JP4017207B2 - Molten metal probe - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a molten metal probe used for measuring dissolved oxygen or solute elements in molten metal.
[0002]
[Prior art]
Conventionally, a device for measuring dissolved oxygen in a molten metal and a device for measuring a solute element in a molten metal are known. The former is configured as shown in FIG. The configuration is as shown in B).
[0003]
As shown in FIG. 1A, an apparatus for measuring dissolved oxygen in a molten metal includes a temperature sensor 1 such as a thermocouple that measures the temperature of the molten metal M, and an external device that is in electrical contact with the molten metal M. It consists of an electrode 2 and an oxygen sensor 3 immersed in the molten metal M. The oxygen sensor 3 constitutes an oxygen concentration cell composed of a solid electrolyte, and includes a solid electrolyte element 4 having oxygen ion conductivity. For example, when the solid electrolyte element 4 composed of a bottomed cylindrical tube is immersed in the molten metal M, the immersed portion constitutes the measurement portion 4a by the outer surface portion that contacts the molten metal M, and the molten metal A reference portion 4 b is configured by an inner surface portion that does not contact M, and a cylindrical chamber 4 c is defined in the tube of the solid electrolyte element 4. The reference electrode 5 in contact with the reference portion 4b is constituted by the reference material 5a filled in the cylindrical chamber 4c, and the metal rod 6a is inserted into the cylindrical chamber 4c and has its tip embedded in the reference material 5a. Thus, the internal electrode 6 is configured. At this time, the solid electrolyte element 4 is made of ceramics mainly composed of zirconia or the like. The reference material 5a is a mixture of Ni powder and NiO powder for making the oxygen activity constant at the measurement temperature, a mixture of Mo powder and MoO ₂ powder, a mixture of Cr powder and Cr ₂ O ₃ powder. Thus, it consists of a powder mixture of metal and its metal oxide, or air or other gas. The internal electrode 6 and the external electrode 2 are made of a metal that is stable in a high-temperature atmosphere and has a high melting point, such as Mo or Mo—ZrO ₂ .
[0004]
Therefore, according to this apparatus, the external electrode 2 and the internal electrode 6 detect the electromotive force E (V) generated by the oxygen partial pressure difference formed between the molten metal M and the reference electrode 5 on both sides of the solid electrolyte element 4. By doing so, the amount of dissolved oxygen in the molten metal M is measured. At this time, the temperature sensor 1 such as a thermocouple is used in combination, and the temperature T (K) of the molten metal M is measured at the same time, and the measured electromotive force E (V) and temperature T (K) are converted by a conversion formula. Thus, the amount of dissolved oxygen (oxygen activity) in the molten metal is determined.
[0005]
On the other hand, an apparatus for measuring a solute element in a molten metal is basically the same as the above-described dissolved oxygen measuring apparatus as shown in FIG. 4 is different in that an outer surface electrode 7 is provided on the outer surface. The outer surface electrode 7 is made of a mixed oxide mainly composed of an oxide of the element to be measured and / or an inorganic compound containing the oxide of the element to be measured, and is coated on the outer surface of the solid electrolyte element 4. Can be dressed. For example, if the element to be measured in the molten metal M is Cr, the outer electrode 7 is made of an inorganic compound containing an oxide of the element to be measured including Cr ₂ O ₃ and / or Cr ₂ O _3. It is a mixed oxide containing the main component. Alternatively, if the element to be measured is Si, the outer surface electrode 7 is a mixed oxide (for example, Al ₂ O ₃ ) whose main component is an inorganic compound containing an oxide of the element to be measured including SiO ₂ and / or SiO _2. And a mixture of TiAl ₂ O ₅ . Further, when the element to be measured is P, the outer electrode 7 is a mixed oxide (for example, a main component of an inorganic compound containing an oxide of the element to be measured including P ₂ O ₅ and / or P ₂ O _5. 4CaO · P ₂ O ₅ and CuO).
[0006]
Therefore, according to this apparatus, since the activity of the element to be measured in the molten metal M is converted into the oxygen activity by the outer surface electrode 7, the electromotive force E (V) generated by the oxygen partial pressure difference is converted to the external electrode 2. By detecting with the internal electrode 6, the concentration of the solute element in the molten metal M is measured. At this time, the temperature sensor 1 such as a thermocouple is used in combination, and the temperature T (K) of the molten metal M is measured at the same time, and the measured electromotive force E (V) and temperature T (K) are converted by a conversion formula. Thus, the solute element concentration in the molten metal is obtained. This point is known from Japanese Patent Laid-Open Nos. 61-142455 and 61-260155.
[0007]
[Problems to be solved by the invention]
The technique for measuring dissolved oxygen or solute elements in molten metal by using the apparatus as described above is theoretically extremely excellent, but has various unsolved problems in practical use. Unless these problems are solved, stable measurement cannot be realized.
[0008]
For example, when high-temperature outside air enters the cylindrical chamber 4c of the oxygen sensor 3, there is a problem that the internal electrode 6 made of Mo rod or the like sublimates and gradually fades, and a sublimation phenomenon occurs inside the cylindrical chamber 4c. There is a problem in that the reference material 5a is adversely affected and becomes unstable.
[0009]
Further, when the outside air enters the cylindrical chamber 4c, the reference material 5a is oxidized, and the stability of the reference electrode 5 is hindered. However, in the conventional apparatus, such an anti-oxidation measure is not sufficiently taken.
[0010]
[Means for Solving the Problems]
In order to solve the above problem, the present inventors found that it is necessary to seal the reference material 5a and the internal electrode 6 inside the cylindrical chamber 4c of the oxygen sensor 3, and tried various experiments. It has been found that a simple mechanical seal structure cannot solve the problems described above. For example, it has been considered to fill the opening at the tail end of the cylindrical chamber 4c with refractory cement and thereby seal the interior from the outside air. However, conventionally used refractory cement is generally used for the cylindrical chamber 4c. Since the coefficient of thermal expansion is different from that of zirconia that constitutes, the intrusion of outside air cannot be reliably prevented.
[0011]
In this regard, as a result of repeated keen research, the inventors of the present invention, when filling the cylindrical chamber 4c of the oxygen sensor 3 with the sealing agent, under a specific condition, the sealing agent selected from a specific material is used. It was learned that the above-mentioned problems can be solved by laminating over predetermined layers, and the results were confirmed as a result of experiments.
[0012]
Therefore, the present invention is configured as a means in the molten metal probe constituting the dissolved oxygen measuring device in the molten metal and the molten metal probe constituting the solute element measuring device in the molten metal as described above. A sealing agent filled in the cylindrical chamber so as to be embedded is selected from Al ₂ O ₃ powder and / or ZrO ₂ powder, and a stable protective layer filled in the cylindrical chamber in contact with the reference material, and graphite powder And / or an oxygen adsorbing layer selected from carbide powder and in contact with the stable protective layer and filled in a cylindrical chamber, and selected from quartz wool and / or alumina wool and / or ceramic wool and in contact with the oxygen adsorbing layer. A relaxation layer filled in the cylindrical chamber, and a consolidated layer made of refractory cement and in contact with the relaxation layer and filled in the cylindrical chamber.
[0013]
By the way, it is preferable that the refractory cement constituting the consolidated layer is selected from ZrO ₂ —SiO ₂ refractory cement or Al ₂ O ₃ refractory cement.
[0014]
Embodiment
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
(First embodiment)
FIG. 2 shows an oxygen sensor 3 according to the first embodiment of the present invention. The oxygen sensor 3 measures the outer surface portion in contact with the molten metal by a solid electrolyte element 4 comprising a bottomed cylindrical tube. The reference portion 4b of the inner surface portion that does not contact the molten metal is configured with the portion 4a, and the reference electrode 5 that is in contact with the reference portion 4b is formed by the reference material 5a filled in the cylindrical chamber 4c. The internal electrode 6 is composed of a metal rod 6a inserted and embedded in the reference material 5a at the tip. The materials and functions of the solid electrolyte element 4, the reference material 5 a, and the internal electrode 6 are the same as those in the above-described prior art, and the oxygen sensor 3 is used in the dissolved oxygen measuring device described with reference to FIG. Is done.
[0016]
On the other hand, the oxygen sensor 3 can be provided with an outer electrode 7 on the outer surface of the solid electrolyte element 4 as indicated by a chain line in FIG. The material and function of the outer surface electrode 7 are the same as those of the prior art described above. When the outer surface electrode 7 is provided in this way, the oxygen sensor 3 is used in the solute element measuring apparatus described with reference to FIG. used.
[0017]
By the way, the cylindrical chamber 4c of the solid electrolyte element 4 is filled with a sealing agent for embedding the internal electrode 6, and the sealing agent is in contact with the reference substance 5a and filled in the cylindrical chamber 4c. A layer 8, an oxygen adsorption layer 9 filled in the cylindrical chamber 4c in contact with the stable protective layer 8, a relaxation layer 10 in contact with the oxygen adsorption layer 9 and filled in the cylindrical chamber 4c, and the relaxation layer The laminated seal structure is formed in four layers with the consolidated layer 11 filled in the opening at the tail end of the cylindrical chamber 4c in contact with 10.
[0018]
The stable protective layer 8 prevents the metal rod 6a constituting the internal electrode 6 from being sublimated by contact with high temperature outside air, but does not itself melt, reduce or oxidize under the conditions of use, and it is a reference substance. It must be a stable substance that does not chemically react with 5a. As a material for satisfying this condition, a simple substance or a mixture of Al ₂ O ₃ or ZrO ₂ is selected, and powder is used in order to facilitate the formation of a seal layer in close contact with the reference material 5a. Incidentally, when selecting the Al ₂ O ₃ powder (alumina powder), it is preferable to use an inert alumina. In the case of activated alumina, it is easy to absorb the components in the reference material 5a, which may affect the reference oxygen value of the reference electrode 5. However, inactive alumina is unlikely to cause such component absorption.
[0019]
Thus, a stable protective layer 8 is formed by filling the cylindrical chamber 4c with a powder selected from Al ₂ O ₃ powder and / or ZrO ₂ powder, and the stable protective layer 8 is in close contact with the reference material 5a. At the same time, the metal rod 6a is firmly embedded.
[0020]
The oxygen adsorption layer 9 prevents the reference material 5a from being oxidized by air entering the cylindrical chamber 4c during a predetermined measurement using the oxygen sensor 3. That is, when air enters, the oxygen adsorption layer 9 easily reacts with oxygen in the air to generate a stable oxide, and prevents oxygen from entering the stable protective layer 8 and the reference material 5a. To do.
[0021]
By the way, the oxide produced | generated by adsorb | sucking to the oxygen adsorption layer 9 must be gas. In the case of a liquid, it may flow down and react with the reference material 5a or the solid electrolyte element 4. In particular, if it flows down to the interface between the reference material 5a and the solid electrolyte element 4, the function of the oxygen sensor 3 is significantly inhibited. Because it ends up.
[0022]
In order to satisfy such conditions, graphite powder or carbide (WC, ZrC, SiC) alone or a mixture thereof is selected, and in addition, in order to facilitate the formation of a seal layer in close contact with the stable protective layer 8, Powder is used. Thus, an oxygen adsorbing layer 9 is formed by filling the cylindrical chamber 4c with a powder selected from graphite powder and / or carbide powder, and the oxygen adsorbing layer 9 is in close contact with the stable protective layer 8, The metal rod 6a is embedded.
[0023]
As described above, in the vicinity of the opening at the tail end of the cylindrical chamber 4c, there are the relaxation layer 10 filled in contact with the oxygen adsorption layer 9 and the consolidated layer 11 filled in contact with the relaxation layer 10. It is provided and the metal rod 6a is embedded.
[0024]
The consolidated layer 11 is made of a refractory cement having a low porosity, and prevents intrusion of outside air. At this time, the refractory cement constituting the consolidated layer 11 needs to be a refractory having the same thermal expansion coefficient as that of the tube-shaped solid electrolyte element 4 as the filling material and having good adhesion. It is. For this reason, it is particularly preferable to select a ZrO ₂ —SiO ₂ fire resistant cement or an Al ₂ O ₃ fire resistant cement among the fire resistant cements.
[0025]
The relaxation layer 10 absorbs and relaxes the expansion and contraction tolerance of a structure composed of a tube of the solid electrolyte element 4 having different thermal expansion coefficients, an oxygen adsorption layer 9 such as graphite powder, and a consolidated layer 11 of refractory cement. In addition, the oxygen adsorption layer 9 reliably adsorbs and oxidizes oxygen that may enter from the outside. In order to satisfy such a condition, the relaxing layer 10 is selected from quartz wool, alumina wool, ceramic wool alone or a mixture.
[0026]
According to the above sealing structure, the oxygen sensor 3 prevents the outside air from entering the cylindrical chamber 4c because the tail end opening of the solid electrolyte element 4 is blocked by the consolidated layer 11 of refractory cement. .
[0027]
However, the refractory cement of the consolidated layer 11 is selected from ZrO ₂ —SiO ₂ refractory cement or Al ₂ O ₃ refractory cement, aiming at good adhesion, and suppressing the generation of gaps due to thermal expansion. However, as long as it is a refractory cement, it is difficult to guarantee complete airtightness, and it allows air to pass through. In particular, it is difficult to prevent the passage of air between the outer periphery of the metal rod 6a and the consolidated layer 11.
[0028]
Therefore, it is presumed that most of the air that has passed through the consolidated layer 11 is guided to the oxygen adsorption layer 9 along the outer periphery of the metal rod 6a. Since the area must be as small as possible, it is not always possible to achieve complete adsorption oxidation by the oxygen adsorption layer 9, and there is a possibility of allowing oxygen to permeate toward the stable protective layer 8.
[0029]
In this regard, a relaxation layer 10 is interposed between the consolidated layer 11 and the oxygen adsorption layer 9, and the inorganic wool material of the relaxation layer 10 holds the outer periphery of the metal rod 6a. The air that intrudes along the metal rod 6a is diffused into the relaxation layer 10 and stays there. For this reason, the air diffused in the relaxation layer 10 is preferably adsorbed and oxidized at the interface 9 a having a large area formed between the relaxation layer 10 and the oxygen adsorption layer 9 and permeates toward the stable protective layer 8. Is preferably prevented.
[0030]
(Second Embodiment)
FIG. 3 shows an oxygen sensor 3 according to a second embodiment of the present invention. Only the temperature measuring means 12 for measuring the temperature of the reference portion 4b of the solid electrolyte element 4 is provided in the first embodiment. Unlike the embodiment, the other configurations are the same as those of the first embodiment. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals as those in FIG. 2, and the above description is used as it is.
[0031]
The temperature measuring means 12 constitutes a sheath thermocouple including an insulator tube 13 and a thermocouple 14 inserted through the insulator tube 13. In the case of the illustrated example, the thermocouple 14 is made of an R thermocouple (platinum rhodium alloy-platinum), and a temperature measuring portion 14a constituting a hot junction is arranged in a groove formed in the radial direction at the tip of the insulator tube 13. Yes. Then, by filling the groove 15 at the tip of the insulator tube 13 with an insulating material 15 made of alumina powder or the like so that the temperature measuring unit 14a is positioned in the vicinity of the reference unit 4b but not in contact with the reference material 5a, The temperature measuring portion 14a is embedded in the insulating agent 15, the tip opening of the insulator tube 13 is sealed by the insulating agent 15, and the opening portion of the groove is filled with the refractory cement 16 over the insulating agent 15. Yes.
[0032]
By the way, according to the second embodiment, at the time of the predetermined measurement using the oxygen sensor 3, the temperature TH of the measurement part 4a of the solid electrolyte element 4 and the temperature TL of the reference part 4b are measured. That is, since the temperature TH is equal to the molten metal temperature, it is measured by the temperature sensor 1 shown in FIG. 1 and the temperature TL is measured by the temperature measuring means 12.
[0033]
In either the dissolved oxygen measuring device shown in FIG. 1A or the solute element measuring device shown in FIG. 1B, the oxygen concentration or solute element concentration is between the internal electrode 6 and the external electrode 2. It is obtained based on the detected electromotive force E (V). However, in actuality, the solid electrolyte element 4 has a temperature difference between the temperature TH of the measurement unit 4a and the temperature TL of the reference unit 4b, and generates a thermoelectromotive force Ee there. (V) includes the thermoelectromotive force Ee, and is not an accurate value for obtaining the oxygen concentration or the solute element concentration.
[0034]
Therefore, according to the second embodiment, since the temperature difference between the temperature TH of the measurement unit 4a and the temperature TL of the reference unit 4b in the solid electrolyte element 4 can be detected, the formula: Ee = (TH−TL) × Seebeck coefficient The thermoelectromotive force Ee can be obtained by subtracting the thermoelectromotive force Ee from the electromotive force E measured between the internal electrode 6 and the external electrode 2 to obtain the correct thermoelectromotive force (E-Ee), It becomes possible to correctly measure the oxygen concentration or the solute element concentration.
[0035]
At this time, when the temperature measuring portion 14a of the thermocouple 14 in the temperature measuring means 12 is brought into contact with the reference material 5a, for example, the platinum component of the R thermocouple contacts and reacts with the Mo component of the reference material 5a. Various problems occur due to the reaction between the thermocouple wire and the reference material, such as the deterioration of the thermocouple 14 by generating a low melting point compound. On the other hand, according to the second embodiment, the insulating agent 15 and the fire resistance Since the temperature measuring portion 14a of the thermocouple 14 is protected by the double seal of the cement 16, such a problem does not occur.
[0036]
【The invention's effect】
According to this invention, the molten metal probe which comprises the dissolved oxygen measuring apparatus in the molten metal of Claim 1, and the molten metal probe which comprises the solute element measuring apparatus in the molten metal of Claim 2 In any case, in the oxygen sensor 3 , the sealing agent filled in the cylindrical chamber 4c so as to embed the internal electrode 6 is selected from at least Al ₂ O ₃ powder and / or ZrO ₂ powder, and the reference material 5a. A stable protective layer 8 filled in the cylindrical chamber 4c in contact with the gas, and an oxygen adsorption layer 9 selected from graphite powder and / or carbide powder and filled in the cylindrical chamber 4c in contact with the stable protective layer 8 Thus, the internal electrode 6 and the reference material 5a are suitably protected, and there is an effect of enabling stable measurement.
[0037]
That is, since the stable protective layer 8 is formed by filling a powder selected from Al ₂ O ₃ powder and / or ZrO ₂ powder, the metal rod 6a constituting the internal electrode 6 is sublimated by contact with high temperature outside air. In addition, the stable protective layer 8 itself is not melted, reduced or oxidized under the conditions of use, and is stable without chemically reacting with the reference material 5a.
[0038]
In addition, since the oxygen adsorption layer 9 is formed by filling a powder selected from graphite powder and / or carbide powder, oxygen in the air that has entered from the outside is preferably oxidized, and the reference material 5a is oxidized. Make sure to prevent it. In addition, since the generated oxide is made into a gas, it flows down like a liquid and reacts with the reference substance 5a or the solid electrolyte element 4, or flows down to the interface between the reference substance 5a and the solid electrolyte element 4 to generate oxygen. The function of the sensor 3 is not inhibited.
[0039]
In particular, according to the present invention, the sealing agent comprises a relaxation layer 10 selected from quartz wool and / or alumina wool and / or ceramic wool, in addition to the stable protective layer 8 and the oxygen adsorption layer 9 as described above, and fire resistance. The oxygen sensor 3 can be a solid assembly structure because it constitutes a four-layer structure composed of the cement consolidation layer 11, and the assembly structure body is made of the inorganic wool material of the relaxation layer 10. together absorb tolerances, allowed function diffusion residence intrusion air, thereby ensuring the reliability of the oxidation by oxygen adsorption layer 9 has the effect of enabling stable measurement.
[0040]
Further according to the present invention according to claim 3, Katayuiso 11 so made of refractory cement or Al ₂ O ₃ refractory cement of ZrO ₂ -SiO ₂ system, the better the the refractory adhesion solid Not only can the binder layer 11 be obtained, but also the porosity of the binder layer 11 is small, and the thermal expansion coefficient between the solid electrolyte element 4 and the solid electrolyte element 4 is small, and the stable oxygen sensor 3 can be provided as an assembly structure. effective.
[Brief description of the drawings]
FIG. 1 shows a conventional apparatus, (A) is a schematic diagram showing an apparatus for measuring dissolved oxygen in molten metal, and (B) shows an apparatus for measuring solute elements in molten metal. FIG.
FIG. 2 is a longitudinal sectional view showing a first embodiment of the present invention.
3A and 3B show a second embodiment of the present invention, wherein FIG. 3A is a longitudinal sectional view, FIG. 3B is an enlarged sectional view of a temperature measuring means, and FIG. 3C is a sectional view taken along the line CC in FIG. (D) is a cross-sectional view of the tip of the temperature measuring means.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Temperature sensor 2 External electrode 3 Oxygen sensor 4 Solid electrolyte element 4a Measurement part 4b Reference | standard part 4c Cylindrical chamber 5 Reference | standard electrode 5a Reference | standard substance 6 Internal electrode 6a Metal rod 7 Outer surface electrode 8 Stable protective layer 9 Oxygen adsorption layer 10 Relaxation layer DESCRIPTION OF SYMBOLS 11 Consolidation layer 12 Temperature measuring means 13 Insulator 14 Thermocouple 14a Temperature measuring part 15 Insulating agent 16 Fireproof cement

Claims (3)

A temperature measuring sensor that measures the temperature of the molten metal, an external electrode that is in electrical contact with the molten metal, and an oxygen sensor that is immersed in the molten metal, the oxygen sensor contacting one side of the molten metal A solid electrolyte element having oxygen ion conductivity, which constitutes a reference part with the other side part that does not contact the molten metal, and a cylindrical chamber that faces the reference part of the solid electrolyte element. A reference electrode made of a reference material and an internal electrode made of a metal rod inserted into the cylindrical chamber and having a tip embedded in the reference material, and a molten metal between the measurement part and the reference part of the solid electrolyte element In an apparatus for measuring dissolved oxygen in a molten metal by detecting an electromotive force generated by an oxygen partial pressure difference of a reference electrode with the external electrode and the internal electrode,
The sealing agent filled in the cylindrical chamber so as to embed the internal electrode is selected from Al ₂ O ₃ powder and / or ZrO ₂ powder and is filled in the cylindrical chamber in contact with the reference substance (5a). A stable protective layer (8), an oxygen adsorbing layer (9) selected from graphite powder and / or carbide powder and filled in a cylindrical chamber in contact with the stable protective layer, quartz wool and / or alumina wool and And / or a relaxation layer (10) selected from ceramic wool and in contact with the oxygen adsorption layer and filled into the cylindrical chamber; and a consolidation layer made of refractory cement and in contact with the relaxation layer into the cylindrical chamber ( A molten metal probe characterized by comprising 11). A temperature measuring sensor that measures the temperature of the molten metal, an external electrode that is in electrical contact with the molten metal, and an oxygen sensor that is immersed in the molten metal, the oxygen sensor contacting one side of the molten metal The outer surface electrode is constituted by a mixed oxide mainly composed of an oxide of the element to be measured and / or an inorganic compound containing the oxide of the element to be measured provided at the part, and is based on the other side which does not contact the molten metal A solid electrolyte element having oxygen ion conductivity constituting a part, a reference electrode made of a reference material filled in a cylindrical chamber facing the reference part of the solid electrolyte element, and a reference substance inserted into the cylindrical chamber It is constituted by an internal electrode composed of embedded metal bar, the electromotive force generated by the oxygen partial pressure of the molten metal and the reference electrode between the outer surface electrode and the reference portion of the solid electrolyte element and the external electrode and the inner An apparatus for measuring the solute elements in the molten metal by detecting the electrodes,
The sealing agent filled in the cylindrical chamber so as to embed the internal electrode is selected from Al ₂ O ₃ powder and / or ZrO ₂ powder and is filled in the cylindrical chamber in contact with the reference substance (5a). A stable protective layer (8), an oxygen adsorbing layer (9) selected from graphite powder and / or carbide powder and filled in a cylindrical chamber in contact with the stable protective layer, quartz wool and / or alumina wool and And / or a relaxation layer (10) selected from ceramic wool and in contact with the oxygen adsorption layer and filled into the cylindrical chamber; and a consolidation layer made of refractory cement and in contact with the relaxation layer into the cylindrical chamber ( A molten metal probe characterized by comprising 11). Refractory cement constituting the Katayuiso (11), the melt according to claim 1 or 2, characterized by comprising selected from refractory cement or Al ₂ O ₃ refractory cement of ZrO ₂ -SiO ₂ system Metal probe.

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