JP2000272927A - Tempered glass products and their production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production process for thermally tempered glass products that can completely avoid the natural damage to thermally tempered glass caused by foreign substances including nickel sulfide. SOLUTION: In the annealing step continuously following the glass-enhancing step where the glass is heated and then cooled down by wind, the thermally tempered and nickel sulfide-containing glass that has thermally residual stress and extends the cracks caused by the stress is continuously and gradually cooled from about 300 deg.C down to 150-200 deg.C at a rate of <=12 deg.C/min. whereby the foreign substance-containing tempered glass is broken by the volume expansion of the foreign substance and removed therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to all glass compositions that can be tempered by air-cooling without any foreign matter which is one of the causes of spontaneous breakage of tempered glass.
The present invention relates to a high-quality tempered glass product and a method for producing the same.

[0002] The air-cooled tempered glass products to which the present invention is applied include everything from plate-like ones such as sheet glass to those having complicated shapes.

[0003]

2. Description of the Related Art As in the usual manufacturing process, wind-cooled tempered glass is heated by heating the glass at a temperature of 600 ° C. or higher, and then rapidly blowing air onto the glass surface (generally, this process is performed in this process). It is manufactured by generating a strong compressive stress on the glass surface and further cooling.

[0004] In glass produced by melting glass raw materials, nickel (Ni) -based metal (for example, stainless shards or sparks of welding) mixed during melting is dissolved in sulfur components (melting components in glass or furnace). Nickel sulfide (N) formed by reaction with gas components in the internal atmosphere
iS). Further, there may be cases in which unmelted foreign substances such as a vitreous erosion phase or a constituent phase of a melting furnace formed by a reaction with a refractory brick or unmelted raw material particles themselves are included.

[0005] These contaminants may have different coefficients of thermal expansion relative to the base glass, or may themselves undergo a phase transition as a function of temperature. For example, in the case of nickel sulfide, there is a boundary of a phase transition between a stable α phase at a high temperature and a stable β phase at a low temperature around 350 ° C., and when the tempered glass is rapidly cooled to reach this temperature or less in a short time. Means that the α phase remains in the glass product in an unstable state (a state in which the glass is supercooled). The α phase gradually changes into a stable β phase when left at room temperature for a long time, and at the same time, the phase transition to the β phase is completed with a volume expansion of 4% or more.

Due to the nature of the air-cooled tempered glass, a strong compressive stress acts on the glass surface and a tensile stress acts on the inside, and as a result, a strong compressive stress acts on the glass base material around the nickel sulfide foreign matter. Cracks form and grow further, eventually leading to breakage of the glass itself.

In order to prevent spontaneous breakage of tempered glass due to glass defects such as nickel sulfide foreign matter contained in the tempered glass product, the glass product produced in the tempering process and returned to room temperature is again fired in a firing furnace. (Generally called a heat soak oven) at a maximum temperature of 30
Maintaining nickel sulfide at a given temperature condition up to 0 ° C. for a certain period of time mainly causes a phase transition from an unstable α-phase to a stable β-phase at room temperature, thereby causing a volume expansion of about 4%. Defective products are removed by breaking the tempered glass products themselves by rapid crack extension.

[0008] This conventional thermal soaking treatment of the type in which the temperature is raised from room temperature is performed, as shown in FIG. 1 showing a conventional process of air-cooled tempered glass soaking treatment. In order to maintain the specified temperature by raising the temperature, much time and cost are required to raise the temperature to the temperature range to be maintained. And the holding time in a certain temperature range is also different,
This has led to lower productivity, lower yield, and higher production costs.

[0009]

[0005] Tempered glass is widely used, especially for sheet glass products, for transportation vehicles, mainly automobiles and railways, and for building materials such as houses and non-houses. In recent years, wind-cooled tempered glazing for building materials has been used in a wide area for openings where many people come in and out, and there is a demand for improved safety quality. Further, depending on the change in the shape of the glass, it is used for various purposes other than the sheet glass.

However, conventionally, the tempered glass sometimes spontaneously breaks at the time of manufacturing or after the tempered glass is manufactured due to the influence of foreign substances contained in the glass base plate and scratches on the glass surface when the glass raw material is melted.

In order to eliminate such a problem, as described above, reheating (annealing) is performed again after the tempered glass is manufactured at the glass manufacturing stage, so that stress distortion is generated around the foreign matter. A method of rapidly expanding a crack starting from a foreign matter or a scratch and removing a defective tempered glass having such a defect is widely used. The process of producing high-quality tempered glass without such natural damage is called a soak process (so-called batch soak process). In this conventional soak process,
The following are problems:

1) After heating and air-cooling (quenching), the air-cooled tempered glass once lowered to room temperature is heated again in the firing furnace, so that the temperature is raised to a predetermined temperature (usually 300 ° C. or lower) or the maximum. It takes a long time to keep in the temperature range, which leads to an increase in the cost of manufacturing.

2) Since the manufacturing process of tempered glass and the process of soaking treatment for removing foreign matter are separated,
It is not possible to reduce the efficiency of production and to improve the productivity by transporting the reinforced product again.

3) In the conventional soak treatment, since the product left at room temperature is heated again, the conditions under which the phase transition of nickel sulfide changes due to the difference in the shape, type, or plate thickness of the glass when the temperature is increased. It was difficult to remove tempered glass products containing these foreign substances.

An object of the present invention is to provide an air-cooled tempered glass product which solves these problems and a method for producing the same.

[0016]

SUMMARY OF THE INVENTION The air-cooled tempered glass of the present invention is one in which undissolved foreign matter and contaminant foreign matter during melting or production of glass such as nickel sulfide are removed. Such an air-cooled tempered glass product is manufactured by performing the following thermal treatment.

That is, after the heat treatment at a temperature of 600 ° C. or more and the subsequent heat treatment (quenching), the glass after the heat treatment is continuously gradually cooled at a constant temperature and time. When nickel sulfide foreign matter is contained in the glass, about 4% volume expansion is caused by a phase transition from the above-mentioned α phase which is stable at high temperature to the β phase which is stable at room temperature. As a result, cracks are simultaneously extended in the glass phase around the foreign matter to break the glass, and a tempered glass containing no such foreign matter is obtained.

According to the present invention, the continuous slow cooling conditions from a temperature range of about 300 ° C. are as follows.

That is, about 300 after air cooling (quenching).
From a temperature range of 150 ° C. at a cooling rate of less than 12 ° C./min.
Slowly cool to 200 ° C. Thereafter, the glass is cooled and taken out to such an extent that the glass does not crack.

Such slow cooling conditions can be determined by preparing a glass sample containing nickel sulfide and conducting a heat treatment experiment.

When the slow cooling condition is required, specifically, the following processes (1) to (4) are sequentially performed to produce a tempered glass product.

(1) As in the normal manufacturing process, the air-cooled tempered glass is heated at a temperature of 600 ° C. or higher, and then the air is rapidly blown onto the glass surface so that the glass surface is strongly compressed. Manufactured by generating stress and further cooling.

(2) In a normal process, the glass is cooled to near room temperature in a subsequent operation. In the present invention, the tempered glass is gradually cooled under the optimal temperature and time conditions. Considering the processing time, in the case of continuous slow cooling, it is desirable to perform the processing with a heat history of less than 12 ° C./min.

(3) Under the above-mentioned appropriate temperature and time conditions, nickel sulfide contained in the glass undergoes a complete phase transition from a high-temperature stable α phase to a low-temperature stable β phase, and at the same time, 4% By generating a compressive stress in the glass around the particles by causing a certain degree of volume expansion, cracks are rapidly developed, and the glass breaks at the internal tensile stress portion, causing breakage.

(4) In the process of the above (2) and (3), the glass containing the nickel sulfide foreign matter rapidly breaks in the annealing furnace or the temperature control furnace, and is further strengthened. It is possible to realize a high-quality tempered glass free from spontaneous breakage by crushing finely and removing defective products and not being shipped as a product.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to set the temperature and time for slow cooling in the quench step, the following processes are sequentially performed.

Preparation of Sample and Heat Treatment Experiment The foreign substances of nickel sulfide used in this heat treatment experiment flowed out into the glass plate obtained in the production of ordinary sheet glass. These nickel sulfide contaminants were confirmed to be NiS (or similar) in composition using an electron beam microanalyzer (EPMA).

To investigate the phase transition of nickel sulfide, a glass plate (about 10 mm thick) containing these particles was polished to a thickness of about 3 mm, and samples A to H were heated to 500 ° C. using a microscope ( A high-temperature microscope was used.

The composition (% by weight) of the sample is as follows.

SiO ₂ 71-73 Al ₂ O ₃ 1.5-1.8 MgO 4.0-4.5 CaO 8-10 Na ₂ O 13-14 K ₂ O 0.5-1.5 Fe ₂ O ₃ 0.02 to 0.05 SO ₃ 0.1 to 0.5 Measurement of phase transition
The temperature was raised to 70 ° C. at a rate of 70 ° C./min or more, and maintained at 350 ° C. for 10 minutes or more to form a completely stable α phase in the glass. Thereafter, cooling was performed at a rate of about 50 ° C./min (reproducing the quenching process), and the state of the transition to the β phase was investigated by in-situ observation under a high-temperature microscope by gradually cooling from about 300 ° C. .

The slow cooling rate was 6 ° C. /
Min, 8 ° C / min for sample B, 8.5 ° C / min for sample C, and 9.0 ° C / min for sample D.
Min, samples E and F were 10.0 ° C./min, sample G was 12.0 ° C./min, and sample H was 15.0 ° C./min.

The phase transition from the α-phase to the β-phase is carried out by setting the polarizing plate in a crossed Nicols state under a polarizing microscope and further 530 μm.
Using a m-sensitive color test plate, the generation state and strength of residual stress due to compression of the glass around the foreign matter with a volume increase of 4% were determined by continuously observing the generation and change of retardation.

The state of the complete transition to the β phase was judged at the time when the state of the compressive stress was maximized (when the retardation was the strongest under a microscope). Table 1 shows the results of the phase transition temperature from α phase to β phase and the time for nickel sulfide defect samples A to H. Open circles indicate that nickel sulfide is in the α-phase state, and open circles indicate that the nickel sulfide is in the β-phase state. The numbers described beside these marks indicate the temperature (° C.).

[0034]

[Table 1]

FIG. 2 is a graph of the results of Table 1. In FIG. 2, the horizontal axis represents time (minutes) and the vertical axis represents temperature (° C.). In the figure, a white mark indicates that nickel sulfide is in the α-phase state, and a black solid mark indicates that the nickel sulfide is in the β-phase state.

According to the coordinate system shown in FIG. 2, when the temperature is gradually cooled to 150 ° C. at a rate of less than 12 ° C./min, the phase is completely transformed into β phase.

As described above, in the slow cooling in the quenching step, the conditions of the slow cooling rate and the temperature at which the nickel sulfide undergoes a phase transition from the α phase to the β phase were determined.

In order to produce a tempered glass having no breakage due to dissolved foreign matter such as NiS according to the present invention, it is preferable to carry out the process according to the process flow shown in FIG.

Heat the glass above 600 ° C.

A reinforcing layer is formed on the surface by air cooling (quenching).

Rapid cooling keeps the residual strain of the reinforcement. At this time, the nickel sulfide is in a stable α-phase state.

The continuous slow cooling is performed from about 300 ° C. in a slow cooling furnace. At this time, it is gradually cooled to 150 ° C. at a cooling rate of less than 12 ° C./min. When nickel sulfide is contained, the glass transitions to the β phase at this point and the glass is broken by volume expansion.

Cooling Ships air-cooled tempered glass without breakage on the user side Regarding the actual temperature control furnace or annealing furnace for these processes, it is installed continuously downstream of the tempering furnace and the quench equipment, and is continuously heated. It is possible to create a processing furnace system that enables a specific soak process. That is, in the slow cooling step after the air cooling, the effect of the present invention can be obtained if a furnace capable of continuous slow cooling from around 300 ° C. can be installed.

When the heat treatment is performed within the range of the temperature and the treatment time according to the present invention, the distribution of the residual stress on the glass surface portion due to the air-cooling is not relaxed, and the degree of the hardening hardly changes. That is, the quality as tempered glass is not impaired.

[0045]

According to the present invention, it is possible to eliminate spontaneous damage of the air-cooled tempered glass due to foreign substances such as nickel sulfide. Furthermore, since the processing can be performed at low cost without lowering the productivity, a great effect can be obtained practically.

[Brief description of the drawings]

FIG. 1 is a view showing a conventional soak process.

FIG. 2 is a diagram showing a temperature-time condition in which a phase transition from an α phase to a β phase is caused by continuous slow cooling during cooling.

FIG. 3 is a diagram showing a soak process according to the present invention.

Claims (4)

[Claims] (1) In a continuous slow cooling step after heating and strengthening the glass by air cooling, the air-cooled tempered glass containing a foreign substance that extends the thermal residual stress and the cracks generated thereby is heated to 300 ° C. A method for producing a tempered glass product, wherein the tempered glass containing the foreign matter is broken and removed by volume cooling of the foreign matter by continuously slow cooling from the vicinity. 2. When the foreign matter contains nickel sulfide,
The slow cooling is performed at a rate of less than 12 ° C./min.
C., and the nickel sulfide undergoes a continuous phase transition from a high-temperature stable α-phase to a low-temperature stable β-phase, and at the same time, causes volume expansion and breaks the glass by rapidly expanding cracks. 2. The method according to claim 1, wherein
A method for producing the tempered glass product according to the above. 3. A tempered glass product produced by the method according to claim 1, wherein the tempered glass product is free of foreign matter that extends thermal residual stress and cracks generated thereby. 4. A tempering furnace for producing an air-cooled tempered glass product, and a temperature control furnace or an annealing furnace continuously installed downstream of the quench equipment, wherein the temperature adjustment furnace or the annealing furnace has a thermal residual furnace. The air-cooled tempered glass product, characterized in that the air-cooled tempered glass containing the foreign matter that expands the stress and the cracks generated by the stress is gradually cooled to break and remove the air-cooled tempered glass containing the foreign matter. Manufacturing equipment.