Method for producing film, method for producing object, method for producing oxide film, and method for producing plated steel material

Abstract

This method for producing a film is provided with: a spectral reflectance calculation step for calculating a spectral reflectance on the basis of reflected light reflected by a light film; an information calculation step of calculating information related to the number of extreme values of the spectral reflectance and the wavelength position relation of the extreme values in a specified wavelength range according to the calculated spectral reflectance; and a control step for controlling the formation condition of the film on the basis of the calculated information.

Description

Technical Field

[0001] This invention relates to methods for manufacturing films, methods for manufacturing objects, methods for manufacturing oxide films, and methods for manufacturing coated steel. Background Technology

[0002] In the past, when manufacturing by forming certain films on the surface of an object, the thickness of the film sometimes becomes important. To determine the thickness of the film formed on the surface of an object, interference spectroscopy, which utilizes the interference of light and is relatively easy and inexpensive to employ, is often used. In interference spectroscopy, light is incident on an object or a single film element on a substrate. The light incident on the film surface is reflected by the light passing through the film and reflected from the substrate or the bottom of the film, exiting from the film surface. This interference yields a unique spectral reflectance corresponding to the film thickness. Furthermore, by analyzing this spectral reflectance, the film thickness can be determined. Methods for evaluating film thickness based on the spectral reflectance obtained by interference spectroscopy include, for example, the methods disclosed in Patent Documents 1, 2, and 3.

[0003] For example, Patent Document 1 discloses a method for forming an oxide layer suitable for improving coating characteristics, where the film thickness is measured by expressing the change in spectral reflectance caused by light interference using the two-wavelength ratio of reflectance. In the method disclosed in Patent Document 1, a sample considered to be the object of measurement is prepared beforehand, and the film thickness and the reflectance ratio of two specific wavelengths in the infrared region of the sample are measured. Furthermore, in the method disclosed in Patent Document 1, a relationship between the reflectance ratio and the film thickness is established based on the measurement results, thereby accurately determining the film thickness based on the specific two-wavelength ratio of the reflectance measured online. Additionally, Patent Document 2 discloses a method for measuring the oxide film formed in the hot rolling process and the subsequent cooling process using interference spectroscopy. In the method disclosed in Patent Document 2, the thickness of the oxide film in a continuous sheet is measured based on a pre-measured relationship between the film thickness and spectral reflectance. Furthermore, Patent Document 3 discloses a method for accurately measuring the film thickness even when the film structure cannot be determined using a film thickness measuring device based on interference spectroscopy. In the method disclosed in Patent Document 3, the theoretical reflectivity of the desired membrane structure is obtained in advance, and the membrane thickness is determined by calculating the correlation between the measured reflectivity and the theoretical reflectivity.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-202968

[0007] Patent Document 2: Japanese Patent Application Publication No. 10-206125

[0008] Patent Document 3: Japanese Patent Application Publication No. 11-160028 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] However, in the method of Patent Document 1, when determining the film thickness based on the spectral reflectance of the film to be measured and controlling it to a thickness suitable for improving coating characteristics, it is necessary to use a sample with a known film thickness to pre-determine the relationship between film thickness and spectral reflectance, and to establish the relationship between the reflectance ratio of two wavelengths and film thickness. Similarly, in the method of Patent Document 2, to determine the film thickness based on spectral reflectance, it is also necessary to pre-determine the relationship between spectral reflectance and film thickness. To pre-determine these relationships, it is necessary to prepare samples of the film to be measured, consisting of the same composition, different film thicknesses, and the same substrate, or to prepare samples by sampling an object on which the film to be measured has been formed on its surface from the production line. However, when it is not possible to prepare samples of the same composition with different film thicknesses for the film to be measured and the substrate, it is impossible to pre-determine the relationship between film thickness and reflectance spectrum. For example, in the steelmaking process illustrated in Patent Document 1, which uses a direct-fired furnace, it is impossible to sample the material midway through the process. Furthermore, the actual composition of the film is unknown, so it is impossible to pre-measure the sample to obtain the relationship between oxide film thickness and reflectance spectrum. Furthermore, in the film thickness measurement method of Patent Document 3 where the film structure cannot be determined, the film thickness can only be measured with a relatively simple and predictable film structure. Therefore, the film thickness cannot be measured when the details of the film structure are unknown. Consequently, the film thickness cannot be evaluated based on the measured reflectance spectrum, and it is impossible to manufacture a film with an appropriate thickness range.

[0011] The present invention was made in view of the above-mentioned problems, and its object is to provide a method for manufacturing a film suitable for subsequent processes, products, objects, oxide films, and coated steel, even if the film thickness cannot be accurately measured.

[0012] Technical solutions for solving technical problems

[0013] In order to solve the above problems and achieve the goal,

[0014] (1) The method for manufacturing the membrane of the present invention comprises: a spectral reflectance calculation step, which calculates the spectral reflectance based on the reflected light obtained by light being reflected by the membrane; an information calculation step, which calculates information related to the number of extreme values ​​of the spectral reflectance and the wavelength position relationship of the extreme values ​​within a specified wavelength range based on the calculated spectral reflectance; and a control step, which controls the formation conditions of the membrane based on the calculated information.

[0015] (2) The method for manufacturing the membrane of the present invention is based on the invention described in (1) above, wherein the controlled formation conditions are one or more, and are formation conditions in the process before the spectral reflectance calculation step and / or formation conditions in the process after the information calculation step.

[0016] (3) The method for manufacturing an object of the present invention includes a film forming step of forming a film on the surface of an object by means of the film manufacturing method of the invention described in (1) or (2) above.

[0017] (4) The method for manufacturing an oxide film of the present invention includes an annealing step for forming an oxide film on the surface of a steel plate, the annealing step including: a spectral reflectance calculation step, which calculates a spectral reflectance based on reflected light obtained by light reflected by the oxide film formed; an information calculation step, which calculates information related to the number of extreme values ​​of the spectral reflectance and the wavelength position relationship of the extreme values ​​within a specified wavelength range based on the calculated spectral reflectance; and a control step, which controls the formation conditions of the oxide film based on the calculated information.

[0018] (5) The method for manufacturing coated steel of the present invention is a method for manufacturing coated steel having a coating film on the surface of coated steel, comprising: an annealing step, forming an oxide film on the surface of the coated steel and reducing the formed oxide film; and a coating step, forming the coating film on the coated steel after the annealing step, the annealing step comprising: a spectral reflectance calculation step, calculating spectral reflectance based on reflected light obtained by light reflected by the oxide film formed on the surface of the coated steel; an information calculation step, calculating information related to the number of extreme values ​​of the spectral reflectance and the wavelength position relationship of the extreme values ​​within a specified wavelength range based on the calculated spectral reflectance; and a control step, controlling the formation conditions of the oxide film in steps prior to the spectral reflectance calculation step and / or controlling the reduction conditions of the oxide film in steps after the information calculation step based on the calculated information.

[0019] Invention Effects

[0020] The manufacturing methods of the membrane, the object, the oxide film, and the coated steel of the present invention have the following effects: even if the thickness of the membrane cannot be accurately measured, a membrane suitable for subsequent processes and products can be manufactured. Attached Figure Description

[0021] Figure 1 This is a diagram showing the schematic structure of a manufacturing equipment using the film thickness evaluation device of the embodiment.

[0022] Figure 2 This is a diagram showing the schematic structure of the film thickness evaluation device according to the embodiment.

[0023] Figure 3 It is a graph showing the time change of air ratio, the time change of plate temperature, and the time change of wavelength position representing the extreme value as a function of spectral reflectance.

[0024] Figure 4 It is a graph showing the relationship between the thickness range of the oxide film, the spectral reflectance, and the wavelength position of the extreme values.

[0025] Figure 5 This is a diagram showing the schematic structure of the film thickness evaluation device in Modified Example 1.

[0026] Figure 6 It is a graph showing the time change of air ratio, the time change of plate temperature, and the time change of wavelength position of extreme values.

[0027] Figure 7 It means in Figure 4 The relationship shown includes an additional graph showing the relationship between the oxide film thickness range, spectral reflectance, and wavelength position of extreme values ​​(judgment criterion 1 and judgment criterion 2) within the specified wavelength range of region T6.

[0028] Figure 8 It means relative to Figure 7 The region corresponding to the T6 region is designated as the T6-1 region, and the relationship between the oxide film thickness range, spectral reflectance, and judgment criteria of the T6-2 region within the specified wavelength range is added as a new T6 region. Detailed Implementation

[0029] Hereinafter, embodiments of the methods for manufacturing the film, the object, the oxide film, and the coated steel of the present invention will be described. However, the present invention is not limited to these embodiments.

[0030] As an example of an object manufactured using the manufacturing method described in this embodiment, a coated steel sheet, specifically a galvanized steel sheet, will be used for illustration.

[0031] In recent years, high-tensile steel sheets used for thick plates, specifically high-tensile galvanized steel sheets (hereinafter referred to as high-strength GA steel sheets), have been used in some automotive parts. Furthermore, various high-strength GA steel sheets, i.e., steel sheets with different strength values, are selected depending on the component being used. In the manufacture of high-strength GA steel sheets, easily oxidizable elements such as Si and Mn are added to the steel sheet to increase its strength. It is known that these easily oxidizable elements are selectively oxidized on the steel sheet surface during the annealing process in the manufacturing of galvanized steel sheets. When the steel sheet surface is coated in the subsequent coating process, this adversely affects the coating characteristics. Specifically, the oxidation of components such as Si and Mn, and the resulting oxides of steel elements on the steel sheet surface, sometimes contribute to non-plating.

[0032] On the other hand, direct-fired heating furnaces, often located in the first half of the annealing process, offer several advantages: superior equipment compactness, improved steel plate permeability, and excellent thermal response characteristics; significant economic benefits; and the ability to ensure good coating properties and increase the upper limit for the addition of Si and Mn. The direct-fired heating furnace is divided into multiple zones, each with a combustion mode corresponding to the load. In each zone, oxidation-promoted heating or reduction heating is continuously performed, with the combustion time controlled on a zone-by-zone basis according to the load. As a result, at the furnace outlet, the temperature of the steel to be coated reaches several hundred degrees Celsius or higher. The rapidly heated steel is then fed to a radiant tube furnace, often located in the second half of the annealing process, where it is annealed for surface reduction before being guided to the coating process.

[0033] As mentioned above, preventing the oxidation of easily oxidizable elements is crucial in the manufacture of high-strength GA steel sheets. In high-strength GA materials with a strength of 590 MPa or higher, the addition of elements such as Si and Mn increases. Therefore, preventing the oxidation of these elements caused by heating in a direct-fired furnace is an effective means of improving plating properties. In a direct-fired furnace, by increasing the air ratio during burner heating, a thick oxide film is formed on the surface of the steel to be plated. Oxygen supplied from this thick oxide film on the surface of the steel causes easily oxidizable elements such as Si and Mn to oxidize internally, thereby suppressing surface oxidation and improving plating characteristics. Here, the air ratio during burner heating refers to the ratio of the supplied air volume to the air volume that reacts precisely with the fuel gas.

[0034] Currently, the relationship between coating characteristics and direct-fired heating furnaces is investigated based on the addition amounts of Si and Mn, aiming to optimize the air ratio and burner flame intensity. However, this method cannot completely prevent non-coating due to drastic variations in process quantities, burner blockage, flame abnormalities, and changes in fuel gas composition during the actual molten galvanized steel sheet manufacturing process. Therefore, controlling the oxidation amount of the oxide layer generated after direct-fired heating is crucial for improving the final coating characteristics of high-strength GA materials. However, the outlet side of the annealing furnace is a harsh environment, making direct measurement of the oxidation amount difficult. Therefore, the thickness of the oxide film is measured and controlled within an appropriate range (hereinafter referred to as oxide film thickness or film thickness) to prevent non-coating. Furthermore, the amount of easily oxidizable elements added to high-strength GA materials varies depending on material properties such as strength; therefore, it is believed that the thickness of the oxide layer generated will differ for each high-strength GA material with different material properties.

[0035] Therefore, directly measuring the oxide film thickness is useful, but due to production line limitations, it is impossible to sample coated steel with an oxide film on its surface. As a result, the actual structure and composition of the film are unclear, making it difficult to measure.

[0036] The following describes a method for manufacturing a film using interference spectroscopy on the outlet side of a direct-fired heating furnace, which is cost-effective and easy to operate, by forming an oxide film of an appropriate thickness on the surface of the steel to be coated without the risk of non-coating.

[0037] Here, the inventors of this application have conducted repeated and in-depth research, and have found that, within a specified wavelength range, information relating to the number of extreme values ​​of spectral reflectance and the wavelength position of these extreme values ​​is correlated with air ratio, plate temperature, and the occurrence of non-coating. Furthermore, the inventors of this application have considered that this information can be used to control film formation. Therefore, in the film manufacturing method of the embodiment, this information is used to control film formation as an alternative to conventional film thickness management. Moreover, the reason for using this information instead of film thickness management is that it can be presumed that it is correlated with the thickness of the film formed based on air ratio, plate temperature, and the occurrence of non-coating. Furthermore, this can theoretically be explained through film interference.

[0038] In the film manufacturing method of the embodiment, based on the spectral reflectance calculated from the reflected light obtained by the film, information related to the number of extreme values ​​of spectral reflectance and the wavelength position relationship of the extreme values ​​is calculated within a specified wavelength range. Furthermore, in the film manufacturing method of the embodiment, based on the calculated information, the film thickness is estimated according to the theory of interference films, and the film formation conditions are controlled. Moreover, the information is not limited to the number of extreme values ​​of spectral reflectance and the wavelength position relationship of the extreme values ​​themselves. That is, in the above information, if using... Figure 4 Similar to regions T1 to T5 described later, this also includes multiple film thickness regions arranged in order of film thickness. Furthermore, these multiple film thickness regions are defined, for example, based on interference estimations of the film, using a fitting method that arranges them in order of film thickness. Additionally, the information mentioned above includes multiple numerical ranges for film thickness, such as A[nm] to B[nm], B[nm] to C[nm], and C[nm] to D[nm]. Moreover, these numerical ranges for film thickness are, for example, converted values ​​simulated using related materials with compositions close to those of the formed film.

[0039] Figure 1 This is a diagram showing the schematic structure of the manufacturing equipment of the film thickness evaluation device 3 according to the embodiment. Figure 1 The manufacturing equipment shown includes: a direct-fired furnace 2 for annealing a traveling sheet of plated steel 1, and a film thickness evaluation device 3 for evaluating the film thickness of the oxide film formed on the surface of the plated steel 1. The direct-fired furnace 2, inside a refractory-covered interior, includes furnace rollers 4, a measuring window 5, a burner 6, and furnace rollers 7. The plated steel 1 is suspended by multiple furnace rollers and can travel along a straight path within the direct-fired furnace 2. Figure 1 The material travels downwards from the top. In the section of the direct-fired furnace 2 corresponding to the straight path, multiple burners 6 are arranged along the conveying direction of the steel to be coated 1. Furthermore, the multiple burners 6 are arranged opposite each other, sandwiching the steel to be coated 1, so that either the front or back side of the steel to be coated 1 can be annealed using burner flames. Additionally, the straight path of the direct-fired furnace 2 is divided into multiple regions, namely, a first region Z1, a second region Z2, a third region Z3, and a fourth region Z4, where the air ratio, fuel gas composition, and burner flame intensity can be specified as annealing conditions. Moreover, the surface of the steel to be coated 1 is heated by the burners 6 respectively located in the first region Z1 to the fourth region Z4, thereby forming an oxide film on the surface of the steel to be coated 1.

[0040] The film thickness evaluation device 3 is positioned in the straight path of the direct-fired heating furnace 2, downstream of the fourth region Z4 in the direction of travel of the steel 1 to be coated, and at the outlet of the direct-fired heating furnace 2. It should be noted that... Figure 1For example, in order to evaluate the film thickness on one side (front) of the coated steel 1, a film thickness evaluation device 3 is provided relative to one side (front) of the coated steel 1, but it is not limited to this. For example, in order to evaluate the film thickness on both sides (front and back) of the coated steel 1, film thickness evaluation devices 3 can be provided on the front and back of the coated steel 1 respectively. Alternatively, multiple film thickness evaluation devices 3 can be provided in the width direction of the coated steel 1.

[0041] Figure 2 This is a diagram showing a schematic structure of the film thickness evaluation device 3 according to the embodiment. The film thickness evaluation device 3 according to the embodiment includes a detection unit 31, a calculation unit 32, a light guide 33, a detector 34, a shutter 35, an instrument air introduction unit 36, a light source 37, an optical fiber 38, a halogen light source 39, a xenon light source 310, and a database 321, etc.

[0042] The detection unit 31 is a unit for detecting reflected and radiated light within a specific wavelength range. The detection unit 31 is equipped with a light guide 33 and a detector 34. The light source unit 37 is a unit equipped with a halogen light source 39 and a xenon light source 310 for generating light with intensity within a specific wavelength range. Specifically, the light source unit 37 is composed of both the halogen light source 39 and the xenon light source 310 to ensure overall intensity in the wavelength region of 400 nm to 1050 nm. The halogen light source 39 and the xenon light source 310 are connected to the light guide 33 in the detection unit 31 via an optical fiber 38. Furthermore, the light source for the light source unit 37 is preferably selected based on the component characteristics of the detection unit 31 (detector 34), and it is not necessary to have two different light sources.

[0043] The light guide 33 is configured to allow the irradiation light L1 to pass through the measurement window 5 provided on the furnace wall of the direct-fired heating furnace 2 and enter the surface of the steel to be plated 1. Furthermore, the detector 34 is configured to acquire the ortho-reflected light L2 from the surface of the steel to be plated 1. Additionally, as the detector 34, for example, a detector capable of measuring wavelengths from 400 nm to 1050 nm can be used, but a detector capable of measuring wavelengths other than these can also be used. In the detection unit 31, in order to suppress the effect of shaking of the ortho-reflected light L2 caused by vibration of the steel to be plated 1, the film thickness measurement position P1 is set on the surface of the portion of the steel to be plated 1 wound around the furnace roller 4. Then, the detection unit 31 irradiates the irradiation light L1 from the light guide 33 to the measurement position P1 on the surface of the steel to be plated 1 through the measurement window 5, and uses the detector 34 to measure the ortho-reflected light L2 reflected at the measurement position P1.

[0044] The arithmetic unit 32 converts the spectrum of reflected light intensity measured by the detector 34 into a reflectance spectrum to evaluate the film thickness.

[0045] The detection unit 31 preferably suppresses heat transfer to the light guide unit 33 and detector 34 in high-temperature environments, or suppresses the impact of dust on precision equipment, and therefore has an instrument air inlet 36 for introducing air into the housing of the detection unit 31. Similarly, the light source unit 37 preferably suppresses heat transfer to the halogen light source 39 and xenon light source 310 in high-temperature environments, or suppresses the impact of dust on precision equipment, and therefore has an instrument air inlet 36 for introducing air into the housing of the light source unit 37. Furthermore, the calculation unit 32 can also be located away from the direct-fired furnace 2. Additionally, the calculation unit 32 can be connected to the detector 34 via a network. For example, the calculation unit 32 can be installed on an external server, and the detector 34 and the external server can be configured to communicate via a network, with the detector 34 accessing the calculation unit 32 on the external server and the calculation unit 32 performing processing. In these cases, the calculation unit 32 may not have an instrument air inlet. On the other hand, when the calculation unit 32 is located near the direct-fired heating furnace 2, it is preferable to have an instrument air inlet for introducing air into the frame of the calculation unit 32, similar to the detection unit 31 and the light source unit 37.

[0046] In the film thickness evaluation device 3 of the embodiment, by separately arranging the detection unit 31 and the light source unit 37, the weight of the detection unit 31 can be reduced, and the angle of the detection unit 31 can be easily adjusted.

[0047] like Figure 1As shown, the film thickness evaluation device 3 of the embodiment measures the coated steel 1 immediately after it is heated by the burner 6 in each of the multiple regions Z1, Z2, Z3, and Z4, that is, immediately after an oxide film has just formed on the surface. The coated steel 1 is red-hot at several hundred [°C] immediately after the oxide film has formed. Therefore, when measuring the positively reflected light L2 incident from the light guide 33 and reflected on the steel plate surface using the detector 34, the measurement is performed while simultaneously including the radiation light from the red-hot coated steel 1.

[0048] Therefore, by closing the shutter 35, which is provided in the detection unit 31 in a manner that can be opened and closed, the irradiation light L1 emanating from the light guide 33 toward the surface of the steel to be coated 1 can be blocked, and the detector 34 can instantaneously measure only the radiated light from the steel to be coated 1. On the other hand, when the shutter 35 is open, the irradiation light L1 emanating from the light guide 33 enters the surface of the steel to be coated 1, so the orthographic reflection light L2 and the radiated light from the surface of the steel to be coated 1 are simultaneously measured by the detector 34. Then, the calculation unit 32 subtracts the spectral radiated light intensity measured when the shutter 35 is closed from the spectral reflection light intensity and spectral radiated light intensity measured when the shutter 35 is open, and calculates the spectral reflection light intensity of the orthographic reflection light L2, taking into account the influence of the radiated light from the red-hot steel to be coated 1.

[0049] Thus, in the film thickness evaluation device 3, by intermittently irradiating the surface of the steel to be coated 1 with illumination light L1 through shutter 35, the spectral reflectance intensity unaffected by the radiation light from the steel to be coated 1 is measured. Furthermore, in the film thickness evaluation device 3, the spectral reflectance is measured by calculating the ratio of the spectral reflectance intensity on the substrate steel plate on which no oxide film has been formed in advance to the spectral reflectance intensity taking into account the influence of the measured radiation light by the calculation unit 32.

[0050] Next, an example of a method for manufacturing a film within an appropriate film thickness range (target film thickness range) using the interference spectroscopy method of the embodiment will be described.

[0051] The membrane manufacturing method of the embodiment includes a spectral reflectance calculation step, an information calculation step, and a control step. In the spectral reflectance calculation step, the spectral reflectance intensity is calculated based on the reflected light obtained from light reflected by the membrane. In the information calculation step, based on the calculated spectral reflectance, information related to the number of extreme values ​​of spectral reflectance and the wavelength position relationship of these extreme values ​​is calculated within a specified wavelength range. In the control step, the membrane formation conditions are controlled based on the information related to the number of extreme values ​​of spectral reflectance and the wavelength position relationship of these extreme values. The formation conditions controlled in this control step are one or more, and are formation conditions in processes preceding the spectral reflectance calculation step and / or in processes following the information calculation step. Examples of these formation conditions include, for instance, the air ratio, fuel gas composition, and burner flame intensity of each of the multiple regions Z1, Z2, Z3, Z3 in the straight path of the direct-fired furnace 2.

[0052] Conventionally, to measure film thickness using interferometric spectroscopy, samples composed of the same composition but different film thicknesses and the same substrate are prepared in advance, or samples are prepared by sampling objects with the film to be measured formed on their surfaces from the production line. Furthermore, the relationship between film thickness and reflectivity needs to be determined based on these prepared samples. However, in the case of a sample immediately after passing through the direct-fired heating furnace 2, as in this embodiment, it is impossible to sample in advance. Therefore, neither actual samples can be used, nor can samples simulating actual samples be prepared. Consequently, the detailed film thickness cannot be determined based on the measured reflectivity, and oxide films cannot be manufactured within an appropriate film thickness range.

[0053] The inventors of this application have conducted repeated and in-depth research and found that even if it is impossible to prepare samples in advance and thus impossible to determine the true value of the film thickness, by clarifying the relationship between the spectral reflectance measured online and the film thickness when that spectral reflectance is obtained, it is possible to manufacture films within an appropriate film thickness range.

[0054] It is known that in interferometric spectroscopy, as film thickness increases, the frequency of spectral reflectance increases, the interval between extreme values ​​within the measurement wavelength range shortens, and the wavelength positions of the extreme values ​​shift towards longer wavelengths. Similarly, in interferometric spectroscopy, it is known that as film thickness decreases, the frequency of spectral reflectance decreases, and the wavelength positions of the extreme values ​​shift towards shorter wavelengths. Therefore, if the wavelength positions of specific extreme values ​​within the measurement wavelength range can be consistently measured, the increase or decrease in film thickness can be determined based on the wavelength positions of these specific extreme values, thus clarifying the relationship between spectral reflectance and film thickness.

[0055] On the other hand, in actual device configurations or setups, the measurement wavelength range is almost always limited due to cost considerations, making it difficult to continuously measure the wavelength positions of specific extreme values. Therefore, experiments were conducted to increase or decrease the film thickness, and the changes in the extreme values ​​of spectral reflectance within the measurement wavelength range accompanying the increase or decrease in film thickness were observed. The results show that the wavelength position relationship of the extreme values ​​measured within a specific wavelength region has characteristics related to a certain range of film thickness. The actual experimental content and results are described below.

[0056] To investigate the formation conditions of oxide film thickness and the changes in spectral reflectance, as well as the occurrence of non-coating in subsequent plating processes, in Figure 1 In the straight path of the direct-fired heating furnace 2 shown, multiple regions Z1, Z2, Z3, and Z4 continuously vary the air ratio. Then, as the furnace travels along the straight path, the thickness of the oxide film formed on the surface of the steel to be coated 1 continuously varies, and the spectral reflectance at this time is measured using the film thickness evaluation device 3. It should be noted that while the burner flame intensity is adjusted to keep the temperature of the steel to be coated 1 (hereinafter referred to as the plate temperature) constant, it is considered impossible to keep the plate temperature completely constant, which will somewhat affect the thickness of the oxide film.

[0057] Figure 3 These are graphs showing the time-varying air ratio, the time-varying plate temperature, and the time-varying wavelength position representing the extreme value of the spectral reflectance. It should be noted that the plate temperature is measured using a radiation thermometer (not shown) on the surface portion of the steel to be plated 1 wound on the furnace roller 7 positioned downstream of the furnace roller 4, as the temperature measurement location.

[0058] Furthermore, the method for detecting the wavelength position of the extreme value involves calculating the rate of change of spectral reflectance measured within a specified wavelength range, and detecting the wavelength position where the sign of the rate of change changes as the extreme value. However, the measured spectral reflectance contains noise, and it is difficult to detect only the extreme value as the target simply by directly calculating the rate of change, which may lead to incorrect detection of the extreme value. Therefore, as a preprocessing step for the measured spectral reflectance, this paper utilizes a polynomial-based curve approximation. Here, polynomial-based curve approximation refers to finding the coefficients of the polynomial that minimizes the sum of the squares of the differences between the data points and the polynomial values. In addition, a 10th-degree polynomial was used in this paper, but polynomials of other degrees can also be used to create several approximate polynomials of different degrees, and the degree that can appropriately approximate the measured spectral reflectance is selected. Furthermore, while polynomial-based curve approximation was used in this paper, taking a moving average of the spectral reflectance is also an effective preprocessing method. On the other hand, in moving averages, increasing the number of average data points can suppress false detections of extreme values ​​caused by subtle noise. However, if there are many average data points, extreme values ​​may be missed when the peak intensity of a particular extreme value is low or the interval between extreme values ​​is short. Conversely, with fewer average data points, extreme values ​​are easily detected even when the peak intensity of a particular extreme value is low or the interval between extreme values ​​is short, but this method is susceptible to noise. Furthermore, the specified wavelength range is 400 nm to 1050 nm, which is easily captured by the reflected light from the oxide film. Thus, the specified wavelength range can be appropriately selected as long as it is within a range where the spectral reflectance of the film being measured is easily measurable.

[0059] Here, in Figure 3The graph showing the time-varying wavelength positions of extreme values ​​is illustrated with a crosshair indicating a single minimum value within a specified wavelength range. Additionally, a circle indicates two extreme values ​​within the measured wavelength range, with the minimum value occurring on the shorter wavelength side. A square indicates two extreme values ​​within the measured wavelength range, with the maximum value occurring on the shorter wavelength side. Finally, a triangle indicates three extreme values ​​within the measured wavelength range, with the minimum value occurring on the shorter wavelength side. According to this graph, the wavelength positions of the spectral extreme values ​​shift due to changes in the air ratio, i.e., changes in the thickness of the oxide film formed on the surface of the coated steel 1. Furthermore, the number of extreme values ​​and their wavelength position relationships change within the wavelength range of 400 nm to 1050 nm. Specifically, from 13:47 to 14:07, as the air ratio decreases, the number of extreme values ​​and their wavelength position relationships change as follows. That is, the number of extrema and their wavelength positions are related as follows: 2 extrema (minimum on the short wavelength side), 3 extrema (minimum on the short wavelength side), 2 extrema (maximum on the short wavelength side), and 1 minimum. The extrema shift towards the short wavelength side. Then, around 14:00, the extrema shift towards the long wavelength side, becoming 2 extrema (maximum on the short wavelength side). Additionally, the extrema shift towards the short wavelength side while simultaneously changing, such as 1 minimum and 2 minimums (minimum on the short wavelength side). The shift towards the long wavelength side around 14:00 is due to the increase in plate temperature, presumably indicating a slight increase in oxide film thickness at that time.

[0060] Based on these results, it is presumed that the information relating to the number of extrema and the wavelength position of these extrema is related to the film thickness. It is presumed that the air ratios at 13:47 and 14:07 are significantly different, resulting in significantly different oxide film thicknesses, but they are the same in terms of the number of extrema and the presence of minima on the shorter wavelength side. However, as the film thickness increases, the frequency of the spectral reflectance increases, thus allowing differentiation based on the interval between the wavelength positions of the extrema (minimum) and the extrema (maximum). Even when there is only one extremum, differentiation is possible within the range of acceptable wavelength positions and equal half-width at half-maximum.

[0061] Furthermore, the inventors of this application, based on Figure 3 The results and insights produced Figure 4 . Figure 4 This is a graph showing the relationship between the oxide film thickness range, spectral reflectance, and the wavelength position of the extreme values ​​within a specified wavelength range. The oxide film thickness range here is estimated based on the aforementioned air ratio, plate temperature, and the occurrence of uncoated areas during subsequent coating processes. Figure 4In this study, following the presumed order of film thickness from thinnest to thickest, a certain range of oxide film thickness is divided into regions T1, T2, T3, T4, and T5. Furthermore, in... Figure 4 In the diagram, regions T1, T2, T3, T4, and T5 correspond to the actual measured spectral reflectance, the number of extreme values ​​in the measured wavelength regions, and the wavelength position relationship of the extreme values. Figure 4 In this case, the T1 to T5 regions can be used as information related to the number of extreme values ​​of the spectral reflectance and the wavelength position of these extreme values, which can be used for controlling film formation, etc. Furthermore, in Figure 4 In such cases, based on the air ratio, plate temperature, and the occurrence of non-coating, it is expected that information related to the number of extreme values ​​and the wavelength position of the extreme values ​​will be related to the above-mentioned film thickness range.

[0062] exist Figure 4 In order to evaluate the oxide film thickness range (region T1 to region T5) based on the wavelength position relationship of the extreme values ​​of spectral reflectance, the wavelength position relationship of the extreme values ​​includes two types of information: determination criterion 1 and determination criterion 2. Determination criterion 1 is information related to the number of extreme values ​​and the wavelength position relationship of the extreme values ​​(the order in which the extreme values ​​are arranged). As described later, determination criterion 1 contains information in all regions from region T1 to region T5. Determination criterion 2 is information about the distance between extreme values ​​that are one of the wavelength position relationships of the extreme values. As described later, determination criterion 2 includes oxide film thickness range regions with information and oxide film thickness range regions without information.

[0063] exist Figure 4 In this process, after determining criterion 1, which is one of the wavelength positional relationships of the extreme values, if criterion 2 exists, the oxide film thickness range of spectral reflectance can be evaluated by determining criterion 2. Furthermore, if it is criterion 3, 4, ..., then the oxide film thickness range is evaluated by determining the criterion with the smallest number in sequence.

[0064] In region T1, there are two extreme values ​​in the measured wavelength region. The short wavelength side has a minimum value, and the wavelength position relationship of the extreme values ​​is minimum → maximum. The interval between the wavelength positions of the extreme values ​​(minimum and maximum) is greater than 350 nm. Therefore, the judgment criterion 1 for the wavelength position relationship of the extreme values ​​is set as "minimum → maximum", and the judgment criterion 2 is set as "interval of extreme values ​​> 350 nm". In region T2, there is one minimum value in the measured wavelength region. In region T3, there are two extreme values ​​in the measured wavelength region. The short wavelength side has a maximum value, and the wavelength position relationship of the extreme values ​​is maximum → minimum. In region T4, there are three extreme values ​​in the measured wavelength region. The short wavelength side has a minimum value, and the wavelength position relationship of the extreme values ​​is minimum → maximum → minimum. In region T5, there are two extreme values ​​in the measured wavelength region. The short wavelength side has a minimum value, and the wavelength position relationship of the extreme values ​​is minimum → maximum. The interval between the wavelength positions of the extreme values ​​(minimum and maximum) is less than 350 nm.

[0065] Then, the estimated oxide film thickness range (regions T1, T2, T3, T4, and T5), the number of extreme values, and the wavelength position relationship of these extreme values ​​are used as information related to the number of extreme values ​​of the spectral reflectance and the wavelength position relationship of these extreme values, and are pre-created as a database. This pre-created database is used, for example, as the database 321 of the calculation unit 32 of the film thickness evaluation device 3. Thus, in the calculation unit 32, the oxide film thickness range (regions T1, T2, T3, T4, and T5) can be determined based on the number of extreme values ​​and the wavelength position relationship of these extreme values ​​in the measured wavelength regions using the spectral reflectance intensity measured by the detection unit 31 and the database 321. Furthermore, the database 321 is not limited to the calculation unit 32 of the film thickness evaluation device 3; for example, the database 321 can be set on an external server. Moreover, the film thickness evaluation device 3 and the external server can be configured to communicate via a network, with the film thickness evaluation device 3 accessing the database 321 of the external server and the calculation unit 32 determining the oxide film thickness range. Furthermore, within the specified wavelength range, the information related to the number of extreme values ​​of spectral reflectance and the wavelength position relationship of these extreme values ​​may not be represented by symbols as in the T1 to T5 regions described above, but rather by converted values ​​applied to approximate the simulated composition of the film. In this case, the range of converted values ​​is used as the oxide film thickness range to create a database. Alternatively, the information related to the number of extreme values ​​of spectral reflectance and the wavelength position relationship of these extreme values ​​may be the number of extreme values ​​of spectral reflectance and the wavelength position relationship of these extreme values ​​themselves. The appropriate choice can be made considering the size of the database and the load on the manufacturing equipment.

[0066] Furthermore, in the aforementioned experiment, by reducing the air ratio in multiple regions Z1, Z2, Z3, and Z4 along the straight path of the direct-fired furnace 2 during the first half of the annealing process, coated steel materials 1 with presumably different oxide film thicknesses were also produced. For these coated steel materials 1, after reducing the surface oxide film in the second half of the annealing process, the coating was applied to the surface of the coated steel materials 1 during the coating process, and the occurrence of uncoated surfaces was investigated. Thus, the relationship between regions T1 to T5 (i.e., information related to the number of extreme values ​​of spectral reflectance and the wavelength position of these extreme values ​​within a specified wavelength range) and the occurrence of uncoated surfaces in the coating process following the annealing process was also investigated. The results showed that within the oxide film thickness range where the number of extreme values ​​corresponding to regions T1 and T2 corresponds to the wavelength position of these extreme values, uncoated surfaces occurred on the surface of the coated steel materials 1. Based on these results, a database can be created regarding the T1 to T5 regions (i.e., information related to the number of extreme values ​​of spectral reflectance and the wavelength position relationship of these extreme values ​​within a specified wavelength range) and the occurrence of uncoated films, which are expected to be formed during normal manufacturing. A method for manufacturing an oxide film using this database as database 321 in the calculation unit 32 of the film thickness evaluation device 3, in a manner that prevents uncoated films from forming on the surface of the coated steel 1, and using information related to the number of extreme values ​​of spectral reflectance and the wavelength position relationship of these extreme values ​​within a specified wavelength range, is as follows.

[0067] To produce molten galvanized steel sheets with a good surface that prevents uncoating, the oxide film thickness in the direct-fired heating furnace 2 is prevented from falling below a certain thickness (regions T1 and T2). Therefore, after confirming region T3, the flow rates of fuel gas and air for burner combustion are increased in multiple regions Z1, Z2, Z3, and Z4 along the straight path of the direct-fired heating furnace 2, respectively, to enhance the burner flame intensity and control the oxide film thickness to reach region T4. This reduces the occurrence of uncoating.

[0068] Furthermore, assuming that the area where no coating can be produced is the T5 region, it is sufficient to maintain the burner flame intensity in the straight path of the direct-fired furnace 2. Additionally, while not required in this embodiment, the upper limit of the oxide film thickness range is determined experimentally beforehand to ensure the film is formed without exceeding a certain oxide film thickness. Moreover, it is preferable to control the burner flame intensity in the straight path of the direct-fired furnace 2 to form an oxide film with an oxide film thickness range where the number of extreme values ​​within a specified wavelength range and the wavelength position relationship of these extreme values ​​do not exceed the upper limit. In these cases, within the specified wavelength range, feedback control is performed on the direct-fired furnace 2 using information related to the number of extreme values ​​of spectral reflectance and the wavelength position relationship of these extreme values.

[0069] Furthermore, for example, if it is desired to set thresholds more precisely in the T3 region for information related to the number of extreme values ​​of spectral reflectance and the wavelength position of said extreme values ​​within a specified wavelength range, a database of the wavelength positions of arbitrary extreme values ​​in the T3 region can be created based on prior experimental results. Moreover, it is preferable to set thresholds for the wavelength positions of arbitrary extreme values ​​within the T3 region.

[0070] In addition, the above experiments are conducted according to steel type. If the number of extreme values ​​and the wavelength position relationship of the extreme values ​​in the measured wavelength region vary according to steel type, then a database can be created according to steel type and applied according to steel type.

[0071] Furthermore, in the manufacturing of molten galvanized steel sheets, if an oxide film is formed on the surface of the steel to be coated 1 using a direct-fired furnace 2 in the first half of the annealing process, then, in the second half of the annealing process, the steel to be coated 1 is subjected to, for example, radiant heating in a radiant tube furnace in a reducing atmosphere. This radiant heating step is configured as a step after the control step. As a result, the oxide film formed on the surface of the steel to be coated 1 changes from an iron oxide layer to a reduced iron layer, while simultaneously, the additive elements inside the steel sheet are internally oxidized by oxygen supplied from the iron oxide layer. Thus, the surface of the steel to be coated 1 is covered only by a reduced iron layer that has good wettability with zinc. In the next step after such a direct-fired furnace 2, namely the radiant heating step, information related to the number of extreme values ​​of the spectral reflectance within a specified wavelength range and the wavelength position relationship of these extreme values ​​can also be utilized. For example, a preliminary investigation can be conducted into the relationship between the furnace temperature and surface condition (whether no residual iron oxide remains and the iron is completely converted to reduced iron) in the radiant furnace for each of the different oxide film thickness regions formed in the direct-fired heating furnace 2, namely regions T1, T2, T3, T4, and T5. Furthermore, in the case of a thicker oxide film, such as region T5, a method can be used to control the furnace temperature of the radiant furnace to promote reduction, thereby measuring the change in the amount of reduction of the oxide film on the coated steel 1 after the film thickness range is determined.

[0072] (Variation Example 1)

[0073] Next, a modified example of the film thickness evaluation device 3 of the embodiment will be described. Figure 5 This is a diagram showing the schematic structure of the film thickness evaluation device 3 in Modified Example 1. The structure of the film thickness evaluation device 3 in Modified Example 1 is basically the same as... Figure 2 The film thickness evaluation device 3 shown has the same structure, but also includes a reference light measurement unit 311. Here, the substrate steel plate with no oxide film formed on its surface, as described in the above paragraph

[0049] , is referred to as the reference measurement sample, and the spectral reflectance intensity measured by the reference measurement sample used in calculating the spectral reflectance is referred to as the reference light.

[0074] Figure 5The reference light measurement unit 311 shown comprises a light guide 331, a detector 341, a reference measurement sample 312, and an instrument air inlet 361. In the reference light measurement unit 311, the optical system is designed such that light emitted from the light guide 331 of the reference light measurement unit 311, for the reference measurement sample 312, can be measured by the detector 341 via orthogonal reflection. Figure 5 In this structure, the light emitted from the light source unit 37 is branched through the optical fiber 38 to the light guides 33 and 331 of the detection unit 31 and the reference light measurement unit 311, respectively, forming a structure that can emit light from each of the light guides 33 and 331.

[0075] In the above paragraph

[0049] , a reference light was measured in advance and used to measure the spectral reflectance. However, depending on the light source, if the light source continues to be used, the filament deteriorates, and the luminous intensity of the light source decreases. Therefore, there is a problem that the luminous intensity spectrum of the light source changes over time. The decrease in luminous intensity is not a constant proportion across all wavelengths; sometimes the decrease proportion varies for each wavelength. Therefore, if the reference light measured in advance is used to calculate the spectral reflectance, and the measured reference light differs from the luminous intensity spectrum of the light source after filament deterioration, an incorrect spectral reflectance will be measured. Especially when using two or more light sources as in this modified example 1, the filament lifespan, deterioration mode, and filament replacement period are different. Therefore, it is difficult to predict and address the decay mode of the luminous intensity spectrum based on the irradiation time, and it is difficult to measure the reference light in advance considering the decay effect.

[0076] Therefore, in the film thickness evaluation device 3 of modified example 1, by setting Figure 5 The reference light measuring unit 311 shown can measure the reference light at any time interval and update it at any time. Therefore, in the measurement of spectral reflectance described in paragraphs

[0047] to

[0049] above, it is possible to cope with the changes in the luminous intensity spectrum of the light source and to calculate the spectral reflectance correctly. The timing for measuring and updating the reference light can be the same as the timing for measuring the spectral reflectance intensity from the plated steel in the detection unit 31, or it can be a timing interval of once every few hours, etc. The luminous spectral intensity does not decay significantly in units of seconds, so even if the reference light is updated at a timing interval of once every few hours, the spectral reflectance can be measured correctly.

[0077] (Variation Example 2)

[0078] Next, a modified example of the database of spectral reflectance and oxide film thickness range in the film manufacturing method of the embodiment will be described. In Modification 2, in order to obtain data reproducibility, an additional step was performed to... Figure 1The air ratio changes in multiple regions Z1, Z2, Z3, and Z4 along the straight path of the direct-fired heating furnace 2 shown are the same as those described in paragraph

[0056] . In this case, by reducing the production line speed, the temperature of the steel plate is intentionally increased, resulting in a thicker oxide film. The experimental results are presented as graphs showing the time variation of the air ratio, the time variation of the plate temperature, and the time variation of the wavelength position of the extreme values. Figure 6 .

[0079] Here, in Figure 6 The graph showing the time-varying wavelength positions of extreme values ​​uses triangles to depict the case where there are three extreme values ​​within the specified wavelength range, with the shortest wavelength side being the minimum. Additionally, the graph uses squares to depict the case where there are two extreme values ​​within the measured wavelength region, with the shortest wavelength side being the maximum. Furthermore, the graph uses circles to depict the case where there are two extreme values ​​within the measured wavelength region, with the shortest wavelength side being the minimum. Finally, the graph uses diamonds to depict the case where there are three extreme values ​​within the specified wavelength range, with the shortest wavelength side being the maximum.

[0080] Based on this curve, the corresponding ratio is clearly defined. Figure 4 The diagram shows the wavelength position relationship of the extreme values ​​in the T5 region and the T6 region, respectively. Specifically, the plate temperature ranges from... Figure 6 The wavelength begins to rise around 12:11. Furthermore, correspondingly, the wavelength position relationship shifts from the extreme values ​​corresponding to the T5 region to a "maximum → minimum → maximum" extreme value relationship, where there are three extreme values ​​in the measured wavelength region and the shortest wavelength side has the maximum extreme value. Based on this result, the T6 region is determined to be the region where the film thickness is thicker than the oxide film in the "maximum → minimum → maximum" range, as determined by criterion 1. Therefore, a new film was fabricated in... Figure 4 The relationships shown are supplemented with the relationship between the oxide film thickness range and the wavelength position of the spectral reflectance and extreme values ​​within the specified wavelength range of region T6 (judgment criterion 1 and judgment criterion 2). The newly created relationships are shown below. Figure 7 .

[0081] exist Figure 7 In the case of the relationship, the wavelength position relationship of the extreme values ​​has two kinds of information: judgment criterion 1 and judgment criterion 2. Both judgment criterion 1 and judgment criterion 2 are related to... Figure 4The criteria are the same. Criterion 1 is information related to the number of extrema and the wavelength position relationship of the extrema (the order of the extrema). Criterion 2 is information about the distance between extrema as one of the wavelength position relationships of the extrema. Criterion 1 has information in the entire oxide film thickness range, while Criterion 2 has oxide film thickness ranges with and without information. In the spectral reflectance of the newly added T6 region, only Criterion 1 exists. Criterion 1 in the T6 region has 3 extrema in the measurement wavelength range, with the extrema on the short wavelength side being the maximum, and the wavelength position relationship of the extrema is "maximum → minimum → maximum".

[0082] Figure 7 and Figure 4 Similarly, information related to the wavelength position relationship (judgment criterion) of the T1 to T6 regions can be used for film formation control, etc., as information related to the extreme values ​​of spectral reflectance. Figure 7 In the same manner as in the above paragraph

[0062] , determination criterion 1, which is one of the wavelength positions of the extreme value, is determined. Then, after determining determination criterion 1, if there is another determination criterion, namely determination criterion 2, which has a wavelength position relationship with the extreme value, the oxide film thickness range can be evaluated by determining determination criterion 2. Furthermore, if it is determination criterion 3, 4, ..., the oxide film thickness range is evaluated by determining the determination criterion with the smaller number in sequence.

[0083] (Variation Example 3)

[0084] Next, another example of a modification to the database of spectral reflectance and oxide film thickness range in the film manufacturing method of the embodiment will be described. In the modified example 2 described above... Figure 6In the middle of the continuous wavelength position relationship of "maximum → minimum → maximum" around 12:11, a "minimum → maximum" (interval between extreme values ​​> 350 nm) was confirmed in the wavelength position relationship corresponding to the extreme values ​​of region T1. Since the plate temperature and air ratio did not change significantly, it is unnatural for the wavelength position relationship of the extreme values ​​of region T1 to appear only momentarily during the continuous wavelength position relationship of "maximum → minimum → maximum" corresponding to region T6 within the oxide film thickness range. Therefore, after investigating the spectral reflectance that appeared around 12:11 and was determined to correspond to the "minimum → maximum (interval between extreme values ​​> 350 nm)" of region T1, it was found that the spectral reflectance exhibited a shape similar to amplitude collapse caused by interference of the spectral reflectance corresponding to region T6. Furthermore, further investigation into the aforementioned amplitude collapse phenomenon... After investigating the phenomenon, it was found that the amplitude reduction was caused by interference of the measured spectral reflectance due to the presence of uneven film thickness, the roughness of the substrate steel plate forming the oxide film, the deviation of positive reflection caused by the plate shaking of the flowing steel plate.

[0085] Therefore, it is predicted to be: Figure 6 The spectral reflectance observed at approximately 12:11, which is considered to correspond to the "minimum → maximum (extreme interval > 350 nm)" of region T1, actually corresponds to the spectral reflectance of region T6. Thus, when the amplitude of the spectral reflectance is reduced, in the extreme value determination method described in the above paragraph

[0058] , the spectral reflectance with reduced amplitude that actually corresponds to region T6 is determined to have a wavelength position relationship corresponding to region T1.

[0086] Therefore, the spectral reflectance with wavelength position relationships of "maximum → minimum → maximum" is defined as the T6-1 region corresponding to the T6 region. Additionally, the spectral reflectance with "minimum → maximum (extremum interval > 350 nm)" that is actually predicted to be in the T6 region but is defined as being in the T1 region is defined as the T6-2 region corresponding to the T6 region. Furthermore, results from repeated online experiments show that, in addition to the wavelength position relationships and intervals of the extreme values, the spectral reflectance can be determined to be in the T1 or T6-2 region by evaluating whether the reflectance difference between the extreme values ​​is greater than or less than 0.2. This is presumably because the amplitude is reduced at the spectral reflectance corresponding to the T6-2 region, thus the reflectance difference between the extreme values ​​is smaller, making it easier to differ from the reflectance difference between the extreme values ​​corresponding to the T1 region.

[0087] Based on the above insights, the inventors of this application have reconstructed the relationship between oxide film thickness range, spectral reflectance, and judgment criteria within a specified wavelength range. The newly constructed relationship is shown below. Figure 8 . Figure 8 Compared to Figure 7 The region corresponding to region T6 is designated as region T6-1, and region T6-2 is added as a new region T6. Additionally, Figure 8 Compared to Figure 7 A new judgment criterion 3 has been added.

[0088] exist Figure 8 In the case of the relationship, the wavelength position relationship of the extreme values ​​has two kinds of information: judgment criterion 1 and judgment criterion 2. Both judgment criterion 1 and judgment criterion 2 are related to... Figure 4 and Figure 7 The same. Judgment criterion 1 is information related to the number of extrema and the wavelength positional relationship of the extrema (the order in which the extrema are arranged). Judgment criterion 2 is information about the distance between extrema, which is one of the wavelength positional relationships of the extrema. Judgment criterion 1 has information across the entire oxide film thickness range, while judgment criterion 2 has oxide film thickness ranges with and without information. Judgment criterion 3 is... Figure 8 The newly added criterion is information about the reflectance difference at extreme values. Criterion 3, like criterion 2, has regions with informational oxide film thickness ranges and regions without informational oxide film thickness ranges. Figure 8 In the same manner as before, the range of oxide film thickness for spectral reflectance is evaluated by the following method: determining criterion 1, then determining criterion 2 if criterion 2 is present, and then determining criterion 3 if criterion 3 is also present.

[0089] Thus, in variation example 3, a prefabricated... Figure 8 The database shown not only uses the positional relationship of extreme values, but also information related to the shape of spectral reflectance, such as the difference in reflectance between the extreme values ​​of spectral reflectance. Using this pre-made database, the oxide film described in paragraphs

[0066] to

[0071] above can be manufactured, and this oxide film can address the problem of amplitude collapse of spectral reflectance caused by uneven film thickness or deviations in positive reflection.

[0090] Industrial availability

[0091] This invention provides a method for manufacturing films suitable for subsequent processes, products, objects, oxide films, and coated steel, even when the film thickness cannot be accurately measured.

[0092] Explanation of reference numerals in the attached figures

[0093] 1: Steel to be coated

[0094] 2: Direct-fired heating furnace

[0095] 3: Film thickness evaluation device

[0096] 4: In-furnace rollers

[0097] 5: Measurement of the window

[0098] 6: Burner

[0099] 7: In-furnace rollers

[0100] 31: Testing Department

[0101] 32: Arithmetic Department

[0102] 33, 331: Optical guide

[0103] 34, 341: Detectors

[0104] 35: Shutter speed

[0105] 36, 361: Instrument air inlet section

[0106] 37: Light Source Section

[0107] 38: Fiber optic

[0108] 39: Halogen light source

[0109] 310: Xenon light source

[0110] 311: Reference Light Measurement Unit

[0111] 312: Samples for reference determination

[0112] 321: Database.

Claims

1. A method for manufacturing a membrane, comprising: The steps for calculating spectral reflectance are as follows: Calculate the spectral reflectance based on the reflected light obtained through reflection from the optical coating. The information calculation step involves, based on the calculated spectral reflectance, calculating information related to the number of extreme values ​​of the spectral reflectance and the wavelength position relationship of these extreme values ​​within a specified wavelength range; and... The control step involves controlling the membrane formation conditions based on the calculated information.

2. The method for manufacturing a membrane according to claim 1, wherein, The controlled formation conditions are one or more, and are formation conditions in processes prior to the spectral reflectance calculation step and / or formation conditions in processes after the information calculation step.

3. A method for manufacturing an object, comprising: The membrane forming step of forming a membrane on the surface of an object by the membrane manufacturing method according to claim 1 or 2.

4. A method for manufacturing an oxide film, wherein, It has an annealing process that forms an oxide film on the surface of the steel plate. The annealing process includes: The spectral reflectance calculation step involves calculating the spectral reflectance based on the reflected light obtained through the light reflected by the formed oxide film. The information calculation step involves, based on the calculated spectral reflectance, calculating information related to the number of extreme values ​​of the spectral reflectance and the wavelength position relationship of these extreme values ​​within a specified wavelength range; and... The control step involves controlling the formation conditions of the oxide film based on the calculated information.

5. A method for manufacturing coated steel, comprising: a method for manufacturing coated steel having a coating film on the surface of the coated steel, comprising: an annealing process of forming an oxide film on the surface of the plated steel material, and reducing the formed oxide film; as well as The plating process, following the annealing process, involves forming the plating film on the steel to be plated. The annealing process includes: The spectral reflectance calculation step involves calculating the spectral reflectance based on the reflected light obtained through the reflection of light by the oxide film formed on the surface of the coated steel. The information calculation step involves, based on the calculated spectral reflectance, calculating information related to the number of extreme values ​​of the spectral reflectance and the wavelength position relationship of these extreme values ​​within a specified wavelength range; and... The control step, based on the calculated information, controls the formation conditions of the oxide film in the process prior to the spectral reflectance calculation step, and / or controls the reduction conditions of the oxide film in the process after the information calculation step.

Images