JP7273300B2 - METHOD FOR MANUFACTURING THIN-WALL INSTALL, AND TWIN-ROLL TYPE CONTINUOUS CASTING APPARATUS - 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. The present invention relates to a method for producing thin cast slabs and a twin roll type continuous casting apparatus.

As a method for manufacturing a thin cast piece of metal, a molten metal pool section is provided with a pair of cooling rolls that have a water cooling structure inside and rotate in mutually opposite directions, and is formed by a pair of rotating cooling rolls and a pair of side weirs. to form and grow solidified shells on the peripheral surfaces of the cooling rolls, and the solidified shells formed on the peripheral surfaces of the pair of cooling rolls are crimped to each other at roll kiss points to obtain a thin wall of a predetermined thickness. A twin roll continuous casting apparatus is provided for producing slabs. Such a twin roll type continuous casting apparatus is applied to various metals.

In the above-mentioned molten metal pool portion, oxides and the like float on the molten metal surface of the molten metal pool portion to form film-like foreign matter called scum. The main composition of scum is an oxide produced by deoxidation or oxidation in the atmosphere, and the main component is alumina (Al ₂ O ₃ ). When this scum is intermittently caught on the peripheral surface of the cooling roll (more specifically, between the peripheral surface of the cooling roll and the solidified shell; hereinafter, it may be simply referred to as the peripheral surface of the cooling roll), cooling It causes surface cracks and wrinkles in thin cast slabs because it causes non-uniform solidification and cooling between rolls and solidified shells. Therefore, in the twin-roll continuous casting apparatus, prevention of scum formation and scum entrainment is a major issue in order to prevent cast slab defects.
Therefore, techniques have been proposed to prevent the scum on the surface of the molten steel from being caught on the peripheral surface of the chill roll when casting a thin cast slab using the above-described twin roll continuous casting apparatus.

For example, Patent Literature 1 proposes a technique of suppressing the generation of scum by creating an inert gas atmosphere in a seal chamber that covers a molten metal pool portion to reduce the oxygen partial pressure in the atmosphere. Ar or N ₂ is used as the inert gas.
However, since the inclusions generated during deoxidation are suspended in the molten metal, it was not possible to suppress the generation of scum caused by these inclusions in the seal chamber.

Further, Patent Document 2 discloses means for suppressing entrainment of scum by arranging a plate-shaped scum weir in the gap between the molten metal pouring nozzle and the cooling roll in the molten metal pool. In this case, the scum that has risen to the surface of the hot water is dammed by the scum dam, so entrainment of the scum can be greatly suppressed. The molten metal passes through the lower tip of the immersed scum weir and reaches the meniscus (the contact start point between the molten metal surface and the chill roll, the solidification start point), and then solidifies on the chill roll peripheral surface, resulting in less scum entrainment. A piece is produced.

However, the longer the casting time, the more scum gradually accumulates on the molten metal surface between the scum weir and the pouring nozzle. Further measures are required for
In order to prevent scum entrainment, the scum weir should be installed as wide as possible. A gap remains in the The accumulated scum may eventually overflow from the edge portion of the scum weir to the area sandwiched between the cooling roll and the scum weir, and may be intermittently caught in the cooling roll.

In general, the main component of scum is alumina (Al ₂ O ₃ ) produced by oxidation of Al, which is a strong deoxidizing element, and has a high melting point. However, since the viscosity is often high, even if it reaches the meniscus, it is difficult to get caught in the cooling rolls immediately. In many cases, entrainment occurs intermittently in the chill roll, since the scum cracks and cut pieces are caught in the chill roll.
Here, since the scum cracks irregularly, sometimes coarse scum pieces are caught in the scum, which tends to cause significant non-uniform solidification. As a result, cracks and dents may occur on the slab surface, or coarse porosity may occur inside the slab.

Therefore, Patent Document 3 discloses a technique of solidifying scum to suppress entrainment of scum. Specifically, a method of attaching scum to some solid and a method of solidifying the scum itself are disclosed. In the former, at least a part of the molten steel surface is covered with a plate-like solid oxide, and the lower surface of the solid oxide in contact with the molten steel captures the scum floating on the molten steel surface. In the latter method, a cooling gas is blown onto the surface of the molten steel, or a solidifying material for cooling, such as powdered MgO or CaO, is added to the surface of the molten metal.

Further, in Patent Document 4, CaO, MgO, CaF ₂ , SiO ₂ , Al ₂ O ₃ and the like are added to the tundish or the molten metal pool to adjust the composition of the scum, and the solid fraction of the scum is increased. A technique is disclosed in which even if scum is involved, no scum flaws are generated and the scum is rendered harmless by controlling it to 5% or more and 60% or less. Powders, small lumps, rods, plates, coated steel wires, and the like are described as forms of the additive.

JP-A-05-261490 JP-A-04-158959 JP-A-2002-273551 JP-A-2000-246402

By the way, in the method disclosed in Patent Document 3, entrainment is greatly suppressed by solidification of scum, but since a large amount of scum accumulates during long-term casting, there is a limit to the amount of scum accumulated. As a result, casting time is constrained. When the accumulation limit is exceeded, the solidified scum is irregularly involved, and sometimes coarse scum pieces are involved, easily causing scum flaws and slab cracks. Moreover, when a large amount of solid-phase scum covers the entire surface of the molten steel, it becomes difficult to accurately detect the molten metal surface level, which may hinder the operation. Therefore, in order to cast a thin cast piece for a long time in a twin-roll type continuous casting apparatus, there is a problem in solidifying the scum.

In addition, in the method disclosed in Patent Document 4, inclusions and scum (hereinafter referred to as scum) in the entire molten steel, including inclusions suspended in the molten steel that cause scum, together with scum on the surface of the molten steel ) need to be reformed. In order to prevent scum flaws from occurring even if scum is involved, it is necessary to control the composition of all scum in the molten steel, not just on the surface of the molten steel, within a target range. If the scum composition is non-uniform, even if the scum composition adjusting additive is added, the scum solid fraction may not satisfy the target range of 5% or more and 60% or less depending on the part. Considering the balance between the amount of scum inflow and the amount of scum discharged (entrained amount), it is necessary to accurately adjust the addition amount of the scum composition-adjusting additive, but uniform reforming is difficult. In addition, the amount of scum itself increases due to the additive.

Furthermore, even if the composition of the entire scum can be accurately controlled, since the solid phase ratio is controlled to 5% or more and 60% or less, the liquid phase remains and is rather likely to be involved. Therefore, it becomes easy to be caught from any part of the entire width of the cooling roll. Since there is still a possibility that scum flaws will occur, it is conceivable that quality requirements, which have become more and more stringent in recent years, cannot be fully satisfied. In addition, if scum adheres to the slab surface, uneven cooling occurs during solidification, resulting in uneven crystal grain size and coarsening of the crystal grains in the scum-involved portion, which easily causes uneven material quality and uneven gloss. In addition, in the case of products with strict appearance quality, there are cases where the burden of pickling the slab, for example, is increased in order to remove the adhering scum more than before. For the above reasons, it is more important to prevent scum entrainment itself in the slab used for the product.

The present invention has been made in view of the above circumstances, and by causing scum to be preferentially caught in the trim width portion of the thin cast slab, it is possible to prevent the scum from being caught in the portion other than the trim width portion. It is an object of the present invention to provide a thin-walled cast product manufacturing method and a twin-roll continuous casting apparatus capable of manufacturing sound thin-walled cast products with few single defects.

In order to solve the above-described problems, a method for manufacturing a thin cast strip according to 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. A method for producing a thin cast slab by forming and growing a solidified shell on the peripheral surface of the thin cast slab, wherein the edge portion of the molten metal pool portion corresponding to the trim width of the thin cast slab is up to 30 mm A CaO-containing material is added to the meniscus of the width end region to lower the melting point of the scum located in the width end region so that the scum is preferentially involved.

According to the method for manufacturing a thin cast strip having this configuration, the CaO-containing melt is supplied to the meniscus of the molten metal pool portion located in the width end region corresponding to the trim width of the thin cast strip. scum (mainly Al ₂ O ₃ ) in the vicinity of the meniscus of the width end region reacts with CaO to lower the melting point. As a result, the scum is preferentially caught in the trim width portion of the thin cast slab, the accumulation of scum is suppressed, and it is possible to prevent the scum from being caught in portions other than the trim width. Therefore, even if the casting time is long, it is possible to produce sound thin cast slabs with few cast slab defects.

Here, in the method for producing a thin cast strip of the present invention, it is preferable to add the CaO-containing material to the vicinity of the meniscus of the width end region.
In this case, CaO can be efficiently supplied to the vicinity of the meniscus of the width end region, and scum can be preferentially caught in the trim width portion of the thin cast strip. In the present invention, the vicinity of the meniscus is defined as a region extending up to 30 mm from the meniscus to the cooling roll side and the molten metal pool side when the molten metal pool is viewed from above.

Moreover, in the method for producing a thin cast strip of the present invention, the CaO-containing material may be added to the molten metal surface of the molten metal pool portion located in the width end region.
In this case, CaO is supplied to the meniscus of the width end region by the flow of the surface of the molten metal pool, and it is possible to preferentially involve the scum in the trim width portion of the thin cast strip. Become.

Furthermore, in the method for producing a thin cast strip of the present invention, the CaO-containing material may be added to the outer peripheral surface of the cooling roll located in the width end region.
In this case, as the cooling roll rotates, CaO is supplied to the meniscus of the width end region, and it becomes possible to preferentially involve the scum in the trim width portion of the thin cast strip.

Further, in the method for producing a thin cast strip of the present invention, the CaO-containing powder may be added.
Alternatively, in the method for producing a thin cast strip of the present invention, the CaO-containing solid matter may be added by being pressed against the outer peripheral surface of the cooling roll.

The twin-roll continuous casting apparatus according to 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 a solidified shell on the peripheral surface of the cooling rolls. A twin-roll continuous casting apparatus for growing and producing thin-walled slabs, wherein CaO is added to the meniscus of the width end region up to 30 mm from the edge of the molten metal pool corresponding to the trim width of the thin-walled slab. It is characterized by having a CaO addition mechanism for adding inclusions .

According to the twin-roll continuous casting apparatus of this configuration, the CaO-containing caster is supplied to the meniscus of the molten metal pool portion located in the width end region corresponding to the trim width of the thin cast strip. Since a CaO addition mechanism for adding substances is provided, scum can be preferentially caught in the trim width portion of the thin cast slab, and scum entrainment in portions other than the trim width can be suppressed. Therefore, even if the casting time is long, it is possible to produce sound thin cast slabs with few cast slab defects.

Here, in the twin-roll continuous casting apparatus of the present invention, the CaO addition mechanism may be configured to add a CaO-containing material made of powder or grain.
Alternatively, in the twin roll continuous casting apparatus of the present invention, the CaO addition mechanism may be configured to press the CaO-containing solid matter against the outer peripheral surface of the cooling roll.

As described above, according to the present invention, the scum is preferentially caught in the trim width portion of the thin cast slab, thereby preventing the scum from being caught in portions other than the trim width portion, resulting in a healthy cast slab with few defects. It is possible to provide a thin cast strip manufacturing method and a twin roll continuous casting apparatus capable of manufacturing thin cast strips.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an example of a twin roll continuous casting apparatus that is an embodiment of the present invention; FIG. 2 is a partially enlarged explanatory view of the twin-roll continuous casting apparatus shown in FIG. 1; FIG. 2 is a cross-sectional explanatory view of the vicinity of the molten steel pool portion of the twin-roll continuous casting apparatus shown in FIG. 1; FIG. 3 is an explanatory top view of the molten steel pool portion shown in FIG. 2; It is an explanatory view showing an example of the CaO addition mechanism in the embodiment of the present invention. It is an explanatory view showing an example of the CaO addition mechanism in the embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the attached drawings. In the following embodiments, the target metal to be cast will be described as steel. 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. In addition, as steel types, for example, 0.001 to 0.01% C ultra-low carbon steel, 0.01 to 0.10% C low carbon steel, 0.10 to 0.4% C medium carbon steel, 0.4 ~1.2% C high carbon steel, austenitic stainless steel represented by SUS304 steel, ferritic stainless steel represented by SUS430 steel, 0.1 to 6.5% Si steel, etc. (% is mass %).
Further, in the present embodiment, the width of the thin cast piece 1 to be manufactured is within the range of 200 mm or more and 1800 mm or less, and the thickness is within the range of 0.8 mm or more and 5 mm or less.

A twin-roll continuous casting apparatus 10 used in the thin-walled cast product manufacturing method of the present embodiment will be described.
A twin roll continuous casting apparatus 10 shown in FIG. A side weir 15 disposed at the end, a tundish 17 for holding the molten steel 3 supplied to the molten steel pool portion 16 formed by the pair of cooling rolls 11, 11 and the side weir 15, and this tundish and a pouring nozzle 18 for supplying molten steel 3 from 17 to the molten steel pool portion 16 .

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.

Here, as shown in FIG. 3, in the twin roll continuous casting apparatus 10 of the present embodiment, a seal chamber 20 is arranged above the molten steel pool portion 16 and the cooling rolls 11, 11, The inside of the seal chamber 20 is a non-oxidizing atmosphere.
Molten steel 3 is stored in the molten steel pool portion 16, and a scum X made of an alumina film or the like is formed on the surface of the molten steel.

A scum weir 19 is provided in the molten steel pool portion 16 in order to prevent the scum X from being caught in the cooling roll 11 . More specifically, as shown in FIGS. 2 and 3, the scum weir 19 has a rectangular flat plate shape and is arranged between the pouring nozzle 18 and the cooling rolls 11, 11. immersed inside.

In this embodiment, as shown in FIG. 4, CaO-containing material is added. The CaO-containing material includes CaO alone, CaO-- _SiO.sub.2 -based oxide, CaO-- _CaF.sub.2 -based flux, and the like.
By adding the CaO-containing material in this way, the scum X located in the vicinity of the meniscus M located in the width end region D corresponding to the trim width T of the thin cast slab 1 reacts with CaO to lower the melting point. The scum X is preferentially caught in the trim width T of the thin cast slab 1 . A portion of the trim width T of the thin cast strip 1 into which the scum X is preferentially caught is called a scum discharge region.

Here, since the trim width T of the thin cast slab 1 is generally about 30 mm at maximum, the width end region D to which the CaO-containing material is added is a region with a maximum of 30 mm from the edge of the molten steel pool. becomes.
In addition, the CaO-containing material is added to the vicinity of the meniscus M in the width end region D (region A in FIG. 4), the outer peripheral surface of the cooling roll 11 in the width end region D (region B in FIG. 4), and the width end region. Any one or two or more points on the surface of the molten steel pool portion 16 in the area D (area C in FIG. 4). The vicinity of the meniscus M in the width end region D (region A in FIG. 4) is a region extending from the meniscus M to the cooling roll 11 side and the molten steel pool portion 16 side by 30 mm, respectively, when the molten steel pool portion 16 is viewed from above. Become. The area B includes the outer peripheral surface portion of the cooling roll 11 in the area A, and the area C includes the melt surface portion of the area A.

When adding the CaO-containing material to the vicinity of the meniscus M in the width end region D (region A in FIG. 4), for example, as shown in FIG. A method of dropping to the vicinity of the meniscus, or spraying CaO-containing granules together with an inert gas such as Ar or N ₂ can be used. In addition, when spraying by mixing with an inert gas, it is preferable to use Ar gas with low thermal conductivity in order to suppress the drop of molten steel temperature. In addition, the above-mentioned granules mean those having an under-sieve particle size of 5 mm or less. This is because if the CaO-containing material has a particle size of 5 mm or less, it is easily dissolved in molten steel. On the other hand, the smaller the particle size, the easier it is to dissolve in molten steel.

When adding the CaO-containing material to the outer peripheral surface of the cooling roll 11 in the width end region D (region B in FIG. 4), for example, as shown in FIG. It may be supplied and dropped onto the outer peripheral surface of the cooling roll 11 . Alternatively, for example, as shown in FIG. 6, a pressing mechanism 40 is used to press a CaO-containing solid material (a bar, a plate, etc.) against the outer peripheral surface of the cooling roll 11 so that it adheres to the outer peripheral surface of the cooling roll 11. may Since the inside and outside of the seal chamber 20 are separated by a heat-resistant cloth or the like, the addition to the outer peripheral surface of the chill roll 11 is preferably performed within the seal chamber 20 .
The pressing mechanism 40 preferably has a function of adjusting the pressing force of the CaO-containing solid material (bar, plate, etc.) so that the amount of the CaO-containing material to be added can be adjusted. For example, the CaO-containing material is pressed against the outer peripheral surface of the cooling roll 11 via an urging member 41 such as a spring. may be configured to adjust the

When the CaO-containing material is added to the molten steel surface of the molten steel pool portion 16 in the width end region D (region C in FIG. A method of dropping the CaO-containing material onto the surface of the hot water, or spraying CaO-containing granules together with an inert gas such as Ar or N ₂ can be used.

Here, the amount of CaO to be added is 10 to 500 g/t-steel with respect to the slab mass corresponding to the trim width T on one side of the thin slab 1 in which the scum X is preferentially involved. preferable.
By setting the addition amount of CaO to 10 g/t-steel or more, the scum X reacts with CaO to sufficiently lower the melting point, and the scum X can be preferentially involved. On the other hand, by setting the amount of CaO to be added to 500 g/t-steel or less, it is possible to suppress the melting point of the scum X from increasing due to the high concentration of CaO, and to stably entrain the scum X.
In the range of 20 to 300 g / t-steel, 50 mass% Al ₂ O ₃ with a sufficiently low melting point in the range of normal molten steel total oxygen (T. [O] = 10 to 70 mass ppm) The composition can be modified to around -50% by mass CaO, and the scum X can be more stably involved.

A specific addition amount can be calculated by multiplying the above addition ratio by the casting amount corresponding to the width of the scum discharge area. For example, if the width of the scum discharge area is 30 mm on one side, the slab thickness is 2 mm, and the casting speed is 50 m/min, the casting amount per 30 mm width on one side is 23.4 kg/min. For a loading of 100 g/t-steel this is calculated to be 2.34 g per minute on the slab side.

When adding to the vicinity of the meniscus M in the width end region D (region A in FIG. 4) or the outer peripheral surface of the cooling roll 11 in the width end region D (region B in FIG. 4), two places per side, the slab In the full width, it is added at a total of four locations.
On the other hand, when it is added to the surface of the molten steel pool portion 16 in the width end region D (region C in FIG. 4), it is added at one point per side and two points in total across the entire width of the slab.
Considering the above-mentioned number of addition locations, the addition amount per location may be calculated.

According to the twin-roll continuous casting apparatus 10 and the method for manufacturing the thin cast strip 1 according to the present embodiment configured as described above, the width end region corresponding to the trim width T of the thin cast strip 1 Since the CaO-containing material is added so that CaO is supplied to the meniscus M, the scum X (mainly Al ₂ O ₃ ) near the meniscus M in the width end region reacts with CaO. to lower the melting point. As a result, the scum X can be preferentially caught in the portion of the trim width T (scum discharge region) of the thin cast slab 1, the accumulation of the scum is suppressed, and the scum X is caught in the portion other than the trim width T. can be prevented. Therefore, even if the casting time is long, it is possible to produce a healthy thin cast slab 1 with few cast slab defects.

Further, in the present embodiment, when CaO-containing material is added to the vicinity of the meniscus M in the width end region D (region A in FIG. 4), CaO can be efficiently supplied to the meniscus M, and thin casting It is possible to preferentially involve the scum X in the portion of the trim width T of the piece 1. - 特許庁

Furthermore, in the present embodiment, when the CaO-containing material is added to the outer peripheral surface of the chill roll 11 in the width edge region D (region B in FIG. 4), CaO is added to the width edge as the chill roll 11 rotates. The scum X is supplied to the meniscus M in the region of the thin cast slab 1, and the scum X can be preferentially caught in the region of the trim width T of the thin cast slab 1.

Further, when the CaO-containing material is added to the surface of the molten steel pool portion 16 in the width end region D (region C in FIG. 4), the flow of the surface of the molten steel pool portion 16 causes CaO to flow into the width end region. The scum X is supplied to the meniscus M of D, and the scum X can be preferentially caught in the portion of the trim width T of the thin cast slab 1 .

Further, in the present embodiment, when the CaO-containing powder is added, the CaO-containing material is added by a method using a screw feeder 30 or a method of spraying with an inert gas such as Ar or _N. can be added.
Alternatively, in the present embodiment, when the CaO-containing solid is pressed against the outer peripheral surface of the cooling roll 11 and added, a part of the CaO-containing solid is removed by friction with the cooling roll 11. CaO can be attached to the outer peripheral surface of the cooling roll 11 and can be supplied to the meniscus M of the width end region D as the cooling roll 11 rotates.

The method for producing thin cast slabs and the twin-roll continuous casting apparatus, which are the embodiments of the present invention, have been specifically described above. can be changed as appropriate within a range that does not deviate from
For example, in the present embodiment, as shown in FIG. 1, a twin-roll continuous casting apparatus provided with pinch rolls has been described as an example. may

The results of experiments conducted to confirm the effects of the present invention will be described below.

C: 0.06% by mass, Si: 1.6% by mass, Mn: 2.2% by mass, P: 0.01% by mass, S: 0.005% by mass, Al: 0.056% by mass A thin-walled cast piece made of carbon steel was produced using the twin-roll continuous casting apparatus shown in the above embodiment. The conditions common to the method for producing thin cast slabs are shown below.
Cooling roll diameter: 1200mm
Casting width: 800mm
Casting thickness: Average 2.0 mm
Casting speed: average 50 m/min (casting amount per minute is 624 kg, casting time of 10 tons is about 16 minutes)
Casting atmosphere: Ar+ _N2
Casting amount: 10 tons Arc angle of molten steel level: 40deg
Molten steel temperature in the molten steel pool: 1522 to 1542°C (Since the liquidus temperature of the molten steel is 1502°C, the degree of superheat is 20 to 40°C.)
Strip trim width: 30mm

Then, the CaO-containing material was added under the conditions shown in Table 1. In addition, in this example, simple CaO was added as the CaO-containing material. In addition, the "granular material" used the particle size under a sieve of 5 mm or less. The "rod" used had a rectangular cross section of 10 mm square and a length of 30 mm. A "plate" having a width of 15 mm, a thickness of 5 mm, and a length of 30 mm was used.

A thin cast slab was cast under the conditions described above, and the surface quality of the obtained thin cast slab was evaluated as follows.

(Maximum size of scum involved other than the trim part)
The parts used for the product other than the trim width of 30 mm at both ends were observed, and the maximum size of the scum involved was measured. Table 1 shows the evaluation results.

(Surface wrinkles of thin cast slab)
After pickling 1 m of the thin cast piece in the steady portion, the front and back surfaces were visually observed to measure the length of wrinkles generated per 1 m ² of the thin cast piece. Table 1 shows the evaluation results.

(Surface cracks in thin cast slabs)
After 1 m of the cast slab was pickled, the front and back surfaces were observed, and cracks with a length of 1 mm or more were investigated visually and using an 8x magnifying glass, and the number of cracks per 1 m ² was measured. Table 1 shows the evaluation results.

Comparative Example 21 is an example in which CaO was not added. Since there was no scum discharge promoting effect limited to the trim width, scum entrainment occurred over the entire width of the slab. Therefore, coarse scum exceeding 20 mm was caught in the part used for the product. In addition, the number of surface wrinkles was 350 mm/m ² and the number of surface cracks was 18/m ² .
Comparative Example 22 is an example in which CaO is added outside the range of the trim width to promote scum discharge. Since the scum was discharged and entangled in the part used for the product, not the part of the trim width, coarse scum exceeding 20 mm was entangled on the surface of the slab used for the product, the surface wrinkle was 300 mm / m ² , and the surface crack was 14 pieces/ ^m2 .

On the other hand, in Examples 1 to 12 of the present invention, since the stipulations of the present invention were satisfied, the scum entrainment position was concentrated in the trim width portion, and the scum entrainment in the portion used for the product was greatly reduced. . Therefore, the maximum scum size on the cast slab surface excluding the trim width portion was 20 mm or less, the length of the surface wrinkles was less than 200 mm/m ² , and the number of surface cracks was suppressed to 5/m ² or less.

From the above results, according to the present invention, by preferentially entangling scum in the trim width portion of the thin cast slab, the accumulation of scum is suppressed, and scum entrainment is prevented in portions other than the trim width portion, It was confirmed that it is possible to provide a thin cast strip manufacturing method and a twin roll type continuous casting apparatus capable of manufacturing sound thin cast strips with few defects.

1 thin cast piece 3 molten steel 5 solidified shell 11 cooling roll 16 molten steel pool (molten metal pool)

Claims (9)

Thin-walled casting 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 a thin cast slab. A method of manufacturing a piece, comprising:
adding a CaO-containing material to the meniscus of the width end region up to 30 mm from the edge of the molten metal pool corresponding to the trim width of the thin cast strip;
A method for producing a thin cast slab, characterized in that the scum located in the width end region is preferentially involved by lowering the melting point thereof . 2. The method of manufacturing a thin cast strip according to claim 1, wherein the CaO-containing material is added to the vicinity of the meniscus of the width end region. 3. The method for producing a thin cast strip according to claim 1, wherein the CaO-containing material is added to the surface of the molten metal pool located in the width end region. 4. The method for producing a thin cast strip according to any one of claims 1 to 3, wherein the CaO-containing material is added to the outer peripheral surface of the chill roll located in the width end region. 5. The method for producing a thin cast slab according to any one of claims 1 to 4, wherein the CaO-containing powder is added. 5. The method for producing a thin cast slab according to claim 4, wherein the CaO-containing solid matter is pressed onto the outer peripheral surface of the cooling roll and added. Twin rolls for producing thin cast slabs by supplying molten metal to a molten metal pool formed by a pair of rotating cooling rolls and a pair of side weirs, and forming and growing a solidified shell on the peripheral surface of the cooling rolls. A continuous casting apparatus comprising:
A twin roll type characterized by comprising a CaO addition mechanism for adding a CaO-containing material to a meniscus of a width end region up to 30 mm from an edge portion of the molten metal pool portion corresponding to the trim width of the thin cast strip. Continuous casting equipment. 8. The twin roll continuous casting apparatus according to claim 7, wherein the CaO addition mechanism is configured to add a CaO-containing material composed of powder particles. 9. The twin roll continuous casting apparatus according to claim 7, wherein the CaO addition mechanism is configured to press the CaO-containing solid matter against the outer peripheral surface of the chill roll.

Images