JP4569873B2 - Steel surface temperature measuring method, surface temperature measuring device, and steel manufacturing method - Google Patents

Description

  The present invention relates to a method and apparatus for measuring the surface temperature of a steel material by radiation measurement in a steel material manufacturing process such as hot rolling and continuous casting, and a method for manufacturing a steel material including a step of measuring the surface temperature by this method, In particular, the present invention relates to a surface temperature measuring method and apparatus capable of accurately measuring a surface temperature in a low temperature range of about 400 ° C. in a step of cooling the steel material, and a method of manufacturing a steel material including a step of measuring the surface temperature by this method.

  When measuring the surface temperature of steel materials being transferred using a radiation thermometer in a hot rolling line, heat treatment / cooling line, etc., there is steam between the steel material to be measured and the radiation thermometer. Or the cooling water splashes, or the surface of the steel material to be measured is covered with a water film or submerged. Under such circumstances, the heat radiation emitted from the temperature-measured steel material may be absorbed or scattered by water vapor, steam, cooling water, etc., resulting in an error in the temperature measurement value or inability to measure. It may occur. Also, in such an environment, the optical window for taking in heat radiation of the radiation thermometer is contaminated by impurities contained in the cooling water, scales peeled off from the steel material to be measured, dust floating in the factory, etc. As a result, the radiation temperature measurement accuracy may be deteriorated. Therefore, radiation temperature measurement in such an environment is unstable and unreliable.

  Therefore, in order to reduce temperature measurement errors caused by the above factors and enable stable radiation temperature measurement, a radiation thermometer has been conventionally used by ejecting purge water from a nozzle toward the steel surface. Various methods have been proposed for measuring the surface temperature of a steel material by forming a water column between the surface of the steel material and detecting radiant energy radiated from the steel material through the water column.

  More specifically, for example, a method for measuring temperature by correcting the radiant energy absorbed by the water column out of the radiant energy detected by a radiation thermometer based on the measured value of the thickness of the water column is proposed. (For example, refer to Patent Document 1).

  According to the method described in Patent Document 1, since a water column is formed between the radiation thermometer and the steel material surface, it is possible to suppress a temperature measurement error that may be caused by disturbance water such as water vapor or scattered water. Have. Moreover, by forming the water column with clean water, it is possible to suppress contamination of the optical window due to impurities contained in the cooling water, scales peeled off from the steel material, dust floating in the factory, and the like.

  However, according to the method described in Patent Document 1, water is ejected from the nozzle with considerable force so that water vapor and scattered water do not enter between the radiation thermometer and the steel material surface. Therefore, the steel material surface is cooled by such purge water, and the surface temperature of the cooled portion is measured, so that there is a problem that the representativeness of the temperature measurement value is impaired. In addition, since the steel material is partially cooled, there is a problem that unevenness of cooling occurs in the steel material and the material becomes non-uniform.

  As a method for improving the problems in the method described in Patent Document 1, there is provided a radiation thermometer for measuring the surface temperature of the object to be measured based on the radiation energy radiated from the object to be measured, and the object to be measured. A water column is formed between them, and the surface temperature of the object to be measured is measured using the radiation thermometer while correcting the amount of radiant energy absorbed by the water column among the radiant energy radiated from the object to be measured. In the temperature measurement method, a temperature measurement method is proposed in which the temperature of the water column is set to 60 ° C. or higher when the water column is formed (see, for example, Patent Document 2).

  According to the method described in Patent Document 2, as in the method described in Patent Document 1, a water column is formed between the radiation thermometer and the object to be measured. It is difficult for scattered water to enter, and it is possible to reduce temperature measurement errors due to absorption and scattering of radiant energy caused by these water vapor and scattered water. Furthermore, the method described in Patent Document 2 is a configuration in which the temperature of the water column is set to 60 ° C. or more, and a boiling film is easily formed on the surface of the object to be measured which is in contact with the water column. It has the advantage that the surface temperature drop is suppressed, the representativeness of the temperature measurement value is not impaired, and the cooling unevenness of the object to be measured can be reduced.

  However, the method described in Patent Document 2 requires a heating device for raising the temperature of the water column to 60 ° C. or higher, and there is a problem that it takes energy cost to raise the temperature of water. Further, as a problem common to the method described in Patent Document 1, since a thickness measuring device (for example, an ultrasonic method) for measuring the thickness of the water column is required, the overall size of the device increases, and the steel material There is a problem that it is difficult to install in a narrow space such as between transport rolls. Further, even if the thickness measuring device can be installed, there is a problem in that the maintenance is hindered such as requiring labor for attaching and detaching, and the stability and reliability of the temperature measurement value is lowered due to the failure of the thickness measuring device.

In order to solve the problems of the conventional methods described in Patent Documents 1 and 2, the inventors of the present invention disclosed in Japanese Patent Application No. 2004-195914 the following methods (a) and (b): Proposed.
(A) A method for measuring the surface temperature of a steel to be measured by detecting thermal radiation emitted from the surface of the steel to be measured with a radiation thermometer disposed opposite to the steel to be measured. In the region where the optical path of thermal synchrotron radiation detected by the thermometer passes, the minimum of the edge of the temperature-measured steel material based on the intersection of the optical axis of the radiation thermometer and the interface between the optical path stability region and the optical path instability region A method for measuring the surface temperature of a steel material, characterized in that the spread angle is set to 75 ° or more.
(B) The thermal radiation light radiated from the lower surface of the measured temperature steel material is detected by a radiation thermometer arranged oppositely to the lower side of the measured temperature steel material through the purge water sprayed from the nozzle toward the lower surface of the measured temperature steel material. Thus, the method is to measure the surface temperature of the steel material to be measured, wherein all the purge water heads Ht (m) with the pass line of the steel material to be measured as a position reference satisfy the following expression. A method for measuring the surface temperature of steel.
-0.36Hg <Ht <0.05
However, Hg (m) means a separation distance between the pass line and the nozzle tip.

Further, as a preferred configuration, a method having the following configuration (c) in the method (a) or (b) has been proposed.
(C) A method for measuring the surface temperature of a steel material, wherein the wavelength of thermal radiation detected by the radiation thermometer is 0.9 μm or less.
Japanese Patent Publication No. 3-69974 JP-A-8-295950

  According to the method proposed in the above Japanese Patent Application No. 2004-195914, temperature measurement errors due to scattering of thermal radiation by disturbance water are suppressed, and the temperature of purge water (water column) for temperature measurement is not raised. In addition, it is possible to suppress temperature measurement errors due to cooling of the steel material surface, and it is possible to suppress temperature measurement errors due to absorption of heat radiation light by disturbance water.

  However, the lower limit of the steel surface temperature that can be measured by radiation by the method proposed in Japanese Patent Application No. 2004-195914 is about 600 ° C., and it is difficult to measure the surface temperature in a low temperature range of about 400 ° C. There was a problem.

  In addition, in order to alleviate the effect of absorption of thermal radiation by the purge water (water column) for temperature measurement, a nozzle for injecting purge water between the surface of the temperature-measured steel material and the radiation thermometer is used as the temperature-measured steel material. When they are close to each other, there is a problem that the temperature-measured steel material easily collides with the nozzle due to fluctuations in the temperature-measured steel pass line, which hinders operation or damages the nozzle and makes temperature measurement difficult. It was.

  The present invention has been made to solve such problems of the prior art, and a surface temperature measuring method and apparatus capable of accurately measuring even a steel surface temperature in a low temperature range of about 400 ° C., and the surface by this method. It is a first object to provide a method for manufacturing a steel material including a step of measuring temperature. It is a second object of the present invention to provide a surface temperature measuring device capable of installing a nozzle for injecting purge water between the surface of the steel material to be measured and the radiation thermometer close to the steel material to be measured. .

  In order to solve the first problem, the inventors of the present invention first made a prototype of a radiation thermometer in which the wavelength of the thermal radiation light to be detected was 0.65 to 0.83 μm, and the temperature characteristics thereof were determined. evaluated. Specifically, the temperature of a radiant heat source (black body furnace, temperature variation of 1 ° C. or less) generally used for evaluating the temperature characteristics of the radiant thermometer is measured using the prototyped radiant thermometer. The variation in temperature value (3σ) was evaluated. The emissivity of the black body furnace, which is a radiant heat source, was 1.0. FIG. 2 is a graph showing an example of the evaluation result. As shown in FIG. 2, in the case of a radiation thermometer having a wavelength of 0.65 to 0.83 μm to detect the thermal radiation light, the temperature measurement value fluctuates greatly at 600 ° C. or less, and the temperature is measured accurately. I found out I couldn't. This is considered to be caused by an increase in the long wavelength component of the emitted thermal radiation when the object to be measured becomes low temperature. Therefore, it has been found that in order to perform radiation measurement at a temperature in a low temperature region of 600 ° C. or lower, it is necessary to shift the wavelength of the thermal radiation light to be detected to a longer wavelength side than 0.65 to 0.83 μm.

  Next, the inventors of the present invention assume that the thermal radiation emitted from the measurement object in the low temperature range is detected through a water column formed between the measurement object and the radiation thermometer, Spectral transmittance was investigated. FIG. 3 shows the spectral transmission of water in the wavelength band of about 0.7 to 1.9 μm when the thickness of the water column interposed between the black body furnace and the radiation thermometer is 3, 11, 50, 100 mm. It is a graph which shows a rate. The water column was formed using tap water at 28 ° C. As shown in FIG. 3, it was found that in the wavelength band longer than 0.65 to 0.83 μm, the water transmittance is high in the wavelength band near 1.1 μm.

  Therefore, the inventors of the present invention prototyped a radiation thermometer in which the wavelength of the thermal radiation light to be detected is 1.00 to 1.20 μm including a wavelength in the vicinity of 1.1 μm, and the temperature characteristics of the radiation thermometer are Evaluated. FIG. 4 is a graph showing an example of the evaluation result. As shown in FIG. 4, in the case of a radiation thermometer having a wavelength of thermal radiation light to be detected of 1.00 to 1.20 μm, if the variation (3σ) of the temperature measurement value is 3 ° C., the allowable range is It was found that measurement was possible up to 310 ° C.

  Furthermore, the inventors of the present invention appropriately change the thickness of the water column interposed between the radiation thermometer and the black body furnace in which the wavelength of the thermal radiation light to be detected is 1.00 to 1.20 μm, The temperature of the body furnace was changed as appropriate, and the water permeability was investigated. FIG. 5 is a graph showing the results of examining the water permeability. As shown in FIG. 5, the transmittance decreases as the thickness of the water column increases, but if the thickness is about 20 mm, a transmittance of about 0.2 is obtained, and the transmittance is sufficient even through the water column. It was found that radiation temperature measurement is possible.

  Therefore, the inventors of the present invention set the thickness of the water column interposed between the radiation thermometer and the black body furnace with the wavelength of the thermal radiation light to be detected between 1.00 and 1.20 μm and the temperature characteristics thereof. Evaluated. FIG. 6 is a graph showing an example of the evaluation result. As shown in FIG. 6, in the case of a radiation thermometer having a wavelength of thermal radiation light to be detected of 1.00 to 1.20 μm, a water column with a thickness of 20 mm is compared with a case without a water column (see FIG. 4). Although the variation in temperature measurement value (3σ) increases, if the variation in temperature measurement value (3σ) is 3 ° C., it is possible to measure the temperature of a measurement object in a low temperature range up to about 330 ° C. I understood that.

As described above, the inventors of the present invention, when the wavelength of the thermal radiation detected by the radiation thermometer is 1.00 to 1.20 μm, the thermal radiation emitted from the surface of the steel material to be measured is the water column. It has been found that the temperature in a low temperature region of about 400 ° C. can be measured with high accuracy even when detecting via a water column or directly detecting without going through a water column .

In addition, the inventors of the present invention prototyped a radiation thermometer having a wavelength of thermal radiation to be detected of 1.05-1.15 μm, which is narrower than 1.00-1.20 μm, and the radiation thermometer. The thickness of the water column interposed between the black body furnace and the black body furnace was changed as appropriate, the temperature of the black body furnace was changed as appropriate, and the water permeability was investigated. FIG. 7 is a graph showing the results of examining the water permeability. As shown in FIG. 7, the transmittance decreases as the thickness of the water column increases, but if the thickness is about 20 mm, the transmittance is about 0.4, and if the thickness is about 50 mm, the transmittance is about 0.2. It was found that the transmittance increased about twice as compared with the case of the radiation thermometer in which the wavelength of the thermal radiation light to be detected shown in FIG. 5 described above was 1.00 to 1.20 μm.

Furthermore, the inventors of the present invention set the thickness of the water column interposed between the radiation thermometer and the black body furnace with the wavelength of the thermal radiation light to be detected to 1.05 to 1.15 μm to 20 mm and 50 mm, Temperature characteristics were evaluated. FIG. 8 is a graph showing an example of the evaluation result. As shown in FIG. 8, in the case of a radiation thermometer having a wavelength of 1.05 to 1.15 μm of the detected thermal radiation light, even when a water column having a thickness of 50 mm is used, variation in temperature measurement value (3σ) Assuming that the allowable range is up to 3 ° C., it was found that the temperature of a measurement object in a low temperature range up to about 400 ° C. can be measured.

  Therefore, when the radiation thermometer radiated from the surface of the steel material to be measured is detected by the radiation thermometer through the purge water jetted toward the surface of the steel material to be measured, the thickness of the water column formed by the purge water is determined. The wavelength of the thermal radiation detected by the radiation thermometer is preferably 1.05 μm or more and 1.15 μm or less because it can be set relatively thick.

The inventors of the present invention have completed the present invention based on the above findings. That is, the present invention is, as described in claim 1 of the appended claims, the surface temperature is disposed opposite the thermal radiation emitted from 400 ° C. or higher 600 ° C. or less of the measurement object surface of the steel material in the temperature measurement objective steel A method of measuring the surface temperature of a steel material to be measured by detecting with a radiation thermometer, wherein the wavelength of the thermal radiation detected by the radiation thermometer is 1.05 μm or more and 1.15 μm or less , the measuring heat radiation emitted from the hot surface of the steel material is detected by the radiation thermometer through the purge water jetted toward a temperature measuring surface of the steel material, and 50mm or less the thickness of the water column which is formed by the purge water The present invention provides a method for measuring the surface temperature of a steel material.
According to such invention, the surface of the steel material is accurately obtained even in a low temperature range of about 400 ° C. by setting the wavelength of the thermal radiation light detected by the radiation thermometer to a long wavelength of only 1.05 μm to 1.15 μm. It is possible to measure the temperature.
Further, according to the present invention, since the thermal radiation light is detected through the water column formed by the purge water jetted toward the surface of the temperature-measured steel material, the temperature measurement error that may be caused by disturbance water such as water vapor or scattered water. Can be suppressed. Moreover, since the wavelength of the thermal radiation light detected by the radiation thermometer is 1.05 μm or more and 1.15 μm or less including the wavelength in the vicinity of 1.1 μm where the water transmittance is relatively high as described above, It has the advantage that the influence of absorption of heat radiation light is small.
The detection element of the radiation thermometer is preferably an InGaAs photodiode.

Further, in order to solve the first problem, the present invention provides, as described in claim 3 , a radiation temperature disposed opposite to a steel material to be measured whose surface temperature is 400 ° C. or more and 600 ° C. or less. An apparatus for measuring the surface temperature of the steel material to be measured by detecting thermal radiation emitted from the surface of the steel material to be measured by the radiation thermometer, the steel material to be measured and the radiation temperature An optical filter disposed between the detector element of the meter and blocking light having a wavelength of less than 1.05 μm and light having a wavelength longer than 1.15 μm, and spaced from the surface of the steel material to be measured. A steel surface temperature measuring apparatus comprising a nozzle for injecting purge water between a surface of a hot steel material and the radiation thermometer, wherein a thickness of a water column formed by the purge water is 50 mm or less Also provided as
The detection element of the radiation thermometer is preferably an InGaAs photodiode.

  Here, the inventors of the present invention set the thickness of the water column interposed between the radiation thermometer and the black body furnace (400 ° C.) with the wavelength of the thermal radiation to be detected being 1.00 to 1.20 μm to 20 mm. The temperature characteristics were evaluated. FIG. 9 is a graph showing an example of the evaluation result. As shown in FIG. 9, when the thickness of the water column varies by 2 mm, a temperature measurement error of 3 ° C. (emissivity is set to 1.0) occurs. Therefore, in order to measure temperature with high accuracy, it is desirable to make the thickness of the water column constant.

Therefore, preferably , the steel surface temperature measuring device includes means for maintaining a distance between the steel material to be measured and the nozzle substantially constant.

  According to such a preferable configuration, since the distance between the steel material to be measured and the nozzle is kept substantially constant, the thickness of the water column formed by the purge water is also substantially constant, and the water column accompanying the variation in the thickness of the water column It is possible to mitigate the influence on the temperature measurement value of the fluctuation of the transmittance of the water, and consequently the absorption of the heat radiation light by the water column. In addition, as a means for maintaining the separation distance between the steel material to be measured and the nozzle substantially constant, for example, the nozzle is attached to the nozzle and is directed toward the surface of the steel material to be measured so as to always contact the surface of the steel material to be measured. A contact roller mechanism including a contact roller to be pressed can be exemplified.

Further, the order first also to achieve the second object, in addition to the problems, the present invention is, as described in claim 5 of the appended claims, the compression at least a portion of said nozzle is made of stainless steel It is formed with a coil spring.

According to such a preferable configuration, even if the measured temperature steel material collides with the nozzle due to the pass line fluctuation and the nozzle is temporarily deformed, the nozzle can be elastically deformed. After passing, the nozzle will return to its original shape. Therefore, it is difficult to cause a problem that the operation is hindered or the temperature is difficult to measure due to breakage of the nozzle, and it is possible to install the nozzle close to the steel material to be measured .

Preferably, as described in claim 6, the radiation thermometer includes an optical fiber having a tip portion disposed in the nozzle and having a tip surface subjected to spherical processing, and The fiber is characterized in that heat radiation light radiated from the surface of the steel material to be measured is received by the tip portion and transmitted to the detection element.

According to such a preferable configuration, in order to transmit the thermal radiation light received at the tip of the optical fiber to the detection element of the radiation thermometer by the optical fiber, the detection element is disposed at a position separated from the steel material to be measured. It is possible to reduce the influence of thermal radiation on the detection element. In addition, even if the temperature-measured steel material collides with the nozzle due to fluctuations in the pass line and the nozzle is temporarily deformed, the optical fiber can be deformed in accordance with the deformation of the nozzle. There is an advantage that a situation in which temperature measurement becomes difficult does not easily occur. Furthermore, since the spherical end is applied to the tip surface of the optical fiber, it is possible to increase the light collection efficiency.

The present invention is as described in claim 7 of the appended claims, is also provided as a method for producing a steel material, characterized in that it comprises the step of measuring the surface temperature by the method of claim 1 or 2 The

According to the present invention, the surface of a steel material is accurately obtained even in a low temperature range of about 400 ° C. by setting the wavelength of thermal radiation detected by a radiation thermometer to a long wavelength of 1.05 μm to 1.15 μm. It is possible to measure the temperature.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings, taking as an example a case where the present invention is applied to a lower part of a cooling zone of a hot-rolled steel sheet production line.

  FIG. 1 is a diagram showing a schematic configuration of a surface temperature measuring apparatus according to an embodiment of the present invention. As shown in FIG. 1, the surface temperature measuring apparatus 100 according to the present embodiment includes a radiation thermometer 1 disposed opposite to a steel material to be measured (steel plate M in the present embodiment), and the surface of the steel plate M (the present embodiment). Then, the surface temperature of the steel sheet M is measured by detecting the thermal radiation emitted from the lower surface with the radiation thermometer 1. Further, the surface temperature measuring apparatus 100 according to the present embodiment includes a nozzle 2 for injecting purge water toward the surface of the steel plate M to form a water column having a thickness of 20 mm.

  The radiation thermometer 1 according to the present embodiment includes an optical fiber 11 having a tip portion disposed in the nozzle 2 and receiving heat radiation light radiated from the surface of the steel plate M. In the present embodiment, the quartz optical fiber 11 is used, but the material is not particularly limited as long as it transmits light having a wavelength of at least 1.00 μm to 1.20 μm. The optical fiber 11 according to this embodiment has a core diameter of 400 μm and an outer diameter of 2 mm including a protective coating, and the tip of the optical fiber 11 is guided by a guide (not shown) provided in the nozzle 2. 2 is positioned so as to pass through the approximate center of 2. And it positions so that the separation distance of the front end surface of the optical fiber 11 which opposes the steel plate M, and the pass line of the steel plate M may be 20 mm (Thereby, the thickness of the water column formed by the nozzle 2 will be 20 mm). ing. The tip surface of the optical fiber 11 is processed to be a flat surface. In this embodiment, the tip surface of the optical fiber 11 is processed into a flat surface. However, spherical processing can be applied to increase the light collection efficiency. Sites other than the tip of the optical fiber 11 disposed in the nozzle 2 are covered with a protective cover 111 made of a stainless steel flexible tube in order to prevent breakage.

  In addition, the radiation thermometer 1 according to the present embodiment detects thermal radiation received at the tip of the optical fiber 11 and transmitted through the optical fiber 11, and displays temperature according to the detected amount of thermal radiation. The temperature display part 12 which performs is provided. The temperature display unit 12 includes a light detection calculation unit 121 and a temperature correction unit 122.

  The light detection calculation unit 121 includes a detection element such as an InGaAs photodiode that photoelectrically converts thermal radiation light transmitted through the optical fiber 11 and outputs a current corresponding to the light amount, and after amplifying the output current from the detection element Further, current voltage conversion and AD conversion are performed, and the water permeability is corrected and converted into temperature. An optical filter (not shown) that blocks light having a wavelength less than 1.00 μm and light having a wavelength longer than 1.20 μm is disposed between the rear end of the optical fiber 11 and the detection element. Thus, the wavelength of the thermal radiation detected by the radiation thermometer 1 (detected by the detection element) is set to only 1.00 μm or more and 1.20 μm or less. Further, correction of the water transmittance in the light detection calculation unit 121 (when the detected heat radiation amount is E and the water transmittance is τ, the heat radiation amount from the measurement target is calculated by E / τ) ( Hereinafter, as the transmittance used for the correction in the light detection unit 121 as appropriate “first correction”), a transmittance of 0.20 measured in advance when the measurement target temperature is 500 ° C. and the thickness is 20 mm is used. It was. The reason why this transmittance is used is that the range of the surface temperature of the steel sheet M that is the measurement target is expected to be about 300 to 600 ° C. from the operating conditions. In addition, the thickness of the water column formed by the nozzle 2 is 20 mm as described above.

  The temperature correction unit 122 is configured to correct the influence of the change in the water transmittance according to the measurement target temperature with respect to the temperature calculated by the light detection calculation unit 121 as described above. Hereinafter, the correction of the water transmittance in the temperature correction unit 122 (hereinafter, the correction in the temperature correction unit 122 will be appropriately referred to as “second correction”) will be described in more detail.

  FIG. 10 shows that the thickness of the water column interposed between the radiation thermometer with the wavelength of the thermal radiation light to be detected set to 1.00 to 1.20 μm and the black body furnace is appropriately changed, and the temperature of the black body furnace is appropriately changed. It is a graph which shows an example of the result of having changed and investigated the transmittance | permeability of the water for every blackbody furnace temperature. As shown in FIG. 10, it can be seen that as the temperature of the black body furnace that is the object of measurement increases, the water permeability increases for any thickness of the water column.

  And whatever temperature the measurement target temperature is, the water permeability when the measurement target temperature is 520 ° C. is fixed (used uniformly) and corrected to measure the temperature of the blackbody furnace. Temperature measurement error (emissivity was set to 1.0) was evaluated. FIG. 11 is a graph showing an example of the evaluation result. As shown in FIG. 11, for example, when the thickness of the water column is 20 mm, the measurement target temperature is about 300 to 300 by fixing and correcting the water permeability 0.21 when the measurement target temperature is 520 ° C. A temperature measurement error of about 10 ° C. is caused in the range of 700 ° C. As shown in FIG. 10, since the water permeability actually increases as the measurement target temperature increases, the fixed water permeability can be increased regardless of the measurement target temperature. This is because a temperature measurement error caused by a change in transmittance occurs when the correction is performed.

In order to reduce the temperature measurement error, the relationship between the temperature to be measured and the temperature measurement error when the water permeability as shown in FIG. 11 is fixed is linearly approximated for each thickness of each water column, and the following equation is used: Correction may be performed according to (1).
T = T1 + (T0−T1) × α (1)
Here, in the above formula (1), T is the corrected temperature measurement value (° C.), T 1 is the temperature measurement value (temperature measurement value corrected using the fixed water permeability) (° C.), T 0 Denotes the temperature to be measured corresponding to the fixed water permeability, and α denotes the slope of the approximate line.

  FIG. 12 shows that when the measurement target temperature is in the range of about 300 to 700 ° C., the thickness of the water column is 20 mm and the water permeability 0.21 when the measurement target temperature is 550 ° C. is fixed and corrected. A graph showing an example of a result of evaluating a temperature measurement error (difference between a temperature measurement value T after correction and a true temperature) obtained when the temperature measurement value T1 obtained by the above is further corrected according to the above equation (1). It is. As shown in FIG. 12, it can be seen that the temperature measurement error is reduced to about 1 ° C. by further correcting according to the equation (1).

  As described above, the temperature measurement value corrected (first correction) using the fixed water permeability is corrected (second correction) according to the equation (1), thereby depending on the measurement target temperature. It is possible to reduce the influence of changing the water permeability.

Therefore, the temperature correction unit 122 according to the present embodiment uses the transmittance used in the first correction in the light detection unit 121 described above (the transmittance measured in advance when the measurement target temperature is 500 ° C. and the thickness is 20 mm). If 0.20) is fixed, α in the equation (1) is identified based on the fact that when the temperature to be measured is 400 ° C., a measured temperature T1 lower by 6 ° C. (ie, T1 = 394 ° C.) is obtained. The second correction is performed in accordance with the following equation (1) ′.
T = T1 + (500−T1) × 0.0575 (1) ′
That is, when T1 = 394 ° C. is substituted into the above equation (1) ′, T≈400 ° C., and the corrected temperature measurement value T is equal to the true temperature of 400 ° C.

  As shown in FIG. 1, the nozzle 2 is configured to inject purge water from the tip toward the surface of the steel plate M by flowing purge water from the outside. The diameter of the tip of the nozzle 2 is φ12 mm, and the flow rate of purge water flowing from the outside is 3 liters / minute, so that the water column formed by the purge water collides with the surface of the steel plate M at high pressure. It becomes a grade which contacts without, and cooling of the steel plate M surface by a water column is suppressed.

  The nozzle 2 according to the present embodiment is formed of a compression coil spring made of stainless steel. The reason why the nozzle 2 is formed by the compression coil spring is that the wire rods constituting the compression coil spring are closely wound in a coil shape, so that the purge water hardly leaks from the gap between the wire rods, and the steel plate M is a pass line. This is because even if the collision occurs due to fluctuation, the compression coil spring is elastically deformed, so that the nozzle 2 can be prevented from being damaged. FIGS. 13A and 13B are explanatory views showing a state in which the nozzle 2 formed by the compression coil spring is elastically deformed. FIG. 13A shows a state where the nozzle 2 is elastically deformed, and FIG. 13B shows a state where the nozzle 2 is restored to its original shape. . As shown in FIG. 13 (a), the steel plate M collides with the nozzle 2 due to the pass line variation (in the example shown in FIG. 13 (a), the downward warp portion generated at the tip of the steel plate M collides with the nozzle 2). Even if the nozzle 2 is temporarily deformed, since the nozzle 2 can be elastically deformed, after the steel plate M whose pass line has fluctuated has passed (after the downward warp portion generated at the tip of the steel plate M has passed) As shown in FIG. 13B, the nozzle 2 returns to its original shape. It is not always necessary to form the entire nozzle 2 with a compression coil spring, and it is sufficient to form a part with a compression coil spring.

  When the nozzle 2 is installed close to the surface of the steel plate M as in the present embodiment, it is preferable that the nozzle 2 is configured to be elastically deformable as described above. In order to configure the nozzle 2 to be elastically deformable, the nozzle 2 may be formed of a cylindrical rubber member in addition to the nozzle 2 being formed of a compression coil spring as described above. As such a rubber member, it is not always necessary to use one having excellent heat resistance. This is because the inner and outer surfaces of the rubber member are cooled by the purge water, so that the rubber member itself does not reach a temperature of 100 ° C. or higher.

  In addition, when the fluctuation | variation of the pass line of the steel plate M is large and the fluctuation | variation of the separation distance of the steel plate M and the nozzle 2 and by extension, the fluctuation | variation of the thickness of a water column become large, in order to maintain temperature measurement precision, the steel plate M and the nozzle 2 It is preferable to provide a means for keeping the separation distance substantially constant. By providing such means, the thickness of the water column formed by the purge water becomes substantially constant, and the variation of the water column transmittance due to the variation of the thickness of the water column, and hence the influence on the temperature measurement value of the absorption of the heat radiation light by the water column. Can be mitigated. As a means for keeping the separation distance between the steel plate M and the nozzle 2 substantially constant, for example, as shown in FIG. 14, the nozzle 2 is attached to the nozzle 2 and faces the steel plate M surface so as to always contact the steel plate M surface. The contact roller mechanism 22 including the contact roller 221 to be pressed can be exemplified. Further, as shown in FIG. 15, a distance meter for measuring the distance between the steel plate M and the nozzle 2 (and thus measuring the thickness of the water column) is attached, and the transmittance of the water column is corrected by the measured value of the distance meter. It is also possible to adopt.

  FIG. 16 is a graph showing an example of a result obtained by actually measuring the temperature of the lower surface of the steel sheet M by the surface temperature measuring apparatus 100 according to the present embodiment described above. FIG. 16 shows the result of measuring the temperature of the upper surface of the steel sheet M with a conventional radiation thermometer (detection element: InGaAs, detection wavelength: 1.0 to 1.6 μm) at the same timing (relatively superior environmental conditions). The temperature measurement results are also shown. As shown in FIG. 16, the tendency of the temperature measurement values on the upper surface and the lower surface of the steel sheet M is substantially the same, and certain reliability is obtained for the temperature measurement values of the surface temperature measurement device 100 according to the present embodiment. I understood that.

  In addition, although this embodiment demonstrated the structure which detects the thermal radiation light radiated | emitted from the lower surface of the steel plate M as a to-be-measured steel material with the radiation thermometer arrange | positioned facing the steel plate M, this invention is limited to this. Instead, it is of course possible to adopt a configuration in which the thermal radiation emitted from the upper surface of the steel plate M as the temperature-measured steel material is detected by a radiation thermometer disposed opposite to the steel plate M. Further, in a production line in which the steel plate M is conveyed in the vertical direction, it is also possible to adopt a configuration in which heat radiation light radiated from the surface of the steel plate M is detected by a radiation thermometer disposed opposite to the surface of the steel plate M. . Furthermore, it is also possible to adopt a configuration in which heat radiation light radiated from the side surface of the temperature-measured steel material such as a steel pipe or a shape steel is detected by a radiation thermometer disposed opposite to the side surface of the temperature-measured steel material.

  Hereinafter, a method for producing a hot-rolled steel sheet by applying the surface temperature measuring device according to the present invention to a production line for the hot-rolled steel sheet will be described.

FIG. 17 is a schematic diagram illustrating a schematic configuration example of a production line for hot-rolled steel sheets.
As shown in FIG. 17, when manufacturing a hot-rolled steel sheet, the slab is first heated to 1000 to 1200 ° C. in the heating furnace 3. Next, the width of the heated and heated slab is determined, and the slab is rolled to a thickness that can be rolled by the finish rolling mill 6 and then rolled to an intermediate member called a coarse bar. Next, if necessary, the coarse bar is reheated by induction heating or the like in the reheating device 5. Next, the finish rolling mill 6 performs rolling until the thickness of the hot-rolled steel sheet targeted for the rough bar is reached. In addition, the temperature of the steel plate after finish rolling in the finish rolling mill 6 is about 700 to 1000 ° C., the thickness is about 1 mm to about several tens of mm, and the plate speed is 600 mpm to 1500 mpm.

  The steel sheet after rolling by the finish rolling mill 6 is cooled to the target temperature in the first cooling zone 7 or the second cooling zone 8 and is wound in a coil shape by the down coiler 9. Alternatively, the cooling history may be controlled by using the first cooling zone 7, the second cooling zone 8, and the non-cooling zone located in the middle thereof. In the first cooling zone 7 and the second cooling zone 8, a large number of cooling nozzles called mist cooling or laminar cooling for jetting cooling water are arranged, and water is jetted from an appropriate number of nozzles. To cool the steel plate. Cooling conditions such as the number and position of nozzles to be ejected are controlled using setup learning, dynamic feedback, and the like.

  In the production line for hot-rolled steel sheets described above, the surface temperature measuring device according to the present invention measures, for example, the temperature of the lower surface of the first cooling zone 7 or the second cooling zone 8 that has conventionally been difficult to measure. (Application 1 in FIG. 17). In the case of a thin steel plate, there is no problem considering that the temperature measurement value from the lower surface roughly represents the representative temperature in the thickness direction of the steel plate.

  Moreover, it is also possible to install the surface temperature measuring device according to the present invention before and after the first cooling zone 7 or the second cooling zone 8 and use it instead of the conventional thermometer (application 2 in FIG. 17). Conventional thermometers may have a low output value due to the influence of steam, particularly at the tip of the coil, but if the surface temperature measuring device according to the present invention is applied, the temperature can be measured from the most advanced part of the coil. .

  Moreover, in the 1st cooling zone 7 or the 2nd cooling zone 8, it is also possible to install the surface temperature measuring device based on this invention above a steel plate, and to measure temperature (application 3 of FIG. 17). Except for the region where the spray or laminar cooling water collides with the steel plate, the temperature can be measured through the water ride even when the cooling water is on the upper surface of the steel plate.

  Moreover, it is also possible to install the surface temperature measuring device according to the present invention in the vicinity of the finishing mill 6 or between the stands of the finishing mill 6 to measure the temperature (application 4 in FIG. 17). Even in such a place, the cooling water of the finishing mill 6 and the cooling water called inter-stand spray exist as disturbance water, but it is possible to measure the temperature while reducing the influence of the disturbance water. . By measuring the steel plate temperature at such a location, it can be used for management and control of the temperature immediately after rolling, which is an important management index.

  Furthermore, if the surface temperature measuring device according to the present invention is installed and measured at a place where the cooling water of the transport roll exists as disturbance water, useful temperature management can be performed (application of FIG. 17). 5, 6).

  As described above, the surface temperature measuring device according to the present invention can be installed at a location as indicated by applications 1 to 6 in FIG. Among these, what is particularly important for the quality control of the steel sheet is the temperature management of the places shown in Applications 1 to 4, and therefore, it is necessary to install the surface temperature measuring device according to the present invention with high temperature measurement accuracy in the places. preferable.

FIG. 1 is a diagram showing a schematic configuration of a surface temperature measuring apparatus according to an embodiment of the present invention. FIG. 2 is a graph showing an example of a result of evaluating a temperature measurement variation of a radiation thermometer in which the wavelength of thermal radiation to be detected is 0.65 to 0.83 μm. FIG. 3 is a graph showing the results of examining the spectral transmittance of water in a wavelength band of about 0.7 to 1.9 μm. FIG. 4 is a graph showing an example of a result of evaluating a temperature measurement value variation of a radiation thermometer in which the wavelength of thermal radiation light to be detected is 1.00 to 1.20 μm. FIG. 5 is a graph showing the results of examining the water transmittance in the wavelength band of 1.00 to 1.20 μm. FIG. 6 is a graph showing an example of a result of evaluating a temperature measurement variation of a radiation thermometer in which the wavelength of thermal radiation detected through a water column having a thickness of 20 mm is set to 1.00 to 1.20 μm. FIG. 7 is a graph showing the results of examining the water transmittance in the wavelength band of 1.05 to 1.15 μm. FIG. 8 is a graph showing an example of a result of evaluating a temperature measurement variation of a radiation thermometer in which the wavelength of thermal radiation detected through a water column having a thickness of 20 mm and a thickness of 50 mm is 1.05 to 1.15 μm. FIG. 9 shows the temperature measurement that occurs when the thickness of the water column interposed between the radiation thermometer and the black body furnace (400 ° C.) with the wavelength of the thermal radiation light set to 1.00 to 1.20 μm is changed from 20 mm. It is a graph which shows an example of the result of having evaluated error. FIG. 10 shows that the thickness of the water column interposed between the radiation thermometer with the wavelength of the thermal radiation light to be detected set to 1.00 to 1.20 μm and the black body furnace is appropriately changed, and the temperature of the black body furnace is appropriately changed. It is a graph which shows an example of the result of having changed and investigated the transmittance | permeability of water. FIG. 11 shows the temperature measurement when the temperature of the measurement target temperature is 520 ° C. and the water permeability is fixed (correctly used) to correct and measure the temperature. It is a graph which shows an example of the result of having evaluated error. FIG. 12 shows that when the measurement target temperature is in the range of about 300 to 700 ° C., the thickness of the water column is 20 mm and the water permeability 0.21 when the measurement target temperature is 550 ° C. is fixed and corrected. It is a graph which shows an example of the result of having evaluated the temperature measurement error obtained when the temperature measurement value obtained by this is further corrected. 13A and 13B are explanatory views showing a state where the nozzle formed by the compression coil spring is elastically deformed. FIG. 13A shows a state where the nozzle is elastically deformed, and FIG. 13B shows a state where the nozzle is restored to its original shape. FIG. 14 is an explanatory diagram for explaining an example of a means for maintaining the distance between the steel material to be measured and the nozzle substantially constant. FIG. 15 is an explanatory diagram for explaining an example of a means for measuring the distance between the steel material to be measured and the nozzle. FIG. 16 is a graph showing an example of a result of actually measuring the temperature of the lower surface of the steel sheet by the surface temperature measuring device according to one embodiment of the present invention. FIG. 17 is a schematic diagram illustrating a schematic configuration example of a production line for hot-rolled steel sheets.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Radiation thermometer 2 ... Nozzle 11 ... Optical fiber 12 ... Temperature display part M ... Steel material to be measured (steel plate)

Claims (7)

The surface temperature of the temperature-measured steel material is measured by detecting the heat radiation emitted from the surface of the temperature-measured steel material having a surface temperature of 400 ° C. or more and 600 ° C. or less with a radiation thermometer arranged opposite to the temperature-measured steel material. A method,
The wavelength of the thermal radiation detected by the radiation thermometer is only 1.05 μm or more and 1.15 μm or less ,
The radiation thermometer radiated from the surface of the steel material to be measured is detected by the radiation thermometer through the purge water sprayed toward the surface of the material to be measured, and the thickness of the water column formed by the purge water is 50 mm or less. A method for measuring a surface temperature of a steel material.   The method for measuring the surface temperature of a steel material according to claim 1, wherein the detection element of the radiation thermometer is an InGaAs photodiode. A radiation thermometer disposed opposite to a temperature-measured steel material having a surface temperature of 400 ° C. or more and 600 ° C. or less, and the radiation thermometer radiated from the surface of the temperature-measured steel material is detected by the radiation thermometer. An apparatus for measuring the surface temperature of a hot steel material,
An optical filter that is disposed between the steel material to be measured and the detection element of the radiation thermometer, and blocks light having a wavelength less than 1.05 μm and light having a wavelength longer than 1.15 μm ;
A nozzle arranged to be spaced apart from the surface of the steel material to be measured, and jetting purge water between the surface of the steel material to be measured and the radiation thermometer,
A steel surface temperature measuring apparatus, wherein a thickness of a water column formed by the purge water is 50 mm or less . 4. The steel surface temperature measuring apparatus according to claim 3 , wherein the detection element is an InGaAs photodiode. At least a part of the surface temperature measuring device of the steel according to claim 3 or 4, characterized in that it is formed of stainless steel compression coil spring of the nozzle. The radiation thermometer includes an optical fiber having a tip portion disposed in the nozzle and having a tip surface subjected to spherical processing,
  The surface temperature measuring device according to claim 5, wherein the optical fiber receives thermal radiation light emitted from the surface of the steel material to be measured at the tip portion and transmits the received light to the detection element. Method for producing a steel material, characterized in that it comprises the step of measuring the surface temperature by the method of claim 1 or 2.

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