JPH09141399A - Method for continuously casting thin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thin cast slab of carbon steel preventing the development of crack and having excellent surface characteristic by controlling an average heat flux within a specific inequility and casting the cast slab by twin roll type continuous casting apparatus. SOLUTION: The thin cast slab is continuously cast by the twin roll type continuous caster apparatus from molten carbon steel satisfying by weight, C<0.06% or from molten carbon steel satisfying 0.06%<=C<0.08% C and C%+0.02% Mn<0.08. In this case, an average heat flux (q) of the casting rolls is controlled within the inequility (q(kcal/m<2> /hr)<=(1300-180D)×10<4> ) and the casting is executed. In the inequility, D is the thickness of the cast slab (mm). The casting roll provided with the recessed and the grooves having 20-25μm depth on the surface is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin-drum type thin plate continuous casting method for casting thin plate cast pieces.

[0002]

2. Description of the Related Art FIG. 1 is an explanatory view of a twin-drum type continuous casting machine. Place the two horizontal casting drums 2, 2'at the same height,
They are arranged in parallel and close to each other, and each of them is indicated by an arrow 6, 6 '.
Rotate in the direction. Side weirs 3 and 3'are installed in close contact with the side surfaces of the casting drums 2 and 2'in the axial direction. The casting drums 2 and 2'are of the internal water cooling type.

Molten steel 1 is applied to drums 2 and 2'and side weirs 3,
It is continuously poured into the upper space (melt pool) formed by 3 '. The molten steel 1 injected is a casting drum 2, 2 '
On the surface of the solidified shell 4 and 4'from the start of contact 2 with the molten steel on the surface of 2 and 2 '. The solidified shells 4, 4'are integrated in the smallest gap 7 of the drum,
The thin cast piece 5 is taken out.

According to this twin-drum type continuous casting machine, a thin plate slab having a plate thickness of 5 mm or less and a plate width of 1000 mm or more is produced.
It can be used as a thin plate as it is without performing a complicated post-process, or by performing a light rolling in the post-process.

The biggest problem at this time is slab surface cracking. The cracking occurs because the shrinkage strain due to the temperature decrease of the solidified shell concentrates in the solidification delay portion. As a preventive measure, [1]
Slows the cooling of the solidified shell and reduces the shrinkage rate,
[2] There is an idea that a concave portion or groove is provided on the mold surface to restrain the solidified shell in a short range to shorten the shrinkage range of the solidified shell to avoid local concentration of shrinkage strain.

Regarding [1], the process of slow cooling is calculated from the change of the water temperature of the water used for cooling the water inside the casting drum, that is, (water temperature at the drum outlet)-(water temperature at the drum outlet). Can be represented by the average heat flux of
The degree of gentle cooling required to prevent cracking, that is, the upper limit of the average heat flux differs depending on the steel type.

In Japanese Patent Laid-Open No. 6-210407, Cr is used.
-Specifies the upper limit of the average heat flux of the casting drum when casting Ni-based stainless steel in the synchronous continuous casting process. However, there is no technology that specifies the average heat flux for carbon steel.

As for [2], JP-A-62-2 is used.
Japanese Patent No. 54953 and Japanese Patent Laid-Open No. 2-295648 are known. In Japanese Patent Laid-Open No. 62-254953, unevenness having a depth of 10 to 200 μm is provided on the surface of the casting drum. Further, Japanese Patent Laid-Open No. 2-295648 discloses
On the surface of the casting drum, a circle with a diameter of 0.4 to 1.2 mm or an ellipse with a depth of 5 to 100 μm and an adjacent distance of 1.2 to
Dimples of 3.0 mm are provided. In each case,
As a result of using a casting drum with a large number of recesses or grooves on the surface, the solidified shell formed on the surface of the drum can be restrained in a short range by the recesses or grooves, and concentrating shrinkage strain can be avoided locally. It is said that cracks, dents and creases can be reduced.

However, since these do not specify the average heat flux of the casting drum, for example, depending on the structure of the casting drum, the average heat flux becomes excessively large, and therefore cracking is prevented when the shrinkage rate of the solidified shell becomes excessively large. It is not possible.

[0010]

Therefore, the present invention is directed to a twin-drum continuous casting method capable of producing a thin plate cast having excellent surface properties without cracking by defining the average heat flux of the casting drum. The challenge is to provide.

[0011]

The gist of the thin plate continuous casting method of the present invention for solving the above problems is as follows. (1) From molten steel of carbon steel with (wt% C) <0.06, or with C and Mn contents of 0.06 ≦ (wt% C) <0.08 and (wt% C) ) +0.02
When a thin plate is continuously cast from a molten carbon steel satisfying (wt% Mn) <0.08 by a twin-drum type continuous casting machine,
It is characterized in that the average heat flux (q) of the casting drum is controlled in the following range for casting. q (kcal / m ² / hr) ≦ (1400-180.
D) × 10 ⁴ [where D is the slab thickness (mm)] (2) In the above item (1), the depth is 20 to 25 on the surface.
A casting drum provided with recesses or grooves of 0 μm is used. (3) In the above item (1) or (2), a casting drum whose surface is made of a Ni or Ni alloy plating layer having a thickness of 0.2 mm or more is used. (4) In the above item (3), the depth (d) of the recess or groove provided on the drum surface is set within the following range. d (μm) ≧ 80−30 · t [where t: Ni or Ni alloy plating layer thickness (mm) on drum surface] (5) C and Mn contents are 0.06 ≦ (wt% C)
<0.08, and (wt% C) + 0.02 (wt% M
n) from molten steel of carbon steel satisfying ≧ 0.08, or
When the thin plate is continuously cast from the molten steel of carbon steel with (wt% C) ≧ 0.08 by the twin-drum type continuous casting machine, the average heat flux (q) of the casting drum is controlled within the following range. It is characterized by doing. q (kcal / m ² / hr) ≦ (1300-180.
D) × 10 ⁴ [where D is the slab thickness (mm)] (6) In the above item (5), the depth is 20 to 25 on the surface.
A casting drum provided with recesses or grooves of 0 μm is used. (7) In the above item (5) or (6), a casting drum whose surface is made of a plating layer of Ni or Ni alloy having a thickness of 0.2 mm or more is used. (8) In the above item (7), the depth (d) of the recess or groove provided on the drum surface is set within the following range. d (μm) ≧ 100−30 · t [where t: Ni or Ni alloy plating thickness (mm) on the drum surface]

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In order to reduce the localized amount of shrinkage strain caused by the temperature decrease of the solidified shell, which is the cause of cracking, the present invention is directed to the component system, the average heat flux of the casting drum, the concave portion of the casting drum surface, It defines the depth of the groove and the thickness of the Ni or Ni alloy plating layer on the surface of the casting drum.

First, the requirements concerning the component system will be described. According to the experimental results of the inventors, the crack generation amount of carbon steel is greatly influenced by the C and Mn contents. That is,
When carbon steels of various component systems are continuously cast by a twin-drum type continuous casting machine under the same conditions, it is possible to classify into a component system with a large amount of crack generation and a component system with a small amount of crack generation. Its component system is
(Wt% C) and (wt% C) + 0.02 (wt% Mn) can be used for classification. Therefore, in the present invention, (wt% C) <0.06, or the content of C and Mn is 0.06 ≦ (wt% C) <0.08 and (wt% C) +0.02 (wt% Mn) <0.08 component system and 0.06 ≦ (wt% C) <0.08 and (wt% C) +0.02 (wt% Mn) ≧ 0.08, or (wt% C) ≧ 0 It was classified into a component system of 0.08.

Next, the requirements for the average heat flux of the casting drum will be described. As described above, gentle cooling is effective for reducing cracks, and specifically, it can be specified by the upper limit of the average heat flux of the casting drum. The more susceptible a steel type is to crack, that is, the more cracked steel can be cast under the same conditions, the more the average heat flux must be reduced to reduce the cracking rate below a certain level. It has been found from the experiments by the inventors of the present invention that it depends not only on the steel type or composition, but also on the thickness of the slab to be manufactured. This is because the solidified shell itself generated on the surface of the casting drum serves as heat transfer resistance between the molten steel and the drum, and as the solidified shell becomes thicker, the average heat flux naturally decreases. In the present invention, the upper limit of the average heat flux that can achieve a crack generation rate of 5 cm / m ² or less is adopted.

The requirements for forming a recess or groove on the surface of the casting drum will be described. According to our experiments,
In order to achieve a crack generation rate of 1 cm / m ² or less, in addition to setting the average heat flow to the upper limit value or less described above, it is necessary to provide recesses or grooves with a depth of 20 μm or more on the drum surface. Therefore, the lower limit is set to 20 μm. Incidentally, JP-A-62-254953 and JP-A-2-2956
Providing grooves or irregularities on the surface of the casting drum as shown in No. 48 is effective in reducing cracking, but the cracking rate of 1 cm / m ² or less cannot be achieved only by satisfying the respective conditions. However, if the depth exceeds 250 μm, the convex grains transferred to the surface of the slab remain even on the product plate after 80% rolling, resulting in uneven gloss, so the upper limit of the depth of the recess or groove provided on the drum surface is set. It was set to 250 μm. The shape other than the depth, the arrangement pattern, and the processing method for forming are not particularly specified, but generally the diameter is 0.2 to 3.0 m.
It is effective to construct and use circular or elliptical dimples having an interval m of 0 to 3.0 mm. As for the groove, the cross-sectional shape is a short shape or a curved shape such as a circular arc, the width is 0.2 to 3.0 mm, and the adjacent interval is 0.5 to
It is effective to dispose it as 5.0 mm in parallel or perpendicular to the roll axis direction and at an angle with a certain angle. Moreover, not only the grooves are formed parallel to each other in one direction, but the grooves formed in a plurality of directions such as a lattice may be arranged to intersect each other.

The thickness requirements for applying a Ni or Ni alloy plating layer on the surface of the casting drum will be described. Each time the casting drum surface makes one revolution, it contacts the molten steel and the solidified shell in the pool and is heated to 500 ° C or higher, and after the cast slab is sent out from the minimum gap of the drum, it is allowed to cool in the atmosphere. The surface undergoes severe heat history, causing severe deterioration such as cracked surfaces. Therefore, for the purpose of extending the life, Ni
Alternatively, Ni alloy plating may be applied. The composition of the plating is not specified, but it is generally pure N
i or Ni-several% Co alloy is used. In this case, 0.
If the thickness of the plating layer is less than 2 mm, the plating layer will be separated from the surface of the casting drum due to the severe heat history during casting. Therefore, the lower limit of the plating layer thickness is set to 0.2 mm.

Finally, when the Ni or Ni alloy plating layer is provided on the drum surface and the recess or groove is provided, the requirements for the depth of the recess or groove will be described. By providing the recess or groove in the Ni or Ni alloy plating layer formed on the surface of the casting drum, the stability of the shape of the recess or groove is increased, and as a result, the certainty of restraining the solidified shell is increased and the local concentration of shrinkage strain can be prevented. Therefore, further reduction of cracks can be achieved. The lower limit of the depth of the recess or groove that is less than or equal to a certain amount of crack generation is expressed by the relationship with the thickness of the Ni or Ni alloy plating layer. Therefore, the lower limit of the depth of the recess or groove that achieves the amount of crack generation 0 is adopted.

[0018]

EXAMPLES Two examples of the present invention will be described with reference to Tables 1 and 2.

(Example 1) First, (wt% C) <0.0
6 from the molten steel of carbon steel or the content of C and Mn is 0.06 ≦ (wt% C) <0.08 and (wt%
C) +0.02 (wt% Mn) <0.08 will be described in the case of continuously casting a thin plate from a molten carbon steel by a twin-drum casting machine. Table 1 shows the investigation results of the components, the main casting conditions, and the crack generation amount. As for the specifications of the casting machine used, the casting drum had a diameter of 1200 mm and a width of 80.
0 mm, internal water-cooled Cu drum. In the case of providing the concave portion on the drum surface, in the first embodiment, the diameter is 0.5 to
Use circular dimples with a size of 1.5 mm to reduce the distance between adjacent
˜3.0 mm, and they were randomly arranged. Except for sample 1, pure Ni plating was applied to the drum surface. To control the injection temperature of the molten steel, the degree of superheat of the molten steel in the tundish was kept constant at 100 ° C. The height of the molten steel surface in the pool is constant at an arc angle of 0.5 rad, and the drum rotation speed is changed to
Slabs of various thickness were cast. Ar, N ₂ and He were used alone or as a mixture as the atmosphere gas in the pool. This atmospheric gas becomes trapped between the concave portion on the drum surface and the solidified shell and becomes a heat transfer resistance. Therefore, the atmosphere gas prevents the molten steel from oxidizing in the pool, and
It was also used for changing the heat flux by changing the gas composition. The amount of cracking was measured by visually observing the entire width × 2 m length with a pickled plate and observing with a 10 times magnifying glass.

The average heat flux of the casting drum is calculated from the temperature change of the water used for cooling the water inside the drum. That is, it is calculated by the following formula. q = (ρCVΔT) / S (1) S = Rθw (2) q: Average heat flux of casting drum (kcal / m ² / h)
r) ρ: density of cooling water 1000 (g / l) C: specific heat of cooling water 1 (cal / g / k) V: amount of cooling water per one side drum 5000 (l / m)
in) ΔT: (water temperature at drum outlet)-(water temperature at drum inlet) (K) S: contact area between molten steel or solidified shell and drum
(M ² ) R: radius of casting drum 0.6 (m) θ: arc angle of molten metal in molten metal pool 0.5 (rad) W: width of casting drum 0.8 (m) Samples 1 to 3 and samples 10, 11, 16-18, 22,
It is an example of (wt% C) <0.06. Samples 1-3
Is because the average heat flux q of the casting drum exceeds the upper limit value (qcr in Table 1) represented by the functional expression of the slab thickness D,
The amount of crack generation exceeds 5 cm / m ² . In Sample 1, since the surface of the casting drum was not plated with Ni, many cracks were generated on the surface of the drum during casting.

Samples 4 to 9 had 0.06 ≦ (wt% C) <
It is 0.08. Samples 4 to 6 are (wt% C) +0.0
Since 2 (wt% Mn) is 0.08 or more,
In Samples 7 to 9, the average heat flux q exceeds the upper limit value qcr, so that the crack generation amount exceeds 5 cm / m ^{2. In} Samples 10 to 27, (wt% C) <0.06, or
0.06 ≤ (wt% C) <0.08 and (wt% C) +
0.02 (wt% Mn) <0.08, and the average heat flux q is the upper limit value qcr or less represented by the functional formula of the cast piece thickness D, so that the crack generation amount is suppressed to 5 cm / m ² or less. is made of.

However, in Samples 10 to 13, since the dimple depth d on the surface of the casting drum is shallower than 20 μm, the crack generation amount cannot be reduced to 1 cm / m ² or less.

In Samples 14 and 15, the dimple depth d on the surface of the casting drum exceeded 250 μm, so cracking could be prevented, but uneven luster occurred in the sheet product produced by rolling a thin sheet slab 80%. It was

In Samples 16 to 21, the dimple depth d on the surface of the casting drum is 20 μm or more, but the N on the surface of the drum is N.
Since the i plating layer thickness is t (mm), it is shallower than the reference value (dcr in Table 1; unit μm) calculated from 80-30 · t, so that the crack generation amount 0 cannot be achieved. Samples 4 and 10
Ni plating was applied to the surface of the casting drum, but the thickness of the plating drum did not reach 0.2 mm, so the plating peeled off during casting.

Samples 22 to 27 are claims 1 to 4 of the present invention.
This is the case when all the conditions up to are satisfied. It was possible to manufacture a rolled plate that achieved an amount of crack generation of 0 and was excellent in normal surface without gloss unevenness.

[0026]

[Table 1] (Example 2) Carbon steel in which the contents of C and Mn are 0.06 ≤ (wt% C) <0.08 and (wt% C) + 0.02 (wt% Mn) ≥ 0.08 A case of continuously casting a thin plate from the molten steel of No. 1 or the molten steel of carbon steel with (wt% C) ≧ 0.08 by a twin-drum type continuous casting machine will be described. Table 2 shows the results of the investigation of the components, the main casting conditions, and the crack generation amount. Specifications of the casting machine used,
The molten steel temperature in the tundish, the handling of the atmospheric gas in the pool, the crack generation amount investigation method, the average heat flux calculation method of the casting drum, and the like are the same as in Example 1. Ni-3% Co alloy was used for plating the drum surface. On the drum surface, the circular dimples used in Example 1 were provided in the casting of Samples 31 to 49, and the lattice-shaped grooves were provided in Samples 51 and 52. This groove has an adjacent distance of 1.5 mm and a width of 0.5 m.
m.

In Samples 31 to 37, since the average heat flux q of the casting drum exceeds the upper limit value qcr represented by the functional expression of the cast piece thickness D, the crack generation amount can be reduced to 5 cm / m ² or less. Absent. In Samples 38 and 39, since the dimple depth d on the surface of the casting drum did not reach 20 μm, the crack generation amount could not be suppressed to 1 cm / m ² or less.

In the sample 40, the dimple depth d is 250 μ
Since it exceeded m, cracking could be prevented, but uneven luster occurred in the plate product produced by rolling the thin plate slab 80%.

In Samples 41 to 44, the dimple depth d on the surface of the casting drum is 20 μm or more, but the reference value calculated from 100-30.t as the Ni plating layer thickness t (mm) on the drum surface (Table 2 Since it is shallower than the inner dcr (unit: μm), the crack generation amount 0 cannot be achieved.

Samples 31 and 38 had Ni on the surface of the casting drum.
-Co plating was applied, but since the thickness did not reach 0.2 mm, peeling of the plating occurred during casting.

Samples 45 to 49 and 51 and 52 are cases where all the conditions of claims 5 to 8 of the present invention are satisfied. It was possible to manufacture a rolled plate that achieved an amount of crack generation of 0 and was excellent in normal surface without gloss unevenness.

[0032]

[Table 2]

[0033]

As described above, the present invention has been described in detail. According to the method of the present invention, a thin plate slab of carbon steel having no cracks and excellent surface properties is continuously produced by a twin-drum type continuous casting machine. Can be cast. Therefore, the thin plate can be manufactured by omitting a part or all of the complicated post-process, which is of great industrial value.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a twin-drum type continuous casting machine.

[Explanation of symbols]

 1 Molten Steel 2 (2 ') Casting Drum 3 (3') Side Weir 4 (4 ') Solidified Shell 5 Thin Plate Slab 6 Rotational Direction of Casting Drum 7 Minimum Drum Gap 8 Drum Starting Point of Contact with Molten Steel

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 7, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0003

[Correction method] Change

[Correction contents]

Molten steel 1 is applied to drums 2 and 2'and side weirs 3,
It is continuously poured into the upper space (melt pool) formed by 3 '. The molten steel 1 injected is a casting drum 2, 2 '
Cooled by the surface of the solidified shell 4, 2, 2 '
4 'is formed. The solidified shells 4 and 4'are integrated in the minimum gap portion 7 of the drum and taken out as a thin cast piece 5.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

According to this twin-drum type continuous casting machine, a thin plate slab having a plate thickness of 5 mm or less and a plate width of 1000 mm or more is produced.
As it is without performing a complicated post-processes, or rear Engineering
It can be used as a thin plate by carrying out mild rolling.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

Regarding [1], the degree of gentle cooling is calculated from the change in the water temperature of the water used for cooling the water inside the casting drum, that is, (water temperature at the drum outlet)-(water temperature at the drum outlet). Can be represented by the average heat flux of
The degree of gentle cooling required to prevent cracking, that is, the upper limit of the average heat flux differs depending on the steel type.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

The requirements for forming a recess or groove on the surface of the casting drum will be described. According to our experiments,
In order to achieve a crack generation rate of 1 cm / m ² or less, in addition to setting the average heat flow to the upper limit value or less described above, it is necessary to provide recesses or grooves with a depth of 20 μm or more on the drum surface. Therefore, the lower limit is set to 20 μm. Incidentally, JP-A-62-254953 and JP-A-2-2956
Providing grooves or irregularities on the surface of the casting drum as shown in No. 48 is effective in reducing cracking, but the cracking rate of 1 cm / m ² or less cannot be achieved only by satisfying the respective conditions. On the other hand, if the depth exceeds 250 [mu] m, the convex portion that is transferred to the slab surface is remaining unevenness of gloss to the product plate after 80% rolling, the upper limit of the depth of the recess or groove provided in the drum surface It was set to 250 μm. The shape other than the depth, the arrangement pattern, and the processing method for forming are not particularly specified, but generally the diameter is 0.2 to 3.0 mm.
The circular or oval dimples with
It is effective to construct and use it with a thickness of 3.0 mm.
The groove has a rectangular or arcuate cross-sectional shape, a width of 0.2 to 3.0 mm, and an interval between adjacent grooves of 0.5 to 5.
It is effective to set 0 mm so as to be parallel or perpendicular to the roll axis direction and obliquely arranged at a certain angle.
Moreover, not only the grooves are formed parallel to each other in one direction, but the grooves formed in a plurality of directions such as a lattice may be arranged to intersect each other.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction contents]

Samples 22 to 27 are claims 1 to 4 of the present invention.
This is the case when all the conditions up to are satisfied. It was possible to manufacture a rolled plate that achieved a crack generation rate of 0 and was excellent in surface properties without uneven gloss.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction contents]

Samples 45 to 49 and 51 and 52 are cases where all the conditions of claims 5 to 8 of the present invention are satisfied. A surface with zero cracking and no uneven gloss
It was possible to manufacture a rolled plate having excellent properties .

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

[0033]

As described above, the present invention has been described in detail. According to the method of the present invention, a thin plate slab of carbon steel having no cracks and excellent surface properties is continuously produced by a twin-drum type continuous casting machine. Can be cast. Therefore, it is possible to manufacture a thin plate by omitting a part or all of complicated post- processes , which is of great industrial value.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B22D 11/22 B22D 11/22 A C25D 3/12 C25D 3/12 7/00 7/00 F ( 72) Inventor Emi Yamada 3434 Shimada, Oita, Nippon Steel Co., Ltd.Nippon Steel Works, Ltd.Hitachi Steel Works (72) Inventor Takashi Arai, 3434, Shimada, Nippon Steel Co., Ltd. Inventor Hatsumi Kirihara 3434 Shimada, Oita, Hikari-shi, Nippon Steel Co., Ltd., Kogaku Steel Works (72) Inventor, Komitsu Mizuki, 3434, Shimada, Shin-Nihon Steel Co., Ltd. Inventor Masafumi Miyazaki 3434 Shimada, Kami-shi, Nippon Steel Co., Ltd., Nippon Steel Co., Ltd., Hikari Steel Works (72) Inventor, Shigenori Tanaka, 1 Kimitsu, Kimitsu-shi Kimitsu Works, Nippon Steel Corporation

Claims (8)

[Claims] 1. From molten steel of carbon steel with (% by weight C) <0.06, or the content of C and Mn is 0.06 ≦.
(Wt% C) <0.08, and (wt% C) +0.0
When continuously casting thin plates from molten steel of carbon steel satisfying 2 (wt% Mn) <0.08 by a twin-drum type continuous casting machine,
A continuous thin plate casting method, characterized in that the average heat flux (q) of the casting drum is controlled in the following range for casting. q (kcal / m ² / hr) ≦ (1400-180.
D) × 10 ⁴ [where D is the slab thickness (mm)] 2. The continuous casting method for thin plates according to claim 1, wherein a casting drum having a recess or groove having a depth of 20 to 250 μm on the surface thereof is used. 3. The continuous casting method for thin plates according to claim 1 or 2, wherein a casting drum whose surface is made of a plating layer of Ni or Ni alloy having a thickness of 0.2 mm or more is used. 4. The continuous thin plate casting method according to claim 3, wherein the depth (d) of the recess or groove provided on the drum surface satisfies the following range. d (μm) ≧ 80−30 · t [where t: Ni or Ni alloy plating layer thickness (mm) on the drum surface] 5. The content of C and Mn is 0.06 ≦ (weight
% C) <0.08, and (wt% C) + 0.02 (weight
Content% Mn) ≧ 0.08
Or molten steel of carbon steel with (wt% C) ≧ 0.08
When continuously casting thin plates with a twin-drum type continuous casting machine,
The average heat flux (q) of the casting drum is controlled within the following range
A method for continuously casting thin plates, which is characterized in that it is manufactured. q (kcal / m^Two/ Hr) ≦ (1300-180 ・
D) x 10^Four [However, D is the slab thickness ( mm)] 6. The continuous casting method for thin plates according to claim 5, wherein a casting drum having a recess or groove having a depth of 20 to 250 μm on the surface thereof is used. 7. The thin plate continuous casting method according to claim 5, wherein a casting drum whose surface is made of a plating layer of Ni or Ni alloy having a thickness of 0.2 mm or more is used. 8. The continuous thin plate casting method according to claim 7, wherein the depth (d) of the recess or groove provided on the drum surface satisfies the following range. d (μm) ≧ 100−30 · t [where t: Ni or Ni alloy plating thickness (mm) on the drum surface]