JP7230597B2 - Pouring nozzle, twin roll type continuous casting apparatus, and method for producing thin cast slab - Google Patents

Description

The present invention supplies molten metal to a molten metal pool formed by a pair of cooling rolls and a pair of side weirs, forms and grows a solidified shell on the peripheral surface of the cooling rolls, and manufactures thin cast slabs. A pouring nozzle used for pouring the molten metal into the molten metal pool in a twin-roll continuous casting apparatus, a twin-roll continuous casting apparatus equipped with the pouring nozzle, and the pouring nozzle It relates to a method for producing a thin cast slab using

A molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs, which has a water-cooling structure inside and is provided with a pair of cooling rolls rotating in opposite directions, as a method for manufacturing a thin-walled cast piece of metal. Molten metal is supplied from a tundish to the part, a solidified shell is formed and grown on the outer peripheral surface of the cooling roll, and the solidified shells formed on the outer peripheral surface of the pair of cooling rolls are pressed against each other at roll kiss points to obtain a predetermined A twin roll continuous casting apparatus is provided for producing thick thin-walled billets. Such a twin roll type continuous casting apparatus is applied to various metals.

In the twin-roll continuous casting machine described above, the obtained thin cast slab is directly rolled. may cause Therefore, in order to stably perform continuous casting, it is necessary to manufacture a thin cast slab having a uniform plate thickness in the width direction.

Here, in the twin-roll continuous casting apparatus described above, the molten metal pool portion formed between the pair of chill rolls extends in a direction parallel to the axis of the chill rolls (the width direction of the thin cast slab). shape.
For this reason, as shown in Patent Documents 1 and 2, for example, the pouring nozzle has a structure having a bottom portion along the direction parallel to the axis of the cooling roll (the width direction of the thin cast piece). A discharge path for molten metal is provided in the vicinity of the bottom portion.

Here, in the pouring nozzle described in Patent Document 1, a discharge hole is formed in a side surface near the bottom portion, and the molten metal supplied from the tundish is discharged toward the outer peripheral surface of the cooling roll. is configured to
On the other hand, in the pouring nozzle described in Patent Document 2, a discharge hole is formed in the bottom portion, and is configured to discharge the molten metal supplied from the tundish downward in the vertical direction. ing.

JP-A-08-155593 JP 2012-115857 A

Here, in the twin roll type continuous casting apparatus described above, since a plate of several millimeters is directly manufactured, the reduction ratio after that cannot be increased. For this reason, the plate thickness distribution during casting is directly linked to the plate thickness and shape of the final product, so plate thickness accuracy during casting is important.
There are two causes for thickness variation of thin cast slabs produced in a twin-roll continuous casting apparatus.

(1) When the molten metal is poured, the discharge flow from the nozzle runs up the roll and the surface height of the molten metal pool fluctuates, and the contact start point (solidification start point) between the molten metal and the cooling roll. changes in the width direction of the chill roll, resulting in a thickness distribution in the width direction.
(2) Equiaxed grains are formed in the molten metal pool due to the temperature drop of the molten metal pool, and the equiaxed grains settle and are caught between the solidified shells near the roll kiss point. Since the thickness of the solidified shell and the thickness of the equiaxed crystals are equal to the thickness of the equiaxed crystals, a plate thickness distribution occurs in the width direction.

Furthermore, in the twin-roll continuous casting apparatus described above, scum composed of oxides is generated on the surface of the molten metal pool. If this scum is caught in the solidified shell, the surface cleanliness of the thin cast slab is lowered, causing defects.
Moreover, if the solidified shell breaks during casting, the molten metal may leak out, so casting must be stopped, and casting cannot be performed stably.

Here, as described in Patent Document 1, when a pouring nozzle configured to discharge molten metal supplied from a tundish toward the outer peripheral surface of the cooling roll is used, the molten metal A flow occurs on the surface of the metal pool portion, and it is possible to suppress scum entrainment. Moreover, since the molten metal is not discharged toward the vicinity of the roll kiss point, breakage of the solidified shell can be suppressed.
However, when the molten metal discharged toward the outer peripheral surface of the cooling roll has a large flow rate and a high flow velocity, the molten metal that collides with the cooling roll runs up along the outer peripheral surface of the cooling roll. Fluctuations in the surface of the molten steel tend to occur, and molten steel stays in the lower part of the nozzle, lowering the temperature, and equiaxed grains tend to occur. For this reason, there was a possibility that plate thickness variation would occur.

On the other hand, as described in Patent Document 2, when a pouring nozzle configured to discharge molten metal supplied from a tundish downward in the vertical direction is used, the molten metal surface fluctuates. In addition, it is possible to suppress the generation of equiaxed crystals, and to suppress the occurrence of plate thickness variation.
However, since the molten metal is discharged toward the roll kiss point, if the flow rate of the molten metal discharge flow is high and the flow velocity is high, the solidified shell may break and stable casting may not be possible. rice field. In addition, the flow near the surface of the molten metal pool becomes insufficient, and scum generated on the surface of the molten metal pool may be involved.

The present invention has been made in view of the circumstances described above, and is capable of sufficiently suppressing plate thickness variation, scum entrainment, and solidified shell breakage, and stably casting high-quality thin-walled slabs. It is an object of the present invention to provide a flexible pouring nozzle, a twin-roll continuous casting apparatus equipped with this pouring nozzle, and a method for producing a thin cast slab using this pouring nozzle.

In order to solve the above-mentioned problems, a pouring nozzle according to the present invention supplies molten metal to a molten metal pool portion formed by a pair of rotating cooling rolls and a pair of side weirs. In a twin-roll continuous casting apparatus for forming and growing a solidified shell to produce a thin cast strip, a pouring nozzle for pouring the molten metal into the molten metal pool, the pouring nozzle being disposed in the molten metal pool. a nozzle body having a bottom portion extending in a direction parallel to the axial center of the cooling roll, and a discharge path for the molten metal being formed on at least side surfaces and a bottom surface of the nozzle body ; The discharge path has a horizontal path formed to face the outer peripheral surface of the cooling roll and a vertical path formed downward in the vertical direction, and a straightening member is disposed inside the nozzle body. A first through hole forming the horizontal path and a second through hole forming the vertical path are formed in the straightening member, and the first through hole and the second through hole A ratio A/B between the total cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is set within a range of 1 or more and 9 or less.

According to the pouring nozzle of this configuration, the molten metal discharge path has a horizontal path formed to face the outer peripheral surface of the chill roll and a vertical path formed downward in the vertical direction. Therefore, the molten metal is discharged toward the outer peripheral surface of the chill roll and downward in the vertical direction.
Further, since the ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path is within the range of 1 or more and 9 or less, the liquid is discharged from the horizontal path toward the outer peripheral surface of the cooling roll. As a result, the flow rate and flow velocity of the discharged molten metal can be suppressed, and it is possible to suppress the occurrence of fluctuations in the molten metal surface. In addition, by ejecting vertically downward, it is possible to suppress the temperature drop immediately below the nozzle and suppress the formation of equiaxed crystals. As a result, it is possible to suppress the occurrence of plate thickness variations.
Further, a constant amount of flow rate and flow velocity of the molten metal discharged toward the outer peripheral surface of the cooling roll can be ensured, and entrainment of scum can be suppressed.
Furthermore, since the flow rate and flow velocity of the molten metal discharged downward from the vertical path can be suppressed, the occurrence of breakage of the solidified shell can be suppressed, and stable casting can be performed.

Further, a first through hole forming the horizontal path and a second through hole forming the vertical path are formed in a rectifying member disposed inside the nozzle body, and the first through hole and the second through hole are formed. 2 Due to the cross-sectional area ratio of the through-holes, the ratio A/B between the cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is set within a range of 1 or more and 9 or less. It is possible to suppress the flow rate and flow velocity of the molten metal discharged toward the surface and the flow rate and flow velocity of the molten metal discharged downward in the vertical direction from the vertical path.

Further, the molten metal pouring nozzle of the present invention supplies molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs to form and grow a solidified shell on the peripheral surface of the cooling rolls. In a twin-roll continuous casting apparatus for producing thin cast slabs, a pouring nozzle for pouring the molten metal into the molten metal pool portion is arranged in the molten metal pool portion. A nozzle body having a bottom portion extending in a direction parallel to an axis, and a discharge passage for the molten metal is formed on at least a side surface and a bottom surface of the nozzle body, and the discharge passage is formed by the cooling roll. and a vertical path formed downward in the vertical direction to equalize the pressure of the molten metal supplied to the inside of the nozzle body. The nozzle body has a first opening facing the outer peripheral surface of the cooling roll and a second opening facing downward in the vertical direction. A ratio A/B between the total cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is in the range of 1 to 9 due to the cross-sectional area ratio of the first opening to the second opening. It is characterized by being inside.

In this case, the pressure loss member provided inside the nozzle body can equalize the pressure of the molten metal supplied to the nozzle body. Therefore, by adjusting the cross-sectional area ratio of the first opening hole and the second opening hole provided in the nozzle body, the ratio A/B of the cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is 1 or more. 9 or less, the flow rate and flow velocity of the molten metal discharged from the horizontal path toward the outer peripheral surface of the cooling roll, and the molten metal discharged from the vertical path downward in the vertical direction. It becomes possible to suppress the flow rate and flow velocity of the molten metal discharge stream.

The twin-roll continuous casting apparatus of the present invention supplies molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs to form and grow a solidified shell on the peripheral surface of the cooling rolls. A twin-roll type continuous casting apparatus for producing thin-walled cast slabs, characterized in that the pouring nozzle described above is arranged in the molten metal pool portion.

According to the twin roll continuous casting apparatus of this configuration, since the above-described pouring nozzle is used, the flow rate and flow velocity of the molten metal discharged from the horizontal path toward the outer peripheral surface of the cooling roll, , the flow rate and flow velocity of the molten metal discharged vertically downward from the vertical path can be suppressed, and the occurrence of plate thickness fluctuation, scum entrainment, and solidified shell breakage can be sufficiently suppressed, resulting in high quality. It is possible to stably cast thin cast slabs.

Here, in the twin roll type continuous casting apparatus of the present invention, the width W1 of the discharge from the horizontal path of the pouring nozzle and the length W2 of the molten metal pool portion in the direction parallel to the axis of the cooling roll are It is preferable that the ratio W2/W1 is within the range of 1.3 or more and 2.5 or less.
In this case, the ratio W2/W1 of the discharge width W1 of the pouring nozzle from the horizontal path to the length W2 of the molten metal pool portion in the direction parallel to the axis of the chill roll is 1.3 or more and 2.5. Since it is within the following range, the molten metal can be uniformly discharged in a direction parallel to the axial center of the cooling roll, and the flow rate of the discharged molten metal can be sufficiently suppressed.

In the method for producing a thin cast strip according to the present invention, molten metal is supplied to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs, and a solidified shell is formed on the peripheral surface of the cooling rolls. A thin-walled cast piece manufacturing method for producing a thin-walled cast piece by growing a thin-walled cast piece, wherein the above-described pouring nozzle is disposed in the molten metal pool portion, and the molten metal pool portion is filled with the above-mentioned It is characterized by pouring molten metal.

According to the method for manufacturing a thin cast strip having this configuration, since the above-described pouring nozzle is used, the flow rate and flow velocity of the molten metal discharged from the horizontal path toward the outer peripheral surface of the cooling roll, and , the flow rate and flow velocity of the molten metal discharged vertically downward from the vertical path can be suppressed, and the occurrence of plate thickness fluctuation, scum entrainment, and solidified shell breakage can be sufficiently suppressed, resulting in high quality. It is possible to stably cast thin cast slabs.

Here, in the thin cast strip manufacturing method of the present invention, the width W1 of the discharge from the horizontal path of the pouring nozzle and the length W2 of the molten metal pool portion in the direction parallel to the axis of the cooling roll are It is preferable to set the ratio W2/W1 within the range of 1.3 to 2.5.
In this case, the ratio W2/W1 of the discharge width W1 of the pouring nozzle from the horizontal path to the length W2 of the molten metal pool portion in the direction parallel to the axis of the chill roll is 1.3 or more and 2.5. Since it is within the following range, the molten metal can be uniformly discharged in a direction parallel to the axial center of the cooling roll, and the flow rate of the discharged molten metal can be sufficiently suppressed.

As described above, according to the present invention, a pouring nozzle capable of sufficiently suppressing plate thickness variation, scum entrainment, and solidified shell breakage, and capable of stably casting high-quality thin-walled slabs, It is possible to provide a twin-roll continuous casting apparatus equipped with this pouring nozzle and a method for producing thin cast slabs using this pouring nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an example of a twin-roll continuous casting apparatus equipped with a pouring nozzle that is an embodiment of the present invention; 1 is a schematic explanatory diagram of a pouring nozzle that is an embodiment of the present invention; FIG. FIG. 3 is a schematic explanatory diagram of a rectifying member provided in the pouring nozzle shown in FIG. 2; FIG. 4 is a schematic explanatory diagram of a pouring nozzle that is another embodiment of the present invention;

EMBODIMENT OF THE INVENTION Below, the pouring nozzle which is embodiment of this invention, and the manufacturing method of a thin cast piece are demonstrated with reference to attached drawing. In addition, this invention is not limited to the following embodiment.

In this embodiment, molten steel is used as the molten metal, and the thin cast slab 1 made of steel is manufactured. The types of steel include, for example, 0.001 to 0.01% C ultra-low carbon steel, 0.02 to 0.05% C low carbon steel, 0.06 to 0.4% C medium carbon steel, and 0.06 to 0.4% C medium carbon steel. 5-1.2% C high carbon steel, austenitic stainless steel typified by SUS304 steel, ferritic stainless steel typified by SUS430 steel, 3.0-3.5% Si oriented electrical steel, 0.1 up to 6.5% Si non-oriented electrical steel, etc. (where % is % by mass).
Further, in the present embodiment, the width of the thin cast piece 1 to be manufactured is in the range of 500 mm or more and 2000 mm or less, and the thickness is in the range of 1 mm or more and 5 mm or less.
Further, in the present embodiment, the molten steel flow rate is in the range of 2.5 kg/s or more and 35 kg/s or less.

As shown in FIG. 1, a twin roll continuous casting apparatus 10 of this embodiment supports a pair of chill rolls 11, 11, bender rolls 12, 12 for bending a thin cast strip 1, and a thin cast strip 1. The pinch rolls 13, 13, the side dams 15 disposed at the widthwise ends of the pair of cooling rolls 11, 11, and the molten steel pool portion defined by the pair of cooling rolls 11, 11 and the side dams 15. 16, and a pouring nozzle 20 for supplying the molten steel 3 from the tundish 18 to the molten steel pool portion 16.
Here, the surface area of the molten steel pool portion 16 (the area of the region surrounded by the cooling rolls 11 and the side weirs 15 when viewed from the top) is set within the range of 0.0035 m ³ or more and 0.08 m ³ or less. ing.

In this twin-roll continuous casting apparatus 10, the molten steel 3 is cooled by contacting the rotating chill rolls 11, 11, thereby forming solidified shells 5, 5 on the peripheral surfaces of the chill rolls 11, 11. , solidified shells 5, 5 respectively formed on a pair of cooling rolls 11, 11 are pressed against each other at roll kiss points, whereby a thin cast strip 1 having a predetermined thickness is cast.

The molten metal pouring nozzle 20 of this embodiment includes a nozzle body 21 and an inner nozzle 26 inserted into the nozzle body 21, as shown in FIG. 2(a).
The inner nozzle 26 has a tubular shape and is inserted from the top of the nozzle body 21, as shown in FIG. 2(a). In addition, in the inner nozzle 26, the molten steel supply hole may be formed in the bottom portion or may be formed in the lower side wall portion.

The nozzle body 21 has an upper region 21a provided with an upper opening into which the inner nozzle 26 is inserted, and a bottom shape along a direction parallel to the axial center of the cooling roll 11 when placed in the molten steel pool portion 16. It includes a lower region 21b and a connecting portion 21c that connects the upper region 21a and the lower region 21b.
As shown in FIGS. 2A and 2B, the lower region 21b is provided with a first opening hole 22A formed on the side surface and a second opening hole 22B formed on the bottom surface. .
In this embodiment, the first opening 22A and the second opening 22B are each formed in a slit shape extending in a direction parallel to the axis of the cooling roll 11 in the lower region 21b.

The _nozzle main body 21 and the inner _nozzle 26 are preferably made of a refractory material having sufficient strength and heat resistance to withstand use _. , MgO, CaO, SiO ₂ , ZrO ₂ , SiC, C, BN, etc., or mixtures thereof.
Materials for the nozzle main body 21 and the inner nozzle 26 are preferably selected as appropriate according to usage conditions. For example, the material (steel type) to be cast is selected in consideration of reactivity and the like. In this embodiment, the material of the nozzle main body 21 and the inner nozzle 26 is alumina graphite (Al ₂ O ₃ +C).

In addition, in the pouring nozzle 20 of the present embodiment, a rectifying member 30 is arranged inside the lower region 21b of the nozzle body 21 described above. As shown in FIG. 3, the rectifying member 30 of the present embodiment has a trapezoidal shape in which the base is smaller than the top when viewed from the side.
In this rectifying member 30, a first through hole 31 extending in the height direction (the Z direction in FIG. 3) and opening to the lower side surface of the rectifying member 30, and a thickness direction of the rectifying member 30 (the A second through hole 32 extending in the height direction (the Z direction in FIG. 3) and opening to the bottom surface of the rectifying member 30 is provided in the central portion (Y direction).

In the present embodiment, as shown in FIG. 3, the first through holes 31 are configured such that a plurality of through holes are arranged in parallel in the width direction (X direction in FIG. 3) of the rectifying member 30. It is configured to be able to discharge the molten steel 3 uniformly in the width direction. It is preferable that the ratio P/D of the hole diameter D of the through holes and the pitch (center-to-center distance of the through holes) P be within the range of 1.3 or more and 2.5 or less. By setting P/D to 1.3 or more, it becomes easier to ensure the strength of the straightening member 30 . on the other hand. By setting P/D to 2.5 or less, it becomes easier to uniformly discharge the molten steel 3 .
Although the second through hole 32 is formed in a slit shape as shown in FIG. 3, the through hole may be formed as described above.

Here, the first through hole 31 is configured to communicate with the first opening 22A of the nozzle body 21, and the second through hole 32 is configured to communicate with the second opening 22B of the nozzle body 21. It is configured.
In this way, the first through hole 31 and the first opening 22A form a horizontal path facing the outer peripheral surface of the cooling roll 11, and the second through hole 32 and the second opening 22B A vertical path is formed downward in the vertical direction, and the molten steel 3 is supplied to the molten steel pool portion 16 by the discharge path composed of the horizontal path and the vertical path.

The ratio A/B between the cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is in the range of 1 or more and 9 or less. As a result of the water model experiment, when the ratio A/B of the cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path exceeds 9, the flow from the discharge path of the horizontal path increases, runs up to the roll, and the water surface fluctuates. occurred. Further, as a result of numerical analysis of flow and heat transfer, when the ratio A/B of the cross-sectional area A of the path to the cross-sectional area B of the vertical path is less than 1, a large difference occurs in the temperature distribution at the roll kiss point, and the shell breaks. It was found that there was a risk of
The lower limit of the ratio A/B between the cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is preferably 2 or more, more preferably 3 or more. The upper limit of the ratio A/B between the cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is preferably 7 or less, more preferably 5 or less.

In this embodiment, as described above, the horizontal path is formed by the first through hole 31 and the first opening 22A, and the vertical path is formed by the second through hole 32 and the second opening 22B. A ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path is adjusted within the range of 1 or more and 9 or less by the cross-sectional area ratio of the first through-hole 31 and the second through-hole 32 . The cross-sectional area of the first through-hole 31 is the sum of the cross-sectional areas of the plurality of through-holes forming the first through-hole 31 .

The rectifying member 30 is preferably made of _a refractory _{material having} sufficient strength and heat resistance to withstand use. , SiO ₂ , ZrO ₂ , SiC, C, BN, etc., or mixtures thereof.
It is preferable to appropriately select the material of the rectifying member 30 according to the usage conditions. For example, the material (steel type) to be cast is selected in consideration of reactivity and the like. In this embodiment, the rectifying member 30 is made of CaO.ZrO ₂ material.

In the twin-roll continuous casting apparatus 10 of the present embodiment, the above-described pouring nozzle 20 is arranged in the molten steel pool portion 16, and the discharge width W1 (this In the embodiment, the ratio W2/W1 between the opening width of the first opening hole 22A) and the length W2 in the molten steel pool portion 16 in the direction parallel to the axis of the cooling roll 11 (that is, the width of the thin cast piece 1) is 1. .3 or more and 2.5 or less. As a result of a water model experiment, when the ratio W2/W1 of the discharge width W1 from the horizontal path and the length W2 in the direction parallel to the axial center of the cooling roll 11 is less than 1.3, the flow from the horizontal discharge path is uniform. However, the flow of scum was inhibited and scum entrainment occurred. Further, when the ratio W2/W1 of the width W1 of discharge from the horizontal path to the length W2 in the direction parallel to the axial center of the cooling roll 11 exceeds 2.5, the flow rate of discharge from the horizontal path increases, and the discharge path of the path increases. The flow from the water increased and ran up to the roll, causing the water surface to fluctuate.
The lower limit of the ratio W2/W1 between the discharge width W1 from the horizontal path of the pouring nozzle 20 and the length W2 in the direction parallel to the axis of the cooling roll 11 in the molten steel pool portion 16 is preferably 2 or more. It is more preferably 3 or more. Also, the upper limit of the ratio W2/W1 between the discharge width W1 from the horizontal path of the pouring nozzle 20 and the length W2 in the direction parallel to the axis of the cooling roll 11 in the molten steel pool portion 16 is preferably 7 or less. It is more preferably 5 or less.

Next, a description will be given of a method for producing thin cast slabs according to the present embodiment using the twin roll continuous casting apparatus 10 described above.

Molten steel 3 is supplied from a tundish 18 through a pouring nozzle 20 to a molten steel pool portion 16 formed by a pair of cooling rolls 11, 11 and a side weir 15. , that is, the region where the pair of cooling rolls 11 and 11 are adjacent to each other faces the drawing direction of the thin cast strip 1 (downward in FIG. 1).

Then, a solidified shell 5 is formed on the peripheral surface of the cooling roll 11 . Then, the solidified shell 5 grows on the peripheral surface of the chill roll 11, and the solidified shells 5, 5 formed on the pair of chill rolls 11, 11 are crimped to each other at the roll kiss points, resulting in a thin wall having a predetermined thickness. A billet 1 is cast.

Here, in this embodiment, the molten steel 3 is supplied into the nozzle body 21 from the tundish 18 via the inner nozzle 26 .
Then, the molten steel 3 is discharged toward the outer peripheral surface of the cooling roll 11 through a horizontal path formed by the first through holes 31 of the rectifying member 30 and the first opening holes 22A provided in the nozzle body 21. , the molten steel 3 is discharged downward in the vertical direction through a vertical path formed by the second through hole 32 of the straightening member 30 and the second opening 22B provided in the nozzle body 21 .

According to the pouring nozzle 20 of the present embodiment configured as described above, the cross-sectional area A of the horizontal path formed by the first through hole 31 and the first opening hole 22A, the second through hole 32 and A ratio A/B to the cross-sectional area B of the vertical path formed by the second opening 22B is set within a range of 1 or more and 9 or less. Since the ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path is 9 or less, the flow rate of the molten steel 3 discharged from the horizontal path toward the outer peripheral surface of the cooling roll 11 is reduced. And the flow velocity can be suppressed, the molten metal can be suppressed from running up to the roll, and the occurrence of fluctuations in the molten metal surface can be suppressed. In addition, it is possible to suppress the generation of equiaxed grains in the temperature immediately below the nozzle by the discharge flow from the vertical direction. As a result, variations in thickness of the thin cast slab 1 to be produced can be suppressed. Moreover, since the ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path is 1 or more, it is possible to prevent the thin solidified shell from being broken by the high-temperature molten metal. In addition, a constant flow rate and flow velocity of the molten steel 3 discharged toward the outer peripheral surface of the chill roll 11 are ensured, and the flow of the molten steel 3 is ensured in the vicinity of the molten steel surface, thereby suppressing the entrainment of scum. can do.

Further, in the present embodiment, a rectifying member 30 is disposed inside the nozzle body 21, and the rectifying member 30 has a first through hole 31 forming a horizontal path and a second through hole forming a vertical path. 32 are formed, and the ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path is 9 or less due to the cross-sectional area ratio of the first through hole 31 and the second through hole 32. Therefore, the flow rate and flow velocity of the molten steel 3 discharged from the horizontal path toward the outer peripheral surface of the cooling roll 11 can be suppressed, suppressing the run-up of the molten metal to the roll, and suppressing the fluctuation of the molten steel surface. It can suppress the occurrence. In addition, it is possible to suppress the generation of equiaxed grains in the temperature directly under the nozzle by the discharge flow from the vertical direction. As a result, variations in thickness of the thin cast slab 1 to be produced can be suppressed. Further, since the ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path is 1 or more, it is possible to prevent the thin solidified shell from being broken by the high-temperature molten metal. In addition, a constant flow rate and flow velocity of the molten steel 3 discharged toward the outer peripheral surface of the chill roll 11 are ensured, and the flow of the molten steel 3 is ensured in the vicinity of the molten steel surface, thereby suppressing the entrainment of scum. can do.

Furthermore, according to the twin-roll continuous casting apparatus 10 and the method for manufacturing the thin cast strip 1 of the present embodiment, the pouring nozzle 20 described above is used. It is possible to suppress the flow rate and flow velocity of the molten steel 3 discharged toward the vertical path, and the flow rate and flow velocity of the molten steel 3 discharged downward in the vertical direction from the vertical path. It is possible to sufficiently suppress the occurrence of entrainment of the solidified shell and breakage of the solidified shell, and to stably cast a high-quality thin cast slab 1.

Further, in the twin-roll continuous casting apparatus 10 and the method for manufacturing the thin cast slab 1 according to the present embodiment, the discharge width W1 from the horizontal path of the pouring nozzle 20 and the axial center of the cooling roll 11 in the molten steel pool portion 16 When the ratio W2/W1 of the length W2 in the direction parallel to is within the range of 1.3 or more and 2.5 or less, the molten metal is uniformly discharged in the direction parallel to the axis of the cooling roll 11. In addition, the flow rate of the discharged molten steel 3 can be sufficiently suppressed.

Although the straightening member, the pouring nozzle, the twin-roll continuous casting apparatus, and the method for producing thin cast slabs, which are embodiments of the present invention, have been specifically described above, the present invention is not limited to these. It can be changed as appropriate without departing from the technical idea of the invention.
For example, in the present embodiment, as shown in FIG. 1, a twin-roll continuous casting apparatus in which bender rolls and pinch rolls are arranged has been described as an example. You can change the design.

In addition, in the pouring nozzle of the present embodiment, the rectifying member is arranged inside the nozzle body, and the cross-sectional area ratio of the first through hole and the second through hole formed in this rectifying member allows the horizontal path Although the ratio A/B between the cross-sectional area A and the cross-sectional area B of the vertical path has been described as being in the range of 1 to 9, it is not limited to this, and the pouring nozzle 120 shown in FIG. , a pressure loss member 130 for equalizing the pressure of the supplied molten steel 3 is disposed inside the nozzle body 121, and is opened so as to face the outer peripheral surface of the cooling roll 11 formed in the nozzle body 121. The ratio A/B of the cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is set to 1 or more and 9 or less by the cross-sectional area ratio of the first opening hole 122A and the second opening hole 122B that opens downward in the vertical direction. It may be within the range.

According to the pouring nozzle 120 shown in FIG. 4, the pressure loss member 130 disposed inside the nozzle body 121 makes it possible to equalize the pressure of the molten steel 3 supplied to the nozzle body 121 . The cross-sectional area ratio of the first opening 122A and the second opening 122B formed in the nozzle body 121 is adjusted so that the ratio A/B between the cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is 9 or less. Therefore, the flow rate and flow velocity of the molten steel 3 discharged from the horizontal path toward the outer peripheral surface of the cooling roll 11 are suppressed, suppressing the run-up of the molten metal to the roll, It is possible to suppress the occurrence of fluctuations. In addition, it is possible to suppress the generation of equiaxed grains in the temperature immediately below the nozzle by the discharge flow from the vertical direction. As a result, variations in thickness of the thin cast slab 1 to be produced can be suppressed. Further, since the ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path is 1 or more, it is possible to prevent the thin solidified shell from being broken by the high-temperature molten metal. In addition, a constant flow rate and flow velocity of the molten steel 3 discharged toward the outer peripheral surface of the chill roll 11 are ensured, and the flow of the molten steel 3 is ensured in the vicinity of the molten steel surface, thereby suppressing the entrainment of scum. can do.

As the pressure loss member 130, a porous refractory or the like used as a filter can be used. As the porous refractory, it is preferable to use, for example, one having 6 or more and 20 or less holes per inch.
Moreover, the pressure loss member 130 is preferably made of _{a refractory} material having _sufficient strength and heat resistance to withstand use. , SiO ₂ , ZrO ₂ , SiC, C, BN, etc., or mixtures thereof.
It is preferable to appropriately select the material of the pressure loss member 130 according to the usage conditions. For example, the material (steel type) to be cast is selected in consideration of reactivity and the like.

Also, side discharge holes may be formed in the width direction end face of the nozzle body. By forming this side discharge hole, it becomes possible to insulate the side dam by the discharge flow of the molten metal. The cross-sectional area of the side discharge hole is much smaller than the cross-sectional areas of the horizontal and vertical paths, and is, for example, 10% or less of the total cross-sectional area of the horizontal and vertical paths. Therefore, there is no particular influence on the state of ejection of molten metal from the horizontal and vertical paths.

The results of experiments conducted to confirm the effects of the present invention will be described below.
Using the twin-roll continuous casting apparatus shown in FIG. % P--0.005% S--0.03% Al) thin-walled slabs were produced.
Tundish capacity: 5t
Cooling roll diameter: 1200mm
Casting width: 800mm
Casting atmosphere: Ar
Slab thickness: 2.0 mm
Slab width: 800mm
Casting amount per unit time: 1.1t/min

Here, as a pouring nozzle, one having the structure shown in Table 1 was used. In Table 1, in the column of method, the item described as "rectifying member" is the pouring nozzle having the structure shown in FIG. 2, and the item described as "pressure loss member" is the note of the structure shown in FIG. It becomes a hot water nozzle. Also, the discharge width W1 of the horizontal path of the pouring nozzle was set as shown in Table 2.
As a result of the casting experiment, the castability, plate thickness accuracy, and slab surface cleanliness were evaluated as follows.

(Castability)
The planned casting amount was set to 4.5 tons, and the case where casting was stopped due to slab breakage was indicated as "x", and the case where the planned casting amount was able to be cast was indicated as "o". Table 2 shows the evaluation results.

(thickness accuracy)
The plate thickness in the plate width direction of the thin cast slab at the position 4 minutes after the start of casting was measured at a pitch of 10 mm using a micrometer, and the plate thickness difference between the maximum plate thickness and the minimum plate thickness was divided by the average plate thickness. The thickness accuracy is "×" when the slab thickness variation rate, which is an index, exceeds 10%, the thickness accuracy is "△" when the slab thickness variation rate exceeds 5% and is 10% or less, and the slab plate A plate thickness accuracy of 5% or less was evaluated as “◯”. Table 2 shows the evaluation results.

(Slab surface cleanliness)
Investigate the number of surface defects in the plate width direction of the thin cast slab at the position 4 minutes after the start of casting. Detergency was evaluated as “Δ”, and surface cleanliness was evaluated as “◯” when there were 3 or less. Table 2 shows the evaluation results.

In Comparative Example 1 in which no vertical path was formed and only a horizontal path was formed, the plate thickness accuracy was "x". The molten steel discharged toward the outer peripheral surface of the chill roll has a large flow rate and a high flow velocity, and the molten steel that collides with the chill roll runs up along the outer peripheral surface of the chill roll, causing fluctuations in the surface of the molten steel. It is presumed that this is because the molten steel stays directly under the nozzle, the temperature of the molten steel decreases, and equiaxed grains are generated.

In Comparative Example 4 in which no horizontal passage was formed and only a vertical passage was formed, casting was stopped because the planned casting amount could not be cast. It is presumed that this is because the flow rate of the molten steel discharged downward in the vertical direction (roll kiss point side) was large and the flow velocity was increased, causing the breakage of the solidified shell. Since casting was discontinued, plate thickness accuracy and surface cleanliness were not evaluated.

In Comparative Examples 2 and 5 in which the ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path exceeded 9, the plate thickness accuracy was "x". The molten steel discharged toward the outer peripheral surface of the chill roll has a large flow rate and a high flow velocity, and the molten steel that collides with the chill roll runs up along the outer peripheral surface of the chill roll, causing fluctuations in the surface of the molten steel. It is presumed that this is because the molten steel stays directly under the nozzle, the temperature of the molten steel decreases, and equiaxed grains are generated.

In Comparative Examples 3 and 6, in which the ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path was less than 1, the expected casting amount could not be cast, and the casting was stopped. It is presumed that this is because the flow rate of the molten steel discharged downward in the vertical direction (roll kiss point side) was large and the flow velocity was increased, causing the breakage of the solidified shell. Since casting was discontinued, plate thickness accuracy and surface cleanliness were not evaluated.

On the other hand, the ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path is set within the range of 1 or more and 9 or less, and the discharge width W1 from the horizontal path of the pouring nozzle and the molten steel pool portion In Examples 13 and 15 of the present invention, in which the ratio W2/W1 of the length W2 in the direction parallel to the axial center of the cooling roll was less than 1.3, the surface cleanliness was "Δ", but in terms of quality It was within the range of no problem, and the castability and plate thickness accuracy were good. It is presumed that the molten steel flow in the molten steel pool was insufficient and scum was involved.

The ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path is set within the range of 1 or more and 9 or less, and the discharge width W1 from the horizontal path of the pouring nozzle and the axis of the cooling roll of the molten steel pool portion In Examples 14 and 16 of the present invention, in which the ratio W2/W1 of the length W2 in the direction parallel to the center exceeds 2.5, the plate thickness accuracy was "Δ", but it is within the range of no problem in terms of quality. The properties and surface cleanability were good. The molten steel discharged toward the outer peripheral surface of the chill roll has a large flow rate and a high flow velocity, and the molten steel that collides with the chill roll runs up along the outer peripheral surface of the chill roll, causing fluctuations in the surface of the molten steel. presumed to be because

In addition, in Examples 1 to 12 of the present invention, the ratio A/B of the cross-sectional area A of the horizontal path to the cross-sectional area B of the vertical path is within the range of 1 or more and 9 or less, and from the horizontal path of the pouring nozzle The ratio W2/W1 of the discharge width W1 of the molten steel pool and the length W2 in the direction parallel to the axial center of the cooling roll in the molten steel pool is set to be within the range of 1.3 or more and 2.5 or less, and castability and plate thickness accuracy , the surface cleanliness was good, and high-quality thin-walled slabs could be stably cast.

From the above results, according to the example of the present invention, it is possible to sufficiently suppress the occurrence of sheet thickness fluctuation, scum entrainment, and solidified shell breakage, and to stably cast a high-quality thin cast slab. confirmed.

1 thin cast slab 3 molten steel (molten metal)
10 twin roll type continuous casting device 11 cooling roll 16 molten steel pool (molten metal pool)
20, 120 pouring nozzles 21, 121 nozzle main bodies 22A, 122A first openings 22B, 122B second openings 30 straightening member 31 first through hole 32 second through hole 130 pressure loss member

Claims (6)

A twin roll type in which molten metal is supplied to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs, and a solidified shell is formed and grown on the peripheral surface of the cooling rolls to produce thin cast slabs. In a continuous casting apparatus, a pouring nozzle for pouring the molten metal into the molten metal pool,
A nozzle body having a bottom portion extending in a direction parallel to the axial center of the cooling roll when placed in the molten metal pool portion, wherein the molten metal is discharged onto at least side surfaces and a bottom surface of the nozzle body. a road is formed,
The discharge path has a horizontal path formed to face the outer peripheral surface of the cooling roll and a vertical path formed downward in the vertical direction,
A rectifying member is disposed inside the nozzle body, and the rectifying member is formed with a first through hole that constitutes the horizontal path and a second through hole that constitutes the vertical path,
A ratio A/B between the total cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is set within a range of 1 or more and 9 or less, depending on the cross-sectional area ratio of the first through hole and the second through hole. A pouring nozzle characterized by: A twin roll type in which molten metal is supplied to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs, and a solidified shell is formed and grown on the peripheral surface of the cooling rolls to produce thin cast slabs. In a continuous casting apparatus, a pouring nozzle for pouring the molten metal into the molten metal pool,
A nozzle body having a bottom portion extending in a direction parallel to the axial center of the cooling roll when placed in the molten metal pool portion, wherein the molten metal is discharged onto at least side surfaces and a bottom surface of the nozzle body. a road is formed,
The discharge path has a horizontal path formed to face the outer peripheral surface of the cooling roll and a vertical path formed downward in the vertical direction,
A pressure loss member for equalizing the pressure of the supplied molten metal is disposed inside the nozzle body, and the nozzle body has a first opening facing the outer peripheral surface of the cooling roll An opening hole and a second opening hole that opens downward in the vertical direction are formed,
A ratio A/B between the total cross-sectional area A of the horizontal path and the cross-sectional area B of the vertical path is set within a range of 1 or more and 9 or less, depending on the cross-sectional area ratio of the first opening hole and the second opening hole. A pouring nozzle characterized by: A twin roll type in which molten metal is supplied to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs, and a solidified shell is formed and grown on the peripheral surface of the cooling rolls to produce thin cast slabs. A continuous casting apparatus,
3. A twin roll continuous casting apparatus, wherein the pouring nozzle according to claim 1 is arranged in the molten metal pool portion. A ratio W2/W1 of the discharge width W1 of the pouring nozzle from the horizontal path to the length W2 of the molten metal pool portion in the direction parallel to the axis of the chill roll is in the range of 1.3 to 2.5. 4. The twin roll continuous casting apparatus according to claim 3, characterized in that the twin roll continuous casting apparatus is set inside. A thin cast slab is produced by supplying molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs to form and grow a solidified shell on the peripheral surface of the cooling rolls. A manufacturing method of
The pouring nozzle according to claim 1 or claim 2 is disposed in the molten metal pool portion, and the molten metal is poured into the molten metal pool portion using the pouring nozzle. A method for producing thin-walled cast slabs. A ratio W2/W1 of the discharge width W1 from the horizontal path of the pouring nozzle to the length W2 of the molten metal pool portion in the direction parallel to the axis of the chill roll is in the range of 1.3 to 2.5. 6. The method for producing a thin cast strip according to claim 5, characterized in that the thickness is inside.

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