JPH0933464A - Method for measuring surface scale of steel plate and method for measuring material quality - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously measure on line not only a scale thickness, but a crystal particle size and a hardness of a stainless steel plate after annealing. SOLUTION: An infrared emission light from a surface of a steel plate 2 is detected in an anneal furnace 3. A quality of the steel plate is measured based on the emission light according to this steel quality-measuring method. A luminance temperature at a wavelength whereby an emissivity is approximately constant even when a scale thickness changes, and a luminance temperature at a wavelength whereby the emissivity changes to a change of the scale thickness are measured by a measuring device 1. A soaking temperature of the steel plate is calculated based on preliminarily obtained emissivity and luminance temperature at the former wavelength. The emissivity at the wavelength is calculated based on the soaking temperature and the latter luminance temperature, based on which the scale thickness is obtained. A soaking period from a predetermined temperature of the steel plate to the soaking temperature is calculated based on the scale thickness and soaking temperature. A quality of the steel plate is measured based on the soaking period and the soaking temperature.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a surface scale measuring method and a material measuring method for a steel sheet, particularly for a stainless steel sheet after annealing, the thickness of the scale formed on the surface thereof,
Also, the present invention relates to a surface scale measuring method and a material measuring method of a steel sheet, which are suitable to be applied when continuously measuring the material of crystal grain size and hardness online.

[0002]

2. Description of the Related Art In order to grow crystal grains of a stainless steel plate and obtain material properties such as mechanical strength, an annealing treatment is performed, and a scale mainly composed of oxide is formed on the surface of the steel plate at that time. The pickling treatment for removal is continued. A process in which these treatments are continuously performed is generally called a CAP (Cold Annealing and Pickling) line.

In this annealing step, it is necessary to appropriately control the temperature rise pattern of the plate temperature to obtain the target material characteristics, and for that purpose, the maximum attainable temperature (soaking temperature) Tss of the plate in the annealing furnace [Tss [ [° C], and the furnace temperature control is performed so as to adjust the time (soaking time) Ts from reaching a certain temperature to Tss.

Originally, it is desirable to measure the plate temperature with high accuracy to control the plate temperature. However, in the furnace, oxide scale grows on the surface, and the degree of growth, for example, the difference in scale thickness causes Since the emissivity changes, conventional emissive thermometers and dichroic thermometers with a fixed emissivity cannot accurately measure the plate temperature. Therefore, the above-described furnace temperature control is performed instead.

In the annealing process by controlling the furnace temperature as described above,
Due to the difference in plate thickness and width of the annealed steel plate, the difference in steel plate composition, etc., the thickness of the scale formed will differ even under the same furnace temperature. Had a tendency to suppress the traveling speed of the steel sheet in order to eliminate the generation of scale residue after pickling. Therefore, the production efficiency may be hindered, or depending on the scale properties, scale pickling may occur due to insufficient pickling, which may deteriorate surface quality characteristics of the stainless steel sheet, for example, cause poor gloss. It was

From this point of view, it is extremely important to accurately measure the thickness of the scale formed on the steel sheet after annealing, but conventionally, means for nondestructively measuring the scale thickness of the surface has been known. Instead, the relative thickness of the scale was determined by a destructive test using a surface analyzer, and the thickness was measured by observing the cross section of the scale portion with an optical microscope.

Although it is not directly related to the technique for measuring the scale thickness on the CAP line, a technique suitable for measuring the surface oxide online is Japanese Patent Publication No.
In order to measure the degree of rust removal of an object to be measured such as a steel plate disclosed in 2-34093, light having a wavelength band near 550 nm is reflected on the surface of the object to be measured, and the amount of reflected light in the wavelength band is measured. The method for measuring red rust and black skin on the surface of the object to be measured with the same detection sensitivity is used as a reference.

Since the crystal grain size is important as a factor that determines the quality characteristics of the stainless steel sheet, it is desired to measure the crystal grain size online, and as a device therefor, ultrasonic backscattered waves are used. A method for estimating the crystal grain size from the strength value of is proposed in the following document. "The
Develoment and Marqueting of New Technolog
y for the Inspection of Rolled Strip "BN
F 6th Alternative Conference.

As another technique for measuring the crystal grain size, the frequency of the backscattering noise of ultrasonic waves is analyzed, and the relationship between the integrated value of the backscattering noise intensity in a specific frequency range and the crystal grain size is used. A method of doing so is disclosed in Japanese Patent Laid-Open No. 4-95870. Further, there is a method in which the coercive force of a steel plate to be measured is measured and the crystal grain size of a steel plate to be measured is determined from the relative ratio between the measured value and the coercive force of a steel plate having a known crystal grain size.
213872. Further, JP-A-5-142168 discloses an on-line measuring method for estimating the crystal grain size from the fluctuation range of the count rate of the diffracted X-ray intensity by X-ray diffraction measurement. All of these methods for estimating the crystal grain size are non-destructive testing methods that replace the conventional destructive testing by microscope observation, and are therefore suitable for online measurement if they can be effectively applied when performing continuous measurement.

[0010]

However, in the measuring method disclosed in Japanese Patent Publication No. 62-34093, the surface of the steel sheet is mechanically derusted by removing the surface scale, for example, by a shot blasting device. It is for quantitatively evaluating the state of the remaining scale afterward, and the oxide of iron is also targeted as the composition of the scale.
In addition, this method irradiates light from an oblique direction and receives the reflected light from the front, so it is good when measuring a steel plate with a lot of diffuse reflection, as in the objects of these prior arts. When measuring a surface having a high gloss and a small diffuse reflection component, such as a scale of a stainless steel plate, there is a problem that the amount of reflected light becomes weak and the measurement sensitivity is poor.

Further, in the method of Japanese Patent Publication No. 62-34093, the wavelength used is limited to around 550 nm.
The scale generated in the AP line is mainly composed of oxides of Cr, Mn, Ni, Si, etc., which are also components of the steel sheet, and according to the results of the spectral reflection spectrum analysis and the like, the ultraviolet is more visible than the visible wavelength range. Alternatively, since the absorption becomes large in the infrared region, it is preferable to perform the measurement using the characteristic. Therefore, the reflection measurement using the green light of 550 nm and the whole white light is not suitable for the scale thickness measurement on the CAP line,
It was difficult to measure the scale thickness with high sensitivity.

Further, in the case of measuring the material quality of the steel sheet described above, the method of measuring the crystal grain size from the intensity of the ultrasonic backscattered wave proposed in the above literature includes the pass line variation of the steel sheet and the scale property of the surface. Since it is easily affected by the above, the measurement accuracy of the crystal grain size is as bad as about ± 10 μm, and there is a problem that it has not been put to practical use.

Further, in the method disclosed in Japanese Patent Laid-Open No. 4-95870, the measurement cannot be performed when the steel plate is running because the ultrasonic probe is placed on the object to be measured, and further, the measurement location If there is a deviation, there is a problem that the measurement error becomes large.

Further, in the method utilizing the coercive force disclosed in Japanese Patent Laid-Open No. 6-213872, it is necessary to control the distance between the measuring object and the detection head with high accuracy, and therefore, it is used when applied to online measurement. There is a problem above.

Further, JP-A-5-14 utilizing X-ray diffraction
The method proposed in 2168 has the drawback that the device management is not easy due to the use of X-rays and is also expensive.

As described above, many methods for measuring the crystal grain size have been proposed, but each of them has its own problems and is not in practical use.

The present invention has been made to solve the above-mentioned conventional problems. In particular, the thickness of oxide scale of Cr, Mn, Ni, Si, etc. after annealing of a steel material such as a stainless steel plate is non-destructive. The first object is to provide a technique that enables highly accurate measurement.

The present invention also provides a technique capable of comprehensively evaluating the quality of a steel sheet by grasping the annealed state of the steel sheet as a whole and measuring the material properties such as the crystal grain size of the target steel sheet online. The second task is to do so.

[0019]

The invention according to claim 1 detects infrared radiation emitted from the surface of a steel sheet and measures the thickness of a surface scale formed on the steel sheet based on the radiation. A method for measuring the surface scale of a steel sheet, wherein the brightness temperature S1 at the wavelength λ1 at which the emissivity is substantially the same even if the scale thickness changes, and the wavelength λ2 at which the emissivity changes with the change of the scale thickness. And the brightness temperature S2 at the wavelength λ1 of the former, and the steel plate temperature is calculated based on the former emissivity ε1 at the wavelength λ1 and the brightness temperature S1 of the former, and the wavelength λ2 is calculated based on the steel plate temperature and the brightness temperature S2 of the latter. The first problem has been solved by calculating the emissivity ε 2 in Eq. 1 and determining the thickness of the scale based on the emissivity ε 2.

According to a second aspect of the present invention, in the first aspect, the steel plate is a stainless steel plate, and the wavelength λ1 at which the emissivity becomes substantially the same value even if the scale thickness changes is in the range of 12 to 20 μm. The wavelength .lambda.2 at which the emissivity changes with the change in thickness is in the range of 2.5 to 4 .mu.m.

A third aspect of the present invention is a steel sheet material measuring method for detecting infrared radiation emitted from the surface of a steel sheet in an annealing furnace and measuring the steel sheet material based on the radiation light. The brightness temperature S1 at the wavelength λ1 at which the emissivity is approximately the same value even if the scale thickness changes and the brightness temperature S2 at the wavelength λ2 at which the emissivity changes with the change in the scale thickness are measured and determined in advance. The soaking temperature of the steel sheet is calculated based on the emissivity ε1 at the wavelength λ1 of the former and the luminance temperature S1 of the former, and the soaking temperature of the steel sheet and the luminance temperature S of the latter are calculated.
The emissivity ε2 at the wavelength λ2 is calculated based on
Calculate the thickness of the scale based on the emissivity ε2, and calculate the soaking time from the predetermined steel plate temperature to the soaking temperature of the steel plate based on the scale thickness and the soaking temperature of the steel plate. The second problem is solved by measuring the material of the steel sheet based on the soaking time and the soaking temperature of the steel sheet.

According to a fourth aspect of the present invention, in the third aspect, the steel plate is a stainless steel plate, and the wavelength λ1 at which the emissivity becomes substantially the same value even if the scale thickness changes is in the range of 12 to 20 μm. The wavelength .lambda.2 at which the emissivity changes with the change in thickness is in the range of 2.5 to 4 .mu.m.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The basic principle of the present invention will be described in detail below.

First, in explaining the invention of claim 1,
As an example of the measurement target, an austenitic stainless steel plate (hereinafter, SUS30), which is a kind of stainless steel plate, is used.
4). The characteristics of this steel plate are:
It can be mentioned that the component contains about 18% Cr and about 8% Ni. There are a plurality of sub-steel species having different material properties from the balance of the components such as the amounts of Cr and Ni and the other components such as C, N, Si and Mn.

As an index representing the chemical composition contained in these steel sheets, the M value, which is a value that quantitatively expresses the austenite stability by using the ratio value of each constituent element, is given by the following (1)
It can be defined by an expression. In this equation (1), f1 has a constant function form, and each variable uses the mass% value of the chemical component.

M = f1 (% C,% N,% Si,% Mn,% Cr,% Ni,% Cu,% Mo,% Nd) (1)

Further, since the steel sheet is rolled down in the cold rolling process which is a pre-process of finish annealing and stores strain energy, the energy affects the recrystallization process of crystal grains during annealing. Therefore, as an indicator of reduction,
Using the plate thickness H before cold rolling and the plate thickness h after rolling, the following (1
The cold reduction rate R [%] shown in the equation 0) is defined.

R = [(H−h) / H] × 100 (2)

It can be said that the above-mentioned two values, M value and R value, are the main indexes in determining the material of the steel sheet before annealing.

Under various annealing conditions, that is, the maximum ultimate temperature (soaking temperature) Tss [° C.] (1050 to 1150) of different plates.
SU) manufactured in a time (soaking time) Ts [sec] (15 to 65 sec) from a certain temperature to Tss.
The scale of S304 is applied to various surface analyzers such as GD
S (glow discharge emission spectrometer), X-ray diffractometer,
As a result of measurement by a spectroscopic ellipsometer for measuring the optical characteristics (for example, refractive index) of the coating and a spectroscope for measuring the reflection characteristics, the following points were clarified.

1) The scale is mainly Cr, Mn, F
It is composed of an oxide such as e. 2) A plurality of layers are present in the scale layer, but the thickness thereof is mainly represented by the thickness of the Cr ₂ O ₃ layer, and the thickness value is 0.1 to 0.5 μm. 3) It has absorption characteristics by the scale film in the short wavelength region from ultraviolet to visible and the infrared wavelength region from near infrared to mid infrared. 4) When the steel plate was heated and the emissivity was measured at a plate temperature of approximately 800 to 1100 ° C., the far infrared region (λ = 12 to 20 μm) was measured.
In m), the emissivity is almost constant regardless of the scale thickness of the surface, whereas in the mid-infrared region (λ = 2.5
.About.4 .mu.m), the emissivity changes depending on the scale thickness. Here, the emissivity is defined by the relative value with the brightness from a black body at the same temperature. 5) When sputtering the scale by the GDS method,
An element that concentrates at the interface between the scale film and base iron, such as S
Focusing on i, the scale film thickness can be quantitatively evaluated from the sputtering time until the peak value of the emission intensity of Si is reached.

Generally, when performing radiation temperature measurement using a radiation thermometer, the temperature T [K] of the object to be measured and the brightness temperature S are measured.
[K], emissivity ε, measurement wavelength λ [μm], and the like have the relationship of the following expression (3).

T [K] = (C2 / λ) ÷ ln [ε {exp (C2 / (λ · S))-1} +1] (3) where C2 is the second constant of Plank. C2 = 1.4388 × 10 ⁴ [μm · K] (4)

Now, based on the knowledge shown in 4) above, a wavelength in the far infrared region is selected (λ = λ1), the emissivity ε1 of SUS304 is measured in advance, and the value is determined. If set, by measuring the brightness temperature S1 at λ = λ1, the soaking plate temperature Tss of the SUS304 steel plate can be obtained by the following formula (5) derived from the formula (3).

Tss [° C.] = (C2 / λ1) ÷ ln [ε1 {exp (C2 / (λ1.S1))-1} +1] -273 = f3 (ε1, S1) (5)

In this way, at the same time as obtaining the soaking plate temperature Tss, the wavelength in the mid-infrared region is also selected (assuming λ = λ2) from the knowledge of the above 4), and λ = λ2. By measuring the brightness temperature S2 of the above, the emissivity ε2 at the wavelength λ2 can be obtained by substituting Tss and S2 into the following formula (6) derived from the formula (3).

Ε 2 = [exp {C 2 / (λ 2 (Tss + 273))}-1] ÷ [exp {C 2 / (λ 2 · S 2)}-1] = f 4 (S 2, Tss) (6)

The relationship between the emissivity ε 2 at the wavelength λ 2 thus obtained and the scale thickness dsc [μm] of the steel sheet was investigated, and the regression equation was calculated by also considering the influence of the M value indicating the amount of the constituent elements of the steel sheet. It was created to obtain the relationship shown in the following formula (7).

Dsc = f5 (ε2, M) = A5ε2 + B5 (7)

Here, A5 and B5 are functions of M and are given by the following equations (7A) and (7B), respectively.

A5 = A51 × M + A52 (7A) B5 = B51 × M + B52 (7B) where A51, A52, B51 and B52 are constants.

From the above, the values of M and ε1 are obtained in advance, and the soaking temperature Tss is obtained by measuring the brightness temperatures S1 and S2 at two wavelengths by using the equations (5) to (7).
And the scale thickness dsc can be calculated.

Therefore, it is possible to simultaneously measure the plate temperature and the scale thickness during the annealing, and it is possible to optimize the annealing conditions and improve the quality control of the steel plate by grasping the annealing condition by controlling the plate temperature and controlling the scale thickness. .

Here, the wavelength λ1 at which the emissivity is substantially the same value even when the scale thickness is changed as shown in the above 4) and the wavelength λ2 at which the emissivity is changed according to the change of the scale thickness.
The preferred range of is described.

(1) The emissivity ε1 was measured while changing λ1, and the plate temperature T was calculated using the measured value. As a result, the error ΔT from the measured value of 2σ (σ: standard deviation) and the wavelength were calculated. There was a relationship in Figure 1 between them. Therefore, in terms of temperature control, ΔT of 2
Since σ = ± 10 ° C. has sufficient accuracy, 2σ of ΔT
The wavelength is limited under the condition of ≤10 ° C, and the preferable range is λ1.
= 12 to 20 μm.

(2) As shown in FIG. 2, λ2 has a sufficient accuracy of 2σ = 0.04 μm of Δdsc for quality control under the condition that 2σ of ΔT ≦ 10 ° C. (λ1 = 1 to 20 μm). Therefore, the estimation error Δdsc of the scale thickness dsc is
2σ ≦ 0.04 μm, and the preferable range is λ2 = 2.5-4 μm.

Next, the invention of claim 3 will be described in detail.
This invention examines the scale thickness, emissivity, soaking temperature (sheet temperature), soaking time, etc. of a plurality of types of stainless steel sheets with different component systems that have been rolled and annealed under various conditions, and each value and crystal It was made by finding that there is a certain relationship with material characteristics such as particle size and hardness.

First, the method of estimating the soaking time will be described. Using SUS304 annealed under the conditions of various soaking temperature Tss and soaking time Ts, the relationship between the scale thickness dsc measurement value of each steel sheet and Tss, Ts, etc. was investigated, and further oxidation increase and oxidation of the scale were performed. When the relationship between the rate constant and its temperature dependence, etc. was analyzed kinetically, the following equation (8) was obtained. Here, A6 and B6 are constants.

Ts = f6 (Tss, dsc) = A6 exp {B6 / (Tss + 273)} · dsc ² (8)

Ts of the above equation (8) is generally a temperature T
It is defined as the time from so to the maximum temperature (soaking temperature) Tss, but there is a limit to the number of plate thermometers installed in the CAP line, and there is also a problem with accuracy, so what time is Tso It is unknown if it was reached by. Therefore, it is difficult to actually measure Ts, but in the above equation (8), Tss, dsc
By substituting for, Ts can be estimated.

Next, a method for estimating the material of the steel sheet, that is, the crystal grain size and hardness will be described. The crystal grain size d [μm] and Vickers hardness Hv [−] of the SUS304 steel sheet annealed under various conditions were measured, and the M value, R, which is an index showing the annealing conditions Tss, Ts and the characteristics of the steel sheet before annealing, R By investigating the relationship with the values, etc., and further treating the growth of crystal grains as a thermal activation process, the following equations (9) and (10) were obtained as relational expressions expressing the crystal grain size d and the Vickers hardness Hv. . Further, as a specific functional expression, expression (9A) was obtained. The coefficients A, B and C in the equation (9A) are functions of M and R described above.

D = f7 (Tss, Ts, M, R) = A7 exp {-B7 / (Tss + 273)} Ts + C7 (9) Hv = f8 (Tss, Ts, M, R) = A8 [A7 exp {-B7 / (Tss + 273)}. Ts + C7] ^{-1 / 2} + B8 (10)

Coefficients A7 and B7 in the above equations (9) and (10)
, C7, A8 and B8 are functions of M and R, respectively, and are given by the following equations.

A7 = exp (A71 × M + A72 × R + A73) (9A) B7 = B71 × M + B72 × R + B73 (9B) C7 = C71 × R + C72 (9C) A8 = A81 × M + A82 (10A) B8 = B81 × M + B82 (10B) where A71, A72, A73, B71, B72, B73, C71,
C72, A81, A82, B81, B82 are constants.

As described above, by using the equations (3) to (10), the brightness temperature is simultaneously measured online in two different wavelength bands, and the relational expression fi obtained in advance is obtained.
(I = 5, 6, 7, 8) and based on the chemical composition and cold rolling reduction information, which are the characteristics of the steel sheet to be measured before annealing, not only the sheet temperature and scale thickness during annealing but also the It is possible to continuously estimate the material properties such as the crystal grain size and hardness of the steel sheet.

Hereinafter, a more specific example of the embodiment will be described in detail with reference to the drawings.

FIG. 3 is a layout diagram showing a schematic configuration of a CAP line applied to one embodiment according to the present invention.

In the CAP line, the central wavelengths of the two different wavelength bands are λ1 = 16 μm and λ2, respectively.
= 3 μm, the infrared radiance measuring device 1 for measuring the brightness temperature is installed at a predetermined position. The stainless steel plate 2 to be measured travels in the annealing furnace 3, and the brightness temperature thereof is measured by the infrared radiance measuring device 1 through the water cooling pipe 4. Since the water cooling pipe 4 is installed in the furnace 3 so as to extend to the vicinity of the steel plate 2, it is possible to reduce the influence of the background light from the furnace wall or the like when measuring with the brightness measuring device 1. it can.

Since the infrared radiance measuring apparatus 1 continuously measures the brightness temperatures S1 and S2 at two different wavelengths λ1 and λ2, as shown in FIG. 4, two optical bandpass filters 5 and 6 has a chopper 7 attached thereto, the chopper 7 is rotated by a motor 8, and a pyroelectric element 9 which is a kind of infrared detecting element measures the brightness temperature at two wavelengths alternately and continuously. . Measuring distance to steel plate L
And the measurement area are the focal length f of the concave mirror 10 and the housing 1
It is defined by the effective diameter of the aperture 12 mounted in the lens 1 and the distance l between the concave mirror 10 and the pyroelectric element 9. The rotation speed of the chopper 7 is determined in consideration of the time constant of the pyroelectric element 9 and is stably controlled by the rotation control device 13. Further, in order to improve the S / N, the lock-in amplifier 1
The phase detection amplification is performed by 4, and the values of S1 and S2 are transferred to the signal processing device 15.

FIG. 5 is a diagram showing the relationship between the analysis value of the scale thickness and the emissivity at two wavelengths λ2 = 3 μm and λ1 = 16 μm. Therefore, in the far infrared region, the emissivity ε
1 (λ = λ1 = 16 μm) is almost constant, while the emissivity ε2 (λ = λ2 = 3 μm) has a constant relationship with the scale thickness dsc in the mid-infrared region. It can be used as the relational expression f5 shown in the expression (7). However, in this case, since the M value is constant, different M
In the case of a stainless steel plate having a value, dsc, S2, M
The relationship of can be obtained separately using a regression equation.

The signal processing device 15 is set with a value of ε 1 obtained in advance, and the transferred brightness temperature measurement value S
Tss is obtained from 1 using the function f3 of the equation (5), and from this Tss and S2, the function f4 of the equation (6) is obtained.
Gives ε 2. The values of M and R shown in the above equations (1) and (2) are sent from the host computer 16 to the signal processing device 15 and stored therein. From the obtained values of S2 and M, the above (7) After dsc is calculated using the function f5 of the equation, the value of Ts is calculated from the previously obtained Tss and dsc using the function f6 of the equation (8). Furthermore, the values of the crystal grain meter d and the hardness Hv are finally estimated from the Ts and the values of Tss, M, R, etc. by using the functions f7, f8.

Table 1 shows the measurement results of the scale thickness dsc, the hardness Hv, and the crystal grain meter d for two steel sheets (A and B) of different zinc types of SUS304 using wavelengths satisfying this embodiment. .

[0063]

[Table 1]

As shown in Table 1, the scale thickness has an error Δdsc of 2σ (σ: standard deviation) of 0.04 μm.
Within the difference Δd between the estimated value of the crystal grain size d and the value of the crystal grain size actually measured using a microscope, 2σ is about ± 5 μm.
The error 2σ between the estimated Hv and the hardness measured with a Vickers hardness meter off-line was within 20 Hv.

The calculated values of Tss, dsc, d, Hv, etc. are output to the output device 17 and the host computer 16
Is transferred to the actuator 18 for changing the process state quantity such as the furnace temperature setting and the plate speed, and the annealing is optimized.

FIG. 4 shows a block diagram of the entire system for performing measurement, processing, output and the like. Further, FIG. 5 shows a flow in which each parameter is calculated in the signal processing device 15.

The relational expression fi (i = 5, 6, 7, 8) for converting and calculating each parameter described above is determined in advance by an off-line annealing experiment. In order to improve the accuracy, the actual operation data may be used for the determination.

The method of the present invention can also be applied to another type of stainless steel plate, for example, a ferritic steel plate SUS430. In that case, an index representing a chemical component, a set emissivity, and a function form fi (i = 5). , 6, 7, 8) and the like may be replaced separately, and processing can be performed by setting from a host computer.

As described in detail above, according to this embodiment,
The sheet temperature and scale thickness after annealing can be measured online, and these values can be used to measure the material properties after annealing, such as crystal grain size and hardness, online. Not only is it possible to quickly grasp and build a quality assurance system, but it is also possible to contribute to homogeneous steel plate production by feeding back to a control system that changes the furnace temperature setting and plate speed to stabilize annealing.

[0070]

As described above, according to the surface scale measuring method of the present invention, the oxide scale thickness can be measured nondestructively and with high accuracy.

According to the material measuring method of the present invention, the crystal grain size and hardness of the annealed stainless steel sheet can be continuously measured online.

[Brief description of drawings]

[Figure 1] Diagram for explaining the grounds for limiting wavelength λ1

[Fig. 2] Diagram for explaining the grounds for limiting wavelength λ 2.

FIG. 3 is an explanatory diagram showing a state of arrangement of measuring devices in CAP.

FIG. 4 is an explanatory diagram showing a schematic configuration of a measuring device and an arithmetic processing system.

FIG. 5 is a diagram showing the relationship between scale thickness and emissivity.

FIG. 6 is a block diagram showing an overall system that performs measurement, processing, output, etc.

FIG. 7 is an explanatory diagram showing a flow in which each parameter is calculated by a signal processing device or the like that constitutes the measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Infrared radiance measuring device 2 ... Stainless steel plate 3 ... Annealing furnace 4 ... Water cooling pipe 5, 6 ... Optical bandpass filter 7 ... Chopper 8 ... Motor 9 ... Pyroelectric element 10 ... Concave mirror 11 ... Housing 12 ... Aperture 13 ... Rotation control device 14 ... Lock-in amplifier 15 ... Signal processing device 16 ... Host computer 17 ... Output device 18 ... Actuator

Claims (4)

[Claims] 1. A surface scale measuring method for a steel sheet, which comprises detecting infrared radiation emitted from the surface of the steel sheet and measuring the thickness of the surface scale formed on the steel sheet based on the radiation. The brightness temperature S1 at the wavelength λ1 where the emissivity is approximately the same value even if the scale thickness changes and the brightness temperature S2 at the wavelength λ2 where the emissivity changes with the change in the scale thickness are measured and obtained in advance. The steel plate temperature is calculated based on the former emissivity ε1 at the wavelength λ1 and the former brightness temperature S1, and the wavelength λ is calculated based on the steel plate temperature and the latter brightness temperature S2.
2. A method for measuring a surface scale of a steel sheet, which comprises calculating the emissivity ε2 in 2 and obtaining the scale thickness based on the emissivity ε2. 2. The steel plate according to claim 1, wherein the steel plate is a stainless steel plate, and the wavelength λ1 at which the emissivity becomes substantially the same value even if the scale thickness changes is in the range of 12 to 20 μm. On the other hand, the wavelength .lambda.2 at which the emissivity changes is in the range of 2.5 to 4 .mu.m. 3. A steel sheet material measuring method in which infrared radiation emitted from the surface of a steel sheet is detected in an annealing furnace, and the steel sheet material is measured based on the radiation, wherein the scale thickness is changed. Even if the brightness temperature S1 at the wavelength λ1 at which the emissivity is approximately the same value and the brightness temperature S2 at the wavelength λ2 at which the emissivity changes with changes in the scale thickness are measured, the former wavelength λ1 The soaking temperature of the steel sheet is calculated based on the emissivity ε1 and the brightness temperature S1 of the former, and the emissivity ε2 at the wavelength λ2 is calculated based on the soaking temperature of the steel sheet and the brightness temperature S2 of the latter. Calculate the thickness of the scale based on the rate ε2, calculate the soaking time to reach the soaking temperature of the steel sheet from a predetermined steel sheet temperature based on the scale thickness and the soaking temperature of the steel sheet, Soaking time and soaking temperature of the steel sheet Material quality measuring method of the steel sheet, characterized by measuring the material of the steel sheet Zui. 4. The steel plate according to claim 3, wherein the steel plate is a stainless steel plate, and the wavelength λ1 at which the emissivity becomes substantially the same value even if the scale thickness changes is in the range of 12 to 20 μm, On the other hand, the wavelength λ2 at which the emissivity changes is in the range of 2.5 to 4 μm.