EP3746410A1

EP3746410A1 - Molten glass stirring chamber

Info

Publication number: EP3746410A1
Application number: EP19746958.8A
Authority: EP
Inventors: Dong Bin Kim; Dong-Won Shin; Euiho Kim; Hyungjin PARK; Yong-kyu KWON; Jihyun Kim; Jucheon EOM; Chonsu MUN; Dongwon Kim
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2018-01-30
Filing date: 2019-01-29
Publication date: 2020-12-09
Also published as: WO2019151747A1; CN111770898B; TWI791744B; CN111770898A; KR102386231B1; JP7267303B2; EP3746410A4; KR20190092161A; JP2021512041A; TW201940439A

Abstract

A stirring chamber includes a stirring vessel configured to receive molten glass; a cover on the stirring vessel; and a stirrer configured to pass through the cover and stir the molten glass. The cover includes a porous heat-resistant body and an inorganic ceramic layer covering a surface of the porous heat-resistant body.

Description

MOLTEN GLASS STIRRING CHAMBER

The disclosure relates to a molten glass stirring chamber capable of reducing defects in glass sheets formed from the molten glass.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority under 35 U.S.C. § 119 of Korean Patent Application Serial No. 10-2018-0011606 filed on January 30, 2018, the content of which is relied upon and incorporated herein by reference in its entirety.

An apparatus for manufacturing flat glass sheets includes a stirring apparatus for stirring molten glass.

The stirring apparatus includes a stirring vessel configured to accommodate molten glass, a cover configured to cover the stirring vessel, and a stirring blade located in the stirring vessel. As time passes, a platinum-based heat source disposed inside the cover reacts with oxygen in the atmosphere. The oxidized platinum is undesirably incorporated into the glass in the form of a platinum condensate, thus causing defects in the glass sheets.

The disclosure provides a molten glass stirring chamber capable of reducing defects occurring from a cover.

According to one or more embodiments, a stirring chamber may include a stirring vessel configured to receive molten glass; a cover positioned on the stirring vessel; and a stirrer passing through the cover and configured to stir the molten glass, wherein the cover comprises a cover body and an inorganic ceramic layer covering a surface of cover body, the cover body being porous.

The inorganic ceramic layer may include a glass layer. The glass layer may include about 80 wt% to about 90 wt% of silica (SiO ₂), about 1 wt% to about 3 wt% of boron oxide (B ₂O ₃), about 2 wt% about 5 wt% of alumina (Al ₂O ₃), about 1 wt% to about 3 wt% of sodium oxide (Na ₂O), about 2 wt% to about 4 wt% of potassium oxide (K ₂O), about 2 wt% to about 6 wt% of zinc oxide (ZnO), and about 0.1 wt% to about 2 wt% of zirconia (ZrO ₂).

The cover body may include a recess and a heat source disposed within the recess. The heat source may be retained in the recess surrounded by an inorganic filler. The inorganic ceramic layer may cover at least a top surface and a bottom surface of the cover body, and an exposed portion of the inorganic filler. The inorganic filler may be a cement.

The cover may further include a noble metal cladding layer covering at least a top surface and a bottom surface of the cover body, the noble metal cladding layer provided on the inorganic ceramic layer. The cover may further include a refractory oxide layer covering a surface of the noble metal cladding layer facing an inner portion of the stirring vessel.

The cover may have a central hole through which the stirrer passes, and may be divided into a first body and a second body along a boundary region, wherein the first body includes a sheet portion protruding horizontally along the boundary region in a longitudinal direction. The sheet portion may at least partially overlap with the second body. The sheet portion may be provided on a lower portion of the first body facing an inner portion of the stirring vessel.

According to one or more embodiments, a stirring chamber may include a stirring vessel configured to receive molten glass; a cover on the stirring vessel; and a stirrer passing through the cover and configured to stir the molten glass, wherein the cover includes a cover body having a central hole which the stirrer passes through, the cover body being porous, wherein the cover body comprises a first body and a second body along a boundary region, and wherein the first body comprises a sheet portion protruding horizontally along the boundary region in a longitudinal direction.

The sheet portion may at least partially overlap with the second body. A surface of each of the first body and the second body may be covered by an inorganic ceramic layer. A lower portion of the first body includes a noble metal cladding layer, and the sheet portion is attached to a surface of the noble metal cladding layer.

According to one or more embodiments, a stirring chamber may include a stirring vessel configured to receive molten glass; a cover on the stirring vessel; and a stirrer passing through the cover and configured to stir the molten glass, wherein the cover includes a noble metal cladding layer at least on a lower surface of the cover, wherein a surface of the precious metal cladding layer facing the melting glass is covered by a refractory oxide layer including about 3 wt% to about 5 wt% of CaO, about 0.2 wt% to about 1 wt% of SiO ₂, about 0.2 wt% to about 1 wt% of Al ₂O ₃, about 0.5 wt% to about 3.5 wt% of HfO ₂, and a balance of ZrO ₂.

The refractory oxide layer may further include about 0.01 wt% to about 0.3 wt% of Fe ₂O ₃ and about 0.01 wt% to about 0.9 wt% of MgO.

A thickness of the refractory oxide layer may be about 2 mil to about 8 mil.

The cover may include a cover body with a central hole which the stirring body passes through, wherein the cover is divided into a first body and a second body along a boundary region extending through the central hole, wherein a surface of each of the first body and the second body is covered by an inorganic ceramic layer, and a sheet portion protruding horizontally across the boundary region is provided on the first body.

Embodiments of the disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a diagram of a glass manufacturing apparatus according to an embodiment of the disclosure;

FIG. 2 is a perspective view of a molten glass stirring chamber according to an embodiment of the disclosure;

FIG. 3 is a perspective view of a first body of a cover according to an embodiment of the disclosure;

FIG. 4 illustrates a cross-section taken along line IV-VI' of FIG. 3;

FIG. 5 is a graph conceptually showing a method of defining an interface between a cover body and an inorganic ceramic layer, with respect to a cross-section taken along line V-V' of FIG. 4;

FIG. 6 is a side cross-sectional view of a first body of a cover according to another embodiment of the disclosure;

FIGS. 7A to 7C are side cross-sectional views sequentially illustrating a method of manufacturing first bodies for covers, according to embodiments of the disclosure;

FIG. 8 is a side cross-sectional view of a first body of a cover according to another embodiment of the disclosure;

FIGS. 9A and 9B are perspective views showing a method of forming a refractory oxide layer on a surface of a first body of a cover, according to an embodiment of the disclosure;

FIG. 10 illustrates a first body of a cover, according to an embodiment of the disclosure;

FIGS. 11A and 11B are cross-sectional views of first bodies of a cover, according to other embodiments of the disclosure;

FIG. 12 is a conceptual diagram illustrating a test apparatus for testing performance of an inorganic ceramic layer, according to an embodiment of the disclosure;

FIG. 13 is a graph showing a result of performing a helium gas leakage test on Example 1 and Comparative Example 1;

FIGS. 14A and 14B are exploded perspective view of samples for sagging comparison test on Examples 2 and 3 and Comparative Examples 2 and 3; and

FIG. 15 is a graph showing a result of performing a sagging comparison test on Examples 2 and 3 and Comparative Examples 2 and 3.

Example embodiments will now be described more fully hereinafter with reference to the accompanying Figures; however, the claims may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey exemplary implementations to those skilled in the art.

In the Figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being "on" another layer or element, it can be directly on the other layer or element, or intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. For example, the term "or" is not exclusive, and may be understood as having the same meaning as "and/or." Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

While such terms as "first," "second," etc., may be used to describe various components, such components must not be limited to the above terms. The above terms are used only to distinguish one component from another. For example, a first component discussed below could be termed a second component, and similarly, a second component may be termed a first component without departing from the teachings of this disclosure.

The terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. An expression used in the singular encompasses the expression in the plural, unless it has a clearly different meaning in the context. It will be understood that the terms, e.g., "comprises," "includes," "including," and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The operations of all methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The embodiments are not limited to the described order of the operations. For example, two consecutively described processes may be performed substantially at the same time or performed in an order opposite to the described order.

As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments should not be construed as being limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing.

FIG. 1 is a diagram of an exemplary glass manufacturing apparatus 1 according to various embodiments.

Referring to FIG. 1, glass manufacturing apparatus 1 may include a melting vessel 100, a fining vessel 200, a molten glass stirring chamber 300, a delivery vessel 500, and a forming apparatus 700. According to some embodiments, the glass manufacturing apparatus 1 may manufacture sheet type glass, although in further embodiments, the glass manufacturing apparatus may manufacture various other glass articles, including glass rods, glass tubes, glass containers and glass envelopes.

The melting vessel 100, the fining vessel 200, the molten glass stirring chamber 300, the delivery vessel 500, and the forming apparatus 700 may be glass manufacturing process stations located in series. Predetermined processes for manufacturing glass products are performed at these stations. According to some embodiments, manufacturing processes performed by the glass manufacturing apparatus may include a down-draw process, a slot-draw fusion-forming process (including a double fusion process), a float glass forming process, and a rolling process.

According to some embodiments, each of the melting vessel 100, the fining vessel 200, the molten glass stirring chamber 300, the delivery vessel 500, and the forming apparatus 700 may include platinum-containing metals such as platinum or platinum-rhodium, platinum-iridium, and combinations thereof. According to some embodiments, each of the melting vessel 100, the fining vessel 200, the molten glass stirring chamber 300, the delivery vessel 500, and the forming apparatus 700 may include palladium, rhenium, ruthenium, and osmium, and other metals. According to some embodiments, the forming apparatus 700 may include a ceramic material or a glass-ceramic material.

The melting vessel 100 receives a batch material 11 from a storage vessel 10. The batch material 11 is inserted into the melting vessel 100 by a batch delivery apparatus 13 powered by a drive device 15. A selective controller 17 may be configured to operate the drive device 15 to introduce a desired amount of the batch material 11 into the melting vessel 100 as indicated by an arrow a1. According to some embodiments, a glass level probe 19 may be used to measure a level of molten glass MG in a standpipe 21 and to transmit the measured level of molten glass MG to the controller 17 through a communication line 23.

According to some embodiments, the fining vessel 200 is connected to the melting vessel 100 by a first conduit 150. The first conduit 150 includes a passage through which the molten glass MG flows. Second and third conduits 250 and 350 described below also provide a passage through which the molten glass MG flows. The first conduit 150 may include a material having electrical conductivity and usable at a high temperature condition. According to some embodiments, the first conduit may include a platinum-containing metal, e.g., platinum, platinum-rhodium, platinum-iridium, or a combination thereof. According to some embodiments, the first to the third conduit may include a metal, e.g., molybdenum, palladium, rhenium, tantalum, titanium, tungsten, ruthenium, osmium, zirconium, or an alloy thereof, and/or zirconium dioxide.

The fining vessel 200 serves as a refining tube. The fining vessel 200 is located downstream of the melting vessel 100. The fining vessel 200 receives the molten glass MG from the melting vessel 100. According to some embodiments, a high temperature process may be performed in the fining vessel 200 to remove blisters (i.e., gaseous inclusions) from the molten glass MG. According to some embodiments, the fining vessel 200 is configured to remove blisters from the molten glass MG while the molten glass MG passes through the fining vessel 200 by heating the molten glass MG. According to some embodiments, as the molten glass MG is heated in the fining vessel 200, a fining agent contained in the molten glass MG may cause a redox reaction, thereby resulting in oxygen and other gases being removed from the molten glass MG. Specifically, the blisters contained in the molten glass MG may include oxygen, carbon dioxide, and/or sulfur dioxide and may be combined with oxygen generated in the reduction reaction of the fining agent, and thus, a volume of the blister may increase. The grown blisters may float toward the free surface of the molten glass MG in the fining vessel 200 and thereby be separated from the molten glass MG. The blisters may be discharged outside the fining vessel 200 through a gas-phase space at an upper part of the fining vessel 200.

According to some embodiments, the molten glass stirring chamber 300 is located downstream of the fining vessel 200. The molten glass stirring chamber 300 may homogenize the molten glass MG supplied from the fining vessel 200. A stirrer 310 may be provided in the molten glass stirring chamber 300, to rotate relative to the molten glass stirring chamber 300 to make the molten glass MG flow and mix therein. The stirrer 310 may stir the molten glass MG to homogenize the molten glass MG before it exits the stirring chamber 300.

The delivery vessel 500 may be located downstream of the molten glass stirring chamber 300. The delivery vessel 500 is connected to the molten glass stirring chamber 300 by a third conduit 350. An outlet conduit 600 is connected to the delivery vessel 500. The molten glass MG is transferred to the inlet 650 of the forming apparatus 700 through the outlet conduit 600.

The forming apparatus 700 receives the molten glass MG from the delivery vessel 500. The forming apparatus 700 may form the molten glass MG into a sheet-shaped glass product, although in further embodiments, the forming apparatus may form the molten glass into objects of other shapes, such as rods, tubes, envelopes, etc. For example, the forming apparatus 700 may include a fusion drawing machine for forming the molten glass MG into a continuous glass ribbon. Molten glass MG flowing into the forming apparatus 700 may overflow in the forming apparatus 700. The overflowing molten glass MG moves in a downward direction by gravity and a combination of suitably arranged rolls such as edge roll 750 and pulling rolls 800 to form the molten glass ribbon.

FIG. 2 is a perspective view of a molten glass stirring chamber 300 according to an embodiment.

Referring to FIG. 2, the molten glass stirring chamber 300 may include a stirring vessel 320 configured to accommodate molten glass MG therein, a cover 330 disposed on the stirring vessel 320, and a stirrer 310 penetrating the cover 330 and configured to stir the molten glass MG.

The stirring vessel 320 may be connected to a second conduit 250 and a third conduit 350. As described above, the molten glass MG is introduced into the stirring vessel 320 through the second conduit 250 and discharged out of the stirring vessel 320 through the third conduit 350.

The stirrer 310 may include a stirring rod 314 and a plurality of blades 312 attached thereto.

The cover 330 is configured to cover an opening of the stirring vessel 320. A center hole 338 through which the stirring rod 314 penetrates may be provided at the center of the cover 330. A heat source 332 may be provided inside the cover 330.

The cover 330 may include two bodies, a first body 330a and a second body 330b. The first body 330a and the second body 330b may be separated from each other, with a boundary region disposed therebetween and intersecting the center hole 338. Although FIG. 2 illustrates an example in which the cover 330 is divided into two bodies, the cover 330 may be divided into three or more bodies in another embodiment.

The first body 330a and the second body 330b may each include a cover body 334 and a heat source 332 embedded therein.

The heat source 332 includes platinum or a platinum alloy and may generate heat when electric power is supplied thereto. Specifically, the heat source 332 may include pure platinum or a platinum alloy. The platinum alloy may be an alloy of platinum and at least one of rhodium (Rh), iridium (Ir), ruthenium (Ru), palladium (Pd), and osmium (Os).

The cover body 334 may include a refractory material. In some embodiments, the cover body 334 may include a porous material. For example, the cover body 334 may include, for example, a material such as Crystallite HF339 (available from BUCHER Emhart Glass) or AN485 (available from Saint Gobain).

FIG. 3 is a perspective view of the first body 330a of cover 330 according to an embodiment, and FIG. 4 illustrates a cross-section taken along line IV-IV' of FIG. 3. Although the following description focuses on the first body 330a, it will be understood by those of ordinary skill in the art that this description may equally apply to the second body 330b, or to additional bodies in embodiments in which the cover 330 is divided into three or more bodies.

Referring to FIGS. 3 and 4, the cover body 334 may be provided with recesses 334R configured to accommodate the heat source 332. The recesses 334R may extend in a direction of line of sight of FIG. 4, or may extend in another direction, such as a circumferential or radial direction of the cover body 334. The heat source 332 may be accommodated in the recess 334R.

The heat source 332 may be embedded and secured in the recess 334R surrounded by an inorganic filler 334f. The inorganic filler 334f may be, for example, a cement.

As illustrated in FIG. 4, the inorganic filler 334f may be at least partially exposed from the cover body 334. In some embodiments, a surface of the inorganic filler 334f may be coplanar with a surface of the cover body 334.

The surface of the cover body 334 may be covered with an inorganic ceramic layer 336. In one embodiment, he inorganic ceramic layer 336 as used herein is an inorganic compound between metallic and non-metallic elements for which the interatomic bonds are either totally ionic, or predominantly ionic and includes a material having crystalline, partly crystalline, or non-crystalline (i.e., glass) structure. In some embodiment, the inorganic ceramic layer 336 may be a glass layer including silica as a main component. For example, the inorganic ceramic layer 336 may include about 80 wt% to about 90 wt% of silica (SiO ₂), about 1 wt% to about 3 wt% of boron oxide (B ₂O ₃), about 2 wt% about 5 wt% of alumina (Al ₂O ₃), about 1 wt% to about 3 wt% of sodium oxide (Na ₂O), about 2 wt% to about 4 wt% of potassium oxide (K ₂O), about 2 wt% to about 6 wt% of zinc oxide (ZnO), and about 0.1 wt% to about 2 wt% of zirconia (ZrO ₂).

In some embodiments, the inorganic ceramic layer 336 may cover an upper surface of the cover body 334. In some embodiments, the inorganic ceramic layer 336 may cover a lower surface of the cover body 334. In some embodiments, the inorganic ceramic layer 336 may cover an exposed surface of the inorganic filler 334f.

It is desirable to prevent or reduce oxygen contact with platinum included in the heat source 332 because the platinum may otherwise be oxidized and lost as gaseous PtO ₂ due to contact with oxygen at high temperature. Undesirably, such gaseous PtO ₂ may be deposited at an undesired position as a condensate, including as inclusions in the molten glass MG within the stirring chamber 300. The inorganic ceramic layer 336 may prevent or reduce the contact of the platinum included in the heat source 332 with oxygen.

A thickness of the inorganic ceramic layer 336 may be in a range of about 1 mm to about 5 mm. If the thickness of the inorganic ceramic layer 336 is too large, particles may be generated due to peeling of the layer 336. On the other hand, if the thickness of the inorganic ceramic layer 336 is too small, the effect of preventing the oxidation of platinum included in the heat source 332 may be insufficient.

On the other hand, when the cover body 334 is porous, an interface between the cover body 334 and the inorganic ceramic layer 336 may be ambiguous. In other words, the inorganic ceramic layer 336 may penetrate into pores of the cover body 334 partially in a region that comes into contact with the porous cover body 334.

FIG. 5 is a graph conceptually illustrating a method of defining the interface between the cover body 334 and the inorganic ceramic layer 336 with respect to the section cut along line V-V' of FIG. 4. In FIG. 5, the horizontal axis represents a position along the line V-V' of FIG. 4, and the vertical axis represents mass fractions of a material constituting the inorganic ceramic layer 336 and a material constituting the cover body 334. Referring to FIG. 5, there may be a section in which the mass fractions of the cover body 334 and the inorganic ceramic layer 336 gradually change around an interface IF at which the cover body 334 is in contact with the inorganic ceramic layer 336. A virtual interface at which the mass fractions of the cover body 334 and the inorganic ceramic layer 336 are respectively about 0.5 may be defined as an interface between the cover body 334 and the inorganic ceramic layer 336.

FIG. 6 is a side cross-sectional view of a first body 330a' according to another embodiment. The first body 330a' of FIG. 6 differs from the first body 330a of FIG. 4 in that an inorganic ceramic layer 336a is formed only on a lower surface of the cover body 334. Therefore, hereinafter, such differences will be mainly described, and redundant descriptions will be omitted.

Referring to FIG. 6, the inorganic ceramic layer 336a is not formed over the entire surface of the cover body 334. In some embodiments, the inorganic ceramic layer 336a may coat only the surface of the cover body 334 on which a heat source 332 is provided. In some embodiments, the inorganic ceramic layer 336a may cover an exposed surface of the inorganic filler 334f. In some embodiments, the inorganic ceramic layer 336a may cover the surface of the cover body 334 that is substantially coplanar with the exposed surface of the inorganic filler 334f. In some embodiments, the inorganic ceramic layer 336a may not cover the surface of the cover body 334 that is not coplanar with the exposed surface of the inorganic filler 334f.

Since the shortest path of oxygen to oxidize platinum in heat source 332 is from the surface on the side where the inorganic filler 334f is located, an effect of preventing oxidation and loss of Pt as in FIG. 4 may be similarly obtained even if the inorganic ceramic layer 336a is formed only on one surface (that is, only on a surface where a recess 334R is formed). Furthermore, the first body 330a' in the embodiment of FIG. 6 uses a smaller amount of the inorganic ceramic layer 336a than in the embodiment of FIG. 4, and thus, the first body 330a' is relatively more cost-efficient and easy to manufacture. In addition, since the first body 330a' may be lighter in weight than the first body 330a of FIG. 4 (due to lesser amounts of inorganic ceramic layer 336), sagging of cover 330 at an operating temperature may be less likely to occur.

FIGS. 7A to 7C are side cross-sectional views sequentially illustrating a method of manufacturing first bodies 330a and 330a', according to embodiments

Referring to FIG. 7A, recesses 334R are formed on a lower surface of a cover body 334. The recesses 334R may have a size sufficient to accommodate a heat source 332 (see FIG. 7B) therein.

Referring to FIG. 7B, the heat source 332 may be disposed in the recesses 334R, and a space between the inner surface of the recess 334R and the heat source 332 may be filled with an inorganic filler 334f. Since the material of the inorganic filler 334f has been described above in detail, a further detailed description thereof is omitted.

Referring to FIG. 7C, an inorganic ceramic material layer 336p is formed on surfaces of the cover body 334 and the inorganic filler 334f. The inorganic ceramic material layer 336p may be, for example, a slurry layer in which an inorganic ceramic material is dispersed in a dispersion medium. In some embodiments, the inorganic ceramic layer 336p may include a mixture in which a solid powder including about 80 wt% to about 90 wt% of silica (SiO ₂), about 1 wt% to about 3 wt% of boron oxide (B ₂O ₃), about 2 wt% about 5 wt% of alumina (Al ₂O ₃), about 1 wt% to about 3 wt% of sodium oxide (Na ₂O), about 2 wt% to about 4 wt% of potassium oxide (K ₂O), about 2 wt% to about 6 wt% of zinc oxide (ZnO), and about 0.1 wt% to about 2 wt% of zirconia (ZrO ₂) is mixed with a dispersion medium such as water at a weight ratio of about 1:2 to about 2:1.

The inorganic ceramic material layer 336p may be formed by brushing, spraying, dip coating, or spin coating, but embodiments of the disclosure are not limited thereto.

Subsequently, the inorganic ceramic material layer 336p is annealed at a temperature of about 800℃ to about 2,000℃ for about 10 seconds to about 60 minutes to form the inorganic ceramic layer 336a, and the first body 330a illustrated in FIG. 4 may be obtained.

The first body 330a' illustrated in FIG. 6 may be manufactured by the same method as that described with reference to FIGS. 7A to 7C, except that the inorganic ceramic material layer 336p is formed only on the lower surface of the cover body 334 in FIG. 7C.

FIG. 8 is a side cross-sectional view of a first body 330a" according to another embodiment. The first body 330a" of FIG. 8 differs from the first body 330a of FIG. 4 in that the first body 330a" further includes a noble metal cladding layer 333 and a refractory oxide layer 337 on one surface of the noble metal cladding layer 333. Therefore, hereinafter, such differences will be mainly described, and a redundant description will be omitted.

The noble metal cladding layer 333 may be formed at least at an upper surface 333US or a lower surface 333LS of the noble metal cladding layer 333. The noble metal is defined as a metal resistant to corrosion and oxidation such as platinum (Pt), gold (Au), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), copper (Cu), and rhenium (Re). In some embodiments, the noble metal cladding layer 333 may be formed on both the upper surface and the lower surface of the cover body 334. In some embodiments, the noble metal cladding layer 333 may also be formed at an inner surface of a center hole 338 (corresponding to a sidewall portion SW of FIG. 8).

The noble metal cladding layer 333 may include, for example, platinum or a platinum alloy. For example, the platinum alloy may be an alloy of platinum and at least one of rhodium (Rh), iridium (Ir), ruthenium (Ru), palladium (Pd), and osmium (Os).

The refractory oxide layer 337 may be provided on a lower surface 333LS of the noble metal cladding layer 333. The refractory oxide layer 337 is made of oxide material that is highly heat resistant. The lower surface 333LS may be a surface facing the stirring vessel 320. The refractory oxide layer 337 covers the platinum or the platinum alloy exposed to high temperature so as to reduce the area of the exposed region, thereby reducing the possibility of a redox reaction of platinum and consequent condensation of the reaction products on interior surfaces of the cover and stirring vessel, where the reaction products may drop into the molten glass MG. This makes it possible to reduce product defects caused by such inclusions.

A thickness of the refractory oxide layer 337 may be in a range of about 1 mil (= 0.001 inches) to about 10 mils. In some embodiments, the thickness of the refractory oxide layer 337 may be in a range of about 2 mils (= 0.002 inches) to about 8 mils.

The lower surface 333LS of the noble metal cladding layer 333 on which the refractory oxide layer 337 is formed may be roughened. In some embodiments, a roughness Ra of the lower surface 333LS of the noble metal cladding layer 333 may be in a range of about 0.1 μm to about 50 μm when measured by the BS EN ISO 4287:2000 standard. Here, Ra is an arithmetic average roughness, which is an arithmetic mean deviation of the roughness profile. If the roughness Ra is too large, flatness after the formation of the refractory oxide layer 337 may be insufficient. If the roughness Ra is too small, adhesion between the refractory oxide layer 337 and the noble metal cladding layer 333 may be insufficient.

FIGS. 9A and 9B are perspective views showing a method of forming the refractory oxide layer 337 on a surface of the first body 330a, according to an embodiment.

Referring to FIG. 9A, an outer surface of the first body 330a may be covered with the inorganic ceramic layer 336. The noble metal cladding layer 333 may be provided on an upper surface and a lower surface of the first body 330a. In addition, the noble metal cladding layer 333 may also be provided at least partially on a sidewall SW of the first body 330a.

Subsequently, the lower surface 333LS of the noble metal cladding layer 333 may be roughened. In FIG. 9A, for convenience of understanding, the first body 330a is turned upside down so that the lower surface 333LS faces upward. The roughening may be performed by, for example, sandblasting, but is not limited thereto. As a result, a roughened lower surface 333SB may be obtained.

Referring to FIG. 9B, the refractory oxide layer 337 is formed on the roughened lower surface 333SB of the noble metal cladding layer 333.

The refractory oxide layer 337 may be a material layer including zirconia (ZrO ₂) as a main component. In some embodiments, the refractory oxide layer 337 may include about 3 wt% to about 5 wt% of calcium oxide (CaO), about 0.2 wt% to about 1 wt% of silica (SiO ₂), about 0.2 wt% to about 1 wt% of alumina (Al ₂O ₃), and about 0.5 wt% to about 3.5 wt% of hafnium oxide (HfO ₂), with the remainder being zirconia (ZrO ₂) and unavoidable impurities. The refractory oxide layer 337 may further include about 0.01 wt% to about 0.3 wt% of iron oxide (Fe ₂O ₃) and about 0.01 wt% to about 0.9 wt% of magnesium oxide (MgO).

In some embodiments, the refractory oxide layer 337 may include about 1 wt% to about 2 wt% of hafnium oxide (HfO ₂), about 2.5 wt% to about 4.5 wt% of calcium oxide (CaO), about 0.2 wt% to about 1.0 wt% of silica (SiO ₂), about 0.3 wt% to about 1.2 wt% of alumina (Al ₂O ₃), about 0.01 wt% to about 0.2 wt% of iron oxide (Fe ₂O ₃), about 0.05 wt% to about 0.2 wt% of titania (TiO ₂), and about 0.01 wt% to about 0.1 wt% of magnesium oxide (MgO), with the remainder being zirconia (ZrO ₂) and unavoidable impurities.

In some embodiments, the refractory oxide layer 337 may be formed by melting a source powder with plasma and spraying the molten source powder. FIG. 9B illustrates a portion of the lower surface 333SB that is exposed so as to show that the refractory oxide layer 337 can be formed on the lower surface 333SB. However, in other embodiments the refractory oxide layer 337 may be formed on the entirety of the roughened lower surface 333SB.

FIG. 10 illustrates a first body 331a of the cover 330, according to an embodiment. The first body 331a may, together with a second body 331b, constitute the cover 330.

Referring to FIG. 10, a sheet portion 339 protruding along a boundary region BD between the first body 331a and the second body 331b may be provided below the refractory oxide layer 337.

Although the sheet portion 339 is attached to a lower surface of the first body 331a, a protruding portion of the sheet portion 339 may at least partially overlap the second body 331b. In other words, the sheet portion 339 may substantially completely cover the boundary region BD except for the center hole 338. In some embodiments, a width G1 by which the sheet portion 339 protrudes from the first body 331a toward the second body 331b may be greater than a gap G2 between the first body 331a and the second body 331b.

The sheet portion 339 may include a metal or an inorganic material. In some embodiments, the sheet portion 339 may include a metal such as platinum or a platinum alloy. In some embodiments, the sheet portion 339 may include a silica-based inorganic material, a zirconia-based inorganic material, or an alumina-based inorganic material. In some embodiments, the sheet portion 339 may include an alloy of platinum and rhodium.

FIGS. 11A and 11B are cross-sectional views of first bodies 331a' and 331a" of a cover, according to other embodiments.

Referring to FIG. 11A, the sheet portion 339 may be directly attached to a surface of the inorganic ceramic layer 336. The first body 331a' of FIG. 11A may be substantially the same as the first body 331a in the embodiment of FIG. 10, except that the refractory oxide layer 337 and the noble metal cladding layer 333 are omitted.

Referring to FIG. 11B, the sheet portion 339 may be directly attached to a surface of the noble metal cladding layer 333. The first body 331a" of FIG. 11B may be substantially the same as the first body 331a in the embodiment of FIG. 10, except that the refractory oxide layer 337 is omitted.

Hereinafter, the constitution and effects of the disclosure will be described in more detail with reference to specific examples and comparative examples. However, these examples are only intended to clarify the disclosure and are not intended to limit the scope of the disclosure.

FIG. 12 is a diagram illustrating a helium gas leakage test apparatus for testing performance of an inorganic ceramic layer, according to an embodiment;

Referring to FIG. 12, a chamber 51 includes an opening 54 on one side, and a sample SA is fixed in the opening 54 of the chamber 51. An inlet valve 52 is opened to supply helium (He) gas at a predetermined pressure in a state in which no leakage occurs between the sample SA and the chamber 51 and an outlet valve 53 is closed.

If there are more paths through which gas can pass through the sample SA, the leakage amount of helium detected through a helium sensor 43 will be increased. In contrast, if there are fewer paths through which gas can pass through the sample SA, the leakage amount of helium detected through the helium sensor 43 will be reduced.

An inorganic ceramic layer including about 85.05 wt% of silica (SiO ₂), about 2.25 wt% of boron oxide (B ₂O ₃), about 3.25 wt% of alumina (Al ₂O ₃), about 1.7 wt% of sodium oxide (Na ₂O), about 2.5 wt% of potassium oxide (K ₂O), about 4.1 wt% of zinc oxide (ZnO), and about 1.15 wt% of zirconia (ZrO ₂) was formed on a porous AN485 (available from Saint Gobain) sample to a thickness of about 3 mm.

The sample (Example 1) having the inorganic ceramic layer and a sample (Comparative Example 1) having no inorganic ceramic layer were fixed at the opening of the chamber, and a helium gas leakage test was performed thereon.

As a result, it was found that, when the inorganic ceramic layer was formed, the leakage of gas was reduced to less than 1/4 of the leakage without the inorganic ceramic layer as illustrated in FIG. 13. Therefore, it can be seen that the inorganic ceramic layer may prevent platinum included in the heat source from being oxidized.

FIGS. 14A and 14B are exploded perspective view of samples for sagging comparison test on Examples 2 and 3 and Comparative Examples 2 and 3.

A longitudinal recess 61r was formed on a surface of a bar-shaped body sample 61, a heat source (not shown) and an inorganic filler 63 were formed in the recess 61r, and then an inorganic ceramic layer 67 was formed thereon (Example 2). A sample was manufactured in the same manner as in Example 2, except that an extending direction of the recess 61r was changed to a direction perpendicular to a longitudinal direction. Samples of Comparative Examples 2 and 3, which were substantially the same as the samples of Examples 2 and 3, were manufactured, except that the inorganic ceramic layer 67 was not formed for comparison.

These samples were supported on two supports 69 spaced apart from each other at a predetermined interval, and then left at 1,500℃ for 3 days. Then, the sagging length at the center between the two supports 69 was measured to obtain the results shown in FIG. 15. The sagging length is a height difference at the center between the original height and the height after heating at 1,500℃ for 3 days.

Referring to FIG. 15, it can be seen that the inorganic ceramic layer 67 also contributes to reduction of sagging of the samples, regardless of the extending direction of the recess. The sagging length for Example 2 is less than a third of that for Comparative Example 2. The sagging length for Example 3 is about a half of that for Comparative Example 3.

While the disclosure has been particularly shown and described with reference to embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the following claims.

Claims

A stirring chamber comprising:

a stirring vessel configured to receive molten glass;

a cover positioned on the stirring vessel; and

a stirrer passing through the cover and configured to stir the molten glass,

wherein the cover comprises a cover body and an inorganic ceramic layer covering a surface of the cover body, the cover body being porous.
The stirring chamber of claim 1, wherein the inorganic ceramic layer comprises a glass layer.
The stirring chamber of claim 2, wherein the glass layer comprises about 80 wt% to about 90 wt% of silica (SiO ₂), about 1 wt% to about 3 wt% of boron oxide (B ₂O ₃), about 2 wt% about 5 wt% of alumina (Al ₂O ₃), about 1 wt% to about 3 wt% of sodium oxide (Na ₂O), about 2 wt% to about 4 wt% of potassium oxide (K ₂O), about 2 wt% to about 6 wt% of zinc oxide (ZnO), and about 0.1 wt% to about 2 wt% of zirconia (ZrO ₂).
The stirring chamber of any of claims 1-3, wherein the cover body includes a recess and a heat source disposed within the recess.
The stirring chamber of claim 4, wherein the heat source is retained in the recess surrounded by an inorganic filler.
The stirring chamber of claim 5, wherein the inorganic ceramic layer covers at least a top surface and a bottom surface of the cover body, and an exposed portion of the inorganic filler.
The stirring chamber of claim 6, wherein the inorganic filler is a cement.
The stirring chamber of any of claims 1-7, wherein the cover further includes a noble metal cladding layer covering at least a top surface and a bottom surface of the cover body, the noble metal cladding layer provided on the inorganic ceramic layer.
The stirring chamber of claim 8, wherein the cover further includes a refractory oxide layer covering a surface of the noble metal cladding layer facing an inner portion of the stirring vessel.
The stirring chamber of any of claims 1-9, wherein the cover has a central hole through which the stirrer passes, and is divided into a first body and a second body along a boundary region,

wherein the first body comprises a sheet portion protruding horizontally along the boundary region in a longitudinal direction.
The stirring chamber of claim 10, wherein the sheet portion at least partially overlaps with the second body.
The stirring chamber of claim 11, wherein the sheet portion is provided on a lower portion of the first body facing an inner portion of the stirring vessel.
A stirring chamber comprising:

a stirring vessel configured to receive molten glass;

a cover on the stirring vessel; and

a stirrer passing through the cover and configured to stir the molten glass,

wherein the cover includes a cover body having a central hole which the stirrer passes through, the cover body being porous,

wherein the cover comprises a first body and a second body along a boundary region, and

wherein the first body comprises a sheet portion protruding horizontally along the boundary region in a longitudinal direction.
The stirring chamber of claim 13, wherein the sheet portion at least partially overlaps with the second body.
The stirring chamber of either one of claims 13-14, wherein a surface of each of the first body and the second body is covered by an inorganic ceramic layer.
The stirring chamber of claim 15, wherein a lower portion of the first body comprises a noble metal cladding layer and the sheet portion is attached to a surface of the noble metal cladding layer.
A stirring chamber comprising:

a stirring vessel configured to receive molten glass;

a cover on the stirring vessel; and

a stirrer passing through the cover and configured to stir the molten glass,

wherein the cover includes a noble metal cladding layer at least on a lower surface of the cover, wherein a surface of the noble metal cladding layer facing the melting glass is covered by a refractory oxide layer including about 3 wt% to about 5 wt% of CaO, about 0.2 wt% to about 1 wt% of SiO ₂, about 0.2 wt% to about 1 wt% of Al ₂O ₃, about 0.5 wt% to about 3.5 wt% of HfO ₂, and a balance of ZrO ₂.
The stirring chamber of claim 17, wherein the refractory oxide layer further includes about 0.01 wt% to about 0.3 wt% of Fe ₂O ₃ and about 0.01 wt% to about 0.9 wt% of MgO.
The stirring chamber of either one of claims 17-18, wherein a thickness of the refractory oxide layer is about 2 mil to about 8 mil.
The stirring chamber of any of claims 17-19, wherein the cover includes a cover body with a central hole through which the stirring body passes, the cover beingdivided into a first body and a second body along a boundary region extending through the central hole,

wherein a surface of each of the first body and the second body is covered by an inorganic ceramic layer, and a sheet portion protruding horizontally across the boundary region is provided on the first body.