JPS6252423A - Method and apparatus for continuously measuring temperature of molten metal - Google Patents

Abstract

PURPOSE:To reduce measuring cost by reducing wear of the parts of a temp. measuring probe, by continuously measuring the temp. of a molten metal using a radiation thermometer having a non-consumption type temp. measuring probe. CONSTITUTION:The blow gas for a temp. measuring probe 10 is allowed to flow not only to cool an optical fiber 11 but also to prevent the penetration of molten steel from the leading end of a tuyere during blowing and the blow gas for a porous nozzle is passed to promote the stirring of molten steel. The radiation energy from the surface of molten steel is condensed by the condensing lens 22 of the temp. measuring probe 10 and guided to a radiation thermometer 2 through the optical fiber 11. The radiation energy guided to the radiation thermometer receives photoelectric conversion in said thermometer to be converted to electric energy corresponding to the quantity of light and said electric energy is subsequently converted to a temp. value. By this method, the contact of the temp. measuring probe with the molten metal is prevented and said probe can be cooled so as not to be melted by the radiant heat from the molten metal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for measuring the temperature of molten metal such as molten steel. More particularly, the present invention relates to a method and apparatus for continuously measuring the temperature of molten metal using a radiation thermometer having a non-consumable temperature probe.

Conventional technology The conventional method for 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 a sublance. It has been 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 CSP and S) and molten steel temperature at the time of tapping.

Conventionally, carbon and temperature in particular have been measured by using a sub-lance and inserting a temperature measuring probe into the molten steel once each in the middle and final stages of blowing.

This temperature measurement probe has a thermocouple installed at the tip of the sublance, but when inserted into molten steel, it melts within a few seconds and cannot be used continuously or reused.

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 highly accurate control of molten steel composition and temperature, and the temperature measurement probe is consumed each time it is measured, resulting in extremely high running costs. There is.

In addition, as top-bottom blowing 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.

Under such a background, as shown in FIG. 6, an optical fiber 61 equipped with a condensing lens at its tip 62, a built-in optical fiber 61 with a condensing lens and an optical fiber built in, and a structure surrounding the condensing lens and optical fiber are constructed. A method has been proposed in which a temperature measuring probe equipped with a mechanism for blowing gas into the steelmaking furnace 63 is installed in a tuyere 64 provided on the furnace wall corresponding to the sump portion of the steelmaking furnace 63. optical fiber 6
1, the radiant energy of the molten steel 65 is transferred to the optical fiber 6.
The temperature is measured with a radiation thermometer 66 connected to 1 and converted into temperature.

However, in this method, solidified steel 67 in the shape of a pine mushroom is generated near the tuyere 64 due to cooling by the blown gas. This solidified steel 67 grows during blowing and comes to cover almost the entire front surface of the tuyere 64 at the end of blowing. Therefore, due to the growth of the solidified steel 67, the field of view of the optical fiber 61 is partially obstructed by the solidified steel 67, and only a portion of the molten steel surface is visible, making accurate temperature measurement impossible, and eventually making measurement itself impossible. .

Therefore, by adding oxygen to the blown gas, we can prevent the formation of condensates that usually form in the form of pine mushrooms.
A method for continuously measuring the radiant energy of molten steel was proposed in JP-A-60-129628.

However, the interface temperature between the injected gas and molten steel changes greatly depending on the mixing degree of oxygen in the injected gas, and it is difficult to fine-tune the gas mixture ratio, so it is necessary to measure the molten steel temperature with high precision. It was difficult.

Furthermore, in order to prevent an increase in interface temperature, a method of blowing only an inert gas through the tuyere was proposed in JP-A-60-61633. However, as mentioned earlier, with this method, a pine mushroom-like solidified substance is formed in the front part of the tuyere due to the cooling effect of gas injection, and as a result, the field of view of the optical fiber is lost, etc. could not be measured.

Problems to be Solved by the Invention An object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a method and apparatus for continuously measuring molten steel temperature with high precision, thereby reducing measurement costs. The aim is to improve measurement accuracy.

Means for Solving the Problems As a result of various studies to develop a method and apparatus capable of solving the above-mentioned problems of the conventional technology and achieving the object of the present invention, the inventor of the present invention discovered an optical fiber buried in the center. .

Using a multi-hole nozzle with a hole for measuring the temperature of molten metal, the gas injected into the surrounding holes promotes stirring of the molten metal, and the gas injected through the temperature measurement hole in the center measures the surface of the molten steel at the tip of the optical fiber. We found that it is effective to hold and measure temperature.

That is, the continuous molten metal temperature measuring method of the present invention includes providing a tuyere on the bottom or wall of the furnace corresponding to the sump of the molten metal container, and flowing an optical fiber in the center and a gas around the optical fiber. A porous nozzle having a temperature measuring probe equipped with a mechanism and having a large number of pores around the tuyere is installed in the tuyere, and gas is blown into the temperature measuring probe and the large number of pores,
The gas blown into the many pores promotes stirring of the molten metal, the gas blown into the temperature probe holds the molten metal surface at the tip of the temperature probe, and the radiant temperature is connected to the optical fiber. It is characterized by continuously measuring the molten metal temperature using a meter.

In addition, in order to carry out the above measurement method, the molten metal temperature continuous measuring device of the present invention has a temperature measuring probe equipped with an optical fiber in the center and a mechanism for flowing gas around the optical fiber, and A porous nozzle having a large number of pores and installed in a tuyere provided in a furnace bottom or a furnace wall corresponding to a sump of a molten metal container, and the temperature measurement of the porous nozzle. first and second gas blowing devices that blow gas into the probe and the plurality of pores, respectively; connected to the optical fiber, and condensing radiant energy from the molten metal through the optical fiber; It is characterized by comprising a radiation thermometer that converts the temperature of the molten metal.

In a preferred embodiment of the present invention, the gas blown into the porous nozzle is an inert gas, and the radiation thermometer detects the temperature drop of the molten metal located in front of the temperature measuring probe by measuring the temperature of the gas blown into the temperature measuring probe. Correct as a function of flow rate.

]J With the above configuration, the gas blown through the pores arranged around the porous nozzle promotes stirring of the molten metal near the tuyere. That is, as the molten metal is actively stirred, the molten metal that has not been cooled by the blown gas is supplied to the vicinity of the tuyere. Considering the heat balance at the tip of the temperature measuring probe, the amount of heat Q1 supplied to the tip of the tuyere by stirring the molten metal, and the amount of heat Q1 supplied to the tip of the tuyere by stirring the molten metal, and The conditions for the formation of a matsumroom-like solidified substance are determined by the magnitude relationship with the amount of heat taken away Q2, and it can be said that a solidified substance will not be formed when Ql > Q2, and conversely, a solidified substance will be formed when Ql < Q2. can.

Therefore, by controlling the amount of gas blown through the pores around the porous nozzle, it is possible to prevent the formation of solidified matter in the vicinity of the tuyere.

In particular, when a multi-hole nozzle is used, the cooling effect of the blown gas is dispersed over a wide area, so there is less localized cooling effect on the molten metal near the tuyere, and the gas blown through the many holes causes agitation. Since the effect is large, it becomes possible to efficiently prevent the formation of coagulum near the tuyere.

Furthermore, in the present invention, since oxygen is not added to the blown gas, there is no exothermic reaction at the interface between the gas and the molten metal at the tip of the temperature measuring probe, and only cooling by the gas exists.

Therefore, it is possible to quantitatively understand this cooling effect, and once the shape of the tuyere is determined, the magnitude of the cooling effect is determined according to the amount of gas blown in from the tip of the temperature measuring probe. Therefore, we calculated the amount of temperature decrease in the molten metal near the tuyere due to gas injection as a function of the amount of gas injected into the temperature probe.
The measured temperature can be corrected.

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

The light beam obtained by the condensing lens provided at the tip of the fiber has a spectrum (which is basically a line spectrum) emitted when components in the molten metal (C, PSS, Si, 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 band in which only the thermal radiation energy from the molten metal is observed. By selecting the wavelength band in this way, only the radiant energy from the molten metal can be measured, making the temperature measurement of the molten metal extremely precise.

The radiation thermometer 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 is blown from the tuyere through the temperature measuring probe and the porous nozzle surrounding it to prevent the temperature measuring probe from coming into contact with the molten metal, or to prevent the temperature measuring probe from coming into contact with the molten metal. The radiant heat of the metal cools the metal so that it does not melt, and further prevents the inflow of molten metal.

Thus, with the molten metal temperature measuring method and apparatus according to the present invention, molten metal temperature can be measured very accurately.

Example Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of a continuous molten metal temperature measuring device according to an embodiment of the present invention. A porous nozzle 1 is installed in a tuyere 4 provided in a refractory brick 3 on the furnace wall of a steelmaking furnace, and a refractory filler 5 is placed in a gap between the porous nozzle l and the tuyere wall 4.
is filled. And, at the rear of the multi-hole nozzle 1,
A metal vibro is connected in an airtight state, and the metal vibro extends to the outside through a through hole provided in an iron skin 7 covering the firebricks 3. It is filled with a refractory filling 8 of.

Further, a temperature measuring hole 15 passes through the center of the multi-hole nozzle 1, and a probe 10 containing an optical fiber 11 is inserted into the temperature measuring hole 15. A radiation thermometer 2 is connected to the outside of the furnace of the optical fiber 11 built into the probe 10. Furthermore, the probe 10,
The metal vibro is equipped with a temperature measuring probe gas blowing device (which can set the gas flow rate to a desired value through the temperature measuring probe gas blowing duct 12 and the porous nozzle gas blowing duct 13, respectively). (not shown) and a gas blowing device for a multi-hole nozzle (not shown) are connected.

Similar to the furnace wall of a steelmaking furnace, the porous nozzle 1 is made of, for example, an Mg0-C refractory brick 14 in this embodiment, and has a temperature measuring hole 15 into which the above-described probe 10 is inserted.
In the illustrated embodiment, is a through hole with a diameter of 7 mm provided on the center line of the refractory brick 14, and the probe 10 has a double tube structure. The porous nozzle 1 is made by inserting a large number of stainless steel thin tubes with inner diameters of 7 mm and 2 mm into the refractory before firing the nozzle refractory.
It can be manufactured by molding and firing, or by cutting the nozzle into strips, machining grooves on their surfaces, and then gluing them together with cement or other materials. In the former case,
Both the temperature measurement hole and the gas blowing hole are cylindrical, and in the latter case, the gas blowing hole is triangular and cylindrical, but either case is suitable for the purpose of use.

FIG. 2 is a cross-sectional view near the tip inside the furnace of the probe IO. The inner tube 21 of the double tube is made of a stainless steel sheath tube with an inner diameter of 2 mm and an outer diameter of 3 [[1I11], and a condensing lens 22 and an optical fiber 11 connected thereto.
It accommodates. In this embodiment, an optical fiber with a condensing lens attached to the tip is used, but the condensing lens is not necessarily required. On the other hand, the outer tube 23 has an inner diameter of 5++
It is made of a stainless steel sheathed tube with an outer diameter of 5 mm, and the space between the inner tube 21 and the outer tube 23 is hollow, and this gap is maintained by the fixing member 24.
It is maintained by Further, the tip of the double tube consisting of the inner tube 21 and the outer tube 23 on the inside of the furnace is slightly set back to the outside of the furnace than the furnace wall of the refractory bricks 14. Furthermore, the hollow part between the inner tube 21 and the outer tube 23 is connected to the duct 12 at the outer end of the furnace, and gas is circulated through the duct 12 by a gas blowing device for the temperature measuring probe. It is configured to blow out in the direction of the tip.

FIG. 3 is a front view of the multi-hole nozzle 1 seen from the direction AA' in FIG. The above-mentioned temperature measuring hole 15 is provided in the center, and a large number of square pores 31 each having a size of 2 ml1 are provided in a mesh shape of 10 mm on a side around the temperature measuring hole 15.

A large number of pores 31 each pass through the refractory brick 14 and are connected to the duct 13 at the outer end of the furnace, and a gas blowing device for a multi-hole nozzle allows gas to flow through the duct 13 and is blown into the furnace. It is configured as follows.

In this example, when a porous nozzle with a diameter of 100 mm is used, the blowing gas has a flow rate of 2 for the temperature measurement probe.
50β/min Ar, flow rate 600 for multi-hole nozzle
ji! /min Ar was used.

In this way, by flowing the blowing gas for the temperature measuring probe, the optical fiber 11 is cooled, and at the same time, molten steel is prevented from entering from the tip of the tuyere during blowing, and the blowing gas for the porous nozzle is allowed to flow. This promotes stirring of molten steel.

Now, the radiant energy from the molten steel surface is collected by the condensing lens 22 of the temperature measuring probe and guided to the radiation thermometer 2 via the optical fiber 11.

It is desirable to use the radiation thermometer 2 in a wavelength range in which only thermal radiation from molten steel is observed and measure the radiant energy, so here we set the dominant wavelength to 0.9 μm, where there is no absorption by the blown gas. Set.

The radiant energy guided to the radiation thermometer is photoelectrically converted there, converting it into electrical energy according to the amount of light, and then converting it into a temperature value.

An example in which the temperature of molten steel during blowing was measured by the temperature measurement method based on this example under the conditions of supplying Ar at a flow rate of 250 β/min for the temperature measuring probe and Ar at a flow rate of 6001 β/min for the porous nozzle will be described below. It is shown by the broken line in Figure 4. In FIG. 4, the molten steel temperature measured with an immersion thermometer is also indicated by a white circle. Looking at this figure 4, although the measured values of the two always almost correspond, there is a certain deviation between the fixed values on both sides, and the measured value of this example is lower than the measured value of the conventional immersion type thermometer. You can see that it is happening. This is due to the gas flow rate blown from the temperature probe.
This is thought to be due to the cooling of the molten steel interface at the tip of the tuyere.

Generally, the heat balance between gas and molten steel at the tip of the tuyere is expressed by the following equation.

To WCp8T Σ(ΔH+ −Qq −) ... [
1] However, W: Mass of molten steel in contact with the bubbles in front of the tuyere and effective for heat exchange C1: Specific heat of molten steel ΔT: Temperature change of molten steel on the surface of the bubbles ΔHi: Enthalpy of component 1 generated by the reaction before the tuyere Q gas: Energy received by gas within the bubble due to heat exchange When an inert gas is used as the blown gas as in the embodiment, ΔH1=0. The quality IW is also considered to be a function of the diameter of the tuyere and the flow rate of the blown gas. Actually, using the tuyere of this example,
The flow rate of the gas for the temperature measuring probe was varied at a flow rate of 60011/min for the gas for the porous nozzle, and the amount of temperature reduction in the molten steel due to gas injection was measured, and the results shown in FIG. 5 were obtained. Therefore, it becomes possible to correct the measured temperature by using the amount of temperature decrease of the molten steel as a function of the flow rate of the temperature measuring probe gas.

Flow rate of human r gas for temperature measurement probe in this example: 250
The temperature reduction amount corresponding to 1/min was set in advance in the radiation thermometer as a correction amount, and the molten steel temperature was measured. The results are shown in FIG. 4 by a dashed line. The measured values after correction agree extremely well with the measured values of the immersion thermometer, and it can be seen that the measurement of molten steel temperature by the method and apparatus of the present invention achieves sufficient accuracy.

In this example, a porous nozzle with pores arranged in a mesh pattern was used, but the arrangement of the pores does not necessarily have to be in a mesh pattern, and may be arranged concentrically or completely irregularly.

Further, in this embodiment, MgOC-based refractory bricks were used as the gas injection tuyeres so that the molten steel would be difficult to solidify, but the present invention is not limited to this.

Effects of the Invention As described in detail above, according to the present invention, there is no need to wear out the parts unlike in conventional temperature measuring methods, and highly accurate temperature measurements can be carried out continuously.

Therefore, the method and apparatus for continuously measuring molten metal temperature of the present invention are extremely useful.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a temperature measuring device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the temperature measuring probe in FIG. 1 near the tip inside the furnace, and FIG. A front view of the multi-hole nozzle 1 seen from the A' direction, FIG. 4 is a graph comparing the molten steel temperature measurement results according to the present invention with the results measured with an immersion thermometer, and FIG. 5 is a temperature measurement probe. Figure 6 is a graph showing the relationship between the gas flow rate and the temperature drop of molten steel, and is a schematic diagram showing a conventional temperature measurement method. [Main reference numbers] 1. Porous nozzle 2.66. Radiation thermometer 3.
14. Firebrick 4.64. Tuyere 5.8. Fireproof filling 6. Metal pipe 7. Iron shell
10...Temperature probe 11, 61...Optical fiber

Claims (6)

[Claims] (1) A tuyere is provided on the furnace bottom or furnace wall, which corresponds to the sump of the molten metal container, and a temperature measuring probe equipped with an optical fiber and a mechanism for flowing gas around the optical fiber is installed in the center. A porous nozzle having a large number of pores around the tuyere is installed in the tuyere, and gas is blown into the temperature measuring probe and the pores, and the gas blown into the pores causes the molten metal to melt. The molten metal surface at the tip of the temperature measurement probe is held by a gas blown into the temperature measurement probe, and the molten metal temperature is continuously measured by a radiation thermometer connected to the optical fiber. Features a continuous measurement method for molten metal temperature. (2) The measuring method according to claim 1, wherein the gas is an inert gas. (3) The temperature drop of the molten metal located in front of the temperature measuring probe is corrected as a function of the flow rate of gas blown into the temperature measuring probe. Measurement method described in. (4) A furnace that has a temperature measuring probe equipped with an optical fiber in the center and a mechanism for flowing gas around the optical fiber, and has many pores around the periphery and corresponds to the sump of the molten metal container. a multi-hole nozzle installed in a tuyere provided in the bottom or the furnace wall; and first and second gas blowers that blow gas into the temperature measuring probe and the plurality of pores of the multi-hole nozzle, respectively. and a radiation thermometer connected to the optical fiber to collect radiation energy from the molten metal via the optical fiber and convert it into the temperature of the molten metal. Continuous measurement device. (5) The measuring device according to claim 4, wherein the gas is an inert gas. (6) The radiation thermometer corrects the temperature drop of the molten metal located in front of the temperature measurement probe as a function of the flow rate of gas blown into the temperature measurement probe. The measuring device according to item 4 or 5.