JPH01186248A - Side weir for twin drum type continuous casting machine - Google Patents

Abstract

PURPOSE:To improve the quality of a metal strip by arranging as pushing upper and lower weirs to side faces of cooling drum at the starting time of the casting and retreat-shifting only the lower part weir from the side face of the drum at the steady state. CONSTITUTION:The side weirs 2a, 2b of the cooling drums 1a, 1b are arranged as dividing into the upper and lower weirs 5, 6. The upper part weir 5 is arranged as always pushing to the side faces of the drum 1a, 1b with a cylinder 7 and the lower part weir 6 is pushed to the side faces of the drum 1a, 1b with a cylinder 8 at the starting time of the casting and retreated with the cylinder 8 at the steady state of the casting. At the starting time of the casting, as the upper and lower weirs 5, 6 are arranged as always bringing into close contact with the side face of the drums 1a, 1b, leakage of molten metal is eliminated and at the steady state of the casting, as the lower part weir 6 is retreated and solidified shell is rolled down under non-restricting condition, the developments of defect and crack are prevented. Therefore, the quality of the metal strip is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a molten metal sump provided between a pair of rotating cooling drums while preventing deterioration in peelability of a thin metal strip due to the occurrence of cast burrs. This invention relates to a side weir used in a twin-drum continuous casting machine that continuously casts thin metal strips.

[Conventional technology]

BACKGROUND ART Recently, a method of directly manufacturing a metal ribbon having a thickness of several squares, which is close to the final shape, from molten metal such as molten steel has been attracting attention. When this continuous casting method is used, there is no need for a hot rolling process with a large processing rate as in the conventional method (and only a light rolling process is required to form the final shape, so the process and equipment can be simplified.

One such continuous casting method is the twin drum method (see Japanese Patent Laid-Open No. 137562/1983).

In this system, as shown in Fig. 4, a pair of cooling drums la, lb rotating in opposite directions are arranged horizontally, and a space is partitioned by the pair of cooling drums la, lb and side weirs 2a, 2b. A hot water reservoir 3 is formed in the recess. The molten metal supplied to the molten metal sump 3 is cooled and solidified at the portions that come into contact with the cooling drums la and lb to form a solidified shell.

As the cooling drums la, lb rotate, this solidified shell moves to a so-called drum gap area where the pair of cooling drums la, lb face each other at the closest position. In the drum gap portion, the solidified shells formed on the back surfaces of the respective cooling drums la and lb are pressed together and integrated to form the intended metal ribbon 4.

The molten metal supplied to the sump 3 is cooled by cooling drums la,
Not only the circumferential surface of the cooling drums la and lb (but also the portions in contact with the side weirs 2a and 2b) are cooled to form a solidified shell. This solidified shell is formed between the sides of the cooling drums la and lb and the side weirs 2a and 2b. The molten metal enters into the gap and spreads out the sides s2a and 2b near the drum gap, increasing the clearance between the side surfaces of the cooling drums la and lb and the inner surfaces of the side weirs 2a and 2b.As a result, the molten metal flows into this gap. is inserted, making the casting conditions unstable.Furthermore, this solidified shell not only generates ears at the end of the metal ribbon 4, but also breaks the solidified shell formed on the circumferential surface of the cooling drums la and lb. , which can also cause breakouts.

Therefore, in order to eliminate the influence of the solidified shell generated on the inner surface of the side weir, Japanese Patent Application Laid-Open No. 148646/1983 proposes a side weir that is divided into two or more parts in the vertical direction as shown in Figure 5. It is proposed to use.

That is, the side weirs 2a and 2b are divided into a fixed lower layer 5 and a movable lower layer 6. The lower layer 5 is cooled by a cooling drum la under a constant surface pressure by a cylinder 7.

It is pressed against the side of 1b. On the other hand, the lower part 1 [6 is the side! In order to accommodate the widening of the solidified shells generated on the inner surfaces of the cooling drums 2a and 2b and the solidified shells on the circumferential surfaces of the cooling drums la and lb, a cylinder 8 or a spring whose pressing force can be controlled is used to press the cooling drums la and lb against the sides. It is assigned. As a result, when a force exceeding a certain value is applied, the lower layer 6 is turned into a cooling drum la.

When the lower layer 6 moves away from the cooling drums 1b and the applied force becomes less than a certain value, the lower layer 6 returns to the side of the cooling drums la, lb, and the molten metal 9 leaks from between the cooling drums la, lb and the side weirs 2a, 2b. It prevents you from doing so.

[Problem to be solved by the invention]

Even in the case where the side weirs 2a, 2b divided in this way are used, the lower layer 6 is connected to the cooling drums la, lb.
is pressed against the side of the For example, cooling drum la,
Even if the lower layer 6 moves in the direction away from lb, the movement is carried out in a state where the force due to the solidified shell is balanced by the force of the cylinder 8 or the spring.

On the other hand, since the solidified shell produced in the pool 3 is still in a high temperature state with low rigidity, it is easily deformed even if a slight force is applied to this solidified shell.

This deformation appears as ears at both ends of the metal ribbon 4, and becomes a hindrance when the cast metal ribbon 4 is rolled in a subsequent process. In this regard, when retreating while pressing the lower layer 6, the cooling drums la, lb ~ side \I
The clearance between 2a and 2b is too thick (this is a defect that actually increases the amount of ears produced).

Therefore, the present invention opens the lower layer of such a split side weir, thereby preventing the solidified shell from being deformed by the lower layer, and producing an excellent quality metal ribbon with a small amount of ear formation. The purpose is to

[Means to solve the problem]

In order to achieve the purpose, the side weir of the present invention is a side weir that partitions both sides of a pair of rotating cooling drums to form a pool, and includes a lower layer that is always pressed against the sides of the cooling drums. It is characterized by comprising a lower layer that is pressed against the circumferential surface of the cooling drum at the start of casting and recedes from the circumferential surface of the cooling drum in a steady state.

〔Example〕

Hereinafter, the features of the present invention will be specifically explained using examples with reference to the drawings.

FIGS. 1(a) and 1(b) show the twin-drum continuous casting machine incorporating the side weir of this embodiment, with the lower layer in the forward position and the backward position, respectively. In addition,
In these figures, the members shown in FIGS. 4 and 5 are designated by the same reference numerals.

The lower layer 6 in this continuous casting machine, like the lower layer shown in FIG. 5, is supported by a cylinder 8 so as to be movable back and forth relative to the sides of the cooling drums la, lb. However, when the casting of the metal ribbon reaches a steady state, the cooling drums 1a and 1b retreat to positions away from the sides of the cooling drums 1a and 1b, as shown in FIG. As a result, the lower side surfaces of the cooling drums la, lb are completely opened, and no gaps are created between the side weirs 2a, 2b and the side surfaces of the cooling drums la, lb, which could cause ears.

The height of the lower layer 6 is determined by the relationship between the casting conditions when a steady state is reached and the position where the solidified shells generated on the circumferential surfaces of the cooling drums la and lb meet.

Specifically, as shown in Fig. 3, the height of the lower layer 6 from the drum gap is h, the angle that this height h makes with respect to the center of the cooling drums la and lb is α, and The meniscus of section 3 is the cooling drum la.

When the angle made at the center of 1b is θ, the angle ratio α/θ is 0.
．． It is preferable to maintain it within the range of 0.02 to 0.1.

The semi-solid shell is subjected to pressure in the drum gap and the semi-solid metal is squeezed upwardly and laterally.

The semi-solid metal squeezed out laterally pushes back the side weirs 2a, 2b, is inserted between the inner surfaces of the side weirs 2a, 2b and the sides of the cooling drums la, lb, and solidifies there. This becomes what is called casting burr.

At this time, if there is no side ¥121.2b in the drum gap, if the degree of solidification is low, leakage will occur due to the high fluidity of the semi-solid metal. However, if solidification has progressed to a certain extent, the semi-solid metal is naturally cooled after being squeezed out and completes solidification. As a result, the squeezed out metal adheres to the sides of the metal ribbon 4 and is pulled out from the drum gap below, as if the width of the metal ribbon 40 had expanded.

The flow limit of this semi-solid metal is determined by the coefficient of the solidification ratio X, and is expressed in relation to the solidification coefficient as follows.

ks = 2 +
represents the solidification coefficient of the solidified shell in the semi-solidified state, and each unit is city·min−0·5. This critical coagulation rate
varies depending on the type of metal, but is generally in the range of 0.2 to 0.8. For example, in stainless steel it is approximately 0.5.

When the angle made by the position where the semi-solid metal at the flow limit meets at the drum gap with respect to the center of the cooling drums la and lb is β, the following equation holds true.

However, as shown in FIG. 3, R is the cooling drum la,
Radius of lb (m), V is cooling drum la, circumferential speed of lb (m/min), S is half of the thickness of metal ribbon 4.0 (mm)
shall be.

In order to prevent the semi-solid metal from leaking out from both sides of the thin metal strip 4, the height h of the side weirs 2a and 2bs of the drum gap portion, that is, the lower layer 6, must be adjusted to the height h of the cooling drums la and lb. It is desirable that the angle α formed with respect to the center be equal to or slightly smaller than the angle β representing the height of the flow limit described above.

Here, the values of k, , k, and X are kl=2
2-30. L=12-18. r=0.2~0.8
This has been experimentally obtained. Therefore, the angle ratio α/θ is 0.02 to 0.1.

This lower layer 6 is formed by cooling drum la at the start of casting.
, pressed against the side of lb. This is to prevent molten metal from flowing out from the sides of the cooling drums la, lb when the solidified shell has not grown sufficiently in the initial stage. When the casting reaches a steady state, the lower layer 6 is moved back, and the side surfaces of the cooling drums la, lb near the drum gap are opened. Note that whether or not it is in a steady state is determined by the stabilization of the shape of the manufactured metal ribbon 4. Furthermore, at the end of casting, the lower layer 6 is pressed against the side surfaces of the cooling drums la, lb again to prevent hot water from leaking from the sides of the cooling drums la, lb.

The solidified shells generated on the circumferential surfaces of the cooling drums la, lb move to the drum gap portion as the cooling drums la, lb rotate. In this process, the solidified shell is subjected to a rolling action by the cooling drums la, lb, and the semi-solidified molten metal is squeezed out onto the side surface of the metal ribbon 4. When a conventional side weir is used, the squeezed molten metal is inserted between the side weir and the sides of the cooling drums la, lb, where it solidifies. The solidified portion in this gap is the cooling drum la.

It stands up in a direction perpendicular to the metal ribbon 4 produced on the circumferential surface of 1b.

However, in this embodiment, since the lower part 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 la and lbO. As a result, it is possible to obtain a metal ribbon 4 in which both ends do not stand up and do not have so-called ears. In addition, since there is no selvage, the thin metal strip 4 is rolled down with both ends free. Therefore, the application of tension that causes defects such as vertical cracks and wrinkles to the metal ribbon 4 is prevented.

Figure 2 compares the end shape of the metal ribbon obtained using this side weir with that obtained using a conventional side weir that contacts the side of the cooling drum. FIG.

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 rolled down in the vicinity of the drum gap is not deformed by the side weirs 2a, 2b, and is transferred to the cooling drums la, l.
It extends in the bO axis direction, indicating that it has been cooled and solidified. In this way, the metal ribbon having both end portions 4a extending in the width direction serves as the cooling drum la.

1b, and could be rolled without having to trim both ends 4a in the subsequent rolling process. Further, since the center portion 4b was not pulled by both end portions 4a, defects such as vertical cracks and wrinkles did not occur in the center portion 4b.

On the other hand, when conventional side weirs are used, the squeezed molten metal is deformed by the side weirs, and as shown in the same figure, both ends 4a stand upright with respect to the center part 4b, creating so-called ears. Form. Since these upright ears impede rolling, it was necessary to trim both ends including these upright portions before rolling the metal ribbon. In addition, cooling drum la, lb side ~ side weir 2a, 2b
With the central portion 4b being pulled by both ends 4a sandwiched between the inner surface and the inner surface, the thin metal strip 4 is pulled from the drum gap.
was fed out, many vertical cracks 4C were detected in the metal ribbon 4.

〔Effect of the invention〕

As explained above, in the present invention, when the casting operation reaches a steady state, the side weir near the drum gap portion where the solidified shell has a large reduction is retreated from the side surface of the cooling drum. Therefore, no upright ears are generated at both ends of the obtained metal ribbon, and a rollable metal ribbon can be produced without essentially needing trimming.

Moreover, since the solidified shell grows on the circumferential surface of the cooling drum in an unrestrained state and is rolled down, a metal ribbon without defects such as vertical cracks and wrinkles caused by tension can be obtained. In addition, since both ends extend in the direction of the main surface, it becomes easy to feed the metal ribbon from the cooling drum.

Furthermore, since no flash is generated between the side surface of the cooling drum and the inner surface of the side weir, damage to the cooling drum is also reduced. In this way, according to the present invention, it has become possible to carry out twin-drum continuous casting operations efficiently and to produce metal ribbons of excellent quality.

[Brief explanation of the drawing]

Fig. 1 shows a twin-drum continuous casting machine incorporating a side weir used in an embodiment of the present invention, and Fig. 2 is a diagram showing the effects of the present invention in comparison with a case using a conventional side weir. 3 is a diagram for explaining a method of determining the height of the lower weir shown in FIG. 1. On the other hand, FIG. 4 shows the main parts of a twin-drum continuous casting machine, and FIG. 5 shows a continuous casting machine equipped with vertically divided side weirs. Patent applicant: Nippon Steel Corporation (1 idiot) Agent: Masu Kobori (and 2 others) (a) 2nd figure (a-1 (b) figure (b) h figure 3 figure 4 h Figure 5

Claims (1)

[Claims] 1. Side weirs that partition both sides of a pair of rotating cooling drums to form a pool, and include an upper weir that is always pressed against the side surfaces of the cooling drums, and an upper weir that is pressed against the circumferential surface of the cooling drums at the start of casting. A side weir for a twin-drum continuous casting machine, comprising a lower weir that recedes from the circumferential surface of the cooling drum in a steady state.