JP2011051858A - Method for homogenizing molten glass solution and component of apparatus for melting glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the generation of electrolytic bubbles when a heat-resistant high-strength component, which is covered with platinum in order to restrain iridium from being oxidized, volatilized and consumed, is used in an apparatus for melting glass. <P>SOLUTION: The method for homogenizing a molten glass solution 78 comprises the steps of: using a composite structure obtained by covering a surface zone, which is a part of the surface of a structure comprising iridium or an iridium-based alloy and is exposed to an oxygen-containing gas atmosphere at the least when used, with a cover 53 based on platinum or a platinum-rhodium alloy as the component 400 of the apparatus for melting glass in such a place that a part of the composite structure is contacted with the molten glass solution 78; and applying a reverse potential to eliminate a potential difference to be generated between the structure and the cover 53 when the composite structure is used. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique in which a component made of a composite structure in which an iridium (Ir) material is covered with a platinum (Pt) material does not generate electrolytic bubbles generated when used in a glass melt.

  Platinum or platinum alloy used as a structural member used at high temperatures is a material that is extremely stable in a high temperature range of 1000 ° C. or higher, even in an oxygen-containing gas atmosphere, and has little oxidation volatilization consumption. . Moreover, platinum has an advantage that it is easy to process even in the cold.

  However, in recent years, in optical glass and glass for liquid crystal display, the kind of heavy metal contained in the glass has been limited in consideration of environmental problems. Therefore, the melting temperature of glass is higher than before. In particular, glass for liquid crystal displays is often melted at a high temperature of 1500 ° C. or higher. Even when platinum or a platinum alloy is used, grain growth tends to occur and the strength decreases particularly in a high temperature range exceeding 1500 ° C. Therefore, in order to solve this problem, oxide dispersion type reinforced platinum in which an oxide is mixed with platinum is often used. However, there is still a problem that the strength is limited and the lifetime is short.

  By the way, iridium is characterized by having higher strength than platinum or a platinum alloy in an environment of a high-temperature oxygen-containing gas atmosphere of 1000 ° C. or higher. However, since iridium is volatilized and consumed by oxidation, it cannot be used in an oxygen-containing gas atmosphere. Therefore, there is a technique for preventing volatilization by applying platinum or the like to iridium and providing an intermediate diffusion layer to prevent mutual diffusion (see, for example, Patent Document 1).

  In addition, as described above, in the glass melting apparatus, platinum parts are often used, but an electromotive force is generated between the glass melting container and the stirrer that stirs the glass melt. There is a disclosure of a technique for generating and suppressing electrolytic bubbles in the melt (see, for example, Patent Document 2 or 3).

Japanese Patent Laid-Open No. 2002-180268 JP-A-3-75229 JP-A-9-67127

  In an apparatus premised on high-temperature use such as a glass melting apparatus, the platinum coating technique of iridium disclosed in Patent Document 1 etc. is applied, so that the parts to be used are formed of iridium, and iridium is not oxidized and evaporated. When the portion that comes into contact with oxygen is covered with platinum, the junction between platinum and iridium becomes a junction between dissimilar metals. Therefore, when the junction is heated by the glass melt, a thermoelectromotive force is generated. When any thermoelectromotive force is generated in the glass melt, electrolytic bubbles are generated in the glass melt as pointed out in Patent Document 2 or 3. Therefore, it becomes an environment in which electrolytic bubbles are likely to be generated at a joint portion between different metals heated to a high temperature with a glass melt. When electrolytic bubbles are generated, the quality of the glass is degraded.

  Accordingly, an object of the present invention is to suppress the generation of electrolytic bubbles when a heat-resistant and high-strength component covered with platinum is used in a glass melting apparatus in order to suppress oxidative volatilization of iridium, that is, a glass melt. It is providing the component for glass melting apparatuses which suppresses generation | occurrence | production homogenization method and generation | occurrence | production of electrolytic foam.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have suppressed the generation of electrolytic bubbles by applying a reverse potential so as to cancel the thermoelectromotive force (potential difference) generated at the junction between dissimilar metals. The present invention has been completed. That is, in the method for homogenizing a glass melt according to the present invention, at least a surface region exposed to an oxygen-containing gas atmosphere during use of a surface of a structure made of iridium or an iridium-based alloy is treated with platinum or a platinum rhodium alloy. A composite structure formed by covering with a cover as a main component is used as a part of a glass melting apparatus where a part of the composite structure is in contact with the glass melt. A potential difference generated between the cover and the cover is canceled by applying a reverse potential.

  In addition, the glass melting device component according to the present invention includes at least a surface region exposed to an oxygen-containing gas atmosphere during use among the surfaces of a structure made of iridium or an iridium-based alloy, and is mainly composed of platinum or a platinum rhodium alloy. A composite structure covered with a cover, a power source for applying a voltage between the structure and the cover, and a voltage of the power source so that a part of the composite structure is in contact with the glass melt. And a voltage adjusting means for adjusting to a reverse potential that cancels a potential difference generated between the structure and the cover. By applying the reverse potential, it is possible to control so as to always cancel the thermoelectromotive force.

  In the glass melting apparatus component according to the present invention, the cover is a two-layer structure cover, and the two-layer structure cover is composed of an outer layer made of platinum or a platinum rhodium alloy and platinum or a platinum rhodium alloy containing a metal species. It is preferable that the metal layer oxide particles are precipitated in a dispersed state on the surface opposite to the surface in contact with the outer layer. This composite structure can be used particularly at high temperatures for a long time.

  The glass melting apparatus component according to the present invention is a stirrer in which the structure has a pipe-shaped or rod-shaped shaft portion and a stirring portion provided at a lower end of the shaft portion, and the cover covers the shaft portion. And a configuration in which contacts for applying a reverse potential to the upper end side of the shaft portion and the upper end side of the cover are included. The glass melting device component is a stirrer.

  Here, in the glass melting apparatus component according to the present invention, an iridium wire coated with ceramic fiber is disposed inside the pipe of the shaft portion, and one end of the iridium wire is at a height at which the stirring unit is attached. It is preferable that the other end of the iridium wire is joined at the upper end side of the shaft portion. In a stirrer, a reverse potential can be directly applied to a location where a thermoelectromotive force is generated.

  The glass melting apparatus component according to the present invention is an electrode in which the structure has a pipe-shaped or rod-shaped shaft portion, the cover covers the shaft portion, and the upper end side of the shaft portion and the cover The form which provided the contact for applying a reverse electric potential to the upper end side of this is included. The glass melting device component is an electrode.

  In the glass melting device component according to the present invention, an iridium wire coated with ceramic fibers is disposed inside the pipe of the shaft portion, and one end of the iridium wire is joined at the lower end portion of the shaft portion. It is preferable to join the other end of the shaft at the upper end side of the shaft portion. In the electrode, a reverse potential can be directly applied to a portion where the thermoelectromotive force is generated.

  In the glass melting apparatus component according to the present invention, the structure is a glass melting container, and the cover covers the entire outer surface of the container and the entire inner surface above the liquid surface of the glass melt. Further, the present invention includes a configuration in which contacts for applying a reverse potential are provided on the iridium exposed surface inside the container that is not covered with the cover and the surface of the cover. The glass melting device component is a glass melting container.

  The present invention can suppress the generation of electrolytic bubbles when a heat-resistant and high-strength component covered with platinum is used in a glass melting apparatus in order to suppress oxidative volatilization of iridium. Moreover, when the glass melting apparatus component according to the present invention is a stirrer, an electrode, or a glass melting container, the generation of electrolytic bubbles can be suppressed.

It is a section schematic diagram of one form of a composite structure. It is a partial expanded sectional view of the location enclosed by the dotted line 6 of FIG. It is a section schematic diagram of the 2nd form of a composite structure. It is a section schematic diagram of the 3rd form of a composite structure. It is the result of the thermoelectromotive force measurement with respect to the temperature of a junction location, joining iridium and platinum. It is the schematic for demonstrating the generation | occurrence | production mechanism of the electrolytic bubble produced when a non-alkali soda lime glass is put on the surface of the butt-welded plate of an iridium plate and a platinum plate, and a non-alkali soda lime glass is put on the surface. It is an image after melting the glass on the platinum-iridium bonding plate, (a) is the whole image, (b) is the image inside the glass on the iridium plate, (c) is the inside of the glass on the platinum plate. It is an image. It is an electric circuit when glass is melted on a platinum-iridium bonding plate, (a) is a test circuit, and (b) is an electric circuit. It is an electric circuit in the case of applying a reverse potential, (a) is a test circuit, (b) is an electric circuit. It is an image after melting the glass in a state in which a reverse potential is applied between platinum and iridium on the platinum-iridium bonding plate to cancel the thermoelectromotive force to zero, (a) is an entire image, (b) Is an image inside the glass on the iridium plate, and (c) is an image inside the glass on the platinum plate. The schematic of the component (stirrer) for glass melting apparatuses which concerns on this embodiment was shown. The surface image of the sample whose addition amount of zirconium is 1 mass% is shown, (a) is the figure heated at 1500 degreeC for 2 hours, (b) is the figure heated at 1500 degreeC for 100 hours, (c) is 1500 degreeC It is the figure heated for 300 hours. The surface image of the sample whose addition amount of zirconium is 2 mass% is shown, (a) is the figure heated at 1500 degreeC for 2 hours, (b) is the figure heated at 1500 degreeC for 100 hours, (c) is 1500 degreeC It is the figure heated for 300 hours. The schematic of the component for glass melting apparatuses (electrode) which concerns on this embodiment was shown. A schematic view of a glass melting apparatus part (glass melting container) according to the present embodiment is shown.

  Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not construed as being limited to these descriptions. As long as the effect of the present invention is exhibited, the embodiment may be variously modified.

  When the material of the glass melting device is iridium having a strength superior to that of platinum or a platinum alloy generally used at a high temperature, as described above, the oxidation and volatilization consumption when exposed to oxygen gas at a high temperature is reduced. Concerned. Therefore, in this embodiment, a composite structure in which iridium is coated with platinum and iridium is oxidized and evaporated is used. Specifically, the composite structure is mainly composed of platinum or a platinum rhodium alloy at least in the surface region of the structure made of iridium or an iridium-based alloy that is exposed to an oxygen-containing gas atmosphere during use. It is covered with a cover. The oxygen-containing gas atmosphere is, for example, an oxygen gas atmosphere, an air atmosphere, or a gas atmosphere in which the oxygen partial pressure is adjusted.

  First, this composite structure will be described. In this embodiment, the cover is a two-layer cover, and the two-layer cover is formed by joining an outer layer made of platinum or a platinum rhodium alloy and an inner layer made of platinum or a platinum rhodium alloy containing a metal species. In addition, it is preferable that the inner layer has metal species oxide particles precipitated in a dispersed state on the surface opposite to the surface in contact with the outer layer. This composite structure can be used particularly at high temperatures for a long time.

  FIG. 1 shows a schematic cross-sectional view of one embodiment of the composite structure. FIG. 2 is a partially enlarged cross-sectional view of a portion surrounded by a dotted line 6 in FIG. As shown in FIG. 1, the composite structure 100 covers at least a surface region 5 of the surface 1a of the structure 1 made of iridium or an iridium-based alloy and is exposed to an oxygen-containing gas atmosphere during use. The cover 4 having a two-layer structure is formed by joining an outer layer 3 made of platinum or a platinum rhodium alloy and an inner layer 2 made of platinum or a platinum rhodium alloy containing a metal species, As shown in FIGS. 1 and 2, the layer 2 has metal species oxide particles 6a deposited in a dispersed state on a surface 2b opposite to the surface 2a in contact with the outer layer 3. In FIG. 1, it is assumed that the surface portion of the surface of the structure 1 that does not have the cover 4 of the two-layer structure, for example, the back surface and the end surface of the structure 1 is not exposed to the oxygen-containing gas atmosphere. Show.

  The structure 1 is a structure such as a device or a component used in the apparatus, and in the present embodiment, the shape is not particularly limited because the shape is various shapes depending on the application. However, in view of the object of the present invention, a structure that is used at a high temperature and requires strength is preferable. The material of the structure 1 is iridium or an iridium-based alloy because it is required to retain higher strength than platinum at a high temperature of 1000 ° C. or higher for a long time. For iridium-based alloys, the main component is iridium, and the subcomponents are rhodium (Rh), rhenium (Re), molybdenum (Mo), tungsten (W), niobium (Nb), Ta (tantalum), Zr (zirconium), Hf. (Hafnium). At this time, the ratio of iridium is, for example, 90% by mass or more.

  Since the surface 1a of the structure 1 is oxidized and volatilized by iridium in a high-temperature oxygen-containing gas atmosphere, at least the surface region 5 that is exposed to the oxygen-containing gas atmosphere during use is covered with a cover 4 having a two-layer structure. Cover. As a result, the surface 1a of the structure 1 is limited in contact with oxygen, so that iridium oxidation and volatilization is less likely to occur.

  The cover 4 having a two-layer structure is formed by joining an outer layer 3 made of platinum or a platinum rhodium alloy and an inner layer 2 made of platinum or a platinum rhodium alloy containing a metal species. The platinum rhodium alloy is preferably 30% by mass or less of rhodium. Here, the outer layer 3 prevents the inner layer 2 from contacting the oxygen-containing gas atmosphere, and further prevents the iridium structure 1 from contacting the oxygen-containing gas atmosphere. On the other hand, the inner layer 2 serves as a diffusion blocking layer that suppresses mutual diffusion with the iridium structure 1. That is, it is preferable that the metal type oxide particles 6a precipitated in a dispersed state on the surface 2b of the inner layer 2 protrude from the surface 2b as shown in FIG. The surface 1a and the surface 2b of the inner layer 2 are not in contact with each other, or even if they are in contact, the contact area is reduced. In other words, the metal seed oxide particles 6a deposited in a dispersed state on the surface 2b of the inner layer 2 serve as a spacer. Then, by limiting the contact between the surface 1a of the structure 1 and the surface 2b of the inner layer 2, mutual diffusion between the structure 1 (iridium or iridium-based alloy) and the inner layer 2 (platinum as a main component) is performed. To suppress the formation of Kirkendall void. The inner layer 2 and the structure 1 may be partially in contact. In this case, due to the presence of the metal species oxide particles 6a, the area where the platinum of the inner layer 2 and the iridium of the structure 1 can mutually diffuse is limited, and the metal species oxide particles 6a themselves are mutually Suppresses diffusion. Thus, since the inner layer 2 plays the role of a diffusion barrier layer, the thickness is preferably 0.1 mm or more, and more preferably 0.2 mm or more. When it is exposed to a high temperature and oxygen-containing gas atmosphere for 1000 hours or more when it is less than 0.1 mm, the contact between the platinum of the inner layer 2 and the iridium of the structure 1 is not caused by the metal species oxide particles 6a. Although there is no risk of progress of interdiffusion, if there is a contact point, there is a risk of progress of interdiffusion to some extent, but as shown in FIG. Not. In such a case, it is desirable that the inner layer 2 has a thickness of 0.1 mm or more.

  The metal seed oxide particles 6a are preferably formed by oxidizing the two-layered cover 4 to oxidize and deposit the metal seeds contained in the inner layer 2 and grain growth. The surface of the structure made of iridium or an iridium base alloy and the cover of the two-layer structure are not brought into contact with each other, and the volume of the gap space can be reduced. Examples of the metal species that can be contained in such platinum as an alloy and that can easily deposit the metal species oxide particles 6a on the surface by oxidation treatment include zirconium (Zr), aluminum (Al), silicon (Si ), Titanium (Ti), yttrium (Y), hafnium (Hf), tantalum (Ta), magnesium (Mg), cerium (Ce), and chromium (Cr). . Regarding the selection of the metal species, conventionally, the same types of metal species that can be applied to the oxide dispersion strengthened platinum can be used.

  As shown in FIG. 2, the metal-type oxide particles may be dispersed as oxide particles 6b in the inner layer 2, and in this case, the inner layer 2 has an oxide on the surface on the 2b side. Is dense oxide-dispersed reinforced platinum. Further, a slight gap space 7 may exist between the inner layer 2 and the structure 1 due to the role of the metal-type oxide particles 6 a as a spacer. This gap space 7 contains oxygen and may be consumed by the oxidization and volatilization of iridium in the structure 1. However, since the amount of oxygen is very small, new oxygen flows into the gap space 7. If restricted so as not to occur, the iridium oxidative volatilization of the iridium in the structure 1 does not become a problem.

  A countermeasure for preventing new oxygen from flowing into the gap space 7 will be described. FIG. 3 is a schematic cross-sectional view of a second form of the composite structure. In FIG. 3, the surface portion of the surface of the structure 1 that does not have the cover 4 of the two-layer structure, for example, the back surface of the structure 1 is illustrated as not being exposed to the oxygen-containing gas atmosphere. Yes. The cover 4 of the two-layer structure of the composite structure 200 according to this embodiment shown in FIG. 3 is welded to the structure 1 over the entire circumference at the edge, and the end face is platinum overlay welded. It is preferable. The gap space 7 is sealed by the welded portion 8, and oxygen does not flow in. In FIG. 3, the welded portion at the edge of the cover 4 having a two-layer structure is indicated by reference numeral 8. In the welded portion 8, the materials constituting the outer layer 3 (platinum), the inner layer 2 (platinum), and the structure 1 (iridium) of the cover 4 having a two-layer structure are alloyed by welding. Specifically, Is an iridium-platinum alloy. Although the inflow of oxygen into the gap space 7 by the welded portion 8 is prevented, the welded portion 8 is made of an iridium-platinum alloy. Is likely to occur. Therefore, by covering the welded portion 8 with platinum overlay welding, contact with the oxygen-containing gas atmosphere is blocked and volatilization consumption is prevented. In FIG. 3, the platinum overlay weld is indicated by reference numeral 9.

  When the cover 4 having a two-layer structure is welded to the structure 1, the gap space 7 is preferably vacuum-sealed. It is possible to further prevent the iridium oxidative volatilization of the structure. Further, swelling due to residual gas is less likely to occur during high temperature use. For example, an exhaust pipe that communicates with the gap space 7 is provided on the cover 4 having a two-layer structure, the edge of the cover 4 having a two-layer structure is welded, and then the gap space 7 is evacuated through the exhaust pipe, The gap space 7 can be vacuum-sealed by sealing with a tube.

  Another measure for preventing new oxygen from flowing into the gap space 7 will be described. FIG. 4 is a schematic cross-sectional view of a third form of the composite structure. Both surfaces of the structure 1 of the composite structure 300 are each covered with a cover 4 having a two-layer structure. Then, the surface region 10 other than the surface region 5 exposed to the oxygen-containing gas atmosphere is disposed in a region not exposed to the oxygen-containing gas atmosphere, for example, in a glass melt or a room filled with an inert gas. New oxygen does not flow into the gap space 7 from the edge of the cover 4 having the layer structure, and the volatilization of the structure 1 can be prevented.

  Thus, since the cover 4 with the two-layer structure suppresses the iridium oxidative volatilization and the generation of the Kirkendall void of the structure 1, the structure 1 to which the cover 4 with the two-layer structure is attached is, for example, 1000 It can be used stably for a long time in a high temperature-oxygen-containing gas atmosphere for more than an hour.

  As an example of the use of the composite structure, for example, as described later, there is a stirring rod for stirring the glass melt. One end of the stirring rod is provided with a stirring portion for stirring, and this stirring portion is completely immersed in the glass melt. The other end of the stirring rod is fixed to a rotating shaft connected to a motor. And the axial part which is not immersed in the glass melt above a stirring part among stirring bars will be exposed to oxygen-containing gas atmosphere. The portion immersed in the glass melt can be used with the iridium structure as it is. Therefore, by covering the surface of the shaft portion exposed to the oxygen-containing gas atmosphere with the cover 4 having a two-layer structure, it is possible to use it for a long time even in a high-temperature oxygen-containing gas atmosphere. Become. Here, it is preferable that the edge of the two-layered cover on the other end side of the stirring rod is further welded with platinum after welding. On the other hand, if the edge of the two-layered cover at one end of the stirring rod is welded and is in a position where the weld is immersed in the glass melt, platinum overlay welding may not be performed. Of course, platinum overlay welding may be performed. The shaft portion of the stirring rod is preferably pipe-shaped or rod-shaped, but if it is pipe-shaped, should the inner surface of the pipe be vacuum sealed so that it is not exposed to the oxygen-containing gas atmosphere? Or it is preferable to seal.

  The cover having a two-layer structure is shaped like a pipe (cylindrical) such as a pipe (cylindrical) as well as a sheet.

  Next, a preferred example of a method for producing a composite structure will be described. The method for manufacturing a composite structure includes a step of forming a two-layer structure by joining an outer arrangement component made of platinum or a platinum rhodium alloy and an inner arrangement component made of platinum or a platinum rhodium alloy containing a metal species (hereinafter referred to as a “two-layer structure”) And the first step), the two-layer structure is subjected to a heat oxidation treatment in an oxygen-containing gas atmosphere to deposit metal species oxide particles in a dispersed state on the surface of the inner arrangement component. Of the surface of the structure made of iridium or an iridium-based alloy, a surface region that is exposed to an oxygen-containing gas atmosphere at least during use is formed in a two-layer structure. And a step of covering with a cover (hereinafter referred to as a third step).

(First step)
The part for outer arrangement | positioning which consists of platinum or a platinum rhodium alloy is a part used as the outer layer 3 of FIG. 1, for example. The part for inner arrangement | positioning which consists of platinum or a platinum rhodium alloy containing a metal seed | species is a part used as the inner layer 2 of FIG. As a material for forming the inner arrangement component, platinum or a platinum rhodium alloy is made of at least one selected from Zr, Al, Si, Ti, Y, Hf, Ta, Mg, Ce, and Cr. Add and make an alloy made by arc melting. The addition amount of the metal species is preferably 0.1 to 3% by mass. This material is used to form the inner placement component. Then, the outer placement component and the inner placement component are joined by a discharge plasma sintering method (SPS, Spark Plasma Sintering), a hot isostatic press method (HIP, Hot Isostatic Press), a hot rolling method, or the like.

(Second step)
The two-layer structure is heated and oxidized in an oxygen-containing gas atmosphere to deposit metal species oxide particles in a dispersed state on the surface of the inner arrangement component to form a two-layer structure cover. Since oxygen diffuses from the surface of the inner arrangement component, the closer to the surface of the inner arrangement component, the more the oxide particles of the metal species are oxidized and the grains grow. When the oxidation treatment is terminated at the stage where the metal species oxide particles are deposited on the surface of the inner placement component, the closer to the surface of the inner placement component, the closer to the surface of the inner placement component, the metal species oxide particles. The gradient composition is present. The oxidation treatment to be heated in an oxygen-containing gas atmosphere is, for example, 1000 to 1500 ° C. and 1 to 500 hours in an air atmosphere. In the second step, the heating temperature and the heating time can be appropriately changed, and are determined based on the dispersion state of the metal species oxide particles deposited on the surface according to the metal species.

  In order to process a cover having a two-layer structure to a desired thickness, for example, 0.1 to 1.0 mm, rolling is convenient. When the rolling process is performed, if it is performed after depositing metal seed oxide particles, it becomes hard and the workability is lowered, and cracks and cracks are likely to occur. Therefore, it is preferable to provide a step of cold rolling or hot rolling the inner placement component before the step of forming the two-layer structure. Moreover, you may have the process of cold-rolling or hot-rolling the said 2 layer structure before the process of forming the said 2 layer structure cover. By rolling, the cover having a two-layer structure is made thick, and in particular, it is easy to control the thickness of the inner layer to 0.1 mm or more.

(Third step)
The third step is a step of forming the composite structure by combining the structure 1 and the cover 4 having a two-layer structure. Specifically, the cover 4 having a two-layer structure is fixed to the structure 1 by means such as welding. Moreover, the edge part (end surface) of the cover 4 of a two-layer structure is welded, and the clearance gap 7 between the structure 1 and the cover 4 of a two-layer structure is sealed or vacuum-sealed.

  By using the composite structure having the above structure, it is possible to suppress the oxidative volatilization of iridium and to prevent the occurrence of Kirkendall voids at the boundary between the structure and the platinum cover. However, when the joining part or the contact part between the structure and the cover is heated to a high temperature by the glass melt, a thermoelectromotive force is generated. It is a phenomenon (Seebeck effect) similar to a thermoelectromotive force by a so-called thermocouple. FIG. 5 shows the result of thermoelectromotive force measurement with respect to the temperature of the joined portion after joining iridium and platinum. In the case of a combination of iridium and platinum, for example, a thermoelectromotive force of about 23 mV is generated at 1500 ° C.

Electrolytic bubbles are generated by this thermoelectromotive force. The present inventors estimate the cause of the generation of electrolytic bubbles as follows. FIG. 6 is a schematic diagram for explaining the generation mechanism of electrolytic bubbles generated when an alkali-free soda-lime glass is put on the surface of a butt weld plate of an iridium plate and a platinum plate and melted by placing the boundary portion on the surface. It is. The thickness of the butt weld plate with the platinum plate was 1 mm, and the glass melting conditions were kept in air at 1475 ° C. for 24 hours, then removed from the electric furnace and cooled at room temperature. Here, an iridium wire (φ1 mm) is welded on the iridium side of the butt weld plate of the iridium plate and the platinum plate, a platinum wire (φ1 mm) is joined on the platinum side, and each wire is taken out of the electric furnace. The potential difference between them was measured. Moreover, when applying the reverse electric potential mentioned later, these iridium wires and platinum wires were used. In the situation in FIG. 6, the glass melt undergoes electrolysis, and bubbles are generated on the anode (oxidation) side. FIG. 7 is an image after melting the glass on the platinum-iridium bonding plate, (a) is the entire image, (b) is the image inside the glass on the iridium plate, (c) is the image on the platinum plate. It is an image inside the glass at. In FIGS. 7B and 7C, the focus of the image is matched with the bubbles inside the glass. When the chemical reactions occurring on the Ir side and the Pt side are summarized, it is assumed that the following reaction occurs.
[Ir side (cathode side, + side)]:
(Chemical Formula 1) Oxide (glass) + 2e ⁻ → O ²⁻
Or (Chemical Formula ² ) O ₂ + 4e ⁻ → 2O ²⁻
In both (Chemical Formula 1) and (Chemical Formula 2), O ²⁻ is generated.
[Pt side (anode side, -side)]:
(Chemical Formula 3) 2O ²⁻ → O ₂ + 4e ⁻
Or (Chemical Formula 4) Pt → Pt ²⁺ + 2e ⁻
However, the standard electrode potential on the anode side (− side) is (Chemical formula 5) 2O ²⁻ → O ₂ + 4e ⁻ → + 0.284V
(Chemical formula 6) Pt → Pt ²⁺ + 2e ⁻ → −1.188 V
Thus, the oxygen generation reaction is more likely to occur than the dissolution of platinum. When the order of these reactions is confirmed, as shown in (1) in FIG. 6, a thermoelectromotive force (potential difference) is generated, and electrons move from the platinum side to the iridium side. At this time, it is assumed that the reaction of Chemical Formula 4 occurs. Next, as shown in (2) in FIG. 6, the reaction of Chemical Formula 1 or Chemical Formula 2 occurs on the iridium side surface in the glass, and oxygen ions are generated. Further, as shown in FIG. 6 (3), oxygen ions in the glass take electrons on the platinum side, so that the reaction of chemical formula 3 occurs. At this time, since the chemical reaction 4 occurs simultaneously on the platinum anode side, and the chemical reaction 7 occurs, Pt dissolves at the stage of FIG. 6 (2) but immediately precipitates, so Pt dissolves. It is speculated that there will be nothing.
(Chemical Formula 7) Pt ²⁺ + 2O ²⁻ → O ₂ + Pt + 2e ⁻
Therefore, it is presumed that these reactions are cycled, a thermoelectromotive force is always generated, and oxygen is generated. FIG. 8 is an electric circuit when glass is melted on a platinum-iridium bonding plate, (a) is a test circuit, and (b) is an electric circuit. As shown in FIG. 8, the thermoelectromotive force generated in the furnace at 1475 ° C. was 21.5 mV.

  As described above, in order to prevent this reaction from occurring, it is necessary to flow a current in the direction opposite to the generated thermoelectromotive force. Therefore, a reverse voltage is applied so that the potential difference is always zero. Specifically, as shown in FIG. 9, the thermoelectromotive force of 21.5 mV generated in the furnace at 1475 ° C. was canceled by applying a reverse potential to 0.0 mV. FIG. 9 shows an electric circuit when a reverse potential is applied, where (a) is a test circuit and (b) is an electric circuit. FIG. 10 is an image after melting the glass in a state in which a reverse potential is applied between platinum and iridium on the platinum-iridium bonding plate to cancel the thermoelectromotive force to zero, and (a) is an entire image. (B) is an image inside the glass on the iridium plate, and (c) is an image inside the glass on the platinum plate. As shown in FIG. 10, when the reverse voltage is applied to cancel the thermoelectromotive force and the potential difference is always zero, the generation of bubbles can be suppressed as shown in the image of FIG. 10 (c). Glass quality was improved.

  The method for homogenizing a glass melt according to the present embodiment is a method of using a platinum-iridium bonded plate in place of the composite structure, that is, using the composite structure as a component of a glass melting apparatus. It is used where a part of the body comes into contact with the glass melt, and the potential difference generated between the structure and the cover during use is canceled by applying a reverse potential. As a result, the generation of electrolytic bubbles in the composite structure, particularly in the vicinity of the cover, can be suppressed, which contributes to the homogenization of the glass.

  In order to apply the reverse potential, specifically, the glass melting apparatus component according to the present embodiment is used. The glass melting apparatus component according to the present embodiment includes the composite structure, a power source that applies a voltage between the structure that constitutes the composite structure, and a cover, and a voltage of the power source that is part of the composite structure Voltage adjusting means for adjusting to a reverse potential that cancels a potential difference generated between the structure and the cover when contacting the glass melt. This is as shown in the electric circuit in the case of applying the reverse potential shown in FIG.

  Since the structure is made of iridium, an iridium wire is connected to the structure, and this iridium wire is used as a wiring for an electric circuit. In addition, in order to prevent the oxidation volatilization consumption of an iridium wire, it is preferable to coat | cover an iridium wire with a ceramic fiber etc. Further, since the cover, in particular, the outer layer is made of platinum, a platinum wire is connected to the outer layer of the cover, and this platinum wire is used as the wiring of the electric circuit. Since both are joints of the same kind of metal, no thermoelectromotive force based on the Seebeck effect is generated at the joints. Specific contact points between the iridium wire and the platinum wire and the composite structure will be described later.

  A voltage is applied between the structure constituting the composite structure and the cover via the iridium wire and the platinum wire. This power source is, for example, a dry battery as shown in FIG. 9B, and may be a DC power source. The voltage adjusting means is, for example, a variable resistor. In order to confirm that the thermoelectromotive force is zero by applying a reverse potential, a voltmeter is placed between the iridium wire and the platinum wire, and the voltage adjusting means is set so that the thermoelectromotive force becomes zero. Give feedback. A known control method can be applied to the control method.

  Examples of the glass melting apparatus component according to this embodiment include a stirrer, an electrode, and a glass melting container. Specific explanation will be given individually.

[Stirrer]
In FIG. 11, the schematic of the components for glass melting apparatuses which concern on this embodiment was shown. The structure 50 of the glass melting apparatus component 400 is a stirrer having a pipe-shaped shaft portion 51 and a stirring portion 52 provided at the lower end of the shaft portion 51, and the cover 53 covers the shaft portion 51, Contacts 54 and 55 for applying a reverse potential to the upper end side of the shaft portion 51 and the upper end side of the cover 53 are provided. The pipe-shaped shaft portion 51 may have a rod shape (not shown).

  FIG. 12 shows a surface image of a sample with an addition amount of zirconium of 1 mass%, (a) is a diagram heated at 1500 ° C. for 2 hours, (b) is a diagram heated at 1500 ° C. for 100 hours, (c ) Is a diagram of heating at 1500 ° C. for 300 hours. FIG. 13 shows a surface image of a sample with an addition amount of zirconium of 2 mass%, (a) is a diagram heated at 1500 ° C. for 2 hours, (b) is a diagram heated at 1500 ° C. for 100 hours, (c ) Is a diagram of heating at 1500 ° C. for 300 hours. As described above, the cover 53 includes a platinum outer layer and an inner layer in which oxide fine particles are dispersed and deposited. The surface of the inner layer (surface facing the structure) has the same microstructure as that shown in FIG. The cover 53 has a lower end immersed in the glass melt 78 and an upper end disposed in a low-temperature portion coming out of the furnace 56. Therefore, the cover 53 covers the portion where the shaft portion 51 is exposed to high temperature and in contact with oxygen gas. Accordingly, the cover 53 blocks oxygen gas and suppresses iridium oxidation and volatilization of the shaft portion 51. In FIG. 11, the upper end and the lower end of the cover 53 are welded to the shaft portion 51 so that oxygen gas (air) is not mixed into the cover 53. Further, an exhaust pipe 77 is provided on the side surface of the cover, and a vacuum sealing process for sealing after vacuuming is performed. By removing the air remaining inside the cover 53, the oxidation volatilization consumption of the shaft portion 51 due to the air is reduced.

  A disc-like plate 57 (preferably made of iridium) is fixed to the upper end side of the shaft portion 51, a brush 59 is applied to the peripheral end surface of the disc-like plate 57, and an iridium wire 61 is provided on the brush 59. Yes. A spring 63 is interposed in the brush 59 so that the brush 59 is surely in contact with the peripheral end surface of the disc-like plate 57. The contact 54 is a portion including a contact portion with the peripheral end surface of the disk-like plate 57 that contacts the brush 59. On the other hand, a disc-like plate 58 (preferably made of platinum) is fixed to the upper end side of the cover 53, a brush 60 is applied to the peripheral end surface of the disc-like plate 58, and a platinum wire 62 is provided on the brush 60. ing. A spring 64 is interposed in the brush 60 so that the brush 60 is surely in contact with the peripheral end surface of the disc-shaped plate 58. The contact 55 is a portion including a contact portion with the peripheral end surface of the disc-like plate 58 that contacts the brush 60.

  In FIG. 11, the portion where the cover 53 and the shaft portion 51 are joined, and particularly the portion immersed in the glass melt 78 has the highest temperature, and a thermoelectromotive force is generated at the dissimilar metal joining portion. Therefore, the iridium wire 65 covered with the ceramic fiber is arranged inside the pipe of the shaft portion 51, and one end 65b of the iridium wire 65 is joined at a height to which the stirring unit 52 is attached, and the other end 65a of the iridium wire 65 is joined. Are preferably joined at the upper end side of the shaft portion 51. A reverse potential can be directly applied to a portion where a thermoelectromotive force is generated in the stirrer. The reason why the iridium wire covered with ceramic fibers (for example, Almax made by Ariake Material Co., Ltd.) is used is to prevent the iridium wire 65 from being oxidized and volatilized.

  In FIG. 11, the iridium wire 61 and the platinum wire 62 are connected to a DC voltage control 70. The DC voltage control 70 is connected to the power source 75 and receives power supply from the power source 75. The DC voltage control 70 has a voltage feedback 72 that monitors the potential difference between the iridium wire 61 and the platinum wire 62, and a voltage monitor 74 and a current monitor 73 are connected to the DC voltage control 70. The DC voltage control 70 further includes a variable resistor 76 and a voltage output 71. The direct current voltage control 70 adjusts the variable resistor 76 so that the measurement result of the voltage feedback 72 becomes zero V with respect to the reverse potential corresponding to the thermoelectromotive force generated by the composite structure. Apply to platinum wire 62. This cancels the thermoelectromotive force generated by the composite structure and suppresses the generation of electrolytic bubbles.

[electrode]
FIG. 14 shows a schematic diagram of a glass melting apparatus component according to this embodiment. The structure of the glass melting apparatus component 500 which is the composite structure 80 is an electrode having a pipe-shaped shaft portion 81, and the cover 82 covers the shaft portion 81, and the upper end side of the shaft portion 81 and the cover 82. Are provided with contacts 83 and 84 for applying a reverse potential. The pipe-shaped shaft portion 81 may have a rod shape.

  As described above, the cover 82 includes a platinum outer layer and an inner layer in which oxide fine particles are dispersed and deposited. The surface of the inner layer (surface facing the structure) has the same microstructure as that shown in FIG. The cover 82 has a lower end immersed in the glass melt 78, and an upper end is disposed in a low temperature portion that has come out of the furnace 56. Therefore, the cover 82 covers the portion where the shaft portion 81 is exposed to high temperature and is in contact with oxygen gas. As a result, the cover 82 blocks oxygen gas and suppresses iridium oxidation and volatilization of the shaft portion 81. In FIG. 14, the upper end and the lower end of the cover 82 are welded to the shaft portion 81 so that oxygen gas (air) is not mixed inside the cover 82. Further, an exhaust pipe 77 is provided on the side surface of the cover, and a vacuum sealing process for sealing after vacuuming is performed. By removing the air remaining inside the cover 82, the oxidation volatilization consumption of the shaft portion due to the air is reduced.

  Unlike the case of the stirrer, the shaft portion 81 does not rotate. Therefore, the contact 83 is a portion including a welded portion between the shaft portion 81 and the iridium wire 85. On the other hand, the contact 84 is a portion including a welded portion between the cover 82 and the platinum wire 86.

  Also in this embodiment, similarly to the embodiment shown in FIG. 11, the iridium wire 65 covered with the ceramic fiber is arranged inside the pipe of the shaft portion 81, and one end 65 b of the iridium wire 65 is arranged at the lower end portion of the shaft portion 81. It is preferable that the other end 65 a of the iridium wire is joined at the upper end side of the shaft portion 81. In the electrode, a reverse potential can be directly applied to a portion where the thermoelectromotive force is generated.

  In FIG. 14, the means for canceling the thermoelectromotive force generated in the composite structure by the DC voltage control 70 or the like is the same as that shown in FIG.

[Glass melting container]
In FIG. 15, the schematic of the component for glass melting apparatuses which concerns on this embodiment was shown. The structure of the glass melting apparatus component 600 that is the composite structure 90 is a glass melting container 91, and the cover 92 is an inner surface above the entire outer surface of the glass melting container 91 and the liquid surface of the glass melt 78. The entire surface is covered, and contacts 93 and 94 for applying a reverse potential to the iridium exposed surface inside the container that is not covered with the cover 92 and the surface of the cover 92 are provided.

  As described above, the cover 92 includes a platinum outer layer and an inner layer in which oxide fine particles are dispersed and deposited. The surface of the inner layer (surface facing the structure) has the same microstructure as that shown in FIG. The cover 92 covers the entire outer surface of the container 91 and the entire inner surface above the liquid level of the glass melt 78, whereby the cover 92 blocks oxygen gas and iridium of the glass melting container 91. Suppresses oxidative volatilization.

  The contact 93 is a portion including a welded portion between the glass melting vessel 91 and the iridium wire 96. On the other hand, the contact 94 is a portion including a welded portion between the cover 92 and the platinum wire 95.

  In FIG. 15, the means for canceling the thermoelectromotive force generated in the composite structure by the DC voltage control 70 or the like is the same as that shown in FIG.

[Modification]
In FIG. 11, without connecting either one of the contacts 54 and 55, the non-connected contact is connected to a glass melting container (for example, made of platinum), thereby canceling the thermoelectromotive force generated in the composite structure. Thus, a reverse potential can be applied. Further, in FIG. 14, the thermoelectromotive force generated in the composite structure is obtained by connecting one of the contacts 83 and 84 without connecting one of the contacts 83 and 84 to a glass melting container (for example, made of platinum). It is possible to apply a reverse potential so as to cancel.

(Comparative Example 1)
In FIG. 11, the form which short-circuits the iridium wire 61 and the platinum wire 62 which were pulled out from the contacts 54 and 55, the form which short-circuits the iridium wire 85 and the platinum wire 86 which were pulled out from the contacts 83 and 84 in FIG. In FIG. 15, there is a form in which the iridium wire 96 and the platinum wire 95 drawn out from the contacts 93 and 94 are short-circuited. According to these forms, it is possible to reduce the thermoelectromotive force generated in the composite structure. However, since it is difficult to make it completely zero, depending on the size and shape of the composite structure, the occurrence of electrolytic bubbles may not be suppressed. In addition, when the iridium wire and platinum wire taken out from the butt-welded plate of the iridium plate and platinum plate in FIG. 6 were short-circuited, the thermoelectromotive force of 21.5 mV decreased to 1.8 mV. The thermoelectromotive force could not be almost zero.

(Comparative Example 2)
In FIG. 11, a configuration in which the iridium wire 61 and the platinum wire 62 drawn out from the contacts 54 and 55 are grounded, in FIG. 14, a configuration in which the iridium wire 85 and the platinum wire 86 drawn out from the contacts 83 and 84 are grounded, or In FIG. 15, there is a form in which the iridium wire 96 and the platinum wire 95 drawn out from the contacts 93 and 94 are grounded. According to these forms, it is possible to reduce the thermoelectromotive force generated in the composite structure. However, since it is difficult to make it completely zero, depending on the size and shape of the composite structure, the occurrence of electrolytic bubbles may not be suppressed.
In addition, when one of the iridium wire and the platinum wire taken out from the butt-welded plate of the iridium plate and the platinum plate in FIG. 6 was grounded, the thermoelectromotive force of 21.5 mV decreased to 12.7 mV. Moreover, when both wires were earth | grounded, the thermoelectromotive force of 21.5 mV fell to 11.2 mV. The thermoelectromotive force could not be almost zero.

DESCRIPTION OF SYMBOLS 1, 50 Structure 1a Structure surface 2 Inner layer 2a The surface 2b which contacts the outer layer 3 of an inner layer The surface 3b opposite to the surface 2a 3 The outer layer 4 The cover 5 of a two layer structure It is exposed to oxygen-containing gas atmosphere at the time of use Surface region 6a Metal species oxide particles (surface)
6b Oxide particles of metal species (in the layer)
7 Crevice space 8 Welded portion 9 Platinum overlay welded portion 10 Surface region 51, 81 Excluding surface region exposed to oxygen-containing gas atmosphere Shaft portion 52 Stirring portion 53, 82, 92 Cover 54, 55, 83, 84, 93 , 94 Contact 56 Furnace 57, 58 Disc-shaped plate 59, 60 Brush 61, 65, 85, 96 Iridium wire 62, 86, 95 Platinum wire 63, 64 Spring 65a The other end of iridium wire 65b One end of iridium wire 70 DC voltage Control 71 Voltage output 72 Voltage feedback 73 Current monitor 74 Voltage monitor 75 Power source 76 Variable resistor 77 Exhaust pipe 78 Glass melt 91 Glass melting vessel 80, 90, 100, 200, 300 Composite structure 400, 500, 600 Glass melting Equipment parts

Claims (8)

  Of the surface of the structure made of iridium or an iridium-based alloy, a composite structure formed by covering at least a surface region exposed to an oxygen-containing gas atmosphere during use with a cover mainly composed of platinum or a platinum rhodium alloy, Used as a part of a glass melting apparatus where a part of the composite structure is in contact with the glass melt, and cancels the potential difference generated between the structure and the cover during the use by applying a reverse potential. A method for homogenizing a glass melt. Of the surface of the structure made of iridium or an iridium-based alloy, at least the surface area exposed to the oxygen-containing gas atmosphere during use is covered with a cover mainly composed of platinum or a platinum rhodium alloy; and
A power source for applying a voltage between the structure and the cover;
Voltage adjusting means for adjusting the voltage of the power source to a reverse potential that cancels a potential difference generated between the structure and the cover when a part of the composite structure comes into contact with the glass melt. Part for glass melting equipment.   The cover is a cover of a two-layer structure, and the cover of the two-layer structure is formed by joining an outer layer made of platinum or a platinum rhodium alloy and an inner layer made of platinum or a platinum rhodium alloy containing a metal species, 3. The glass melting apparatus according to claim 2, wherein the inner layer has oxide particles of the metal species precipitated in a dispersed state on a surface opposite to a surface in contact with the outer layer. Parts.   The structure is a stirrer having a pipe-shaped or rod-shaped shaft portion and a stirring portion provided at the lower end of the shaft portion, and the cover covers the shaft portion, and the upper end side of the shaft portion and The glass melting apparatus component according to claim 2 or 3, wherein a contact for applying a reverse potential is provided on an upper end side of the cover.   An iridium wire coated with ceramic fiber is disposed inside the pipe of the shaft portion, and one end of the iridium wire is joined at a height at which the stirring portion is attached, and the other end of the iridium wire is connected to the shaft portion. The glass melting device part according to claim 4, wherein the glass melting device is joined at an upper end side.   The structure is an electrode having a pipe-shaped or rod-shaped shaft portion, the cover covers the shaft portion, and applies a reverse potential to the upper end side of the shaft portion and the upper end side of the cover. The glass melting apparatus part according to claim 2 or 3, wherein a contact is provided.   An iridium wire coated with ceramic fiber is disposed inside the pipe of the shaft portion, and one end of the iridium wire is joined at the lower end portion of the shaft portion, and the other end of the iridium wire is connected to the upper end side of the shaft portion. The glass melting apparatus part according to claim 6, wherein the glass melting apparatus part is joined.   The structure is a glass melting container, and the cover covers the entire outer surface of the container and the entire inner surface above the liquid surface of the glass melt and is not covered with the cover. The glass melting apparatus component according to claim 2, wherein a contact for applying a reverse potential is provided on the exposed surface of iridium and the surface of the cover.