JPS61262454A - Detection of slag intrusion into molten steel flow - Google Patents

Abstract

PURPOSE:To discriminate exactly the inflow of slag into a molten steel in the stage of discharging the molten steel by an immersion nozzle in the bottom of a primary vessel into a secondary vessel by measuring continuously the internal pressure of the immersion nozzle and detecting the pressure change thereof. CONSTITUTION:The slag 1 and molten steel 2 in a molten steel pan 3 are discharged through a pan nozzle 4 and a long nozzle 5 for sealing into a tundish 6. The change of the internal pressure in the long nozzle 5 for sealing is continuously measured by a pressure transmitter 8 via a pressure take-out piping 7. The time when the negative pressure level decreases to some extent or below or when the negative pressure level decreases sharply is discriminated as the slag outflow. The inflow of the slag is thus discriminated.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention detects the outflow of slag from the primary container at the end of the flow when molten steel flows down from the primary container to the secondary container, and stops the flow. This invention relates to a slag outflow detection method for minimizing the amount of slag flowing into a secondary container.

(Prior art) Conventional technology for detecting slag intrusion into a molten steel flow includes automatic detection methods such as vibration measurement and impedance measurement, in addition to the commonly used visual judgment method. For example, as a vibration measurement method, “Tetsu to Hagane v+ '81-8847
An example of this is described in ``Development of Detection Device for RCC/Ladle Slag Outflow,'' and an impedance measurement method is described in 11 Iron and Steel n '80-5813 ``Slag Outflow Prevention Device When Using a Ladle Seal Nozzle.'' It is stated in. However, the visual judgment method has the drawback that it is subject to variations due to individual differences among judges, and that judgment cannot be made in cases where the injection part cannot be seen, such as in a case where the injection part is not visible.

In addition, the vibration measurement method and the impedance measurement method require the sensor to be placed close to the downstream side, which causes problems in maintainability and operability, and has the disadvantage that the equipment is large-scale and expensive.

(Objective of the Invention) The present invention is a very single device that eliminates problems in sensor maintainability and operability when molten steel flows down from a primary container to a secondary container, and detects slag outflow at the end of the flow. This is a slag outflow detection method that is automated and minimizes the amount of slag outflow.

(Structure and operation of the invention) The present invention is a detection method that achieves the above-mentioned purpose, and its gist is that the molten steel in the primary container is transferred to the secondary molten steel by a submerged nozzle connected to the bottom outlet of the primary molten steel container. This method of detecting slag intrusion into a molten steel flow is characterized in that the internal pressure of the immersion nozzle is continuously measured when the molten steel flows out into a container, and the inflow of slag is determined based on the pressure change.

Below, tandy, steel, etc. from the molten steel ladle in continuous steel casting
The present invention will be described in detail by taking as an example the detection of slag outflow to a pipe.

FIG. 1 shows the state of use of the present invention, where 1 is a slag;
2 is molten steel, 3 is a molten steel ladle, 4 is a ladle nozzle, 5 is a long nozzle for sealing, 6 is a tundish, 7 is a pressure extraction pipe, and 8 is a pressure transmitter. Generally, when transferring molten steel from the ladle 3 to the tundish 16, in order to prevent re-oxidation and nitrification, the downstream flow of molten steel from the ladle is shielded from the atmosphere, and the four-ring nozzle 5 is crimped onto the ladle nozzle 4, as shown in this figure. The structure is such that the inside is insulated with inert gas.
The present invention takes out the pressure pipe 7 from such a long sealing nozzle 5, continuously measures the static pressure of the inert gas inside the nozzle, and detects the outflow of slag from the pressure level and pressure fluctuation. It is the law.

FIG. 2 is an enlarged view of the long nozzle section, and numeral 9 is downstream of the molten steel flow. The molten steel flowing down from the stripe through the ladle nozzle 4 entrains inert gas at the surface of the molten metal in the 10-minute nozzle 5 due to its kinetic energy, and is carried away with it to the outside of the nozzle. Therefore, while the molten steel is flowing down, the gas pressure inside the long nozzle 5 is always maintained at negative pressure. However, when slag flows downstream, the density of the flowing liquid decreases, the viscosity increases, and the flow rate itself decreases, so the flowing kinetic energy decreases and the amount of inert gas involved also decreases. This reduces the degree of negative pressure of the gas within the long nozzle 5, and this is detected via the pressure pipe 7. In other words, the pressure piping 7 is installed on the wall of the long nozzle that is not directly exposed to the molten steel flow.While measuring the gas pressure inside the nozzle, when the negative pressure level falls below a certain level, or when the negative pressure level suddenly drops. This is detected as a slag outflow. Although it depends on the sealing performance of 4 and 5, one criterion for determining slag contamination is when the negative pressure level decreases by about 100 m of water column. This standard is appropriately set based on the conditions of outflow from the molten steel outflow device.

(Example) When the slag outflow detection according to the present invention was applied to an actual machine using the method shown in Fig. 1, the gas pressure inside the long nozzle was approximately 2 seconds earlier than the conventional visual judgment. The amount of slag fluctuates by about 1,100 m + water column, and by stopping the flow of molten steel from the primary vessel at this point, the amount of slag flowing out can be significantly reduced.

Furthermore, when measuring the gas pressure inside the nozzle using such a method, if metal is inserted into the pressure piping, the pressure piping will be blocked and pressure measurement will become impossible. In order to avoid this, a four-lase plug 10 may be attached to the tip of the pressure pipe as shown in FIG. 4, and good detection can be achieved.

(Effects of the Invention) As described above, the present invention is a detection method using a very simple device that measures the gas pressure inside the long nozzle and detects the outflow of slag from the pressure level and pressure fluctuation.
It can be easily incorporated into actual equipment without any major equipment modification. Furthermore, it is not affected by metal adhesion to the inner wall of the nozzle or cleaning of the inside of the nozzle when replacing the pan, and is an excellent method that can stably automate the detection of slag outflow throughout the entire cast.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view showing an embodiment of the present invention.
FIG. 3 is a cross-sectional view of the pressure measuring section same as above, FIG. 3 is a diagram showing an example of the result of slag outflow detection applied to an actual machine, and FIG. 4 is an enlarged cross-sectional view of the pressure extraction section of FIG. 3. 1... Slag 2... Molten steel 3... Molten steel ladle 4... Ladle nozzle 5... Long tongue for seal/L/6... Tundish 7... Pressure extraction piping 8... Pressure Transmitter 9... Molten steel flow downstream 10... For preventing metal intrusion? -Las plug 11...Inert gas spray pipe. Figure 1 Figure 2

Claims (1)

[Claims] When the molten steel in the primary container flows out into the secondary molten steel container by the immersion nozzle connected to the bottom outflow part of the primary molten steel container, the internal pressure of the immersion nozzle is continuously measured, and from the pressure change, A method for detecting slag intrusion into a molten steel flow, characterized by determining slag inflow.