JPS6160364B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for radiation-measuring the surface temperature of an object in a high-temperature furnace.

The temperature of the slab in the heating furnace prior to the hot rolling process is one of the things that needs to be accurately measured both for rolling purposes and for heat management reasons. Since this is a radiation temperature measurement environment where the noise is stronger than the temperature of the object to be measured, a powerful means for eliminating outside light noise is required. A water-cooled shield tube is effective in eliminating external light noise in radiation temperature measurement, but bringing a water-cooled shield tube into a high-temperature heating furnace may cause water leaks that may locally cool the object to be measured. This is undesirable because if it occurs, it may lead to a serious accident. Therefore, we devised a temperature measurement method in which the shielding cylinder is left to be heated by the furnace temperature, and the temperature of the shielding cylinder is actually measured and corrected to obtain the accurate temperature of the object to be measured. (Gan-Sho 54-63469). However, if the temperature of the shield tube itself is over 1,000 degrees, it becomes difficult to actually measure the temperature of the shield tube with a thermocouple.

The present invention aims to improve these points by using a radiometer to measure the temperature of the shield tube, thereby eliminating the need for thermocouples. That is, the device for measuring the surface temperature of an object in a furnace according to the present invention has a scanning radiometer placed opposite the object to be measured in the furnace, and a perforated shield in the middle of the optical path of the radiometer to the object to be measured. The radiometer is surrounded by a heat-resistant shielding cylinder having a plate, and the upper and lower parts of the perforated shielding plate constitute a blackbody furnace, and the temperature of the object to be measured is passed through the hole in the perforated shielding plate, and the perforated shielding plate is connected to the radiometer. The radiometer is configured to scan the shielding plate portion around the hole, and the radiometer output when the radiometer receives radiant energy incident through the hole of the perforated shielding plate and from the shielding plate portion around the hole. The present invention is characterized in that it is equipped with an arithmetic device that calculates the temperature of the temperature-measuring object from the radiometer output when receiving the radiant energy, which will be described in detail below with reference to embodiments.

In the drawing, 10 is a furnace wall of a high-temperature heating furnace, and 12 is a temperature-measuring object in the heating furnace, which is a slab in this example. 14
is a scanning radiometer, which is installed outside the furnace facing the object 12, and the optical path between it and the object is surrounded by a shielding tube 16. The shielding cylinder 16 is made of a heat-resistant material such as silicon carbide (SiC), has a perforated shielding plate 16a provided inside the middle part, and has a bamboo cylinder shape. 16b is the hole. The shielding cylinder includes the shielding plate 16a and the upper shielding cylinder part, and the shielding plate 16a and the lower shielding cylinder part respectively constitute blackbody furnaces BF ₁ and BF ₂ .
For this purpose, it is preferable that the ratio L/D between the length L and the diameter D be selected to be 1 to 5 or more, or that the inner surface be blackened or surface roughened so as to satisfy the blackbody furnace conditions. Since the object 10 moves, a gap is provided between the lower end surface of the shielding cylinder 16 and the object 12, but the length H of this gap is made sufficiently small to prevent external light noise from entering from the furnace wall, etc. .

In this device, the radiometer 14 alternately receives radiant energy G ₁ entering through the hole 16b and radiant energy G ₂ entering from the shielding plate portion around the hole by its scanning function, and the arithmetic unit 18 receives the radiometer output in each case. Calculate the temperature of the object 12. That is, the radiant energy G ₂ from the shielding plate is G ₂ =Eb(T ₂ )...(1) from the above-mentioned blackbody furnace condition. Here, Eb(Ti) is the temperature Ti (in this example, i
= 2) is the radiant energy emitted by the black body, and the shielding plate temperature is assumed to be T ₂ . The radiant energy G ₁ that enters through the hole 16b is expressed by the following formula.

G ₁ = ε _a Eb (T ₁ ) + r _a Eb (T ₂ ) + ηEb (T ₃ ) ...(2) Here, T ₁ is the temperature of the object to be measured 12, T ₃ is each temperature of the furnace wall, ε _a , r _a are the effective emissivity and effective reflectance of the object 12, and η is the stray light noise mixing rate from the furnace wall. That is, the first term on the right side of the above equation (2) is the radiant energy from the object 12, and the second term is the radiant energy from the blackbody furnace BF ₁ reflected on the surface of the object 12.
The third term represents the mixed stray light radiant energy. The emissivity ε _a is the apparent emissivity of the object 12, and includes, in addition to the radiant energy emission rate of the object 12, the reflectance on the surface of the object of the radiant energy emitted by something other than the object 12. . However, if the object to be measured is fixed, such as a slab, the former can be assumed to be known (0.85, with almost no error), and the latter can be determined by determining the shape of the shield cylinder, the distance H from the object 12, etc. After taking a predetermined value, ε _a may be a known constant (for example, 0.868). 2nd right side
The term Eb (T ₂ ) is measured by the radiometer as G ₂ because the temperatures of the blackbody furnaces BF ₁ and BF ₂ are the same (T ₂ ). When η is sufficiently small, the reflectance r _a
may be set as 1−ε _a . The third term on the right side can be ignored if the interval H is made small to prevent stray light noise from entering, but since η is still a value determined by the geometrical shape, it may be determined by actual measurement. Ignoring the third term on the right side, the object temperature T ₁ can be found from the formula below.

Eb (T ₁ ) = 1/ε _a (G ₁ − r _a G ₂ ) ...(3) Since the relationship between T ₁ and Eb (T ₁ ) is expressed by a blank equation, for example, it can be expressed as a graph. Find T ₁ from Eb(T ₁ ).

This temperature measuring device can measure the temperature of objects inside a high-temperature furnace without contact, and without using dangerous means for high-temperature furnaces such as water cooling mechanisms, and without the need for auxiliary temperature measuring means such as thermocouples. It is extremely effective because temperature can be measured using only a scanning radiometer and a heat-resistant shield tube.

[Brief explanation of the drawing]

The drawings are explanatory diagrams showing embodiments of the present invention. In the figure, 10 is a furnace wall, 12 is a temperature measuring object, 14 is a scanning radiometer, 16 is a heat-resistant shielding cylinder, 16a is a perforated shielding plate, and 18 is a calculation device.

Claims (1)

[Claims] 1. A scanning radiometer is placed facing the temperature-measuring object in the furnace, and the optical path of the radiometer to the temperature-measuring object is surrounded by a heat-resistant shielding tube with a perforated shielding plate in the middle. A blackbody furnace is configured above and below the shielding plate, respectively, and the radiometer is configured to scan the object to be measured through the hole in the perforated shielding plate and the shielding plate portion around the hole in the perforated shielding plate. and a radiometer output when the radiometer receives radiant energy incident through the hole of the perforated shielding plate, and a radiometer output when the radiometer receives radiant energy from the shielding plate portion around the hole. A device for measuring the surface temperature of an object in a furnace, characterized in that it is provided with an arithmetic device for determining the temperature of the object to be measured.