JPS5844191B2 - Method for detecting molten metal level in container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting the liquid level of molten metal (hereinafter referred to as metal) stored in a molten metal storage container such as a ladle.

In general, various methods are known for measuring the liquid level of metal inside a container, as shown below, but all of them have drawbacks such as accuracy, measuring means, and durability of the detection end, and none of them are necessarily satisfactory. Ta.

By the way, let's talk about these: (1) Optical method (photoelectric conversion method) Direct observation of the molten metal surface (the interface between the inner wall of the container and the molten metal) from above the container with a television camera or using a photovoltaic cell. , which detects the radiant energy of molten metal as a change in brightness, but in high-temperature processes such as those used in ladle, slag inevitably floats to the surface of molten metal, or heat insulating materials are added, which makes it impossible to observe. In many cases, this is possible, and since the surrounding area is heated by the molten metal, the boundary surface is not clear and the detection accuracy is poor.

(2) Float type There is no float material that will not be corroded by molten metal (also slag,
Calibration (Calibration) Metal may adhere to the float and cause a change in float specific gravity.
arises the need for.

Therefore, there is no one that can withstand long-term use and provide stable accuracy.

(3) Levels are detected by creating a 0N OFF state in an electric circuit using an immersed electrode and molten metal, but the electrode wears out so much that it is impossible to use it for a long period of time, and the current pattern flowing through the electrode is This makes it difficult to determine the boundary point between slag and metal, and the detection accuracy is poor.

(4) Thermocouple method Several sets of thermocouples are embedded in the wall of the container to indirectly detect the metal level from changes in temperature distribution. However, embedding and wiring the thermocouples is difficult, and the Because the inner wall is made of firebrick, heat conduction is poor (detection accuracy is poor).

(5) Electromagnetic induction method (example of mold level meter using coil) (5-1)
Patent Application No. 47-25058 (Japanese Unexamined Patent Application No. 48-93539)
In the method of the above publication, a coil long in the depth direction is provided on the outer wall of the mold, and the coil is connected to a bridge circuit on one side of the impedance, so that changes in the height of the molten steel in the mold are detected by changes in the temperature of the mold wall. The level is detected by using the change in the magnitude of the eddy current generated in the mold due to the resulting change in the resistivity of the mold wall, which is not very accurate.

That is, since it is measured indirectly from the amount of variation in coil impedance due to temperature change, the temperature distribution at the metal boundary is not sharp and the determination is ambiguous.

Furthermore, since molding is a cooling process, the influence of cooling water is also significant.

(5-2) In the patent application No. 49-15040, one detection coil is buried near the outer skin of the intake vortex.
This is achieved by installing a parallel resonant circuit so that the rise and fall of the hot water level is detected as a change in the impedance of the detection coil.

However, this method detects when the hot water level acts on the detection coil, causing an overcurrent change, or when the metal temperature acts on the detection coil, changing the coil impedance. (with a large number of turns), you will not be able to obtain a signal change, and if you want to obtain a sufficient signal, you will have to bring it closer to the molten steel.

On the other hand, in the case of this type, the main factor in the change in coil impedance is due to the temperature change on the container wall, and as mentioned in (5-1) above, the temperature distribution on the wall is not sharp, and therefore the accuracy is affected. Good detection is not possible.

The present invention was developed in view of the above-mentioned situation, and its characteristics are that it generates a magnetic field by passing a high-frequency current through the transmitting end buried in the ceiling-resistant side wall of the container, and The purpose is to detect the induced voltage at the side wall buried receiving end, compare the detected value with a preset level value to determine the difference, and determine the molten metal level from the difference signal value.
Molten metal level detection inside a container with a simple device configuration that can detect metal levels with high accuracy regardless of operating conditions, and also makes it possible to improve the maintainability of the detection device by extending the life of the detection end. The purpose is to obtain equipment.

An embodiment for carrying out the present invention will be described below based on the drawings.

1 is the ladle, M is the metal stored in the ladle, S is the slag floating on the metal, 1a is the side wall of the ladle, 2 is the detection end of the metal level, and the transmitting end 2a and the detection end 2b are respectively attached. It is buried in the side wall of the pot, preferably at the same level.

As shown in FIG. 4, this detection end is made by winding a heat-resistant coil 3b around a fire-resistant insulating coil bobbin 3a and covering it with, for example, a recrystallized heat-resistant insulating tube so that the heat-resistant strands do not come into contact with each other. There is.

4 is a high frequency oscillator, and the oscillation end (
It is connected to the transmitting coil (transmitting coil) 2a, and constitutes a transmitting system.

The receiving side (receiving coil) 2b is provided within the magnetic field of the transmitting end 2a and is connected to a level display 9 via a high frequency tuning amplifier 6, a rectifier circuit 1, and a level comparator 8, and 10 is a level setting device. It is connected to the level comparator 8 and constitutes a receiving system.

Next, a case will be described in which the metal level in the container is detected using the above-mentioned device.

A magnetic field is generated by passing a high frequency current from the high frequency oscillator 4 to the oscillation end 2a via the high frequency amplifier 5.

Since the receiving end is within the magnetic field, it detects the induced voltage value that differs depending on the receiving end and the object facing the receiving end, such as metal, slag, or an air layer, and performs signal processing by the receiving system. Go and detect the metal level.

For example, as shown in FIG. 1, when the level of the metal M in the ladle 1 is higher than that of the detection end 2 (the facing object is metal M), the induced voltage at the reception end 2b decreases, As shown in FIG. 5a, the voltage is low V1.

Subsequently, when the metal M in the ladle is tapped and the object facing it is displaced from the metal layer to the slag layer, the induced voltage at the receiving end 2b increases from vl to V2, and this voltage v2 is the slag layer. This shows that the rising point of the voltage V1 to V2 is the true metal level.

The level comparator 8 of the reception system receives the set voltage V of the level setter 10.

is set under the condition that Vl<vo<V2, so when the induced voltage is input, the level comparator changes at the point where the induced voltage value shifts from vl to v2 as shown in Figure 5. 8 becomes an ON level, which is outputted and inputted to the level display 9, and the operator is notified of the presence of metal at a preset detection end position by means of notification such as lighting a lamp or sounding a buzzer.

In addition, the signal shown in Figure 5 is from the metal M outflow control valve (
(not shown) can also be used as a control signal.

Furthermore, in Fig. 5a, the displacement from V2 to V3 is the induced voltage output when the slag layer is displaced from the air layer, and the level of the slag layer S is also determined from the change in the induced voltage. be.

In the above embodiment, a case is described in which a pair of detection ends (a transmission end and a reception end) are used, but the invention is not limited to this, and multiple sets can be arranged along the vertical direction of the ladle to enable detailed metal level management. can be done.

For example, if a detection end is provided at the lower limit of the ladle, metal M
In addition to being able to predict the amount remaining at the end of the outflow, it is also possible to accurately grasp the timing of opening and closing the ladle valve, enabling stable operation, which has a great effect on actual operation.

In addition, since the detection end used in carrying out the present invention is made of a heat-resistant wire covered with an insulating tube as described above, it is insulated even if carbon in the melt or other impurities enters the coil bobbin during long-term use. Since it does not cause defects and has high durability, it has an extremely large effect on equipment maintenance.

By constructing and using the present invention as described above,
The metal level can be detected with high precision even in adverse environments such as the presence of metal objects floating on the surface of the hot water, high heat, dust, etc., and the life of the detection end can be extended, which is effective for equipment maintenance and stabilizes operations. The contribution it makes to the development of society is extremely important.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing the arrangement of a detection end for implementing the present invention. FIG. 2 is a plan view showing an embodiment of a level detection device for carrying out the present invention. FIG. 3 is an enlarged vertical sectional view of the main part of FIG. 1. FIG. 4 is an external view showing the configuration of a detection end used for implementing the present invention. FIG. 5 is a waveform diagram showing the effect of the present invention.

Claims (1)

[Claims] 1. Generate a magnetic field by passing a high-frequency current through a transmitting end buried in the fireproof side wall of the container, detect the induced voltage at a receiving end buried in the side wall within the magnetic field, and set the detected value to a preset level value. A method for detecting the level of molten metal in a container, characterized in that the level of molten metal in a container is determined by comparing the values of