Temperature measurement method, temperature measurement device, temperature control method, temperature control device, steel material manufacturing method, and steel material manufacturing facility

Abstract

A temperature measurement method according to the present invention comprises: a spectroscopic measurement step for measuring a spectroscopic radiation spectrum from a billet, said spectroscopic radiation spectrum including at least three or more wavelengths having different spectroscopic radiance at the same temperature; an acquisition step for acquiring a characteristic quantity of the surface of the billet at a measurement point of the spectroscopic radiation spectrum; a determination step for determining the form of the surface of the billet on the basis of the feature amount acquired in the acquisition step; and a selection step for selecting, on the basis of the determination result of the determination step, a temperature calculation method for calculating the temperature of the measurement point from the spectroscopic radiation spectrum measured in the spectroscopic measurement step.

Description

Technical Field

[0001] The present invention relates to a temperature measuring method, a temperature measuring device, a temperature control method, a temperature control device, a steel manufacturing method, and steel manufacturing equipment. Background Art

[0002] Typically, steel billets prepared for hot rolling are heated to a target extraction temperature in a heating furnace before being hot rolled. Therefore, the steel billets must be uniformly heated in the heating furnace to reach the target extraction temperature. To achieve this, the furnace temperature and the billet extraction temperature must be constantly monitored. On the other hand, accurately determining the billet extraction temperature improves the accuracy of the temperature prediction model used to predict the billet temperature, which is beneficial for improving the accuracy of the billet extraction temperature and improving the operation of the heating furnace. Against this backdrop, numerous methods for measuring the billet extraction temperature have been proposed. Furthermore, when scale forms on the surface of a steel billet, accurately measuring the billet temperature is difficult. Therefore, Patent Documents 1 and 2 propose methods for determining the presence of scale on the billet surface. Specifically, Patent Document 1 describes a method for determining the presence of scale by determining whether the difference between the maximum value of the actually measured extraction temperature and the calculated extraction temperature based on the furnace operating conditions is below a positive threshold. Patent Document 2 describes a method for determining the presence or absence of scale based on the temperature of the steel slab at a scale-removed portion and the temperature of the steel slab at a portion where scale removal has not been performed.

[0003] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Publication No. 2019-167574 Patent Document 2: Japanese Patent Application Laid-Open No. 2017-1070 Patent Document 3: Japanese Patent No. 5987563 Summary of the Invention

[0004] Problems to be solved by the invention

[0005] However, in the method described in Patent Document 1, it is difficult to determine the presence or absence of scale when there is a deviation between the calculation conditions of the heating furnace extraction temperature and the measurement state, such as when the conveyance of the steel billet is stopped after the steel billet is extracted from the heating furnace due to an operational failure or the like. In addition, when scale exists in the entire temperature measurement range of the steel billet, a measurement error sometimes occurs in the maximum value of the heating furnace extraction temperature. On the other hand, in the method described in Patent Document 2, it is necessary to measure the steel billet temperature before and after the scale removal process, so there are problems such as the need for multiple devices and the inability to prepare the installation environment of the devices. In addition, when water from the water used in the scale removal process is attached to the scale removal position, there is a possibility of measurement error in the steel billet temperature. Based on the above, it is required to provide a technology that can measure the heating furnace extraction temperature of the steel billet with high precision regardless of the morphology of the steel billet surface.

[0006] The present invention has been completed in view of the above-mentioned problems, and its object is to provide a temperature measurement method and temperature measurement device capable of measuring the temperature of a steel billet with high accuracy, regardless of the surface morphology of the steel billet. Furthermore, another object of the present invention is to provide a temperature control method and temperature control device capable of controlling the temperature of a steel billet to a target temperature with high accuracy, regardless of the surface morphology of the steel billet. Furthermore, another object of the present invention is to provide a steel manufacturing method and manufacturing equipment that can improve the steel manufacturing yield and prevent equipment failures caused by warping or impact of the steel billet, as well as equipment damage caused by excessive loads such as excessive loads.

[0007] Means for solving problems

[0008] [1] The temperature measurement method involved in the present invention includes: a spectroscopic measurement step of measuring a spectroscopic radiation spectrum from a steel billet containing at least three wavelengths having different spectral radiation rates at the same temperature; an acquisition step of acquiring a characteristic value of the steel billet surface at a measurement point of the spectroscopic radiation spectrum; a determination step of determining the morphology of the steel billet surface based on the characteristic value acquired in the acquisition step; and a selection step of selecting a temperature calculation method based on a determination result of the determination step, wherein the temperature calculation method calculates the temperature of the measurement point based on the spectroscopic radiation spectrum measured in the spectroscopic measurement step.

[0009] [2] In the invention of [1] above, the feature quantity may include brightness and shape.

[0010] [3] In the invention of [1] or [2] above, the morphology of the surface of the steel slab may include oxide scale and water adhesion.

[0011] [4] The temperature measuring device involved in the present invention comprises: a spectroscopic measurement unit for measuring the spectral radiation spectrum from the steel billet at at least three wavelengths with different spectral radiation rates at the same temperature; an acquisition unit for acquiring a characteristic value of the steel billet surface at a measurement point of the spectral radiation spectrum; and a computing unit for determining the morphology of the steel billet surface based on the characteristic value acquired by the acquisition unit, and selecting a temperature calculation method based on the determination result, wherein the temperature calculation method calculates the temperature of the measurement point according to the spectral radiation spectrum.

[0012] [5] The temperature control method of the present invention includes a step of controlling the temperature of the steel billet based on the temperature of a measuring point, wherein the temperature of the measuring point is calculated according to a temperature calculation method selected by the temperature measurement method of any one of the above-mentioned [1] to [3] of the present invention.

[0013] [6] The temperature control device of the present invention includes a unit for controlling the temperature of the steel billet based on the temperature of a measuring point calculated according to the temperature calculation method selected by the temperature measuring device of the present invention [4].

[0014] [7] The method for manufacturing a steel material of the present invention includes the step of controlling the temperature of a steel billet using the temperature control method of the present invention described in [5].

[0015] [8] The steel manufacturing equipment of the present invention includes the temperature control device of the above-mentioned [6] of the present invention.

[0016] Effects of the Invention

[0017] The temperature measurement method and temperature measurement device of the present invention can measure the temperature of a steel billet with high precision, regardless of the billet surface morphology. Furthermore, the temperature control method and temperature control device of the present invention can control the billet temperature to a target temperature with high precision, regardless of the billet surface morphology. Furthermore, the steel manufacturing method and manufacturing equipment of the present invention can improve the steel manufacturing yield rate and prevent equipment failures caused by warping and impact of the steel, as well as equipment damage caused by excessive loads such as excessive loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram showing the configuration of a hot-rolled steel sheet manufacturing facility to which a temperature measuring method, a temperature measuring device, a temperature control method, and a temperature control device according to one embodiment of the present invention are applied. Figure 2 It is a schematic diagram showing the structure of a temperature measuring device according to one embodiment of the present invention. Figure 3 Schematic diagram showing an example of the imaging range of a spectral image. Figure 4 A diagram showing an example of a spectral image and a spectral radiation spectrum. Figure 5 It is a diagram for explaining the operation of the feature quantity measuring device. Figure 6 This is a flowchart showing the flow of temperature measurement processing according to one embodiment of the present invention. Figure 7 Is used to illustrate Figure 6 FIG. 1 is a diagram showing an example of a temperature measurement process. Figure 8 Is used to illustrate Figure 6 FIG. 2 is a diagram showing another example of the temperature measurement process. Figure 9 This is a diagram showing an example of image data of a steel billet. Figure 10 It means from Figure 9 The image data shown is a diagram of an area where the brightness is below a threshold value extracted. Figure 11 This is a diagram showing an example of image data of a steel billet. Figure 12 It means from Figure 11 The image data shown is a diagram of an area where the brightness is below a threshold value extracted. Figure 13 This is a diagram showing an example of image data of a steel billet. Figure 14 It means from Figure 13 The image data shown is a diagram of an area where the brightness is below a threshold value extracted. DETAILED DESCRIPTION

[0019] Hereinafter, a temperature measuring method, a temperature measuring device, a temperature control method, and a temperature control device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0020] Hot-rolled steel plate manufacturing equipment

[0021] First, refer to Figure 1 , the structure of a hot-rolled steel sheet manufacturing facility to which a temperature measuring method, a temperature measuring device, a temperature control method, and a temperature control device according to one embodiment of the present invention are applied will be described.

[0022] Figure 1 Schematic diagram showing the structure of a hot rolled steel sheet manufacturing facility to which a temperature measuring method, a temperature measuring device, a temperature control method, and a temperature control device according to an embodiment of the present invention are applied. Figure 1As shown, a hot-rolled steel plate manufacturing facility 1 includes multiple heating furnaces 2 arranged in parallel, a conveyor line 3, and a rolling mill 4. The rolling mill 4 includes a roughing mill, a finishing mill, a run-out table, a coiler, and the like. In this manufacturing facility 1, a steel slab S is heated to a target temperature in the heating furnaces 2 and then removed from one of the multiple heating furnaces 2 to the conveyor line 3. The steel slab S is then transported via the conveyor line 3 to the rolling mill 4 for hot rolling.

[0023] Temperature measuring device

[0024] Next, refer to Figures 2 to 5 , the structure of a temperature measuring device as one embodiment of the present invention is described.

[0025] Figure 2 Schematic diagram showing the structure of a temperature measuring device according to one embodiment of the present invention. Figure 2 As shown in FIG. 1 , a temperature measurement device 10 as one embodiment of the present invention includes a spectroscopic camera 11 , a feature quantity measurement device 12 , and a computing device 13 .

[0026] The spectroscopic camera 11 measures the spectral radiation spectrum (the relationship between wavelength and spectral brightness) of the steel slab S by capturing a spectral image of the steel slab S extracted from the heating furnace 2, and outputs the data of the measured spectral radiation spectrum to the computing device 13. The spectroscopic camera 11 is equivalent to a spectroscopic measurement unit. When the capturing range of the spectral image is linear, as in Figure 3 As shown, the spectroscopic camera 11 may be installed to capture a spectroscopic image of the region R in the sheet width direction from above the slab S. Thus, the slab S can be conveyed along the conveyor line 3 to capture a spectroscopic image of the entire surface of the slab S.

[0027] Figure 4 (a) and (b) show an example of the spectral image and spectral radiation spectrum of the steel billet S. Figure 4 In the case of the examples shown in (a) and (b), the imaging range of the spectroscopic camera 11 is the width direction of the billet S. Therefore, the horizontal direction of the spectroscopic image corresponds to each measurement point on the billet S, and the spectroscopic radiation spectrum at each measurement point on the billet S is measured ( Figure 4 (b)). If reference data is acquired in advance using a blackbody furnace or other similar method and the calculation temperature for the operating data is set to a positive value, the spectral emissivity spectrum can be calculated from the spectral emissivity spectrum. Furthermore, by setting a spectral emissivity that serves as a reference for, for example, the spectral emissivity of a descaled portion, it is also possible to calculate fluctuations in the spectral emissivity spectrum.

[0028] The characteristic quantity measuring device 12 is composed of a camera, a shape meter, etc., and measures the characteristic quantity of the surface of the steel billet S at the measuring point of the spectral reflection spectrum measured by the spectroscopic camera 11. As the characteristic quantity measured by the characteristic quantity measuring device 12, the brightness, shape, depth, position in the steel billet plane, position on the conveyor line 3, etc. of the surface area including the measuring point can be exemplified. In addition, as the characteristic quantity measured by the characteristic quantity measuring device 12, the length in the width direction and the length direction, the aspect ratio, the maximum value of the length, etc. of the surface area including the measuring point can be exemplified. More specifically, as Figure 5 As shown, at each measurement point (x, y) on the steel billet, a spectroscopic camera 11 measures the spectral radiation spectrum L(x, y), and a feature quantity measuring device 12 measures the feature quantity z(x, y). The spectral radiation spectrum L(x, y) is a scalar quantity that includes the spectral brightness of multiple wavelengths. When the feature quantity measuring device 12 is a camera, the feature quantity z(x, y) corresponds to brightness. When the feature quantity measuring device 12 is a shape meter, the feature quantity z(x, y) corresponds to depth information. Furthermore, the feature quantity z(x, y) may be a scalar quantity, or, when the feature quantity measuring device 12 is a color camera, a vector quantity consisting of three values: RGB.

[0029] The computing device 13 uses the spectral radiation spectrum measured by the spectroscopic camera 11 and the characteristic quantities of the surface of the steel slab S measured by the characteristic quantity measuring device 12 to perform a temperature measurement process described below, thereby calculating the temperature of the steel slab S. The computing device 13 may also calculate the temperature of the steel slab S based on the spectral radiation rate calculated from the spectral radiation spectrum or its fluctuation.

[0030] Temperature measurement processing

[0031] Next, refer to Figure 6 , a flow of temperature measurement processing as one embodiment of the present invention is described.

[0032] Figure 6 This is a flowchart showing the flow of temperature measurement processing as one embodiment of the present invention. Figure 6 The flowchart shown starts when an execution instruction for the temperature measurement process is input to the arithmetic device 13 , and the temperature measurement process proceeds to the process of step S1 .

[0033] In step S1, the computing device 13 causes the feature quantity measurement device 12 to measure the feature quantity at each measurement point. In step S2, the computing device 13 acquires a predetermined feature quantity for each measurement point based on the measurement results obtained in step S1 (acquisition step). Meanwhile, in step S3, the computing device 13 causes the spectroscopic camera 11 to measure the spectral radiation spectrum at each measurement point. The computing device 13 then acquires a spectral radiation spectrum for each measurement point based on the obtained measurement results (spectroscopic measurement step). Using the spectral radiation spectrum acquired in the spectroscopic measurement step S3 and acquisition step S2, along with the predetermined feature quantity, the computing device 13 proceeds to step S4.

[0034] In the process of step S4, the computing device 13 determines the morphology of the surface of the steel slab S at the measurement point of the spectral radiation spectrum based on the characteristic quantity of the surface of the steel slab S measured by the characteristic quantity measuring device 12. Specifically, the computing device 13 determines whether scale or water adhesion exists at the measurement point of the spectral radiation spectrum based on the characteristic quantity of the surface of the steel slab S measured by the characteristic quantity measuring device 12. For example, Figure 7 As shown, when the measurement point of the spectral radiation spectrum is included in the image area with a brightness exceeding the threshold, the operation device 13 determines that the steel billet S is exposed at the measurement point. On the other hand, when the measurement point of the spectral radiation spectrum is included in the image area with a brightness below the threshold, the operation device 13 determines that water is attached to the measurement point. Figure 8 As shown, if the measurement point of the spectral radiation spectrum is contained within an image region where the brightness exceeds a threshold, the computing device 13 determines that the steel slab S is exposed at the measurement point. On the other hand, if the measurement point of the spectral radiation spectrum is contained within an image region where the brightness is below the threshold and the width and length dimensions exceed thresholds, the computing device 13 determines that water is attached to the measurement point. Furthermore, if the measurement point of the spectral radiation spectrum is contained within an image region where the brightness is below the threshold and the width and length dimensions are below the threshold, the computing device 13 determines that scale is present at the measurement point. This completes step S4, and the temperature measurement process proceeds to steps S5_1 through S5_n (here, for example, n ≥ 3).

[0035] In steps S5_1 through S5_n, the computing device 13 selects a temperature calculation method based on the surface morphology of the steel slab S at the measurement point determined in step S4, and uses the selected temperature calculation method to calculate the temperature at the measurement point. For example, if it is determined that there is no scale or water adhesion at the measurement point, the computing device 13 calculates the spectral emissivity of the steel slab S at a predetermined wavelength based on the spectral reflectance spectrum, and calculates the temperature at the measurement point using the calculated spectral emissivity and a previously assumed spectral emissivity at the predetermined wavelength (step S5_1, temperature calculation method 1). Alternatively, if it is determined that water adhesion exists at the measurement point, the computing device 13 calculates the spectral emissivity of the steel slab S at a wavelength that is pre-set based on the spectral reflectance spectrum at the measurement point and is less susceptible to emissivity fluctuations caused by water adhesion, and uses the calculated spectral emissivity to calculate the temperature at the measurement point (step S5_2, temperature calculation method 2). Furthermore, if it is determined that scale is present at the measurement point, the computing device 13 calculates the spectral emissivity of the steel slab S at a wavelength that is pre-set based on the spectral reflectance spectrum at the measurement point and is less susceptible to emissivity fluctuations caused by scale, and uses the calculated spectral emissivity to calculate the temperature at the measurement point (step S5_n, temperature calculation method n). The computing device 13 may also calculate a temperature measurement value that is less affected by emissivity fluctuations by using the method using principal components described in Patent Document 3.

[0036] Alternatively, in step S5_1, the temperature may be calculated using a monochromatic radiation thermometer method, in step S5_2, the temperature may be calculated using a two-color thermometer method, and in step S5_n, the temperature may be calculated using the method described in Patent Document 3. The monochromatic radiation thermometer method calculates the temperature based on Planck's emissivity using a predetermined emissivity ε based on the brightness at a single, specified wavelength λ, and the two-color thermometer method calculates the temperature based on Planck's emissivity using a predetermined emissivity ratio ε1 / ε2 based on the brightness at two, specified wavelengths λ1 and λ2. Alternatively, in step S5_1, the temperature may be calculated using a monochromatic radiation thermometer method using wavelength λ1, in step S5_2, the temperature may be calculated using wavelength λ2, and in step S5_n, the temperature may be calculated using a monochromatic radiation thermometer method using wavelength λ3. In other words, in steps S5_1 through S5_n, the temperature calculation method with the smallest error may be selected based on the situation. In this embodiment, a temperature calculation method is selected based on the surface morphology of the steel slab S at the measurement point determined in step S4, and the selected temperature calculation method is used to calculate the temperature at the measurement point. However, the determination in step S4 can be omitted, and the temperatures of the measurement points can be pre-calculated using all temperature calculation methods (steps S5_1 to S5_n). An appropriate temperature can then be selected from the temperatures calculated based on the determination results in step S4. In other words, the order of steps S4 and S5_1 to S5_n can be reversed, with the determination in step S4 performed for each measurement point after calculation using temperature calculation methods 1 to n (steps S5_1 to S5_n). The results of steps S4 to S5_n can also be stored and accumulated in a storage device (not shown). In this case, it is more preferable to assign position information, time information, material information, or manufacturing condition information to each measurement point and store and accumulate them, as this facilitates the creation of the steel slab temperature distribution described later when needed.

[0037] Afterwards, based on the processing results of steps S1 to S5_n, the computing device 13 creates a billet temperature distribution (step S6). The billet temperature distribution is preferably created in a manner that forms an area of ​​a predetermined size. In addition, the created billet temperature distribution can also be assigned to a storage device not shown in the figure for storage and accumulation. At this time, the position information, time information, material information or manufacturing condition information of each measurement point can also be saved. In addition, it can also be displayed on a display device not shown in the figure. At this time, the position information, time information, material information or manufacturing condition information of each measurement point can also be displayed. According to the purpose of using the billet temperature distribution created in this embodiment, the size of the area and the output method can be appropriately selected. As an example, n in the processing of step S5 is described as n≥3, but the present invention is not limited to this. Even if n≥2, the effect can be obtained. In the case of a billet, n≥3 is preferred.

[0038] As can be seen from the above description, in the temperature measurement process which is one embodiment of the present invention, the spectroscopic camera 11 measures the spectral radiation spectrum from the steel billet including at least three wavelengths having different spectral radiation rates at the same temperature, the characteristic quantity measuring device 12 obtains the characteristic quantity of the steel billet surface at the measurement point of the spectral radiation spectrum, the computing device 13 determines the morphology of the steel billet surface based on the characteristic quantity obtained by the characteristic quantity measuring device 12, and calculates the temperature of the above-mentioned measurement point according to the spectral radiation spectrum based on the determination result, thereby being able to measure the temperature of the steel billet with high precision regardless of the morphology of the steel billet surface.

[0039] Example

[0040] Figure 9 This is an example of image data of a steel billet with water deposited in the center. When calculating the temperature distribution of the steel billet using a single temperature calculation method as in the past for such image data, the temperature in the center decreases. Therefore, the water deposited portion is extracted by multiplying the brightness of the image data by a threshold. Figure 10 In the example, 1 / 2 of the maximum brightness of the billet portion is used as a threshold value, and an example is shown in which areas with brightness below the threshold value are extracted. Thus, by changing the temperature calculation method in the extracted area and other areas, a more accurate temperature calculation can be performed. However, simply multiplying the brightness by the threshold value is not sufficient. Figure 11 The image data of other steel billets are shown in Figure 12 The same threshold is shown in Figure 11 The image data shown is the extracted area. Figure 12 The largest area shown is assumed to be the water adhesion area, but in addition to this, a number of smaller areas assumed to be the oxide scale area are extracted. Therefore, the temperature calculation method can be changed in the water adhesion area, the oxide scale area, and other areas based on the size of each area. Figure 13 Showing image data of other billets, Figure 14 The following figure shows the areas extracted using the same threshold. In this data, water-adherent areas are not extracted, but rather multiple small areas assumed to be scale areas. Therefore, using only the brightness threshold cannot distinguish between water-adherent and scale areas. However, by also setting thresholds for the width and length of the area, it is possible to distinguish between water-adherent and scale areas, thereby changing the temperature calculation method.

[0041] While the above describes an embodiment in which the invention developed by the present inventors is applied, the present invention is not limited to the description and drawings that constitute part of the disclosure of the present invention related to this embodiment. For example, the spectroscopic camera 11 may also function as the feature quantity measuring device 12. In this case, the acquisition step S1 is also performed during the spectroscopic measurement step S3. Furthermore, the spectral reflectance spectrum does not necessarily need to be a spectrum covering a continuous wavelength range; it only needs to include a spectrum containing at least three wavelengths with different spectral emissivities at the same temperature. Furthermore, while the present embodiment determines both the presence of scale and / or water adhesion at the measurement point, it is also possible to determine only one of the presence of scale or water adhesion at the measurement point. Furthermore, for example, by utilizing a temperature control method or temperature control device, which is one embodiment of the present invention, steel products can be manufactured while controlling the temperature of a steel billet, thereby improving the steel product manufacturing yield. Furthermore, by installing a temperature control method or temperature control device, which is one embodiment of the present invention, in known or existing manufacturing equipment, particularly in equipment for heating steel billets, the steel product manufacturing yield can be improved. Furthermore, equipment failures caused by warping and impact of steel materials, as well as equipment damage caused by excessive loads, can be prevented before they occur. Thus, other embodiments, examples, and application technologies created by those skilled in the art based on this embodiment are all within the scope of the present invention.

[0042] Industrial Application Possibilities

[0043] According to the present invention, a temperature measurement method and a temperature measurement device can be provided that can measure the temperature of a steel billet with high accuracy, regardless of the billet surface morphology. Furthermore, according to the present invention, a temperature control method and a temperature control device can be provided that can control the temperature of a steel billet to a target temperature with high accuracy, regardless of the billet surface morphology. Furthermore, according to the present invention, a steel manufacturing method and a manufacturing device can be provided that can improve the steel manufacturing yield and prevent equipment failures caused by warping or impact of the steel, as well as equipment damage caused by excessive loads such as loads.

[0044] Description of labels 1Hot rolled steel plate manufacturing equipment 2Heating furnace 3 conveyor lines 4Rolling equipment 10 Temperature measuring device 11 Spectroscopic Camera 12 Feature quantity measuring device 13 computing device S billet.

Claims

1. A temperature measurement method, comprising: A spectroscopic measurement step of measuring a spectroscopic radiation spectrum from the steel billet including at least three or more wavelengths having different spectral radiation indices at the same temperature; an acquisition step of acquiring a characteristic quantity of the surface of the steel billet at a measurement point of the spectral radiation spectrum; a determination step of determining the morphology of the surface of the steel billet based on the feature quantity acquired in the acquisition step; as well as A selection step of selecting a temperature calculation method based on the determination result of the determination step, the temperature calculation method calculating the temperature of the measurement point from the spectral radiation spectrum measured in the spectral measurement step.

2. The temperature measurement method according to claim 1, wherein: The feature quantities include brightness and shape.

3. A temperature measuring device comprising: A spectrometer unit for measuring the spectroscopic radiation spectrum from the steel billet at at least three wavelengths having different spectral radiation indices at the same temperature; an acquisition unit that acquires a characteristic value of a surface of a steel billet at a measurement point of the spectral radiation spectrum; and The computing device determines the morphology of the surface of the steel billet based on the feature amount acquired by the acquiring unit, and selects a temperature calculation method based on the determination result, the temperature calculation method calculating the temperature of the measurement point based on the spectral radiation spectrum.

4. A temperature control method comprising the step of controlling the temperature of a steel billet based on a temperature at a measurement point calculated according to a temperature calculation method selected by the temperature measurement method according to claim 1 or 2. 5 . A temperature control device comprising means for controlling the temperature of a steel billet based on a temperature at a measurement point calculated according to a temperature calculation method selected by the temperature measuring device according to claim 3 .

6. A method for manufacturing a steel material, comprising the step of controlling the temperature of a steel billet using the temperature control method according to claim 4.

7. A steel material manufacturing facility comprising the temperature control device according to claim 5.

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