JP2006017589A - Surface temperature measuring method and device of steel product, and manufacturing method of steel product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a temperature measurement error caused by scattering of thermal radiation light or the like generated by disturbance water existing between the surface of a steel product whose temperature is to be measured and a radiation thermometer. <P>SOLUTION: In this method, the surface temperature of the steel product M whose temperature is to be measured is measured by detecting the thermal radiation light radiated from the surface of the steel product M whose temperature is to be measured by the radiation thermometer arranged oppositely to the steel product M whose temperature is to be measured. The method is characterized by setting at 75° or more. the minimum expansion angle θ of the edge part E of the steel product M whose temperature is to be measured based on an intersection point between an interface between an optical path stable domain S1 in a domain where an optical path of the thermal radiation light detected by the radiation thermometer and an optical path unstable domain S2, and the optical axis of the radiation thermometer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and apparatus for measuring the surface temperature of a steel material by radiation temperature measurement, and a method for manufacturing a steel material by measuring the surface temperature by this method. In particular, the present invention solves the problem that radiation temperature measurement is hindered by cooling water used for heat treatment of steel materials, cooling water for rolling mills and transport rolls, etc., and even in such an environment, the steel materials are accurate. The present invention relates to a surface temperature measuring method and apparatus capable of measuring the surface temperature of steel, and a method for producing a steel material by 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 thermal 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.

  Further, by forming a water column between the temperature-measured steel plate and the radiation thermometer, and receiving radiation light from the surface of the temperature-measured steel plate through the water column with the radiation thermometer, the surface of the temperature-measured steel plate A method for measuring the surface temperature of a steel sheet, characterized in that the temperature of hot water forming the water column is set to 70 ° C. or higher and the water pressure of the hot water is set to 1 atm or lower is proposed. (For example, refer to Patent Document 3).

Also by the method described in Patent Document 3, advantages similar to those of the method described in Patent Document 2 can be obtained. However, similarly to the method described in Patent Document 2, a heating device for raising the temperature of the water column to 70 ° C. or higher is necessary, and there is a problem that the energy cost for raising the temperature of the water is increased.
Japanese Patent Publication No. 3-69974 JP-A-8-295950 JP 2003-185501 A

Summarizing the contents described above, it can be said that there are mainly the following three problems in measuring the surface temperature of a steel material by radiation temperature measurement. That is,
<First issue>
Temperature measurement error due to scattering of thermal radiation due to cooling water, steam, water vapor, etc. existing between the surface of the steel material to be measured and the radiation thermometer (hereinafter collectively referred to as disturbance water) (Referred to as scattering error as appropriate).
<Second problem>
To suppress temperature measurement error (hereinafter referred to as cooling error as appropriate) due to cooling of the steel surface without raising the temperature of purge water (water column) for temperature measurement.
<Third issue>
Suppressing temperature measurement errors (hereinafter referred to as absorption errors as appropriate) caused by absorption of thermal radiation by disturbance water (including the need for measuring the thickness of the water column).

  Scattering error is caused when the interface between water and air such as water droplets or steam is present in the optical path of the thermal radiation to be detected by the radiation thermometer, and the thermal radiation is refracted or scattered and the optical path changes. Arise. Such a change in the optical path includes a case where the entire beam of the thermal radiation light is bent, and a case where the beam is expanded or converged in whole or in part. In general, due to such a change in the optical path, the position and area of the measurement region on the surface of the steel material to be measured that is to be measured by the radiation thermometer change, or heat from a region other than the measurement region partially. Temperature detection error occurs due to detection of synchrotron radiation. Such a scattering error is not necessarily caused only by the disturbance water existing between the steel material to be measured and the radiation thermometer, but the disturbance of the purge by the disturbance water causes the thermal radiation light to be detected in the purge. The optical path may be disturbed, or the optical path of the thermal radiation to be detected in the purge or at the purge interface may be disturbed depending on the performance of the purge itself.

  Here, the inventors of the present invention have intensively studied that when the surface of the steel material to be measured has a certain extent of isothermal surface, the optical path stability region of the heat radiation light due to the purge is not necessarily measured. It has been found that it is not necessary to reach the surface of the hot steel material. In other words, even when the optical path is disturbed near the surface of the steel material to be measured due to disturbance water or the like, the disturbance of the optical path is limited to the vicinity of the surface of the steel material to be measured, and the surface of the steel material to be measured can be regarded as being isothermal to some extent. It has been found that if there is a spread, the thermal radiation light from this isothermal surface is mainly detected, and the temperature measurement error, that is, the scattering error is suppressed. More specifically, for example, as shown in FIG. 1, an optical path stable region where the optical path is not disturbed by disturbance water or the like such as in a purge nozzle is brought close to a temperature-measured steel material to be measured to some extent. It was found that the scattering error can be suppressed to the extent that there is no problem if the optical path instability region is suppressed in the vicinity of the surface of the steel material to be measured. The present invention has been completed based on the knowledge of the inventors of the present invention.

  That is, in order to solve the first problem, according to the present invention, the heat radiation emitted from the surface of the steel material to be measured is arranged opposite to the steel material to be measured, as described in claim 1 of the claims. A method of measuring a surface temperature of a steel material to be measured by detecting with a radiation thermometer, wherein an optical path stable region and an optical path unstable region in a region through which an optical path of thermal radiation detected by the radiation thermometer passes A method for measuring the surface temperature of a steel material is characterized in that the minimum spread angle of the edge portion of the steel material to be measured is set to 75 ° or more with reference to the intersection between the interface of the radiation thermometer and the optical axis of the radiation thermometer. It is.

  According to such an invention, the optical path instability region is suppressed in the vicinity of the surface of the steel material to be measured, and the scattering error can be suppressed to the extent that there is no problem. The “optical path stable region” means a region where the optical path does not vary among regions through which the optical path of the thermal radiation detected by the radiation thermometer passes. In contrast, the “optical path unstable region” means a region where the optical path fluctuates. The “minimum divergence angle of the temperature-measured steel edge with respect to the intersection” refers to the temperature-measured steel from the intersection of the interface between the optical path stable region and the optical path unstable region and the optical axis of the radiation thermometer. It means the smallest angle among the angles formed by the perpendicular line dropped on the surface and the straight line connecting the intersection and the temperature-measured steel material edge.

  More specifically, the “optical path stable region” is, for example, a region from the tip of a purge nozzle that ejects liquid or gas to the light receiving surface of the radiation thermometer (in contrast, the optical path unstable region is The region from the nozzle tip to the surface of the steel material to be measured may be considered. In this case, in order to suppress the scattering error to the extent that there is no problem, the minimum spread angle of the temperature-measured steel material edge portion with the nozzle tip as a reference may be set to 75 ° or more. The “optical path stable region” is the region from the tip of the liquid or gas potential core ejected from the purge nozzle to the light receiving surface of the radiation thermometer (in contrast, the optical path unstable region is the temperature measured from the tip of the potential core. It may be regarded as a region up to the steel surface. In this case, in order to suppress the scattering error to the extent that there is no problem, the minimum spread angle of the temperature-measured steel material edge portion with respect to the potential core tip may be set to 75 ° or more. Furthermore, when adopting a configuration for detecting thermal radiation light through a waveguide such as an optical fiber, the “optical path stability region” is the region from the waveguide tip to the light receiving surface of the radiation thermometer (inversely, the optical path instability region). Can also be considered as a region from the tip of the waveguide to the surface of the steel material to be measured. In this case, in order to suppress the scattering error to the extent that there is no problem, the minimum divergence angle of the temperature-measured steel material edge portion with respect to the waveguide tip may be set to 75 ° or more.

  Next, the inventors of the present invention, in particular, when performing radiation temperature measurement on the lower surface of the measured temperature steel material, more specifically, the thermal radiation emitted from the lower surface of the measured temperature steel material, the lower surface of the measured temperature steel material In the case of measuring the surface temperature of the steel material to be measured by detecting with a radiation thermometer disposed below the steel material to be measured through the purge water jetted from the nozzle toward the first, the first problem is We studied earnestly to solve it. As a result, considering that the disturbance water has fallen directly above the nozzle, if the disturbance water flow rate at the nozzle tip is too large compared to the purge water flow rate, the disturbance of the purge water due to the disturbance water extends into the nozzle. It has been found that the temperature measurement error (scattering error) may increase due to the spread of the unstable region. To prevent this, the flow rate of the purge water at the nozzle tip should be about the same as or higher than the flow rate of the disturbance water, but the maximum velocity in the direction of the disturbance water drop is the distance from the pass line to the nozzle tip. Determined. Therefore, it can be seen that in order to suppress the scattering error as described above, it is sufficient to apply energy to the purge water to blow up to a height in the vicinity of the pass line.

  In addition, as described above, the inventors of the present invention provide the temperature-measured steel material via the purge water sprayed from the nozzle toward the temperature-measured steel material lower surface with the heat radiation emitted from the temperature-measured steel material lower surface. In the case where the surface temperature of the steel material to be measured is measured by detecting with a radiation thermometer arranged oppositely below, a intensive study was made to solve the second problem. As a result, when the purge water collides with the lower surface of the temperature-measured steel material, the collided area is cooled, but if this collision pressure is kept below a predetermined value, cooling is suppressed even if the purge water is at room temperature. I found out.

The present invention arranges the findings of the inventors of the present invention described above with the concept of a total head derived from Bernoulli's equation and defined by the sum of velocity head, pressure head and position head. As a result, it was completed. That is, in order to solve the first and second problems, as described in claim 2 of the present invention, the present invention uses heat radiated light emitted from the lower surface of the measured temperature steel material as the measured temperature steel material. A method for measuring a surface temperature of a steel material to be measured by detecting with a radiation thermometer disposed below the steel material to be measured through purge water jetted from a nozzle toward the bottom surface. The present invention provides a method for measuring the surface temperature of a steel material, characterized in that all the heads Ht (m) of the purge water satisfying the following formula (1) with respect to the position of the pass line of the steel material.
-0.36Hg <Ht <0.05 (1)
However, Hg (m) means the separation distance between the pass line (the lowest position that the lower surface of the steel material to be measured can take) and the tip of the nozzle.
More preferably, −0.36Hg <Ht <0.01.

  According to such an invention, by setting the total head Ht of purge water to be larger than −0.36 Hg, the disturbance of the purge water due to the disturbance water is caused by the disturbance water even when the disturbance water has fallen directly above the nozzle. The temperature measurement error (scattering error) does not increase. On the other hand, by making the total head Ht of the purge water smaller than 0.05 (more preferably smaller than 0.01), the collision pressure of the purge water against the lower surface of the steel material to be measured is suppressed, and the purge water is kept at room temperature. Even if it exists, it is possible to suppress cooling. Note that “using the pass line of the steel material to be measured as a position reference” means that the position head (potential head) of the purge water in the pass line is set to 0 (m).

  An absorption error is an error caused by absorption of thermal radiation to be detected by disturbance water. In other words, the temperature to be measured depends on the conditions of the cooling water, fluctuations in the pass line of the steel to be measured (position fluctuation in the vertical direction on the bottom surface of the steel to be measured), presence or absence of steam due to changes in ambient temperature and humidity, etc. The amount (thickness) of disturbance water existing between the steel material and the radiation thermometer changes, and the degree of absorption and attenuation of thermal radiation by the disturbance water changes accordingly. An error occurs due to fluctuations.

  Here, the inventors of the present invention have intensively studied that, if the wavelength of the thermal radiation detected by the radiation thermometer is limited to a predetermined value or less, the temperature measurement caused by the change in the thickness of the disturbance water. It has been found that the error can be reduced and the thickness measuring device for the water column can be made unnecessary even when the radiation temperature is measured through the water column. The present invention has been completed based on the knowledge of the inventors of the present invention.

  That is, in order to further solve the third problem, according to the present invention, the wavelength of the thermal radiation detected by the radiation thermometer is 0.9 μm or less as described in claim 3. Is preferred.

  According to such an invention, as will be described later, it is possible to reduce a temperature measurement error associated with a change in the thickness of disturbance water. More preferably, the wavelength of the thermal radiation detected by the radiation thermometer is 0.85 μm or less.

  In addition, this invention is equipped with the radiation thermometer arrange | positioned facing temperature-measured steel materials as described in Claim 4 of a claim, The thermal radiation light radiated | emitted from the surface of temperature-measured steel materials is said radiation temperature. An apparatus for measuring a surface temperature of a steel material to be measured by detecting with a meter, and an interface between an optical path stable region and an optical path unstable region in a region through which an optical path of thermal radiation detected by the radiation thermometer passes Further, the present invention is also provided as a steel surface temperature measuring device in which the minimum spread angle of the temperature-measured steel material edge portion based on the intersection of the radiation thermometer and the optical axis of the radiation thermometer is set to 75 ° or more.

Further, according to the present invention, as set forth in claim 5, the radiation thermometer disposed opposite to the lower surface of the steel material to be measured, and the purge water between the lower surface of the steel material to be measured and the radiation thermometer. A device for measuring the surface temperature of the steel material to be measured by detecting thermal radiation emitted from the bottom surface of the steel material to be measured by the radiation thermometer through the purge water. In addition, all the heads Ht (m) of the purge water with the pass line of the steel material to be measured as a position reference satisfy the following formula (1), and the steel surface temperature measuring device is also provided. .
-0.36Hg <Ht <0.05 (1)
However, Hg (m) means a separation distance between the pass line and the nozzle tip.
More preferably, −0.36Hg <Ht <0.01.

  Preferably, as described in claim 6, the steel surface temperature measuring device has a wavelength longer than 0.9 μm between the steel material to be measured and the detection element of the radiation thermometer. An optical filter that blocks light is provided.

  The present invention is also provided as a method for producing a steel material, characterized in that the surface temperature is measured by the method according to any one of claims 1 to 3 as described in claim 7. The

  According to the present invention (the invention according to claim 1), the interface between the optical path stable region and the optical path unstable region in the region through which the optical path of the thermal radiation detected by the radiation thermometer passes, the optical axis of the radiation thermometer, By setting the minimum divergence angle of the temperature-measured steel edge relative to the intersection of the above to 75 ° or more, the optical path instability region is suppressed in the vicinity of the surface of the temperature-measured steel and the scattering error is not problematic. It is possible to suppress. Further, according to the present invention (the invention according to claim 2), even if the disturbance water falls directly above the nozzle by making all the heads Ht of the purge water larger than -0.36Hg, The disturbance of the purge water due to the disturbance water does not reach the nozzle so much, and the temperature measurement error (scattering error) does not increase. On the other hand, by making the total head Ht of the purge water smaller than 0.05 (more preferably smaller than 0.01), the collision pressure of the purge water against the lower surface of the steel material to be measured is suppressed, and the purge water is kept at room temperature. Even if it exists, it is possible to suppress cooling.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings as appropriate.
<First Embodiment>
As shown in FIG. 2, the surface temperature measuring apparatus according to the present embodiment includes a radiation thermometer 1 disposed opposite to a steel material to be measured (a steel plate M in the present embodiment), and radiates from the surface of the steel plate M. This is a device for measuring the surface temperature of the steel sheet M by detecting the emitted thermal radiation light with the radiation thermometer 1. Moreover, the surface temperature measuring apparatus according to the present embodiment includes a nozzle 2 for injecting a purging liquid or gas toward the surface of the steel sheet M, and the optical axis of the radiation thermometer 1 passes through the nozzle 2. It is configured as follows.

  As shown in FIG. 3, the radiation thermometer 1 includes a temperature measuring head 11, an optical window 12 attached to the tip of the temperature measuring head 11, and a steel plate housed in the temperature measuring head 11 through the optical window 12. A light receiving optical system (which is an optical system for adjusting a detection field of view and configured by a lens, a field stop, etc.) 13, a control panel 14, and a light receiving optical system 13 that receives thermal radiation from M. And an optical fiber 15 for transmitting the heat radiation light to the control panel 14. In the control panel 14, a detection unit 141 including a detection element such as a Si photodiode that photoelectrically converts heat radiation light transmitted by the optical fiber 15 and outputs a current corresponding to the amount of light, and the detection unit 141. After the output current is amplified, a calculation unit 142 that performs current-voltage conversion and AD conversion and converts it to temperature, and an output unit 143 for outputting the temperature data converted by the calculation unit 142 to the outside are arranged. Yes.

  The nozzle 2 is connected to the tip of the temperature measuring head 11 and is configured to inject purge water, air, or the like from the tip toward the surface of the steel sheet M by flowing purge water, air, or the like from the outside.

  In addition, about the radiation thermometer 1 and the nozzle 2, since a well-known structure is applicable variously, the description is abbreviate | omitted about a more detailed structure.

  Here, the surface temperature measuring apparatus according to the present embodiment includes an interface between the optical path stable region S1 and the optical path unstable region S2 in the region through which the optical path of the thermal radiation detected by the radiation thermometer passes, and the radiation thermometer. It is characterized in that the minimum spread angle θ of the edge portion E of the steel plate M with respect to the intersection point P with the optical axis is set to 75 ° or more. More specifically, the vicinity of the nozzle 2 of the surface temperature measuring apparatus according to the present embodiment is in the form shown in any of FIGS. In the case shown in FIG. 1 (injecting purge water from the tip of the nozzle 2), the optical path stability region S1 is a region from the tip of the nozzle 2 to the light receiving surface of the radiation thermometer, and the optical path unstable region S2 is the nozzle. 2 It can be considered that the region extends from the tip to the surface of the steel plate M. Further, in the case shown in FIG. 4 (injecting air from the tip of the nozzle 2), the optical path stable region S1 is from the tip of a stable purge region called a potential core C generated by the air injected from the nozzle 2. It becomes a region to the light receiving surface of the radiation thermometer, and the optical path unstable region S2 can be considered to be a region from the tip of the potential core C to the surface of the steel plate M. Furthermore, the mode shown in FIG. 5 is a configuration that detects thermal radiation light via a waveguide F such as an optical fiber that protrudes from the tip of the nozzle 2 toward the steel plate M (more specifically, for example, in FIG. In this case, the optical path stability region S1 is a region from the front end of the waveguide F to the light receiving surface of the radiation thermometer. Thus, the optical path unstable region S2 can be considered as a region from the front end of the waveguide F to the surface of the steel plate M. 1, 4, and 5, the minimum spread angle θ of the steel plate M edge portion E with respect to the intersection P is a perpendicular line from the intersection P to the surface of the steel plate M, and the intersection P and the steel plate. It means the smallest angle among the angles formed by the straight line connecting the edge portion E of M.

  Hereinafter, a test carried out to determine the minimum divergence angle θ will be described. As shown in the outline of the test in FIG. 6, the plane light source L with uniform brightness is considered as the steel material to be measured, and purged with water sprayed from the nozzle 2 between the plane light source L and the radiation thermometer. Then, a test was conducted in which the purge water was disturbed by disturbance water jetted from the side. And the output change of the radiation thermometer before and behind injecting disturbance water was investigated, changing the positional relationship of this disorder | damaging position (position of nozzle 2 front-end | tip) and the planar light source L variously.

  FIG. 7 shows the test results. Here, the horizontal axis of FIG. 7 plots the spread angle θ when the region from the tip of the nozzle 2 to the flat light source L is the optical path unstable region S2, and the vertical axis is a radiation thermometer before and after injecting disturbance water. Was plotted as a temperature measurement error. As shown in FIG. 7, it has been found that if the spread angle θ is set to 75 ° or more, the temperature measurement error can be suppressed to 10 ° C. or less. Therefore, also in the embodiment shown in FIGS. 1, 4 and 5, the spread angle θ is set to 75 ° or more.

  According to the surface temperature measuring apparatus according to the present embodiment described above, the interface between the optical path stable region S1 and the optical path unstable region S2 in the region through which the optical path of the thermal radiation detected by the radiation thermometer passes, and the radiation temperature. By setting the minimum divergence angle of the steel plate M edge E based on the intersection point P with the optical axis of the meter to 75 ° or more, the optical path unstable region S2 is suppressed in the vicinity of the surface of the steel plate M, and scattering errors are a problem. (The temperature measurement error is 10 ° C. or less).

  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.

<Second Embodiment>
The surface temperature measuring apparatus according to the present embodiment is also similar in configuration to the above-described configurations shown in FIGS. 1 to 5, and a radiation thermometer disposed opposite to the lower surface of the steel material to be measured (steel plate M in the present embodiment). 1 and a nozzle 2 for injecting purge water between the lower surface of the steel plate M and the radiation thermometer 1, and the radiation thermometer 1 radiates heat radiation emitted from the lower surface of the steel plate M through the purge water. It is a device that measures the surface temperature of the steel sheet M by detecting it. However, the surface temperature measuring apparatus according to the present embodiment injects the purge water so that all the purge water heads Ht (m) satisfying the following formula (1) with the pass line of the steel plate M as a position reference. It is characterized by the configuration.
-0.36Hg <Ht <0.05 (1)
However, Hg (m) means a separation distance between the pass line and the nozzle tip. Further, “using the pass line of the steel plate M as a position reference” means that the position head (potential head) of purge water in the pass line is set to 0 (m). More preferably, −0.36Hg <Ht <0.01.

  Hereinafter, the reason why the purge water ejected from the nozzle 2 is set so as to satisfy the condition of the above formula (1) will be described.

  First, the conditions of the water temperature and flow rate of the purge water injected from the nozzle 2 were changed as appropriate, and a test for investigating the surface temperature drop of the steel plate M during running (steel plate speed 600 mpm to 1200 mpm) was performed. In addition, the surface temperature fall of the steel plate M is the temperature measured by the normal radiation thermometer (without purge water) arranged opposite to the upper surface of the steel plate M and the radiation temperature according to the present embodiment arranged opposite to the lower surface of the steel plate M. It was calculated by the difference from the temperature measurement value via purge water by the total 1. FIG. 8 shows the test results. Here, the horizontal axis of FIG. 8 plots the collision pressure of purge water in the pass line of the steel plate M (calculated value calculated from the flow rate of purge water and the distance between the nozzle tip and the pass line) logarithmically, and the vertical axis represents The amount of temperature drop on the surface of the steel sheet M (corresponding to cooling error) was plotted. As shown in FIG. 8, when the collision pressure is 0 (that is, when the purge water does not contact the lower surface of the steel plate M), the lower surface of the steel plate M is not cooled, but the amount of temperature decrease is increased as the collision pressure increases. That is, it can be seen that the cooling error also increases. The increase in the temperature measurement error is more remarkable when the temperature of the purge water is lower. However, if the impact pressure of the purge water on the lower surface of the steel plate M is 0.5 KPa or less, the influence of the water temperature is poor, and even at room temperature (20 ° C.), the cooling error is 10 ° C. or less (more preferably, It was found that if the collision pressure is 0.1 KPa or less, the cooling error is 5 ° C. or less).

  On the other hand, the ratio of the flow rate of the purge water sprayed from the nozzle 2 and the flow rate of the disturbance water that has fallen directly above the nozzle 2 (hereinafter referred to as a flow rate ratio as appropriate) at the tip of the nozzle 2 is changed as appropriate. A test was conducted to investigate the effect on temperature measurement error (temperature measurement error based on the absence of disturbance water). More specifically, as in the first embodiment described above, the flat light source L with uniform brightness shown in FIG. 6 is considered as the steel plate M to be measured, and a nozzle is provided between the flat light source L and the radiation thermometer. The temperature was measured while purging with water jetted from 2. Then, the disturbance water is dropped from the lower surface of the planar light source L (corresponding to the pass line) toward the tip of the nozzle 2 and the position of the nozzle 2 tip is appropriately changed in the vertical direction (thereby causing disturbance water at the tip of the nozzle 2). The flow rate ratio was changed by changing the flow rate), and the relationship between the flow rate ratio and the temperature measurement error of the steel plate M (simulated by the flat light source L) was investigated. FIG. 9 shows the test results. Here, the horizontal axis of FIG. 9 plots the ratio of the flow rate of purge water to the flow rate of disturbance water, and the vertical axis plots temperature measurement error (corresponding to scattering error). As shown in FIG. 9, it was found that the temperature measurement error (scattering error) becomes 10 ° C. or less when the flow rate ratio between the purge water and the disturbance water is 0.8 or more.

  Next, the results shown in FIGS. 8 and 9 were arranged in terms of the total head. The organized results are shown in FIG. Here, the horizontal axis of FIG. 10 plots all the heads Ht of the purge water with the pass line of the steel plate M as a reference, and the vertical axis plots the temperature measurement error. In FIG. 10, the data plotted with “x” is obtained by extracting the maximum value of the cooling error (temperature decrease amount) for each collision pressure with respect to all the data of the water temperature 20 ° C. to 60 ° C. in FIG. The pressure is converted into all the heads Ht of the purge water with the pass line of the steel plate M as the position reference, and the maximum value of the extracted cooling error corresponding to the converted all heads Ht is plotted. That is, the data plotted with “×” is data indicating the relationship between all the heads Ht and the cooling error. In addition, as a method of converting each collision pressure shown in FIG. 8 to all the heads Ht, when the steel plate M is not running, the height at which the purge water from which each collision pressure is obtained reaches (position of the pass line) The height (reference height) was measured, and the height was used as the total head Ht corresponding to each collision pressure. This is because the speed head and the pressure head are both zero at the height at which the purge water reaches when the steel plate M is not running (the reached height), and therefore the reached height as the position head is the total head. This is because it corresponds to Ht. In FIG. 10, data in which all heads Ht are less than 0 among data plotted with “x” is not data obtained directly from FIG. 8. The fact that all the heads Ht are less than 0 means that the purge water and the steel plate M are not in contact with each other, so that the cooling error (temperature decrease amount) is naturally zero, and is plotted.

  The data plotted with “□” is plotted based on a polygonal line ABC approximating the relationship between the flow rate ratio and the scattering error (temperature measurement error) shown in FIG. That is, each flow rate ratio along the polygonal line ABC is converted into all the heads Ht of purge water with the pass line of the steel plate M as a position reference, and the same data as the data plotted with “x” among all the converted heads Ht. Only all heads Ht are extracted, and scattering errors corresponding to the extracted all heads Ht are plotted. In addition, as a method of converting each flow rate ratio shown in FIG. 9 to all the heads Ht, when there is no flat light source L (simulating the steel plate M), the height at which the purge water obtained by each flow rate ratio reaches ( A method was used in which a pass line (height with respect to the lower surface of the planar light source L) as a position reference was measured and the height was set to all the heads Ht corresponding to the respective flow rate ratios.

  Furthermore, the data plotted with “●” is a plot of the square root of the square sum of the cooling error (data plotted with “×”) and the scattering error (data plotted with “□”) for each head Ht. It is.

  As shown in FIG. 10, when all the heads Ht of the purge water satisfy the condition of −0.0144 <Ht <0.05, the temperature measurement error (data plotted by “●”) is 10 ° C. or less. I understood. More specifically, when disturbance water falls from the pass line directly above the nozzle 2 by making all the heads Ht of the purge water larger than −0.0144 (boundary line indicated by D in FIG. 10). Even so, the disturbance of the purge water due to the disturbance water does not reach the nozzle 2 so much, and the temperature measurement error (scattering error) can be 10 ° C. or less. On the other hand, by making the total head Ht of purge water smaller than 0.05 (boundary line indicated by E in FIG. 10) (more preferably, smaller than 0.01 (boundary line indicated by F in FIG. 10)), The collision pressure of the purge water against the lower surface of the steel plate M is suppressed, and a temperature measurement error (cooling error) can be suppressed.

  The value of −0.0144 that defines the lower limit of all the heads Ht is a value when the separation distance Hg between the pass line and the nozzle tip is 0.04 (m), and is generally −0. It can be considered that it is defined by .36 Hg. This is because when the flow rate ratio between purge water and disturbance water is 0.8 (see FIG. 9) at the tip of the nozzle 2, the distance from the tip of the nozzle 2 to the pass line and the top of the purge water from the tip of the nozzle 2 This is because the position head of the purge water at the top is represented by −0.36 Hg (both the pressure head and the velocity head are 0) based on the pass line. The value 0.05 defining the upper limit of all the heads Ht corresponds to the value of all the heads when the top of the purge water is jetted so as to be located 50 mm above the pass line. The collision pressure at the pass line position is 0.5 KPa (a value of 0.01 that defines a more preferable upper limit of all the heads Ht is the value when the top of the purge water is jetted 10 mm above the pass line. This corresponds to the value of all the heads, and at this time, the collision pressure at the pass line position of the purge water is 0.1 KPa). The position of the lower surface of the steel plate M in the hot rolling line is a normal pass line (the lowermost position that can be taken by the lower surface of the steel plate M to be transported, and the top position of the transport roll corresponds to this) as a lower limit. Since it fluctuates within a range of about 30 mm upward, the upper limit of all heads Ht is regulated to 0.05, so that the collision pressure of purge water within the fluctuating range becomes 0.5 kPa or less (as a more preferable aspect, If the upper limit of the head Ht is defined as 0.01, the collision pressure of purge water within the fluctuation range becomes 0.1 kPa or less), and the cooling error can be reduced (see FIG. 8).

  It should be noted that the configurations of the first and second embodiments described above are combined (in the configuration of the second embodiment, the optical path stability region and the optical path in the region through which the optical path of the thermal radiation detected by the radiation thermometer passes). Both the scattering error and the cooling error can be reduced by setting the minimum spread angle of the edge of the steel material to be measured to 75 ° or more based on the intersection of the interface with the stable region and the optical axis of the radiation thermometer. It is preferable in that it can be performed. In the first and second embodiments described above, an optical filter that blocks light having a wavelength longer than 0.9 μm between the steel plate M and the detection element (photodiode, etc.) of the radiation thermometer. More preferably, the optical filter is preferably provided with an optical filter that blocks light having a wavelength longer than 0.85 μm. More specifically, the optical filter is preferably provided between the detection unit 141 disposed in the control panel 14 and the output end of the optical fiber 15. The reason will be described below.

  In the rolling / cooling process of a steel material, a general steel material management temperature is from room temperature to 1200 ° C., and particularly in a low alloy steel material, a temperature history of 500 ° C. to 1200 ° C. may be important. In radiation temperature measurement for such a temperature range, a radiation thermometer using a Si photodiode that detects light having a wavelength of 0.65 μm to 1.1 μm is generally used.

  FIG. 11 shows the results of measuring the spectral absorption characteristics of water. As shown in FIG. 11, in an effective detection wavelength range of Si photodiode, which is 0.65 to 1.1 μm, a longer wavelength is more strongly absorbed. On the other hand, the heat radiation light from the black body has a long wavelength and extremely high intensity of the heat radiation light, and is longer than, for example, a wavelength shorter than 0.9 μm at a temperature of 600 to 700 ° C. or lower. Strongly radiated at a wavelength. Therefore, the light energy detected by the radiation thermometer is largely influenced by light of a long wavelength, and is strongly influenced by the absorption of water. The same applies to a radiation thermometer using a detector other than a Si photodiode if the effective detection wavelength is in the range of 0.65 to 1.1 μm.

  FIG. 12 shows a change in temperature measurement value (temperature measurement error) when the effective thickness of water existing between the radiation thermometer and the temperature-measured steel material varies by 30 mm in the temperature-measured steel material of about 700 ° C. The measurement results are shown. In a production line for hot-rolled steel plates and thick steel plates, in a steady production state, the maximum variation in the pass line of the steel plate (the positional variation in the vertical direction of the lower surface of the steel plate) may be about 30 mm.

  Here, the horizontal axis of FIG. 12 plots the thickness of water existing between the radiation thermometer and the steel material to be measured, and the vertical axis plots the temperature measurement error. As shown in FIG. 12, in the case of “no filter” (when light of all wavelengths is detected without blocking the long wavelength component), for example, the thickness is 30 mm with respect to the reference thickness of 200 mm. If it fluctuates, a temperature measurement error of about 14 ° C. occurs (the temperature measurement value changes by about 14 ° C.). In addition, when the long wavelength component is not cut off, if the thickness of the reference water is increased, the temperature measurement error is reduced. However, in order to obtain a temperature measurement error of 10 ° C. or less, for example, a water thickness of 400 mm or more is necessary. It becomes. In addition, when the surface temperature of the steel material to be measured increases, this temperature measurement error increases, and it is necessary to further increase the thickness of water. However, since the device for increasing the thickness of water becomes unnecessarily large, there is a problem in greatly restricting the installation conditions.

  On the other hand, as shown in FIG. 12, in the case of a “cutoff wavelength of 0.85 μm” (when detecting light with a wavelength longer than the wavelength of 0.85 μm), regardless of the thickness of the reference water, Even if the thickness varies by 30 mm, it is possible to suppress the temperature measurement error to about 6 ° C.

  FIG. 13 shows each cutoff wavelength (when the thickness of water used as a reference is 50 mm to 300 mm and the thickness is changed by 30 mm with respect to the thickness of water used as a reference for a steel material to be measured at 700 ° C. The result of measuring the temperature measurement error (absorption error) according to the upper limit of the wavelength detected by the radiation thermometer is shown. Moreover, FIG. 14 shows the measurement corresponding to each cutoff wavelength when the thickness of the reference water is 200 mm, the temperature of the steel material to be measured is changed from 500 ° C. to 1000 ° C., and the water thickness is changed by 30 mm. The result of measuring the temperature error (absorption error) is shown. As shown in FIG. 13 or FIG. 14, when the cutoff wavelength is longer than 0.90 μm, the temperature measurement error starts to increase. As shown in FIG. 14, when detecting light having a wavelength of 0.90 μm or less, even when the temperature-measured steel material is 1000 ° C., the temperature measurement error can be suppressed to about 12 ° C. (0.85 μm or less). In the case of detecting light of a wavelength of (2), it is effective in that the temperature measurement error can be suppressed to 10 ° C. or less. For the above reasons, in the first and second embodiments, an optical filter (more preferably, 0 mm) that blocks light having a wavelength longer than 0.9 μm between the steel plate M and the detection element of the radiation thermometer. It is preferable to provide an optical filter that blocks light having a wavelength longer than .85 μm.

  The optical filter that blocks light having a wavelength longer than 0.9 μm (more preferably, longer than 0.85 μm) is a filter that completely blocks light having a wavelength longer than 0.9 μm (or 0.85 μm). It does not mean only a filter that cuts off (that is, the transmittance is 0%), but a filter that has a transmittance set to be smaller than 2 to 3% for light of the long wavelength.

  The preferred configuration described above can be applied not only when water is used as a purge but also when a gas such as air is used as a purge. In the case of purging with air, disturbance water may enter the purge area to some extent, but if the variation in the effective thickness of water in the optical path is 30 mm or less, the detection wavelength is set to 0.9 μm or less. Absorption errors due to disturbance water can be suppressed (preferably by setting it to 0.85 μm or less). Further, even when water is present only in the vicinity of the steel material to be measured, such as when a water film is formed on the surface of the steel plate M regardless of the purge, it is possible to suppress the influence of the water film.

  According to the above preferred configuration, since a conventional water column thickness measuring device is not required, the size and weight of the surface temperature measuring device can be reduced (the configuration shown in FIG. 3 is a schematic diagram when the preferred configuration is adopted). As well as easy removal and excellent maintainability, and further, there is no concern about the failure of the thickness measuring device, thereby increasing the reliability.

  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. 15 is a schematic diagram illustrating a schematic configuration example of a production line for hot-rolled steel sheets.
As shown in FIG. 15, when manufacturing a hot-rolled steel sheet, first, the slab is 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. 15). 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. 15). 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 apparatus based on this invention above a steel plate, and to measure temperature (application 3 of FIG. 15). 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. 15). 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.

  Further, 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. 15). 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 schematic diagram showing a configuration in the vicinity of a purge nozzle in a surface temperature measuring apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a schematic configuration of a surface temperature measuring apparatus according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing an internal configuration of the surface temperature measuring apparatus shown in FIG. FIG. 4 is a schematic diagram showing another configuration in the vicinity of the purge nozzle in the surface temperature measuring apparatus according to one embodiment of the present invention. FIG. 5 is a schematic diagram showing still another configuration in the vicinity of the purge nozzle in the surface temperature measuring apparatus according to one embodiment of the present invention. FIG. 6 is an explanatory diagram for explaining an outline of a test for investigating the influence of disturbance of the optical path caused by disturbance water on the temperature measurement value. FIG. 7 is a graph showing the results of the test shown in FIG. FIG. 8 is a graph showing the influence of the temperature of the purge water and the collision pressure on the temperature measurement value. FIG. 9 is a graph showing the influence of the ratio of the purge water flow rate to the disturbance water flow rate on the temperature measurement value. FIG. 10 is a graph showing the influence of all the purge water heads on the temperature measurement value. FIG. 11 shows the results of measuring the spectral absorption characteristics of water. FIG. 12 is a graph showing the relationship between water thickness and temperature measurement error. FIG. 13 is a graph showing the relationship between the cutoff wavelength and the temperature measurement error. FIG. 14 is another graph showing the relationship between the cutoff wavelength and the temperature measurement error. FIG. 15 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 M ... Temperature-measured steel material (theta) ... Minimum spreading angle of steel material edge part S1 ... Optical path stable area S2 ... Optical path unstable area

Claims (7)

It is a method for measuring the surface temperature of a temperature-measured steel material by detecting the thermal radiation emitted from the surface of the temperature-measured steel material with a radiation thermometer arranged opposite to the temperature-measured steel material,
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 stable region and the optical path unstable region in the region through which the optical path of the thermal radiation detected by the radiation thermometer passes A method for measuring the surface temperature of a steel material, wherein the minimum spread angle is set to 75 ° or more. By detecting the thermal radiation emitted from the lower surface of the measured temperature steel material with 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, A method for measuring the surface temperature of a steel material to be measured,
A method for measuring the surface temperature of a steel material, wherein all the heads Ht (m) of the purge water satisfying the following formula (1) with the pass line of the steel material to be measured as a position reference.
-0.36Hg <Ht <0.05 (1)
However, Hg (m) means a separation distance between the pass line and the nozzle tip.   The method for measuring the surface temperature of a steel material according to claim 1 or 2, wherein the wavelength of the thermal radiation detected by the radiation thermometer is 0.9 µm or less. A device that measures the surface temperature of the steel material to be measured by detecting the thermal radiation emitted from the surface of the steel material to be measured with the radiation thermometer. There,
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 stable region and the optical path unstable region in the region through which the optical path of the thermal radiation detected by the radiation thermometer passes An apparatus for measuring the surface temperature of steel, wherein the minimum spread angle is set to 75 ° or more. A radiation thermometer disposed opposite to the surface of the steel to be measured, and a nozzle for injecting purge water between the surface of the steel to be measured and the radiation thermometer, and heat radiation radiated from the surface of the steel to be measured An apparatus for measuring the surface temperature of a steel material to be measured by detecting light with the radiation thermometer through the purge water,
An apparatus for measuring the surface temperature of a steel material, wherein all the heads Ht (m) of the purge water satisfying the following formula (1) with the pass line of the steel material to be measured as a position reference.
-0.36Hg <Ht <0.05 (1)
However, Hg (m) means a separation distance between the pass line and the nozzle tip.   6. The surface temperature of the steel material according to claim 4, further comprising an optical filter that blocks light having a wavelength longer than 0.9 μm between the steel material to be measured and the detection element of the radiation thermometer. measuring device.   A surface temperature is measured by the method in any one of Claim 1 to 3, The manufacturing method of the steel materials characterized by the above-mentioned.

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