JPH11160154A - Temperature measuring method and device for molten metal and metal pipe-covered optical fiber used for this method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the temperature and level of a high-temperature molten metal at a low cost. SOLUTION: The tip section of an optical fiber 11 is inserted into a molten metal together with a metal pipe 12 covering the optical fiber 11. The light emitted from the tip section of the optical fiber 11 is guided to a radiation thermometer 3 through the optical fiber 11, and the temperature of the molten metal is detected. The level of the molten metal is judged, based on the feed quantity of the optical fiber 11 and the temperature change measured by the radiation thermometer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature measuring method and apparatus for measuring the temperature of a high-temperature liquid metal such as molten steel, and to a metal tube coated optical fiber used in the method and apparatus.

[0002]

2. Description of the Related Art In a continuous casting process, for example, it is necessary to accurately know the temperature of molten steel and the level of molten steel during casting in order to improve the quality and the production yield. Conventionally, as a method of measuring the temperature of molten steel in a tundish or mold, a consumable immersion thermocouple in which a solidification chamber into which molten steel flows is provided inside a carbon sleeve and a thermocouple is attached to the solidification chamber. Also, a contact thermometer using a thermocouple covered with a ceramic protection tube is used. An eddy current type distance detector is used as a method for measuring the level of molten steel.

[0003]

The consumable immersion thermocouple deteriorates in one measurement because the thermocouple directly contacts the molten steel. For this reason, the temperature measuring probe at the tip is detachable, and this temperature measuring probe is exchanged for each measurement. Since such an expensive temperature measuring probe is disposable for each measurement, it has been difficult to increase the number of measurements.

When the thermocouple is covered with a ceramic protective tube, the measurement can be performed continuously because the thermocouple does not directly contact the molten steel. However, in this case, too, the durability of the ceramic protective tube is limited due to heat shock or erosion due to slag.
It had only about 0 to 50 hours and could not be used repeatedly for a long time.

The eddy current type distance detector used for measuring the level of molten steel can accurately measure the level in a steady state and is useful for level control. However, since the measuring range is as narrow as 200 mm or less. At the start of casting
The level measurement for the start could not be performed. Therefore, it has been difficult to automate the auto start.

The present invention has been made in order to solve the above-mentioned disadvantages, and is used for a method and an apparatus for measuring the temperature of a molten metal capable of measuring the temperature of a high-temperature molten metal at low cost and with high accuracy, and to be used in the method and the apparatus. It is an object of the present invention to provide a metal tube-coated optical fiber.

[0007]

According to a first aspect of the present invention, there is provided a method for measuring the temperature of a molten metal, comprising: inserting a tip of an optical fiber covered with a metal tube into the molten metal together with the metal tube; The temperature of the molten metal is measured by a radiation thermometer connected to the other end of the molten metal.

According to a second aspect of the present invention, there is provided a method for measuring the temperature of molten metal according to the first aspect, wherein the optical fiber is sent out.
The method is characterized by comprising a step of inserting the tip into the molten metal to measure the temperature of the molten metal, and a step of pulling up the tip of the optical fiber from the molten metal when the temperature is not measured.

In a third aspect of the present invention, there is provided a method for measuring the temperature of a molten metal, comprising sending out an optical fiber covered with a metal tube, inserting the tip of the optical fiber into the molten metal together with the metal tube, and connecting the optical fiber to the other end of the optical fiber. The temperature of the molten metal is measured by a connected radiation thermometer, and the temperature distribution in the molten metal is measured based on the relationship between the measured temperature of the molten metal and the feed amount of the optical fiber.

According to a fourth aspect of the present invention, there is provided a method for measuring the temperature of a molten metal, comprising sending out an optical fiber covered with a metal tube, inserting the tip of the optical fiber into the molten metal together with the metal tube, The temperature of the molten metal is measured by a radiation thermometer connected thereto, and the level of the molten metal is determined based on the output of the radiation thermometer and the feed amount of the optical fiber.

According to a fifth aspect of the present invention, there is provided a method for measuring a temperature of a molten metal according to the first aspect, wherein the molten metal is molten steel in a tundish, and the molten metal in the tundish is heated based on an output of a radiation thermometer. Features.

A method for measuring the temperature of a molten metal according to a sixth invention is characterized in that, in the third invention, the temperature of the molten powder sprayed on the molten metal is also measured.

A method for measuring the temperature of a molten metal according to a seventh aspect of the present invention is the method according to the fourth aspect, wherein the molten metal is molten steel in a mold of a continuous casting machine. It is characterized in that the flow rate of molten steel moving into the mold is controlled.

According to an eighth aspect of the present invention, there is provided an apparatus for measuring a temperature of a molten metal, comprising: an optical fiber covered with a metal tube; an optical fiber conveying means for feeding the tip of the optical fiber into the molten metal together with the metal tube; A radiation thermometer for measuring the temperature of the molten metal connected to the other end.

According to a ninth aspect of the present invention, there is provided a molten metal temperature measuring apparatus according to the eighth aspect, further comprising a level determining means for determining a level of the molten metal based on an output of the radiation thermometer and a feed amount of the optical fiber. It is characterized by the following.

Further, the method of measuring the temperature of the molten metal according to the first to seventh aspects of the invention and the apparatus for measuring the temperature of the molten metal according to the eighth and ninth aspects of the present invention are also applicable to the light covered with a metal tube. It is characterized by using a fiber.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a tip of an optical fiber is inserted into a molten metal as a temperature measuring element together with a metal tube coated with the optical fiber. When the tip of the optical fiber is inserted into the molten metal, the coating burns out just by bringing the tip of the optical fiber close to the molten metal, and the optical fiber itself is easily broken when inserted into the molten metal. Although the optical fiber cannot be inserted into the metal, the optical fiber can be inserted into the molten metal together with the metal tube without damaging the optical fiber itself.

Further, the metal tube covering the optical fiber is made of a stainless steel tube.
It has a melting point on the order and protects the optical fiber without melting the metal tube for several seconds even when the tip is inserted into the molten metal. Moreover, heat resistance can be ensured by forming the optical fiber which is the core wire from quartz glass having a softening point of 1600 ° C. or higher.

When this metal tube and the tip of the optical fiber are inserted into the molten metal, the temperature of the metal tube and the tip of the optical fiber becomes the same as that of the molten metal, and the tip of the optical fiber satisfies the condition of a black body. I have. For this reason, the emitted light only depends on the temperature without being affected by the tip shape of the optical fiber. The emitted light is guided to a radiation thermometer through an optical fiber, and the temperature of the molten metal is detected by the radiation thermometer.

Further, the metal tube and the optical fiber are sent out and inserted into the molten metal, and after measuring the temperature, the metal tube and the optical fiber are rolled up and pulled up from the molten metal for maintenance.

Further, based on the relationship between the measured temperature of the molten metal and the feed amount of the optical fiber, the temperature distribution in the molten metal is measured or the level of the molten metal is determined, so that the temperature and the level of the molten metal are determined. Control.

[0022]

FIG. 1 is a block diagram showing an embodiment of the present invention. As shown in the figure, for example, a temperature measuring device for measuring the temperature of molten steel includes a metal tube-coated optical fiber 1 wound around a supply drum 2, a radiation thermometer 3, and a recorder 4. As shown in FIG. 2, the optical fiber 1 made of quartz glass is coated with a metal tube 12 made of a stainless steel tube. The space between the coating layer 13 of the optical fiber 11 and the metal tube 12 is filled with jelly 14 as needed. The metal tube-coated optical fiber 1 is used as a temperature measuring element as well as a light transmission path, and its tip is inserted into molten steel. The radiation thermometer 3 detects and indicates the temperature of the molten steel from the radiated light at the tip of the metal tube-coated optical fiber 1 guided through the metal tube-coated optical fiber 1, and indicates the temperature directly from the luminance output of the radiated light. An external radiation thermometer or a two-color thermometer that obtains a temperature from comparison of two wavelengths of luminance is connected to the metal tube-coated optical fiber 1 via the optical fiber connector 5.

When measuring the temperature of molten steel with this temperature measuring device, the tip of the metal tube-coated optical fiber 1 is inserted into the molten steel. If an ordinary optical fiber with only a coating layer is inserted into molten steel and used, the coating layer will burn out just by bringing the tip part close to the molten steel, and the optical fiber itself will break when inserted into the molten steel. The coated optical fiber 1 covers the optical fiber 11 with the metal tube 12 and inserts the optical fiber 11 together with the metal tube 12 into the molten steel. Since the optical fiber 11 is protected by this, it can be inserted into molten steel without damaging the optical fiber 11 and the coating layer 13. Further, since the metal tube 12 made of a stainless steel tube covering the optical fiber 11 has a melting point of about 1400 to 1430 ° C., it does not immediately melt even when inserted into high-temperature molten steel, and protects the optical fiber 11 for several seconds. doing. Further, since the optical fiber as the core wire is also formed of quartz glass having a softening point of 1600 ° C. or higher, the shape can be maintained without melting.

When the tip of the optical fiber 1 coated with a metal tube is inserted into molten steel, the temperature of the tip of the metal tube 14 and the tip of the optical fiber 11 become the same as the temperature of the molten steel, and the tip of the optical fiber 11 satisfies the condition of a black body. . The tip of the optical fiber 11 emits a radiation light depending only on the temperature of the molten steel. The emitted light is sent to the radiation thermometer 3 through the metal tube-coated optical fiber 1. The radiation thermometer 3 calculates the temperature from the wavelength of the transmitted radiation, detects and displays the temperature of the molten steel, and sends the temperature output to the recorder 4 for recording. Since the distal end of the metal tube-coated optical fiber 1 having a small heat capacity is inserted into the molten steel,
The temperature of the tip can immediately follow the temperature of the molten steel, and the temperature of the molten steel can be measured quickly and accurately. In addition, the DC radiation light sent to the radiation thermometer 3 is intermittently converted by a photochopper into an AC signal, and then amplified.
By detecting the amplified AC signal in synchronization with the photo-chopper, stable amplification can be achieved.

If the distal end of the metal tube-coated optical fiber 1 is inserted into the molten steel for a long time after detecting the temperature of the molten steel, if the coating layer 13 of the optical fiber 11 is gasified by high temperature and oxygen is blown out from the distal end, there is no oxygen. burn. Therefore, immediately after measuring the temperature of the molten steel, the distal end of the metal tube-coated optical fiber 1 is pulled up from the molten steel. Then, when measuring the temperature of the molten steel, the tip used as the temperature measuring element is cut off, and a new tip is inserted into the molten steel to measure the temperature.
Thus, the temperature of the molten steel can be measured by repeatedly using one metal tube-coated optical fiber 1.

Next, the operation of actually measuring the temperature of the molten steel by the temperature measurement configured as described above will be described with a specific example.

[Example of Measuring Molten Steel Temperature in Mold of Continuous Casting Machine] FIG. 3 is a block diagram showing a case where the above temperature measuring device is used for measuring the temperature of molten steel in the molding of a continuous casting machine. As shown in the figure, in the continuous casting machine, the tundish 31
, Molten steel 33 is poured into a mold 34 through an immersion nozzle 32. A powder 35 is usually sprayed on the molten steel 33 in the mold 34. In order to measure the temperature of the molten steel in the mold 34, the metal tube-coated optical fiber 1 wound around the supply drum 2 is continuously or intermittently sent out at a constant speed by the fiber conveying means 36, and the metal tube-coated optical fiber 1 is coated. The tip of the optical fiber 1 is inserted into the molten steel 33 from above the powder 35. As described above, the temperature is measured by the radiation thermometer 3 while the tip of the metal tube-coated optical fiber 1 is sent out, and the temperature is recorded on the recorder 4, as shown in the characteristic diagram of the sending time and the temperature change in FIG. , Metal tube coated optical fiber 1
The temperature immediately rises at time t1 when the tip of is inserted into the molten steel 33, and saturates at the temperature T of the molten steel 33. The temperature T of the molten steel 33 can be measured by detecting the saturation temperature.

When the feed speed of the fiber transport means 36 is controlled while the distal end of the metal tube-coated optical fiber 1 is being fed, as shown in the temperature change characteristic diagram of FIG.
The temperature T1 of the molten powder 35 can be measured distinctly from the temperature T of the molten steel 33. Also, the molten powder 35
And the temperature distribution in the depth direction of the molten steel 33 can also be measured. However, if inserted for a long time, the metal tube 1
2 is melted, and the tip of the metal tube-coated optical fiber 1 is melted and damaged. Therefore, once the measurement is completed, the fiber conveying means 36 is inverted to pull up the metal tube-coated optical fiber 1 at high speed and rewind it to the supply drum 2. Wait for the next measurement. By repeating this operation, the temperature of the molten steel 33 in the mold 34 can be accurately measured.

When measuring the temperature of the molten steel 33, if the length of immersion of the metal tube-coated optical fiber 1 in the molten steel 33 is shortened and the immersion time is shortened, the consumption of the metal tube-coated optical fiber 1 is reduced. Can be reduced. This immersion time is determined by the temperature measurement time. The time required for temperature measurement is determined by the response time of the radiation thermometer 3 ignoring the transmission of radiation light, but if a semiconductor element is used as the light receiving element of the radiation thermometer 3,
It can respond in the order of milliseconds, the amount of consumption of the metal tube coated optical fiber 1 can be suppressed to about 1 cm by one measurement, and the temperature of the molten steel 33 can be repeatedly measured at a low price. .

When the temperature repeatedly measured becomes lower than the set temperature, the heating by the plasma torch 37 is strengthened, and the temperature of the tundish 31 is increased to control the temperature so that the temperature becomes constant. Can be stabilized.

The temperature of the molten steel 33 is measured while changing the measurement position in the mold 34, and as shown in FIG.
The temperature distribution in the mold 34 can also be measured by using a multipoint temperature measuring device in which a plurality of metal tube-coated optical fibers 1 are connected to the radiation thermometer 3 via an optical switch 38. The flow distribution of the molten steel flow from the nozzle 32 can also be measured from the temperature distribution in the mold 34, which can contribute to stabilization of the operation of the continuous casting machine.

In the above example, the molten steel 3 in the mold 34
Although the case of measuring the temperature of No. 3 has been described, the temperature of the molten steel 33 in the mold 34 and the level of the molten steel 33 can also be measured.

[Example of Measuring the Temperature and Level of Molten Steel in Mold of Continuous Casting Machine] FIG. 7 is a configuration diagram in the case of measuring the temperature and the level of molten steel 33 in the mold 34 of the continuous casting machine. As shown in the figure, the level of the molten steel 33 in the mold 34 in the steady state is measured by a level detector 41 composed of an eddy current type distance detector. The distal end of the metal tube-coated optical fiber 1 is set at the initial level detection position L1 in the mold 34. The temperature output terminal of the radiation thermometer 3 is connected to the level discriminating means 42.
The level discriminating means 42 discriminates that the molten steel 33 in the mold 34 has reached the initial level detection position L1, and a threshold value TH corresponding to the initial level detection position L1 is set in advance.

When the nozzle stopper 43 is opened from the closed state in this state, the molten steel 33 in the tundish 31
2 and is poured onto the damper 44, and the level of the molten steel 33 in the mold 34 gradually increases. When the molten steel 33 approaches the tip of the metal tube-coated optical fiber 1 at the initial level detection position L1, the molten steel 3 entering the metal tube-coated optical fiber 1
The radiation light of the radiation thermometer 3 increases, and the temperature output of the radiation thermometer 3 gradually rises as shown in FIG. This temperature output is sent to the level determining means 42. The level discriminating means 42 compares the sent temperature of the molten steel 33 with the threshold value TH. Then, when the molten steel 33 touches the tip of the metal tube-coated optical fiber 1,
Since the temperature output of the radiation thermometer 3 indicates the temperature of the molten steel 33, it rises sharply. When the temperature sent from the radiation thermometer 3 exceeds the threshold value TH, the level determination means 44
Is determined to have reached the initial level detection position L1, and an initial level detection signal is sent to the nozzle stopper position control means 45. When receiving the initial level detection signal, the nozzle stopper position control means 45 adjusts the position of the nozzle stopper 43 to control the flow rate of the molten steel to the value of the second stage. Further, the extraction of the damper 44 and the pulling of the metal tube-coated optical fiber 1 are automatically performed by the initial level detection signal. And mo
When the level of the molten steel 33 in the field 34 reaches the measurement range of the eddy current type level detector 41, the molten steel level control is performed by the output of the level detector 41. Also, by repeating the feeding and pulling of the metal tube-coated optical fiber 1,
The temperature of the molten steel 33 in the field 34 is measured.

When the initial level detection position L1 of the molten steel 33 in the mold 34 is detected, the set position of the tip of the metal tube coated optical fiber 1 can be arbitrarily changed. L1 can be set in a wide range. Therefore, it was difficult to automate
A start can be realized.

The diameter of the metal tube-coated optical fiber 1 is 1 m.
Since it is as small as about m to about 2 mm, it can be easily used for continuous casting of a small section such as a billet, and the industrial effect is extremely large.

In the above example, the case where one metal tube-coated optical fiber 1 is used has been described. However, as shown in FIG. 6, the tip portions of the plurality of metal tube-coated optical fibers 1 are set at different levels. In this case, the level change of the molten steel 33 at the initial stage can be detected.

In the above embodiment, the case where the temperature and the level of the molten steel 33 in the mold 34 of the continuous casting machine are measured has been described. However, the temperature and the level of the molten steel 33 in the tundish 31 may be measured. it can.

[Example of Measuring Temperature and Level of Molten Steel in Tundish] FIG. 9 is a configuration diagram in the case of measuring the temperature and level of molten steel 33 in the tundish 31. As shown in the figure,
The metal tube-coated optical fiber 1 is inserted continuously or intermittently at a constant speed by the fiber transport means 36 from the measurement hole 51 formed in the upper lid of the tundish 31. When the distal end of the metal tube-coated optical fiber 1 reaches the surface of the molten steel 33, the temperature output of the radiation thermometer 3 rapidly changes as shown in FIG. When this rapid temperature change is detected by the level discriminating means 42, the level discriminating means 42 calculates the level of the molten steel 33 in the tundish 31 from the feed amount of the metal tube-coated optical fiber 1 sent from the feed control means 52. The level discriminating means 42 sends the calculated level detection signal to the level control means 53 and also sends it to the feed control means 52 to stop the feeding operation of the fiber conveying means 36 and stop the insertion of the metal tube-coated optical fiber 1. After detecting the temperature and level of the molten steel 33, the metal tube-coated optical fiber 1 is once rewound by the fiber transport means 36, and waits for the next measurement.

In this way, the temperature and level of the molten steel 33 in the tundish 31 can be simultaneously detected, which can greatly contribute to automation and stabilization of the tundish operation.

In each of the embodiments described above, the case where the distal end of the metal tube-coated optical fiber 1 is used as a temperature measuring element while keeping the linear shape, however, as shown in FIG.
If the distal end of the metal tube-coated optical fiber 1 is bent into a substantially U-shape or bent to 90 ° or more to form the temperature measuring element 1 a, when the metal tube-coated optical fiber 1 is sent toward the molten steel 33, The radiation of the molten steel 33 can be prevented from directly entering the portion. Therefore, when the tip is inserted into the molten steel 33, the temperature output of the radiation thermometer 3 can be raised more rapidly, and the temperature and level of the molten steel 33 can be detected with higher accuracy.

In the above embodiment, the case where the temperature and the level of the molten steel 33 are measured in the continuous casting has been described. However, the temperature and the level of the molten metal in other devices can be measured in the same manner. Can be applied.

[0043]

As described above, according to the present invention, the tip of the optical fiber is inserted into the molten metal together with the metal tube as a temperature measuring element. Can be reliably inserted.

When the tip of the optical fiber is inserted into the molten metal together with the metal tube, the temperature of the metal tube and the tip of the optical fiber become the same as that of the molten metal, and radiated light depends only on the temperature. In addition, the temperature of the molten metal can be accurately measured.

If the tip of the optical fiber is inserted into the molten metal for a long time, the coating layer of the optical fiber is gasified by high temperature and burns if oxygen is blown out from the tip. Therefore, immediately after the temperature of the molten metal is measured, the temperature of the molten metal can be measured by repeatedly using one optical fiber by immediately pulling up the tip of the optical fiber from the molten metal.

Further, since the emitted light is transmitted by the optical fiber, stable measurement can be performed without being affected by noise.

Further, the temperature distribution in the molten metal and the level of the molten metal can be determined from the feed amount of the optical fiber and the temperature change measured by the radiation thermometer, and the temperature of the molten steel in the tundish and the mold of the continuous casting machine can be determined. It can control the temperature and level of the molten steel inside with high accuracy, and can greatly contribute to automation and stabilization of the process operation.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a metal tube-coated optical fiber.

FIG. 3 is a configuration diagram when used for measuring the temperature of molten steel in a mold of a continuous casting machine.

FIG. 4 is a characteristic diagram of a sending time and a temperature change.

FIG. 5 is a characteristic diagram of a sending time and a temperature change.

FIG. 6 is a configuration diagram showing another embodiment.

FIG. 7 is a configuration diagram for measuring the temperature and level of molten steel in the mold of the continuous casting machine.

FIG. 8 is a characteristic diagram of a temperature change with respect to a level of molten steel.

FIG. 9 is a configuration diagram when measuring the temperature and level of molten steel in a tundish.

FIG. 10 is a front view showing a metal tube-coated optical fiber of another embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 metal tube-coated optical fiber 3 radiation thermometer 11 optical fiber 12 metal tube 36 fiber conveying means 42 level discriminating means 52 feed control means

Continuing from the front page (72) Inventor Shuichi Yamamoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Yukei Kondo 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Stock In company

Claims (11)

[Claims] 1. A tip of an optical fiber covered with a metal tube is inserted into a molten metal together with the metal tube, and the temperature of the molten metal is measured by a radiation thermometer connected to the other end of the optical fiber. A method for measuring the temperature of a molten metal. 2. A step of sending out the optical fiber and inserting the tip into the molten metal to measure the temperature of the molten metal, and a step of pulling up the tip of the optical fiber from the molten metal when the temperature is not measured. The method for measuring the temperature of a molten metal according to claim 1, comprising: 3. An optical fiber covered with a metal tube is sent out, its tip is inserted into the molten metal together with the metal tube, and the temperature of the molten metal is measured by a radiation thermometer connected to the other end of the optical fiber. A method for measuring the temperature of a molten metal, comprising: measuring and measuring a temperature distribution in the molten metal based on a relationship between the measured temperature of the molten metal and the measured feed amount of the optical fiber. 4. An optical fiber covered with a metal tube is fed out, its tip is inserted into the molten metal together with the metal tube, and the temperature of the molten metal is measured by a radiation thermometer connected to the other end of the optical fiber. A method for measuring the temperature of a molten metal, comprising measuring and measuring the level of the molten metal based on the output of a radiation thermometer and the feed amount of an optical fiber. 5. The method according to claim 1, wherein the molten metal is molten steel in a tundish, and the molten metal in the tundish is heated based on an output of a radiation thermometer. 6. The method for measuring the temperature of a molten metal according to claim 3, wherein the temperature of the molten powder sprayed on the molten metal is also measured. 7. The molten metal is molten steel in a mold of a continuous casting machine, and based on a result of determining a level of the molten metal,
The method for measuring the temperature of a molten metal according to claim 4, wherein the flow rate of the molten steel moving from the tundish into the mold is controlled. 8. An optical fiber covered with a metal tube, an optical fiber conveying means for feeding the tip of the optical fiber into the molten metal together with the metal tube, and a temperature of the molten metal connected to the other end of the optical fiber. A temperature measuring device for molten metal, comprising: a radiation thermometer for measuring. 9. The molten metal temperature measuring device according to claim 8, further comprising a level determining means for determining a level of the molten metal based on an output of the radiation thermometer and a feed amount of the optical fiber. 10. An optical fiber coated with a metal tube used in the temperature measuring method according to claim 1. 11. An optical fiber coated with a metal tube used in the temperature measuring device according to claim 8.