JPH0360577B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of controlling vibration of a mold using ultrasonic waves in continuous metal casting.

[Prior Art] In continuous metal casting, a large number of ultrasonic transducers (ultrasonic transducers are abbreviated as transducers in this specification) are arranged in a mold in order to vibrate the inner wall of the mold near the meniscus of molten metal. A technique for vibrating adjacent vibrators by changing their vibration frequencies is well known, as described, for example, in Japanese Patent Application No. 1976-17-1983.
FIG. 1 is a diagram showing an example of the external appearance of a continuous casting mold in which transducers 1-1 to 1-6 are arranged and ultrasonic oscillators 2-1 to 2-6. The inner wall of mold 3 is vibrator 1-1
Although the vibration is caused by the excitation described in steps 1-6 to 1-6, for example, in order to prevent seizure or sticking between the inner wall surface of the mold and the molten metal 4, the inner wall of the mold must be kept at a desired level of vibration at all wall surfaces near the meniscus. It is necessary to be able to stand. In the conventional method of controlling this vibration, for example, as shown in FIG.
2-6 is connected, and the frequency and power are set and vibrated using frequency setters 7-1 to 7-6 and power setters 6-1 to 6-6 provided in advance in the ultrasonic oscillator. However, due to open-loop control, the power fluctuates in response to load fluctuations (impedance fluctuations), making it difficult to maintain a constant vibration amplitude. Furthermore, as shown by the dotted line in Fig. 5, the vibration control method for light loads where the amplitude changes significantly with respect to frequency fluctuations is, for example, the third method.
A frequency automatic tracking constant amplitude control method as shown in FIG. 4 is common. This automatic tracking constant amplitude control method first uses the voltage at the vibrator terminal as a vibration amplitude detection method.
E〓, current I〓, control impedance Z〓d, mechanical terminal speed υ〓, and force coefficient A〓, the following equation shows the relationship.

E〓=Z〓dI〓+A〓υ〓=(Z〓d＋Z〓m)I〓 Z〓mI〓=A〓υ〓 As shown in the above equation, the impedance of the vibrator is equal to the control impedance Z〓d which is unrelated to vibration. It is given by the sum of Z〓m, which is based on vibration. Therefore, by subtracting the voltage drop due to the control impedance Z〓d from the electrical terminal voltage of the vibrator, a voltage proportional to the vibration can be obtained. As an example of this specific detection method, as shown in FIG.
A common method is to detect

Next, in the automatic frequency tracking method, as shown in FIG.
When a closed circuit is formed using the vibration detection circuit shown in Fig. 3 as a feedback section (feedback section transfer coefficient: β〓), the oscillation condition μ〓β
〓
=I〓 is established, and the oscillation frequency is ＜μ〓+＜β〓=2nπ(
n:
(an integer) is automatically selected.

Next, in the constant amplitude control method, as shown in FIG. A control signal is input to the oscillator amplifier section, and the amplitude is controlled to always be constant.

As described above, the conventional automatic frequency tracking constant amplitude control is a vibration control method for light loads where the amplitude changes significantly with respect to frequency fluctuations, as shown by the dotted line in FIG.

Therefore, in a vibration control method for an ultrasonic vibration mold in which a plurality of ultrasonic vibrators are arranged and vibrated by changing the vibration frequency of adjacent vibrators, for example, by changing the frequency of the adjacent ultrasonic vibrators, If this is attempted, the amplitude will be significantly reduced, and the amplitude in the mold width direction will become non-uniform as shown in FIG. 9, resulting in uneven amplitude, causing problems such as burning and staking in the mold.

Regarding the vibration control method for an ultrasonic vibrating mold in which a plurality of ultrasonic vibrators are arranged and vibrated by changing the vibration frequency of adjacent vibrators, the present inventors filed an application before filing the present invention. Special request made in 1986
In the invention of No. 214174 of an excitation method for an ultrasonic vibration mold for continuous casting, the difference in the excitation frequency of each vibrator of a continuous casting mold in which a plurality of vibrators with the same vibration characteristics are arranged is within 2KHz. It has been found that by changing the excitation frequency within a range, interference between adjacent ultrasonic waves is reduced, and it is possible to excite the mold uniformly and with increased amplitude.

[Problems to be Solved by the Invention] The present invention provides an ultrasonic vibration mold in which a plurality of ultrasonic vibrators are arranged and vibrates the adjacent vibrators by changing their vibration frequencies. The purpose of this method is to provide a vibration control method that can be set arbitrarily and can be set at a constant amplitude, thereby constantly applying desired vibrations to all wall surfaces near the meniscus of the inner wall of the mold.

[Means for Solving the Problems] The present invention provides a vibration control method for an ultrasonic vibration mold in which a plurality of ultrasonic vibrators are arranged and the vibration frequencies of adjacent vibrators are changed and vibrated. The child 1 is provided with a frequency generator 21, a power setting comparator 22, a high frequency transformer 24, a shunt 27, a voltage divider 30, and a power control circuit 26, so that the frequency generator 21 generates a necessary frequency, and the power setting comparator 22, the power setting comparator 22 sets in advance the initial power to be supplied to the vibrator 1, the initial power is input to the vibrator via the high frequency output transformer 24, and the primary side of the output transformer 24 is By detecting the current and voltage actually supplied to the vibrator using the current shunt 27 and voltage divider 30 provided in the The power is integrated, the integrated true power is input to the power setting comparator 22, and compared with the initial power set in advance, so that the true power supplied to the vibrator is always the same as the initial setting power. This is a vibration control method for an ultrasonic vibration mold for continuous metal casting, which is characterized by controlling the ultrasonic vibration amplitude to a constant value.

[Function] The object to be vibrated in the present invention is a metal continuous casting mold, and the load is heavier than that of an ultrasonic cleaner or the like, which is often used. As shown in FIG. 5, the amplitude change with respect to frequency becomes more gradual as the load becomes heavier (solid line). Therefore, the amount of amplitude change with respect to frequency fluctuation becomes small.
On the other hand, as shown in Figure 6, the relationship between the amplitude A and the ultrasonic oscillator power P (output transformer primary side voltage x current) is A = k√ (k: coefficient) based on the actual measurement results under heavy load conditions. It has been obtained.

The present invention performs constant power control based on this relationship, thereby controlling the vibration amplitude to be substantially constant. Power fluctuations can be caused by impedance fluctuations before and after pouring the molten metal or due to changes in the vibrator temperature, but even in such cases, the vibration amplitude can be kept almost constant by constant power control.

FIG. 7 shows a vibration control circuit used in carrying out the method of the present invention, and this vibration control circuit is provided for each vibrator. The vibration frequency is set in advance by the frequency generator 21, and the power is set by the power setting comparator 22. The output matching inverter 23, the output transformer 24, and the impedance matching coil 25 are controlled by the power setting signal.
Power is input to the vibrator through the oscillator.

On the other hand, the shunt 27 detects the current on the primary side of the output transformer, the voltage divider 30 detects the voltage on the primary side of the output transformer, and the signals are sent to the amplifier 2.
8 and 31 and input to the power control circuit 26 via control circuits 29 and 32. In this way, the input power is detected and the output is sent to the power setting comparator 22.
The amplitude was controlled at a constant level by comparing the power and controlling the power so that it was always equal to the set power.

[Example] An embodiment of the present invention will be described based on FIG.

A large number of vibrators are arranged near the meniscus of the molten metal in a continuous casting mold, and each vibrator is connected to an ultrasonic oscillator with a built-in circuit that performs amplitude control by performing the constant power control of the present invention, Supply power to the vibrator. To explain specifically, as shown in Figure 7,
The frequency generator 21 sets in advance a frequency of about 10 to 30 KHz close to the resonant frequency when the vibrator is installed in the mold, and the power setting comparator 22 generates a power of several hundred W for each vibrator. Set. In response to the power setting signal, power is applied from the output matching inverter 23 to the vibrator via the output transformer 24 and the impedance matching coil 25. On the other hand, the shunt 27 detects the current on the primary side of the output transformer, and the voltage divider 30 detects the voltage on the primary side of the output transformer. In this embodiment, the respective voltage and current values are, for example, 25V and 4A when the initial setting power is 100W. Assuming that the voltage and current on the secondary side of the output transformer, which are the actual power consumption of the vibrator 1 at this time, are approximately 500V and 0.2A, the detected voltage and current signals are transmitted to the amplifiers 28 and 31, respectively. Amplification and control circuit 29,3
2 to the power control circuit 26. The true power is input to the power setter 22, a comparison is made, and the power is controlled so that it is always equal to the initial setting power. As a factor of variation in power consumption, for example, when a vibration load such as a variation in vibrator temperature varies, electrical impedance (=secondary side voltage/secondary side current) changes equivalently. Now, if the impedance were to double, the secondary voltage and current would be 500V and 0.1A, and as a result,
The primary side voltage and current are 25V and 2A, and the power is 50W, which is half the set value. The constant power control of the present invention increases the primary voltage so that the power is at the set value. In this case, control is performed to increase the voltage to 35.5V (=initial voltage 25V×√impedance change ratio 2). As a result of constant power control, the primary voltage and current are 35.5V and 2.83A, approximately 100W, and the secondary voltage and current are 710V and 0.139A, and the initial setting power is approximately 100W.
automatically adjusted. In this way, by controlling the power and vibrating the inner wall of the mold with each vibrator with a constant amplitude, the amplitude distribution on the inner wall of the mold in the meniscus area is much more uniform than the conventional amplitude distribution. It has been confirmed through actual measurements that the In addition, it has been confirmed that the surface quality of the product slab cast under such an amplitude state of the mold inner wall is smooth with few defects.

[Effects of the Invention] In the present invention, since the control circuit performs frequency control using a simple separate excitation method and amplitude control using power control, maintenance is easy and the cost of control equipment can be reduced. According to the present invention, the frequency of each vibrator can be arbitrarily set variably and constant amplitude control is possible, making it possible to always apply desired vibrations to all wall surfaces near the meniscus of the inner wall of the mold. Ta.

Therefore, seizure of the molten metal and the inner wall of the mold is eliminated, and breakout accidents can be prevented. Also, since the quality of the slab surface is improved, scratch removal and surface maintenance are simplified or unnecessary, resulting in lower yields and Efficiency is greatly improved.

[Brief explanation of drawings]

Figure 1 is a diagram showing the appearance of a continuous casting mold equipped with a large number of transducers and an ultrasonic oscillator, and Figure 2 is an example of a cross section of a continuous casting mold equipped with a large number of transducers and the transducers. 3 is a diagram showing an example of a vibration amplitude detection circuit using the bridge method, FIG. 4 is a conventional frequency automatic tracking constant amplitude control block diagram, and FIG. is a diagram showing the relationship between amplitude and frequency due to load, Figure 6 is a diagram showing the relationship between power (voltage x current) and amplitude confirmed in experiments, and Figure 7 is an example of the vibration control circuit of the present invention. Figure shown. 1,1-1~1-6: Vibrator, 2,2-1~2
~6: Ultrasonic oscillator, 3: Mold, 4: Molten metal, 5:
Amplifier, 6: Power setting device, 7: Frequency setting device,
11: Amplitude setter, 12: Voltage comparison control circuit, 1
3: Amplification section, 14: Resonant phase circuit, 15: Output matching inverter circuit, 16: Feedback section, 17: Voltage input amplifier, 21: Frequency generator, 22: Power setting comparator, 23: Output matching inverter, 2
4: Output transformer, 25: Impedance matching coil, 26: Voltage control circuit, 27: Current shunt, 2
8: current amplifier, 29: current control circuit, 30: voltage divider, 31: voltage amplifier, 32: voltage control circuit.

Claims (1)

[Claims] 1 In a vibration control method for an ultrasonic vibration mold in which a plurality of ultrasonic vibrators are arranged and vibrated by changing the vibration frequency of adjacent vibrators, each vibrator 1 is
A power control circuit 26 including a frequency generator 21, a power setting comparator 22, a high frequency transformer 24, a shunt 27, and a voltage divider 30 is provided, and the frequency generator 21 generates a frequency, inputs it to the power setting comparator 22, and outputs the frequency. The initial power to be supplied to the vibrator 1 is set in advance by the power setting comparator 22, and the initial power is input to the vibrator via the high frequency output transformer 24.
The shunt 27 and voltage divider 30 provided on the primary side of the output transformer 24 detect the current and voltage actually supplied to the vibrator, and input the current and voltage to the power control circuit 26 to reduce vibration. The true power supplied to the transducer is integrated, the integrated true power is input to the power setting comparator 22, and compared with the preset initial power, the true power supplied to the transducer is always set to the initial value. A vibration control method for an ultrasonic vibration mold for continuous casting of metal, characterized in that the vibration is controlled to be the same as a set electric power.