JPH0736940B2 - Twin-drum type continuous casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to a basin provided between a pair of rotating cooling drums while preventing deterioration of peelability of a metal ribbon due to occurrence of casting burrs. The present invention relates to a twin-drum type continuous casting method for continuously casting thin metal strips from steel.

[Prior Art] Recently, attention has been focused on a method for directly producing a metal ribbon having a thickness of about several mm close to a final shape from a molten metal such as molten steel. According to this continuous casting method, it is possible to simplify the process and equipment because the hot rolling process with a large working rate as in the conventional case is not required and the rolling to the final shape may be light.

As one of such continuous casting methods, there is a twin drum method (see Japanese Patent Laid-Open No. 60-13756). In this system, as shown in FIG. 4, a pair of cooling drums 1a and 1b that rotate in opposite directions are horizontally arranged and partitioned by the pair of cooling drums 1a and 1b and side dams 2a and 2b. The basin 3 is formed in the recess. The molten metal supplied to the basin 3 is cooled by the portions in contact with the cooling drums 1a and 1b.
It solidifies to a solidified shell.

The solidified shell moves to a so-called drum gap portion where the pair of cooling drums 1a and 1b face each other at a position closest to each other as the cooling drums 1a and 1b rotate. In the drum gap portion, the solidified shells formed on the surfaces of the respective cooling drums 1a and 1b are pressed and integrated with each other to form the desired metal ribbon 4.

The molten metal supplied to the pool 3 is cooled by the cooling drums 1a and 1b.
Not only the peripheral surface of the, but also the portion contacting the side dams 2a and 2b is cooled to form a solidified shell. This solidified shell enters between the side surfaces of the cooling drums 1a, 1b and the side dams 2a, 2b, spreads the side dams 2a, 2b in the vicinity of the drum gap portion, and the side surfaces of the cooling drums 1a, 1b and the side dams 2a, 2b. Increase the clearance between the inner surface of 2b. As a result, molten metal is inserted into this gap and the casting conditions become unstable.
Further, this solidified shell not only causes ears to be generated at the end of the metal ribbon 4, but also breaks the solidified shell generated on the peripheral surfaces of the cooling drums 1a and 1b and causes breakout.

Therefore, in order to eliminate the influence of the solidified shell generated on the inner surface of the side weir, in JP-A-60-148646, a side weir divided into two or more parts in the vertical direction is used as shown in FIG. Is proposed.

That is, the side weirs 2a, 2b are divided into a fixed upper weir 5 and a movable lower weir 6. The upper weir 5 is a cylinder 7
Are pressed against the side surfaces of the cooling drums 1a and 1b with a constant surface pressure. On the other hand, the lower weir 6 is provided with a cylinder 8 or a spring that can control the pressing force so as to correspond to the width expansion of the solidified shell generated on the inner surface of the side weirs 2a, 2b and the solidified shell on the peripheral surface of the cooling drums 1a, 1b. Cooling drum 1a, 1b
Is pressed against the side of. As a result, when a force above a certain value is applied, the lower weir 6 moves away from the cooling drums 1a and 1b, and when the applied force falls below a certain value, the lower weir 6 returns to the lateral direction of the cooling drums 1a and 1b. , Molten metal 9
Are prevented from leaking from between the cooling drums 1a, 1b and the side weirs 2a, 2b.

[Problems to be Solved by the Invention]

Even when the side weirs 2a, 2b divided in this way are used, the lower weir 6 is pressed against the side surfaces of the cooling drums 1a, 1b. For example, even if the lower weir 6 moves in the direction away from the cooling drums 1a, 1b, the movement is performed in a state where the force of the solidification shell and the force of the cylinder 8 or the spring are balanced. On the other hand, the solidified shell generated in the pool 3 is
Since the solidified shell is still in a high temperature state with low rigidity, it is likely to be deformed even when a slight force is applied to the solidified shell.

This deformation appears as ears at both ends of the metal ribbon 4 and becomes an obstacle when rolling the cast metal ribbon 4 in the subsequent process. In this respect, when the lower weir 6 is retracted while being pressed, the clearance between the cooling drums 1a, 1b and the side weirs 2a, 2b becomes large, which is a defect that rather increases the amount of ears generated.

Therefore, according to the present invention, by opening the lower weir of such a split side weir, the deformation of the solidified shell due to the lower weir is prevented, and a metal ribbon of excellent quality with a small amount of ears is produced. The purpose is to

[Means for Solving the Problems]

The present invention divides both sides of a pair of rotating cooling drums to form a basin, and comprises an upper weir that is constantly pressed against the side surface of the cooling drum, and a lower weir that is movably pressed. , By using side weirs divided into upper and lower parts, at the start of casting, the lower weir is pressed against the side surface of the cooling drum, and in a steady state, the lower weir is retracted from the side surface of the cooling drum to continuously Characterized by casting.

〔Example〕

Hereinafter, the features of the present invention will be specifically described by way of examples with reference to the drawings.

1 (a) and 1 (b) show a twin drum type continuous casting machine in which side weirs are incorporated, with the lower weirs in the forward position and the backward position, respectively. In these figures, members and the like shown in FIGS. 4 and 5 are designated by the same reference numerals.

The lower weir 6 in this continuous casting machine is supported by a cylinder 8 simultaneously with the lower weir shown in FIG. 5 so as to be able to move forward and backward with respect to the side surfaces of the cooling drums 1a and 1b. However, when the casting of the metal ribbon reaches a steady state, it is retracted to a position retracted from the side surfaces of the cooling drums 1a and 1b as shown in FIG. 1 (b). As a result, the cooling drums 1a and 1b
The lower part of the side surface is completely opened, and a gap that causes the generation of ears is not generated between the side dams 2a and 2b and the side surfaces of the cooling drums 1a and 1b.

The height of the lower weir 6 is determined by the relationship between the casting conditions when the steady state is reached and the position where the solidified shells generated around the cooling drums 1a and 1b meet.

Specifically, as shown in FIG. 3, the height of the lower weir 6 from the drum gap portion is h, and this height h is the cooling drum.
When the angle formed with respect to the centers of 1a and 1b is α and the angle with which the meniscus of the basin 3 forms the center of the cooling drums 1a and 1b is θ, the angle ratio α / θ can be maintained in the range of 0.02 to 0.1. preferable.

The semi-solidified shell is subjected to pressure in the drum gap portion, and the semi-solidified metal is squeezed upward and sideways. The semi-solidified metal squeezed out to the side pushes back the side weirs 2a and 2b, is inserted between the inner surfaces of the side weirs 2a and 2b and the sides of the cooling drums 1a and 1b, and solidifies there. This is what is called casting burr.

At this time, if the side gaps 2a and 2b are not provided in the drum gap portion, when the degree of solidification is low, the molten metal leaks due to the high fluidity of the semi-solidified metal. However, when the solidification is progressing to some extent, the semi-solidified metal is naturally cooled after being squeezed out to complete the solidification. As a result, the squeezed metal appears as if the width of the metal ribbon 4 has expanded.
It adheres to the side of the metal ribbon 4 and is pulled out downward from the drum gap portion.

The flow limit of this semi-solidified metal is grasped by the coefficient of the solidification rate X, and is expressed as follows in relation to the solidification coefficient.

k ₃ = k ₂ + x (k ₁ −k ⁺ where k ₁ is the solidification coefficient of the liquidus line, k ₂ is the solidification coefficient of the in-phase line, and k ₃ is the solidification coefficient of the semisolidified solidification shell. , each unit is mm · min ^-0.5. the critical coagulation factor x is is different depending on the type of metal, generally in the range of 0.2 to 0.8. for example, a stainless steel, at approximately 0.5 is there.

When the angle at which the semi-solidified metal of the flow limit meets at the drum gap portion is β with respect to the centers of the cooling drums 1a and 1b, the following equation holds.

However, as shown in FIG. 3, R is the radius (m) of the cooling drums 1a and 1b, v is the peripheral velocity (m / min) of the cooling drums 1a and 1b,
s is half the thickness (mm) of the metal ribbon 4.

Then, in order to prevent the semi-solidified metal from leaking from the both sides of the thin metal strip 4 due to molten metal leakage, the side weirs 2a, 2b in the drum gap portion, that is, the height h of the lower weir 6 is set to the cooling drums 1a, 1b. It is desirable that the angle α formed with respect to the center of is equal to or slightly smaller than the angle β representing the height of the flow limit.

Here, the values of k ₁ , k ₂ and x are k ₁ = 22-30, k ₂ =
It has been experimentally obtained that 12 to 18, x = 0.2 to 0.8. Therefore, the angle ratio α / θ is 0.02 to 0.1.

This lower weir 6 has cooling drums 1a, 1 at the start of casting.
Pressed on the side of b. This is because the cooling drum 1a, 1
This is to prevent molten metal from flowing out from the side of b. When the casting reaches a steady state, the lower weir 6
Is retreated to open the side surfaces of the cooling drums 1a and 1b in the vicinity of the drum gap. Whether or not it is in the steady state is determined by stabilizing the shape of the metal ribbon 4 to be manufactured. At the end of casting, the lower weir 6 is pressed against the side surfaces of the cooling drums 1a, 1b again, and the cooling drums 1a, 1b are
Prevent hot water leakage from the side.

The solidified shell generated around the cooling drums 1a and 1b moves to the drum gap portion with the rotation of the cooling drums 1a and 1b. In this process, the solidified shell is subjected to the rolling action by the cooling drums 1a and 1b, so that the molten metal in the semi-solidified state becomes the metal ribbon 4
Squeezed to the side of. In the case of using a conventional side weir, the squeezed molten metal is inserted between the side weir and the side surfaces of the cooling drums 1a and 1b and solidified there. The solidified portion in this gap stands upright in the direction perpendicular to the metal ribbon 4 formed on the peripheral surfaces of the cooling drums 1a and 1b.

However, in this embodiment, since the lower weir 6 is retracted at the position where the molten metal is squeezed out, the molten metal is cooled and solidified along the axial direction of the cooling drums 1a and 1b. As a result, it is possible to obtain the metal ribbon 4 in which both ends do not stand up and so-called ears do not occur. Further, since the ears are not generated, the metal ribbon 4 is pressed with both ends free. Therefore, it is possible to prevent the tensile force that causes defects such as vertical cracks and wrinkles from acting on the metal ribbon 4.

FIG. 2 compares the end shape of the metal strip obtained by using this side weir with the metal strip obtained by using the side weir of the type that contacts the side surface of the conventional cooling drum. It is the figure shown.

In the case of this embodiment, both end portions 4a extend in the same direction as the plane of the central portion 4b as shown in FIG. 2 (a). This is because the molten metal squeezed out when the solidified shell is pressed in the vicinity of the drum gap portion does not undergo the deformation action of the side dams 2a, 2b and extends in the axial direction of the cooling drums 1a, 1b to cool it. -Indicates that it has solidified. In this way, the metal ribbon having the both ends 4a extending in the width direction is easily carried out from between the cooling drums 1a and 1b, and can be rolled without trimming the both ends 4a in the subsequent rolling step. It was Moreover, since the central portion 4b is not pulled by the both end portions 4a, defects such as vertical cracks and wrinkles did not occur in the central portion 4b.

On the other hand, when the conventional side weir is used, the squeezed molten metal is deformed by the side weir, and FIG.
As shown in, both end portions 4a stand upright with respect to the central portion 4b and form so-called ears. Since this upright edge hinders rolling, it was necessary to trim both ends including this upright portion in advance and then roll the metal ribbon. Also,
In a state where the central portion 4b is pulled by both end portions 4a sandwiched between the side surfaces of the cooling drums 1a, 1b to the side dams 2a, 2b,
Since the thin metal strip 4 was sent out from the drum gap,
A large number of vertical cracks 4c were detected on the metal ribbon 4.

〔The invention's effect〕

As described above, in the present invention, when the casting operation reaches the steady state, the side dam near the drum gap portion where the solidification shell has a large reduction is retracted from the side surface of the cooling drum. Therefore, upright ears are not generated at both ends of the obtained metal ribbon, and it is possible to manufacture a rollable metal ribbon without essentially performing trimming. Further, since the solidified shell grows on the peripheral surface of the cooling drum in an unrestrained state and is pressed, a metal ribbon without defects such as vertical cracking wrinkles due to tension can be obtained. Further, since both ends extend in the direction of the main surface, the work of sending out the metal ribbon from the cooling drum becomes easy. Furthermore, since there is no casting burr between the side surface of the cooling drum and the inner surface of the side dam, damage to the cooling drum is reduced. In this way
According to the present invention, the twin-drum type continuous casting operation can be efficiently performed, and it is possible to produce a metal ribbon of excellent quality.

[Brief description of drawings]

FIG. 1 shows a twin-drum type continuous casting machine incorporating the side weir used in the embodiment of the present invention, and FIG. 2 compares the effects of the present invention with the conventional side weir in the case of continuous casting. It is the figure shown, and FIG. 3 is a figure for demonstrating the method of determining the height of the lower weir of FIG. On the other hand, FIG. 4 shows a main part of a twin-drum type continuous casting machine, and FIG. 5 shows a continuous casting machine provided with side weirs divided in the vertical direction.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Gone Yamane 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries Ltd. Hiroshima Works (72) Inventor Katsumi Hirata 4-chome Kannon-shin, Nishi-ku, Hiroshima 6-22 No. 22 in Mitsubishi Heavy Industries Ltd. Hiroshima Works (56) Reference JP-A-63-115653 (JP, A)

Claims (1)

[Claims] 1. A pair of rotating cooling drums are divided into both ends to form a pool of molten metal, and an upper weir that is constantly pressed against the side surface of the cooling drum and a lower weir that is pressed forward and backward. Using side weir divided into upper and lower,
A twin-drum type continuous casting method, characterized in that, at the start of casting, the lower dam is retracted from the side surface of the cooling drum to perform continuous casting.