JPS6031261B2 - Consumable sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a consumable sensor for measuring oxygen concentration and temperature in molten steel.

Conventionally, consumable probes that are immersed in molten steel and simultaneously measure its oxygen concentration and temperature have a sensor as a detection part,
It consists of a protection tube. The general structure of this sensor is shown in Figure 1, in order to measure oxygen concentration,
A fixed electrolyte 2 that has oxygen ion conductivity at high temperatures, a standard electrode powder 3 that serves as a reference for oxygen concentration measurement, and a standard electrode powder 3
and solid electrolyte 2 to isolate it from the molten steel.
, a lead wire 5 for taking out the output of the element, and a lead pin 6 for transmitting the output from the lead wire 5 to the meter.
An oxygen concentration battery as an oxygen concentration measuring means is composed of a zirconia electrode 1, a molten iron electrode 20 consisting of a molten iron lead 21, which is an output lead on the molten iron side, and a lead pin 22, which transmits the output to a meter. A ceramic housing 30' is incorporated. In addition, in order to measure the temperature, (10) polar thermocouple wire 12 and (1) polar thermocouple wire 12'
, a quartz tube 11 for protecting these thermocouple wires 12 and 12' from molten steel, and (10) polar pins 13 and (1) polar pins 13 for transmitting the thermocouple output to the meter.
A thermocouple electrode 10 consisting of 1 and 2 is similarly incorporated into a ceramic housing.

Note that a consumable sensor including an oxygen concentration measuring element generally does not use a plastic housing. This is because the plastic burns during measurement and generates gas.
This is because boiling of molten steel causes unstable measurement instructions or measurement errors. The lead pins 6, 13, 13', 22 of each pole are led to a plug 31 attached to the bottom of the housing 30 and form the contacts of the connector.

Moreover, inside the housing 30, the respective poles 1 and 1 are provided.
0, 20, and each pole lead pin 6,
13, 13', 22, the lead wire 5 of the zirconia pole 1, and a portion of the (10) and (1) thermocouple wires 12, 12' are filled with cement 40 in order to protect them from molten steel. . Furthermore, a cap 32 is attached to the tip of the housing 30 in order to mechanically protect the exposed portions of the cement 40 of each pole 1, 10, and 20 when handling the sensor and dipping it into molten steel. It is being Conventional expendable sensors with the above configuration are usually made very compact in order to reduce the cost of the sensor itself and the protective tube installed in it, and the distance between the poles in the housing 30 is very small. placed in close proximity.

In such a sensor, the cement 40 is currently a problem.

Since the poles are placed close together in this manner, the filling cement must have high insulation resistance both at room temperature and at high temperatures during measurement. This is because when the insulation resistance between the electrodes of each output is low in the two outputs of the measuring element, that is, the output of the oxygen concentration battery and the output of the thermocouple, the output voltage is divided and the output voltage of the element is divided. If the true output of the two elements is not transmitted to the meter, and if the insulation resistance between both elements is low, their outputs will interfere with each other, and the true output will not be transmitted to the meter.

Another requirement for the cement 40' is that it must have fire resistance and thermal shock resistance that can withstand the temperature of molten steel.

This is because if the fire resistance is low, cement will melt into the molten steel during measurement, changing the oxygen concentration near the sensor, causing measurement errors, and causing CO bubbles to occur, making the measurement instructions unstable. This is because it does. Furthermore, the cement must not emit water vapor or gas during measurement. The release of water vapor, gas, etc. during measurement must be suppressed as much as possible because it may cause incorrect measurement instructions or measurement errors in oxygen concentration measurement. However, the reality is that among the currently commercially available cements, the only cements that can solve all of the problems raised at the same time are special cements that are extremely expensive and have difficult usage conditions. Such special cements cannot be used to produce sensors on an industrial scale.

The purpose of this invention is to use commercially available inexpensive cement in combination to achieve fire resistance and thermal shock resistance that can withstand the temperature of molten steel, high electrical insulation at high temperatures, and no release of water vapor or gas during measurement. The present invention provides a consumable sensor that satisfies three conditions: it requires only a small amount of use. According to the present invention, in the immersion type consumable sensor having at least an oxygen concentration measuring element as a measuring means, the sensor has a housing, and inside the housing, different types of cement are layered to form each measuring element. Fix it,
The object of the present invention is to provide a consumable sensor characterized in that the layer on the tip side of the housing is made of cement that has fire resistance, thermal shock resistance, and does not emit gas, and the other layers are made of electrically insulating cement.

A preferred embodiment of the present invention will now be described with reference to FIG. 2 based on the drawings.

Incidentally, the same parts as those of the conventional sensor shown in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted. In FIG. 2, the housing 30 has a simple shape, and this housing 30
The parts of each pole 1, 10, and 20 that require electrical insulation, that is, the part of the zirconia pole 1 that is exposed from the IJ-doped pin 6 and the lead wire 5 from the quartz tube 4, are Until a part of the lower end of the quartz tube 4 is buried, and at the thermocouple electrode 1, the lead pins 13, 13'
Then, the first cement 41 is applied to the portion corresponding to the depth A from the exposed portion of the quartz tube 11 of the thermocouple wires 12, 12' until a portion of the lower end of the quartz tube 11 is buried.
The remaining upper layer at depth B is filled with second cement 42, resulting in a two-layer cement structure.

In general, inexpensive commercially available cements used in consumable sensors are broadly classified into air-hard zircon cement and hydraulic high-purity alumina cement.

Air-hard zirconium cement hardly absorbs moisture from the atmosphere even if it is left alone after sensor fabrication, as shown in curve a in Figure 3, which shows the change in water absorption rate of cement over time. As can be seen from curve a in FIG. 4, which shows the change in insulation resistance between the electrodes over time, the insulation resistance between the electrodes also does not decrease.

Therefore, as shown in curve a in Figure 5, which shows the change in insulation resistance when a sensor using only air-hard zircon cement is immersed in molten steel, the insulation resistance value between the electrodes during measurement is The decline is not small. However, since air-hard zircon cement has a low fire resistance, it melts into the molten steel during measurement and changes the oxygen concentration near the sensor, causing measurement errors and causing CO bubbles in the measurement. Do not pass it as sensor cement to make the indication unstable. 6th
The figure shows an example of measurement using a sensor using only pneumatic zirconium cement.
Due to the generation of air bubbles, the oxygen concentration measurement instructions are fluctuating greatly.

On the other hand, hydraulic high-purity alumina cement has a fire resistance of 2.
It has a fire resistance rating of 170,000 or more that can withstand immersion into molten steel.

However, as shown in curve b in Figure 3, hydraulic high-purity alumina cement tends to adsorb moisture in the atmosphere after sensor fabrication, and therefore, as shown in curve b in Figure 4, the insulation between the electrodes is Resistance tends to decrease. Therefore, when a sensor using only hydraulic high-purity alumina cement is immersed in molten steel, the insulation resistance between the electrodes decreases rapidly, as seen in curve b in FIG. 5. Figure 7 shows an example of measurement using a sensor using hydraulic high-purity alumina cement.

As the insulation resistance between the zirconia electrode and the molten iron electrode of the oxygen concentration battery decreases, the oxygen concentration indication gradually decreases, and the moisture in the adsorbed cement erupts into the molten steel, causing the measurement indication to fluctuate. There is. Based on this knowledge of commercially available cement, air-hard zircon cement is used as the first cement to be filled into the depth A of the lower layer in the embodiment shown in FIG.

As is clear from Figures 4 and 5, air-hard zircon cement has a high degree of electrical insulation from room temperature to high temperature, and has a large filling volume, so it has strong adhesion, and the , 20 can be held and fixed securely.
Further, as the second cement to be filled into the depth B of the upper layer, a hydraulic high-purity alumina cement is used.

This high-purity alumina cement has excellent fire resistance and thermal shock resistance, and since it does not contain a binder, it does not emit gas during measurement. Each of the curves C in FIGS. 3 and 4.5 corresponds to the curve C in FIG. This figure shows the consumable sensor of the present invention shown in Examples.

As seen in Figure 3, the water absorption rate of the sensor of this invention is slightly higher than that of air-hardened zircon cement (curve a), but much higher than that of hydraulic high-purity alumina cement (curve b). As a result, as shown in curve C in Figure 4, the change in insulation resistance between the poles over time is also 100%.
Maintain a high value near 0 MO.

Therefore, even when the consumable sensor of the present invention is immersed in molten steel, the insulation resistance value between the electrodes during measurement does not decrease much as shown by curve C in FIG. FIG. 8 is a graph showing a measurement curve measured by a sensor according to an embodiment of the present invention.

As is clear from this measurement curve, stable indications were obtained for both oxygen concentration and temperature, and it was confirmed that the measured values themselves were accurate. In the embodiment shown in FIG. 2, the thickness B of the cement 42 using hydraulic high-purity alumina cement filled in the upper layer is a thickness that can prevent the air-hard zircon cement 41 from melting. It is sufficient if the thickness is thin, and it is desirable that the thickness be as thin as possible.

This is because, as can be seen from the graph of FIG. 3, hydraulic high-purity alumina cement has a high water absorption rate, and when immersed in molten steel, adsorbed moisture is ejected as water vapor, causing measurement errors. However, if the thickness B is thin, the ejection of water vapor can be stopped at an early stage of the measurement, and the ejection of water vapor during the measurement can be eliminated. In fact, it has been confirmed that the effect of the invention can be obtained by coating the cement 42 on top of the cement 41.

Further, the cement 41 is not limited to air-hard zircon cement, and the cement 42 is not limited to hydraulic high-purity alumina cement. Of course, any suitable cement having fire resistance, thermal shock resistance, and no gas generation may be used.

As explained above, with the consumable sensor of this invention,
A sensor that has at least an oxygen concentration measuring element as a measuring means has three requirements: fire resistance and thermal shock resistance that can withstand the temperature of molten steel, high electrical insulation at high temperatures, and no gas emission during measurement. A sensor that satisfies the conditions was realized by combining the features of two commercially available, inexpensive types of cement, allowing stable indications and high-precision measurements, making it suitable for industrial production and at a low sensor price. This is something that could have been done.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of a subordinate consumable sensor;
Fig. 2 is an explanatory diagram showing one embodiment of the consumable sensor of the present invention, Fig. 3 is a graph showing changes in water absorption rate of cement over time, and Fig. 4 is a change in insulation resistance between electrodes over time. Fig. 5 is a graph showing the change in insulation resistance between the electrodes during measurement, Fig. 6 is a graph showing the measurement curve using a sensor using air-hard zircon cement, and Fig. 7 is a graph showing the change in insulation resistance between the electrodes during measurement. FIG. 8 is a graph showing a measurement curve by a sensor using hard high-purity alumina cement. FIG. 8 is a graph showing a measurement curve by a consumable sensor of the present invention. 1... Zirconia electrode, 2... Solid electrolyte, 3... Standard electrode powder, 4... Quartz tube, 5
...Lead wire, 6...Lead pin, 10...Thermocouple electrode, 11...Quartz tube, 12.
・・・・・・(10) Polar thermocouple Qin wire, 12′・・・・・・(
1) Polar thermocouple wire, 13...(10) Polarized pin, 13'...(-) Polarized pin, 20. ．．・．．・・・
Molten iron pole, 21... Molten iron lead, 22... Lead pin, 30... Housing, 31... Plug, 32
...Cap, 40...Cement, 41...First cement, 42...Second cement. Figure 1 Figure 2 Figure 5 Figure 3 Figure 4 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1. In an immersion type consumable sensor having at least an oxygen concentration measuring element as a measuring means, the sensor has a housing, and inside the housing, different types of cement are layered to fix each measuring element, and the tip of the housing is A consumable sensor characterized in that the side layer is made of cement that is fire-resistant, thermal shock-resistant, and does not release gas, and the other layer is made of electrically insulating cement.