JPH0576997A - Method for oscillating mold for vertical type continuous casting - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the breakout of the slab by promoting the inflow of the mold powder between the mold and the solidified shell. [Structure] When the longitudinal vibration of the mold 9 retreats the pair of long sides 1 of the mold by the hydraulic cylinder 4 during the positive strip period to increase the distance between the mold and the solidification shell, high-frequency vibration is applied to the pair of long sides 1 of the mold. During the negative strip period, the high frequency vibration is stopped, the pair of molds are moved forward, and horizontal vibration is applied at the same cycle as the longitudinal vibration so as to return to the original position. This facilitates the inflow of mold powder between the mold and the solidified shell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of vibrating a vertical continuous casting mold, and more particularly to a method of vibrating a vertical continuous casting mold for controlling the amount of mold powder flowing between the mold and the solidification shell. .

[0002]

2. Description of the Related Art In performing continuous casting by a vertical continuous casting machine, generally, a mold is vertically vibrated vertically, and at the same time, a mold powder is added onto molten steel in the mold.
The action of this mold powder is closely related to the vibration condition of the mold, and it is important to adjust the vibration condition so that an appropriate amount of mold powder flows between the mold surface and the solidification shell. Therefore, as a method of vibrating the mold, as shown in FIG. 2, a method in which the vibration speed V _{m of the} mold becomes a sine wave is generally used. On the other hand, as disclosed in JP-A-2-290656,
A method (hereinafter referred to as horizontal vibration) for applying expansion / contraction vibration to the mold in the horizontal direction (lateral direction) in synchronization with the vertical vibration of the mold has also been proposed.

That is, the method of vibrating the vertical continuous casting mold proposed in the above publication is such that the vertical vibration of the vertical continuous casting mold which forms a casting space by two pairs of molds is a pair of positive and negative strips during the vertical strip period. The mold is retracted to increase the distance between the mold and the solidifying shell, and during the negative strip period or the positive strip period, the pair of molds is moved forward again so that the distance between the mold and the solidifying shell is reduced to the original position. Horizontal vibration is given by returning to.

[0004]

However, while the above method is effective in promoting the inflow of the liquid mold powder in the vicinity of the molten steel meniscus in the mold, the inflow of the solid mold powder in the vicinity of the lower part of the mold is not effective. There was a problem that it was difficult to adjust the inflow. The present invention is
In view of the current situation as described above, while increasing or decreasing the distance between the mold and the solidification shell, the high-frequency vibration is applied to the mold to control the inflow amount of the mold powder to prevent breakout or improve the surface property of the slab. It is an object of the present invention to provide a vibrating method of a vertical continuous casting mold that can be performed.

[0005]

According to the present invention for achieving the above object, the vertical vibration of a vertical continuous casting mold for forming a casting space with two pairs of molds has a pair of molds in a positive strip period or a negative strip period. Move the mold backwards
Increase the distance between the solidification shells, and during the negative strip period or the positive strip period, the pair of molds is again moved forward and returned to the original position. Horizontal vibration is applied at the same period as the vertical vibration for vertical continuous casting. In the mold vibration method, longitudinal vibrations of the two pairs of molds apply a high frequency vibration in the same direction as the forward / backward direction of the pair of molds in a positive strip period or a negative strip period, or the entire period thereof. It is a mold vibration method for vertical continuous casting.

The frequency of the high frequency vibration is preferably in the range of 5 times or more the vertical mold frequency.

[0007]

[Operation] As shown in FIG. 1, generally, in a mold 9 of a slab continuous casting machine, a method of clamping a pair of mold short sides 2 with a pair of mold long sides 1 is adopted. The long side 1 of the mold is moved by opening / closing 4 through a hydraulic circuit including an upper clamp opening / closing solenoid valve 5, a lower clamp opening / closing solenoid valve 6, a hydraulic motor 7 and a hydraulic tank 8. Reference numeral 3 denotes a short side clamping spring.

In FIG. 2, Z is a sine waveform showing the position of the mold due to longitudinal vibration, and V _m is the vibration speed of the mold at that position. Also, the longitudinal vibration of the mold and the withdrawal speed V _{c of the} slab
Due to the interaction with the mold, a period in which the vibration speed V _m of the mold is slower than the drawing speed V _{c of} the slab is called a positive strip period T _P , and a period faster than the drawing speed V _{c of the} slab is called a negative strip period T _N. .

[0009] First breakout prevention will be described, the present invention FIG. 3 (a), (b), the distance X between the positive strip period T normal mold 9 and the solidified shell 12 in Figure 4 to _{P The} mold 9 is moved backward to increase _m (closed), and the distance between the mold 9 and the solidification shell 12 is X.
_While expanding from _m (closed) to X _n (open), the mold 9 is subjected to high-frequency vibration in the horizontal direction, and during the negative strip period T _N , the mold 9 is advanced again to return to the original position of X _m. Then, horizontal vibration of the mold 9 is performed at right angles to the mold drawing direction.

As described above (see FIG. 1), the opening and closing of the long side 1 of the mold by the hydraulic cylinder 4 for clamping the short side of the mold causes horizontal vibration of the long side 1 of the mold through a hydraulic circuit and high frequency to the long side 1 of the mold. The same hydraulic circuit is used to apply vibration, and high frequency vibration is also applied. Depending on the frequency of high frequency, a vibration generator (eg, ultrasonic generator) separately provided on one side of the long side of the mold may be used. When giving too caused the distance between the mold long and short sides in the casting, because the penetration into the gap of the molten steel 11 is likely to occur, X _n -X _m is less desirable 0.5mm within at 1 mm.

On the other hand, considering the frictional force between the mold 9 and the solidification shell 12 as shown in FIG. 4, the frictional force applied to the solidification shell 12 is maximum when the mold 9 rises at the maximum speed (positive strip period). Becomes Therefore, increasing the distance X between the mold 9 and the solidified shell 12 at this time increases the inflow amount of the mold powder 10 and is effective in reducing the frictional force. In addition, when high frequency vibration is applied to the long side surface of the mold at this time, as shown in FIG. 3A, the effect is doubled. This means that the mold powder near the lower end of the mold 9
This is because the temperature of 10 is generally lower than the freezing point, and the high-frequency vibration promotes the flow-down behavior of the mold powder layer solidified.

Next, measures for preventing oscillation marks will be described. As shown in FIGS. 3 (c) and 3 (d), the vibration of the vertical continuous casting mold 9 causes the mold 9 to move backward during the negative strip T _N , and the mold 9 and the solidified shell are
The distance between the molds 12 is increased from X _m to X _n , and sufficient mold powder 10 is flown between the mold 9 and the solidification shell 12 to make the mold 9
By reducing the frictional force between the surface and the solidified shell 12,
12 The amount of bending deformation at the tip can be reduced. Also at this time, the mold 9
When high frequency vibration is applied to the mold 9 when the mold is moved backward, its effect is increased.

As described above, in the breakout prevention measure, the mold 9 is retracted and high frequency vibration is applied during the positive strip period, and as the oscillation mark prevention measure, the mold 9 is retracted and the high frequency wave is generated during the negative strip period. Apply vibration. That is, the period of applying the high frequency vibration may be a period corresponding to the period in which the distance between the mold and the solidified shell is expanded, but may be the entire period of one cycle of the longitudinal vibration.

[0014]

EXAMPLES Examples of the present invention will be described below. Example 1 According to the present invention, the amount of inflow of mold powder between the mold and the solidification shell and the breakout occurrence state when a slab of low carbon aluminum killed steel was cast by vibrating the mold were determined by the vibration conditions when the mold was moved backward. Table 1 shows the results obtained by changing the value. As shown in Table 1, it is understood that the high frequency vibration applied when the mold is retracted is preferably 5 times or more the longitudinal vibration frequency. Further, the same effect was obtained not only at the time of retreating but also when applied to the entire one cycle.

[0015]

[Table 1]

Example 2 A stainless steel SU was prepared by vibrating a mold according to the method of the present invention.
The oscillation mark depth of the S 304 slab was measured using a mold powder having a viscosity of 1.3 poise at 1300 ° C. Table 2 shows the results obtained by changing the vibration conditions during the backward movement of the pair of molds. As is clear from Table 2, it is found that the high frequency vibration applied when the mold is retracted is preferably at least 5 times the longitudinal vibration frequency. Further, the same effect can be obtained not only when retreating, but also when applied to all the one cycle.

[0017]

[Table 2]

[0018]

According to the present invention, it becomes possible to easily adjust the conditions for inflow of the mold powder between the long side surface of the mold and the solidified shell, and prevent slab breakout and reduce oscillation marks. It is possible to obtain a slab with excellent surface properties.

[Brief description of drawings]

FIG. 1 is a configuration diagram of equipment such as a mold used for carrying out the present invention.

FIG. 2 is a graph showing changes with time in the vibration speed of the vertical mold, the slab drawing speed, and the like.

FIG. 3 is a graph showing a vibration waveform of a vertical mold, and a waveform and timing of retreating and advancing the mold.

FIG. 4 is a schematic view between a mold and a solidification shell.

[Explanation of symbols]

 1 Mold long side 2 Mold short side 3 Short side clamping spring 4 Short side clamping hydraulic cylinder 5 Upper clamp opening / closing solenoid valve 6 Lower clamp opening / closing solenoid valve 7 Hydraulic motor 8 Hydraulic tank 9 Water cooling mold 10 Mold powder 11 Molten steel 12 Solidification shell

Claims (2)

[Claims] 1. The vertical vibration of a vertical continuous casting mold for forming a casting space with two pairs of molds retreats the pair of molds to increase the distance between the mold and the solidification shell during a positive strip period or a negative strip period. In the negative strip period or the positive strip period, in the mold vibration method for vertical continuous casting, in which horizontal vibration is applied at the same cycle as the longitudinal vibration so as to advance the pair of molds back to their original positions, the two pairs are used. Vertical vibration of the mold of the positive strip or negative strip period, or high frequency vibration is applied in the same direction as the forward and backward direction of the pair of molds over the entire period, the mold vibration for vertical continuous casting Method. 2. The mold vibration method for vertical continuous casting according to claim 1, wherein the frequency of the high frequency vibration is in the range of 5 times or more of the mold frequency in the longitudinal direction.