JP3550828B2 - Thermocouple structure - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a high-temperature high-precision thermocouple structure.
[0002]
[Prior art]
Conventional thermocouples have been developed to accurately measure the temperature of high-temperature liquids and gases. The thermocouple adapts various measuring materials in order to measure the temperature in the temperature range of 300 ° C to 1400 ° C. In many cases, the thermocouple wire is weak against an oxidizing or reducing atmosphere, and the wire is generally used in a protective pipe. In a conventional thermocouple, for example, a wire made of a W-Re material constituting a thermocouple is passed from one end to the other in a spaced-apart state through a protective pipe made of Al ₂ O ₃ , and the tip of the wire is joined. The elongated protective pipe is filled with an insulating material such as MgO, thereby protecting the wires and preventing the wires from contacting each other to ensure heat resistance.
[0003]
In addition, the protective tube that houses the thermocouple is manufactured using the following materials. That is, the conventional protective tube is a heat-resistant sheath tube (heat-resistant temperature: 600 ° C.), BN (heat-resistant temperature: 1000 ° C.), porcelain (heat-resistant temperature: 1400 ° C.), alumina (heat-resistant temperature: 1600 ° C.), high chromium steel ( Various protective tubes such as heat-resistant temperature: 1050 ° C. and alundum (heat-resistant temperature: 1400 ° C.) are used. A thermocouple made of such a protective tube is damaged in one measurement and cannot be used again when used up to the heat-resistant temperature, so that it is usually about 600 ° C. to 800 ° C., and even at a high temperature of about 1000 ° C. It is currently used as a temperature measurement.
[0004]
Further, examples of thermocouples in which Si ₃ N ₄ is formed in a protective pipe include those disclosed in JP-A-55-121972, JP-A-61-246636, and JP-A-2-217361. .
[0005]
The hermetically sealed silicon nitride sintered body disclosed in Japanese Patent Application Laid-Open No. 55-121972 can be applied to a protection tube of a thermocouple, and is a Si ₃ N ₄ sintered body having a limited bulk specific gravity generated by a reaction sintering method. The aggregate was humidified in a humidified N ₂ atmosphere so as to have a specific dew point, and heat-treated at 1250 to 1500 ° C to make the surface airtight.
[0006]
Further, the protective tube for continuous temperature measurement of molten steel disclosed in JP-A-61-246636 can be used as a protective tube for a thermocouple, and an AlN is provided between a protective tube made of reactive sintered silicon nitride and an alumina inner tube. A protective tube in which powder was filled and alumina wool was further filled in the upper part of the AlN powder was produced, in which the erosion rate by molten steel was reduced, and measurement of the molten steel temperature for a long time was enabled.
[0007]
Further, the reaction sintered silicon nitride ceramics disclosed in JP-A-2-217361 can be used as a protection tube for a thermocouple, and a compact formed by molding Si powder is heated at about 1200 to 1600 ° C. in a N ₂ atmosphere. Reaction sintered.
[0008]
[Problems to be solved by the invention]
However, a protection tube for protecting a conventional thermocouple actually causes considerable damage to the protection tube at an ambient temperature of 1000 ° C. or more, or is discarded after a single use with a conventional thermocouple. There are also things. For this reason, the current state of the related art thermocouple is that the cost is high, and it is difficult to measure the temperature of the high-temperature furnace or the molten metal. For example, when the thermocouple is formed in a small-diameter pipe shape, there is a problem in manufacturing in order to appropriately adjust the strength of the protection tube for protecting the thermocouple and the density of the filler in the protection tube. Further, since a protective tube made of BN is oxidized in the presence of O ₂ , it is presently used after exhausting O ₂ in the furnace.
[0009]
A conventional thermocouples, as described above, the thermocouple to prepare a protective pipe in _Al 2 _{O 3,} heat-resistant temperature of the _Al 2 _{O 3} is about 800 ° C.. That is, in the protective pipe of Al ₂ O _3, the enclosed MgO is porous, and O ₂ easily penetrates into the inside of the porous MgO, and W-5% Re or W- 5% used as a high-temperature thermocouple is used. 26% Re has a problem that it is easily oxidized due to the presence of O ₂ and is disconnected. Therefore, in the thermocouple made of the Al ₂ O ₃ protective pipe as described above, in the temperature measurement in a temperature atmosphere of 800 ° C. or more, the durability of the thermocouple has to be sacrificed, and a special temperature measurement is required. It had many problems such as using technology.
[0010]
Also, as the structure of the thermocouple, even when the protective tube is made of silicon nitride by reaction sintering, a pair of different types of wires extending in the longitudinal direction from one end to the other end are arranged in the protective tube. If an appropriate material is not selected as a filling member to be filled in the tube, a gap is generated between the inner surface of the protective tube and the filling member, and the wire is oxidized with O ₂ present in the protective tube to break the wire or heat shock. There is a problem that it is damaged by receiving.
[0011]
[Means for Solving the Problems]
An object of the present invention is to solve the above-mentioned problems, and to form a protective pipe with a heat-resistant ceramic such as Si ₃ N ₄ or SiC, and to insulate the ceramic such that a space is densely embedded in the protective pipe. A thermocouple printed band made of a tungsten (W) -rhenium (Re) alloy or platinum (Pt) -rhodium (Rh) on the outer surface of the insulator, and a thermocouple printed band in a protective pipe. An object of the present invention is to provide a thermocouple structure that is highly durable and has excellent heat shock resistance and high durability.
[0012]
The present invention relates to a protective pipe made of heat-resistant ceramic, a columnar insulator made of a composite material of TiN and Si ₃ N ₄ fitted in the protective pipe, and a longitudinally extending outer end of the insulator from one end to the other end. A pair of different types of printed bands printed so as to be spaced apart in the direction, a temperature sensing portion connected to both ends of the printed band formed at one end of the protection pipe, and the other end of the protection pipe The present invention relates to a structure of a thermocouple composed of connectors respectively connected to the print bands provided in the above.
[0013]
Alternatively, the present invention provides a protective pipe made of a heat-resistant ceramic, an insulating coating made of a composite material of TiN and Si ₃ N ₄ which covers a columnar base fitted in the protection pipe and an outer periphery of the base. A pair of printed bands of different types printed on the outer surface of the insulator so as to extend in the longitudinal direction from one end to the other end, and the printed band formed at one end of the protective pipe The present invention relates to a thermocouple structure composed of a temperature sensing part connected to both ends of the protection pipe and a connector provided at the other end of the protection pipe and connected to the print band.
[0014]
Further, one of the print bands is made of W-5% Re, and the other print band is made of W-26% Re. Further, the temperature sensing part is configured by sintering a thin film of Si ₃ N ₄ or SiC coated on an end of the protection pipe. Further, the protection pipe is made of Si ₃ N ₄ or SiC.
[0015]
Further, the connector provided at the end of the protection pipe is formed of a lead wire which is metallized with the Ag-Cu-Ti powder and connected to the print band. Further, the printed band and the lead wire are joined to each other so as not to be short-circuited on an Al ₂ O ₃ cylinder disposed on the outer surface of the insulator portion protruding from the protection pipe.
[0016]
Further, a portion where the surface of the insulator is exposed without printing the printed band is adhered to an inner surface of the protection pipe.
[0017]
The structure of this thermocouple is such that a protection pipe is made by selecting Si ₃ N ₄ as a material of a protection tube for protecting the thermocouple, while an insulator is made of a composite material in which Si ₃ N ₄ and TiN are mixed. Then, a powder paste obtained by pulverizing and atomizing W-Re on the outer surface of the insulator is printed from one end to the other end on one half or less of the surrounding surface, and two printed bands are printed. The entire periphery of the tip is printed with the paste to connect the two strips, and the insulator on which the printed strips are printed is inserted into the protective pipe and sintered. It is possible to provide a thermocouple having extremely excellent performance. Further, the composite material obtained by mixing 10 to 15% of TiN with Si ₃ N ₄ does not shrink due to sintering, but rather expands slightly, and the insulator closely adheres to the protective pipe of Si ₃ N ₄ to protect the composite material. because prevents intrusion O ₂ in the region of the printing zone located between the pipe and the insulator, a thermocouple print zone without be disconnected by oxidation, it is possible to improve the durability.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a thermocouple structure according to the present invention will be described with reference to the drawings. 1 is a sectional view showing an embodiment of the structure of the thermocouple according to the present invention, FIG. 2 is an enlarged sectional view taken along line AA of FIG. 1, and FIG. 3 is a printed band in the structure of the thermocouple shown in FIG. It is a perspective view which shows the insulator.
[0019]
The structure of this thermocouple mainly includes a protection pipe 1 made of heat-resistant and corrosion-resistant ceramics, a columnar insulator 9 made of a composite material of TiN and Si ₃ N ₄ inserted into the protection pipe 1, A pair of different types of conductor printed bands 2, 3 printed on the outer surface 16 of the body 9 so as to extend from one end to the other in the longitudinal direction, and a printed band 2, formed on one end of the protective pipe 1. 3 is composed of a conductor print ring 8 forming the temperature sensing part 4 to which both ends are connected, and a connection line 5 forming a connector 11 respectively connected to the print bands 2 and 3 provided at the other end of the protection pipe 1. I have. One print band 2 is made of W-5% Re material, the other print band 3 is made of W-26% Re, and the print ring 8 is made of W-Re. The print bands 2 and 3 and the print ring 8 can be made of a combination of platinum and rhodium platinum or a combination of W and WMo (Mo: 25%), in addition to W-Re. Further, the temperature sensing part 4 is configured by sintering a thin film 7 of Si ₃ N ₄ or SiC coated on the end of the protection pipe 1.
[0020]
The connector 11 provided at the end of the protective pipe 1 is composed of connection lines, that is, lead wires 5 connected to the printed bands 2 and 3 by metallizing with silver brazing material and Ag-Cu-Ti powder. . The Al ₂ O ₃ cylindrical body 14 disposed on the outer surface 16 of the portion of the insulator 9 protruding from the protection pipe 1 has a printed band 2, 3 and a lead wire 5 so that the printed bands 2, 3 do not short-circuit with each other. Are joined together. Furthermore, the printed belts 2 and 3 are not printed on the insulator 9, and the surface 6 of the insulator 9, that is, the portion 6 where the outer surface 16 is exposed, is bonded to the inner surface of the protective pipe 1.
[0021]
A mounting bracket 10 is fixed to the other end of the protection pipe 1 for mounting a thermocouple to another component. The mounting portion at the end of the protruding lead wire 5 on the mounting bracket 10 side constitutes the connector 11. The connector 11 is configured to be connected to a terminal of a temperature measuring device. The joint between the mounting fitting 10 and the protection pipe 1 is formed by converting the powder paste of Si and Ti filled in the hole 15 of the protection pipe 1 into a composite material by sintering, and the two are firmly adhered by the composite material. It is fixed.
[0022]
In the structure of the thermocouple, the protection pipe 1 is made of Si ₃ N ₄ or silicon carbide SiC which is excellent in heat resistance, corrosion resistance and heat shock resistance. When the protection pipe 1 is made of Si ₃ N ₄ , it is preferable that the insulator 9 fitted into the protection pipe 1 be made of a mixed material composed of Si ₃ N ₄ and titanium nitride TiN. Si ₃ when the N ₄ protective pipe 1 is arranged an insulator 9 of the filling member of the mixed material and Si ₃ N ₄ and TiN are insulator mixed material comprises non-shrink ceramics by sintering 9, and it is possible to provide an extremely stable thermocouple structure without generating a gap or the like between the protection pipe 1 and the insulator 9. Further, tungsten (W) line is a high-melting material, its thermal expansion coefficient of 4.6 × ^{10 -} is a 6 / K. The thermal expansion coefficient the _Si 3 _{N 4} is 3.1 × ^{10 -} since it is 6 / K, the _Si 3 _{N 4} and W, the thermal expansion coefficient has approximate, therefore, the thermocouple by a combination of both Is preferable in consideration of the coefficient of thermal expansion.
[0023]
The protective pipe 1, other _Si 3 _{N 4,} can be made from _Si 3 _{N 4} containing _{Y 2 O 3, Al 2 O} 3, SiO 2. In the longitudinal direction of the protective pipe 1, a large number of holes 15 are formed at intervals, and the holes 15 are filled with a mixed powder mainly composed of Si and Ti and sintered integrally in an N ₂ atmosphere. As a result, the protective pipe 1 and the insulator 9 are firmly joined together. In this case, the surface of the filled member of the filled composite material is coated with Si ₃ N _4, and the inside and outside of the protection pipe 1 through the hole 15 is prevented by the coating layer.
[0024]
At the end of the protective pipe 1, in order to fix the mounting bracket 10, Ag-Cu-Ti powder is applied to the insulator 9 exposed in the hole 15 formed in the protection pipe 1, and the mounting bracket 10 and the insulator 9 are fixed. Are fixed. A glass layer 13 containing Y ₂ O ₃ , Al ₂ O ₃ , and SiO ₂ is applied to the end on the connector 11 side to seal the end of the protective pipe 1.
[0025]
In the structure of this thermocouple, for example, as the insulator 9 serving as a core, a mixed powder of 90 wt% of Si powder and 10 wt% of Ti powder, or a mixed powder obtained by mixing a small amount of silicon nitride powder with the mixed powder in some cases. Is sintered in an N ₂ atmosphere to react with Si and Ti to form a composite of non-shrinkable ceramics composed of Si ₃ N ₄ and TiN. That is, it is produced in a non-shrinkable ceramic composite material composed of Si ₃ N ₄ and TiN that does not shrink during sintering. Next, different types of conductor printed bands 2 and 3 are printed on the outer surface of the insulator 9, and a printed conductor ring 8 is printed on the end of the insulator 9. Next, a paste of a mixed powder of 90 wt% of Si powder and 10 wt% of Ti powder is applied to the surface of the insulator 9 on which the conductor film is printed, and the paste is inserted into the protective pipe 1 made of silicon nitride, and N ₂ By integrally sintering in the atmosphere, the paste is converted into a non-shrinkable ceramic composite material of Si ₃ N ₄ and TiN that does not shrink and the insulator 9 is fixed to the protective pipe 1. At this time, when the powder of Si and Ti is housed in the protective pipe 1 and integrally sintered, if a number of holes 15 are formed in the longitudinal direction of the protective pipe 1, Si and Ti react with each other and react with Si. ₃ N ₄ and it is a composite of non-expansion ceramics consisting of TiN. After sintering, the holes 15 may be closed with a coating layer 17 of Si ₃ N ₄ , and the composite insulator 9 in the protection pipe 1 constitutes a protection film for the wires 2 and 3.
[0026]
Next, another embodiment of the structure of the thermocouple according to the present invention will be described with reference to FIG. The structure of the thermocouple of this embodiment has the same configuration as that of the above embodiment except that the structure of the insulator is different from that of the above embodiment. I do. In the structure of the thermocouple of this embodiment, an insulator 19 corresponding to the insulator 9 is composed of a columnar base 20 fitted into the protective pipe 1 and a composite of TiN and Si ₃ N ₄ covering the outer periphery of the base 20. The insulating cover 18 is made of a material. A pair of different types of printed bands 2 and 3 are printed on the outer surface of the insulating cover 18 of the insulator 19 so as to extend in a longitudinal direction from one end to the other end. The insulator 19 on which the printed bands 2 and 3 are printed is fitted into the protective pipe 1 and integrally sintered, whereby the insulator 19 and the protective pipe 1 are fixed.
[0027]
【The invention's effect】
As described above, the structure of the thermocouple according to the present invention is composed of a protective pipe made of ceramics, and a temperature-sensitive portion is formed at the tip thereof, so that the thermocouple is heat-resistant and corrosion-resistant. It has excellent shock properties and is suitable for temperature control and temperature measurement of high-temperature furnaces such as molten metal furnaces, plasma melting furnaces, and electric furnaces. This thermocouple structure is particularly suitable for measuring high temperatures in an oxidizing / reducing atmosphere. Further, since the mounting bracket fixed to the end of the protective pipe is firmly fixed, a thermocouple excellent in heat resistance, heat shock resistance, and durability can be provided. In particular, the filled insulator in a protective pipe is made of a composite material with TiN to Si ₃ N ₄ which Deki by reaction sintering of Si and Ti, the insulator has no shrinkage sintering during sintering Since non-shrinkable ceramics are formed, a dense structure can be formed in the protective pipe, and the printed band can be firmly held and protected by a structure that prevents O ₂ intrusion. Excellent durability and temperature measurement The accuracy becomes high, and a stable and reliable thermocouple can be provided.
[0028]
Since the structure of this thermocouple is excellent in heat resistance and heat shock resistance, it can be used repeatedly, and its manufacturing cost, running cost, etc. are lower than those manufactured using conventional materials such as NB. It can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of a structure of a thermocouple according to the present invention.
FIG. 2 is an enlarged cross-sectional view showing one embodiment along line AA in FIG. 1;
FIG. 3 is a perspective view showing an insulator having a printed band printed on a surface thereof and a lead wire joined to the insulator in the structure of the thermocouple of FIG. 1;
FIG. 4 is an enlarged sectional view showing another embodiment taken along line AA in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Protective pipe 2, 3 Print strip 4 Temperature sensing part 5 Lead wire 6 Gap 7 Thin film 8 Print ring 9, 19 Insulator 10 Mounting bracket 11 Connector 15 Hole 17 Coating layer 18 Insulation coating 20 Base

Claims (8)

A protection pipe made of heat-resistant ceramic, a columnar insulator made of a composite material of TiN and Si ₃ N ₄ fitted in the protection pipe, and spaced longitudinally from one end to the other end on the outer surface of the insulator A pair of conductor printed bands of different types printed so as to extend, a conductor temperature sensing portion connected to both ends of the printed band formed at one end of the protection pipe, and provided at the other end of the protection pipe. And a structure of a thermocouple constituted by connectors respectively connected to the printed band. A protective pipe made of a heat-resistant ceramic, an insulator made of a columnar substrate fitted into the protective pipe, and an insulating coating made of a composite material of TiN and Si ₃ N ₄ covering the outer periphery of the substrate; A pair of different types of conductor printed bands printed on the outer surface of the insulator so as to extend in a longitudinal direction from one end to the other end are connected to both ends of the printed band formed at one end of the protective pipe. The structure of a thermocouple comprising a conductor temperature sensing part and a connector provided at the other end of the protection pipe and connected to the printed band. The thermocouple structure according to claim 1 or 2, wherein one of the printed bands is made of W-5% Re and the other of the printed bands is made of W-26% Re. Structure of the thermocouple according to the protective pipe any one of claims 1 to 3, which is made from Si ₃ N ₄ or SiC. The temperature sensing section, the structure of the thermocouple according to claim 1, which is constituted by sintering a thin film the Si ₃ N ₄ or SiC coated on an end portion of the protective pipe . 6. The connector according to claim 1, wherein the connector provided at an end of the protection pipe includes a lead wire that is metallized on the print band with Ag—Cu—Ti powder and connected thereto. Thermocouple structure. 7. The printed band and the lead wire are joined to each other on the Al ₂ O ₃ cylindrical body disposed on the outer surface of the portion of the insulator protruding from the protection pipe so as not to be short-circuited to each other. Thermocouple structure. The structure of the thermocouple according to any one of claims 1 to 7, wherein a portion where the surface of the insulator is exposed without printing the printed band is adhered to an inner surface of the protection pipe.

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