JP7695529B2 - Submerged nozzle for twin-roll continuous casting apparatus, twin-roll continuous casting apparatus, and method for producing thin-walled cast strip - Google Patents

Description

The present invention relates to a twin-roll continuous casting apparatus that supplies molten metal to a molten metal pool formed by a pair of chill rolls and a pair of side weirs, and forms and grows a solidified shell on the peripheral surface of the chill rolls to produce thin-walled slabs. The invention relates to an immersion nozzle for a twin-roll continuous casting apparatus that is used when pouring the molten metal into the molten metal pool, a twin-roll continuous casting apparatus equipped with the immersion nozzle for a twin-roll continuous casting apparatus, and a method for producing thin-walled slabs using the immersion nozzle for a twin-roll continuous casting apparatus.

As a method for producing thin metal slabs, a twin-roll continuous casting machine is provided that has an internal water-cooling structure, is equipped with a pair of cooling rolls that rotate in opposite directions, supplies molten metal from a tundish to a molten metal pool formed by the pair of rotating cooling rolls and a pair of side gates, forms and grows a solidified shell on the outer circumferential surface of the cooling rolls, and presses the solidified shells formed on the outer circumferential surfaces of the pair of cooling rolls together at the roll kiss point to produce a thin slab of a predetermined thickness. Such twin-roll continuous casting machines are used for various metals.

In the above-mentioned twin-roll continuous casting apparatus, the molten metal pool portion formed between the pair of chill rolls has a shape that extends in the longitudinal direction (the width direction of the molten metal pool portion) parallel to the axis of the chill rolls.
When molten metal is supplied to this molten metal pool using a pouring nozzle, if the flow of molten metal becomes uneven in the longitudinal direction parallel to the axis of the chill roll (width direction of the molten metal pool), the height of the molten metal surface in the molten metal pool will fluctuate in the longitudinal direction parallel to the axis of the chill roll, causing uneven plate thickness in the width direction of the thin-walled cast strip. The pouring nozzle is structured to include an outer nozzle and an inner nozzle inserted inside the outer nozzle, and molten metal is supplied from the inner nozzle to the outer nozzle and then from the outlet of the outer nozzle to the molten metal pool.

When molten metal is fed into the mold from the submerged entry nozzle, if the discharge flow from the submerged entry nozzle fluctuates or becomes uneven, ripples will form in the molten metal pool, causing abnormal solidification that can become caught up and destabilize the casting, or uneven solidification in the mold can cause wrinkles or cracks on the surface of the slab, compromising the quality and material properties of the slab. In particular, in thin-wall casting processes, the stability and uniformity of the nozzle discharge flow must be adjusted more precisely.

As a measure to stabilize and uniformize the nozzle discharge flow, for example, Patent Documents 1 and 2 disclose a technique for adjusting the discharge flow by providing an obstacle inside the submerged nozzle to prevent the molten metal from flowing downward. However, adhesion or accumulation of inclusions in the molten metal or solidification of the molten metal itself can cause the flow of the molten metal to be so obstructed that the desired discharge flow cannot be obtained.

Moreover, Patent Documents 3 to 5 disclose a method of controlling the flow direction by providing a pressure loss member inside the outer nozzle.
Here, Patent Document 3 proposes using a porous refractory material as the pressure drop member.
Patent Documents 4 and 5 propose a pressure drop member in which a porous refractory material is formed with through holes.

Japanese Unexamined Patent Publication No. 165257/1983 Japanese Patent Application Publication No. 10-113752 Japanese Patent Application Publication No. 11-342455 Japanese Unexamined Patent Publication No. 61-289953 Japanese Patent Application Publication No. 07-068357

During steady-state casting, molten metal is stored inside the outer nozzle, and the discharge hole of the inner nozzle is immersed in the molten metal.
On the other hand, at the start of casting, no molten metal is stored inside the outer nozzle, and the discharge hole of the inner nozzle is exposed to the internal space of the outer nozzle. When molten metal is discharged from the discharge hole of the inner nozzle in this state, depending on the opening position and opening direction of the discharge hole, the discharge flow from the inner nozzle may cause the outflow distribution in the width direction from the outer nozzle to the molten metal pool to become non-uniform, which may cause disturbances in the flow of molten metal in the molten metal pool.

In more detail, the inner nozzle is usually provided with discharge holes in the width direction of the outer nozzle (the direction parallel to the axis of the cooling roll when installed in the molten metal pool portion), and the flow of molten metal tends to be stronger at the widthwise ends of the molten metal pool portion and weaker at the widthwise end center of the molten metal pool portion. This causes remelting of the solidified shell at the widthwise ends of the molten metal pool portion and poor solidification at the widthwise end center of the molten metal pool portion, which may make it difficult to start casting stably.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an immersion nozzle for a twin-roll continuous casting apparatus, a twin-roll continuous casting apparatus, and a method for manufacturing thin-walled slabs, which can stabilize casting and suppress deterioration of slab quality and material by making the widthwise flow distribution of molten metal flowing out from the immersion nozzle into the molten metal pool at the start of casting more uniform and steadily supplying molten metal from the tundish to the molten metal pool.

In order to solve the above-mentioned problems, the present invention provides an immersion nozzle for a twin-roll continuous casting apparatus, which is used in a twin-roll continuous casting apparatus that supplies molten metal to a molten metal pool portion formed by a pair of rotating chill rolls and a pair of side gates, and produces a thin-walled cast strip by forming and growing a solidified shell on the peripheral surface of the chill rolls, and which has an outer nozzle and an inner nozzle that supplies molten metal into the outer nozzle, and when the outer nozzle is disposed in the molten metal pool portion, the outer nozzle is arranged to extend in a direction parallel to the axis of the chill roll. the outer nozzle has a side wall portion extending along a center axis of the cooling roll, an end wall portion intersecting an axis of the cooling roll, and a bottom portion formed at lower ends of the side wall portion and the end wall portion, an outlet for the molten metal is formed near the bottom portion of the outer nozzle, a pressure loss member is disposed inside the outer nozzle above the outlet port, and a plurality of guide ridge portions extending in a vertical direction are formed on the inner surface of the side wall portion of the outer nozzle above the pressure loss member, and the guide ridge portions are formed above the outlet hole of the inner nozzle .

According to the twin-roll continuous casting apparatus submerged nozzle of this configuration, a pressure loss member is disposed above the discharge port inside the outer nozzle, and a plurality of guide ridges extending in the vertical direction are formed on the inner surface of the side wall of the outer nozzle above the pressure loss member. Therefore, when the discharge hole of the inner nozzle is exposed to the internal space of the outer nozzle at the start of casting, and a portion of the molten metal discharged from the inner nozzle collides with the inner surface of the side wall of the outer nozzle, a downward flow of molten metal is formed along the guide ridges, and the molten metal falls to the pressure loss member before reaching the widthwise end of the outer nozzle. In addition, a portion of the molten metal discharged from the inner nozzle reaches the widthwise end of the outer nozzle. This makes it possible to more uniformly distribute the molten metal in the width direction flowing out from the submerged nozzle to the molten metal pool at the start of casting.

In the submerged nozzle for a twin-roll continuous casting machine according to the present invention, the pressure loss member is preferably formed with a plurality of through holes extending therethrough in the vertical direction.
In this case, since the pressure loss member is provided with a plurality of through holes, clogging of the pressure loss member can be suppressed, and casting can be performed more stably.
When the pressure loss member is provided with a plurality of through holes, the outflow distribution of the molten metal from the outer nozzle is strongly affected by the discharge flow from the inner nozzle. However, by forming a plurality of guide protrusions extending in the vertical direction on the inner surface of the side wall of the outer nozzle, it is possible to make the outflow distribution in the width direction of the molten metal flowing out from the submerged entry nozzle into the molten metal pool at the start of casting more uniform.

In the submerged nozzle for a twin-roll continuous casting apparatus according to the present invention, it is preferable that the width W of the guide ridge portion is within the range of 5 mm or more and 30 mm or less, the protrusion height H of the guide ridge portion is within the range of 3 mm or more and 20 mm or less, and the pitch P of the multiple guide ridge portions is within the range of 5 mm or more and 60 mm or less.
In this case, since the width W, protrusion height H and pitch P of the guide ridges are within the above-mentioned ranges, the guide ridges can reliably form a downward flow of molten metal flowing vertically downward, making it possible to further uniform the widthwise flow distribution of the molten metal flowing out from the submerged nozzle into the molten metal pool at the start of casting.

The twin-roll continuous casting apparatus of the present invention is a twin-roll continuous casting apparatus that supplies molten metal to a molten metal pool formed by a pair of rotating chill rolls and a pair of side gates, and produces a thin-walled cast piece by forming and growing a solidified shell on the peripheral surface of the chill roll, and is characterized in that it is equipped with the above-mentioned twin-roll continuous casting apparatus submerged nozzle as a submerged nozzle that pours the molten metal into the molten metal pool.

The twin-roll continuous casting machine of this configuration is equipped with the above-mentioned twin-roll continuous casting machine submerged nozzle, which makes it possible to further uniformize the widthwise flow distribution of the molten metal flowing from the submerged nozzle into the molten metal pool at the start of casting, stabilizing casting and suppressing deterioration of the quality and material of the cast piece.

The method for producing a thin-walled cast slab of the present invention is a method for producing a thin-walled cast slab by supplying molten metal to a molten metal pool portion formed by a pair of rotating chill rolls and a pair of side weirs, and forming and growing a solidified shell on the peripheral surface of the chill rolls to produce a thin-walled cast slab, characterized in that the molten metal is poured into the molten metal pool portion using the above-mentioned submerged nozzle for a twin-roll continuous casting apparatus.

According to this method for manufacturing thin-walled cast slabs, the molten metal is poured into the molten metal pool using the submerged nozzle for the twin-roll continuous casting apparatus described above. This makes it possible to further uniformize the widthwise flow distribution of the molten metal that flows out from the submerged nozzle into the molten metal pool at the start of casting, and allows for the stable production of high-quality thin-walled cast slabs.

The present invention provides an immersion nozzle for a twin-roll continuous casting apparatus, a twin-roll continuous casting apparatus, and a method for manufacturing thin-walled slabs, which can stabilize casting and suppress deterioration of slab quality and material by making the widthwise flow distribution of molten metal flowing out of the immersion nozzle into the molten metal pool at the start of casting more uniform and steadily supplying molten metal from the tundish to the molten metal pool.

FIG. 1 is a schematic explanatory diagram showing an example of a twin-roll continuous casting apparatus using a submerged entry nozzle for a twin-roll continuous casting apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a molten steel pool portion of the twin-roll continuous casting apparatus shown in FIG. 1 . 1 is a schematic diagram of an embodiment of a submerged nozzle for a twin-roll continuous casting apparatus according to the present invention, in which (a) is a vertical cross-sectional view parallel to the axis of a chill roll when the submerged nozzle is disposed in a molten steel pool portion, and (b) is a cross-sectional view perpendicular to the axis of the chill roll when the submerged nozzle is disposed in a molten steel pool portion. 3A is a cross-sectional view taken along line A-A in FIG. 3, FIG. 3B is a cross-sectional view taken along line B-B in FIG. 3, and FIG. 3C is an explanatory view of an enlarged cross-section of the guide protrusion formed in the submerged nozzle for a twin-roll continuous casting apparatus according to an embodiment of the present invention. FIG. 4 is an enlarged cross-sectional explanatory view showing another example of a guide protrusion portion of the submerged nozzle for use in a twin-roll continuous casting apparatus according to an embodiment of the present invention.

Below, an embodiment of the present invention, an immersion nozzle for a twin-roll continuous casting apparatus (hereinafter referred to as an immersion nozzle), a twin-roll continuous casting apparatus, and a method for manufacturing a thin-walled cast piece, will be described with reference to the attached drawings. Note that the present invention is not limited to the following embodiment.

In this embodiment, molten steel is used as the molten metal, and a thin-walled cast slab 1 made of a steel material is manufactured. Examples of steel types include 0.001-0.01% C extra low carbon steel, 0.02-0.05% C low carbon steel, 0.06-0.4% C medium carbon steel, 0.5-1.2% C high carbon steel, austenitic stainless steel such as SUS304 steel, ferritic stainless steel such as SUS430 steel, 3.0-3.5% Si grain-oriented electrical steel, 0.1-6.5% Si non-oriented electrical steel, etc. (% is by mass).
In this embodiment, the width of the thin-walled cast strip 1 to be produced is within a range of 300 mm or more and 2000 mm or less, and the thickness is within a range of 1 mm or more and 5 mm or less.

As shown in FIG. 1, the twin-roll continuous casting apparatus 10 of this embodiment includes a pair of chill rolls 11, 11, bender rolls 12, 12 for bending the thin cast strip 1, pinch rolls 13, 13 for supporting the thin cast strip 1, side dams 15 arranged at the widthwise ends of the pair of chill rolls 11, 11, a tundish 18 for holding molten steel 3 to be supplied to a molten steel pool portion 16 defined by the pair of chill rolls 11, 11 and the side dams 15, and an immersion nozzle 20 for supplying molten steel 3 from the tundish 18 to the molten steel pool portion 16.

As shown in FIG. 2 , the molten steel surface in the molten steel pool portion 16 has a rectangular shape surrounded on all four sides by the peripheral surfaces of the pair of chill rolls 11, 11 and a pair of side weirs 15, 15, and the submerged nozzle 20 is disposed in the center of this rectangular molten steel surface.
In this embodiment, as shown in Figure 2, in the molten steel pool portion 16 and the submerged nozzle 20 arranged in the molten steel pool portion 16, the direction along the axial direction of the chill roll 11 is defined as the "width direction", and the direction perpendicular to the axial direction of the chill roll 11 is defined as the "thickness direction".

In this twin-roll continuous casting device 10, as shown in FIG. 1, the molten steel 3 comes into contact with the chill rolls 11, 11 rotating in the R direction and is cooled, so that solidified shells 5, 5 grow on the peripheral surfaces of the chill rolls 11, 11, and the solidified shells 5, 5 formed on the pair of chill rolls 11, 11 are pressed together at the drum kiss points, thereby casting a thin-walled cast piece 1 of a predetermined thickness.

Here, as the above-mentioned submerged nozzle 20, the submerged nozzle for use in a twin-roll continuous casting apparatus according to this embodiment is used.
As shown in FIG. 3 , the submerged nozzle 20 includes an outer nozzle 30 and an inner nozzle 21 that is inserted into the outer nozzle 30 .

3, the inner nozzle 21 is tubular with a closed lower end, and is disposed facing the internal space of the outer nozzle 30. When the inner nozzle 21 is disposed in the molten steel pool portion 16, discharge holes 22, 22 are provided facing both sides in the axial direction of the chill rolls 11, 11.
The shape of the inner nozzle 21 is not limited to the above-mentioned shape as long as it can discharge the ink evenly into the internal space of the outer nozzle 30 .

When positioned in the molten steel pool portion 16, the outer nozzle 30 has a side wall portion 31 extending in a direction parallel to the axis of the chill roll 11, an end wall portion 32 intersecting the axis of the chill roll 11, and a bottom portion 33 formed at the lower ends of the side wall portion 31 and the end wall portion 32, and has an internal space along the molten steel pool portion 16.
3B, the lower region of the outer nozzle 30 is gradually thinner in thickness going downward. The lower end of the lower region of the outer nozzle 30 is provided with a discharge port 36 that opens in a direction facing the cooling roll 11.
Here, the width direction length of the lower region of the outer nozzle 30 is set within a range of 40 to 80% of the width of the thin-walled cast strip 1 to be cast.

A pressure loss member 27 is disposed inside the lower region of the outer nozzle 30, above the discharge port 36. By disposing the pressure loss member 27, the molten steel 3 is stored inside the outer nozzle 30 in a steady state.
In this embodiment, the pressure-loss member 27 is preferably formed with a plurality of through-holes penetrating in the thickness direction.

A plurality of guide ridges 38 extending in the vertical direction are formed on the inner surface of the side wall portion 31 of the outer nozzle 30 at positions above the pressure loss member 27 .
In this embodiment, the lower region of the outer nozzle 30 is shaped so that its thickness gradually decreases toward the bottom, as shown in FIG. 3(b), and the guide protrusion portion 38 is formed so as to extend in the vertical direction and gradually move toward the center in the thickness direction as it extends downward.

In this embodiment, as shown in FIG. 4C, the guide ridge 38 is configured so that a cross section perpendicular to the extending direction thereof is rectangular.
Here, it is preferable that the width W of the guide protrusion 38 is within a range of 5 mm to 30 mm.
Moreover, it is preferable that the protruding height H of the guide ridge portion 38 is within a range of 3 mm or more and 20 mm or less.
Furthermore, it is preferable that the pitch P of the plurality of guide ridges is within a range of 5 mm to 60 mm.

4(a) and 4(b), in this embodiment, the guide protrusions 38 are formed uniformly in the width direction on the inner surface of the side wall 31. Also, the protrusion height H is constant in the extension direction.
In this embodiment, as shown in FIG. 3 , the guide ridges 38 are formed above the discharge holes 22 , 22 of the inner nozzle 21 .

Next, we will explain the method for producing thin-walled cast strips, which is the present embodiment, using the above-mentioned submerged nozzle 20 and twin-roll continuous casting device 10.

Molten steel 3 is supplied from a tundish 18 through an immersion nozzle 20 to a molten steel pool 16 formed by a pair of chill rolls 11, 11 and a side weir 15, and each chill roll 11, 11 is rotated in the direction of rotation R, i.e., so that the area where the pair of chill rolls 11, 11 are adjacent to each other faces the drawing direction of the thin-walled cast slab 1 (downward in FIG. 1).

As a result, a solidified shell 5 is formed on the peripheral surface of the chill roll 11. The solidified shell 5 then grows on the peripheral surface of the chill roll 11, and the solidified shells 5, 5 formed on each of the pair of chill rolls 11, 11 are pressed together at the roll kiss point, thereby casting a thin-walled cast piece 1 of a predetermined thickness.

Here, at the start of casting, no molten steel 3 is stored inside the outer nozzle 30, and the discharge hole 22 of the inner nozzle 21 is exposed to the internal space of the outer nozzle 30, and in this state, molten steel 3 is discharged from the discharge hole 22 of the inner nozzle 21.
Then, when the discharged molten steel 3 collides with the inner surface of the side wall portion 31 of the outer nozzle 30, it flows downward along the guide protrusion portion 38 extending in the vertical direction, generating a downward flow of the molten steel 3. As a result, a part of the molten steel 3 discharged from the inner nozzle 21 falls into the pressure loss member 27 before reaching the width direction end portion of the outer nozzle 30. In addition, a part of the molten steel 3 discharged from the inner nozzle 21 reaches the width direction end portion of the outer nozzle 30. As a result, the molten steel 3 is supplied uniformly in the width direction from the discharge port 36 of the outer nozzle 30 to the molten steel pool portion 16.

During steady casting, since the pressure loss member 27 is disposed inside the outer nozzle 30, the molten steel 3 is stored inside the outer nozzle 30 and the discharge hole 22 of the inner nozzle 21 is immersed in the molten steel 3. In this state, the molten steel 3 is supplied from the inner nozzle 21 into the outer nozzle 30.
As a result, the molten steel 3 is supplied uniformly in the width direction from the discharge port 36 of the outer nozzle 30 to the molten steel pool portion 16 .

According to the present embodiment of the submerged nozzle 20 for a twin-roll continuous casting apparatus, which is configured as described above, the pressure loss member 27 is disposed inside the outer nozzle 30 above the discharge port 36, and a plurality of guide ridges 38 extending in the vertical direction are formed at a position above the pressure loss member 27 on the inner surface of the side wall portion 31 of the outer nozzle 30. Therefore, when molten steel 3 is discharged from the inner nozzle 21 with the discharge hole 22 of the inner nozzle 21 exposed to the internal space of the outer nozzle 30 at the start of casting, when a portion of the discharged molten steel 3 collides with the inner surface of the side wall portion 31 of the outer nozzle 30, a downward flow of the molten steel 3 is formed along the guide ridges 38, and the molten steel 3 falls into the pressure loss member 27 before reaching the widthwise end of the outer nozzle 30. In addition, a portion of the molten steel 3 discharged from the inner nozzle 21 reaches the widthwise end of the outer nozzle 30. This makes it possible to more uniformly distribute the molten steel 3 in the width direction supplied from the submerged nozzle 20 to the molten steel pool portion 16 at the start of casting.

In addition, in this embodiment, when the pressure loss member 27 has multiple through holes, clogging of the pressure loss member 27 can be suppressed, and casting can be performed more stably. As described above, by forming multiple guide protrusions 38 extending in the vertical direction on the inner surface of the side wall portion 31 of the outer nozzle 30, it is possible to make the flow distribution in the width direction of the molten steel 3 supplied from the submerged nozzle 20 to the molten steel pool portion 16 more uniform, even when the pressure loss member 27 has multiple through holes.

In addition, in this embodiment, when the width W of the guide ridge portion 38 is in the range of 5 mm or more and 30 mm or less, the molten steel 3 that collides with the guide ridge portion 38 can be reliably guided downward.
Here, the lower limit of the width W of the guide ridge 38 is more preferably 10 mm or more, and even more preferably 15 mm or more. On the other hand, the upper limit of the width W of the guide ridge 38 is more preferably 25 mm or less, and even more preferably 20 mm or less.

In addition, in this embodiment, when the protruding height H is set to 3 mm or more, the molten steel 3 colliding with the guide ridge portion 38 can be reliably guided downward. On the other hand, when the protruding height H is set to 20 mm or less, the generation of metal at the guide ridge portion 38 can be suppressed.
Here, the lower limit of the protruding height H of the guide ridge portion 38 is more preferably 5 mm or more, and even more preferably 8 mm or more. On the other hand, the upper limit of the protruding height H of the guide ridge portion 38 is more preferably 15 mm or less, and even more preferably 12 mm or less.

In addition, in this embodiment, when the pitch P of the guide ridges 38 is 5 mm or more, it is possible to suppress the generation of metal between the guide ridges 38. On the other hand, when the pitch P of the guide ridges 38 is 60 mm or less, the molten steel 3 that collides with the guide ridges 38 can be reliably guided downward.
Here, the lower limit of the pitch P of the guide ridges 38 is more preferably 10 mm or more, and even more preferably 25 mm or more. On the other hand, the upper limit of the pitch P of the guide ridges 38 is more preferably 50 mm or less, and even more preferably 40 mm or less.

Furthermore, according to the twin-roll continuous casting apparatus 10 and the method for manufacturing thin-walled cast strip of this embodiment, the above-mentioned submerged nozzle 20 is used, so that it is possible to further uniformize the outflow distribution in the width direction of the molten steel 3 flowing out from the submerged nozzle 20 into the molten steel pool 16 at the start of casting, thereby stabilizing casting and suppressing deterioration of the quality and material of the cast strip.

The above describes in detail the submerged nozzle for a twin-roll continuous casting apparatus, the twin-roll continuous casting apparatus, and the method for manufacturing a thin-walled cast strip, which are embodiments of the present invention. However, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention.

In this embodiment, as shown in FIG. 3C, a cross section perpendicular to the extending direction is rectangular. However, the present invention is not limited to this.
For example, as shown in Figures 5(a) and 5(b), the cross section perpendicular to the extension direction may be triangular. Also, as shown in Figures 5(c) and 5(d), the cross section perpendicular to the extension direction may be arc-shaped. Furthermore, there is no particular limitation on the shape of the portion between the guide ridges.

Below, we explain the results of experiments conducted to confirm the effectiveness of the present invention.

Using the twin-roll continuous casting apparatus described in the embodiment, a thin-walled slab of low-carbon aluminum-killed steel (containing 0.01 mass% C, 0.24 mass% Si, 0.5 mass% Mn, 0.036 mass% Al, with the remainder being Fe and unavoidable impurities) was cast under the following conditions and with a submerged nozzle.

(Casting conditions)
Diameter of cooling roll: 1200 mm
Chill roll width: 1300 mm
Thin-walled cast thickness: 3.0 mm
Casting speed: 50 mpm

(Submerged Entry Nozzle)
It has an outer nozzle and an inner nozzle.
Inner dimensions: long side 510 mm x short side (top 300 mm, bottom 60 mm)
Nozzle material: Al ₂ O ₃ -C
Pressure loss member: Maximum thickness 36 mm, with through holes (diameter 12 mm x 20, evenly spaced along the long side)
Material of pressure loss member: ZrO ₂ --CaO--C

In the present invention, the guide ridges described in the embodiment were formed on the inner surface of the side wall of the outer nozzle. The guide ridges had a width W of 17 mm, a pitch P of 34 mm, and a protruding height H of 10 mm.
In the comparative example, no guide protrusions were formed on the inner surface of the side wall of the outer nozzle.

Using the above-mentioned submerged nozzle, 100 channels were cast and the casting conditions were confirmed.

In the comparative example, in 45 out of 100 channels, the slab broke due to poor solidification caused by drift at the start of casting, and casting could not be started stably. In addition, the maximum deviation in the molten steel pool surface height during steady state was 15 mm. And in areas where the deviation in the molten steel surface height was large, vertical cracks occurred on the surface of the slab.

In contrast, in the present invention, casting could be started stably in all 100 channels, and the planned amount could be completely cast. In addition, the deviation in the molten steel pool surface height during steady-state operation was kept to a maximum of 2.5 mm, and the occurrence of vertical cracks on the surface of the cast slab could be suppressed.

From the above, it has been confirmed that the present invention can provide an immersion nozzle for a twin-roll continuous casting apparatus, a twin-roll continuous casting apparatus, and a method for manufacturing thin-walled slabs, which can stabilize casting and suppress deterioration of slab quality and material by making the widthwise outflow distribution of molten metal flowing out of the immersion nozzle into the molten metal pool at the start of casting more uniform and steadily supplying molten metal from the tundish to the molten metal pool.

Reference Signs List 1 Thin-walled cast piece 10 Twin-roll continuous casting apparatus 20 Submerged nozzle for twin-roll continuous casting apparatus 21 Inner nozzle 22 Discharge hole 27 Pressure loss member 30 Outer nozzle 31 Side wall portion 36 Discharge port 38 Guide protrusion portion

Claims (5)

A twin-roll continuous casting apparatus for supplying molten metal to a molten metal pool formed by a pair of rotating chill rolls and a pair of side weirs, and forming and growing a solidified shell on a peripheral surface of the chill rolls to produce a thin-walled cast strip, comprising:
An outer nozzle and an inner nozzle for supplying molten metal into the outer nozzle,
the outer nozzle has a side wall portion extending in a direction parallel to an axis of the chill roll when the outer nozzle is disposed in the molten metal pool portion, an end wall portion intersecting the axis of the chill roll, and a bottom surface portion formed at lower ends of the side wall portion and the end wall portion,
a discharge port for the molten metal is formed in the vicinity of the bottom surface of the outer nozzle, and a pressure loss member is disposed inside the outer nozzle above the discharge port,
a plurality of guide ridges extending in a vertical direction are formed on an inner surface of the side wall portion of the outer nozzle at a position above the pressure loss member, and the guide ridges are formed above a discharge hole of the inner nozzle . The submerged nozzle for a twin-roll continuous casting machine according to claim 1, characterized in that the pressure loss member has a plurality of through holes formed therethrough in the vertical direction. The submerged nozzle for a twin-roll continuous casting apparatus according to claim 1 or 2, characterized in that the width W of the guide ridge portion is within a range of 5 mm to 30 mm, the protruding height H of the guide ridge portion is within a range of 3 mm to 20 mm, and the pitch P of the multiple guide ridge portions is within a range of 5 mm to 60 mm. 1. A twin-roll continuous casting apparatus for producing a thin-walled cast strip by supplying molten metal to a molten metal pool portion formed by a pair of rotating chill rolls and a pair of side gates, and forming and growing a solidified shell on a peripheral surface of the chill rolls,
4. A twin-roll continuous casting apparatus comprising the submerged nozzle for use in a twin-roll continuous casting apparatus according to claim 1 as a submerged nozzle for pouring the molten metal into the molten metal pool portion. A method for producing a thin cast slab by supplying molten metal to a molten metal pool formed by a pair of rotating chill rolls and a pair of side weirs, and forming and growing a solidified shell on a peripheral surface of the chill rolls, comprising the steps of:
A method for producing a thin-walled cast strip, comprising pouring the molten metal into the molten metal pool using the submerged entry nozzle for a twin-roll continuous casting apparatus according to any one of claims 1 to 3.

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