JPH0337455B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibration method for vibrating a mold in continuous casting.

As is well known, in the continuous casting method to obtain slabs by continuously pouring molten metal such as molten steel into a mold,
In order to reduce wear between the mold and slab, prevent seizure, and perform stable casting, it is recommended to use a lubricant such as powder and vibrate the mold in the direction of pulling out the slab. Normal.
Figure 1 shows a typical example of a conventional continuous casting machine. In FIG. 1, molten metal 2 in a tundish 1 is poured into a mold 4 through a submerged nozzle 3, and the molten metal 2 solidifies from the inner surface of the mold 4 to obtain a slab 5. Powder 6, which functions as a lubricant, a heat insulator, a cleaning agent, etc., is sprinkled onto the surface of the molten metal 2 in the mold 4. Furthermore, the mold 4 is vibrated in the direction in which the slab 5 is pulled out as shown by an arrow 7 by a well-known vibration device (not shown), and the mold 4 and the slab 5 are vibrated relative to each other.

By the way, in continuous casting as described above, particularly in continuous casting using powder, depressions called oscillation marks are formed on the surface of the slab due to relative vibration between the mold and the slab. Such oscillation marks not only impair the appearance of the slab (casting surface), but also when the depressions of the oscillation marks become deep, the depressions act as notches and cause cracks on the surface of the slab. There are also problems such as defects caused by slag entrainment (so-called slag). Therefore, it is preferable to avoid or reduce the occurrence of oxidation marks as much as possible. The above-mentioned oscillation marks are caused by the accumulation of slag made of the melted powder on the inner wall surface of the mold when the mold is raised, and when the mold is lowered, the slag solidifies and becomes a solidified shell of the slab. It is known that this is caused by creating a dent. Therefore, since the amount or time of rise of the mold is considered to have a strong influence on the size (depth) of the oscillation mark, it is recommended to reduce the amount of relative displacement between the mold and slab. It is known to be effective in reducing silage marks. However, if only the amplitude of the mold is reduced, the surface of the mold and the slab will seize, making it impossible to achieve the original purpose of oscillation. In other words, in the past, mold vibration was generally set at a vibration stroke of 5 to 20 mm and a vibration frequency of 70 to 150 cycles/min, mainly from the perspective of preventing seizure, and if the cycle was higher than this and the amplitude was small, seizure would occur. However, even a small amplitude within this range is not effective in reducing oscillation marks. Therefore, in the past, in order to prevent burn-in, it was necessary to give up on reducing the oscillation marks to some extent.

This invention was made in view of the above circumstances, and an object of the present invention is to provide a mold vibration method that reduces or avoids the occurrence of oscillation marks while ensuring the anti-seizure function of the oscillation of the mold. That is.

In other words, the mold vibration method of the present invention not only generates relatively low-cycle, large-amplitude vibrations similar to conventional ones, that is, vibrations with a vibration frequency of 70 to 150 cycles/min and a vibration stroke of 5 to 20 mm, but also The maximum vibration speed is greater than the maximum speed of
The low cycle
The large-amplitude vibration prevents seizure, and at the same time, the high-cycle, small-amplitude vibration reduces oxidation marks.

The mold vibration method of the present invention will be explained in more detail below.

FIG. 2 shows an example of an apparatus for carrying out the method of the present invention, and FIG. 3 shows an example of vibration waveforms of a mold according to the present invention. In FIG. 2, the same elements as those shown in FIG. 1 are denoted by the same reference numerals, and the explanation thereof will be omitted.

In FIG. 2, the mold 4 is supported by a vibrating frame 11 via an elastic support beam 10 made of a spring material or the like. As shown by the arrow 12 and FIG. 3A, the cylinder is configured to vibrate in the direction of drawing out the slab at a large amplitude and low cycle comparable to conventional mold vibration. On the other hand, mold 4
A high frequency exciter 13 driven by a Uras motor or the like is attached. As shown by the arrow 14 and FIG. 3B, this high-frequency vibrator 13 generates vibrations in the direction of drawing out the slab, which have a maximum speed larger than the maximum vibration speed of the vibration frame 11, a small amplitude, and a high cycle. It is for giving to 4. Therefore, the mold 4 has a large amplitude, low cycle vibration as shown in FIG.
A composite vibration as shown in FIG. 3C, which is a combination of the vibration shown in FIG. B, is applied in the slab drawing direction.

Here, using only the high frequency exciter 13,
If only high-cycle vibrations are applied to the mold 4, the amount of relative displacement between the slab and the mold is small, so seizure is likely to occur as described above. Therefore, in this invention, we not only apply small-amplitude, high-cycle vibrations, but also combine large-amplitude, low-cycle vibrations that are comparable to the conventional normal mold amplitude to improve the total vibration between the mold and the slab. The amount of relative displacement is increased. Here, from the viewpoint of preventing the occurrence of seizure, the vibration mode on the low cycle side is set to have a vibration stroke of about 5 to 20 mm and a vibration frequency of 70 to 150 cycles/minute, similar to the conventional normal mold vibration as described above. On the other hand, in order to reduce or avoid the formation of oscillation marks, it is necessary to reduce the amplitude of high-cycle vibrations as much as possible, with a vibration stroke of 0.1 to 0.5 mm and a vibration frequency of 2000.
~20000 cycles/min.

Note that if the maximum speed of vibration on the high cycle side is equal to or smaller than the maximum speed on the low cycle side, the mold may not actually rise or fall during one cycle of vibration on the high cycle side. For example, if the maximum rising speed of the mold due to vibration on the high cycle side is slower than the descending speed of the vibration frame due to vibration on the low cycle side, the mold will not actually rise during the rise process of vibration on the high cycle side. Become. In this case, the generation of oscillation marks will be affected by the vibrations on the low cycle side, making it impossible to reduce or avoid the formation of oscillation marks. It must be greater than the maximum speed of vibration on the side.

Furthermore, although the example in Fig. 3 shows the case where a sine wave is used as the vibration waveform on the low cycle side and the vibration waveform on the high cycle side, it is needless to say that it is not limited to a sine wave. The vibration waveform and the vibration waveform on the high cycle side may be made different.

Next, an example will be described in which continuous casting of steel was performed by applying the mold vibration method of the present invention.

Example: When continuously casting a steel slab with a slab size of 220 mm x 1400 mm at a drawing speed of 1.5 m/min, the vibrating frame had the same level of vibration as conventional mold vibration, that is, frequency 120 cycles/min, amplitude ±5 mm, and maximum speed 63 mm. At the same time, vibrations were applied using a high-frequency exciter at a frequency of 5000 to 10000 cycles, an amplitude of ±0.2 mm, and a maximum speed of 105 to 210 mm/second. As a result, the depth and length of the oscillation mark can be made much smaller than in the past. It was also confirmed that burn-in hardly occurred.

As is clear from the above explanation, according to the mold vibration method of the present invention, it is possible to prevent seizure of slabs during continuous casting, and at the same time reduce or avoid the occurrence of oscillation marks. It has various remarkable effects, such as being able to easily obtain slabs with excellent surface texture, and effectively preventing the occurrence of cracks from the oscillation marks and defects such as gouges in the oscillation marks. can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the main parts of continuous casting equipment for implementing the conventional mold vibration method, and FIG. 2 is a schematic diagram showing an example of the main parts of continuous casting equipment for implementing the mold vibration method of the present invention. , FIGS. 3A to 3C are waveform diagrams showing examples of vibration waveforms used in the method of the present invention, where A is the vibration waveform on the low cycle side, B is the vibration waveform on the high cycle side, and C is the vibration waveform of both. Shows a complex vibration waveform. 2... Molten metal, 4... Mold, 5... Slab, 1
1... Vibration frame, 13... High frequency exciter.

Claims (1)

[Scope of Claims] 1. In a continuous casting method for obtaining slabs by continuously pouring molten metal into a mold, the vibration frequency is set to 70 to 150 cycles per second in the same direction as the direction in which the slab is pulled out from the mold. 2000 to 20,000 cycles/min and a vibration stroke of 0.1 to 0.5 mm. A continuous casting mold vibration method characterized by applying small amplitude vibration in combination.