HK1175770B

HK1175770B - Consecutive molding method for crystallized glass and device thereof

Info

Publication number: HK1175770B
Application number: HK13102676.2A
Authority: HK
Inventors: 许国铨; 姜岩浜; 曲超
Original assignee: 湖州大享玻璃制品有限公司; 大享容器工业股份有限公司
Priority date: 2011-05-16
Filing date: 2013-03-04
Publication date: 2016-02-12

Description

Method and apparatus for continuously forming crystallized glass

Technical Field

The present invention relates to a method for continuously forming crystallized glass and an apparatus for continuously forming crystallized glass.

Background

In general, crystallized glass is obtained by melting a glass raw material containing a crystal nucleus-forming component, forming the molten glass into a plate-like shape to obtain a crystalline glass, and applying a crystallization heat treatment to the crystalline glass. To date, a manufacturing method and a manufacturing apparatus have been developed to improve the producibility of crystallized glass. For example, a continuous forming apparatus for crystallized glass is disclosed (for example, see japanese patent laid-open publication No. 2005-41726), which can continuously perform a series of steps from melting, forming, crystallizing, annealing, and cutting of a glass raw material.

In a method for manufacturing crystallized glass by continuously melting, forming, crystallizing, annealing, and cutting a glass raw material, a crystallization step is a rate determining step. The reason for this is that: the heat treatment for crystallization requires a multistage temperature treatment that does not affect the glass sheet by a rapid temperature change in order to suppress the occurrence of waviness, deformation, cracking, and cracking in the glass sheet.

For example, in a continuous forming apparatus described in japanese patent application laid-open No. 2005-41726, the crystallization apparatus includes: a heat-insulating region for holding the belt-like plate glass at a temperature near a glass transition temperature; in the 1 st heating area, the temperature of the strip plate glass is raised to the nucleation temperature; a nucleus formation region in which the band-shaped plate glass is kept at a nucleus formation temperature; a2 nd heating area for heating the strip plate glass to the crystal growth temperature; a crystal growth region for holding the belt-shaped plate glass at a crystal growth temperature; and an annealing zone for removing the deformation of the belt-shaped crystallized glass plate.

Disclosure of Invention

In the continuous forming method of crystallized glass, if the heat treatment step for crystallization can be improved, the heat treatment time required for crystallization is shortened, and the production speed is increased. On the other hand, the production speed is increased, and it is also necessary to suppress the occurrence of waviness, deformation, cracking, and cracks in the glass sheet.

The invention provides a method for continuously forming crystallized glass, which can shorten the heat treatment time required for crystallizing a strip glass plate and can inhibit the generation of ripples, deformation, cracks and cracks in the crystallized glass.

Further, an object of the present invention is to provide a continuous forming apparatus for crystallized glass, which can shorten a heat treatment region required for crystallization of a ribbon-shaped plate glass and can suppress generation of waviness, deformation, breakage, and cracks in the crystallized glass.

The inventor finds that: a method for continuously forming crystallized glass, comprising subjecting a strip-shaped plate glass obtained by roll forming to a rolling forming without: a heat treatment step of maintaining the temperature at about the glass transition temperature; and a heat treatment step of maintaining the temperature at a crystal nucleus formation temperature, wherein the temperature is raised to a temperature higher than the crystal growth temperature while the crystal nucleus formation temperature is being input, and the crystallized glass can be continuously formed.

Specific means for solving the foregoing problems are as follows.

The present invention provides a method for continuously forming crystallized glass, comprising:

a melting step of melting a glass raw material to obtain molten glass;

a forming step of rolling and forming the molten glass into a belt shape to obtain belt-shaped plate glass;

a crystallization step of heat-treating the belt-shaped plate glass to crystallize the plate glass to obtain a belt-shaped crystallized glass plate; and

a cutting step of cutting the belt-shaped crystallized glass plate;

and the crystallization step has:

a temperature raising step of raising the temperature of the ribbon-shaped plate glass obtained in the forming step to a temperature higher than a crystal nucleus formation temperature in an atmosphere at which crystal nuclei are formed and at which crystals are grown to form a ribbon-shaped crystallized glass plate; and

and a slow cooling step of gradually cooling the belt-shaped crystallized glass plate.

Preferably, in the above method, the crystallization step further includes, between the temperature raising step and the slow cooling step:

and a heat-retaining step of retaining the ribbon-shaped crystallized glass plate at a temperature not lower than the crystal growth temperature.

Preferably, in the above method, between the melting step and the forming step, the continuous forming method further includes:

an adjustment step of adjusting the uniformity, viscosity, and liquid level of the molten glass obtained by the melting step; and

and a devitrification prevention step of preventing devitrification of the molten glass after the adjustment step.

The present invention also provides a continuous forming apparatus for crystallized glass, comprising:

a melting device that melts a glass raw material to obtain molten glass;

a forming device for rolling and forming the molten glass into a belt shape to obtain belt-shaped plate glass;

a crystallization device for obtaining a belt-shaped crystallized glass plate by heat-treating the belt-shaped plate glass and crystallizing the belt-shaped plate glass; and

a cutting device for cutting the belt-shaped crystallized glass plate;

and the crystallization apparatus has:

a temperature raising section for holding the ribbon-shaped glass sheet obtained by the forming apparatus in an environment at a crystal nucleus formation temperature and raising the temperature to a temperature higher than or equal to a crystal growth temperature to form crystal nuclei and grow crystals at the same time to form a ribbon-shaped crystallized glass sheet; and

and a slow cooling region for gradually cooling the belt-shaped crystallized glass plate.

Preferably, in the above apparatus, the crystallization apparatus further includes, between the heating region and the slow cooling region:

a heat-retaining region for retaining the belt-shaped crystallized glass plate at a temperature higher than the crystal growth temperature.

Preferably, in the above apparatus, between the melting apparatus and the forming apparatus, the continuous forming apparatus further includes:

an adjusting device for adjusting the uniformity, viscosity and liquid level of the molten glass obtained by the melting device; and

and the devitrification-resistant equipment is used for preventing the molten glass passing through the adjusting equipment from devitrifying.

According to the present invention, there can be provided a method for continuously forming crystallized glass, which can reduce the heat treatment time required for crystallization of a ribbon-shaped plate glass and can suppress the occurrence of waviness, deformation, breakage, and cracks in the crystallized glass.

Further, according to the present invention, it is possible to provide a continuous forming apparatus for crystallized glass, which can shorten the heat treatment area required for glass crystallization of a ribbon plate and can suppress the occurrence of waviness, deformation, breakage, and cracks in the crystallized glass.

Drawings

FIG. 1 is a schematic view showing an embodiment of an apparatus for continuously forming crystallized glass according to the present invention.

FIG. 2A and FIG. 2B are graphs showing the gradient of the ambient temperature in the crystallization apparatus in each of the embodiments of the continuous forming apparatus for crystallized glass of the present invention.

FIG. 3 is a schematic view showing another embodiment of the continuous forming apparatus for crystallized glass according to the present invention.

FIG. 4A and FIG. 4B are graphs showing the gradient of the ambient temperature in the crystallization apparatus in each of the other embodiments of the continuous forming apparatus for crystallized glass of the present invention.

[ description of element symbols ]

10. Continuous forming equipment for 50 crystallized glass

11. 51 melting device

12. 52 adjustment device

12a, 52a liquid level control apparatus

12b, 52b stirring device (stirring rod)

12c, 52c heating element

12d, 52d thermocouple

13. 53 anti-devitrification device

13a, 53a heat preservation equipment (heat preservation refractory)

13b, 53b lip brick

13c, 53c Stent

13d, 53d heating element

14. 54 roll forming equipment

14a, 54a upper side roller shaft

14b, 54b lower side roller shaft

14c, 54c cooling water tank

15. 55 handling equipment

16. 56 pressing roll shaft

17. 57 crystallizing equipment (roller type tunnel kiln)

18. 58 heating element

19. 59 conveying roller shaft

20. 60 thermocouple

24. 64 heating area

65 heat-insulating region

26. 66 slow cooling area

27. 67 cutting device

28. 68 stirring device

A belt-shaped plate glass

B belt-shaped crystallized glass plate

C-cut crystallized glass plate

Detailed Description

The present invention relating to a first aspect is a method for continuously forming crystallized glass, including:

a melting step of melting a glass raw material to obtain molten glass;

a cutting step of cutting the belt-shaped crystallized glass plate;

and the crystallization step has:

The method for continuously forming crystallized glass of the present invention can continuously perform a series of steps from melting, forming, crystallizing, annealing, and cutting of a glass raw material by sequentially performing the melting step, the forming step, the crystallizing step, and the cutting step.

The melting step is as follows: and a step of obtaining molten glass by melting the glass raw material by heating. The heating temperature is not particularly limited as long as the glass raw material is melted. The melting step may comprise: in the process of preparing the glass raw material before melting the glass raw material, it is preferable to continuously prepare the glass raw material until the glass raw material is melted from the viewpoint of productivity.

The forming steps are as follows: and a step of rolling and forming the molten glass into a belt shape to obtain a belt-shaped plate glass. The roll forming method may be a known method, and for example, a roll forming method of rolling a molten glass by a pair of rolls may be used.

The crystallization step is as follows: and a step of obtaining a belt-shaped crystallized glass plate by heat-treating the belt-shaped plate glass and crystallizing the glass. The crystallization step will be described in detail below.

The cutting-off step is as follows: and a step of cutting the belt-shaped crystallized glass plate into a desired length. The cutting method may be a known method, and for example, a cutting method using a diamond cutter or a cutting method using a water jet cutter may be used.

The crystallization step comprises: a temperature raising step of raising the temperature of the ribbon-shaped plate glass obtained in the forming step to a temperature higher than a crystal nucleus formation temperature in an atmosphere at which crystal nuclei are formed and at which crystals are grown to form a ribbon-shaped crystallized glass plate; and a slow cooling step of gradually cooling the belt-shaped crystallized glass plate.

In the temperature raising step, the temperature of the environment around the belt-shaped plate glass may be raised from the crystal nucleus formation temperature to the crystal growth temperature or higher in order to raise the temperature of the belt-shaped plate glass. In the slow cooling step, the ambient temperature around the belt-shaped crystallized glass plate may be gradually lowered to gradually cool the belt-shaped crystallized glass plate.

The crystallization step is a heat treatment process for crystallizing the band plate glass, and is started by putting the band plate glass into an environment at a crystal nucleus formation temperature. That is, the present invention does not include a heat treatment step of maintaining the temperature near the glass transition temperature, which is included in the known continuous forming method. In the present invention, the vicinity of the glass transition temperature means a range within. + -. 10 ℃ of the glass transition temperature.

The temperature rising step is as follows: and a step of directly putting the ribbon-shaped plate glass obtained in the forming step into an environment at a crystal nucleus formation temperature and raising the temperature of the ribbon-shaped plate glass to a temperature higher than a crystal growth temperature. The temperature raising step is a step of raising the temperature of the belt-shaped plate glass to form crystal nuclei and grow crystals. The temperature of the belt-shaped plate glass put into the environment of the nucleation temperature is continuously raised to a temperature higher than the crystal growth temperature, and nucleation and crystal growth are performed.

The temperature raising step may be performed such that, in the ribbon glass, nucleation occurs first and then crystal growth occurs as the temperature is raised. The temperature raising step may be performed simultaneously with the formation of crystal nuclei and the growth of crystals in the ribbon glass. In the temperature raising step, nucleation and crystal growth may occur sequentially or simultaneously.

The temperature for forming the crystal nuclei may be any temperature at which the crystal nuclei can be formed. The nucleation temperature is suitably selected in accordance with the glass composition.

The nucleation temperature is preferably set to a nucleation temperature in a conventional crystallized glass production method or a temperature in the vicinity thereof. The nucleation temperature is usually 600-1000 ℃, and the ideal state is 650-900 ℃, and the more ideal state is 700-850 ℃. The nucleation temperature is preferably a substantially constant temperature.

The crystal growth temperature is not particularly limited, and depends on the glass composition of the ribbon glass. The crystal growth temperature is preferably set to the crystal growth temperature in the known crystallized glass production method or to the vicinity thereof. The crystal growth temperature is usually 50 ℃ to 400 ℃ higher than the nucleation temperature. The crystal growth temperature is, specifically, 750 ℃ to 1100 ℃ in a more ideal state, and 800 ℃ to 1000 ℃ in a more ideal state. The growth temperature of the crystal is 850-1000 ℃ when the beta-quartz solid solution or the beta-spodumene is separated out from the strip plate glass.

In the temperature raising step, the temperature to be reached by the temperature raising is not particularly limited as long as it is not lower than the crystal growth temperature. From the viewpoint of production efficiency, it is preferable that the reaching temperature is the crystal growth temperature. From the viewpoint of promoting crystal growth, the reaching temperature is preferably higher than the crystal growth temperature, and a temperature exceeding 880 ℃ is generally preferable depending on the glass composition. The temperature of the arrival temperature is preferably about 10 to 30 ℃ higher than the crystal growth temperature.

In this temperature raising step, the temperature gradient of the temperature raising is not particularly limited. The temperature gradient of the temperature rise is a condition selected in accordance with the glass composition or thickness of the ribbon glass, under which nucleation and crystal growth can be sufficiently performed.

The temperature rise rate can be set to, for example, 1 ℃/min to 20 ℃/min. When the beta-quartz solid solution or the beta-spodumene is precipitated from the strip plate glass, the temperature is raised at a heating rate of 1-10 ℃/min.

The lower the temperature rise rate, the less likely waviness, deformation, cracking, and cracking occur in the ribbon-shaped plate glass, but from the viewpoint of the production rate, the higher the temperature rise rate is, the more preferable.

The time required for the temperature raising step is preferably 0.5 hours or more from the viewpoint of sufficiently advancing the crystal nucleus formation and crystal growth to increase the degree of crystallization, and preferably 1 hour or less from the viewpoint of improving the production efficiency.

In the temperature raising step, the formation of crystal nuclei can be facilitated by adding a nucleus-forming component such as TiO2, ZrO2, P2O5, F2, or the like to the glass raw material in advance.

The slow cooling step comprises the following steps: and gradually cooling the belt-shaped crystallized glass plate to remove the permanent strain from the belt-shaped crystallized glass plate and simultaneously form the homogenized glass. In the present invention, slow cooling means cooling at a cooling rate capable of eliminating the degree of deformation. In the slow cooling step, the temperature gradient of cooling is not particularly limited and is selected in accordance with the glass composition or size of the ribbon glass sheet. For example, the cooling is preferably performed at a cooling rate of 1 to 40 ℃/min. Of course, the slower the cooling rate, the less permanent deformation.

The crystallization step, preferably between the temperature increasing step and the slow cooling step, further comprises: and a heat-retaining step of retaining the belt-shaped crystallized glass plate at a temperature higher than the crystal growth temperature for a predetermined period of time. By including the heat-retaining step, crystal nucleus formation and crystal growth (particularly crystal growth) can be further performed, and crystallized glass having a high degree of crystallization can be obtained.

The holding temperature in the heat-keeping step may be a temperature higher than the crystal growth temperature. When the temperature reached in the temperature raising step is the crystal growth temperature, the holding temperature in the temperature maintaining step may be the temperature reached in the temperature raising step. When the temperature reached in the temperature raising step exceeds the crystal growth temperature, the holding temperature in the temperature maintaining step may be higher than the crystal growth temperature and lower than the temperature reached in the temperature raising step.

The temperature at the heat-retaining step is preferably maintained at a temperature almost constant (less than. + -. 5 ℃ C.).

The holding time in the heat-retaining step is not particularly limited, and conditions for sufficiently growing crystals can be appropriately selected. The holding time of the heat-preserving step is preferably 10 minutes to 3 hours.

The present invention is not limited to the heat treatment step in which the conventional crystallized glass continuous forming method is considered to require the ribbon-shaped plate glass to be kept at a temperature near the glass transition temperature, but the ribbon-shaped plate glass obtained by the roll forming is directly put at the crystal nucleus formation temperature, and the temperature is raised to the crystal growth temperature or higher without the heat treatment step in which the ribbon-shaped plate glass is kept at the crystal nucleus formation temperature. Therefore, the entire treatment time of the crystallization step can be shortened, and the time of the temperature raising step and the slow cooling step can be lengthened without lengthening the entire treatment time of the crystallization step. When the temperature raising step time is made longer, the temperature gradient of the temperature raising can be made gentle, and therefore, waviness, deformation, breakage, and cracks are less likely to occur in the ribbon-shaped sheet glass. Further, when the slow cooling step time is made longer, the temperature gradient of the slow cooling can be made gentle, and the temperature gradient of the slow cooling can be made into a plurality of stages, so that the deformation of the ribbon-shaped crystallized glass plate formed by crystallization can be effectively removed. As a result, the crystallized glass obtained by the present invention was excellent in flatness, impact strength and the like.

The present invention can suppress the occurrence of waviness, deformation, cracking, and cracks in a ribbon-shaped crystallized glass plate by changing the heat treatment required for crystallization to the temperature raising step. The mechanism is not limited to a specific theory, but is inferred as follows.

The crystalline glass generally expands at elevated temperatures and contracts during nucleation and crystal growth. Therefore, when the heat treatment for raising the temperature, the heat treatment for crystal nucleus formation, the heat treatment for raising the temperature in the next stage, and the heat treatment for crystal growth are sequentially performed in the heat treatment step for crystallization, the expanded portion and the contracted portion coexist in the continuous piece of belt-shaped plate glass in the heat treatment step for crystallization so as to be adjacent to each other. When a heat treatment time required for crystallization cannot be sufficiently secured in a continuous piece of belt-shaped plate glass, the expanded portion and the contracted portion of the belt-shaped crystallized glass plate may be adjacent to each other and may cause waviness, deformation, breakage, and cracking in the belt-shaped crystallized glass plate.

In the present invention, since the heat treatment step required for crystallization is the temperature raising step, the temperature shift in the heat treatment step required for crystallization is continuous, and the formation of crystal nuclei and the crystal growth in the ribbon-shaped plate glass proceed continuously or simultaneously. Therefore, we conclude that: in a continuous piece of strip-shaped plate glass, the expansion part and the contraction part do not mutually abut and coexist, so that the occurrence of waviness, deformation, breakage, and cracks in the strip-shaped crystallized glass plate can be suppressed.

The method for continuously forming crystallized glass of the present invention is preferably as follows: between the melting step and the forming step, further comprising:

an adjustment step of adjusting the uniformity, viscosity and liquid level of the molten glass obtained by the melting step; and

The present invention homogenizes the molten glass by including the adjusting step and the devitrification prevention step, controls the viscosity of the molten glass, prevents devitrification of the molten glass, and can supply the molten glass to the forming step at a constant flow rate.

The adjusting step is composed of stirring the molten glass to be uniform, heating the molten glass to control viscosity, and controlling the liquid level of the molten glass. Controlling the liquid level of the molten glass according to: the liquid level of the molten glass introduced from the melting step to the adjusting step is detected, and a signal corresponding to the amount of change in the liquid level is fed back to a glass raw material charging facility into which the glass raw material is charged, and the amount of the raw material charged into the melting facility is corrected.

The anti-devitrification step is preferably carried out in the following manner: comprises heat-insulating molten glass and heat-melting glass. The molten glass before the introduction into the forming step is kept at a predetermined temperature by heat-insulating and heating, thereby preventing devitrification of the molten glass.

The crystallized glass plate obtained through the above-described steps may be subjected to a polishing step of polishing the surface for adjusting the thickness, surface finishing, or the like, or a processing step of processing the crystallized glass plate into a predetermined size or shape, as required.

The method for continuously forming crystallized glass of the present invention is suitable for the apparatus for continuously forming crystallized glass of the present invention described below.

The present invention relating to a second aspect is a crystallized glass continuous forming apparatus, comprising:

a melting device that melts a glass raw material to obtain molten glass;

a cutting device for cutting the belt-shaped crystallized glass plate;

and the crystallization apparatus has:

a temperature raising region for holding the ribbon-shaped glass plate obtained by the forming apparatus in an environment at a crystal nucleus formation temperature and raising the temperature to a temperature higher than a crystal growth temperature to form crystal nuclei and grow crystals at the same time to form a ribbon-shaped crystallized glass plate; and

The continuous forming apparatus for crystallized glass of the present invention comprises the melting apparatus, the forming apparatus, the crystallizing apparatus, and the cutting apparatus in this order, and thus a series of steps from melting, forming, crystallizing, annealing, and cutting of a glass raw material can be continuously performed.

The melting equipment is as follows: an apparatus for obtaining molten glass by heating and melting glass raw materials. The melting apparatus may be constituted by a furnace having a heating mechanism necessary for melting the glass raw material, and various known glass melting furnaces may be used. The melting apparatus may include a preparation mechanism for preparing the glass raw material before the heating mechanism necessary for melting the glass raw material.

The forming equipment comprises: and rolling the molten glass into a belt shape to obtain belt-shaped plate glass. The rolling method in the forming apparatus is not particularly limited, and may be, for example, a roll forming method in which rolling is performed by a pair of rolls.

The crystallization equipment comprises: and a device for obtaining a belt-shaped crystallized glass plate by heat-treating the belt-shaped plate glass and crystallizing the glass. The crystallization apparatus will be described in detail below.

The cutting equipment comprises: an apparatus for cutting a belt-shaped crystallized glass plate into a predetermined length. In this cutting apparatus, the cutting method may be a known method, and may be, for example, cutting with a diamond cutter or cutting with a water jet cutter.

The crystallization apparatus comprises:

The crystallization equipment comprises: the temperature raising region is provided at the most upstream side in the direction in which the belt-shaped sheet glass is conveyed, and the heat treatment region held at the glass transition temperature and the heat treatment region held at the crystal nucleus formation temperature, which are provided in the known continuous forming apparatus, are not provided.

The temperature raising region is a region in which the ribbon-shaped plate glass obtained by the forming apparatus is accommodated in an environment at a crystal nucleus formation temperature and the ribbon-shaped plate glass is raised to a temperature higher than or equal to a crystal growth temperature. The temperature rise region is a region in which crystals grow while crystal nuclei are formed by raising the temperature of the belt-shaped plate glass. The temperature of the belt-shaped plate glass accommodated in the temperature raising region is continuously raised to a temperature higher than the crystal growth temperature while the belt-shaped plate glass passes through the temperature raising region, and nucleation and crystal growth are performed.

The nucleation temperature may be any temperature capable of forming crystal nuclei, and is preferably set to the nucleation temperature in the known crystallized glass production method or a temperature in the vicinity thereof. The nucleation temperature is usually 600-1000 ℃, the ideal sample state is 650-900 ℃, and the more ideal sample state is 700-850 ℃.

The crystal growth temperature is not particularly limited, and varies depending on the glass composition of the ribbon glass. The crystal growth temperature is preferably set to a temperature at or near the crystal growth temperature in the known crystallized glass production method. The crystal growth temperature is usually 50 ℃ to 400 ℃ higher than the nucleation temperature. The crystal growth temperature is, specifically, 750 ℃ to 1100 ℃ in a more ideal state, and 800 ℃ to 1000 ℃ in a more ideal state.

In the temperature raising region, the temperature of the most downstream portion (outlet portion) in the direction in which the belt-shaped sheet glass is conveyed may be equal to or higher than the crystal growth temperature, and the upper limit is not particularly limited. From the viewpoint of production efficiency, the temperature of the most downstream portion is preferably the crystal growth temperature. From the viewpoint of promoting crystal growth, the temperature of the most downstream portion is preferably a temperature exceeding the crystal growth temperature, and a temperature exceeding 880 ℃ is generally preferable in terms of the glass composition. The temperature of the most downstream part is preferably about 10 to 30 ℃ higher than the crystal growth temperature.

In the temperature raising region, a temperature gradient is provided, and the temperature of the belt-like plate glass is preferably raised gradually as it is conveyed toward the outlet of the crystallization apparatus. In the heating region, the temperature gradient in the region is not particularly limited. The temperature gradient of the temperature rise is a condition selected in accordance with the glass composition or thickness of the ribbon glass, under which nucleation and crystal growth can be sufficiently performed. The temperature gradient becomes gradually lower, and the occurrence of waviness, deformation, cracking, and cracks in the ribbon-shaped plate glass becomes less likely, but from the viewpoint of the production speed, the temperature gradient is preferably steeper.

The length of the temperature raising region and the speed of conveying the belt-shaped sheet glass in the temperature raising region are not particularly limited, and conditions under which crystal nuclei are sufficiently formed and crystals are sufficiently grown may be appropriately selected.

The speed of conveyance of the strip-shaped plate glass in the heating zone may be appropriately selected in accordance with the throughput of the melting apparatus and/or the forming apparatus. Further, when the conveyance speed of the belt-shaped sheet glass in the temperature raising region is slow, the length of the temperature raising region can be shortened in accordance with the conveyance speed, and when the conveyance speed of the belt-shaped sheet glass in the temperature raising region is fast, the length of the temperature raising region can be lengthened in accordance with the conveyance speed.

The slow cooling area is as follows: in order to remove permanent strain from the belt-shaped crystallized glass plate and form a uniform glass, the area of the belt-shaped crystallized glass plate is gradually cooled. In the slow cooling region, the temperature gradient in the region is not particularly limited and is selected in accordance with the glass composition or the size of the ribbon glass. Of course, the slower the temperature gradient, the less permanent deformation.

The crystallization equipment, the more ideal appearance is between the heating area and the slow cooling area, and more has: a heat-retaining region for retaining the belt-shaped crystallized glass plate at a temperature higher than the crystal growth temperature for a predetermined time. By providing the heat retaining region, nucleation and crystal growth (particularly crystal growth) can be further performed, and crystallized glass having a high degree of crystallization can be obtained.

The ambient temperature of the soaking region may be a temperature higher than the crystal growth temperature. When the temperature of the most downstream portion (outlet portion) of the temperature-increasing region is the crystal growth temperature, the ambient temperature of the heat-retaining region may be the temperature of the most downstream portion of the temperature-increasing region. When the temperature of the most downstream part of the temperature-raising region exceeds the crystal growth temperature, the ambient temperature of the heat-preserving region may be higher than the crystal growth temperature and lower than the temperature of the most downstream part of the temperature-raising region.

The temperature of the heat-retaining area is preferably kept almost constant (less than + -5 ℃).

The length of the heat-retaining region and the speed of conveying the belt-shaped glass sheet in the heat-retaining region are not particularly limited, and the conditions for crystal growth can be appropriately selected.

Further, the speed of conveying the belt-like sheet glass in the holding region can be appropriately selected in accordance with the throughput of the melting apparatus or/and the forming apparatus. Further, when the conveyance speed of the belt-shaped plate glass in the heat-retaining region is slow, the length of the heat-retaining region can be shortened in accordance with the conveyance speed, and when the conveyance speed of the belt-shaped plate glass in the heat-retaining region is fast, the length of the heat-retaining region can be lengthened in accordance with the conveyance speed.

The present invention does not have a heat treatment region where it is considered necessary to maintain a ribbon-shaped plate glass at a temperature near the glass transition temperature and a heat treatment region where the ribbon-shaped plate glass is maintained at the crystal nucleus formation temperature in the known crystallized glass continuous forming apparatus, and the ribbon-shaped plate glass drawn out from the forming apparatus is directly stored at the crystal nucleus formation temperature and heated to a temperature higher than or equal to the crystal growth temperature. Therefore, the entire length of the crystallization apparatus can be shortened, and the heating region and the slow cooling region can be lengthened without lengthening the entire length of the crystallization apparatus. When the temperature rise region is made longer, the temperature gradient of the temperature rise can be made gentle, and therefore, waviness, deformation, cracking, and cracks are less likely to occur in the belt-shaped plate glass. Further, when the slow cooling region is made longer, the temperature gradient of the slow cooling can be made gentle, and the temperature gradient of the slow cooling can be made into a plurality of stages, so that the deformation of the crystallized glass sheet in the form of a ribbon can be effectively removed. As a result, the crystallized glass obtained by the present invention has excellent impact strength.

The present invention can suppress the occurrence of waviness, deformation, cracking, and cracks in a ribbon-shaped crystallized glass plate by changing a heat treatment region required for crystallization to the temperature increase region. Although the mechanism is not bound to a specific theory, we conclude that the mechanism is as follows.

The heat treatment region required for crystallization is provided with: in the case of a heat treatment region required for temperature rise, a heat treatment region required for nucleation, a heat treatment region required for temperature rise in the next stage, and a heat treatment region required for crystal growth, an expanded portion and a contracted portion coexist so as to be adjacent to each other in a continuous piece of band-shaped plate glass in the heat treatment region required for crystallization. When a heat treatment time required for crystallization cannot be sufficiently secured in a continuous piece of strip-shaped plate glass, waviness, deformation, cracking, and cracking may occur in the strip-shaped crystallized glass plate when the expanded portion and the contracted portion thereof are adjacent to each other and coexist.

In the present invention, since the heat treatment region required for crystallization is the temperature raising region, the temperature distribution in the heat treatment region required for crystallization is continuous, and the formation of crystal nuclei and the crystal growth in the ribbon-shaped plate glass proceed continuously or simultaneously. Therefore, we conclude that: the expansion portion and the contraction portion of a continuous piece of strip-shaped plate glass do not mutually abut and coexist, and the occurrence of waviness, deformation, breakage, and cracks in the strip-shaped crystallized glass plate can be suppressed.

The continuous forming apparatus for crystallized glass according to the present invention preferably has, between the melting apparatus and the forming apparatus, the following:

and a devitrification resistance device for preventing devitrification of the molten glass after passing through the regulating device.

The invention homogenizes the molten glass by the adjusting device and the devitrification prevention device, controls the viscosity of the molten glass, prevents the molten glass from devitrification, and can supply the molten glass to the forming device at a predetermined flow rate.

The adjusting means is composed of a homogenizing means for homogenizing the molten glass, a viscosity control means for controlling the viscosity of the molten glass, and a liquid level control means for controlling the liquid level of the molten glass. The homogenizing apparatus is provided with a device for stirring molten glass. The viscosity control device is provided with a heating device for heating the molten glass. The liquid level control means detects the liquid level of the molten glass introduced from the melting means to the adjusting means, and feeds back a signal corresponding to the amount of change in the liquid level to glass raw material charging means into which the glass raw material is charged, thereby correcting the amount of raw material charged into the melting means. Since the liquid level control means can measure the height of the liquid level of the molten glass passing through the adjusting means and correct the amount of the raw material to be charged, the thickness of the strip-shaped sheet glass formed by the forming means can be controlled to a predetermined thickness. Therefore, the crystallized glass can be automatically manufactured in a large scale, and the stabilization of the quality can be planned, and the program management can be easily performed.

The anti-devitrification device has the ideal mode that: comprises a heat-insulating means for insulating molten glass and a heating means for heating the molten glass. The molten glass before being introduced into the forming apparatus is maintained at a predetermined temperature by the heat-insulating means and the heating by the heating means, thereby preventing devitrification of the molten glass.

The continuous forming apparatus for crystallized glass of the present invention is preferably as follows: between the forming apparatus and the crystallizing apparatus, there is further provided a pressing roller for pressing the belt-like plate glass output from the forming apparatus. The surface of the belt-like sheet glass discharged from the forming apparatus is formed into a flat roll surface by the press roll. By providing the press roll shaft, the belt-shaped plate glass formed by the forming apparatus can be flattened and introduced into the crystallizing apparatus.

The continuous forming equipment for crystallized glass of the present invention is an ideal crystallized glass manufacturing equipment widely used for manufacturing crystallized glass such as substrates for high-tech products such as substrates for color filters, substrates for image sensing, etc., brackets for electronic component firing, electromagnetic oven panels, optical components, microwave oven frames, window glass for fire doors, front glass for petroleum stoves, wood stoves, and materials for buildings, and the continuous forming processing is started from glass raw materials.

The embodiment of the continuous forming apparatus for crystallized glass according to the present invention will be described below with reference to the drawings. However, the present invention is not limited to this embodiment.

Fig. 1 is a schematic view showing an example of the continuous forming apparatus for crystallized glass according to the present invention.

A crystallized glass continuous forming apparatus 10 (hereinafter referred to as "continuous forming apparatus 10") includes: a melting apparatus 11, an adjusting apparatus 12, a devitrification prevention apparatus 13, a roll forming apparatus 14, a crystallization apparatus 17 (a roll tunnel kiln 17), and a cutting apparatus 27.

The melting apparatus 11 is an apparatus for melting a glass raw material into a molten glass, and may be a batch furnace having functions of melting, refining, homogenizing, etc. of a glass raw material, or a connection furnace of a type in which the above-described functions are connected as a unit.

The molten glass obtained in the melting apparatus 11 is conveyed to an adjusting apparatus 12 disposed downstream in the conveying direction. The adjusting device 12 is a device for adjusting the uniformity, viscosity and liquid level of the molten glass. The adjustment device 12 is provided with a liquid level control device 12a, a stirring device 12b (stirring rod 12 b), a heating element 12c, and a thermocouple 12 d.

The liquid level control means 12a detects the liquid level of the molten glass, and feeds back a signal corresponding to the amount of change in the liquid level to glass raw material charging means (not shown) for charging the glass raw material into the melting means 11, thereby correcting the amount of charged raw material. As mentioned above, the liquid level in the regulating device 12 is adjusted to a predetermined value.

The stirring device 12b stirs the molten glass to homogenize it.

The heating element 12c heats the molten glass. The temperature of the molten glass is adjusted by the heating element 12c and the thermocouple 12d, and the viscosity of the molten glass is adjusted to a predetermined value.

The molten glass flowing out of the self-regulating apparatus 12 flows into the devitrification prevention apparatus 13 disposed downstream in the conveying direction. The devitrification prevention device 13 is provided with a heat insulating device 13a (heat insulating refractory 13 a), a lip brick 13b, and a bracket 13 c. The holding device 13a holds the molten glass at a predetermined temperature. The lip 13b guides the molten glass to the roll forming device 14. The bracket 13c is a supporter supporting the lip tile 13 b. Further, although not necessarily required, a heating element 13d may be provided in the devitrification prevention apparatus 13. The heating element 13d is a heating device disposed through the bracket 13c, and the bracket 13c and the lip 13b are heated by the heating element 13 d.

The devitrification prevention means 13 keeps the temperature of the molten glass at a predetermined level before the molten glass is introduced into the roll forming means 14 by keeping the temperature by the heat keeping means 13a, thereby preventing devitrification of the molten glass. When the heating element 13d is provided in the devitrification prevention device 13, the molten glass can be prevented from devitrification by heating with the heating element 13 d.

The molten glass flowing out of the self-regulating device 12 and passing through the devitrification prevention device 13 is supplied to a roll forming device 14 disposed downstream in the conveying direction. The roll forming device 14 roll-forms the molten glass into a belt-shaped sheet glass. The roll forming apparatus 14 is provided with an upper roller 14a, a lower roller 14b, and a cooling water tank 14 c. The rollers constituting the upper roller 14a and the lower roller 14b may be commercially available ones, and are made of a material having excellent heat resistance, thermal shock resistance, high-temperature strength, and thermal crack resistance.

The upper roll shaft 14a and the lower roll shaft 14b are arranged to face each other, and the molten glass supplied between the pair of roll shafts is formed into a belt shape by roll forming. The cooling water tank 14c continuously supplies water to the inside thereof for cooling the molten glass, cools the glass that is rolled and formed into a belt shape, and maintains the belt shape.

The glass rolled and formed into a ribbon shape by the roll forming device 14 is carried by a carrying device 15 disposed downstream in the carrying direction. The conveyance means 15 is composed of a plurality of rollers arranged in a row and conveys the rolled sheet glass. The conveyance means 15 may be constituted by a mechanism capable of conveying the belt-like plate glass, such as a heat-resistant belt, in addition to the roller shaft.

A pressing roller 16 for pressing the belt-shaped sheet glass roll-formed by the roll forming device 14 is provided on the upper side of the upstream side in the conveying direction of the conveying device 15. The press roll shaft 16 is made of steel having excellent heat resistance, and is composed of 1 to several roll shafts. After the roll forming device 14 roll-forms the glass into a belt shape, a flat belt-shaped sheet glass a is formed by pressing by the press roll shaft 16. The pressing roller 16 is not necessarily required and may be omitted depending on the surface properties of the belt-shaped sheet glass roll-formed by the roll forming device 14.

The belt-like plate glass A is conveyed by the conveying means 15 and introduced into the crystallizing means 17. The crystallization device 17 is composed of the following regions in order from the upstream in the conveying direction: a temperature raising region 24 for accommodating the belt-shaped plate glass A and raising the temperature to a temperature higher than the crystal growth temperature to form a belt-shaped crystallized glass plate B by growing crystals while forming crystal nuclei; and a slow cooling region 26 for gradually cooling the belt-shaped crystallized glass plate B. The temperature rise region 24 and the slow cooling region 26 control the ambient temperature of each region so as to have a temperature gradient as shown in fig. 2A or fig. 2B. The temperature gradient shown in fig. 2A is: the temperature gradient of the slow cooling is set to be slow. The temperature gradient shown in fig. 2B is: the temperature gradient of the slow cooling is set to be in multiple stages of rapid cooling, heat preservation and rapid cooling.

The crystallization device 17 is a commercially available roll tunnel kiln provided with heating elements 18, carrying rolls 19, thermocouples 20, and a stirring device 28.

The heating elements 18 are arranged in the number of 1 or a plurality of heating elements 18 on the side wall of the furnace above and below the carrying roller 19 in the heating area 24 and the slow cooling area 26, and a thermocouple 20 is provided for each heating element 18 to control the temperature with the accuracy of + -5 ℃. The stirring device 28 stirs the air in each zone and homogenizes the temperature of each zone. By using these apparatuses, the crystallization heat treatment can be surely performed, and the crystallization of the rolled and formed strip plate glass can be easily and surely performed. Further, the heating source may be selected from a SiC heating element, a silicon molybdenum rod heater, gas, electricity, and the like as appropriate according to the desired temperature.

The transport roller shaft 19 is composed of a heat-resistant roller shaft, and continuously transports the belt-shaped plate glass in the crystallization device 17 without stagnation.

The temperature rise region 24 is a region in which the band-shaped plate glass a is stored in an environment at a crystal nucleus formation temperature and is raised to a temperature equal to or higher than a crystal growth temperature. The temperature raising region 24 is provided with a temperature gradient as shown in fig. 2A or 2B, and the temperature of the belt-shaped plate glass a is gradually raised as the belt-shaped plate glass a is conveyed toward the outlet of the crystallization apparatus 17. The ribbon-shaped plate glass A becomes a ribbon-shaped crystallized glass plate B by forming crystal nuclei through the temperature raising region 24 and growing crystals.

The slow cooling zone 26 is: in order to remove the permanent strain from the belt-shaped crystallized glass plate B and form a uniform glass, the region of the belt-shaped crystallized glass plate B is gradually cooled. The slow cooling zone 26 is provided with a temperature gradient as shown in fig. 2A or fig. 2B, and the belt-shaped crystallized glass plate B is gradually cooled as it is conveyed toward the outlet of the crystallization apparatus 17.

The belt-shaped crystallized glass plate B obtained by crystallizing the belt-shaped plate glass A by the crystallizing device 17 is conveyed to the cutting device 27 disposed downstream in the conveying direction. The cutting device 27 cuts the belt-shaped crystallized glass plate B to a predetermined size. The crystallized glass plate C cut by the cutting means 27 is transported to a secondary processing factory and is subjected to secondary processing to obtain a finished product.

FIG. 3 is a schematic view showing another example of the continuous forming apparatus for crystallized glass according to the present invention.

The crystallized glass continuous forming apparatus 50 (hereinafter referred to as "continuous forming apparatus 50") includes: a melting apparatus 51, a regulating apparatus 52, a devitrification prevention apparatus 53, a roll forming apparatus 54, a crystallization apparatus 57 (a roller tunnel kiln 57), and a cutting apparatus 67.

The melting device 51, the adjusting device 52, the devitrification prevention device 53, the roll forming device 54, and the cutting device 67 correspond to the melting device 11, the adjusting device 12, the devitrification prevention device 13, the roll forming device 14, and the cutting device 27 in the continuous forming device 10, respectively, and the respective configurations are the same as those described in the continuous forming device 10.

The adjustment device 52 is provided with a liquid level control device 52a, a stirring device 52b (stirring rod 52 b), a heating element 52c, and a thermocouple 52 d. The liquid level control device 52a, the stirring device 52b, the heating element 52c, and the thermocouple 52d correspond to the liquid level control device 12a, the stirring device 12b (stirring rod 12 b), the heating element 12c, and the thermocouple 12d in the continuous forming apparatus 10, respectively, and the respective configurations are the same as those described in the continuous forming apparatus 10.

The devitrification preventing device 53 is provided with a heat insulating device 53a (heat insulating refractory 53 a), a lip 53b, and a bracket 53c, and may be provided with a heating element 53 d. The heat retaining device 53a, the lip brick 53b, the bracket 53c, and the heating element 53d correspond to the heat retaining device 13a, the lip brick 13b, the bracket 13c, and the heating element 13d in the continuous forming device 10, respectively, and the respective configurations are the same as those described in the continuous forming device 10.

The roll forming device 54 is provided with an upper roller 54a, a lower roller 54b, and a cooling water tank 54 c. The upper roller 54a, the lower roller 54b, and the cooling water tank 54c correspond to the upper roller 14a, the lower roller 14b, and the cooling water tank 14c of the continuous forming apparatus 10, respectively, and have the same configuration as that of the continuous forming apparatus 10.

The continuous molding device 50 includes a conveying device 55 and a press roller 56 downstream of the roll forming device 54 in the conveying direction. The conveying means 55 and the press roller 56 correspond to the conveying means 15 and the press roller 16 in the continuous forming apparatus 10, respectively, and the respective configurations are the same as those described in the continuous forming apparatus 10.

The crystallization device 57 is composed of the following regions in order from the upstream side in the conveying direction: a temperature rise region 64 for accommodating the belt-shaped plate glass A and raising the temperature to a temperature higher than the crystal growth temperature to form a belt-shaped crystallized glass plate B by growing crystals while forming crystal nuclei; a heat-retaining region 65 for retaining the belt-shaped crystallized glass plate B at a temperature equal to or higher than the crystal growth temperature; and a slow cooling zone 66 for gradually cooling the belt-shaped crystallized glass plate B. The temperature raising region 64, the heat retaining region 65, and the slow cooling region 66 control the ambient temperature of each region so as to have a temperature gradient as shown in fig. 4A or 4B. The temperature gradient shown in fig. 4A is: the temperature gradient of slow cooling is set to a steady and slow descending mode. The temperature gradient shown in fig. 4B is: the temperature gradient of the slow cooling is set to a multi-step descending mode of rapid cooling, heat preservation and rapid cooling.

The crystallization apparatus 57 is a commercially available roll tunnel kiln provided with heating elements 58, a carrying roll 59, a thermocouple 60, and a stirring apparatus 68.

The heating element 58, the carrying roller shaft 59, the thermocouple 60, and the stirring device 68 correspond to the heating element 18, the carrying roller shaft 19, the thermocouple 20, and the stirring device 28 in the continuous forming device 10, respectively, and the respective configurations are the same as those described above for the continuous forming device 10.

The temperature rise region 64 is a region in which the band-shaped plate glass a is stored in an environment at a crystal nucleus formation temperature and is raised to a temperature equal to or higher than a crystal growth temperature. The temperature raising region 64 is provided with a temperature gradient as shown in fig. 4A or 4B, and the temperature of the belt-shaped plate glass a is gradually raised as the belt-shaped plate glass a is conveyed toward the outlet of the crystallization apparatus 57. The ribbon-shaped plate glass A passes through the temperature raising region 64 to form crystal nuclei and grow crystals, thereby forming a ribbon-shaped crystallized glass plate B.

The heat-retaining region 65 is a region in which the belt-shaped crystallized glass plate B is held at a temperature equal to or higher than the crystal growth temperature for a certain period of time, and is a region in which the temperature is retained at the most downstream portion (outlet portion) of the heating region 64 in the temperature gradient shown in fig. 4A and 4B. The band-shaped crystallized glass plate B can further undergo nucleation and crystal growth (particularly crystal growth) by passing through the heat retaining region 65, thereby increasing the degree of crystallization.

The slow cooling zone 66 is: the region of the belt-shaped crystallized glass plate B is gradually cooled to remove the permanent strain from the belt-shaped crystallized glass plate B and to form a uniform glass. The slow cooling zone 66 is provided with a temperature gradient as shown in fig. 4A and 4B, and the belt-shaped crystallized glass plate B is gradually cooled as it is conveyed toward the outlet of the crystallization apparatus 57.

The glass raw material is melted by the melting device 51 to be molten glass. The molten glass is conveyed to the regulating device 52, flows out of the regulating device 52, and flows into the devitrification prevention device 53. The molten glass is supplied to the roll forming device 54 through the devitrification prevention device 53. The molten glass is rolled and formed by a roll forming device 54 to be a strip-shaped plate glass A. The belt-like plate glass A is conveyed by the conveying means 55 and introduced into the crystallizing means 57. The strip-shaped plate glass A is crystallized by the crystallization device 57 into a strip-shaped crystallized glass plate B. The belt-shaped crystallized glass plate B is conveyed to the cutting means 67, and cut into a predetermined size by the cutting means 67 to obtain a crystallized glass plate C. The crystallized glass plate C is transported to a secondary processing factory and is secondarily processed into a finished product.

The present invention will be described more specifically with reference to the following examples, but the scope of the present invention is not limited to the examples shown below.

The impact strength of the crystallized glass plate obtained in the following examples and comparative examples was evaluated by calculating the breakage rate (%) in the following manner using an impact testing apparatus described in International Electrotechnical Commission (IEC) publication 817 "spring-driven impact testing apparatus and calibration thereof".

The surface of the crystallized glass plate which was impact-cut into a size of 30 cm. times.30 cm. times.4 mm was impact-cut 3 times at 5 positions using an impact tester of 0.5J. The crystallized glass plate was judged as passing with no crack or breakage, and as failing with crack or breakage, and the rate of failure (the number of failing pieces relative to the total number of pieces supplied to the test) was regarded as the breakage rate (%).

In the example, an apparatus having the same configuration as the continuous molding apparatus shown in fig. 1 and 3 was prepared and implemented. In a comparative example, a device having the same configuration as that of the continuous molding device disclosed in patent document 1 was prepared and implemented. In the crystallization steps of examples and comparative examples, the temperature was the ambient temperature in each zone of the crystallization apparatus.

Example 1 is:

a glass raw material prepared into a composition of mass percent of SiO263.5%, Al2O321.5%, MgO 0.5%, ZnO1.5%, BaO 1.8%, TiO22.8%, ZrO21.5%, B2O30.3%, P2O51.0%, Na2O0.7%, K2O 0.5.5%, Li2O 3.6.6%, As2O30.5% and V2O50.3% is put into a melting device. The glass raw material was melted at 1670 ℃ and then was rolled and molded into 170cm × 250m × 4mm by a molding machine to obtain a ribbon-shaped plate glass.

The belt-shaped plate glass obtained as described above was transported from the molding machine to the crystallizing machine, and introduced into a temperature rising zone having an inlet temperature of 730 ℃, and the belt-shaped plate glass was heated to 880 ℃ at a rate of 1 ℃/min and passed through the temperature rising zone to form crystal nuclei, and crystals were grown to form a belt-shaped crystallized glass plate.

Subsequently, the belt-shaped crystallized glass plate was gradually cooled to 100 ℃ at a rate of 10 ℃/min and passed through a slow cooling zone.

Then, the belt-shaped crystallized glass plate was cut into a plate having a length of 100cm along the conveying direction by a cutting device.

Therefore, a solid solution of β -quartz as the main crystal was precipitated, and a black crystallized glass plate was obtained. The crystallized glass plate is free from waviness, deformation, cracking, and cracks, and has a flat and beautiful appearance. The breakage rate of the crystallized glass plate is 5% or less.

Example 2 is:

glass raw materials prepared to the mass percentage of SiO264.0%, Al2O322.0%, MgO 0.5%, ZnO1.0%, BaO 2.0%, TiO22.5%, ZrO21.5%, B2O30.3%, P2O50.8%, Na2O0.8%, K2O 0.3.3%, Li2O 3.8.8% and As2O30.5% are put into a melting device. The glass raw material was melted at 1650 ℃ and then was rolled and molded into 170cm × 250m × 4mm by a molding machine to obtain a ribbon-shaped plate glass.

The belt-shaped plate glass obtained as described above is transported from the molding machine to the crystallization machine, and is put into a temperature rise region having an inlet temperature of 750 ℃, and the belt-shaped plate glass is heated to 1000 ℃ at a rate of 2 ℃/min and passed through the temperature rise region to form crystal nuclei, and crystals are grown to form a belt-shaped crystallized glass plate.

Subsequently, the belt-shaped crystallized glass plate was gradually cooled to 100 ℃ at a rate of 5 ℃/min and passed through a slow cooling zone.

Therefore, β -spodumene was precipitated as a main crystal, and a white crystallized glass plate was obtained. The crystallized glass plate is free from waviness, deformation, cracking, and cracks, and has a flat and beautiful appearance. The breakage rate of the crystallized glass plate is 5% or less.

Example 3 is:

The belt-shaped plate glass obtained as described above was transported from the molding machine to the crystallizing machine, and introduced into a temperature rising zone having an inlet temperature of 730 ℃, and the belt-shaped plate glass was heated to 880 ℃ at a rate of 1.5 ℃/min and passed through the temperature rising zone to form crystal nuclei and grow crystals to form a belt-shaped crystallized glass plate.

Next, the belt-shaped crystallized glass plate was further crystallized by introducing the belt-shaped crystallized glass plate into a heat-retaining region of 880 ℃ and passing the belt-shaped crystallized glass plate through the heat-retaining region while retaining the belt-shaped crystallized glass plate at 880 ℃ for 30 minutes.

Example 3, which was provided with the heat-keeping step, can reduce the total time required for crystallization more than example 1, which did not have the heat-keeping step. The breakage rate of example 3 was about the same as that of example 1.

Comparative example 1 is:

The belt-shaped plate glass obtained as described above was transported from the molding machine to the crystallizing machine, and charged into a temperature zone of 630 ℃ and held at 630 ℃ for 10 minutes while passing through the temperature zone, at a temperature near the glass transition temperature.

Subsequently, the belt-shaped plate glass was heated up to 730 ℃ at a rate of 10 ℃/min and passed through the first heating zone.

Thereafter, the belt-shaped plate glass was put into a temperature region of 730 ℃ and allowed to pass through the temperature region while being maintained at 730 ℃ for 20 minutes, and crystal nuclei were formed in the belt-shaped plate glass.

Next, the band-shaped plate glass forming the crystal nuclei was heated to 880 ℃ at a rate of 1 ℃ per minute and passed through a second temperature-raising zone.

Subsequently, the ribbon-shaped crystallized glass plate in which crystal nuclei were formed was introduced into a temperature range of 880 ℃ and allowed to pass through the temperature range, and was kept at 880 ℃ for 30 minutes, thereby growing crystals to obtain a ribbon-shaped crystallized glass plate.

Thereafter, the belt-shaped crystallized glass plate was gradually cooled to 100 ℃ at a rate of 10 ℃/min and passed through a slow cooling zone.

Claims

1. A method for continuously forming crystallized glass, comprising the steps of:

(1) the mixture is prepared into SiO in percentage by mass₂63.5％、Al₂O₃21.5％、MgO0.5％、ZnO1.5％、BaO1.8％、TiO₂2.8％、ZrO₂1.5％、B₂O₃0.3％、P₂O₅1.0％、Na₂O0.7％、K₂O0.5％、Li₂O3.6％、As₂O₃0.5％、V₂O₅0.3% of the compositionPutting the glass raw material into melting equipment; melting the glass raw materials at 1670 ℃;

(2) rolling and molding the glass plate into a sheet of 170cm × 250m × 4mm by a molding machine to obtain a ribbon-shaped plate glass; transporting the belt-shaped plate glass obtained in the above manner from the molding apparatus to a crystallizing apparatus, introducing the belt-shaped plate glass into a temperature rising region having an inlet temperature of 730 ℃, raising the temperature of the belt-shaped plate glass to 880 ℃ at a rate of 1.5 ℃/min, passing the belt-shaped plate glass through the temperature rising region, forming crystal nuclei, and growing crystals to form a belt-shaped crystallized glass plate;

(3) introducing the belt-shaped crystallized glass plate into a heat-retaining region of 880 ℃ and allowing the belt-shaped crystallized glass plate to pass through the heat-retaining region, while maintaining the temperature at 880 ℃ for 30 minutes to further crystallize the belt-shaped crystallized glass plate; then, the belt-shaped crystallized glass plate is gradually cooled to 100 ℃ at a speed of 10 ℃/min and passes through a slow cooling area;

(4) then, cutting the belt-shaped crystallized glass plate into plates with the length of 100cm along the conveying direction by using cutting equipment;

precipitating a beta-quartz solid solution as a main crystal to obtain a black crystallized glass plate;

wherein the above forming method is performed by a continuous forming apparatus for crystallized glass, the continuous forming apparatus comprising:

a melting device that melts a glass raw material to obtain molten glass;

a cutting device for cutting the belt-shaped crystallized glass plate;

and the crystallization apparatus has:

a temperature raising region for directly accommodating the ribbon-shaped glass sheet obtained by the forming apparatus in an environment at a crystal nucleus formation temperature and raising the temperature to a temperature higher than a crystal growth temperature to form crystal nuclei and grow crystals at the same time to form a ribbon-shaped crystallized glass sheet; and

a heat-insulating region for maintaining the ribbon-shaped crystallized glass plate at a temperature equal to or higher than a crystal growth temperature;

and a slow cooling zone for gradually cooling the belt-shaped crystallized glass plate, wherein the temperature gradient of the slow cooling is set to a multi-stage descending mode of rapid cooling-heat preservation-rapid cooling.