JPS6196425A - Measuring method of steel plate temperature - Google Patents

Abstract

PURPOSE:To ensure a high accuracy by arranging a radiation thermometer inclined to the normal direction of the surface in one part of steel plate of the travelling steel plates in parallel and by elevating the apparent emissivity by the multipath reflection of the radiation caused on the opposing surface. CONSTITUTION:The multipath reflection caused between the upper part steel plate 11A and lower part steel plate 11A being wound by the plate pass roll inside a furnace wall 12 is detected by the radiation temp. detector 14 which is arranged with inclination at the angle theta to the normal direction of the surface of the steel plate 11B. The installation angle theta is set in the range of 7-20 deg. so as to make the multipath reflection times >=six times and the peak value of the output of a detector 14 is outputted to a display recording device 19 via a radiation ray temp. convertor 18 with mechanically scanning the detector 14 by a driving device 16. The measurement of high accuracy is thus enabled by so making that the apparent emissivity by the multipath reflection of the steel plate is elevated and the maximum value of the multipath reflection is caught.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a steel plate thermometer 414 method.

[Prior Art] Conventionally, many radiation thermometers have been used that can measure the surface temperature of a moving steel plate in a non-contact manner in a furnace or elsewhere.

Here, the following equation holds for the radiation amount of the steel plate as the object to be measured, that is, the power P (input, S) detected by the radiation thermometer.

P (in, S) = ε・P (λ, T) ... (1) Also,
When there is disturbance light H in a furnace or the like, the power P(λ, S) becomes a combined radiation amount as shown in the following equation.

Here, P (in, T) is expressed by the Wien equation below.

P (in, T) = C, - person・exp (Cz/in T)
・(3) Where, T: temperature of the object to be measured, emissivity of the two-liquid object to be measured, input: wave Q, C, = 3. ? 415XIQ
W m', C=0.0143FJ8ra-.

[Problems to be solved by the invention] However, when measuring the temperature of a steel plate in a furnace, etc.
(2) is small and fluctuates, and the influence of the disturbance light on the second term on the right side of equation (2) is large and several times that of the first term, resulting in the disadvantage that measurement accuracy cannot be improved.

In order to eliminate the above-mentioned disadvantages, we used an Owan type surface thermometer and a specular reflector to create a pseudo black body strip.

A temperature measurement method was devised to create this condition.

However, with these methods, measurement is difficult due to cloudiness that occurs on the mirror surface inside the furnace.In addition, temperature measurement methods that utilize multiple reflections of the wedge formed between the steel plate and its conveyor roll (especially Kaisho 55-14184
2) has also been proposed, but this method requires measurement in a very narrow area sandwiched between the roll and the steel plate, making it difficult to install the measuring device.

An object of the present invention is to enable measurement of steel plate temperature with high accuracy.

[Means for Solving the Problems] The steel plate temperature measuring method according to the present invention detects multiple reflections of radiation occurring on opposing surfaces of steel plates running in parallel.
The measurement is carried out using a radiation thermometer which is arranged at an angle with respect to the normal direction of the above-mentioned surface of the steel plate.

[Function] According to the present invention, multiple reflections between opposing steel plates are used,
By increasing the apparent emissivity, it becomes possible to measure the steel plate temperature with high precision.

[Example] FIG. 1 is a schematic sectional view showing a first embodiment of the present invention.

Inside a furnace wall 12 forming a continuous annealing furnace, the steel plate 11 is wound around a small threading roll (not shown) in a folded state, and is capable of running in parallel and in opposite directions. IIA
is the upper steel plate, and IIB is the lower steel plate. In addition, the furnace wall 12
An optical window 13 is formed therein.

A radiation thermometer detector 14 is installed outside the furnace wall 12. The detector 14 includes the L portion plate 11A and the lower steel plate 11.
This makes it possible to detect multiple reflections that occur with B. Here, the detector 14 is arranged perpendicularly to the edge of the steel plate and so as to measure the vicinity of the edge of the lower steel plate 11B.
It is arranged at an angle of θ with respect to the normal direction of the surface of B. In order to prevent the visual field from being lost due to the upper and lower steel plates 11A and 11B, and to enhance the effect of multiple reflection, it is preferable that the angle θ is 7 degrees≦θ≦20 degrees.

15 is a protective case for the detector 1'4. 16 is a detector driving device, which is coupled to the mount 17 of the detector 14 and mechanically scans the detector 14, thereby driving the steel plate 11.
This makes it possible to measure when the plate width changes. 16A is a rotating device using a motor, and the rotational force of the rotating device 16A can be transmitted to the pedestal 17 via connecting rods 16B and 16C. The connecting rod 16C is connected to the support tube 16
It is said that it can be supported by D.

Further, 18 is a radiation thermometer converter, which is equipped with an emissivity correction circuit and a peak picker circuit.

The converter 18 is connected to the drive device 16 by a peak picker circuit.
The maximum value among the measured values of one scan is held and can be sequentially output to the display/recording device 19.

If the number of reflections is N in the arrangement in the continuous annealing furnace of the first embodiment, the apparent emissivity i is, where ρ
is the reflectance (ρ=1−ε), and γ is the ratio of the mirror surface, which represents the reflection characteristics of the steel plate.

Here, assuming that there is disturbance light due to the furnace wall at - temperature, the power P (input, S) detected by the detector 14 is calculated from equation (2), taking into account the thermal W equilibrium state, P (λ, 5)=e@r(enter,
T) + (1-e) ・P (λ, to)... (5). Also, if it is N26 or more, it can be set, so install the radiation thermometer detector 14 in Figure 1. The angle θ is set so that the number of reflections is N22.

Next, the results of confirming the effects of the first embodiment described in 2 through actual measurements will be explained.

The brightness temperature Sla when measuring the steel plate 11A with a radiation thermometer with a wavelength of 0.91 Lm at a steel plate temperature T = 828°C and a furnace wall temperature - sufficiently low to be ignored is S
1a=754°C, and the brightness temperature Slb when the steel plate 11B is measured as shown in FIG. 1 is S1b=803.
The temperature was 5°C, which was about 50°C higher. Calculated from tt4 degree temperature stb and steel plate temperature T, due to multiple reflections,
The apparent emissivity was e = 0.718.

((1) 2 used), at this time, the emissivity ε is ε = 0.35
Therefore, using equation (B), y=0.75 is obtained. Under these conditions, if a radiation thermometer with a wavelength of 0.91 Lm is used, the emissivity ε of the steel plate changes within the range of 0.35≦ε≦0.8, so the apparent emissivity? From equation (6), 0
．． 718≦te≦0. It becomes f341.

When measuring the temperature of a cold-rolled steel sheet in a furnace, the emissivity ε
is often near the lower limit above, so it is released. The emissivity correction value of the radiation thermometer detector 14 may be set to j = 0.718.

With this setting, when a steel plate with temperature T = 80 (1°C and ε = 0.8) passes through, the temperature indication value based on the above emissivity setting is 819°C, and the maximum error is 18°C, which is different from the conventional The ratio of specular reflection can be regarded as a constant value for the same product type. Therefore, the emissivity setting value should be determined in advance depending on the product type, such as dull or bright.

In addition, in the first embodiment of Section 1, the radiation thermometer detector 1
4 is set perpendicular to or parallel to the traveling direction of the steel plate, but the same effect can be obtained even if the direction is set diagonally.

As described above, the first embodiment detects the amount of radiation due to multiple reflections of the steel plate, uses predetermined emissivity setting values for each type, and has a scanning mechanism to capture the maximum value of multiple reflections. Since the temperature of the steel plate is measured using the same method, there is little variation and it is a very effective method.

FIG. 2 is a schematic sectional view showing a second embodiment of the present invention.

The steel plate 21 is passed through one plate roll 23 inside the furnace wall 22.
It is possible to run in parallel and in the opposite direction in a folded state where it is wound around.

A radiation thermometer 24 is installed outside the furnace wall 22. The thermometer 24 is capable of detecting multiple reflections occurring between the opposing surfaces of the steel plates 21. Here, thermometer 24
are arranged to be inclined at an angle θ with respect to the normal direction of the surface of the steel plate 21. The smaller the angle θ, the greater the effect of multiple reflection, but due to restrictions due to the installation of the radiation thermometer, it is suitable that the angle θ is 30 degrees and θ<80 degrees. 25
is a protective case for the thermometer 24, and 26 is a thermocouple attached to the furnace wall 22 for measuring the furnace wall temperature.

A flange 27 is provided with N2 gas piping to remove deposits from the optical window of the radiation thermometer 2.4.

28 is a calculation device, which calculates the apparent emissivity from the emissivity and reflection characteristic coefficient, and calculates the preset apparent emissivity, the indication of the radiation thermometer 24, and the indication of the thermocouple 26. It is possible to calculate the temperature T of the steel plate using this method. 29 is a temperature display recording device.

If the number of reflections is N in the arrangement of the second embodiment, the apparent emissivity i is as follows. Here, ρ is the reflectance (ρ=1−ε), and γi is the ratio of specular reflection, which represents the reflection characteristics of the steel plate. here,
Assuming that there is disturbance light from the furnace wall at temperature Tw, thermometer 2
4 detects the power P (on.

S) can be set from equation (2), taking into account the thermal equilibrium state.

The effectiveness of the second embodiment will be explained by performing error evaluation under the following conditions: 0, the furnace wall temperature is low, the second term on the right side is negligible, and N≧6 or more.

When a Si cell with a wavelength input of 0.91 Lm is used as the radiation thermometer 24, the emissivity ε of the steel plate 21 is 0.35≦ε≦0.
It can be considered to be within the range of 80. Temperature T = 800″
At C, when ε = 0.35 and a steel plate of ε = 0.8 passes, in the normal case, using equation (1), the indication is T = 841.2℃, which is 41.2 This results in an error of ℃.

On the other hand, according to the second embodiment, the temperature instruction is T
= 1312.8°C, and the error is 12.8°C, which is less than 1/3 compared to the above case. (Here, the temperature index T is calculated by setting y = 0.8, and the range of change in the apparent emissivity is 0.7 using equation (8).
29≦i≦0.952, and ζ was used instead of ε in equation (1). ).

Furthermore, due to the reflection characteristics, the value of γ for cold-rolled steel sheets varied between 0.75 and 0.80 depending on the product type as a result of actual measurements, but the temperature indication change due to this was T = 8.
At 00℃, ε=0.35, the maximum is 15.4℃,
In this case as well, the error is much smaller than in the conventional method, and this adjustment can be determined in advance depending on the variety of Dal, Prite, etc.

Further, emissivity ε is often near the lower limit value of ε in cold-rolled steel sheets, and a constant value near the lower limit value is used as the set value of ε.

Furthermore, since the apparent emissivity is increased even in the presence of disturbance light, the same error reduction effect as described above can be achieved.

As described above, in the second embodiment, multiple reflections between steel plates are used, and the emissivity ε and the ratio of specular reflection by product type are set in advance. Since the steel plate temperature T is measured using the apparent emissivity, the brightness temperature indication S of the radiation thermometer, and the furnace wall temperature Tw, highly accurate temperature measurement with little variation is possible.

Note that the present invention is equally applicable to steel plates running in parallel outside the furnace.

[Effects of the Invention] As described above, the steel plate temperature measurement method according to the present invention detects the multi-hair reflection of radiation occurring on the opposing surfaces of steel plates running in parallel with respect to the normal direction of the surface of one steel plate. The temperature is measured using a radiation thermometer installed at an angle. Therefore, it becomes possible to measure the steel plate temperature with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing a first embodiment of the invention, and FIG. 2 is a schematic sectional view showing a second embodiment of the invention. 11, IIA, IIB, 21... Steel plate, 14.24.
... Radiation thermometer. Agent Patent Attorney Osamu Shiokawa Figure 1 Figure 2

Claims (1)

[Claims] (1) Multiple reflections of radiation occurring on opposing surfaces of steel plates running in parallel are measured by a radiation thermometer installed at an angle with respect to the normal direction of the surface of one of the steel plates. Steel plate temperature measurement method.