TW201922638A - Production method for glass article and production device therefor - Google Patents

Abstract

This production device 1 for a glass article: is provided with a molding furnace 2 having a furnace wall 5 and a molding part 6 surrounded by the furnace wall 5; molds a first melt glass GM while causing same to flow into the molding part 6 to produce a glass plate GA as a glass article; and is provided with a protective glass layer 8 on the interior-facing surface of the furnace wall 5.

Description

Manufacturing method of glass article and manufacturing device thereof

The present invention relates to a method for manufacturing a glass article and a device for manufacturing the same.

In the manufacturing steps of glass articles such as sheet glass, in order to stabilize the temperature of the molten glass, a furnace wall surrounds the periphery of the molding portion that is shaped while flowing the molten glass. As one type of the furnace wall, Patent Document 1 discloses a furnace wall having an oxide film mainly containing silicon dioxide. The oxide film is a film formed by oxidizing the surface of a furnace wall including a silicon carbide sintered body, and is a type of silica containing crystals (cristobalite). [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2013-79156

[Problems to be Solved by the Invention] In the manufacturing process of a glass article, the deterioration of the furnace wall of the forming furnace affects the productivity or quality of the glass article. In the furnace wall having an oxide film disclosed in Patent Document 1, resistance to, for example, vapors vaporized from molten glass is not necessarily sufficient, and there is still room for improvement.

Specifically, as disclosed in Patent Document 1, when a furnace wall of a forming furnace includes a silicon carbide refractory, an oxide film formed by oxidizing the surface of the silicon carbide refractory is easily self-melting glass. Evaporated vapor erosion. In addition, the oxygen in the air may diffuse into the oxide film, thereby allowing oxygen to penetrate from the surface of the oxide film to the refractory. Thereby, oxidation of silicon carbide (SiC) occurs in the refractory, and carbon dioxide gas is generated as shown in the following formula. SiC + 2O ₂ → SiO ₂ + CO ₂ ↑

At this time, the viscosity of the oxide film of the refractory is lowered by the reaction with the vaporized from the molten glass and the heat during use of the furnace wall. The oxide film in this state may be broken by bubbles of carbonic acid gas generated as described above, and a plurality of cracked portions may be formed in the oxide film. In addition, with the rupture of the oxide film, fragments of the oxide film may be scattered into the furnace and adhere to the molten glass, causing defects in the obtained glass article.

In addition, the above-mentioned defects in the glass article mainly including the refractory constituting the furnace wall may occur similarly when the refractory constituting the furnace wall is made of a material other than silicon carbide.

The object of the present invention is to improve the durability of the furnace wall surrounding the molten glass, and to suppress the occurrence of defects in the obtained glass article that mainly include the refractory constituting the furnace wall. [Means for solving problems]

The present invention, which was pioneered in order to solve the above-mentioned problems, is a method for manufacturing a glass article, which includes forming a first molten glass while forming a portion around a molding section surrounded by a furnace wall including a refractory furnace, and manufacturing the glass article The method for manufacturing a glass article includes the step of forming a protective glass layer on a furnace inner surface of a furnace wall. According to the said structure, the furnace inner surface of a furnace wall is protected by the protective glass layer. Compared with an oxide film, a protective glass layer is easy to acquire resistance to the vapor | steam vaporized from a 1st molten glass, and it is easy to maintain oxygen barrier property. Therefore, it becomes difficult to oxidize the refractory, and it is possible to suppress the occurrence of a defect in the obtained glass article, which mainly includes the refractory constituting the furnace wall.

In the above configuration, it is preferable that the step of forming the protective glass layer is performed separately before the step of manufacturing the glass article. That is, the step of forming the protective glass layer may be performed simultaneously during the implementation of the step of manufacturing the glass article. However, in this case, there is a possibility that the protective glass layer is not sufficiently formed at the beginning of the production of the glass article. Therefore, it is preferable to separately implement the step of forming a protective glass layer before the step of manufacturing the glass article, so that the protective glass layer is sufficiently formed on the inside of the furnace wall of the forming furnace from the beginning of the production of the glass article. . Thereby, in the obtained glass article, it is possible to more reliably suppress the occurrence of defects having the refractory constituting the furnace wall as a main factor.

In the above configuration, the furnace wall preferably includes silicon carbide or silicon nitride refractory, and in the step of forming a protective glass layer, vaporized boron oxide is supplied into the furnace of the forming furnace. In this way, the vaporized boron oxide reacts with silicon dioxide existing on the surface of the furnace inner side of the furnace wall to form a protective glass layer on the surface of the furnace inner side of the furnace wall.

In the above configuration, it is preferable that in the step of forming the protective glass layer, the second molten glass containing boron oxide is supplied to the forming section, and the boron oxide is vaporized from the second molten glass. In this way, boron oxide vaporized from the second molten glass reacts with silicon dioxide existing on the furnace inner surface of the furnace wall to form a protective glass layer on the furnace inner surface of the furnace wall. In addition, if the second molten glass is continuously supplied to the forming portion, the concentration of boron oxide vaporized in the forming furnace can be maintained at a high state, so that the reaction between boron oxide and silicon dioxide frequently occurs. Therefore, it is possible to promote the formation of a protective glass layer on the furnace inner surface of the furnace wall.

In the above configuration, the supply temperature of the second molten glass is preferably higher than the supply temperature of the first molten glass. As described above, in the step of forming the protective glass layer, the amount of boron oxide vaporized from the second molten glass increases. Therefore, it is possible to promote the formation of a protective glass layer on the furnace inner surface of the furnace wall.

In the said structure, it is preferable that content of the boron oxide of a 2nd molten glass is more than content of the boron oxide of a 1st molten glass. As described above, in the step of forming the protective glass layer, the amount of boron oxide vaporized from the second molten glass increases. Therefore, it is possible to promote the formation of a protective glass layer on the furnace inner surface of the furnace wall.

The present invention, which was pioneered in order to solve the above-mentioned problems, is a glass article manufacturing apparatus including a furnace wall and a forming furnace surrounded by the furnace wall. The glass article manufacturing apparatus is characterized in that The inner surface of the furnace includes a protective glass layer. According to the configuration, it is possible to obtain the same effect as the corresponding configuration.

In the above configuration, it is preferable that the furnace wall includes silicon carbide or silicon nitride refractory, and the protective glass layer contains boron oxide. [Effect of the invention]

According to the present invention as described above, it is possible to improve the durability of the furnace wall surrounding the molding portion, and to suppress the occurrence of defects in the obtained glass article that mainly includes the refractory constituting the furnace wall.

Hereinafter, embodiments of a glass article manufacturing apparatus and a glass article manufacturing method will be described based on the attached drawings.

<Glass Article Manufacturing Apparatus> As shown in FIG. 1, the glass article manufacturing apparatus 1 is an apparatus for manufacturing a glass plate GA as a glass article from a first molten glass GM. In addition, in this embodiment, the glass plate GA is a glass original plate for selecting one or more product glass plates.

The glass article manufacturing apparatus 1 includes a forming furnace for forming a glass ribbon GR from a first molten glass GM 2, a spin-cooling furnace 3 for slowly cooling the glass ribbon GR, and a cutting of a glass plate GA from the glass ribbon GR. Department 4.

The forming furnace 2 includes a furnace wall 5 including a refractory, a forming section (also referred to as a forming body) 6 for forming a glass ribbon GR from the first molten glass GM, and a self-backing of the glass ribbon GR at a position below the forming section 6. Edge rollers 7 clamped on both sides.

The furnace wall 5 includes a top wall 5 a and a side wall 5 b so as to surround the periphery of the forming portion 6, and an amorphous protective glass layer 8 is formed on the surface of the furnace inner side of each wall portion. The cover glass layer 8 contains boron oxide and is maintained in a semi-fused state by, for example, heat in a furnace. The thickness of the protective glass layer 8 is preferably 0.2 mm to 2 mm. The protective glass layer 8 may be formed only on a part of the furnace wall 5 (for example, the top wall 5 a) of the forming furnace 2. Further, the protective glass layer 8 may be formed so as to extend from a furnace inner surface of the furnace wall 5 of the forming furnace 2 to a part of a furnace inner surface of the furnace wall 9 of the cold cooling furnace 3.

The refractory constituting the furnace wall 5 of the forming furnace 2 is silicon carbide. Since silicon carbide has relatively high thermal conductivity and soaking properties, the thermal conductivity and soaking properties of the furnace wall 5 can be improved. This makes it possible to stabilize the forming temperature of the first molten glass GM and stabilize the quality of the glass ribbon GR and the glass sheet GA.

The molding portion 6 is a glass ribbon GR formed from the first molten glass GM by an overflow down-draw method, and has a substantially wedge-shaped cross section in which an overflow groove 6 a is formed at an upper end portion. The molding section 6 causes the first molten glass GM overflowing from above the overflow groove 6 a of the molding section 6 to flow down along both side surfaces 6 b, respectively, and joins them at the lower end portion 6 c to form a plate shape. In addition, the forming section 6 is not limited to the above-mentioned configuration, and may be a configuration that performs a forming method other than the overflow down-draw method such as the orifice down-draw method or the re-draw method.

The edge roller 7 restricts the width direction shrinkage of the first molten glass GM at a position below the forming section 6 to produce a glass ribbon GR having a predetermined width.

The Xu-cooling furnace 3 is provided below the edge roller 7 to perform a distortion-removing treatment on the glass ribbon GR, and includes a furnace wall (side wall) 9 so as to surround the periphery of the glass ribbon GR. The Xu cold furnace 3 includes a plurality of annealing rollers 10 provided in the vertical direction. In addition, in order to prevent the updraft generated in the furnace, a partition (not shown) having an opening through which the glass ribbon GR can pass may be provided at a predetermined position such as a boundary between the forming furnace 2 and the spin-cooling furnace 3.

The refractory constituting the furnace wall 9 is silicon carbide. Since silicon carbide has relatively high thermal conductivity and soaking properties, the thermal conductivity and soaking properties of the furnace wall 9 can be improved. Thereby, the slow cooling temperature of the glass ribbon GR can be stabilized, and the quality of the glass ribbon GR and the glass plate GA can be stabilized.

A support roller 11 for holding the glass ribbon GR from both sides of the front and back is provided below the Xu cold furnace 3. Between the support roll 11 and the edge roll 7, or between the support roll 11 and the annealing roll 10 anywhere, tension is given to help thin the glass ribbon GR.

The cutting section 4 is configured to cut the glass ribbon GR in the lowered vertical posture (for example, a vertical posture) in a width direction by a predetermined length by lowering the position of the support roller 11 and to separate the glass ribbon GR from the glass ribbon GR. The glass plates GA were cut out one by one. Here, the width direction is a direction orthogonal to the long side direction (conveying direction) of the glass ribbon GR, and in this embodiment substantially coincides with the horizontal direction.

The cutting unit 4 includes a wheel cutter (not shown), and by walking on the surface GRx of the glass ribbon GR in a vertical posture, a scribe is formed along the width direction of the glass ribbon GR. line) S1; the first support portion 12 abuts from the back GRy to the area where the score line S1 is formed; and the second support portion 13 supports a glass ribbon corresponding to a portion corresponding to the glass plate GA to be cut out In the state of the widthwise end portion of GR, an operation is performed to apply a bending stress to the score line S1 and the vicinity thereof.

The wheel cutter has a structure in which the scribe line S1 is formed while facing the entire width or a part of the width direction of the glass ribbon GR while descending while following the falling glass ribbon GR. In the above-mentioned embodiment, a score line S1 is also formed in the width direction of the width direction end (ear portion) of the glass ribbon GR which has a relatively large thickness. The score line S1 may be formed by laser irradiation or the like.

The first support portion 12 is formed so as to extend along the width direction of the glass ribbon GR, and has a configuration in which the glass ribbon GR is lowered while following the falling glass ribbon, and is connected to the entire width or a part of the glass ribbon GR (for example, the central portion) Abut.

The second support portion 13 includes a chuck mechanism that clamps both ends of the glass ribbon GR in the width direction from both the front and back sides. In the present embodiment, a plurality of second support portions 13 are provided in the widthwise both end portions of the glass ribbon GR at intervals in the longitudinal direction of the glass ribbon GR. The plurality of second support portions 13 provided at one end in the width direction are all held by the same arm (not shown). In the same manner, all of the plurality of second support portions 13 provided at the other end in the width direction are also held by the same arm (not shown). In addition, by the movement of each arm, the plurality of second support portions 13 are lowered while following the falling glass ribbon GR, and as shown by an arrow A, the second support portion 13 is used to move the supported glass ribbon GR to the second support portion. 13 is a fulcrum. Thereby, bending stress is applied to the score line S1 and its vicinity, and the glass ribbon GR is cut along the score line S1 in the width direction. As a result of said cutting, the glass plate GA is cut out from the glass ribbon GR. In addition, in the present embodiment, the cut glass plate GA is transferred to another conveyance member (not shown) by the second support portion 13. In addition, the second support portion 13 is not limited to a support form for clamping, and may support only one of the front and back surfaces of the glass ribbon GR (or glass plate GA) by suction suction.

Here, in the present embodiment, the cutting unit 4 performs breaking and cutting, but is not limited to this, and other cutting methods such as laser cutting and laser fusing may be performed. Further, the cutting unit 4 may also switch the direction after the glass ribbon GR is guided by the direction changing unit (for example, a plurality of guide rollers) in a posture change from a vertical posture to a horizontal posture (for example, a horizontal direction). The downstream side of the section cuts the glass ribbon GR in the lateral position in the width direction.

<The manufacturing method of a glass article> The manufacturing method of a glass article includes the process of manufacturing the glass plate GA from the 1st molten glass GM using the manufacturing apparatus 1 which has the said structure. In detail, as shown in FIG. 1, the step of manufacturing the glass plate GA includes: a forming step of forming the glass ribbon GR from the first molten glass GM by using the forming furnace 2; A step of cooling, and a step of cutting the glass ribbon GR that has been cooled (cooled) by the cutting unit 4 in the width direction by a predetermined length. In addition, the ear portion of the glass plate GA may be cut by a subsequent step.

The method for manufacturing a glass article further includes a step of forming a protective glass layer 8 on the furnace inner surface of the furnace wall 5 of the forming furnace 2 of the manufacturing apparatus 1 before the step of manufacturing the glass plate GA.

In the step of forming the protective glass layer 8, as shown in FIG. 2, the second molten glass GMx containing boron oxide is supplied to the forming section 6 and overflows from the overflow groove 6 a of the forming section 6. The second molten glass GMx is the same as in the case of ordinary molding, and is preferably continuously supplied. Thereby, the boron oxide contained in the vapor S vaporized (evaporated) from the second molten glass GMx reacts with the silicon dioxide existing on the inner surface of the furnace by the oxidation of the silicon carbide contained in the furnace wall 5. As a result of the reaction, a protective glass layer 8 is formed on the furnace inner surface of the furnace wall 5. Here, the supply time of the second molten glass GMx varies depending on the content of boron oxide or the supply temperature, and is, for example, 3 to 30 days.

The protective glass layer 8 easily obtains resistance to vapors vaporized from the first molten glass GM, and thus easily maintains oxygen barrier properties. Therefore, oxidation of the silicon carbide contained in the furnace wall 5 is unlikely to occur. This also suppresses the generation of carbonic acid gas from the furnace inner surface of the furnace wall 5, so that it is difficult for the oxide film to be broken due to the bubbles of the carbonic acid gas as a main factor. Therefore, in the obtained glass sheet GA, it is possible to suppress the occurrence of defects having the refractory constituting the furnace wall 5 as a main factor.

Examples of the first molten glass GM and the second molten glass GMx include soda glass, soda-lime glass, borosilicate glass, and aluminosilicate glass. , Alkali glass, alkali free glass, etc. The glass composition of the alkali-free glass includes, for example, mass%, SiO ₂ 50% to 70%, Al ₂ O ₃ 12% to 25%, B ₂ O ₃ 0% to 12%, Li ₂ O + Na ₂ O + K ₂ O (total amount of Li ₂ O, Na ₂ O, and K ₂ O) 0% to less than 1%, MgO 0% to 8%, CaO 0% to 15%, SrO 0% to 12%, BaO 0% to 15%. The glass composition of the alkali-containing glass used as the strengthened glass includes, for example, 50% to 80% of SiO ₂ , 5% to 25% of Al ₂ O ₃ , 0% to 15% of B ₂ O ₃ , and Na _{2 in} terms of mass%. O 1% to 20%, K ₂ O 0% to 10%.

As the first molten glass GM, it is preferable to include SiO ₂ 55% to 70%, Al ₂ O ₃ 10% to 25%, B ₂ O ₃ 0% to 3%, and Li ₂ O + Na _{2 in} terms of mass%. O + K ₂ O (total amount of Li ₂ O, Na ₂ O, and K ₂ O) 0% to less than 1%, MgO 0% to 8%, CaO 2% to 12%, SrO 0% to 8%, BaO 0% ~ 15% high strain point glass. The reason for this is that in the high strain point glass, the content of B ₂ O _{3 is} small, and it is difficult to generate defects with refractory as the main factor. Therefore, the effect of suppressing the occurrence of defects in this embodiment is significant.

From the viewpoint of promoting the formation of the protective glass layer 8, the second molten glass GMx preferably contains a component that reacts with a component of the refractory. For example, the second molten glass GMx preferably contains 5% by mass or more of boron oxide (B ₂ O ₃ ), and more preferably contains 10% by mass or more.

In the step of forming the protective glass layer 8, from the viewpoint of increasing the amount of boron oxide in the vapor S to promote the formation of the protective glass layer 8, it is preferable that the supply temperature T0 of the second molten glass GMx is higher than that of the glass sheet GA. The supply temperature (forming temperature) T1 of the first molten glass GM in the step of. Although it also differs depending on the glass composition, for example, when the supply temperature T1 is 1100 ° C to 1200 ° C, the supply temperature T0 may be set to a temperature higher than 1200 ° C to 1350 ° C. Here, the supply temperature refers to the temperature of the molten glass in the forming section, and in this embodiment, it means the temperature of the molten glass on both side surfaces 6b of the forming section.

Here, in the case of focusing only on the supply temperature T0, from the viewpoint of increasing the amount of boron oxide in the vapor S, the supply temperature T0 is preferably 1200 ° C or higher, more preferably 1250 ° C or higher, and particularly preferably 1300 ° C. the above.

In the step of forming the protective glass layer 8, it is not necessary to shape the second molten glass GMx into a plate shape under the forming portion 6. Therefore, from the viewpoint of increasing the amount of boron oxide vaporized from the second molten glass GMx, it is preferable to maintain the viscosity (for example, 2000 Pa · s or less) to such an extent that the second molten glass GMx cannot be pulled. High temperature. In the example shown in the figure, the second molten glass GMx becomes a drop-shaped glass GD and is dropped (dropped) from the forming portion 6. At this time, it is preferable that the edge roller 7 and / or the annealing roller 10 are retracted from the reference position BP when the glass ribbon is formed by increasing the facing distance between the rollers, so as to prevent the second molten glass falling from the forming portion 6 from adhering. GMx (drop-shaped glass GD). Further, a recovery unit (not shown) such as a cage that collects the dropped second molten glass GMx may be provided in the furnace of the forming furnace 2 or the soaking furnace 3.

The glass composition of the second molten glass GMx used in the step of forming the protective glass layer 8 may be the same as or different from the glass composition of the first molten glass GM used in the step of manufacturing the glass plate GA. When the content of boron oxide in the first molten glass GM is small (for example, when the content of boron oxide is less than 5% by mass), it is preferable that the second molten glass GMx is the same as the first molten glass GM. Different glass composition, so that the content of boron oxide is higher than that of the first molten glass GM. When the glass composition of the second molten glass GMx is different from that of the first molten glass GM, the substrate is replaced after the step of forming the protective glass layer 8.

In addition, the present invention is not limited to the above-mentioned embodiment, nor is it limited to the above-mentioned effects. The present invention can be variously modified without departing from the gist of the present invention.

In the said embodiment, although the case where the 2nd molten glass containing boron oxide was supplied to the shaping | molding part in the process of forming a protective glass layer was described, the method of forming a protective glass layer is not limited to this. For example, the refractory container containing the second molten glass containing boron oxide may be arranged in a furnace of a forming furnace, or a gas containing boron oxide may be directly supplied into the furnace of the forming furnace.

In the embodiment, in the step of forming the protective glass layer, boron oxide vaporized from the second molten glass is reacted with silicon dioxide existing on the inner surface of the wall of the furnace wall of the forming furnace to form the protective glass layer. The case has been described, but the method for forming the protective glass layer is not limited to this. A substance that reacts with silicon dioxide existing on the furnace inner surface of the furnace wall may be an alkali metal oxide (for example, Na ₂ O, K ₂ O, etc.) as long as it has reactivity with silicon dioxide. In this case, in the step of forming the protective glass layer, for example, a molten glass containing 10% by mass of an alkali metal oxide may be supplied.

In the said embodiment, although the case where the furnace wall was a silicon carbide refractory was demonstrated, it can also be a silicon nitride refractory. Alternatively, it may include silicon carbide and / or silicon nitride, and further include other refractory materials.

In the said embodiment, although the case where the process of forming a protective glass layer was implemented separately before the process of manufacturing a glass article was demonstrated, the process of forming a protective glass layer may be implemented simultaneously with the process of manufacturing a glass article. That is, a glass article can also be manufactured while forming a protective glass layer.

Although the case where a glass plate is manufactured as a glass article was demonstrated in the said embodiment, a glass article is not limited to this. The glass article may be, for example, a glass roll or a glass tube in which a glass ribbon is wound into a roll shape. The glass roll is formed by forming the glass ribbon in the forming section in the same manner as the glass plate, and then the glass ribbon conveyed in the longitudinal direction is rolled into a roll shape under the cooling furnace, or the glass ribbon conveyed in the horizontal direction is rolled downstream of the direction changing section It is obtained by winding into a roll. In the case of a glass roll, it is preferred that the ear of the glass ribbon is cut and wound into a roll shape, and the glass ribbon and a protective sheet (such as a resin sheet) are preferably overlapped and rolled together Around. On the other hand, a glass tube is obtained, for example, by manufacturing using a danner method. In the case of a manufacturing apparatus of a glass tube, a molding part is cylindrical, and it is also called a shaping sleeve. The first molten glass was wound while being rotationally driven toward the forming portion, and the first molten glass was formed into a tube shape.

1‧‧‧ Glass manufacturing device

2‧‧‧forming furnace

3‧‧‧Xu Cold Furnace

4‧‧‧ cutting section

5‧‧‧furnace wall

5a‧‧‧Top wall

5b‧‧‧ sidewall

6‧‧‧forming department

6a‧‧‧ overflow tank

6b‧‧‧side

6c‧‧‧ lower end

7‧‧‧Edge roller

8‧‧‧ protective glass layer

9‧‧‧ furnace wall

10‧‧‧annealing roller

11‧‧‧ support roller

12‧‧‧ the first support

13‧‧‧ 2nd support

A‧‧‧arrow

BP‧‧‧reference position

GA‧‧‧ glass plate (glass article)

GD‧‧‧Drop-shaped glass

GM‧‧‧The first molten glass

GMx‧‧‧ 2nd molten glass

GR‧‧‧glass ribbon

GRx‧‧‧ surface

GRy‧‧‧Back

S‧‧‧Steam

S1‧‧‧ scribed

FIG. 1 is a schematic diagram showing the overall configuration of a glass article manufacturing apparatus and the steps of manufacturing the glass article. FIG. 2 is a schematic diagram showing a step of forming a protective glass layer.

Claims (8)

A method for manufacturing a glass article, comprising the steps of forming a first molten glass while forming a first molten glass while forming a portion surrounded by a furnace wall of a forming furnace, comprising: a furnace in the furnace wall; A step of forming a protective glass layer on the inner surface. The method for manufacturing a glass article according to item 1 of the scope of patent application, wherein the step of forming a protective glass layer is performed separately before the step of manufacturing the glass article. The method for manufacturing a glass article according to item 1 or item 2 of the scope of application for a patent, wherein the furnace wall comprises a silicon carbide or silicon nitride refractory, and in the step of forming a protective glass layer, The furnace of the forming furnace is supplied with vaporized boron oxide. The method for manufacturing a glass article according to item 3 of the scope of patent application, wherein in the step of forming a protective glass layer, a second molten glass containing boron oxide is supplied to the forming section, and boron oxide is allowed to pass through. The second molten glass is vaporized. The method for manufacturing a glass article according to item 4 of the scope of patent application, wherein the supply temperature of the second molten glass is higher than the supply temperature of the first molten glass. The method for manufacturing a glass article according to item 4 or item 5 of the scope of patent application, wherein the content of boron oxide in the second molten glass is greater than the content of boron oxide in the first molten glass. A manufacturing apparatus for a glass article includes a forming furnace having a furnace wall and a forming section surrounded by the furnace wall, and characterized in that a protective glass layer is included on a surface of the furnace inner side of the furnace wall. The device for manufacturing a glass article according to item 7 of the scope of the patent application, wherein the furnace wall includes silicon carbide or silicon nitride refractory, and the protective glass layer contains boron oxide.