JPH0360849A - Apparatus for continuously casting strip - Google Patents

Abstract

PURPOSE:To prevent the development of involution of defective shell into the obtd. continuous cast steel strip by giving fine vibration to long side weirs in a mold formed with both drums and side dams at the time of continuously casting the steel strip with twin drum type continuous casting method. CONSTITUTION:Molten steel 2 in a tundish 1 is caused to flow into gap between drum 7A, 7B for cooling mutually rotated in the reverse direction A, B from a bottom nozzle 4 to form pouring basin 13 and the continuous cast strip 9 is continuously drawn while forming and developing solidified shells 8A, 8B with rotation of both drums 7A, 7B. The refractory-made long side weirs 15A, 15B are arranged in parallel to axes of both drums 7A, 7B in pouring basin 13 and at the time of starting the continuous casting, these are pulled upward and saved from both drums, and at the time, when the molten steel surface 2a in the pouring basin 13 comes to the stationary position, the long side weirs 15A, 15B are descended and set at 0.5-5mm gap from surfaces of the drums 7A, 7B. Then, the fine vibration of 10-200Hz frequency and 0.01-5mm amplitude commanded with electric hydraulic servo devices 18A, 18B is applied to the long side weirs 15A, 15B with a vibrating frame 16. Even if small solidified shell is developed in the long side weir, as this is dropped into the pouring basin with the vibration, defect caused by the involution of shell onto surface of the continuous cast strip 9 is not developed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a continuous thin plate casting device, and in particular, a device for storing molten steel between a narrowing type rotary mold constituted by twin drums or twin belts, etc., and rotating the mold. The present invention relates to a long side weir mechanism in a mold of a continuous thin plate casting apparatus that continuously manufactures thin plates.

[Prior Art] A twin-drum type continuous thin plate casting apparatus is a casting apparatus suitable for manufacturing thin plates with a thickness of approximately several millimeters, and therefore, it is currently desired to put it into practical use. In a conventional twin-drum continuous thin plate casting apparatus, a molten metal pool is formed by two drums and a side dam, and the molten metal discharged from a pouring nozzle accumulates in this molten metal pool. When casting with this twin-drum type casting device, the limit of the ripples on the surface of the molten metal pool caused by the flow of molten metal from the pouring nozzle and the constant scene control based on molten metal flow rate control is ±3 to ±5 mm. It is impossible to avoid vertical fluctuations in the hot water level due to the inclusion of errors. Furthermore, a jamming phenomenon occurs due to the defective shell floating on the surface of the molten metal. For this reason, in the conventional twin-drum type continuous thin plate casting apparatus, wrinkles occur on the surface of the cast thin plate, making it unusable as a product and requiring improvement.

Therefore, in order to eliminate the conventional hot water wrinkles, as described in Japanese Patent Application Laid-open Nos. 60-30555, 60-27448, and 62-40955,
In conventional casting equipment, it has been proposed to provide various types of long side weirs to prevent ripples, thereby solving the problem of water wrinkles.

[Problems to be Solved by the Invention] However, in the conventional twin-drum type continuous thin plate casting apparatus having a long-side weir, a new problem has arisen in that surface defects occur. Here, we will consider the causes of surface defects using drawings. Figure 1 shows an example of the main part configuration of a conventional twin-drum continuous thin plate casting machine equipped with a long side weir, and Figure 2 shows the structure of a defective shell. Indicates the occurrence situation. In FIG. 1, reference numeral 1 denotes a tundish dish, and the molten metal 2 stored in the tundish dish 1 passes through a gap formed below a stopper 3 and passes through a molten metal nozzle 4 to two drums on the left and right in the figure. A,
7B (long side mold) and two side dams 6A and 6B (short side mold) arranged in the short side direction at both ends of the drum.
is not shown in FIG. (See FIG. 8) is injected into a molten metal pool 13 formed by the molten metal. Drums 7A and 7B are rotating in directions A and B, respectively. Long side weirs 5A and 5B are arranged in the molten metal pool 13 in the longitudinal axis direction of the drum, and these long side weirs 5A and 5B are fixed to a fixed wall portion. The hot water in the molten metal pool 13 is heated to the drum 7A by the rotation of the drums 7A and 7B.

It is pushed out downward from the gap between 7B, and the thin plate 9 is formed. In this configuration, the undulations of the molten metal in the molten metal pool 13 are suppressed by the long side weirs 5A, 5B, so that a stable solidified shell 8A is formed on the predetermined surfaces of the drums 7A, 7B.
, 8B are formed, and a thin plate 9 is manufactured as shown.

However, in the conventional thin plate continuous casting apparatus, triangular surface defects 12 are randomly generated on the surface of the thin plate 9, as shown in FIG. As shown in Figure 2, fluctuations in the hot water surface (fluctuation height difference ΔH) and undulations (fluctuation height difference Δh) occur in the hot water surface, which causes defects near the contact area between the long side weir 5A and the scene. This is because a shell 10 of . It is thought that the occurrence of defective shells is due to the fact that this area is in contact with normal temperature gas such as air and the upper part of the long side weir 5A where the temperature has not risen sufficiently, so that it is easy to solidify.

Furthermore, defective shells 11 occur at locations where the flow of the molten metal is insufficient. These defective shells 10.11 grow and fall or fall repeatedly, so they do not disappear forever, and therefore triangular defects 12 are formed on the surface of the thin plate 9.
occurs.

As described above, in all conventional continuous casting apparatuses, it is difficult to prevent the occurrence of surface defects, and this point has been an obstacle to the practical application of continuous thin plate casting apparatuses.

The object of the present invention is to provide a continuous thin plate that can continuously cast a thin plate with good surface quality by eliminating hot water wrinkles, which are defects on the surface of a thin plate, and triangular defects caused by jamming of defective shells. Our objective is to provide casting equipment.

[Means for Solving the Problems] A thin plate continuous casting apparatus according to the present invention includes two long-side molds that are arranged so that their rotation axes are parallel to each other and rotate to opposite sides, and a mold that rotates at both ends of the long-side molds. The two long-side molds and the two side dams form a molten metal pool, and the molten metal is heated by the rotating action of the two long-side molds. In a thin plate continuous casting machine that manufactures a thin plate by cooling the molten metal in a pool and forming a solidified shell on the surface of each of the long side molds, and extruding it in a crimped state from the gap between the long side molds, each of the long side molds is It is configured to include a long side weir disposed close to the long side weir, and an excitation device that applies vibrations to the long side weir that satisfy required conditions.

[Function] According to the present invention, even if a defective shell that becomes a triangular defect occurs, it is shaken off by vibration action in a small state before it grows, and a good thin plate without any practical problems is manufactured.

[Example code] Embodiments of the present invention will be described below with reference to the accompanying drawings.

The thin plate continuous casting apparatus according to the present invention prevents the occurrence of the above-mentioned defective shells 10.11, and basically, even if defective shells occur, they are shaken off in a small state before they grow. This makes it possible to manufacture good thin plates (slabs) without any practical problems. In other words, the basic configuration is to apply slight vibrations at the required frequency and amplitude to the long side weir in a steady state where the molten metal is at a predetermined level, and to shake off defective shells by the acceleration of the applied vibrations. .

Therefore, the configuration of the thin plate continuous casting apparatus according to the present invention is basically the same as the configuration shown in FIG. The difference is that a vibration device configuration is added. Therefore, in the following description, the same reference numerals will be used for the same elements shown in FIG. The configuration of the vibration device, which is a characteristic mechanical element of the present invention, is shown in FIGS. 7 to 9.
This will be described later with reference to the figures.

Next, first, the principle of the microvibration given to the long side weir according to the present invention will be explained.

At the start of pouring, as shown in FIG. 3, the molten metal 2 falling from the pouring nozzle 4 into the molten metal pool 13 generates molten metal splash 27, so the long side weirs 5A and 5B are retracted to a required position above.

Then, as shown in FIG. 4, when the surface 2a of the molten metal 2 in the molten metal pool 13 reaches a steady position of a predetermined level,
Long side weirs 5A, 5 in a state of slight vibration due to vibration
Lower B to the specified position.

The long side weirs 5A and 5B according to this embodiment are arranged in the vertical up-down direction C.
Since the microvibration is given to the
Even if 1 occurs, it will be shaken off before the defective shell 10.11 grows, and the large defective shell will be transferred to the long side weir 5A,
5B is never formed. The embodiment shown in FIG. 4 is a vertical excitation.

In addition, as for the shape of the long side weir, as shown in FIG. It can also be formed to expand.

This shape of the long side weir 14 allows the defective shell 10.11 to be easily removed, as is clear from its cross-sectional shape. In addition, as a method of giving the above-mentioned microvibration, the sixth
As shown in the figure, it is also possible to apply it in a direction parallel to the axial direction of the drums 7A, 7B. In this case, it is axial horizontal vibration.

Note that the long side weir needs to have the function of contacting and supporting the high-temperature molten metal 2 and the function of suppressing the occurrence of defective shells as much as possible, so it is necessary to use a refractory with heat insulation and heat storage properties, For example, it is desirable to be made of a material such as ceramic fiber or fused silica.

Next, conditions for microvibration applied to the long side weir will be explained.

In order to shake off the defective shells 10.11 adhering to the long side weir, it is necessary to apply a slight vibration that generates a force greater than the adhesion force. For example, the acceleration due to vibration is α: acceleration (
m/s2), a: half amplitude (m), f: frequency (
Hz), then α=a(2πf)2, so the acting force is: F: Acting force (Kg), W weight (Kg)
9: If gravitational acceleration (9.8 m/s2), then F=W・
It is expressed as α/9. Therefore, if this force F is set to a value larger than the adhesion force of the defective shell, the defective shell can be quickly and reliably peeled off from the long side weir.

Therefore, assuming the shape of the defective shell to be a rectangular parallelepiped,
Let the lengths of the three sides be x, y, z (cm),
On the other hand, the adhesion force is P. (g/cd), and shell specific gravity as γ(g/cd).
/aIF), the force required to peel off the defective shell is Fo=Po-X-y (g). This F
. The required excitation acceleration G corresponding to . is expressed by the following relationship: F=W・α7g Go =α/g.

The adhesion force of the defective shell varies depending on the type of refractory that forms the long side weir, but in the case of fused silica it is approximately 2 g/
Since the thickness of the defective shell is about 0.1 cm.
, 7 is 7.8 g/cm3 (in the case of steel), the above required excitation acceleration G. becomes.

Generally, the relationship between the excitation acceleration G, the half amplitude a, and the frequency f is expressed by the following formula. In this relational expression, G=2.5
When the necessary excitation conditions to be satisfied between a and f in order to obtain 6 are determined, the table shown in FIG. 11 is obtained. As a result, if the half amplitude a is targeted to be within 1 mm, the frequency needs to be 25 Hz or higher.

Therefore, the slight vibration applied to the long side weir only needs to satisfy the above-mentioned vibration conditions determined depending on the material of the long side weir. The direction of vibration may be horizontal, vertical, or a direction created by combining the vertical and horizontal directions.

It should be noted that the long side weir is disposed close to the surfaces of the drums 7A and 7B with a wide gap provided therebetween, and this gap facilitates vibration and avoids contact wear.

Next, the configuration of the vibration device that vibrates the long side weir will be explained. 7 and 8 show a first embodiment of the vibration device. The left and right long side weirs 15A and 15B in the figure are fixed to holders 17A and 17B, respectively.
It is attached to the vibrating frame 16 with bolts or the like via 7B. The vibrating frame 16 is supported by vibrating cylinders 19A and 19B fixedly disposed on the left and right sides, and each of the vibrating cylinders 19A and 19B produces a vibrating action in the vertical direction. The vibrations of the vibration cylinders 19A, 19B are controlled to have the frequency and amplitude commanded by the electro-hydraulic servo devices 18A, 18B. For this reason, Nagabe Weir 15
A and 15B also perform vibrations satisfying the above-mentioned conditions. At the start of pouring, the strokes of the vibration cylinders 18A and 18B are increased to maintain the long side weirs 15A and 15B in an elevated state to avoid splashing.

FIG. 9 shows a second embodiment of the vibration device, which is a vibration device driven by a motor. The vibrating frame 20 fixes and supports each of the long side weirs 15A and 15B.
The end portion of the long side weir 15A on which the long side weir 15A is fixed is connected to the drive shaft of a motor 22 via an eccentric shaft 21.
The end portion on the side where 5B is fixed is swingably supported by a link 24. With this configuration, when the motor 22 is rotated in the direction E in the figure, the vibrating frame 2o performs a rocking motion and generates vibrations, giving vibrations to the long side weirs 15A and 15B. The vibration in this case is a combination of vertical and horizontal vibrations. Further, the eccentric shaft 21 and the link 24 are supported by lifting cylinders 23A and 23B, respectively. These lifting cylinders 23A, 23B operate to raise the long side weirs 15A, 15B to a required position when pouring starts, and lower them when the steady state is reached. FIG. 10 shows a third embodiment of the vibration device.

This vibration device connects long side weirs 25A and 25B to drum 7A,
7B is vibrated in the direction F along the circumferential surface. Means 26A, 26B for applying vibration to the long side weirs 25A, 25B
As such, either the above-mentioned electro-hydraulic servo device or motor drive device can be applied.

In the above embodiment, an example was explained in which the vibrator was applied to a twin-drum type continuous casting machine, but it goes without saying that the vibration device according to the present invention can be applied to a twin-belt type continuous casting machine.

[Effects of the Invention] As is clear from the above description, according to the present invention, in a continuous thin plate casting machine such as a twin drum type, a long side weir having a required vibration state is arranged close to each drum. Therefore, it is possible to prevent the adhesion and growth of defective shells on the 4° surface on the molten metal pool side of the long side weir, and it is possible to continuously cast a thin plate with a sound surface quality and no problem in practical use. Furthermore, since the long side weir is placed in an upper position when pouring starts, splash adhesion can be prevented.

[Brief explanation of drawings]

Fig. 1 is a conventional twin-drum continuous casting machine equipped with a fixed long side weir, Fig. 2 is a diagram showing the adhesion state of defective shells in a conventional fixed long side weir, and Fig. 3 is a thin plate according to the present invention. A diagram showing the state in which the long side weir is raised at the start of pouring of the continuous casting equipment, Figure 4 is a diagram showing the long side weir in a vertically excited state in a steady state, and Figure 5 is a diagram showing the other long side weirs. 6 is a diagram showing the long side weir in a horizontally vibrating state, FIG. 7 is a front view showing the vibrating device applied to the thin plate continuous casting apparatus according to the present invention, and FIG. 8 is the same. A side view of the vibration device, FIG. 9 is a front view showing another embodiment of the vibration device, FIG. 10 is a front view showing a further modified example of the vibration device, and FIG. 11 is a front view showing another embodiment of the vibration device. FIG. 3 is a table showing the relationship between frequency f and half amplitude a of applied vibrations. [Description of symbols] 2... Molten metal 4... Molten metal nozzles 5A, 5B, 14. 15A, 15B, 25A. 25B... Long side weir 6A, 6B... Side dam 7A, '7B... Drum 8A, 8B... Solidified shell 10.11... Defective shell 13... Molten metal pool 16.20...◆ Vibration frames 18A, 18B...Electro-hydraulic servo devices 19A, 19
B... Vibration cylinder 22... Motor 23A, 23B◆... Cylinder

Claims (5)

[Claims] (1) It has two long-side molds arranged so that their rotation axes are parallel and rotates to opposite sides, and side dams arranged in the short-side direction at both ends of the long-side molds. , a molten metal pool is formed by the long side mold and the side dam, and based on the rotational action of the two long side molds, a solidified shell is formed on the surface of each of the long side molds while cooling the molten metal in the molten metal pool. In a continuous thin plate casting apparatus that manufactures a thin plate by extruding it in a crimped state from a gap between the long side molds, a long side weir is arranged close to each of the long side molds, and a vibration is applied to the long side weir. A thin plate continuous casting apparatus characterized by comprising: a vibration excitation device that gives the following effects. (2) In claim 1, the vibration excitation device includes a vibration source and a vibration frame, the long side weir is fixed to the vibration frame, and the vibration generated by the vibration source passes through the vibration frame to the long side weir. A thin plate continuous casting device characterized by being added to a side weir. (3) In claim 1, the frequency of the long side weir is 10 to 10.
A thin plate continuous casting apparatus characterized by having a frequency of 200Hz and an amplitude of 0.01 to 5.0mm. (4) In claim 1, the long side weir is moved to an upper position when pouring starts, and the long side weir is moved to a lower position when the molten metal level in the molten metal pool reaches a steady state level. A thin plate continuous casting device characterized by being equipped with a changing device. (5) In claim 1, the distance between the tip of the long side weir and the surface of the long side mold is 0.5 to 5.0 mm, and the tip of the long side weir has a tapered shape. Thin plate continuous casting equipment.