JPS5987329A - Method for measuring temperature of steel - Google Patents

Abstract

PURPOSE:To measure the temperature of a steel plate with high precision, by measuring the radiation energy from the steel plate, which is reflected alternately between the steel plate and an inclined reflective plate, with a radiation thermometer which is inclined to the steel plate. CONSTITUTION:The reflective plate such as an Al plate having a high reflection factor is so provided that it faces a steel plate 1 to be measured and is inclined to the steel plate 1 by 1-3 deg.. A radiation thermometer 3 is so provided that it is inclined to the steel pate 1 by 60-70 deg.. The radiation energy from the steel plate 1 is reflected alternately between the steel plate 1 and the reflective plate 2 and is made incident to the radiation thermometer 3; and the apparent emissivity of the steel plate 1 becomes higher due to this multiple reflection of the radiation energy, and high-precision measurement is performed by measuring this radiation energy of a high emissivity with the radiation thermometer 3.

Description

[Detailed description of the invention] The present invention relates to a method for measuring the temperature of a steel plate.

Generally used to measure the surface temperature of steel plates without contact.

A radiation thermometer is used.

=1- The radiation thermometer converts the radiant energy emitted from the object to be measured into temperature, and is configured so that the temperature display can be adjusted according to the emissivity of the object to be measured.

Therefore, when measuring the surface temperature of a steel plate with a radiation thermometer, it is extremely important to determine the emissivity of the steel plate surface.

Conventionally, radiation thermometers that take emissivity into consideration are equipped with a bowl-shaped reflector, which is installed directly above the bone plate surface to multiple-reflect the radiant energy from the steel plate surface. There is one that increases the rate and removes the effect of emissivity.

However, since the radiation thermometer described above requires one reflector to be installed close to the surface of the steel plate, it is not suitable for measuring the temperature of a continuously moving steel plate.

Another example of a radiation thermometer that uses multiple reflections of emissivity is to install a rotating sector at the top of the cavity and change the size of the opening.

There are some that measure temperature.

2- However, although this thermometer can obtain high measurement accuracy, it has a complicated mechanism and is large in size, which limits the installation location and is expensive.

From the above-mentioned viewpoint, this invention can be carried out very easily by
The present invention also provides a temperature measurement method that can measure the surface temperature of a steel plate with high accuracy.

A reflective plate having a high specular reflectance is installed facing the steel plate at an angle of 10 to 3 degrees with respect to the steel plate, and the radiant temperature is directed toward the steel plate at an angle of 60 to 70 degrees with respect to the steel plate. The radiation thermometer is characterized in that a thermometer is installed, and the radiation energy from the steel plate that is alternately reflected between the steel plate and the reflecting plate is measured by the radiation thermometer.

The method of this invention will be explained with reference to the drawings.

FIG. 1 is a detailed explanatory diagram of the present invention.

As shown in FIG. 1, a reflective plate 2 having a high reflectance such as an aluminum plate is placed opposite the steel plate l that is the object to be measured.
is installed so as to be inclined at an angle α with respect to the steel plate 1. In the figure, d is between one end 0 of the reflector plate 2 and the steel plate 1 (between 0 and 0)
The distance -a+ is the distance between the other end A of the reflector plate 3-2 and the steel plate l (between A and B).

! is the length between the reflecting plates 2OOA.

In this state, the radiation thermometer 3 is installed with the radiation thermometer 3 facing the 0 point and tilted by θ with respect to the steel plate 1.

The radiant energy of the steel plate 1 is alternately reflected between the steel plate 1 and the reflecting plate 2 and is incident on the radiation thermometer 3. In this way, the apparent emissivity of the steel plate 1 increases due to multiple reflections of the radiant energy.

This high emissivity radiation energy enters the radiation thermometer 3.

Here, the above apparent emissivity will be explained with reference to FIG. 2.

The surface of steel plate l and the surface of reflector plate 2 are 1. For example, if light is incident on these surfaces, assuming that it is perfectly mirror-reflected, the light incident on Pl on the steel plate surface at an angle θ will be reflected on steel plate 1.
Reflection is repeated multiple times alternately in the order P1→P2→P, .

That is, this means that the radiant energy from each point -PI + T2 + T3... is reflected at each point and enters the radiation thermometer 3 from Pl, and the number of reflections of the radiant energy 4- The larger the number, the higher the apparent emissivity.

The number of reflections of this radiant energy is determined by the parameters θ and al dA under the assumption of perfect specular reflection. Here, among the number of reflections of radiant energy, if the number of reflections on the surface of the steel plate l is n41 and the number of reflections on the surface of the reflecting plate 2 is n2, the radiation thermometer 3 detects the number of times of reflection when each of the above parameters is constant. The radiant energy E is expressed by the following formula.

...(1) However, ε1: emissivity of the steel plate.

ε2: Emissivity of the reflector.

rI: Reflectance of steel plate.

T2: Reflectance of the reflector.

T1: Temperature of steel plate.

T2: Temperature of the reflector.

Eb(T): Blackbody energy at temperature T.

−5= In equation 1, the first term is the radiant energy from steel plate 1,
The second term is the radiant energy from the reflector 2.

Now, if the temperature of the reflective plate 2 is significantly lower than that of the steel plate 1, Eb(T1)>Eb(T2) holds true. Therefore.

If the apparent emissivity of the steel plate 1 is ε; then Equation 1 can be simplified as follows.

If the temperature of the reflector plate 2 is normal temperature and the reflectance of the reflector plate 2 is high, the apparent emissivity of the steel plate 1 is calculated using Equation 2.

For example, when θ=60° to 70°, α, a/f (
Figure 3 shows the number of reflections of radiant energy when 1 = 1) is used as a parameter, and d/11 = 0.2,
In the case of ε2-0.03, the value of the apparent emissivity of the steel plate 1 is shown in FIG. 4 when the emissivity ε1 of the steel plate 1 and the inclination angle α of the reflection plate 2 are used as parameters.

As is clear from Fig. 3, if α〉O, then the radiation 6− The number of energy reflections does not depend on d and Q. That is.

Even if the steel plate l vibrates vertically with respect to the reflector plate 2, the number of reflections of the radiant energy does not change. but.

When the steel plate l is undulated in the vertical direction, α changes. In this case, it is sufficient to rotate the reflector plate 2 around the zero point and hope for the maximum value of the output from the radiation thermometer 3.

On the other hand, as is clear from Fig. 4, if the emissivity of the steel plate 1 is 0.2 or more in the vicinity of α-r~3°, the apparent emissivity will be 0.85 or more, and the emissivity must be corrected. T-island measurement can be carried out with high accuracy even without

Therefore, in the present invention, the reflective plate is installed facing the steel plate and inclined at 1° to 3° with respect to the steel plate.

The radiation thermometer was installed at a position of 60° to 70' with respect to the steel plate.

FIG. 5 shows the relationship between the emissivity of the steel plate when a reflector is installed opposite the steel plate coming out of the heating furnace according to the method of the present invention and the emissivity of the steel plate when no reflector is installed.

As is clear from Figure 5, the emissivity of the steel plate without a reflector varies greatly from 0.22 to 0.91, whereas the emissivity of the steel plate with a reflector installed varies considerably. It can be seen that the emissivity increases to 0.85 to 0.99, and there is no need to correct the emissivity.

As explained above, according to the present invention, the extremely useful effect of being able to measure the temperature of a steel plate with high accuracy without correcting the emissivity of the steel plate is brought about.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the principle of the invention, and FIG. 2 is an explanatory diagram showing the state of reflection of radiant energy. FIG. 3 is a diagram showing the relationship between the inclination of one reflector and the number of reflections of radiant energy, FIG. 4 is a diagram showing the relationship between the inclination of one reflector and apparent emissivity, and FIG. 5 is a diagram showing the relationship between the inclination of one reflector and the apparent emissivity. FIG. 7 is a diagram showing the relationship between the emissivity when a reflector is not installed and the emissivity when a reflector is installed. In the drawings, l... Steel plate 2... Reflection plate 3... Radiation thermometer 8-

Claims (1)

[Claims] A reflective plate having a high specular reflectance is installed facing the steel plate at an angle of 1° to 3° with respect to the steel plate, and the radiant temperature is directed toward the steel plate at an angle of 600 to 70′ with respect to the steel plate. The radiation thermometer measures the radiation energy from the steel plate that is alternately reflected between the steel plate and the reflecting plate. How to measure the temperature of steel plates.