JPH08254502A - Method and apparatus for measurement of scale property of steel material - Google Patents

Abstract

PURPOSE: To measure the scale thickness of Cr, Mn, Si or the like nondestructively and with high accuracy after the annealing of a steel material such as a stainless steel plate or the like by a method wherein reflected light is detected in an ultraviolet to visible wavelength region and the scale thickness is found on the basis of the intensity of the reflected light. CONSTITUTION: Light from an Hg-Xe lamp 22 is changed into parallel light so as to perpendicularly irradiate a stainless steel plate 10 through an integrating sphere 24. Reflected light which contains diffused light reflected from the steel plate 10 is returned again to the integrating sphere 24 so as to be passed through interference filters 26, 28 whose transmittance becomes a peak at wavelengths whose central wavelengths correspond to the base line of the Hg-Xe lamp 22, and the intensity of the reflected light at the respective wavelengths is detected by photodetectors 30, 32. A signal which has been detected is sent, via an amplifier 40, to a signal conversion device 42 in which the relationship between a scale-property judgment value such as a scale thickness, a descaling property or the like and a reflectance has been decided in advance and in which an exchange expression has been stored, and its result is output to an output device 44.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring the scale property of steel materials, and in particular, the thickness of the scale formed on a stainless steel plate by the annealing step and the scale attached to it in the next pickling step. The present invention relates to a scale property measuring method and apparatus for steel, which enables continuous online measurement of scale properties such as ease of descaling during melting (referred to as descaling property).

[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 process, it is necessary to appropriately control the temperature rising pattern of the plate temperature to obtain the target material characteristics, and therefore the maximum temperature Tss (° C.) of the plate in the annealing furnace is required.
Then, the furnace temperature control is performed so as to adjust the 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, but 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 is different, the conventional emissive thermometer or the two-color thermometer with a fixed emissivity has a problem that the plate temperature cannot be accurately measured.

Therefore, as an alternative, although the furnace temperature is controlled, the thickness of the scale to be formed and the size of the scale to be removed are changed due to the difference in the thickness of the steel sheet to be annealed, the difference in the width and the like, and the difference in the steel plate composition. The scale property was further different, and when pickling in the next step, there was 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 is hindered, or the scale remains due to insufficient pickling, depending on the properties of the scale.
It has also been a cause of deterioration of surface quality characteristics of the stainless steel sheet, for example, defective gloss.

Conventionally, there is no means for nondestructively measuring the scale thickness of the surface and the scale property related to the descaling property, and the relative scale thickness can be obtained by the destructive test by the surface analyzer or the scale part It has been performed to observe the cross section of the above with an optical microscope to measure the thickness. or,
Regarding the scale property, only the sensory inspection is performed by the visual judgment of the worker, and the offline scale property measurement for optimizing the operation of the entire CAP line and improving the quality characteristic has been realized. There was a problem of not having.

Although not directly related to the technique for measuring the scale thickness on the CAP line, the following techniques are suitable as techniques suitable for measuring the oxide on the surface online.

First, as shown in Japanese Patent Publication No. 62-34093, in order to measure the degree of rust removal of an object to be measured such as a steel plate,
A method in which light having a wavelength band near 550 nm is reflected on the surface of the object to be measured, the amount of reflected light in the wavelength band is measured, and red rust and black skin on the surface of the object to be measured are detected with the same detection sensitivity. Is disclosed.

Further, in Japanese Patent Laid-Open No. 59-63508, a light source for irradiating a light beam to each position in the width direction of the steel plate surface, and an optical sensor for receiving light reflected by each of the light source from each position in the width direction of the steel plate surface. And a means for measuring the descaling state at each position in the width direction of the steel sheet surface based on the output of each of the optical sensors, a descaling treatment state measuring apparatus for a steel sheet is disclosed. In this apparatus, the amount of reflected light of the light irradiated obliquely from the steel sheet is measured from the front side, and the state of the steel sheet surface after the descaling process (defective descaling such as leftover scale or uneven spot) is measured.

[0010]

However, both of the above-mentioned two measuring methods remove the surface scale, for example, the scale remaining after the surface of the steel sheet is mechanically derusted by a shot blasting device or the like. Is quantitatively evaluated, and the oxide of iron is also targeted as the composition of the scale.

Therefore, it is not possible to estimate the descaling property, which indicates how much the attached scale can be treated and removed in the chemically treated pickling step.

In either method, light is emitted from an oblique direction and the reflected light is received in front,
Like the object of these prior arts, it is good when measuring a steel plate with a lot of diffuse reflection, but when measuring a surface with high glossiness and a small diffuse reflection component, like a scale of a stainless steel plate, There is also a problem that the amount of reflected light becomes weak and the measurement sensitivity is poor.

Further, in Japanese Patent Publication No. 62-34093, the wavelength used is limited to around 550 nm.
In 63508, the wavelength used is not particularly limited, and white light using a fluorescent lamp is adopted. However, C
The scale on the AP line is mainly composed of oxides of Cr, Mn, Ni, Si, etc., which are also the 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 was not suitable for the scale thickness measurement on the CAP line, and it was difficult to measure the scale thickness with high sensitivity.

The present invention has been made to solve the above-mentioned conventional problems. In particular, the thickness of the oxide scale of Cr, Mn, Ni, Si, etc. after annealing of a steel material such as a stainless steel plate can be nondestructive. The first purpose is to enable highly accurate measurement.

A second object of the present invention is to make it possible to accurately predict the ease of scale removal of the steel material after annealing in the next pickling step before the descaling treatment (pickling). To do.

A third object of the present invention is to make it possible to simultaneously measure the scale thickness and the ease of descaling of a steel material after annealing by the same apparatus.

[0017]

SUMMARY OF THE INVENTION The present invention provides a scale property measuring method for a steel product, which comprises detecting the surface reflection light of an annealed steel product and measuring the scale thickness of the steel product based on the reflection light. Was detected in the visible to ultraviolet wavelength range, and the scale thickness was determined from the reflected light intensity at at least one wavelength of a predetermined wavelength or less in the wavelength range, thereby achieving the first object. It is a thing.

The wavelength used for obtaining the scale thickness is 450 nm or less.

The present invention also provides a scale property measuring method for a steel material, which detects surface reflected light of a steel material after annealing and predicts easiness of descaling of the steel material based on the reflected light. The second object is achieved by detecting in the visible wavelength region from ultraviolet and predicting the ease of descaling from the reflected light intensity at at least two wavelengths in the wavelength region. .

The present invention also detects the surface reflected light of a steel material after annealing, measures the scale thickness of the steel material based on the reflected light, and predicts the easiness of descaling. In the measurement method, the reflected light is detected in the visible wavelength region from ultraviolet, and the scale thickness is obtained from the reflected light intensity at at least one wavelength of a predetermined wavelength or less in the wavelength region, and the scale wavelength is the same. The third object is achieved by predicting the ease of descaling from the reflected light intensities of at least two wavelengths.

Further, the wavelength used to obtain the scale thickness is also used as one of the wavelengths used to predict the ease of descaling.

The present invention also detects the surface reflected light of the steel material after annealing, measures the scale thickness of the steel material based on the reflected light, and predicts the scale property of the steel material for predicting the ease of descaling. In the measuring device, a light source that irradiates the surface of the steel material with light having a spectrum in the ultraviolet to visible wavelength range, an integrating sphere that captures the reflected light from the surface of the steel material, and a light with a plurality of spectroscopic elements provided on the integrating sphere. The scale thickness is obtained from the detection element and the reflected light intensity detected by the photodetection element at at least one wavelength of at least two wavelengths, and the scale thickness is determined from the reflected light intensity at least two wavelengths. The third object is achieved by including means for predicting the ease of scale.

[0023]

According to the present invention, as a result of detailed examination of the reflection spectrum in the ultraviolet to visible wavelength region of a stainless steel plate under various annealing conditions, the reflected light intensity value at a specific wavelength shows that the scale thickness of the steel plate surface and various It was made by finding that there is a certain relationship with the descaling property under pickling conditions.

First, as an example of the measurement object of the present invention, an austenitic stainless steel plate (hereinafter referred to as SUS304), which is a kind of stainless steel plate, will be taken up.
The characteristic of this steel sheet is that its composition contains approximately 18% Cr,
Included is about 8% Ni. This Cr,
There are a plurality of sub-steel grades having different material properties among the same steel grades, depending on the amount of Ni and the amounts of other contained components such as Si and Mn.

Various SUS304 scales manufactured under various annealing conditions, that is, different Tss and Ts, were subjected to various surface analyzers such as GDS (Glow Discharge Optical Emission Spectrometer) and X-ray diffractometer, and further the optical characteristics of the coating (for example, As a result of measurement with a spectroscopic ellipsometer for measuring the refractive index) or a spectroscope for measuring the reflection characteristic, the scale is mainly Cr or M.
n, Si, etc., the presence of multiple layers in the scale layer, the scale thickness is estimated to be about 0.1 to 0.2 μm, and the spectral complex refractive index of the scale. (N ₁ = n ₁ −ik ₁ , where i ² = −1)
It has been clarified that the value of can be almost determined, and that absorption in the low wavelength region from ultraviolet to visible is large.

The relative value of the scale thickness is GDS
It was also confirmed that, when the scale is sputtered by the method, the element concentrated at the interface between the scale coating and the base metal is focused and can be expressed by the sputtering time until the peak of the element is reached. This value is used as a relative value of the scale thickness, and is hereinafter referred to as a dimensionless amount dsc.

First, using SUS304 annealed under various Tss and Ts conditions, and using a spectroscope with a built-in integrating sphere, the spectral reflectance R in the ultraviolet to visible wavelength region is measured.
(Λ) was measured. Where λ is the wavelength (250-800
nm), and the reflectance standard uses an unannealed and scale-free SUS304 steel plate. For these steel sheets, the dsc value, which is an index of scale thickness, was analyzed by the GDS method.

By selecting the type of acid to be used from a and b, the pickling conditions are changed and the descaling property is evaluated by visual judgment. A: Descaling is possible only with acid a , B: Almost descaled with acid a, and a small amount of scale remains with acid b. C: Unscaleable under both conditions a and b. D: Not scaleable with acid a, but under the condition of acid b. It was classified into four types of results, which can be descaled.

Next, when the correlation between the spectral reflectance R (λ) and the dsc value was examined, when a visible low wavelength was selected from ultraviolet,
It became clear that there is a good correlation between the two. As an example, if λ = 405 nm (= λ1),
The correspondence between the dsc value and R (λ) is shown in FIG. Here, the measurement results of steel sheet samples 1 (○ mark) and 2 (x mark) of different steel types are shown. Similar relationships have been obtained for more types of stainless steel, and by using this relationship, the scale thickness dsc can be estimated with a measurement accuracy within ± 10%.

As a measurement result, another wavelength, for example, 500n
m, 546 nm, 600 nm, etc., the scale thickness dsc and the respective reflectances R (500), R (54
6), R (600) does not have a linear correlation with each other, and it has been clarified that the relational expression has a bivalent or trivalent functional form in the range of variation of the scale thickness. As an example thereof, FIG. 2 shows the relationship between the dsc value and R (546). From this figure, it can be seen that the change in R (546) in the range of the dsc value of about 8 to 15 (arbitrary unit) is small and the scale thickness cannot be estimated. At wavelengths of 600-700 nm,
Although the change in reflectance with respect to the dsc change becomes smaller, the general relationship between the film thickness and the wavelength, and further, the absorptivity also decrease, and thus the degree of the change in reflectivity with respect to the change in scale thickness naturally becomes smaller. It is inferred.

It has also been confirmed that as the wavelength is lengthened, the reflectance is increased or decreased in a vibrational manner, and the change is also reduced.

On the other hand, using the measurement result of the spectral complex refractive index N ₁ by the spectroscopic ellipsometer and the value of the spectral complex refractive index N ₂ = n ₂ −ik ₂ of the base SUS304, the wavelength, incident angle, refraction angle, etc. are given. Then, the relationship between the film thickness and the reflectance was calculated, and it was also confirmed that the linear relationship was obtained as in the experimental result when the wavelength range of low visible wavelength was used.

FIG. 3 shows a measurement example of the relationship between the used wavelength and the scale thickness estimation error. As is clear from FIG. 3, the target accuracy of ± 15% or less is achieved in the region where the wavelength used is 450 nm or less. From the above, it is desirable that the wavelength used is 450 nm or less.

Next, using the measurement results at λ = 254 nm (= λ2), the correspondence between the two-dimensional distribution of R (λ1) and R (λ2) and the descaling properties A to D was investigated. The results shown in are obtained. From this, the classification from A to D and the combination pattern of the two reflectances correspond well, and it is possible to determine the pattern of descaling property.

In the above example, the scale thickness and the descaling property are measured using the common wavelength λ 1. However, by changing this wavelength, for example, in the former measurement, λ =
365 nm (= λ1), for the latter measurement, λ = 254 nm (= λ2) and λ = 405 nm (= λ3) as in the above example.
It is also possible to utilize a total of three different wavelengths.

In addition, the reflectance in the wavelength (= λ0) and the wavelength region (λ = λa to λb) with little absorption is measured at the same time, and the scale thickness variation such as the light source intensity variation and the measurement distance variation to the steel plate is measured. It can also be used to correct a variable factor that is not related to. This method is a correction method that is used for general film thickness measurement, which utilizes the absorptivity of the film.

From the above results, it has been clarified that the present invention makes it possible to measure the scale properties represented by the scale thickness and descaling property of the stainless steel sheet by measuring the reflection intensity at a plurality of wavelengths. These reflection intensity measurements are
It can be basically realized even when the measurement target is moving. Therefore, if the device configuration is such that the measurement can be performed with a distance between the spectroscopic measurement system and the measurement target, online and non-contact measurement of the scale thickness and properties can be realized.

Although the above description has been made for SUS304, the same method can be applied to other steel types, for example, stainless steel such as SUS430 and ordinary steel.

[0039]

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

Two different wavelengths λ 1 = 254 nm, λ 2
= 405 nm and using a Hg-Xe lamp as a light source, a first embodiment of the present invention is shown in FIGS.

As shown in FIG. 5, the traveling stainless steel plate 10 has a pickling line 14 after leaving the annealing process 12.
Are continuously transported to.

Scale property measuring apparatus 20 according to the present invention
Is installed at a place where the vibration of the plate is suppressed by the roll 16 while keeping the distance from the steel plate 10 constant.

The scale property measuring device 20 is constructed as shown in FIG.

That is, the light from the Hg-Xe lamp 22, which is the light source, is collimated and radiated vertically to the stainless steel plate 10 through the integrating sphere 24. Here, the reason why the integrating sphere is used is that the roughness of the scale surface or the base surface is different for each steel type or coil, and the situation of diffuse reflection changes, which causes an error in the reflected light intensity value to be measured. This is because there is a concern that

Reflected light including diffused light reflected from the steel plate 10 returns to the integrating sphere 24 again, and has center wavelengths of 2 respectively.
The interference filter 2 having a peak transmittance at 54, 405 nm and a wavelength corresponding to the base line of the Hg-Xe lamp 22.
The reflected light intensities at these wavelengths are detected by the two photodetector elements 30 and 32, respectively.

The photodetector elements 30 and 32 are arranged on the integrating sphere 24, for example, at a position of ± 90 ° with respect to the light emitting / receiving port 25.

The detected signal is passed through the amplifier 40, the scale property judgment value such as scale thickness and descaling property, and the like.
The signal is transmitted to the signal conversion device 42 in which a conversion formula having a predetermined relationship with the reflectance is stored, and the result is output to the output device 44.

The conversion formula for calculating the scale thickness is as follows:
For example, the first-order approximation formula shown in FIG. 1 can be used.

As a conversion formula for classifying the descaling property, a statistical method using a multivariate analysis method such as a discriminant function based on two reflectance values, or a non-linear mapping by a neural network or the like. A method of identifying the relationship can be considered.

When the number of wavelengths used for measurement is further increased and patterns are classified using multiple wavelengths in the ultraviolet to visible wavelength range, the latter method using a neural network is particularly effective.

The conversion formula used for determining the scale thickness and the descaling property is the final formula based on the measurement data and the analysis result of the actual stainless steel plate 10 after the scale property measuring device 20 is installed on the CAP line. Is decided.

As the light source, a halogen lamp or a metal halide lamp having a high light intensity in the ultraviolet wavelength range can be used. An optical fiber is used to separate the lamp main body and the power supply unit from the light irradiation unit. It is also possible to arrange them. As for the wavelength to be used, 365 nm is also used as λ3, or 600 to 700 with small absorption by the scale.
It is also possible to select and add wavelengths in the range of nm. In that case, the number of photodetectors with an interference filter may be increased and arranged on the integrating sphere.

The entire spectrum obtained by using a diode array type parallel photodetector with a built-in diffraction grating and a small spectroscope 52 utilizing an optical fiber 50, rather than using these plural wavelength separation elements individually (For example 200-
FIG. 7 shows a second embodiment of the present invention in which a signal in the wavelength range of 800 nm) is transmitted to the signal converter 54 to be subjected to arithmetic processing.

In the second embodiment, a metal halide light source 60 having an optical fiber 62 and a condenser optical system 64 is used as a light source.

Even if the optimum measurement wavelength differs depending on the steel type of the steel sheet to be measured, the apparatus configuration of the second embodiment allows the wavelength to be freely selected, so that the applicable range of the present invention is expanded. .

In the above embodiment, the steel plate 10 and the integrating sphere 24 are used.
Although the distance between them is kept constant, a measurement error may occur when the plate thickness of the steel plate 10 changes greatly. Therefore, as shown in FIG. A method may be considered in which the distance is constantly controlled to be constant by providing the distance sensor 70 that measures the distance.

In addition, in the scale property measuring device of the present invention,
By providing a mechanism for scanning in the plate width direction, it is possible to grasp the scale generation state in the plate width direction.

[0058]

EFFECTS OF THE INVENTION According to the present invention, the scale thickness during steel production can be directly measured, and the descaling property in the next step can also be predicted. Therefore, the optimum pickling condition and line speed depending on the generation of scale can be determined. You can choose. Therefore, rewashing due to remaining scale can be omitted, product yield can be improved,
The surface properties can be improved.

Further, it is possible to provide effective information for investigating the relationship between the annealing condition and the scale formation condition. It is also possible to feed back the scale thickness information after annealing to the emissivity information in the furnace and convert it to information on the actual plate temperature, which can be used for factor analysis that determines the material quality of steel. It is possible.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of measuring the scale thickness according to the present invention from the relationship between the reflectance at a wavelength of 450 nm and the scale thickness.

FIG. 2 is a graph showing the relationship between reflectance and scale thickness at a wavelength of 546 nm as a comparative example.

FIG. 3 is a diagram showing the relationship between the wavelength used and the scale thickness estimation error.

FIG. 4 is a diagram illustrating the principle of predicting the descaling property according to the present invention based on the relationship between the reflectance and the descaling property at wavelengths of 254 nm and 405 nm.

FIG. 5 is a process diagram showing a state in which an embodiment of a scale property measuring device according to the present invention is installed in a CAP line.

FIG. 6 is a cross-sectional view showing a specific configuration of the first embodiment of the scale property measuring device.

FIG. 7 is a sectional view showing a specific structure of the second embodiment as well.

[Explanation of symbols]

 10 ... Stainless steel plate 12 ... Annealing process 14 ... Pickling line 20 ... Scale property measuring device 22 ... Hg-Xe lamp 24 ... Integrating sphere 26, 28 ... Interference filter 30, 32 ... Photodetector 42, 54 ... Signal converter 50 , 62 ... Optical fiber 52 ... Small spectroscope 60 ... Metal halide light source 64 ... Condensing optical system

Claims (6)

[Claims] 1. A method for measuring the scale property of a steel material, which comprises detecting the surface reflected light of an annealed steel material and measuring the scale thickness of the steel material based on the reflected light, wherein the reflected light has a wavelength from ultraviolet to visible wavelength. A method for measuring a scale property of a steel material, which comprises detecting a scale thickness from a reflected light intensity at at least one wavelength of a predetermined wavelength or less within the wavelength range. 2. The method for measuring scale properties of steel according to claim 1, wherein the wavelength used for obtaining the scale thickness is 450 nm or less. 3. A method for measuring the scale property of a steel material, which comprises detecting the surface reflected light of an annealed steel material and predicting the ease of descaling of the steel material based on the reflected light. A method for measuring the scale property of a steel material, which comprises detecting in a visible wavelength region and predicting the ease of descaling from the reflected light intensity at at least two wavelengths in the wavelength region. 4. A method for measuring the scale property of a steel material, which detects the surface reflected light of an annealed steel material, measures the scale thickness of the steel material based on the reflected light, and predicts the ease of descaling. Then, the reflected light is detected in the wavelength range from ultraviolet to visible, and the scale thickness is obtained from the reflected light intensity at at least one wavelength of a predetermined wavelength or less in the wavelength range, and the scale thickness is calculated. A method for measuring the scale property of a steel material, which comprises predicting the ease of descaling from the intensity of reflected light at at least two wavelengths. 5. The steel scale according to claim 4, wherein the wavelength used to determine the scale thickness is also used as one of the wavelengths used to predict the ease of descaling. Property measurement method. 6. A scale property measuring device for a steel product, which detects the surface reflected light of an annealed steel product, measures the scale thickness of the steel product based on the reflected light, and predicts the ease of descaling. A light source that irradiates the surface of the steel material with light having a spectrum in the ultraviolet to visible wavelength range, an integrating sphere that captures the reflected light from the surface of the steel material, and a photodetector with a plurality of spectroscopic elements provided on the integrating sphere. And from the reflected light intensity at at least one wavelength of at least two wavelengths detected by the photodetector,
A scale property measuring device for steel material, comprising means for determining scale thickness and predicting ease of descaling from reflected light intensities at at least two wavelengths.