JPH02127952A - Method for detecting level of molten metal in mold - Google Patents

Abstract

PURPOSE:To easily and surely detect molten metal level in a mold with an instrument having low cost by coiling detection coil to a mold in a continuous casting machine, applying high frequency voltage and measuring variation of impedance or current value. CONSTITUTION:The voltage is supplied into the detection coil 14 coiled to the mold 2 from an electric source device 18. The voltage and the current are detected with the sensors 22, 23 and transmitted to the control device 24. As the impedance or current value read from these electric signals is varied with the molten metal level, the molten metal level is obtd. with calculation. Relation between the molten metal level and the impedance or the current value is to be beforehand calibrated. By using the instrument having low cost and utilizing skin effect phenomenon of a solenoid, the molten metal level in the mold can be easily and surely detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a molten metal in a mold configured to accurately detect the amount of molten metal in a mold in a continuous casting machine without being interfered with by ambient conditions. This invention relates to a level detection method.

[Conventional technology]

A method for detecting the molten metal level (meniscus) in a mold (referred to as a mold) of continuous casting equipment for billets, which usually has a round or square cross section, is disclosed in Japanese Patent Laid-Open No. 4
A method that measures the molten metal level by embedding a thermocouple in the mold and detecting temperature changes depending on the presence or absence of molten metal, as disclosed in Publication No. 8-101323, and a method that uses an industrial television camera are used. It is being

However, the thermocouple method is not used much because it handles minute voltages as a signal medium and is easily interfered with by noise and difficult to adjust, and requires time and effort to maintain.The industrial TV camera method is more common. .

Figure 7.8 is a diagram showing an example of an industrial television camera system.

In the figure, molten metal 3 flowing down from a tundish 1 into a mold 2 is cooled within the mold 2 and gradually solidifies from the outer periphery to become a slab 4. Reference numeral 5 denotes an industrial television camera, which is installed diagonally above the mold 2 and photographs the inside of the mold 2.

The photographed image is displayed on the monitor 6, and the image shows a clear contrast in brightness between the molten metal part and its surroundings, for example, the molten metal part is white and the surrounding area 8 is black. Therefore, the boundary 9 between white and black indicates the level of molten metal in the mold 2, and the position can be determined according to its height.

If this signal is processed by the control device 10, the level of the molten metal can be detected.

[Challenges to be solved by the present invention] However, in the above-mentioned conventional example, the disadvantages of the thermocouple method are as mentioned above. ) Maintenance is time-consuming, (
4) The problem is that level detection is discontinuous and stepwise, making precise level detection impossible. In particular, the drawback of (4) is serious, and in the end, this method is only used to detect the upper and lower limits.

On the other hand, the method using the industrial television camera shown in FIGS. 7 and 8 has the following problems. That is, (1) the level detection range is narrow; This is because the tray 1 is located directly above the mold 2, and the camera can only be mounted diagonally above the mold, so the mounting angle θ becomes small and the field of view 12 becomes narrow (FIG. 8). (2) Easy to malfunction. This is because the camera shadows everything in its field of view at the same time, so if there is flame or splatter from the mold scene, the level will be unclear. Therefore, these must be blown away by the air purge 13. In addition, there are various operations on the mold, and when powder is added and adjustment operations using jigs are performed, all of these operations are also photographed and the images overlap, making it difficult to accurately detect the level. (3) Equipment is expensive. Since this method requires complex signal processing and control, the equipment related to these is expensive.

Furthermore, JP-A-62-166065 discloses a method of measuring from the side of the mold using a gamma ray type level meter and a method of performing on-site measurement using an eddy current type level meter during continuous casting of slab materials. , γ-ray level meters are very expensive and are not used very often. Furthermore, a vortex level meter is a method of measuring by installing it above the hot water surface, but in the case of billet material, the upper opening of the mold is narrow, making it impossible to install a vortex level meter.

The present invention has been made in view of the above-mentioned conventional problems, and aims to solve the above-mentioned problems by, for example, providing a detection coil in the mold.

[Means to solve the problem]

This invention involves winding a detection coil around the mold of a continuous casting machine,
The amount of molten metal in the mold is detected by applying a high frequency voltage to the detection coil and measuring changes in impedance or current value of the detection coil during continuous casting of slabs. This is a level detection method.

[Effect]

Since this invention is constructed as described above, when the detection coil is wound in a solenoid shape as shown in Fig. 5, the equivalent circuit seen from terminals 15 and 16 is expressed as shown in Fig. 6 (a). . Here, R1 is coil resistance and XI is coil reactance.

When the metal 17 is inserted into this solenoid-shaped detection coil as shown in FIG. 5(B), the equivalent circuit becomes FIG. 6(0). Here, R2 is the resistance of the metal object 17, and x2 is its reactance. These R2 and X2 vary depending on the length of the metal object 17.

The impedance of the detection coil 14 now viewed from the terminals 15 and 16 is as follows. Normally, in a solenoid, XI>Rz, so if R1 is ignored in the above equation, the impedance is Rz +
J (L + Xz). As this circuit, a circuit as shown in FIG. 4 is constructed. Here, the power source 18 uses an AC power source, and the frequency of the power source must be appropriately selected in consideration of the skin effect. Furthermore, if a constant voltage power supply is used in this circuit, and if the voltage is defined as v1 current, the change in Z can be understood as a change in current from the relationship V=ZI.

In this way, the current flowing through this coil or the impedance changes depending on the length of the metal inside the detection coil 14.
This principle can be used to detect the level of molten metal within a mold. Once the relationship between the level of the molten metal and the above-mentioned current value is calibrated in advance by conducting an experiment, the level of the molten metal can be known from then on simply by reading the current value.

〔Example〕

1 to 3 are diagrams showing embodiments of the present invention.

FIG. 1 is a partial view of a continuous casting machine having a mold for detecting the level of molten metal, in which voltage is supplied from a power supply 18 to a detection coil 14 via a wiring 20.

Also, since the mold 2 vibrates up and down during operation,
A part of the wiring is provided with a movable part 21.

In this embodiment, the power supply voltage is 50V and the frequency is about 1kHz. The voltage applied to the detection coil 14 and the flowing current are detected by the sensors 22 and 23 and sent to the control device 24 as a signal. Therefore, the impedance can be determined using these electrical signals, or the current value can be read and the level of molten metal can be determined by calculation. However, as explained in the section on the effect above, the relationship between the level of molten metal and the impedance or current value may be calibrated in advance.

Further, FIG. 1 above shows an example in which a mold containing a solenoid, which is a detection coil, is used. This mold is the second
As shown in the figure.

Since the billet mold 2 has a round or square cross section (FIG. 2(b)), it is easy to wind the solenoidal coil therein. Figure 3 shows an example in which a coil is wound around the outside of the mold. In this case, the thickness of the mold is large, so there is a risk that the magnetic flux will not reach the molten metal due to the skin effect. The power supply frequency may be selected as required.

[Effects of the Invention] As explained above, according to the present invention, there is no problem unlike the conventional TV camera monitor type, and there is no need for very expensive equipment such as a gamma ray type level meter. First, by using an inexpensive device and utilizing the skin effect phenomenon of a solenoid, the level of molten metal in the mold can be easily and accurately determined.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the apparatus for use in the present invention, and FIG.
Figure (a) is a side view of the mold with a built-in detection coil in Figure 1, figure (b) is a view taken in the direction of arrow A in figure (a), and Figure 3 is a side view of the mold with a built-in detection coil. Figure 4 shows the equivalent circuit of the mold part in Figure 1, Figure 5 (A) shows the detection coil, Figure 5 (B) shows the detection coil with a metal object inside,
Figure 6 (a) and (b) are respectively shown in figure 5 (a) and (b).
7 is a level detection device used in the conventional method, and FIG. 8 is an explanatory diagram of the operation of the device shown in FIG. 7. 2...Mold, 14...Detection coil (solenoid), 4...Billet. Patent applicant: Kawasaki Steel Corporation Representative Patent attorney: Tetsuya Mori

Claims (1)

[Claims] (1) A detection coil is wound around the mold of a continuous casting machine, and a high frequency voltage is applied to the detection coil during continuous casting of slabs, and changes in the impedance or current value of the detection coil are measured. A method for detecting the level of molten metal in a mold, the method comprising detecting the amount of molten metal.