JP2881434B2 - Prevention method of thermocouple deterioration of protective tube type continuous thermometer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for preventing deterioration of a thermocouple of a protective tube type continuous thermometer for continuously measuring the temperature of a molten metal or the like.

(Prior art) Conventionally, radiation thermometers, optical pyrometers, thermoelectric thermometers, and the like have been provided as methods for measuring the temperature of hot molten metal such as hot metal and molten steel. A thermometer is preferred, and the most commonly used is a consumable thermometer that protects the tip of a platinum-rhodium thermocouple (hereinafter referred to as a PR thermocouple) with a quartz tube. When the thermocouple is immersed, the thermosensitive part melts in a very short time (10 to 20 seconds) and becomes unusable, so the temperature measurement must be completed in a short time, and The thermometer had to be replaced. Therefore, it is difficult to control the quality and operation, and the cost of measuring the temperature is high. Therefore, a thermometer capable of measuring the temperature continuously for a long time is strongly desired. As shown in No. 38290, the outer part inserted into a high-temperature measurement temperature atmosphere is made of boron nitride as a main component, and in addition, metal molybdenum, zirconia ceramic composite Protection tube is provided.

However, in the case of a thermometer using these protective tubes, in a continuous temperature measurement of hot metal and molten steel, the life of the protective tubes eroded by the molten metal in 5 to 10 hours is insufficient. However, recently, boride-based ceramics have been provided as a preferable material for such a protective tube, that is, a material having the highest corrosion resistance to molten metal such as hot metal and molten steel, and having sufficient strength, heat resistance and thermal conductivity. ing. Examples of such a boride-based ceramic material include ZrB ₂ , TiB ₂ , and TaB ₂ .

In particular, ZrB ₂ most satisfies the above material conditions.

(Problems to be Solved by the Invention) However, since the boride-based ceramic contains a non-oxide as a main component, when the boride-based ceramic is used as a material for the protective tube, the inside of the protective tube is exposed to a reducing atmosphere at a high temperature. On the other hand, a PR thermocouple used as a temperature measuring sensor is easily deteriorated in a reducing atmosphere, and when the temperature of molten metal such as hot metal or molten steel is continuously measured, the rapid change in electromotive force or There is a problem that disconnection occurs, and the temperature cannot be measured in a very short time as compared with the service life due to erosion of the protective tube, and a continuous thermometer capable of measuring the temperature for a long time has been strongly desired.

(Means for Solving the Problems and Action) The gist of the present invention is to measure the temperature of a high-temperature fluid while protecting a temperature measuring sensor with a protective tube made of a boride-based ceramic material. A method for preventing deterioration of a thermocouple of a continuous thermometer with a protective tube is characterized in that the reducing atmosphere generated is naturally diffused or forcibly discharged from the open end of the protective tube.

The material of the protective tube, the are preferred boride ceramic particularly ZrB ₂ as, for a non-oxide as a main component, tends inner protective tube becomes a reducing atmosphere at elevated temperatures.

In the present invention, a reducing atmosphere generated from the inside of the protective tube is naturally diffused or forcibly discharged from the opening end of the protective tube for the purpose of preventing this and enabling continuous temperature measurement for a long time. .

The natural diffusion method of the reducing atmosphere is to open the protective tube intentionally without covering the open end of the protective tube with a fitting or the like. Particularly, when the open end is arranged upward, the high-temperature reducing atmosphere in the protective tube is used. Convection effect is also added, and a more preferable result is obtained. Further, the forced discharge method may be any method such as replacement by introducing a gas such as air into the protective tube, suction of an air or the like by an ejector, or a pump.

As a result, there is no stagnation of the reducing atmosphere generated in the protective tube, so that the thermocouple is not deteriorated and the life can be effectively prevented from being shortened.

EXAMPLES The present invention will be described in detail with reference to examples shown in the drawings.

Example 1 As shown in FIG. 1, a thermometer was a boride ceramic Zr.
A PR thermocouple 2 is disposed inside a protective tube 1 mainly composed of B ₂ , and the terminal of the thermocouple is connected to a temperature recorder 4 using a compensating lead 3. FIG. 2 shows the details of the connection between the thermocouple and the compensating conductor invented for the purpose of effectively exerting the function of the present invention. The terminal box 5 has an opening 6 and the lower part has a protective tube. The upper portion of the protective tube is gripped, and a space having a diameter larger than the diameter of the upper open end 11 of the protective tube is provided in the grip portion. A connection terminal 7 of the compensating lead wire and an air introduction part 8 for cooling the terminal are provided above the terminal box 5. With such a configuration, diffusion of the reducing atmosphere generated in the protective tube is effectively performed from the opening 6 of the terminal box 5. Further, the more effective diffusion is performed by the exhaust effect of the terminal cooling air 9.

The shape of the protection tube and the terminal box and the presence or absence of air for cooling the terminal may be arbitrary, and the opening of the terminal box is preferably large.

The molten steel temperature of 1520 to 1580 ° C. was measured in a tundish of a continuous casting facility using a continuous thermometer having such a configuration. As a result, the temperature was accurately and normally measured for about 70 hours without interruption due to deterioration of the thermocouple.

(Comparative Example 1) When the temperature was measured with a thermometer using the protective tube 1 in which the upper open end 11 was sealed, the temperature could not be measured as soon as about 5 hours due to the disconnection of the thermocouple.

(Embodiment 2) As shown in FIG. 3, a bypass pipe 10 is provided in the air introducing section 8, and a part of the terminal cooling air is introduced into the inside of the protection pipe upper opening end 11 by the bypass pipe 10. The temperature of the hot metal at 1400 to 1550 ° C was measured at a gutter near the taphole of the blast furnace using a continuous thermometer with the following structure. As a result, the temperature was accurately and normally measured for about 85 hours without interruption due to deterioration of the thermocouple.

(Comparative Example 2) When the same hot metal was measured with a thermometer using a protective tube in which the upper opening end 11 was sealed, the temperature could not be measured due to disconnection of the thermocouple after the temperature measurement for about 10 hours.

(Effect of the Invention) As described above, according to the method of the present invention,
Long-term continuous temperature measurement of high-temperature molten metal such as hot metal and molten steel enables long-term continuous temperature measurement, reducing temperature measurement costs, significantly improving the reliability of thermometers, and dramatically improving operation and quality control accuracy. It has extremely large effects such as stabilization of operation, quality improvement, and productivity improvement.

Although the description has been given of the molten metal, the present invention is not limited to this, but can be widely used, for example, when measuring the temperature of the atmosphere in a high-temperature furnace.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view of a protective tube type continuous thermometer used in the present invention, and FIGS. 2 and 3 show details of a connecting portion between a thermocouple and a compensating lead wire of the continuous thermometer. FIG. DESCRIPTION OF SYMBOLS 1 ... Protective tube, 2 ... PR thermocouple 3 ... Compensation conductor, 4 ... Temperature recorder 5 ... Terminal box, 6 ... Opening 7 ... Connection terminal, 8 ... Air introduction part 9 ... Terminal cooling air, 10 ... Bypass tube 11 ... Protective tube upper open end

Continuation of front page (72) Inventor Hiroshi Takeji 2-4-10-106 Midorioka, Takasago City, Hyogo Prefecture (56) References JP-A-63-169081 (JP, A) JP-A-62-150129 (JP, A) JP-A-56-66716 (JP, A) JP-A-58-167427 (JP, U) JP-A-62-123528 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01P 1/08

Claims (1)

(57) [Claims] When a temperature of a high-temperature fluid is measured while protecting a temperature measuring sensor with a protective tube made of a boride-based ceramic, a reducing atmosphere generated from the inside of the protective tube is filled with an opening end of the protective tube. A method for preventing thermocouple deterioration of a protective tube type continuous thermometer characterized by more natural diffusion or forced discharge.