JPH0327847A - Method for supplying molten metal in continuous casting for cast strip - Google Patents

Abstract

PURPOSE:To promote industrialization of continuous casting of a cast strip by discharging molten metal in the direction toward one pair of short wall side plates and casting from a submerged nozzle and supplying treatment for preventing metal solidification and sticking in the submerged nozzle. CONSTITUTION:The submerged nozzle is inserted into casting space constituting with one pair of circulating bodies set as mutually facing and one pair of the short wall side plates positioned at both side edge parts thereof to supply the molten metal, Then, the molten metal is discharged in the direction toward one pair of the short wall side plates respectively through discharging holes 8a, 8b from the submerged nozzle. Further, the molten metal is discharged in the direction toward casting through a discharging hole 9. Further, the treatment for preventing the solidification of molten metal in the submerged nozzle or sticking of solidified metal to the submerged nozzle, is applied. By this method, various conditions indispensable for the stable casting at the time of supplying the molten metal can be satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for supplying molten metal to a casting space in continuous casting of thin slabs for directly manufacturing thin slabs from molten metal.

(Prior Art) Recently, various types of continuous casting machines have been proposed that continuously produce thin slabs such as sheet bars directly from molten metal (the following will be explained using the example of "molten steel"). . For example, belt casters, block casters, twin roll casters, etc. are shown in FIG. 4 as a typical example.

The exemplary synchronous belt caster is of the constriction type and includes a plurality of guide wheels 3B, 3b, 3c, respectively, while maintaining a gap to hold the cast material, such as molten steel or solidified shell, over a predetermined distance. A metal belt supports a pair of long side surfaces arranged opposite to each other and moves circularly through the metal belt}1.2, and supports a short side surface that is in close contact near each side edge between the two metal belts. The upper and lower concave short side plates 4 and 5 are used to confine the casting space on four sides.

When molten steel is supplied into the casting space from the nozzle 6, the molten steel that has come into contact with the metal belts 1 and 2 cooled by the cooling pads 7a and 7b is drawn downward while forming a solidified shell.

In order to enable oxidation-free injection into the casting space, it is advantageous to use a nozzle of the type that can be immersed into the molten steel. When injecting molten steel with an immersion nozzle, the following (
If conditions 1) to (3) are satisfied, stable casting can be performed continuously.

(1) To increase the speed of the molten steel flow toward the short side plate and to inhibit the formation or development of a solidified shell on the short side plate.

(2) Slow down the flow of molten steel from the nozzle in the casting direction to prevent the solidified shell that has formed in the narrowed part of the belt from being destroyed or remelted, and to prevent inclusions from being carried into this part.

(3) To avoid stagnation of molten steel in the vicinity of the meniscus by generating a molten steel flow near the meniscus, and to prevent the solidified shell from adhering to the nozzle and from becoming too thick.

Now, regarding the shape of the immersion nozzle, especially the discharge port, in order to satisfy the above conditions, optimization studies are being conducted using water model experiments and computer-based three-dimensional flow analysis, but until all conditions are satisfied. has not yet been reached.

For example, Japanese Patent Laid-Open No. 62-296944 discloses an example of a submerged nozzle used in general continuous casting, in which the molten steel discharge ports are opened in three directions: the direction of the mold and the pouring direction.

(Problem to be Solved by the Invention) If this immersion nozzle is applied to a belt caster, the above conditions (1) and (2) can be satisfied, but
When the flow rate of molten steel in the direction of the short side of the mold is made faster and the flow rate of molten steel in the pouring direction is made slower, the molten steel flowing towards the short side eventually flows in this direction to supplement the flow in the pouring direction, and therefore the molten steel flow at the meniscus disappears and the molten steel flows into the meniscus. Since stagnation occurs, condition (3) cannot be satisfied.

Therefore, the object of the present invention is to prevent the solidified shell from adhering to the nozzle and to prevent the melting process without controlling the flow of molten steel, thereby achieving stable continuous casting.

(Means for Solving the Problems) This invention provides a pair of circulating bodies disposed opposite each other that circulate while maintaining a gap for holding molten metal over a certain distance, and both sides of the circulating bodies. In order to supply molten metal by inserting an immersion nozzle into a casting space formed by a pair of short-side side plates with a narrowed middle part and a pair of upper-wide-lower concave shapes located at the edges, from the immersion nozzle, 1. Thin casting characterized by discharging molten metal in the direction toward the pair of short side plates and in the casting direction, and further taking measures to avoid solidification of the molten metal in the immersion nozzle or adhesion of the solidified metal to the immersion nozzle. This is a method of supplying molten metal in continuous casting of pieces.

Now, FIG. 1 shows a submerged nozzle that is directly used in this invention. As shown in Figure (a), the shape is such that the thickness is gradually thinned from top to bottom to correspond to the concave-shaped gap between the metal belts constituting the mold. Oval discharge ports 8a, 8 are provided on opposite sides of the short side plates of the mold.
b, respectively, and a slit-shaped discharge port 9 is opened in the lower end face in the casting direction. In addition, a chuck-type heating device 1 is placed in the middle of the nozzle, which also serves as a support for the nozzle.
0 is fixed and the area around the nozzle is heated to prevent the solidified shell from adhering and elongating.

As a nozzle heating means, a heating element 11 may be embedded in the middle of a similar nozzle, as shown in FIG.

Furthermore, as shown in FIG.
3, and similarly the adhesion of the solidified shell around the nozzle,
And growth may be prevented.

Furthermore, around the nozzle, BN, MoSz, CaCO3
It is also advantageous to apply a release material such as.

Of course, it is also possible to use a suitable combination of the above-mentioned means.

(Function) In conditions (1) to (3) necessary for stable casting described above, (
Condition 3) can be satisfied by the means shown in Figures 1 to 3, and therefore, when forming the discharge port of the immersion nozzle, it is sufficient to satisfy the remaining conditions (1) and (2). In addition to stabilizing casting, it also increases the freedom of nozzle design. In other words, stable casting is possible using a submerged nozzle having a discharge hole of a simple shape, so that it becomes possible to manufacture the nozzle on an industrial scale.

(Example) Using the belt caster shown in Fig. 4 with the heating element shown in Fig. 2 incorporated into the immersion nozzle shown in Fig. 1, low carbon aluminum killed steel was cast at a speed of 10 or 15 m/min.
Thickness 30mm, width 1240mm and length 513m+
Casting was carried out to produce slabs. Two types of nozzles were used according to the following conditions A to D, with the slit width d of the discharge port at the lower end being 0.07 mm and 0.27 mm, depending on the thickness of the slab.

A: Casting speed 10n+/min - slit width 0.07m
mB:〃l5〃1〃0.07〃 C:〃lO〃-〃0.27〃 D:〃l5〃-〃0.27〃 First, when casting was performed without heating the nozzle with a heating element, Under conditions A and B, a good slab was obtained up to the middle (length 70 m), but after that, a solidified shell formed around the nozzle of the meniscus, became long, and finally connected with the long side shell and broke out. reached. On the other hand, in conditions C and D, no signs of solidification of the solidified shell around the nozzle were observed, but in particular in condition D, the flow of molten steel in the pouring direction was too fast, so wrinkles and cracks were observed as a result of shell remelting. .

Next, when the nozzle was heated by a heating element and casting was performed, good slabs were obtained under both conditions A and B, and naturally no solidified shell was observed around the nozzle. That is, even when the flow of molten steel in the casting direction is small as in conditions A and B, stable casting could be performed by following the present invention.

(Effects of the Invention) According to the present invention, it is possible to satisfy all the conditions necessary for stable casting when supplying molten metal, and the industrialization of continuous casting of thin slabs can be further promoted.

[Brief explanation of drawings]

FIG. 1(a) is a perspective view showing the immersion nozzle used in this invention, FIG. 1(b) is a sectional view of the nozzle, FIG. A diagram showing the part where the bolus ring is embedded in the nozzle. Figure 4 is an explanatory diagram of the belt caster. 1, 2...Metal belts 3a, 3b, 3c-guide roll 4.5...Short side plate 6...Immersion nozzle 7a,
7b...Cooling pad 8a, 8b, 9...Discharge port 10...Heating device 11...Heating element 1
2... Blowout hole l3... Bolus ring Figure 1 (a) (b) Figure 2 Figure 3

Claims (1)

[Claims] 1. A pair of circulating bodies arranged opposite each other, which circulate while maintaining a gap for holding molten metal over a certain distance, and located on both side edges between the circulating bodies. In order to supply molten metal by inserting the immersion nozzle into the casting space, which is made up of a pair of short-side side plates that are concave in shape at the top and bottom and constricted in the middle, the immersion nozzle is inserted into the pair of short-side side plates. Melting in continuous casting of thin slabs, characterized by discharging molten metal in the direction toward which it is directed and in the casting direction, respectively, and further taking measures to avoid solidification of the molten metal in a submerged nozzle or adhesion of the solidified metal to the submerged nozzle. Method of supplying metals.