JPH0458568B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steel plate surface temperature measuring device for measuring the temperature of a steel plate running in a furnace such as a continuous annealing furnace.

For example, when measuring the temperature of a steel plate running in a continuous annealing furnace, it is possible to accurately measure the temperature of the steel plate using a contact thermometer, but since the steel plate is running, the temperature of the steel plate cannot be measured accurately. There is a risk of damaging the thermometer probe, and the thermometer probe itself also wears out, making continuous measurement impossible.

On the other hand, in the case of a non-contact method in which temperature is measured by installing a radiation thermometer on the furnace wall, a temperature measurement error occurs due to so-called backlight noise, in which radiant energy from the furnace wall enters the temperature measurement point of the thermometer. Moreover, in recent years, there has been a trend for a wide variety of products to be produced on a single production line, and thus variations in the emissivity of steel plates occur due to differences in steel types and operating conditions, which is a major source of error in temperature measurements.

For this reason, several methods have been proposed for measuring temperature using a radiation thermometer without being affected by backlight noise or fluctuations in emissivity, and these methods will be described below.

The most easily used is a radiation thermometer with a bowl. This method uses multiple reflections to increase the emissivity, and is suitable for manual measurement, but is unsuitable for automatic measurement, and is rarely used for continuous lines.

As a continuous measurement device that utilizes the effect of multiple reflections, there is a device that measures true temperature and emissivity at the same time by installing a rotating sector on the top of the cavity and changing the size of the opening. . Although this device has high measurement accuracy, it is large and expensive.

In addition, two blackbody radiation sources with different temperatures are installed facing the objects in the reactor, and a thermometer measures the temperature of the sum of the energy obtained when the blackbody radiation energy is reflected on the steel plate and the energy from the steel plate. After that, there is a method of calculating the emissivity and true temperature, but although it is possible to measure with high precision like the above-mentioned device, it is large and expensive.

Another method that utilizes multiple reflections is that the apparent emissivity of the wedge portion formed by the steel plate and the roll that contacts the steel plate over a predetermined length is infinitely large, so that heat exchange with the steel plate can be carried out sufficiently. There is a method (Japanese Unexamined Patent Publication No. 141642/1983) that takes advantage of the fact that the temperature approaches 1" and controls this area using a radiation thermometer.

However, there are the following problems when applying this method to temperature measurement of a steel plate running in a continuous annealing furnace.

In other words, when measuring the temperature of the wedge formed by the steel plate and the roll, the angle θ between the steel plate and the optical axis of the radiation thermometer should be as small as possible (θ = 20° or less) for highly accurate temperature measurement. However, when measuring the wedge section from directly above the tunnel section on the exit side of the heat treatment furnace, especially when applying to an existing furnace,
There is a problem in that the length of the tunnel part is short and the angle θ when viewing the wedge part from directly above is 20 degrees or more, making it difficult to measure with high precision.

SUMMARY OF THE INVENTION An object of the present invention is to provide a steel plate surface temperature measuring device that can measure the temperature of a steel plate traveling in a furnace such as a continuous annealing furnace with high precision using a radiation thermometer.

That is, the present invention provides a system in which a steel plate runs through a tunnel connecting heating, soaking, slow cooling, etc. zones in an industrial furnace such as a continuous annealing furnace. A radiation thermometer or radiation temperature distribution meter is installed so as to measure the temperature at an angle of 20° or less to the steel plate so that the wedge part formed by the steel plate and the roll that changes the direction of the steel plate is heated. The goal is to measure the Therefore, since the surface temperature of the steel plate is higher than room temperature, the radiant energy radiated from the steel plate is substantially larger than the surrounding radiant energy, and can be sufficiently separated from its output effect. Note that normal temperature is, for example, a temperature that is about 10 to 50 degrees higher than the atmosphere in the factory.

Hereinafter, the present invention will be explained in detail based on examples.

Figures 1 to 3 show an embodiment of the present invention, in which 1 is a heat treatment furnace that is part of a continuous annealing furnace, and 2 is a furnace wall of this furnace 1, which is made of bricks and iron skin. . 3 is a rotating roll for changing the traveling direction of the steel plate 4 coming out of the heat treatment furnace 1 and sending it to the next process, and as shown in the figure, the steel plate 4 is in contact with the roll over about one quarter of the entire circumference. The structure is such that the direction can be changed while doing so. Reference numeral 5 denotes a measuring tube, which is installed so that the energy radiated from the wedge portion formed by the roll 3 and the steel plate 4 enters the entrance of the radiation thermometer 6. 7 is a window glass.

Therefore, since the steel plate 4 is in contact with approximately one quarter or more of the entire circumference of the roll, the temperatures of the rotating roll 3 and the steel plate 4 are close to isothermal, and the wedge portion can be regarded as a black body. Therefore, at this time, the apparent emissivity approaches "1" in principle.

Next, we will discuss the effect. First, the apparent emissivity near the wedge portion formed by the steel plate 4 and the roll 3 will be explained with reference to FIG. Multiple reflections occur near the wedge portion O. Assuming that the light incident from direction A is completely specularly reflected between the roll 3 and the steel plate 4, A → P ₁ → Q ₁ →
As P ₂ →Q ₂ →..., the light enters the depths of the wedge portion O, and the amount reflected in the A direction becomes extremely small. This means that the radiant energy from each point P ₁ , Q ₁ , P ₂ , Q ₂ , ... repeats multiple reflections between the roll 3 and the steel plate 4 and is radiated in the A direction. This means that it can be regarded as a black body with an apparent emissivity close to 1. Therefore, the apparent emissivity depends on the number of reflections at the wedge and increases as it approaches the contact area. That is, the reflected line depends on the incident position X and the incident angle θ.

Figure 5 shows the angle of incidence θ (∠AP ₁ P) and the position of incidence X (=
OP ₁ /R: R is the radius of the roll 3) and the number n of multiple reflections are determined geometrically. The number of reflections on the roll is n ₁ , and the number of reflections on the steel plate is n ₂ , that is, n=n ₁
+n ₂ , the apparent emissivity ε ^* is calculated in a series and is expressed by equation (1).

ε ^* = ε ^* ₁ + ε ^* ₂ ...(1) ε ^* ₁ = ε _p・1−(r _p r _r ) ⁿ¹ /1−r _p r _r ε ^* ₂ =ε _r・r _p・1−( r _p r _r ) ⁿ² /1−r _p r _r where, ε _p : Emissivity of the steel plate ε _r : Emissivity of the roll r _p : Reflectance of the steel plate r _r : Reflectance of the roll It is clear from this Figure 5 As shown, the optimal reflection position is approximately 0.05 to 0.2 for X/R at 0 to 20 degrees.
(Especially 0.05 to 0.1 for 0 to 13 degrees).
Further, it was assumed that the temperatures of the steel plate 4 and the roll 3 were equal.
This can be said to be correct from the standpoint of heat transfer engineering, and the contact surface is 1/4 of the circumference of the roll 3.
The heat transfer is also very good, and the temperature at the boundary is the same. If there is a difference between the roll surface temperature and the temperature Tin before the steel plate 4 contacts the roll 3, heat will transfer between the roll 3 and the steel plate 4, and the temperature of the steel plate after the roll contact will change.
Tout immediately becomes equal to the temperature of roll 3.

In Fig. 6A and B, the emissivity of the roll is ε _r =0.3,
The emissivity ε _p of the steel plate 4 is set as a parameter (ε _p =0.2, 0.3,
...0.6), the relationship between the incident position (=X/R) and the apparent emissivity is expressed as follows: This is a case in point. Even if the emissivity of the steel plate 4 is small or changes greatly, the wedge part
The apparent emissivity near O' is extremely close to 1, so it can be seen that highly accurate temperature measurement is possible by measuring the temperature in this area.

FIG. 7 shows the relationship between the maximum value of the apparent emissivity in the wedge portion and the angle of incidence θ, using the emissivity of the steel plate 4 as a parameter. It can be seen that when the incident angle (that is, the measurement angle) θ becomes 20° or more, the apparent emissivity of the steel plate 4 with a low emissivity (0.3 or less) no longer approaches 1. Furthermore,
From Figures 6A and B, the smaller the angle of incidence (i.e., measurement angle) θ is, the more advantageous it is for temperature measurement, and the area where the apparent emissivity is close to 1 is wide, and the field of view is sufficient even with a commercially available radiation thermometer. It turns out that it can be secured. Also,
The fact that the apparent emissivity near the wedge portion O' is 1 also means that all backlight noise is absorbed and is not affected by it.

Above, we have described that it is possible to measure the true temperature by measuring the temperature of the wedge part O' formed by the rotating roll 3 and the steel plate 4. I will explain the main points.

For example, when measuring the wedge part from the top of the furnace wall 2 as shown in Fig. 8, it is necessary to ensure a sufficient measurement distance L, and in the case of a continuous annealing furnace, the measurement distance is generally L cannot be made long, and in particular, it is almost impossible to apply it to the existing furnace 1.

In addition, as shown in FIG. 9, a mirror 8 is
It is also possible to guide the heat radiation energy from the wedge portion to the radiation thermometer 6 through the mirror 8, but the reflectance and set angle of the mirror 8 must be maintained, which requires complicated maintenance.

On this point, if a viewing window is installed on the side surface of the furnace wall 2 as in this embodiment, it is possible to make the measurement angle θ sufficiently small even if the measurement distance L is short. Note that the optical axis is slightly tilted with respect to the roll center axis (g-g' in Figure 3), but the intersection of the optical axis and the roll axis (point h in Figure 3)
It is sufficient that the distance is within the width of the steel plate 4, that is, between i and i' in FIG. In this case, regarding the apparent emissivity, the reflection position is h in the normal direction of the roll center axis g-g'.
Since it can be considered that the optical axis h-h' is projected onto -h'', the discussion regarding FIGS. 6A and 6B can be applied as is.

In the above embodiment, a radiation thermometer was used, but the 10th embodiment
As shown in the figure, a one-dimensional temperature distribution meter (e.g. linear array camera, CCD
By installing a camera, etc.) 9 and detecting the maximum value of the obtained temperature distribution with the maximum body detector 10, a value corresponding to the maximum emissivity near the wedge portion (i.e., infinitely close to 1) is detected. It is possible to obtain a close value), and it is possible to further reduce errors caused by deviations in the visual field, etc.

FIG. 11 shows the measurement results when the temperature distribution meter is applied to a continuous annealing furnace. This temperature distribution has a pattern similar to that examined in FIGS. 6A and 6B, and its validity has been confirmed, and highly accurate temperature measurement can be expected.

FIG. 12 shows the maximum value of the temperature distribution as shown in FIG. 11 detected by the maximum detector 10 and recorded in time series. Curve A in the figure is the result of measurement using the present invention, curve B is the result of measuring the steel plate temperature from the top of the tunnel using an existing radiation thermometer (without emissivity correction), and the black dots are the contact temperature. This is the value obtained by intermittently measuring the steel plate temperature with a meter. As is clear from this figure, the results of the present invention (the example shown in FIG. 10) and the results of the contact thermometer are in agreement, demonstrating its validity. In contrast, existing radiation thermometers not only indicate 60 to 70 degrees lower, but also the emissivity of the steel plate has increased due to changes in the steel type.
When changing from 0.34 to 0.24, the temperature measurement error increases.

As described above, according to the present invention, when a heat-treated steel plate continuously flows in an industrial furnace such as a continuous annealing furnace, the rotating rolls that change the direction of flow in order to pass through a tunnel connecting each heat treatment furnace are provided. Since the steel plate is in good contact with about one-fourth or more of the roll's entire circumference, and the steel plate and the rotating roll can be considered to be at approximately the same temperature, the wedge formed by the two can be placed in contact with the steel plate sufficiently. By measuring with a radiation thermometer or temperature distribution meter at a small angle,
Highly accurate temperature measurement is possible. Specifically, the temperature detection direction of the radiation thermometer or the temperature distribution meter is arranged so as to face the wedge portion. Furthermore, as a specific range based on the experimental results, the intersection angle between the extension line of the temperature detection direction and the steel plate surface is limited to 0° to 20°, and the incident position where the extension line of the temperature detection direction and the steel plate surface intersects. Distance X from to the roll contact point
is limited to 0.05 to 0.2 times the roll radius R.
In this way, by limiting the incident angle and the incident position of the extension line of the temperature detection direction of the radiation thermometer or temperature distribution meter to the above-mentioned values, temperature measurement accuracy can be further improved. In addition, the measurement window for securing the optical path can be easily installed on the side wall of the furnace, making it easy to apply to existing furnaces. Furthermore,
Since high-precision temperature measurement is possible, it is now possible to strictly set the temperature inside the furnace, and a significant energy saving effect can be expected. In addition, high-precision temperature measurement can be achieved without being affected by emissivity fluctuations or furnace walls, which can contribute to improving the accuracy of furnace temperature control, which has the advantage of producing high-quality steel sheets.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the steel sheet surface temperature measuring device according to the present invention, FIGS. 2 and 3 are a side view and a plan view of the same embodiment applied to a continuous annealing furnace, and FIG. The figure is an explanatory diagram of the apparent emissivity near the wedge formed by the steel plate and the rotating roll. Figure 5 is a graph showing the relationship between the reflection position and the number of reflections. Figures 6A and B are the graphs showing the relationship between the reflection position and the apparent number of reflections. A graph showing the relationship between reflectance using the emissivity of the steel plate as a parameter. Figure 7 is a graph showing the relationship between the angle of incidence and apparent emissivity. Figures 8 and 9 show a radiation thermometer installed on the upper part of the furnace wall. FIG. 10 is a configuration diagram when a temperature distribution meter is used, FIG. 11 is a temperature distribution diagram, and FIG. 12 is a graph showing an example of measurement by the embodiment shown in FIG. 10. 1... Heat treatment furnace, 2... Furnace wall, 3... Rotating roll, 4... Steel plate, 5... Tube, 6... Radiation thermometer,
7... Window glass, 9... Temperature distribution meter, 10... Maximum value detector.

Claims (1)

[Scope of Claims] 1. A roll that changes the orientation of the steel plate and a running steel plate in a tunnel connecting each zone of heating, soaking, slow cooling, etc. in an industrial furnace are approximately one-fourth of the entire circumference of the roll or A wedge portion is formed by the steel plate and a roll that contacts the steel plate at a temperature higher than that and changes the direction of the steel plate, and the wedge portion is formed so that the temperature detection direction is at an angle greater than 0 degrees and less than 20 degrees with respect to the surface of the steel plate. an incident position where the extension line of the temperature detection direction intersects on the surface of the steel plate and a distance X from this incident position to the contact position with the roll as desired.
A steel sheet surface temperature measuring device characterized in that a radiation thermometer or a temperature distribution meter is installed on a side wall of the tunnel portion so that R is 0.05 to 0.2 times the radius R of the roll. 2. The steel plate according to claim 1, wherein a temperature detection direction of a radiation thermometer or a temperature distribution meter installed on a side wall of a tunnel portion has a set angle with respect to the steel plate surface that is greater than 0 degrees and smaller than 13 degrees. Surface temperature measuring device.