JPS6160365B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermocouple for measuring high temperature.

Optical pyrometers or thermocouples are commonly used to measure the temperature of hot, red-hot substances. Optical pyrometers have the advantage of being able to measure temperature indirectly, but the measurement site is limited to the surface of the substance and cannot measure internal temperature.

Thermocouples are more advantageous when trying to measure the internal temperature of a substance. However, when trying to measure the temperature of a high-temperature substance, if the protective tube that normally covers the thermocouple comes into contact with a molten high-temperature substance or is exposed to high-temperature gas, the protective tube will be damaged by the thermal shock. This poses a serious problem when used for a long period of time, as it may fall off or undergo chemical reactions and become corroded. Additionally, thermocouples using tungsten wires have extremely low oxidation resistance, so they cannot be used in oxidizing atmospheres, and if they are to be used, the protective tube must be gas-sealed, which complicates the equipment used. There were flaws.

The present invention eliminates the above-mentioned conventional drawbacks, and provides a high-temperature thermocouple that does not fall off even when subjected to thermal shock and can be protected from the atmosphere. The details of the invention will be explained.

The present invention is achieved by integrally casting the thermocouple having the above object with a protective tube made of cast refractory.

By the way, if you make a circuit by joining one end of two types of metal wires of a thermocouple and keep the temperature at the junction point and the other end of both wires different, the circuit will have an effect that is approximately proportional to the temperature difference between the two ends. It uses the principle of generating electricity. Various metals are used as the material for the metal wire depending on the measurement temperature, atmosphere, etc., and each metal has its own coefficient of thermal expansion.

On the other hand, in the present invention, since the thermocouple is cast in close contact with the refractory structure, if there is a large difference in coefficient of thermal expansion between the thermocouple and the refractory structure, thermal stress may occur and one or the other may be damaged. . For example, if tungsten wire is used, and if a refractory made of silica, alumina, and zirconia (trade name: Monofrac S3) is used as a cast refractory structure, the coefficients of thermal expansion of the two are almost the same, so they can be cast as is. It can be expanded, but the expansion rates are usually different. In such cases, a protective tube made of refractory material is used, a thermocouple is inserted into the protective tube, and the tube is fixed in a mold, and molten cast refractory material is injected into the mold. It is possible to melt the protective tube made of solid material and use the melted portion as a thermal cushion material to absorb the thermal stress generated due to the difference in thermal expansion between the two.

In this way, the thermocouple itself is cast in the cast refractory either directly or through a protective tube.
In other words, since the thermocouple is embedded in a refractory, the thermocouple and the surrounding cast refractory material come into close contact, and the temperature of the outer surface of the refractory material, the temperature of the molten high-temperature material, quickly reaches the thermocouple. The temperature measurement speed is significantly increased. Also, since it is extremely dense compared to conventional sintered protection tubes, it has corrosion resistance and good airtightness against the atmosphere. Furthermore, since the thermocouple also serves as a holder for the cast refractory, it will not fall off even if the cast refractory is damaged by thermal shock.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 illustrates an embodiment of the present invention.
The one indicated by reference numeral 1 in the figure is a W-Re thermocouple, and a protective tube 2 made of sintered alumina, which is a fireproof structure, is fitted to this thermocouple 1, and graphite paste is applied to the head of the thermocouple. A graphite protection tube 3 is then fitted, this is suspended and fixed in a mold 4, and a cast refractory 5 mainly composed of mullite is injected and cast so as to be integrated. Due to the heat during casting, it becomes almost semi-molten and becomes fixed to the thermocouple.
By cooling and solidifying this, a furnace wall brick having a structure in which its outer periphery was surrounded by cast refractory material 5 was obtained. By constructing this brick as part of the furnace wall, a furnace body with a built-in temperature measuring thermocouple was formed.

FIG. 2 illustrates another embodiment of the present invention, in which the same or corresponding parts as in FIG. 1 are designated by the same reference numerals.

In this example, a WWRe thermocouple coated with graphite paste is used as the thermocouple 1, and while this is inserted into a U-shaped protection tube 2 made of Sinterkolund, silica, alumina, and zirconia are It is integrally cast with a cast refractory structure 5 as the main component, and can be used as a thermocouple to which a temperature measuring protection tube is fixed.

In other embodiments, 1r-
A 1R/Rh thermocouple was used, a two-hole Sinterkold tube was inserted through the thermocouple, and this was fixed in a mold. A molten material mainly composed of silica and alumina was poured into the mold and slowly cooled. When the material obtained in this way was cut into a long and thin rod shape and immersed in molten steel to measure the temperature, the response speed was 2.
It was more than twice as fast.

Furthermore, the present invention is not limited to the above-described embodiments; for example, in the above-described embodiments, if the portion of the thermocouple 1 that protrudes from the cast refractory 3 cannot withstand the oxidizing atmosphere, the protrusion Protective parts such as graphite pipes and zircon coatings can be used separately to protect the parts from the oxidizing atmosphere.

As is clear from the above description, according to the present invention, a structure in which the thermocouple is cast in a cast refractory is adopted, so that the temperature of a high-temperature substance in a molten state, such as molten steel, is The external surface temperature of the thermocouple is immediately transmitted to the thermocouple, and the temperature measurement speed is significantly increased. Furthermore, since it is dense, it is less likely to be corroded by molten steel, etc., and has good airtightness against the atmosphere, so thermocouples made of molybdenum or the like, which have low oxidation resistance, can be used even in an oxidizing atmosphere.
Furthermore, since the cast-in thermocouple also serves as a holding material for the cast refractory, even if the cast refractory is damaged by thermal shock, accidents such as the cast refractory falling off are prevented.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional side views illustrating an embodiment of the present invention, and FIG. 3 is a schematic front view of the installed state. 1... Thermocouple, 2, 3... Protection tube, 5... Cast refractory, 4, 6... Firebrick, 7... Block.

Claims (1)

[Claims] 1. A thermocouple for high temperature measurement, characterized in that the thermocouple is integrally cast into a cast refractory structure so as to have a desired shape.