KR19980050629A - Method and device for measuring surface temperature of object in furnace - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for accurately measuring a heated object, especially a steel surface temperature, in a furnace using a radiation thermometer.

The present invention for achieving the above object is to radiate the radiated energy from the object to be heated through the through-opening part connected to the shield member on the cavity installed opposite to the surface of the object to be heated in the furnace and the insulation attached to the back of the shield member. The technical gist of this method is to measure the surface temperature of the object to be heated by detecting it with a radiation thermometer installed in the chamber. At this time, it is optimal to insert and install a pin member between the cavity-shaped shield member and the heat insulating member.

Description

Method and device for measuring surface temperature of object in furnace

The present invention relates to a method and an apparatus for measuring the surface temperature of a heated object in a furnace, in particular a heated material such as steel slab, steel sheet steel and the like.

In general, the surface temperature of steel materials such as slabs and steel sheets heated in a heating furnace in the manufacturing process of steel sheets is measured by a radiation thermometer. In addition to radiation energy from steel materials, radiation temperature sources such as ambient heating burners and low buckles are used for radiation thermometers. As the light from the light enters and these light are reflected from the surface of the steel to be heated and enter the light, accurate temperature measurement cannot be performed.

Light distribution noise varies depending on the measurement environment, but exists inevitably. Highly reliable temperature measurement cannot be realized even if a high precision radiation thermometer is prepared without the intensity or compensation of light distribution noise.

Conventionally, the measurement of steel surface temperature is performed by measuring the temperature of the steel material to be heated by one radiator using two radiation thermometers, and by measuring the furnace wall temperature by the other one, based on the signals obtained by both radiation thermometers. The method of removing the internal furnace reflected light is common. However, this method does not correct the emissivity of the steel to be heated, so it is difficult to eliminate the measurement error.

As a countermeasure against light distribution noise, a shielding plate is used to shield the light distribution noise. For example, when the shielding plate is placed against the surface of the furnace heated steel, and the radiation energy from the heated steel entering through the center opening of the shielding is measured with a radiation thermometer, the radiation thermometer in the direction of the wall of the furnace by the shielding plate. A method of obtaining the surface temperature of the steel to be heated is proposed by cutting off the radiation noise of the furnace and reducing the light distribution noise by the shielding plate from the instruction obtained by the radiation thermometer (Japanese Patent Publication No. 62-22089). However, this method has a disadvantage in that the shielding plate changes the temperature of the object to be heated under the influence of disturbance light.

In order to lower the temperature of the shield itself and to reduce radiation from the shield, a water-cooled shield is also used, but there is a problem that the water-cooled shield cools the object to be opposed and causes trouble in accurate temperature measurement. It is not desirable to have a serious accident, if any.

As a countermeasure against light distribution noise, a black body cavity is formed near the surface of the object to be heated, the radiation energy from the surface of the object to be detected is detected, and the radiation energy from the inner wall of the cavity is detected to detect the radiation energy from these detected values. There is a method of measuring the surface temperature of the object to be heated. For example, in the case of detecting the radiated energy of a heated object in a furnace with a radiation thermometer, a shielding tube is formed in the middle of the shielded cylinder by surrounding the optical path of the radiation thermometer to the heated object. A black body cavity is formed in the upper and lower parts of the shielding plate, and the radiation energy from the surface of the object to be heated is detected through the through hole with a radiation thermometer, and the radiation energy from the shield plate around the through hole is detected. It is also proposed to calculate the surface temperature of the object to be heated from these detected values (Japanese Patent Application No. 61-60634).

In addition, after enclosing the optical path of the radiation thermometer to the object to be heated with a shielding tube, a shielding plate with a through hole is mounted in the middle of the shielding tube, and a heater is installed in the inner wall of the cylindrical cavity (black body cavity) under the shielding plate. Next, the surface temperature of the object to be heated is measured through the through-hole with a radiation thermometer, and the current flowing through the heater is controlled so that the measured internal temperature is the same as the temperature measured by the thermocouple. A method of measuring the surface temperature of a heated object by adding a correction value determined from a negative temperature difference and an emissivity of a heated object to a radiation thermometer indication value has also been proposed (Japanese Patent Application No. 57-50628).

However, these methods are subject to combustion flames, radiant heat from the furnace walls and reflected heat in the furnace, so the temperature inside the cavity fluctuates, so the blackbody cavity does not become a complete blackbody, which limits the temperature compensation. It is not easy to match the temperature of the object to be heated with the temperature of the cavity inner wall. The installation of a cylindrical cavity provided with a heater in the furnace also causes a complicated structure.

The present invention is to solve the above-mentioned problems in the measurement of the surface of the object to be heated in the furnace, the purpose is to prevent the incident light reflected in the furnace, even if the emissivity of the object to be heated is not affected. A method and apparatus for measuring the surface temperature of an object in a furnace that enables measurement of the surface temperature of an object to be heated, in particular of a heated steel, using only a radiation thermometer, without requiring a correction according to the integrated temperature measurement by a thermocouple or the like. To provide.

1 is a cross-sectional view showing the concept of a measuring method of the present invention.

2 is a cross-sectional view showing one example of the apparatus of the present invention.

3 is a cross-sectional view showing another embodiment of the present invention.

4 is a graph showing an example of the relationship between temperature error and H / R.

5 is a graph showing another example of the relationship between temperature and difference and H / R.

Fig. 6 is a graph for obtaining the constant c of the correction equation.

* Explanation of symbols for main parts of the drawings

1: Cavity shield member

2: pin member

3: insulation member

4: radiation thermometer

5: water cooling tube

6: condenser

7: optical fiber

8: through opening

9: tube

10: fixed time

In the method for measuring the surface temperature of the object in the furnace according to the present invention for achieving the above object, in the method for measuring the surface temperature of the object to be heated in the furnace with a radiation thermometer, the cavity disposed facing the surface of the object to be heated Measuring the surface temperature of the object to be heated by detecting radiation energy from the object to be heated with a radiation thermometer installed at the rear of the insulation member through a shielding member having a shape and a through opening connected to a heat insulating member attached to the rear surface of the shielding member. It is characterized by 1.

In addition, the present invention is the heat insulating member through the radiation member from the object to be heated through the through-opening portion of the shield member on the cavity provided against the surface of the object to be heated and the pin member and the heat insulating member disposed on the rear of the shield member Measuring the surface temperature of the object to be heated by detecting with a radiation thermometer installed at the rear, and the cavity of the shielding member is cylindrical, conical and hemispherical, and the gap between the cavity of the radius R and the surface of the object to be heated A second and third feature is that the ratio of H, i.e., H / R is 2 or less.

The fourth feature of the method for measuring the surface temperature of the object to be heated in the heating furnace of the present invention is that the cavity of the blocking member is placed on the surface of the object to be heated H / R ≦ 2 (R: radius of the cavity, H: cavity and the object to be heated). The luminance temperature T _al is measured by arranging at an interval H that satisfies the surface), and then the shielding member cavity is placed at an interval H that satisfies H / R 2 at the surface of the object to be heated, and again the radiance temperature T _{a. -1} is measured and the luminance temperature T _a by the radiation thermometer obtained from the relationship between the radiation energy incident on the radiation thermometer and the radiation energy in the vertical direction of the object to be heated and the light emission noise, and the surface of the object to be heated. in - (T _a T _f) in, T _s as _{a T-1} or the surface of the object to be heated a temperature measured value, roon T _f of the shield member to the temperature value T _s, T _f roon the relationship T _s = T _a -c the closest substituting the temperature T ₁ of the pin by calculating from the equation c , By corrected using the value of the luminance value of the temperature T _{2 a-c} the value of the measured T ₁ and the calculation will obtain a surface temperature of the heated object, features of claim 5 is that the heating object gangjaein.

An apparatus for measuring the surface temperature of an object in a furnace according to the present invention includes a cavity-like shielding member disposed opposite to a surface to be heated, a fin member and a heat insulating member attached to a rear surface of the shielding member, and a radiation thermometer disposed behind the heat insulating member. And a through opening is opened to the shielding member, the fin member and the insulating member to detect radiation energy from the object to be heated by the radiation thermometer through the through opening, and to measure the surface temperature of the object to be heated. The water cooling tube is provided on the rear surface of the heat insulating member, and the light collecting tube of the radiation thermometer is disposed in the water cooling tube, and the radiation thermometer is an optical fiber radiation thermometer in which the main body and the light collecting unit are connected by optical fibers. It is a 1st, 2nd, and 3rd characteristic.

In the present invention, the first feature is to provide the cavity-like shielding member near the surface of the heated object, and the second feature is to arrange the heat insulation member on the rear surface of the cavity-like shielding object. The cavity shielding member is heated only by the radiant heat of the object to be heated, such as the steel to be heated, and can match the cavity temperature with the temperature of the object to be heated without providing an auxiliary heating device. Since the size of the object to be heated, such as steel, is much larger than the size of the cavity, the solid angle of the object to be viewed from the cavity is approximately 2π even when the cavity and the surface of the object to be heated are separated from each other.

Therefore, if the cavity rear surface is completely insulated, the cavity temperature matches the object temperature to be heated. When the cavity temperature is always close to the temperature of the object to be heated, a black body space is formed directly below the cavity. Under these conditions, reflected light in the furnace is blocked so that the effective emissivity of the object to be heated is close to 1.0. When the surface temperature of the object to be heated, such as steel, is measured with a radiation thermometer attached to the tip of the black body cavity, the type of steel or the scale of the surface of the steel is changed to change the emissivity or the temperature of the heated object. Surface temperature can be measured accurately.

Hereinafter, embodiment of this invention is described using a object to be heated as steel.

In the preferred device configuration of the present invention, as shown in FIG. 1, the shield member 1 on the cylindrical cavity is disposed opposite the surface of the steel S heated in the heating furnace F, and the rear surface of the shield member 1 is disposed. The pin member 2 and the heat insulating member 3 are attached thereto. The water cooling tube 5 is attached to the rear surface of the heat insulating member 3, and the radiation thermometer 4 and the light collecting part 6 are disposed in the water cooling tube 5. 7 is an optical fiber which connects the radiation thermometer 4 and the condensing part 6. The shield member 1, the fin member 2, and the heat insulating member 3 are installed by connecting a Kanto opening 8, and through the through opening 8, radiated energy from the steel to be heated S is measured by a radiation thermometer ( 4) to receive light. The radiation thermometer 4 may be stored in the water cooling tube 5, and the temperature rise thereof can be prevented from rising by storing the radiation thermometer or its condenser in the water cooling tube 5, whereby more accurate temperature measurement can be performed.

The fin member 2 acts as a heating source of the cavity C of the cavity-like shielding member 1, and in the heating in a high temperature atmosphere as in the present invention, the heat transfer between the members is mainly controlled by the radiant heat transfer. There is also a good heat shielding effect in the heat transfer environment. The present invention does not require a fin member 2 between the cavity-shaped shielding member 1 and the heat insulating member 3, and the present invention also applies the direct insulation member 3 to the rear surface of the cavity-shaped shielding member 1. Although the effect of can be achieved, since the said effect of the pin member 2 is not acquired, the temperature of the cavity C may become difficult to become the surface temperature of the steel material S in some cases.

The cavity shape is not limited to a cylindrical shape, but may be hemispherical or conical. As a material of the cavity-like shielding member 1 which forms a cavity, heat resistant inorganic materials, such as stainless steel, another heat-resistant metal material, graphite, silicon carbide (SiC), aluminum, can be used. In the case of using stainless steel, the inner surface of the cavity becomes black by heating, which is a good condition for forming a black body cavity. As a heat insulating member, a well-known fireproof heat insulating material, such as alumina, magnesia, and zirconia, can be used.

The surface temperature of the steel (S) is T _s , the internal temperature is T _f , the temperature of the cavity (C) is T _c , and each pin (2-1), (2-2) of the pin member (2), ... The temperature of (2-k) is T _i (i = 1,2, ..., k), and the inner diameter of the cavity C is 2R, the gap between the cavity C and the surface of the steel material S. When H is set, the temperature of the cavity and the fin is determined by the temperature of the adjacent member under the heat transfer, and the following relational expression is established.

T _i ⁴ ≒ (1/2) (T _i-1 ⁴ + T _{i + l} ⁴ ) ........... (1 )

T _c = ((1 / k) ((k-1) T _s ⁴ + T _f ⁴ )) ^1/4 ............... (2)

As can be seen from Equation (2), as the number of pins increases, the temperature of the blackbody cavity (C) coincides with the steel surface temperature regardless of the low temperature. Table 1 shows the relationship between T _s and T _c when the number of pins in formula (2) increases. According to Table 1, as the number of pins increases, the cavity temperature approaches the steel surface temperature.

In the present invention, through the pin member, the black body cavity (C) is further insulated from the rear side, and the cavity inner surface which always faces the steel surface is sufficiently wide even if the distance from the steel surface is large. It always sequences the heat only on the steel surface. Therefore, as can be seen from Equation (2), the cavity temperature is maintained at the steel surface temperature even if the interval H is increased without being affected by the cavity inner diameter 2R, the gap H between the cavity and the steel surface.

In addition, as a specific method for attaching the fin member and the heat insulating member to the blocking member on the cavity, for example, as shown in FIG. 2, the tube 9 made of a heat-resistant metal material may be used as the shielding member 1 on the cavity and the fin member ( 2) and a method of inserting and fixing the central portion of the heat insulating member 3, and a method of inserting and fixing the fixing rod 10 to these members as shown in FIG.

In the apparatus configuration of FIG. 1, when the steel surface temperature is measured, the radiant energy from the heated object incident on the radiation thermometer is expressed as follows.

N (T _a ) = ε _n N (T _s ) + (1-ε _n ) {F _e N (T _C ) + F _f N (T _f )} ....... (3)

F _e = 2πJ _o ^R rρ (θ) (H ² / r ² + H ² )) ... ....(4)

Fr = 2π _o ^H R ² ρ (θ) (h / R ² + h ² )) dh ............................... (5)

In the above formulas (3)-(5), T _a is the luminance temperature of the radiation thermometer, T _c is the temperature of the cavity, T _f is the low temperature ε _n is the emissivity in the vertical direction from the steel surface, θ is the radiation incident angle, F _e Is the form factor between the measuring point of the radiation thermometer and the blackbody cavity, F _f is the form factor between the measuring point and the heating furnace, r is the variable in the cavity radial direction, and h is the number of planes in the cavity height direction.

As shown in Equation (3), the radiation energy incident on the radiation thermometer is an amount in which the direct radiation light from the steel of the right side claim 1, the black body cavity of the second and third terms, and the reflected light from the furnace overlap. ρ (θ) is a reflection angle characteristic and is approximated by the following equation.

ρ (θ) = C0S ⁿ θ ......................................... (6)

The index n of the formula (6) is a parameter representing the reflectance angle characteristic of the steel. If n is small, diffuse reflection characteristic is emphasized. If n is large, specular reflection characteristic is emphasized.

Based on the above equation, the relationship between the temperature error (T _a -T _s ) and H / R is obtained and shown in FIGS. 4 and 5. 4 is an example of a steel with strong mirror reflection characteristics, and FIG. 5 is an example of strong diffusion reflection characteristics. The upper part of the graph shown in the drawing shows that the low temperature is higher than the steel surface temperature (Roon: 1,300 ℃, the steel surface temperature: 1,200 ℃), and the lower part is low temperature of the steel surface (lower temperature: 1,100 ℃, the steel surface temperature: 1,200). ° C) and calculated by changing the emissivity to 0.6, 0.8, 1.0.

The steel in the furnace is covered with a thick scale and the emissivity is around 0.7-0.8. When the emissivity approaches 1.0, the radiation energy decreases and the error is drastically reduced. The parameters related to the reflection angle characteristics show an example of n = 4 as a material with strong specular reflection and n = 4 as a material with strong diffuse reflection. The steel with strong specular reflection has a smaller temperature error for H change than the steel with strong diffuse reflection, but regardless of the reflection characteristic, if H / R≤2, the temperature error is within ± 10 ° C. As a result of measuring the surface temperature of the steel material heated in the actual furnace by changing the H / R value by using the apparatus of the present invention of FIG. 1, it can be confirmed that the relationship with the relationship shown in FIGS.

As described above, the temperature error is small in the range of H / R ≤ 2, but when H / R 2, as shown in Figures 4 and 5, the effect of the furnace reflection light can not be ignored, according to the present invention, H is Even if it increases, the cavity temperature is secured to a temperature close to the steel surface temperature and the black body condition is maintained, so the difference between the luminance temperature and the steel surface temperature is not extremely enlarged. Therefore, the surface temperature of the steel can be measured to a good degree by correcting the luminance temperature measured by the radiation thermometer to low temperature.

If the temperature T ₁ of the pin 2-1 closest to the black body cavity is used as the low temperature T _f , the following correction equation can be derived.

T _s (surface temperature of calibrated steel) = T _ac (T ₁ -T _a ) ...... (7)

Provided that T _f T _s and c are integers. Using this correction equation, the temperature error (T _a -T _s ) can be set to H, especially since the measurement error (t _a -t _s ) falls within ± 5.0 ° C, especially in the 1.0 H / R 4.0 range. .

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

In the apparatus configuration of FIG. 2, the surface temperature of slab heated in the furnace was measured. In addition, the number of pins was set to five sheets, and it was set as H = 150mm (H / R = 2.0). The steel surface temperature was measured by welding a thermocouple to the steel surface, and the temperature of the furnace and the cavity was also measured. These measured values are shown in Table 2 together with the luminance temperature measured by the radiation thermometer.

As shown in Table 2, when the cavity is approached to the steel surface so that H / R = 2, the difference (temperature error) between the measured steel surface temperature and the luminance temperature measured by the radiation thermometer is small and shows excellent measurement error. .

Example 2

In Example 1, it was set as H = 300mm (H / R = 4.0) and it measured similarly to Example 1. The results are shown in Table 3.

By modifying the correction equation (7), T _a -T _s = c (T ₁ -T _a ). Substituting the formula shown in Table 3 into the transplant and substituting the measured pin temperature T ₁ therein, the values of (T _a -T _s ) and (T _l -T _a ) are calculated as shown in Table 4, According to the graph shown, the value of c becomes c = 0.494. Based on this c value, the luminance temperature is corrected by the above equation (7), and the correction value of the steel surface temperature (T _a -c (T ₁ -T _a )). ) Is shown in Table 4, and the measured temperature difference is extremely small.

(Note) T _{f s} ≥T For the case of the correction U, T _f T _s are non-corrected

In this embodiment, the measured value is used as the steel surface temperature, but instead of using the measured value, the cavity is first disposed at an interval H satisfying H / R ≦ 2 on the steel surface, and then the luminance temperature T _a-1 is measured. It is also possible to arrange | position a cavity at the space | interval H which satisfy | fills H / R2 on a steel surface, and to measure luminance temperature Ta _-2 again, and to obtain a correction value using Ta _-1 as steel surface temperature.

According to the present invention, a method for measuring the surface temperature of an object in a furnace that enables the surface of a heated object, particularly a heated steel, heated in a furnace to accurately measure the degree even when the steel type or the emissivity varies. An apparatus is provided. According to the present invention, the surface temperature of the object to be moved in the furnace can be accurately measured, as well as the object to be stopped in the furnace, as well as the steel sheet being annealed while traveling in the continuous annealing furnace. .

Claims (11)

In the method of measuring the surface temperature of the object to be heated in the furnace by a radiometer, the through opening connected to the cavity-shaped shield member provided to face the surface of the object to be heated and the heat insulating member attached to the rear surface of the shield member Method for measuring the surface temperature of the object to be heated by detecting the radiation energy from the object to be heated by the radiation thermometer installed behind the heat insulating member through the. The cavity of the shielding member is cylindrical, conical and hemispherical, and the ratio of the interval H between the cavity and the surface of the object to be heated, H / R, is 2 or less with respect to the radius R of the lower end. Method for measuring the surface temperature of an object in a furnace. The cavity of claim 1, wherein the cavity of the shield member is cylindrical, conical and hemispherical, and first the cavity of the barrier member is placed on the surface of the object to be heated H / R≤2 (R: cavity radius, H: cavity and heated). The luminance temperature T _a-1 is measured by arranging at an interval H that satisfies the surface of the object), and then the cavity of the shielding member is placed at an interval H that satisfies H / R 2 on the surface of the object to be heated again. The luminance temperature T _{a -2} is measured and the luminance temperature T _a , p obtained by the relationship between the radiation energy incident on the radiation thermometer and the radiation energy in the vertical direction of the object to be heated and the radiation energy due to light distribution noise is measured. the surface temperature T _s, roon of the heating body T _f is the relation _{T s = T a - c (} T f - T a) to be expressed, and the surface temperature measured value, roon T _f of T _al, or heating an object as the above T _s to the value of the shield member to a temperature T _l of the closest pin Characterized in that the mouth to the equation calculates a c from a, to obtain a surface temperature of a heated object by the correction using the value of the calculated c value and the measured T ₁ to the value of the brightness temperature T _a-2 Method for measuring the surface temperature of the object in the furnace. The method of measuring the surface temperature of an object in a furnace according to any one of claims 1 to 3, wherein the object to be heated is a steel material. In the method for measuring the surface temperature of the object to be heated in the furnace by a radiation thermometer, the shielding member on the cavity provided to face the surface of the object to be heated and the fin member and the heat insulating member disposed on the rear surface of the shielding member Method for measuring the surface temperature of the object to be heated by detecting the radiation energy from the object to be heated by the radiation thermometer installed in the rear of the insulating member through the connected through opening. 6. The cavity of the shielding member is cylindrical, conical and hemispherical, and the ratio of the interval H between the cavity and the extracorporeal surface to be heated to the radius R of the lower end, H / R is 2 or less. Method for measuring the surface temperature of an object in a furnace. 6. The cavity of claim 5, wherein the cavity of the shielding member is cylindrical, conical and hemispherical. First, the cavity of the blocking member is removed from the surface of the object to be heated by H / R≤2 (R: cavity radius, H: cavity and heated). The luminance temperature T _a-1 is measured by arranging at an interval H that satisfies the surface of the object), and then the cavity of the shielding member is placed at an interval H that satisfies H / R 2 on the surface of the object to be heated again. The luminance temperature T _{a -2} is measured and the luminance temperature T _a , p obtained by the relationship between the radiation energy incident on the radiation thermometer and the radiation energy in the vertical direction of the object to be heated and the radiation energy due to light distribution noise is measured. the surface temperature T _s, roon T _f of the heating object is a relation _{T s = T a - c (} T f - T a) to be expressed, and the surface temperature measured value, roon of T _a-1 or a heating object as said T _s T _f temperature of the best available pin on the shield member of the value T ₁ Characterized in that the assignment to the equation calculates a c from a, to obtain a surface temperature of a heated object by the correction using the value of the calculated c value and the measured T ₁ values T _a-2 of the brightness temperature Method for measuring the surface temperature of the object in the furnace. The method for measuring the surface temperature of an object in a furnace according to any one of claims 5 to 7, wherein the object to be heated is a steel material. An apparatus for measuring the surface temperature of an object to be heated in a furnace with a radiation thermometer, comprising: a cavity-like shielding member disposed opposite to the surface of the object to be heated, a fin member and an insulation member attached to the rear of the shielding member, and the rear of the insulation member A radiation thermometer disposed in the chamber is provided, and the through opening is extended to the shielding member, the fin member and the heat insulating member, and the radiation energy from the object to be heated is detected by the radiation thermometer through the through opening. Surface temperature measuring apparatus of the object in the furnace, characterized in that for measuring the surface temperature. 10. The apparatus of claim 9, wherein the heat insulating member is provided with a water cooling tube at a rear surface thereof, and a light collecting portion of a radiation thermometer is disposed in the water cooling tube. The surface temperature measuring apparatus of an object in a furnace according to claim 9, wherein said radiation thermometer is an optical fiber type radiation meter in which a main body and a light collecting part are connected by an optical fiber.