JPH05297012A - Method and device for measuring of meniscus flow velocity of molten metal - Google Patents

Abstract

PURPOSE:To measure the flow velocity of a meniscus part of a molten metal with a flow directly below a free surface without any contact and with a high accuracy and provide a compact device for it. CONSTITUTION:A primary coil 1 is laid out and first and second secondary coils 2a and 2b are laid out on both sides, while sandwiching the primary coil 1, vertically to the flow direction directly above the meniscus with a flow directly below a free surface. An AC current is applied to the primary coil 1 for forming a line of force 4 and then meniscus flow velocity is detected from the phase difference of electromotive force which is generated at the secondary coils 2a and 2b due to distortion of the line of force 4 caused by the flow directly below the free surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to measurement of a flow velocity of a molten metal having a free surface just below the free surface, and more particularly to a method and an apparatus for continuously measuring the flow velocity in a non-contact manner.

[0002]

2. Description of the Related Art When refining or casting molten metal, the flow of molten metal is an important control target factor from the viewpoint of product quality and reaction efficiency. Particularly, the flow velocity of the free surface, which is the contact interface with the refining flux and the heat insulating material, is important, and proper refining and casting can be performed by properly controlling this flow velocity.

In general, molten metal is at a high temperature, and flow velocity measurement using a normal flow velocity sensor such as a Pitot pipe cannot cause various problems such as clogging of the pipe due to solidification.

For this reason, for example, "Iron and Steel '82 -S92.
0 "and JP-A-59-104512, the rod is immersed in the molten metal through the free surface,
A flow velocity measuring method has been proposed in which the dynamic pressure received by the rod is detected by a strain gauge installed on a support arm of the rod. However, in this method, since the rod needs to be directly immersed in the molten metal, deformation of the rod due to solidification adhesion of the metal, melting loss, etc. is unavoidable.

As a non-contact flow velocity sensor, Japanese Patent Application No. 1-
As seen in No. 134329, a meniscus of a weld metal, in which a primary coil is arranged directly above the meniscus in parallel with the flow direction and secondary coils are arranged on both sides of the primary coil, and the meniscus flow velocity is detected from the electromotive force difference generated in each secondary coil. A velocity measurement method has been previously proposed by some of the inventors of the present application.

[0006]

However, this electromotive force difference method has a problem that the electromotive force difference with respect to the flow velocity is small. For this reason, it is necessary to shorten the surface distance between the sensor and the meniscus surface, and it is difficult to secure the distance between the sensor and the molten metal surface. Further, it is difficult to increase the number of coil windings in order to eliminate the above-mentioned drawbacks in terms of downsizing the sensor.

An object of the present invention is to provide a measuring method capable of measuring the flow velocity of the meniscus portion more accurately in a molten metal having a flow just below the free surface, and a compact measuring device capable of measuring it with high precision. ..

[0008]

In order to achieve the above object, according to the measuring method of the present invention, a primary coil is provided immediately above a meniscus having a flow just below a free surface and perpendicular to the flow direction,
Secondary coils are arranged on both sides of the primary coil perpendicularly to the flow direction, alternating current is applied to the primary coil to form lines of magnetic force, which appear due to the distortion of the lines of magnetic force due to the flow just below the free surface, resulting in a flow velocity. The flow velocity is detected from the corresponding phase difference of the electromotive force between the secondary coils.

The apparatus of the present invention for performing such detection is a primary coil (1); first and second secondary coils (2a, 2b) provided on both sides of the primary coil (1); The primary coil (1)
An AC power supply (7) connected to the; and a phase difference between the electromotive force (Ea) of the first secondary coil (2a) and the electromotive force (Eb) of the second secondary coil (2b). A means (18) for converting (Δφ) into an electric signal representing the flow velocity (v) of the molten metal. The symbols in parentheses are used for corresponding elements or corresponding matters in the embodiments described later with reference to the drawings.

[0010]

The principle of measuring the meniscus flow velocity of molten metal according to the present invention will be described with reference to the drawings. Please refer to FIG. 1 and FIG. In these drawings, 1 is a primary coil, 2
Reference numerals a and 2b denote secondary coils, 3 a molten metal surface, 4 magnetic lines of force, and 5a and 6b iron cores. Secondary coil 2
a and 2b have the same number of turns, and are arranged on both sides of the primary coil 1 with the primary coil 1 perpendicular to the flow direction. Iron core 5,6
The a and 6b have the function of increasing the permeability of the magnetic force existing in the coils 1, 2a and 2b.

In such a structure, the molten metal free surface 3
If there is no flow of molten metal directly below the
When an alternating current is applied to the electromotive force E, an electromotive force E induced in the secondary coil 2a is induced by the symmetrical magnetic field lines 4 as shown in FIG.
a is equal to the electromotive force Eb induced in the secondary coil 2b, and the phase difference φa and φb of the electromotive forces Ea and Eb induced in the secondary coils 2a and 2b with respect to the voltage applied to the primary coil 1 are equal. Are equal. Ie 2
The phase difference Δφ = φb−φa between the electromotive forces Ea and Eb induced in the next coils 2a and 2b is zero.

However, if there is a flow of the molten metal directly below the free surface 3 of the molten metal, the molten metal moves in the magnetic field induced by the alternating current flowing through the primary coil 1, so that an induced current is generated in the molten metal. As shown in FIG. 2, the magnetic field produced by the induced current causes the magnetic lines of force between the molten metal 3 and the magnetic cores 5, 6a, 6b to be distorted to the downstream side of the molten metal flow. Therefore, the secondary coil 2 arranged on the upstream side
A level difference occurs between the electromotive force Ea induced in a and the electromotive force Eb induced in the secondary coil 2b arranged on the downstream side, and as shown in FIG. A phase difference Δφ = φb−φ between a change in the electromotive force Ea of the secondary coil 2a and a change in the electromotive force Eb of the secondary coil 2b.
yields a.

Therefore, the flow velocity is known and the secondary coil 2a
And a molten metal having a constant distance between 2b and the free surface, a phase difference Δφ = φb− between the electromotive force Ea induced in the secondary coil 2a and the electromotive force Eb induced in the secondary coil 2b.
When φa was measured, a graph as shown in FIG. 3 was obtained. As shown in this figure, the meniscus flow velocity v of the molten metal and the phases of the electromotive forces Ea and Eb of the respective secondary coils 2a and 2b (for example, the phase difference φa with respect to the applied voltage of the primary coil 1;
φb) has a unique correspondence. That is, if a graph of this kind is prepared in advance, or a signal converter for converting the phase (φa, φb) into the molten metal flow velocity v is prepared in this kind of relation, each secondary coil By detecting the phases (φa, φb) of the electromotive forces Ea and Eb of 2a and 2b, the flow velocity v below the free surface of the molten metal can be measured without contact. Particularly, in this case, as shown in the graph of FIG. 3, the two are in a substantially proportional relationship, so that the measurement process, for example, the conversion from the phase (φa, φb) to the flow velocity v is further simplified and the accuracy is high.

[0014]

【Example】

Example 1 FIG. 4 shows a first example of the molten metal flow velocity measuring apparatus of the present invention. This device has a primary coil 1, a secondary coil 2
a, 2b, and an iron core 5 around which these coils are wound,
Flow velocity measuring end 1 in which 2a and 2b are combined as shown in FIG.
2, AC power supply 7, and flow velocity detection circuit 18. In the first embodiment, the flow velocity detection circuit 18 is the phase angle detector 8
a, 8b, a zero-cross detector 17, and a flow velocity calculator 9. The primary coil 1, the secondary coils 2a and 2b are coaxially wound, and the secondary coils 2a and 2b are
Have the same number of turns, the secondary coil 2a is arranged on the upstream side of the primary coil 1 with respect to the flow of the molten metal, and the secondary coil 2b is arranged on the downstream side thereof in a direction perpendicular to the flow direction.

The AC power supply 7 is connected to the primary coil 1, and an AC current of about several amperes is passed through the AC power supply 7 to generate a magnetic field 4.
(Fig. 1). The zero cross detector 17 of the flow velocity detection circuit 18 generates a zero cross pulse Pzp (FIG. 6) at the zero cross point of the voltage applied to the primary coil 1, and supplies it to the phase angle detectors 8a, 8b and 9.

The phase angle detectors 8a and 8b are respectively a filter circuit for removing noise of the induced voltages Ea and Eb of the coils 2a and 2b, an amplifier for amplifying the induced voltages Ea and Eb,
A zero-cross pulse generator that generates zero-cross pulses Pza and Pzb (FIG. 6) at the zero-cross point of the amplified induced voltage, a counter that starts timing when the zero-cross pulse Pzp that occurs at the zero-cross point of the primary coil applied voltage arrives, and , And an output latch that latches the clock value (φa, φb) of the counter in response to the zero-cross pulses Pza and Pzb generated at the zero-cross points of the induced voltages Ea and Eb, and the clock value (φa , Φ
b) is given to the flow velocity calculator 9.

The flow velocity calculator 9 is an input latch that takes in the measured values (φa, φb) in response to a zero-cross pulse Pzp generated at the zero-cross point of the voltage applied to the primary coil. Phase difference between induced voltage Ea of coil 2a and induced voltage Eb of secondary coil 2b Δφ = φb−φa
And a phase difference / flow velocity converter for converting this into an electric signal indicating the flow velocity v of the molten metal in the relationship shown in FIG.
An output latch for latching an electrical signal indicative of the flow velocity v,
The flow velocity signal (v) is output via this output latch.

Such a flow velocity measuring device is used, for example, to measure the meniscus flow velocity in a continuous casting mold of molten steel. An example will be described with reference to FIG. In this, 10 is a tundish, 11 is a dipping nozzle, 12
Is a flow velocity measuring end (1 to 6: details in FIG. 1), 13 is a meniscus flow (reverse flow that rises and flows substantially parallel to the molten metal surface),
Reference numeral 14 is a mold, 15 is a solidified shell in a slab, and 16 is a powder layer having a thickness of about 50 mm.

The flow velocity measuring end 12 includes coils 1, 2a and 2b.
The axis of is perpendicular to the flow direction of the reverse flow 13 of molten steel supplied from the immersion nozzle 11 into the water-cooled mold 14, and the secondary coil 2a is upstream of the flow and the secondary coil 2b is downstream (FIG. 2). As described above), the tundish 10 is hung at the bottom (in other embodiments, it may be arranged directly above the meniscus.) In this, the capacity of the tundish 10 is set to 60 tons, and the temperature of the low coal of 1550 ° C. Aluminum killed steel, discharge port diameter 70m
m, through a reverse Y-type dipping nozzle 10 with a discharge angle of 45 °, was poured into a water-cooled copper mold 14 and continuously cast a slab of 250 mm in thickness and 1400 mm in width at a drawing speed of 1.8 / min. .. During this time, the primary coil 1 of the flow velocity measuring end 12
Further, the height of the flow velocity measuring end 12 from the meniscus was changed variously while an alternating current of 5 A and 2 kHz was applied to form a magnetic field.

On the other hand, in the comparative example, a part of the inventor of the present application has previously proposed Japanese Patent Application No. 1-134329, in which a primary coil is provided directly above the meniscus in parallel with the flow direction and two coils are provided on both sides of the primary coil.
By arranging the secondary coils and detecting the meniscus flow velocity from the electromotive force difference generated in each secondary coil, the height from the meniscus is increased while forming the magnetic field by applying the same casting conditions and the same alternating current as above. Various changes were made to obtain the upper limit interfacial distance that enables stable flow velocity measurement. The results are shown in Table 1. Table 1 also shows the number of coil turns of the primary coil and the secondary coil of the apparatus used for measuring the flow velocity.

[0021]

[Table 1]

As shown in Table 1, according to the present invention, the flow velocity can be stably measured up to the face-to-face distance of 400 mm, and the number of coil turns can be greatly reduced, so that the apparatus can be made compact. ..

Second Embodiment FIG. 7 shows a second embodiment of the molten metal flow velocity measuring device of the present invention. The structure of the flow velocity measuring end 12 of this device is the same as that of the above-mentioned first embodiment and is shown in FIG. This second
In the embodiment, the structure of the flow velocity detection circuit 18 is slightly different from that of the first embodiment described above, and the flow velocity detection circuit 18 shown in FIG. 7 includes zero cross detectors 8az and 8bz and a flow velocity calculator 9cp.

The zero-cross detectors 8az and 8bz respectively include a filter circuit for removing noise in the induced voltages Ea and Eb of the coils 2a and 2b, an amplifier for amplifying the induced voltages Ea and Eb, and a zero-cross point at the zero-cross point of the amplified induced voltages. It includes a zero-cross pulse generator for generating pulses Pza and Pzb (FIG. 6), each of which is a zero-cross pulse P.
Za and Pzb are given to the flow velocity calculator 9cp.

The flow velocity calculator 9cp has a zero-cross pulse P
The counter that starts clocking in response to za and the clocked value of the counter in response to zero-cross pulse Pzb (Δφ = φ
b-φa), an internal latch for latching, and a phase difference / flow velocity converter for converting the time value (Δφ = φb-φa) held by the internal latch into an electric signal indicating the flow velocity v of the molten metal in the relationship shown in FIG. And an output latch that latches an electric signal indicating the flow velocity v, and outputs the flow velocity signal (v) via this output latch.

[0026]

As described above, in the present invention, since the non-contact flow velocity measurement utilizing the electromagnetic effect is performed, the problem of metal adhesion to the measuring device or melting damage of the device can be prevented, It becomes possible to perform continuous measurement with stable time. For example, in continuous casting or the like, the molten steel supply rate from the tundish (10) to the mold (14) is controlled based on the flow velocity signal (v) to control non-metal. It is possible to manufacture a good slab with few inclusions. In addition, the device according to the present invention is non-contact, so that the flow velocity measuring end (12) is
Is compact, the equipment cost is low, the maintenance is easy, and the service life is long.

[Brief description of drawings]

FIG. 1 is a flow velocity measuring end 12 used in an embodiment of the present invention.
3 is a front view showing the external appearance of the above, showing a case where the molten metal immediately below the flow velocity measuring end 12 is stationary.

FIG. 2 is a flow velocity measuring end 12 used in an embodiment of the present invention.
FIG. 4 is a front view showing the appearance of the above, showing the case where the molten metal immediately below the flow velocity measuring end 12 is flowing.

FIG. 3 is a graph showing the relationship between the flow velocity of the molten metal 3 shown in FIG. 2 and the phase difference of the induced voltages induced in the secondary coils 2a and 2b.

FIG. 4 is a block diagram showing a first embodiment of the device of the present invention.

5 is a longitudinal sectional view of a continuous casting mold part assembled with the first embodiment shown in FIG.

6 is a time chart showing changes in applied voltage Ep of primary coil 1 and induced voltages Ea and Eb of secondary coils 2a and 2b shown in FIG.

FIG. 7 is a block diagram showing a second embodiment of the device of the present invention. 1: Primary coil (primary coil) 2a, 2b: Secondary coil (first and second secondary coils) 3: Molten metal free surface 4: Magnetic field lines 5: Iron core 6a, 6b: Iron core 7: AC power supply ( AC power supply) 8a, 8b: Phase angle detector 9, 9cp: Flow velocity calculator 10: Tundish 11: Immersion nozzle 12: Flow velocity measuring end 13: Meniscus flow 14: Mold 15: Shell 16: Powder 17: Zero cross detector 18 : Flow velocity detection circuit (means for conversion)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Shin Tera 5-3 Tokai-cho, Tokai City Nippon Steel Corporation Nagoya Steel Works

Claims (2)

[Claims] 1. A primary coil is disposed directly above a meniscus having a flow directly below a free surface, and a secondary coil is disposed perpendicularly to the flow direction, and secondary coils are disposed on both sides of the primary coil so as to sandwich the primary coil. Applying an alternating current to the coil to form lines of magnetic force,
A method for measuring the meniscus flow velocity of molten metal, which detects the meniscus flow velocity from the phase difference of the electromotive force generated in each secondary coil due to the distortion of magnetic field lines due to the flow just below the free surface. 2. A primary coil; first and second secondary coils provided on both sides of the primary coil; an AC power source connected to the primary coil; and an electromotive force of the first secondary coil. And a means for converting the phase difference between the electromotive force of the second secondary coil and an electric signal representing the flow velocity of the molten metal;