JPH02268950A - Method for controlling channeling flow of molten steel in continuous casting mold - Google Patents

Abstract

PURPOSE:To attain stable manufacture of a cast strip without any defect by supporting a submerged nozzle fitted to lower part in a tundish as possible to incline toward right and left sides through a fulcrum at the upper end part and controlling the inclining angle of the above nozzle so as to suppress channeling flow in a mold. CONSTITUTION:Temps. detected with plural thermocouples 9 embedded into the right and left inner walls in the mold 2 are monitored with a temp. monitoring device 10. When the temp. difference detected with the thermocouples 9 at the right and left sides exceeds the prescribed value, it is decided that the channeling flow develops. At the time of being decided, command is transmitted to a submerged nozzle inclining control device 16 from the monitoring device 10, and by driving the hydraulic cylinder 12, the submerged nozzle 14 is inclined. By repeating the above operation until the temp. difference of the right and left inner walls in the mold 2 becomes less than the prescribed value, the main flow 6a of the molten steel is equally distributed into discharge holes 5 at right and left sides to suppress the channeling flow of the molten steel 6. Further, in the case of using an eddy current type molten metal surface meter 17, when difference of the molten steel levels according to the development of rising 6b of the molten steel surface exceeds the prescribed value, it is decided that the channeling flow develops, the channeling flow is suppressed with the operation followed to the above.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is directed to a continuous casting mold in which the drift of molten steel injected into the mold from a submerged nozzle attached to a tundish via a sliding nozzle can be suppressed. This invention relates to a molten steel drift control method.

<Prior art> Conventionally, in continuous casting, as shown in FIG. The melt is injected into the mold 2 through a pair of left and right discharge holes 5 provided in the lower side wall! A polarized flow may occur in which the flow velocity of 116 differs between the left and right sides. 1 shows a hydraulic cylinder that controls the opening degree of the sliding nozzle 3.

Is this drifting caused by controlling the injection amount of molten steel 6? ■
Therefore, since the opening of the sliding nozzle 3 is narrowed, the main flow 6a of molten steel falling through the immersion nozzle 4 becomes uneven on the left and right sides due to its structure. This is because the flow rate of one side of the 1116 injected into the mold 2 is high and the flow rate of the other side is low.

Furthermore, alumina or the like adheres to and grows in the discharge hole 5 of the immersion nozzle 4, and the opening area of the discharge hole 5 becomes unbalanced between the left and right sides, which often promotes uneven flow.

As mentioned above, on the side where the flow velocity of the molten steel injected from the discharge hole 5 of the immersion nozzle 4 is high, the collision force against the inner wall surface of the mold 2 is large, and the molten steel is divided upward and downward along the inner wall surface with great force. Become. In this way, the upward flow causes a bulge 6b in the mold 2, which prevents the powder 7 on the molten metal surface from being supplied to the inner wall surface of the mold 2, resulting in insufficient supply and uneven formation of the solidified shell 8. This causes wrinkles and cracks in the cast slab. Further, since the lower flow reaches deep into the molten steel 6, it prevents nonmetallic inclusions from floating and causes nonmetallic inclusion defects in the slab.

On the other hand, when the flow rate of molten steel discharged from the discharge hole 5 is low or when the flow rate of molten steel discharged suddenly changes, stagnation is likely to occur in the flow of molten steel in the discharge hole 5, and the nozzle may be clogged due to the adhesion of deoxidation products such as alumina. This makes it difficult to carry out multiple series castings, which not only impairs productivity but also increases the cost of refractories.

In this way, once the drifting occurs, it is very difficult to eliminate it, and when the drift becomes severe, the mold 2
Operational troubles such as breakouts due to re-melting of the solidified shell 8 formed within the mold 2 and defects on the slab surface due to changes in the scene within the mold 2 are likely to occur, and in the worst case, casting will have to be stopped.

As mentioned above, if there is a difference in the flow velocity of molten steel discharged from the left and right discharge holes 5 due to the drifting flow generated in the Imagin nozzle 4, this will not only hinder the continuous casting operation but also cause deterioration of the quality of the slab. do not have.

Therefore, in order to prevent the molten steel from drifting in the immersion nozzle during squeeze injection of molten steel using a sliding gate in continuous casting, Japanese Utility Model Publication No. 56-95465 proposes that an electric current [11s! A technique has been disclosed in which a stirring device is attached to apply a stirring force in the opposite direction to the drift of the molten steel flow to offset the drift.

However, in the prior art disclosed in the above-mentioned publication, the molten steel flowing down through the refractory of the immersion nozzle is agitated by electric current, so the device is large-scale and equipment costs are high. Further, a protective means is required to deal with heat radiation from the meniscus of the molten steel in the mold, and there are problems in that continuous use in the process is extremely difficult and leads to an increase in power consumption.

Furthermore, Japanese Patent Application Laid-Open No. 63-295056 proposes a method in which a plate-like member is provided vertically inside a submerged nozzle and the inner hole is partitioned to equalize the discharge flow. On the one hand, it has the disadvantage that it is prone to melting damage and has a short lifespan, but on the other hand, it also has the disadvantage that deposits tend to grow on the plate-shaped member, which tends to cause blockage.

<Problems to be Solved by the Invention> The present invention solves the above-mentioned problems of the prior art, controls the opening degree of the sliding nozzle provided at the bottom of the tundish, and provides a pair of left and right discharge holes provided on the side wall of the lower end of the immersion nozzle. It is an object of the present invention to provide a method for injecting molten steel into a mold in continuous casting, which can balance the flow rate of molten steel injected from the left and right discharge ports when injecting molten steel into the mold via the molten steel.

<Means for Solving the Problems> To achieve the above object, the present invention provides a method for controlling the drift of molten steel in a continuous vE casting mold, in which an immersion nozzle attached to a tundish via a sliding nozzle is connected via a fulcrum at the upper end. The immersion nozzle is supported so as to be movable left and right, and the tilting angle of the immersion nozzle is controlled so as to suppress drifting of flow within the mold.

The drift in the mold can be detected, for example, by the temperature difference between the short sides of the mold on the left and right sides of the immersion nozzle, or by the difference in the level of molten steel in the mold.

As described above, in the present invention, the immersion nozzle is moved from side to side by one turn via the fulcrum at the upper end so as to suppress the difference in the level of molten steel in the mold between the left and right sides of the immersion nozzle or the difference in the temperature between the inner walls of the mold between the left and right sides. The main flow of molten steel injected through the sliding nozzle flows down the center of the inner hole of the submerged nozzle. Therefore, the main flow of molten steel is evenly distributed to the left and right discharge holes, and drifting of the molten steel injected into the mold is suppressed.

<Example> Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2. Components in the figure that are the same as those in FIG. 5 are given the same reference numerals to simplify the explanation.

Thermocouples 9 are embedded in the inner walls of the left and right short sides bordering the immersion nozzle 4 of the mold 2. The temperature detected by the thermocouples 9 is monitored by a temperature monitoring device 10, and the temperature of the left and right inner walls of the mold 2 is monitored. Due to the difference, that is, the heat removal imbalance, non-uniform flow, that is, drift, of the melt w46 injected from the left and right discharge holes 5 is detected. The temperature measurement value becomes higher on the short side inner wall where the flow velocity is higher due to the drift because there is more fresh molten steel flow than on the other side.

The immersion nozzle 4 is supported so as to be movable left and right by a support shaft 11 provided at a fulcrum at the upper end. That is, the immersion nozzle 4 and the holding portion 4a form a sliding surface through concave and convex arc contact with each other.

A hydraulic cylinder 12 is connected to the upper end of the immersed nozzle 4, and the immersed nozzle 4 operates the hydraulic cylinder 12 by switching the ftTa1l valve 13 to adjust the tilt angle of the immersed nozzle 4.

14 is an oil tank, and the hydraulic pump 1 is connected from the oil tank 14.
Hydraulic pressure is applied to the hydraulic cylinder 12 via 5.

The immersion nozzle (IJ'Ivj control device 16 controls the tilting angle of the immersion nozzle 4 by switching the solenoid valve 13 and operating the hydraulic cylinder 12 in response to a command from the temperature monitoring device IO based on the temperature condition detected by the thermocouple 9. .

In the above case, the thermocouple 9 was embedded in the inner wall of the mold 2 to detect the drift of the molten steel injected from the discharge hole 5 of the immersion nozzle 4. A hot water level gauge is disposed above the surface near the inner wall of the mold 2 to detect the swell 6b of the surface caused by the drift of the molten steel injected from the discharge hole, and based on this, the immersion nozzle 4 is moved. You can also do it like this.

Next, the operation of the present invention will be described. The temperature detected by a plurality of thermocouples 9 embedded in the left and right inner walls of the mold 2 is monitored by a temperature monitoring device. When the submerged nozzle 4 is in a vertical position as shown in FIG.
Since the opening of the sliding nozzle 3 is injected in a constricted state, the main flow 6a of molten steel falling in the immersion nozzle 4 becomes uneven on the left and right, and as a result, the molten steel 6 injected into the mold 2 from the left and right discharge holes 5 is It is unavoidable that the flow is biased, with one side having a high flow rate and the other side having a low flow rate.

Therefore, in the present invention, such drifting of molten steel in the mold 2 is monitored by the temperature monitoring device 10, and when the difference in temperature detected by the left and right thermocouples 9 exceeds a predetermined threshold, it is determined that drifting has occurred. When it is determined that a drift has occurred, the temperature monitoring device 10 issues a command to the submerged nozzle tilting control device 16, switches the solenoid valve 13, operates the hydraulic cylinder 12, and moves the submerged nozzle 4 around 1 as shown in FIG. make it move. θ indicates the tilt angle of the immersion nozzle 4.

When the above-mentioned operation is repeated at a certain timing until the detected temperature difference between the left and right inner walls of the mold 2 becomes below the threshold value, the main flow of molten steel 6a falling in the immersion nozzle 2 flows down the center of the inner hole. As a result, the main flow of molten steel 6a is evenly distributed to the left and right discharge holes 5, and the drift of the molten steel 86 injected into the mold 2 is suppressed.

On the other hand, a vortex level gauge 1 is installed above the hot water surface of the mold 2.
7, when the scene level difference detected by the left and right eddy current type water level gauges 17 due to the occurrence of the scene swell 6b exceeds a predetermined threshold, it is determined that a drift has occurred, and according to the above case. The filling angle of the immersion nozzle 4 is controlled, and the molten steel injected from the left and right discharge holes 5 is Aim to equalize the flow rate.

Figure 3 shows the relationship between the tilting angle (θ) of the immersed nozzle and the drift index of the molten steel injection flow over time.
It can be seen that the number of floors can be controlled with good responsiveness.

Furthermore, Figure 4 shows a comparison of the magnitude of the drift index and the frequency of inclusions in the conventional method in which the immersion nozzle is not tilted and in the present invention method in which the immersion nozzle is tilted. It can be seen that not only can the drift index be significantly reduced compared to the conventional method, but also the effect of reducing inclusions in the slab is large.

The method for detecting drifting was explained by detecting the mold wall temperature and the molten steel level on the left and right sides of the immersion nozzle.
For example, it may be determined from the difference in surface temperature of the molten steel on the left and right sides of the immersion nozzle.In short, any means that can detect the drift in the mold can be used.

<Effects of the Invention> As explained above, according to the present invention, drifting of the molten steel injected into the mold through the discharge hole of the immersion nozzle can be easily prevented by restricting injection through the sliding nozzle provided at the lower part of the tundish. I can do it. As a result, not only can the number of nozzle clogging of the immersion nozzle be halved, making it possible to carry out multiple castings, but also it is possible to stably produce slabs without defects.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, Fig. 2 is a partial longitudinal cross-sectional view showing the implementation status of the present invention, Fig. 3 is a graph showing the correspondence between the drift index and the tilt angle, and Fig. 4 5 is a graph comparing the drift index and the frequency of inclusions between the conventional method and the method of the present invention, and FIG. 5 is a partial longitudinal sectional view showing the conventional example. l... Tandy 3... Slidey 5... Discharge hole, 7... Powder, 9... Thermocouple, Sheet, Gunno 2... Mold, Zulu, 4... Immersion nozzle, 6. ... Molten steel, 8... Solidified shell, lO... Temperature monitoring device, 11... Support shaft, 12... Hydraulic cylinder, 13... Solenoid valve, 14... Oil tank, 15...・Hydraulic pump, 16... Immersion nozzle tilting control 7g device, 17... Whirlpool type scene needle, 1 day...
hydraulic cylinder.

Claims (1)

[Scope of Claims] 1. When injecting molten steel into a mold from a submerged nozzle attached to a tundish via a sliding nozzle, the submerged nozzle is supported so as to be tiltable left and right via a fulcrum at the upper end; A method for controlling drifting of molten steel in a continuous casting mold, comprising controlling the tilt angle of the immersion nozzle so as to suppress drifting of the flow in the mold. 2. When injecting molten steel into the mold from the immersion nozzle attached to the tundish via the sliding nozzle, detect the temperature of the inner walls of the left and right molds facing the discharge hole of the immersion nozzle, and insert the immersion nozzle into the upper end. A method for controlling drifting of molten steel in a continuous casting mold, characterized in that the immersion nozzle is supported so as to be tiltable left and right via a fulcrum, and the tilting angle of the immersion nozzle is controlled so as to suppress a temperature difference between the inner walls of the mold. 3. Instead of detecting the inner wall temperature of the mold on the left and right sides of the immersion nozzle, the level of molten steel in the molds on the left and right sides of the immersion nozzle is detected, and the tilt angle of the immersion nozzle is controlled so as to suppress the difference in the level of molten steel in the mold. Method described.