JPS6320145A - Control method for mold oscillation of continuous casting equipment - Google Patents

Abstract

PURPOSE:To prevent sloshing phenomenon at the time of transition period for an operation by returning back number of mold oscillation changed to pass out of dangerous region for sloshing, to the original calculated number of oscillation after passing the dangerous region. CONSTITUTION:In case of finding the number of mold oscillation in the dangerous region for sloshing, for example, a damping circuit is passed through as setting it to upper limit value in the dangerous region, to send a command oscillation value to a mold oscillation control device. After passing the dangerous region, a number of oscillation S=RXV, in which multiplies a control constant R to the production command velocity V, is operated and in case of comparing S with a mold oscillation lower limit L is found and so again the number of oscillation S=RXV is adopted to return back the command oscillation value to the original calculating number of oscillation. In this way, the casting operation is possible to pass the dangerous region within the time of no big development of sloshing on the molten metal practically. Therefore, at even the time of transition period for the operation, fluctuation of the molten surface does not occur and the operation without any adverse effect on the cast billet quality is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of Industry-1-) The present invention relates to a mold vibration control method during the transition period of continuous casting operations.

(Prior art and its problems) In the continuous casting method, it is necessary to reduce the friction between the slab and the mold to prevent burning, breakout, or breakout accidents of the slab. Therefore, in order to reduce the friction between the mold and the slab, continuous casting is carried out using the so-called mold vibration method, in which the mold is vibrated downward by -1-.

However, in general, mold vibration type casting (in which the vibration of the mold is set so that the maximum descending speed of the mold is greater than the withdrawal speed of the slab) increases the vibration frequency by -1-1 to prevent defects in the outer layer. It is necessary to reduce the occurrence rate, but it is necessary to reduce the vibration frequency during the stable operation period (not during the operation transition period (initial casting period, when replacing the Tr, when there is a problem with the injection system, etc.) [7] Surface vibration of the molten steel called tsusing is induced, which has a negative effect on the quality of the slab.
There is a technical problem in that the vibration frequency cannot be increased unnecessarily.

(Problems to be solved by the invention) The present invention aims at reducing the surface vibration of molten copper called filtrate level sloshing especially during the transitional period of operation when operating by increasing the vibration frequency θν number to reduce the incidence of oscillation defects. It is an object of the present invention to provide a control shift method that prevents this from occurring.

(Means for Solving the Problem (8y)) The present invention sets the mold vibration frequency proportionally by multiplying the slab withdrawal speed V by a proportionality constant F determined by the negative strip rate, while at the same time setting the mold vibration frequency to a lower limit determined by the operating conditions. In controlling the mold vibration of continuous casting equipment so that it does not fall below the vibration frequency, sloshing prevention only during stable operation 11-
As shown in Figure 1, in the region where the frequency during stable operation overlaps with the sloshing frequency calculated from the mold shape, the proportionality constant rt determined by the negative strip rate may be changed so that there is no overlap. However, in order to prevent the sloshing phenomenon during the transitional period of operation, as shown in Fig. 1, the sloshing circumference θkU (z of When the danger zone is reached, the mold should be vibrated at a frequency outside the danger zone, and when the danger zone is reached, the vibration frequency should be returned to the original calculated frequency. This product was completed after discovering that it was impossible to deal with the sloshing phenomenon of the filtrate level in In order to control the mold vibration of continuous casting equipment so that it does not fall below the lower limit frequency determined by the operating conditions, the mold vibration when the casting speed decreases or increases is controlled in proportion to the mold withdrawal speed. However, when the sloshing danger area calculated based on the mold shape is reached, the mold vibration frequency is changed so that it passes outside the sloshing danger area, and it passes through the sloshing danger area. "Controlling the vibration to return it to the original calculated vibration frequency" is a mold vibration control method for a continuous casting machine.

Changes to make the mold vibrate outside the sloshing danger area can be made as shown in the dashed line in Figure 1.Changes in the casting = 3- mold vibration frequency to the 1-glow direction can also be made as shown in the dotted line in Figure 1. Although it is possible to change the slab quality I- in the direction of lowering the mold frequency, it is preferable to change it in the direction of increasing the mold vibration frequency.

In addition, in order to avoid sudden changes in mold frequency, if a step-like change in frequency occurs, a cushion (damping) is used to change the frequency for 5 seconds (Practical - 1 - time during which sloshing does not grow significantly). It is better to control the circuit individually.

Hereinafter, the present invention will be described in detail based on specific examples shown in the accompanying drawings.

(Example) In general, two methods, a conventional electric motor drive method and an electro-hydraulic servo drive method, are used to control the descending speed of the mold and the withdrawal speed of the slab. Detect the drawing speed ■, and set the frequency command value N so that the mold vibration frequency is proportional to the above drawing speed by multiplying the slab drawing speed ■ by the ratio R determined by the negative strip ratio using a frequency setting device. On the other hand, if the pulling speed is extremely low, if only proportional control is used, the frequency will drop drastically and the mold wall will seize. The lower limit value ■7 is received from the lower limit setter (the mold vibration of the continuous casting device is controlled and staggered through the J lower limit limiter).
(see figure).

As shown in FIG. 4, the present invention is characterized in that the control system shown in FIG. 2 is provided with a frequency setting function.

That is, in the drawing, the sloshing frequency N during the transition period
s5 to 9 (indicating the 5th to 9th sloshing frequencies) are determined considering the mold shape, and are within the sloshing danger area ±
2 NsX 0, 02 [T-rz], set the sloshing danger region frequency l], and
snXn, 02) [T-1z] signal and Nsn - (2N
5nXO, 02) [Calculate the nzl signal and output it.

On the other hand, the vibration frequency S-4* is obtained by multiplying the casting command speed (actual operating speed) ■ by the control constant R (it is preferable to adopt a proportional constant adjusted to avoid sloshing during stable operation). V is calculated and compared with the mold vibration lower limit value I, and the lower limit area is determined by S≦I7. ■ If it is 7 or less, s
Correct the lower limit of the frequency to = r, and on the other hand, ■7 or more -1-
If so, the frequency S = I'(*
V is calculated in step 12, and the frequency command value S is sent to the mold vibration control device.

Also, −1− frequency S−R*V and N5n−1−(2N
snx O, 02) [T-1zl signal and N5n-(2N
snXO, 02) [T-T z ] signal in combination with U
- In the transition period (J), interference with the 5th to 9th sloshing danger areas is determined.

That is, S≦Nsn −(2N5nX O, 02) II−
Judgment of 1zl and S≧Nsn+ (2N5nX O, 0
2) Combining the judgment of [1-rz:], if either one does not satisfy the 11-item condition, the frequency is not corrected because it is not in the sloshing danger area, and the -1-item frequency S- R*
Adopt V.

On the other hand, when none of the conditions -1- are satisfied, the above-mentioned sloshing danger region exists, so the cut-off signal shown by the broken line causes the frequency S = r (*V to be calculated on January 1-, while S = Nsn+ (2N5nX O, 02) [
Hzl is calculated, and the vibration command value is set to, for example, the second limit value of the "dangerous region" so as to move upward from the above-mentioned sloshing danger region, and the vibration command value is sent to the mold vibration control device via the damping circuit.

In addition, when calculating the frequency S so that it deviates downward from the slot song danger area, S = Nsn - (
2N5nX O, 02) [1 (zl may be calculated.

After passing through the dangerous area, either one of the judgment conditions described in "-" becomes equal to l:i, so the conventional calculation described in "-" is performed.
Again, the vibration frequency S=R*V is adopted, and the vibration command value is sent to the mold vibration control device.

Once a stable operating state is reached, fluctuations in the hot water level can be avoided by setting the control constants to avoid the sloshing phenomenon (see Japanese Patent Application No. 148054/1982).

(Operations and Effects of the Invention) As is clear from the explanation below, according to the present invention, the mold frequency is proportional to the mold frequency by multiplying the slab withdrawal speed ■ by the proportionality constant R determined by the negative strip rate. On the other hand, in order to control the mold vibration of continuous casting equipment so that it does not fall below the lower limit frequency determined by the operating conditions, the mold vibration when the casting speed decreases or increases is proportional to the mold withdrawal speed. When the sloshing danger area calculated based on the mold shape is reached, the mold vibration frequency is changed so that it passes outside the sloshing danger area, and when it passes through the sloshing danger area, the original calculated vibration Since it is controlled so that the molten metal surface returns to normal, it is possible to pass through the dangerous area within a time period in which sloshing does not grow significantly. Therefore, even during the transition period of operation, fluctuations in the molten metal level do not occur, and operation can be performed without adversely affecting the quality of the slab.

[Brief explanation of the drawing]

Fig. 1 is a graph illustrating the mold vibration control method of the present invention, Fig. 2 is a frequency calculation logic diagram of the conventional mold vibration control method, and Fig. 3 is a graph illustrating the conventional control method.
FIG. 4 is a logic diagram in which the method of the present invention is applied to the control method of FIG. 2. S... Mold vibration frequency, 17... Lower limit of frequency, Nsn
...S[1 Tunng frequency, ■...Casting command value.

Claims (1)

[Claims] (1) The mold frequency is set proportionally by multiplying the slab withdrawal speed V by the proportionality constant R determined by the negative strip rate, while the mold frequency of the continuous casting equipment is set so as not to fall below the lower limit frequency determined by the operating conditions. To control vibration, while controlling the mold vibration when the casting speed decreases or increases in proportion to the mold withdrawal speed, when the sloshing danger area calculated based on the mold shape is reached, the mold vibration frequency is adjusted to the above sloshing danger area. A mold vibration control method for a continuous casting apparatus, characterized in that the mold vibration is controlled so that the vibration frequency is changed to pass outside the sloshing danger area, and the vibration frequency is returned to the original calculated vibration frequency when the vibration passes through the sloshing danger area.