JP2006132959A - Magnesium sensor probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnesium sensor probe capable of measuring the concentration of magnesium included in a measuring object such as molten metal. <P>SOLUTION: This magnesium sensor probe 1 has a solid electrolyte layer 2 using zirconia as a base material, a reference material holding part 3 arranged on one surface side of the solid electrolyte layer 2, and an electrode part 4 arranged on the one surface side of the solid electrolyte layer 2 and contacting with the measuring object. The electrode part 4 uses oxide including the magnesium as a base material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnesium sensor probe.

  The prior art will be described taking a spheroidal graphite cast iron-based molten metal as an example. In spheroidal graphite cast iron-based molten metal, it is required to measure the concentration of magnesium contained in the molten metal. However, such a magnesium sensor probe has not been developed. Therefore, in practice, the concentration of magnesium contained in the molten metal cannot be measured. After the molten metal has solidified into a product, the concentration of magnesium contained in the spheroidal graphite cast iron constituting the product is measured by analysis. I had to do it. For this reason, there has been a limit to improving the quality of spheroidal graphite cast iron.

Patent Document 1 discloses an apparatus for measuring the concentration of a metal element dissolved in a molten metal. This device comprises a stabilized solid electrolyte layer of zirconia, a reference electrode set in contact with the inner surface of the solid electrolyte layer, and a potential difference for measuring the potential difference between the reference electrode and the molten metal. Measuring means and an electrode part that contacts the outer surface of the solid electrolyte are provided.
Japanese Patent Laid-Open No. 61-260155

  The apparatus according to Patent Document 1 described above is not intended for measuring the concentration of magnesium contained in molten metal or the like.

  This invention is made | formed in view of the above-mentioned actual condition, and makes it a subject to provide the magnesium sensor probe which can measure the density | concentration of magnesium contained in measuring objects, such as a molten metal.

  The inventor has been eagerly developing a magnesium sensor probe. And a solid electrolyte layer based on zirconia, a reference substance holding portion for holding a reference substance provided on one side of the solid electrolyte layer, and a measurement object provided on one side of the solid electrolyte layer. It is known that if it is provided with a contact electrode part and the base material of the electrode part is an oxide containing magnesium, it can function as a magnesium sensor probe capable of measuring the concentration of magnesium contained in the measurement object. A magnesium sensor probe according to the present invention was developed.

The principle by which the concentration of magnesium can be measured is not necessarily clear, but is presumed as follows. The case where the electrode part provided in the solid electrolyte is a magnesium sensor probe formed of MgO, which is a typical oxide containing magnesium, and the object to be measured is a molten metal containing magnesium will be described as an example. . In this case, it is presumed that the equilibrium reaction of Formula 1 occurs at the interface between the electrode part (MgO) provided in the solid electrolyte and the measurement object. Here, in Formula 1, MgO means MgO contained in the electrode part provided in the solid electrolyte, and Mg means Mg contained in the molten metal. O ₂ means oxygen contained in the molten metal. The equilibrium constant K1 in the equilibrium reaction of Equation 1 is basically based on Equation 2. Here, the activities a _Mg and a _MgO can be considered as fixed values, and the oxygen partial pressure P _O2 of the reference material can be considered as a fixed value at a certain temperature. Therefore, oxygen contained in the molten metal If the partial pressure P _O2 is obtained as an oxygen sensor, the concentration of Mg contained in the molten metal can be obtained.

  That is, the magnesium sensor probe according to the present invention includes a solid electrolyte layer based on zirconia, a reference material holding part for holding a reference material provided on one side of the solid electrolyte layer, and a solid electrolyte layer. And an electrode portion that is provided on one side and is in contact with an object to be measured. The electrode portion includes an oxide containing magnesium as a base material.

Zirconia constituting the solid electrolyte is an oxygen ion conductor in a high temperature region. The zirconia can be stabilized zirconia stabilized by doping with an oxide dopant. As the oxide dopant, one or more of MgO, Y ₂ O ₃ , Yb ₂ O ₃ , CaO, and CeO ₂ can be employed. As a dopant, it can contain 0.1-15 mol%. For example, the zirconia can be stabilized zirconia stabilized with 9 mol% magnesia dope.

The electrode portion provided in the layer is formed using an oxide containing magnesium as a base material. As the oxide containing magnesium, an oxide containing magnesium (MgO) or a complex oxide containing M element in addition to magnesium can be used. Examples of the M element include iron (Fe), aluminum (Al), gallium (Ga), chromium (Cr), cerium (Ce), germanium (Ge), lithium (Li), tantalum (Ta), ytterbium (Yb), and the like. 1 type, or 2 or more types. Examples of the composite oxide include MgAl ₂ O ₄ , MgFe ₂ O ₄ , MgCrO ₄ , MgCr ₂ O ₄ , MgGa ₂ O ₄ , Mg ₂ GeO ₃ , MgGeO ₃ , Mg _0.8 Fe ₂ O ₄ , MgLi ₂ GeO _4. , MgFeTaO ₄ , MgYbFeO ₄ , Mg _0.8 Al ₂ O ₄ , Mg ₂ SiO ₄ , MgBaSiO ₄ , MgTe ₂ O _{5, and the} like.

  Here, the oxide containing magnesium can have a composition formula represented by MgxMyOz. M may be one element or two elements. M may be one or more selected from the group consisting of Al, Fe, Cr, Ga, Ge, Fe, Li, Ta, Yb, Si, Ba, and Te. In the above composition formula represented by MgxMyOz, x may be 1 plus or minus 0.5, that is, 0.5 to 1.5, particularly 0.75 to 1.25, although it varies depending on the element. It can be. y can be from 0.5 to 2.5, in particular from 0.75 to 2.25. Although z varies depending on x and y, it can be 2.5 to 6.5, and particularly 2.25 to 6.25. However, it is not limited to this.

As a reference material, the form formed with the mixture of a metal and a metal oxide is employable. As the reference substance, for example, a form formed of a mixture of chromium (Cr) and chromium oxide (Cr ₂ O ₃ ) can be adopted. The oxygen partial pressure of the reference material at a specific temperature can be considered as a fixed value.

  The magnesium sensor probe can include a potential difference measuring unit that measures a potential difference between the electrode portion and the measurement object. The magnesium sensor probe can include a second electrode portion that contacts the measurement object. The magnesium sensor probe can have a temperature sensor that measures the temperature of the measurement object. The object to be measured may be a high-temperature molten metal containing magnesium or possibly containing magnesium. Examples of the molten metal include iron-based molten metal, aluminum-based molten metal, copper-based molten metal, and titanium-based molten metal. Therefore, the magnesium sensor probe according to the present invention can be used for measuring the concentration of magnesium contained in the iron-based molten metal. As the iron-based molten metal, magnesium such as spheroidal graphite cast iron (FCD), caterpillar graphite cast iron (FCV), flake graphite cast iron (FC), etc., cast steel-based molten metal, stainless steel-based molten metal, etc. Examples of the molten metal containing or that may be contained.

  ADVANTAGE OF THE INVENTION According to this invention, the magnesium sensor probe which can measure the magnesium concentration contained in a measuring object can be provided.

  A magnesium sensor probe 1 according to this embodiment includes a layer 2 formed of a solid electrolyte based on zirconia, a reference material holding unit 3 provided on one side of the solid electrolyte layer 2, and a solid electrolyte. The electrode unit 4 is provided on one side of the layer 2 and is in contact with the measurement object 9. Furthermore, zirconia is regarded as stabilized zirconia stabilized with 9 mol% of a stabilizing aid, magnesia.

The layer 2 has a bottomed cylindrical shape having a bottom portion 21 and side wall portions 22 so as to form a space 20. The reference material holding unit 3 is formed of a solid reference material 30 held in a space 20 formed by the inner wall surface 2 i of the layer 2. The reference material 30 is formed of a mixture of a metal and an oxide of the metal. The reference material 30 is formed of a mixture of chromium (Cr) and chromium oxide (Cr ₂ O ₃ ). Specifically, it is set to chromium (Cr): chromium oxide (Cr ₂ O ₃ ) = 9: 1 (weight ratio). It is inferred that the equilibrium reaction of Formula 3 occurs in the reference material 30. In this case, the equilibrium constant K2 is basically based on Equation 4. a _Cr, a _{Cr2 O3} since it is possible to think basically 1 and may be considered as fixed values at an oxygen partial pressure P _O2 is the temperature in the reference material 30.

An electromotive force is generated based on the oxygen partial pressure in the reference material 30 and the oxygen partial pressure P _O2 of oxygen contained in the measurement object 9 (metal melt). That is, zirconia functions as an oxygen concentration cell based on the high oxygen partial pressure and the low oxygen partial pressure, and an electromotive force is generated. If the partial pressure P _{O2 of} oxygen contained in the measurement object 9 (metal melt) is obtained based on the electromotive force, the concentration of magnesium (Mg) contained in the measurement object 9 (metal melt) is obtained. be able to. The layer 2 has an outer diameter of 4 millimeters, an inner diameter of 3 millimeters, and a length of 30 millimeters, but is not limited thereto.

The electrode portion 4 attached to the solid electrolyte layer 3 is laminated on the outer wall surface 2p of the cylindrical layer 2 and uses an oxide containing magnesium as a base material. Here, the oxide containing magnesium is basically a composite oxide (MgFe ₂ O ₄ ) containing magnesium and iron. In forming the electrode part 4, a paste mainly composed of a composite oxide containing magnesium and iron (MgFe ₂ O ₄ ) is used, and the paste is applied to the outer wall surface 2p of the cylindrical layer 2 to a predetermined temperature (1400). ˜1500 ° C.) for a predetermined time (1 hour) and firing in an air atmosphere. Note that the oxide containing magnesium may be MgO.

  FIG. 2 is a conceptual diagram showing a state in which the magnesium sensor probe 1 is immersed in a molten metal surface. As shown in FIG. 2, the magnesium sensor probe 1 includes a bottomed cylindrical layer 2 that enters the measurement object 9, a second electrode portion 4B that enters the measurement object 9, and a potential difference measuring unit. The potentiometer 5 is provided. The second electrode portion 4B is formed using a refractory metal (for example, molybdenum) as a base material. And the layer 2 and the 2nd electrode part 4B are connected with the potentiometer 5 through the conducting wire 5c. The measurement object 9 is an iron-based molten metal such as a cast iron molten metal containing magnesium. The temperature of the measuring object 9 is 1000-1700 degreeC and 1100-1650 degreeC.

When the temperature of the zirconia constituting the layer 2 increases, oxygen ions move inside the zirconia. Accordingly, an electromotive force is generated between the electrode portion 4 and the second electrode portion 4B as an oxygen concentration cell. The electromotive force is basically proportional to the logarithm of the ratio of oxygen partial pressures on both sides of the solid electrolyte formed of zirconia. If the partial pressure P _{O2 of} oxygen contained in the measurement object 9 (metal melt) is obtained based on the electromotive force, the concentration of magnesium (Mg) contained in the measurement object 9 (metal melt) is obtained. be able to.

(Application example)
3 and 4 show application examples. A magnesium sensor probe 1 according to an application example includes a body 6 as a base portion based on ceramics, and a bottomed cylindrical layer 2 formed of a solid electrolyte based on zirconia provided in the body 6. A second electrode portion 4B provided on the body 6 and made of a refractory metal material such as morideden, a hollow tube 7 holding a thermocouple 70 provided on the body 6, and a body 6. A cover 8 and a paper cylinder 82 attached to the body 6. The cover 8 can cover the layer 2, the second electrode portion 4B, and the hollow tube 7, and has a hole 8a through which the molten metal enters.

(Test Example 1)
According to Test Example 1, the oxide containing magnesium constituting the electrode part 4 is based on a composite oxide containing Mg and iron (MgFe ₂ O ₄ ) as in the case of Example 1. The molten metal temperature was 1451 ° C. The composition of the molten metal contains magnesium. By weight%, carbon is 3.67%, silicon is 0.91%, chromium is 0.023%, and the balance is substantially iron and inevitable impurities. As the molten metal, 30 kg of iron was melted to obtain a molten metal, and magnesium was added to the molten metal. Then, the magnesium sensor probe 1 was immersed in a molten metal surface containing magnesium for 10 seconds.

  Similarly, the sensor probe 1 according to the comparative example was also tested. The sensor probe 1 according to the comparative example includes a solid electrolyte layer 2 based on zirconia, and does not include the electrode unit 4 and the reference material holding unit 3. The test results are shown in FIG. 5, the horizontal axis of FIG. 5 indicates time, the vertical axis of FIG. 5 indicates electromotive force, Δ indicates Test Example 1, and ○ indicates a comparative example. The electromotive force 10 seconds after the start of immersion was taken as the output value. The output value Vc1 of the comparative example was −193 mV. The output value of Test Example V1 was +20.83 mV.

(Test Example 2)
According to Test Example 2, the oxide containing magnesium constituting the electrode part 4 is based on a composite oxide (MgFe ₂ O ₄ ) containing magnesium and iron. The molten metal temperature was 1327 ° C., and the magnesium sensor probe 1 was immersed in molten metal containing magnesium for 10 seconds. The molten metal composition is basically the same as in Test Example 1. The sensor probe 1 according to the comparative example was also tested. The test results are shown in FIG. 6, the horizontal axis of FIG. 6 indicates time, the vertical axis of FIG. 6 indicates electromotive force, Δ indicates Test Example 2, and ○ indicates a comparative example. The electromotive force 10 seconds after the start of immersion was taken as the output value. As shown in FIG. 6, the output value Vc2 of the comparative example was −177 mV. The output value V2 of the test example was +280 mV.

(Test Example 3)
According to Test Example 3, the oxide containing magnesium constituting the electrode part 4 is based on a composite oxide containing Mg and aluminum (Mg _0.8 Al ₂ O ₄ ). The molten metal temperature was 1328 ° C. The molten metal composition is basically the same as in Test Example 1. The magnesium sensor probe 1 was immersed for 10 seconds in a molten metal containing magnesium. Similarly, the sensor probe 1 according to the comparative example was also tested. The test results are shown in FIG. 7. The horizontal axis of FIG. 7 indicates time, the vertical axis of FIG. 7 indicates electromotive force, Δ indicates Test Example 3, and ○ indicates a comparative example. The electromotive force 10 seconds after the start of immersion was taken as the output value. The output value Vc3 of the comparative example was −177 mV. As shown in FIG. 7, the output value V3 of the test example was −108 mV.

(Test Example 4)
According to Test Example 4, the oxide containing magnesium constituting the electrode part 4 is based on a composite oxide (MgFe ₂ O ₄ ) containing magnesium and iron. The molten metal temperature was 1450 ° C., and the magnesium sensor probe 1 was immersed for 10 seconds in molten metal containing magnesium. Similarly, the sensor probe 1 according to the comparative example was also tested. The electromotive force 10 seconds after the start of immersion was taken as the output value. In Test Example 4, the concentration of magnesium contained in the molten metal was changed. The test results are shown in FIG. As shown by the characteristic line W1 in FIG. 8, there was a correlation between the concentration (% by weight) of magnesium contained in the cast iron melt and the electromotive force. The electromotive force increased as the concentration (% by weight) of magnesium contained in the cast iron melt increased. The magnesium concentration was measured by fluorescent X-ray analysis.

(Test Example 5)
According to Test Example 5, the oxide containing magnesium constituting the electrode portion 4 is based on a composite oxide containing magnesium and aluminum (Mg _0.8 Al ₂ O ₄ ). The molten metal temperature was 1450 ° C., and the magnesium sensor probe 1 was immersed for 10 seconds in molten metal containing magnesium. The electromotive force 10 seconds after the start of immersion was taken as the output value. In Test Example 5, the concentration of magnesium contained in the molten metal was changed. The test results are shown in FIG. As shown by the characteristic line W2 in FIG. 9, a correlation was observed between the concentration (% by weight) of magnesium contained in the cast iron melt and the electromotive force. The electromotive force increased as the concentration (% by weight) of magnesium contained in the cast iron melt increased.

(Other embodiments)
According to the test example described above, the reference material 30 is formed of a mixture of chromium (Cr) and chromium oxide (Cr ₂ O ₃ ), but is not limited thereto, and nickel and nickel oxide, molybdenum and molybdenum. Oxides, iron and iron oxides, aluminum and aluminum oxides can also be used. Here, according to the test example described above, the molten metal is iron-based, but the present invention is not limited thereto, and the molten metal is also applied to aluminum-based molten metal, copper-based molten metal, titanium-based molten metal, and the like. In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications without departing from the scope of the invention.

It is sectional drawing of the principal part of a sensor probe. It is a principle diagram of a sensor probe. It is sectional drawing of a sensor probe. It is a bottom view of a sensor probe. It is a graph showing the test results at the time when the composite oxide containing magnesium and iron (MgFe ₂ O ₄₎ was used sensor probe having an electrode portion as a base. It is a graph showing the test results at the time when the composite oxide containing magnesium and iron (MgFe ₂ O ₄₎ was used sensor probe having an electrode portion as a base. It is a graph showing the test results at the time of using the sensor probe having an electrode portion for composite oxide containing magnesium and aluminum (Mg _0.8 Al ₂ O ₄₎ as a base material. Is a graph showing test results indicating the relationship between the magnesia concentration and electromotive force at the time when the composite oxide containing magnesium and iron (MgFe ₂ O ₄₎ was used sensor probe having an electrode portion as a base. Is a graph showing test results indicating the relationship between the magnesia concentration and electromotive force at the time when using a sensor probe having an electrode portion for composite oxide containing magnesium and aluminum (Mg _0.8 Al ₂ O ₄₎ as a base material.

Explanation of symbols

  In the figure, 1 is a sensor probe, 2 is a layer, 20 is a space, 21 is a bottom part, 22 is a side wall part, 3 is a reference substance holding part, 30 is a reference substance, 4 is an electrode part, 6 is a body, and 8 is a cover. Indicates.

Claims (8)

A solid electrolyte layer based on zirconia, a reference material holding part for holding a reference material provided on one side of the solid electrolyte layer, and a measurement object provided on one side of the solid electrolyte layer An electrode part that comes into contact with,
A magnesium sensor probe characterized in that the electrode part is based on an oxide containing magnesium.   2. The magnesium sensor probe according to claim 1, wherein the oxide containing magnesium is an oxide or composite oxide containing magnesium.   3. The magnesium sensor probe according to claim 1, wherein the oxide containing magnesium has a composition formula represented by MgxMyOz. Here, x is 0.5 to 1.5, y is 0.5 to 2.5, and z is 2.5 to 6.5.   The magnesium sensor probe according to any one of claims 1 to 3, wherein the magnesium sensor probe is used for measuring magnesium contained in a molten metal as a measurement object.   5. The magnesium sensor probe according to claim 1, further comprising a potential difference measuring unit that measures a potential difference between the electrode portion and the measurement object.   The magnesium sensor probe according to any one of claims 1 to 5, further comprising a second electrode portion that contacts the measurement object.   The magnesium sensor probe according to any one of claims 1 to 6, further comprising a temperature sensor that measures a temperature of an object to be measured.   The magnesium sensor probe according to any one of claims 1 to 7, wherein the reference substance is formed of a mixture of a metal and a metal oxide.

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