JP2000246404A - Continuous casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display the ejector effect while avoiding the influence with a roll just below a mold and to stabilize the flow-in of powder at high speed casting by introducing high pressure fluid spouted downward toward a cast slab from a slit nozzle to the reverse cast slab side through a guide part. SOLUTION: Molten steel 2 poured into the mold 1 is cooled and the produced cast slab shell 3 is drawn out downward through rolls 5 just below the mold. Further, the powder 4 supplied on the surface of the molten steel 2 is made flow-in between the mold 1 and the cast slab shell 3 to prevent the burning of the cast slab shell 3 onto the mold 1. In this continuous casting of the steel, the high pressure gas 6 of air, etc., is spouted in the width direction of the cast slab shell 3 and along the advancing direction from the gas spouting slit nozzle 7 arranged at the lower part of the mold 1 to promote the flow-in of the powder 4 with the ejector effect. Further, the protruding arc-shaped guide part 8 having the curvature radius R of three or more times of the slit width (d) is disposed at the reverse cast slab side of the slit nozzle 7 to introduce the spouted flow 9 so as not to collide against the roll 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to continuous casting.
The present invention relates to a continuous casting apparatus that can smoothly flow lubricating powder between a mold and a slab.

[0002]

2. Description of the Related Art In a conventional continuous casting apparatus for steel using a fixed mold, as shown in FIG. 2, molten steel 2 contacting the mold 1 via a lubricating powder 4 at the upper portion of the mold 1 starts to solidify, and The piece is pulled out in the casting direction while growing the outer shell (hereinafter referred to as a shell) 3 to form a cast piece. Usually, in order to prevent the shell 3 from seizing on the mold 1, a lubricating powder (hereinafter referred to as powder) 4 is caused to flow between the mold 1 and the shell 3 while applying vibration to the mold 1.

[0003] In order to increase the productivity of continuous casting, it is necessary to perform high-speed casting. As a problem in this case, there is a problem that the inflow of the powder 4 is insufficient. This is because when the casting is performed at a speed higher than the inflow speed of the powder 4 flowing between the mold 1 and the shell 3 due to the oscillation of the mold 1, the lubrication between the mold 1 and the shell 3 is performed. The amount of powder 4 that must be supplied is insufficient,
Is interrupted, the shell 3 comes into direct contact with the mold 1 and seizure occurs, and as a result, there is a disadvantage that a breakout easily occurs. In order to perform high-speed casting while avoiding such a situation, the inflow speed of the powder 4 must be increased to a speed suitable for high-speed casting, and the lubrication between the mold 1 and the shell 3 must be properly maintained.

As a method for improving the inflow speed of the powder 4, for example, a slit nozzle 7 is provided in the mold width direction near the inner surface of the lower part of the mold 1, and the high-pressure gas 6 is directed downward from the slit nozzle 7 in the slab traveling direction. There is a method in which the pressure between the mold 1 and the shell 3 is reduced by the ejector effect to promote the inflow of the powder 4, and the applicant has already filed an application as Japanese Patent Application No. 9-103281, and is suggesting.

[0005]

However, in the case of a continuous casting machine having a roll (support roll) 5 directly below a mold, the high-pressure gas 6 injected from the slit nozzle 7
In order to reduce the ejector effect and reduce the pressure between the mold 1 and the shell 3 to a sufficiently reduced pressure, the turbulence occurs between the mold 1 and the roll 5 because the flow is interrupted by colliding with the roll 5 immediately below the mold 1. As a result, there is a problem that the effect of improving the inflow speed of the powder cannot be sufficiently obtained.

According to the present invention, as described above, even when the roll is directly below the mold, the ejector effect can be sufficiently exhibited by securing a gas flow that is not affected by the roll, and the mold 1 It is an object of the present invention to provide a continuous casting technique capable of ensuring a reduced pressure state between the shells 3 and performing stable powder inflow even in high-speed casting.

[0007]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and the means 1 includes a slit nozzle for blowing a high-pressure fluid downward toward a slab at least at a lower portion of a long side of a mold. A continuous casting mold having a continuous casting mold and a roll immediately below the mold, wherein a guide portion for guiding the high-pressure fluid blown out from a nozzle of the slit to an opposite slab side is provided. It is.

The means 2 includes a guide portion for guiding the flow of the high-pressure fluid blown out from the slit nozzle toward the slab, wherein the guide portion guides the flow of the high-pressure fluid to the roll as much as possible and guides the high-pressure fluid to the opposite side of the slab. The continuous casting apparatus according to the first aspect, wherein the continuous casting apparatus is configured as possible.

[0009] The means 3 is characterized in that the guide portion is positioned on the side opposite to the slab of the slit nozzle discharge port, and the shape thereof is formed in a convex arc shape with a radius of curvature of three times or more the slit width. The continuous casting apparatus according to the above means 1 or 2.

[0010] The means 4 is a continuous casting apparatus according to any one of means 1 to 3, characterized in that the guide portion is formed separately from the mold body and attached to the bottom of the mold body. is there.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The metal to be cast by applying the continuous casting mold of the present invention includes various types such as steel, aluminum and titanium, and it is particularly preferable to apply the present invention to continuous casting of steel.

The high-pressure fluid may be any of a high-pressure gas (air, nitrogen, inert gas, water vapor, etc.), a high-pressure liquid (water, etc.), and a mixture of a high-pressure gas and a liquid (air, water droplets, etc.). In the description, a case of a high-pressure gas which is usually used simply will be described as an example.

In the present invention, the shape of the guide portion for guiding the high-pressure gas is preferably an arc shape for ease of workability. However, a smooth curved surface whose curvature radius is gradually changed within a range satisfying the condition of the means 3 is preferable. It is possible to employ a set of flat surfaces obtained by approximating a curved surface with a polyhedron, since substantially no significant difference can be exhibited.

Further, the slit nozzle 7 and the guide portion 8
As shown in FIG. 1, the lower part of the mold 1 may be formed by direct perforation or the like, or a slit nozzle 7a and a guide 8a may be integrally formed at the bottom of the mold 1 as shown in FIG. These components may be mounted, or these components may be mounted individually.

The apparatus of the present invention will be described below with reference to FIG. FIG. 1 is a vertical sectional view perpendicular to the inner surface of a mold showing an example of the present invention. A slit nozzle 7 for blowing out high-pressure gas 6 along the surface of the shell 3 in the casting direction is provided in the lower part of the mold 1 in the width direction of the shell 3. A guide portion 8 that is curved in a convex shape with a radius of curvature equal to or more than three times the slit width of the slit nozzle 7 (the width of the injection port of the slit nozzle) is provided on the side of the slit nozzle 7 opposite to the blowout port of the slab.
The high-pressure gas 6 is supplied to the slit nozzle 7 from the same supply source, or the slit nozzle 7 is divided into a plurality of units, and the high-pressure gas 6 is supplied to individual units independently from individual gas supply sources. Alternatively, a structure having the following structure may be used.

According to the present invention, in a continuous casting apparatus, a high-pressure gas 6 is jetted from a lower portion of a mold 1 provided with a roll 5 below along a casting direction, so that an ejector effect is exerted by the flow of the high-pressure gas so that a mold 1 is produced. The pressure between the shell 3 and the shell 3 is reduced to obtain the effect of improving the inflow of the lubricating powder 4. In this case, when the injected gas collides with the roll 5, the gap between the mold 1 and the roll 5 is increased. Turbulence occurs, and a sufficient ejector effect cannot be obtained. Therefore, in order to obtain the ejector effect more effectively,
Before the high-pressure gas flow injected in the casting direction collides with the roll 5, the high-pressure gas flow is guided to the non-slab side, which is an open space, so that interference by the roll 5 is minimized and the high-pressure gas flow becomes turbulent. Need to be prevented.

In the present invention, as shown in FIG. 1, a guide portion 8 utilizing the Coanda effect is provided on the side opposite to the slab of the discharge port of the slit nozzle 7 so that the slit nozzle 7 at the lower portion of the mold 1 is directed in the casting direction. The injected gas actively induces the flow so as to flow toward the non-slab side.

As a method of guiding the flow of the high-pressure gas injected from the lower part of the mold to the opposite side of the slab, a method of previously directing the injection direction of the slit nozzle toward the opposite side of the slab or switching to a position in the traveling direction of the injected high-pressure gas flow can be used. A method of providing a plate and switching the gas flow to the opposite side of the slab may be considered. However, in the former method, the position of the slit discharge port must be provided at a position distant from the inner surface of the mold, so that the ejector effect due to the gas flow between the mold and the shell is reduced. Further, in the latter method, lubricating powder is stuck to the switching plate, which may obstruct the flow of the powder, and may further induce breakout. In the present invention, by providing the guide portion for guiding the gas flow on the opposite side of the slab, the slit discharge port can be made closer to the inner surface of the mold, and the maximum ejector effect can be obtained, and the flow of the powder can be reduced. A stable operation can be performed without hindrance.

[0019]

EXAMPLE An operation example in which casting was performed by the apparatus of the present invention is shown in Table 1.
It was shown to. Table 1 shows operating conditions and operating results for each of the examples and comparative examples. As operating conditions, the distance between the meniscus and the lower part of the mold was 800 m.
m, the roll diameter D is 150 mmφ, the distance H from the lower part of the mold to the center of the roll axis is 115 mm, and the distance l from the inner surface of the mold at the lower part of the long side of the mold is 0.2 mm. Using a continuous casting apparatus provided with a slit nozzle 7, the slit nozzle 7
By supplying high-pressure air of N liter / min, while injecting a gas of 90 m / s from the discharge port of the slit nozzle 7, the slab size is 250 mm thick × 1200 mm width, and the casting speed is 1.3 mpm. Steel was cast.

[0020]

[Table 1]

In this embodiment using the apparatus of the present invention, the amount of reduced pressure generated between the mold 1 and the roll 5 immediately below the mold was measured by the ejector effect due to the flow of the high-pressure gas injected from the slit nozzle 7. In comparison with the casting by the conventional continuous casting apparatus, the casting in Examples 1 and 2 by the continuous casting apparatus of the present invention improved the reduced pressure by 6 times. The comparative example is a comparison result with respect to the third aspect. However, since the radius of curvature R of the guide portion 8 was less than the range of the present invention, the gas flow could not be sufficiently induced, and the ejector effect was not realized. As compared with Examples 1 and 2, the pressure reduction amount was small.

Next, the powder inflow (the powder inflow here is the amount of powder required for casting one ton of slab) was measured. Was improved 1.2 times. In the comparative example, the improvement was only 1.1 times that of the conventional example.

Further, the number of occurrences of BO detection during casting was investigated. Here, the BO detection is a method of detecting in advance the occurrence of a breakout due to running out of lubricating powder in the mold from a temperature change of a thermocouple embedded in the mold. In the conventional example, the number of occurrences was 3 times / day, whereas in Examples 1 and 2, no BO detection was particularly generated. Further, in the comparative example, BO detection occurred at a frequency of once / day.

[0024]

According to the continuous casting apparatus of the present invention, even when a roll is installed immediately below the mold, the reduced pressure space can be easily formed near the lower part of the mold without being affected by the roll with a simple structure. The powder inflow speed is improved, and stable casting without breakout due to powder breakage can be achieved even at high speed casting.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a case where a slit is directly formed on a mold in a continuous casting apparatus of the present invention.

FIG. 2 is a schematic view of a conventional continuous casting apparatus in which a slit is provided below a mold.

FIG. 3 is a schematic view showing another example of the device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mold 2 Molten steel 3 Slab shell 4 Powder 5 Roll 6 High pressure gas 7 Gas discharge slit nozzle 8 Guide part 9 Gas flow

Continuation of the front page (72) Inventor Yasuhiko Kawada 1 Nishinosu, Oita, Oita, Nippon Steel Corporation Oita Works (72) Inventor Kensuke Okazawa 3-35-1, Ida, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Nippon Steel Corporation Technology Development Division F term (reference) 4E004 AA08 AA10 MB14 MC11

Claims (4)

[Claims] 1. A continuous casting mold having a slit nozzle for blowing a high-pressure fluid downward toward a slab at least at a lower portion of a long side of a mold, and a continuous casting apparatus having a roll immediately below the mold, wherein the blowout from the slit nozzle is performed. A continuous casting apparatus provided with a guide portion for guiding the high-pressure fluid to the side opposite to the slab. 2. A guide section for guiding the flow of the high-pressure fluid blown out from the slit nozzle toward the slab, so that the high-pressure fluid collides with the roll as much as possible and can be guided to the opposite slab side. The continuous casting apparatus according to claim 1, wherein the apparatus is configured. 3. The method according to claim 2, wherein the guide portion is positioned on the side opposite to the slab of the slit nozzle discharge port, and has a convex arc shape with a radius of curvature three times or more the slit width. The continuous casting apparatus according to claim 1 or 2. 4. The continuous casting apparatus according to claim 1, wherein the guide portion is formed separately from the mold main body, and is attached to a bottom portion of the mold main body.