JP6213101B2 - Scum weir, thin slab manufacturing method and thin slab manufacturing apparatus - Google Patents

Description

  The present invention relates to a scum used in a thin-walled slab manufacturing method for manufacturing a thin-walled slab by supplying molten metal to a molten-metal reservoir formed by a pair of cooling drums and a pair of side weirs via an immersion nozzle. The present invention relates to a weir, a method for producing a thin cast piece using the scum weir, and a production apparatus for the thin cast piece.

  As described above, as a method of manufacturing a thin metal slab, for example, as shown in Patent Documents 1 and 2, a pair of cooling drums and a pair of side weirs provided with a cooling drum having a water-cooling structure therein are provided. The molten steel (molten metal) is supplied to the molten steel pool portion (molten metal pool portion) formed by forming a solidified shell on the peripheral surface of the cooling drum, and the solidified shell formed on each of the pair of cooling drums There is provided a twin-drum continuous casting method in which a thin slab having a predetermined thickness is manufactured by pressure bonding with each other at a drum kiss point.

  Here, in the above-mentioned molten steel pool part, it is known that oxides and the like float on the molten steel surface and so-called scum is generated. When this scum reaches the solidification start point of the cooling drum, it is caught between the cooling drum and the solidified shell as the cooling drum rotates, resulting in non-uniform solidification, resulting in surface defects of thin-walled slabs, etc. There is a risk of it. In addition, when the height of the molten steel surface fluctuates at the solidification start point of the cooling drum, solidification may not be stable.

Therefore, Patent Document 3 proposes a method of manufacturing a thin cast slab having a good surface quality by preventing the scum from being caught by solidifying the scum.
Patent Documents 4 and 5 propose a technique for suppressing fluctuations in the height of the molten steel surface at the start point of scum entrainment or solidification by disposing a scum weir in the molten steel pool.

  Here, since the scum weir is disposed between the pair of cooling drums, it is difficult to sufficiently perform preheating. And since molten steel over 1500 degreeC is supplied to a molten steel pool part and a scum weir is immersed and used for this molten steel, the outstanding heat resistance and thermal shock resistance are requested | required of a scum weir. Therefore, BN (boron nitride) is generally used for conventional scum weirs. In addition, as disclosed in Patent Documents 4 and 5, the scum weir is also required to have characteristics such as corrosion resistance, particle size, strength, and volume stability (low thermal deformation). Therefore, Patent Document 4 proposes a scum weir made of graphite and a metal oxide.

By the way, in the above-mentioned twin drum type continuous casting method, a thin cast piece having a thickness of several millimeters can be directly manufactured from molten metal, so that a hot working step such as hot rolling can be omitted. For this reason, twin drum type continuous casting methods include, for example, Cu-containing steel (˜2 mass% Cu), Al-containing steel (0.1 to 4 mass% Al), P-containing steel (˜0.15 mass% P), Si-containing It is particularly suitable for the production of brittle materials such as steel (~ 4 mass% Si) and hard work materials.
Thus, for example, Patent Documents 6 and 7 disclose that electromagnetic steel containing Al and Si is manufactured by a twin drum continuous casting method.

Japanese Patent Laid-Open No. 04-300049 JP 2002-113555 A JP 2002-273551 A JP 2003-039139 A JP 2003-266154 A JP 2004-323972 A JP 2008-132534 A

Incidentally, when an Al-containing steel containing 0.02 mass% or more of Al is produced by the above-described twin-drum continuous casting method, an alumina film is formed on the molten steel surface of the molten steel pool portion.
The upper space of the molten steel reservoir is generally an inert gas atmosphere such as Ar. However, since Al oxidizes with an extremely small oxygen partial pressure to form an alumina film, 0.02 mass% In the Al-containing steel containing Al described above, it has been substantially difficult to prevent an alumina film from being formed on the molten steel surface of the molten steel pool.

  The alumina coating formed on the molten steel surface of the molten steel pool is wound between the cooling drum and the solidified shell during casting. At this time, the alumina film is pulled in the drum rotation direction, and accordingly, the molten steel surface at the cold solidification start point of the cooling drum is lowered. Further, when the alumina coating is entrained, the alumina coating is broken by the molten steel static pressure, the molten steel flows out from the broken portion, the molten steel surface rises, and the molten steel surface at the cooling solidification start point of the cooling drum rises. Then, a new alumina film is formed on the molten steel surface.

  As described above, when the Al-containing steel containing Al of 0.02 mass% or more is manufactured by the above-described twin-drum continuous casting method, the alumina film is intermittently entrained by repeatedly entraining and breaking the alumina film. And the height of the molten steel surface at the solidification start point fluctuates up and down. In particular, the above-mentioned alumina film has a relatively high strength and is not easily broken, and is formed firmly on the molten steel surface between the scum weir and the cooling drum. There was a possibility that the fluctuation of the height of the surface became large and casting could not be carried out stably.

  Further, as described above, when the alumina film is intermittently entrained, the entrained alumina film becomes a heat transfer resistance between the cooling drum and the solidified shell, and the solidified shell is not uniform in the longitudinal direction of the casting. There was a possibility of causing unevenness of the slab thickness. In addition, since the alumina coating is randomly generated in the width direction of the cooling drum, the solidified shell and the thickness of the slab may be uneven in the width direction of the slab.

  The present invention has been made in view of the above-described situation, and suppresses intermittent entrainment of the alumina film, so that the molten metal surface at the solidification start point (the free surface of the molten metal and the alumina film on the upper surface). Scum weir and thin-walled casting that can stably produce thin-walled slabs with excellent quality by suppressing fluctuations in height, non-uniformity of solidified shell and non-uniformity of slab thickness It aims at providing the manufacturing method of a piece, and the manufacturing apparatus of a thin cast piece.

  In order to solve the above-mentioned problems, the present inventors have intensively studied, and as a result, the alumina film is intermittently formed by modifying the composition of the alumina film formed on the molten metal surface of the molten metal reservoir to lower the melting point. It was found that it is possible to suppress typical entrainment, and to suppress fluctuations in the height of the molten metal surface at the solidification start point, and non-uniformity of the solidified shell and slab thickness.

The present invention has been made on the basis of the above-described knowledge, and the scum weir according to the present invention is provided through a submerged nozzle in a molten metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs. A thin cast slab manufacturing method for manufacturing a thin cast slab by supplying molten metal made of Al-containing steel containing Al of 0.02 mass% or more, and forming and growing a solidified shell on the peripheral surface of the cooling drum In the scum weir disposed in the molten metal reservoir portion, at least a region of the surface facing the cooling drum side that is in contact with the molten metal surface of the molten metal reservoir portion is CaO in a range of 10 mass% to 50 mass%. It is characterized by being comprised with the CaO containing refractory material contained within the following ranges.

In the scum weir with this configuration, the CaO-containing refractory in which at least a region of the surface facing the cooling drum that is in contact with the molten metal surface of the molten metal pool portion contains CaO in a range of 10 mass% to 50 mass%. Since it is comprised with the material, in the part which contacted the scum weir among the alumina membrane | film | coats formed in the molten metal surface, melting | fusing point falls by supplying CaO. As a result, the alumina coating on the molten metal surface is locally weakened and easily broken, and is easily caught in the cooling drum.
Therefore, by using the scum weir of the present invention, the intermittent entrainment of the alumina film is suppressed, the variation of the height of the molten metal surface at the solidification start point, the non-uniformity of the solidified shell and the non-uniform thickness of the slab Therefore, it is possible to stably manufacture a high-quality thin cast slab.

Here, if the content of CaO in the CaO-containing refractory material is less than 10 mass%, the alumina film cannot be sufficiently lowered in melting point, and the above-described effects may not be achieved.
On the other hand, when the CaO content in the CaO-containing refractory material exceeds 50 mass%, the strength of the CaO-containing refractory material itself is insufficient, and the scum weir may be melted early.
From the above, in the scum weir according to the present invention, the content of CaO in the CaO-containing refractory material is set within a range of 10 mass% or more and 50 mass% or less.

Further, in the scum weir according to the present invention, the CaO-containing refractory material includes CaO in a range of 10 mass% to 50 mass%, MgO in a range of 20 mass% to 90 mass%, and free C in a range of 0 mass% to 40 mass%. It may be contained within the following range.
In this case, since CaO is contained in the range of 10 mass% or more and 50 mass% or less as described above, the alumina film formed on the molten metal surface has a low melting point and suppresses intermittent entrainment of the alumina film. be able to. Moreover, since MgO is contained within the range of 20 mass% or more and 90 mass% or less, the strength of the scum weir itself can be ensured, and the scum weir can be prevented from being melted at an early stage. Furthermore, free C may be added as appropriate because it has the effect of improving thermal shock resistance. In addition, when adding free C, in order to prevent the fall of a graphite particle, it is preferable to restrict | limit the content of free C to 40 mass% or less. In the present invention, free C refers to carbon that does not form a compound.

Furthermore, in the CaO-containing refractory material, (CaO) / (MgO), which is a ratio of the CaO content (mass%) and the MgO content (mass%), is in the range of 0.2 to 1.5. It is preferable that
In this case, since the above (CaO) / (MgO) is 0.2 or more, the content of CaO is ensured, and the alumina film formed on the molten metal surface can be surely lowered in melting point. It becomes possible. Moreover, since the above-mentioned (CaO) / (MgO) is 1.5 or less, the content of MgO is ensured, and the scum weir can be prevented from being melted at an early stage.

Further, in the scum weir according to the present invention, the CaO-containing refractory material includes CaO in a range of 10 mass% to 50 mass%, ZrO ₂ in a range of ₂₀ mass% to 85 mass%, and free C in a range of 5 mass% to 40 mass%. It is good also as what contains within the range of% or less.
In this case, since CaO is contained in the range of 10 mass% or more and 50 mass% or less as described above, the alumina film formed on the molten metal surface has a low melting point and suppresses intermittent entrainment of the alumina film. be able to. Moreover, since ZrO ₂ is contained within the range of 20 mass% or more and 85 mass% or less, the strength of the scum weir itself can be ensured, and the scum weir can be prevented from being melted at an early stage. Furthermore, since free C is contained in the range of 5 mass% or more and 40 mass% or less, it is possible to suppress the occurrence of cracking due to thermal expansion strain at the start of casting and to suppress the dropping of graphite particles, thereby extending the life of the scum weir. Can be planned.

Further, in the CaO-containing refractory material, (CaO) / (ZrO ₂ ), which is a ratio of the CaO content (mass%) and the ZrO ₂ content (mass%), is 0.2 or more and 1.5 or less. It is preferable to be within the range.
In this case, since the above (CaO) / (ZrO ₂ ) is 0.2 or more, the content of CaO is ensured, and the alumina film formed on the molten metal surface is surely lowered in melting point. Is possible. Moreover, since the above-mentioned (CaO) / (ZrO ₂ ) is 1.5 or less, the content of ZrO ₂ is ensured, and the scum weir can be prevented from being melted at an early stage.

Further, in the scum weir according to the present invention, a region of the surface facing the cooling drum side that is in contact with the molten metal surface of the molten metal reservoir is composed of the CaO-containing refractory material, and the immersion nozzle side is The facing surface is preferably made of BN .
In this case, an area of the surface facing the cooling drum of the scum weir that is in contact with the molten metal surface of the molten metal reservoir is made of the CaO-containing refractory material so that the alumina coating located on the cooling drum side is locally formed. Therefore, the melting point can be lowered and the intermittent entrainment of the alumina film can be suppressed. Moreover, since the molten metal discharged from the immersion nozzle collides with the surface facing the immersion nozzle side of the scum weir, the scum is made of BN having superior resistance to melting than the CaO-containing refractory material. The life of the weir can be extended. It should be noted that the resistance to erosion can be evaluated by the amount of wear after holding the molten metal discharged from the immersion nozzle for a predetermined time.

The method for producing a thin-walled slab according to the present invention includes a molten metal pool part formed by a pair of rotating cooling drums and a pair of side weirs, and Al containing 0.02 mass% or more of Al through an immersion nozzle. A method for producing a thin-walled cast slab comprising supplying a molten metal comprising steel and forming and growing a solidified shell on the peripheral surface of the cooling drum to produce a thin-walled cast slab, wherein A scum weir is disposed, and the superheat degree of the molten metal measured between the immersion nozzle and the scum weir is set to 5 ° C. or more, and the flow rate of the molten metal between the cooling drum and the scum weir Is 5 cm / sec or more.

According to the method for producing a thin cast piece having this configuration, at least a region of the surface facing the cooling drum that is in contact with the molten metal surface of the molten metal reservoir is within a range of 10 mass% or more and 50 mass% or less of CaO. A scum weir composed of a CaO-containing refractory material is used, and the degree of superheat of the molten metal (difference between the molten metal temperature and the liquidus temperature) measured between the scum weir and the immersion nozzle is 5 ° C. As described above, since the flow rate of the molten metal between the scum weir and the cooling drum is 5 cm / sec or more, the temperature of the molten metal located between the scum weir and the cooling drum is increased, and the alumina film is broken. It can be promoted, and intermittent entrainment of the alumina film can be suppressed.
In order to ensure that the above-described effects are achieved, it is preferable that the flow rate of the molten metal between the scum weir and the cooling drum is 10 cm / sec or more.

Here, in the method for manufacturing a thin cast slab according to the present invention, the molten metal may be Al-containing steel containing Al in a range of 0.1 mass% to 4.5 mass%.
Al-containing steel containing Al in the range of 0.1 mass% to 4.5 mass% is liable to form an alumina film on the molten metal surface (molten steel surface). By using a scum weir composed of a CaO-containing refractory material containing CaO within a range of 10 mass% or more and 50 mass% or less, the region in contact with the molten metal surface of the metal pool portion can intermittently entrain the alumina coating. Therefore, it is possible to stably cast a thin slab made of the above-described Al-containing steel.

The thin-walled slab manufacturing apparatus according to the present invention includes an Al containing 0.02 mass% or more of Al through a dipping nozzle in a molten metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs. A thin-walled slab manufacturing apparatus for supplying a molten metal comprising steel and forming and growing a solidified shell on the peripheral surface of the cooling drum to manufacture a thin-walled slab, The scum weir is provided.

  According to the thin-walled slab manufacturing apparatus having this configuration, the area of the molten steel pool portion that contacts the molten metal surface of the molten metal pool portion of at least the surface facing the cooling drum is CaO in a range of 10 mass% to 50 mass%. Since a scum weir composed of a CaO-containing refractory material contained within the following range is provided, the intermittent entrainment of the alumina film is suppressed, and the fluctuation of the height of the molten metal surface at the solidification start point is suppressed. Therefore, it is possible to stably produce a high-quality thin cast slab.

  As described above, according to the present invention, by suppressing the intermittent entrainment of the alumina film, the fluctuation of the height of the molten metal surface at the solidification start point, the non-uniformity of the solidified shell and the thickness of the slab are not. It is possible to provide a scum weir, a thin cast piece manufacturing method, and a thin cast piece manufacturing apparatus capable of stably producing a thin cast piece excellent in quality while suppressing uniformity.

It is explanatory drawing which shows the manufacturing apparatus of the thin cast slab which is embodiment of this invention. FIG. 2 is an enlarged explanatory view of a molten steel pool portion in FIG. 1. It is upper surface explanatory drawing of the molten steel pool part in FIG. It is explanatory drawing of the scum weir which is 1st embodiment of this invention. It is explanatory drawing of the scum weir which is 2nd embodiment of this invention. It is explanatory drawing of the scum weir which is other embodiment of this invention.

  Hereinafter, a scum weir according to an embodiment of the present invention, a method for manufacturing a thin cast piece using the scum weir, and a manufacturing apparatus for the thin cast piece will be described with reference to the accompanying drawings. In addition, this invention is not limited to the following embodiment.

First, a scum weir 20 according to this embodiment and a thin cast slab manufacturing apparatus 10 provided with the scum weir 20 will be described.
As shown in FIG. 1, the thin-walled slab manufacturing apparatus 10 according to the present embodiment supports a pair of cooling drums 11 and 11, bender rolls 12 and 12 that bend the thin-walled slab 1, and the thin-walled slab 1. Pinch rolls 13, a pair of cooling drums 11, a side weir 15 disposed at an end in the width direction, and a molten steel pool portion defined by the pair of cooling drums 11, 11 and the side weir 15 A tundish 18 for supplying the molten steel 3 to the nozzle 16 and an immersion nozzle 19 are provided.
Here, as shown in FIG. 2, the molten steel 3 is stored in the molten steel pool portion 16, and the alumina coating X is formed on the molten steel surface H.

  The molten steel reservoir 16 is provided with a scum weir 20 according to this embodiment. More specifically, as shown in FIGS. 2 and 3, the scum weir 20 is disposed between the immersion nozzle 19 and the cooling drums 11 and 11, and a part of the scum weir 20 is immersed in the molten steel 3. In the present embodiment, as shown in FIGS. 2 and 4, the scum weir 20 has a rectangular flat plate shape, and the immersion depth D in the molten steel 3 is 5 mm or more. The above-described alumina film X is formed on the molten steel surface H between the scum weir 20 and the cooling drum 11 and also on the molten steel surface H between the immersion nozzle 19 and the scum weir 20.

  2 and 4, the scum weir 20 has a two-layer structure, and the first layer 21 disposed on the cooling drum 11 side has CaO in a range of 10 mass% to 50 mass%. The second layer 22 arranged on the immersion nozzle 19 side is composed of a CaO-containing refractory material to be contained, and the refractory material (BN in the present embodiment) has better erosion resistance against the molten steel 3 than the CaO-containing refractory material. ).

In the present embodiment, the CaO-containing refractory material constituting the first layer 21 contains CaO in the range of 10 mass% to 50 mass%, and MgO in the range of 20 mass% to 90 mass%, Free C is contained in the range of 0 mass% or more and 40 mass% or less. In addition, (CaO) / (MgO), which is the ratio of the CaO content (mass%) and the MgO content (mass%), is in the range of 0.2 to 1.5.
Below, the reason which prescribed | regulated the composition of the CaO containing refractory material as mentioned above is demonstrated.

[CaO]
CaO has the effect of reducing the melting point of the alumina coating X formed on the molten steel surface H of the molten steel pool portion 16. Therefore, the alumina film formed on the molten steel surface H between the scum weir 20 and the cooling drum 11 by configuring the first layer 21 formed on the cooling drum 11 side of the scum weir 20 with the CaO-containing refractory material. It becomes possible to lower the melting point of X locally and to facilitate breakage.
Here, when the content of CaO in the CaO-containing refractory material is less than 10 mass%, there is a possibility that the effect of lowering the melting point of the alumina coating X cannot be sufficiently achieved. On the other hand, when the CaO content in the CaO-containing refractory material exceeds 50 mass%, the scum weir 20 (first layer 21) may be deteriorated early.
From the above, in this embodiment, the content of CaO in the CaO-containing refractory material is set in the range of 10 mass% or more and 50 mass% or less.

[MgO]
MgO retains the above-mentioned CaO particles, and has an effect of suppressing CaO particle dropout and excessive melting loss. Therefore, it becomes possible to extend the life of the scum weir 20 (first layer 21) by containing MgO.
Here, when the content of MgO in the CaO-containing refractory material is less than 20 mass%, the CaO particles cannot be sufficiently retained, and the scum weir 20 (first layer 21) may be deteriorated at an early stage. On the other hand, when the content of MgO in the CaO-containing refractory material exceeds 90 mass%, the content of CaO is not ensured, and the alumina coating X may not be lowered in melting point.
From the above, in this embodiment, the content of MgO in the CaO-containing refractory material is set in the range of 20 mass% to 90 mass%.

[(CaO) / (MgO)]
When (CaO) / (MgO), which is the ratio between the CaO content (mass%) and the MgO content (mass%), is less than 0.2, the CaO supply rate decreases due to the influence of MgO. There is a possibility that the alumina film X formed on the molten steel surface H cannot be lowered in melting point. On the other hand, when (CaO) / (MgO) exceeds 1.5, the content of MgO is insufficient, and the scum weir 20 (first layer 21) may deteriorate early.
From the above, in this embodiment, (CaO) / (MgO) is set within the range of 0.2 to 1.5.

[Free C]
Free C refers to carbon that is present alone without forming a compound. When this free C is contained, the thermal shock resistance is improved, so it may be added as appropriate.
Here, when the content of free C in the CaO-containing refractory material exceeds 40 mass%, the graphite particles are likely to fall off, and the amount of erosion may be increased.
From the above, in this embodiment, the content of free C in the CaO-containing refractory material is set within a range of 0 mass% or more and 40 mass% or less.

Next, the manufacturing method of the thin cast piece by the thin cast piece manufacturing apparatus 10 provided with the scum weir 20 which is this embodiment is demonstrated.
Each of the pair of cooling drums 11 and 11 is directed in the rotation direction R, that is, the region where the pair of cooling drums 11 and 11 are close to each other is directed in the drawing direction of the slab (downward in FIG. 1). The cooling drums 11 and 11 are rotated.

Then, the molten steel 3 is supplied from the tundish 18 through the immersion nozzle 19 to the molten steel pool 16 defined by the pair of cooling drums 11 and 11 and the side weir 15.
In the present embodiment, the molten steel 3 is Al-containing steel containing Al in the range of 0.1 mass% to 4.5 mass% and Ca in the range of 0.0020 mass%.
Further, the upper space of the molten steel pool portion 16 including the space between the scum weir 20 and the cooling drum 11 has an Ar gas atmosphere, and Ar gas is interposed between the cooling drum 11 and the solidified shell 5. I am letting.

  As shown in FIG. 3, the discharge flow from the immersion nozzle 19 is arranged so as to face the immersed scum weir 20. Part of the flow F1 of the molten steel 3 discharged from the immersion nozzle 19 collides with the scum weir 20 toward the side weir 15 and collides with the side weir 15 toward the immersion nozzle 19. Further, a part flow F2 of the molten steel 3 discharged from the immersion nozzle 19 passes below the scum weir 20 and collides with the cooling drum 11, moves toward the side weir 15 and collides with the side weir 15. It heads for the immersion nozzle 19 side.

Here, in the embodiment, the flow velocity of the molten steel 3 between the cooling drum 11 and the scum weir 20 (flow velocity of the flow F2) is set to 5 cm / sec or more. In the present embodiment, as shown in FIG. 3, the flow rate of the molten steel 3 at a quarter position P of the width of the cooling drum 11 is configured to be 5 cm / sec or more, preferably 10 cm / sec or more. It is comprised so that.
Furthermore, in this embodiment, the superheat degree (difference between molten steel temperature and liquidus temperature) of the molten steel measured between the immersion nozzle 19 and the scum weir 20 is in the range of 5 ° C. or more and 50 ° C. or less. The temperature of the molten steel is preferably adjusted to be in the range of 10 ° C. or higher and 50 ° C. or lower.

When the molten steel 3 comes into contact with the rotating cooling drum 11 and is cooled, the solidified shell 5 grows on the peripheral surface of the cooling drum 11, and the solidified shell 5 formed on the pair of cooling drums 11, 11, respectively. The thin cast piece 1 having a predetermined thickness is cast by pressing the five members together at the drum kiss point.
At this time, the scum weir 20 immersed in the molten steel pool portion 16 prevents inclusions (scum) floating above the molten steel 3 stored in the molten steel pool portion 16 from entering the cooling drum 11 side, Involvement of the scum into the thin cast slab 1 is suppressed. Further, the scum weir 20 suppresses fluctuations in the height of the molten steel surface H at the solidification start point S of the cooling drum 11.

According to the scum weir 20, the method for manufacturing a thin cast piece, and the thin cast piece manufacturing apparatus 10 of the present embodiment configured as described above, the scum weir 20 is disposed on the surface facing the cooling drum 11 side. Since the first layer 21 is composed of a CaO-containing refractory material containing CaO within a range of 10 mass% to 50 mass%, the alumina coating X is in a portion of the scum weir 20 in contact with the first layer 21. Is supplied, and the melting point is locally lowered. As a result, the alumina coating X present between the scum weir 20 and the cooling drum 11 is locally weakened and easily broken, and is frequently or continuously wound around the cooling drum 11 in a short cycle. It will be. Thus, if the alumina film breaks easily, the amount of fluctuation in the height of the molten steel surface H at the solidification start point S is significantly reduced.
Therefore, the intermittent entrainment of the alumina coating X can be suppressed, and the height of the molten steel surface H at the solidification start point S can be prevented from greatly fluctuating up and down. Therefore, it is possible to stably produce a high-quality thin cast slab.

And since the CaO containing refractory material which comprises the 1st layer 21 arrange | positioned in the surface which faces the cooling drum 11 side among the scum weirs 20 contains MgO within the range of 20 mass% or more and 90 mass% or less, scum The strength of the weir 20 (first layer 21) itself can be secured, and the scum weir 20 (first layer 21) can be prevented from deteriorating early.
Furthermore, since (CaO) / (MgO), which is the ratio of the CaO content (mass%) and the MgO content (mass%), is in the range of 0.2 to 1.5, CaO And MgO in a well-balanced manner, the alumina film X formed on the molten steel surface H can be made to have a low melting point, and intermittent entrainment of the alumina film X can be suppressed, and the scum weir 20 (first layer 21) It is possible to extend the service life.
Further, in the present embodiment, when the CaO-containing refractory material constituting the first layer 21 contains free C within a range of 0 mass% to 40 mass%, the thermal shock resistance can be improved, Generation of cracks at the start of casting can be suppressed.

  Moreover, in this embodiment, the 2nd layer 22 arrange | positioned in the surface which faces the immersion nozzle 19 side among the scum weirs 20 is more resistant to erosion with respect to the molten steel 3 than the CaO containing refractory material which comprises the 1st layer 21. Since it is made of an excellent refractory material, specifically, it is made of BN, even if the molten steel 3 discharged from the immersion nozzle 19 collides, it does not easily melt and the life of the scum weir 20 Extension becomes possible.

In the present embodiment, the flow rate of the molten steel 3 between the cooling drum 11 and the scum weir 20 is 5 cm / sec or more, preferably 10 cm / sec or more. The temperature of the molten steel 3 located between the weirs 20 can be maintained high, and the breakage of the alumina film X having a low melting point can be promoted.
Furthermore, in this embodiment, the superheat degree (difference between molten steel temperature and liquidus temperature) of the molten steel measured between the immersion nozzle 19 and the scum weir 20 is in the range of 5 ° C. or more and 50 ° C. or less. The temperature of the molten steel is preferably adjusted to be in the range of 10 ° C. or more and 50 ° C. or less, so that the fracture of the alumina film X having a low melting point can be promoted, and intermittent engagement of the alumina film X is achieved. It can suppress and can cast a thin-walled slab stably. Here, when the superheat degree of the molten steel measured between the immersion nozzle 19 and the scum weir 20 exceeds 50 ° C., the discharge flow from the nozzle may cause the solidified shell to be re-dissolved. It is preferable.

  Furthermore, in this embodiment, the molten steel 3 is Al-containing steel containing Al in a range of 0.1 mass% to 4.5 mass% and Ca in a range of 0.0020 mass% or less. Such Al-containing steel can be efficiently manufactured by casting as a thin-walled slab because hot working is difficult. Moreover, although the alumina membrane | film | coat X is formed in the surface of the molten steel 3, a thin cast piece can be stably cast by using the scum weir 20 which is this embodiment.

Next, the scum weir 120 which is 2nd embodiment of this invention is demonstrated with reference to FIG.
The scum weir 120 according to the present embodiment is used in the thin cast piece manufacturing apparatus 10 shown in FIG. 1 as in the first embodiment.

As shown in FIG. 5, the scum weir 120 includes a block member 121 disposed in a region in contact with the molten steel surface H of the molten steel pool portion of the surface facing the cooling drum side, and a dam body that supports the block member 121. 122. The block member 121 is detachably attached to the dam body 122.
Here, the above-mentioned block material 121 is composed of a CaO-containing refractory material containing CaO within a range of 10 mass% to 50 mass%, and the weir body 122 that supports the block material 121 is composed of a CaO-containing refractory material. Also, it is made of a refractory material (BN in the present embodiment) having excellent resistance to erosion against molten steel.

In the present embodiment, the CaO-containing refractory material that constitutes the block material 121 arranged in the region of the surface facing the cooling drum side of the scum weir 120 that is in contact with the molten steel surface H of the molten steel pool portion is 10 mass% or more and 50 mass% of CaO. %, Within a range of ₂₀ mass% or more and 85 mass% or less, and free C within a range of 5 mass% or more and 40 mass% or less. Further, (CaO) / (ZrO ₂ ), which is a ratio of the CaO content (mass%) and the ZrO ₂ content (mass%), is in the range of 0.2 to 1.5.
Below, the reason which prescribed | regulated each component as mentioned above is demonstrated.

[CaO]
As described in the first embodiment, CaO has an effect of lowering the melting point of the alumina coating X.
Here, when the content of CaO in the CaO-containing refractory material is less than 10 mass%, there is a possibility that the effect of lowering the melting point of the alumina coating X cannot be sufficiently achieved. On the other hand, when the CaO content in the CaO-containing refractory material exceeds 50 mass%, the scum weir 120 (block material 121) may be deteriorated at an early stage.
From the above, in this embodiment, the content of CaO in the CaO-containing refractory material is set in the range of 10 mass% or more and 50 mass% or less.

[ZrO ₂ ]
ZrO ₂ retains the above-mentioned CaO particles, and has an effect of suppressing CaO particle dropout and excessive melting loss. Therefore, it becomes possible to extend the life of the scum weir 120 (block material 121) by containing ZrO ₂ .
Here, when the content of ZrO ₂ in the CaO-containing refractory material is less than 20 mass%, the CaO particles cannot be sufficiently retained, and the scum weir 120 (block material 121) may be deteriorated at an early stage. On the other hand, when the content of ZrO ₂ in the CaO-containing refractory material exceeds 85 mass%, the content of CaO is not ensured, and the alumina film X may not be lowered in melting point.
From the above, in this embodiment, the content of ZrO ₂ in the CaO-containing refractory material is set in the range of 20 mass% or more and 85 mass% or less.

[(CaO) / (ZrO ₂ )]
When (CaO) / (ZrO ₂ ), which is the ratio of the CaO content (mass%) to the ZrO ₂ content (mass%), is less than 0.2, the CaO supply rate is affected by ZrO _2. May decrease, and the alumina film X may not be lowered in melting point. On the other hand, when (CaO) / (ZrO ₂ ) exceeds 1.5, the ZrO ₂ content is insufficient, and the scum weir 120 (block material 121) may be deteriorated early.
From the above, in this embodiment, (CaO) / (ZrO ₂ ) is set within a range of 0.2 or more and 1.5 or less.

[Free C]
Free C refers to carbon that is present alone without forming a compound. When this free C is contained, the thermal shock resistance is improved.
Here, when the content of free C in the CaO-containing refractory material is less than 5 mass%, the thermal shock resistance cannot be improved, and cracking may occur in the scum weir 120 (block material 121) at the start of casting. There is. On the other hand, when the content of free C in the CaO-containing refractory material exceeds 40 mass%, the graphite particles are likely to fall off and the amount of erosion may be increased.
From the above, in this embodiment, the content of free C in the CaO-containing refractory material is set in the range of 5 mass% or more and 40 mass% or less.

  According to the scum weir 120 of the present embodiment configured as described above, the block material 121 arranged in the region in contact with the molten steel surface H of the molten steel pool portion of the surface facing the cooling drum side has 10 mass of CaO. %, It is composed of a CaO-containing refractory material contained within a range of 50 mass% or less, and as in the first embodiment, the intermittent entrainment of the alumina coating X can be suppressed, and the molten steel surface at the solidification start point S. While fluctuation in the height of H can be suppressed, non-uniformity of the solidified shell and non-uniformity of the slab thickness can be suppressed, and a high-quality thin cast slab can be stably manufactured.

Then, CaO-containing refractory material constituting the block material 121 disposed in the region in contact with the molten steel surface H of the molten steel reservoir of the surface facing the cooling drum side, the ZrO ₂ in the range of 20 mass% or more 85 mass% Since it contains, the intensity | strength of the scum weir 120 (block material 121) itself can be ensured, and it can suppress that the scum weir 120 (block material 121) deteriorates early.
Furthermore, since the CaO-containing refractory material constituting the block material 121 contains free C within a range of 5 mass% or more and 40 mass% or less, the thermal shock resistance can be improved, and cracks are generated at the start of casting. Can be suppressed.

Furthermore, since the ratio (CaO) / (ZrO ₂ ), which is the ratio of the CaO content (mass%) and the ZrO ₂ content (mass%), is in the range of 0.2 to 1.5. , CaO and ZrO ₂ are contained in a well-balanced manner, and the alumina film X formed on the molten steel surface H can be made to have a low melting point to suppress intermittent entrainment of the alumina film X. The life of the material 121) can be extended.

Moreover, in this embodiment, the dam body 122 arrange | positioned in the surface which faces the immersion nozzle side among the scum dams 120 is a refractory material having better erosion resistance against molten steel than the CaO-containing refractory material constituting the block material 121. Specifically, since it is made of BN, even if the molten steel supplied from the immersion nozzle collides, it is not easily melted and the life of the scum weir 120 can be extended. It becomes.
Furthermore, in this embodiment, since the block material 121 is detachably attached to the dam body 122, when the block material 121 is melted early, only the block material 121 is replaced and used. be able to.

As mentioned above, the scum weir, the method for manufacturing a thin cast piece, and the apparatus for producing a thin cast piece, which are embodiments of the present invention, have been specifically described, but the present invention is not limited to this, and the technical features of the present invention are not limited thereto. Changes can be made as appropriate without departing from the spirit.
For example, in the present embodiment, the description has been made with the bender roll and the pinch roll provided, but the arrangement of these rolls and the like is not limited, and the design may be changed as appropriate. Further, the configuration of the tundish, the immersion nozzle, etc. is not limited to this embodiment, and the design may be changed as appropriate.

In the present embodiment, Al-containing steel containing 0.1 mass% or more and 4.0 mass% or less of Al and 0.0020 mass% or less of Ca is targeted. However, the present invention is not limited to this, and other metal materials are used. (Al deoxidized steel containing 0.02 mass% or more of Al or the like) may be the target.
Moreover, in this embodiment, as shown in FIG.4 and FIG.5, although demonstrated as what comprised a part of scum weir with CaO containing refractory material, as shown in FIG. 6, it is not limited to this. The scum weir 220 may be entirely composed of a CaO-containing refractory material.

In the first embodiment, the first layer 21 of the scum weir 20 has been described as being composed of a refractory material containing CaO and MgO. However, the present invention is not limited to this, and CaO and ZrO ₂ are not limited thereto. And a free refractory material containing free C, or another CaO-containing refractory material.
Similarly, in the second embodiment, the block material 121 of the scum weir 120 has been described as being composed of a refractory material containing CaO, ZrO ₂ and free C. However, the present invention is not limited to this. And refractory material containing MgO, or other CaO-containing refractory material.

In the first embodiment, the second layer 22 of the scum weir 20 has been described as being made of BN that is more resistant to molten steel than the CaO-containing refractory material. However, the present invention is limited to this. Alternatively, other refractory materials may be used.
Similarly, in the second embodiment, the weir body 122 of the scum weir 120 has been described as being made of BN that is more resistant to molten steel than the CaO-containing refractory material. However, the present invention is limited to this. Alternatively, other refractory materials may be used.

Below, in order to confirm the effect of this invention, the comparative experiment result implemented by changing the composition of the refractory material which comprises a scum weir is demonstrated.
Here, in all the refractory materials described later, the maximum particle size of the graphite particles was 300 μm or less, the average particle size was 100 μm or less, the maximum particle size of the oxide was 100 μm or less, and the average particle size was 50 μm or less.

  In the apparatus for producing a thin cast slab described in the present embodiment, C: 0.003 mass%, Si: 3.0 mass%, Mn: 0.2 mass%, using scum weirs having the compositions shown in Tables 1 and 2 A thin cast slab made of Al-containing steel containing P: 0.01 mass%, S: 0.001 mass%, Al; 0.6 mass% was cast under the following conditions.

Diameter of cooling drum: 1200mm
Casting width: 1300mm
Casting speed: Average 60m / min
Immersion depth of scum weir: 30 mm
Scum weir width: 1250 mm
Total thickness of scum weir: 30 mm
Spacing between scum weir / cooling drum: 30 mm
Flow rate between scum weir / cooling drum: 5 cm / sec or more Superheat degree in molten steel pool: 25 ° C target, within 15-35 ° C casting atmosphere: Ar
Casting thickness: Average 1.8mm
Casting amount: 10ton

In addition, the molten steel superheat degree (difference between molten steel temperature and liquidus temperature) in a molten steel pool part can be measured with a radiation thermometer, a thermocouple, etc., for example. When a radiation thermometer is used, the molten steel surface is covered with an alumina film, so that it is necessary to correct the emissivity as compared with the temperature measurement result obtained by another method (for example, a thermocouple). Moreover, you may grasp | ascertain the temperature fall amount at the time of molten steel flowing from a tundish to a molten steel pool part, and may manage with molten steel temperature, such as a tundish which supplies molten steel to an immersion nozzle.
Further, the flow velocity of the molten steel between the scum weir and the cooling drum can be calculated from the moving speed of the scum floating on the molten steel surface in the molten metal surface monitor image.

  The scum weir has the structure shown in FIG. 5, and the refractory material having the composition shown in Tables 1 and 2 has a full width in the range of ± 10 mm up and down with respect to the surface of the molten steel in the surface of the surface facing the cooling drum. A block material composed of The weir body is made of BN, and a groove is formed in a region where the block material is arranged, and the above-described block material is incorporated in the groove. Specifically, five plate materials having a height of 20 mm, a thickness of 20 mm, and a width of 250 mm were incorporated in the width direction.

  Using the above scum weir, casting the thin cast slab under the above conditions, the amount of fluctuation of the molten steel surface in the steady state, the surface property of the thin cast slab, the thickness of the thin cast slab, the casting The amount of erosion of the later block material was evaluated by the following procedure. The evaluation results are shown in Tables 3 and 4.

[Amount of erosion of block material]
Evaluation was made by the average value of the amount of erosion at the positions of 1/4, 1/2, 3/4 in the width direction and 10 mm from both edges. It converted into the amount of melting loss per 100 tons of casting amounts, and evaluated by the following references | standards.
◎; 10 mm or less ○; 15 mm or less ×;

[Variation of molten steel surface height]
It was measured from a monitor screen for controlling the surface height during casting. Among the fluctuations in the height of the molten steel surface that occurs when the alumina coating on the molten steel surface is involved in the steady part casting time, an average value of 10 times is obtained from the largest one and evaluated according to the following criteria. Note that large fluctuations suddenly caused by other factors were not measured.
◎; 4 mm or less ○; 6 mm or less ×;

[Surface properties of thin cast slabs]
Three pieces of 2 m long slabs were extracted from the steady part, pickled, and then examined for surface cracks by visual inspection and an 8-fold magnifier. In addition, many cracks were observed in the area | region where the alumina membrane | film | coat was wound. Cracks with a length of 1 mm or more were counted, and the number per 1 m of cast slab was evaluated according to the following criteria.
◎; 3 pieces / m or less ○; 5 pieces / m or less ×; More than 5 pieces / m

[Thickness variation of thin-walled slab]
About the steady-state part 5ton slab, the width | variety center part thickness was measured by the X-ray plate thickness meter at a 100-mm space | interval in the casting direction. Standard deviation was calculated and evaluated according to the following criteria.
◎; 25 μm or less ○; 50 μm or less ×;

  No. shown in Table 1. A1 to A13 are examples of the present invention and comparative examples using MgO—CaO refractory materials. No. A14 is a comparative example using a conventionally used BN-based refractory material.

Comparative Example No. in which the content of CaO was less than 10 mass%. In A12, the fluctuation amount of the height of the molten steel surface exceeded 6 mm. Moreover, the surface property of the slab was poor, and the variation in the thickness of the slab was large. It is presumed that the supply of CaO is small and the alumina film cannot be sufficiently lowered in melting point, and the alumina film is intermittently entrained.
Comparative Example No. in which the content of CaO exceeds 50 mass%. In A13, the amount of scum weir damage exceeded 15 mm. It is presumed that CaO was preferentially melted.
Comparative Example No. composed of BN In No. 14, the fluctuation of the height of the molten steel surface exceeded 6 mm. Moreover, the surface property of the slab was poor, and the variation in the thickness of the slab was large. It is presumed that the alumina film was not lowered in melting point and the alumina film was intermittently entrained.

On the other hand, the present invention example No. In A1 to A11, the scum weir erosion amount is 15 mm or less, the fluctuation amount of the molten steel surface height is suppressed to 6 mm or less, the surface property of the slab is good, and the slab thickness variation is also suppressed. It was.
In particular, Invention Example No. in which (CaO) / (MgO), which is the ratio of the CaO content (mass%) and the MgO content (mass%), is in the range of 0.2 to 1.5. . In A1 to A7, the amount of scum weir loss was suppressed to 10 mm or less, and the amount of fluctuation in the height of the molten steel surface was suppressed to 4 mm or less.
In Example No. (CaO) / (MgO) of less than 0.2. In A8, the fluctuation amount of the height of the molten steel surface exceeded 4 mm, and the evaluation was good. It is presumed that the CaO supply rate has decreased.
Example No. (CaO) / (MgO) exceeded 1.5. In A9, the scum weir was slightly larger than 10 mm, and the evaluation was good. It is presumed that MgO is insufficient with respect to CaO, and the strength of the scum weir itself is insufficient.
Example No. in which the content of MgO was less than 20 mass%. In A10, the amount of scum weir damage exceeded 10 mm, and the evaluation was good. This is presumably because MgO was insufficient and the strength of the scum weir itself was insufficient.
Example No. in which the free C content exceeds 40 mass%. In A11, the amount of scum weir damage exceeded 10 mm, and the evaluation was good. It is presumed that graphite particles were partially dropped. In this case, the alumina film attached to the scum weir is easily wound on the cooling drum when the graphite particles fall off from the scum weir main body in addition to lowering the melting point by CaO.

No. shown in Table 2 B1 to B14 are examples of the present invention and comparative examples using a ZrO ₂ —CaO-based refractory material.

Comparative Example No. in which the content of CaO was less than 10 mass%. In B13, the fluctuation amount of the height of the molten steel surface exceeded 6 mm. Moreover, the surface property of the slab was poor, and the variation in the thickness of the slab was large. It is presumed that the supply of CaO is small and the alumina film cannot be sufficiently lowered in melting point, and the alumina film is intermittently entrained.
Comparative Example No. in which the content of CaO exceeds 50 mass%. In B14, the amount of scum weir damage exceeded 15 mm. It is presumed that CaO was preferentially melted.

On the other hand, the present invention example No. In B1 to B12, the scum weir erosion amount is 15 mm or less, the fluctuation amount of the molten steel surface height is suppressed to 6 mm or less, the surface property of the slab is good, and the slab thickness variation is also suppressed. It was.
In particular, the present invention in which (CaO) / (ZrO ₂ ), which is the ratio of the CaO content (mass%) and the ZrO ₂ content (mass%), is in the range of 0.2 to 1.5. Example No. In B1 to B7, the amount of scum weir loss was suppressed to 10 mm or less, and the amount of fluctuation in the height of the molten steel surface was suppressed to 4 mm or less.
Example No. in which (CaO) / (ZrO ₂ ) was less than 0.2. In B8, the fluctuation amount of the height of the molten steel surface exceeded 4 mm, and the evaluation was good. It is presumed that the CaO supply rate has decreased.
Example No. (CaO) / (ZrO ₂ ) exceeded 1.5. In B9, the scum weir was slightly larger than 10 mm, and the evaluation was good. It is presumed that ZrO ₂ was insufficient with respect to CaO, and the strength of the scum weir itself was insufficient.
Example No. in which the content of ZrO ₂ was less than 20 mass%. In B10, the amount of scum weir damage exceeded 10 mm, and the evaluation was good. It is estimated that ZrO ₂ was insufficient and the strength of the scum weir itself was insufficient.
Example No. in which the content of free C was less than 5 mass%. In B11, the amount of scum weir damage exceeded 10 mm, and the evaluation was good. It is presumed that cracks occurred at the start of casting and partly dropped off.
Example No. in which the free C content exceeds 40 mass%. In B12, the amount of scum weir damage exceeded 10 mm, and the evaluation was good. It is presumed that graphite particles were partially dropped.

Next, the composition of the refractory material constituting the scum weir was fixed, and the effects of the compositions shown in Tables 5 and 6 on various steel types were evaluated.
No. In C1-C9, No. 1 of Example 1 was used. A refractory material (MgO—CaO refractory material) having the composition of A5 was used.
No. In D1 to D9, No. 1 in Example 1 was obtained. A refractory material having a composition of B5 (ZrO ₂ —CaO refractory material) was used.

The casting conditions were set as follows. In addition, about the flow rate between a scum weir / cooling drum and the superheat degree in a molten steel pool part, it implemented on the conditions of Tables 7 and 8.
Here, since the molten steel temperature in the molten steel pool portion gradually decreases after the start of casting, in Tables 7 and 8, the values measured in the steady portion of casting (intermediate portion of the total casting amount 10 t) are described.

Diameter of cooling drum: 1200mm
Casting width: 1300mm
Casting speed: Average 60m / min
Immersion depth of scum weir: 30 mm
Scum weir width: 1250 mm
Total thickness of scum weir: 30 mm
Spacing between scum weir / cooling drum: 30 mm
Flow velocity between scum weir / cooling drum: Conditions described in Tables 7 and 8 Superheat degree in molten steel pool: Conditions described in Tables 7 and 8 Casting atmosphere: Ar
Casting thickness: Average 1.8mm
Casting amount: 10ton

  Casting thin-walled slabs under the above-mentioned conditions, the fluctuation amount of the molten steel surface in the steady state, the surface property of the thin-walled slab, the fluctuation amount of the thickness of the thin-walled slab, the amount of erosion of the block material after casting Was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 7 and Table 8.

Comparative Example No. in which the degree of superheat of the molten steel pool was less than 5 ° C. C8 and Comparative Example No. In D8, the fluctuation amount of the height of the molten steel surface exceeded 6 mm. Moreover, the surface property of the slab was poor, and the variation in the thickness of the slab was large. It is presumed that the molten steel temperature was low and the alumina coating could not be sufficiently melted, and the alumina coating was intermittently generated.
Comparative example No. in which the flow rate of the molten steel between the scum weir / cooling drum was less than 5 cm / sec. C9 and Comparative Example No. In D9, the fluctuation amount of the molten steel surface height exceeded 6 mm. Moreover, the surface property of the slab was poor, and the variation in the thickness of the slab was large. It is presumed that the temperature of the molten steel located between the scum weir and the cooling drum was lowered and the alumina film could not be sufficiently melted, and the alumina film was intermittently entrained.

On the other hand, the degree of superheating of the molten steel and the flow rate of the molten steel between the scum weir / cooling drum are within the scope of the present invention. C1 to C7 and Invention Example No. In D1 to D7, the fluctuation amount of the molten steel surface height was suppressed to 6 mm or less, the surface property of the slab was good, and the thickness variation of the slab was also suppressed.
Moreover, it was confirmed that the same effect can be obtained even when molten steels having various compositions are used.

  From the above results, according to the scum weir, the thin cast piece manufacturing method and the thin cast piece manufacturing apparatus according to the present invention, since the alumina film is easily wound, the molten metal surface level is stabilized, the quality and the cast thickness. It was confirmed that a thin cast slab of high Al content steel with excellent uniformity can be stably cast.

1 Thin-walled slab 3 Molten steel (molten metal)
5 Solidified shell 10 Thin-walled slab manufacturing device 11 Cooling drum 15 Side weir 16 Molten steel reservoir (molten metal reservoir)
19 Immersion nozzle 20, 120, 220 Scum weir

Claims (9)

A molten metal made of Al-containing steel containing 0.02 mass% or more of Al is supplied to a molten metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs via an immersion nozzle, and the cooling In the method for producing a thin-walled slab by forming and growing a solidified shell on the peripheral surface of the drum to produce a thin-walled slab, a scum weir disposed in the molten metal reservoir,
At least a region of the surface facing the cooling drum that is in contact with the molten metal surface of the molten metal reservoir is composed of a CaO-containing refractory material containing CaO in a range of 10 mass% to 50 mass%. Characteristic scum weir.   The CaO-containing refractory material contains CaO in a range of 10 mass% to 50 mass%, MgO in a range of 20 mass% to 90 mass%, and free C in a range of 0 mass% to 40 mass%. The scum weir according to claim 1.   In the CaO-containing refractory material, (CaO) / (MgO), which is a ratio of the CaO content (mass%) and the MgO content (mass%), is in the range of 0.2 to 1.5. The scum weir according to claim 2. The CaO-containing refractory material contains CaO in a range of 10 mass% to 50 mass%, ZrO2 in a range of ₂₀ mass% to 85 mass%, and free C in a range of 5 mass% to 40 mass%. The scum weir according to claim 1. In the CaO-containing refractory material, (CaO) / (ZrO ₂ ), which is a ratio of the CaO content (mass%) and the ZrO ₂ content (mass%), is in the range of 0.2 to 1.5. The scum weir according to claim 4, wherein Of the surface facing the cooling drum side, a region in contact with the molten metal surface of the molten metal reservoir is made of the CaO-containing refractory material,
The scum weir according to any one of claims 1 to 5, wherein the surface facing the immersion nozzle is made of BN . A molten metal made of Al-containing steel containing 0.02 mass% or more of Al is supplied to a molten metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs via an immersion nozzle, and the cooling A method for producing a thin-walled slab by producing a thin-walled slab by forming and growing a solidified shell on a peripheral surface of a drum,
The scum weir according to any one of claims 1 to 6 is disposed in the molten metal reservoir,
While setting the superheat degree of the molten metal measured between the immersion nozzle and the scum weir to 5 ° C. or more,
A method for producing a thin cast slab, wherein a flow rate of the molten metal between the cooling drum and the scum weir is 5 cm / sec or more.   The said molten metal is Al containing steel which contains Al within the range of 0.1 mass% or more and 4.5 mass% or less, The manufacturing method of the thin cast slab of Claim 7 characterized by the above-mentioned. A molten metal made of Al-containing steel containing 0.02 mass% or more of Al is supplied to a molten metal reservoir formed by a pair of rotating cooling drums and a pair of side weirs via an immersion nozzle, and the cooling A thin-walled slab manufacturing device that forms and grows a solidified shell on the peripheral surface of a drum to manufacture a thin-walled slab,
The scum weir according to any one of claims 1 to 6, wherein the molten metal pool part is provided with a thin cast slab manufacturing apparatus.

Images