JPH0234606Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The purpose of this project is to improve an oxygen concentration measuring device, that is, a device that is immersed in molten metal, molten slag, or gas atmosphere and measures its oxygen concentration based on the electromotive force generated between the standard electrode and the measuring electrode. The purpose of this method is to accurately and quickly measure oxygen concentration by making it possible to measure electromotive force values with high accuracy and stability, and with a fast response speed. Originally, in this type of oxygen concentration measuring device,
1) In order to improve reproducibility, it is necessary to always construct an equivalent oxygen concentration battery using the same materials, and 2) To speed up the response speed, speed up measurement work and simplify the probe exterior configuration. Therefore, in order to reduce costs, it is desirable to use a highly stabilized material for the electrolyte of the detection element to reduce the heat capacity of the detection element, thereby speeding up the electrochemical and thermal equilibrium of the oxygen concentration battery. 3) The measurable oxygen concentration range is wide, for example several ppm in the steel manufacturing process.
It is required to be applicable to the oxygen concentration range from 100 ppm to several hundred ppm. Therefore, in the case of the tablet-type detection element in the conventional oxygen concentration measuring device shown in Fig. 4, safety stabilized zirconia is used as the electrolyte, which is fused and fixed to a quartz support tube. Because the degree of fusion is not constant over the entire circumference, the electrolyte may separate during measurement, or oxygen permeation through the fused portion may increase in low oxygen concentration areas, and quartz (SiO ₂ ) may dissociate, causing the electrolyte to separate near the surface of the electrolyte. On the other hand, the Tamman type shown in Fig. 5 has the problem of not being able to accurately measure the oxygen concentration due to changes in the oxygen concentration of The problems caused by the fused parts in the case of the tablet type are solved. Moreover, since partially stabilized zirconia has a large effect on electron conduction, electron conduction correction must be performed during measurement, and this correction value becomes an error factor. This takes time for equilibrium, which slows down the response speed. On the other hand, in the case of a thermal spray type detection element in which a standard electrode and electrolyte are layered on the tip of a metal lead by thermal spraying, and fully stabilized zirconia is used as the electrolyte, the entire structure can be made compact, so the measured electromotive force is There is no need for correction for the electrochemical and thermal equilibrium, and the response speed is 1 to 2 seconds faster than the above-mentioned Tammann type detection element shown in FIG.
However, since the entire element functions as a battery, when this detection element is incorporated into the probe detection part and immersed in molten metal, such as molten steel, the binder for fixing the element, adsorbed moisture, adsorbed oxygen, etc. will be absorbed at the tip of the probe. The gas is generated from the end face of the refractory cement and disturbs the interface between the elements that make up the oxygen concentration battery and the molten steel, making the measured electromotive force value unstable. This temporarily increases the temperature, which causes measurement errors. This proposal addresses the above-mentioned drawbacks of conventional oxygen concentration detection elements.
It was devised to solve the problem and improves the thermal spray type detection element to further speed up the response speed and improve the stability and accuracy of the measured value. The fixed end of the element to the probe is coated with a refractory layer that is stable at high temperatures and has good heat conduction, and the standard electrode and electrolyte layer are provided only at the tip of the element. The oxygen concentration measuring device of the present invention will be explained below with reference to the attached drawings. As shown in FIG. The oxygen concentration detection element 2 _is fixedly provided so as to protrude from the end face ₁ of _the detection part.
The standard electrode 7 is formed by thermal spraying a metal oxide, and this standard electrode is completely coated with fully stabilized zirconia, such as ZrO ₂ · CaO or ZrO ₂ · Y ₂ O ₃ , or ThO with high oxygen ion conductivity. A solid electrolyte 8 is provided by thermally spraying _{2.Y 2} O _3, etc., and from this solid electrolyte 8, the metal lead 6 from the detection part end face 1' to the position where it enters the refractory cement 5 of a predetermined size is heated under high temperature conditions. Refractories that are stable and have good heat conduction, such as
The refractory layer 9 is provided by thermal spraying Al ₂ O ₃ , MgO, CaO, and thus the fixed end side of the oxygen detection element 2 to the probe P is coated with the refractory layer 9 having good heat conduction. This not only speeds up the thermal equilibrium of the standard electrode 7 and speeds up the response, but also prevents the measurement value from becoming unstable even if gas such as oxygen blows out from the detection end face 1' at the tip of the probe. This is done to ensure that no errors occur. As an experiment regarding this refractory layer 9, the diameter

[Table] According to the above experimental example, by providing the refractory layer 9, it is possible to improve the response and measurement accuracy, and also to increase the length of the refractory layer 9 from the end surface 1' of the detection part. A stable measurement waveform can be obtained by making it 10 mm or more. On the other hand, as an embodiment of the present invention, as shown in FIG. In the case where it is configured to reach the position inside the cement 5, the above-mentioned refractory layer 9
As shown in the figure, a solid electrolyte 8 is fitted over a predetermined protruding length from within the refractory cement 5, and the function as a detection part for oxygen concentration measurement is provided by the standard electrode 7 solid at the tip that is not covered with the refractory layer 9. It is also possible to work with an electrolyte 8. In Fig. 1, 10 is a protective cap, and 11 is a protective cap.
1 is a ceramic housing, 12 is a paper tube, 13 is a heat-resistant tube, and 14 is a thermocouple wire. According to the oxygen concentration measuring device of the present invention as described above, the oxygen concentration detection element 2 is constructed by thermally spraying the standard electrode 7 and the fixed electrolyte 8 on the metal lead 6, thereby making it compact. Not only can the electrochemical equilibrium and thermal equilibrium of 7 be quickly achieved to improve the responsiveness during measurement, but also the detection part end face 1'
By covering the fixed side end of the element 2 protruding from the probe with a highly thermally conductive refractory layer 9 that is stable at high temperatures up to the position within the refractory cement 5 of the probe detection section, the detection section using an oxygen concentration battery is is limited to only the tip of element 2 and separated from the probe detection end,
Even if oxygen or other gases come out from the probe detection end face, the adverse effect of this on the sensing part of the element can be prevented or reduced, so the measured waveform can be kept stable and there is no need to worry about deterioration in measurement accuracy. Furthermore, since the refractory layer is made of a material with good thermal conductivity, there is no risk of delaying the thermal equilibrium of the standard electrode.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of essential parts showing an embodiment of the oxygen concentration measuring device of the present invention, Fig. 2 is a cross-sectional view of a detection element showing another embodiment, and Fig. 3 is a conventional thermal spray type detection element and a detection element of the present invention. 3 is a graph showing the results of a comparative experiment of electromotive force values when using . Figure 4, Figure 5,
FIG. 6 is a sectional view showing the configuration of an oxygen concentration detection element in a conventional oxygen concentration measuring device. P...Probe, 1...Detection unit, 2...Oxygen concentration detection element, 3...Measurement side electrode, 4...Temperature measurement element, 5...Fireproof cement, 6...Metal lead, 7
... Standard electrode, 8 ... Fixed electrolyte, 9 ... Refractory layer, 10 ... Protective cap, 11 ... Housing, 12 ... Paper tube, 13 ... Heat-resistant tube, 14 ... Thermocouple wire.

Claims (1)

[Scope of utility model registration request] A standard electrode and a solid electrolyte are thermally sprayed on the tip of a metal lead that protrudes from the end surface of the detection section at the tip of the probe, and the area from the solid electrolyte to the end surface of the detection section is covered with a refractory layer with good thermal conductivity. An oxygen concentration measuring device characterized by having an oxygen concentration detection element composed of: