JP2003211259A - Method for continuously casting steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for reducing defects appearing on the surface of a steel slab by preventing development of break-out in continuous casting of the steel and making the depth of oscillation marks which emerge during continuous casting shallow. <P>SOLUTION: When the continuous casting of the steel is performed, a mold powder control plate 3 vertically vibrated synchronizing with a vertically oscillated mold 2 is set in the mold 2 from the upper part. Then, the oscillation mark depth developed on the surface of the steel slab 11 is reduced by making the amplitude of oscillation of this mold powder control plate 3 to a size such that the tip part 10 of the mold powder control plate 3 is located in a mold power fused layer 4 in the mold when the mold powder control plate 3 is descended and the flow of the powder fused layer 4 near a meniscus is suppressed by bringing the control plate to such a position. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method and a continuous casting mold capable of obtaining a steel slab having a shallow oscillation mark depth.

[0002]

2. Description of the Related Art Conventionally, in continuous casting of molten metal, especially molten steel, it is essential to prevent breakout and to continuously and stably cast powder between the molten steel and the mold in which the mold is vertically vibrated. Is. However, on the other hand, a depression called an oscillation mark is formed on the surface of the steel piece in accordance with the vibration of the mold. Since this oscillation mark portion causes cracks on the surface of the slab, it is desired to make the depth of the oscillation mark as shallow as possible.

In the method for vibrating a vertical continuous casting mold disclosed in Japanese Patent Application Laid-Open No. 6-344102, a pair of mold surfaces is molten steel at the same cycle as the vertical vibration cycle of the mold composed of two pairs of mold surfaces. Continuous casting is performed by relatively approaching and separating from the solidified shell. In this mold vibration method,
Longitudinal oscillation period is 0 at the beginning of positive strip time zone
%, And 100% at the end, a vibration method of a continuous casting mold is shown in which at least one pair of mold surfaces is separated from the molten steel solidification shell at 25% to 75%, and is approached to the original position at other times. Has been done. In addition, JP-A-7
In the continuous casting method of steel disclosed in Japanese Patent Publication No. 963603, when performing continuous casting of steel using a continuous casting mold having a magnetic field generating coil on the back surface of a mold plate, the vibration cycle of the continuous casting mold The pulse current is applied to the magnetic field generating coil in synchronism with, and the electromagnetic force generated at that time is applied to the initial solidification shell in the direction orthogonal to the plate surface of the mold plate to reduce the amount of mold powder consumed. A method of adjusting and reducing the depth of the oscillation marks is shown.

However, in both cases, it is necessary to install a vertical mold for controlling the depth of the oscillation mark and a magnetic field generating coil, which requires a large capital investment.

Further, the document CAMP-ISIJ vol.
14 (2001) -894: "Effect of Flux Flow on Oscillation Depth", by making a control plate fixed in the mold powder melting layer, the flow of the mold powder melting layer is obstructed, and accordingly, the meniscus. It has been shown that it is possible to suppress the molten steel flow in the vicinity and thereby reduce the oscillation mark by reducing the amount of molten steel that overlaps. However, this method also reduces the powder inflow necessary to prevent seizure of the mold and molten steel,
There is a risk of causing a breakout.

[0006]

The problem to be solved by the present invention is to prevent the breakout without a large capital investment and to reduce the depth of the oscillation mark generated during continuous casting of steel. The object of the present invention is to provide a method and apparatus for reducing the defects generated on the surface of the billet.

[0007]

Means for Solving the Problems In the invention of claim 1, the means for solving the above problems vibrates up and down in synchronism with the vertically moving mold 2 when performing continuous casting of steel. The tip 10 of the mold powder control plate 3 is located in the mold powder melting layer 4 in the mold when the amplitude of the mold powder control plate 3 descends, and is located at the position. Is a size capable of suppressing the flow of the mold powder molten layer 4 in the vicinity of the meniscus, thereby reducing the depth of the oscillation mark on the surface of the billet, which is a continuous casting method for steel.

According to the second aspect of the invention, in the continuous casting mold 2 for steel, a mold powder control plate 3 capable of vertically vibrating in synchronism with the vertically moving mold 2 is provided inside the mold 2 from above. It is a mold for continuous casting characterized by the above.

According to the third aspect of the present invention, the mold powder control plate 3 provided inside the mold 2 from above has a distance from the center 8 when the width from the center 8 of the mold 2 to the mold wall 9 is W. Mold powder control plate 3 capable of vertically vibrating in synchronization with the mold 2 between 0.5 W and 0.98 W
It is the continuous casting mold 2 according to the means of claim 2.

In the invention of claim 4, the mold powder control plate 3 vibrating up and down is set so as to have an amplitude such that the lowest descent point of the control plate tip 10 reaches the position where it is immersed in the mold powder melting layer 4. It is the continuous casting mold 2 according to the means of claim 2 or claim 3 characterized in that.

The operation of the means of the present invention will be described. Since the mold powder control plate 3 is synchronized with the vibration of the mold 2, when the mold 2 descends, the mold powder control plate 3 also descends. Then, since the tip 10 of the mold powder control plate 3 is positioned inside the mold powder melting layer 4 by the lowering of the control panel 3, the flow of the mold powder melting layer 4 is suppressed by the mold powder control plate 3. Accordingly, the flow of molten steel 7 near the meniscus is suppressed, and as a result, the oscillation mark depth 13 on the side surface of the steel piece becomes shallow. Further, when the mold 2 rises, the mold powder control plate 3 rises, so that the amount of mold powder 5 necessary for preventing seizure is supplied by flowing between the mold 2 and the molten steel 7. This makes it possible to reduce the oscillation mark depth 13 without causing breakout.

In this case, assuming that the distance from the mold center 8 to the mold wall 9 is W, it is desirable that the installation position of the mold powder control plate 3 be a distance from the mold center 8 to 0.5W to 0.98W. If the distance at the installation position is smaller than 0.5 W or larger than 0.98 W, the ability to suppress the flow velocity of the molten steel 7 near the meniscus becomes low,
It is difficult to make the oscillation mark depth 13 shallow. Further, the tip 10 of the mold powder control plate 3 that moves up and down by vibration is set to be the lowest point in the mold powder melting layer 4. If it is not set in this way, the mold powder control plate 3 comes into contact with the molten steel 7, and the quality of the steel slab 11 obtained by the generation of deckle or the inclusion of the mold powder 5 is deteriorated. Becomes Furthermore, when the tip 10 of the mold powder control plate 3 does not reach the mold powder melting layer 4, a sufficient effect of reducing the molten steel flow velocity in the vicinity of the meniscus cannot be obtained.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of a mold and a mold powder control plate according to one embodiment of the present invention. Figure 2
FIG. 4 is a cross-sectional view schematically showing a partial cross section of a continuously cast steel slab.

As shown in FIG. 1, 380 mm × 490 m
Molten steel 7 was supplied to the mold 2 through the immersion nozzle 1 from a tundish (not shown) installed above the mold 2 having a cross-sectional area of m, and continuous casting was performed at a casting speed of 0.50 m / min. At this time, the tip 10 of the mold powder control plate 3 made of a refractory material in the mold 2 is at a position 30 mm below the inner surface of each mold 2 and at a position where the mold powder melt layer 4 is attached when the mold 2 descends. installed. Further, the installation position of the mold powder control plate 3 is 0.5 W from the center 8 when the distance between the center 8 of the mold 2 and the mold wall 9 is W.
It was installed at a position of ~ 0.98W. The mold powder control plate 3 was installed so as to oscillate up and down in synchronization with the mold 2.

The vibration of the mold 2 provided with the mold powder control plate 3 has a vibration frequency of 100 to 300 cpm, a stroke of 2 to 5 mm, and a sine waveform, and the mold 2 is used to convert the steel type SUJ2 steel into the molten steel in the tundish. Superheat 2
It was cast at 0 to 40 ° C. In FIG. 1, the molten steel 7 in the mold 2 is cooled from the mold wall 9 side of the mold 2 to form a solidified shell 6.

As shown in FIG. 2, the oscillation mark depth 13 of the steel slab 11 when cast under the above conditions is about 150 μm on average, and when casting is performed under the same conditions without installing the mold powder control plate 3. It was confirmed that the oscillation mark depth 13 was made shallower than the average of 250 μm.

[0017]

As described above, by using the mold in which the mold powder control plate is installed in the mold of the present invention, the oscillation mark depth generated in the continuously cast steel piece can be continuously cast by the conventional mold. Compared with the method, it is possible to reduce the number, and it is possible to cast a steel slab with few surface defects.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a mold and a mold powder control plate according to an embodiment of the present invention.

FIG. 2 is a sectional view schematically showing a part of a continuously cast steel slab. It is the figure which expanded the steel piece cross section.

[Explanation of symbols]

1 immersion nozzle 2 molds 3 Mold powder control plate 4 Mold powder melting layer 5 Mold powder 6 solidification shell 7 Molten steel 8 center 9 Mold wall 10 Tip 11 billet 12 Operation mark 13 Operation mark depth

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Claims (4)

[Claims] 1. When performing continuous casting of steel, when the mold powder control plate descends, the tip of the mold powder control plate is adjusted so that the amplitude of the mold powder control plate vibrates up and down in synchronism with the vertically moving mold. Located in the mold powder molten layer in the mold, and by having a size that can suppress the flow of the mold powder molten layer in the vicinity of the meniscus by the position of the oscillation mark depth of the billet surface. A continuous casting method for steel, which is characterized by reduction. 2. A continuous casting mold for continuous casting of steel, characterized in that a mold powder control plate capable of vertically vibrating in synchronism with the vertical mold is provided inside the mold from above. . 3. The mold powder control plate provided from above in the mold is such that when the width from the center of the mold to the mold wall is W, the distance from the center is between 0.5W and 0.98W. The mold for continuous casting according to claim 2, wherein the mold powder control plate is capable of vertically vibrating in synchronization with the mold. 4. The mold powder control plate which vibrates up and down is set so as to have an amplitude such that the lowest descent point of the control plate tip reaches a position where it is immersed in the mold powder molten layer. The continuous casting mold according to claim 2 or claim 3.