JPS59193318A - Measurement of melted metal level in continuous casting mold - Google Patents

Abstract

PURPOSE:To measure melted metal level easily and accurately while being little affected by melted metal and attached foreign matter such as slag by making an ultrasonic wave incident entirely into an ultrasonic wave propagation rod immersed into the melted metal to measure the arrival time of the reflected wave. CONSTITUTION:A sensor 4 is composed of an ultrasonic wave propagation rod 5, and an ultrasonic wave probe 9 contacting the upper end face 10 thereof 5 and the lower part of the ultrasonic wave propagation rod 5 is immersed into a melted metal 2. An incident ultrasonic wave 13 from the ultrasonic wave probe 9 is reflected on the boundary 14 of the immersed and non-immersed parts of the ultrasonic wave propagation rod 5 and inputted into the probe as a reflected ultrasonic wave 15. The peak t3 due to the reflection from foreign matter 19 can be removed by setting the threshold properly thereby enabling the detection of the reflected ultrasonic wave 15 from the surface (the boundary 14) of the melted metal 2 without errors. The ultrasonic wave propagation rod 5 is made of fine ceramics employing boron nitride, zirconium or the like excellent in the heat resistance, corrosion resistance and ultrasonic wave propagating property.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of measuring molten metal level using ultrasound in a continuous casting mold, and in particular, with one end of an ultrasonic propagation rod immersed in molten metal. Ultrasonic waves are introduced into the inside of an ultrasonic propagation rod as a bar wave, and the molten metal level is measured based on the arrival time of the reflected wave to improve the accuracy of the measurement.Generally, in continuous casting equipment, fluctuations in the molten metal level are measured. It is extremely important to keep the quality of slabs manufactured by continuous casting equipment as low as possible, especially to maintain good surface quality, and to prevent equipment wear and tear due to overflow of molten metal. This is a challenge. Therefore, from the viewpoint of maintaining quality and saving labor, various automatic casting technologies for continuous casting equipment have been developed.
Whether or not the molten metal level can always be kept constant is determined by the measurement accuracy of the molten metal level. Furthermore, the ease of installing a level sensor within the continuous casting mold is also important in evaluating the practicality of the Rehersen.

By the way, a method for measuring molten metal level using ultrasonic waves has been proposed in the past, as disclosed in Japanese Patent Application Laid-open No. 56-12.
There are those described in No. 6062 and No. 52-72256. That is, these methods inject ultrasonic waves as surface waves onto the surface of a continuous casting mold or special propagation body, measure the reflection time of the surface waves from a position at the same height as the molten metal surface, and measure the molten metal level. It is something to be measured. However, since surface waves are elastic waves that propagate on the surface of an elastic body that is a propagator, they are more susceptible to surface conditions than bar waves in which the entire rod, including its interior and surface, is a propagator. There is a characteristic that That is, a strong reflected wave of the surface wave is generated at a deformed portion of the surface of the propagating body or at a height position of the surface of the molten metal in which the propagating body is immersed.

The inventors conducted experiments and found that the use of surface waves was not suitable for the above-mentioned applications.

In other words, it has been found that a portion of molten metal or slag often adheres as foreign matter to the upper part of the inner wall of a continuous casting mold, and if even a small amount of said foreign matter adheres, it has been found that a strong reflected wave is generated. . In that case, two or more reflected waves appear in the received waveform, one reflected from the foreign object and the other reflected from the molten metal surface, and it is difficult to identify which of them is the reflected wave from the molten metal surface. there were.

This invention was made to solve these conventional problems, and its feature lies in the use of ultrasonic waves as bar waves.

In the case of bar waves as well, if the foreign matter adheres to the ultrasonic propagation rod that is being propagated, a reflected wave will be generated there. However, as mentioned above, since the entire rod is a propagating body, the relative of the reflected wave to the incident wave is The intensity is much smaller than for surface waves.

Therefore, by using a bar wave, the reflected waves from the molten metal surface position can be clearly distinguished from the reflected waves (noise) caused by attached foreign matter. Furthermore, by setting an appropriate darkness value, it is possible to avoid the incidence of reflected waves from deposits, so that reflected waves from the molten metal surface position can be detected without error. The ultrasonic propagation rod used in this invention includes:
A plate-shaped body is included in addition to the bar material, and as a result, a plate wave, which is an ultrasonic wave propagated to the plate-shaped body, is a type of the above-mentioned bar wave.

That is, in the method of measuring the level of molten metal in a continuous casting mold according to the present invention, one end of the ultrasonic propagation rod is immersed in the molten metal in the continuous casting mold, and the other end of the ultrasonic propagation rod is immersed in the molten metal in the continuous casting mold. Ultrasonic waves are incident as a bar wave on the end of the ultrasonic propagation rod, and the reflected ultrasonic waves generated at the boundary between the immersed and non-immersed parts of the ultrasonic propagation rod are detected, and the propagation time within the ultrasonic propagation rod is calculated. It is characterized by measuring the molten metal level.

Next, the present invention will be explained based on illustrated embodiments.

In the figure, reference numeral 1 denotes a continuous casting mold, into which molten metal 2 is supplied from a Kundinsh nozzle (not shown). A bracket 3 is fixed to the upper edge of the continuous casting mold 1, and a sensor 4 is attached to the bracket 3.

The sensor 4 includes an ultrasonic propagation rod 5, a flange 6 and a box 7 that are integrally fixed to the upper end of the ultrasonic propagation rod 5, and an upper end surface 10 of the ultrasonic propagation rod 5 that is biased by a spring 8 inside the box 7. The ultrasonic probe 9 is in contact with the ultrasonic probe 9. The lower part of the ultrasonic propagation rod 5 is immersed in the molten metal 2. Reference numeral 19 indicates foreign matter (molten metal, slag, etc.) attached to the surface of the propagation rod 5.

The ultrasonic propagation rod 5 is made of a material with excellent heat resistance, corrosion resistance, and ultrasonic propagation properties, such as poron nitride (boron nitride/BN) or zirconia (zirconium dioxide/Z).
Fine ceramics made from materials such as r0z) are suitable, and the shape may be a plate. Further, in the case of a rod, the cross-sectional shape may be polygonal, elliptical, etc. in addition to circular. In the case of a plate shape, the entire plate serves as a propagating body, so the ultrasonic waves propagated through the plate are particularly called plate waves. Since the ultrasonic propagation rod as used in the present invention includes a plate-shaped body, the ultrasonic wave as a rod wave also includes the plate wave.

Reference numeral 11 denotes an ultrasonic generator/receiver, which is connected to the ultrasonic probe 9 of the sensor 4 through an electric wire 12, and causes the ultrasonic probe 9 to emit ultrasonic waves toward the ultrasonic propagation rod 5. 1
Reference numeral 3 denotes an incident ultrasonic wave that is emitted, enters the ultrasonic propagation rod 5, and propagates.
The reflected ultrasonic wave 15 is reflected by the ultrasonic probe 9.
is input. When an object (here, the ultrasonic propagation rod 5) to which the ultrasonic waves are propagated is in contact with an object (here, the molten metal 2) that has a different ultrasonic transmission speed than that object, the contact portion (here, the molten metal 2) This is because there is a property of reflection at the boundary 14). Ultrasound reflected by foreign object 19 2
0 is also input to the ultrasound probe 9. The incident ultrasonic waves that are not reflected by the boundary work 4 continue straight, reach the lower end 17 of the ultrasonic propagation rod 5, are reflected there, and are input to the ultrasonic probe 9 as reflected ultrasonic waves 18. Ru.

FIG. 3 shows the display section 16 of the CR,T display.
The waveform displayed here is the received waveform of the reflected ultrasonic wave reflected and input to the ultrasonic probe 9.

Here, the first peak (to) is the reflected wave from the upper end surface 10. In addition, the upper end surface 10 and the lower end 17 of the ultrasonic propagation rod 5
The value obtained by dividing the distance by the propagation velocity (Vp) and doubling this value matches the time between (t2) and (tO), so (t2) is the reflected wave from the lower end 17. I understand that. Further, by appropriately setting the darkness value, the peak (t3) due to reflection from the foreign object 19 can be removed. Therefore, the reflected ultrasonic wave 15 from the surface (boundary 14) of the molten metal 2 to be measured can be detected without error at (tl) between them. ff17 Chi, molten metal level (
The distance between the upper end surface 10 and the boundary 14) is (tl) and (t
O) multiplied by the propagation velocity (Vp) is 2
It can be found by dividing by.

The above embodiment adopts a method of reading the reflected ultrasound 15 input to the ultrasound probe 9 from the display section 16 of the CRT display of the ultrasound generator/receiver 11. 11 can of course be connected to an electronic computer to automatically measure the molten metal level.

The ultrasonic generator/receiver 11 has a built-in known electric circuit for converting input reflected ultrasonic waves into a constant signal.

As explained above, according to the present invention, one end of the ultrasonic propagation rod is immersed in molten metal, and the ultrasonic wave is incident on the entire ultrasonic propagation rod from the other end as a bar wave,
We decided to measure the molten metal level based on the arrival time of this reflected wave. In this way, an ultrasonic propagation rod that is separate from the continuous casting mold is used to propagate the ultrasonic waves, and since the ultrasonic waves are propagated throughout the rod, the directivity of the ultrasonic waves is good. It is hardly affected by attached foreign matter such as. Therefore, it is possible to clearly detect the reflected ultrasonic waves from the boundary between the immersed part and the non-immersed part of the molten metal, so that the molten metal level can be easily and accurately measured. Further, since the measuring instrument used in the present invention can be made small and lightweight, it can be easily attached to the mold and does not interfere with the casting operation. Furthermore, by appropriately selecting the length of the ultrasonic propagation rod, the measurement width of the molten metal level can be increased, allowing for the observation of an increase in the molten metal level at the beginning of continuous casting, and the prevention of occasional overflow of molten metal. It also has the effect of being able to detect and prevent this.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a sectional view showing the ultrasound propagation rod and ultrasound probe shown in FIG. 1, and FIG. C in the ultrasonic generation receiver shown
FIG. 3 is an explanatory diagram showing a waveform appearing on the display section of the RT display. DESCRIPTION OF SYMBOLS 1... Continuous casting mold, 2... Molten metal, 4... Sensor, 5... Ultrasonic propagation rod, 9... Ultrasonic probe, 13... Incident ultrasonic wave, 14... ...Boundary, 15.18
...Reflected ultrasound. Patent Applicant Kawasaki Steel Co., Ltd. Agent Patent Attorney Tetsuya Mori Agent Patent Attorney Yoshiaki Naito Agent Patent Attorney Shimizu Authorized Agent Patent Attorney Submitted by Yuze

Claims (1)

[Claims] With one end of the ultrasonic propagation rod immersed in the molten metal in the continuous casting mold, ultrasonic waves are incident on the other end of the ultrasonic propagation rod as a bar wave, and the ultrasonic propagation rod is In a continuous casting mold, the molten metal level is measured by detecting the reflected ultrasonic waves generated at the boundary between the immersed part and the non-immersed part of the molten metal, and measuring the propagation time in the ultrasonic propagation rod. How to measure molten metal level.