JPS6017701Y2 - mold level meter - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a mold level meter used, for example, in a continuous casting process, and particularly relates to an improvement of a magnetic mold level meter.

In the continuous casting process, in order to maintain the quality of the steel products being cast, it is required to control the molten metal level in the mold so that it is always within a certain level range.

Due to these demands, for example, multiple temperature sensors are installed on the mold wall, such as a temperature sensor type mold level meter that measures the hot water level position from the temperature distribution of the mold wall, or a temperature sensor type mold level meter that measures the hot water level position from changes in radiation transmittance. Radiation type mold level meters, and magnetic mold level meters that detect the position of the hot water level by forming an alternating magnetic field within the mold and detecting the position of the hot water level by utilizing the changes in the state of the magnetic field as the position of the hot water level changes, have been proposed. has been done.

Among the mold level meters for each of these formations, it is possible to continuously measure the hot water level position over a relatively wide range.
Magnetic mold level meter is excellent.

A conventional magnetic mold level meter will be explained using FIG.

In the figure, 1 shows a mold made of a steel plate, and 2 shows the surface of molten steel.

In a conventional mold level meter, a pair of coils 3 and 4 are installed at the upper end of a mold 1, and one of the coils 3 is operated as an excitation coil and the other as a detection coil.

That is, AC power of about 1 kHz, for example, is applied to the coil 3 from an excitation source 5, and an AC magnetic field 6 is formed within the mold 1 by this AC power.

The alternating current magnetic field 6 intersects the mold wall 1a of the mold 1 and generates eddy currents 7 in the mold wall 1a.

The eddy current 7 generates a secondary magnetic field 8, which is detected by the detection coil 4, subjected to amplification, span adjustment, etc. by the signal processing circuit 9, and outputted as a measurement signal e to the output terminal 10.

The relationship between the measurement signal e and the position of the hot water level 2 exhibits a change in the normal measurement region, as shown by curve A in FIG. 2, in which the lower the position of the hot water level 2, the larger the measurement signal e becomes.

The reason for this is that the lower the hot water level 2, the lower the mold 1.
The wall surface 1a of the mold wall 1a is largely exposed, and therefore the effective area for interaction between the alternating current magnetic flux generated by the excitation coil 3 and the mold wall 1a becomes large, which increases the area in which the eddy current 7 is distributed on the mold wall 1a. It is thought that the secondary magnetic field 8 becomes stronger as the temperature increases.

In the conventional magnetic mold level meter, which allows the position of the hot water level 2 to be determined from the value of the measurement signal e by determining the curve A in advance, as described above, the excitation coil 3 and the detection coil 4 are connected to the mold 1. Since the coils are arranged in parallel at the upper end of the coils, the primary magnetic flux 6 generated by the excitation coil 3 directly interlinks with the detection coil 4.

Therefore, the detection coil 4 detects the primary magnetic flux 6 in addition to the secondary magnetic field 8, and has the drawback of being greatly influenced by this primary magnetic field.

In other words, in the measurement signal e, the signal due to the primary magnetic field 6 is at most 8
It may reach around 0%.

The signal due to this primary magnetic flux 6 is an unnecessary signal, and it is originally desirable that this signal not be mixed into the measurement signal e.

In other words, if the primary magnetic field 6 changes due to the surrounding conditions, such as a change in the position of the mold cover or the movement rate of the Dandesho car, the signal component due to the primary magnetic flux 6 will also change, and this fluctuation will cause an error in the measured value. .

However, since the detection coil 4 is required to detect the secondary magnetic field 8, it cannot be magnetically shielded.

Therefore, conventionally, the rate at which the primary magnetic field 6 directly interlinks with the detection coil 4 is reduced by installing the excitation coil 3 and the detection coil 4 as far apart as possible.

Furthermore, for this reason, there is also the disadvantage that this electromagnetic mold level meter cannot be installed in small molds.

The purpose of this invention is to provide a new structure of a detection section that eliminates the influence of the primary magnetic field from the detection coil and obtains a signal directly related to the hot water level.

Therefore, according to this invention, since the signal obtained from the detection coil is not mixed with the signal due to the primary magnetic field, it is possible to obtain a measurement signal that is not affected by the primary magnetic field.

Therefore, improvement in measurement accuracy can be expected. An embodiment of this invention will be explained in detail below using FIG. 3.

In FIG. 3, parts corresponding to those in FIG. 1 will be described with the same reference numerals.

In this invention, the value of the eddy current 7 flowing through the wall of the mold 1 is directly measured, and the position of the hot water level 2 can be determined from the value of the eddy current 7.

Therefore, in the example shown in FIG. 3, a window 11 is formed on the wall of the mold 1, and the eddy current detection means 12 is attached to the mold wall using this window 11.

In the example shown in FIG. 3, the eddy current detection means 12 is constituted by a magnetic core 13 surrounding a part of the mold wall and a detection coil 14 wound around the magnetic core 13.

Further, the magnetic core 13 is covered with a magnetic shield case 15 as shown in FIG. 4, for example, so as to magnetically shield the current detection means 12 from the primary magnetic field 6 generated from the excitation coil 3.

According to this structure, when an eddy current 7 flows through the part of the mold wall surrounded by the magnetic core 13, a magnetic flux φ proportional to the eddy current 7
A signal corresponding to the eddy current 7 circulating through the magnetic core 13 can be obtained from the detection coil 14.

As described above, the eddy current 7 exhibits a change that becomes larger as the position of the molten steel level 2 is lower.

In other words, the larger the mold wall is exposed, the larger the area of intersection between the primary magnetic field 6 and the mold wall becomes.

As a result, the area over which eddy currents are distributed in the molded wall soil becomes large, and it can be considered that the total sum of eddy currents becomes large.

In fact, it was possible to obtain a measurement signal from the detection coil 14 that had the same characteristics as the curve A shown in FIG. 2 with respect to changes in the position of the hot water level 2.

However, because the signal due to the primary magnetic field 6 is not superimposed on this signal due to the effect of the magnetic shield case 15, a measurement signal with a good S/N ratio could be obtained.

Therefore, even if there is a magnetic change around the mold 1, for example, the measured value is unlikely to change, and highly accurate measurement can be performed.

Although the above description shows the case where the window 11 is formed directly on the mold wall, in reality, for example, as shown in FIG. It is also possible to form a notch 17 on the lower side of this block 16, use this notch 17 to attach the eddy current detection means 12 so as to surround the block 16, and then attach the block 16 to the upper side of the mold 1. good.

Even in this case, by electrically connecting the block 16 and the wall of the mold 1, a part of the eddy current 7 flowing through the mold wall flows through the block 16, and changes in the eddy current 7 can be detected. , it can be easily set into the mold currently in operation.

Further, in the embodiment shown in FIG. 3, the magnetic core 13 is used for the eddy current detection means 12, but the detection coil 14 may be an air-core coil as shown in FIG.

By making the detection coil 14 an air-core coil, there is an advantage that the influence of the temperature characteristics of the magnetic core can be eliminated.

Further, as shown in FIG. 7, a magnetically sensitive element such as a Hall element may be attached to the upper surface of the mold wall, and the eddy current detecting means 12 may be constituted by this magnetically sensitive element.

By using a magnetically sensitive element in this manner, an advantage is obtained in that eddy currents can be detected without forming a window 11 on the mold wall.

As described above, according to this invention, there is no influence from the excitation magnetic field, and therefore highly accurate measurement can be performed.

In addition, since it is not affected by the excitation magnetic field, the excitation coil 3 and the eddy current detection means 12 can be installed close to each other, making it possible to obtain a mold level meter that can be applied to small molds, and its effect is extremely large in practical use. It is.

[Brief explanation of the drawing]

Figure 1 is a perspective view to explain a conventional magnetic mold level meter, Figure 2 is a graph to explain its operation,
FIG. 3 is a sectional view showing one embodiment of this invention, FIG. 4 is a perspective view showing an example of a shield case used in this invention, FIG. 5 is a perspective view showing another embodiment of this invention, and FIG. The drawings and FIG. 1 are a sectional view and a perspective view showing another embodiment of the main part of this invention. 1: Mold, 2: Hot water surface, 3: Excitation coil, 12: Current detection means, 15: Shielding means.

Claims (1)

[Scope of utility model registration request] A mold level meter comprising an excitation coil that distributes a primary magnetic flux on a conductive mold wall, and a current detection means that detects an eddy current flowing in the conductive mold wall.