JP5768477B2 - Method for measuring temperature of workpiece, method for manufacturing workpiece, and heating device for workpiece - Google Patents

Description

  The present invention relates to a method for measuring a temperature of a workpiece, which is a material heated in a heating furnace, in a non-contact manner, a method for manufacturing a workpiece, and a heating device for the workpiece.

  For metals such as steel and aluminum, rolling or extruding metal lumps (hereinafter sometimes collectively referred to as “workpieces”) formed in a predetermined size called slabs or burettes. A processed product such as a plate is formed by processing into a predetermined shape by molding or the like. At that time, the workpiece is heated to a predetermined temperature before the processing is performed. As a heating means for that purpose, for example, a heating furnace can be cited, and examples thereof include a continuous heating furnace and a bullet heating furnace.

  The heating furnace has a pre-tropical zone, a heating zone, and a soaking zone, and individual workpieces inserted in succession pass through each zone in order to maintain a predetermined uniformity and reach the target extraction temperature. Heated. The workpiece heated to the target extraction temperature is extracted from the heating furnace and used for equipment for rolling and extrusion. At that time, if the temperature of the workpiece when extracted from the heating furnace is low, processing becomes difficult. Therefore, it is important to monitor the temperature at which the workpiece is extracted from the furnace.

  For this reason, it is necessary to measure the temperature of the workpiece in the heating furnace, but it is difficult to directly measure the temperature of the workpiece in the heating furnace with a contact-type thermometer. Therefore, the temperature of the workpiece is usually determined by creating a heat transfer model for the workpiece based on the temperature measured in the furnace by thermocouples installed on the ceiling or side of the furnace and solving the heat conduction equation. To be predicted.

  The heat conduction equation includes parameters that depend on material properties and overall heat absorption parameters that vary with furnace properties. Therefore, in order to identify the overall heat absorption rate parameter, conventionally, the temperature of the workpiece in the heating furnace was actually measured using a heat-resistant data logger, and this was consistent with the calculation result of the heat transfer model. The overall heat absorption rate was adjusted as follows.

  However, temperature measurement of workpieces using heat-resistant data loggers is a complicated task and cannot be performed frequently, and cannot be performed each time the furnace operating conditions are changed. There is a risk that the calculation accuracy will be reduced. Therefore, from the viewpoint of avoiding difficult processing, in order to heat the workpiece to the safe side, the extraction temperature from the heating furnace tends to be managed higher, and the energy consumption in the heating furnace increases. Was invited.

  Therefore, it is desirable to directly measure the temperature of the workpiece, and the temperature of the workpiece is measured in a non-contact manner using a radiation thermometer. However, when measuring the surface temperature of the workpiece with a radiation thermometer, the radiation (heat radiation energy) from the inner wall of the furnace or flame in the heating furnace is reflected on the surface of the workpiece (hereinafter referred to as “ Stray light ”), which affects the temperature measurement of the radiation thermometer, resulting in an error in temperature measurement.

On the other hand, Patent Documents 1 and 2 disclose methods for measuring the temperature of a workpiece in a heating furnace as accurately as possible with a radiation thermometer.
The invention described in Patent Document 1 measures the temperature of two or more furnace wall portions that affect the radiated light on the workpiece and corrects the surface temperature of the workpiece based on this temperature. It is a method to do.
In the invention described in Patent Document 2, a shielding plate is arranged opposite to the surface of the workpiece in the heating furnace, and radiation energy from the workpiece that is incident through the central opening of the shielding plate is converted into a radiation thermometer. This is a method of blocking the stray light from the furnace wall to the radiation thermometer by a shielding plate and measuring the surface temperature of the workpiece.

JP 61-292528 A Japanese Examined Patent Publication No. 62-22089

However, the conventional techniques described in Patent Documents 1 and 2 have the following problems.
In the measurement method described in Patent Document 1, measurement of the furnace wall surface temperature may be difficult or the measurement accuracy may be deteriorated due to dropping off of the refractory constituting the inner wall of the heating furnace. Management may not be possible. In addition, since the furnace wall temperature differs (temperature distribution occurs) in the vicinity of the heating means such as a burner provided in the heating furnace and the part away from the heating means, a strict temperature is also required. It is difficult to manage.

  In the method described in Patent Document 2, the gap between the surface of the workpiece and the shielding plate is made small in order to avoid the influence of surface reflection. For this reason, for example, when carrying in the work material into the heating furnace and carrying out the work material from the heating furnace using the walking beam, the work material moves up and down during the conveyance of the work material. Therefore, the position of the shielding plate must be moved using a drive mechanism or the like each time. Therefore, the apparatus configuration becomes complicated, equipment costs increase, and a problem arises in workability. In order not to move the position of the shielding plate, it is also possible to carry in and carry out the work material using rollers, but because the work materials are not all the same size (thickness), In some cases, the gap between the workpiece and the shielding plate becomes large, and the surface reflection cannot be blocked by the shielding plate, and there is a problem that strict temperature control cannot be performed.

  This invention is made | formed in view of this situation, and makes it a subject to provide the temperature measuring method of the workpiece which can measure the temperature of a workpiece easily and highly accurately by non-contact. Moreover, the manufacturing method of the processed goods containing the said temperature measurement method and the heating apparatus of a workpiece are provided.

  The present invention will be described below.

The invention according to claim 1 is a method for measuring the temperature of a workpiece in a heating furnace with a radiation thermometer, and is a surface of a steel material existing in the heating furnace that faces the extraction port of the heating furnace. The measurement part, which is the part that should be temperature-measured, is measured by a radiation thermometer installed outside the furnace, and the measurement is performed by connecting the measurement part and the radiation thermometer. The angle between the line and the line connecting the measurement site and the upper end of the extraction port, and the line connecting the measurement site and the radiation thermometer are the lower end of the extraction door provided at the measurement site and the extraction port. This is a method for measuring the temperature of a workpiece , which is performed within 3 seconds after the extraction door is opened when any angle formed with respect to the line connecting the two becomes 25 degrees or more.

According to a second aspect of the present invention, in the temperature measurement method for a workpiece according to the first aspect , the temperature measurement is performed a plurality of times at different times.

According to a third aspect of the present invention, in the method for measuring a temperature of a workpiece according to the first or second aspect , the radiation thermometer includes a CCD camera that images the measurement site and generates image information, and a CCD camera And an image processing apparatus capable of converting this into temperature information based on the image information.

According to a fourth aspect of the present invention, in the method for measuring a temperature of a workpiece according to the third aspect , the CCD camera and the image processing apparatus photograph a uniform surface illumination with the CCD camera in advance, and the sensitivity for each CCD element. to previously obtain the characteristic, when the temperature measurement of the measurement site of the steel material and corrects sensitivity depending on sensitivity characteristics.

The invention described in claim 5 is the method of measuring temperature of the workpiece according to claim 3 or 4, further measures the temperature of the CCD camera itself, the temperature measurement of the measurement site of the steel material on the basis of the temperature In this case, the measured value is corrected.

The invention according to claim 6, the temperature of the steel material to be extracted from the heating furnace using a temperature measuring method of the workpiece according to any one of claims 1 to 5 is installed in a heating furnace thermocouple and extraction predicted temperature of the steel material computed on the basis of the temperature values measured with, for deviation calculated, to make the heating of the other steel material subsequent to changing the heating condition of the heating furnace on the basis of the deviation It is the manufacturing method of the processed goods characterized.

  According to the present invention, temperature measurement of a workpiece in a heating furnace can be easily performed with high accuracy in a non-contact manner.

It is a figure showing a heating device with a figure explaining a first embodiment. It is the figure which paid its attention to the extraction opening vicinity among FIG. It is a graph which shows the relationship between (phi) and a temperature measurement error. It is a graph which shows the relationship between the elapsed time after opening an extraction door, and the fall of surface temperature. It is a figure explaining 2nd embodiment and is a figure equivalent to FIG. It is a figure showing the difference | error of the brightness | luminance for every pixel. It is a graph showing the relationship between the temperature of a camera itself, and a temperature measurement error. FIGS. 8A and 8B are diagrams illustrating a third embodiment, in which FIG. 8A is a plan view of a heating furnace, and FIG.

  The above-mentioned operation and gain of the present invention will be clarified from the following embodiments for carrying out the invention. Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these embodiments.

FIG. 1 is a diagram for explaining the first embodiment. FIG. 1 is a diagram showing a heating device portion in a steel line production line by hot rolling.
In a steel sheet production line by hot rolling, a slab 1 as a workpiece manufactured by casting or the like is heated to a predetermined temperature by a heating furnace 10 and is provided in the production line by an out-of-furnace conveying means 3. It is transported to each facility. Here, each equipment can include, for example, a descaler, a sizing press, a roughing mill, a finishing mill, a cooling device, etc., and each equipment is processed, and a steel sheet as a processed product having a desired shape and properties is obtained. Manufactured.

The heating device includes a heating furnace 10 and a temperature measuring means 16.
In the present embodiment, the heating furnace 10 is a continuous heating furnace, which includes a furnace body 11 and includes a pre-tropical zone 12, a heating zone 13, and a soaking zone 14. And the inlet 11a for carrying in the slab 1 in the furnace body 11, and the extraction port 11b which extracts the heated slab 1 out of a furnace are provided. The extraction port 11b is provided with an extraction door 15 that opens and closes the extraction port 11b. Here, the slab 1 is conveyed by the in-furnace conveying means 2.

  Here, the pre-tropical zone 12, the heating zone 13, and the soaking zone 14 can have the same configuration as that of a known heating furnace, and the form thereof is not particularly limited. Further, it is not always necessary to provide all of these, and it is sufficient if there is at least a zone corresponding to the heating zone 13.

  Further, as described above, the furnace body 11 is provided with the extraction port 11b, and the extraction door 15 is provided therein. FIG. 2 shows a view focusing on the vicinity of the extraction port 11b.

The extraction port 11 b is an opening provided in the furnace body 11 in order to extract the slab 1 that has been heated and soaked from the furnace body 11. In this embodiment, the upper end of the extraction port 11b is provided so as to hang down from the furnace ceiling 11c, and is formed by the lower end of the furnace wall 11d through which the slab 1 passes when the slab 1 is extracted.
In this embodiment, the lower end of the furnace wall 11d thus forms the upper end of the extraction port 11b. However, the present invention is not limited to this, the furnace wall 11d is not provided, and the ceiling end of the furnace is the extraction port. You may form the upper end of.

As can be seen from FIGS. 1 and 2, the extraction door 15 is a door body that can close and open the extraction port 11 b. In this embodiment, the extraction door 15 opens and closes by sliding up and down along the furnace wall 11d. Therefore, the extraction door 15 is normally closed so that the temperature in the furnace does not decrease as much as possible, and is opened when the slab 1 is extracted outside the furnace.
Although the extraction door 15 that opens and closes by sliding has been described in the present embodiment, the opening and closing operation is not limited to this, and other modes may be used. Examples thereof include an extraction door that opens and closes so as to rotate about one side of the door body.

The temperature measuring means 16 includes a temperature sensor 17 and an open / close detection sensor 18.
The temperature sensor 17 is a sensor that can measure the temperature of the slab 1 without contact, and is specifically a radiation thermometer. A well-known thing can be used as a radiation thermometer, and the form is not specifically limited.
The temperature sensor 17 is disposed toward the extraction port 11 b of the furnace body 11. More specifically, as can be seen from FIGS. 1 and 2, the temperature sensor 17 is a measurement site included in the surface of the slab 1 that is transported and that faces the extraction port 11 b when the extraction door 15 is opened. It is installed so that it can be measured. As a result, as described later, the temperature of the slab 1 that is a workpiece can be measured easily and accurately. Details will be described later.

  The open / close detection sensor 18 is a sensor that detects the open / close state of the extraction door 15, and provides the temperature sensor 17 with information on the open / close of the extraction door 15. Since the temperature measurement is performed when the extraction door 15 is opened, the opening / closing detection sensor 18 can make the timing for measuring the temperature appropriate.

  As described above, the temperature of the workpiece 1 in the heating furnace 10 can be accurately measured by the configuration of the heating device including the temperature measuring means 16.

  Next, the example which measures the temperature of the slab 1 in the heating furnace 10 with the heating apparatus of this embodiment is demonstrated. However, for the sake of clarity, an example in which the temperature of the slab 1 is measured by the heating device of the present embodiment will be described here, but the device used is not limited to this and is measured for the following purpose. Any other form of heating device may be used.

  The slab 1 manufactured by continuous casting or the like is inserted into the furnace body 11 from the insertion port 11a by the in-furnace transport means 2. The slab 1 inserted into the furnace body 11 is moved in the furnace body 11 by the in-furnace transport means 2, and passes through the pre-tropical zone 12, the heating zone 13, and the soaking zone 14 in order, and is heated and heated.

  When the heated slab 1 approaches the extraction port 11b, the extraction door 15 that has been closed to extract the slab 1 out of the furnace body 11 is opened. When the extraction door 15 is opened, the opening / closing detection sensor 18 of the temperature measuring means 16 detects that the extraction door 15 is opened, and the temperature sensor 17 measures the temperature of the slab 1.

  Here, the temperature of the slab 1 is obtained by measuring the measurement site included in the surface of the slab 1 that faces the extraction port 11b, as indicated by the broken lines in FIGS. As a result, it is possible to perform highly accurate measurement that is simple and has few errors. The reason is as follows.

  When the extraction door 15 is opened, the surface of the slab 1 that faces the extraction port 11b has a small area, and the surface faces the extraction port 11b. Since they are not opposed, there is no specular reflection component from the furnace wall that occupies most of the stray light. Thereby, the influence on the temperature measurement by stray light is greatly reduced.

In the conventional technology, since the surface for measuring the slab faces the wall that forms the furnace ceiling, the radiated light (thermal radiation energy) from the flame used for heating is reflected on the slab surface and emitted as stray light. Incident on the thermometer. This causes an error in the surface temperature of the slab to be measured.
On the other hand, if the slab surface temperature is measured with a radiation thermometer after being extracted from the heating furnace and installed on the outside-conveying means, the slab surface will be cooled because time has passed since extraction. There is a problem with accuracy. Moreover, scales grow on the surface of the slab after extraction, and the scales impair accurate temperature measurement because they have lower thermal conductivity than metals. In that case, since the temperature of the scale surface peeled off from the slab surface may be measured, the error is large. Further, after the scale is removed, surface cooling due to the water jet used for removing the scale and a decrease in surface temperature due to heat radiation occur, and it cannot be used for slab temperature management in a heating furnace.

  Therefore, by measuring the temperature of the measurement site included in the surface of the slab facing the extraction port as in the present invention, it is possible to easily measure the temperature accurately even when the slab is in the furnace. .

Here, the temperature measurement of the slab 1 is preferably performed at a position where the position of the slab 1 becomes θ and φ shown in FIG.
θ is an angle formed by a line connecting the measurement site of the slab 1 and the radiation thermometer with respect to a line connecting the measurement site and the upper end of the extraction port 11b. Φ is an angle formed by a line connecting the measurement site of the slab 1 and the radiation thermometer with respect to a line connecting the measurement site and the lower end of the extraction door 15. By setting θ and φ to 25 degrees or more, it is possible to further increase the temperature measurement accuracy.
That is, if the angle between the line connecting the measurement site of the slab 1 and the radiation thermometer and the line connecting the edge of the opening formed by the lower end of the extraction port 11b or the extraction door 15 and the measurement site is 25 degrees or more. This increases the accuracy of temperature measurement.

  Based on the spectral reflectance of the hot-rolled steel sheet, the influence of φ on the measurement temperature shown in FIG. 2 was calculated. FIG. 3 shows the measurement temperature error when the temperature of the heating door, which is a stray light source, is 1350 ° C. and the measurement target temperature is 1250 ° C. As φ becomes larger (as the extraction door opens), the measured temperature error becomes smaller, and when 25 °, the measured temperature error becomes about 5 ° C.

  That is, if θ and φ are 25 degrees or more, the temperature measurement error can be suppressed within 5 ° C., and the accuracy is greatly improved. This is presumably because the main component of stray light related to the surface to be measured is from the furnace wall 11d and the ceiling 11c in the furnace, and the influence of stray light becomes smaller as θ and φ increase.

  Moreover, it is preferable that the temperature measurement of the slab 1 is performed within 3 seconds after the extraction door 15 is opened. Thereby, the influence of the temperature fall of the slab 1 resulting from external air inflow by the extraction door 15 opening can be suppressed small. FIG. 4 shows the elapsed time (seconds) after the extraction door is opened on the horizontal axis and the surface temperature (° C.) of the slab 1 measured on the vertical axis. As can be seen from FIG. 4, the surface temperature of the slab decreases with time after the extraction door is opened. According to the result, the error can be suppressed within 5 ° C. by performing the measurement within 3 seconds after the extraction door is opened.

  However, as can be seen from FIG. 4, if the temperature is measured at a plurality of elapsed times after the extraction door is opened, for example, within 10 seconds after the extraction door is opened, the extraction door is opened based on the result. It is possible to extrapolate the temperature before opening. Therefore, the elapsed time does not necessarily need to be within 3 seconds, and the temperature before opening the extraction door can be estimated by measuring the temperature at a plurality of times. However, in order to increase the accuracy of estimation, it is preferable to have data measured within 3 seconds after the extraction door is opened.

The temperature measured as described above can be used as a reference for determining whether or not the conditions for the processing step (rolling in this embodiment) arranged in the lower step (downstream side) are satisfied. . This is because if the temperature of the slab extracted from the heating furnace is low, processing (rolling) becomes difficult.
Furthermore, the measured temperature may be feedback-processed and used as control data for the heating furnace. That is, the deviation between the obtained temperature of the slab 1 and the predicted extraction temperature of the workpiece calculated based on the temperature measurement value by the thermocouple installed in the heating furnace is obtained. Based on this deviation, the target temperature of other subsequent workpieces is changed according to the deviation, and the heating conditions of the heating furnace are changed based on this to heat the subsequent workpieces. Thereby, the accuracy of temperature control of the subsequent workpiece can be improved.

  After the temperature measurement as described above, the extracted slab 1 is placed on the out-of-furnace transport means 3 and transported to the lower process side to perform various processing and the like, and processed products having desired shapes and properties ( Steel plate) is manufactured.

  FIG. 5 is a diagram for explaining the second embodiment and corresponds to FIG. This embodiment is different from the first embodiment only in the temperature measurement means, and the other parts are the same as those in the first embodiment, and therefore illustration and description thereof are omitted. Here, the temperature measurement means 26 in this embodiment and the temperature measurement by this are demonstrated.

  The temperature measuring means 26 includes a camera 27, an image processing device 28, and an open / close detection sensor 18. Since the opening / closing detection sensor 18 is common to the first embodiment, the same reference numerals are given and the description thereof is omitted.

  In this embodiment, the camera 27 which is a two-dimensional CCD camera is used, and the measurement site included in the surface of the slab 1 facing the extraction port 11b is photographed in the same manner as described in the first embodiment. To do. The captured image signal is taken into the image processing device 28, and the image signal is converted into temperature. Thereby, the temperature of the slab 1 can be measured with high accuracy as in the first embodiment.

  Further, according to the second embodiment, it is easier to adjust the temperature measurement range than the temperature sensor 17 described in the first embodiment. That is, the measurement site of the slab 1 extracted from the heating furnace may have a greater distance from the position where the temperature sensor is arranged (for example, 5 m), whereas the measurement site of the slab that is the measurement target is about 300 mm. It is small. Therefore, when a spot type radiation thermometer is used, it may be difficult to adjust the measurement range and position. On the other hand, the measurement range and position can be easily adjusted by using the camera 27 as in the present embodiment.

  In order to be able to measure the temperature of the measurement site of the slab using the camera and the image processing apparatus as described above, a known system can also be used. Here, an example for realizing temperature measurement with higher accuracy will be described.

  In order to convert the image captured by the two-dimensional camera 27 into temperature, a black body furnace, which is a black body heat radiation source, was measured and the relationship between temperature and camera output was examined. As a result, it was found that the output of the black body furnace taken by the camera 27 differs depending on the position in the screen. In order to investigate more specifically, as a result of photographing with a camera 27 a planar light source in which white LEDs are arranged at regular intervals, as shown in “before correction” in FIG. It has been found that the number of pixels is reduced to about 0.9 times. When the influence is converted into temperature, when a 1200 ° C. region is measured, a difference of about 5 ° C. occurs between the image center and the image edge. Therefore, in order to show the same temperature regardless of the position of the screen, correction was performed according to the following procedure.

An image obtained by photographing a planar light source in which white LEDs are arranged at regular intervals with the camera 27 is taken as a reference image (reference image).
Cover the lens surface of the camera 27 so that light does not enter, and take a zero image (zero point image).
A difference in output at each pixel between the reference image and the zero point image is calculated to create a sensitivity correction image. Here, the sensitivity corrected image was based on the following equation. Here, (I, J) are coordinates, I is the horizontal pixel position of the image, and J is the vertical pixel position of the image.
Sensitivity corrected image (I, J) = pixel output of reference image (I, J) −pixel output of zero point image (I, J)
A sensitivity correction value is obtained by dividing the sensitivity correction image at each pixel (I, J) by the sensitivity correction image at the center pixel (α, β). That is, the following equation.
Sensitivity correction value (I, J) = sensitivity correction image at (I, J) / sensitivity correction image at center pixel (α, β) where α is the center position of the pixel in the horizontal direction of the image and β is the vertical direction of the image Is the center pixel position.
Adjust the field of view so that the blackbody furnace is photographed at the image center position (α, β), examine the relationship between the blackbody furnace temperature and the camera output, and obtain a function for converting the camera output to the temperature.
T = F (V (α, β))
Here, T is temperature, F is a function for converting camera output to temperature, and V (α, β) is the output of the center pixel (α, β) of the camera image.
The relationship between the output and temperature at each pixel (I, J) of the video is expressed by the following equation.
T = F {V (I, J) / sensitivity correction value (I, J)}
Here, V (I, J) is an output at each pixel (I, J) of the video.

  As described above, the sensitivity correction value is calculated so that the output at each pixel (I, J) is the same as the reference value with the output at the center pixel (α, β) as the reference value. As a result, as represented by “after correction” in FIG. 6, the sensitivity variation in the entire image could be suppressed to 2% or less.

  In addition, since the surroundings of a heating furnace become high temperature, it is preferable to store the surroundings of a camera in a water-cooled container. Further, since the water temperature varies depending on the season, the ambient temperature of the camera also varies. The output fluctuation when the ambient temperature of the camera changed was investigated. FIG. 7 shows the result. It was found that when the ambient temperature of the camera was varied during temperature measurement of the black body furnace held at a constant temperature of 1308 ° C., the temperature measurement value fluctuated following the temperature variation. The relationship between the camera temperature and the temperature measurement value can be approximated by a straight line. That is, by measuring the camera temperature and correcting the temperature measurement value of the slab by the camera, the temperature can be measured with higher accuracy.

Hereinafter, a specific example will be described.
The slab 1 is stopped at a position about 1 m before the extraction port 11b (upstream side in the transport direction) and is held for a predetermined time so as to reach a soaking temperature inside the slab. When the extraction door 15 is fully opened, the height of the extraction port 11b is 0.8 m, and the width direction (the rear side / front side in FIG. 5) is 10 m. Therefore, θ is about 39 degrees, which is in a range where the measurement error can be sufficiently reduced. Here, the extraction door 15 is fully open, so there is no need to consider φ.

Further, the camera 27 is installed so as to be substantially horizontal from the center of the measurement site so as to photograph the measurement site of the slab 1 and is separated from the measurement site by about 7 m in order to protect it from the heat radiation from the heating furnace 10. The position.
A lens having a focal length of 50 mm is attached to the camera 27 so that the entire measurement site of the slab 1 can be photographed. The camera 27 is a 1/3 type CCD, the number of effective pixels is 640 × 480, and “GigEvision” is used as a communication interface. The specifications of the camera 27 may be other combinations, and can be determined by the size of the measurement site, the measurement distance, the measurement range to be obtained, and the like.
When GigVision is used as the communication interface, the communication cable length can be extended up to 100 m. Therefore, even if the camera 27 and the image processing device 28 are separated from each other, they can be connected directly, eliminating the need for a cable extension instrument. An inexpensive system can be constructed.

The luminance image obtained by photographing with the camera 27 is converted to obtain gradation data which is digital data. The gradation data value depends on the resolution of the CCD element, and is represented by 8 bits, that is, 0 to 255 in this example. The above-described reference image for obtaining the sensitivity-corrected image of the camera 27 is obtained by photographing the LED illumination that provides uniform surface illumination, and adjusting the brightness of the LED illumination so that the gradation data at the center of the image is about 200. did. For LED illumination, chip LEDs with white light emission color are arranged at a pitch of 8 mm, the length is 500 mm, the width is 700 mm, and a diffusion plate is placed on the light output side of the LED and diffused to obtain uniform illumination. A fluorescent lamp may be used as the uniform surface light source.
A zero-point image for obtaining a sensitivity-corrected image of the camera was taken by capping the camera lens and cutting off the light. As described above, the sensitivity correction value is obtained by subtracting the zero point image from the reference image to obtain a sensitivity correction image, and dividing the gradation data of each pixel by the gradation data of the image center coordinates (320, 240). It was. The relationship between the gradation data and the temperature was obtained by photographing the black body furnace in the center of the camera field of view. The exposure time of the camera is adjusted so that the gradation data of the camera is 250 at the upper temperature limit of the measurement site. The relationship between the gradation data and the temperature is obtained by the following equation.
Image center coordinates: T = A × (V) B
Other than the image center: T (I, J) = A × (V / sensitivity correction value (I, J)) B
Here, A and B are constants, V is gradation data, I is the horizontal pixel position of the image, and J is the vertical pixel position of the image. However, it is not necessary to fix the above relational expression, and an expression that matches the relationship between the gradation data and the temperature may be determined by the least square method or the like. Alternatively, temperature conversion using a table of gradation data and temperature may be used.

When the image processing device 28 detects that the extraction door 15 is fully opened from the open / close detection sensor 18, it immediately sends a shooting start signal to the camera 27 and starts shooting. If the gradation data obtained by shooting includes 255, the image is saturated and the accurate temperature cannot be obtained. In that case, the exposure time of the camera 27 is shortened and the image is taken again to obtain the luminance image, and then the gradation data is obtained. In an unsaturated image, gradation data at a predesignated position is converted to temperature using the relational expression shown above. The housing temperature in the vicinity of the CCD element of the camera 27 is measured with a thermometer. If there is a temperature difference between the housing temperature near the CCD element when the relational expression between the gradation data and temperature is found and the housing temperature near the CCD element when actually measuring, Used to correct.
T1 = T + C × (t1-t0)
Here, t1 is the current temperature, t0 is the temperature at the time of temperature calibration, C is a constant, T is the temperature before correction, and T1 is the temperature after correction.

  By the measurement as described above, the measurement range can be easily set and the temperature can be measured with high accuracy.

  FIG. 8 is a diagram for explaining the third embodiment. FIG. 8A is a schematic diagram of the burette heating furnace 30 in a heating device in plan view, FIG. 8B is a cross-sectional view taken along the line AA in FIG. The figure which paid its attention to the vicinity of the extraction port 31b was represented. The third embodiment is an example in which a burette 4 is used as a workpiece and a burette heating furnace 30 is applied as a heating furnace of a heating device. In the third embodiment, only the forms of the workpiece and the heating furnace are different from those of the first embodiment, and the basic concept is the same as that of the first embodiment. That is, the temperature of the burette 4 in the furnace can be measured easily and accurately by measuring the measurement site included in the surface of the burette 4 on the surface facing the extraction port 31b with the temperature measuring means installed outside the furnace. Is possible. Therefore, the temperature measuring means 16 and 26 described above can be similarly applied as the temperature measuring means.

  As can be seen from FIG. 8A, the burette heating furnace 30 is conveyed so that the burette 4 flows on the circumference. Therefore, the position where the bullet 4 is inserted and the position where it is extracted are close. That is, the burette 4 inserted into the furnace body 31 of the burette heating furnace 30 is extracted from the extraction port 31b through the pre-tropical zone 32, the heating zone 33, and the soaking zone 34 while moving on the circumference. .

  In the burette heating furnace 30, as can be seen from FIG. 8B, an extraction door 35 is provided at the extraction port 31b, and the temperature can be measured in the same manner as the temperature measuring means 16 and 26 described above.

1 Slab (work material)
2 In-furnace transport means 3 Out-of-furnace transport means 4 Burette (work material)
10 Continuous heating furnace (heating furnace)
DESCRIPTION OF SYMBOLS 11 Furnace 11b Extraction port 15 Extraction door 16 Temperature measurement means 17 Temperature sensor 18 Opening / closing detection sensor 26 Temperature measurement means 27 Camera 28 Image processing apparatus 30 Bullet heating furnace (heating furnace)

Claims (6)

A method for measuring the temperature of a steel material in a heating furnace with a radiation thermometer,
Among the surfaces of the steel material existing in the heating furnace, the measurement site that is included in the surface facing the extraction port of the heating furnace and that should be subjected to temperature measurement was installed outside the heating furnace. The measurement is performed by the radiation thermometer,
In the measurement, an angle formed by a line connecting the measurement site and the radiation thermometer with respect to a line connecting the measurement site and the upper end of the extraction port, and the measurement site and the radiation thermometer After the opening of the extraction door when the angle between the line connecting the measurement site and the line connecting the lower end of the extraction door provided at the extraction port is 25 degrees or more A method for measuring the temperature of a workpiece within 3 seconds .   The method for measuring a temperature of a workpiece according to claim 1, wherein the temperature measurement is performed a plurality of times at different times. The radiation thermometer is
A CCD camera that images the measurement site and generates image information;
The method for measuring a temperature of a workpiece according to claim 1, further comprising: an image processing device capable of converting the image information from the CCD camera into temperature information.   The CCD camera and the image processing apparatus previously photograph uniform surface illumination with the CCD camera, obtain sensitivity characteristics for each CCD element, and perform the sensitivity measurement when measuring the temperature of the measurement site of the steel material. 4. The method for measuring a temperature of a workpiece according to claim 3, wherein the sensitivity is corrected in accordance with the characteristics.   5. The workpiece according to claim 3, wherein the temperature of the CCD camera itself is measured, and the measured value is corrected when measuring the temperature of the measurement site of the steel material based on the temperature. Temperature measurement method.   The temperature measurement value by the thermocouple installed in the temperature of the said steel material extracted from the said heating furnace using the temperature measuring method of the workpiece as described in any one of Claims 1-5 A deviation of the predicted extraction temperature of the steel material calculated on the basis of the above, and a heating product of the subsequent steel material is heated by changing the heating condition of the heating furnace based on the deviation Production method.