JPH0666822A - Method of measuring surface flow rate of in-mold molten steel in continuous casting - Google Patents

Abstract

PURPOSE:To continuously measuring the surface flow rate of molten steel by Fourier-transforming at a high speed a measurement signal from an eddy current type level meter between a mold and a dipping nozzle to arithmetically process an energy spectrum and using a frequency in a low frequency area and a given relational expression. CONSTITUTION:A dipping nozzle 2 is provided at the center of a mold 1, so that molten steel discharged from a discharge port 3 flows in the mold 1 as shown in arrows 4-7. An eddy current type level meter 9 is provided between the mold 1 and the nozzle 2, and its measurement signal is input to a processor 11 via an input 10 and Fourier-transformed at a high speed to arithmetically process an energy spectrum. The waveform distribution of the energy spectrum is shown in a straight line in a low frequency area of 0.02-0.08Hz. In a higher frequency area, it comes to white noise condition due to measured noise. The value of the energy spectrum at about 0.1Hz is represented as the secondary function of a molten steel surface flow rate. The molten steel surface flow rate can be, therefore, measured by frequency-analyzing the output of the level meter 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the surface velocity of molten steel in a mold in continuous casting.

[0002]

2. Description of the Related Art Regarding the measurement of molten steel surface velocity in a mold,
There is a contact-type technique for measuring the surface velocity of molten steel in a mold. In this method, an immersion body to which a strain gauge is attached is immersed in molten steel, the force exerted by the molten steel surface flow velocity in the mold is measured by the strain gauge, and converted into a flow velocity.

Japanese Patent Laid-Open No. 294053/1993 discloses an immersion nozzle having a molten steel discharge hole facing the shorter side of the mold, which is disposed in the center of the mold to perform continuous casting. At least one melt level meter is placed between each short side, the level measurement value is subjected to fast Fourier transform to obtain the energy spectrum, and the frequency components of both are compared to determine the molten steel drift in the mold. It describes a method of determining the presence or absence of occurrence, the direction of the occurrence of drift and the degree thereof.

[0004]

In order to measure the molten steel surface flow velocity in the mold, current measuring techniques rely on the contact method. However, when continuously measuring the molten steel surface flow velocity in the mold, it is difficult to measure for a long time by the contact method. Moreover, the method described in Japanese Patent Laid-Open No. 3-294053 has not yet been able to determine the molten steel surface flow velocity in the mold.

In order to advantageously solve the problems of the prior art, the present invention is to measure the molten steel surface flow velocity in a mold by a non-contact method.

[0006]

The gist of the present invention is to dispose a vortex type level meter between a mold and an immersion nozzle at a predetermined height from the molten steel surface, and to input the measurement signal of the level meter. Then, the calculation processing of the energy spectrum is performed by the fast Fourier transform by the calculation device, and the frequency of the low frequency range and the relational expression of the energy spectrum value and the molten steel surface flow velocity in the mold created in advance, It is a method for measuring a molten steel surface flow velocity in a mold in continuous casting, which is characterized by continuously measuring a molten steel surface flow velocity flowing in a direction.

[0007]

The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention.

As shown in FIG. 1, a dipping nozzle 2 is arranged in the center of a mold 1, and its discharge hole 3 is directed toward the mold 1.
The molten steel flow discharged from the discharge hole 3 flows in the mold 1 with an arrow 4,
It flows like 5, 6, and 7. That is, the molten steel flow 4 from the discharge hole 3 reduces its velocity while flowing in the molten steel 8 stored in the mold 1, and becomes a reverse flow by colliding with the short side of the mold 1. One of the reversing flows is an ascending flow 5 toward the surface of the molten metal, and the other is a descending flow 6 toward the downside. Further, the ascending flow 5 further reverses after reaching the molten steel surface, and becomes a molten steel surface flow 7 flowing from the mold 1 toward the immersion nozzle 2.

A vortex type level meter 9 is disposed between the mold 1 and the immersion nozzle 2 at a predetermined height above the molten steel surface. Then, the measurement signal from the eddy current level meter 9 is input to an input device 10 such as an A / D converter, and is further subjected to fast Fourier transform by a calculation device 11 such as a microcomputer to perform energy spectrum calculation processing.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 2 shows an example of the energy spectrum waveform distribution when the molten metal surface level is measured. The horizontal axis shows the frequency (Hz) and the vertical axis shows the energy spectrum value after fast Fourier transform. . 0.02 to 0. in FIG.
The low frequency range of 08 Hz is represented by a straight line, and the slope is −5.
/ 3. Further, in the high frequency range of 0.08 Hz or higher, measurement noises are overlapped with each other and are in a state of white noise.

The sharp peak at 2.5 Hz is the natural frequency of the vibration cycle that causes the mold to vibrate so that smooth casting occurs during casting.

FIG. 3 is a diagram in which the energy spectrum value at 0.1 Hz is plotted against the molten steel surface flow velocity in the mold measured by the contact method in the frequency analysis result obtained in FIG. The method of measuring the molten steel surface flow velocity in the mold by the contact method is to immerse the dip body to which a strain gauge is attached in molten steel, measure the force exerted by the molten steel surface flow velocity in the mold with a strain gauge, and convert it into a flow velocity. .

As can be seen from FIG. 3, the energy spectrum value at 0.1 Hz is expressed in the form of a quadratic function with respect to the molten steel surface flow velocity in the mold measured by the contact method. The present inventors have proved that they are expressed in the form of a quadratic function from the laws of physics.

Thus, the molten steel surface velocity in the mold can be measured by measuring the molten steel surface level using the vortex level meter and performing frequency analysis.

[0017]

According to the present invention, the surface flow velocity of molten steel in a mold can be continuously measured in a non-contact manner.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a waveform distribution of an energy spectrum when the molten metal surface level is measured.

FIG. 3 is a diagram in which an energy spectrum value at 0.1 Hz is plotted against a molten steel surface flow velocity in a mold measured by a contact method.

[Explanation of symbols]

 1 Mold 2 Immersion Nozzle 3 Discharge Hole 4 Molten Steel Flow 5 Upflow 6 Downflow 7 Molten Steel Surface Flow 8 Molten Steel 9 Level Meter 10 Input Device 11 Computing Device

Claims (1)

[Claims] 1. A vortex flow level meter is disposed between the mold and the dipping nozzle at a predetermined height above the molten steel surface, a measurement signal of the level meter is input to an input device, and a fast Fourier transform is performed by an arithmetic device. Convert and perform energy spectrum calculation processing,
Mold in continuous casting characterized by continuously measuring the molten steel surface velocity flowing from the mold in the direction of the immersion nozzle by the relational expression of the frequency of low frequency range, the energy spectrum value created in advance and the molten steel surface velocity in the mold Method for measuring surface velocity of molten steel.