JPH07260593A - Thermocouple protecting tube - Google Patents

Abstract

PURPOSE:To prevent damage and improve heat resistance and corrosion resistance by interposing heat resisting thermoplastic material between the outer peripheral surface of a fixing groove formed at the connecting part of a thermocouple protecting tube and the connecting part inner peripheral surface of the terminal part of an adapter. CONSTITUTION:The outer peripheral surface including a fixing groove 7 provided over the whole outer peripheral surface of the connecting part of a thermocouple protecting tube formed of ceramic material is provided with a thermoplastic metal ring 9 (made of copper) inserted from above the protecting tube 1. The metal ring 9 is then inserted into a terminal part 6 formed in the recessed shape of an adapter 2 to which an extension tube 3a is previously connected, and clamp-fixed by a set screw 5 from a through hole at the side face of the terminal part 6. The clamp-fixing of the protecting tube 1 is thereby attained, and the center in the longitudinal axis direction can be set easily. The connection of the protecting tube 1 can be attained by simple work of only fitting thermoplastic material (metal ring 9 or metal sheet) to the outer peripheral surface of the protecting tube 1, inserting it into the terminal part 6 of the adapter 2 and fastening it by the set screw 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermocouple protection tube for measuring the temperature of molten metal, and more particularly to a ceramic thermocouple protection tube.

[0002]

2. Description of the Related Art Recently, a protective tube made of ceramics such as silicon nitride or silicon carbide has been used in place of a metallic thermocouple protective tube. However, since these ceramic thermocouple protection tubes were manufactured by the reaction sintering method of nitriding or carbonizing metallic silicon, only 30 kg / mm ²
It had only a moderate flexural strength and could not sufficiently withstand mechanical stress and impact during temperature measurement. Regarding a thermocouple protection tube made of ceramics, Japanese Patent Publication No. 4-44628 proposes a thermocouple protection tube for measuring the temperature of a molten metal having a two-layer structure. That is, the inner layer of the two-layer structure made of silicon nitride or sialon ceramics having a high mechanical strength and impact resistance, the outer layer is mainly BN-SiO ₂
Since it is made of —Al ₂ O ₃ —Y ₂ O ₃ , it has good melt welding resistance and oxidation resistance. Therefore, this protective tube has remarkably high resistance to impact load, thermal shock, welding and oxidation, and further has sufficient corrosion resistance. Therefore, this thermocouple protection tube is supposed to have a significantly long life. The proposed thermocouple protection tube solves the conventional problems by improving the ceramic material and adopting a two-layer structure.

[0003]

Generally, a ceramic thermocouple protection tube is more expensive than a conventional metal protection tube, so that it is not possible to form the entire protection tube with ceramics, Only the portion inserted and requiring heat resistance is made of ceramics, and the remaining portion is made of metal.

Specifically, as shown in FIG. 4, a ceramic thermocouple protection tube 1 is provided with an extension tube 3 via a metal adapter 2.
The extension pipe 3a is connected to another extension pipe 3b via the elbow 4, and the extension pipe 3b is fixed to a terminal box (not shown). A thermocouple (not shown) is inserted into the thermocouple protection tube 1 through the extension tubes 3b and 3a. Then, only the protective tube 1 is immersed in the molten metal whose temperature is to be measured. Since the tip portion 10 of the thermocouple protection tube 1 is formed in a sealed state, the thermocouple inserted in the thermocouple protection tube 1 does not come into direct contact with the molten metal.

FIG. 3 is a longitudinal sectional view of an essential part in which the ceramic thermocouple protection tube 1 and the extension tube 3a in FIG. 4 are enlarged and attached by the metal adapter 2. The same parts as in FIG. 4 are the same. It is indicated by a reference numeral. As shown in FIG. 3, the conventional method of connecting the ceramic thermocouple protection tube 1 and the extension tube 3a to each other through the metal adapter 2 is as shown in FIG. The fixing groove 7 is formed by processing a predetermined width in the direction, the thermocouple protection tube 1 is fitted into the concave portion formed at the tip of the adapter 2, and is tightened and fixed by the set screw 5 through the through hole on the side surface of the adapter terminal portion 6. It is a thing. In this case, set screw 5
Since the tip and the fixing groove 7 are fastened and fixed by direct point contact, there is a problem that the point contact portion is damaged as a starting point due to mechanical stress or thermal stress generated at the time of fastening or during use. Therefore, it is an object of the present invention to provide a long-life thermocouple protection tube that can prevent damage to the ceramic thermocouple protection tube during tightening or during use and that has excellent heat and corrosion resistance.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, in which a thermocouple protection tube for measuring molten metal made of a ceramic material and an extension tube are made of a metal material. When connecting via the adapter, a thermoplastic resin is formed between the outer peripheral surface of the fixing groove formed in the connecting portion of the thermocouple protection tube formed of the ceramic material and the inner peripheral surface of the connecting portion of the terminal portion of the adapter. The material (metal ring or thin metal plate) is interposed. At least one fixing groove is formed, and the fixing groove and the connecting portion of the terminal portion are fixed by fixing means. The fixing means is for fixing a fixing screw by inserting a set screw into a hole penetrating the side surface of the connecting portion of the adapter terminal portion. In this clamping and fixing, the tip of the set screw plastically deforms the heat-resistant plastic material (metal ring or thin metal plate) to bring it into close contact with the surface of the fixing groove, thereby achieving surface contact instead of conventional point contact. For this reason, stress concentration on the ceramic protection tube can be reduced, and the thermocouple protection tube made of a ceramic material is not damaged. In addition, since the surface is clamped and fixed, eccentricity does not occur. The number of setscrews is preferably 3 (120 ° intervals) to 4 (90 ° intervals) for even tightening.

It is characterized in that one or more fixing grooves are formed. For example, a thermocouple protection tube made of a ceramic material has an outer diameter of 32 mm and a total length of 10
In the case of a large diameter and long length such as 00 mm, forming two or more fixing grooves further increases the degree of surface contact, so that good tightening and fixing can be obtained and damage to the thermocouple protection tube and prevention of deviation can be achieved. Suitable for core prevention.

The ceramic material forming the thermocouple protection tube of the present invention is a silicon nitride sintered body such as silicon nitride or sialon. Then, an outer layer containing MgO as a main component is formed on the surface layer of the silicon nitride sintered body or BN for the purpose of improving the resistance to molten metal corrosion, the resistance to molten metal adhesion, and the resistance to oxidation on the surface of the ceramic protection tube. And it is desirable to form an outer layer containing SiO ₂ . With these,
The life of the thermocouple protection tube made of a silicon nitride sintered body is dramatically improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a mounting portion showing an embodiment in which a thermocouple protection tube of the present invention is fastened and fixed. Note that, also in FIG. 1, the same portions shown in FIG. 3 are denoted by the same reference numerals.

(Embodiment 1) In FIG. 1, the thermocouple protection tube 1 is formed on the outer peripheral surface including one fixing groove 7 provided over the entire outer circumference of the connecting portion of the thermocouple protection tube 1 formed of a ceramic material. Plastic metal ring from above (copper, wall thickness 1.
5 mm) 9 was inserted. In this case, the inner diameter of the copper ring 9 is processed to a size that allows loose fitting so that it does not slip off from the outer diameter of the thermocouple protection tube 1. Next, SUS304 to which the extension pipe 3a is connected in advance
It was inserted into the adapter terminal portion 6 formed in the concave shape of the adapter 2 made of, and fixed by tightening the set screw 5 from the through hole on the side surface of the adapter terminal portion 6. In this embodiment, the set screw 5 is made of chrome molybdenum steel (SCM material), and the set screw 5 is
By tightening, the 1.5 mm thick portion of the copper ring 9 is pressed by the tip of the set screw 5 to be deformed, as shown in FIG. 1, and comes into close contact with the groove surface of the fixing groove 7. Further, the outer peripheral surface portion of the copper ring 9 that does not deform comes into close contact with the inner peripheral surface of the adapter terminal portion 6 of the adapter 2. As described above, the thermocouple protection tube 1 can be clamped and fixed, and the core in the vertical axis direction can be easily set. As described above, in the present invention, a plastic material (metal ring or metal thin plate) is fitted to the outer peripheral surface of the thermocouple protection tube in which the fixing groove is formed, and inserted into the adapter terminal portion,
The connection of the thermocouple protection tube can be achieved by a simple operation of just tightening the set screw. The set screw 5 is made of a material harder than the heat-resistant plastic metal ring 9, such as stainless steel,
It is required to be chrome molybdenum steel (SCM material), nickel chrome steel (SNC material), or the like. In this embodiment, the plastic material is a copper ring, but it may be a thin plate.
Alternatively, a ring or a thin plate made of brass, stainless steel or the like may be used. In short, any material may be used as long as it can be plastically deformed by the set screw 5 at room temperature and closely adhere to the fixing groove 9 to withstand the temperature during use.

Here, the thermocouple protection tube 1 uses sialon ceramics, and its material characteristic is that the density is 3.26 g / c.
m ³ , bending strength was 90 kg / mm ² , and fracture toughness K _IC was 5.8 MPa · m ^1/2 . The sialon sintered body is 70% by weight of silicon nitride powder containing 65% by weight or more of α phase.
Above, one kind or more and 20% by weight or less of oxides of group IIIa elements of the periodic table and 20% by weight of aluminum oxide powder
A mixture of the following and 15% by weight of aluminum nitride solid solution (AlN-SiO ₂ ) powder was sintered, and further,
A surface layer containing magnesium oxide as a main component is formed on the sintered body. This thermocouple protection tube, 680 ° C
As a result of continuous use for 1 year to measure the temperature of the molten aluminum, there is no damage at the joint between the ceramic protection tube and the adapter, and it has excellent corrosion resistance, molten metal adhesion resistance, and oxidation resistance. It could be used free.

(Example 2) 82.7% by weight of Si
₃N_Four, 5.8 wt% Y₂O₃, 3.8 wt% Al
₂O₃And 7.7 wt% AlN polytype for protective tubes
It is used as a ceramic material and BN is added on top of this sintered body.
SiO₂As a main component (specifically, BN-SiO₂−
Al₂O₃-Y₂O₃) A surface layer was formed. Wall thickness 1m
Example 1 was repeated except that a copper metal ring of m was used.
It was Set screw for 1 mm thick copper metal ring
5 (see FIG. 1) provides complete contact with the fixing groove 7.
It was Immerse the attached protective tube in the molten cast iron
Then, the temperature was measured. The surface of the protective tube was slightly dissolved
But 1400 to 1500 without causing damage or cracks
It was able to withstand a temperature of ° C for 30 hours.

(Embodiment 3) FIG. 2 is a vertical sectional view of a mounting portion of a thermocouple protection tube showing another embodiment of the present invention. In FIG. 2, the same parts as those in FIG. 1 are designated by the same reference numerals. In FIG. 2, except that a metal ring 9 made of copper having a thickness of 1.5 mm is interposed on the outer peripheral surface including two fixing grooves provided over the entire outer peripheral surface of the connecting portion of the thermocouple protection tube 1, The same as 1. The attached protective tube was dipped in a 680 ° C molten aluminum and subjected to temperature measurement. As a result, continuous use for 2 years was possible without causing damage or cracks.

In the first to third embodiments, the number of setscrews in the fixing groove position of the thermocouple protection tube is illustrated and explained, but a plurality of setscrews, for example, three (120 °) at equal intervals.
It is needless to say that the intervals) to 4 (90 ° intervals) may be used and does not affect the essence of the present invention.

[0015]

As described above, the thermocouple protection tube of the present invention has a plastic metal ring or a thin metal plate between the outer peripheral surface of the fixing groove of the thermocouple protection tube and the inner peripheral surface of the adapter terminal portion. By interposing, and by making the metal ring or the metal thin plate plastically deform by the set screw and closely contacting with the fixing groove,
Since the surface contact connection can be achieved, it is possible to prevent the breakage of the thermocouple protection tube originating from the tip of the set screw, which has occurred in the past. Further, since the thermocouple protection tube can be easily and quickly attached, the assembly work time can be shortened, and the core can be prevented from being displaced during assembly. Therefore, the thermocouple protection tube of the present invention can be stably used and has a long life.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an attached state in which a thermocouple protection tube is clamped and fixed in an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing a mounting state in which a thermocouple protection tube is clamped and fixed in another embodiment of the present invention.

FIG. 3 is an enlarged longitudinal sectional view of a main part showing a mounting state of a conventional thermocouple protection tube.

FIG. 4 is a schematic overall view of a conventional thermocouple protection tube.

[Explanation of symbols]

 1 Thermocouple Protection Tube 2 Adapter 3a Extension Tube 3b Other Extension Tube 4 Elbow 5 Set Screw 6 Adapter Terminal 7 Fixing Groove 8 Void 9 Metal Ring 10 Tip of Protection Tube

Claims (5)

[Claims] 1. When connecting a thermocouple protection tube for measuring molten metal temperature made of a ceramic material and an extension tube through an adapter made of a metal material, a thermocouple protection tube made of the ceramic material is used. A heat resistant plastic material is interposed between the outer peripheral surface of the fixing groove formed in the connecting portion and the inner peripheral surface of the connecting portion of the terminal portion of the adapter, and the fixing groove and the connecting portion of the terminal portion are fixed by a fixing means. Thermocouple protection tube characterized by being fixed. 2. The thermocouple protection tube according to claim 1, wherein at least one fixing groove is formed. . 3. The thermocouple protection tube according to claim 1, wherein the heat resistant plastic material is a metal ring or a thin metal plate. 4. The heat resistant plastic material is made of any one of copper, brass and stainless steel.
The thermocouple protection tube according to any one of 1 to 3. 5. The thermocouple protection tube according to claim 1, wherein the ceramic material is a silicon nitride sintered material such as silicon nitride or sialon.