JPS61292528A - Correction in temperature measurement for steel material in furnace - Google Patents

Abstract

PURPOSE:To accurately correct the effect of radiation from the wall of a heating furnace by measuring at least two furnace wall portions having the effect of radiation on a steel material being heated in the furnace when the temperature of the steel material is measured. CONSTITUTION:A radiation thermometer 3 for measuring the temperature of a steel material 2 is provided in the necessary position of the wall 1 of a heating furnace and a detection output from the thermometer 3 is inputted to an arithmetic unit 5. Further, first and second furnace wall thermometers 41 and 42, respectively, are mounted in two positions near the position of the furnace wall 1 wherein the thermometer 3 is provided, and within a range having the effect of radiation on the steel material 2. The detection output of the thermometers 51 and 52 is inputted to the unit 5 via auxiliary arithmetic units 51 and 52 and coefficient setting units 53 and 54, respectively. The arithmetic units 51 and 52 calculate a back light noise L from the detection output of the thermometers 41 and 42 and the setting units 53 and 54 set the degree of effect on the position of the furnace wall 1 wherein the thermometer 3 is provided in accordance with the coefficients a1 and a2, respectively, obtained in advance. The unit 5 operates the addition of the output of the setting units 53 and 54 and performs a calculation for correcting the output of the thermometer 3.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for measuring the surface temperature of steel materials being heated in a furnace. The present invention relates to a method for correcting the influence of radiation from the furnace wall when measuring temperature of steel materials.

[Conventional technology]

When using a radiation thermometer to measure the surface of steel materials such as slabs that are being heated in a furnace, there is generally a positive temperature measurement error because the radiation from the furnace wall is reflected on the steel surface. .

Various temperature measurement methods have been proposed to eliminate this influence from the furnace wall (hereinafter referred to as backlight noise), and one representative example is the furnace wall temperature correction method. This furnace wall temperature correction method has been put into practical use to some extent.

As shown in FIG. 2, this conventional furnace wall temperature correction method involves installing a radiation thermometer 3 at a desired location on the furnace wall 1, and at a portion near the portion of the furnace wall 1 where the radiation thermometer 3 is installed. To,
A furnace wall thermometer 4 is attached to measure the temperature of the furnace wall 1 in this vicinity, and the detection signals of the radiation thermometer 3 and the furnace wall thermometer 4 are input to the calculation device 5, and the measured value of the radiation thermometer 3 is The temperature of the steel material 2 is calculated by correcting it with the measurement signal from the wall thermometer 4.

That is, the temperature of the furnace wall 1 is detected by the thermometer 4.

This detected furnace wall temperature Tw.

L (S)=εL (T)+ (1-g)L
It is used as Tw in the equation (Tw)... (1).

In addition, in this equation (1), S is the apparent temperature obtained from the radiation thermometer 3, T is the surface temperature of the steel material 2, ε is the emissivity of the steel material 2, Tw is the measured furnace wall temperature, L
(T) is the radiance from a blackbody at temperature T.

L (S) represents the amount of energy radiated per unit time from a unit area of a black body at a temperature S within a unit solid angle.

However, in general, the actual radiance from an object at temperature S is expressed as εL (S) (0<ε≦1).

Now, if the effective furnace wall temperature of the furnace is Tw' and the temperature measured by the furnace wall thermometer 4 is Tw, then if the emissivity ε is correct, then after correcting the furnace wall temperature Tw and the emissivity ε, The relationship between the apparent temperature S and the surface temperature T is based on the above-mentioned equation (1).

L (S)=L (T)+ (1/ε-1)・(L (
Tw' ) -L ('h) ] ... (2).

In short, if the effective furnace wall temperature TW' and the measured temperature Tw are equal, the apparent temperature S and the surface temperature T will be equal.

[Problem that the invention seeks to solve]

However, in an actual heating furnace, there may be a temperature difference of several tens of degrees Celsius or more between the effective furnace wall temperature Tw' and the measured temperature Tw, and accordingly, the temperature measurement error is generally 30 degrees Celsius or more. It will also be extended.

In the prior art shown in FIG. 2, the main reason why the temperature Tw measured by the furnace wall thermometer 4 differs greatly from the effective furnace wall temperature Tw' is that the temperature distribution inside the furnace is not uniform. Therefore, the measured temperature Tw cannot accurately represent the source of backlight noise on the surface of the steel material 2.

This inevitably occurs in heating furnaces such as continuous heating furnaces where temperature distribution inevitably occurs within the furnace, and i! It is not possible to pay ¥.

The present invention was devised to solve the problems and inconveniences in the conventional examples described above, and aims to provide a method that can accurately correct the influence of radiation from the furnace wall. .

[Means and effects for solving the problems] The present invention will be described below with reference to FIG. 1, which shows an embodiment of the present invention.

The method for correcting the temperature measurement of steel material in a furnace according to the present invention is such that when the temperature of the steel material 2 being heated in the heating furnace is measured using the radiation thermometer 3, the temperature of the steel material 2 at the temperature measurement position is at least Measure the temperature Tivn of the furnace wall at two locations,
As a linear combination of the radiation given to the surface of the steel material 20 by the measured temperature value of each furnace wall portion, the shadow habit that the whole furnace gives to the radiation temperature measurement of the steel material surface temperature T is calculated, and the radiation temperature is A total of three temperature measurements are corrected.

That is, since the temperature distribution inside the heating furnace generally changes in the direction of progress of the steel material 2, the temperature distribution in the furnace wall l on which the radiation thermometer 3 for measuring the temperature of the steel material 2 in the heating furnace is installed. Measure the temperature at several points on the furnace wall 1 before and after the section, that is, at multiple points on the furnace wall 1 where radiation affects the steel material 2, and calculate the linear combination of the backlight noise amount of the measured values at each temperature measurement point to calculate the effective furnace wall 1. This is the estimated value of the amount of noise given by the wall temperature Tw'.

In short, in radiometric thermometry, the amount of backlight noise is.

Rather than being proportional to temperature, the radiance of the radiation source at each temperature is L (Tw+), L (Twi), ...L
Since it is proportional to (Twn), it is taken as the effective furnace wall temperature TW'.

L (Tw')' = αIL (Tivt) + αz
L ('hz) +-.

-・+dnL (Twn) ...The coefficient αi when using (3) is determined by the geometric relationship between the furnace body shape and the steel material 2, so the optimum value of the coefficient αi is determined experimentally in advance. You can leave it there.

Since this predetermined coefficient 11i has sufficient practical universality, it can be used as a constant coefficient from now on.

In short, the coefficient αi is mainly determined by the distance relationship between the ceiling of the heating furnace and the temperature measurement point of the steel material 2, so strictly speaking, if the height of the steel material 2 changes, the coefficient αi should also change. , in the actual heating furnace.

Depending on the purpose, the three similar materials are heated in a dedicated furnace, such as a billet for a billet or a slab for a slab, so the coefficient αj does not change significantly. In normal operation, the factor 4i need not vary according to the individual size of the steel 2.

Generally, the variation in the emissivity of the steel material 2, the error in the thermometer itself, etc. are larger than the effect of the change in the coefficient 41 on the temperature measurement.

〔Example〕

In the case of the embodiment shown in FIG. 1, similarly to the conventional example shown in FIG. The detection output from the radiation thermometer 3 is input to the calculation device 5, where it is corrected by the calculation.The difference from the conventional example shown in FIG. 2 is that the radiation At two locations near the location on the furnace wall 1 where the thermometer 3 was installed, that is, at two locations within the range where the radiation affects the steel material 2.

A first oven wall thermometer 41 and a second oven wall thermometer 42 are installed, and the detection outputs of the two oven wall thermometers 41 and 42 are input to the auxiliary calculator 5L 52 and the coefficient setter 53 and 54, respectively. This means that the data is input to the arithmetic unit 5 through the .

Both side auxiliary calculators 51.52 calculate backlight noise L (Tw+), L (
Twz), and the coefficient setter 53.
54 is.

Coefficient α1 determined in advance. a2, the degree of influence at the location of the furnace wall 1 where the radiation thermometer 3 is installed is set, and the arithmetic unit 5 in the embodiment shown in FIG. ,．． The outputs of the radiation thermometer 3 are added together to perform calculations for correcting the output of the radiation thermometer 3.

The coefficient α2 is set in advance to a value suitable for the furnace body shape and the dimensions of the steel material 2 through experiments, etc., so it is a correction value close to the backlight noise of the effective furnace wall temperature Tw'.

(2+L (TW+) +a2L
(Tw2) can be obtained. This coefficient (11
, ax can be set, unless the relationship between the geometry of the furnace body and the dimensions of the steel material 2 changes significantly.

The coefficients (lb, (is) can be set to constant values, and can be used as they are for heating the steel material 2 later.

The method of the present invention is implemented and measured using the configuration shown in FIG. 1, and at the same time a thermocouple is attached directly to the steel material 2.
When the surface temperature of the steel material 2 was actually measured and this measured temperature was compared with the measured value of the radiation thermometer 3 corrected by the method of the present invention, the actual measured value of the thermocouple directly attached to the steel material 2 was 1043°C.
On the other hand, the measured value of radiation thermometer 3 corrected by the method of the present invention was 1048°C.

The measured values of steel material 2 were measured by the conventional means shown in FIG. 2 under exactly the same conditions.

The temperature reached 1076°C.

As is clear from the actual measurement results, it has become clear that the method of the present invention can measure the surface temperature of the steel material 2 much more accurately than the conventional means.

In the case of the embodiment shown in FIG. 1, both coefficients (Lb, (Lx
The relationship is αI+(2J=1, and theoretically it should be set as such, but in actual case.

4++α1≠1 may be satisfied.

in short.

L (Tw') = α+L (Tw+) +dzL
(Twz)... (4) If tw' =TW+ =T
If w2, it must be mountain + α2-1, but conversely, Tw' f-Tw+ ≠Tw2, tw' ≠T
In the normal case where w2 is, it is possible that equation (4) is satisfied with α1+4z≠1. However, in reality (1+
, 0-2, Lx = ll+ +
Setting it to 1 reduces the degree of freedom and makes it easier to decide.

Furthermore, it goes without saying that the number of furnace wall thermometers 4 installed, that is, the number of furnace wall temperature measurement points, is not limited to two, and may be two or more locations. .

Furthermore, in the explanation so far, the use of a shielding tube for reducing backlight noise from the furnace wall 1 has not been considered, but the presence or absence of a shielding tube is irrelevant to the essence of the present invention.

〔Effect of the invention〕

As is clear from the above explanation, the correction method for temperature measurement of steel materials in a furnace according to the present invention can improve the accuracy of temperature measurement of steel materials in a furnace, thereby improving the quality of steel materials and reducing the energy required for heating. It is extremely effective in this regard, and furthermore, unless there is a change in the geometrical furnace body, it exhibits excellent effects such as not requiring changes in coefficient settings.

[Brief explanation of drawings]

FIG. 1 shows an example of the simplest configuration in which the three methods of the present invention are implemented. FIG. 2 is a diagram showing a typical configuration of the conventional method. Explanation of symbols 1; Furnace wall 52; Steel material; 3; Radiation thermometer; 4.41° 42; Furnace wall thermometer. Applicant: Kawasaki Steel Co., Ltd.

Claims (1)

[Claims] When measuring the temperature of steel material being heated in a heating furnace using a radiation thermometer, the temperature of at least two furnace wall portions where radiation affects the steel material at the temperature measurement position is measured, and the temperature is measured at the temperature measurement position. The temperature measurement value of the radiation thermometer is corrected by calculating the degree of influence of the entire furnace on the radiation temperature measurement of the steel surface temperature, using the temperature measurement value of each furnace wall portion as a linear combination of the radiation applied to the steel surface. Correction method for temperature measurement of steel materials in the furnace.