JP2000304617A - Surface temperature of steel material measuring method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the steel plate temperature to be measured under a condition that emissivity of a steel plate changes and rolling oil exists on the surface of the steel plate like a part between rolling stands. SOLUTION: A plurality of radiation thermometers 20, 22 having a measuring wavelength λ1 wherein absorption of radiation energy of rolling oil 12 is large are arranged at mutually different measuring angles θ1, θ2. A radiation thermometer 24 having a measuring wavelength λ2 wherein absorption of radiation energy of the rolling oil 12 is small is arranged. From a relational equation of three luminance temperatures S1, S2, S3 measured by the radiation thermometers 20, 22, 24 and emissivity ε0 and thickness t of the rolling oil which are previously measured, the surface temperature T of a steel plate 10 in which influence of the rolling oil is eliminated is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the surface temperature of a steel material having a liquid on its surface, and more particularly to a method for measuring the surface temperature of a steel material during rolling or after rolling. Also, the present invention relates to a method and an apparatus for measuring a surface temperature of a steel material capable of accurately measuring the surface temperature of the steel material whose emissivity fluctuates irrespective of the presence of a liquid and fluctuation of the emissivity.

[0002]

2. Description of the Related Art Many methods and apparatuses for measuring the surface temperature of steel have been proposed. For example, Japanese Unexamined Patent Publication
As in 164622, a method and an apparatus for measuring the surface temperature of a steel sheet from the power ratio of the emissivity obtained from the outputs of a plurality of radiation sensors whose measurement wavelength and measurement angle can be changed, and as in Japanese Patent Application Laid-Open No. Hei 5-27345, The P-polarized component and the S-polarized component of the radiation radiated to the Brewster angle are captured, and the temperature of the metal or semiconductor covered with a transparent oxide thin film, etc. is determined from these radiated radiances by the effect of the emissivity fluctuation due to the interference effect A device that performs measurement without receiving the noise has been proposed.

[0003]

However, in the conventional method, as shown in FIG. 1 during or after rolling,
When a liquid such as the rolling oil 12 is present on the surface of the steel sheet 10, the radiant energy is absorbed by the rolling oil 12, and the radiation thermometer 20 cannot accurately measure the steel sheet temperature. In addition, if measures are taken to remove the rolling oil 12 with air or the like in order to prevent this, the temperature of the steel sheet decreases, and there is a problem that the actual temperature cannot be measured.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. For example, a steel material having a liquid such as rolling oil on its surface and having a variable emissivity, such as during or after rolling, is provided. It is an object to accurately measure a surface temperature.

[0005]

SUMMARY OF THE INVENTION According to the present invention, when measuring the surface temperature of a steel material having a liquid on its surface, a radiation thermometer having a measurement wavelength at which the absorption of radiant energy by the liquid is large is performed by using different measurement angles. And at least one radiation thermometer having a measurement wavelength at which absorption of radiant energy by the liquid is small, and at least three brightness temperatures measured by each radiation thermometer are determined in advance. The object of the present invention is to solve the above problem by calculating the surface temperature of a steel material excluding the influence of the liquid from the relational expression between the emissivity of the liquid and the film thickness.

When measuring the surface temperature of a steel material having a liquid on its surface, three or more radiation thermometers having measurement wavelengths at which radiation energy is absorbed by the liquid are arranged at different measurement angles from each other. From at least three luminance temperatures measured by the radiation thermometer and the relational expression between the emissivity and the film thickness of the liquid determined in advance, the surface temperature of the steel material excluding the influence of the liquid is calculated, This has solved the above-mentioned problem.

[0007] The present invention also provides a steel surface temperature measuring device for measuring the surface temperature of a steel material having a liquid present on the surface, the device having a measurement angle different from each other. A plurality of radiation thermometers having a large measurement wavelength, at least one radiation thermometer having a measurement wavelength at which absorption of radiant energy by the liquid is small, a mechanism for holding each radiation thermometer at a predetermined angle, and each radiation thermometer; At least three brightness temperatures measured by a thermometer;
From the relational expression between the emissivity of the liquid and the film thickness obtained in advance,
The above problem is also solved by using a data processing means for calculating and outputting the surface temperature of the steel material excluding the influence of the liquid.

In addition, a steel surface temperature measuring device for measuring the surface temperature of a steel material having a liquid on its surface is provided with a measuring wavelength, which is disposed at different measurement angles from each other and at which radiant energy is absorbed by the liquid. Three or more radiation thermometers, a mechanism for holding each radiation thermometer at a predetermined angle, at least three brightness temperatures measured by each radiation thermometer,
From the relational expression between the emissivity of the liquid and the film thickness obtained in advance,
The above-mentioned problem is also solved by using a data processing means for calculating and outputting the surface temperature of the steel material excluding the influence of the liquid.

According to the present invention, a plurality of radiation thermometers having a measurement wavelength at which absorption of radiant energy by a liquid such as rolling oil existing on the surface of a measurement object (steel material) is arranged at different measurement angles from each other, and At least one radiation thermometer having a measurement wavelength at which absorption of radiant energy by the liquid is small, or a radiation thermometer having a measurement wavelength at which radiant energy is absorbed by the liquid is provided at different measurement angles. Using a relationship between the emissivity of the liquid and the film thickness determined in advance, using three or more units, the relational expression of the measured temperature (brightness temperature), steel temperature, emissivity, etc. obtained from each radiation thermometer Thus, by obtaining the unknown steel material temperature, accurate temperature measurement can be performed without being affected by the emissivity fluctuation of the steel material due to the influence of the liquid.

FIG. 2 shows an example of the relationship (spectral transmittance) between the transmittance and the wavelength of a rolling oil having a film thickness of 15 μm. As is clear from the figure, there is a region where light is hardly transmitted near the wavelength of 3.4 μm. If the thickness of the rolling oil is sufficiently large, the light from the steel material does not pass at all, but the light from the steel material is actually transmitted because it is thin.

Therefore, by selecting this wavelength, FIG.
As shown in the figure, the radiation energy E from the steel material (steel plate 10)
The s is attenuated during the passage of the rolling oil 12 through the oil film, and the radiation thermometer 20 captures most of the radiant energy Eo from the rolling oil itself.

FIG. 3 shows an example of the relationship between the emissivity ε of the rolling oil at a temperature of 250 ° C. and the film thickness t. From the figure, the film thickness t
It can be understood that the emissivity ε of the rolling oil increases in the region where the thickness is small in proportion to the film thickness t. Utilizing this, as illustrated in FIG. 4, one radiation thermometer 20 is disposed directly above the steel plate 10, and the other radiation thermometer 22 is measured obliquely, so that the actual film thickness t is Even if it is the same, as shown in FIG. 5, the film thickness t 'apparently becomes larger when the light is incident obliquely. Accordingly, the apparent emissivity also increases, and a difference occurs in the brightness temperature.

In addition to the wavelength of 3.4 μm, there is a region having a high transmittance, that is, a region which is hardly absorbed. If a radiation thermometer having this measurement wavelength (for example, 3.5 μm) is selected, the radiant energy from the steel plate 10 will occupy a large part. From this, the emissivity of the steel material can be determined.

Therefore, as shown in FIG. 6, for a plurality of unknown steel temperature Ts, emissivity .epsilon.s of steel material and film thickness t of rolling oil 12, a plurality of measuring instruments having a measuring wavelength .lambda. Radiation thermometers 20, 22, and 3.4μ
at least one radiation thermometer 2 with a measurement wavelength λ2 other than m
4 (for example, (1) and (2) below)
By taking the equation (3), the steel material temperature Ts can be obtained.

[0017] Alternatively, as shown in FIG. 7, for example, at least three radiation thermometers 20, 22, and 26 at different measurement angles, each having a measurement wavelength λ 1 = 3.4 μm, 3
The steel material temperature Ts can also be obtained by taking one of the two relational expressions (for example, the expressions (1), (2), and (17)).

[0016]

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

In the first embodiment of the present invention, as shown in FIG. 8, above the steel plate 10 between the rolling stands 30 and 32, there is a measurement wavelength λ1 = 3.4 μm at which absorption of radiant energy by rolling oil is large. Two radiation thermometers 20, 2
2, and one radiation thermometer 24 having a measurement wavelength λ 2 = 3.5 μm where the absorption of radiation energy by the rolling oil is small.
Place. The measurement angle θ is such that, with respect to the normal direction of the steel sheet 10, the radiation thermometer 20 is θ1 = 0 °, and the radiation thermometers 22 and
4 is θ2 = 60 °.

The measured temperatures (brightness temperatures) of the radiation thermometers 20, 22, and 24 are taken into a data processing device 50 via amplifiers 40, 42, and 44, respectively.

The relational expression between the emissivity of the rolling oil and the film thickness is input to the data processor 50 in advance. Then, the steel sheet temperature Ts is obtained from three relational expressions relating to the radiance obtained from the luminance temperature S of each radiation thermometer and the steel sheet temperature Ts. This result is displayed on the temperature display 52 or sent to the host computer 54 and used for temperature management and line control.

Here, from the relational expression of the radiance, the steel plate temperature T
A method for obtaining s will be specifically described.

Assuming that the luminance temperatures of the radiation thermometers 20, 22, and 24 are S1, S2, and S3, respectively,
For radiances L1, L2, and L3 of 0, 22, and 24, the following relational expression holds.

L1 (S1) = κ · εs (λ1) · L1 (Ts) + (1−κ) εo · L1 (To) (1) L2 (S2) = κ ′ · εs (λ1) · L1 ( Ts) + (1−κ ′) εo · L1 (To) (2) L3 (S3) = εs (λ2) · L2 (Ts) (3) where Ts: steel sheet temperature To: rolling oil temperature ( = Ts) εs: emissivity of steel plate εo: emissivity of rolling oil (known) κ, κ: transmittance of rolling oil, and transmittance κ of rolling oil is represented by the following equation.

Κ = exp (−α · t) (4) κ ′ = exp (−α · t ′) (5) where α: absorption coefficient of rolling oil (known) t: film of rolling oil Thickness t ': Apparent oil film thickness of rolling oil

In the equations (1) to (3), εs (λ1),
εs (λ2) is almost equal because λ1 and λ2 are close wavelengths, and can be set as εs. Also, the oil temperature To
Since the film thickness is thin, it can be regarded as substantially the same as the steel sheet temperature Ts.

The equations (1) to (3) are further developed. The radiance L can be expressed by the following Wien equation.

[0026]

(Equation 1)

By substituting this, the equations (1) to (3) become
The following equations (7) to (9) are obtained.

[0028]

(Equation 2)

Εs is obtained from the equation (9), and (7)
By substituting each into the equation (8), the following equation is obtained.

[0030]

(Equation 3)

Therefore, the equations (10) and (11) are as follows.

F ₁ (T) = κ · F ₃ (T) + εo (1-κ) (12) F ₂ (T) = κ ′ · F ₃ (T) + εo (1-κ ′) (13) )

Here, κ and κ ′ are expressed by the above-mentioned equations (4) and (5). The relationship between t and t 'is shown in FIG. 5, where t' = t / cos θ '.

By substituting equations (4) and (5) into equations (12) and (13) and transforming them, the following equation is obtained.

[0035]

(Equation 4)

If t is eliminated from the equations (14) and (15), the following relational expression can be derived.

InA (T) = cos θ ′ · lnB (T) (16)

Accordingly, the steel sheet temperature T can be obtained by solving the equation (16).

In the first embodiment, two wavelengths, λ1 and λ2, are used. However, as in the second embodiment having the main configuration shown in FIG. 7, the measured radiation temperature is the same as λ1. The total film thickness is t, t ', t "(t', t ', t3) at three levels, for example, θ1 = 0 °, θ2 = 40 °, and θ3 = 80 °. Even if t ″ is an apparent film thickness), the same can be obtained. In this case, the above equation (3) becomes as shown in the following equation (17).

L1 (S3) = κ ″ · εs (λ1) · L1 (Ts) + (1−κ ″) εo · L1 (To) (17)

In the above embodiment, the wavelength λ1
= 3.4 μm and λ 2 = 3.5 μm, but the wavelength is not limited to these.

In the above embodiment, the present invention provides:
Although it was also applied to the measurement of the surface temperature of a steel sheet coated with rolling oil, the application of the present invention is not limited to this, and there is a liquid such as oil or water other than the rolling oil. It is clear that the present invention can be similarly applied to the measurement of the surface temperature of the steel material.

[0043]

According to the present invention, even if the emissivity of the steel material fluctuates and the liquid such as rolling oil is present on the surface of the steel material, such as between rolling stands, the surface temperature of the steel material is reduced. Can be measured accurately.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a steel sheet on which rolling oil is applied, for explaining a conventional problem and the principle of the present invention.

FIG. 2 is a diagram showing a measurement example of a spectral transmittance of rolling oil for explaining the principle of the present invention.

FIG. 3 is a diagram showing a measurement example of the relationship between the emissivity of rolling oil and the film thickness.

FIG. 4 is a sectional view showing an experimental method for confirming the effectiveness of the present invention.

FIG. 5 is a diagram showing a relationship between an actual film thickness and an apparent film thickness for explaining the principle of the present invention.

FIG. 6 is a sectional view showing a basic arrangement example of a radiation thermometer according to the present invention.

FIG. 7 is a sectional view showing a modification of the arrangement of the radiation thermometer.

FIG. 8 is a block diagram showing the overall configuration of the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Steel plate 12 ... Rolling oil t, t ', t "... Oil film thickness 20, 22, 24, 26 ... Radiation thermometer S1, S2, S3 ... Brightness temperature 50 ... Data processing device 52 ... Temperature display T ... Steel plate temperature

Claims (4)

[Claims] When measuring the surface temperature of a steel material having a liquid on its surface, a plurality of radiation thermometers having a measurement wavelength at which absorption of radiant energy by the liquid is large are arranged at different measurement angles from each other; At least one radiation thermometer having a measurement wavelength at which absorption of radiant energy by the liquid is small, at least three brightness temperatures measured by each radiation thermometer, emissivity and film thickness of the liquid determined in advance, and Calculating the surface temperature of the steel material excluding the influence of the liquid from the relational expression (1). 2. When measuring the surface temperature of a steel material having a liquid on its surface, three or more radiation thermometers having measurement wavelengths at which radiant energy is absorbed by the liquid are arranged at different measurement angles from each other. It is characterized in that the surface temperature of the steel material excluding the influence of the liquid is calculated from at least three brightness temperatures measured by the radiation thermometer and the relational expression between the emissivity and the film thickness of the liquid which is obtained in advance. A method for measuring the surface temperature of steel materials. 3. A steel surface temperature measuring device for measuring a surface temperature of a steel material having a liquid on its surface, wherein the measuring device is disposed at different measurement angles and has a large absorption of radiant energy by the liquid. A plurality of radiation thermometers having wavelengths; at least one radiation thermometer having a measurement wavelength at which absorption of radiation energy by the liquid is small; a mechanism for holding each radiation thermometer at a predetermined angle; and each radiation thermometer Calculate the surface temperature of the steel material excluding the influence of the liquid from at least three luminance temperatures measured by the above and the relational expression between the emissivity and the film thickness of the liquid determined in advance,
A data processing means for outputting, and a device for measuring the surface temperature of steel. 4. A steel surface temperature measuring device for measuring a surface temperature of a steel material having a liquid on its surface, wherein the measurement device is disposed at different measurement angles from each other and absorbs radiant energy by the liquid. Three or more radiation thermometers having wavelengths, a mechanism for holding each radiation thermometer at a predetermined angle, at least three brightness temperatures measured by each radiation thermometer, the emissivity of the liquid determined in advance, From the relational expression with the film thickness, calculate the surface temperature of the steel material excluding the effect of the liquid,
A data processing means for outputting, and a device for measuring the surface temperature of steel.