filter circuit. Figure 3 (C) is a diagram showing the vibration level obtained by further processing the signal (17), Figure 2 is a schematic diagram showing an embodiment of the device of the present invention, and Figure 3 (4) is a diagram showing the vibration level obtained by processing the signal (17). A diagram showing the output signal of the output device when the frequency is higher than Hz, and (B) of the same diagram is a diagram showing the rate of change. 1... Ladle, 2... Tundish, 3... Molten steel, 7... Vibration detector, 8... Amplifier, 9... Converter, 10... Filter circuit, 11 &...・Smoothing circuit, 12... Arithmetic unit, 13... Molten pouring stop output device, 14
...Pouring control machine, 16...Slag. Applicant Kawasaki Steel Co., Ltd. Agent Patent attorney Taketo Toyota (and 1 other person) (18)

Claims (2)

[Claims] (1) When pouring molten metal into a second container from a first container such as a ladle with slag floating on the surface of the molten metal, vibrations of the second container accompanying the pouring are detected, and A temporary increase in the detected value as slag begins to flow out of the second container is detected, and pouring into the second container is stopped based on the detection result. Method. (2) A vibration detector that detects vibrations of a container into which molten metal is to be poured, and a converter that is connected to this vibration detector via an amplifier and converts the output signal of the vibration detector into a predetermined vibration component. , a filter circuit that removes vibration components caused by disturbances from among the converted vibration components, a smoothing circuit that smoothes the output signal from this filter circuit, and an output value of the smoothed signal and a preset value. a computing unit that compares the calculated reference value with a reference value and outputs a signal when the difference exceeds a certain value; and a pouring stop output unit that outputs a stop signal based on the output signal of this computing unit. A molten metal pouring stop device comprising: a molten metal pouring control device for stopping pouring of molten metal into the container according to a stop signal outputted from a molten metal pouring stop output device.