JPH06307944A - Thermocouple type thermometer for measuring temperature of molten metal - Google Patents

Abstract

PURPOSE:To provide a thermocouple type thermometer for measuring the temperature of molten metal which can measure the temperature of molten steel stably for a long time. CONSTITUTION:The thermocouple type thermometer 1 is constituted by inserting a molybdenum zirconia rod 3 into an alumina tube 4 and then inserting the alumina tube 4 into an alumina graphite tube 2. When the temperature measuring contact side 5 is immersed into molten steel, a temperature measuring contact is formed between the molybdenum zirconia rod 3 and the alumina graphite tube 2 through the molten steel and thermoelectromotive force is produced. But since the melting point is higher than the temperature of molten steel and the temperature stability is excellent, consumption is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a thermocouple type thermometer for measuring the temperature of a molten metal such as molten steel, and more particularly to a thermocouple type thermometer having a small consumption and a long life. Moreover, the present invention relates to a thermocouple type thermometer for measuring the temperature of a molten metal capable of detecting the temperature of the molten metal in a stable state for a long period of time.

[0002]

2. Description of the Related Art Molten steel produced in a converter or an electric furnace is continuously cast, for example, by adjusting the composition, degassing, or degassing from a tundish in a molten steel treatment facility before continuous casting. It is pouring into. By the way, from the viewpoint of preventing the operation from being hindered due to lack of superheat and ensuring the quality of the continuous cast slab over the entire length, a tundish equipped with a molten steel heating device has recently been used.

In this case, in order to maintain the temperature of the molten steel within an appropriate temperature range, that is, to control the temperature of the molten steel, it is necessary to control the electric power supplied to the molten steel heating device. To control the electric power input to the molten steel heating device to control the temperature of the molten steel poured into the tundish, the temperature of the molten steel must be stable.
Moreover, it is necessary to continuously detect and feed back the detected value to the power input device to control the input power, but a thermocouple type thermometer has been conventionally used for temperature control of molten steel. The thermocouple type thermometer generally incorporates a high temperature thermocouple in a refractory insulating tube that can be immersed in molten steel.
However, since this thermocouple thermometer is protected by an insulating tube, it requires a response time of, for example, 2 to 3 minutes, and is not always sufficient for controlling the temperature of molten steel.

[0004] By the way, there is a structure in which an insulating material for protecting the temperature measuring unit is removed and the structure is exposed to accelerate the response time of the temperature measuring. This utilizes molten steel as one of the metals, and more specifically, the tip of molybdenum is immersed in molten steel, and between the other end side of this molybdenum and the roll that rolls to the slab through the molten steel. The circuit is configured to detect the thermoelectromotive force. However, scales and flux adhere to the surface of the slab, and in addition to having electrical insulation properties, they also have a contact resistance and a contact potential difference, so a weak heat of 20 to 30 mV is generated. There is a drawback that the electromotive force cannot be accurately detected.

Further, a temperature difference (about 200 to 300 ° C.) always occurs between the support bearing and the fixed portion of the roll,
Since this constitutes a local thermocouple, a parasitic thermoelectromotive force is generated, which adversely affects the measurement accuracy. In addition, since the molybdenum wire immersed in the molten steel is in contact with the molten steel, the average temperature of the immersion length can be measured, but the original point temperature cannot be measured. There was also a drawback.

[0006] Therefore, the applicant of the present application has proposed in Japanese Patent Application No. 30496 of 1991 that a thermocouple is composed of metallic molybdenum and iron, and the tips of these are immersed in molten steel. What is immersed in molten steel,
That is, a structure was proposed in which an insulating tube was inserted into a bottomed metal molybdenum tube, an iron wire was inserted into this insulating tube, and the tip of the iron wire was brought into contact with the bottom of the metal molybdenum tube. According to such a thermocouple, as described above, in addition to being excellent in thermal response because it is immersed in molten steel,
Since a large thermoelectromotive force can be obtained, the input power to the molten steel heating device can be controlled with high accuracy.

[0007]

[Patent Document 1] Japanese Patent Application No. 3-
In the former thermocouple proposed by the applicant of the present application in No. 30496, iron paired with metallic molybdenum is also immersed in molten steel. Although the outer periphery of iron is covered with an insulating pipe and only the tip surface contacts the molten steel, the temperature of the molten steel is almost equal to the melting temperature of iron, so that the consumption of iron is severe. On the other hand, according to the latter thermocouple, since iron is protected by metal molybdenum and does not come into direct contact with molten steel, the problem relating to the consumption of iron is solved, but metal molybdenum oxidizes at high temperature and long-term From the perspective, long-term stability was not always sufficient.

Therefore, the object of the present invention is to provide a molten metal having a low wear of the members constituting the thermocouple type thermometer and capable of measuring the temperature of molten steel in a stable state for a long period of time and having excellent durability. In order to provide a thermocouple type thermometer for measuring temperature.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the fact that the problems relating to the above-mentioned conventional examples can be reliably solved if the thermocouple is made of a material having a high melting point and excellent high temperature stability. Therefore, the feature of the main means adopted by the thermocouple thermometer according to claim 1 of the present invention is that one end side is immersed in molten metal to detect the temperature of the molten metal. A thermocouple thermometer for measuring a temperature of a molten metal is characterized in that an electrically conductive carbon-containing refractory material and a cermet are electrically insulated.

Further, a main feature of the thermocouple type thermometer according to the present invention is that the one end is immersed in a molten metal to detect the temperature of the molten metal. In the thermocouple type thermometer, a bottomed cylindrical molybdenum cermet, and an iron cermet in which one end side is in close contact with the bottom of the molybdenum cermet in a conductive manner while being inserted inside the molybdenum cermet through an insulating refractory material. It consists of and.

[0011]

According to the thermocouple type thermometer according to claim 1 of the present invention, the thermocouple type thermometer has a structure in which the carbon-containing conductive refractory having conductivity is electrically insulated from the cermet. Therefore, the melting temperature of each is higher than the temperature of molten steel, and since the carbon-containing conductive refractory and cermet are different substances, the temperature-measuring junction formed between them through molten steel Thermoelectromotive force is generated.

Further, according to the thermocouple type thermometer according to claim 2 of the present invention, the thermocouple type thermometer has a bottomed cylindrical molybdenum cermet and an insulating refractory inside the molybdenum cermet. Since it is composed of an iron cermet in which one end side of the molybdenum cermet is in close contact with the bottom of the molybdenum cermet in a conductive manner, the melting temperature is higher than the temperature of molten steel. Since cermet is a different substance, thermoelectromotive force is generated at the temperature measuring contact formed between the bottom part of the molybdenum cermet and the close contact part of the iron cermet.

[0013]

EXAMPLE A thermocouple-type thermometer for measuring a molten metal temperature according to an example of the present invention will be described below with reference to FIG. 1 showing a side cross-sectional configuration and a reference temperature (° C.)-Thermoelectromotive force (mV). This will be described with reference to FIG. 2 of the relationship graph diagram.

That is, as shown in FIG. 1, this thermocouple type thermometer 1 has a well-known oxidation inside an alumina-graphite (Al ₂ O ₃ -C) tube 2 which is a carbon-containing refractory. Molybdenum-zirconia (Mo-ZrO ₂ ) rod 3 which is a cermet made of a combination of a metal and a metal, has not only a very high thermal conductivity but also a high melting point and is chemically stable even at a high temperature. Inserted alumina (Al
₂ O ₃ ) tube 4 is inserted. Then, these alumina graphite tube 2, molybdenum zirconia rod 3,
The one end side of the alumina tube 4, that is, the left side in the same figure, is flush with the other end side of the right side, and the molybdenum zirconia rod 3 projects. In this case, one end side of the surface of the thermocouple type thermometer 1 becomes the temperature measuring contact side 5 immersed in molten steel (not shown), and the other end side is connected with a thermoelectromotive force lead wire (not shown). It is the power deriving side 6.

The operation mode of the thermocouple type thermometer 1 having the above structure will be described below. When the temperature measuring contact side 5 of the thermocouple type thermometer 1 is immersed in molten steel, the alumina / graphite tube 2 and molybdenum A temperature-measuring contact is formed between the zirconia rod 3 and a thermoelectromotive force according to the temperature of the molten steel, which is derived from the thermoelectromotive force deriving side 6 to detect the temperature of the molten steel.

Since the alumina / graphite tube 2 and the molybdenum / zirconia rod 3 are both immersed in the molten steel, the thermal response is excellent. For example, in the conventional case, the time delay was about 2 to 3 minutes, whereas in the present embodiment, it was about 10 to 30 seconds, and it was confirmed that the thermal response was extremely excellent.

Further, since both the alumina / graphite tube 2 and the molybdenum / zirconia rod 3 have a melting point higher than the melting temperature of molten steel and have excellent high temperature stability, they are easily consumed as in the conventional case. In addition, the change over time in the thermoelectromotive force due to alteration is less than in the conventional case.

The thermoelectromotive force (mV) with respect to the reference temperature (° C.) of the thermocouple type thermometer 1 according to the embodiment of the present invention is shown in Table 1 below.

[0019]

[Table 1]

When plotting the thermoelectromotive force (mV) with respect to the reference temperature (° C) shown in Table 1 above, the thermoelectromotive force (mV) on the vertical axis, and the reference temperature (° C) on the horizontal axis,
As shown in FIG. 2, the linearity is extremely excellent, and moreover,
It was confirmed that there was no problem in terms of reproducibility and that it could be put to practical use. By the way, there are various types of carbon-containing refractories and cermets. Further, even in the case of molybdenum-zirconia which is a cermet, there is a case where the content ratios of molybdenum and zirconia are different. In the present embodiment, the case where the thermocouple is constituted by the alumina graphite tube 2 which is a carbon-containing refractory and the molybdenum-zirconia rod 3 which is a cermet has been described. For example, magnesia graphite (Mgo-C) and molybdenum It is also possible to form a thermocouple with zirconia.

Next, a thermocouple type thermometer 10 according to another embodiment of the present invention will be described with reference to FIG. 3 which is a side sectional view for explaining the structure. Reference numeral 11 in the drawing is made of magnesia graphite. Outer diameter is 2 with external protection tube 15 fitted
It is a bottomed cylinder having an inner diameter of 10 mm and a diameter of 0 mm, that is, a molybdenum cermet having a bottom portion 11a on one end side. The molybdenum cermet 11 has an iron piece 13 which is a metal piece in which a through hole 13a having an axis line which coincides with an axis line passing through the radial center of the molybdenum cermet 11 is formed in close contact with the bottom portion 11a. It is set up.

In this case, molybdenum cermet 1
In order to prevent the crack of No. 1, the outer diameter of the iron piece 13 is set to be slightly smaller than the inner diameter of the molybdenum cermet 11 in consideration of the difference in thermal expansion between the molybdenum cermet 11 and the iron piece 13 as shown in FIG. Preferably.

Further, inside the molybdenum cermet 11, an internal insulating pipe 14 made of an insulating refractory is fitted in contact with the end face of the iron piece 13, and the internal insulating pipe 14 has an outer diameter of 6 mm. Rod-shaped iron cermet 1
2 is inserted and the tip is a through hole 13a of the iron piece 13.
Are fitted and connected to. In this case, the bottom 11a side of the molybdenum cermet 11 becomes the temperature measuring contact side 16 immersed in molten steel (not shown), and the thermoelectromotive force derivation side 17 to which the thermoelectromotive force derivation wire (not shown) is connected to the counter bottom 11a side.
Becomes The use of the iron piece 13 is for more reliable conduction between the bottom portion 11a of the molybdenum cermet 11 and the iron cermet 12.

The thermocouple type thermometer 10 having the above structure will be described below.
The molybdenum cermet 11 and the iron cermet 12 form a temperature measuring contact via the iron piece 13, so that when the temperature measuring contact side 16 is immersed in the molten steel, a heat generation proportional to the temperature of the molten steel is generated. Since power can be obtained, this embodiment has the same effect as the above embodiment. In this case, since the molybdenum cermet 11 is directly immersed in the molten steel, the response delay is 0.
It was within 5 seconds and could be used in a stable state for 150 hours.

By the way, in the above, the alumina / graphite tube 2 is externally fitted to the alumina tube 4 into which the molybdenum / zirconia rod 3 is inserted, and is integrally formed.
Although the examples of the thermocouple type thermometer in which the iron cermet 12 is inserted and integrally formed in the molybdenum cermet 11 have been described, for example, all the members to be combined are formed into a rod shape. Since the rods may be electrically insulated from each other by providing a predetermined space between them, the structure is not particularly limited to the one described in this embodiment.
Further, although the case of measuring the temperature of the molten steel has been described as an example, the technical idea according to the present invention can be applied to the temperature measurement of the temperature of the molten metal other than the molten steel.

[0026]

As described in detail above, the first aspect of the present invention
According to the thermocouple-type thermometer according to, since the carbon-containing conductive refractory and cermet are different substances, thermoelectromotive force is generated in the temperature measuring contact formed between them through molten steel, and,
According to the thermocouple type thermometer according to the second aspect of the present invention, since the molybdenum cermet and the iron cermet are different substances, the temperature measuring contact formed between the molten metal and the same kind of metal piece through the metal piece. Thermoelectromotive force is generated in the molten metal, but the parts immersed in the molten metal have a higher melting point than the temperature of the molten metal and are therefore less likely to be consumed. Since the stability is maintained for a long period of time, it is possible to control the temperature of the molten steel in the tundish with high accuracy, which greatly contributes to the improvement of the continuous casting operation efficiency and the quality assurance of the continuous casting slab over the entire length. You can

[Brief description of drawings]

FIG. 1 is a side sectional configuration explanatory diagram of a thermocouple type thermometer according to an embodiment of the present invention.

FIG. 2 is a relational graph diagram of reference temperature (° C.)-Thermoelectromotive force (mV) of the thermocouple type thermometer according to the example of the present invention.

FIG. 3 is a side sectional view showing a thermocouple type thermometer according to another embodiment of the present invention.

[Explanation of symbols]

 1 ... Thermocouple type thermometer 2 ... Alumina / graphite tube 3 ... Molybdenum / zirconia rod 4 ... Alumina tube 5 ... Temperature measuring contact side 6 ... Thermoelectromotive force derivation side 10 ... Thermocouple type thermometer 11 ... Molybdenum cermet, 11a ... Bottom 12 ... Iron cermet 13 ... Iron piece 14 ... Insulation tube 15 ... External protection tube 16 ... Temperature measuring contact side 17 ... Thermoelectromotive force derivation side

Claims (2)

[Claims] 1. A thermocouple-type thermometer for measuring the temperature of a molten metal, wherein one end is immersed in the molten metal to detect the temperature of the molten metal, and a conductive carbon-containing refractory material having conductivity.
A thermocouple type thermometer for measuring a molten metal temperature, which is electrically insulated from a cermet. 2. A thermocouple type thermometer for measuring a temperature of a molten metal, wherein one end side is immersed in the molten metal to detect the temperature of the molten metal, wherein a molybdenum cermet having a cylindrical shape with a bottom and an inner side of the molybdenum cermet. A thermocouple type thermometer for measuring the temperature of a molten metal, which comprises an iron cermet having one end side thereof in close contact with the bottom of the molybdenum cermet in a conductive manner while being inserted through an insulating refractory.