JPS60129628A - Continuous measurement of molten steel temperature - Google Patents

Abstract

PURPOSE:To measure accurately and continuously molten steel temperature, by combining gas blasting techniques in a dual blast refining process and irradiated energy measuring techniques using a microlens and optical fiber. CONSTITUTION:A temperature measuring unit 1 of a temperature measuring apparatus is set in a tuyere 3 perforated at the bottom of the furnace proper 2. This unit 1 is connected to a monochromic thermometer 5 through an optical fiber 4. Further, blasting gas is mainly composed of algon and oxygen. As the monochromic thermometer 5, it is desirable that use of an emission spectrum emitted on the occasion of oxidation reaction of ingredients of the molten steel, C, P, S, Fe, etc. is avoided and for the measurement of the irradiated energy, such wavelengths be used that permits observation of thermal radiation from the molten steel only.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for measuring the temperature of molten steel. More specifically,
The present invention relates to a method for continuously measuring the temperature of molten steel using a radiation thermometer having a non-consumable temperature measuring section. , 1 turn □ The conventional method of measuring the temperature of extremely high temperature molten steel, such as molten steel during blowing in a converter, is to attach a consumable thermocouple to the tip of the sublance. is commonly adopted.

To explain in detail the case of hot metal blowing using a converter, the main issue is to control the molten steel components (mainly c, p, s) and molten steel temperature at the time of tapping.

Conventionally, it has been widely practiced to measure carbon and temperature in particular by using a sublance and inserting a measuring probe into the molten steel once each in the middle and final stages of blowing.

This measurement probe has a thermocouple installed at the tip of the sublance, but it melts in a few seconds when inserted into molten steel, making it impossible to use it continuously or even reuse it.

Therefore, in the past, temperatures were measured intermittently at selected times, such as during the middle and final stages of blowing. However, this intermittent measurement method using conventional technology is insufficient for controlling the composition and temperature of molten steel with high precision, and also has problems such as the probe being worn out each time a measurement is made, resulting in extremely high running costs. be.

In addition, as top-bottom combined blowing has been adopted in recent years, it has become necessary to control the molten steel temperature at each stage of blowing.
There is a demand for continuous measurement of molten steel temperature.

An object of the present invention is to solve the problems of the above-mentioned conventional techniques and to provide a method for continuously measuring the temperature of molten steel, thereby contributing to an improvement in the end point temperature consistency rate during steel manufacturing. At the same time, it is intended to replace temperature measurement using a sublance probe, which has conventionally been a consumable type, and to reduce measurement costs.

A further object of the present invention is to provide a method for accurately and continuously measuring the temperature of molten steel during converter blowing, and to improve decarbonization and dephosphorization in the converter.
The aim is to suitably perform various refining reactions such as.

-11B11 The present invention provides a method for continuously measuring the temperature of molten steel in a steelmaking furnace, which combines a gas blowing technique from the siding in complex blowing and a radiant energy measuring technique using a microlens and an optical fiber.

More specifically, according to the present invention, a tuyere is provided on the furnace wall corresponding to the warming section of a steelmaking furnace, and an optical fiber is provided with a condensing lens at the tip, and an optical fiber with the lens and the fiber incorporated therein. molten steel temperature continuous, characterized in that a temperature measuring unit equipped with a mechanism for ejecting gas around the fiber is installed in the separate port, and the molten steel temperature is continuously measured by a radiation thermometer connected to the fiber; A measurement method is provided.

Furthermore, according to a preferred embodiment of the present invention, the radiant energy of molten steel is measured in a wavelength band that avoids the emission spectrum caused by the oxidation reaction of molten steel components, and further,
Adjust the oxygen partial pressure of the gas injected through the siding so that the injected gas neither cools nor heats the molten steel.゛ ・ ・ The molten steel temperature measuring method according to the present invention has an important feature in its temperature measuring section.

First, the temperature measurement location is the molten steel surface near the inner tip of the slats bored in the wall of the furnace body, which corresponds to the sump. Here, the term "furnace wall" refers to both the side wall and bottom of the furnace body.

From this point, an optical fiber with a condensing lens is inserted at the tip to guide the radiant energy of the molten steel out of the furnace.

Further, as the temperature measuring means, a radiation thermometer that measures radiant energy from the surface of the molten steel is used.

The light beam obtained by the condensing lens provided at the tip of the fiber is based on the spectrum (which is basically a line spectrum) emitted when molten steel components ('c, P, S, St, etc.) oxidize. Contains various spectra that cause measurement noise. Therefore, it is preferable to provide the thermometer body with a filter that selectively transmits only the energy in the wavelength range where only the thermal radiation energy from the molten steel is detected. By selecting the wavelength band in this way, only the radiant energy from the molten steel can be measured, making the temperature measurement of the molten steel extremely accurate.

The radiation temperature needle used in the present invention is preferably a narrow band acid thermometer that corresponds to the wavelength range of the emission spectrum of the temperature range to be measured.

Furthermore, a sufficient flow rate of gas was blown through the slats around the temperature measuring member so that the tip of the siding would not get stuck, and the temperature measuring member was 7 g.
It prevents contact with steel or cools it so that it does not melt due to radiant heat from molten steel, and also prevents /8 steel from flowing out.

At this time, if only inert gas is flowed, the surface of the molten steel will be cooled by the gas and an error will occur in the measured temperature. Therefore, an appropriate amount of oxygen is mixed with the injected gas to increase the reaction of the molten steel near the blown area. It is preferable to measure by increasing the temperature of the molten steel and canceling out the drop in molten steel temperature caused by inert gas injection. An appropriate value is determined in advance for the oxygen partial pressure in the blown gas, and the blowing is performed according to this value.

Thus, with the method for measuring molten steel temperature according to the present invention, molten steel temperature can be measured extremely accurately.

Part 11: Effects of the present invention will be explained by specific examples with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing a situation in which bottom-blowing temperature measurement panels are attached to a converter. As shown in the figure, in this embodiment, a temperature measuring section 1 of the temperature measuring device used in the method of the present invention is installed in a tuyere 3 bored at the bottom of a furnace body 2, and this temperature measuring section 1 is connected to an optical fiber 4. It is connected to the monochromatic thermometer 5 via.

In addition, the blown gas is mainly argon and oxygen.

In this embodiment, the temperature measuring tuyere is installed at the bottom of the converter furnace, but other embodiments, such as installing it on the side wall of the furnace body, do not depart from the scope of the present invention.

FIG. 2 is a schematic cross-sectional view of a temperature measuring section with a triple tube structure. Among the triple tubes, the innermost tube 11 accommodates a condensing lens 12 and an optical fiber 13 connected thereto, and
The tip inside the furnace is slightly set back to the outside of the furnace compared to the other tubes. Between the innermost pipe 11 and the middle pipe 14, and between the middle pipe 14
and the outermost tube 15 are hollow, and the space between them is maintained by a fixing member 16. The blowing gas is configured to flow from the outer end of the container tube through ducts 17 and 18 and blow out toward the tip of the temperature measuring section.

In this embodiment, a single core fiber with a diameter of 1 mm (core diameter of 100 μm, cladding diameter of approximately 150 μm) is incorporated in the intermediate tube 14, and a microlens with a diameter of approximately 2 mm is incorporated at the tip as the condensing lens 12. . The fiber does not necessarily have to be single-core if the grain size allows, but considering the possibility that molten steel will enter the tuyere during blowing and damage the condensing lens, it is recommended that the fiber be as thin as possible. This is desirable because it avoids the risk of molten steel flowing out of the furnace.

In this way, by flowing gas around the fiber in two layers, the fiber is cooled and, at the same time, it is possible to prevent molten steel from entering from the tips of the blades during blowing.

In addition, we adjusted the gas composition of the gas blown into the lining, and added a little O1 to the inert gas (argon). A mixture of gases is injected through the triple tube to prevent the formation of coagulates that normally accumulate in a manshroom shape at the tips of the siding.
This prevents cooling of the molten steel by the blown gas, or conversely, heat generation due to the reaction between oxygen in the blown gas and molten steel components (C, Fe, etc.).

FIG. 3 shows the relationship between the amount of blown gas and the molten steel temperature measured by the method of the present invention.

Further, FIG. 4 shows the degree of temperature measurement error caused by the method of the present invention when the composition of the blown gas is changed.

It can be seen from FIGS. 3 and 4 that there is an appropriate range for the blown gas flow rate and gas composition as described above.

That is, if the blown gas flow rate exceeds the (.) point in FIG. 3G, the molten steel will be further cooled by the blown gas, and accurate measurement cannot be expected. On the other hand, a certain amount of blown gas is required to cool the siding and prevent molten steel from leaching out of the furnace, and for actual measurements, a blown gas amount near the ia1 point is required. . .

Also, as shown in Figure 4, if the oxygen molar concentration in the blown gas is below the fb1 point, the heat of reaction between the molten steel components and oxygen is insufficient;
The cooling of the F6 steel by the blown gas cannot be canceled out, and at points (C) and above, the temperature of the molten steel measured at the measuring section is caused by the heat of reaction. Therefore, Mt.) ~.

A blowing gas with an oxygen molar concentration, ie an oxygen partial pressure, between IcI is preferred.

As a monochromatic thermometer, it avoids the emission spectrum emitted during the oxidation reaction of molten steel components such as c, p, s, and Fe, and measures the radiant energy by using a wavelength range where only thermal radiation from molten steel is observed. Therefore, the dominant wavelength was set to 0.9 μm, which is free from the influence of the emission spectrum of the oxidation reaction and absorption by the blown gas.

In this example, a narrow band monochromatic thermometer (e.g. 5.'
5 nm) is used. The reason why the sensitive wavelength is narrowed is not only to avoid the emission spectrum of the oxidation reaction mentioned above, but also to achieve the following output characteristics with respect to radiant energy:
This is because the value can be determined within the range of practical accuracy by calibrating at three points in the operating temperature range and determining the three coefficients A and BXC.

As the thermometer, not only a monochromatic radiation thermometer but also a two-color temperature needle can be used as long as the above conditions are met.

1 An example of measuring the temperature of /8 steel during converter blowing using the temperature measuring method of the present invention is shown in FIG. FIG. 5 also shows the /8 steel temperature measured with an immersion type thermometer.

In the figure, the solid curve shows the continuous temperature measurements by the method of the present invention, and the white circles show the measurements by the conventional immersion type temperature needle.

The two are in good agreement, and is it due to the method of the present invention? g&Vi
It can be seen that the temperature measurement has achieved sufficient accuracy.

Lesson I: As detailed above, the method for measuring molten steel temperature according to the present invention does not wear out the parts unlike the conventional temperature measuring method.
With proper settings, it is possible to continuously provide highly accurate measurement results.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a situation in which temperature measuring panels are attached to the bottom of the converter. FIG. 2 is a diagram schematically showing the structure of the temperature measuring section. FIG. 3 is a graph showing the influence of the blowing gas flow rate on the measured temperature. FIG. 4 is a graph showing the influence of the oxygen concentration of the blown gas on the measured temperature. FIG. 5 is a graph showing a comparison between the temperature measurement results obtained by the temperature measurement method according to the present invention and the temperature measurement results obtained using a dipping type temperature needle. (Main reference numbers) 1: Temperature measuring part, 2: Furnace body, 3: Panel, 4: Optical fiber, 5: Monochromatic thermometer, 11: Innermost tube, 12: Condensing lens, 13: Optical fiber, 14: Intermediate Pipe, 15: Outermost pipe, 16: Fixing member, 17.18: Duct, 3 2 Fig. 5 0 io Zυ

Claims (1)

[Claims] (13) Provided with a siding on the furnace wall corresponding to the warming section of the steelmaking furnace,
It was equipped with an optical fiber equipped with a condensing lens at its tip, a condenser and a mechanism incorporating the fiber and ejecting gas around the lens and the fiber. A method for continuously measuring molten steel temperature, characterized in that a temperature measuring section is installed in the tuyere, and the molten steel temperature is continuously measured by a radiation thermometer connected to the fiber 4. (In the method for continuously measuring molten steel temperature according to claim 1, the method is characterized in that the temperature is measured in a wavelength band that avoids the emission spectrum caused by the oxidation reaction of molten steel components. (9 ) In the molten steel temperature continuous measurement method according to claim 1 or 2, the radiation temperature needle is a narrow band acid thermometer corresponding to the wavelength range of the emission spectrum of the molten steel in the temperature range to be measured. A method for continuously measuring temperature of molten steel, characterized in that: (4) In the method for continuously measuring temperature of molten steel according to any one of claims 1 to 3, the oxygen partial pressure of the gas blown from the tuyeres is A method for continuously measuring the temperature of molten steel, which is characterized by adjusting the blown gas so that it neither cools nor heats the molten steel.・