JP2710946B2 - Continuous ribbon casting machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of continuously supplying a molten metal (hereinafter, referred to as a molten metal) between a pair of rolls, belts, and other rotationally driven cooling bodies. The present invention relates to a continuous casting apparatus for a ribbon which directly produces a ribbon.

[Conventional technology]

The continuous casting method of a thin ribbon is a method of directly obtaining a thin plate or a thin strip material from a molten metal, and its realization is strongly expected in terms of manufacturing cost and yield, and many proposals have been made. Many of these are related to the improvement of the surface properties of a product, such as a thin plate or a thin strip, and a supply system of the molten metal for turning the molten metal into a wide film-like flow. Japanese Patent Application Laid-Open No. 62-38745 discloses that a lower end portion of a nozzle, which is vertically provided at a lower portion of a molten metal container, is brought into contact with an inclined surface of a refractory inclined plate, and a peripheral side wall of the lower end portion of the nozzle is inclined. An opening is provided in the side wall of the portion corresponding to the downward direction of the inclination of the plate surface, and the molten metal spouted from the opening is spread on the inclined plate surface as a steady laminar flow and the upper portion between the rolls of the twin roll continuous casting device is formed. There is disclosed and proposed a method of supplying a molten metal to a molten pool having a depression formed therein.

[Problems to be solved by the invention]

Many of the proposals, including those proposed in the above-mentioned publications, relate to a molten metal flow before reaching a molten metal pool, for example, a material to be supplied to a laminarized molten metal flow pool or an upper peripheral surface of a driven roll or a width thereof. Many are intended to obtain a uniform flow state in the direction.

In the proposal of the above publication, the inclined plate surface immediately below the tip of the vertical tubular nozzle is strongly eroded by the collision of the molten metal, and a depression is generated early, and thereafter, the molten metal flowing along the surface of the depression is sprayed at the boundary of the depression. It was found that the flow after the separation from the inclined plate surface as an upward flow became turbulent.

SUMMARY OF THE INVENTION An object of the present invention is to provide a continuous ribbon casting apparatus capable of producing a product having excellent surface properties by continuously maintaining a molten metal flow in a nozzle in a laminar flow.

[Means for solving the problem]

The present invention provides a continuous casting apparatus for a ribbon which supplies molten metal via a nozzle to a peripheral surface of a rotationally driven cooling body and cools and solidifies the same. In the figure, the downstream portion is substantially symmetrical to the left and right with respect to the extension of the upstream portion, and the downstream portion has a bottom portion having a downward inclination angle of 30 ° or less with respect to the horizontal or horizontal, and the downstream portion has an upstream side. Consists of a side wall portion having a divergent broad parabolic shape as a vertex and a ceiling portion facing the bottom surface,
The ceiling portion of the downstream portion extends to the middle position in the extension direction with respect to the bottom portion, and the downstream edge extends as if spanning the width direction, or the slit portion or the small portion extending in the width direction extends at the halfway position. The molten metal fills the inner surface shape and flows down on the downstream side edge or on the upstream side of the row of slits or small holes.

[Action]

The nozzle used in the present invention includes a substantially horizontal tubular upstream portion and a downstream portion following the upstream portion, and the inner surface of the downstream portion includes a bottom portion, a side wall portion, and a ceiling portion. The ceiling portion extends only halfway in the flow-down direction with respect to the bottom portion, or has a slit or a row of small holes in the middle portion. Then, the molten metal that has reached the downstream portion expands the flow direction at the inlet portion in the left-right direction, and fills the inside of the inner surface shape at the portion upstream of the portion where the ceiling extends or the row of slits or small holes. In the meantime, you can't have a free surface. Therefore, even if a depression due to erosion is formed by the collision of the molten metal, excessive turbulence does not occur, and the turbulence generated slightly becomes a flow calmed down in a small dimension between the bottom and the ceiling by a small number of Reynold nozzles. .
Then, in a portion having no ceiling or a portion downstream of the row of slits or small holes, the molten metal flow separates from the ceiling surface as described later, and finally flows down from the lower end edge of the bottom surface of the nozzle as a wide film-like flow. Further, in the nozzle of the present invention, since the molten metal does not generate a violent collision as in the above-mentioned disclosed example, a uniform flow can be achieved for a long time.

By carefully flowing this downstream stream into the pool or directly supplying it to the peripheral surface of the rotating body driven by rotation, it is possible to obtain a product having excellent surface properties for a long time. Similarly, the nozzles of the present invention do not produce droplets, thus preventing surface or internal defects from being introduced into the product without re-melting in the pool.

In the nozzle of the present invention, when the molten metal flows down the inclined bottom surface, the molten metal tends to gradually increase its speed due to the inclination, and thus tends to peel off from the ceiling surface. In this case, a problem is liable to occur due to the fact that the peeling point varies with time and the peeling point varies depending on the position in the width direction of the nozzle. For this reason, in the present invention, as shown in FIG. 1, the ceiling portion is provided to an appropriate position in the downflow direction, or the ceiling surface is continuously slit or intermittently formed at a relatively small interval in the width direction of the nozzle. Small holes 9 and 9 '(Fig. 4) are provided, and an appropriate gas is blown from these openings, or the atmosphere gas is sucked by the self-priming action of the molten metal stream, thereby separating the molten metal from the ceiling surface. Is controlled to start from a fixed position. Further, by using an inert gas or the like as the above-mentioned gas, the role of protection from oxidation can be achieved.

In the apparatus of the present invention, it is important to connect the tundish and the nozzle in an airtight manner. This prevents the molten metal from blowing out from the portion, and prevents suction of an atmospheric gas such as air from the portion, and prevents the flow in the nozzle from being disturbed by the gas suction.

In the present invention, Ti, Al
If it contains elements that are easily oxidized, keep the part after the nozzle in a vacuum or an appropriate protective gas, or house the casting equipment together with the melting furnace in a tank and consistently vacuum or protect melting and casting It is necessary to perform in an atmosphere.

In the present invention, it may be advantageous to provide a flow straightening plate that receives a molten metal flow having a uniform flow velocity and liquid volume in the width direction by a nozzle and further directs the flow directly to the peripheral surface of the pool or the cooling body. That is, for various reasons, turbulence may occur or the flow rate of a specific portion in the width direction may be unevenly distributed. In this case, the rectifying plate can make the flow rate deviation or the like uniform. The current plate is also effective in correctly guiding the flow of the molten metal to a specific portion of the cooling body or pool.

〔Example〕

As shown in FIG. 1, a repeated test with water-glycerin revealed that a horizontal straight tubular upstream portion A, a bottom portion B having an angle α to the horizontal of 15 °, a divergent substantially parabolic side wall C and a ceiling portion having an apex upstream portion A were obtained. Thus, the shape of the nozzle 2 consisting of the downstream part, which is substantially symmetrical with respect to the extension line E of the upstream part A in the plan view A, is obtained. A nozzle having the same inner surface dimensions of the above-mentioned nozzle, a straight pipe portion made of boron nitride, and a downstream portion polished with tar-impregnated alumina was manufactured.

As shown in FIG. 2, using this nozzle, the roll 3a on the molten metal supply side is cast iron water-cooled with a diameter D ₁ = 500 mmφ and a width of 300 mm. The ribbon was rotated in the same direction at the same peripheral speed (20 to 200 m / min steplessly), and the thin strip could be cast smoothly by the device having the support guide plate 4 downstream of the same. In addition, refractory end plates were pressed against both end surfaces of both rolls at an appropriate pressure to form side walls. This embodiment is as follows. Molten metal: SUS580 1580
° C molten steel, nozzle: straight pipe inner diameter d = 10mm, α = 15 °, β
= 10 °, W = 270mm, h = 2mm.

After the test, the nozzle was disassembled and the state of erosion was checked, but no abnormal erosion was found.

This has enabled a nozzle capable of continuously obtaining a uniform flow even after long-time use.

(Other Embodiment) FIG. 3 shows an example in which the filter is attached to an intermediate tundish having a ceramic filter 8.

FIG. 4 shows an example of a nozzle provided with small holes 9 scattered linearly in the width direction or slits 9 'continuous in the width direction on the ceiling portion, and forcibly removes molten metal from the inner surface of the ceiling. , Or for protecting the molten metal from oxidation, and the gas may be either pressure feed or suction of the molten metal, respectively. The gas pressure at the time of pumping may be about 2 to 3 mmAq.

FIG. 5 shows an embodiment in which the portion below the nozzle is housed in the chamber 12, which is an example of casting in an inert gas or in a vacuum. However, the molten metal is melted and refined in the atmosphere,
When the absolute pressure is set to 100 torr or less, gas may be released from the molten metal.

FIG. 6 shows an example in which the molten metal flowing down from the nozzle 2 is relayed by the current plate 15 and supplied to the peripheral surface of the roll 3a. The provision of the flow straightening plate 15 has effects such as a reduction in uneven distribution of the flow of the molten metal in the width direction, a correct guide to a limited local part, a reduction in a head at a supply part to the molten metal pool, and the like.

〔The invention's effect〕

As described above, in the apparatus of the present invention, the erosion in the downstream portion of the nozzle is suppressed, and a uniform flow can be continuously obtained even after the erosion occurs. The problem in mass production is solved.

[Brief description of the drawings]

FIG. 1 is a view for explaining an embodiment of the nozzle of the present invention, and FIG.
FIG. 3 is a view showing a test situation, FIG. 3 is a view of an embodiment of an upstream portion of the nozzle, FIG. 4 is a view of an embodiment in which a small hole 9, a slit 9 ', etc. are provided in a ceiling portion of the nozzle, FIG. Is a diagram of an embodiment in which the part after the nozzle is housed in a vacuum or gas chamber,
FIG. 6 is a view of an embodiment in which a current plate 15 is provided between the nozzle and the molten metal pool. 1: Intermediate tundish, 2, 2 : Nozzle, 3a, 3b: Roll,
4: Support guide plate, 6a: molten metal, 6b: molten metal flow, 6c: band-shaped solid metal, 7: roll bearing, 8: ceramic filter, 9,9 ':
Small holes, slits, etc., 10: gas control valve, 11: gas inlet pipe, 12: chamber, 13: exhaust port, 14: vacuum seal, 15: rectifying plate

Claims (4)

(57) [Claims] In a continuous casting apparatus for a ribbon, which supplies a molten metal to a peripheral surface of a cooling body driven by rotation through a nozzle, and cools and solidifies the molten metal, the nozzle includes an upstream portion which is a substantially horizontal conduit, In the plan view, the downstream part comprises a downstream part which is substantially symmetrical to the left and right with respect to the extension of the upstream part, and the downstream part has a horizontal or horizontal bottom surface having a downward inclination angle of 30 ° or less with respect to the horizontal, and the upstream side. Consisting of a side wall having a substantially parabolic shape and a ceiling facing the bottom,
The ceiling portion of the downstream portion extends to the middle position in the extension line direction with respect to the bottom portion, and the downstream edge extends as if spanning the width direction, or at the middle position, a slit or the like extending in the width direction. A continuous casting apparatus for a thin strip, characterized in that the molten metal fills the inner surface shape and flows down on the upstream side of the downstream side edge or the row of slits or small holes. . 2. The continuous strip casting apparatus according to claim 1, wherein a portion below the nozzle is accommodated in a vacuum or inert gas tank. 3. A melting furnace for supplying molten metal to a tundish, wherein a portion below the melting furnace is accommodated in a tank, and the inside of the tank is evacuated or under an inert gas atmosphere. The continuous casting apparatus for a ribbon according to any one of claims 1 and 2. 4. The continuous casting apparatus for a ribbon according to claim 1, wherein a straightening plate having a downward inclination is provided between the nozzle and the cooling body.