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 that use hydrogen ion conductive ceramics. [Background technology]

[0002] A hydrogen sensor using a proton-conductive 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 solid electrolyte that exhibits proton conductivity, and the hydrogen concentration in the molten metal is measured 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] A gas with a known hydrogen concentration must usually be supplied to the reference electrode side. The concentration (activity) of the hydrogen to be measured is measured based on the Nernst equation by measuring the electromotive force generated between the reference hydrogen gas and the hydrogen to be measured that is in contact with the other side of the proton-conductive solid electrolyte (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-344347 [Patent Document 2] Patent Publication No. 2021-7139 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, the hydrogen concentration in molten metal is measured by cooling a sample of the molten metal and analyzing the cooled metal. This requires time for measurement. Furthermore, the amount of hydrogen released from the metal varies as it cools, making the measured value unstable.

[0006] In contrast, as mentioned above, hydrogen sensors using proton-conductive solid electrolytes (hydrogen ion-conductive ceramics) are a method that can directly measure the hydrogen concentration in molten metal, and as such can quickly determine the hydrogen concentration in the molten metal and provide feedback during refining, thereby shortening the refining time, eliminating the need to deviate from the alloy composition and reduce yield, and increasing measurement accuracy.

[0007] However, when measuring the hydrogen concentration in molten metal, a container such as a cylinder of hydrogen gas with a reference concentration is required to introduce hydrogen gas of a known concentration to the reference electrode side, and a device for introducing the hydrogen gas with the reference concentration is also required, which makes the hydrogen sensor system complicated.In addition, the management of the supplied hydrogen gas is also required, which is cumbersome.

[0008] It is also possible to use disposable hydrogen sensors in high-temperature molten metals such as molten steel. In the case of hydrogen sensors that introduce hydrogen gas at a reference concentration into the reference electrode, this poses the problem of having to connect a supply pipe for hydrogen gas at the reference concentration when installing the hydrogen sensor. Therefore, a complex device must be designed to automate the replacement of hydrogen sensors.

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

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

[0011] However, when hydrogen gas generated within the operating temperature range is used as the standard, the generated hydrogen gas must be contained within the storage chamber, making the hermeticity (sealability) of the storage chamber important. However, there are cases where the storage chamber cannot be sealed sufficiently, and the quantitative measurement capability of such a hydrogen sensor is impaired. For example, there is a problem that the seal breaks 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 it is a hydride that does not decompose to generate hydrogen gas even in the operating environmental temperature range, for example, at high temperatures such as molten steel, the hydrogen activity of the hydride becomes high, so if the hydrogen ion conducting ceramics on the reference electrode side or the reference electrode and the hydride are in contact, it can play the role of the reference electrode, and 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 being made of hydrogen ion conducting ceramics, the tubular portion being filled with a reference substance, the reference electrode being arranged to be in electrical contact with the reference substance, and the reference substance including 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, characterized in that the hydride is one or more selected from TiH , , ,

[0014] , , x ,

[0017] , x , , , , ,

[0016] ,

[0015] , (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, characterized in that the reference substance further includes a metal that melts in the measurement temperature range.

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

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

[0019] (6) The hydrogen sensor probe for molten metal according to (5) above, further 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 reference concentration hydrogen gas to the reference electrode side and do not require a sealed hydrogen gas storage chamber, thereby providing the effect of enabling measurement of the hydrogen concentration in molten metal with a simple system and simple configuration. Furthermore, if the probe is disposable, the effect of making the probe easy to replace and facilitating automation is also provided. [Brief explanation of the drawings]

[0021] [Figure 1] Examples of hydrogen sensors for molten metals according to the present invention [Figure 2] An example of a hydrogen sensor probe for molten steel using the hydrogen sensor for molten metal of the present invention [Figure 3] 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) DETAILED DESCRIPTION OF THE INVENTION

[0022] DETAILED DESCRIPTION OF THE INVENTION As described 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 ambient temperature range.

[0024] At high temperatures such as those of molten metal, for example, 1000 °C or higher, the hydrogen activity of 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 serve as a reference electrode even without generating hydrogen gas. Rather, if hydrogen gas is generated, the electromotive force caused by the hydrogen concentration difference 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 preferably in the range of composition x that does not generate hydrogen gas. Among them, the range where 0 < x ≤ 1.1 for the said x is more preferable.

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

[0028] It is preferable that the reference material further contains a metal that melts in the measurement temperature range. If a metal that melts in the measurement temperature range and the hydride are applied to the reference electrode side of a hydrogen sensor as shown in Figure 1, the metal will melt during measurement, improving contact with the reference electrode, the hydrogen ion conductive ceramic, and the hydride. Therefore, there is no need to increase the filling capacity of the reference material portion of Figure 1.

[0029] The reference material preferably further contains a metal that does not melt in the measurement temperature range on the reference electrode side. It is more preferable to mix the metal that does not melt in the measurement temperature range with the hydride and fill the reference material portion in Figure 1, as this improves electrical contact between the reference electrode and the hydride.

[0030] That is, it is more preferable that the reference material contains both a metal that melts in the measurement temperature range and a metal that does not melt in 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 metals of the present invention is a material that can absorb hydrogen ions (H + Any oxide composition may be used as long as it exhibits SiO2 conductivity. For example, the oxide may be at least one selected from the group consisting of Ca-Zr-O, Ca-Zr-In-O, Sr-Ce-O, Ba-Zr-O, and alkaline earth metal-doped alumina, but is not limited thereto.

[0032] One example of such oxides is a hydrogen ion conducting oxide with a perovskite structure (basic composition formula ABO3). In the perovskite structure, A is typically an alkaline earth metal, B is cerium or zirconium, and A or B is partially substituted with a cation M having a lower valence. The general formula is: 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 earth elements with a valence of 3, such as Y, Sc, In, etc. Examples 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 etc.

[0033] In such a composition, oxygen vacancies are generated due to the electrically neutral condition. Proton conductivity is exhibited when water molecules in the atmosphere are captured in these oxygen vacancies. Particularly preferred are hydrogen ion conductive ceramics that are stable at high temperatures of 1000°C or higher, 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 to be measured. For example, if the molten metal is molten steel, examples of the metal that can be used include nickel, tungsten, platinum, rhodium, palladium, titanium, iridium, and molybdenum, all of which have melting points higher than the temperature of the molten steel whose hydrogen concentration is to be measured. Molybdenum and tungsten are particularly preferred.

[0035] The measurement electrode is preferably a metal or oxide that is electronically conductive 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 to be measured. For example, if the molten metal is molten steel, nickel, tungsten, platinum, rhodium, palladium, titanium, iridium, and the like, which have melting points higher than the temperature of the molten steel whose hydrogen concentration is to be measured, can be used. When constructing a hydrogen sensor that is disposable after a single 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, is used.

[0036] The hydrogen sensor for molten metal of the present invention can be used as a hydrogen sensor probe for molten metal, for example, by attaching it to a paper sleeve to make it a disposable (single measurement) hydrogen sensor probe for molten metal. The hydrogen concentration is calculated from the measured electromotive force based on the Nernst equation, but the Nernst equation also includes a temperature term, so the measurement temperature is also required. Therefore, the hydrogen concentration in the molten metal is calculated using the temperature of the molten metal measured separately when measuring the electromotive force with the hydrogen sensor probe.

[0037] The hydrogen sensor probe for molten metal can further be equipped with a temperature-measuring thermocouple. 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 temperature-measuring thermocouple.

[0038] Next, specific embodiments of the present invention will be described with reference to FIGS.

[0039] FIG. 1 is a cross-sectional view showing a hydrogen sensor for molten metals according to a first embodiment of the present invention. This hydrogen sensor for molten metals has a tubular portion (Tammann tube shape) with one end closed, and a lead wire (molybdenum) of a reference electrode 1 extends from the open end. The Tammann tube portion 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 The electrode is formed of a hydrogen ion conductive ceramic made of a perovskite type complex oxide such as ZnO.

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

[0041] The lead wire (molybdenum) of the measuring electrode 2 is attached to the outside of the Tammann tube-shaped portion 4 so that it can come into contact with the molten metal. When the molten metal comes into contact with the outside of the Tammann tube-shaped portion 4, it also functions as an electrode, so the lead wire of the measuring electrode 2 is arranged so that it can come into contact with the molten metal.

[0042] It is also possible to mix metal powder (copper, manganese, nickel, etc.) that melts in the measurement temperature range together with the reference material 3 (hydride powder).

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

[0044] 2 is a diagram showing a hydrogen sensor probe for molten steel according to a second embodiment of the present invention, showing the layout (cross-sectional view) of a disposable (consumable) probe in which the hydrogen sensor of FIG. 1 is attached to a paper sleeve 15. The terminal of the measuring electrode 12 is 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. In other words, when molten steel comes into contact with the outside of the Tammann tube, it also functions as an electrode, so when the molten steel comes into contact with the molten steel electrode iron ring 13, the electromotive force generated between the measuring electrode 12 and the reference electrode 11 can be measured via the terminal of the measuring electrode 12.

[0045] The probe is fitted with an iron cap 14 to protect the hydrogen sensor section. Because it is a consumable probe, there is a high chance that the hydrogen sensor section will be damaged when storing a large number of replacement probes or when replacing the probes, so the iron cap is used to protect it. 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 drilled in the iron cap to allow molten steel to pass through.

[0046] Fig. 3 shows a hydrogen sensor probe for molten steel according to a third embodiment of the present invention, and shows a layout (cross-sectional view) in which a temperature-measuring thermocouple 20 is also attached to the hydrogen sensor probe of Fig. 2. The hydrogen sensor section is the same as in Fig. 2, but a temperature-measuring thermocouple (e.g., a platinum-platinum-rhodium alloy thermocouple) is also attached, and 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] These hydrogen sensors and hydrogen sensor probes were used to measure the electromotive force generated between the hydrogen in molten steel melted by induction heating and a reference electrode. When the hydrogen sensor or hydrogen sensor probe was immersed in the molten steel, the electromotive force began to increase and reached a stable value within 10 seconds (note that because the molten steel was very hot, 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 accurately in situ, which can shorten the refining time and increase the yield. For example, in the hydrogen reduced iron process, degassing (dehydrogenation) in molten steel is important, and the present invention can greatly contribute to the monitoring of the hydrogen concentration in molten steel. [Explanation of symbols]

[0050] 1 Reference electrode 2 Measuring electrode 3 Reference material 4 Tamman tube shape part 5. Fillers 6. Heat-resistant adhesive 10 Hydrogen sensor 11 Reference electrode 12 Measuring electrode terminal 13 Iron ring (molten steel pole) 14 Iron Cap 15 Paper Sleeve 20 Thermocouple 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, a measuring electrode on the side in contact with the molten metal, and A tubular section with one end closed Equipped with the tubular portion is made of hydrogen ion conductive ceramics, The tubular portion is filled with a reference substance; the reference electrode is positioned in electrical contact with the reference material; The reference material contains a hydride that does not decompose even in the measurement temperature range. A hydrogen sensor for molten metal characterized by:

2. The hydride is TiH x (0<x≦1.1), ZrH x 2. The hydrogen sensor for molten metal according to claim 1, wherein the hydrogen sensor is one or more selected from the group consisting of (0<x≦1.1), rare earth metal hydrides, and rare earth metal hydrides.

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

4. 4. The hydrogen sensor for molten metal according to claim 1, wherein the reference material further contains a metal that does not melt in the measurement temperature range.

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

6. 6. The hydrogen sensor probe for molten metal according to claim 5, further comprising a thermocouple.

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