JPH11179496A - Divided flow plate for continuously casting thin sheet and method for continuously casting thin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the stagnation of molten metal flow, to prevent the development of stuck shell and to obtain stable operation in high quality by arranging plural vertical divided flow plates dividing molten metal flowing passage in the width direction or horizontal divided flow plates vertically divided in a bottom nozzle for twin roll horizontal pouring. SOLUTION: In the twin roll horizontal pouring type thin sheet continuous casting method, the divided flow plates 3 provided with the vertical divided flow plates 2 dividing the molten metal passage into three or more are arranged in the bottom nozzle 4 supplying the molten metal onto the rolls. The above plural vertical divided flow plates 2 are desirable to have the sum of the chickness <=0.5 times of the flow passage width and to have the ratio of any flow passage width at the width center part and the flow passage width at the width end parts of 0.25-1.0 at the flow-in side and 1.0-3.0 at the flow-out side. Further, as the divided flow plates 3, the horizontal divided flow plates 1 dividing the molten metal flow passage into vertically two can be used. The horizontal divided flow plates 1 are desirable to have the thickness 0.25-0.75 times of molten metal surface height to have the ratio of the flow passage height in the upper surface and the lower surface of 0.5-2.0 at the flow-in side and 1.0-2.0 at the flow-out side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a molten metal (hereinafter, referred to as molten metal).
The present invention relates to a flow dividing plate for continuous sheet casting and a sheet continuous casting method used in sheet continuous casting for producing a sheet directly from a molten metal.

[0002]

2. Description of the Related Art Compared with a conventional continuous slab casting method, a thin plate continuous casting method has an advantage that a manufacturing cost can be reduced because a hot rolling step can be omitted. The continuous casting method of a thin plate includes an upper pouring method and a horizontal pouring method. The horizontal pouring method has the following features.

(A) Hot water is supplied in the horizontal direction, and the molten metal head is small, so that the level of the hot water in the nozzle can be easily controlled and uniform hot water supply with a wide width is possible. (b) The equipment cost is small because the equipment height is low. (c) The slab is conveyed in the horizontal direction, the stress due to its own weight is small even for materials having low high-temperature strength, and there is no cracking or breaking of the slab, so that stable casting can be performed.

The lateral pouring method includes a twin roll method and a single roll method. The twin roll method is superior to the single roll method because the quality of the slab is uniform on the upper and lower surfaces.

As an example of a casting nozzle for continuous casting of a thin plate, Japanese Utility Model Laid-Open No. 7-37447 discloses a casting nozzle for a single roll or twin roll lateral pouring method.

FIG. 8 is a schematic view of continuous casting of a thin plate by a twin-roll lateral pouring method using a casting nozzle disclosed in the publication. FIG. 1A is a longitudinal sectional view, and FIG. 1B is a plan view.

In FIG. 1, a molten metal 10 is provided on a bottom nozzle side wall 1.
3 and a pair of side nozzles 5. The molten metal 10 is cooled by the upper roll 8 on the molten metal surface 12 side and by the lower roll 9 on the bottom nozzle 4 side, forms two solidified shells, and is pressed into a thin plate, that is, a slab 11.

The bottom nozzle 4 seals the bottom surface of the molten metal by the front edge of the bottom contacting the peripheral surface of the lower roll 9, and the side nozzle 5 contacts the peripheral surface of the lower roll 9, and
By contacting the side surface with the end surface of the upper roll 8 and the outer surface of the bottom nozzle side wall 13, the side surface of the molten metal is sealed.

In FIG. 1, the molten metal forms a triple boundary at each of the molten metal / lower roll / bottom nozzle, molten metal / upper roll / atmosphere gas, molten metal / lower roll / side nozzle and molten metal / upper roll / side nozzle. doing. The intersections of these triple boundaries form quadruple boundaries at each of the following points: molten metal / lower roll / bottom nozzle / side nozzle and molten metal / upper roll / atmospheric gas / side nozzle.

[0010] The molten metal 10 supplied between the rolls is subjected to viscous resistance by the bottom nozzle side wall 13 and the side nozzle 5,
As shown in FIG. 3B, the flow velocity tends to be large at the center of the width and small at the end near the inner wall surface of the side nozzle 5, and the molten metal flow tends to stay at the width end.

At the triple boundary line or quadruple boundary point, the molten metal is surrounded by the roll and the nozzle refractory, and is easily cooled by heat removal from the surroundings, so that the temperature of the molten metal is lowered. Especially,
At the quadruple boundary point, abnormal solidification is apt to occur, and the solidified substance adheres to the refractory to form the fixed shell 14.

As shown in FIG. 1 (a), the vertical flow velocity distribution of the molten metal flow is larger near the surface than at the lower surface where viscous resistance is applied from the bottom surface. Therefore, the above 3
In the heavy boundary line, the temperature of the molten metal tends to be lower on the lower surface than on the upper surface, and the fixed shell at the quadruple boundary point tends to be generated on the lower roll side. Further, as described above, when the temperature of the molten metal is different between the upper and lower rolls, a difference in the surface quality of the slab tends to occur.

The sticking shell is likely to be formed immediately after the start of casting. This is because the temperature of the roll and the casting nozzle is low immediately after the start of casting, and the molten metal is cooled by radiation of the molten metal surface and heat removal from the refractory such as the tundish and the casting nozzle.

When the fixed shell is formed, the following (a) to (c)
Problem arises.

(A) The roll surface is covered with a fixed shell, so that an appropriate solidification time cannot be secured, and the thickness of the cast solidified shell is uneven in the width direction.

(B) The fixed shell which has fallen off from the refractory is caught in the slab, resulting in a fatal surface defect called a biting flaw.

(C) When the fixed shell comes off, a part of the refractory is broken, causing troubles such as steel leakage, which may hinder stable operation.

[0018] The quality and operational problems of the anchoring shells also arise in the single-roll lateral pouring method.

Japanese Patent Publication No. 7-10423 discloses a method for reducing the adhesion of coagulated material at a casting nozzle portion by using an upper weir called a nozzle casting weir in a single roll lateral pouring method as a measure against the above-mentioned fixed shell. An apparatus is disclosed.

Japanese Patent Application Laid-Open No. Hei 5-318039 discloses that the inventors of the present invention used an upper weir called an immersion weir in a single roll or twin roll lateral pouring method, and formed a solidified shell at the boundary between a casting nozzle and a cooling roll. A method and apparatus for preventing generation is disclosed.

[0021]

Problems to be Solved by the Invention
The method of suppressing the formation of a sticking shell using an upper weir disclosed in Japanese Patent Application Laid-Open No. 23-318039 or Japanese Patent Application Laid-Open No. Hei 5-318039 is an effective technique to some extent in a single roll lateral pouring method. (A) to (c) below
There is a problem.

(A) In the twin-roll horizontal pouring method, when an upper weir is installed near the triple boundary on the lower roll side, the flow of the molten metal passing through the triple boundary is accelerated to suppress the formation of a fixed shell. However, a stagnation area of the molten metal flow is likely to be generated in the vicinity of the molten metal surface, and a fixing shell is likely to be generated even in the triple boundary portion on the upper surface side where there is no problem, and in particular, fixing is likely to occur in the vicinity of the quadruple boundary point.

(B) In the twin roll horizontal pouring method, it is preferable to supply the molten metal to the upper and lower rolls under uniform conditions. However, Japanese Patent Publication No. Hei.
When the upper weir disclosed in Japanese Patent No. 8039 is used in the twin-roll horizontal pouring method, since the flow of the molten metal on the upper surface side and the lower surface side becomes uneven, the solidification on the upper and lower roll surfaces is not uniform, and the product The quality may deteriorate.

(C) Further, due to the structure of the apparatus used for the twin roll lateral pouring method, it is extremely difficult to install the upper weir so that the upper weir interferes with the upper roll and effectively suppresses the sticking shell.

Even when the upper weir is not used, the above-described uneven flow velocity of the molten metal in the vertical direction tends to cause the formation of a fixed shell at the lower triple boundary. As a countermeasure, there is a method of increasing the degree of superheat of the molten metal. However, if the degree of superheat is excessively increased, there is a possibility that a vertical crack is generated in the slab.

An object of the present invention is to provide a means and a casting method for preventing the occurrence of a sticking shell and enabling high-quality and stable operation in continuous casting of a thin plate by the twin-roll horizontal pouring method.

[0027]

Means for Solving the Problems The present inventors have conducted research on a continuous casting method of a thin plate by a twin-roll horizontal pouring method, and have obtained the following findings (a) to (f).

(A) The fixed shell is formed by abnormal solidification of the molten metal due to stagnation of the molten metal flow at the width end and cooling near the quadruple boundary point.

(B) In order to prevent the fixed shell, the imbalance in the melt flow in the vertical direction is eliminated, the melt flow at the width end is promoted, and the sensible heat of the melt flow itself is supplied to cool the melt from the surroundings. It is effective to mitigate this.

(C) As means (b) above, it is effective to equalize the flow of the molten metal in the vertical direction and supply hot water mainly to the width end. As the means, a flow dividing plate composed of one horizontal flow dividing plate and a plurality of vertical flow dividing plates arranged on the horizontal flow dividing plate is used.

(D) The cross-sectional area of the molten metal channel is reduced by increasing the thickness of the horizontal flow dividing plate, and the flow velocity of the molten metal is increased.
By placing the horizontal flow dividing plate at an appropriate position, the flow velocity of the molten metal can be equalized in the vertical direction.

(E) The flow of the molten metal at the width end can be promoted by arranging the vertical flow dividing plate so that the flow path of the molten metal at the width end is wide at the inflow side and narrow at the outflow side. (f) If the molten metal flow is properly distributed, the degree of superheat of the molten metal can be reduced.

FIG. 7 is a schematic diagram of the flow of the molten metal in the case where the flow dividing plate is installed based on the above examination. FIG. 1A is a longitudinal sectional view, and FIG. 1B is a plan view. In FIG.
0, the bottom nozzle 4 having the bottom nozzle side wall 13, the side nozzle 5, the molten metal surface 12, the casting slab 11, and the upper and lower rolls 8 and 9 are denoted by the same reference numerals as those in FIG. 8 and have the same functions. The bottom nozzle 4 is provided with a flow dividing plate 3 including a horizontal flow dividing plate 1 and a vertical flow dividing plate 2.

As shown in FIG. 7 (a), compared to the conventional method of FIG. 8, the molten metal flow in the vertical direction is made uniform, and as shown in FIG. 7 (b), the molten metal flow at the width end is reduced. Expected to be accelerated.

Based on the above findings, the gist of the present invention lies in the following (1) to (6). (1) In the twin roll horizontal pouring method, the melt flow path is
A flow dividing plate for continuous casting of a thin plate, comprising a vertical dividing plate divided into two or more sections.

(2) The sum of the thicknesses of the plurality of vertical flow dividing plates is not more than 0.5 times the width of the flow path, and the flow width of one of the flow paths at the center of the width and the flow at the end of the width. The ratio of the width of the channel to the inflow side is 0.2
The flow splitting plate for continuous casting of a thin plate according to the above item (1), wherein the flow splitting ratio is 5 to 1.0, and 1.0 to 3.0 on an outflow side.

(3) A flow dividing plate for continuous casting of a thin plate, comprising a horizontal flow dividing plate for dividing a molten metal flow path into upper and lower two parts in a twin roll horizontal pouring method.

(4) The thickness of the horizontal flow dividing plate is 0.2
5 to 0.75 times, and the ratio of the height of the upper channel to the lower channel is 0.5 to 1.0 on the inflow side and 1.
The flow dividing plate for continuous casting of a thin plate according to the above (3), wherein the ratio is 0 to 2.0.

(5) The method according to (1), further comprising: a horizontal flow dividing plate for dividing the molten metal flow path into two upper and lower parts, and a vertical flow dividing plate for dividing the molten metal flow path into three or more in the width direction. The flow dividing plate for continuous casting of a thin plate according to any one of items (1) to (4).

(6) The flow dividing plate for continuous casting of a thin plate according to any one of (1) to (5) is used, and the degree of superheat of the molten metal is 20 to 80.
A continuous casting method for a thin plate, characterized in that the casting is performed at ℃.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view showing an example of the shape of the flow dividing plate of the present invention used in the twin-roll horizontal pouring method. Figure (a)
Is a shunt plate 3 having only three vertical shunt plates 2, FIG. 2 (b) is a shunt plate 3 having only a horizontal shunt plate 1, and FIG. 2 (c) is a shunt having a horizontal shunt plate 1 and a vertical shunt plate 2. Plate 3. Figures (a) to (c)
5 shows a state in which the flow dividing plate 3 is incorporated in the bottom nozzle 4 indicated by a broken line. In the figure, the flow dividing plate 3 is a bottom nozzle 4
Although it is shown as a part to be incorporated in the bottom nozzle 4, it may be integrated with the bottom nozzle 4 or other parts. In FIG. 1C, the horizontal shunt plate 1 and the vertical shunt plate 2 are integrated, but may be combined.

FIG. 2 shows a configuration example of a casting nozzle using the flow dividing plate of the present invention. The casting nozzle for supplying the molten metal includes a bottom nozzle 4 and a pair of side nozzles 5. The flow dividing plate 3 is combined with the upper weir 6 and incorporated into the bottom nozzle 4.

FIG. 3 is a schematic view showing an example of a continuous sheet casting apparatus for a twin roll horizontal pouring method using a flow dividing plate according to the present invention.
(a) is a longitudinal sectional view, and (b) is a plan view. In the figure, the side wall of the bottom nozzle 4 is widened so that the molten metal flow path from the tundish 7 is widened, and the flow dividing plate 3 is also widened. However, the flow dividing plate of the present invention is not necessarily required. It doesn't have to be widespread.

In the figure, the casting space in the twin-roll horizontal pouring method is composed of an upper roll 8, a lower roll 9, a bottom nozzle 4, and a pair of side nozzles 5. In the example shown in the figure, the body length of the upper roll 8 is the same as the width of the slab 11, and the body length of the lower roll 9 is longer than the upper roll 8.

The bottom nozzle 4 forms a flow path of the molten metal, supplies the molten metal 10 in the tundish 7 on the upstream side between the rolls, makes close contact with the lower roll 9, and slides on the peripheral surface thereof to melt the molten metal. Hold the bottom of.

The side nozzle 5 has an upper roll 8
At the same time, the bottom surface slides on the peripheral surface of the lower roll 9 to hold the side surface of the molten metal.

The flow dividing plate 3 is incorporated in the flow path of the molten metal on the inner surface of the bottom nozzle 4, and divides the flow path of the molten metal into two vertical divisions by the horizontal distribution plate 1 and four vertical divisions by the vertical distribution plate 2. .

The upper weir 6 is incorporated in the upper part on the inflow side of the flow dividing plate 1 to prevent floating substances such as scum generated on the surface of the upstream tundish 7 from flowing out between the rolls. Is not an essential component.

A casting method using the flow dividing plate of the present invention will be described with reference to FIG. The molten metal 10 is injected from a ladle or a melting furnace (not shown) into the tundish 7, reaches the bottom nozzle 4 directly connected to the tundish 7, and flows into a flow path formed by the flow dividing plate 3.

The molten metal 10 that has flowed in is appropriately divided up and down by the horizontal flow dividing plate 1 arranged at the middle of the surface level, and is also appropriately divided in the width direction by the plurality of vertical flow dividing plates 2. . Compared to the case where there is no flow dividing plate, the cross-sectional area of the molten metal flow path is reduced by the arrangement of the horizontal flow dividing plate 1 and the vertical flow dividing plate 2, and the flow velocity of the molten metal is increased.

The molten metal 10 whose flow velocity has been appropriately increased through the flow dividing plate 3 is supplied to the casting space, and the upper and lower rolls 8 and 9
Is solidified evenly on the peripheral surface of the upper and lower rolls 8 and 9, and is pressed into contact with the closest contacts to form a slab 11.

The details of the flow dividing plate of the present invention will be described below. The embodiments of the flow dividing plate of the present invention are only the vertical flow dividing plate 2 of FIG. 1 (a), only the horizontal flow dividing plate 1 of FIG. 1 (b), or FIG.
May be combined with the horizontal distribution plate 1 and the vertical distribution plate 2.

In order to properly distribute the flow of the molten metal at the width center and the width end, the vertical flow dividing plate 2 is at least two, preferably 3-5.
The configuration of the sheet is good. The effect does not change even if six or more vertical flow dividing plates are arranged. When using a flow dividing plate having a vertical distribution plate and a horizontal distribution plate, the number of the vertical distribution plates 2 may be changed on the upper and lower surfaces of the horizontal distribution plate 1, and it is not always necessary to arrange them at the same position in the vertical direction. Further, the shape of the vertical flow dividing plate 2 does not necessarily have to be vertical, and any shape may be used as long as the flow path is partitioned in the width direction.

Hereinafter, preferred dimensions and arrangement of the flow dividing plates will be described. It is preferable that the sum of the thicknesses of the vertical flow dividing plates 2 is 0.5 times or less the width of the flow path. Even if the thickness of the vertical flow dividing plate 2 is small, the rectifying effect of the molten metal in the width direction can be exhibited.
If the sum of the thicknesses of the vertical distribution plates 2 exceeds 0.5 times the width of the flow channel, the rectification effect may be reduced. That is, when the number of the vertical flow dividing plates is two or three, the thickness per one becomes large, and the stagnation area or the turbulence of the molten metal flow is likely to occur near the outflow side end. In the case of 4 to 5 sheets, since the width of each flow path becomes small, the flow rate of the molten metal is affected by the shape difference of the inflow side end, and the expected flow distribution effect may not be obtained. is there.

It is preferable that the thickness of the vertical flow dividing plate is small.
In addition, it is preferable that the shapes of the inflow side and the outflow side end are the same at the same thickness. Although there is no lower limit for the thickness, it is sufficient that the thickness does not cause damage due to insufficient strength of the flow dividing plate material. For the refractory materials normally available, the lower limit of the thickness is 20.
It is about 80 mm / sheet.

Normally, the thickness of the vertical flow dividing plate 2 is constant in the flow direction and the vertical direction, but it is necessary to maintain a preferable range of the sum of the above thicknesses and a preferable range of each divided flow width described later. If
It may be tapered.

In order to prevent the formation of a fixed shell at the quadruple boundary point at the width end of the bottom nozzle, the flow velocity of the molten metal is preferably larger at the width end than at the center. For this reason, the inflow width of the flow path at the width end is set to be equal to or greater than the inflow width of the flow path at the center,
It is preferable to cope by making the outflow width equal or smaller. Therefore, on the inflow side, the vertical flow dividing plate is arranged so that the ratio of the width of the flow path at the center of the width to the width of the flow path at both width ends is 1.0 or less on the inflow side and 1.0 or more on the outflow side. Is preferred.

FIG. 4 is a schematic diagram for explaining the dimensions of the flow channel width. Although FIG. 1 shows a flow dividing plate having a horizontal flow dividing plate 1 and a vertical flow dividing plate 2, the following description is also applied to a type without a horizontal flow dividing plate.

In the same figure, when three vertical distribution plates A, B and C are used, the side walls of the bottom nozzle and the flow ends R1 and R4 at the width ends determined by the vertical distribution plates A and C are used. , There are flow paths R2 and R3 in the central part sandwiched by the vertical distribution plates A, B and C. The arrangement of the vertical flow dividing plate 2 is symmetrical in the width direction, and the thickness of the vertical flow dividing plate is all the same, and the width Wci of the flow passages at the inlets of the flow passages R2 and R3 in the central portion is assumed.
Wci = (the interval Pi between the inflow portions of the vertical distribution plate A and the vertical distribution plate B) − (the thickness T of the vertical distribution plate), and the inflow width Wei of the flow path at the width end is Wei = (the bottom nozzle Inflow width Wni) × 0.5− (thickness T of the vertical flow dividing plate) × 1.5− (inflow channel width Wci at the center of the width) Therefore, the ratio Rri of the inflow channel width is Rri = (The flow width Wci at the center of the width) / (the flow width Wei at the width end).

Similarly, for the width Wco of the outlet flow path at the center portions R2 and R3, Wco = Po−T, and the outflow width Weo of the flow path at the end of the width is expressed as Weo = Wno × 0.5−T × 1.5- (outflow channel width Wco at the center of the width) Therefore, the ratio Rro of the outflow channel width is represented by Rro = Wco / Weo.

If the ratio Rri of the width of the flow path on the inflow side exceeds 1.0, the amount of molten metal flowing into the flow path on the end side in the flow dividing plate becomes small, so that stagnation near the quadruple boundary point is suppressed. There is a possibility that the effect of preventing the fixed shell cannot be obtained. If the Rri is less than 0.25, the flow path in the central portion becomes too narrow, and there is a possibility that a fixed shell is generated in the central portion. Rri
Is more preferably in the range of 0.5 to 0.8.

If the ratio Rro of the width of the flow path on the outflow side is less than 1.0, the flow speed of the molten metal from the flow path on the end side in the flow dividing plate becomes small, so that the stagnation of the molten metal at the width end is suppressed. Then, there is a possibility that the effect of preventing the fixed shell cannot be obtained. Said Rro
If the ratio exceeds 3.0, the outflow velocity in the flow path in the central portion is reduced, and there is a possibility that a fixed shell is generated in the central portion.
The more preferable range of Rro is 1.2 to 2.0.

In FIG. 4, the cross-sectional shape of the vertical flow dividing plate 2 is represented by a rectangle or a parallelogram. However, the end faces on the inflow side and the outflow side are preferably tapered so as not to cause turbulence or stagnation of the molten metal. Should be streamlined. The dimension of the width of the flow passage is defined by a size in which the vertical cross section of the vertical flow dividing plate is regarded as a rectangle or a parallelogram regardless of the taper shape of the inlet and the outlet of the vertical flow dividing plate.

FIG. 5 is a plan view showing an example of the arrangement of the vertical flow dividing plate 2 of the flow dividing plate. FIG. 3A shows an example in which three vertical flow dividing plates have a flow path width ratio of 0.7 on the inflow side and 1.2 on the outflow side. FIGS. 7B and 7C show examples in which the number of the vertical flow dividing plates 2 is two and five, respectively, and the ratio of the flow channel width is about 0.7 on the inflow side and about 1.0 on the outflow side.
5 is an example.

The shape and arrangement of the vertical flow dividing plate 2 are restricted by the shape of the bottom nozzle. The longer the length of the vertical distribution plate in the flow path direction is, the more rectifying effect is. However, the minimum width of the flow path of the flow distribution plate (the width corresponding to Wni in the type shown in FIG. 4) is 2.0.
Since the effect does not change even if the length is longer than twice, it is preferable that the upper limit of the length is 2.0 times the minimum flow path width and the lower limit is 0.5 times.

The function of the horizontal flow dividing plate 1 is to substantially equalize the amount of molten metal supplied to the upper roll and the amount of molten metal to the lower roll.
The objective is to make the quality of both sides of the slab almost uniform and to increase the flow velocity. The molten metal on the lower surface of the horizontal distribution plate receives the flow resistance from the bottom and the horizontal distribution plate, while the flow path on the upper surface is only the flow resistance of the horizontal distribution plate. It is shorter than the lower channel. Therefore, when the horizontal flow dividing plate is placed in the middle of the level of the molten metal, the flow velocity of the upper surface flow path at the outlet tends to increase.

In order to make the flow velocity uniform on the upper and lower surfaces, the height of the upper inlet is made smaller than the height of the lower inlet (upper channel height / lower channel height <1.0). In the outlet, it is preferable that the height of the outlet on the upper surface is equal to or larger than the height of the outlet on the lower surface (the height of the upper surface passage / the height of the lower surface passage ≧ 1.0). However, if the height of the flow path on the upper surface on the inflow side is too small, the inflow amount becomes too small. Therefore, it is preferable to set the lower limit of the upper surface flow path height / the lower surface flow path height to 0.5. On the outflow side, if the height of the lower flow path is too small, the flow resistance increases and the flow velocity may be reduced. Therefore, the upper limit of the upper flow path height / the lower flow path height is set to 2.0. Is preferred. More preferably, the above ratio is 0.6 to 0.9 at the inlet, and 1.1 to 0.9 at the outlet.
It is good to be 1.5.

Here, the flow path height is defined as the height when the vertical cross section of the horizontal flow dividing plate is regarded as a rectangle having the same thickness regardless of the taper shape of the inlet and the outlet of the horizontal flow dividing plate. It shall be.

Even if two or more horizontal flow dividing plates are arranged, the effect is not improved. The thickness of the horizontal diversion plate is 0.2
It is preferable to set it to 5 to 0.75 times. If the thickness of the horizontal flow dividing plate is less than 0.25 times the height of the molten metal, the effect of increasing the flow velocity cannot be obtained sufficiently because the reduction in the cross-sectional area of the molten metal flow path is not sufficient. When the thickness of the horizontal flow dividing plate exceeds 0.75 times the height of the molten metal surface, the height of the flow path is reduced, and particularly, the ratio of the molten metal surface area to the volume of the molten metal is increased on the upper surface side. There is a risk of skinning due to cooling. More preferably, the thickness of the horizontal flow dividing plate is 0.4 to 0.6 of the molten metal level.
It is better to double.

The end faces on the inflow side and the outflow side of the horizontal flow dividing plate are preferably shaped so as not to cause turbulence or stagnation of the molten metal. In FIG. 1 or FIG. 2, the end face has a square shape for the sake of simplicity, but a tapered shape, more preferably a streamlined shape is preferable.

FIG. 6 shows an example of the sectional shape of the horizontal flow dividing plate of the present invention. 2A and 2B are examples in which the thickness of the horizontal flow dividing plate 1 is about 0.5 times the height of the molten metal surface, and FIG. (b) is streamlined. FIGS. 3 (c) and 3 (d) show examples in which the thickness of the horizontal flow dividing plate 1 is 0.75 times and 0.25 times the height of the molten metal, respectively, and FIG. The tapered shape is shown in FIG.

Other points to consider when designing the bottom nozzle are:
The width of the flow path on the inner surface of the bottom nozzle is preferably tapered and widened from upstream to downstream. This has the effect of reducing the horizontal cross-sectional area of the metal surface, increasing the metal surface rising speed at the start of casting, and reducing the heat radiation area.

Although the material of each member constituting the flow dividing plate is not limited, a refractory having heat resistance and corrosion resistance to molten metal is used. For example, fused silica, magnesia, alumina,
It is a simple substance such as zirconia, sialon, carbon, boron nitride, or a composite thereof.

When the flow dividing plate of the present invention as described above is used in the twin-roll horizontal pouring method, the molten metal is preferentially supplied to the vicinity of the triple boundary and the quadruple boundary, thereby suppressing the formation of the fixed shell.
A slab having a uniform solidification structure on the upper and lower surfaces of the slab can be manufactured.

The apparatus used for the casting nozzle and the twin-roll horizontal pouring method shown in FIG. 3 has an example in which the lower roll has a longer body length than the upper roll, and the bottom surface of the side nozzle is slid on the lower roll peripheral surface. However, the present invention is not limited to the above example. For example, the same effect as in the above example can be obtained by a twin-roll lateral pouring method in which the body lengths of the upper roll and the lower roll are made equal and the side surface of the side nozzle is slid on the end faces of the upper and lower rolls. The upper roll may have the same diameter as or a different diameter from the lower roll.

In casting using the flow dividing plate of the present invention,
It is necessary to control the degree of superheat of the molten metal in an appropriate range. If the degree of superheat is too low, a sticking shell is likely to be generated, which not only causes a biting flaw but also makes the operation unstable such as slab breakage. If the degree of superheat is too high, the operation will be stable, but slabs will have many vertical cracks. Therefore, it is preferable to set the temperature as low as possible within a range in which the fixing shell does not occur. In the casting method of the present invention, the degree of superheat needs to be 20 to 80 ° C, and more preferably 30 to 70 ° C. When the flow dividing plate having the vertical flow dividing plate and the horizontal flow dividing plate of the present invention is used, the molten metal is appropriately divided in both the width direction and the vertical direction, so that an operation aiming at the lower limit of the degree of superheat is possible. However, in the flow dividing plate including only the vertical flow dividing plate of the present invention, since there is no appropriate branch flow of the molten metal in the vertical direction, a fixed shell is easily generated on the lower surface, and the lower limit of the degree of superheat is not preferable. Similarly, since there is no appropriate branch flow in the width direction in the case of only the horizontal branch plate, a fixed shell is likely to be generated at the width end, and the lower limit of the degree of superheat is not preferable.

[0077]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An SU having a thickness of 2.0 mm and a width of 700 mm was obtained by a twin-roll horizontal pouring method using a flow dividing plate 3 shown in FIG. 1 and a casting nozzle (bottom nozzle 4 and side nozzle 5) shown in FIG.
An S304 stainless steel thin plate was cast, and the operation stability and the presence or absence of a surface defect of the slab were examined. For comparison, casting without using a flow dividing plate was also performed.

As the flow dividing plate, a horizontal dividing plate only, a vertical dividing plate only, and a combination of a horizontal dividing plate and a vertical dividing plate were used. As the material of the casting nozzle, fused silica was used for the bottom nozzle and the side nozzle, and alumina was used for the flow dividing plate and the upper weir.

When a flow dividing plate is used, the size of the current dividing plate is
(Width of the inflow portion 400 mm / width of the outflow portion 600 mm) × length 400 mm × height 250 mm. The water level at the front of the bottom nozzle was 180 mm.

The diameter of the upper roll is 1500 mm and the body length is 700 mm. The diameter of the lower roll is 1500 mm and the body length is 1
000 mm, and the inside of each of the upper and lower rolls was water-cooled. The casting speed was 0.85 m / s.

The molten metal was supplied to the tundish after the superheat was adjusted to 15 to 110 ° C. in a melting furnace disposed immediately above the tundish. Tables 1 and 2 show the superheat conditions, the dimensional conditions of the flow dividing plate, and the casting results.

[0082]

[Table 1]

[0083]

[Table 2]

No. Nos. 1 and 2 are tests of a comparative example not using a flow dividing plate. Three or less are examples of the present invention. No.
In the case of No. 1, when the degree of superheat of the molten metal was 70 ° C., the operation was unstable and the slab was broken. No. In the case of No. 2, the operation was stabilized when the degree of superheat was set to 110 ° C., but many vertical cracks were found in the slab.

No. Tests 3 to 14 are tests using only a vertical flow dividing plate. No. Nos. 3 to 7 and Nos. 10 to 14 vertical flow dividing plates were constituted by three sheets. No. The influence of the degree of superheat was investigated in 3-7.

No. In No. 3, the degree of superheat was 20 ° C., which was the lower limit of the present invention. The operation was almost stable, although there were signs of breakage. Biting flaws were scattered on the upper and lower surfaces of the slab. Although the quality was within an acceptable range, it was found that the degree of superheat was insufficient with only the vertical shunt plate in consideration of the fluctuation range of the molten metal temperature.

No. In No. 4, the degree of superheat was 30 ° C. Although the operation was stable, unevenness of the solidified structure was observed on the upper and lower surfaces of the slab. Although the quality was within an acceptable range, it was found that the degree of superheating was somewhat insufficient with the vertical shunt plate alone, considering the fluctuation range of the molten metal temperature.

No. In No. 5, since the degree of superheat was set to 50 ° C., the operation was stable, and the slab surface was sound. No. No. 6 has a degree of superheat of 80 ° C., and the ratio of the flow path width at the center to the flow path width at the width end is 1.0 on the inflow side and 1.0 on the outflow side.
Casting was possible without any problems in operation stability and surface quality.

No. In No. 7, the degree of superheat was set to 90 ° C., exceeding the limit of the present invention. The condition of the flow dividing plate is No. Same as 6.
The operation was stable, but there were many vertical cracks. N below
o. In the tests from 8 to 14, the degree of superheat was 50 ° C.

No. 8 was composed of two vertical flow dividing plates.
Casting was possible without any problems in operation stability and surface quality. No.
9 was composed of five vertical flow dividing plates. Casting was possible without any problems in operation stability and surface quality.

No. In No. 10, the total thickness of the vertical flow dividing plates was set to 0.68 times the entire width of the inflow-side flow path. During operation, the slab was broken, and the upper and lower surfaces of the slab had many bite flaws. No. 11
On the inflow side, the width of the flow path at the center was 1.2 times the width end.
During the operation, the slab was broken, and the lower surface side end of the slab had many bite flaws.

No. Reference numeral 12 denotes the outflow side, in which the flow path width at the center is 0.7 times the width end. During the operation, the slab was broken, and the lower surface side end of the slab had many bite flaws. No. Reference numeral 13 denotes the inflow side, in which the width of the flow path at the center is 0.2 times the width end. During operation, the slab was broken, and bites were generated on the upper and lower surfaces of the slab.

No. Reference numeral 14 denotes an outflow side, in which the width of the flow path at the center is 2.5 times the width end. During operation, the slab was broken, and a biting flaw was generated at the center of the upper and lower surfaces of the slab. No. 15-2
No. 4 was constituted only by a horizontal flow dividing plate. No. In Nos. 15 to 17, the influence of the degree of superheat was investigated.

No. No. 15 has a superheat degree of 20 ° C., which is the lower limit of the present invention. The operation was almost stable, but biting flaws were sporadic on the upper and lower surfaces of the slab. Acceptable quality,
Considering the fluctuation range of the molten metal temperature, it was found that the degree of superheat was insufficient with only the horizontal flow dividing plate.

No. No. 16 set the degree of superheat to 30 ° C. The operation was stable, but unevenness of the solidification structure was observed on the lower surface of the slab. Although the quality was within an acceptable range, it was found that the degree of superheat was somewhat insufficient with only the horizontal shunt plate in consideration of the fluctuation range of the molten metal temperature. As a countermeasure, the degree of superheat was further increased, and the degree of superheat was set to 50 ° C. in the following tests.

No. In No. 17, the operation was stable and the slab surface was sound. No. In No. 18, the ratio of the height of the flow path on the upper and lower surfaces of the horizontal flow dividing plate was 1.0. The operation was stable and the slab surface was sound. No. In No. 19, the thickness of the horizontal flow dividing plate was set to 0.22 times the height of the molten metal surface. The operation was stable,
Biting flaws occurred on the lower surface. No. In No. 20, the thickness of the horizontal flow dividing plate was set to 0.83 times the height of the molten metal surface. The operation was stable, but biting flaws occurred on the lower surface.

No. Reference numeral 21 denotes an inflow side in which the height of the flow path on the upper surface is set to 1.25 times that of the flow path on the lower surface. The operation was stable, but biting flaws occurred on the lower surface. No. Reference numeral 22 denotes an outflow side, in which the height of the upper channel is 0.8 times that of the lower channel. The operation was stable, but biting flaws occurred on the lower surface.

No. Reference numeral 23 denotes an inflow side in which the height of the upper channel is 0.43 times the height of the lower channel. The operation was stable,
Biting flaws occurred on the upper surface. No. Reference numeral 24 denotes an outflow side, in which the height of the upper channel is 2.33 times that of the lower channel. The operation was stable, but biting flaws occurred on the lower surface.

Test No. 2 in Table 2 Reference numerals 25 to 36 denote flow dividing plates composed of a horizontal dividing plate and a vertical dividing plate. No. 25
In the case of -27, the influence of the degree of superheat was investigated. No. No. 25 had a superheat degree as low as 15 ° C., which was less than the lower limit of the present invention. The operation was unstable and biting flaws were scattered on the upper and lower surfaces. No. In No. 26, the degree of superheating was set to the lower limit of 20 ° C. of the present invention. The operation was stable, but unevenness of the solidified structure was observed on the upper and lower surfaces. Although the quality was within an acceptable range, the degree of superheat was found to be slightly insufficient in consideration of the fluctuation range of the molten metal temperature.

As a countermeasure, the degree of superheat was set to 30 ° C. in the following tests. No. At 27, the operation was stable and the slab surface was sound. No. Numeral 28 designates the ratio of the height of the upper and lower passages on the inflow side and the outflow side of the horizontal distribution plate to 1.
0, 1.0, and the ratio of the width of the flow channel between the width center portion and the width end portion on the inflow side and the outflow side of the vertical flow dividing plate is 1.0, respectively.
1.0. The operation was stable and the slab surface was sound.

No. Reference numeral 29 denotes the inflow side of the vertical flow dividing plate, in which the width of the flow path at the center of the width is 1.2 times the width end. Although the operation was stable, biting flaws occurred frequently at the lower end of the slab on the lower side. N
o. Reference numeral 30 denotes the outflow side of the vertical flow dividing plate, in which the flow path width at the center of the width is 0.7 times the width end. Although the operation was stable, biting flaws occurred frequently at the lower end of the slab on the lower side.

No. In No. 31, the thickness of the horizontal flow dividing plate was set to 0.22 times the height of the molten metal surface. Although the operation was stable, biting flaws frequently occurred on the lower surface of the slab. No. In No. 32, the thickness of the horizontal flow dividing plate was set to 0.83 times the height of the molten metal surface. Although the operation was stable, biting flaws occurred frequently on the upper surface of the slab.

No. Reference numeral 33 denotes the inflow side of the horizontal flow dividing plate, and the flow path height on the upper surface is 1.25 times the lower surface. The operation was stable, but biting flaws occurred on the lower surface. No. Reference numeral 34 denotes an outflow side of the horizontal flow dividing plate, and the height of the flow path on the upper surface is set to 0.8 times the lower surface. The operation was stable, but biting flaws occurred on the upper surface.

No. Reference numeral 35 denotes an inflow side of the horizontal flow dividing plate, and the height of the flow path on the upper surface is set to 0.43 times the lower surface. The operation was stable, but biting flaws occurred on the upper and lower surfaces. No. Reference numeral 36 denotes an outflow side of the horizontal flow dividing plate, and the flow path height on the upper surface is 2.33 times the lower surface. The operation was stable, but biting flaws occurred on the upper and lower surfaces.

From the above test results, if the dimensions of the flow dividing plate were properly selected in the casting of stainless steel, the degree of superheat was 30 ° C. for the vertical dividing plate only or the horizontal dividing plate only. The above degree of superheat is preferable, and it has been found that a superheat degree of 20 ° C. or more is necessary in the case of a flow dividing plate composed of a horizontal distribution plate and a vertical distribution plate. On the other hand, in order to prevent vertical cracks, the upper limit of the degree of superheat must be 80 ° C.
In each case, it was found that the preferable range of the degree of superheat was 30 to 70 ° C.

[0106]

By using the flow dividing plate of the present invention, it is possible to prevent the occurrence of a fixed shell and to stably produce a slab having uniform upper and lower surfaces.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a flow dividing plate for continuous casting of a thin plate according to the present invention, wherein FIG. 1 (a) is a configuration having only a vertical distribution plate, FIG. 1 (b) is a configuration having only a horizontal distribution plate, and FIG. Is a configuration provided with a horizontal distribution plate and a vertical distribution plate.

FIG. 2 is a configuration diagram of a casting nozzle using the flow dividing plate of the present invention.

FIG. 3 is a schematic view of a continuous sheet casting apparatus using a flow dividing plate of the present invention, wherein FIG. 3 (a) is a longitudinal sectional view and FIG. 3 (b) is a plan view.

FIG. 4 is an explanatory diagram of dimensions of a vertical flow dividing plate of the current dividing plate of the present invention.

FIG. 5 is a plan view showing an example of the arrangement of vertical flow dividing plates of the flow dividing plate of the present invention. FIG. 1.2 is an example. FIGS. 7B and 7C show examples in which the number of vertical flow dividing plates is 2 and 5, respectively, and the ratio of the flow channel width is about 0.7 on the inflow side and about 1.5 on the outflow side.
This is an example.

FIG. 6 is a cross-sectional view of various shapes of the horizontal flow dividing plate of the present invention. FIG. 6 (a) has a tapered cross section on the inflow / outflow side, and the thickness of the horizontal flow distribution plate is 0. Fig. 5 (b) shows an example in which the cross section on the inflow / outflow side has a streamlined shape, and the thickness of the horizontal shunt plate is 0.5 times the height of the molten metal, and Figs. Are examples in which the thickness of the horizontal flow dividing plate 1 is 0.75 times and 0.25 times the height of the molten metal, respectively.

FIGS. 7A and 7B are schematic views of the flow of molten metal when the flow dividing plate of the present invention is used, wherein FIG. 7A is a longitudinal sectional view and FIG. 7B is a plan view.

8A and 8B are schematic diagrams of the flow of molten metal when a casting nozzle according to the related art is used, wherein FIG. 8A is a longitudinal sectional view and FIG. 8B is a plan view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Horizontal distribution plate 2 Vertical distribution plate 3 Distribution plate 4 Bottom nozzle 5 Side nozzle 6 Upper weir 7 Tundish 8 Upper roll 9 Lower roll 10 Melt 11 Cast piece 12 Hot surface 13 Bottom nozzle side wall 14 Adhesive shell A, B, C Vertical Divider plates R1, R4 Channels at the width end R2, R3 Channels at the center T Thickness of vertical divider plate Wci Channel width at the inlet at the center of the Wci width Wco Channel width at the outlet at the center at the width Wei Width Inflow width of the end flow path Weo width Outflow width of the end flow path Wni Inflow width of the bottom nozzle Wno Outflow width of the bottom nozzle Pi Distance at the inflow part of the vertical flow dividing plate Po Distance at the flow part of the vertical flow dividing plate

Claims (6)

[Claims] 1. A flow dividing plate for continuous casting of a thin plate, comprising a vertical flow dividing plate for dividing a molten metal flow path into three or more in a width direction in a twin-roll horizontal pouring method. 2. The flow path width of one of the flow paths at the center of the width and the flow path at the end of the width, wherein the sum of the thicknesses of the plurality of vertical flow dividing plates is 0.5 times or less the flow path width. Ratio of 0.25 on the inflow side
The split plate for continuous casting of a thin sheet according to claim 1, wherein the split plate is 1.0 to 1.0 and 1.0 to 3.0 on an outflow side. 3. A flow dividing plate for continuous casting of a thin plate, comprising a horizontal flow dividing plate for dividing a molten metal flow path into upper and lower two parts in a twin-roll horizontal pouring method. 4. The thickness of the horizontal flow dividing plate is 0.25 of the molten metal level.
0.75 times, and the ratio of the height of the upper channel to the lower channel is 0.5 to 1.0 on the inflow side and 1.0 on the outflow side.
The flow dividing plate for continuous casting of a thin plate according to claim 3, wherein the ratio is 2.0 to 2.0. 5. A horizontal flow dividing plate for dividing a molten metal flow path into two upper and lower parts, and a vertical flow dividing plate for dividing a molten metal flow path into three or more in a width direction. The flow dividing plate for continuous casting of a thin plate according to any one of the above. 6. A continuous casting method for a thin plate, comprising casting the molten metal at a superheat degree of 20 to 80 ° C. using the flow dividing plate for continuous casting of a thin plate according to any one of claims 1 to 5.