Surface temperature measurement method, surface temperature measurement device, method for manufacturing hot-dip galvanizing steel sheet, and apparatus for manufacturing hot-dip galvanizing steel sheet

Abstract

The surface temperature measurement method of the present application obtains the amount of radiation light of the surface of a measurement target object, irradiates light to the surface of the measurement target object under specular reflection conditions, obtains the amount of specular reflection light, irradiates light to the surface of the measurement target object under diffuse reflection conditions, obtains the amount of diffuse reflection light, calculates the emissivity of the surface of the measurement target object using a model representing the relationship between the emissivity of the surface of the measurement target object and the specular reflectance and the diffuse reflectance, the obtained amount of specular reflection light, and the obtained amount of diffuse reflection light, and calculates the surface temperature of the measurement target object using the obtained amount of radiation light and the calculated emissivity.

Description

TECHNICAL FIELD

[0001] The present application relates to a surface temperature measurement method, a surface temperature measurement apparatus, a method of manufacturing a hot-dip galvanizing steel sheet, and a manufacturing apparatus for a hot-dip galvanizing steel sheet. BACKGROUND

[0002] In a hot-dip galvanizing line (hereinafter referred to as CGL) in a steel process, temperature management is a very important work in the quality management of the material and plating. In particular, in the alloying process of heating the steel sheet after zinc adhesion, if the steel sheet temperature is too high, powdering occurs, and if the steel sheet temperature is too low, the alloying is insufficient. Further, in high-strength materials, if the steel sheet temperature is too high, the crystal grain size is coarsened and the material characteristics are reduced. Therefore, the CGL requires very strict temperature management.

[0003] Here, as a heating method of the steel sheet, electromagnetic induction heating (hereinafter referred to as IH), heat transfer using radiant heat, and the like. In addition, as a method of this temperature management, there is a method of calculating the steel sheet temperature immediately after heating by heat transfer calculation, electromagnetic field simulation, from the output of IH or direct heating, and the conveying speed or sheet size of the steel sheet and the temperature of the molten zinc pot. However, in this method, a slight deviation in the thickness of the steel sheet or the pass line causes a deviation in the calculation result of the steel sheet temperature. Therefore, it is still important to directly measure the steel sheet temperature.

[0004] Therefore, as a method of directly measuring the steel sheet temperature, a radiation thermometry method, a temperature measuring roll method (refer to Non-Patent Literature 1), and the like have been proposed. However, in the manufacturing of a hot-dip galvanizing steel sheet, since the emissivity of the steel sheet surface greatly varies depending on the progress of alloying, the use of a radiation thermometer in which the emissivity is set to a fixed value in advance causes a large measurement error. Therefore, some efforts have been made to solve the problem of the emissivity setting required for the radiation thermometry method.

[0005] Specifically, a multiple reflection type radiation thermometer that uses multiple reflections of radiation light to make the emissivity close to 1 has been invented. In addition, a wedge type radiation thermometer that assumes that the roll and the steel sheet are isothermal and uses multiple reflections generated in the gap therebetween (refer to Patent Literature 1), a bowl type radiation thermometer that makes a member having a concave shape with a high reflectivity such as gold close to the measurement target (refer to Patent Literature 2), and the like have been developed.

[0006] Further, a method of measuring the reflectance of the measurement object by using the law that the sum of the integrating sphere reflectance and the radiance of the measurement object is 1, and estimating the radiance by estimating the integrating sphere reflectance has been proposed (see Patent Document 3). In addition, there is a method called tracer thermometer which measures the radiance of the surface of the measurement object under multi-wavelength or different polarization conditions, and simultaneously estimates the information of the surface change caused by alloying and the temperature by prior learning (see Non-Patent Document 2).

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Application Laid-Open Publication No. Hei 4-58568

[0010] Patent Document 2: Japanese Patent Application Laid-Open Publication No. Hei 10-185693

[0011] Patent Document 3: Japanese Patent Application Laid-Open Publication No. Hei 5-209792

[0012] Non-Patent Documents

[0013] Non-Patent Document 1: Iron and Steel 79(7), 765-771, 1993

[0014] Non-Patent Document 2: Iron and Steel 79(7), 772-778, 1993

[0015] Non-Patent Document 3: JIS C 1612 Performance Test Method for Radiation Thermometers SUMMARY

[0016] However, when the surface of the steel sheet is at a high temperature, the steel sheet cannot be brought into contact with the roll in a state where molten zinc is adhered to the surface of the steel sheet. Therefore, there is no roll before the rear stage of the pass line of the steel sheet, and the temperature of the steel sheet cannot be measured by using a temperature measuring roll or the like.

[0017] On the other hand, the progress of the alloying reaction differs depending on the kind, size, and conveying conditions of the steel sheet. For example, in a case where the steel sheet is heated for alloying, the temperature of the steel sheet as a target is about 450 to 550°C, and in a case where the temperature of the steel sheet is measured by using an InGaAs element suitable for the radiation thermometry, the change in the radiance of the surface of the steel sheet before and after the alloying is about 0.2 to 0.7. This is a difference of 60°C or more when converted into the temperature, and the temperature of the steel sheet cannot be accurately measured.

[0018] In addition, in order to solve the problem of the variation in the emissivity, various methods as described above have been proposed, but the wedge-shaped radiation thermometer, like the temperature measuring roller, cannot be applied immediately after heating when there is a demand for temperature measurement. In addition, the bowl-shaped radiation thermometer also requires very small peeling of the rolling line, but since the variation in the rolling line cannot be suppressed by the roller after the molten zinc adheres in the CGL, it is difficult to apply due to peeling.

[0019] In addition, the method of estimating the integral sphere reflectance to estimate the emissivity, although there are cases of application in other cold-rolled steel sheet processes, the diffusivity of the surface of the steel sheet during alloying is very high, and thus the estimation accuracy of the integral sphere reflectance and the emissivity is low. Furthermore, since the tracer thermometer is not based on a physical model, it is easily affected by unexpected disturbances, phenomena, and practical use is limited.

[0020] Therefore, a technique is expected to be provided which can measure the temperature of a steel sheet in a hot-dip galvanizing system with high accuracy regardless of the variation in the emissivity of the surface of the hot-dip galvanizing steel sheet during the production of the hot-dip galvanizing steel sheet.

[0021] The present application was completed in view of the above problems, and aims to provide a surface temperature measurement method and a surface temperature measurement device which can measure the surface temperature of a measurement object with high accuracy regardless of the variation in the emissivity of the surface of the measurement object. In addition, another object of the present application is to provide a method and an apparatus for producing a hot-dip galvanizing steel sheet which can measure the temperature of a steel sheet in a hot-dip galvanizing system with high accuracy regardless of the alloying process, and can produce a hot-dip galvanizing steel sheet with a good yield.

[0022] The surface temperature measurement method according to the present application includes: a first imaging step of obtaining the amount of radiation light from the surface of a measurement object; a second imaging step of irradiating light to the surface of the measurement object under a specular reflection condition, and obtaining the amount of specular reflection light; a third imaging step of irradiating light to the surface of the measurement object under a diffuse reflection condition, and obtaining the amount of diffuse reflection light; an emissivity calculation step of calculating the emissivity of the surface of the measurement object using a model representing the relationship between the emissivity of the surface of the measurement object and the specular reflectance and the diffuse reflectance, the amount of specular reflection light obtained in the second imaging step, and the amount of diffuse reflection light obtained in the third imaging step; and a temperature measurement step of calculating the surface temperature of the measurement object using the amount of radiation light obtained in the first imaging step and the emissivity calculated in the emissivity calculation step.

[0023] Preferably, the emissivity calculation step is executed when the amount of specular reflection light obtained in the second imaging step is less than a predetermined value, and a fixed value is used as the emissivity in the temperature measurement step when the amount of specular reflection light obtained in the second imaging step is equal to or more than the predetermined value.

[0024] Preferably, the above-mentioned second photographing step and the above-mentioned third photographing step each include a step of correcting the amount of specularly reflected light and the amount of diffusely reflected light by subtracting the amount of radiated light obtained in the above-mentioned first photographing step.

[0025] Preferably, the above-mentioned first photographing step, the above-mentioned second photographing step, and the above-mentioned third photographing step include a step of receiving light using a light-receiving element having a plurality of fields of view, the light-receiving element allocating the ranges in which the above-mentioned amount of radiated light, the above-mentioned amount of specularly reflected light, and the above-mentioned amount of diffusely reflected light are obtained along a conveying direction of the measurement target object.

[0026] Preferably, the above-mentioned measurement target object is a hot-dip galvanizing steel sheet.

[0027] The surface temperature measuring apparatus according to the present application includes a first photographing device that obtains an amount of radiated light from a surface of a measurement target object; a second photographing device that obtains an amount of specularly reflected light by irradiating light to the surface of the measurement target object under a specular reflection condition; a third photographing device that obtains an amount of diffusely reflected light by irradiating light to the surface of the measurement target object under a diffused reflection condition; a radiance calculating device that calculates a radiance of the surface of the measurement target object using a model that indicates a relationship between the radiance and specular reflectance and diffused reflectance of the surface of the measurement target object, the amount of specularly reflected light obtained by the second photographing device, and the amount of diffusely reflected light obtained by the third photographing device; and a temperature measuring device that calculates a surface temperature of the measurement target object using the amount of radiated light obtained by the first photographing device and the radiance calculated by the radiance calculating device.

[0028] Preferably, the above-mentioned measurement target object is a hot-dip galvanizing steel sheet.

[0029] The method of manufacturing a hot-dip galvanizing steel sheet according to the present application includes a manufacturing step of manufacturing a hot-dip galvanizing steel sheet, wherein the manufacturing step of manufacturing a hot-dip galvanizing steel sheet includes a temperature measuring step of measuring a surface temperature of the hot-dip galvanizing steel sheet by the surface temperature measuring method according to the present application, and a step of controlling a manufacturing condition of the manufacturing step using the surface temperature measured by the temperature measuring step.

[0030] The manufacturing apparatus of a hot-dip galvanizing steel sheet according to the present application includes the surface temperature measuring apparatus according to the present application, and an apparatus that manufactures a hot-dip galvanizing steel sheet based on a surface temperature of the hot-dip galvanizing steel sheet measured by the surface temperature measuring apparatus.

[0031] According to the surface temperature measurement method and apparatus of the present invention, the surface temperature of the object to be measured can be determined with high accuracy regardless of variations in the emissivity of the object's surface. Furthermore, according to the manufacturing method and equipment for hot-dip galvanized steel sheets of the present invention, the temperature of the steel sheet in the hot-dip galvanizing production line can be measured with high accuracy regardless of the alloying process, resulting in high-yield production of hot-dip galvanized steel sheets. Attached Figure Description

[0032] Figure 1 This is a diagram showing the configuration of an experimental apparatus as one embodiment of the present invention.

[0033] Figure 2 This is a graph illustrating an example of the relationship between emissivity and specular reflectivity (specular reflectance value) and diffuse reflectivity (diffuse reflectance value).

[0034] Figure 3 This is a graph showing the relationship between the thermocouple temperature and the radiation temperature measurement results in the example of the present invention and the monochromatic radiation thermometer.

[0035] Figure 4 This diagram illustrates an application example of a temperature measuring device, as one embodiment of the present invention, on an actual production line.

[0036] Figure 5 It means Figure 4 The diagram shows a variation of the application example.

[0037] Figure 6 It means Figure 4 The diagram shows a variation of the application example.

[0038] Figure 7 This diagram illustrates the setup conditions for a light source used for specular reflection.

[0039] Figure 8 This is a diagram used to illustrate the setup conditions for a light source used for diffuse reflection.

[0040] Figure 9 This is a graph showing the actual temperature measurement results before and after filtering.

[0041] Figure 10 This is a diagram showing the configuration of a first modified example of a temperature measuring device as an embodiment of the present invention.

[0042] Figure 11 This is a diagram showing the configuration of a second modified example of a temperature measuring device as an embodiment of the present invention.

[0043] Figure 12 It is a graph showing the changes in brightness values ​​of self-illuminating, averaged specular reflection, and diffuse reflection light.

[0044] Figure 13 is a graph showing surface temperatures measured by the present example and Comparative Examples 1 and 2.

[0045] Figure 14 is a graph showing the relationship between the degree of alloying and the surface temperature of the present example and Comparative Example 2. DETAILED DESCRIPTION

[0046] The radiation thermometry is a method of theoretically determining the amount of radiation of a measurement target according to the temperature and the emissivity and calculating the surface temperature of the measurement target using the measured amount of radiation and the pre-set emissivity. Here, the emissivity of the measurement target varies in the range of 0 to 1 depending on the state and shape of the surface of the measurement target. Therefore, in order to measure the surface temperature of the measurement target with high accuracy, it is necessary to set the emissivity of the measurement target to a correct value. Therefore, many commonly used radiation thermometers pre-measure the emissivity of the measurement target or use a known emissivity of the measurement target, and pre-set the emissivity to a fixed value. Then, the amount of radiation light is measured, and the surface temperature of the measurement target is calculated from the calibration curve. It should be noted that, as a method of measuring the emissivity as described here, there are a method of measuring the ratio of the amount of radiation light to the measurement site by applying a black body paint with a known emissivity, or a method of theoretically converting the surface temperature value obtained by other measurement methods such as a thermocouple into the amount of radiation and comparing them.

[0047] On the other hand, in the general radiation thermometer in which the emissivity is pre-set to a fixed value, in the case where the actual emissivity greatly deviates from the set emissivity, a large measurement error occurs. In particular, on the outlet side of the IH heating alloying process after the zinc pot, since the surface of the steel sheet can take all states from the state close to the mirror surface before alloying to the state close to the rough surface after alloying, if the emissivity is pre-set to a fixed value, a large deviation from the actual emissivity is inevitably caused. In addition, since the progress of the degree of alloying greatly varies depending on the composition and manufacturing conditions, it is also difficult to predict the surface state and the emissivity in advance. Therefore, in order to perform the radiation thermometry with high accuracy, the inventors and others have studied to accurately estimate the emissivity in real time with respect to the surface state of the measurement target that varies, and to convert the radiation brightness into the temperature using the estimated emissivity. Here, as a method of estimating the emissivity, the Kirchhoff's law that the sum of the emissivity and the integrating sphere reflectance is 1 is focused on. The method of calculating the integrating sphere reflectance from the information of the reflection distribution is described in Patent Literature 3, but it is difficult to accurately measure the parameter of the diffusion of the specular reflection component that greatly affects the accuracy, and sufficient accuracy cannot be obtained. However, it can be considered that the reflection characteristics of the measurement target have a close physical relationship with the emissivity, and are also an important clue to estimate the emissivity with respect to the surface that changes in the process of alloying of the hot-dip galvanized steel sheet.

[0048] Therefore, the inventors of this invention, focusing on the fact that reflective properties are generally expressed as the sum of specular and diffuse reflection, studied the relationship between specular and diffuse reflection and emissivity of the surface state during the alloying process of hot-dip galvanized steel sheets. The results showed that, as described later, the surface state during the alloying process undergoes two stages: Step S1, from a state where the specularity becomes very high due to zinc hot-dip galvanizing, the specularity gradually decreases, while the diffuseness increases to an almost completely diffuse surface; Step S2, from a state where it becomes a completely diffuse surface, the diffuse reflectivity gradually decreases. Furthermore, it was found that the emissivity remains unchanged in Step S1, while in Step S2, where there is almost no specular reflection component, according to Kirchhoff's law, the emissivity increases as the diffuse reflectivity decreases. These stages are difficult to follow by either specular reflection or diffuse reflection alone; by combining both reflective components, the progress of alloying and the emissivity can be accurately estimated. Then, based on these insights, the inventors of the present invention conducted repeated and in-depth research and proposed the following technical idea: In the hot-dip galvanizing production line, surface images of hot-dip galvanized steel sheets are taken under specular reflection and diffuse reflection conditions, and the emissivity is calculated in real time according to the pre-modeled relationship between emissivity and specular and diffuse reflection, thereby enabling high-precision measurement of the surface temperature of hot-dip galvanized steel sheets.

[0049] Specifically, when measuring the surface temperature of hot-dip galvanized steel sheets using this invention, firstly, the radiation thermometer is calibrated and the relationship between emissivity and specular and diffuse reflectivity is modeled. Here, since the surface temperature of the target hot-dip galvanized steel sheet is approximately 450–550°C, an InGaAs element is preferably used as the radiation thermometer. Furthermore, long-pass filters, short-pass filters, and band-pass filters are preferably used to minimize the wavelength sensitivity. Various calibration methods exist for the radiation thermometer; as an example, the method described in Non-Patent Document 3 can be applied. The radiation thermometer described here is an optical sensor with surface, line, or single element components, which functions as a radiation thermometer by being calibrated at various temperatures under blackbody conditions.

[0050] The relationship between emissivity and specular reflectivity and diffuse reflectivity can be illustrated by, for example, using... Figure 1 The experimental setup shown is used to model the specular reflection, diffuse reflection, and radiant light intensity when hot-dip galvanized steel sheets are heated. The following section... Figure 1 The structure of the experimental setup and the steps of modeling it are explained.

[0051] In use Figure 1The experimental apparatus shown models the relationship between the emissivity and the specular reflectance and the diffuse reflectance by first welding a thermocouple 1 to the surface of the hot-dip galvannealed steel sheet S before alloying, and further applying a black body spray 2 to a portion of the surface of the hot-dip galvannealed steel sheet S. Next, the hot-dip galvannealed steel sheet S is placed on a heater 3 capable of uniformly heating the entire hot-dip galvannealed steel sheet S. The heating method can be any of heat transfer, IH heating, and electric current heating as long as it is capable of uniformly heating the hot-dip galvannealed steel sheet S, but in the case of welding the thermocouple 1, it is necessary to somehow prevent IH heating, electric current heating from affecting the measurement.

[0052] Next, a radiation thermometer 4, a specular reflectance light source 5 that irradiates light to the surface of the hot-dip galvannealed steel sheet S under specular reflection conditions, and a diffuse reflectance light source 6 that irradiates light to the surface of the hot-dip galvannealed steel sheet S under diffuse reflection conditions are provided. Note that in order to make the light projection angle and the light receiving angle of the specular reflectance light source 5 coincide, the radiation thermometer 4 cannot be provided on the front surface of the hot-dip galvannealed steel sheet S, but it is preferable to be provided as perpendicular to the surface of the hot-dip galvannealed steel sheet S as much as possible within the range where it can be provided. In addition, the diffuse reflection conditions are preferably an angle of 45° or more different from the specular reflection conditions. In addition, it is preferable to be able to switch the lighting / off of the specular reflectance light source 5 and the diffuse reflectance light source 6 by a power source or a shutter or the like.

[0053] Note that the hot-dip galvannealed steel sheet in the present specification is not particularly limited as long as it contains zinc in the plated layer. As the hot-dip galvannealed steel sheet, a hot-dip galvanized steel sheet (GI), an alloyed hot-dip galvanized steel sheet (GA) obtained by alloying a hot-dip galvanized steel sheet, a Zn-Al-Mg plated steel sheet (for example, a Zn-6 mass% Al-3 mass% Mg alloy plated steel sheet, a Zn-11 mass% Al-3 mass% Mg alloy plated steel sheet), a Zn-Al plated steel sheet (for example, a Zn-5 mass% Al alloy plated steel sheet, a Zn-55 mass% Al alloy plated steel sheet), and the like can be exemplified.

[0054] Further, one or two or more of nickel, cobalt, manganese, iron, molybdenum, tungsten, titanium, chromium, aluminum, magnesium, lead, antimony, tin, copper, silicon can be contained in the zinc-based hot-dip plated layer as a small amount of a different metal element or an impurity. In addition, two or more of the same or different zinc-based hot-dip plated layers can be formed in the above-described zinc-based hot-dip plated layer.

[0055] Next, a model representing the relationship between the emissivity and the diffuse reflectance and the specular reflectance is generated using the above-described experimental apparatus. Specifically, the following processes (a) to (e) are repeatedly performed while gradually heating the hot-dip galvannealed steel sheet S.

[0056] (a) The amount of radiation light is obtained by taking an image of the surface of the hot-dip galvannealed steel sheet S by turning off the specular reflectance light source 5 and the diffuse reflectance light source 6 or closing the shutter.

[0057] (b) Obtain the sum of specular reflection and radiant light by illuminating only the specular reflection light source 5 or by taking a surface image of the hot-dip galvanized steel plate S with the shutter open.

[0058] (c) Obtain the sum of diffuse reflection and radiation by illuminating only the diffuse light source 6 or by taking a surface image of the hot-dip galvanized steel plate S with the shutter open.

[0059] (d) The specular reflection and diffuse reflection light amounts are calculated by subtracting the light amount obtained in process (a) from the light amounts obtained in processes (b) and (c). At this point, considering the difference in light amount caused by the different exposure times in the capture of each surface image, corrections are implemented.

[0060] (e) The surface temperature measured by thermocouple 1 is compared with the surface temperature measured by calibrated radiation thermometer 4, or if radiation thermometer 4 is a line sensor or a surface sensor, the emissivity component is compared with the emissivity of the part coated with blackbody spray 2, thereby calculating the emissivity.

[0061] It should be noted that the heating rate is preferably set in such a way that the exposure time and measurement time are taken into consideration, so that the surface state of the hot-dip galvanized steel sheet S can be photographed in approximately the same manner in processes (a) to (c). Thus, for example, it is possible to produce... Figure 2 The model shown represents the relationship between the emissivity and specular reflectivity of the surface of the hot-dip galvanized steel sheet S and the relationship between the emissivity and diffuse reflectivity of the surface of the steel sheet S within the heating temperature range of the hot-dip galvanized steel sheet S.

[0062] Figure 2 (a) and Figure 2 (b) Examples of the relationship models between emissivity and specular reflectivity (specular reflectance value) and between emissivity and diffuse reflectivity (diffuse reflectance value) obtained through the above modeling steps, respectively. For example... Figure 2 As shown, the surface state of hot-dip galvanized steel sheet consists of two processes: S1, where the specularity gradually decreases and the diffuseness increases to an almost completely diffuse surface; and S2, where the diffuse reflectance gradually decreases from the state of becoming a completely diffuse surface. Here, to accurately estimate emissivity, an index corresponding one-to-one with the emissivity is needed. If only specular reflection is present, there is no variation in specular reflection in areas of high emissivity, making estimation difficult. If only diffuse reflection is present, it has broad sensitivity to emissivity variations, but sometimes two emissivities can be obtained for a single diffuse reflection amount. Therefore, by adding specular reflection information, it is possible to determine which of the two corresponding emissivities is correct, thus allowing for high-precision estimation of emissivity by combining specular and diffuse reflection amounts.

[0063] Based on this model, by measuring the specular and diffuse reflectance of the surface of hot-dip galvanized steel sheets, the emissivity of the steel sheets can be estimated with high accuracy. Therefore, regardless of how the emissivity of the hot-dip galvanized steel sheet surface changes during manufacturing, the surface temperature of the hot-dip galvanized steel sheet can be calculated with high accuracy using the amount of radiant light and the emissivity. Furthermore, by manufacturing hot-dip galvanized steel sheets based on the calculated surface temperature, a high yield rate can be achieved.

[0064] It should be noted that the specular reflectance and diffuse reflectance of hot-dip galvanized steel sheets can be determined by measuring the relative values ​​of their specular and diffuse reflectances with respect to a sample sheet whose reflectance is close to 1, which is typically used as a reference. Examples of sample sheets for determining specular reflectance include gold mirrors and aluminum mirrors, while barium sulfate can be used for determining diffuse reflectance. Alternatively, the above modeling can be performed using the reflected light intensity as a reference. In this case, it is preferable to apply a light source with a constant illumination intensity to an imaging system with constant sensitivity, and use the resulting brightness value itself as the model. Furthermore, while a shutter is used in the above modeling steps, it is not necessarily necessary to use a shutter if specular reflection, diffuse reflection, and self-illuminating images with the same surface condition can be obtained. Alternatively, multiple samples with different alloying degrees can be prepared without using a shutter, their specular and diffuse reflectances measured, and the samples further heated to a point where the surface condition remains unchanged, and the emissivity determined as the model.

[0065] When applying the temperature measurement method, as one embodiment of the present invention, to an actual circuit, the radiant light, specular reflection light, and diffuse reflection light are obtained from the hot-dip galvanized steel sheet of the actual circuit. Then, the emissivity is calculated using a model based on the obtained specular reflection and diffuse reflection light. Various methods can be considered for calculating the emissivity. For example, if the number of points in the model obtained in the experiment is set to N, the specular reflection light is set to rs, the diffuse reflection light is set to rd, and the emissivity is set to e, then the model can be represented as a three-dimensional vector (rs). n rd n e n (n = 1, ..., N). In practical applications, if the number of points in the model is insufficient, interpolation can be used to increase the number of points. Additionally, once rs is determined... n rd n Just e n In the case where the condition is uniquely determined, e can be approximated as a function of rs and rd, as in e = f(rs, rd).

[0066] Here, if the specular reflection amount obtained in the actual measurement is set as Rs and the diffuse reflection amount is set as Rd, then the coordinate position (alloying degree) and emissivity on the model during measurement can be estimated by minimizing the distance, as shown in the following mathematical formula (1). It should be noted that the specular reflection amount and the diffuse reflection amount can be weighted as needed. In addition, of course, the same result can be obtained even if the norm of the distance is changed.

[0067]

[0068] Furthermore, in this case, steps S1 and S2 can be separated as distinct physical phenomena. Therefore, one can first select which of steps S1 and S2 the surface condition of the hot-dip galvanized steel sheet should be classified as, and then calculate the coordinate position on the model within each process. For example, as the simplest method, a threshold is set for specular reflectance; if the specular reflectance is above the threshold, it is classified as step S1, and if it is below the threshold, it is classified as step S2. Then, if it is step S1, the emissivity hardly changes, so the emissivity is set to a fixed value (approximately 0.2); if it is step S2, the coordinate position and emissivity on the model can be estimated based on the value of diffuse reflection. Furthermore, since many methods have been proposed for determining the optimal coordinate position on the model, any method can be used as long as the coordinate position on the model can be accurately determined.

[0069] In practice, in the laboratory, the result of temperature measurement calculated and corrected based on specular reflectance and diffuse reflectance (example of the present invention) and the result of temperature measurement with emissivity fixed at 0.2 (monochromatic radiation thermometer) are presented by comparing with the temperature measured using thermocouple 1. Figure 3 .exist Figure 3 In the diagram, the vertical axis represents the radiation temperature measurement result, and the horizontal axis represents the thermocouple temperature measurement result, which serves as the true value. In this measurement, the hot-dip galvanized steel sheet was gradually heated, and the temperature was measured during the alloying process. In the region near the start of heating in the hot-dip galvanized steel sheet before alloying, the actual emissivity is approximately 0.2. Therefore, both the monochromatic radiation thermometer with a fixed emissivity of 0.2 and the present invention example, which estimates the emissivity to be approximately 0.2 by measuring various reflectivities, are consistent with the thermocouple temperature measurement results. Then, as alloying occurs, the actual emissivity gradually increases, and the temperature value measured by the monochromatic radiation thermometer, assuming an emissivity of 0.2, shifts upwards compared to the thermocouple measurement, such as... Figure 3The error finally becomes about 60°C. In contrast, in the present example, since the emissivity is estimated from each reflectance, the actual change in emissivity can be corresponded to at the time of temperature measurement. Therefore, with respect to the variation in the emissivity of the surface generated in steps S1 and S2, the present example is almost consistent with the temperature measurement result of the thermocouple. In actual operation, the degree of progress of alloying varies depending on various operation conditions, and is not necessarily related to temperature. Therefore, in the temperature measurement target region, it is necessary to accurately measure the temperature regardless of the degree of progress of alloying, and the error becomes large in the monochromatic radiation thermometer which assumes a specific emissivity. In contrast, in the present example, the emissivity can be accurately estimated regardless of the degree of progress of alloying, and therefore the temperature measurement can be performed with high accuracy at all times.

[0070] An example in which the temperature measurement device of one embodiment of the present application is applied to an actual line is shown in Figure 4 In Figure 4 In the example shown, the temperature measurement device 10 of one embodiment of the present application is provided immediately after the molten zinc is attached to the steel sheet in the molten zinc pot 11 and heated to the alloying target temperature in the heating furnace 12 (the inlet side of the heat retaining zone 13). The temperature measurement device 10 includes Figure 1 The radiation thermometer 4, the mirror reflection light source 5, and the diffuse reflection light source 6 shown are provided. At this time, when the surface temperature of the hot-dip galvanizing steel sheet S is about 450 to 550°C, the radiation light becomes large, and thus the mirror reflection light source 5 and the diffuse reflection light source 6 need to be very strong. In particular, the light amount of the diffuse reflection light is weak compared to the mirror reflection light, and thus a halogen lamp is most preferably used. Note that the halogen lamp needs a time of several minutes or more from lighting to stabilization of the light amount, and thus it is preferable to use the shutter 7 to switch between lighting and extinction and to be always lit. Alternatively, if the light amount is a problem, an infrared LED can be used, and if the reflection polarization characteristics of the object are a problem, an infrared laser can be used.

[0071] In addition, in the example shown in Figure 4 In the example shown, the mirror reflection light source 5 is provided on the downstream side of the transport direction of the hot-dip galvanizing steel sheet S with respect to the diffuse reflection light source 6, but the positions of the mirror reflection light source 5 and the diffuse reflection light source 6 can be reversed as shown in Figure 5 In addition, the mirror reflection light source 5 and the diffuse reflection light source 6 can be provided at the same position of the rolling line of the hot-dip galvanizing steel sheet S as shown in Figure 6 With respect to the positions of the mirror reflection light source 5 and the diffuse reflection light source 6, it is preferable to consider environmental factors such as variation of the rolling line, easiness of dust accumulation, and further heat influence.

[0072] Note that since there are no conveying rolls in the several tens of meters of the rear section of the molten zinc bath of the CGL, the rolling line is unstable. Although there is also a technique of using electromagnets to achieve stabilization of the rolling line (see Patent Literature 3), basically, it is to suppress the wobble of the setting position of the air knives that uniformize the amount of adhesion of the molten zinc, so the position and inclination of the rolling line after the alloying heating that is the object of temperature measurement fluctuate. Therefore, it is preferable to design the setting conditions and the irradiation light of the mirror reflection light source 5 and the diffuse reflection light source 6. Hereinafter, examples of the setting conditions of the mirror reflection light source 5 and the diffuse reflection light source 6 are described with the configuration shown in FIG. 1 as a premise, but the idea is the same in other configurations. Figure 4

[0073] Now, the length direction of the hot-dip galvanizing steel sheet S is set as the y-axis direction, the width direction of the hot-dip galvanizing steel sheet S is set as the c-axis direction, the fluctuation amount of the rolling line position of the hot-dip galvanizing steel sheet S from the reference position is set as ±Ad, the angle fluctuation amount of the surface of the hot-dip galvanizing steel sheet S in the x-axis direction from the reference angle is set as ±Ax, and the angle fluctuation amount of the y-axis direction from the reference angle is set as ±Ay.

[0074] First, the setting conditions of the mirror reflection light source 5 and the diffuse reflection light source 6 are described with reference to FIGS. 2 and 3. Figure 7 (a), (b) describe the setting conditions of the mirror reflection light source 5. In order to stably measure the brightness under the mirror reflection conditions regardless of the rolling line fluctuation, the condition is to set the light emitting surface of the mirror reflection light source 5 at the position that becomes the mirror reflection condition even if the rolling line of the hot-dip galvanizing steel sheet S fluctuates. In other words, if the distance from the radiation thermometer 4 to the rolling line is set as L, the incident angle of the mirror reflection light source 5 and the light receiving angle of the radiation thermometer 4 are set as φ1, and the distance from the mirror reflection light source 5 to the rolling line is set as L1, the difference in the irradiation position on the surface of the hot-dip galvanizing steel sheet S caused by the fluctuation amount of the rolling line in the y-axis direction is ±Ad x sin φ1, and in addition, the difference in the shooting position is also ±Ad x sin φ1. Furthermore, if the y-axis angle fluctuation amount is set as ±Ay, the position of the mirror reflection light source 5 that becomes the mirror reflection direction with respect to the shooting field of view of the radiation thermometer 4 fluctuates ±L1 Ay / cos φ. In addition, the x-axis direction is not affected by the rolling line fluctuation on the irradiation position and the shooting position, but if the x-axis angle fluctuation amount of ±Ax is considered, the position of the mirror reflection light source 5 that becomes the mirror reflection direction with respect to the field of view of the radiation thermometer 4 fluctuates ±L1 Ax / cos φ1. Therefore, it is preferable to make the size of the light emitting surface of the mirror reflection light source 5 larger, including the fluctuation amount of ±L1 Ax / cos φ1 in the x-axis direction and ±(2Ad x sin φ1 + L1 Ay / cos φ) in the y-axis direction.

[0075] Next, the setting conditions of the mirror reflection light source 5 and the diffuse reflection light source 6 are described with reference to FIGS. 4 and 5. Figure 8 ​(a), (b) describe the setting conditions of the diffuse reflection light source 6. In order to stably measure the brightness of the diffuse reflection condition regardless of the rolling line variation, the condition is that even if the rolling line of the hot-dip galvanizing steel sheet S is varied, it is set in a manner of uniformly irradiating the photographing range. This is because, unlike the case of the specular reflection light source 5, in the case of diffuse reflection, the influence of the light projection angle and the light receiving angle on the diffuse reflection light amount is small. In other words, if the distance from the diffuse reflection light source 6 to the rolling line is set to L2, the difference in the irradiation position on the surface of the hot-dip galvanizing steel sheet S caused by the variation amount of the rolling line in the y-axis direction is ±Ad x sin φ2, and the difference in the photographing position is ±Ad x sin φ1, but the displacement direction of the irradiation position and the photographing position is opposite in arrangement. In addition, there is no influence of the rolling line variation on the irradiation position and the photographing position in the x-axis direction. Therefore, the diffuse reflection light source 6 is preferably disposed at a position capable of uniformly irradiating the distance L2 in the range of ±Ad (sin φ2 - sin φ1) in the y-axis direction. The above setting condition is more preferably further provided with a margin in view of other setting accuracy and the like.

[0076] In addition, the diffuse reflection light source, while being applied to the optical system of the diffuse reflection condition which is a low reflectance condition, must ensure a sufficient amount of reflected light with respect to spontaneous light, and thus requires very strong irradiation. However, in the case of using an infrared light source, such as a halogen light source, which is too strong, the light source itself can heat the hot-dip galvanizing steel sheet, changing the surface temperature of the hot-dip galvanizing steel sheet. Therefore, from the viewpoint of radiative heat transfer, it is preferable to satisfy the condition shown in the following equation (2). Here, the allowable temperature variation amount is set to ΔT (°C), the output power of the diffuse reflection light source is set to P (W), the absorptivity (emissivity) of the hot-dip galvanizing steel sheet in the irradiation region of the diffuse reflection light source is set to ε h , the irradiation area of the diffuse reflection light source to the hot-dip galvanizing steel sheet is set to α (mm 2 ), the thickness of the hot-dip galvanizing steel sheet is set to t (mm), the specific gravity of iron is set to ρ (g / mm 3 ), the specific heat of iron is set to c (J / g), the irradiation region of the diffuse reflection light source in the length direction of the hot-dip galvanizing steel sheet is set to l (m), and the conveying line speed of the hot-dip galvanizing steel sheet is set to v (m / s).

[0077]

[0078] For example, the allowable temperature variation amount ΔT (°C) is set to 1 (°C), the output power P (W) of the halogen light source is set to 100 (W), the absorptivity (emissivity) ε h of the hot-dip galvanizing steel sheet in the irradiation region of the halogen light source is set to 0.8, and the irradiation area α (mm 2 ) of the halogen light source to the hot-dip galvanizing steel sheet is set to 10,000 (mm 2), the thickness t (mm) of the hot-dip galvanizing steel sheet was 1 (mm), the specific gravity p (g / mm 3 ) of iron was 0.78 (g / mm 3 ), the specific heat c (J / g) of iron was 0.435 (J / g), the irradiation area 1 (m) of the halogen light source in the length direction of the hot-dip galvanizing steel sheet was 100 (m), and the conveying line speed v (m / s) of the hot-dip galvanizing steel sheet was 0.5 (m / s), the temperature rise at the irradiation site was 0.471 (°C), which was lower than the allowable temperature variation amount 1 (°C). Therefore, under these conditions, it is preferable to use a halogen light source having an output power of 100 (W).

[0079] Further, in the present embodiment, the amount of radiated light, the amount of specularly reflected light, and the amount of diffusely reflected light are switched to take pictures of the moving hot-dip galvanizing steel sheet at different times. In this case, it is most preferable to complete the total of three times of taking pictures, one time for the amount of radiated light measurement, one time for the amount of specularly reflected light measurement, and one time for the amount of diffusely reflected light measurement, within a range in which the surface properties can be considered to be the same. That is, in the present embodiment, when the emissivity is estimated from the specularly reflected brightness and the diffusely reflected brightness, since the same state in which alloying progresses is assumed, it is difficult to estimate the emissivity based on the model in the case where the amount of specularly reflected light measurement and the amount of diffusely reflected light measurement are performed with different surface properties. Further, in the case where the surface properties at the time of the amount of radiated light measurement are different from those at the time of the emissivity estimation, the actual emissivity and the estimated emissivity are different. However, the distribution of the degree of unevenness of alloying of the hot-dip galvanizing steel sheet varies within a narrow range, and in the case where the same surface properties are not obtained due to the relationship between the responsiveness of the mechanical shutter, the exposure time, and the conveying speed of the hot-dip galvanizing steel sheet, it is preferable to correct using filtering in the spatial direction or the time direction. Specifically, by using the average value, the maximum value, the minimum value, the median value, the percentile of the amount of radiated light, the amount of specularly reflected light, the amount of diffusely reflected light, the emissivity, and the surface temperature within a certain range of taking pictures or during a certain period of time, filtering is performed, and it is possible to reduce the influence of the degree of unevenness of alloying. Figure 9 (a) and (b) respectively show the actual temperature measurement results before and after filtering. The filtering is set to 30 seconds, and the median value of the amount of radiated light, the amount of specularly reflected light, and the amount of diffusely reflected light is used. That is, the median value of all measurement values for 15 seconds before and after each measurement point is calculated, and this calculation result is used as the measurement point after filtering. As shown in (a) and (b), it can be confirmed that although there is no physical factor, the temperature values that greatly fluctuate upward and downward can be suppressed from fluctuating by filtering. Figure 9 (a) and (b) respectively show the actual temperature measurement results before and after filtering. The filtering is set to 30 seconds, and the median value of the amount of radiated light, the amount of specularly reflected light, and the amount of diffusely reflected light is used. That is, the median value of all measurement values for 15 seconds before and after each measurement point is calculated, and this calculation result is used as the measurement point after filtering. As shown in (a) and (b), it can be confirmed that although there is no physical factor, the temperature values that greatly fluctuate upward and downward can be suppressed from fluctuating by filtering.

[0080] It should be noted that in the case where the above-described filtering process is used, it is possible that a delay is generated due to the process. In this case, by using the configuration of the temperature measurement device shown in the modified example below, it is possible to measure the surface temperature more promptly without delay.

[0081] [First variation example]

[0082] Figure 10 This describes the configuration of a first modified example of a temperature measuring device as an embodiment of the present invention. For example... Figure 10 As shown, in this modified example, three radiation thermometers are arranged in series relative to the conveying direction of the hot-dip galvanized steel sheet S and at the same width direction on the hot-dip galvanized steel sheet S: a radiation thermometer 4a without a light source, a radiation thermometer 4b with a specular reflection light source 5, and a radiation thermometer 4c with a diffuse reflection light source 6. It should be noted that the arrangement order of the three radiation thermometers is arbitrary, but it is preferable that the illumination light from the light sources does not interfere with each other. With this configuration, the imaging data of each radiation thermometer can be aligned according to the conveying speed of the hot-dip galvanized steel sheet S and the distance between each radiation thermometer, and a powerful halogen light source can be used at high shooting cycles without switching the light source using a mechanical shutter. Furthermore, the same area on the surface of the steel sheet can be photographed within the shooting cycle of the radiation thermometers.

[0083] [Second variation example]

[0084] Figure 11 This illustrates a second variation of the temperature measuring device as an embodiment of the present invention. In this variation, a radiation thermometer 4 is constructed from a line sensor or surface sensor having a long field of view along the conveying direction of the hot-dip galvanized steel sheet S. Then, as... Figure 11 As shown, the field of view along the length of the radiation thermometer 4 is divided into three parts, and light shields 9a and 9b are provided. Each field of view is photographed as a radiation light area, a specular reflection light illumination area, and a diffuse reflection light illumination area. With this configuration, a powerful halogen light source can be used at high shooting cycles without switching the light source using a mechanical shutter. It should be noted that the configuration of the light source and the size of the light shields 9a and 9b are preferably selected in a way that the illumination light from the light source does not interfere with each other. Furthermore, the design preferably takes into account the difference in spectral sensitivity characteristics between the ends and the center of the shooting field of view. Specifically, for the field of view of diffuse reflection conditions that have a large impact on emissivity and the field of view of measuring radiation light quantity, it is preferable to have the same distance from the center of the field of view. In particular, when using short-pass filters, long-pass filters, and band-pass filters, since the incident angle of light to the radiation thermometer is different at the ends and the center of the shooting field of view, it is preferable to perform correction. Furthermore, since diffuse reflection has a greater impact on accuracy than specular reflection, it is preferable to configure the light source and sensor such that the incident positions of the radiated light and diffuse reflection components are at the same distance from the center position within the field of view.

[0085] The above describes embodiments in which the present invention is applied, but the present invention is not limited by the description and drawings constituting a part of the disclosure of the present invention of the embodiments. For example, the present embodiments take a hot-dip galvannealed steel sheet as a measurement target, but the measurement target is not limited to a hot-dip galvannealed steel sheet, and the present invention can be applied to all substances in which the emissivity is uniquely determined from specularly reflected light and diffusely reflected light. Thus, other embodiments, examples, and application techniques, etc. based on the present embodiments, which are completed by those skilled in the art, etc. are all included in the scope of the present invention.

[0086] In addition, the present invention can also be applied to a temperature measurement step included in a manufacturing method of a hot-dip galvannealed steel sheet, and the temperature of the hot-dip galvannealed steel sheet is measured in a known or existing manufacturing step of the hot-dip galvannealed steel sheet. That is, the manufacturing method of the hot-dip galvannealed steel sheet includes a temperature measurement step of measuring the surface temperature of the hot-dip galvannealed steel sheet by the temperature measurement method related to the hot-dip galvannealed steel sheet of the present invention, and a step of controlling the manufacturing conditions of the hot-dip galvannealed steel sheet based on the measured surface temperature of the hot-dip galvannealed steel sheet.

[0087] In this case, it is preferable to provide a temperature measurement step of measuring the temperature of the hot-dip galvannealed steel sheet at the middle of the manufacturing step using the temperature measurement method related to the present invention. In particular, in the hot-dip galvannealed steel sheet, it is preferable to measure the temperature of the steel sheet whose emissivity varies depending on the alloying degree of plating. In the case of using feedback control, the temperature measurement step controls the conditions of one or more processes before the temperature measurement step included in the manufacturing step using the temperature measured in the temperature measurement step. If used in the case of measuring the temperature in the transport of the steel sheet to which zinc is attached or not attached, it is most preferable to maximize the effect of the present invention.

[0088] More specifically, after zinc is attached to the surface of the steel sheet, immediately after the heating device for advancing alloying, the output of the heating device can be feedback controlled to reach the temperature at the outlet side of the heating device that becomes a suitable alloying degree. Furthermore, a factor such as a dew point that affects the ease of alloying can be fed back to the actuator in the previous process to control the alloying degree to be suitable. In particular, it is most preferable to be provided at the middle of a hot-dip galvannealing line that imparts a zinc-based hot-dip plating to the steel sheet.

[0089] Further, in the case of alloying using an induction heating furnace (referred to as an IH heating furnace), the temperature is most preferably measured immediately after the highest point of the temperature during the alloying process after plating, that is, the IH heating furnace outlet side, in a hot-dip galvanizing line. If the highest temperature during the alloying process is too low, the alloying does not sufficiently proceed, and if the highest temperature is too high, the grains of the structure become coarse, which adversely affects the material quality, and the alloying can excessively proceed, so temperature management is very important. By controlling the output of the IH heating furnace using the present device so that the temperature after the IH outlet side is within a prescribed management range, a hot-dip galvanizing steel sheet of a target material quality and degree of alloying can be manufactured.

[0090] It should be noted that, for the above reasons, the present application is most effective for manufacturing an alloyed hot-dip galvanizing steel sheet (GA) in a hot-dip galvanizing steel sheet.

[0091] In addition, the present application can also be applied to a temperature measuring device that constitutes a manufacturing apparatus for a hot-dip galvanizing steel sheet, and a hot-dip galvanizing steel sheet is manufactured using the manufacturing apparatus based on the surface temperature of the hot-dip galvanizing steel sheet measured by the temperature measuring device according to the present application. In this case, the manufacturing apparatus for the hot-dip galvanizing steel sheet can be known, unknown, or existing. In addition, the manufacturing apparatus for the hot-dip galvanizing steel sheet is provided with a zinc-based hot-dip plating apparatus for imparting a zinc-based hot-dip plating to a steel sheet. Furthermore, the temperature measuring device according to the present application is preferably provided within the conveying apparatus. Further, it is most preferable to be provided between two conveying rollers provided within the zinc-based hot-dip plating apparatus. It should be noted that, for the above reasons, the present application is most effective for manufacturing an alloyed hot-dip galvanizing steel sheet (GA) in a hot-dip galvanizing steel sheet.

[0092] Further, the present application can also be applied to a steel sheet quality management method in which the quality of a steel sheet is managed by measuring the temperature of the steel sheet. Specifically, in the present application, the temperature of a steel sheet is measured in a temperature measuring step, and based on the measurement results obtained in the temperature measuring step, the quality of the steel sheet can be managed. In a subsequent quality management step, based on the measurement results obtained in the temperature measuring step, it is determined whether the manufactured steel sheet satisfies a previously specified criterion, and the quality of the steel material is managed. According to such a steel sheet quality management method, a high-quality steel sheet can be provided. It should be noted that, for the above reasons, the present application is most effective for manufacturing an alloyed hot-dip galvanizing steel sheet (GA) in a hot-dip galvanizing steel sheet.

[0093] [EMBODIMENT]

[0094] In the present embodiment, a model shown in FIG. 1 is used, and the surface temperature of a hot-dip galvanizing steel sheet is measured by the temperature measuring device according to the present application. Figure 2 Figure 4 ​The surface temperature of the hot-dip galvanizing steel sheet at the exit side of the induction heating furnace that actually measures the CGL was shown. It is known that at the exit side of the IH heating furnace, the surface emissivity greatly varies due to the galvanizing and the alloying of the steel sheet. The radiation thermometer uses a surface sensor with an InGaAs element, and adopts an optical system that transmits only light of a wavelength of 1550 ± 50 nm through a long-pass filter. An infrared LED is used as a light source for specular reflection, and a halogen light source and a mechanical shutter are used as light sources for diffuse reflection. The exposure time of each shot was set so that the amount of radiation light was 150 μs, and the amounts of specular reflection light and diffuse reflection light were 200 μs, and the amounts of specular reflection light and diffuse reflection light were corrected by subtracting the radiation light component, respectively. The obtained amounts of light were subjected to 30-second median filtering. Figure 12 . Figure 12 The horizontal axis indicates the measurement time (unit: hour), and the vertical axis indicates the brightness value. Then, the measurement results of Figure 12 were used to set a threshold value for the specular reflectance, and if it was equal to or higher than the threshold value, it was step S1, and if it was lower than the threshold value, it was step S2, and the coordinate position on the model and the emissivity were estimated using a fixed emissivity (about 0.2) in step S1, and the value of the diffuse reflection component in step S2.

[0095] The temperature measurement results of the present example, comparative example 1 (monochromatic radiation temperature measurement) in which the emissivity was calculated as a fixed value to calculate the surface temperature, and comparative example 2 (simulation) in which the surface temperature was calculated using heat transfer calculation for the same measurement region of the hot-dip galvanizing steel sheet are shown in Figure 13 . In Figure 13 , the horizontal axis indicates the measurement time (unit: hour), and the vertical axis indicates the relative temperature (unit: °C). The relative temperature indicates how many °C have changed from a certain reference temperature that is set to 0°C. As shown in Figure 13 , it is known that the surface temperature of comparative example 1 deviates greatly from the surface temperature of comparative example 2, and in contrast, the general tendency of the surface temperature of the present example is consistent with the surface temperature of comparative example 2. Furthermore, the degree of alloying of the portion in which the surface temperature of the present example differs from the surface temperature of comparative example 2 is shown in Figure 14 . In Figure 14In the graph, the vertical axis represents the relative measurement temperature (in °C), and the horizontal axis represents the relative degree of alloying (in mass%). The relative measurement temperature indicates how many °C a reference temperature has changed from 0 °C. Conversely, the relative degree of alloying indicates how many mass% a reference degree of alloying has changed from 0% by mass. Furthermore, for hot-dip galvanized steel sheets, the degree of alloying is expressed as a mass percentage (mass%) of Fe concentration when the entire alloying phase is set to 100% by mass. Both excessively high and low values ​​indicate poor quality. The degree of alloying can generally be measured using methods such as calculating the mass of iron contained in the chemically separated components or using X-ray diffraction (XRD).

[0096] Since the size and conveying speed of hot-dip galvanized steel sheets are constant, a physical correlation between the degree of alloying and surface temperature can be expected. However, as... Figure 14 As shown, no correlation was observed in Comparative Example 2. In contrast, a clear correlation can be seen in the present invention example. Therefore, according to the present invention example, it is believed that temperature changes related to emissivity variations that could not be grasped in Comparative Example 2 can be obtained. As can be seen from the above, according to the present invention, the surface temperature of hot-dip galvanized steel sheets during the alloying process can be measured with high precision.

[0097] Industrial availability

[0098] According to the present invention, a surface temperature measuring method and a surface temperature measuring device can be provided that can measure the surface temperature of the object being measured with high accuracy regardless of variations in the emissivity of the object's surface. Furthermore, according to the present invention, a method and equipment for manufacturing hot-dip galvanized steel sheets can be provided that can measure the temperature of steel sheets in a hot-dip galvanizing production line with high accuracy and produce hot-dip galvanized steel sheets with good yield regardless of the alloying process.

[0099] Symbol Explanation

[0100] 1. Thermocouple

[0101] 2 Blackbody Spray

[0102] 3 heaters

[0103] 4. 4a, 4b, 4c radiation thermometers

[0104] 5. Light source for specular reflection

[0105] 6. Light source for diffuse reflection

[0106] 7 shutter speeds

[0107] 8 computing devices

[0108] 9a, 9b light-shielding panels

[0109] 10 temperature measuring device

[0110] 11 molten zinc pot

[0111] 12 heating furnace

[0112] 13 heat retaining band

[0113] S hot-dip galvannealed steel sheet

Claims

1. A surface temperature measurement method, comprising the following steps: The first step in the imaging process is to obtain the amount of radiant light from the surface of the object being measured. The second shooting step involves irradiating the surface of the object to be measured with light under specular reflection conditions to obtain the amount of specular reflected light. The third shooting step involves irradiating the surface of the object to be measured with light under diffuse reflection conditions to obtain the diffuse reflection light quantity. The emissivity calculation step involves using a model representing the relationship between the emissivity of the surface of the object being measured and its specular and diffuse reflectivity, the amount of specular reflected light obtained in the second imaging step, and the amount of diffuse reflected light obtained in the third imaging step to calculate the emissivity of the surface of the object being measured. as well as In the temperature measurement step, the surface temperature of the object being measured is calculated using the amount of radiation obtained in the first imaging step and the emissivity calculated in the emissivity calculation step. The emissivity calculation step is performed if the amount of specular reflection light obtained in the second imaging step is less than a specified value, and if the amount of specular reflection light obtained in the second imaging step is greater than or equal to a specified value, a fixed value is used as the emissivity in the temperature measurement step.

2. The surface temperature measurement method according to claim 1, wherein, The second and third shooting steps each include the step of correcting the amount of specular reflection light and the amount of diffuse reflection light by subtracting the amount of radiant light obtained in the first shooting step.

3. The surface temperature measurement method according to claim 1 or 2, wherein, The first shooting step, the second shooting step, and the third shooting step include the step of receiving light using a light-receiving element with multiple fields of view, the light-receiving element distributing the range of the amount of radiant light, the amount of specular reflection light, and the amount of diffuse reflection light along the transport direction of the object being measured.

4. The surface temperature measurement method according to claim 1 or 2, wherein, The object being measured is a hot-dip galvanized steel sheet.

5. The surface temperature measurement method according to claim 3, wherein, The object being measured is a hot-dip galvanized steel sheet.

6. A surface temperature measuring device, comprising: The first imaging device acquires the amount of radiation light on the surface of the object being measured; The second imaging device irradiates light onto the surface of the object to be measured under specular reflection conditions to obtain the amount of specular reflected light. The third imaging device illuminates the surface of the object to be measured with light under diffuse reflection conditions to obtain the amount of diffuse reflected light. The emissivity calculation device calculates the emissivity of the object's surface using a model representing the relationship between the emissivity, specular reflectivity, and diffuse reflectivity of the object's surface, the specular reflectance obtained by the second imaging device, and the diffuse reflectance obtained by the third imaging device; and The temperature measuring device uses the amount of radiation light obtained by the first imaging device and the emissivity to calculate the emissivity, and then calculates the surface temperature of the object being measured. The emissivity calculation device calculates the emissivity when the amount of specular reflected light obtained by the second imaging device is less than a specified value, and when the amount of specular reflected light obtained by the second imaging device is greater than or equal to the specified value, the temperature measuring device uses a fixed value as the emissivity.

7. The surface temperature measuring device according to claim 6, wherein, The object being measured is a hot-dip galvanized steel sheet.

8. A method for manufacturing hot-dip galvanized steel sheet, comprising the steps of manufacturing hot-dip galvanized steel sheet. The manufacturing steps for hot-dip galvanized steel sheets include: The temperature measurement step of measuring the surface temperature of the hot-dip galvanized steel sheet by the surface temperature measurement method according to any one of claims 1 to 5, and the step of controlling the manufacturing conditions of the manufacturing step using the surface temperature measured by the temperature measurement step.

9. A manufacturing equipment for hot-dip galvanized steel sheets, comprising: The surface temperature measuring device as described in claim 6 or 7, and Equipment for manufacturing hot-dip galvanized steel sheets based on the surface temperature of the hot-dip galvanized steel sheet measured by the surface temperature measuring device.

Images