JPH0890216A - Method for preventing inclusion of slag at the time of flowing out molten metal - Google Patents

Abstract

PURPOSE: To restrain the inclusion of slag and to improve the yield of molten metal by reducing molten metal flow-out rate into a receiving vessel from the point of time when the molten metal weighed value in the vessel reaches a prescribed value and further, reducing the flow-out accompanied with the reduction of the molten metal. CONSTITUTION: At the time of detecting the variation of the molten metal wt. with a load cell 9, on which the molten metal remaining quantity in a molten metal holding vessel 1 reaches the prescribed value, the flow rate adjusting device (SN) 5 starts an opening degree contracting movement to reduce the flow-out of the receiving vessel 3 for molten metal. Probability entrapping the slag into the molten metal near a flow-out hole of the SN 5 is reduced by reducing the flow-out rate. The SN 5 continues the flow-out of the molten metal with the preset little quantity of the molten metal with an SN positional detector 8 and finally, the SN 5 is fully opened to complete the flow-out. Since the flow-out is not stopped on the way in such a way, the inclusion of the slag is restrained and the yield of the molten metal can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transferring molten metal such as molten steel from a molten metal container to another receiving container and preventing slag from entering the receiving container when flowing out.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting slag inclusion in molten metal flowing out, for example, Japanese Patent Laid-Open No. 59-6528.
As shown in 0, the electromagnetic coil attached to the outer periphery of the metal runner tube has a plurality of windings wound around the protection tube coaxially with the protection tube, so that slag appears in the runner. There is a method of detecting. Also, JP-A-61-26
In 2454, when the molten metal is flown from the pouring container to the receiving container by the dipping nozzle, the internal pressure of the dipping nozzle is continuously measured, and the change in the pressure is detected to accurately grasp the outflow of the slag and melt the molten metal. A method of controlling metal runoff is described.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
It has the following problems. When the molten metal flows out from the lower part of the molten metal container to the receiving container through the immersion nozzle, the slag, which has a lower specific gravity than the molten metal, floats on the surface of the molten metal in the container, but near the end of the outflow. Due to the vortex flow formed near the outlet of the immersion nozzle, the slag is caught in the vortex, mixes in the molten metal, and flows out from the nozzle. For this reason, the slag detector detects the mixed slag before the outflow of the molten metal is completely completed, and the outflow amount adjusting device such as a sliding nozzle or a stopper performs a closing operation by this signal to prevent the outflow of the molten metal. Stop and finish the work. Therefore, a part of the molten metal remains in the receiving container without flowing out, and the yield of the molten metal flowing into the receiving container is reduced.

In order to improve the outflow yield of the molten metal flowing out to the receiving container, a method of completely closing the outflow amount adjusting device after a lapse of a certain time from the time when the slag detector detects the slag, and ending the outflow, Alternatively, a method of lowering the slag detection sensitivity of the slag detector may be considered, but in both cases, the slag flowing out to the receiving container increases, so that the cleanliness of the molten metal deteriorates.

Further, in order to suppress the generation of vortices generated near the outlet of the immersion nozzle in the final stage of the outflow in the container, a method of changing the immersion nozzle from an ordinary circular cross section to an elliptical cross section and flowing out the molten metal is also considered. To be However, in this method, the durability of the dipping nozzle is lowered, and it is difficult to use it for a long time, and therefore it is difficult to use it industrially.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the gist thereof is: 1) Molten metal receiving container into another molten metal receiving container. When flowing out, the amount of residual molten metal in the molten metal storage container is measured, and when the measured value reaches a predetermined value, the opening of the outflow amount adjusting device of the storage container is narrowed down, and the molten metal to the receiving container is reduced. The amount of slag mixed in the molten metal flowing out of the container is reduced as much as possible,
Further, the molten metal flows out to the receiving container, and the opening degree of the outflow amount adjusting device is further narrowed down as the remaining amount of the molten metal decreases, so that the molten metal flows out. Prevention method.

2) The slag at the time of molten metal outflow according to 1), wherein the opening of the flow rate adjusting device is narrowed down by a timer regardless of the measured value of the amount of residual molten metal in the molten metal container. There is a mixing prevention method.

[0008]

[Function] Usually, in the molten metal outflow work from the metal container to the receiving container, a flow rate adjusting device (hereinafter referred to as a sliding nozzle (SN)) is operated to narrow the opening at the beginning of the outflow and adjust the opening at the end. It is wide open and the amount of molten metal flowing out is constantly supplied to the receiving container. This is to prevent the molten metal static pressure in the container from decreasing and the outflow amount to decrease with the decrease in the amount of molten metal in the container. In such an operation, since the SN is almost fully opened at the final stage of the outflow, as described above, the slag floating on the surface of the molten metal has a large chance of being caught in the molten metal at the time of outflow, which hinders the cleanliness of the molten metal. There is.

Therefore, in the present invention, after flowing out a predetermined amount of molten metal contrary to normal working conditions, it is operated in the direction of narrowing the SN to prevent the outflow of slag as much as possible. Can deal with manufacturing such as. In the present invention, when the SN is narrowed down, the amount of molten metal remaining in the molten metal container is measured by some means (for example, a load cell), the remaining amount reaches a predetermined amount, and there is a risk that slag entrapment may occur. From the point when

[0010] At this point, it is possible to set sufficiently piled up from the past record of slag outflow by the slag detector. Also,
In addition, it is possible to set by a timer based on the amount of molten metal stored in the storage container, the amount of outflow per hour to the storage container, and the like. Furthermore, the operation of further narrowing down the SN opening as the remaining amount of the molten metal in the molten metal container can be reduced can be preset based on the past slag mixing record as described above.

The present invention will be described in detail below with reference to the drawings. FIG. 1 shows an example of an outflow control device for preventing the mixing of slag according to the present invention, which comprises a molten metal container 1, a dipping nozzle 2 and a receiving container 3, and a receiving container at the lower part of the container. It is composed of SN5 for adjusting and controlling the outflow amount of the molten metal flowing out to the container. S
The slag detector 4, the slag detector control panel 6, the process computer 7, and the SN position detector 8 are connected to N5,
The SN opening is controlled by a signal from the process computer 7. On the other hand, a load cell 9 is installed in the molten metal container 1, measures the remaining amount of molten metal, and sends the value to the process computer 7. The slag detector 4 in this example is for obtaining a signal when the SN is finally closed and the outflow of the molten metal is completely stopped.

A method for controlling the slag mixture by using the above apparatus will be described. 2 and 3 show an example of the flow of outflow control according to the present invention, and FIG. 4 is an SN opening operation diagram in the case of FIG. When the remaining amount of molten metal in the molten metal container reaches a predetermined set amount (α),
When the weight change is detected by the load cell installed in the molten metal container, the operation of narrowing down the SN opening is started,
Reduces the flow of molten metal into the receiving vessel. The reduced outflow reduces the opportunity for slag to become entrained in the molten metal near the SN outlet. In this case, the SN continues the outflow of the molten metal with a small opening (θ = X) set in advance by using the opening position detector.

The determination of the SN narrowing-down start time may be performed by an opening setting method that narrows the SN to a predetermined opening after a fixed time (T1) by a timer, not by the load cell of the molten metal container. This operation is repeated to finally close the SN when the outflow to the receiving container is completed. In this way, the outflow of the molten metal is not stopped midway, so that there is no solidification of the molten metal due to the temperature decrease, the possibility of clogging the SN is low, and the outflow of the molten metal can be carried out more reliably. The molten metal outflow control for preventing the mixing of these slags is performed according to the kind of the molten metal flowing out and the outflow rate.
It is also possible to change the pattern of set values such as the opening degree of N and the time of the timer.

[0014]

[Example] From a molten steel container having a capacity of 300 t to a capacity of 70 t
The apparatus for injecting the molten steel into the mold through the molten steel receiving container was used to control the amount of outflow into the receiving container, and 10 t of molten steel was injected from the molten steel receiving container to the molten steel receiving capacity molten steel receiving container per minute. As the slag sensor, the same device is used for both the inventive example and the comparative example, and the slag detection threshold of the slag sensor is 1
It was set to 0%. Table 1 shows the results of carrying out the present invention together with comparative examples.

[0015]

[Table 1]

In Examples 1 to 3, the initial SN narrowing time was set to the residual molten steel amount measurement value of 30 t in the molten steel container, and the SN opening at that time was set to 50% of the fully opened state. Further, in the second embodiment, when the calculated residual molten steel amount in the container is 20 t, S
Performed throttle control with N opening of 30% (total number of throttles 2
)), In Example 3, the calculated residual molten steel amount in the container is 20 t, 1
At 0 t, the SN opening was controlled to be 30% and 20% respectively (throttle number: 3 times).

In Examples 4 to 6, the first SN narrowing time was set to 27 minutes by starting the injection from the molten steel container to the receiving container or by a timer. Further, in the fifth embodiment, the SN opening is controlled to be 30% after 28 minutes by the injection start or the timer (throttle number is 2 times in total), and in the third embodiment, the SN opening is controlled by the injection start or the timer after 28 minutes and 29 minutes. Aperture control was performed with the apertures of 30% and 20% (three times of total reduction).

Table 1 also shows a comparison of the residual molten steel in the molten steel storage container according to the present invention and the comparative example and the amount of slag flowing into the receiving container. By the method according to the present invention, the amount of molten steel remaining in the storage container and the amount of slag flowing into the receiving container were reduced as compared with the comparative example, the yield of the molten steel was improved, and the cleanliness of the molten steel in the receiving container was also improved.

[0019]

As described above, according to the method for preventing slag mixing when molten metal flows out according to the present invention, when the molten metal flows out from the molten metal container to the receiving container, the molten metal in the receiving container The amount of slag that flows into the container can be suppressed, and the molten metal remaining in the storage container can be reduced, so that the molten metal yield is improved and the cleanliness of the molten metal in the receiving container is good. Becomes

[Brief description of drawings]

FIG. 1 shows a component device according to the invention.

FIG. 2 is an outflow control flowchart according to the present invention.

FIG. 3 is another outflow control flowchart according to the present invention.

FIG. 4 is a diagram showing an operation of an SN opening when the outflow control of FIG. 2 is performed.

[Explanation of symbols]

 1 Molten Metal Storage Container 2 Immersion Nozzle 3 Storage Container 4 Slag Detector 5 Flow Rate Regulator (SN) 6 Slag Sensor Control Panel 7 Process Computer 8 SN Position Detector 9 Load Cell θ SN Opening T1 Setting Time

Claims (2)

[Claims] 1. When the molten metal flows out of the molten metal container into another molten metal receiving container, the amount of residual molten metal in the molten metal container is measured, and the measured value reaches a predetermined value. From that point on, the opening of the outflow adjusting device of the storage container is narrowed down, the outflow amount of the molten metal into the receiving container is reduced, and the slag mixed in the outflowing molten metal from the storage container is suppressed and received as much as possible. Continuation of molten metal into the container, further narrowing the opening of the outflow amount adjusting device as the residual amount of molten metal becomes smaller, the molten metal is flowed out, the method for preventing slag mixing at the time of molten metal outflow . 2. The slag at the time of molten metal outflow according to claim 1, wherein the opening of the flow rate adjusting device is narrowed down by a timer regardless of the magnitude of the measured value of the amount of residual molten metal in the molten metal container. How to prevent contamination.