JP2010265534A - Method for heating ferritic stainless steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To heat a ferritic stainless steel while further reducing the probability in the occurrence of delayed failure. <P>SOLUTION: In the method for heating a ferritic stainless steel, a continuously cast ferritic stainless steel member is charged into a heating furnace wherein the surface temperature of the steel member is ≥150°C before hot rolling, and the steel member is heated in such a manner that the temperature rising rate in the surface temperature of the steel member is controlled to ≤15.5 °C/min in the range of the surface temperature of 150 to 700°C by the heating furnace. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for heating ferritic stainless steel that prevents the occurrence of cracks.

  So-called “ferritic stainless steel” containing Cr in high purity and having a reduced content of C and N is used in various applications such as building materials, electrical parts, and automobiles. However, ferritic stainless steel is disclosed in the following Patent Document 1 and Patent Document 2, for example, during cooling after continuous casting, during slab surface maintenance after cooling, and in the subsequent hot rolling process. During heating, cracks penetrating the cross section of the steel material (hereinafter also referred to as “placement cracks”) may occur.

  If this crack occurs, it cannot be used for rolling and is scrapped, so the cost of production up to that time is wasted. For example, slab breaking during heating, rolling interruption due to falling in the furnace, etc. Due to the malfunction, efficiency is reduced. Therefore, the occurrence of cracking has a great influence on the manufacturing cost and the manufacturing efficiency.

  There is a finding that such a placement crack occurs when the residual level due to thermal stress exceeds the fracture limit at the steel temperature due to cooling or heating from continuous casting to heating by a heating furnace. In order to suppress the residual stress to a low level, for example, various conditions such as a water cooling condition during continuous casting, a subsequent air cooling condition, and a temperature of the steel material under care are improved by trial and error. As a result, compared to the beginning of the production of ferritic stainless steel, it is possible to reduce the occurrence of cracks.

JP-A-6-328214 JP-A-6-346143 Japanese Patent Laid-Open No. 62-56517 JP 61-292528 A JP-A-62-22089 JP 2005-134153 A

  As these improvements, for example, a production method as disclosed in Patent Documents 1 to 3 can be mentioned. In the manufacturing method of Patent Document 1, the slab temperature immediately after completion of slab solidification in a continuous casting machine is such that the temperature difference between the slab wide surface center surface temperature and the slab narrow surface central temperature is within 200 ° C. To control the cooling. At the same time, the slab is once cooled to room temperature in an air cooling or heat retaining pit. After that, when reheating again for hot rolling, the temperature deviation between the surface temperature at the center of the wide surface and the surface temperature at the center of the narrow surface is changed until the temperature at the center of the slab reaches 200 ° C. Control to be within 200 ° C.

  Moreover, in the manufacturing method of patent document 2, in the process of cooling continuously cast ferritic stainless steel to room temperature, the wide surface of the slab is in a temperature region of 300 ° C. or higher, and the end temperature of the slab is set to be equal to or higher than the center temperature of the wide surface. While temporarily heating, the cooling rate is kept below 40 ° C./hr.

  Furthermore, in the production method of Patent Document 3, a continuous cast slab of ferritic stainless steel or a slab obtained by subjecting the slab to ingot rolling is shown in a diagram showing the relationship between the surface temperature of the slab or slab and the elapsed time. Cool down so that it does not pass through dangerous areas (high temperature side and low temperature side).

  The manufacturing methods of these Patent Documents 1 to 3 reduce the thermal stress generated in the steel material by limiting the temperature difference or the cooling rate, and the high temperature side danger zone described in Patent Document 3 is , Which suppresses the generation of intermetallic compounds that embrittle the steel.

  However, among the operating conditions from the continuous casting process to the heating furnace before hot rolling, for example, variation in the finishing temperature due to fluctuations in the casting speed and fluctuations in the maintenance time, heating furnace charging temperature, heating rate and temperature There are a wide variety of factors that affect the cracking, such as variation in distribution. As a result of these various factors fluctuating, it was difficult to sufficiently prevent the occurrence of cracks even in the manufacturing methods of Patent Documents 1 to 3 described above.

  The present invention has been made in view of the above problems, and an object of the present invention is to heat ferritic stainless steel while further reducing the probability of occurrence of cracking.

  In order to solve the above problems, according to one aspect of the present invention, before hot rolling a continuously cast ferritic stainless steel material, the steel material is charged into a heating furnace at a surface temperature of 150 ° C. or higher. The steel material is heated by the heating furnace so that the rate of temperature rise of the surface temperature of the steel material is 15.5 ° C./min or less in the range of the surface temperature of 150 to 700 ° C., A method for heating ferritic stainless steel is provided.

  Here, in the heating method of the ferritic stainless steel, the surface temperature of the steel material is charged into a heating furnace at 200 ° C. or higher, and the surface of the steel material is within the surface temperature range of 200 to 700 ° C. by the heating furnace. It is preferable to heat the steel material so that the temperature rise rate is 15 ° C./min or less.

  Further, in the heating method of the ferritic stainless steel, a temperature specifying position which is a position on the steel material for specifying the surface temperature is determined in advance, and before the surface temperature of the steel material reaches 700 ° C., the heating furnace The surface temperature at the temperature specific position of the steel material being heated at is measured at a first time and a second time after a predetermined time has elapsed from the first time, and the measured surface temperature and the first Based on the elapsed time from the time 1 to the second time, the rate of temperature increase until the surface temperature of the steel material reaches 700 ° C. is predicted, and the rate of temperature increase of the surface temperature of the steel material is 15 ° C. The heating furnace may be controlled so as to be less than / min.

  Further, in the method for heating ferritic stainless steel, a temperature known object for correcting stray light in the heating furnace is installed in the vicinity of the luminance measuring unit, and in the surface temperature measurement of the steel material, the luminance measurement is performed. Using the unit, by measuring the radiant energy of the steel material and the temperature known object by a monochromatic luminance having a wavelength at which absorption and emission by the gas in the furnace do not occur, the measured monochromatic luminance is corrected to stray light, and the steel material The temperature may be determined.

  Further, in the heating method of the ferritic stainless steel, when obtaining the temperature of the steel material, based on the radiant energy of the temperature known object and the temperature of the temperature known object, a stray light amount is calculated, and the calculated The temperature of the steel material may be calculated based on the amount of stray light and the radiant energy of the steel material.

  Further, in the heating method for ferritic stainless steel, the luminance measuring unit is an imaging device that captures a monochromatic luminance distribution of radiant energy of the steel material and the temperature known object as an image of a predetermined number of pixels, and the temperature known The object may be arranged at a position where an area occupying the image captured by the imaging apparatus is 25 pixels or more.

  In the method for heating ferritic stainless steel, the temperature-known object may be arranged at a position where an area occupying an image captured by the imaging device is 100 pixels or more.

  Moreover, in the heating method of the ferritic stainless steel, the emissivity of the known temperature object may be within a range of 0.1 before and after the emissivity of the steel material.

  Further, in the method for heating ferritic stainless steel, the luminance measurement unit is used to further measure the radiant energy of the furnace inner wall of the heating furnace, and record the difference in radiant energy between the furnace inner wall and the temperature known object. Then, based on the recorded difference in the radiant energy, it may be determined whether the emissivity of the temperature-known object has changed over time.

  Further, in the heating method of the ferritic stainless steel, if a change with time of the emissivity of the known temperature object occurs, calculate the emissivity after change with time, and use the emissivity after change with time, Stray light correction may be performed.

In the method for heating ferritic stainless steel, the temperature known object may be disposed at a position that satisfies at least one of the following conditions (A), (B), and (C).
(A) A position where the stray light distribution in the furnace is substantially the same as the position of the steel material, and a position separated from the furnace wall by a distance where the stray light amount is substantially the same. (C) Position where no flame is sandwiched between the steel materials

  As described above, according to the present invention, it is possible to heat the ferritic stainless steel while further reducing the probability of occurrence of setting cracks.

It is explanatory drawing for demonstrating the structure of the heating control apparatus and heating furnace which concern on the 1st Embodiment of this invention. It is explanatory drawing for demonstrating the structure of the heating control apparatus and heating furnace which concern on the same embodiment. It is explanatory drawing for demonstrating the heating method of the ferritic stainless steel which concerns on the same embodiment. It is explanatory drawing for demonstrating the Example of the heating method of the ferritic stainless steel which concerns on this invention. It is explanatory drawing for demonstrating the Example of the heating method of the ferritic stainless steel which concerns on this invention. It is explanatory drawing for demonstrating the Example of the heating method of the ferritic stainless steel which concerns on this invention. It is explanatory drawing explaining the characteristic 2 which the temperature measuring method which concerns on the embodiment has. It is explanatory drawing explaining the characteristic 3 which the temperature measuring method which concerns on the embodiment has. It is explanatory drawing explaining the characteristic 3 which the temperature measuring method which concerns on the embodiment has. It is explanatory drawing explaining the characteristic 4 which the temperature measuring method which concerns on the embodiment has. It is explanatory drawing explaining the condition 1 of the characteristic 5 which the temperature measuring method which concerns on the embodiment has. It is explanatory drawing explaining the condition 2 of the characteristic 5 which the temperature measuring method which concerns on the embodiment has. It is explanatory drawing explaining the characteristic 5 which the temperature measurement method which concerns on the embodiment has. It is explanatory drawing explaining the Example of the temperature measurement method which concerns on the embodiment. It is explanatory drawing explaining the Example of the temperature measurement method which concerns on the embodiment. It is explanatory drawing for demonstrating the temperature measuring method which concerns on related technology. It is explanatory drawing for demonstrating the temperature measuring method which concerns on related technology.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  In the following, in order to facilitate understanding of each embodiment of the present invention, first, the outline of each embodiment of the present invention will be described, and then the method for heating ferritic stainless steel of each embodiment of the present invention Will be described. After that, examples of effects according to the embodiments of the present invention will be described together with examples.

  Moreover, the heating furnace used with the heating method of the ferritic stainless steel of each embodiment of this invention has the temperature measuring apparatus which can measure the surface temperature of the steel material of the ferritic stainless steel which is a to-be-heated material. As long as this temperature measuring device can measure the surface temperature of the steel material, it is possible to use various devices, but in each embodiment of the present invention, in particular, in order to enhance the effect, A temperature measuring method and apparatus capable of accurately measuring the surface temperature of a steel material are used. By using this temperature measuring method and apparatus, the effect of each embodiment can be remarkably enhanced. Therefore, after explaining the above contents, the temperature measuring device will be described in detail.

That is, the following will be described in the following order so that each embodiment of the present invention can be easily understood.
1. 1. Outline of first embodiment 2. Details of heating method of ferritic stainless steel according to the first embodiment About Example 4. Temperature measuring method and apparatus used in the first embodiment

  In the following, for convenience of explanation, a “continuous steel heating furnace” will be described as an example of the heating furnace. However, the heating furnace controlled by the present invention is not limited to the continuous steel heating furnace. That is, it goes without saying that the heating furnace may be various ones usually used for heating steel materials.

(1. Overview of the first embodiment)
1A and 1B are explanatory diagrams for explaining the configuration of a heating control device and a heating furnace according to a first embodiment of the present invention. Here, FIG. 1B has shown sectional drawing which cut | disconnected the heating furnace 1 in FIG. 1A by the AA line. In addition, as shown to FIG. 1A, each structure of the heating furnace 1 does not necessarily exist on the same plane (for example, the burner 2 and the temperature measurement apparatus 100). However, in FIG. 1B, for convenience of explanation, each main component is shown on the same sectional view. As above-mentioned, below, the case where the heating control apparatus which concerns on each embodiment of this invention is applied to the continuous steel material heating furnace is mentioned as an example, and is demonstrated. First, the heating furnace will be described.

<1-1. Heating furnace>
As shown in FIG. 1A, the heating furnace 1 heats the steel material F while conveying the steel material F, which is an example of a ferritic steel material, in the furnace length direction (also referred to as an x-axis direction or a conveyance direction). That is, the steel material F shown in FIG. 1A has one side of the heating furnace 1 (charging side, negative on the x axis) so that the furnace width direction (also referred to as y-axis direction) is the longitudinal direction as shown in FIG. 1B. It is also referred to as the direction side.) It is charged from the charging inlet IN provided in the furnace wall at the end. And the steel material F is extracted from the extraction port OUT provided in the furnace wall of the other side (extraction side, x-axis positive direction side) end part of the heating furnace 1 with a conveying apparatus.

  In addition, although it does not specifically limit as a conveying apparatus, In the heating furnace 1 which concerns on this embodiment, the example using a walking beam is shown. As shown in FIG. 1A, the walking beam type conveying apparatus is configured such that a skid beam 3 having the same length as the furnace length direction is supported by a plurality of skid posts 4, and a steel material F is placed on the skid beam 3. Is placed. The combination of the skid beam 3 and the skid post 4 is also called a skid. As shown in FIG. 1B, a plurality of skids are arranged in the furnace width direction.

  This skid is classified into a fixed skid and a movable skid, and the fixed skid and the movable skid are alternately arranged as shown in FIG. 1B. The movable skid moves back and forth in the furnace length direction (x-axis direction) while moving up and down in the furnace height direction (also referred to as the z-axis direction). As a result, the steel material F is transported forward while the movable skid moves forward from the state supported by the skid beam 3 of the movable skid. Thereafter, when the movable skid moves downward, the steel material F is now supported by the fixed skid. Then, after the movable skid moves forward, the movable skid moves backward and then rises to support the steel material F again. By repeating the operation of the movable skid, the steel material F is sequentially conveyed in the furnace length direction.

  In the heating furnace 1, a plurality of burners 2 (or burners 2 ′) are arranged, and the burners 2 are cooked. Accordingly, the steel material F is heated by the frame (flame) ejected from the burner 2 while being transported to the transport device, that is, in the furnace. In the heating furnace 1 shown in FIG. 1A and FIG. 1B, a frame is formed in the furnace width direction while forming a pair so as to be opposed to both furnace walls in the furnace width direction as shown in FIG. A “side burner” is used to form However, the arrangement position of the burner 2 is not particularly limited, and may be a so-called “axial burner” that is arranged on the furnace ceiling or the hearth and forms a frame in the conveying direction. The type of the burner 2 is not particularly limited, and various burners such as a gas fuel burner, a liquid fuel burner, and a regenerative burner can be used.

  In the heating furnace 1, the heating state of the steel material F is controlled mainly by adjusting the conveying speed of the steel material F by the conveying device, the combustion amount of each burner 2, and the like by a control device (not shown).

The heating furnace 1 according to the first embodiment of the present invention has been described above.
Next, the configuration of the heating control apparatus 10 according to the first embodiment of the present invention will be described with reference to FIGS. 1A and 1B.

<1-2. Configuration of Heating Control Device>
As shown in FIGS. 1A and 1B, the heating control device 10 includes a temperature measuring device 100, a storage unit 142, a position determination unit 11, a management point temperature specifying unit 12, a management point temperature storage unit 13, and a rising point. A temperature speed calculation unit 14, a determination unit 15, a heating furnace control unit 23, and an ambient temperature measurement device 200 are included.

  The temperature measuring devices 100 are respectively disposed at a plurality of locations along the conveying direction of the steel material F, that is, the furnace length direction. And the temperature measuring apparatus 100 measures the temperature distribution of the surface of the steel material F which passes the arrange | positioned location.

  In FIG. 1A, the case where the temperature measuring apparatus 100 is arrange | positioned at each of four places along a conveyance direction is illustrated. Here, in order to distinguish each temperature measuring device 100, the temperature measuring device 100 arrange | positioned at each location is also called temperature measuring device 100A-100D, respectively. And when it says the temperature measuring apparatus 100, arbitrary temperature measuring apparatuses 100A-100D shall be shown.

  The number of the temperature measuring devices 100 arranged is not particularly limited, but at least two are arranged. And the arrangement position of the temperature measuring apparatus 100 will not be specifically limited if it arranges along the conveyance direction.

  The temperature measuring device 100 is preferably a temperature measuring device that performs radiation temperature measurement, for example. However, as described above, the temperature measuring device 100 is not particularly limited as long as the temperature distribution on the surface of the steel material F can be measured. However, the temperature measuring apparatus 100 used in the present embodiment, which will be described in detail later, can accurately measure the temperature distribution on the surface of the steel material F. Therefore, it is desirable to use the temperature measuring apparatus 100 described later in detail. 1A and 1B show an example in which a temperature measuring device 100 described later in detail is used. Therefore, the temperature measuring apparatus 100 mainly performs radiation temperature measurement. Therefore, the imaging device 110 of the temperature measuring device 100, the temperature known object 120, and the like are arranged at a position where the radiation light from the steel material F can be imaged.

  The temperature measuring device 100 is controlled by the heating control device 10 and measures the temperature distribution of the steel material F at a predetermined timing. That is, when the steel material F enters the temperature measurement region Ar, the temperature measurement device 100 images the radiance of the steel material F and images the surface temperature distribution. Therefore, it is desirable that the heating control device 10 itself always keeps track of which position the steel material F is being conveyed. Further, the temperature measuring devices 100A to 100D are controlled so as to sequentially measure at least the same steel material F. That is, when one steel material F with a temperature measuring device 100A is imaged, the temperature measuring devices 100B to 100D measure the temperature of the steel material F when the steel material F passes through each arrangement location (temperature measurement region Ar). I do. As a result, a certain steel material F is measured at each location by all or two or more temperature measuring devices 100. The steel material F to be temperature-measured may be all the steel materials F that are transported and heated, but may be one or more steel materials F selected by the heating control device 10.

  Further, the temperature measurement result is recorded in the storage unit 142 by each temperature measurement device 100. At this time, it is preferable that the temperature measurement results for a certain steel material F are collectively recorded in the storage unit 142. That is, the temperature measurement results obtained by the temperature measuring devices 100A to 100D are associated with each other or are all associated with one steel material F that is a temperature measurement object. As a result, a plurality of temperature measurement results for one steel material F and a plurality of temperature measurement results for another steel material F are distinguished from each other. In addition, since this heating control apparatus 10 can control the heating degree for every steel material F, below, operation | movement, a process, etc. with respect to one steel material F are demonstrated, and the same with respect to the other steel materials F is demonstrated. A description of the operation and processing will be omitted as appropriate.

  The position determining unit 11 is based on the distribution of the surface temperature of the steel material F measured by a certain temperature measuring device (for example, the temperature measuring device disposed in the heating furnace 1 at the position closest to the charging inlet IN). The part with the highest temperature in the predetermined region is determined and set as a temperature management point which is a part used for temperature management of the steel material F. The temperature management point is an example of a temperature specifying position for specifying the surface temperature of the steel material F based on the temperature distribution of the surface temperature of the steel material F measured by the temperature measuring device 100.

  This temperature management point may be determined based on, for example, an operation record or the like, but may be obtained from actual measurement by the temperature measurement device 100A. A temperature management point will be described for each of these determination methods.

First, the determination method based on the operation performance etc. in the heating furnace 1 is demonstrated.
It is rare that a steel material F that has been charged in the heating furnace 1 and has not been heated until now becomes a heating target. Therefore, in this case, the position determination unit 11 determines the temperature management point based on the past operation results. The operation results include, for example, product quality results such as a state before heating, a state during heating, a state after heating, and a state after subsequent processing for the steel material F that has been heated in the past. For example, when there is a track record in which the quality of the steel material F has deteriorated after heating or after a subsequent rolling step, the surface temperature of the steel material F is highest at least before, during or after heating. This maximum temperature position is recorded in advance as an operation result. According to the heating control device 10 according to the present embodiment, this position is specified based on the temperature distribution measurement result because the temperature measurement device 100 can measure the temperature distribution of the steel material F. Can do. And the position determination part 11 sets this highest temperature position to the position which should manage temperature in order to maintain quality favorable. Since the data about such a maximum temperature position varies depending on the steel type, size, and the like of the steel material F, the position determination unit 11 stores the maximum temperature position in advance as a database in advance for each steel type, size, etc. of the steel material F. . This database may be included in the position determination unit 11 itself, or may be recorded in another storage device (for example, the storage unit 142). And the position determination part 11 acquires characteristic information like identification information, a steel type, size, etc. about the steel material F which is a heating control object from the higher-order control apparatus which controls the heating furnace 1, for example. Then, the position determination part 11 specifies steel material F from a database based on characteristic information, and determines the highest temperature position matched with the steel material F to the said temperature control point.

Next, a determination method based on actual measurement by the temperature measurement apparatus 100A will be described.
The temperature measuring device 100 </ b> A is disposed relatively to the charging side of the heating furnace 1 among the plurality of temperature measuring devices 100 provided in the heating furnace 1, that is, the place closest to the charging port IN. The temperature measuring device 100A measures the surface temperature distribution of the steel material F that has passed below the temperature measuring device 100A. Although depending on the heating performance by the heating furnace 1, the highest temperature position on the surface of the steel material F is expected to be relatively high during heating by the heating furnace 1 as compared with other positions. As a result, the temperature is expected to be higher than other reference positions. Then, the position determination part 11 determines the highest temperature position in the surface of the steel material F as a temperature control point based on the temperature distribution which the temperature measurement apparatus 100A measured. The maximum temperature position means a position where the temperature of the steel material F measured by the temperature measuring device 100A is the highest temperature, and is the highest compared to all other positions during or after heating. It does not have to be temperature. As described above, this maximum temperature position is a position that is expected to be higher than other reference positions as a result of being relatively higher than other positions or higher than a desired temperature. Means.

  However, when performing position determination based on this actual measurement, an abnormal temperature position is generated in the surface temperature distribution measured by the temperature measuring device 100A, which is not suitable for determination as a reference point because the temperature is locally high or low due to some abnormality. It is also possible to do. In this case, in order to prevent the position determination unit 11 from selecting such an abnormal temperature position as a temperature management point, the area of the position where the temperature is the highest based on the surface temperature distribution measured by the temperature measurement device 100A. (It may be the number of pixels). Then, when the area is less than the predetermined threshold, the position determination unit 11 confirms whether or not the area is equal to or higher than the threshold at the next highest temperature position. As a result, the position determining unit 11 can determine the highest temperature position where the area is equal to or greater than the threshold value as the highest temperature position. The abnormal temperature position has a smaller area than the surface area of other normal steel materials F, and the area varies depending on the specifications of the heating furnace 1, the characteristics of the steel materials F, the heating state, and the like. Therefore, it is desirable to previously obtain a threshold value (for example, the maximum area) for the area of the abnormal temperature position based on actual measurement.

  In determining the temperature control point, it is possible to appropriately set whether the temperature management point is based on the actual operation value or the actual measurement value. For example, when the operation result for the steel material F is in the database, the temperature control point is determined based on the operation result, and when the operation result is not in the database, it can be determined based on the actual measurement value. . Or, for example, the determination based on the operation results only when the credibility that it is preferable to maintain the product quality is determined based on the operation results, etc., based on the past operation results, control results, etc. It is also possible to perform. The same applies to the case of actual measurement values. However, when the temperature management point is determined based on the actual measurement value, that is, the measurement result by the temperature measuring device 100A, it is not necessary to prepare a database in advance, and since it is actually determined at the highest temperature position, it is easier and easier. A reliable position can be determined.

  The management point temperature specifying unit 12 specifies the surface temperature of the steel material F at the temperature management point based on the measurement results of the temperature measuring devices 100A to 100D with the temperature management point determined by the position determination unit 11 as a reference. That is, the management point temperature specifying unit 12 determines the temperature management point in the measurement results of the temperature measuring devices 100A to 100D acquired from the storage unit 142 based on the information on the position of the temperature management point transmitted from the position determination unit 11. Each position is specified, and the temperature at the specified position is obtained from the corresponding measurement result. Moreover, when the management point temperature specific | specification part 12 specifies the position of the temperature management point in the measurement result of each temperature measuring apparatus 100A-100D, the information showing the position of the steel material F in the heating furnace 1 acquired separately, Can be used together.

Here, before the surface temperature at the temperature management point of the steel material F specified as described above reaches 700 ° C., the management point temperature specifying unit 12 is at the temperature management point of the steel material F being heated in the heating furnace 1. It is preferable to control the temperature control device 100 so that the surface temperature can be specified at a certain arbitrary time t ₁ and at least two times t ₂ after a predetermined time has elapsed from the time t ₁ . Specifically, the management point temperature specifying unit 12 to the temperature measuring device 100, is preferably controlled so as to measure the temperature distribution on the surface of the steel F at least a time t ₁ and time t _2. In this case, the management point temperature specifying unit 12 also specifies the time t ₁ and the time t ₂ when the temperature measurement is performed by the temperature measuring device 100 in association with the surface temperature at the temperature management point of the steel material F.

The management point temperature specifying unit 12, the surface temperature of the steel material F at the temperature control point identified from each measurement result, and, the time at which the temperature measuring has been performed (e.g., time t ₁ and time t _2), The temperature measurement devices 100 </ b> A to 100 </ b> D where the measurement is performed and at least one of the positions in the conveyance direction (installation location of the temperature measurement device 100) and the steel material F are associated and recorded in the management point temperature storage unit 13.

The temperature increase rate calculation unit 14 includes the surface temperature of the steel material F at the temperature control point specified by the control point temperature specifying unit 12 and any two different times when the measurement of the surface temperature is performed (for example, time t _1). and the time _{t 2)} elapsed time between (e.g., elapsed time _(t 2 _-t 1)) and on the basis to calculate the heating rate of the steel F. Furthermore, the temperature increase rate calculation unit 14 increases the temperature increase until the surface temperature of the steel material F reaches 700 ° C. from the calculated temperature increase rate (for example, the temperature increase rate from time t ₁ to time t ₂ ). The speed (temperature increase rate in the range where the surface temperature of the steel material F is 150 ° C. to 700 ° C. (preferably 200 ° C. to 700 ° C.)) is predicted, and the predicted temperature increase rate is output to the determination unit 15. .

  The determination unit 15 determines whether or not the predicted value of the temperature increase rate input from the temperature increase rate calculation unit 14 is 15.5 ° C./min or less (preferably 15 ° C./min) or less. Is output to the heating furnace controller 23.

  In the heating furnace control unit 23, the determination result output from the determination unit 15, that is, the predicted value of the temperature increase rate input from the temperature increase rate calculation unit 14 is 15.5 ° C./min or less, or 15. The heating state of the heating furnace 1 is controlled based on whether the temperature is over 5 ° C./min. More specifically, when the predicted value of the heating rate input from the heating rate calculation unit 14 exceeds 15.5 ° C./min, the heating furnace control unit 23 increases the heating rate on the surface of the steel material F. The heating state of the heating furnace is controlled so as to be 15 ° C./min or less.

  As described above, various methods can be used as the heating state control method for adjusting the temperature rising rate of the surface of the steel material F, and in particular, “furnace temperature adjustment by the burner 2” and “adjustment of the conveyance speed”. It is preferable to control at least one of "." Which of the two heating adjustments is performed is preferably determined by the heating furnace control unit 23 based on the temperature distribution of the steel material F, the energy efficiency, the heating time limit, and the like. In order to perform this heating adjustment, the heating furnace controller 23 further includes a furnace temperature controller 231 and a conveyance speed controller 232 as shown in FIG. 1A. Each heating adjustment method and characteristic examples will be described in each configuration, and these configurations will be described below.

  The furnace temperature control unit 231 controls the furnace temperature of the heating furnace 1 based on the determination result transmitted from the determination unit 15. More specifically, the furnace temperature control unit 231 determines how much the atmospheric temperature needs to be adjusted based on the furnace atmosphere temperature and the temperature increase rate calculated by the temperature increase rate calculation unit 14. In order to adjust the ambient temperature by the determined amount, the fuel flow rates of the burner 2 and the burner 2 ′ (hereinafter sometimes simply referred to as “burner 2”) are adjusted. When adjusting the fuel flow rate of the burner 2, refer to the furnace atmosphere temperature measured by the atmosphere temperature measuring device 200 arranged at a predetermined position of the heating furnace 1 (for example, a plurality arranged in the conveying direction). May be. Thereby, the furnace atmosphere temperature can be changed for each predetermined region in the heating furnace 1, and the furnace temperature can be controlled more precisely. It is desirable that the adjustment amount of the fuel flow rate of each burner 2 is determined in advance corresponding to the average heating temperature and temperature distribution based on the operation results, adjustment results, experimental results, and the like.

  When heating adjustment by the furnace temperature control unit 231 is performed, it is possible to control the heating of the ferritic stainless steel material without reducing productivity because the conveyance speed is not reduced compared to other heating adjustments. is there. Note that, from the standpoint of preventing a decrease in productivity and the like, a lower limit value of the temperature increase rate of the steel material F is provided, and when the temperature increase rate is lower than the lower limit value, the furnace temperature control unit 231 increases the ambient temperature. Thus, the burner 2 will be controlled.

  The conveyance speed control unit 232 controls the conveyance speed of the steel material F by the conveyance device based on the determination result transmitted from the determination unit 15. That is, the conveyance speed control unit 232 adjusts the in-furnace time for each steel material F. It is desirable that the adjustment amount of the conveyance speed is determined in advance corresponding to the average heating temperature and the temperature distribution based on the operation results, the adjustment results, the experimental results, and the like.

  In addition, when controlling both a furnace temperature and a conveyance speed, the furnace temperature control part 231 and the conveyance speed control part 232 cooperate with each other, and the temperature increase rate of the surface of the steel material F is 15 degrees C / min or less. Thus, the heating furnace 1 is controlled.

  The configuration of the heating control apparatus 10 according to the first embodiment of the present invention has been described above. According to this heating control device 10, the maximum temperature position, which is the portion having the highest temperature, is detected as a temperature control point from the temperature distribution of the steel material F in the temperature measurement region Ar of each of the temperature measurement devices 100A to 100D. By paying attention to the temperature control point, it is possible to control the heating of the ferritic stainless steel material in the heating furnace.

  The method for heating a ferritic stainless steel material using such a temperature control point is based on the actual measurement values by the temperature measuring devices 100A to 100D, and is more accurate than the case of using the simulation or the atmospheric temperature of the heating furnace 1. In addition, it is possible to determine the heating state of the steel material F, and it is possible to avoid cracks.

  Moreover, in the position determination part 11 which determines the temperature management point used as a reference | standard, the determination based on the operation performance etc. or the determination based on actual measurement is performed as mentioned above. When determining the reference temperature management point, the position determination unit 11 according to the present embodiment determines the position having the highest temperature in the region whose area is equal to or greater than a predetermined threshold as the temperature management point. It is possible. Accordingly, it is possible to prevent a location where the temperature is locally high due to some abnormality from being determined as the reference point.

  In addition, as an example of the cause of such a locally high temperature, when the heating target is the steel material F, a blister scale is cited. The surface of the steel material F is heated and heated to raise the temperature, and is covered with an oxide scale generated by the oxidation. The surface temperature of the steel material F in the present embodiment usually indicates the temperature of the scale surface, but is not limited to the scale surface temperature. A part of this scale may swell locally due to a difference in thermal expansion from the ground iron, and may be lifted from the ground iron. This swollen state is called a blister. In the lifted state, the heat received by the scale from the surroundings is less likely to be taken away by the ground iron, resulting in a higher temperature than the scale surface in contact with the ground iron. Therefore, if the maximum temperature position is simply determined as the temperature control point, the blister scale may be selected as the reference point. However, such a blister scale has a smaller area than other scale surfaces. Therefore, by excluding abnormal temperature positions such as blister-like scales by a predetermined area (threshold), it is possible to prevent the accuracy of heating control of the ferritic stainless steel material from being lowered.

  In order to perform accurate heating control in this way, it is very important that each of the temperature measuring devices 100A to 100D can measure an accurate surface temperature distribution. Therefore, it is desirable to use the temperature measuring device 100 using the principle of radiation temperature measurement, which will be described in detail later, as this temperature measuring device 100. When this temperature measuring device 100 is used, the heating control of the ferritic stainless steel material is accurate. It is possible to further improve the property.

(2. Details of heating method for ferritic stainless steel)
Then, the heating method of the ferritic stainless steel which concerns on the 1st Embodiment of this invention is demonstrated in detail.

  In the method for heating ferritic stainless steel according to the present embodiment, before hot rolling the continuously cast ferritic stainless steel, the surface temperature of the steel is 150 ° C. or higher, preferably 200 ° C. or higher. The temperature increase rate of the surface temperature of the steel material is 15.5 ° C./min or less, preferably 15 ° C./min or less in the surface temperature range of 150 to 700 ° C., preferably 200 to 700 ° C. Thus, the ferritic stainless steel material is heated.

  Here, referring to FIG. 2, in the method for heating a ferritic stainless steel material according to the present embodiment, the charging temperature of the ferritic stainless steel material to the heating furnace is set to 150 ° C. or higher, and 150 to 700 ° C. by the heating furnace. The reason why the heating control is performed so that the rate of temperature rise of the surface temperature of the steel material is 15.5 ° C./min or less in the range of the surface temperature of will be described. FIG. 2 is an explanatory diagram for explaining a method for heating ferritic stainless steel according to the present embodiment.

  The present inventors conducted intensive research to avoid the occurrence of cracks during heating of the high-purity ferritic steel in the heating furnace.In the continuous casting machine, the temperature transition from completion of casting to charging of the heating furnace, The temperature history was investigated in detail. In addition, a steel material sample was cut out from an actual slab and subjected to a destructive test, and the easiness of destruction when a thermal shock was applied mainly at the time of temperature rise was investigated.

  As a result, when it is inserted into a heating furnace under a condition of less than 150 ° C., heat enters from the surface of the steel material and the surface starts to heat up first, and tensile thermal stress begins to be applied inside due to thermal expansion of the surface. It was found that even the slight thermal stress could not withstand the steel material and cracked inside. Therefore, when it is charged into the heating furnace under a condition of less than 150 ° C., a crack occurs in most cases. Therefore, after the continuous casting, it is necessary to keep the temperature of the steel material so that the temperature of the steel material does not fall below 150 ° C. during the time for cleaning the surface of the steel material and the waiting time until charging the heating furnace.

  In addition, for the steel materials having the components shown in Table 1 below, the present inventors investigated the charging temperature of the steel materials and the heating rate by the temperature survey at the initial stage of heating in the heating furnace, and found a causal relationship with the occurrence of cracking. investigated. The generated crack is a crack penetrating in the thickness direction in the range of about 2/3 to 3/4 of the center in the width direction of the steel material. Therefore, the occurrence of the crack can be visually confirmed. Therefore, also in this survey, the determination of the occurrence of cracks is made visually. In addition, the case where the occurrence of cracking can be visually confirmed is (1) the case where the heating of the steel material is completed and the steel material is extracted from the heating furnace, or (2) the surface generated inside the steel material. There are cases where cracks that did not appear in the steel can be visually confirmed by penetrating the surface when stress is applied during rolling. Check if it occurs, and if any of the cases are cracked, it is determined that the crack has occurred. Judged.

  The results of the survey conducted as described above are shown in FIG. The horizontal axis in FIG. 2 indicates the charging temperature (° C.) of the steel material into the heating furnace, and the vertical axis indicates the rate of temperature increase (° C./min) at the initial temperature increase in the steel material heating furnace. Also, the white circles in FIG. 2 indicate conditions under which no cracking occurred, and the black circles indicate conditions under which cracking has occurred. In FIG. 2, the temperature increase rate on the vertical axis indicates the temperature increase rate in the range of 700 ° C. or lower when the charging temperature is 700 ° C. or lower. The temperature increase rate in the range of temperature-charging temperature +100 degreeC is shown. That is, in FIG. 2, the definition of the rate of temperature rise differs between 700 ° C. and below and over 700 ° C.

  As shown in FIG. 2, similarly to the above-described destructive test result of the steel material sample, when the heating start temperature of the steel material, that is, the charging temperature to the heating furnace is lower than 150 ° C., the occurrence rate of cracking becomes extremely high. Further, when the temperature of the steel material is heated at a heating rate exceeding 15.5 ° C./min when the charging temperature to the heating furnace is 700 ° C. or less, the rate of increase in the surface temperature of the steel material is high, and the thermal expansion of the steel material surface increases. As a result of the increase, the tensile stress inside the steel material whose temperature rise is slow increases, and the tensile stress exceeds the proof stress of the steel material. In addition, when the charging temperature to the heating furnace is 200 ° C. or more, and when the charging temperature to the heating furnace is 700 ° C. or less and the rate of temperature rise of the steel material is 15 ° C./min or less, it is more reliable. It has also been found that cracks can be prevented from occurring.

  From the above results, before hot rolling the high-purity ferritic stainless steel material continuously cast, the surface temperature of the steel material is charged into a heating furnace at 150 ° C. or higher, and 150 to 700 ° C. by the heating furnace. In the range of the surface temperature, it was found that the occurrence of setting cracks can be avoided by heating the steel material so that the rate of temperature rise of the surface temperature of the steel material is 15.5 ° C./min or less. Moreover, before hot rolling the high-purity ferritic stainless steel material continuously cast, the surface temperature of the steel material is charged into a heating furnace at 200 ° C. or higher, and the surface temperature of 200 to 700 ° C. is measured by the heating furnace. It was also found that the occurrence of cracks can be avoided more reliably by heating the steel material so that the rate of temperature rise of the surface temperature of the steel material is 15 ° C./min or less in the above range.

  From the above knowledge, in the method for heating ferritic stainless steel according to the present embodiment, before hot rolling the continuously cast ferritic stainless steel material, the surface temperature of the steel material is 150 ° C or higher, preferably 200 ° C. The temperature of the steel material is increased to 15.5 ° C./min or less in the surface temperature range of 150 to 700 ° C., preferably 200 to 700 ° C. The ferritic stainless steel material was heated so as to be 15 ° C./min or less.

Further, in the method for heating ferritic stainless steel according to the present embodiment, a temperature specifying position (temperature control point) that is a position on the steel material for specifying the surface temperature of the steel material is determined in advance, and the surface temperature of the steel material is 700. Before reaching ° C., the surface temperature at the specific temperature position of the steel material being heated in the heating furnace is measured at a _first time t ₁ and a second time t ₂ after a predetermined time has elapsed from the first time. Based on the measured surface temperature and the elapsed time (t ₂ -t ₁ ) from time t ₁ to time t ₂ , the rate of temperature increase until the surface temperature of the steel material reaches 700 ° C. is predicted, and the steel material It is preferable to control the heating furnace so that the temperature rise rate of the surface temperature is 15.5 ° C./min or less, preferably 15 ° C./min or less.

  In this way, the steel surface temperature is measured at any two different times in the region where the surface temperature of the steel material is within 700 ° C. after the steel material is heated, and the temperature rise rate of the steel material surface is predicted based on the result. In addition, the conditions obtained from the above-mentioned findings that can prevent the occurrence of set cracks, that is, whether the temperature rise rate of the surface temperature of the steel material is 15.5 ° C./min or less, preferably 15 ° C./min or less are satisfied. If the condition that can avoid the occurrence of cracking is not satisfied, by adjusting the furnace temperature of the heating furnace to suppress the heating rate, stable cracking does not occur Quality ferritic stainless steel can be manufactured.

  In addition, when the steel material is continuously transported in the heating furnace and is operated under the condition that it does not stay in the heating furnace, the measurement time of the temperature at the temperature control point on the steel material surface is the temperature rise of the steel material. It is not always necessary for speed prediction. That is, in this case, the surface temperature of the steel material is measured at two predetermined locations, and the temperature is increased from the time required for the steel material to move the distance between the two measurement locations and the measured measurement temperature. The speed may be predicted.

(3. About Example)
As mentioned above, although the heating method of the ferritic stainless steel which concerns on the 1st Embodiment of this invention was demonstrated in detail, Then, referring to FIGS. 3-5, the heating of the ferritic stainless steel which concerns on this invention is demonstrated. An example of the method will be described in detail. 3-5 is explanatory drawing for demonstrating the Example of the heating method of the ferritic stainless steel which concerns on this invention.

  This example uses a heating furnace 1 as shown in FIG. 1A in which temperature measuring devices 100 are provided at four locations along the steel material conveyance direction (furnace length direction), and the ferrite system having the composition shown in Table 1 is used. It is the example which implemented the heating control of the stainless steel material F. FIG. The steel material F charged into the heating furnace 1 from the heating furnace charging inlet IN (the temperature of the steel material F at the time of charging is about 200 ° C.) is sequentially transferred from the burner 2 to the heating furnace extraction port OUT side by the skid. Heated by a flame.

  The steel F being heated in the heating furnace 1 is measured for temperature distribution on the surface of the steel F by a temperature measuring device 100 (100A to 100D) installed near the upper end on one side of the side wall on which the burner 2 is installed. The The temperature distribution data measured by the temperature measuring device 100 is transmitted to the heating control device 10 as described above.

  Using the temperature distribution result measured by the temperature measuring apparatus 100, the temperature at the temperature control point is detected by the procedure described below. The position of the surface of the steel material F to be a temperature control point is determined by the following method or the like based on the steel material temperature given to the crack and the thermal stress generated by the steel material temperature distribution, and is shown in FIG. 2 described above. Such a temperature is finally determined based on the relationship between the actual temperature and the crack occurrence state. In this example, the temperature control point was determined to be the center in the longitudinal direction of the steel material F and the center in the short side thickness direction from the relationship between the actual temperature and the crack occurrence state.

Here, the reason why the temperature management point is determined to be the center in the longitudinal direction of the steel material F and the center in the short side thickness direction will be described with reference to FIG. First, the reason why the central part in the longitudinal direction of the steel material F is selected is that the part is considered as a representative point that is not easily affected by heat input from both ends of the steel material F in the longitudinal direction. Moreover, if the steel from the short sides and long sides (upper and lower surfaces) of the steel material F is heated, the temperature rise of the steel edges F _e containing short side is the largest, therefore, also the largest thermal expansion due to heating. On the other hand, the central portion F _c in the width direction of the steel material F is hardly the most heating, cracking placed tensile stress acts is likely to occur in the central portion F _c of the width direction. Therefore, the center point in the thickness direction of the short side of the steel material F is determined as a point to be temperature-controlled (temperature management point) as a place where the temperature is likely to rise.

Next, while tracking the position of the steel material F conveyed to the steel material extraction side, the temperature distribution on the surface of the same steel material F is measured at each measurement position of the temperature measuring devices 100A, 100B, 100C, and 100D. Based on this, the temperature at the temperature control point of the steel material F is specified. For example, as shown in FIG. 4, first, the temperature distribution on the surface of the steel material F ₁ immediately after charging into the heating furnace 1 is measured by the temperature measuring device 100 </ b> A and transmitted to the heating control device 10. After that, when the steel material F is conveyed to the steel material extraction side by the skid, the temperature distribution on the surface of the steel material F ₁ (indicated by a broken line in FIG. 4) is measured by the temperature measuring device 100B and measured by the temperature measuring device 100A. Similar to the temperature distribution, it is transmitted to the heating control device 10. In this way, the temperature at the temperature control point of the steel material F is specified by the heating control device 10 from the measurement result of the temperature distribution of the surface of the steel material F at each measurement position of each temperature measuring device 100A, 100B, 100C, 100D. The

  In FIG. 5, the temperature transition in the temperature control point of the steel material F after charging to the heating furnace 1 measured as mentioned above is shown. The vertical axis in FIG. 5 indicates the surface temperature (° C.) at the temperature control point of the steel material F, and the horizontal axis in FIG. 5 indicates the elapsed time (minutes) from when the steel material F is inserted into the heating furnace 1. Yes.

  As shown in FIG. 5, in this example, the heating rate of the steel material F in the temperature range of 200 ° C. to 700 ° C. when the temperature reaches 700 ° C. predicted by the heating rate calculation unit 14 of the heating control device 10 is 15 ° C. / It was found from the determination result of the determination unit 15 (indicated by “□ plot” in FIG. 5) that there is a possibility of exceeding the minute. Therefore, in order to adjust the furnace temperature of the heating furnace 1 by the heating furnace control unit 23, the burner 2 located in the vicinity of the measurement position of the temperature distribution of the steel material F (in this embodiment, the arrangement position of the temperature measuring devices 100A and 100B). 'The combustion load was lowered. The results of the temperature transition at the temperature control point of the steel material F when the furnace temperature is adjusted in this way are shown by “● plot” in FIG.

  As is apparent from FIG. 5, by adjusting the furnace temperature of the heating furnace 1, the temperature increase rate in the region of 200 to 700 ° C. of the temperature at the management point of the steel material F becomes 15 ° C./min or less, thereby preventing the occurrence of cracking. I was able to.

  Thus, the surface temperature of the steel material F in the heating furnace 1 is measured in a region within 700 ° C. from the temperature at the time of charging (150 ° C. or more, preferably 200 ° C. or more), and the measurement result Based on the above, after predicting the heating rate of the surface of the steel material F, it is determined whether or not there is a possibility that a crack will occur in the steel material F, and if there is a possibility that a crack will occur, It was found that by adjusting the furnace temperature of the heating furnace 1 to suppress the rate of temperature increase, it is possible to manufacture a product with stable quality without causing cracks in the steel material F.

(4. Temperature measuring method and apparatus used in the first embodiment)
Next, a temperature measurement method used in the first embodiment of the present invention and an apparatus for carrying out the method will be described. In addition, as above-mentioned, in embodiment of this invention, various things can be used for the temperature measuring method and apparatus, if the temperature of the steel material surface is measured. However, the temperature measurement method and apparatus described below can measure the temperature very accurately compared to other temperature measurement methods and apparatuses. Since it becomes possible to accurately measure the surface temperature, the steel material heating method and the heating control device according to the embodiment of the present invention further enhance the effects as described above, and more accurately determine the ripe heat of the steel material. It becomes possible. Therefore, in the following, this temperature measuring method and apparatus will be described in detail with reference to FIGS.

  In the following, in order to facilitate understanding of how this temperature measurement method and apparatus can accurately measure temperature compared to other temperature measurement methods and apparatuses according to related technology, A related technique will be described, and then a temperature measurement method used in the embodiment of the present invention will be described. Then, after describing a temperature measuring device for realizing this method, examples of the temperature measuring method and device used in the embodiment will be described. Furthermore, an example of the effect of the temperature measurement method and apparatus used in this embodiment will be described in comparison with Patent Documents 4 to 6.

That is, below, the temperature measurement method and apparatus used in the present embodiment will be described in the following order 4-1. Related technology 4-2. Outline of temperature measurement method according to this embodiment 4-3. Example of temperature measuring apparatus according to this embodiment 4-4. Measurement example by temperature measuring apparatus according to this embodiment 4-5. Examples of effects of temperature measuring device according to this embodiment

<4-1. Related Technology>
The related art will be described with reference to FIGS. 15 and 16. 15 and 16 are explanatory diagrams for explaining a temperature measurement method according to the related art.

  When measuring the surface temperature of a steel material in a heating furnace in a non-contact manner, generally, a method of measuring thermal radiation energy from the object surface such as a radiation thermometer is used. However, in the heating furnace, there is radiant energy radiated from the inner wall of the furnace, a flame or the like. This radiant energy is reflected by the surface of the steel material and enters a sensor such as a radiation thermometer. Therefore, the radiation thermometer etc. displays the temperature corresponding to the sum of the thermal radiant energy radiated from the steel material and the reflected energy reflected from the surface of the steel material by the radiant energy radiated from the inner wall or flame, etc. A temperature error corresponding to the reflected energy occurs. This reflected energy is called by various names such as stray light, reflected light, external light, back light, stray light noise, etc., all of which are the same, and is hereinafter referred to as “stray light”.

  For example, in measurement under outdoor air conditions or room temperature conditions, the radiant energy emitted from the atmosphere or indoor walls is smaller than the radiant energy of a high-temperature steel material, so stray light errors do not become a problem. However, in a heating furnace having a high-temperature flame or a furnace wall, errors due to stray light are large, and therefore accurate temperature measurement is difficult.

  Therefore, a method for correcting the influence of stray light and obtaining a true object temperature has been developed. According to the method related to this related art, as shown in FIG. 15, first, a temperature known object 912 is placed in a heating furnace 911, and is calculated by the heat radiation theory from the known temperature of the object 912 by the calculation means 918. Based on the difference between the surface brightness and the measured value of the apparent brightness of the object 912, the amount of stray light in the heating furnace 911 is quantified. Further, the true radiant energy of the steel material is obtained by subtracting the amount of stray light in the heating furnace 911 from the apparent brightness of the steel material 913 measured by the optical surface temperature measuring means 914 such as a radiation type thermometer having a camera. To obtain the temperature. The temperature is displayed by the temperature display unit 919. As such a related technique, for example, Patent Document 5 is cited.

  In this method, an easily conceivable form is to place a known temperature object in the vicinity of the steel material and to compare the steel material with the known temperature object in order to reduce the stray light correction error.

However, such a form has the following problems.
Problem 1: When a steel material moves, it is difficult to place an object with a known temperature in the vicinity thereof.
Problem 2: If an object with a known temperature is placed near the steel, that is, away from the camera, the number of pixels of the object with a known temperature in the image is reduced.

The problem 1 will be described.
When the steel material moves, for example, in a walking beam type heating furnace or the like, there is a possibility that an object having a known temperature is damaged by the movement of the steel material. As a countermeasure, if a mechanism for moving the shielding plate according to the movement of the steel material is provided, the measurement system itself becomes complicated, which is not practical.

The problem 2 will be described.
For example, in order to arrange a steel material at a distant position or measure the temperature of a relatively small steel material, it is necessary to use an imaging device having a certain degree of resolution so that the steel material can be imaged. For example, when a 400,000-pixel camera is used as the imaging device, the viewing angle of one pixel is a small region having a width of 0.08 degrees and a height of about 0.08 degrees. When a temperature-known object is placed at a position away from the camera, the area of the temperature-known object that occupies the image becomes very small. Therefore, the output of one pixel is affected by spatial fluctuations, temporal fluctuations, signal processing system disturbances, etc. Will cause some variation.

  FIG. 16 shows an example of output variations in units of pixels. As shown in FIG. 16, there is a large variation in the output of one pixel unit, and there is a possibility that the measurement accuracy is lowered due to this variation. Therefore, in order to obtain high measurement accuracy, it is necessary to define an area instead of a single pixel and take the average value of the pixels in the area, and at least 5 × 5 pixels, preferably an average of 10 × 10 pixels or more Should be taken.

  However, considering a case where an object with a known temperature is placed in the vicinity of a steel material 6 meters away from the camera, for example, the width corresponding to a viewing angle of 0.08 degrees per pixel is about 10 millimeters. In order to take an average of 10 × 10 pixels, an area of 100 × 100 millimeters must be averaged.

  On the other hand, as the temperature known object 912, as shown in FIG. 15, it is practical to use a thermocouple thermometer 916 with a protective tube 917, which usually has a diameter of about 20 to 30 millimeters. As such, it is impractical to install a large temperature known object of 100 × 100 millimeters.

  As a result of earnest research on the conventional temperature measuring device and the temperature measuring device related to this related art, the present inventors have come up with the problems 1 and 2 as described above. In response to this problem, the inventors have further improved the effect of stray light by installing a temperature-known object, for example, a thermocouple with a protective tube, in the vicinity of the imaging device, not in the vicinity of the steel material, by means such as the following. Invented a temperature measurement method that can be corrected automatically, and found that the effect can be remarkably improved when used in the heating furnace according to the above embodiment.

<4-2. Overview of Temperature Measurement Method According to this Embodiment>
Hereinafter, an outline of the temperature measurement method according to the embodiment of the present invention will be described.
This temperature measuring method has the following features 1 to 3 roughly based on the temperature measuring method according to the related art described above.

Feature 1: When a temperature-known object for correcting stray light is installed in the vicinity of the imaging device and the radiation energy of the steel material is measured, a wavelength that does not cause absorption and emission by the gas in the furnace is selected, and its monochromatic color The luminance is measured, and the temperature obtained by correcting the obtained monochromatic luminance with stray light.
Feature 2: The temperature-known object is arranged at a position where the size is at least 25 pixels, preferably 100 pixels or more, in terms of the number of pixels of the imaging device.
Characteristic 3: The object whose temperature is known uses a material whose emissivity is in the range of 0.1 before and after the emissivity of the steel material.

  The temperature measurement method according to the present embodiment will be described while sequentially explaining these features.

[4-1-1. Feature 1]
Feature 1: When a temperature-known object for correcting stray light is installed in the vicinity of the imaging device and the radiation energy of the steel material is measured, a wavelength that does not cause absorption and emission by the gas in the furnace is selected, and its monochromatic color The luminance is measured, and the temperature obtained by correcting the obtained monochromatic luminance with stray light.

  In this feature 1, “the wavelength at which absorption and emission by the furnace gas do not occur” does not mean that absorption and emission do not occur completely, but a wavelength at which absorption and emission are less likely to occur compared to other wavelengths. means. Further, “monochromatic luminance” and “single wavelength” mean that they are not all wavelengths, and include, for example, luminance of a wavelength having a predetermined width depending on wavelength selection accuracy. The temperature measurement process by the feature 1 and the temperature measurement method according to the present embodiment will be described as follows.

  For example, if the object with known temperature and the steel are close to each other, the amount of stray light incident on both is almost equal, so the stray light obtained from the measurement result of the object with known temperature is also irradiated to the steel. What is necessary is just to correct | amend the radiant energy of the made steel material. However, when both are separated as in the present embodiment, the equality of stray light amounts is not necessarily guaranteed.

  Therefore, in the method of the present embodiment, the following means are roughly used in order to ensure the equality of the stray light amount between the temperature known object and the steel material.

Means 1: Select a wavelength at which absorption and emission by the gas in the furnace do not occur, and measure a single wavelength.
Mean 2: The stray light correction calculation formula is created by strictly applying the theory of radiant heat transfer in order to enable theoretical evaluation of errors due to temperature distribution in the furnace.

(Means 1)
Each means will be specifically described below.
In the combustion furnace, there are carbon dioxide and water vapor generated by the combustion of fuel. These gas bodies absorb the radiant energy in the furnace and radiate energy according to their temperature. Since the gas temperature varies depending on the position in the furnace, the amount of stray light in the furnace varies depending on the position. However, the energy absorbed and emitted by gases such as carbon dioxide and water vapor is limited to some specific wavelength ranges in the spectrum. Therefore, stray light correction that does not include the influence of the gas in the furnace is possible by measuring the wavelength that avoids both the absorption / radiation wavelength region of carbon dioxide and the absorption / radiation wavelength region of water vapor.

  Therefore, in the present embodiment, by measuring a wavelength satisfying the above conditions, for example, a single wavelength of 1 μm, it is possible to correct stray light under a condition in which the position of the temperature-known object and the steel material is separated. As in this embodiment, there is no precedent for an example in which the single wavelength condition is essential for the purpose of stray light correction.

(Means 2)
The calculation for correcting stray light in accordance with the use of a single wavelength uses the Plank equation for calculating radiant energy of a single wavelength, not the Stefan-Bolzmann equation used in general radiant heat transfer calculation. Specifically, the calculation is performed according to the following procedures 1 to 7.

  Procedure 1: In advance, an off-line blackbody standard furnace is used to create a relational expression between the output of the imaging device and the blackbody luminance.

  First, the temperature of the blackbody standard furnace is maintained at T [K]. The black body luminance E at the temperature T is calculated according to Planck's law (the following equation 101).

・・・（式１０１）

... (Formula 101)

Here, each constant of the above-mentioned formula 101 is as follows.
E: Black body luminance of wavelength λ [W / m ³ ]
λ: wavelength [m]
T: Temperature [K]
C1: Constant 3.74 × 10 ⁻¹⁶ [W / m ² ]
C2: Constant 0.014387 [μm · K]

  Next, the standard temperature point of the blackbody standard furnace is measured by the imaging device, and the output L of the imaging device is obtained. The same measurement is sequentially performed by changing the temperature T, and a relational expression between E and L is created by the least square method or the like. Here, the relational expression between E and L is represented by the following expression 102.

・・・（式１０２）

... (Formula 102)

  Since the relational expression represented by the expression 102 means a characteristic expression specific to each imaging apparatus, it is necessary to create it for each imaging apparatus when a new imaging apparatus is introduced. However, since this is a characteristic unique to the imaging apparatus, once this procedure 1 is performed, it is not necessary to perform it again thereafter. In the present embodiment, for example, a wavelength of 1 μm is used as the measurement wavelength λ, and an optical filter can be used to select this wavelength. However, the measurement wavelength λ may be other wavelengths, and the wavelength selection method may be, for example, using an imaging element that captures only a specific wavelength, or a specific wavelength included in the imaging device, in addition to the optical filter. It goes without saying that various methods can be used such as extracting the wavelength by image analysis.

Procedure 2: In an actual furnace, a black body luminance E ₁ is calculated from Planck's law from the temperature T ₁ [K] of a thermocouple with a known temperature, for example, a thermocouple with a protective tube, as shown in Equation 103 below.

・・・（式１０３）

... (Formula 103)

Step 3: The image pickup device measures the temperature known object, obtaining an output L _1. The above characteristic equation created off-line (wherein 102), calculates the luminance corresponding to the output L _1.

The luminance calculated in this procedure 3 is an apparent luminance including reflection of stray light, and corresponds to a quantity called emissivity in the field of radiant heat transfer. This is represented as _{G 1.} That is, the luminance G ₁ is expressed by the following formula 104.

・・・（式１０４）

... (Formula 104)

Procedure 4: The stray light amount J is calculated from E ₁ and G _{1 according} to the following equation 105.

・・・（式１０５）

... (Formula 105)

In this equation 105, ε ₁ is the emissivity of an object with a known temperature.
Here, the derivation process of Equation 105 will be described. The monochromatic radiation amount A radiated from the object surface at the temperature T is obtained by multiplying the black body luminance E calculated from Planck's law by the emissivity ε of the object surface. That is, the monochromatic radiation amount A is expressed by the following formula 106.

・・・（式１０６）

... (Formula 106)

  Further, the amount B of the in-furnace stray light (external irradiation) J reflected from the object surface is expressed by the following formula 107 from the radiant heat transfer theory.

・・・（式１０７）

... (Formula 107)

  The “apparent luminance” G measured by the imaging apparatus is the sum of A and B, and is expressed by the following formula 108.

・・・（式１０８）

... (Formula 108)

By transforming this formula, formula 109 for calculating the stray light amount J is obtained. Therefore, by substituting E ₁ , G ₁ and ε ₁ into this equation 109, the above equation 105 is derived.

・・・（式１０９）

... (Formula 109)

Step 5: The image pickup device measures the steel to obtain an output L _2. Then, the above characteristic equation (equation 102), calculates the luminance corresponding to the output _{L 2.} This luminance is an apparent luminance including reflection of stray light. This is represented as _{G 2.} That is, the luminance G ₂ is expressed by the following formula 110.

…（式１１０）

... (Formula 110)

The output L ₂ as measured by the imaging device here is expressed as a distribution to the surface of the steel material. That is, the output L ₂ for a given position in the captured image of the imaging apparatus corresponds to predetermined portions of the steel material which is captured in the captured image, output L ₂ takes a different value for each position in the captured image sell. Accordingly, the luminance G ₂ calculated from the output L ₂ is also a distribution with respect to the steel material. Incidentally, for convenience of explanation, the luminance G ₂ is, be described as the average luminance of the luminance or more points of one point in the luminance distribution. However, the subsequent calculation or the like for the luminance G _2, by performing each position corresponding to a steel material in the captured image, in this temperature measuring method, it is needless to say that can measure the temperature distribution.

Step 6: From the _{G 2} and the procedure stray light amount J calculated in item 4 (Formula 105), calculates the blackbody intensity _{E 2} of the steel by Equation 111 below.

・・・（式１１１）

... (Formula 111)

In the above formula 111, ε ₂ is the emissivity of the steel material.
Here, the derivation process of this equation will be described.
Using the following expression 112 (the above expression 108) derived in the above step 4 and modifying this expression to obtain the black body luminance E, the above expression 111 is obtained.

・・・（式１１２）

... (Formula 112)

Procedure 7: From this E ₂ , the temperature T ₂ [K] of the steel material is obtained using the inverse function (equation 113) of the following Planck's law.

・・・（式１１３）

... (Formula 113)

Here, in the above equation 113, the base of Log is a natural logarithm.
By using the stray light correction method (procedure 1 to procedure 7) described here, the temperature of the steel material can be obtained even when the temperature-known object and the steel material are separated. The reason will be described below.

  The radiant energy from the object of known temperature and the steel material is the sum of the amount of radiation from the object itself and the amount of reflection of stray light received from inside the furnace. As in the equation 108 derived in the above-mentioned procedure 4, the radiant energy of the temperature known object and the steel material is expressed by the following equations 114 and 115.

・・・（式１１４）

・・・（式１１５）

... (Formula 114)

... (Formula 115)

  Here, the subscript 1 represents a temperature known object, and the subscript 2 represents a steel material. The first term on the right side of each equation is the amount of radiation from the object itself, and the second term is the amount of reflection of stray light from the furnace on the object surface.

In the related art, correction is performed by adding or subtracting the difference ΔG (= G ₂ −G ₁ ) of the radiant energy, and the relationship between the apparent luminance G and the black body luminance E in the above two formulas 114 and 115. The brightness E is obtained by using the same, and the temperature of the steel material is obtained. Therefore, in the method of the related art, it is necessary that ε ₁ and ε _{2 in} the above two expressions are equal, and (1-ε ₁ ) J ₁ and (1-ε ₂ ) J ₂ are equal. That is, since it is a requirement that the emissivity of the object having the known temperature and the steel material are equal and the total of the stray light amount J over the measurement wavelength band is equal, it is necessary to place both in the vicinity where it is clear that the stray light is equal. It is.

On the other hand, in the temperature measurement method of the present embodiment, as shown in the description of the correction calculation procedure, the equality of both types is not a requirement. That is, since a single wavelength with a small difference in stray light amount is used in the furnace, the second term (1-ε ₁ ) J ₁ and (1-ε ₂ ) J _{2 in} the above equation do not have to be equal, and the emissivity Even if ε and stray light J differ depending on the position, the measurement error can be reduced.

In general, the material heated in the heating furnace has a high emissivity because the surface is oxidized in the case of a metal material, and the emissivity of the material itself is high in the case of a nonmetallic material. Usually, the emissivity of the object to be heated is a value exceeding 0.8. Therefore, (1-ε) is smaller than ε, and the second term (1-ε) J is smaller than the first term εE in the above equation. Therefore, even if there is little difference in the stray J ₂ of the stray light J ₁ and a steel position of the temperature known object position, is only a difference in the second term relatively value is small occurs, the influence of the expression of the calculation result Is small. In the present embodiment, the measurement wavelength λ is set to a wavelength with less absorption / radiation by the furnace gas. Therefore, it is possible to very small difference between the stray J ₂ of the stray light J ₁ and a steel position of the temperature known object position. Therefore, in this embodiment, it is possible to calculate as J ₁ = J ₂ without arranging the temperature known object and the steel material close to each other. Even if the difference between J ₁ and J ₂ is different by about 10%, there is no significant effect on the error. This is because if the emissivity is about 0.8 and the difference in J is about 0.2, the difference on the right side of the above equation is only about (1−0.8) × 10% = 2%. It is.

  For the above reasons, if the temperature measurement method of this embodiment that performs single wavelength measurement is used, even if a temperature known object is placed at a position where there is a slight difference in stray light, temperature measurement can be performed without greatly reducing accuracy. is there. That is, it is not necessary to place an object with a known temperature near the steel material.

[4-1-2. Feature 2]
Feature 2. The temperature-known object is arranged at a position where the size is at least 25 pixels, preferably 100 pixels or more, in terms of the number of pixels of the imaging device.

The feature 2 will be described as follows.
As shown in Problem 2 above, in the related technology, since the area occupied by one pixel of the imaging device is small, the output of one pixel is affected by, for example, spatial and temporal fluctuations, disturbance of the signal processing system, and the like. Some variation occurs. FIG. 6 shows an actual measurement value of an output of one pixel unit of a temperature known object.

  When the standard deviation of the actually measured values shown in FIG. 6 was calculated, σ = 11 ° C. Therefore, it is clear that if the stray light correction is performed using the measurement value of only one pixel, the error is large and it is not practical. Therefore, in the temperature measurement method of this embodiment, such a problem can be solved by taking an average value of a plurality of pixels and performing correction calculation using the average value.

Hereinafter, specific conditions will be described based on the considerations of the inventors who have derived this feature 2.
As described above, the standard deviation of one pixel unit was 11 ° C. Since the standard deviation when n average values are taken is inversely proportional to the square root of the number, if the average of 25 pixels is taken, the standard deviation is about 2 ° C., which is 1/5. If the average value of 100 pixels is taken, it is inversely proportional to the square root 10 of 100, so it is about 1/10 of 1/10.

  In the temperature measurement in the furnace, a standard deviation of 2 ° C. is almost practical, and 1 ° C. is sufficient. Therefore, it is necessary to place a temperature known object at a position where the number of pixels of at least 25 pixels (for example, 5 × 5 pixels), preferably 100 pixels (for example, 10 × 10 pixels) or more can be obtained.

  For example, it is appropriate to use a thermocouple with a protective tube as a known temperature object. Since the outer diameter of the thermocouple with a protective tube used in the heating furnace is about 20 to 30 mm, the measurement range is about 10 mm in the vertical and horizontal directions and about 10 mm in the circular shape.

  On the other hand, for example, in a commonly used CCD camera having about 400,000 pixels, the viewing angle of one pixel is about 0.08 degrees × 0.08 degrees. Therefore, the viewing angle when viewing 5 × 5 = 25 pixels is 0.4 ° × 0.4 °. Since tan 0.4 degree = 0.070, in order to capture a range of 10 mm × 10 mm at a viewing angle of 0.4 degree × 0.4 degree, it should be placed closer to the camera than 10 mm / 0.0070 = 1400 mm. I must.

  Although the calculation is performed for the case where the measured portion of the temperature-known object is 10 mm, if the same calculation is performed when the size is different, the position where the temperature-known object is to be placed is the size Y of the measured portion. On the other hand, it is desirable that the distance X from the imaging device satisfies the following expression 116.

・・・（式１１６）

... (Formula 116)

  Based on such considerations, the present inventors have derived Feature 2 described above. Therefore, in this embodiment, the temperature-known object has a position where the size is at least 25 pixels (for example, 5 × 5 pixels), preferably 100 pixels (for example, 10 × 10 pixels) or more in the number of pixels of the imaging device. Placed in. In other words, for a temperature known object, if the size of the measured part of the temperature known object is Y and the distance from the imaging device is X, X is set so as to satisfy Equation 116 above. More specifically, X is set to a value smaller than 1400 mm when a CCD camera having about 400,000 pixels is used as the imaging device and Y is 10 mm. As a result, in the temperature measurement method according to the present embodiment, the measurement error of the imaging apparatus can be reduced and the temperature measurement accuracy can be improved.

[4-1-3. Feature 3]
Feature 3. The material whose temperature is known uses a material whose emissivity is in the range of 0.1 before and after the emissivity of the steel material.

The feature 3 will be described as follows.
The inventors of the present invention theoretically examined the measurement results when the measurement conditions were variously changed, that is, the error in the temperature after stray light correction, with respect to the temperature measurement method of the present embodiment.

  The examination conditions are as follows. In a combustion furnace having a length of 12 m and a height of 2.5 m, the inner wall temperature is 1200 ° C., the temperature of the steel placed on the hearth is 900 ° C., and the emissivity of the steel is 0.86. Heat transfer calculation was performed, and the theoretical values of the amount of radiant heat transfer and the amount of reflected stray light on each surface under the conditions satisfying the above characteristics 1 and 2 were obtained. The calculation method is described by Yoshio Kato, “Introduction to Heat Transfer” (Yokendo) p. 377-p. The procedure shown in 382 was used.

  By applying the stray light correction calculation method described in the above feature 1 to the calculation result, the position of the temperature known object is set to the left wall position in the furnace in the furnace width direction as the origin 0 m point, and from the 0 m point to the right 12 m point The stray light correction value when changed every 2 m was calculated. The position of the imaging device was the left 0 m point, and the position of the steel material was the center in the furnace width direction, that is, the 6 m point. The calculation results are shown in FIG. The emissivity ε shown in FIG. 7 is the emissivity of an object whose temperature is known, and the emissivity of the steel material is fixed at 0.86.

  As shown in FIG. 7, according to this calculation result, for example, when the emissivity of the known temperature object is equal to the emissivity 0.86 of the steel material, the corrected temperature of the steel material is The difference is within 3 ° C. with respect to the true temperature of 900 ° C. of the steel material.

  However, when there is a difference in emissivity ε between the steel material and the temperature-known object, it can be seen that the temperature difference becomes large. In the range of emissivity ε = 0.86 of the steel material and emissivity of the object having a known temperature of 0.81 to 0.91, that is, around 0.05, it is ± 6 ° C. with respect to the true temperature 900 ° C. When the emissivity of an object having a known temperature is in the range of 0.76 to 0.96, that is, about 0.1 to about ± 13 ° C.

  If an error up to about 10 ° C. is allowed in consideration of practicality, the emissivity of an object with a known temperature varies slightly depending on the temperature and emissivity level, but a material that is within about 0.1 before and after the steel emissivity is selected. The measurement error should be further reduced if it is preferably within about 0.05 or so.

  On the other hand, in the related technology, a method of correcting stray light based on the luminance of an object whose temperature is known is adopted. In this related technique, the positional relationship between the steel material and the temperature-known object is not clearly shown, but in the drawings illustrated as examples, the temperature-known object is placed in the vicinity of the steel material, and both are placed in the vicinity as an embodiment. It is thought that this is assumed.

  According to the knowledge of the inventors, as described above, when there is a large difference between the temperature of the steel and the furnace inner wall, for example, the temperature of the steel is 900 ° C. and the temperature of the furnace inner wall is 1200 ° C., the vicinity of the furnace wall Then, it is strongly affected by stray light from the furnace wall. However, when the emissivity of an object whose temperature is known and the emissivity of a steel material are approximately the same, the effect becomes small. This is shown in FIG. FIG. 8 shows the calculation result when the emissivity ε of the known temperature object in FIG. 7 is 0.86, which is equal to that of the steel material, and the calculation result when the emissivity ε is 0.76 away from the value. That is, in FIG. 8, the ● plot is an example in the case where the emissivity of the steel material and the temperature known object is similar, and the x plot is an example in the case where the emissivity of the temperature known object is different from that of the steel material. Again, the steel was placed in the center of the furnace, i.e. 6 m.

  As shown in FIG. 8, when the emissivity is different, not only the temperature error increases, but also the difference between the vicinity of the furnace wall and the center increases. For this reason, in the related art, since there is no regulation of emissivity, although it is not clearly shown, it is considered that, as an embodiment, a temperature known object has to be placed in the vicinity of the steel material.

  However, in this embodiment, by regulating the emissivity of the temperature known object, as shown in the ● plot of FIG. 8, even if the temperature known object is placed at a position away from the steel material at the 6 m point, the error is small. Measurement is possible.

  The features 1 to 3 included in the temperature measurement method according to the embodiment of the present invention have been described above. The temperature measurement method according to this embodiment has the following features 4 and 5 in addition to the above features 1 to 3 in order to maintain and improve the measurement accuracy.

Feature 4: Dealing with time-dependent changes in emissivity Feature 5: Position of an object with a known temperature defined by the stray light quantity distribution in the furnace

  Next, features 4 and 5 will be described.

[4-1-4. Feature 4]
Feature 4: Dealing with changes in emissivity over time

The feature 4 will be described as follows.
When a thermocouple with a metal protective tube is used as a known temperature object, the emissivity of the known temperature object may change slightly due to the effect of oxidation due to long-term use or the like. Further, when a thermocouple with a ceramic protective tube is used, there is no fear of oxidation, but the possibility of emissivity change due to adhesion of soot and furnace dust cannot be excluded. Therefore, in the temperature measurement method according to the present embodiment, such a change with time of the emissivity of the known temperature object can be dealt with by the following means.

Means 1: Method for Grasping Change in Emissivity over Time Generally, in order to measure the emissivity on the surface of an object, it is necessary to measure the temperature and luminance of the object under conditions without stray light. Therefore, it is difficult to grasp the emissivity if the object is installed in the furnace. However, if the operating conditions of the furnace are constant, the stray light quantity distribution in the furnace does not vary, and the relationship between the radiance from the object whose temperature is known and the radiance from the inner wall of the furnace is considered to be constant. Using this phenomenon, the difference between the furnace inner wall brightness in the field of view of the imaging device and the temperature known object brightness is recorded over a long period of time, and the presence or absence of emissivity changes with time is grasped by managing the trend under the same temperature conditions. Can be managed. For example, it can be determined that the emissivity of the temperature known object has changed when the change in the difference between the furnace inner wall brightness and the temperature known object brightness exceeds a predetermined threshold. And when emissivity changes, in order to maintain temperature measurement precision, the countermeasure by the following means 2 can be taken.

Mean 2: How to cope with change in emissivity with time. The best means is to replace an object having a known temperature with a new one. When the exchange is impossible and the change value of the emissivity can be estimated from the trend management data of the means 1, the following method may be used for correction. That is, in the following equation 117 (the above equation 105) for calculating the stray light amount J derived by the means 2 of the above feature 1, the equation 118 using the emissivity ε _x after change with time instead of the standard emissivity ε. Thus, the amount of stray light J is calculated.

・・・（式１１７）

・・・（式１１８）

... (Formula 117)

... (Formula 118)

  After calculating the stray light amount J, the procedure 5 and subsequent items of the above feature 1 are calculated according to the above-described calculation procedure, and the temperature after the stray light correction is calculated. FIG. 9 shows an example in which correction calculation is performed for emissivity with time by this method. As shown in FIG. 9, when the emissivity of an object having a known temperature increases with time with respect to the reference emissivity of 0.86, the corrected temperature decreases. However, according to the temperature measurement method according to the present embodiment, an output with a correct temperature of 900 ° C. can be obtained by calculating using the above feature 4.

  That is, the temperature measurement method according to the present embodiment has the feature 4 to reduce the influence of the emissivity of the temperature known object over time, etc., and improve the temperature measurement accuracy even for long-term use. Can be maintained.

Emissivity after change over time ε _x
It should be noted that the emissivity ε _x after time change used here can be derived as follows.
As described above, the means 1 records the difference between the furnace inner wall luminance and the temperature known object luminance in the field of view of the imaging device over a long period of time. At this time, the difference between the brightness of the part of the furnace where the change in emissivity with time is considered to be relatively stable and hardly changed, for example, the brightness of the furnace wall that has not been repaired or repaired for a long time, and the known temperature of the object is also included. Record. Hereinafter, this site is also referred to as “comparison site”. When the furnace inner wall is a comparison part, the furnace inner wall brightness recorded by the means 1 can be set as the brightness of the comparison part.

Here, the apparent luminance of the comparison portion is Gw, and the temperature known object luminance is Gt. That is, a change in the difference ΔG (= Gt−Gw) between the comparison site luminance Gw and the temperature-known object luminance Gt is recorded for a long period. Note that the “apparent luminance G” measured by the imaging apparatus is expressed by the above formula 108, so that the initial temperature known object (Gt ₁ ), the initial comparison site (inner wall, etc.) (Gw ₁ ), and long-term elapsed The apparent luminances of the later known temperature object (Gt ₂ ) and the comparison part (Gw ₂ ) after a long period of time are as follows.

・・・（式Ａ１）

... (Formula A1)

In this formula A1, Et is the black body luminance of the temperature known object, Jt is the stray light amount of the temperature known object, ε _w , the emissivity of the comparison part, Ew is the black body luminance of the comparison part, and Jw is the comparison part. Is the amount of stray light. Here, since the comparison site is a site where the change in emissivity with time is relatively stable and considered almost unchanged, the emissivity of the comparison site becomes constant at ε _w before and after the elapse of the period. Further, by making the temperature at the time of measurement constant, the black body luminance Et of the known object does not change before and after the lapse of the period. Furthermore, since the in-furnace stray light condition is rarely changed, the stray light amount Jt of the known object and the stray light amount Jw of the comparison part do not change before and after the passage of the period.

From this equation A1, the initial luminance difference ΔG ₁ and the luminance difference ΔG ₂ after the elapse of the period are expressed by the following equations A2 and A3.

・・・（式Ａ２）

・・・（式Ａ３）

... (Formula A2)

... (Formula A3)

Therefore, the temporal change amount (ΔG ₂ −ΔG ₁ ) of the luminance difference ΔG can be calculated as in the following formula A4.

・・・（式Ａ４）

... (Formula A4)

From this formula A4, it can be seen that the amount of change in emissivity (ε _x −ε) of an object whose temperature is known is proportional to the amount of change in apparent luminance over time (ΔG ₂ −ΔG ₁ ).

Here, if the proportionality constant between (ε _x −ε) and (ΔG ₂ −ΔG ₁ ) is K (= Et−Jt), the proportionality constant K can be obtained as follows.

  Since Et is the black body luminance of an object whose temperature is known, it can be calculated from the known temperature value according to the above equation 103. On the other hand, Jt is the amount of stray light received by an object with a known temperature, and therefore can be calculated from the output L of the imaging apparatus using the above formulas 104 and 105. Therefore, the proportionality constant K (= Et−Jt) can be obtained by performing these measurements and calculations in advance. Further, the equation A4 can be calculated as the following equation A5.

・・・（式Ａ５）

... (Formula A5)

Therefore, by substituting the calculated proportionality constant K and the temporal change amount of the apparent luminance difference (ΔG ₂ −ΔG ₁ ) into the equation A5, the emissivity ε _x of the temperature known object after the temporal change is obtained. Can do. In addition, since the comparison calculation after a long period of time is performed under the in-furnace condition for which the proportional constant K is calculated, Et and Jt can be kept unchanged. It can be used until it is exchanged.

Note that the emissivity ε _x of the temperature-known object after the change with time needs to be calculated using data in which the conditions in the furnace (temperature and stray light amount) are equivalent. Therefore, of the long-term data measured and recorded, the known thermometer temperature and the temperature of the comparison site (furnace wall inner surface, etc.) are almost the same as the initial stage, and the furnace operating conditions (furnace stray light conditions) are It is desirable to extract a large number of data in time zones that are substantially the same, and calculate the emissivity ε _x using the average value. It is also possible to test the certainty of the results by statistical methods based on the variance of the data.

[4-1-5. Feature 5]
Feature 5: Position of an object with a known temperature defined by the stray light quantity distribution in the furnace

The feature 5 will be described as follows.
As described above, in this embodiment, the object whose temperature is known does not need to be arranged in the vicinity of the steel material by using a wavelength that does not cause reflection / absorption by the furnace gas or the like. The stray light inside has a distribution according to the position. Therefore, in the temperature measurement method according to the present embodiment, the temperature known object is placed at a position where the stray light amount is equivalent to the stray light amount at the steel material position in order to further improve the measurement accuracy. The restriction of the position of the temperature known object due to the stray light distribution or the like is defined by the following three conditions.

Condition 1: Position where the stray light amount is substantially the same as the position of the steel material in the distribution of stray light in the furnace Condition 2: A position where the angle with respect to the measurement surface of the steel material is not less than an angle at which the emissivity of the steel material does not change Condition 3: With the steel material Position where no flame is sandwiched between

  Each condition will be described below.

Condition 1: A position where the stray light distribution is almost the same as the position of the steel material in the furnace stray light distribution. If there is a temperature distribution on the inner wall of the furnace, the vicinity of the inner wall of the furnace is strongly affected by the temperature of the nearby inner wall of the furnace. The amount of light may be different from the general part in the furnace. FIG. 10 shows the result of calculating the stray light amount based on the data of the inventors when some of the furnace wall temperatures are different. This is the stray light distribution when a part of the inner walls of the furnace is 1100 ° C. in a furnace maintained at a furnace inner wall temperature of 1200 ° C. The horizontal axis in FIG. 10 is the distance from the furnace wall at 1100 ° C. The amount of stray light in an area less than 0.25 m from the furnace inner wall is significantly different from the amount of stray light at other positions. Therefore, in the temperature measurement method according to the present embodiment, the influence of the stray light distribution in the furnace due to the temperature distribution of the furnace inner wall is reduced by arranging the temperature known object at a position separated by 0.25 m or more from the furnace inner wall, Measurement accuracy can be further improved.

Condition 2: The position where the angle of the steel material with respect to the measurement surface is equal to or greater than the angle at which the emissivity of the steel material does not change. Generally, depending on the substance, the surface emissivity may vary depending on the radiation direction. This is illustrated, for example, in Figure 2.81 of the Chemical Engineering Handbook 3rd edition. On the other hand, in the temperature measurement method according to this embodiment, a temperature-known object and a steel material are placed in the same field of view of the imaging device, and correction calculation is performed by comparing the brightness. Therefore, in order to prevent the emissivity of the steel material from changing with respect to the emissivity of the object with known temperature, place the object with known temperature at the position where the angle with respect to the measurement surface of the steel material is an angle within the range where the emissivity does not change. Must be within the field of view of the imaging device.

  The inventors who have come up with such a problem use steel materials (steel materials), place temperature-known objects at various angles, measure the temperature of the steel materials by the method described above, and determine the angle from the size of the error. Judged the limit of. As a result, as shown in FIG. 11, it was concluded that this angle should be 13 degrees or more.

  Therefore, in the temperature measurement method according to the present embodiment, the influence on the temperature measurement due to the change in the emissivity of the steel material is reduced by arranging the temperature known object at a position where the angle with respect to the measurement surface of the steel material exceeds 13 degrees. Thus, the temperature measurement accuracy can be further improved.

Condition 3: Position where no flame is sandwiched between steel materials In this embodiment, since monochromatic light, for example, radiation having a wavelength of 1 μm, which avoids the radiation spectrum of carbon dioxide and water vapor, which are thermal radiation gases in the combustion gas, is measured, Compared with wavelength radiation measurement type thermometers, it is less susceptible to flames. However, since the flame contains free radicals or the like that are thermally radioactive, stray light correction errors may occur if a flame is interposed between the flame and the steel material. Therefore, in the temperature measurement method according to the present embodiment, the influence of the flame is reduced by maintaining a positional relationship in which the flame is not sandwiched between the steel material, the temperature known object, and the imaging device. This positional relationship is defined by the positional relationship between the steel material of the furnace to which the present technology is applied and the flame. Specifically, as shown in FIG. 12, the horizontal distance from the measurement point (steel) to the flame end is X ₁ , the height from the measurement point to the flame bottom is Y ₁ , and the temperature is known from the measurement point. When the horizontal distance to the object is X ₀ and the height is Y ₀ , the position of the temperature known object is set so as to satisfy the following equation 119.

・・・（式１１９）

... (Formula 119)

  As described above, the position of the temperature known object, which is defined by the stray light distribution in the furnace, by combining the conditions 1 to 3, is shown as follows.

In other words, this position is
Condition 1: The distance from the inner wall of the furnace is 0.25 m or more,
Condition 2: The angle formed between the measured point and the temperature known object is 13 degrees or more with respect to the surface of the measured point,
Condition 3: The horizontal distance from the measured point to the end of the flame is X ₁ , the height from the measured point to the flame is Y ₁ , the horizontal distance from the measured point to the temperature known object is X ₀ , and the height is Y When it is set to ₀ , it is set so as to satisfy the above equation 119.

  An example of the position of this temperature known object is the hatched area in FIG. The temperature measurement method according to the present embodiment can further improve the temperature measurement accuracy of the steel material by disposing a temperature known object within this range.

The temperature measuring method used in the embodiment of the present invention has been described above.
Next, an example of a temperature measuring apparatus according to the present embodiment that actually executes such a method will be described.

<4-3. Example of temperature measuring apparatus according to this embodiment>
As shown in FIG. 12, the temperature measuring device 100 measures the temperature of the steel material F arranged in the heating furnace 1. In FIG. 12, a furnace that performs heating with a burner 2 (an example of various burners such as a regenerative burner, a side burner, a roof burner, and an axial flow burner) is illustrated as the heating furnace 1. The heating furnace 1 to which the measuring apparatus 100 can be applied is not limited to this example. When the temperature measuring device 100 is used in the embodiment of the present invention, it is desirable to insert the imaging device 110 and the temperature known object 120 from the furnace side wall or the furnace ceiling. That is, in this case, the horizontal direction shown in FIG. 12 corresponds to the furnace width direction.

  As shown in FIG. 12, the temperature measurement device 100 includes an imaging device 110, a temperature known object 120, a calculation unit 130, a display unit 141, and a storage unit 142.

  The imaging device 110 is an example of a luminance measurement unit, and is arranged so that the steel material F and the temperature-known object 120 can be captured in the same visual field. FIG. 12 shows the case where the imaging device 110 is inserted into the heating furnace 1, but in this case, the imaging device 110 has a heat resistant structure. The imaging device 110 only needs to be able to image the inside of the heating furnace 1. For example, the imaging device 110 may be disposed outside the heating furnace 1 by providing a window in the heating furnace 1 with heat-resistant glass or the like. Is possible.

  In addition, the imaging device 110 includes, for example, a wavelength selection filter (not shown) so as to be able to capture the luminance of a predetermined wavelength so as to satisfy the above feature 1. This wavelength selection filter is an example of a wavelength selection unit, and transmits light of a predetermined wavelength. The wavelength selection unit is not limited to the wavelength selection filter. For example, the imaging device 110 can capture the luminance of all wavelength bands (or a predetermined wavelength band) that can be imaged, and the image analysis unit 131 can extract only light of a predetermined wavelength. In this case, the image analysis unit 131 also serves as a wavelength selection unit. In addition, as an image pickup element of the image pickup apparatus 110, an element that picks up only a single color luminance of a predetermined wavelength can be used. In this case, the imaging device 110 also serves as a wavelength selection unit.

  As such an imaging device 110, for example, a camera using an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) can be used. For example, an IP (imaging plate) can be used. As long as the luminance value in the captured image can be accumulated, any configuration may be used. And from such an imaging device 110, the luminance value received by each pixel in the captured image is output as an electrical signal.

  On the other hand, the temperature-known object 120 is disposed at a position satisfying the above-described features 1, 2, and 5, and includes, for example, a protective tube and a thermometer inserted inside the protective tube. The protective tube is made of, for example, a material that satisfies the emissivity defined in the above feature 3. When the metal material is a steel material F, examples of such a material include ceramic materials such as alumina, alumina / silica, silicon carbide, and quartz, and metal materials such as Inconel, Hastelloy, and stainless steel. Moreover, as a thermometer, contact-type thermometers, such as a thermocouple thermometer and a resistance thermometer, can be used, for example. Examples of the thermocouple thermometer include a platinum-platinum rhodium thermocouple, and examples of the resistance thermometer include a platinum resistance thermometer. However, these thermometers are appropriately changed according to the temperature of the heating furnace 1 and the temperature band to be measured. The temperature of the known temperature object 120 is output to the calculation unit 130 (stray light calculation unit 22).

  The calculation unit 130 analyzes the image captured by the imaging device 110 and calculates the temperature of the steel material F from the monochromatic luminance of the steel material F. At that time, the calculation unit 130 corrects this temperature as described above. For this purpose, as shown in FIG. 12, the calculation unit 130 includes an image analysis unit 131, a stray light calculation unit 132, a stray light correction unit 133, a temperature calculation unit 134, an emissivity change unit 135, and a storage unit 136. Have

  The image analysis unit 131 analyzes a captured image (an image including a single wavelength luminance value) captured by the imaging device 110, and corresponds to an output value corresponding to the luminance value of the temperature known object 120 and a luminance value of the steel material F. The output value is calculated. Then, each of the image analysis units 131 outputs an output value for the temperature known object 120 to the stray light calculation unit 132 and outputs an output value for the luminance value of the steel material F to the stray light correction unit 133. At this time, the image analysis unit 131 calculates the output value corresponding to the luminance value of the temperature known object 120 from the average value of a plurality of pixels, because the temperature known object 120 is arranged at the position having the characteristics 1 and 2. Similarly, the average value can be used for the steel material F. Therefore, temperature calculation accuracy errors can be reduced.

  The stray light calculation unit 132 calculates the stray light amount J by executing the procedure 2 to the procedure 4 of the feature 1 based on the output value corresponding to the luminance value of the temperature known object 120. Note that the procedure 1 has already been processed, and the above formulas 1 and 2 are already recorded in the stray light calculation unit 132. The stray light calculation unit 132 uses the recorded formulas 1 and 2. Then, Step 2 to Step 4 are executed.

  The stray light correction unit 133 executes Step 5 and Step 6 of the above feature 1 based on the output value corresponding to the luminance value of the temperature-known object 120 and the stray light amount J calculated by the stray light calculation unit 132 to correct stray light. Then, the black body luminance of the steel material F is calculated.

  Based on the black body luminance of the steel material F calculated by the stray light correction unit 133, the temperature calculation unit 134 calculates the temperature of the steel material F subjected to the stray light correction by executing the procedure 7 of the above feature 1. The calculation result is displayed on the display unit 141 or recorded in the storage unit 142. The display unit 141 includes, for example, a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display (PDP), a field emission display (FED), and an organic display. An electroluminescence display (organic EL, OELD: Organic Electroluminescence Display), a video projector, or the like can be used.

  On the other hand, the image analysis unit 131 further extracts an output value corresponding to the brightness of the furnace inner wall of the heating furnace 1 and outputs it to the emissivity changing unit 135. Then, the emissivity changing unit 135 calculates the furnace inner wall luminance from the output value, and records the difference between the furnace inner wall luminance and the temperature known object luminance in the storage unit 136. The emissivity changing unit 135 and the storage unit 136 execute the above feature 4 by using these pieces of information, and appropriately update the radiance of the temperature known object 120 used by the stray light calculation unit 132.

  Note that the arithmetic unit 130 may be configured by, for example, a general-purpose or dedicated computer. The computing unit 130 can be configured by causing the computer to execute a program that realizes the functions of the above-described configurations. The computer includes a CPU (Central Processing Unit), a recording device such as an HDD (Hard Disk Drive), a ROM (Read Only Memory), a RAM (Random Access Memory), and a LAN (Local Area Network). Communication devices connected to the computer, input devices such as a mouse / keyboard, magnetic disks such as flexible disks, optical disks such as various CDs (Compact Discs), MOs (Magneto Optical) disks, DVDs (Digital Versatile Discs), and semiconductors Drives that read and write to removable storage media such as memory, display devices such as monitors, speakers, headphones, etc. And an output device such as an audio output device. And this computer can implement | achieve the function of each structure of the calculating part 130 by running the program recorded on the recording device and the removable storage medium, or the program acquired via the network.

<4-4. Measurement Example Using Temperature Measuring Device According to this Embodiment>
Next, the example which measured the steel material F surface temperature arrange | positioned in a combustion furnace (an example of the heating furnace 1) as a metal material with the temperature measuring method and temperature measuring apparatus which concern on embodiment of this invention is shown. The combustion furnace used here has a length of 8 m (corresponding to the furnace width direction in the case of the heating furnace 1), a width of 2 m, and a height of 2 m, and heats the steel material F by LNG (Liquid Natural Gas). The steel material F is approximately 5 m and has a thickness of 50 mm. The imaging device 110 used a CCD camera with 380,000 pixels. The CCD camera has a wavelength filter function, and using this wavelength filter function, single wavelength radiation with a wavelength of 1.0 ± 0.2 μm was measured. At this time, since the wavelength filter function has a width of about ± 0.2 μm, the imaging device 110 actually measures only the radiated light having a wavelength of 0.8 to 1.2 μm. However, a wavelength having such a width can be regarded as a single wavelength for practical use and industrial use. Therefore, the imaging device 110 does not need to capture strict single-wavelength light, and only needs to capture light having a wavelength that can be regarded as an industrially single wavelength.

  A radiation thermometer tester was commissioned to test the relationship between the temperature of the thermometer test blackbody furnace and the output value of the CCD camera. The verification temperature range is 900 ° C to 1250 ° C. Using the obtained test data, a fitting calculation by the least square method is performed, and the following expression 21 is obtained as a specific form of the characteristic expression 20 (the expression 102) of the imaging device 110 in the stray light correction calculation procedure. It was.

・・・（式２０）

・・・（式２１）

... (Formula 20)

... (Formula 21)

  Here, G is the gain setting value of the CCD camera, SS is the shutter speed setting value, L is the output of the CCD camera, E is the luminance corresponding to the temperature of the black body furnace, and the temperature at which the test was performed , 900 ° C., 1000 ° C., 1100 ° C., 1200 ° C., and 1250 ° C., the values calculated by the Planck equation described above. As a specific calculation method, five coefficients in the equation were determined by a nonlinear least square method with E as a dependent variable and G, SS, and L as independent variables. This characteristic formula is specific to the CCD camera used in this embodiment, and must be created individually when the CCD camera model is different or when the imaging device 110 other than the CCD camera is used.

  As shown in FIG. 13, the CCD camera was inserted obliquely downward from a measurement port opened on the side wall of the furnace. The horizontal distance from the farthest measurement point (position 1) of the steel material F to the camera is 6 m, and the height from the horizontal plane on which the steel material F is placed to the CCD camera is 1.6 m. This is a positional relationship in which no flame enters the line connecting the tip of the CCD camera and the farthest measurement point (position 1) of the steel material F. The center line of the CCD camera is directed toward the center (position 2) of the steel material F, specifically, the depression angle is 21 degrees. This dip angle is selected so that the entire surface of the steel material F, that is, the position 1 to the position 3 is included in the field of view of the camera, and may be appropriately determined in consideration of the shape of the furnace and the position where the steel material is placed. Thus, the temperature measuring device 100 can measure the temperature distribution of the entire surface of the steel material F by keeping the entire surface of the steel material F within the field of view.

  The temperature known object 120 uses a thermocouple with a protective tube and has an outer diameter of 17 mm. This thermocouple with a protective tube is inserted horizontally at a position 0.2 m below the CCD camera tip, protrudes 0.3 m from the inner surface of the furnace wall into the furnace, and the tip is within the field of view of the CCD camera. . If the positional relationship is within the visual field of the CCD camera, it is not always necessary to insert it horizontally. Depending on the structure of the furnace, it may be advantageous in terms of strength to open the ceiling and insert it vertically. Since this thermocouple works as an object having a known temperature, the protective tube covering the outside must have a known emissivity. In this embodiment, an alumina / silica ceramic protective tube having an emissivity of 0.85 was used.

  In this example, since the emissivity of the steel material F was 0.86, it is almost the same as the emissivity of the thermocouple protective tube, but the emissivity is different as long as it is within the range satisfying the above feature 3. May be. The type of thermocouple used was a JISB type thermocouple. The type of thermocouple may be appropriately selected depending on the temperature used. Further, instead of the thermocouple, another temperature sensor such as a platinum resistance thermometer may be used.

  The viewing angle of the CCD camera is sufficiently large at 60 degrees on the left and right and 45 degrees on the top and bottom, and in addition to the steel material F, the inner wall surface of the furnace is also included in the field of view. The brightness of the inner wall of the furnace and the brightness of the surface of the thermocouple protection tube are stored for a long time by the storage unit 136 connected to the thermocouple, and the trend of the difference is managed to change the emissivity of the thermocouple protection tube over time. If the change is detected, the temperature known object emissivity used for the stray light calculation is corrected so that the difference in luminance is equal. In this correction, among the stored data, the furnace temperature is a certain temperature (in this embodiment, a range of 1190 ° C. to 1210 ° C.), and the temperature of the known temperature object is a certain temperature (this implementation). In the example, only the data in the range of 1170 ° C. to 1190 ° C. was extracted, and the heat radiation conditions in the furnace were equivalent.

  The luminance measurement range of the object having a known temperature in the CCD camera was a circular portion having a surface of about 10 mm in diameter, and an average value of about 200 pixels was measured. The temperature of the steel material F is in the range from 900 ° C to 1250 ° C. Three points of position 1, position 2, and position 3 shown in FIG. 13 were measured. Position 1 is about 6 m in horizontal distance from the CCD camera, position 2 is about 4 m, and position 3 is about 2 m away.

  FIG. 14 shows the result of performing the stray light correction calculation by the temperature measurement method according to the present embodiment and comparing it with the temperature measured by the thermocouple thermometer embedded in each position of the steel material F. In FIG. 14, the vertical axis represents the measured temperature obtained by performing the stray light correction calculation by the temperature measuring method according to the present embodiment, and the horizontal axis represents the embedded thermocouple measured temperature. Further, the solid line in FIG. 14 represents a line (horizontal axis = vertical axis) in which the measured temperature by this method (after correction of stray light) coincides with the actually measured temperature of the embedded thermocouple. As shown in FIG. 14, the measurement points at positions 1 to 3 were located on the solid line, and the embedded thermocouple measured temperature and the measured temperature (after stray light correction) by this method showed good agreement. Therefore, it can be seen that the temperature measurement method according to the present embodiment can accurately measure the temperature of the steel material F. In addition, the temperature measurement method according to the present embodiment further measures the surface temperature distribution of the steel material F by measuring the temperature at each location in the captured image of the steel material F as in positions 1 to 3. It is possible to measure well.

<4-5. Examples of effects of temperature measuring device and the like according to this embodiment>
Finally, examples of advantageous effects on the above-described Patent Documents 4 to 6 will be described so that the effects of the temperature measurement method used in the embodiment of the present invention can be easily understood. However, it is needless to say that the effects described here are merely examples and do not limit the effects of the temperature measurement method according to the present embodiment.

[4-5-1. Patent Document 4]
In the temperature measurement method described in Patent Document 4, a shielding plate is provided on the surface of the temperature measurement object to block stray light in the furnace. The shielding plate is cooled with water to prevent thermal radiation from the shielding plate itself. The error due to the radiation emitted by the shielding plate is obtained by actually measuring the temperature T _{2 of the} shielding plate and obtaining a corrected true temperature T ₁ from the apparent radiation energy G _{1 according} to the following equation 22. Eb (T) represents radiant energy at temperature T.

・・・（式２２）

... (Formula 22)

  In Patent Document 4, it is necessary to place a shielding plate near the steel material. However, when the steel material moves, for example, in a walking beam heating furnace, the shielding plate may be damaged by the movement of the steel material. If a mechanism for moving the shielding plate according to the movement of the steel material is provided, the measurement system itself becomes complicated. In addition, it is difficult to completely block stray light with the light shielding plate, and the accuracy may decrease depending on the path of stray light.

  On the other hand, in the temperature measurement method and the like described in the present embodiment, there is no need to place a structure near the steel material. Therefore, the temperature measurement method described in the present embodiment does not require the use of a shielding plate, its water cooling device, a complicated measurement system, or the like with respect to the above-mentioned Patent Document 4, and measures the temperature with a simple device configuration. be able to. Further, in this temperature measurement method and the like, the amount of stray light is calculated and stray light correction is performed, so that the influence of stray light that cannot be blocked by the light shielding plate can be reduced, and high-precision temperature measurement is possible. .

[4-5-2. Patent Document 5]
In the temperature measurement method described in Patent Document 5, the surface temperature T corrected from the apparent temperature S of the radiation thermometer is obtained by the following equation representing the luminance L using the measured temperature Tw of the furnace wall and the effective temperature Tw ′ of the furnace wall. .

・・・（式２３）

... (Formula 23)

  At this time, the furnace wall effective temperature Tw ′ is calculated by the primary expression 24 of the brightness of the actually measured temperatures Tw1, Tw2,... Twn of two or more thermometers installed on the furnace wall.

・・・（式２４）

... (Formula 24)

Coefficient a ₁ of the linear _expression, a 2, _... a _n is previously set to a value adapted to the dimensions of the pre-furnace body shape and steel by experiments or the like.

In Patent Document 5, stray light sources in the furnace are mainly a flame and a furnace wall. However, in this patent document 5, although the influence of the stray light from the furnace wall can be corrected to some extent, it is difficult to correct when the radiant energy from the flame changes. Stray temperature and size of the furnace or flame emanating always from the flame if constant heating furnace without using a flame, the coefficients a _1, a 2, _... is included as a constant value to a _n, if flame fluctuation The coefficients a ₁ , a ₂ ,... _An are considered to change. In general, in a heating furnace, the amount of combustion in the combustion device is appropriately adjusted in order to appropriately control the temperature in accordance with the amount of the object to be heated and the reached temperature, so that the flame state changes with time. On the other hand, Patent Document 2 does not show a correction means corresponding to a change in flame. Therefore, it is difficult to apply this Patent Document 5 to a heating furnace using a flame.

  On the other hand, in the temperature measurement method and the like described in the present embodiment, the temperature known object is arranged in the furnace space so that both the stray light emitted from the furnace wall and the stray light emitted from the flame are irradiated to the temperature known object. Further, the positional relationship between the flame, the steel material, and the temperature known object is defined as shown in the feature 5 above. Therefore, in the temperature measurement method described in the present embodiment, it is possible to appropriately correct the fluctuation of the radiant energy of the flame.

  On the other hand, in the temperature measurement method and the like described in the present embodiment, the temperature known object is arranged in the furnace space so that both the stray light emitted from the furnace wall and the stray light emitted from the flame are irradiated to the temperature known object. Further, the positional relationship between the flame, the steel material, and the temperature known object is defined as shown in the feature 5 above. Therefore, in the temperature measurement method described in the present embodiment, it is possible to appropriately correct the fluctuation of the radiant energy of the flame.

[4-5-3. Patent Document 6]
Patent Document 6 is as described in the related art, and the effects and the like according to the embodiment of the present invention have been described in detail in the above description. However, the temperature measurement device according to the embodiment of the present invention further includes a temperature. By installing a known object in the vicinity of the camera away from the steel material and imaging monochromatic luminance at a wavelength where absorption and emission by the furnace gas do not occur, various obstacles due to the movement of the steel material described in Patent Document 4 are avoided. At the same time, it is possible to increase the angle of view of a temperature known object, which is usually a small object, to obtain a sufficient number of pixels, and to improve the stray light correction accuracy.

  In the above embodiment, the features of the temperature measurement method and the like according to the first embodiment of the present invention are described separately from features 1 to 5 so that the features can be easily understood. However, the features 1 to 5 do not limit the features of the first embodiment of the present invention, and the features of the first embodiment of the present invention are described in detail in the features 1 to 5 respectively. Needless to say, each of the features described therein is also included.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Burner 10 Heating control apparatus 11 Position determination part 12 Control point temperature specific | specification part 13 Control point temperature memory | storage part 14 Temperature rising rate calculation part 15 Judgment part 23 Heating furnace control part 100 Temperature measuring device 110 Imaging device 120 Temperature known object DESCRIPTION OF SYMBOLS 130 Calculation part 131 Image analysis part 132 Stray light calculation part 133 Stray light correction part 134 Temperature calculation part 135 Emissivity change part 136 Storage part 141 Display part 142 Storage part 200 Ambient temperature measuring device 231 Furnace temperature control part 233 Conveyance speed control part F Steel material

Claims (11)

Prior to hot rolling the continuously cast ferritic stainless steel material, the surface temperature of the steel material is charged to a heating furnace at 150 ° C or higher,
The ferrite is characterized in that the steel is heated by the heating furnace so that the rate of temperature rise of the surface of the steel is 15.5 ° C./min or less in the range of the surface temperature of 150 to 700 ° C. To heat stainless steel.   The steel material is charged into a heating furnace at a surface temperature of 200 ° C. or higher, and the heating temperature at the surface temperature range of 200 to 700 ° C. is 15 ° C./min or less. The method for heating ferritic stainless steel according to claim 1, wherein the steel material is heated as described above. Predetermining a temperature specifying position that is a position on the steel material for specifying the surface temperature,
Before the surface temperature of the steel material reaches 700 ° C., the surface temperature at the temperature specific position of the steel material being heated in the heating furnace is a first time and a second time after a predetermined time has elapsed from the first time. Measured with the time of
Based on the measured surface temperature and the elapsed time from the first time to the second time, a temperature increase rate until the surface temperature of the steel material reaches 700 ° C. is predicted, The method for heating ferritic stainless steel according to claim 1 or 2, wherein the heating furnace is controlled so that a temperature rising rate of the surface temperature is 15 ° C / min or less. A temperature known object for correcting stray light in the heating furnace is installed in the vicinity of the luminance measuring unit,
In the surface temperature measurement of the steel material,
Using the luminance measurement unit, by measuring the radiant energy of the steel material and the temperature known object by monochromatic luminance having a wavelength at which absorption and emission by the furnace gas do not occur,
4. The method for heating ferritic stainless steel according to claim 3, wherein the temperature of the steel material is obtained by correcting the measured monochromatic luminance with stray light. When determining the temperature of the steel material,
Based on the radiant energy of the temperature known object and the temperature of the temperature known object, the amount of stray light is calculated,
The method for heating ferritic stainless steel according to claim 4, wherein the temperature of the steel material is calculated based on the calculated stray light amount and the radiant energy of the steel material. The luminance measuring unit is an imaging device that images a monochromatic luminance distribution of radiant energy of the steel material and the temperature known object as an image of a predetermined number of pixels,
6. The method for heating ferritic stainless steel according to claim 4, wherein the temperature known object is arranged at a position where an area occupied in an image captured by the imaging apparatus is 25 pixels or more.   The method of heating ferritic stainless steel according to claim 6, wherein the temperature known object is arranged at a position where an area occupied in an image captured by the imaging device is 100 pixels or more.   The method of heating ferritic stainless steel according to any one of claims 4 to 7, wherein the emissivity of the temperature known object is within a range of 0.1 before and after the emissivity of the steel material. . Using the brightness measurement unit, further measure the radiant energy of the inner wall of the heating furnace,
Record the difference in radiant energy between the furnace inner wall and the temperature known object,
The method for heating ferritic stainless steel according to any one of claims 4 to 8, wherein the presence or absence of a change with time of the emissivity of the object of known temperature is grasped based on the recorded difference of the radiant energy. . When a change with time of the emissivity of the temperature known object occurs, calculate the emissivity after the change with time,
The method for heating ferritic stainless steel according to claim 9, wherein the stray light correction is performed using the emissivity after the change with time. The said temperature known object is arrange | positioned in the position which satisfy | fills at least any one among the conditions of the following (A), (B), and (C), It is any one of Claims 4-10 characterized by the above-mentioned. To heat ferritic stainless steel.
(A) A position where the stray light distribution in the furnace is substantially the same as the position of the steel material, and a position separated from the furnace wall by a distance where the stray light amount is substantially the same. (C) Position where no flame is sandwiched between the steel materials

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