JP2002214051A - Thermocouple for molten metal and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermocouple for a molten metal which is easily manufactured, with no variation among products while excellent in durability. SOLUTION: The perimeters of a pair of metal wires 3a and 3b of heterogeneous metals constituting a thermocouple and a measuring contact point 13 where the chip of them are connected together, are embedded in a rod-like insulating ceramics body 10. A protecting layer 5 comprising a material different from the ceramics is formed on the outside surface of the ceramics body 10. Compensating conductive wires 15 and 16 are connected to the base ends of the pair of metal wires 3a and 3b, respectively, and a reference contact point to which a potentiometer is connected is provided to the end of the compensating conductive wires 15 and 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermocouple for molten metal having excellent durability suitable for measuring the temperature of molten metal such as cast iron molten metal and a method for producing the same.

[0002]

2. Description of the Related Art As an alternative to a consumable thermocouple conventionally used for measuring the temperature of a molten metal, the present applicant has disclosed a tungsten-rhenium inside a protective tube made of silicon nitride Si ₃ N ₄ . (W-5Re, W-26Re) accommodates a pair of metal strands, and heat-resistant glass powder or reaction-sintered silicon nitride Si containing silicon nitride Si ₃ N ₄ as a main component in the space of the protection tube _Three
It proposes a thermocouple molten metal filled with powder of N _4.
This is because the product tends to vary depending on the filling amount of powder such as heat-resistant glass.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermocouple for molten metal which is easy to manufacture, has no variation in products, and has excellent durability, and a method for manufacturing the same. is there.

[0004]

In order to solve the above-mentioned problems, the present invention relates to a configuration in which the periphery of a pair of metal wires made of dissimilar metals constituting a thermocouple and the tip of the pair of metal wires are formed. A measuring contact connected to each other is embedded in a rod-shaped insulating ceramic body, and a protective layer having a component different from that of the ceramic is formed on an outer surface of the insulating ceramic body. And a reference contact for connecting a potentiometer to the end of the compensating wire.

Further, according to the method of the present invention, a conductive paste containing a dissimilar metal constituting a thermocouple is printed on opposing inner surfaces of a pair of molded bodies made of insulating ceramic powder, and the pair of molded bodies is formed. Sandwiching a plate-shaped intermediate molded body made of an insulating ceramic powder between them; and simultaneously pressing and heating the pair of molded bodies and the intermediate molded body by a hot press method, and simultaneously sintering the pair of molded bodies. The method is characterized by comprising a step of connecting the tips of the conductive pastes of the molded bodies to each other, and a step of connecting a compensating wire to the base ends of the conductive pastes of the pair of molded bodies.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, tungsten-rhenium (W-5Re, W-26Re), platinum-rhodium (Pt) are coated on the inner surfaces of a pair of compacts made of insulating ceramic such as silicon nitride Si ₃ N _4. , Pt-Rh) or a pair of metal wires made of a different kind of metal, or a conductive paste containing a different kind of metal is printed, and a pair of metal wires or a conductive material is formed between a pair of molded bodies. A bar-shaped insulating ceramic body is formed with a plate-shaped intermediate body made of insulating ceramic sandwiched except for the tip of the conductive paste, and the tips of a pair of metal wires or conductive paste are connected to each other. To form a measurement contact. On the outer surface of the rod-shaped insulating ceramic body, a sheet of a molybdenum Mo-based compound such as molybdenum-zirconium boride Mo-ZrB ₂ is wound or a paste containing a molybdenum Mo-based compound is applied to form a protective layer. Sintered together by hot pressing.

The sintered rod-shaped insulating ceramic body has durability against thermal shock and mechanical shock and protects a pair of metal wires or conductive paste. Molybdenum Mo
The protective layer of the system compound enhances the corrosion resistance of the sintered rod-shaped insulating ceramic body to the molten metal and prevents adhesion of the molten metal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a thermocouple for molten metal according to the present invention is made of an insulating ceramic powder such as silicon nitride Si ₃ N _4, preferably a pair of left and right of the molded body 2 forming a semicircular section Tungsten-rhenium (W-5Re, W-26R)
e), a pair of metal wires 3a, 3b made of different kinds of metal constituting a thermocouple such as platinum-rhodium (Pt, Pt-Rh) are embedded or bonded. Terminals 14a, 1 made of metal or conductive ceramic are provided at the base ends of the metal wires 3a, 3b.
4b is connected. Pair molded body 2 is a plate-shaped intermediate molded body 4 made of insulating ceramic powder such as silicon nitride Si ₃ N ₄ of
Is formed, the rod-shaped insulating ceramic body 10 is formed, and the measuring contacts 13 are formed by connecting the tips of the metal wires 3a and 3b to each other. Insulating ceramic body 1
Molybdenum on an outer surface of the 0 - protective layer 5 of a molybdenum Mo compounds such as zirconium boride Mo-ZrB ₂ is formed. The rod-shaped insulating ceramic body 10 and the molded body 2 are sintered by applying pressure and heating by a hot press method. Metal strand 3a,
Compensating wires 15 and 16 are connected to terminals 14a and 14b of 3b, respectively, and reference contacts for connecting a potentiometer are formed at ends of the compensating wires 15 and 16. Compensating conductors 15, 16
Is for connecting the measuring contact 13 and a reference contact for connecting the potentiometer, and makes the thermoelectric characteristics of the metal wires 3a, 3b and the conducting wire match.

As shown in FIG. 2, the metal wires 3a and 3b are insulated from each other inside the sintered ceramic body 10. A molybdenum Mo-based protective layer 5 is formed on the outer surface of the sintered insulating ceramic body 10.

As shown in FIG. 3, in order to manufacture a thermocouple for molten metal according to the present invention, a pair of left and right formed bodies 2 of silicon nitride Si ₃ N _{4 having a} substantially semicircular cross section are opposed to each other. The inner surface is made of tungsten-rhenium (W-5Re, W-26R
e), a pair of metal wires 3a, 3b made of different kinds of metals constituting a thermocouple such as platinum-rhodium (Pt, Pt-Rh) are embedded or tungsten-rhenium (W-5Re, W-26R).
e) Print a paste obtained by mixing a binder with a powder of platinum or rhodium (Pt, Pt-Rh). Next, an insulating ceramic main body 10 is formed by sandwiching a plate-shaped intermediate molded body 4 formed from an insulating ceramic powder such as silicon nitride Si ₃ N ₄ between a pair of molded bodies 2. Then, a paste in which a binder is mixed with a powder of a molybdenum Mo-based compound such as molybdenum-zirconium boride Mo-ZrB ₂ to be the protective layer 5 is applied to the outer surface of the insulating ceramic body 10, or the protective layer 5 is formed. A sheet of a molybdenum Mo-based compound is wound, inserted into a pair of molds having a substantially semicircular cross section or a pair of upper and lower molds having a substantially semicircular cross section, and is squeezed by hot pressing and sintered.

The intermediate molded body 4 is shorter than the molded body 2,
When squeezing a pair of compacts 2 from both sides, one pair of compacts 2
The tips 2a of the metal wires 3a, 3b printed on the inner surfaces of the two are connected to each other to form a measurement contact 13.

Finally, a sheet of a molybdenum Mo-based compound is wound around a pair of compacts 2 and inserted into a mold, and subjected to hot pressing at a temperature of about 1400 ° C. and a pressure of 100 to 3 ° C.
Sintering is performed by heating under pressure at 00 kg / cm ² .

The protective layer 5 made of a molybdenum Mo-based compound is sintered by sandwiching the intermediate molded body 4 between a pair of molded bodies 2 by hot pressing, and then applied to the outer surface of the molded body 2.
Subsequently, it may be heated again so as to be in close contact with the molded body 2.

[0014]

According to the present invention, as described above, the periphery of a pair of metal wires made of dissimilar metals constituting a thermocouple and the measuring contact formed by connecting the tips of the metal wires to each other are connected. Embedded in a rod-shaped insulating ceramic body, a protective layer of a component different from that of the ceramic is formed on an outer surface of the insulating ceramic body, and a compensating conductor is connected to a base end of the pair of metal wires. In addition, a reference contact for connecting a potentiometer to the end of the compensating lead wire is provided, so that the measuring contact for the molten metal is stable and reproducibility for repeated use is obtained.

Silicon nitride A film of a metal wire is formed by printing on a flat inner surface of a pair of molded bodies having a semicircular cross section made of ceramic such as Si ₃ N _4, and silicon nitride is sandwiched between the pair of molded bodies.
A plate-shaped intermediate molded body made of ceramics such as Si ₃ N ₄ is sandwiched, and a sheet of a molybdenum Mo-based compound is wound around the outer surfaces of a pair of molded bodies, and then heated and sintered while being pressed by a hot press method. Therefore, it is easy to process and helps to reduce manufacturing costs.

Since the measuring contact is buried inside the insulating ceramic body by the hot pressing method, the manufacturing is simple, the product has no variation and the durability is excellent.

By providing a protective layer of a molybdenum (Mo) compound on the insulating ceramic body, the corrosion resistance to the molten metal is improved.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a thermocouple for molten metal according to the present invention.

FIG. 2 is a plan sectional view of the thermocouple for molten metal.

FIG. 3 is a front sectional view showing a manufacturing process of the thermocouple for molten metal.

[Explanation of symbols]

A1 to A4: Thermocouple 2: Molded body 2a: Tip 3a: Metal wire 3b: Metal wire 4: Intermediate molded body 5: Protective layer 10: Insulating ceramic body 13: Measurement contact 14a: Terminal 14b: Terminal 15 : Compensating lead 16:
Compensating conductor

Claims (8)

[Claims] 1. A rod-shaped insulative ceramic body is connected to a pair of metal wires made of dissimilar metals constituting a thermocouple and a measuring contact formed by connecting the tips of the metal wires to each other. A protective layer having a component different from that of the ceramic is formed on the outer surface of the insulating ceramic body, and a compensating conductor is connected to a base end of each of the pair of metal wires. A thermocouple for molten metal, comprising a reference contact for connecting a potentiometer to the thermocouple. 2. The thermocouple for molten metal according to claim 1, wherein said insulating ceramic body is made of one of silicon nitride and sialon. 3. The thermocouple for molten metal according to claim 1, wherein said pair of metal wires are made of tungsten-rhenium W-Re having different components. 4. The thermocouple for molten metal according to claim 1, wherein said pair of metal wires are made of tungsten-rhodium Pt-Rh having different components. 5. The thermocouple for molten metal according to claim 1, wherein said protective layer contains a molybdenum-based compound. Wherein said protective layer is a molybdenum - boride comprised of zirconium Mo-ZrB _2, a thermocouple for molten metal according to claims 1 to 6. 7. A conductive paste containing a dissimilar metal constituting a thermocouple is printed on opposing inner surfaces of a pair of molded bodies made of insulating ceramic powder, and the insulating ceramic is placed between the pair of molded bodies. A step of sandwiching a plate-shaped intermediate molded body made of powder; and pressing and heating the pair of molded bodies and the intermediate molded body by hot pressing to simultaneously sinter them together, A method for manufacturing a thermocouple for molten metal, comprising: a step of joining the tips of the pastes to each other; and a step of connecting a compensating wire to the base ends of the conductive pastes of the pair of compacts. 8. A pair of metal wires made of a dissimilar metal constituting a thermocouple is bonded to opposing inner surfaces of a pair of molded bodies made of insulating ceramic powder, and the pair of molded bodies is interposed between said pair of molded bodies. A step of sandwiching a plate-shaped intermediate molded body made of insulating ceramic powder, and sintering the pair of molded bodies and the intermediate molded body by pressing and heating by a hot press method,
Joining one end of the metal strand of the pair of molded bodies to one another,
Connecting a compensating lead wire to the other end of the metal strand of the pair of compacts.