JPH03210942A - Method for continuously casting steel - Google Patents

Abstract

PURPOSE:To reduce friction between a mold and a cast billet and to slowly cool the cast billet by applying high frequency oscillation specified in amplitude and frequency in thickness direction of the cast billet. CONSTITUTION:In the continuous casting mold 1 for steel, the high frequency oscillation having 10 - 500mu amplitude and 1,000 - 10,000 cpm frequency is applied in the thickness direction of cast billet 6 with an oscillating generator 2. By this method, the friction between the cast billet 6 and the mold 1 is reduced and slow cooling to the cast billet is executed. In this result, the development of breakout caused by sticking and longitudinal crack in the cast billet 6 are prevented. The oscillating generator 2 uses eccentric type motor, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for continuous casting of steel in which a mold is vibrated at high frequency in the thickness direction of a slab.

(b) In conventional continuous casting methods for steel, lubricants are used to prevent seizure between the casting and the slab and to continue stable casting without breakouts. An oscillation movement was carried out in which the mold was moved back and forth up and down.

Conventionally, this oscillation is a movement in the same plane as the slab, and it is inevitable that the oscillation moves in the opposite direction to the casting direction of the slab. At this time, the solidified shell of the meniscus is bent and a so-called oscillation mark is generated on the mold surface.6 Depending on the viscosity of the lubricant and the conditions of the oscillation stroke, this oscillation mark becomes deeper. This is where surface defects occur. In addition, air bubbles are trapped in the pressed and bent oscillation marks and remain inside as pinhole defects.

In order to solve the second problem, many methods have been proposed for applying ultrasonic vibration to the mold to prevent sticking (for example, Japanese Patent Application Laid-Open No. 1-122845). However, these methods are difficult to use because the ultrasonic vibration generator itself has a small output.
It is necessary to install many vibrators in order to obtain the desired vibration conditions by attaching them to a continuous casting mold. Furthermore, since a large number of vibrators are arranged, control is required to prevent their vibrations from interfering with each other and canceling each other out. If even one of the oscillators becomes abnormal, there is a strong possibility that they will cancel each other out, and in terms of maintenance,
There are many difficulties. The vibrators are quite expensive, and installing a large number of them will result in very high equipment costs.

Further, although the vibration frequency is large at 5 to 50 KH2, the amplitude is small at 1 to several microns, and the anti-sticking effect as large as expected cannot be observed.

(C) Problems to be Solved by the Invention The problems to be solved by the present invention are to reduce the friction between the mold and the slab by effectively applying high-frequency vibrations of relatively large amplitude to the slab; The object of the present invention is to obtain a method for continuous casting of steel that allows gradual cooling of slabs.

(d) Means for Solving the Problems The continuous steel casting method of the present invention is characterized in that the continuous casting mold for steel has an amplitude of 10 to 500μ and a frequency of 1000 to 10,000.
The above problem is solved by applying high frequency vibration of epH in the thickness direction of the slab to reduce the friction between the mold and the slab and to cool the slab slowly.

(e) Action The relationship between the vibration conditions of the working mold and the frictional force is shown in Figure 2. If we take (amplitude) x (S frequency) as the vibrational energy, the vibrational energy will reach approximately 5xlO', which will reduce the frictional force. We found that there is a major inflection point.

Therefore, it has been found that ultrasonic vibrations of around 10 KHz are not necessarily required.

Therefore, in the present invention, high frequency vibration is applied to the slab in the thickness direction.

The gap between the mold and the slab is estimated to be about 500 to 1000μ. Even when vibrations with an amplitude of about 5 μm were applied to the gap, the amount of powder consumed could not be ensured, and the anti-sticking effect was not necessarily clear.

Therefore, in the present invention, the amplitude of high frequency vibration is set to 10 to
It was set to 500μ. The reason for this is that, as mentioned above, if the powder is less than 10μ, the anti-sticking effect will be small due to the increased powder consumption, and if it is more than 500μ, there will be a misalignment between the mold and the support downstream of the mold (e.g. cooling grid) due to lateral vibration of the mold. This is because there is a risk of a breakout occurring. Preferably 50-200
The optimum value is around μ.

In the present invention, the vibration frequency is 1000 to 10000 cp.
+Il. It was discovered that at this frequency, cavitation is formed in the molten powder between the mold and the slab, and vertical cracking can be prevented by the gradual cooling effect due to the reduction in the amount of heat removed from the mold.

As shown in FIG. 2, a sufficient friction reduction effect is ensured when the vibration energy is approximately 5×1 G'. Furthermore, vibration generators in this range are relatively inexpensive and can also provide high output.

(F) Embodiment An embodiment of the continuous steel casting method of the present invention will be described with reference to FIGS. 1 to 6.

As shown in FIG. 1, in the continuous steel casting method of the present invention, high-frequency vibrations having an amplitude of 10 to 500 μ and a frequency of 1,000 to 110,000 cp are applied to a steel continuous casting mold 1 by a vibration generator 2 to reduce the thickness of a slab 6. Add in direction. Thereby, the friction between the mold 1 and the slab 6 is reduced, and the slab is cooled slowly. As a result, breakout due to stay soaking can be prevented, and vertical cracking of the slab can be prevented.

Although the vibration generator 2 is not particularly limited, it is sufficient to use an eccentric motor. According to this, 10 to 50
For example, as shown in Fig.
If you install one, you can get enough vibration. 1000-100
Although the frequency range of 00 eps is audible, it does not pose a particular problem if soundproofing measures are taken.

Furthermore, unlike ultrasonic vibration, the vibration according to the present invention vibrates the entire mold 1, so as shown in FIG.
If you fix it with a disc spring, etc., there is no particular difficulty in terms of equipment. Preferably, the mold 1 is supported on the base 4 by the elastic member 5.

Next, specific examples of the present invention will be described.

Three strands of the medium carbon steel shown in Table 1 were cast in a one-point straightening continuous casting machine with a radius of curvature of 10 g+.

No. 1 strand uses a conventional oscillation mold.

No.2 strand has a mold equipped with an ultrasonic vibrator,
For strand No. 3, a high frequency vibration mold according to the method of the present invention was used. For each mold, a billet of size 200 and r200 square is made at a speed of 2. Cast at Oz/min.

Table 1 (wt%) No.1 strand mold vibration condition is stroke 5 m
The ultrasonic vibration of No. m, 200 cpm, No. 2 strand has an amplitude of 5/L, and the Wc frequency is 18 KHz, and the vibration dye of No. 3 strand has an amplitude of 120 μ and a vibration frequency of 6000 ep-.

Figure 3 shows the amount of powder consumed. No. according to the method of the present invention,
3 strands are the most common.

The effect of the high frequency vibration of the method of the present invention is clear from the fact that the number of breakout predictions shown in FIG. 4 is the smallest.

Figure 5 shows the results of investigating the temperature fluctuations of the copper plate.

The No. 3 strand had the least variation, indicating the development of a uniform shell.

Furthermore, [-] FIG. 6 shows the occurrence of vertical cracks on the surface. N
The number of 003 strands was the lowest, and the slow cooling effect due to high frequency vibration was confirmed.

(g) Effects According to the present invention, the continuous casting mold has a diameter of 10 to several 100 μ, 10
By applying high-frequency vibration of 00 to 110,000 cp, it is possible to prevent sticking and to cool slowly between the mold and the slab, thereby preventing vertical cracking.

[Brief explanation of drawings]

FIG. 1 is a side view of a mold in which the continuous steel casting method of the present invention is carried out. Figure 2 is a graph showing the relationship between vibration and frictional force. Figure 3 is a graph showing powder consumption. FIG. 4 is a graph showing the number of breakout predictions. Figure 5 is a graph showing the side temperature results of the copper plate. Figure 6 is a graph showing the occurrence of vertical cracks. 1: fs type 2: Vibration generator 3: Bearing 4: Base 5: Elastic member 6: Slab

Claims (1)

[Claims] By applying high-frequency vibrations with an amplitude of 10 to 500 μ and a frequency of 1,000 to 10,000 cpm in the thickness direction of the slab in continuous steel casting molds, the friction between the mold and the slab can be reduced and the slab can be cooled slowly. A continuous casting method for steel.