JP2007010476A - Steel plate temperature measuring method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for measuring the temperature of sheet steel suitable for performing online and continuous measurements on the surface temperature of sheet steel heat-treated in an annealing furnace. <P>SOLUTION: A heat-resisting material having a high emissivity in the infrared wavelength region is embedded in part of a furnace wall of the heating furnace. Radiances of a plurality of wavelengths in directions of regular reflection of radiant light from the heat-resisting material at the surface of the sheet steel are measured in each of a plurality of polarization angle components. The emissivity of the sheet steel is computed on the basis of signals of measured radiance each in the plurality of polarization angle components in the plurality of wavelengths and the surface temperature of the heat-resisting material. The surface temperature of the sheet steel is computed on the basis of this emissivity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for measuring the surface temperature of a continuously manufactured steel sheet, and in particular, a steel sheet temperature measuring method suitable for continuously measuring the surface temperature of a steel sheet heat-treated in an annealing furnace online. It relates to the device.

  In order to grow the crystal grains of the stainless steel plate and obtain the desired material properties such as mechanical strength, annealing treatment is performed, and the scale mainly composed of oxide formed on the steel plate surface at that time The pickling process for removing is performed following the previous annealing process. A process in which a series of these processes is performed continuously is generally called a CAP (Cold Anealing and Pickling) line, and is positioned as an important process for producing stainless steel.

  In the annealing treatment, it is necessary to appropriately manage the temperature rising pattern of the steel plate temperature to obtain the target material characteristics, and therefore, the steel plate temperature management in the annealing furnace is important. For that purpose, Tss [° C], which is the highest temperature (soaking temperature) of the steel sheet in the heating furnace, and time (soaking time) Ts [sec.] Until it reaches Tss from a certain reference temperature The temperature control of the heating furnace is performed so as to adjust to the above.

  Originally, it is desirable to measure the steel plate temperature with high accuracy and control the heating furnace temperature. However, in the furnace, oxide scale is generated on the surface of the steel plate, and the generated state is the furnace atmosphere and the furnace temperature at the steel plate speed. Therefore, the thickness of the oxide scale produced varies. Since the emissivity of the steel sheet surface differs depending on the scale thickness, it has been difficult to measure the temperature of the steel sheet. That is, there is a problem that accurate temperature measurement cannot be performed even with a conventional radiation thermometer that sets the emissivity in advance or a two-color thermometer that is considered to have little influence on the emissivity fluctuation.

  Also, in such annealing treatment by furnace temperature control, it is generated even under the same furnace temperature due to differences in dimensions such as plate thickness and width of the steel sheet to be annealed, differences in steel sheet components, steel sheet speed, etc. Since the thicknesses of the scales were different, when pickling in the next step, there was a tendency to suppress the running speed of the steel sheet in order to eliminate the generation of scale residue after pickling. For this reason, if the production efficiency is hindered or the remaining scale is generated because the pickling conditions are not appropriate, the surface properties of the steel sheet are impaired, the quality deteriorates, and the final product has poor gloss. It was also the cause. As described above, it is important not only to obtain the material characteristics of the steel sheet but also to measure the temperature of the steel sheet with high accuracy and implement the heating furnace temperature control from the viewpoint of production efficiency.

  In order to measure the steel plate temperature with high accuracy, it is necessary to correct the emissivity fluctuation when the emissivity fluctuation occurs due to the generation of a scale on the surface. That is, a method of actually measuring the emissivity using an appropriate means is useful, and many methods have been proposed so far.

  For example, Patent Literature 1 proposes a method for estimating the emissivity by obtaining in advance a relational expression between the relationship between spectral radiances under different measurement conditions and the change in emissivity of the measurement target. The measurement conditions are such that the wavelength, the incident / exit (reflection) angle, the polarization angle component, and the like are different.

  Patent Document 2 describes a measurement method for performing measurement at two wavelengths simultaneously. First, by using a long wavelength so that the emissivity is not affected by the thickness variation of the scale generated on the surface of the stainless steel plate, the emissivity in the scale thickness variation range is identified in advance. There has been proposed a method for obtaining a steel sheet temperature based on a constant emissivity. Also, in this method, the thickness of the scale can be measured based on the steel plate temperature information by using another wavelength whose emissivity is correlated with the scale thickness.

  Further, many methods for identifying emissivity by irradiating light from an external light source on the steel sheet surface and actually measuring the reflectivity have been proposed.

  However, the techniques disclosed in Patent Document 1 and Patent Document 2 measure from the direction perpendicular to the steel plate to be measured, and apply these methods to temperature measurement in a state of being heated in the furnace. In this case, there is a problem that the furnace wall radiation of the heating furnace is reflected on the steel plate, so that it enters the radiation thermometer as back light noise. For this reason, in Patent Documents 1 and 2, the reflected light of the furnace wall radiation enters the radiation thermometer. There are no ingenuity. As this measure, a method is generally adopted in which a water-cooled light shielding tube is inserted into the furnace and the radiant energy is measured through the light shielding tube. However, the inside of the furnace is hot, and it is necessary to provide several cooling paths inside to cool the light-shielding tube itself. May occur. When water leakage actually occurs, water adheres to the surface of the in-furnace steel plate and damages the surface, which is inconvenient because it causes actual damage to the product. Therefore, periodic maintenance of the water-cooled light-shielding tube is also required, which causes a problem that it increases work cost and load.

  Also, in the method of identifying the emissivity by irradiating the steel plate surface with light from an external light source and actually measuring the reflectance, the same problem as described above occurs because a similar water cooling structure is usually required.

As a technique for avoiding the above problems, there is a technique disclosed in Patent Document 3. In this technology, a pseudo black body is installed in the furnace, and the sum of the self-luminous brightness of the steel plate and the radiant energy reflected by the pseudo black body reflected on the steel plate to be measured is the P and S polarization components of a specific wavelength. The emissivity is obtained from the polarized radiance ratio, and the steel sheet temperature is measured with high accuracy. Since it is not necessary to insert a water-cooled light-shielding tube in the furnace, it can be said that this is a system with good maintainability and high practicality.
Japanese Patent Laid-Open No. 2-85730 JP-A-9-33464 JP 2002-303551 A

  However, when the technique of Patent Document 3 is applied to a stainless steel plate manufacturing process, there is a problem that emissivity fluctuation cannot be corrected. In other words, in a CAP of a normal stainless steel production line, various stainless steel plates having different components and mechanical properties are often produced through the same process, for example, a typical stainless steel plate having a high Cr content. In addition to the austenitic stainless steel plate SUS304, a ferritic stainless steel plate SUS430 with a large amount of Cr and Ni and many types of stainless steel plates with different contents of other constituent elements are continuously produced. Therefore, in order to produce material characteristics such as mechanical characteristics according to the target conditions, temperature conditions in the furnace, that is, Tss [° C.] which is the highest temperature (soaking temperature) described above, Conditions such as time to reach Tss from a certain reference temperature (soaking time) Ts [sec.] Vary depending on the type of stainless steel sheet. Therefore, not only the scale components and thickness generated on the surface are different, but also the temperature measurement range is usually different.

  As described above, in the technique disclosed in Patent Document 3, when various types of steel plates are manufactured, emissivity correction is performed in which P and S polarization components of a specific wavelength are measured and the emissivity is obtained from the polarization radiance ratio. There is a problem that is not enough. That is, if a plurality of relations are not obtained as a relational expression of the polarization radiance ratio and emissivity obtained in advance for use in correction, the technique shown in Patent Document 3 is applied to all the steel sheets to be manufactured. It is difficult to apply.

  The present invention has been made in view of the above circumstances, and the object thereof is a steel plate temperature measurement method suitable for continuously measuring the surface temperature of a steel plate heat-treated in an annealing furnace online. Is to provide a device.

  The invention according to claim 1 of the present invention is a steel plate temperature measurement method for measuring a temperature of a steel plate having a specularity with a scale formed on a surface, which is placed in an annealing heating furnace, and a part of the furnace wall of the heating furnace. Embedded with a heat-resistant material having a high emissivity in the infrared wavelength region, and the radiance was measured at a plurality of polarization angle components in the direction in which the emitted light from the heat-resistant material was regularly reflected on the surface of the steel plate, The emissivity of the steel sheet is calculated based on each radiance signal of a plurality of polarization angle components at a wavelength and the surface temperature of the heat-resistant substance, and the surface temperature of the steel sheet is calculated based on the emissivity. This is a method for measuring the temperature of a steel sheet.

  The invention according to claim 2 of the present invention is the steel plate temperature measurement method according to claim 1, wherein the wavelength is two wavelengths, and the plurality of polarization angle components are two of P-polarized light and S-polarized light. The relationship of the emissivity with respect to the radiance ratio between the P-polarized light and the S-polarized light at each of the two wavelengths is obtained in advance for each type of measurement object, and the previously obtained relationship and the P-polarized light and the S-polarized light measured at the two wavelengths are It is a steel plate temperature measuring method characterized by identifying the emissivity of the measuring object which changes according to a scale thickness fluctuation | variation based on the radiance ratio.

  The invention according to claim 3 of the present invention is a steel plate temperature measuring device for measuring a temperature of a steel plate having a specularity with a scale formed on the surface, which is placed in the furnace under annealing heating conditions. A radiance that measures the radiance of a plurality of polarization angle components in a direction in which radiant light from a heat-resistant substance with high emissivity in the infrared wavelength region embedded in the furnace wall is regularly reflected on the surface of the steel plate. Based on a measuring device, a thermometer for measuring the surface temperature of the refractory material, and each radiance signal and a surface temperature of the refractory material at a plurality of polarization angle components at wavelengths measured by the radiance measurement device. A steel plate temperature measuring device comprising: an arithmetic unit that calculates an emissivity of the steel plate and calculates a surface temperature of the steel plate based on the obtained emissivity.

  The invention according to claim 4 of the present invention is the steel sheet temperature measuring device according to claim 3, wherein the plurality of wavelengths are two wavelengths, and the plurality of polarization angle components are two of P-polarized light and S-polarized light. The relationship of emissivity with respect to the radiance ratio of P-polarized light and S-polarized light at each of the two wavelengths is obtained in advance for each type of measurement object, and the previously obtained relationship and the P-polarized light and S measured at the two wavelengths are obtained. A steel sheet temperature measuring device characterized by identifying an emissivity of a measurement object that changes in accordance with a scale thickness variation based on a radiance ratio with polarized light.

  The invention according to claim 5 of the present invention is the steel plate temperature measuring method according to claim 1 or 2, wherein the steel plate is a stainless steel plate.

  According to the present invention, the temperature of the stainless steel plate in the furnace can be obtained with high accuracy, and temperature control based on the actual temperature can be performed instead of the steel plate manufacturing by the furnace temperature management and control conventionally used. By applying the present invention to an actual CAP process, it is suitable for the target temperature history depending on the difference in dimensions such as the thickness and width of the steel sheet to be annealed, the difference in steel sheet components, the difference in steel sheet speed, etc. Since the temperature rise pattern can be realized, not only the traveling speed of the steel sheet is reduced, the productivity increases, but also the condition of the scale generated on the surface is ascertained from the emissivity information and the pickling conditions are adjusted. It can also be made appropriate, and the surface property of the steel sheet can be improved by suppressing the remaining scale. In other words, it is possible to improve surface quality characteristics such as good material characteristics and gloss of the final product.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a stainless steel plate temperature measuring apparatus according to the present invention. In the figure, reference numeral 1 denotes an annealing furnace for continuously annealing a traveling steel plate. In the case of a stainless steel plate, for example, it is a high temperature heat treatment furnace called a CAP process. The inside is covered with a refractory, and the inside is heated and maintained at a high temperature by a method such as a radiant tube or a direct fire burner.

  Reference numeral 2 denotes a traveling stainless steel plate (the vertical direction on the paper is the traveling direction, and the left-right direction in the paper is the steel plate width direction), and is heated in a heat treatment furnace according to a temperature rising pattern of a predetermined condition. In order to run stably in the furnace, it runs along the roll 3. Reference numeral 4 denotes a heat-resistant substance embedded in the furnace wall, which has a certain area and is arranged in the same direction as the side surface on the furnace wall inner surface side. 5 is a radiance measurement apparatus installed outside the furnace, and is arranged in a direction in which the angle of θ is estimated from the normal line at the center position of the steel sheet surface in the direction (width direction) orthogonal to the traveling direction of the stainless steel sheet 2. Is done. The refractory material 4 is embedded in the position of the radiance measuring device 5 and the mirror surface, and the center position of the refractory material is arranged at an angle θ from the center position in the width direction of the steel sheet surface with respect to the normal direction. Yes.

  The radiance measuring device 5 has a structure capable of simultaneously measuring P and S polarized luminances at two wavelengths. The radiance measuring device 5 includes (a) thermal radiation energy from a stainless steel plate, (b) energy of a component in which the thermal radiation energy of the heat-resistant substance is regularly reflected on the surface of the stainless steel plate, and (c) a furnace that covers the surroundings. The total energy of the heat radiation energy of the inner refractory and the energy reflected from the steel plate surface or heat-resistant material is measured. However, the energy that the radiant energy of the furnace refractory covering (c) is reflected on the surface of the steel sheet or heat-resistant material is that the surface of the steel sheet to be measured has specular reflection characteristics, Energy measured by a radiance measurement device because the emissivity of the material is made as high as possible (for example, a material with an emissivity of 0.95 or more is selected), and the reflection component from the heat-resistant material can be reduced. The components can be regarded as the above two (a) and (b). Thus, the heat-resistant substance can be treated as a pseudo black body because of its high emissivity.

  Reference numeral 6 denotes a measurement window that partitions between the radiance measuring device 5 installed outside the furnace and the annealing furnace 1, and serves to suppress the outflow of gas from the inside of the furnace. It is preferable to use an inorganic material such as special glass having excellent light transmission characteristics in a wavelength band for measuring luminance. Further, purge is performed using an inert gas or the like so that gas components adhere to and contaminate the inner surface of the measurement window and disturb light transmission characteristics and cause light attenuation. Reference numeral 7 denotes a contact-type thermometer for measuring the surface temperature of the heat-resistant substance. For example, a plurality of thermocouples can be used to measure the average temperature of the surface.

  Reference numeral 8 denotes an arithmetic unit, which is a component of specular reflection on the surface of the stainless steel plate of the thermal radiation energy from the stainless steel plate and the heat radiation energy of the heat-resistant material for P and S polarized light of two wavelengths measured by the radiance measuring device 5. The surface temperature of the stainless steel plate 2 is calculated on the basis of the total four measured values of energy and the measured value by the contact thermometer 7. Reference numeral 9 denotes a storage device that stores the relationship between the radiance ratio of two polarized light and the emissivity, which vary depending on the type of stainless steel plate, the thickness of the surface scale, the radiation measurement wavelength, and the like. By sending the information stored in the storage device 9 to the calculation device 8, the above-described calculation is performed to calculate the final surface temperature value, and the result is output to the output device 10. Further, this result is sent to the process management control device 11 and can be used for setting the speed and heating conditions of the steel sheet, for example.

Below, the basic principle of the temperature measurement which concerns on this invention is demonstrated in detail.
The detection signal E at a specific wavelength λ by the radiance measuring device is the sum of radiation from the stainless steel plate to be measured and radiation signal reflected from the surface of the stainless steel plate from the heat-resistant material embedded in the furnace wall. It can be expressed as (1).
E = k {ε _λ (θ) L _{λ, b} (T ₁ ) + q (1−ε _λ (θ)) L _{λ, b} (T ₂ )} (1)
Where ε _λ (θ) is the spectral emissivity of the object to be measured in the θ direction with respect to the normal direction of the steel sheet surface, T ₁ is the temperature of the object to be measured (stainless steel sheet), and T ₂ is a refractory material embedded in the furnace wall _Where L _{λ , b} (T ₁ ) is the spectral radiance of the black body at the wavelength λ of the temperature T ₁ , and L _{λ, b} (T ₂ ) is the spectral radiance of the black body at the wavelength λ of the temperature T _2. is there. k is a coefficient for converting radiance L _{λ, b} (T) as a physical quantity into an electrical output signal of the radiation thermometer, and q (0 ≦ q ≦ 1) is a coefficient representing the degree of specular reflection.

The spectral direction emissivities of p- and s-polarized light are assumed to be ε _{p, λ} (θ), ε _{s, λ} (θ), respectively. When various coefficients are also replaced with the state corresponding to the polarized light, the output signals at one wavelength of the radiance measuring apparatus are expressed by equations (2) and (3), respectively.
E _p −qk _p L _{λ, b} (T ₂ ) = ε _{p, λ} (θ) k _p {L _{λ, b} (T ₁ ) −qL _{λ, b} (T ₂ )} (2)
E _s −qk _s L _{λ, b} (T ₂ ) = ε _{s, λ} (θ) k _s {L _{λ, b} (T ₁ ) −qL _{λ, b} (T ₂ )} (3)

When the surface roughness of the object does not depend on the direction, there is no difference in polarization reflection characteristics, so that it can be regarded as q _p = q _s = q. By arranging the right sides of the expressions (2) and (3), the following expressions (4) and (5) are obtained.
E _p −qk _p L _{λ, b} (T ₂ ) = ε _{p, λ} (θ) k _p {L _{λ, b} (T ₁ ) −qL _{λ, b} (T ₂ )} (4)
E _s −qk _s L _{λ, b} (T ₂ ) = ε _{s, λ} (θ) k _s {L _{λ, b} (T ₁ ) −qL _{λ, b} (T ₂ )} (5)

_{E p, b (T),} E s, b (T) is blackbody of p- polarized radiation luminance of each temperature T, when the detection signal of the s- polarized light radiance, that each expressed by the following equation it can.
E _{p, b} (T) = k _p L _{λ, b} (T) (6)
E _{s, b} (T) = k _s L _{λ, b} (T) (7)

The left side of the equations (4) and (5) can be measured when q is known. Therefore, when the ratio is taken and arranged using the equations (4) and (5), the equation (8) is obtained.
{E _p −qE _{p, b} (T ₂ )} / {E _s −qE _{s, b} (T ₂ )} / k _r = ε _{p, λ} (θ) / ε _{s, λ} (θ) = Rps ... (8)
Here, according to the equations (6) and (7), k _r = k _p / k _s is a known constant value, the right side is the polarization emissivity ratio Rps, and the emissivity correction method using the polarization radiance ratio It is shown that the above principle holds even in the furnace. Therefore, if the relationship between ε _{p, λ} (θ) or ε _{s, λ} (θ), or their sum ε _λ (θ) and Rps is obtained prior to in-core radiation temperature measurement, it is measured in the furnace. The emissivity is obtained from Rps. When Rps is obtained by the equation (8), the emissivity ε _λ (θ) is obtained from the characteristic curve of Rps-ε _λ (θ).

The value of the thus ε obtained _{λ (θ), E b (} T , which is calculated based on the value measured by contact thermocouple value of radiance E measured at radiance measuring device By combining with the value of ₂ ), the spectral radiation signal E _b (T ₁ ) from the steel sheet is calculated based on the following equation (9).
E _b (T ₁ ) ＝ {E −q (1−ε _λ (θ)) E _b (T ₂ )} / ε _λ (θ) (9)
Further, the temperature T ₁ (° C.) is calculated from the following equation (10).
T ₁ = C ₂ / A / [ln C−ln (E _b (T ₁ ))] − B / A−273.15 (10)
Here, C ₂ is Planck's second constant, and A, B, and C are constants specific to the radiance meter, and are determined by experimentally obtaining calibration data.

  In equation (9), there is a coefficient q representing the degree of specular reflection, but it is experimentally known that the value is close to 1 when the refraction angle θ is shallower than 60 °. ing. Therefore, here, the temperature is calculated by setting the value of q to 1. However, it is also possible to use the value after adjusting the value of q by examining the condition that minimizes the temperature measurement error by examining the characteristics of the measurement object in detail.

As described above, the basic principle at a specific wavelength has been explained. Depending on the type of stainless steel plate, two wavelengths are combined, Rps (λ ₁ ) at one wavelength λ ₁ and a wavelength less than that wavelength. Using the relationship with ε _λ2 (θ) at λ ₂ may be more effective for emissivity estimation. The details of the point of selectively using two wavelengths, which is one of the features of the present invention, will be described in the section of the following embodiments.

  FIG. 2 is a diagram showing an example of an apparatus for realizing polarized radiance measurement according to the present invention. When using 3.9 μm as the first wavelength and 1.55 μm as the second wavelength, an example of an apparatus that simultaneously measures the P and S polarized radiances for each wavelength is shown.

  First, the radiant energy to be received is transmitted through 21 condenser lens systems and guided to a plurality of light receiving elements. The light divided into two paths by the first half mirror 22 is further branched into two paths by the second half mirror 23, and an element (P-polarization element) 25 that transmits P-polarized light is transmitted through one path. The radiance is measured by the thermopile 29 that is transmitted through and is a detection element for 3.9 μm. The radiance is measured by a thermopile 30 that is a detection element for 3.9 μm through another element branched by the second half mirror 23 and transmitted through an element (S-polarized element) 26 that transmits S-polarized light. .

  Similarly, in another path branched by the first half mirror 22, the P and S polarized radiance at 1.55 μm is measured. That is, the third half mirror 24 is branched into two paths. In one of the paths, the radiance is measured by the InGaAs element 31 which is a 1.55 μm detection element via the P-polarization element 27 and branched. In the second path, the radiance is measured by the InGaAs element 32 which is a detection element for 1.55 μm through the S polarizing element 28. The radiance signals measured by the above four sets of polarizing elements and detection elements are sent to the amplification processor 33 and utilized as final radiance data. That is, it is sent to the arithmetic unit 8 shown in FIG.

  As described above, an example in which the measurement of two wavelengths and two polarizations is incorporated in the same apparatus has been described. However, it is also possible to share the measurement at two wavelengths with different apparatuses. In that case, it is necessary to match the field of view so as to measure the same position on the surface to be measured. In FIG. 2, the optical axis for matching the measurement surface is defined. However, since there are two measurement wavelengths, it is necessary to consider that the transmission characteristics of the lens differ depending on the wavelength. Therefore, it is preferable to use a material for the condensing lens 21 in the vicinity of the center for measurement at 1.55 μm, and another material for use in the vicinity of 3.9 μm for measurement. In addition, in order to reduce the attenuation of luminance energy, it is necessary to consider the wavelength characteristics and bandwidth of each half mirror or polarizing element. In addition, the light receiving angle for measuring the polarized radiance is preferably 60 ° or more from the viewpoint of ensuring the specularity of the measurement target. Considering the influence of the vertical vibration of the measurement object, about 70 ° is suitable for practical use. In this embodiment, the case of two wavelengths having different wavelengths is shown, but there are cases where the two wavelengths are the same, that is, measurement is possible even with one wavelength. FIGS. 3 and 4 show the relationship between the pseudo blackbody emissivity and the temperature estimation error, and the incident angle and the temperature estimation error. According to this, in order to obtain an error of 10 ° C. or 5 ° C., it is understood that the emissivity should be 0.95 and the incident angle should be 70 ° or more.

  Next, an example in which the emissivity is obtained from the measured Rps value is shown below. Simulating the annealing process of stainless steel sheet, Tss [° C] which is the highest temperature (soaking temperature) in the furnace described above, and the time (soaking time) Ts from reaching a set reference temperature to Tss The polarization radiance when the thickness of the scale generated on the surface was changed by changing the conditions such as [sec.] was measured under two conditions of 3.9 μm and 1.55 μm as wavelengths. The measurement angle at this time was 70 ° with respect to the normal direction.

  Usually, SUS304 and SUS430 have different heating conditions. The maximum temperature is about 1200 ° C in the former and about 900 ° C in the latter. When the thickness of the generated scale was measured using a spectroscopic ellipsometer, it was about 0.6 μm in the case of SUS304 and about 0.4 μm in the case of SUS430. When the radiance measurement results under these conditions were examined in detail, the measured Rps value and the emissivity data calculated from the calculation of the surface temperature measurement data with a thermocouple based on the measured radiance value. In response, the following conclusions were obtained. In other words, SUS304 uses 3.9μm to measure Rps, and when taking correspondence with emissivity, the relationship when using emissivity at 1.55μm is clear, and SUS430 has a relationship between Rps and emissivity. In both cases, it was found that using 1.55 μm can provide a good response.

  These experimental data are shown in FIGS. Fig. 5 shows the characteristics of SUS304, and Fig. 6 shows the characteristics of SUS430 steel, both of which show a substantially linear monotonous relationship. These relationships can be described as a linear or quadratic approximation function. is there. It can also be seen that the Rps value increases as the scale thickness increases, and since there is a one-to-one relationship between the two, it is also possible to estimate the scale thickness from the measured Rps value. is there.

  The same relationship is also obtained with other steel types such as stainless steel plates, such as SUS420, and it can be dealt with by slightly correcting the relationship curve between Rps and emissivity. Since the types of steel plates that run on the production line can be known in advance, by selecting and using the relational expression between Rps and emissivity, it is possible to estimate the emissivity corresponding to many types of steel plates, and thus the obtained radiation The temperature can be measured with high accuracy using the rate. Moreover, if the information of the scale thickness estimated from the measured value of Rps is used in combination with the steel plate temperature information, it is also possible to indirectly estimate the amount of heat energy obtained by the steel plate. That is, the crystal grain size and product quality characteristics such as mechanical characteristics (tensile strength, elongation, etc.) can be continuously monitored.

  The above describes the results of investigating the relationship of emissivity in advance.Next, the structure of the present invention was actually assembled to simulate an atmosphere filled with back-radiation in the furnace, and a mirror surface for the radiance measurement device. The results of examining the performance of emissivity correction temperature measurement in detail by placing a heat-resistant substance at the reflection position will be described.

  As an example of a heat-resistant substance, a SiC material, which is a ceramic material, was used. This material not only has excellent heat resistance, but also has a black surface, the measured emissivity is 0.95 or more at 3.9 μm or 1.55 μm, and the value is stable even after long-term use. It has also been confirmed. Therefore, it is suitable for use in an actual annealing furnace. As the surface temperature, a plurality of thermocouples were used and an average value of these values was used. Actually, the measurement shown in Fig. 1 was performed with a reduced configuration, and the emissivity was estimated from the measured Rps using the above Rps-emissivity relational expression. 9) The temperature of the stainless steel plate was calculated based on the equations (10). The measurement angle was 70 °. Further, the surface temperature was compared with the steel plate temperature calculated with the measured value of the thermocouple welded to the steel plate as correct.

  As a result of the above, even when various scale thickness conditions, temperature ranges, types of stainless steel plates, etc. were changed, the difference between them was within about 5 ° C, indicating the validity of the method and apparatus according to the present invention. It was. As a result of performing a measurement using a normal single wavelength for comparison, the temperature measurement error has reached several tens of degrees Celsius in the case of vertical light reception and a wavelength of 0.9 μm, and the emissivity correction effect of the present invention is sufficient. Therefore, it was shown that the method of actually measuring the back radiation with a heat-resistant substance is effective.

  Actually, the method according to the present invention can be applied to a CAP process for producing a stainless steel plate, and plate temperature control by temperature measurement with high accuracy can be realized. In this case, the above-described SiC plate material is used as the heat-resistant material, and it has been confirmed that a size of about 500 mm square is sufficient for the dimensions from the conditions such as the reflection characteristics of the steel plate.

It is a figure which shows the structural example of the stainless steel plate temperature measuring apparatus which concerns on this invention. It is a figure which shows the example of an apparatus which implement | achieves the polarized radiance measurement which concerns on this invention. It is a figure which shows the relationship between a pseudo black body emissivity and a temperature estimation error. It is a figure which shows the relationship between an incident angle and a temperature estimation error. It is a characteristic view which shows an example (example of a SUS304 steel plate) between the parameter | index Rps showing polarization radiance ratio, and spectral emissivity (epsilon). It is a characteristic figure showing an example (example of a SUS430 steel plate) of relation between index Rps showing polarization radiance ratio and spectral emissivity ε.

Explanation of symbols

1 Annealing furnace
2 Stainless steel plate
3 rolls
4 refractory materials
5 Radiance measurement device
6 Measurement window
7 Thermocouple
8 Arithmetic unit
9 Storage device
10 Output device
11 Control device for process management
21 Condensing lens system
22 half mirror
23 half mirror
24 half mirror
25 P polarizing element
26 S polarizing element
27 P polarizing element
28 S polarizing element
29 Thermopile
30 Thermopile
31 InGaAs device
32 InGaAs devices
33 Amplification processor

Claims (5)

In the steel plate temperature measurement method for measuring the temperature of a steel plate having a specularity with a scale generated on the surface, placed in an annealing furnace,
A heat resistant material having a high emissivity in the infrared wavelength region is embedded in a part of the furnace wall of the heating furnace, and the radiance is polarized in a direction in which radiant light from the heat resistant material is regularly reflected on the surface of the steel plate. Measured in the angular component,
Calculate the emissivity of the steel sheet based on each radiance signal and the surface temperature of the heat-resistant substance in a plurality of polarization angle components at the measured wavelength,
A steel sheet temperature measuring method, wherein the surface temperature of the steel sheet is calculated based on the emissivity. In the steel plate temperature measuring method according to claim 1,
The wavelength is two wavelengths, and the plurality of polarization angle components are two of P-polarized light and S-polarized light, and the relationship of emissivity with respect to the radiance ratio of P-polarized light and S-polarized light at each of the two wavelengths is measured in advance. Obtained for each type of object, and identifies the emissivity of the measurement object that changes according to the scale thickness variation based on the previously obtained relationship and the radiance ratio of P-polarized light and S-polarized light measured at two wavelengths. A steel plate temperature measuring method characterized by the above. In the steel plate temperature measuring device for measuring the temperature of the steel plate having a specularity with a scale formed on the surface, placed under annealing heating conditions in the furnace,
The radiation light from the heat-resistant material having a high emissivity in the infrared wavelength region embedded in the furnace wall of the heating furnace is arranged in a direction in which it is regularly reflected on the surface of the steel sheet, and the radiance is reduced with respect to a plurality of polarization angle components. A radiance measuring device to measure,
A thermometer for measuring the surface temperature of the heat-resistant substance;
The emissivity of the steel sheet is calculated based on the radiance signal of each of a plurality of polarization angle components at the wavelength measured by the radiance measuring apparatus and the surface temperature of the heat-resistant material, and the obtained emissivity is based on the obtained emissivity. And a computing device for calculating the surface temperature of the steel plate. In the steel plate temperature measuring device according to claim 3,
The plurality of wavelengths are two wavelengths, and the plurality of polarization angle components are two of P-polarized light and S-polarized light, and the relationship of the emissivity with respect to the radiance ratio of P-polarized light and S-polarized light at each of the two wavelengths. The emissivity of the measurement object that changes in accordance with the change in scale thickness based on the previously obtained relationship and the radiance ratio of P-polarized light and S-polarized light measured at two wavelengths is obtained in advance for each type of measurement object. A steel plate temperature measuring device characterized by identifying. In the steel sheet temperature measuring method according to claim 1 and claim 2,
The steel sheet temperature measuring method, wherein the steel sheet is a stainless steel sheet.

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