JPS58116961A - Discharging method of molten metal - Google Patents

Abstract

PURPOSE:To minimize the amt. of the residual molten steel in the end period of casting and to improve yield considerably by forming the stagnating area of molten steel in a vessel for molten metal around the discharging hole of said vessel including said hole and making the stagnating area deeper than the limit of slag inclusion into the molten steel. CONSTITUTION:A tundish 2 is provided with a discharging hole 8 and a discharging nozzle 9, and is formed with a recessed part 10. The part 10 is made deeper than the limit value (t) of slag inclusion of the tundish to be used normally. When molten steel 3 is charged through a charging pipe 12 into the tundish 2, the flow of the molten steel is formed in a flat part 11 and the molten steel 3 creates a stagnating state in the part 10, then even if slag 4 is layered, the limit (t) is maintained and the inclusion of slag is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to minimizing the amount of molten metal remaining in a molten metal container such as a tundish or ladle at the end of casting, thereby greatly improving the yield during casting. There's something about it.

The shape of a tundish, which is commonly used in conventional continuous casting of molten steel, has a flat bottom surface, where an injection pipe for molten steel is located, and a spout pipe at the other end, which allows the flow of molten steel from the injection pipe to the spout pipe. It has been formed, poured into a mold, and cast.

At the end of continuous casting using such a tundish, as the amount of molten steel decreases, there is a strong possibility that slag and heat insulating material floating on the surface of the molten steel will be caught up in the injected molten steel. For example, when maintaining the depth of residual molten steel in the tundish at 100 IIm, the remaining amount at 250t/cast is 2t, 8
Although the remaining amount of 2t was measured at 0t/caat, there was still a large risk of slag and heat insulating material getting caught.

On the other hand, continuous casting equipment tends to be larger due to the demand for improved productivity, and the problem of increased residual molten steel is becoming noticeable. Furthermore, with the diversification of required steel types, the need for small-lot casting is increasing, and countermeasures are desired.

In other words, as production of multiple steel types and smaller lots progresses, 250t/ca
For example, when casting of ST is in the direction of 80t/cast, as mentioned above, there is 2t of remaining metal for both 250t and 80, so the yield for 250t is 99.2%, but for 80t the yield is 99.2%. If this happens, it will drop to 97.5%, which will become a big problem.

Furthermore, recently there has been a strong demand for manufacturing clean steel with few non-metallic inclusions, and for example, a method for manufacturing clean steel has been proposed in Japanese Patent Publication No. 52-36085, but the present invention solves the above-mentioned problems. The gist of this is to flatten the bottom of a molten metal container such as a tundish or ladle used when casting molten metal to form a molten steel flow, and to form a stagnation area for molten steel near the pouring hole. The molten metal pouring method is characterized in that the molten metal remaining in the container at the end of casting is reduced by making the retention area deeper than the slag entrainment limit t in the molten steel, and further The bottom of a molten metal container such as a tundish or ladle used when casting molten metal is flattened to form a molten steel flow, a molten steel retention area is formed near the pouring hole, and the molten steel retention area is used as a slag for the molten steel. The molten metal pouring method is characterized in that the molten metal is made deeper than the entrainment limit t, and the molten metal remaining in the container is reduced by adjusting the flow rate of molten steel in the pouring hole at the end of casting.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a schematic diagram of a tundish to which the method of the present invention is applied. In the figure, a tamp 1 and a casing 2 are provided with a pouring hole 8 and a pouring nozzle 9, and a concave portion 10 is formed.

The concave portion 10 is made deeper than the slag entrainment limit value (1) of a commonly used tundish.

That is, in the present invention, the area where a certain required molten steel head is required is narrowed down to the vicinity including the pouring hole, and the shape of this area is made to have a deeper container depth to reduce the amount of remaining molten steel.

Therefore, in the present invention, when the molten steel is poured into the tundish 2 through the 3-car injection pipe 12, a molten steel flow is formed in the flat part 11, and necessary inclusions are floated and captured. In this case, the molten steel 3 forms a stagnation state in the concave part IO, and even if the slag 4 is thickened in layers, the slag entrainment limit t is reached.
is maintained, and no slag entrainment occurs.

According to experiments, the slag entrainment limit is as shown in Figure 2.

The horizontal axis indicates the outflow velocity per cross-sectional area of the pouring nozzle. The slag entrainment limit is greatly affected by the outflow speed, and when 4t/NR of molten steel is flown out from a nozzle with a diameter of 80 mm, the outflow speed is 800t/m7.
/Mjl, the required depth is 10011E or more.

Another embodiment of the invention is shown in FIGS. 3 and 4. FIG. 3 shows an example in which a strut horn (-5) is installed directly above the molten steel pouring hole, 6D, and FIG. 4 shows an example in which a baffle plate 13 is installed at the tip of the arm 6.

That is, by providing a flow rate adjustment mechanism such as a stopper directly above the molten steel spout, as the molten steel head becomes smaller, it is easy to reduce the flow rate so as not to entrain surface slag, heat insulating material, etc.

The principle of the method of restricting the flow rate with a stopper or the like is to lower the limit of slag entrainment by suppressing the outflow speed, as shown in FIG. 2 described above.

Furthermore, it is practical to install a baffle plate directly above the molten steel spout, since it improves the grooved surface shape of the molten steel when it is not installed, and prevents surface slag, heat insulating material, etc. from getting caught up in the baffle plate.

The principle of the baffle plate method is to suppress the apparent outflow speed as described above by dispersing the influence of the outflow speed from just above the spout to the surrounding area.

Furthermore, FIG. 5 shows an example in which a porous refractory material 7 is embedded in the periphery of the pouring hole 8. That is, by installing a gas blowing device in the vicinity of the molten metal outlet and blowing an inert gas such as Ar into the molten steel in the concave mold, the amount of remaining molten metal can be further reduced.

The pressure of inert gas injection, the area of the blown refractory, etc. can be determined based on the injection hole size and tundish scale.

Next, Table 1 shows an example in which the method of the present invention was compared with the conventional method for 250t/cast and 80t/cat.

Table 1 It is clear that the method of the present invention significantly improves yield. Figure 6 shows the defective rate of ultrasonic flaw detection for cast slabs. As is clear from the drawings, it is clear that according to the method of the present invention, even if the amount of remaining molten steel is reduced, the defective rate is low.

[Brief explanation of the drawing]

FIG. 1(,) is a cross-sectional front view of the present invention, FIG. 1(b) is a plan view of FIG. 1(a), FIG. 2 is a graph of the slag entrainment limit and outflow velocity, and FIGS. FIG. 5 is a detailed explanatory diagram of the present invention, and FIG. 6 is a graph of the defective rate of ultrasonic flaw detection and the amount of remaining molten steel. 2... Tundish 3... Molten steel 9... Injection nozzle 10... Concave part 11... Flat part Hayabusa 6vJ Remaining brick 4 scale Uoη)

Claims (1)

[Claims] 1. A tundish used when casting molten metal;
By flattening the bottom of a molten metal container such as a ladle to form a molten steel flow, forming a stagnation area for molten steel near the pouring hole, and making the stagnation area deeper than the limit t for slag entrainment into molten steel. ,
A method for pouring molten metal, comprising reducing the amount of molten metal remaining in the container at the end of casting. 2. Flatten the bottom of a molten metal container such as a tundish or ladle used when casting molten metal to form a molten steel flow, form a molten steel retention area near the pouring hole, and make the molten steel retention area In addition to deepening the slag entrainment limit t,
A method for pouring molten metal, which comprises reducing the amount of molten metal remaining in the container by adjusting the flow rate of molten steel in a pouring hole at the end of casting. 3. The molten metal pouring method according to claim 2, wherein a stopper is provided in the molten metal pouring hole to adjust the flow rate of the molten steel. 4. The molten metal pouring method according to claim 2, wherein the molten steel flow rate is adjusted by blowing inert gas from the periphery of the molten metal pouring hole.