JPH04253552A - Continuous casting machine for thin metallic strip - Google Patents

Abstract

PURPOSE:To execute stable continuous casting by preventing the reaction of the scum weirs to be immersed into the molten metal in a pouring basin with the molten metal in the continuous casting machine of a twin drum system. CONSTITUTION:A pair of the scum weirs formed with protective films, such as oxide films, on the wall surfaces facing at least cooling drums are disposed over the transverse direction of these cooling drums.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous metal ribbon casting apparatus such as a belt type or twin drum type, and more particularly to the structure of a scum weir disposed in a sump.

0002

2. Description of the Related Art A conventional twin-drum continuous casting apparatus will be explained based on FIG.
A scum weir 6 is provided between the nozzle 3 and the cooling drum 1 to inject the molten metal 5 into the molten metal 5. It is constructed by partially immersing it. The scum weir 6 prevents the molten metal flow discharged from the nozzle 3 from undulating the meniscus portion R by easing the molten metal flow and causing the meniscus portion R to ripple and deteriorate the surface quality of the slab S. (Refer to Japanese Patent Application Laid-open No. 165255/1983). Typically, such scum weirs are made of boron nitride (BN) material to provide heat resistance and thermal shock resistance.

0003

However, the portion of the scum weir made of BN material that is immersed in the molten metal is difficult to use for a long time due to the reaction with the molten metal. In addition, if the molten metal is SUS304 stainless steel, BN may react with the molten steel and dissociate, and the dissociated N may dissolve into the molten steel, causing local changes in the components on the slab surface. reacts with oxygen in molten steel to form boron oxide (B2O
3) is generated, causing surface cracks in the slab.

0004

[Means for Solving the Problems] The present invention solves the above-mentioned problems, and as a result of investigating the state of BN material in high-temperature molten metal, it is possible to prevent dissociation while maintaining the properties of nitrides such as BN. In order to do this, it has become clear that the most effective means is to thermally spray or apply a protective film, for example, a thin film of oxide such as ZrO2 or Al2O3, on the surface of the scum weir.

That is, the present invention provides an apparatus for continuously casting metal ribbon by supplying molten metal to a pool formed by a pair of rotating cooling drums and a pair of side weirs. The continuous casting apparatus for metal ribbon is characterized in that a pair of scum weirs having at least a protective film formed on the wall facing the cooling drum are immersed and disposed in the molten metal.

[0006]

[Function] The drum weir is made of high-temperature molten metal, such as SUS304.
In the case of stainless steel, since it is immersed at about 1500°C, its surface is likely to dissociate, creating the risk of contaminating the molten metal. As mentioned above, the material used for the scum weir is nitride-based ceramics such as BN, which has good heat resistance and thermal shock resistance and has little adhesion to bare metal, but when the molten metal is steel, the ceramics may react with the molten steel. N dissociates and dissolves into the molten steel, locally changing the components on the slab surface and producing boron oxide, which induces cracks on the slab surface.

That is, a reaction of BN→B+N 2B+3O→B2O3 occurs, and N and B2O3 contaminate the molten steel. In order to prevent the scum weir from reacting and dissociating with the molten metal, a protective film such as ZrO2, Al2O3, etc. is applied to the surface of the scum weir.
It is extremely effective to thermally spray or apply a thin film of oxide such as.

FIG. 2 shows this coating effect. Figure 2 shows the continuous casting apparatus shown in Figure 1, using SUS304 stainless steel as the molten metal and BN as the material for the scum weir, with no coating on the scum weir surface, and ZrO2 in the cooling drum of the molten steel immersion part of the scum weir. This figure shows the state of surface cracks in slabs cast using four types of scum weirs, one in which the wall surface facing the above-mentioned area was thermally sprayed, and one in which ZrO2 or Al2O3 was thermally sprayed on both sides of the wall surface of the above-mentioned portion.

[0009] According to this, it can be seen that when an oxide film is formed at least on the portion facing the cooling drum, surface cracks in the slab are significantly reduced.

0010

[Example] Cooling drum 1 and side weir 2 shown in Fig. 1 are made of molten stainless steel with SUS304 composition and temperature of 1500°C.
Pour the hot water into the pool 4 in between, and make the wall thickness 2mm and the board width 800mm.
A thin-walled cast slab was produced at a casting speed of 80 m/min. At this time, the end of the scum weir 6 made of BN was immersed in the molten steel over approximately the entire width of the cooling drum 1, and ZrO2 was sprayed onto the wall surface of this immersed portion facing the cooling drum 1 to a thickness of 10 mm.
A film of about μm was formed.

Scum with a film thickness of about 0.5 mm was floating on the surface of the molten stainless steel poured into the sump 4, but due to the immersion in the scum weir 6, the scum was not rolled onto the cooling drum. There was no encroachment, and the BN component in the scum weir facing the cooling drum did not dissolve during casting, and the surface quality of the obtained slab was extremely good.

0012

Effects of the Invention As described in detail above, the present invention forms a protective coating such as ZrO2 on the part of the scum weir that is immersed in the hot water pool, so it has excellent heat resistance and thermal shock resistance as a material for the scum weir. It is possible to use BN or the like, which allows stable continuous casting for a long period of time, which has an extremely large industrial effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing a continuous casting apparatus of the present invention.

FIG. 2 is a diagram showing the relationship between the type of scum weir surface coating and the surface crack occurrence area of the slab.

[Explanation of symbols]

1...Cooling drum 2...Side weir 3...Nozzle 4... Hot water pool part 5...Molten metal 6...Scum weir 7...Oxide film S...Metal ribbon R...Meniscus part

Claims (2)

[Claims] Claim 1: In an apparatus for continuously casting metal ribbon by supplying molten metal to a pool formed by a pair of rotating cooling drums and a pair of side weirs, at least a wall surface facing the cooling drums is provided with protection. 1. A continuous casting apparatus for metal ribbon, characterized in that a pair of scum weirs each having a film formed thereon are disposed across the width of the cooling drum, and the lower part of the scum weir is immersed in the molten metal. 2. The device according to claim 1, wherein the protective film is an oxide film.