JP2001050796A - Molten metal level measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an electrode from bending and poor measurement due to crossing from generating by coating the part of the electrode contacting with molten metal with insulating material of lower melting point than the molten metal. SOLUTION: This electrode is constructed so that electrode bars 27, 28 are fitted to electrode holders 25, 26, and the extreme end parts of the electrode bars 27, 28 are soaked in molten metal in a vessel 11. When the molten metal is molten steel 14, it is desirable to use silcone rubber or polyolefin for insulating material. For example, in the case of using silicone rubber, the volumetric specific resistance is 2×1015 Ωcm to be larger than 2×10-5 Ωcm of molten steel 14, it can be perfectly insulated, and even when conductive material covers the surface of the molten steel 14, a signal route is not changed. A signal generated by a pseudorandom signal generator propagates in the electrode bar 27, returns into the electrode bar 28 through the vicinity of the surface of the shortest route of the molten steel 14, and by measuring a time up to return of the signal, the surface level of the molten steel is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to
The present invention relates to a molten metal level measuring device that immerses a book electrode and measures the molten metal level based on the time required for a signal to propagate from one electrode to the other electrode through the molten metal.

[0002]

2. Description of the Related Art In a continuous casting facility, the operation is stabilized and the quality of a cast product is improved by controlling the level of molten metal in a mold. In particular, keeping the level of the molten metal constant is indispensable for improving the surface properties of the cast product, and various measuring devices for measuring the level of the molten metal have been proposed and used. For example, there are an electromagnetic induction type range finder, a range finder using radiation, an optical range finder, and the like.

[0003] In these distance measuring systems, emphasis has been placed on distance measurement in a relatively narrow range, mainly for the purpose of controlling the level of molten metal in a steady state. Therefore, measurement of displacement in a wide range such as the entire mold (from the lower end to the upper end) has not been considered much.

However, in recent years, in the movement for automation of equipment and further improvement of product quality, control of molten metal level at the beginning of casting, that is, until molten metal reaches a predetermined level, has been emphasized. . Therefore, it is necessary to measure the molten metal level at the beginning of casting, but in this case, the displacement of the molten metal level is large, and it is difficult to measure by the above-described method.

Therefore, research and development are being pursued in search of these improvements and new systems. As such a technique, an ultrasonic method, an electromagnetic wave method, and the like have been proposed. inside that,
The method using a pseudo-random signal has attracted attention because distance measurement is possible even in various noisy environments such as a continuous casting facility.

For example, Japanese Patent Laying-Open No. 2-145985 proposes a distance measurement method using two pseudo-random signals having the same pattern and slightly different frequencies. this is,
In this method, a pseudo-random signal is transmitted from an antenna, and a distance is measured from a time delay of a reflected wave.

Japanese Patent Laid-Open Publication No. Hei 2-98868 proposes a technique for transmitting a pseudo-random signal on a carrier wave instead of transmitting the pseudo-random signal directly from an antenna in a similar distance measurement method. This is a technique of selecting an appropriate wavelength according to the use environment by using a carrier wave.

[0008] Japanese Patent Application Laid-Open No. Hei 7-119130 discloses that 2
There has been proposed a technique of immersing a book electrode and transmitting a pseudo-random signal therein to measure a distance. According to this technique, it is preferable to use a metal having a higher melting point than the molten metal as the electrode, or to automatically rewind (the electrode) into the molten metal, and to use the same material as the molten metal for the electrode. It states that melting does not affect the components of the molten metal.

In the technique described in Japanese Patent Application Laid-Open No. H11-6756, the electrode is taken into the solidified shell of the slab and dragged into the molten metal by setting the melting point of the electrode material lower than that of the molten metal. Is preventing that. Further, according to this technique, if the distance between the two electrodes exceeds twice the maximum amount of deflection of the electrodes due to the flow of the molten metal, it is possible to prevent the two electrodes from bending and coming into contact with each other to cause a short circuit. Has been described.

[0010]

In the techniques described in Japanese Patent Application Laid-Open Nos. 2-145985 and 2-98685, it is necessary to transmit a signal for distance measurement (pseudo-random signal) from an antenna. However, in general, in a narrow space such as in a mold, it is difficult to separate the reflection from the molten metal level due to the influence of multiple reflection of radio waves. Further, since various devices for casting are installed around the upper part of the mold, there is also a problem that there is no space for installing the antenna.

The technique described in Japanese Patent Application Laid-Open No. Hei 7-119130 can solve the problem caused by using radio waves as in the prior art described above. Easy to be taken into. When the electrode is integrated with the slab as described above, the electrode is dragged together with the sensor into the molten steel at the time of starting the slab drawing, so that the subsequent measurement becomes impossible and the slab itself becomes defective. On the other hand, if the electrodes are not taken into the solidified shell of the slab, the two electrodes may bend due to the strong molten steel flow discharged from the immersion nozzle in the mold, and the electrodes may intersect. In this case, the distance measurement value is a value up to the short-circuit point, and the measurement of the molten steel level is completely impossible.

The technique described in Japanese Patent Application Laid-Open No. 11-6756 can solve the problems caused by the integration of the electrode and the slab and the intersection of the electrodes as in the above-mentioned prior art. Errors are likely to occur due to disturbance. For example, introduction of a conductive material different from a molten metal such as powder causes disturbance. As described above, when disturbance occurs during the rise of the molten metal in the mold, the signal propagation path changes (that is, the signal propagation time changes), which causes a measurement error.

FIG. 4 shows the situation near the surface of molten steel in the case where the measurement is defective. When the powder charged around the electrode melts, a powder film is formed on the surface of the molten steel as shown in FIG. 4, and a signal propagates on the surface layer. As a result, since the length of the signal propagation path changes, an error occurs in the distance measurement value.

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and it is possible to prevent a measurement failure due to bending or crossing of an electrode and to measure a molten metal level which can be measured even when there is a disturbance near the electrode. An object of the present invention is to provide a measuring method of

[0015]

The above object is achieved by the following invention. The present invention relates to a molten metal level measuring device that immerses two electrodes in a molten metal and measures the level of the molten metal by the time that a signal propagates from one electrode through the molten metal to the other electrode. A molten metal level measuring device, wherein a portion of the electrode that contacts the molten metal is coated with an insulating material having a lower melting point than the molten metal.

According to the present invention, the influence of a conductive substance such as powder floating on the surface of the molten metal is removed by coating the portion of the electrode which comes into contact with the molten metal with an insulating material. Further, after the coated electrode comes into contact with the molten metal, the insulating material has a lower melting point than the molten metal and thus melts and floats on the surface of the molten metal. Below the surface of the molten metal (molten metal level), the electrode and the molten metal come into direct contact, and a signal propagation path is formed at the position of the molten metal level.

In addition, the position where the electrode is coated is such that all portions that come into contact with the molten metal are covered. In this way, disturbances above the molten metal level can be blocked, and the molten metal level can be measured accurately.

It is desirable that the melting point of the material of the electrode body (the contents of the coating) be lower than that of the molten metal. Thereby, the electrode immersed in the molten metal is gradually melted from the tip portion, and it is possible to prevent the electrode tip portion from being taken into the solidified shell accompanying the solidification of the molten metal.

[0019]

FIG. 1 is a view showing an example of an embodiment of the present invention, particularly showing an electrode portion. In this figure, the tips of the electrode rods 27 and 28 are immersed in the molten metal 14 in the container 11. Electrode is electrode rod 2
7, 28 are attached to the electrode holders 25, 26.

When the molten metal 14 is molten steel, it is preferable to use silicon rubber or polyolefin as the insulating material.
For example, if silicon rubber is used, its volume resistivity is 2 × 10 ¹⁵ Ωcm, which is sufficiently larger than 2 × 10 ^-5 Ωcm of molten steel, and can be completely insulated. Therefore,
Even if the conductive material covers the surface of the molten steel, the signal path does not change.

FIG. 2 is a diagram showing an example of an embodiment of a signal processing system. Here, a measurement method using a pseudo random signal is used. The first and second pseudo-random signal generators 21 and 22 generate pseudo-random signals having the same pattern and slightly different frequencies. The signal generated by the first pseudo-random signal generator 21 propagates through the electrode rod 27 attached to the electrode holder 25.

Next, the signal propagates near the surface, which is the shortest path of the molten metal 14, and returns inside the electrode rod 28 attached to the electrode holder 26. By measuring the time until this signal returns, the surface level of the molten metal 14 is determined. Here, in order to increase the accuracy of time measurement, the following signal processing is performed using two signals having slightly different frequencies.

First, the first multiplier 23 outputs the product (first multiplied value) of the two pseudo-random signals generated by the pseudo-random signal generators 21 and 22. At the same time, the second multiplier 24 multiplies the product of the signal generated by the first pseudo-random signal generator 21 and returned from the molten metal 14 by the signal generated by the second pseudo-random signal generator (second multiplication). Value). The filters 31 and 32 are low-pass filters or band-pass filters, and remove high-frequency components of the first and second multiplication values.

Here, the pseudo random signal generators 21 and 2
The frequency of the signal generated in 2 is f, f + Δf, and the number of bits per period of the pseudo random signal is k (same pattern)
And The period of the pseudo-random signal is k / f, k / (f
+ Δf). Since these two pseudo-random signals have the same pattern every cycle k / Δf, their multiplication value also shows a peak every cycle k / Δf.

The peak positions of the first and second multiplied values are determined by the phase difference between the two signals input to the multiplier. When the phase difference is the same, the peak positions of the two multiplied values are the same. From the shift between the peak positions of the first and second multiplication values, the first
The phase difference between the signal input to the second electrode and the signal returned to the second electrode can be found. The position of the molten metal level can be measured by obtaining the signal propagation time from the phase difference and converting it to a distance.

When the returned pseudo-random signal (phase difference) is delayed by one cycle (k / f), the peak of the second multiplied value is one cycle (the multiplied value of the multiplied value). Repetition cycle: k / Δf). As described above, since the periods of the first and second multiplication values are expanded to f / Δf times the period of the pseudo random signal, the phase difference, the signal propagation time, and the measurement accuracy of the position of the molten metal level are measured. Is improved by f / Δf times.

[0027]

EXAMPLE The level of molten steel in a mold in an early stage of casting of a continuous steel casting machine was measured using a level measuring apparatus having an electrode of the present invention. The electrodes had the configuration shown in FIG. 1 described above. A 5 mmφ rod made of SUS was used for the electrode material, and silicon rubber was used for the insulating material. The measurement results are shown in FIG. For comparison, the measurement results obtained when using only SUS electrodes (without insulating material coating) were used.
It is shown in FIG.

As is clear from FIG. 3 (a), it can be seen that the molten steel level gradually increases in the inventive method. On the other hand, in the comparative method, the measured value sharply rises during the rise of the molten steel level (in the circle in FIG. 3B). This indicates that the level of the upper molten steel fluctuated because the lubricating powder supplied to the upper surface of the molten steel was melted and the signal propagated through that portion as in the case of the above-described prior art (FIG. 4).

As described above, the level measuring apparatus of the present invention performs stable and accurate measurement even when a conductor other than molten metal exists as a disturbance, such as in the early stage of casting of a continuous casting machine. be able to.

[0030]

According to the present invention, by covering the portion of the electrode immersed in the molten metal with an insulating material having a lower melting point than the molten metal, it is possible to eliminate the influence of disturbance in the portion above the molten metal level. it can. Further, since the insulating material has a lower melting point than the molten metal, the insulating material in the molten metal is melted and removed, and a signal propagation path is formed at a position at the level of the molten metal. As a result, a stable measurement of the molten metal level can be performed even in an unsteady state such as at the beginning of casting.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an embodiment (electrode portion) of the present invention.

FIG. 2 is a diagram illustrating an example of an embodiment of a signal processing system.

FIG. 3 is a diagram showing a measurement result of a molten steel level in a mold in an early stage of casting. (A) Invention method (b) Comparative method

FIG. 4 is a diagram showing a situation near the surface of molten steel when a measurement failure occurs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Container 13 Nozzle 14 Molten metal 15 Powder 21, 22 1st, 2nd pseudorandom signal generator 23, 24 1st, 2nd multiplier 25, 26 Electrode holder 27, 28 Electrode rod 29, 30 Insulating material ( Coating) 31, 32 Filter

Claims (1)

[Claims] Claims 1. An electrode is immersed in a molten metal,
In a molten metal level measuring device that measures the level of a molten metal by the time that a signal propagates from one electrode through the molten metal to the other electrode, an insulation that has a lower melting point than the molten metal is provided at the part of the electrode that contacts the molten metal A molten metal level measuring device characterized by being coated with a material.