Hydrogen sensor for molten metal and hydrogen sensor probe for molten metal

Abstract

To provide a hydrogen sensor and a probe capable of measuring the hydrogen concentration in molten metal without using hydrogen gas as a reference substance on the reference electrode side.SOLUTION: The hydrogen sensor for molten metal has two electrodes provided via a hydrogen ion-conducting ceramic and measures the hydrogen concentration in molten metal by an electromotive force generated between the electrodes. One of the electrodes is a measuring electrode located on the side in contact with the molten metal, and the other electrode is a reference electrode containing a reference substance. The reference substance contains a hydride that does not decompose even in the measurement temperature range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen sensor for molten metal and a hydrogen sensor probe for molten metal using hydrogen ion conductive ceramics. [Background technology]

[0002] A hydrogen sensor using a proton-conducting solid electrolyte has been proposed as a method for measuring the hydrogen concentration in molten metal (Patent Document 1). A galvanic cell type sensor is constructed using a sensor element made of a proton-conducting solid electrolyte, and a method has been proposed to measure the hydrogen concentration in the molten metal from the electromotive force generated by the difference between the hydrogen concentration (activity) of the solid electrolyte on the reference electrode side of the sensor element and the hydrogen concentration (activity) in the molten metal.

[0003] Typically, a gas of known hydrogen concentration needs to be supplied to the reference electrode side. By measuring the electromotive force generated between the reference hydrogen gas and the hydrogen concentration to be measured in contact with the other side of the proton-conducting solid electrolyte, the concentration (activity) of the hydrogen to be measured is measured based on the Nernst equation (Patent Document 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-344347 [Patent Document 2] Japanese Patent Publication No. 2021-7139 [Overview of the project] [Problems that the invention aims to solve]

[0005] Generally, the hydrogen concentration in molten metal is measured by cooling a sample of the molten metal and analyzing the cooled metal. Therefore, the measurement is time-consuming. Furthermore, the amount of hydrogen released from the metal during cooling varies, resulting in unstable measurement values.

[0006] In contrast, as mentioned above, hydrogen sensors using proton-conducting solid electrolytes (hydrogen ion-conducting ceramics) can directly measure the hydrogen concentration in molten metal. This allows for rapid determination of the hydrogen concentration in the molten metal, providing feedback during the refining process. This can shorten the refining time, prevent the alloy composition from being incorrect and thus reduce yield, and improve measurement accuracy.

[0007] However, when measuring the hydrogen concentration in molten metal, a cylinder or other container of hydrogen gas of a known concentration is required to introduce hydrogen gas of a known concentration to the reference electrode side, and a device for introducing the hydrogen gas of that concentration is also necessary, which complicates the hydrogen sensor system. Furthermore, managing the supplied hydrogen gas is also required, making the process cumbersome.

[0008] Furthermore, for high-temperature molten metals such as molten steel, it might be possible to use disposable hydrogen sensors. In the case of hydrogen sensors that introduce a reference concentration of hydrogen gas to the reference electrode side, a problem arises in that the supply pipe for the reference concentration of hydrogen gas must also be connected when installing the hydrogen sensor. Therefore, automating the replacement of hydrogen sensors would require designing a complex device.

[0009] If a hydrogen sensor could be developed that did not require the introduction of a reference concentration hydrogen gas to the reference electrode side, the aforementioned problems would not occur, and the hydrogen concentration in molten metal could be measured more easily.

[0010] Patent Document 1 discloses that, in an attempt to solve the above problem, a reference substance is contained in a containment chamber on the reference electrode side of the sensor, and the hydrogen gas generated when the reference substance decomposes in the operating environment temperature range is used as the reference.

[0011] However, when using hydrogen gas generated within the operating temperature range as a reference, it is necessary to contain the generated hydrogen gas in the containment chamber, making the airtightness (sealing ability) of the containment chamber important. However, it may not be possible to seal it sufficiently, and in such cases, the quantitative accuracy of the hydrogen sensor will be compromised. For example, there is a problem that the seal may break due to the pressure of the generated hydrogen gas.

[0012] The present invention has been made in view of the above problems, and an object thereof is to provide a hydrogen sensor for molten metal and a hydrogen sensor probe for molten metal (hereinafter simply referred to as "probe") that can measure the hydrogen concentration in molten metal without using hydrogen gas as a reference substance on the reference electrode side.

Means for Solving the Problems

[0013] The inventors of the present invention have found that even if a hydride that does not decompose to generate hydrogen gas even in the operating environmental temperature range has a high hydrogen activity in the hydride at high temperatures such as molten steel, if the hydrogen ion conductive ceramics on the reference electrode side or the reference electrode is in contact with the hydride, it can play the role of the reference electrode, and thus the present invention has been achieved. The present invention has been further studied and includes the following aspects.

[0014] (1) A hydrogen sensor for molten metal that measures the hydrogen concentration in molten metal by the electromotive force generated between two electrodes, comprising a reference electrode, a measurement electrode on the side in contact with the molten metal, and a tubular portion with one end closed. The tubular portion is made of hydrogen ion conductive ceramics, the tubular portion is filled with a reference substance, the reference electrode is arranged to be in electrical contact with the reference substance, and the reference substance contains a hydride that does not decompose even in the measurement temperature range. A hydrogen sensor for molten metal characterized by this.

[0015] (2) The hydrogen sensor for molten metal according to (1) above, wherein the hydride is one or more selected from TiH x (0 < x ≦ 1.1), ZrH x (0 < x ≦ 1.1), rare earth metal hydrides.

[0016] (3) The hydrogen sensor for molten metal according to (1) or (2) above, wherein the reference substance further contains a metal that melts in the measurement temperature range.

[0017] (4) A hydrogen sensor for molten metal according to any of (1) to (3) above, characterized in that the reference material further includes a metal that does not melt in the measurement temperature range.

[0018] (5) A hydrogen sensor probe for molten metal, characterized by comprising any of the hydrogen sensors for molten metals described in (1) to (4) above.

[0019] (6) The hydrogen sensor probe for molten metal according to (5), further characterized by comprising a thermocouple. [Effects of the Invention]

[0020] The hydrogen sensor and probe for molten metal of the present invention eliminate the need to introduce a reference concentration of hydrogen gas to the reference electrode side and does not require a sealed hydrogen gas containment chamber, thus enabling the measurement of hydrogen concentration in molten metal with a simple system and configuration. Furthermore, when using disposable probes, the probes can be easily replaced, facilitating automation. [Brief explanation of the drawing]

[0021] [Figure 1] Example of a hydrogen sensor for molten metal according to the present invention [Figure 2] Example of a hydrogen sensor probe for molten steel using the molten metal hydrogen sensor of the present invention [Figure 3] An example of a hydrogen sensor probe for molten steel using the hydrogen sensor for molten metal of the present invention (with thermocouple for temperature measurement). [Modes for carrying out the invention]

[0022] The present invention will now be described in detail. As mentioned above, the present invention relates to a hydrogen sensor and probe that can measure the hydrogen concentration in molten metal without using hydrogen gas as a reference substance on the reference electrode side.

[0023] As described above, the reference substance in the hydrogen sensor for molten metal according to the present invention includes a hydride that does not decompose even in the measurement temperature range, that is, a hydride that does not decompose to generate hydrogen gas even in the operating environment temperature range.

[0024] At high temperatures such as those of molten metal, for example, 1000 °C or higher, the activity of hydrogen in the hydride increases. Therefore, if the hydrogen ion conductive ceramics on the reference electrode side or the reference electrode is in contact with the hydride, it can play the role of the reference electrode even without generating hydrogen gas. Rather, if hydrogen gas is generated, the electromotive force generated by the concentration difference of hydrogen between the measurement electrode and the reference electrode becomes unstable due to the generation condition and diffusion condition of the hydrogen gas, making it impossible to accurately measure the hydrogen concentration.

[0025] Therefore, the hydride used as the reference substance in the present invention only needs to be one that does not decompose to generate hydrogen gas even in the measurement temperature range, for example, 1000 °C or higher.

[0026] Titanium hydride TiH x is one preferred hydride in the present invention, and it is preferable to set the range of the composition x that does not generate hydrogen gas. Among them, the range where 0 < x ≤ 1.1 is more preferable.

[0027] Zirconium hydride ZrH x is another preferred hydride, and it is preferable to set the range of the composition x that does not generate hydrogen gas. Among them, the range where 0 < x ≤ 1.1 is more preferable. Rare earth metal hydride ReHx is yet another preferred hydride, and it is preferable to set the range of the composition x that does not generate hydrogen gas. Among them, the range where 0 < x ≤ 1.5 is more preferable.

[0028] The reference substance preferably further contains a metal that melts within the measurement temperature range. When the metal that melts within the measurement temperature range and the hydride are applied to the reference electrode side of the hydrogen sensor as shown in FIG. 1, in the measurement state, the metal melts, improving the contact with the reference electrode, the contact with the hydrogen ion conductive ceramics, and the contact with the hydride. Therefore, there is no need to improve the filling property of the reference substance portion in FIG. 1.

[0029] The reference substance preferably further contains a metal that does not melt within the measurement temperature range on the reference electrode side. It is more preferable that when the metal that does not melt within the measurement temperature range is mixed with the hydride and filled in the reference substance portion of FIG. 1, the electrical contact between the reference electrode and the hydride is improved.

[0030] That is, it is more preferable that the reference substance contains both a metal that melts within the measurement temperature range and a metal that does not melt within the measurement temperature range together with the hydride.

[0031] The hydrogen ion conductive ceramics used in the tubular portion of the hydrogen sensor for molten metal of the present invention may have any composition as long as it is an oxide that exhibits hydrogen ion (H + ) conduction. For example, examples of the form include at least one selected from the group of Ca-Zr-O system, Ca-Zr-In-O system, Sr-Ce-O system, Ba-Zr-O system, and alumina-based systems doped with alkaline earth metals, but it is not limited thereto.

[0032] As an example of these, hydrogen ion conductive oxides having a perovskite structure (basic composition formula ABO3) can be mentioned. In the perovskite structure, typically, A is an alkaline earth metal, B is composed of cerium or zirconium, and A or B is partially substituted with a cation M having a lower valence. General formula: AB 1-x M x O 3-δ (x is at most about 0.2), A site (+2 valence): Ba, Sr, Ca, B site (+4 valence): Ce, Zr, M (+3 valence, so-called dopant): rare earths having a trivalent valence, Y, Sc, In, etc. Examples thereof include SrCe 0.95 Yb0.05 O 3-δ BaCe 0.9 Y 0.1 O 3-δ BaZr 0.9 Y 0.1 O 3-δ CaZr 0.9 In 0.1 O 3-δ These are some examples.

[0033] In such compositions, oxygen vacancies are formed under electrically neutral conditions. Proton conductivity is exhibited when water molecules from the atmosphere are incorporated into these oxygen vacancies. Particularly preferred are hydrogen ion conductive ceramics that are stable at high temperatures above 1000°C, such as Ba-Zr-O oxides.

[0034] The reference electrode is preferably a metal or oxide that has electronic conductivity and does not melt even in the measurement temperature range. For example, it is a metal or alloy with a melting point of 1000°C or higher. It is also a metal with a melting point higher than the temperature of the molten metal whose hydrogen concentration is being measured. For example, if the molten metal is molten steel, examples of metals with a melting point higher than the temperature of the molten steel whose hydrogen concentration is being measured include nickel, tungsten, platinum, rhodium, palladium, titanium, iridium, molybdenum, etc. Molybdenum and tungsten are particularly preferred.

[0035] The measuring electrode is preferably a metal or oxide that has electronic conductivity and does not melt even in the measurement temperature range. For example, a metal or alloy with a melting point of 1000°C or higher. It is also a metal with a melting point higher than the temperature of the molten metal to which the hydrogen concentration is being measured. For example, if the molten metal is molten steel, examples of metals with a melting point higher than the temperature of the molten steel to which the hydrogen concentration is being measured include nickel, tungsten, platinum, rhodium, palladium, titanium, iridium, etc. When constructing a hydrogen sensor that is to be used only once for measurement, it may be preferable to use the same metal as the molten metal, for example, if the molten metal is molten steel, iron, which is the main component of molten steel.

[0036] The hydrogen sensor for molten metal of the present invention can be a hydrogen sensor probe for molten metal, for example, it can be attached to a paper sleeve to be a disposable (single measurement) hydrogen sensor probe for molten metal. The hydrogen concentration is determined from the measured electromotive force based on the Nernst equation, but since the Nernst equation also has a temperature term, the measured temperature is also required. Therefore, the hydrogen concentration in the molten metal is calculated using the temperature value of the molten metal, which is measured separately when the electromotive force is measured with the hydrogen sensor probe.

[0037] The hydrogen sensor probe for molten metal can be further equipped with a thermocouple for temperature measurement. With this configuration, the hydrogen concentration in the molten metal can be calculated from the electromotive force of the hydrogen sensor using the temperature value measured by the thermocouple.

[0038] Next, specific embodiments of the present invention will be described with reference to Figures 1 and 2.

[0039] Figure 1 is a cross-sectional view showing a hydrogen sensor for molten metal according to a first embodiment of the present invention. This hydrogen sensor for molten metal has a tubular section (Tammann tube shape) with one end closed, and a lead wire (molybdenum) of the reference electrode 1 protrudes from the open end. The Tammann tube-shaped section 4 is made of SrCe 0.95 Yb 0.05 O 3-δ BaCe 0.9 Y 0.1 O 3-δ BaZr 0.9 Y 0.1 O 3-δ CaZr 0.9 In 0.1 O 3-δ It is formed from hydrogen ion conductive ceramics consisting of perovskite-type composite oxides such as the above.

[0040] The closed tubular portion of the Tammann tube-shaped section 4 is filled with reference material 3 and is in contact with the lead wire of the reference electrode 1. The reference material contains TiH 1.0The container is filled with the aforementioned powder. To prevent the aforementioned reference material from leaking out, an insulating refractory powder filler 5 is further filled in. The refractory powder is alumina powder. A heat-resistant adhesive 6 is applied to prevent these fillers from leaking out and to fix the lead wires of the reference electrode 1.

[0041] The lead wire (molybdenum) of the measuring electrode 2 is positioned outside the Tammann tube-shaped section 4 so that it can come into contact with the molten metal. The lead wire of the measuring electrode 2 is positioned so that it can come into contact with the molten metal, as the molten metal will function as an electrode when it comes into contact with the outside of the Tammann tube-shaped section 4.

[0042] In addition, metal powders that melt within the measurement temperature range (copper, manganese, nickel, etc.) can be mixed with the aforementioned reference substance 3 (hydride powder).

[0043] Furthermore, metal powders that do not melt even in the measurement temperature range (such as tungsten, molybdenum, chromium, titanium, etc.) can be mixed together with the aforementioned reference substance 3 (hydride powder).

[0044] Figure 2 shows a hydrogen sensor probe for molten steel, which is a second embodiment of the present invention. It shows a cross-sectional view of a disposable (consumable) probe in which the hydrogen sensor of Figure 1 is attached to a paper sleeve 15. The terminals of the measuring electrode 12 are fixed to an iron ring 13 to which the hydrogen sensor 10 is attached, and this iron ring 13 also serves as the molten steel electrode. That is, when molten steel comes into contact with the outside of the Tammann tube shape, it also functions as an electrode. Therefore, when molten steel comes into contact with the molten steel electrode iron ring 13, the electromotive force generated between the molten steel and the reference electrode 11 via the terminals of the measuring electrode 12 can be measured.

[0045] In this probe, an iron cap 14 is provided to protect the hydrogen sensor. Since it is a consumable probe, there are many opportunities for damage to the hydrogen sensor when storing numerous replacement probes or when replacing probes, so an iron cap is provided for protection. The iron cap 14 dissolves in molten steel, so the hydrogen sensor 10 comes into contact with the molten steel, enabling measurement of the hydrogen concentration. A hole may be made in the iron cap to allow molten steel to pass through.

[0046] Figure 3 shows a hydrogen sensor probe for molten steel, which is a third embodiment of the present invention. It shows a configuration (cross-sectional view) in which a thermocouple 20 for temperature measurement is also attached to the hydrogen sensor probe of Figure 2. The hydrogen sensor part is the same as in Figure 2, but a thermocouple for temperature measurement (for example, a platinum-platinum-rhodium alloy thermocouple, etc.) is also attached. The hydrogen concentration in the molten steel is calculated from the temperature value of the molten steel measured by this thermocouple and the electromotive force generated in the hydrogen sensor.

[0047] Using these hydrogen sensors and hydrogen sensor probes, the electromotive force generated between hydrogen in molten steel melted by induction heating and a reference electrode was measured. When the hydrogen sensor or hydrogen sensor probe was immersed in the molten steel, the electromotive force began to increase and stabilized within 10 seconds (however, because the molten steel was at a high temperature, the hydrogen sensor or thermocouple broke if left for more than 10 seconds).

[0048] When the same measurement was performed in molten steel with different hydrogen concentrations, a good correlation was observed between the generated electromotive force (temperature corrected) and the hydrogen concentration in the molten steel, confirming the effectiveness of the hydrogen sensor and hydrogen sensor probe of the present invention. [Industrial applicability]

[0049] According to the present invention, the hydrogen concentration in molten metal can be measured simply and more accurately in situ, which can shorten the refining time and increase the yield. For example, in the hydrogen-reduced iron process, degassing (dehydrogenation) of molten steel is of increasing importance, and the present invention can greatly contribute to monitoring this process (hydrogen concentration in molten steel). [Explanation of symbols]

[0050] 1 Reference electrode 2 Measuring electrode 3 Reference material 4. Tammann tube-shaped section 5. Filler 6. Heat-resistant adhesive 10 Hydrogen Sensor 11 Reference electrode 12 Measuring electrode terminals 13. Iron ring (molten steel electrode) 14 Iron cap 15 paper sleeves 20 Thermocouples for temperature measurement

Claims

1. A hydrogen sensor for molten metal that measures the hydrogen concentration in molten metal by the electromotive force generated between two electrodes, reference electrode, The measuring electrode on the side that comes into contact with the molten metal, and A tubular section with one end closed. Equipped with, The aforementioned tubular portion is made of hydrogen ion conductive ceramics. The aforementioned tubular portion is filled with a standard substance. The reference electrode is arranged to be in electrical contact with the reference material. The aforementioned reference substance includes a hydride that does not decompose even within the measurement temperature range. A hydrogen sensor for molten metal characterized by the following features.

2. The hydride is TiH x (0<x≦1.1), ZrH x The hydrogen sensor for molten metal according to claim 1, characterized in that it is one or more selected from (0 < x ≤ 1.1) and rare earth metal hydrides.

3. The hydrogen sensor for molten metal according to claim 1 or 2, characterized in that the reference material further includes a metal that melts in the measurement temperature range.

4. The hydrogen sensor for molten metal according to any one of claims 1 to 3, characterized in that the reference material further includes a metal that does not melt in the measurement temperature range.

5. A hydrogen sensor probe for molten metal, characterized by comprising a hydrogen sensor for molten metal according to any one of claims 1 to 4.

6. Furthermore, the hydrogen sensor probe for molten metal according to claim 5 is characterized by comprising a thermocouple.

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