Twin-roll continuous casting method

Abstract

To provide a twin-roll continuous caster for producing a slab on which cracking is less likely to occur in edges during rolling, and a method of twin-roll continuous casting.SOLUTION: A twin-roll continuous caster 1 comprises a casting nozzle 14 that supplies molten metal into a molten-metal pool 13 formed by one pair of casting rolls 11 and one pair of side weirs 12. Brush rolls 21 for removing extraneous matter on surfaces of the casting rolls 11 are respectively provided to face the one pair of casting rolls 11a, 11b. The brush roll 21 consists of a center brush roll 21c that faces an axially central portion of the casting roll 11 and edge brush rolls 21e that face edges at both ends of the casting roll 11, in which the center brush roll 21c and the edge brush rolls 21e are provided with different drive mechanisms.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention , Double relates to a roll-type continuous casting method.

Background Art

[0002] The twin-roll type continuous casting method is a method of directly casting molten metal into a thin plate-like cast slab. In the twin-roll type continuous casting apparatus used in this casting method, molten metal (for example, molten metal such as molten steel) is supplied into a mold formed by a pair of rotating casting rolls (twin rolls) and a pair of side dams that abut against both end faces of the rolls, and a molten metal pool having a predetermined molten metal level is formed in the mold. The molten metal in this molten metal pool is cooled at the contact portion with the surface of the casting roll to form and grow a solidification shell, and the solidification shell is pressed and integrated at the roll gap formed at the closest portion of the pair of casting rolls, whereby a strip-shaped cast slab is cast. In this case, the solidification shell starts to solidify from the point where the molten metal contacts the casting roll, continues to grow, and becomes a solidification shell having a predetermined thickness at the roll kiss point, and this shell is pressed to form a cast slab having a constant thickness.

[0003] In the twin-roll type continuous casting method, when molten metal is poured into a mold formed by twin rolls and side dams, crystal nuclei are generated on the peripheral surface of the casting roll, and a part of them grows parallel to the temperature gradient in the molten metal. As a result, a columnar crystal structure is formed as the solidification structure.

[0004] In such a casting apparatus for performing twin-roll type continuous casting, metal oxides and the like adhere to the surface of the casting roll during operation. When this deposit touches the molten metal, non-uniform solidification of the cast slab occurs. Therefore, conventionally, in order to prevent this, for example, as disclosed in Patent Document 1, a brush roll for removing the deposit on the surface of the casting roll is provided.

[0005] Further, Patent Document 2 discloses a brush pushing method for extending the life of a brush roll by operating so that the pushing amount becomes constant according to the wear rate of one brush roll.

[0006] In addition, Patent Document 3 discloses a brush roll that can effectively remove deposits on a casting roll by implanting spiral brush pieces.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] A slab cast by twin-roll casting can obtain a columnar crystal structure with uniform orientation in the thickness direction over the entire surface, which may improve material properties. On the other hand, when the slab is rolled, the edge portion is likely to break when the entire thickness of the edge portion has a columnar crystal structure. Therefore, when the edge portion contacts the side guide during rolling, ear cracking may occur, leading to a decrease in yield.

[0009] However, all of the disclosures in Patent Documents 1 to 3 above are a single brush roll provided along the longitudinal direction of the casting roll, and are for uniformly removing deposits on the casting roll in the longitudinal direction. That is, it cannot change the solidification structure in the axial direction of the slab.

[0010] An object of the present invention is to provide a twin-roll continuous casting apparatus and a twin-roll continuous casting method for manufacturing a slab in which ear cracking of the edge portion is less likely to occur during rolling.

Means for Solving the Problems

[0011] To solve the above problems, the present invention provides a twin-roll continuous casting apparatus comprising a pair of casting rolls rotating in opposite directions, a pair of side dams slidably contacting both end faces of the casting rolls in the axial direction, and a casting nozzle for supplying molten metal into a molten metal pool formed by the pair of casting rolls and the pair of side dams, and casting a strip-shaped slab from the molten metal in the molten metal pool. A twin-roll continuous casting method using Brush rolls for removing deposits on the surfaces of the casting rolls are respectively provided opposite to the pair of casting rolls. The brush rolls include a central brush roll facing the central portion in the axial direction of the casting roll and edge brush rolls facing the edge portions at both ends of the casting roll. The central brush roll and the edge brush rolls are provided with different drive mechanisms. , After the casting roll starts operating, the brush roll at the edge part delays the contact start time with the casting roll. The time T from when the casting roll starts operating until the brush roll at the edge part starts contacting the casting roll satisfies T 50 ≦ T < T 100 and is characterized by this. Further, from another aspect, the present invention is a twin-roll continuous casting method using a twin-roll continuous casting apparatus including a pair of casting rolls rotating in opposite directions, a pair of side dams slidingly contacting both end faces in the axial direction of the casting rolls, and a casting nozzle for supplying molten metal into a molten metal pool formed by the pair of casting rolls and the pair of side dams. A brush roll for removing deposits on the surface of the casting roll is provided opposite to each of the pair of casting rolls. The brush roll includes a central brush roll facing the central part in the axial direction of the casting roll and an edge brush roll facing the edge parts at both ends of the casting roll. The central brush roll and the edge brush roll are provided with different drive mechanisms, and the central brush roll and the edge brush roll have an overlapping part in the axial direction. After the casting roll starts operating, the edge brush roll delays the contact start time with the casting roll. The time T from when the casting roll starts operating until the edge brush roll starts contacting the casting roll satisfies T 50 ≦ T < T 100 and is characterized by this. However, T 50 = (50 × d × R × π) / (100 × A × z × V) T 100 = (100 × d × R × π) / (100 × A × z × V) A: Coefficient d: Solidification shell thickness (mm) R: Diameter of the casting roll (mm) z: Mn concentration in molten steel (mass%) V: Casting speed (mm / s)

[0015] The coefficient may be A = 0.012.

Advantages of the Invention

[0016] According to the present invention, by providing a brush roll divided into an axial center portion and an edge portion facing the casting roll, the deposits on the center portion and the edge portion of the casting roll can be adjusted, an equiaxed crystal structure can be formed in the edge portion, and ear cracking can be prevented.

Brief Description of the Drawings

[0017] [Figure 1] It is a perspective view schematically showing an example of the configuration of a twin-roll continuous casting apparatus. [Figure 2] It is a plan view seen from the molten metal pool surface side of the twin-roll continuous casting apparatus of FIG. 1. [Figure 3] It is a front view of the twin-roll continuous casting apparatus of FIG. 1. [Figure 4] It is a side view showing an example of the arrangement of the brush roll according to an embodiment of the present invention. [Figure 5] It is a front view of FIG. 4. [Figure 6] It is a diagram for explaining the difference in the solidification structure of the cast slab, where (a) is a front view of the casting roll and the cast slab, (b) is an enlarged cross-sectional view of the gap portion of (a) when no oxide adheres to the casting roll, and (c) is an enlarged cross-sectional view of the gap portion of (a) when an oxide adheres to the casting roll. [Figure 7] It is a graph showing the relationship between the number of immersion times and the Mn deposit thickness in the mold immersion experiment for each amount of Mn. [Figure 8] It is a graph showing the relationship between the Mn deposit thickness and the decrease value of the shell thickness in the mold immersion experiment.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0019] First, with reference to FIGS. 1 to 3, the configuration of a general twin-roll continuous casting apparatus will be described. FIG. 1 is a perspective view schematically showing an example of the configuration of the twin-roll continuous casting apparatus. FIG. 2 is a schematic plan view seen from the molten metal pool surface side showing the configuration of the twin-roll continuous casting apparatus of FIG. 1, and FIG. 3 is a schematic front view showing the configuration of the twin-roll continuous casting apparatus of FIG. 1.

[0020] As shown in FIGS. 1 to 3, the twin-roll continuous casting apparatus 1 mainly includes a pair of casting rolls 11 (11a, 11b), a pair of side dams 12 (12a, 12b), and a casting nozzle 14. A strip-shaped slab (metal strip) St is cast from the molten metal in the molten metal pool 13 formed by the pair of casting rolls 11 and the pair of side dams 12.

[0021] The pair of casting rolls 11a and 11b rotate in opposite directions (such that each of the casting rolls 11a and 11b faces the molten metal pool 13). The twin-roll continuous casting apparatus 1 continuously casts the molten metal supplied from a ladle or tundish or the like and injected into the molten metal pool 13 from the casting nozzle 14. In the twin-roll continuous casting apparatus 1, the molten metal is injected between the pair of rotating casting rolls 11, and a solidification shell is formed on the surface of each of the casting rolls 11a and 11b due to heat extraction from the surface of each casting roll 11a and 11b. The two solidification shells are pressed together at the point where the distance in the gap (roll gap) G between the pair of casting rolls 11a and 11b is the smallest, forming a single strip-shaped slab St.

[0022] The casting roll 11 is required to have little thermal deformation due to heating caused by contact with the molten metal, not to undergo fatigue fracture due to repeated heating and cooling, and to have stable thermal conditions for solidifying the molten metal. To satisfy these conditions, the casting roll 11 preferably has, for example, a three-layer structure of stainless steel - copper alloy - nickel plating and a cooling water channel is provided inside.

[0023] In addition, since the casting nozzle 14 comes into contact with the molten metal, it is preferably made of a refractory material having sufficient strength, heat resistance, etc. to withstand use. As the material of this refractory, a refractory made of a single component such as CaO·ZrO2, Al2O3, MgO, CaO, SiO2, ZrO2, SiC, C (graphite), BN, etc. may be used, or a refractory made of a composite component of the above components may also be used.

[0024] As described above, the slab St cast by such a twin-roll continuous casting apparatus 1 has a columnar crystal structure with uniform orientation in the thickness direction over the entire surface, which may improve the material properties. On the other hand, when the edge portion of the slab St comes into contact with the side guide during rolling, ear cracking may occur. Since ear cracking occurs at the grain boundaries of the columnar crystal structure, in order to prevent ear cracking, it is necessary to make the edge portion have an equiaxed crystal structure at least in the thickness direction by more than half. In order to generate an equiaxed crystal structure only in the edge portion, it is considered that the heat transfer in the edge portion may be suppressed.

[0025] In twin-roll casting, an oxide mainly composed of Mn is formed on the surface of the casting roll 11. It is known that when casting is performed without removing the oxide, heat transfer is suppressed and the slab thickness of the slab St becomes smaller. Therefore, conventionally, a brush roll for removing the oxide formed on the casting roll 11 is provided facing the casting roll 11. In the present embodiment, the brush roll is divided into three at the central portion in the axial direction and the edge portions at both ends of the casting roll 11. And, by delaying the rotation start time of the brush roll at the edge portion with respect to the brush roll at the central portion, a method of depositing an oxide on the edge portion of the casting roll 11 to create an equiaxed crystal structure was devised.

[0026] Hereinafter, an example of the arrangement of the brush roll according to the embodiment of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a side view showing an example of the arrangement of the brush roll 21 with respect to the casting roll 11, and FIG. 5 is a front view.

[0027] As shown in FIGS. 4 and 5, the brush roll 21 is divided into a central brush roll 21c facing the central portion in the axial direction of the casting roll 11 and edge brush rolls 21e facing the edge portions at both ends, and three of each are installed facing the respective casting rolls 11a and 11b. It is preferable that the three brush rolls 21e, 21c, and 21e are installed so that a part overlaps in the axial direction of the casting roll 11 as shown in FIG. 4. Therefore, as shown in FIG. 5, they are arranged with the height positions seen from the front shifted. The central brush roll 21c and the edge brush roll 21e are provided with different drive mechanisms. In the present invention, the edge portion means within 100 mm from both axial ends of the casting roll 11, and may be about several tens of mm.

[0028] The brush roll 21 applied to the present invention may be a conventionally used one as described in the above patent documents, for example. Also, the central brush roll 21c and the edge brush roll 21e may have the same material and diameter. Also, the arrangement of the brush rolls 21c and 21e may be interchanged at the position in the front direction shown in FIG. 5. In the present embodiment, the central brush roll 21c always rotates during the operation of the twin-roll continuous casting apparatus 1 to remove the oxide formed on the casting roll 11, and the edge brush roll 21e delays the rotation start time, that is, the contact start time with the casting roll 11, by a timer.

[0029] FIG. 6 is a diagram for explaining the difference in the solidification structure of the cast slab St to be cast between the case where no oxide adheres to the casting roll 11 and the case where an oxide adheres. FIGS. 6(b) and (c) are cross-sectional views showing an enlarged view of the gap G between the pair of casting rolls 11a and 11b shown in FIG. 6(a), where (b) shows the case where no oxide adheres, and (c) shows the case where an oxide adheres. As shown in FIG. 6(b), when no oxide adheres to the casting rolls 11a and 11b, a columnar crystal structure is formed as the solidification structure over the entire thickness. On the other hand, as shown in FIG. 6(c), when the oxide 31 adheres to the surfaces of the casting rolls 11a and 11b, the heat extraction from the mold is suppressed, and an equiaxed crystal structure is formed. The present invention forms an equiaxed crystal structure by delaying the rotation start time of the brush roll 21e at the edge portion so that the oxide 31 adheres to the edge portion of the casting roll 11 as shown in FIG. 6(c).

[0030] Next, a method for obtaining the rotation start delay time of the brush roll 21e at the edge portion will be described.

[0031] The present inventors have found that the amount of the oxide (adhesion product) mainly composed of Mn adhering to the surface of the casting roll 11 can be calculated by the following formula (1) from the amount of Mn in the molten steel and the rotation speed of the casting roll. y = a × z × x ···(1) However,[[]] y: Thickness of the oxide (adhesion product) mainly composed of Mn on the surface of the casting roll (μm) a: Coefficient z: Mn concentration in the molten steel (mass%) x: Rotation speed of the casting roll (revolutions)

[0032] Also, it has been found that the reduction thickness of the solidification shell is proportional to the thickness of the adhesion product on the surface of the casting roll as shown in the following formula (2). D = b × y ···(2) However,[[]] b: Coefficient D: Reduction thickness of the solidification shell (mm)

[0033] Also, the equiaxed crystal ratio is defined by the following formula (3). E = D / d × 100 ···(3) However, E: Equiaxed crystal ratio (%) d: Slab thickness (mm)

[0034] When expressing D in Equation (3) by Equation (2) and y in Equation (2) by Equation (1), and representing the coefficient a × b = A, the following Equation (4) can be obtained. E = A × z × x / d × 100 ···(4)

[0035] On the other hand, the time T (s) at the x-th rotation of the casting roll can be expressed by the following Equation (5) using the casting speed and the diameter of the casting roll. T = R × π × x / V ···(5) However, R: Diameter of the casting roll (mm) V: Casting speed (mm / s)

[0036] Transform Equation (5) into x = (T × V) / (R × π) and substitute it into Equation (4), then Equation (6) can be obtained. E = (100 × A × z) × T × V / (d × R × π) ···(6)

[0037] When transforming Equation (6), T = (E × d × R × π) / (100 × A × z × V) and thus, for example, the time T 50 (s) required to make the equiaxed crystal ratio at the edge part 50%, and the time T 100 (s) required to make the equiaxed crystal ratio 100% can be obtained by the following Equation (7) and Equation (8) with 50% and 100% substituted into E respectively. T 50 = (50 × d × R × π) / (100 × A × z × V) ···(7) T 100 = (100 × d × R × π) / (100 × A × z × V) ···(8)

[0038] Experimentally, it is known that when the equiaxed crystal ratio of the edge portion of the slab St is 50% or more, ear cracking is rapidly reduced. On the other hand, according to the definition, an equiaxed crystal ratio of 100% means that the reduced thickness of the solidification shell is equal to the slab thickness. Since the equiaxed crystal zone is at a high temperature, when the equiaxed crystal ratio is 100%, the slab cannot withstand its own weight and cracks occur in the edge portion. The cracks in this edge portion progress, and the casting stops due to the slab breaking. Therefore, in order to suppress ear cracking, it is considered that the rotation start time of the brush roll in the edge portion should be adjusted so that the equiaxed crystal ratio of the edge portion is 50% or more and less than 100%. That is, the timer of the brush roll 21e in the edge portion is set so that the time T is T obtained by the formulas (7) and (8). 50 Above, T 100 During less than, that is, by setting the rotation start time to be delayed so as to satisfy the following formula (9), ear cracking can be prevented. T 50 ≦T<T 100 ···(9)

[0039] In addition, the specific numerical values of the coefficient a obtained from the relationship between the Mn deposit thickness in the above formula (1), the Mn concentration in the molten steel, and the rotation speed of the roll, and the coefficient b obtained from the relationship between the reduced thickness of the shell thickness and the Mn deposit thickness in the formula (2) can be determined, for example, by the following mold dipping experiment simulating the twin-roll process.

[0040] Using a 200 kg atmospheric melting furnace, steels with 0.05% C - 0.6% Si - 1%, 3%, 5% Mn - 0.01% P - 0.0015% S were melted, and a copper mold with dimensions of 150 mm × 80 mm × 20 mm t was immersed for 1 second. The surface of the mold was nickel-plated to simulate the roll surface of a twin-roll and roughened by shot. Before the experiment, the mold was pickled with dilute hydrochloric acid, and this mold was repeatedly immersed in the melting furnace, and the solidified shell was removed each time. For each mold after immersion, after allowing the mold to cool to room temperature, the surface of the mold was quickly wiped with gauze containing dilute hydrochloric acid, and this gauze was subjected to warm extraction and ICP analysis to determine the amount of Mn deposits adhering to the mold surface, which was converted from density to thickness to obtain the Mn deposit thickness y (μm). The relationship between the number of immersions and the Mn deposit thickness y obtained from this experiment is shown in Fig. 7. Note that the number of immersions is synonymous with the rotation speed x of the brush roll 21 of the twin-roll continuous casting apparatus 1.

[0041] Also, for the 5% Mn steel, a total of 6 immersions were performed to investigate the relationship between the Mn deposit thickness y and the reduction thickness D of the solidified shell. The solidified shell thickness was measured with a micrometer at a pitch of 5 mm in the range of ±30 mm width centered at the origin of the width of the solidified shell to obtain the thickness of one-sided shell. Note that in the immersion experiment, since it was for one-sided shell, twice the obtained experimental value was taken as the shell thickness. The difference in the shell thickness of the first immersion was taken as the reduction value of the shell thickness. The relationship between the Mn deposit thickness y and the reduction thickness D of the shell thickness obtained from this experiment is shown in Fig. 8.

[0042] As shown in Fig. 7, the Mn deposit thickness y (μm) was linearly proportional to the Mn concentration (%) in the molten steel and the number of immersions (rotation speed x of the roll). From this slope, the coefficient a in Equation (1) was set to 0.03, and Equation (1) could be changed to Equation (1’). y = 0.03×z×x ···(1’)

[0043] Also, as shown in Fig. 8, the relationship between the Mn deposit thickness (μm) and the reduction thickness D (mm) of the shell thickness was linearly proportional with a slope of 0.4. Therefore, the coefficient b in Equation (2) was set to 0.4, and Equation (2) could be changed to Equation (2’). D = 0.4×y ···(2’)

[0044] As described above, the coefficients a and b can be determined through experiments. Alternatively, the coefficient b may be determined by simulations such as heat transfer calculations. If the coefficients are set as a = 0.03 and b = 0.4 respectively, then A = 0.012, and T 50 (s), T 100 (s) are obtained from equations (7’) and (8’). T 50 =(50×d×R×π) / (1.2×z×V) ···(7’) T 100 =(100×d×R×π) / (1.2×z×V) ···(8’)

[0045] As described above, the preferred embodiments of the present invention have been explained, but the present invention is not limited to such examples. It is obvious that those skilled in the art can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims, and it is naturally understood that they also belong to the technical scope of the present invention.

Example

[0046] Using a twin-roll continuous casting apparatus 1 having a pair of casting rolls 11a and 11b with a width of 600 mm and a diameter of 600 mm, casting of 5 tons of 0.05%C - 0.6%Si - 5%Mn - 0.010%P - 0.0015%S - 0.03%Al steel was carried out. A brush roll 21c with a width of 500 mm and a diameter of 80 mm was arranged to face the central part in the axial direction of the casting roll 11, and a brush roll 21e with a width of 60 mm and a diameter of 80 mm was arranged to face both edge parts of the casting roll 11. The rotational speed of the brush roll 21 was set to 1000 rpm, and casting was carried out with a casting speed of 70 m / min and a cast slab thickness of 1.4 mm. The cast slab was sampled from the end stage of casting. The solidification structure was observed, and the equiaxed crystal ratio in the range of ±20 mm from the center of the width was defined as the equiaxed crystal ratio at the center of the width, and the equiaxed crystal ratio in the range of 50 mm from the edge was defined as the equiaxed crystal ratio at the edge part.

[0047] The method for measuring the equiaxed crystal ratio is as follows. The cast slab was cut, the cross-section was embedded and polished, and picric acid etching was performed. Then, the columnar crystal thickness was measured using an optical microscope, and the equiaxed crystal thickness was obtained by subtracting the columnar crystal thickness from the cast slab thickness. Furthermore, the ratio of equiaxed crystals was obtained by dividing the equiaxed crystal thickness by the cast slab thickness and multiplying by 100. This operation was performed for each sample at a pitch of 10 mm, and the values were obtained and averaged to determine the equiaxed crystal ratio.

[0048] The brush roll 21c at the center was brought into contact with the casting roll 11 and rotated simultaneously with the casting roll 11 to start casting. Casting was performed with the start of contact of the brush roll 21e at the edge portion with the casting roll 11 delayed by a time T from the start of casting, and the equiaxed crystal ratio and the presence or absence of ear cracking in the range of 50 mm from the edge were evaluated. The results are shown in Table 1. Here, T calculated by Expression (7’) and Expression (8’) with coefficients a = 0.03 and b = 0.4 50 and T 100 are 18.8 s and 37.7 s, respectively. As shown in Table 1, when the time T for delaying the start of rotation of the brush roll 21e at the edge portion is set to 50 ≦T<T 100 the equiaxed crystal ratio at the edge portion becomes 50% or more, and ear cracking can be prevented. On the other hand, if the delay time is too short, the equiaxed crystal ratio at the edge portion cannot be increased sufficiently, and ear cracking occurs. Also, if the delay time is too long, the cast slab breaks, and casting stops midway, and no cast slab can be obtained.

[0049]

Table 1

Industrial Applicability

[0050] The present invention is useful for strip casting technology for directly casting a molten metal into a thin plate-shaped cast slab (strip).

Explanation of Signs

[0051] 1 Twin-roll type continuous casting apparatus 11, 11a, 11b Casting rolls 12, 12a, 12b Side weir 13 Molten metal pool 14 Casting nozzle 21, 21c, 21e Brush roll St Slab

Claims

1. A twin-roll continuous casting method using a twin-roll continuous casting apparatus comprising a pair of casting rolls rotating in opposite directions, a pair of side dams slidably contacting both end faces in the axial direction of the casting rolls, and a casting nozzle for supplying molten metal into a molten metal pool formed by the pair of casting rolls and the pair of side dams, and casting a strip-shaped slab from the molten metal in the molten metal pool, Brush rolls for removing deposits on the surfaces of the casting rolls are provided opposite to the pair of casting rolls respectively, The brush rolls consist of a central brush roll facing the central portion in the axial direction of the casting roll and an edge brush roll facing the edge portions at both ends of the casting roll, and the central brush roll and the edge brush roll are provided with different drive mechanisms, The edge brush roll delays the start time of contact with the casting roll after the casting roll starts operating, The time T from when the casting roll starts operating until the edge brush roll starts contacting the casting roll is T 50 ≦ T < T 100 A twin-roll continuous casting method, characterized by satisfying the above. However, T 50 = (50 × d × R × π) / (100 × A × z × V) T 100 = (100 × d × R × π) / (100 × A × z × V) A: Coefficient d: Solidification shell thickness (mm) R: Diameter of the casting roll (mm) z: Mn concentration in molten steel (mass%) V: Casting speed (mm / s)

2. A twin-roll continuous casting method using a twin-roll continuous casting apparatus comprising a pair of casting rolls rotating in opposite directions, a pair of side dams slidably contacting both end faces of the casting rolls in the axial direction, and a casting nozzle for supplying molten metal into a molten metal pool formed by the pair of casting rolls and the pair of side dams, and casting a strip-shaped slab from the molten metal in the molten metal pool, brush rolls for removing deposits on the surfaces of the casting rolls are respectively provided opposite to the pair of casting rolls, the brush rolls consist of a central brush roll facing the central part in the axial direction of the casting roll and edge brush rolls facing the edge parts at both ends of the casting roll, and the central brush roll and the edge brush roll are provided with different drive mechanisms, the central brush roll and the edge brush roll have an overlapping part in the axial direction, the edge brush roll delays the start time of contact with the casting roll after the casting roll starts operating, the time T from when the casting roll starts operating until the edge brush roll starts contacting the casting roll is T 50 ≦ T < T 100 characterized by satisfying the above, a twin-roll continuous casting method. However, T 50 = (50 × d × R × π) / (100 × A × z × V) T 100 = (100 × d × R × π) / (100 × A × z × V) A: coefficient d: solidification shell thickness (mm) R: diameter of the casting roll (mm) z: Mn concentration in molten steel (mass%) V: casting speed (mm / s)

3. The twin-roll continuous casting method according to claim 1 or 2, characterized in that the coefficient is A = 0.012.

Images