JP4102332B2 - Ladle pouring method in continuous casting equipment - Google Patents

Description

  The present invention relates to a method for pouring molten metal from a ladle into a tundish without mixing slag in a high-throughput continuous casting facility.

  In a facility for continuously casting molten metal such as molten steel, molten metal is poured from a ladle into a tundish through a long nozzle, and continuous casting is performed while pouring from the tundish into a mold. Since the slag floats on the upper surface of the molten metal in the ladle, a part of the slag also flows into the tundish at the end of the pouring and becomes an inclusion, which deteriorates the quality of the slab. For this reason, it is desirable to detect the outflow of slag at the end of pouring and stop the pouring by operating the sliding nozzle.

  In Patent Document 1, when the amount of remaining hot water in the ladle reaches a predetermined value, the sliding nozzle is stopped to open and close, and the pressure of the inert gas sealed in the long nozzle that leads the molten steel from the ladle to the tundish is set. A method of detecting and detecting slag outflow by a change in pressure is disclosed. However, since the molten steel temperature is lowered at the end of injection for detecting slag, there is a problem that a hole for injecting an inert gas into the long nozzle is clogged, and the frequency at which measurement becomes impossible increases. In addition, since the hole was made in the long nozzle, the strength was lowered, and the long nozzle could be broken during pouring, leading to deterioration in quality and productivity.

  Patent Document 2 discloses a method of attaching a vibration accelerometer to a long nozzle support device for pouring molten metal into a tundish, and detecting slag outflow from the attenuation rate of the vibration output. This method uses the fact that the vibration output is also rapidly attenuated as a result of the specific gravity of the fluid flowing out abruptly decreasing simultaneously with the slag outflow. However, this method can detect accurately during ultra-low throughput casting with an average injection flow rate of 2 t / min or less, but it cannot detect slag outflow accurately when the average injection flow becomes large.

In other words, when the average injected flow exceeds 2 t / min, the hunting of vibration output gradually increases due to the generation of vortices, and if slag outflow determination is performed only with the damping rate of vibration output, it is determined that slag outflow is very early. As a result, a large amount of molten metal remains in the ladle and the yield deteriorates. In particular, when the average injected flow is high throughput exceeding 6 t / min, the output is hardly attenuated even when the slag flows out, and it is completely impossible to detect the slag outflow by using this vibration output attenuation factor. It was possible.
JP 2003-33852 A Japanese Patent No. 3138581

  The present invention solves the above-mentioned conventional problems, accurately detects the outflow of slag even in the case of a high-throughput continuous casting facility in which the average injection flow exceeds 6 t / min, and is applied to the tundish at the end of pouring. It was made to provide a ladle pouring method in a continuous casting facility that can prevent the inflow of slag, eliminate the deterioration of the quality of the slab due to inclusions, and reduce the amount of hot water in the ladle to improve the yield. It is a thing.

In order to solve the above problems, the present invention is to pour molten metal from a ladle of a high-throughput continuous casting facility having an average injection flow rate of 6.0 t / min or more into a tundish through a long nozzle. In doing so, the ladle pouring amount is reduced to 5.0 t / min or less, and the presence or absence of slag outflow is detected from the attenuation rate of the vibration output of the vibration accelerometer attached to the long nozzle support device. The slag outflow detection method calculates the average value of the output of the vibration accelerometer when the amount of remaining hot water in the ladle falls below a predetermined value. Then, a value smaller than the average value is determined as a slag outflow threshold value, and the slag outflow is judged when the sampling output falls below the threshold value for an arbitrary number of consecutive times.

According to the ladle pouring method in the continuous casting equipment of the present invention, the ladle pouring amount from the ladle to the tundish is reduced from 6.0 t / min to 5.0 t / min at the end of pouring. After squeezing, measure the damping rate of the vibration output of the vibration accelerometer attached to the long nozzle support device. Although hunting occurs when the ladle pouring amount is reduced in this way, macroscopically, the vibration output gradually attenuates as soon as the slag outflow begins, so it is possible to detect slag outflow by setting the threshold appropriately. It becomes. In order to appropriately set the threshold value, in the ladle pouring method in the continuous casting equipment of the present invention , the average value of the output of the vibration accelerometer when the amount of remaining hot water in the ladle becomes a predetermined value or less, A method is adopted in which a value smaller than the average value is determined as the slag outflow threshold. Then, when the sampling output continuously falls below this threshold for an arbitrary number of times, it is determined that slag has flowed out, and pouring is terminated. For this reason, according to the present invention, even in the case of a high-throughput continuous casting facility with an average injection flow rate of 6.0 t / min or more , the outflow of slag is accurately detected, and the inflow of slag into the tundish at the end of pouring is performed. It was possible to prevent the deterioration of slab quality due to inclusions, and to reduce the amount of hot water in the ladle to improve the yield .

Preferred embodiments of the present invention are shown below.
In FIG. 1, 1 is a ladle, 2 is a tundish, and molten metal such as molten steel in the ladle 1 is poured into the tundish 2 through a long nozzle 3. The present invention is intended for a high-throughput continuous casting facility having an average injection flow rate of 6.0 t / min or more.

  A vibration accelerometer 5 is attached to a long nozzle support device 4 that supports the long nozzle 3. The vibration accelerometer 5 is preferably attached to the end of the arm of the long nozzle support device 4 opposite to the long nozzle 3 in order to avoid the influence of high heat. A commercially available product can be used as the vibration accelerometer 5.

  At the time of pouring from the ladle 1, vibration is caused by the molten metal flowing inside the long nozzle 3, so the vibration accelerometer 5 detects this vibration and sends it to the signal converter 7 through the relay box 6. The signal converter 7 converts this into an electric signal and inputs it to the sequencer 8. The vibration output is displayed on the display screen 9 so that the operator can see it. As will be described below, the sequencer 8 determines the presence or absence of slag outflow from the change in the damping rate of the vibration output. When it is determined that slag outflow occurs, the sequencer 8 issues a command to the hydraulic drive system 10 to operate the sliding nozzle 11 and pour hot water. You can stop.

  When the average injection flow rate is 2.0 t / min or less, as shown in FIG. 2, the vibration output of the vibration accelerometer 5 abruptly attenuates simultaneously with the slag outflow. This is because the specific gravity of slag is smaller than that of molten metal. For this reason, slag outflow can be accurately detected from the attenuation rate of the vibration output. However, in a high throughput state where the average injection flow rate is 6.0 t / min or more, the vibration output is not attenuated even if slag is caught at the end of pouring as shown in FIG. It is assumed that this is because a strong vortex is generated in the ladle 1 and an air tower is also generated. For this reason, as described above, when the average injected flow has a high throughput exceeding 6 t / min, the slag outflow cannot be detected by the method using the attenuation rate of the vibration output.

  Therefore, in the present invention, the pouring amount of the ladle from the ladle to the tundish is reduced from the high throughput state of 6.0 t / min or more to 5.0 t / min or less at the end of the pouring. When the ladle pouring amount is reduced to 5.0 t / min or less in this way, the vibration output attenuates macroscopically as shown in FIG. Therefore, the vibration output average value of the vibration accelerometer when the amount of remaining hot water in the ladle becomes equal to or less than a predetermined value is set to A, and a value obtained by multiplying this by an appropriate attenuation factor is set to B. It is possible to detect slag outflow by a method of determining that slag outflow occurs when the value falls below the threshold. When the slag outflow is detected, the sliding nozzle 11 is closed and pouring is stopped.

However, as described above, when it is determined that the slag flows out when the vibration output first falls below the threshold value, the amount of remaining hot water in the ladle 1 may be large and the yield may be reduced. Therefore, in the present invention, the average value A of the output of the vibration accelerometer when the amount of remaining hot water in the ladle becomes equal to or less than a predetermined value is calculated, and a value B smaller than the average value is determined as the slag outflow threshold. A method is adopted in which slag outflow is determined when the sampled vibration output continuously falls below this threshold for an arbitrary number of times .

  For example, if it is determined that the slag has flown out when the threshold value is continuously decreased three times, it is determined that the slag has flowed out at a timing T3 surrounded by a circle in the graph of FIG. This is later than the timing T1 when it first falls below the threshold, but because it is the initial stage of slag outflow, the slag inflow to the tundish 2 is effectively suppressed, and moreover than when pouring is terminated at the timing T1. The amount of remaining hot water in the ladle 1 will be greatly reduced.

  Whether to give priority to preventing foreign matter from entering the slab or to yield should be determined according to the quality required for the product to be cast. That is, in the case of strict quality materials, it is preferable to completely suppress slag outflow at the expense of yield by setting the threshold value high and reducing the number of consecutive times. On the other hand, for general materials, the threshold value is set low and the number of continuous times is set to be large so that the amount of hot water in the ladle can be reduced and the yield can be improved.

  Using the high-throughput continuous casting equipment shown in the embodiment, the slag outflow detection experiment was performed under various conditions as shown in Table 1, and the amount of remaining hot water in the ladle and the amount of inflow slag into the tundish were measured. . In Table 1, the slag detection judgment column in the circle indicates that the sensor has detected before the operator, and the cross indicates that the operator has detected slag outflow first.

  Numbers 1 and 2 are comparative examples in which the ladle pouring amount was not reduced at the end of pouring, and the amount of slag flowing into the tundish exceeded 60 kg. Others are examples of the present invention, and when the amount of remaining hot water in the ladle became 3 tons, the amount of pouring of the ladle was reduced. In this embodiment, since the data sampling time is 100 ms, three consecutive times means that the vibration output has fallen below the threshold for 300 ms.

  As apparent from the data in Table 1, according to the embodiment of the present invention, it is possible to detect the slag outflow earlier than the operator and stop the pouring. Moreover, it can be seen that the amount of remaining hot water is smaller than that of the comparative example, and the amount of slag flowing into the tundish is greatly reduced.

It is a perspective view which shows embodiment of this invention. It is a wave form diagram which shows transition of the vibration output in the state whose average injection | pouring flow rate is 2.0 t / min or less. It is a wave form diagram which shows transition of the vibration output in the state whose average injection | pouring flow rate is 6.0 t / min or more. It is a wave form diagram which shows transition of the vibration output in the state which restrict | squeezed the ladle pouring amount to 5.0 t / min or less.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ladle 2 Tundish 3 Long nozzle 4 Long nozzle support device 5 Vibration accelerometer 6 Relay box 7 Signal converter 8 Sequencer 9 Display screen 10 Hydraulic drive system 11 Sliding nozzle

Claims (1)

When pouring molten metal from a ladle of a high-throughput continuous casting facility with an average injection flow rate of 6.0 t / min or more into a tundish through a long nozzle, the ladle pouring rate is 5.0 t / min or less. A ladle in a continuous casting facility that detects the presence or absence of slag outflow from the vibration output attenuation rate of the vibration accelerometer attached to the long nozzle support device, and stops pouring when slag outflow is detected. A pouring method , and
The detection method of slag outflow is
Calculate the average value of the output of the vibration accelerometer when the amount of remaining hot water in the ladle falls below the predetermined value, determine a value smaller than the average value as the slag outflow threshold, and continue sampling output any number of times. How to judge slag outflow when it is below the threshold
A ladle pouring method in a continuous casting facility.

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