JPS61150757A - Initial heating method of molten steel in intermediate vessel in continuous casting of steel - Google Patents

Abstract

PURPOSE:To maintain a casting temp. at a prescribed temp. from the beginning of casting and to execute stable casting without nozzle clogging by providing a molten metal well chamber of small volume in the intermediate vessel for receiving a molten steel from a ladle and heating the same by powerful electromagnetic induction in the initial period of casting. CONSTITUTION:The molten steel 13 from the ladle 2 enters the inside of a tundish 1 and enters the molten metal well chamber 5 through a communicating hole 8 at the bottom end of a tunnel type gate 6. The molten steel is quickly heated by a coil 12 of a powerful electric power channel type induction heater 9 upon rising of the molten steel surface to the level 13a and is made to overflow at the level 13b so as to be poured from the nozzle 4. The molten steel 13 heated quickly up to the prescribed temp. in the chamber 5 of small volume is satisfactorily poured from the beginning without clogging of the nozzle 4. The molten steel is poured always at the optimum temp. by the subsequent heating control by which the stable continuous casting is executed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for heating molten steel in an intermediate vessel in continuous steel casting, and particularly to a method for heating molten steel in a tundish when a large tundish is used. be.

(Prior art 1) Generally, when continuously casting molten steel, the molten steel is transferred from a ladle to a tundish, which is an intermediate container, and is poured into a mold from this tundish. At the initial stage of pouring, heat is radiated to the tundish refractory, The degree of molten steel in the tundish decreases significantly due to heat radiation from the molten metal surface to the atmosphere, etc. This decrease in the temperature of molten steel in the tundish occurs when the ladle is replaced during continuous casting, and due to the final heat of casting, etc. This can also occur if the injection is interrupted.

In order to prevent such a drop in the temperature of the molten steel in the tundish, a method of heating the molten steel in the tundish by electromagnetic induction using a groove-type induction heating device is disclosed in Japanese Patent Application Laid-Open No. 57-1115674.
Disclosed in the issue.

(Problem to be Solved by the Invention) However, when performing electromagnetic induction heating using a groove-type induction heating device, the static pressure of the molten steel injected into the tundish at the initial stage of casting is not high enough. When power is turned on, the pinch force caused by electromagnetic pressure causes the molten steel circuit to break in the narrow groove-shaped molten steel passage of the groove-type induction heating device, making it impossible to supply electricity, making it impossible to supply power stably. There is a problem in that the nozzle is clogged due to a drop in the temperature of the molten steel in the tundish, making stable casting impossible.

Therefore, as a measure to solve the above-mentioned problem at the early stage of casting, it is necessary to increase the static pressure of the molten steel in the tundish in a short period of time at the early stage of casting. For tundishes of 10 tons or less, it is possible to fill the molten steel to the planned level in the tundish in a short time, but for large tundishes of 10 tons or more, it takes too long to fill the tundish to the planned level. By the time the molten steel is filled, the temperature of the molten steel has already begun to drop. Therefore, especially when using a large tundish, it is highly desirable to be able to fill the molten steel to a predetermined level in a short time and perform electromagnetic induction heating.

The use of a large-diameter ladle nozzle was proposed as a way to fill a large tundish with molten steel to the expected level in a short time, but the large materials in the tundish were subject to severe erosion, and during regular pouring, the use of a large ladle nozzle was proposed. There is a problem that the level of molten steel cannot be sufficiently controlled.

(c) Means for Solving Problems) The present invention was developed in view of the above-mentioned problems.1 The present invention provides an initial heating method for molten steel to prevent a drop in temperature of molten steel at the time of pouring due to a large tundish. According to the present invention, in a continuous casting method, the molten steel is transferred from a ladle to an intermediate container, the molten steel is heated by electromagnetic induction to a required casting temperature in the intermediate container, and then poured from the intermediate container into a mold. , a small-volume sump chamber is provided in the intermediate container, the molten steel poured into the intermediate container at the initial stage of casting is filled in the sump chamber, and the molten steel in the sump chamber is heated by electromagnetic induction and cast into a mold. It is characterized by being immersed.

(Function) - According to the present invention, a part of the tundish, for example,
By installing a relatively small reservoir surrounded by a weir and heating the molten steel in the reservoir by electromagnetic induction, it is possible to input high power in a short time even with a conventional normal diameter ladle nozzle. Sufficient static pressure of the molten steel can be obtained, and therefore high electric power can be applied to heat the molten steel to the required casting temperature and stable casting can be performed in a short period of time after the start of injection into the tundish.

(Embodiment) FIGS. 1 and 2 show an example in which a tundish is provided with a water reservoir according to the present invention.

In the drawings, 1 is a tundish, 2 is a ladle, 8 is a ladle nozzle, and 4 is a tundish nozzle. In the example shown, the water reservoir chamber 5 is surrounded by two weirs 6 and 7 and is provided between the ladle nozzle 8 and the tundish nozzle 4 in the tundish 1, and the weir 6 of the ladle nozzle 8 is located at the lower end of the tundish nozzle 8. The weir 7 on the tundish nozzle 4 side is of an overflow type.

The molten steel in the trough chamber 5 is heated by communicating the channel 10 of the groove-type induction heating device 9 into the trough-type induction heating device 9 and energizing the heating filter 12 attached to the iron core 11 of the trough-type induction heating device 9. It is configured as follows.

It is preferable that the volume of the pool chamber 5 is large enough to form a pool of molten steel of 3 to 10 tons, and if it is less than 3 tons, the temperature of the molten steel in the pool chamber will rise more than necessary due to electromagnetic induction heating, resulting in fire resistance. This is undesirable because it increases the wear and tear on the product and at the same time, the rapid agitation of the molten steel causes wholesalers to get caught up in the scum on the surface of the molten steel.

Moreover, if it is more than 10 tons, it is not preferable because the time required for pouring into the molten metal into the molten metal into the molten steel becomes long and at the same time, the molten steel in the molten steel in the molten metal is heated to a uniform temperature and the temperature of the molten steel poured into the mold fluctuates. The sump chamber 5 is preferably located on the upstream side of the tundish nozzle, so that the heated molten steel can be supplied to the mold without any subsequent temperature drop.

Next, an explanation will be given of an operation in which the tundish chamber 5 is provided in the tundish 1 as described above and molten steel is heated in the light period.

The molten steel 18 injected from the ladle 2 through the ladle nozzle 82 is first poured into the tunnel-shaped layer 6 from the droplet in the tundish 1.
It enters the water reservoir chamber 5 through the lower end communication hole 8. After that, when the depth of the steel bath increases and the molten steel surface rises from the tundish bottom to the level shown by the dashed line 18a in FIG. The coil 12 is energized, thereby heating the molten steel in the molten metal sump chamber 5.
This continues until the height of the overflow weir 7 is reached as shown in . The melt 18 then overflows and subsequently flows through the tundish nozzle 4 into the mold (not shown) of the continuous casting machine.

Over 70 - The height of the weir 7 is such that heating with high power starts when the molten steel surface reaches a predetermined level 13a from the bottom of the molten metal sump chamber 5, so the temperature of the molten steel poured into the mold becomes the optimum temperature. It is preferable to adjust the height to obtain a heating time of 800 to 9QQIIll, for example.

A drainage gland 14 is provided at the lower end of the overflow counterfeit weir 7 to prevent molten steel from remaining at the end of casting. The drain hole 14 is closed by a soluble base plug 15.
keep it closed. The soluble base stopper 15 is preferably made of a material such that the discharge hole 14 does not open until the molten steel fills the sump chamber 15, but opens at the end of casting. Alloys can be used, 5 to 1
Select a material that can completely melt in 0 minutes and open the discharge holes 1'' and 4.

Figure 3 shows a comparison of the changes in molten steel temperature in the tundish between the method of the present invention and the conventional method B. In the conventional method B, a tundish with a capacity of 80 tons was used,
As shown in Fig. 8, when the maximum power is applied to the groove type induction heating device after approximately 4 minutes have elapsed since the start of pouring molten steel into the tundish, and aluminium-based steel is cast, the initial casting time as shown by broken MB in Fig. 8. However, according to the method of the present invention, a water reservoir with a capacity of about 5 tons was provided in the tundish, the height of the overflow weir was set to about 800 m, and a groove-type induction heating device 1 with an electric capacity of 2500 kW was installed. Attach the base to the side of the tundish chamber, turn on the maximum power 1 minute after the start of injection into the tundish as shown by to in Figure 4, and turn on the maximum power.
By heating the molten steel in the sump chamber with a power of 2 o o kW, it is possible to prevent the temperature drop at the initial stage of casting and maintain the molten steel temperature almost constant during continuous casting, as shown by the solid line A in Figure 8. did it. Moreover, as a result of repeated tests under the above conditions, as shown in Table 1, not only was it possible to prevent the temperature from decreasing at the initial stage of casting, but the average value was actually increased to +1°C. Table 2 shows the nozzle clogging prevention results. In addition, in FIG. 4, H indicates the depth of molten steel at which the maximum power can be applied.

Table 1 Table 2 (Effects of the Invention) According to the present invention, it is possible to prevent the temperature of molten steel in the tundish from decreasing in the initial stage of casting, and the clogging of the molten steel in the tundish and the phenomenon of nozzle clogging due to solidification are eliminated. , it is possible to achieve the effect that continuous casting can be performed stably.

[Brief explanation of drawings]

Fig. 1 is a schematic vertical cross-sectional view of a tundish showing an embodiment of the method of the present invention; Fig. 2 is a diagrammatic plan view showing a part of the tundish shown in Fig. 1 as a section; Fig. 8 is an inside of the tundish; Graph showing changes in molten steel temperature. Figure 4 is a graph showing the relationship between molten steel height and injection time in a large tundish.

Claims (1)

[Claims] 1. In a continuous casting method in which molten steel is transferred from a ladle to an intermediate container, the molten steel is heated by electromagnetic induction to the required casting temperature in the intermediate container, and then poured from the intermediate container into a mold, a volume of the molten steel is transferred to the intermediate container. A steel manufacturing method characterized in that a small trough chamber is provided, the molten steel poured into an intermediate container is filled in the trough chamber, and the molten steel in the trough chamber is heated by electromagnetic induction and cast into a mold. Initial heating method for molten steel in an intermediate vessel in continuous casting.