JP4155632B2 - Dissolved hydrogen sensor in molten metal - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a sensor for dissolved hydrogen in molten metal using a solid electrolyte having proton conductivity.
[0002]
[Prior art]
Gas components such as oxygen and hydrogen are contained in the molten metal, particularly in the molten steel. If solidified as it is, it causes cracks and internal defects, so these are removed by degassing in vacuum or in an inert gas. It is necessary to detect how much of these gases have been removed by the degassing process. Conventionally, dissolved oxygen in molten steel has been detected by a solid electrolyte oxygen sensor, but dissolved hydrogen has a high temperature, so there is no sensor to detect it, and degassing treatment has to be performed in an unmanaged state.
[0003]
[Problems to be solved by the present invention]
An object of this invention is to provide the sensor which detects the dissolved hydrogen in the unprecedented high temperature molten metal.
[0004]
[Means for Solving the Problems]
The dissolved hydrogen sensor according to the present invention that has solved the above problems includes a first electrode made of a proton conductive solid electrolyte in contact with a molten metal in which hydrogen to be measured is dissolved, and a contact with the molten metal of the first electrode. A second electrode made of a metal and a metal oxide formed on the surface facing and the back face, a third electrode made of an oxide ion conductive solid electrolyte in contact with the molten metal, and the third electrode A first electrode for measuring a fourth electrode made of the metal and the metal oxide formed on a surface in contact with the molten metal and a surface facing the molten metal, and an electromotive force E12 between the first electrode and the second electrode; a power measuring means, and a second electromotive force measuring means for measuring the electromotive force E34 between third electrodes and the fourth electrodes, Tona is, the electromotive force and the third electrode between the first electrode and the second electrode By taking the difference in electromotive force between the fourth electrodes, the electromotive force due to oxygen is canceled and the high temperature It is characterized by detecting hydrogen in the molten metal .
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the first electrode made of a proton conductive solid electrolyte that comes into contact with a molten metal in which hydrogen is dissolved include, for example, proton-oxide ion mixed conductivity on the surface of a fluorite-type oxide that is an oxide ion conductive electrolyte. An electrolyte in which ABO ₃ type perovskite oxide, which is an electrolyte, is laminated in a film shape can be used. The shape of the first electrode is different when the first electrode is used as a base and when the second electrode described later is used as a base. When the first electrode is used as a base, the first electrode is fired after being press-molded into a predetermined shape such as a cylindrical shape or a test tube. In the case of using the second electrode as a base, for example, a cylindrical second electrode is used as a base, and a solid electrolyte is formed in a film shape on the outer peripheral surface to form the second electrode.
[0006]
The ABO ₃ type A element is one or more elements selected from the group consisting of alkaline earth metals (Sr, Ca, Ba). B element is a metal element of the fluorite-type oxide or a part thereof, alkaline earth metal (Mg, Ca, Sr, Ba), and rare earth element (Sc, Y, La, Nd, Sm, Eu, Gd, It is a metal element of a fluorite-type oxide produced by substitution solid solution of 1 to 30 mol% with one or more elements selected from the group consisting of Dy, Ho, Yb).
[0007]
Examples of such ABO ₃ type perovskite oxide include SrZrO ₃ , BaCeO ₃ , SrCeO ₃ , BaZrO ₃ , and CaZrO ₃ .
The perovskite oxide film can be formed on the surface of the fluorite-type oxide by plasma spraying, sputtering, or the like, but the following method is simple and excellent in cost. That is, for example, at least one of an alkaline earth metal inorganic acid salt, an organic acid salt, and an organic metal compound is applied to the surface of the fluorite-type oxide, and the temperature is 800 ° C. or higher in an oxidizing atmosphere such as the air. A perovskite oxide film can be formed by heating and baking. The thickness of the perovskite oxide is desirably 10 μm or more. This is because when the film thickness is less than 10 μm, hydrogen enters the fluorite-type oxide layer and reduces it.
[0008]
As the fluorite-type oxide, a part of zirconia (ZrO ₂ ) or ceria (CeO ₂ ) is replaced with alkaline earth metal (Mg, Ca, Sr, Ba) and rare earth elements (Sc, Y, La, Nd, Sm, Desirable is stabilized zirconia or stabilized ceria in which 1 to 30 mol% of a substitutional solid solution with an oxide of one or more elements selected from the group consisting of Eu, Gd, Dy, Ho, and Ba) is used. The fluorite-type oxide is excellent in oxide ion conductivity and has no problem of cracking due to thermal expansion.
[0009]
Examples of such fluorite-type oxides include (ZrO ₂ ) _0.89 (CaO) _0.11 , (ZrO ₂ ) _0.92 (Y ₂ O ₃ ) _0.08 , (CeO ₂ ) _0.9. (Y ₂ O ₃ ) _{0. 1} , (CeO ₂ ) _0.8 (CaO) _0.2 , (CeO ₂ ) _0.8 (SrO) _{0.2, and the} like.
According to experiments conducted by the inventors, the second electrode composed of the metal and the metal oxide is composed of a metal having excellent electrical conductivity such as Pt, Au, Fe, Ni, Cu, Zn, Cr, and Mo, Fe It was shown that the hydrogen detection sensitivity becomes high when the mixture is a metal oxide such as ₂ O ₃ , Ni ₂ O ₃ , Cu ₂ O, ZnO, Cr ₂ O ₃ , and Mo ₂ O ₃ . Furthermore, when the metal is Cu and the metal oxide is Cu ₂ O, or when the metal is Cr and the metal oxide is Cr ₂ O ₃ , it is shown that the detection sensitivity is further increased.
[0010]
The second electrode, which is a mixture of the metal and the metal oxide, is produced differently when the second electrode is used as a base and when the first electrode made of the proton conductive solid electrolyte is used as a base. When the second electrode is used as a base, it is formed as follows, for example. That is, a metal and a metal oxide powder are mixed at an appropriate ratio, press-formed into a shape such as a cylinder or a flat plate, and then fired at 800 ° C. or higher.
[0011]
When the metal is the same as the metal oxide metal such as Cu and Cu ₂ O and Cr and Cr ₂ O ₃ , the second electrode can be formed using only the metal or metal oxide powder. For example, after Cu ₂ O powder is press-molded and fired in a reducing atmosphere, a part of Cu ₂ O is reduced to form a mixture of Cu and Cu ₂ O. Alternatively, the Cr powder is press-molded and then fired in an oxidizing atmosphere, whereby a part of Cr is oxidized and becomes a mixture of Cr and Cr ₂ O ₃ . In the case of using the first electrode as a base, for example, the metal and metal oxide powder can be press-fitted into a test tube first electrode to form a second electrode.
[0012]
The third electrode made of an oxide ion conductive solid electrolyte in contact with the molten metal is the same as the oxide ion conductive electrolyte forming the first electrode. That is, for example, when the oxide ion conductive electrolyte of the first electrode is a fluorite type oxide (ZrO ₂ ) _0.89 (CaO) _0.11 , the oxide ion conductive electrolyte of the third electrode is also (ZrO _{2 0.89} (CaO) _0.11 .
[0013]
The fourth electrode is made of the same metal and metal oxide as the second electrode, and the manufacturing method is the same. That is, when the second electrode is a mixture of Cr and Cr ₂ O ₃ , the fourth electrode is also a mixture of Cr and Cr ₂ O ₃ .
The first electromotive force measuring means is connected to the first electrode, the second electrode and the lead wire, and measures the electromotive force E12 between both electrodes, and a normal voltmeter, ammeter, galvanometer, or the like is used.
[0014]
The second electromotive force measuring means is connected to the third electrode and the fourth electrode by a lead wire, and measures the electromotive force E34 between both electrodes, and a normal voltmeter, ammeter, galvanometer or the like is used.
The connection between the first electromotive force measuring means and the first electrode and the connection between the second electromotive force measuring means and the third electrode are performed via molten metal, respectively. Specifically, a metal cylinder or the like of Ni, Mo, W or the like excellent in electrical conductivity and heat resistance is immersed in molten metal, and one end is connected to the first electromotive force measuring means and the second electromotive force measuring means. This is achieved by connecting the lead wires. According to the experiments by the inventors, when the second electrode and the fourth electrode are a mixture of Cr and Cr ₂ O ₃ , the metal cylinder immersed in the molten metal is made of Mo of the same family as Cr, It was shown that hydrogen detection sensitivity was higher when the lead wire was also made of Mo wire.
[0015]
[Action]
In general, oxygen, nitrogen and the like are dissolved in the molten metal in addition to hydrogen. In the vicinity of the first electrode made of a proton conductive solid electrolyte in contact with the molten metal, hydrogen becomes protons and generates electrons. The generated protons move through the first electrode and reach the second electrode. The generated electrons pass through the lead wire connecting the first electrode and the second electrode, and reach the second electrode through the first electromotive force measuring means. If it does so, the metal oxide which comprises a 2nd electrode will work as an oxidizing agent, a metal oxide, a proton, and an electron will react, and a metal oxide will be reduced. In this series of reactions, electrons move from the first electrode to the second electrode.
[0016]
On the other hand, oxygen reacts with electrons to generate negative oxygen ions in the vicinity of the third electrode made of an oxide ion conductive solid electrolyte in contact with the molten metal. The generated oxygen ions move in the first electrode to reach the second electrode, and move in the third electrode to reach the fourth electrode. If it does so, the metal which comprises a 2nd electrode and a 4th electrode will work as a reducing agent, a metal and oxygen ion will react, a metal will be oxidized, and an electron will be generated. Electrons generated at the second electrode pass through the lead wire and reach the first electrode through the first electromotive force measuring means. The electrons generated at the fourth electrode pass through the lead wire connecting the fourth electrode and the third electrode, and reach the third electrode through the second electromotive force measuring means.
[0017]
Therefore, electrons due to the reaction of both hydrogen and oxygen contribute to the electromotive force E12 measured by the first electromotive force measuring means, but only oxygen is included in the electromotive force E34 measured by the second electromotive force measuring means. Since the electrons by the reaction of (2) contribute, the amount of hydrogen can be known from the difference between both electromotive forces, that is, E12-E34.
[0018]
【Example】
Examples of the present invention will be shown to describe the present invention more specifically.
FIG. 1 shows a cross-sectional view of the main part in which the dissolved hydrogen sensor of this embodiment is mounted in the molten metal to be measured.
The present dissolved hydrogen sensor 1 includes a first electrode 11 made of a cylindrical proton conductive solid electrolyte with a closed lower end contacting the molten metal 4, and a metal and a metal press-fitted into the cylindrical first electrode 11. In the second electrode 12 made of an oxide, the third electrode 13 made of a cylindrical oxide ion conductive solid electrolyte with a closed lower end contacting the molten metal 4, and the cylindrical third electrode 14 A first electrode 14 made of a press-fitted metal and metal oxide, a metal cylinder 18 having one end immersed in the molten metal 4, and the other end connected to the second electrode 12 by a lead wire 17. The power measuring means 15 and the second electromotive force measuring means 16 having one end connected to the metal cylinder 18 and the other end connected to the fourth electrode 14 by a lead wire 17 .
[0019]
In the dissolved hydrogen sensor 1, the upper end portion is fixed to the mounting jig 2 so that the first electrode 11 and the third electrode 13 are symmetrical left and right with the metal cylinder 18 in the middle, and the lower end portion is melted in the container 3. It is immersed in the metal 4. In the present embodiment, the lead wires 17 are symmetric in order to facilitate the handling of the lead wires 17, but the hydrogen sensor may not be symmetric in terms of performance and function.
[0020]
The first electrode 11 made of a cylindrical proton conductive solid electrolyte includes a cylindrical fluorite-type oxide 111 having an inner diameter of 20 mm, an outer diameter of 25 mm, and an inner space depth of 50 mm, and a film-like film formed on the outer peripheral surface thereof. And perovskite oxide 112.
Cylindrical fluorite-type oxide 111 is stabilized zirconia, (CaO) _0.11 ( ZrO ₂ ) _0.89 , and commercially available (CaO) _0.11 ( ZrO ₂ ) _0.89 powder is used as a mold. After being molded into a cylindrical shape with a pressure of 1 ton / cm ² , it was fired in a firing furnace in air at 1500 ° C. for 5 hours.
[0021]
The membranous perovskite oxide 112 is SrZrO ₃ , and a saturated aqueous solution (paste) of Sr nitrate in alkaline earth metal is applied to the outer peripheral surface of the cylindrical fluorite-type oxide 111 and dried at room temperature. The film was fired in air at 1200 ° C. for 10 hours, and the film thickness was 10 μm.
The second electrode 11 is a mixture of Cr and Cr ₂ O ₃ , and after inserting a lead wire 17, which is a Mo wire having a thickness of 1 mm, into the center of the cylindrical fluorite-type oxide 111, Cr and Cr ₂ It was made by press-fitting a powder in which O ₃ was mixed at a ratio of 1: 1. The length of the second electrode is 40 mm.
[0022]
The third electrode 13 made of a cylindrical oxide ion conductive solid electrolyte has exactly the same composition, manufacturing method, dimensions, and shape as the cylindrical fluorite-type oxide 111. That is, the solid electrolyte 15 is made of (CaO) _0.11 ( ZrO ₂ ) _0.89 , and is a cylinder having an inner diameter of 20 mm, an outer diameter of 25 mm, and an inner air depth of 50 mm.
The fourth electrode 14 has exactly the same composition, manufacturing method, and dimensions as the second electrode. That is, the fourth electrode 14 is obtained by press-fitting a powder in which Cr and Cr ₂ O ₃ are mixed at a ratio of 1: 1 into the cylindrical third electrode 13.
[0023]
The metal cylinder 18 whose lower end is immersed in the molten metal 4 is made of Mo having a diameter of 6 mm and a length of 40 mm. A lead wire 17 which is a Mo wire having a thickness of 1 mm is fixed to the upper end portion.
The first electromotive force measuring means 15 for measuring the electromotive force E12 between the first electrode 11 and the second electrode 12 is a voltmeter. Similarly, the second electromotive force measuring means 16 for measuring the electromotive force E34 between the third electrode 13 and the fourth electrode 14 is the same type of voltmeter.
[0024]
FIG. 2 shows the relationship between the electromotive force difference E12-E34 of the present dissolved hydrogen sensor and the dissolved hydrogen partial pressure when the molten metal 4 is a molten steel having a temperature of 1600 to 1650 ° C. and the dissolved hydrogen partial pressure is changed. It can be seen that hydrogen can be detected with good linearity when the hydrogen partial pressure is in the range of 0.0001 to 0.1 atm.
[0025]
【The invention's effect】
The dissolved hydrogen sensor of the present invention includes a second electrode and a fourth electrode as common electrodes, a first electrode made of a proton conductive solid electrolyte, and a third electrode made of an oxide ion conductive solid electrolyte. The difference between the electromotive force E12 between the first electrode and the second electrode and the electromotive force E34 between the third electrode and the fourth electrode is taken to cancel the electromotive force due to oxygen and detect hydrogen in the high-temperature molten metal. Can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view in which a dissolved hydrogen sensor according to an embodiment is mounted in molten metal.
FIG. 2 is a graph showing a relationship between an electromotive force and a hydrogen partial pressure of a dissolved hydrogen sensor of an example.
[Explanation of symbols]
1 .... dissolved hydrogen sensor, 2 .... mounting jig, 3 .... container, 4 .... molten metal, 11 .... first electrode made of proton conductive solid electrolyte, 12 .... made of metal and metal oxide 2 electrode, 13 ... third electrode made of oxide ion conductive solid electrolyte, 14 ... fourth electrode made of metal and metal oxide, 15 ... first electromotive force measuring means, 16 ... second electromotive force Measuring means, 17 ... lead wire, 18 ... metal cylinder, 111 ... fluorite type oxide, 112 ... perovskite oxide.

Claims (6)

A first electrode made of a proton conductive solid electrolyte in contact with a molten metal in which hydrogen to be measured is dissolved; A second electrode made of an oxide, a third electrode made of an oxide ion conductive solid electrolyte in contact with the molten metal, and a surface of the third electrode facing away from the surface in contact with the molten metal. a fourth electrode comprising a said metal and said metal oxide, a first electromotive force measuring means for measuring the electromotive force between the first electrode and the second electrode, the third electrode and the fourth electrode a second electromotive force measuring means for measuring the electromotive force between, Ri Tona,
By taking the difference between the electromotive force between the first electrode and the second electrode and the electromotive force between the third electrode and the fourth electrode, the electromotive force due to oxygen is canceled and hydrogen in the high-temperature molten metal is removed. A sensor for detecting dissolved hydrogen in a molten metal. The dissolved hydrogen sensor according to claim 1, wherein the metal is Cu and the metal oxide is Cu ₂ O. The dissolved hydrogen sensor according to claim 1, wherein the metal is Cr and the metal oxide is Cr ₂ O ₃ . In the proton conductive solid electrolyte, an ABO ₃ type perovskite oxide that is a proton-oxide ion mixed conductive electrolyte is laminated on the surface of a fluorite-type oxide that is an oxide ion conductive electrolyte, The element A is one or more elements selected from the group consisting of alkaline earth metals (Sr, Ca, Ba), and the B element is a metal element of the fluorite-type oxide or a part thereof as an alkaline earth Substitution with one or more elements selected from the group consisting of metals (Mg, Ca, Sr, Ba) and rare earth elements (Sc, Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Yb) The dissolved hydrogen sensor according to claim 1, wherein the dissolved hydrogen sensor is a metal element of the fluorite-type oxide produced by The dissolved hydrogen sensor according to claim 1, wherein the oxide ion conductive solid electrolyte is a fluorite-type oxide. The fluorite type oxide is stabilized zirconia or stabilized ceria, and the ABO ₃ type perovskite oxide is SrZrO ₃ , BaCeO ₃ , SrCeO ₃ , BaZrO ₃ , or CaZrO _3. The dissolved hydrogen sensor described.

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