JPH0625382B2 - Calibration method of radiation thermometer in continuous annealing furnace. - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for calibrating a radiation thermometer in a continuous annealing furnace for accurately measuring the temperature of a steel sheet conveyed by rolls with a radiation thermometer.

[Conventional technology]

Generally, when measuring the temperature of a steel sheet by a radiation thermometer, since the radiation thermometer is a device that measures the apparent temperature by the luminance of the heat radiation of the measured object, the luminance of the heat radiation of the measured object, It is a prerequisite to know the emissivity, which is the ratio of this to the brightness of the thermal radiation of a black body at the same temperature. Therefore,
When the temperature of the DUT is calculated by correcting the radiation energy detected by a radiation thermometer calibrated in a blackbody furnace, etc., by calculating the surface emissivity of the DUT, the setting error of the surface emissivity is directly reflected as the measurement error. Become.

In the past, in order to know this emissivity, an experiment was conducted in which the temperature of a sample prepared in advance was measured by both a thermocouple and a radiation thermometer, and the emissivity was determined so that the indicated values would match. However, since emissivity is affected by surface roughness such as surface roughness and oxide film thickness, and many other factors, it takes a lot of time and effort to obtain data in the accuracy range necessary for operation. Moreover, the error due to the difference between the actual machine and the experimental device was unavoidable. Therefore, since it is very difficult to obtain an accurate emissivity value, it is not easy to improve the accuracy of temperature measurement with a radiation thermometer. Therefore, in order to reduce the temperature measurement error due to the setting error of the emissivity, there is a device used as a standard thermometer at the site, for example, “Measurement control” Vol. 34, No. 11, 1985. As disclosed in. This is a surface thermometer that measures the surface temperature by bringing the apparent emissivity close to 1 by utilizing the multiple reflection by a hemispherical bowl.

[Problems to be solved by the invention]

In the surface thermometer as described above, in order to bring the apparent emissivity close to 1, the route of radiation observation is also a problem, so the part to be subjected to multiple reflection should be stable on the measured object. Must be very close. However, when the steel plate flutters during passing like a continuous annealing furnace, not only does the measurement error increase due to changes in the emission direction of radiation, but there are also defects due to contact between the steel plate and the multiple reflection part. There is also a possibility of causing damage to the surface thermometer due to breakage of the steel plate, and there are various problems when applied to an actual machine.

The present invention has been made in view of such conventional problems, and an object thereof is to solve the above problems by calibrating the set emissivity of a radiation thermometer by the output of a thermocouple embedded in a roll. I am trying.

[Means for solving problems]

This invention embeds a thermocouple inside a roll for conveying a steel plate in a continuous annealing furnace, and based on the output from the thermocouple during the conveyance of a steel plate, radiates temperature in a continuous annealing furnace to calibrate the set emissivity of a radiation thermometer. This is the calibration method for the meter.

[Action]

Embed a thermocouple inside the steel plate transport roll, and use the roll temperature obtained from the output from the thermocouple as a reference when the steel plate is in a transport state where there is almost no difference between the steel plate temperature and the roll temperature. Thus, the set emissivity of the radiation thermometer provided near the roll can be calibrated to eliminate the setting error.

Moreover, the responsiveness is fast because the radiation thermometer measures the steel plate whose temperature fluctuates, not by the roll having thermal inertia.

〔Example〕

The present invention will be described below with reference to the drawings. 1 to 4 are views showing an embodiment of the present invention.

In FIGS. 1 and 2, 1 is a roll for conveying a steel plate provided in a continuous annealing furnace, and 2 is a thermocouple embedded in the roll. Reference numeral 5 is a steel plate wound around the roll 1, 3 is a radiation thermometer attached to the furnace wall 6 of the continuous annealing furnace, and 4 is a light-shielding tube for blocking radiant energy from other than the steel plate 5.

Now, when the temperature of the roll 1 is measured in the width direction of the steel plate by the thermocouple 2, the temperature distribution is roughly divided into three patterns in the steady state (see FIG. 3).
In the steady state, it is considered that the amount of heat flowing due to the temperature difference between the end portion and the central portion and the amount of heat flowing between the roll 1 and the steel plate 5 wound around the roll are almost equal to each other. 5 is a case where heat transfer is being performed from the roll 1 to the roll 1, and pattern B is a case where heat transfer is being performed from the roll 1 to the steel plate 5. And the pattern C is a case where there is no heat transfer in the roll 1 and the temperature of the steel plate is equal to the roll temperature. It is possible to easily calibrate the set emissivity of the radiation thermometer 3 using the roll temperature in the state of the pattern C.

In actual operation, there are many cases of pattern A and pattern B, but it is easy to set the state of pattern C by changing the operating conditions (furnace temperature, strip running speed, etc.).

Further, it is desirable to provide a plurality of thermocouples 2 to be embedded in the roll 1 in the plate width direction, but the temperature difference between the end part and the center part of the roll 1 is not so large, and therefore the temperature of the roll 1 and the steel plate temperature are not so large. When using in a situation where the difference is negligible,
There is no problem even with one.

In the case of a steady state in which the temperature distribution in the width direction of the roll 1 is uniform and there is no temperature difference from the steel plate temperature, the radiation thermometer is based on the temperature of the roll 1 obtained from the output (thermoelectromotive force) of the thermocouple 3. Calibrate the set emissivity of 3.

The reason why the temperature of the roll 1 itself is not used as the true temperature of the steel plate 5 and the calibration means of the radiation thermometer 3 is used is as follows. That is, in a steady state, if the temperature distribution in the roll is uniform, it can be considered that the roll temperature is equal to the steel plate temperature, but if the steel plate temperature changes,
This does not hold. The roll temperature in the unsteady state where the steel plate temperature fluctuates is influenced by a number of factors such as the thermal inertia of the roll, the thermal resistance between the steel plate and the roll, and the thermal boundary condition between the steel plate and the atmosphere in the continuous annealing furnace. To be done. Therefore, it is extremely difficult to find the true temperature of the steel sheet that fluctuates from the roll temperature. This is a problem when the target steel plate temperature fluctuates in a short cycle, such as in a continuous annealing furnace for general cold-rolled steel plates. If it is not possible, it will not be suitable for practical use.

In this respect, the radiation thermometer directly measures the brightness temperature of the steel sheet and thus has a good responsiveness, and if the emissivity is set correctly, a sufficiently reliable measurement value can be obtained regardless of whether it is steady or unsteady.

FIG. 4 shows an embodiment in which the set emissivity of the radiation thermometer is calibrated by the equipment having the configuration shown in FIG. This is an example of steel plate temperature measurement at the heating section outlet side when two types of materials A and B having different surface oxidizabilities are treated at the same load and the same furnace temperature in a continuous annealing furnace.

The emissivity is different between the material A and the material B, and if the emissivity set for the material A remains unchanged, a continuous error occurs in the measured value. On the other hand, as shown by the solid line, in the equipment having the emissivity calibration means according to the present invention, as shown by the solid line, a correct temperature measurement can be obtained except for the time portion required for the calibration at the joint portion of the material A and the material B. To be

〔The invention's effect〕

As described above, according to the present invention, since it has been possible to improve the measurement accuracy of the steel sheet temperature in the continuous annealing furnace, conventionally,
Considering the error of the emissivity set value, it is possible to lower the steel plate temperature that was set higher than the metallurgically necessary temperature, and to achieve an actual fuel reduction of about 5%. Was obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of the equipment of an embodiment according to the present invention, FIG. 2 is a schematic view of the inside of the roll in FIG. 1, FIG. 3 is a relationship diagram of the temperature of the roll and the steel plate, and FIG. 4 is an embodiment and a conventional example. FIG. 1 ... Roll, 2 ... Thermocouple, 3 ... Thermocouple, 5 ... Steel plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeo Onishi 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Chiba Works

Claims (1)

[Claims] 1. When measuring the temperature of a steel sheet with a radiation thermometer installed in a continuous annealing furnace, a thermocouple is embedded inside a steel sheet conveying roll in the continuous annealing furnace, and the thermocouple is conveyed during the conveyance of the steel sheet. A method for calibrating a radiation thermometer in a continuous annealing furnace, which comprises calibrating a set emissivity of the radiation thermometer based on an output from