JPH01122645A - Method for controlling vibration of ultrasonic vibrating mold for continuous casting of metal - Google Patents

Abstract

PURPOSE:To prevent seizure of molten metal in a mold to the inner wall of the mold by controlling amplitude of each vibrator to the fixed value at the time of vibrating the mold for continuous casting with plural ultrasonic vibrators. CONSTITUTION:Plural vibrators 1-1-1-6 are fitted to the mold 3 for continuous casting composing of four pieces of steel plate, etc., and it is prevented by vibrating the mold 3 with the ultrasonic generators 2-1-2-6 that the continuous casting can not be executed caused by seizure of the molten steel 4 in the mold 3 to the inner wall of the mold 3. In this case, the frequency of vibration is set by a frequency generator 21 and the power of vibration is set by a power setting comparator 22 and the power is applied to the vibrator by power setting signal from an output matching inverter 23 through an output transformer 24 and an impedance matching coil 25. On the other hand, the primary current of the output transformer 24 is detected by a shunt 27 and the voltage is detected by a potentiometer 30 and both are amplified by amplifiers 28, 31, respectively and inputted to a power control circuit 26 through control circuits 29, 32 to control the amplitude to the fixed value and the seizure of the molten steel to the inner wall of the mold is prevented.

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 in, for example, Japanese Patent Application No. 197617/1983.

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 the mold 3 is vibrated by vibrations by the vibrators 1-1 to 1-6. For example, in order to prevent the inner wall surface of the mold from seizing or staining between the inner wall surface of the mold and the molten metal 4, the inner wall of the mold should be vibrated in all areas near the meniscus. It is necessary that the wall surface of the machine is always maintained at the desired vibration level.

In the conventional method of controlling this vibration, for example, as shown in FIG. 2, ultrasonic oscillators 2-1 to 2-6 are connected to each vibrator 1-1 to 1-6, and In the so-called separately excited method, in which frequency and power are set and vibrated using the frequency setters 7-1 to 7-6 and power setters 6-1 to 6-6 provided, open-loop control prevents load fluctuations (impedance fluctuations). ), and it was difficult to maintain a constant vibration amplitude.

Also, as a vibration control method for light loads where the amplitude changes significantly with frequency fluctuations, as shown by the dotted line in Figure 5, for example, the frequency automatic tracking constant amplitude control method as shown in Part 3 and Figure 4 is common. It is. In this automatic tracking constant amplitude control method, first, the relationship among the voltage E of the vibrator terminal, the electric current, and the braking impedance is shown as a vibration amplitude detection method.

ZmI=A υ As in the above equation, the impedance of the vibrator is given by the sum of the damping impedance Zd, which is unrelated to vibration, and <Zm, which is based on vibration. Therefore, by subtracting the voltage drop due to the braking impedance Zd 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, a common method is to assemble a bridge circuit of a vibrator and impedances Z1 to Z3, as shown in FIG. 3, and detect an output voltage E2 proportional to Zml.

Next, the automatic frequency tracking method uses the ultrasonic oscillator amplification section 13 (amplification section transfer function: μ) and the vibration detection circuit shown in FIG. When a closed circuit is formed, the oscillation condition; l#=I is established, and a frequency satisfying the oscillation frequency μ+β=2nπ (n: 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, with automatic frequency tracking constant amplitude control, it is impossible to arbitrarily change the vibration frequency of adjacent vibrators and excite them, which is effective for flattening the vibration amplitude of the area where you want to vibrate. Amplitude unevenness occurs, resulting in burn-in, sticking, and the like.

[Problems to be Solved by the Invention] The present invention is an ultrasonic vibration mold in which a plurality of ultrasonic vibrators are arranged and vibrates by changing the vibration frequency of adjacent vibrators. 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 an ultrasonic vibration mold in which a plurality of ultrasonic vibrators are arranged and vibrates adjacent vibrators by changing their vibration frequencies.
The ultrasonic vibration amplitude is controlled to be a constant value by controlling the integrated value of the primary side DC voltage and current of the high-frequency cadence of the ultrasonic oscillator for each vibrator to a constant value, This is a vibration control method for an ultrasonic vibration mold for continuous metal casting.

[Operations] The object to be vibrated in the present invention is a metal continuous spinning type, which has a heavier load than an ultrasonic cleaner or the like which is often used. As shown in Figure 5, the amplitude change with frequency is heavy load (solid line).
It becomes gentle. Therefore, the amount of amplitude change with respect to frequency fluctuation becomes small.

On the other hand, the relationship between the amplitude A and the ultrasonic oscillator power P (output transformer primary side voltage x current) is as shown in Figure 6.
, = kEv (k: coefficient) has been obtained from actual measurement results under heavy load conditions.

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.

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

The vibration frequency is set in advance by the frequency generator 21, and the power is set by the power setting comparator 22. In response to the power setting signal, power is applied to the vibrator from the output matching inverter 23 via the output transformer 24 and the impedance matching coil 25.

On the other hand, the current on the output transformer secondary side is detected by the current regulator 27, and the voltage on the output transformer primary side is detected by the voltage divider 30, and the signals are amplified by amplifiers 28 and 31, respectively, and transmitted through control circuits 29 and 32. and input it to the power control circuit 26. In this way, the input power was detected, the output thereof was input to the power setting comparator 22, a match comparison was performed, and the amplitude was controlled to be constant by controlling the power so that it was always equal to the set power.

[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. With the present invention, the frequency of the vibrator can be arbitrarily set variably and constant amplitude control is possible, making it possible to always apply the desired vibration 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, improving yield and efficiency. is significantly improved.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the external appearance of a continuous casting mold equipped with a large number of vibrators and an ultrasonic oscillator. Figure 2 is an example of a cross section of a continuous casting mold equipped with a large number of vibrators and the oscillators. Figure 3 is a diagram showing an example of a vibration amplitude detection circuit using the bridge method; Figure 4 is a conventional frequency automatic tracking constant amplitude control block diagram; Figure 6 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 by experiment, Figure 7 is an example of the vibration control circuit of the present invention. Diagram showing. 1 (]-1 to 1-6): Vibrator, 2 (2-1 to 2
-6): Ultrasonic oscillator, 3: Mold, 4: Molten metal, 5: Amplifier, 6: Power setting device, 7: Frequency setting device, 11: Amplitude setting device. 12: Voltage comparison control circuit, 13: 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 Lance, 25: Impedance matching coil,
26: voltage control circuit, 27: shunt, 28: current amplifier, 29: current control circuit, 30: voltage divider, 31: voltage amplifier, 32: voltage control circuit. Patent applicant Nippon Steel Corporation

Claims (1)

[Claims] In an ultrasonic vibration mold in which multiple ultrasonic vibrators are arranged and vibrated by changing the vibration frequency of adjacent vibrators, the primary side DC voltage and current of the high-frequency output transformer of the ultrasonic oscillator for each vibrator are integrated. 1. A vibration control method for an ultrasonic vibration mold for continuous casting of metal, the method comprising controlling the amplitude of ultrasonic vibration to a constant value by controlling the amplitude of the ultrasonic vibration to a constant value.