JP2000088667A - Fiber-reinforced thermocouple - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long-life fiber-reinforced thermocouple that can be repeatedly used by improving a temperature-sensing response property, durability, and a heat-resistance property. SOLUTION: A fiber-reinforced thermocouple is composed of an internal pipe 2 that has a heat-reception part 4 being exposed outside at its tip, a fiber aggregate 5 that is wound around a part in contact with a metal molten metal outside the internal pipe 2, at the same time, has a covered surface, and is composed of coating fiber, a filler 8 that is made of a heat-resistant material being filled into the internal pipe 2, and metal wires 6 and 7 of different compositions that are arranged in the filler 8, at the same time, compose a temperature-sensing part 9 where the end part is connected. A protection pipe 1 is composed of the internal pipe 2 and the fiber aggregate 5. The coating is composed of alumina, silicon carbide, silicon nitride, or silicon oxide. A core part made of the fiber body of coating fiber is composed of carbon, silicon carbide, silicon nitride, alumina, or their aggregate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber-reinforced thermocouple for measuring a temperature of a molten metal such as iron.

[0002]

2. Description of the Related Art Conventionally, a thermocouple for measuring the temperature of a molten steel at about 1700 ° C. has a relatively high melting point as a material and is made of Pt-Rh, which is stable in the air, as a strand.
A structure in which an element wire is fixed to a pipe made of alumina silica fiber is used. Such thermocouples cannot be accurately measured after once measuring the temperature of the molten steel, and are discarded. The thermocouple cannot be used repeatedly many times. Thermocouples themselves are extremely expensive.

Further, as a thermocouple, a protective tube is made of a material such as cermet, and a Pt wire and a Pt-R are formed inside the protective tube.
A structure having a h-line or a W-Re alloy line is known.

Japanese Patent Application Laid-Open No. Hei 6-160200 discloses a sheath-type thermocouple with an airtight terminal. The thermocouple does not cause a measurement error even if a temperature gradient occurs in the terminal due to a transient temperature change or the like, and a wire made of a dissimilar metal wire of an alumel wire and a chromel wire is placed in a stainless steel sheath. Insulated from each other and stored together with inorganic insulating material.
The base end side of the sheath is hermetically sealed by the hermetic terminal portion. An insulating sleeve is inserted inside two Kopearl through pipes attached to the ceramic end plate of the airtight terminal,
Each of the metal wires is drawn out through the inside thereof without making direct contact with the through pipe.

[0005]

However, the thermal shock resistance of the cermet protection tube is 1.5 times that of the Si ₃ N ₄ protection tube.
Twice the strength of the thermocouple of the Si ₃ N ₄ protection tube.
When the protective tube is directly immersed in a molten iron at a temperature exceeding 700 ° C., a crack or the like is generated in the protective tube within a relatively short time, which leads to breakage. In addition, the Pt-Rh thermocouple cannot be used in an inert gas atmosphere, and its usable temperature in the atmosphere is 1500 ° C. The limit temperature is, for example, the upper limit of the guaranteed temperature in measuring the temperature of molten iron. The temperature exceeds the melting point, and the temperature is close to the melting point and the life is short. Pt
-The thermoelectromotive force of the PR thermocouple using the Rh wire is about 1/15 that of the CA thermocouple and about 1/7 that of the W-Re thermocouple, and is smaller than those thermocouples. There is a problem that the accuracy of the temperature is poor and the response is poor. for that reason,
At the site, in order to measure the temperature of the molten metal in the blast furnace, the operator is forced to stay at the measurement place for about 8 seconds until the temperature stabilizes near the blast furnace.

Further, when the protection tube of the thermocouple is formed in a laminated structure, there is a problem that heat transfer in the protection tube is poor and response is slow. By the way, the W-Re thermocouple can be used in the air and in an inert gas atmosphere, and the usable temperature in the air is 400 ° C., which is the limit temperature. Temperature is 2300 ° C
Is the limit temperature.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems by using a wire having a melting point of, for example, 2 mm.
By using a W-Re wire at a temperature of 300 ° C. or higher, and by arranging carbon-inorganic fibers having increased resistance to the molten metal as a protective layer on the outer peripheral surface of the protective tube, thermal shock is reduced, It is an object of the present invention to provide a fiber-reinforced thermocouple that can improve the life of a protective tube and enable repeated temperature measurement of 700 times.

[0008] The present invention comprises an inner tube having a heat receiving portion exposed to the outside at an end thereof, and a coated fiber having a coating which is multiply wound around a portion of the inner tube which is in contact with the molten metal on the outer surface thereof. And a filler made of a heat-resistant material filled in the inner tube, and a different temperature measuring part disposed in the filler and connected at an end. The present invention relates to a fiber-reinforced thermocouple composed of a pair of metal wires having a composition.

[0009] The film coated on the surface of the fiber,
It is made of alumina, silicon carbide, silicon nitride, and silicon oxide. Further, the core portion made of the fiber body of the coated fiber constituting the fiber assembly may be any one of carbon fiber, silicon carbide fiber, silicon nitride fiber, and alumina fiber.
Alternatively, it is composed of an aggregate thereof.

The inner tube is made of ceramic, cermet,
It is formed of any of heat-resistant metals.

The metal wire is made of W-5Re alloy and W-26.
It is made of a Re alloy or a Pt and Pt-Rh alloy.

The filler is a heat-resistant ceramic made of reaction-sintered silicon nitride containing titanium. Alternatively, the filler is composed of a mixture of an inorganic substance converted from an organosilicon polymer as a silicon nitride powder filler and a heat-resistant ceramic powder. Alternatively, the filler is made of a material in which a powder containing at least one of silicon nitride, silicon carbide, aluminum nitride, and alumina is used as a filler and bonded with a dehydration condensation type glass. Further, the filler is a material containing O, Al, Mg, and P.

This fiber-reinforced thermocouple is, as described above,
Since the protective tube is composed of the inner tube and the fiber assembly of the protective layer provided on the outer peripheral surface, the protective tube itself has a structure reinforced with outer fibers, and even if the protective tube is subjected to thermal shock, cracks will occur. Without extending to the inside, the life of the protection tube is improved, the durability of the thermocouple is improved, and the thermocouple itself can be used, for example, 700 times.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fiber-reinforced thermocouple according to the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of a fiber-reinforced thermocouple according to the present invention, FIG. 2 is an enlarged cross-sectional view of the fiber-reinforced thermocouple of FIG. 1 taken along line AA, and FIG. FIG. 2 is an enlarged cross-sectional view of a carbon fiber covered with a coating film.

The fiber-reinforced thermocouple according to the present invention comprises an inner tube 2 having a heat receiving portion 4 exposed to the outside at its tip, a filler 8 made of a heat-resistant material filled in the inner tube 2, and a filler 8 in the filler 8. And a pair of metal wires 6, 7, 7.
And a fiber assembly 5 composed of a fiber having a coating which is wound multiple times around a portion of the inner tube 2 which is in contact with the molten metal to be measured and which has a coating on the surface. The protective tube 1 includes an inner tube 2 and a fiber assembly 5, and the fiber assembly 5 forms a protective layer for the inner tube 2. The heat receiving portion 4 of the inner tube 2 is a portion exposed to the outside at the forefront of the protective tube 1 and is a region for measuring a temperature in contact with a molten metal such as a steelmaking molten metal. It is a portion that penetrates the aggregate 5 and is exposed to the outside from the fiber aggregate 5.

As shown in FIG. 3, in the fiber assembly 5, individual covering fibers 11 are wound around the inner tube 2 to form a protective layer of the inner tube 2. In each of the coated fibers 11, a coating 12 made of silicon carbide, alumina, silicon nitride, or silicon oxide is coated on an outer peripheral surface of a core portion 15 made of a fibrous body. The core 15 made of the fiber body of the covering fiber 11 is made of any one of carbon fiber, silicon carbide fiber, silicon nitride fiber, and alumina fiber, or an aggregate thereof. Therefore, since the core portion 15 made of a fibrous body is covered with the coating 12 of ceramics or the like, it is not exposed to the outside and does not come into direct contact with air, that is, oxygen.

The inner tube 2 provided with the heat receiving portion 4 is formed of any one of ceramics, cermet, and heat-resistant metal. The inner tube 2 is made of, for example, a cermet layer based on Mo having a small thermal expansion coefficient and hardly reacting with iron, for example, Mo / ZrO ₂ , Mo / ZrN, Mo / Zr.
It is made from any one of B ₂ and Mo-ZrC or a composite thereof. Therefore, since the molten iron does not adhere to the outer surface of the heat receiving section 4 of the inner tube 2, the responsiveness to temperature measurement does not deteriorate.

The metal wires 6 and 7 are made of W-5Re alloy and W-2
6Re alloy or Pt and Pt-Rh alloy. In this embodiment, the pair of metal wires 6 and 7 as the temperature detector 3 are formed of a tungsten-rhenium alloy wire. The composition of one metal wire 6 is W-5Re,
The composition of the other metal wire 7 is W-26Re. W
-5Re wire metal wire 6 and W-26Re wire metal wire 7
Are arranged so as to extend while being buried in the filler 8 in the inner tube 2 of the protective tube 1. The ends of the metal wires 6 and 7 are connected to form a temperature measuring section 9, and the temperature measuring section 9 is in close contact with the inner surface 10 of the heat receiving section 4 of the inner tube 2. The other end of the metal wire 6 of the W-5Re element wire and the other end of the metal wire 7 of the W-26Re element wire extend from the sealing member 13 provided in the opening 14 at the end of the protection tube 1. One end is connected to a measuring instrument through a stainless steel support rod fixed by a collet chuck.

The filler 8 is made of reaction-sintered silicon nitride to which titanium is added, and is made of a heat-resistant ceramic having a heat-resistant porous structure. Further, O, Al,
Mg and P are contained. The filler 8 has a heat-resistant porous structure, is configured to have a small thermal conductivity, and blocks the transfer of heat to regions other than the temperature measurement region. In other words, the heat capacity of the temperature measurement region can be reduced. The temperature measurement responsiveness can be improved. For example, the filler 8 can be configured to have a low thermal conductivity by being configured to have a structure having many voids.

Alternatively, the filler 8 is composed of a mixture of an inorganic substance converted from an organosilicon polymer as a silicon nitride powder filler and a heat-resistant ceramic powder. When the filler 8 is composed of a mixture of an inorganic substance and a heat-resistant ceramic powder, carbon or BN is contained in the mixture to absorb oxygen contained in the air contained in the filler 8, so that the temperature detector can be used. The adverse effects such as oxidation of the metal wires 6 and 7 can be cut off, the disconnection of the metal wires 6 and 7 can be prevented, and the durability can be improved.

Alternatively, the filler 8 is made of a material in which a powder containing at least one of silicon nitride, silicon carbide, aluminum nitride, and alumina is used as a filler and bonded with a dehydration condensation type glass.

Further, since the fiber assembly 5 has heat resistance and excellent erosion resistance, and has a multi-layer structure of fibers, even if cracks occur in the outermost shell layer due to thermal shock, the fiber is gradually applied to the inner layer. Because it breaks, it does not lead to catastrophic breakage, for example, like a conventional ceramic shell. Further, the inner tube 2 inside the fiber assembly 5 can be filled with an inert gas such as N ₂ or Ar when the filler 8 is filled and manufactured. The sealing member 13 is fitted to form a sealed state.

-Example 1-An inner tube made of Mo-ZrO ₂ having one end closed and the other end open by applying a slurry containing alumina as a main component to the surface of a carbon fiber, and then using a filament winding device. 2 to form a fiber assembly 5 on the outer periphery of the inner tube 2. The protective tube 1 was placed in a glass tube and sintered by a hot isostatic press (HIP) method to form a carbon fiber layer fiber assembly 5 on the outer peripheral surface of the inner tube 2. Silicon nitride, aluminum phosphate [Al (PO ₄ )], magnesia (Mg)
Fill with a slurry solution consisting of O). Then, the inner tube 2
A metal wire 6 of a W-5Re wire and a metal wire 7 of a W-26Re wire having a wire diameter of 0.2 mm, a length of 200 mm, and a welded tip were inserted therein, and were cured by a heat treatment by a dehydration condensation reaction. . Open end 14 of inner tube 2 in protective tube 1
Was sealed with a sealing member 13 made of dense glass made of B ₂ O ₃ and ZnO. Next, though not shown, the protection tube 1 was fixed to a stainless steel support rod via a collet chuck.

Example 2 A carbon fiber, a silica fiber and an alumina fiber were wound around the protective tube 1 while twisting. When the protective tube 1 around which the fiber was wound was immersed in the molten iron, it was found that only the silica fiber was melted and a coating was formed on the surface of the carbon fiber.

Example 3 After immersing carbon fibers in a polycarbosilane solution, the protective tube 1
And heat-treated in a nitrogen atmosphere.
Polycarbosilane turned into silicon carbide and formed a coating on the surface of the carbon fiber.

Example 4 Using the thermocouples prepared in Examples 1, 2 and 3, the temperature of a steel melt at about 1750 ° C. was measured. It was about 10 seconds. The temperature of the molten steel was measured with these thermocouples more than 700 times, and it was found that the thermocouples had durability and could be used repeatedly.

For comparison, as a comparative example, a thermocouple was manufactured using a protective tube made of a monolithic material without using the fiber assembly 5 as in the present invention. Similarly, the thermocouple of the comparative example was placed in a molten steel at about 1750 ° C. to measure the temperature, and its responsiveness was tested. The thermocouple of the comparative example was unusable due to the cracks extending to the inside of the thermocouple due to thermal shock by repeated temperature measurement several ten times or more.

[0028]

As described above, the fiber-reinforced thermocouple according to the present invention has a structure in which the protective tube has a structure in which the inner tube having a high thermal conductivity is wound with a fiber assembly, and thus has high heat resistance and high durability. The temperature measurement responsiveness can be greatly improved. In addition, the outer fiber assembly does not allow the cracks in the protective tube to propagate to the inside, and the temperature of the molten steel can be measured accurately and quickly over 700 times, and the durability can be improved. Can provide a long life thermocouple.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a fiber-reinforced thermocouple according to the present invention.

FIG. 2 is an enlarged cross-sectional view of the fiber-reinforced thermocouple of FIG.

FIG. 3 is an enlarged cross-sectional view of a carbon fiber covered with a film constituting a fiber assembly.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Protective tube 2 Inner tube 3 Temperature detector 4 Heat receiving part 5 Fiber assembly 6,7 W-Re strand 8 Filler 9 Temperature measuring part 10 Inner surface of inner tube 11 Coated fiber 12 Coated 13 Sealing member (with heat-resistant member and (Glass) 14 open end 15 core made of fibrous body

Claims (9)

[Claims] 1. An inner tube provided with an externally exposed heat receiving portion at the tip and a coated fiber having a coating coated on the surface and wrapped around a portion of the inner tube in contact with the molten metal outside. A protective tube composed of a fiber assembly, a filler made of a heat-resistant material filled in the inner tube, and a different composition constituting a temperature measuring part disposed in the filler and having an end connected. Fiber-reinforced thermocouple consisting of a pair of metal wires. 2. The fiber-reinforced thermocouple according to claim 1, wherein said coating covering the surface of said fiber is formed of alumina, silicon carbide, silicon nitride, and silicon oxide. 3. The core portion made of the fiber body of the coated fiber constituting the fiber aggregate is made of any one of carbon fiber, silicon carbide fiber, silicon nitride fiber, and alumina fiber, or an aggregate thereof. The fiber-reinforced thermocouple according to claim 1, wherein the thermocouple is formed. 4. The fiber-reinforced thermocouple according to claim 1, wherein the inner tube is formed of any one of ceramics, cermet, and heat-resistant metal. 5. The metal wire comprises a W-5Re alloy and a W-2 alloy.
The fiber-reinforced thermocouple according to any one of claims 1 to 4, comprising a 6Re alloy or a Pt and Pt-Rh alloy. 6. The fiber-reinforced thermocouple according to claim 1, wherein the filler is made of a heat-resistant ceramic made of reaction-sintered silicon nitride to which titanium is added. 7. The method according to claim 1, wherein said filler is composed of a mixture of an inorganic substance converted from an organosilicon polymer as a silicon nitride powder filler and a heat-resistant ceramic powder. Fiber reinforced thermocouple. 8. The method according to claim 1, wherein the filler is made of a material in which a powder containing at least one of silicon nitride, silicon carbide, aluminum nitride, and alumina is combined as a filler with a dehydration condensation type glass. The fiber-reinforced thermocouple according to any one of claims 1 to 5. 9. The fiber reinforced thermocouple according to claim 1, wherein the filler contains O, Al, Mg, and P.