JPH0682045B2 - Oxide film measuring device in heat treatment furnace for steel strip - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oxide film measuring device for measuring an oxide film thickness of a steel strip in a continuous heat treatment furnace in which a steel strip is directly heat-treated by a direct flame burner.

[Conventional technology]

As a heating method for a continuous heat treatment furnace, an indirect heating method using a radiant tube and an open flame heating method are known.

Among these, for example, the direct-fired heating method using a burner as described in Japanese Patent Publication No. 62-21051 has a better heating capacity than the indirect heating method, and moreover, since cold rolling oil can be burned out, It has the advantage of omitting the cleaning equipment, and is widely used in hot dip galvanizing lines and magnetic steel sheet continuous processing lines.

[Problems to be Solved by the Invention]

However, since the burner flame directly collides with the steel strip in the direct heating system using the burner, when a burner abnormality such as clogging of the burner occurs, the steel strip may be rapidly oxidized to deteriorate the quality of the product. Further, when such a steel strip is plated with a molten metal, there is a problem that the plating adhesion is significantly impaired.

Further, since a large number of burners are usually used in a furnace of this type, it is extremely difficult to detect defective burners.

[Means for Solving the Problems]

The present invention has been made in order to advantageously solve the above-mentioned drawbacks.When the steel strip is subjected to heat treatment in a heat treatment furnace, for example, a direct-fired heating furnace, the steel strip in the middle of the direct-fired heating zone or in the latter stage Temperature and emissivity are detected by a thermometer with emissivity measurement function installed close to one side, and the temperature is detected by a monochromatic thermometer installed close to the other side of the steel strip. Based on the value, the oxide film thickness on both sides of the steel strip is measured, and by this, the quality control is strengthened and nozzle troubles are prevented by detecting defective burners.

As described above, in the present invention, since the thermometer having the emissivity measuring function is used on one surface of the steel strip and the monochromatic thermometer is used on the other surface, the film thickness on both sides of the steel strip is extremely simple and accurate. Can be measured.

[Work]

When measuring the oxide film thickness of the steel strip with a thermometer having an emissivity measurement function, the radiance emitted by the steel strip is measured with the thermometer,
By inputting this radiance, the emissivity and temperature are calculated in the calculation device. That is, in this computing device, the relationship between the radiance and the emissivity is obtained in advance according to the type of steel strip, the measurement environment, the state of the surface treatment, etc., and is stored as a function inside the computing device. By inputting, the temperature and emissivity of the steel strip can be obtained at the same time.

Next, the temperature and the emissivity are input to the film thickness calculating device. It has been confirmed that the emissivity and the film thickness have a correlation close to a quadratic characteristic. This correlation is stored in the film thickness calculation device as a polygonal line characteristic or an nth-order approximate expression, and stored in this memory. Based on this, the oxide film thickness is calculated from the input emissivity.

That is, the film thickness calculation device has a polygonal line characteristic or an nth-order approximation formula obtained in advance according to the type of steel strip, the measurement environment, the state of surface treatment, etc., and the correlation between them is stored in the memory unit. Then, the detected emissivity is input to the memory unit, and the abnormality is checked and the temperature is corrected based on the temperature detected by the film thickness calculation unit and the film thickness output from the memory unit to obtain the film thickness of the steel strip.

On the other hand, the monochromatic thermometer normally detects the radiance with the thermometer and calculates the temperature in the arithmetic unit by assuming the emissivity.

When this is installed on the back surface of a thermometer having an emissivity measuring function, the location measured by the monochromatic thermometer is almost the same as the location measured by the thermometer having the emissivity measuring function. By comparing the temperature measured by the thermometer and the temperature measured by the thermometer having the emissivity measuring function, the accurate emissivity of the portion measured by the monochromatic thermometer can be obtained based on the difference. The obtained emissivity is output to the film thickness calculator,
The film thickness calculating device calculates the film thickness of the steel strip by the same method as described above.

The oxide film thickness on both sides of the steel strip thus obtained is sent to another system control device, which controls the nozzles of the direct-fired heating furnace.

Hereinafter, the present invention will be further described with reference to the drawings.

〔Example〕

FIG. 2 shows the thermometer 4 of the present invention in the furnace body 2 on the outlet side of the direct-fired heating furnace.
And FIG. 8 is a schematic perspective view in which 8 are arranged.

The steel strip 1 is heated by an open flame burner (not shown) of an open flame heating furnace and then sent through the furnace body 2 to the next step. Openings 3 and 3-
1 is provided. Thermometers 4, 8 are provided above or below the openings 3, 3-1 at a position of about 45 °, and the thermometers 4, 8 are provided so as to be able to run across the width of the steel strip. The details of the temperature measuring device are shown in FIG.

A thermometer having an emissivity measuring function, for example, a two-wavelength type thermometer 4 is arranged in proximity to the one surface A of the steel strip 1 so as to be able to run across.
The thermometer 4 and the arithmetic unit 5 constitute a temperature measuring system. The thermometer 4 emitted from the steel strip surface A through the oxide film A ₁
Radiation _X signal 11 and radiance _Y by receiving light of wavelength
Output signal 12. The arithmetic unit 5 inputs the signals 11 and 12, obtains the temperature T ₁ and the emissivity ε _X from the signals 11 and 12, and inputs these as signals 13 and 14 to the film thickness arithmetic unit 6 to calculate the film thickness. Then, the film thickness signal 15 is output to the display / control device 7. In the film thickness calculating device 6, the input emissivity is compared with a memory of the relationship between the film thickness and the emissivity of the steel strip which is preset in the memory section of the device 6, and from this value, the film of the device 6 is calculated. The film thickness is calculated by the thickness comparison calculator. At this time, the temperature is corrected by the temperature T ₁ input by the device 6, and the accurate film thickness t ₁ of the oxide film A ₁ at the position where the thermometer 4 receives the light is obtained.

On the other hand, on the other surface B of the steel strip 1, a monochromatic thermometer 8 is arranged so as to be scannable. The thermometer 8 and the arithmetic unit 9 constitute a temperature measuring system. The thermometer 8 receives a single-wavelength light beam emitted from the steel strip surface B through the oxide film B ₁ and outputs a radiance _Z signal 16. The arithmetic unit 9 inputs the signal 16, calculates the temperature T ₂ from the emissivity ε assumed to be the signal 16, and outputs the temperature T 18 and the assumed emissivity signal 17 to the film thickness arithmetic unit 10. Since the membrane thickness calculation unit 10 is input the signal 13 of temperatures T ₁ from the arithmetic unit 5, emissivity and temperature T ₁ compares the detected temperature T ₂ above, was assumed from the difference previously Correct ε and calculate the correct emissivity ε ₀ . The temperature thus obtained
Based on T ₂ and the emissivity ε ₀ , the film thickness t ₂ of the oxide film B ₁ at the position where the monochromatic thermometer 8 receives the light is calculated by the memory unit and the film thickness comparison calculation unit of the calculation device 10.

The film thickness t ₁ , t ₂ obtained by the film thickness calculation device 6, 10 is the film thickness signal 15,
19 is output to the display / control device 7, and the film thickness in the width direction of the steel strip is output by scanning the thermometer. The display / control device 7 controls, for example, the operation of the burner or detects a defective burner based on the film thickness signal.

As described above, the thermometer including the above-mentioned device is arranged in the middle and / or the outlet side of the direct-fired heating furnace so as to sandwich both sides of the steel strip as described above. of the N ₂ gas thermometer scanning aperture 3, 3-1 provided in the furnace wall and projecting from the end portion of the thermometer One to purge the temperature measuring pointゝ, scanning the temperature meter Then, the light beam emitted from the steel strip is received. In this way, the oxide film thickness in the width direction of the running steel strip is measured.

〔The invention's effect〕

As described above, the present invention is designed to measure the oxide film thickness formed on both sides of the steel strip of the direct heating zone of the continuous annealing furnace with a thermometer and a monochromatic thermometer having an emissivity measuring function. The oxide film thickness can be measured easily and at a low cost compared to the method of measuring only the oxide film thickness with a thermometer having an emissivity measurement function.
Very suitable for practical use. Further, since the present invention makes it possible to grasp the state of the oxide film on both sides of the steel strip, it is possible to strengthen quality control, and also to grasp the cause when quality defects occur and burner defects in the direct heating zone. It has a great effect such that the detection of can be performed easily and accurately.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an apparatus of an oxide film temperature measuring system of the present invention,
FIG. 2 is a schematic perspective view showing a state in which the apparatus of the present invention is used in a furnace body on the outlet side of a direct-fired heating furnace. 1 ... Steel strip, 2 ... Direct-fired heating furnace, 3, 3-1 ... Scanning opening, 4 ... Thermometer with emissivity measurement function, 5 ... Calculation device, 6 ... Film thickness calculation Device, 7 ... Display / control device, 8 ... Monochromatic thermometer, 9 ... Computing device, 10 ... Film thickness computing device, 11 ... Radiance _X signal, 12 ... Radiance _Y signal, 13 ... Temperature signal, 14 ... emissivity signal, 15 ... film thickness signal, 16 ... radiance _Z signal, 17 ... set emissivity signal, 18 ... temperature signal, 19 ... film thickness signal.

Claims (2)

[Claims] 1. A thermometer having a steel strip emissivity measuring function is provided in the vicinity of one of the steel strips in the middle of or after the direct heating type heating zone, and in the vicinity of the other surface of the steel strip. Is provided with a monochromatic thermometer for measuring the temperature of the steel strip, and further with an arithmetic unit for inputting the radiance signal from each of the thermometers, and the steel strip temperature and emissivity obtained by the arithmetic unit An oxide film measuring device in a heat treatment furnace for a steel strip, comprising a film thickness calculating unit for calculating the film thickness of an oxide film attached to the surface. 2. The apparatus according to claim 1, wherein each of the thermometers can be continuously scanned in the width direction of the steel strip.