JPH0211347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring the thickness of a slag layer on the surface of a slab during continuous casting of metal such as molten steel. The results are compared with past operational data and measurement results regarding how to deal with defects and cracks on the surface of the slab, and control is performed to change the manipulated variables such as slab withdrawal speed, powder supply conditions, mold vibration conditions, etc. The present invention relates to a device for measuring the thickness of a slag layer on the surface of a slab.

Continuous casting of molten metal is performed as shown in Figure 1.
This is accomplished by injecting molten metal 4 from a tundish 1 into a mold 2 having a predetermined cross-sectional shape and dimensions, and continuously drawing it out as a slab 3 from below the mold 2.

In continuous casting, powder 5 is deposited on the free surface of molten metal 4 in mold 2, as shown in FIG.
is supplied. The powder 5 is melted by the heat of the molten metal 4, flows between the inner wall surface of the mold 2 and the surface of the slab 3, and functions as a lubricant.

On the other hand, in continuous casting, as shown in FIG. 3, the rotary motion of the motor 6 is periodically applied to a vibration table 9 supported on a base and on which the mold 2 is placed via a spring 8 by a cam 7. This is converted into a vertical motion and transmitted, thereby applying vibration in the vertical direction to the mold 2. By this,
The powder 5 helps the flow of molten slag between the inner wall surface of the mold 2 and the surface of the slab, and prevents seizure between the slab and the mold.

Depending on the lubrication condition between the mold 2 and the slab 3,
Scratches and cracks may occur on the surface of the slab 3, and breakout (hereinafter referred to as BO) may occur.

These troubles are said to be caused by the quality of the powder flowing between the inner surface of the mold 2 and the slab 3. Measurement and evaluation of the powder inflow state between the mold 2 and the slab 3 (measuring the lubrication state), a means of detecting information on the occurrence of surface flaws, and an effective method for preventing the above-mentioned troubles. The reality is that there is no way to do so.

As a method of measuring the lubrication state between the mold 2 and the slab 3, CRM's M.
L.Tektor method (JP-A-53-45628, JP-A-54
-112338) has been proposed.

Mold 2 and slab 3 depending on the vibration condition of the mold.
The method of measuring the lubrication state between the two indirectly measures the state of powder inflow, and is an average measurement method. Therefore, there is a drawback that it is not possible to estimate the location of surface scratches or cracks that occur depending on the powder inflow situation, or to control the powder inflow situation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a slag thickness measuring device that directly detects the slag thickness of a slab discharged from a mold of a continuous casting machine, and in a one-to-one relationship with each part of the slab surface.

The present invention will be described in detail below with reference to the drawings. FIG. 4 shows an example of the structure of the present invention, in which a lens 6 condenses the radiant energy emitted from the surface of the slab 3 to which the slag film 50 is attached;
a rotary filter 7 that extracts radiant energy in two specific wavelength bands from the collected radiant energy; a motor 9 that rotates the filter 7;
The image sensor 8 detects light that has become radiant energy only in a specific wavelength band by the filter 7 and generates a voltage according to its intensity. It is a standard for off-line correction of differences in the characteristics of the elements of the multiple image sensors 8. A laser 10 for irradiating light that becomes , a lens 11 for uniformly spreading the laser light over the entire image sensor, and an image sensor 8
an amplifier 12 that amplifies the output of the radiant energy of the two specific wavelength bands, a thickness calculator 13 that calculates the thickness of the slag film attached to the slab 3 using the amplified output of the radiant energy of the two specific wavelength bands, Temperature calculator 1 that calculates the surface temperature of the slab 3 using the energy measurement value and the slag film thickness measurement value
4. Recorder 1 for recording the outputs of computing units 13 and 14
5. Consists of a computer 16 and a display device 17 that compare the output results with past results and display changes in operating conditions. The radiant energy Eλθ from the slab 3 at the temperature θ is attenuated by the slag film 50 attached to the slab 3, but it is
If the thickness of the slag film is l, and the radiation energy from the surface of the slag film 50 is E'λ _T , then E'λ _T = Eλθ・exp(−αλθ・l)...(1) However, αλθ is the wavelength The damping constant is determined by .

In addition, the radiant energy Eλθ of wavelength λ from the slab 3 at temperature θ is calculated from Winn's formula as follows: Eλθ=ελθC ₁ λ ^-5 exp(−C ₂ /λS)...(2) However, ελθ is the emissivity, and S is the emissivity. The blackbody temperatures C ₁ and C ₂ are constants.

Therefore, from equations (1) and (2), the radiant energy E′λ T of wavelength λ from the surface of slag film 50 at temperature _T
is as follows.

E′λ _T =ελθC ₁ λ ^-5 exp(−αλθ・l−C ₂ /λS)…
...(3) Furthermore, the radiant energy E'λ _T from the surface of the slag film 50 at temperature T is written as E'λ _T = C ₁ λ ^-5 exp (−C ₂ /λ _T ) ...(4) Express. Therefore, from equations (3) and (4), lnελθ=C ₂ /λ(1/S-1/T)+αλθ・l...
…(5) becomes.

The radiant energy emitted from the slab 3, attenuated by the slag film 50, and emitted from the surface of the slag film 50 is passed through a guide pipe 18 as shown in FIG. Filter 7 that can switch bands
The radiant energy emitted from the surface of the slag film 50 at approximately the same position is measured by the image sensor 8 at two different measurement wavelengths λ ₁ and λ ₂ .
_{If detected by _ _}
l...(6) lnελ ₂ θ=C ₂ /λ ₂ (1/S-1/T ₂ )+αλ ₂ θ・
l...(7) However, T ₁ can be expressed as the temperature measurement value at wavelength λ ₁ and T ₂ can be expressed as the temperature measurement value at wavelength λ ₂ .

The guide pipe 18 is used to prevent harmful effects caused by bad environments such as water, steam, and dust, and FIG. 6 shows an example thereof. FIG. 7 is a side view of FIG. 6, and the slab 3 side is sealed with an air curtain by constantly blowing air from above. Additionally, a small amount of pressure is applied inside the pipe to prevent anything outside the pipe from flowing backwards. This guide pipe 18 is just one example, and any guide pipe may be used as long as it has the same function. Also, if the surrounding environment is good, there is no need to use it.

The image sensor 8 is made up of a large number of elements, such as CCD elements, arranged horizontally in a row parallel to the surface of the slab to be measured, and the length is the length of the surface of the slab to be measured divided by the number of elements. The thickness of the slag film 50 can be measured using the minimum unit. However, since energy dispersion may be considered, it is preferable to manage several elements together and calculate the average. Furthermore, since each element of the image sensor 8 has different characteristics, it is necessary to perform off-line correction by uniformly irradiating light with a constant intensity. As a specific example, FIG. 4 shows an example using laser light, but other methods may be used. Figures 8a and 8 show Figure 4 in more detail.
Figure b. FIG. 8a shows a state in which the slag film thickness is being measured, and FIG. 8b shows a state in which correction is in progress. During correction, the light from the slab 3 is blocked behind the mirror 19, and the image sensor 8 detects only the laser light. The light emitted from the laser 10 is
The light is expanded by the lens 11, reflected by the mirror 19, and uniformly enters the image sensor 8. The output characteristics are sent to the thickness calculator 13 and the temperature calculator 14 and used for correction of each calculation. The laser 10 used here is preferably a semiconductor laser. In the example shown in FIG. 4, the filter 7 is a rotary switching filter, as shown in the front view in FIG. As long as high-speed switching at time intervals is possible, any method may be used, such as a method of switching by moving up and down, a method of switching by moving left and right. Furthermore, the two specific frequency bands of the filter 7 are the two bands in which the slag film thickness can be measured best. The fact that the filter 7 has been switched is transmitted from the motor that rotates the filter 7 to the thickness calculator 13 and the temperature calculator 14.

Now, calculating l from equations (6) and (7), l=λ ₁ lnελ ₁ θ−λ ₂ lnελ ₂ θ+C ₂ (1/T ₁ −1/T ₂
)/λ ₁ αλ ₁ θ−λ ₂ αλ ₂ θ……(8). Here, λ ₁ and λ ₂ are the wavelengths specified by the filter 7, the emissivity ε and the attenuation rate α can be measured in advance, and the slag film thickness l is the temperature measurement value T ₁ , T ₂ That is, it is determined based on the information detected by the image sensor 8. Therefore, in the thickness calculator 13, the image sensor 8
From the radiant energies E′λ _1T1 and E′λ _2T2 on the surface of the slag film 50 of two wavelengths detected by
The thickness of the slag film is determined and input into the recorder 15 and calculator 16. The temperature calculator 14 includes
E'λ _1T1 , E'λ _2T2 and the output of the thickness calculator 13 are input. The temperature calculator 14 calculates the ratio of E'λ _1T1 and E'λ _2T2 , corrects the temperature attenuated by the thickness of the slag film, calculates the true surface temperature of the slab 3, and sends it to the recorder 15 and computer 16. I am typing. Recorder 1
5 continuously records slag film thickness information and slab surface temperature. The computer 16 compares the slag film thickness information and surface temperature information with good information from past castings, predicts the occurrence of surface scratches and BO, and displays the predicted status on the display device 17. The operator changes the operating conditions based on the display. That is, the slag film thickness and surface temperature are optimized by increasing/decreasing the drawing speed, increasing/decreasing the mold vibration frequency, exchanging powder, adjusting the amount of mold cooling water, etc.

As described above, the present invention uses two specific wavelength bands of radiant energy emitted from the slab and powder to measure the thickness and surface temperature of the slag film directly under the mold using an image sensor. There are advantages to mention.

(1) The principle of a general radiation thermometer can be used to utilize the radiant energy from the slab.

(2) Since the attenuation of two specific wavelengths is used, the thickness of the slag film can be detected with high accuracy.

(3) Since two wavelengths are used and the radiant energy attenuated by the thickness of the slag film is corrected, the surface temperature of the slab can be measured accurately.

(4) Since the measurement is performed using an image sensor with a large number of elements, the slag film thickness distribution and surface temperature distribution can be measured easily and at high speed.

In addition, since the slag layer thickness is measured based on the radiant energy emitted by the slab at the bottom of the mold of the continuous casting equipment, (1) the current casting operation status can be understood and prompt measures can be taken to deal with abnormalities in the slag layer thickness; This can contribute to stable operations.

(2) The surface temperature of the slab can also be measured at the same time, making it possible to detect surface defects and predict BO based on the fluctuation state of the measured surface temperature.

[Brief explanation of drawings]

Figure 1 is a sectional view showing an overview of continuous casting equipment, Figure 2 is a sectional view showing the state of powder in the mold,
Figure 3 is a side view showing the outline of the mold vibration device;
FIG. 4 is a block diagram showing the configuration of one device for carrying out the present invention, and FIG. 5 is a block diagram of the filter 7 shown in FIG.
6 is a perspective view showing an example of a guide pipe that protects the measurement optical path from dust, and FIG. 7 is a sectional view thereof. FIGS. 8a and 8b are plan views showing one device configuration for correcting differences in output characteristics of image sensors. FIG. 8a shows the slag film thickness being measured, and FIG. 8b shows the device being corrected. 1: Tendishu, 2: Mold, 3: Slab,
4: Molten metal, 5: Powder, 50: Slag film, 6: Lens, 7: Filter, 8: Image sensor, 9: Motor, 10: Laser, 1
1: lens, 12: amplifier, 13: thickness calculator,
14: Temperature calculator, 15: Recorder, 16: Calculator, 17: Display device, 18: Guide pipe, 1
9: Mirror.

Claims (1)

[Scope of Claims] 1. A lens for concentrating the radiant energy emitted from the surface of the slab having a slag layer on its surface, in the lower part of the mold of the continuous casting device, and for detecting two types of specific wavelength bands from the condensed radiant energy. an image sensor that generates a voltage according to the intensity of radiant energy;
Continuous casting comprising an amplifier that amplifies the output from the image sensor, and a calculator that calculates the thickness of the slag layer on the surface of the slab from the intensity signal of the radiant energy in the specific wavelength band from the amplifier using the following formula. Measuring _device for _{the thickness} of _the slag _layer on _the surface of _the slab in
)/λ ₁ αλ ₁ θ−λ ₂ αλ ₂ θ where, l: Thickness of the slag layer on the surface of the slab, λ ₁ , λ ₂ : Two wavelengths specified by the filter, ελ ₁ θ: Wavelength λ ₁ emissivity at wavelength λ 2, ελ ₂ θ: emissivity at wavelength λ ₂ , C ₂ : constant, T ₁ : temperature measurement at wavelength λ ₁ , T ₂ : temperature measurement at wavelength λ ₂ , αλ ₁ θ: emissivity at wavelength λ _1. αλ ₂ θ: Attenuation constant determined by wavelength λ ₂ .