JP2000272926A - Thermally tempered glass by air jet and its 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 of 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 held at a prescribed temperature for a prescribed time whereby glass is continuously transferred from the α-phase that is stable at elevated temperature to the β-phase that is stable at lower temperature to break the nickel sulfide-containing glass by the volume expansion of the foreign substance and remove 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 not only plate glass usually used in architectural glass products but also those having a complicated shape such as a bent product or a container.

[0003]

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

[0004] The tempered glass contains nickel (Ni) -based metal (stainless steel or fragments of welding sparks) or the like mixed in at the time of melting, and sulfur components in the glass base (melting components in the glass and gas components in the atmosphere in the furnace). With nickel sulfide (NiS) formed in the reaction with

[0005] Further, there may be cases in which undissolved 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 undissolved raw material particles themselves are included.

These contaminants may have a different coefficient of thermal expansion than the surrounding glass, or may themselves undergo a phase transition as a function of temperature. For example, in the case of nickel sulfide,
When there is a boundary of the phase transition between α phase stable at high temperature and β phase stable at low temperature around 350 ° C, and the air-cooled tempered glass is rapidly cooled in the temperature range of 350 ° C or higher, and reaches below this temperature in a short time. Means that the α phase remains in the glass product in an unstable state. Usually, such a state is referred to as a state in which the glass is supercooled.

The α phase of the nickel sulfide gradually undergoes a phase transition to 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.

[0008] 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, so that a strong compressive stress acts on the glass around the nickel sulfide particles. Cracks form and grow further, eventually leading to breakage of the glass itself.

In order to prevent spontaneous damage of the tempered glass due to foreign matter defects such as nickel sulfide contained in the tempered glass product, the glass product produced in the tempering process and returned to normal temperature is again fired in a firing furnace (generally, Is called a heat soak furnace), and is heated up to a maximum temperature of 300 ° C. and held for a certain period of time, thereby mainly converting nickel sulfide from an unstable α phase at room temperature to a stable state. By causing a phase transition to the β phase, a volume expansion of about 4% is generated, and a defective product is removed by a breakage of the product by rapid expansion of a generated crack. Such a process is called a thermal soak process (heat soak).

FIG. 1 shows the heat history of such a conventional soak process. As shown in FIG. 1, in the conventional heat soak of a type in which the temperature is raised from room temperature, the tempered glass once cooled to room temperature is maintained at a predetermined temperature by raising the temperature again. Spend a lot of time and money on heating up.

In the case where the glass is plate-shaped, the temperature rise rate and the holding time in a constant temperature range are also different due to the difference in heat flow rate and specific heat in the heat soak with respect to the change in the plate thickness. This has led to a decrease in yield or an increase in production cost.

[0012]

SUMMARY OF THE INVENTION Tempered glazing is widely used for vehicles such as automobiles and railways, and for building materials such as houses and non-houses. Particularly, reinforced sheet glass for building materials is used at high places and in a wide area at openings where many people come and go, and there is also a demand for an improvement in safety quality in the PL method.

Further, depending on the change in the shape of the glass, the glass is used for various purposes other than the sheet glass, and spontaneous breakage of glass products for containers and the like is observed.

As natural damage not caused by foreign matter or defects inside the glass, the tempered glass sometimes spontaneously breaks at the time of manufacturing or after the tempered glass is manufactured due to the influence of scratches on the glass surface.

In order to eliminate the damage caused by foreign matter and defects inside the glass in the problem of spontaneous damage, as described above, at the present stage of glass manufacture, reheating is performed again after the manufacture of tempered glass. (Annealing) to generate stress distortion around foreign matter, rapidly expand cracks starting from the contained foreign matter and defects, and widely use thermal soak treatment to remove defective tempered glass. .

In the above-described conventional thermal soak process (so-called batch soak process, etc.), the following problems arise.

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

2) Further, since the phase transition of nickel sulfide greatly depends on the rate of temperature rise, many conditions must be set in order to find the optimum processing conditions.

3) Since the manufacturing process of the tempered glass and the process of the thermal soak treatment for removing the nickel sulfide foreign matter are separated, the efficiency of the manufacturing is lowered, such as transporting the tempered product again. Also, productivity cannot be improved.

4) In the conventional thermal soak treatment, since the product once left at room temperature is heated again, if the shape, type, or thickness of the glass is different at the time of raising the temperature, the conditions under which the phase transition of nickel sulfide occurs. Differently (mainly holding temperature and time), it was difficult to completely 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.

[0022]

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, in a part of a slow cooling step that is continuous after the heating at 600 ° C. or higher and the subsequent air cooling strengthening (quenching), the glass is kept at a constant temperature and time, thereby reducing the temperature of the glass. When a foreign substance of nickel sulfide is contained therein, a phase transition from an α phase which is stable at a high temperature to a β phase which is stable at room temperature causes a volume expansion of about 4%, and at the same time, a foreign substance around the foreign substance is generated. The crack is extended to the glass phase to break the glass, and a tempered glass free of these foreign substances is obtained.

An example of the holding conditions at the time of continuous slow cooling from a temperature range of about 300 ° C. is 1 to 180 to 280 ° C.
Hold for 20 minutes. Or 180-26
It is desirable to hold at 0 ° C. for 7 to 20 minutes. More desirably (in order to completely change the phase of nickel sulfide to the β phase), it is preferable to maintain the temperature at 180 to 260 ° C for 12 to 30 minutes.

Other examples of the holding conditions (temperature and time) are as follows.

280 ° C (at least 20 minutes) 260 ° C (at least 7 minutes) 240 ° C (at least 6.5 minutes) 220 ° C (at least 9 minutes) 200 ° C (at least 11) 180 ° C. (at least 13 minutes or more) 160 ° C. (at least 15 minutes or more) The conditions of temperature and time above are for the case where the foreign matter is nickel sulfide. If there is a difference in thermal expansion between unmelted foreign matter and glassy melting defects derived from the melting tank or raw material at the time of glass melting, use the difference in thermal expansion between the foreign matter and the glass base. Then, it is possible to break and remove the tempered glass.

The temperature and time holding conditions when the foreign substance is nickel sulfide can be determined by preparing a glass sample containing nickel sulfide and conducting a heat treatment experiment.

When the holding conditions are determined, specifically, the following processes are sequentially performed to produce a tempered glass product.

(1) The air-cooled tempered glass is heated at 600 ° C. or higher and then rapidly blown with air on the glass surface as in the usual manufacturing process. (Quench)), which produces strong compressive stress on the glass surface and is further cooled.

(2) In a normal process, the glass is cooled to near room temperature in the subsequent operation. In the present invention, the tempered glass is held for a certain period of time under the optimum temperature condition.

(3) Under 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, a volume of about 4%. Cracks develop rapidly by causing expansion to generate compressive stress in the glass around the particles. Glass breaks suddenly in the portion of the internal tensile stress, causing breakage.

(4) In the process of the above (2) and (3), the glass containing these nickel sulfide foreign matters is rapidly broken inside the temperature control furnace or the annealing furnace, and further strengthened. Crushed finely to remove defective products. Ultimately, high quality tempered glass without spontaneous breakage can be realized.

[0033]

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

Preparation of Sample and Heat Treatment Experiment The nickel sulfide particles used in this heat treatment experiment flow out into the glass plate obtained in the production of ordinary plate glass. These nickel sulfide foreign matters 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 the sample was heated to 500 ° C. using a microscope (hereinafter, referred to as a microscope). A high temperature microscope) was used.

Measurement of phase transition
The temperature was raised to 50 ° C. at a rate of 70 ° C./min or more, and maintained at a temperature of 350 ° C. for 10 minutes or more to form a stable α phase in the glass.

Thereafter, cooling is performed at a rate of about 50 ° C./min (the quenching process is schematically reproduced), and when the temperature reaches the following temperature, the temperature is kept constant and is kept for a certain time. The state of the phase transition to the β phase was also investigated by in-situ observation under a high-temperature microscope.

The phase transition of the nickel sulfide from the α phase to the β phase can be performed by placing the polarizing plate in a crossed Nicols state under a polarizing microscope, and further inserting a 530 μm sensitive color test plate at a diagonal position to obtain 4% The generation of residual stress due to the compression of the glass around the foreign matter with the increase in the volume of the particles was performed by continuously observing the change in retardation.

The state of complete phase transition to the β phase was confirmed 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 glass samples 1 used in the investigation.
5 are shown. Samples 1, 2, and 3 have a composition of S
iO ₂ , Al ₂ O ₃ , MgO, CaO, Na ₂ O, K ₂
O, Fe ₂ O ₃ , and SO ₃ are contained in the proportions by weight shown in the table. Sample 4 has the above composition, and further contains Fe ₂ O
₃ as a coloring component, and Sample 5 further contains a trace amount of Se.

[0041]

[Table 1]

EXPERIMENTAL EXAMPLE 1 FIG. 2 is a coordinate system showing the experimental results of phase transition for sample 1. In FIG. 2, the horizontal axis represents the retention time (minutes),
The vertical axis indicates the holding temperature (° C.). In the figure, the mark x indicates that the nickel sulfide is in the α phase, the mark 不 完全 indicates the incomplete β phase, and the mark ● indicates the complete β phase.

From this coordinate system, it can be seen that the phase transition of nickel sulfide from the stable α phase to the complete β phase may be maintained at any of the following temperatures and times.

280 ° C (at least 20 minutes) 260 ° C (at least 7 minutes) 240 ° C (at least 6.5 minutes) 220 ° C (at least 9 minutes) 200 ° C (at least 11) 180 ° C. (at least 13 minutes or more) 160 ° C. (at least 15 minutes or more) The temperature conditions of at least 160 ° C. are discontinuous, but the complete β-phase region is curved in the coordinate system of FIG. When surrounded by 10, the temperature and time included in this region can be arbitrarily selected as a condition.

Experimental Example 2 The same test was performed on another sample 2 in which the heat treatment conditions were the same as those in Experimental Example 1, and the results of measuring the conditions for the phase transition from α phase to β phase were shown in FIG. .

Experimental Example 3 The other sample 3 was subjected to the same heat treatment conditions as in Experimental Example 1
FIG. 4 shows the results of performing the same test and measuring the conditions for the phase transition from the α phase to the β phase.

From the results shown in FIGS.
It can be seen that if the temperature is maintained at 60 ° C. for 7 to 20 minutes, the α phase can sufficiently undergo a phase transition to a stable β phase at a low temperature.

Experimental Example 4 A test was performed on a sample 4 of a light blue toned glass under the same heat treatment conditions as in Experimental Example 1, and FIG. 5 shows the results of an examination of the conditions for the phase transition to the β phase.

Experimental Example 5 A test was conducted on light brown toned glass sample 5 under the same heat treatment conditions as in Experimental Example 1, and FIG. 6 shows the results of an examination of the conditions for the phase transition to the β phase.

FIG. 7 shows the region where all of the samples 1 to 5 can transition to the stable β phase. According to this,
It is desirable to hold at 160 to 260 ° C. for 12 to 30 minutes.

As described above, in the slow cooling step after the quench, the conditions of the holding temperature and the time for causing the phase transition of nickel sulfide from the α phase to the β phase were determined.

In order to produce an air-cooled tempered glass free from breakage due to dissolved foreign matters such as nickel sulfide according to the present invention, it is preferable to carry out the process according to the following process flow.

Tempering Cooling (quenching) Maintained at 160 to 280 ° C. for a certain time. When nickel sulfide is contained, the glass transitions to the β phase at this point and the glass is broken. Regarding the actual temperature control furnace or annealing furnace for the process, it can be continuously installed downstream of the strengthening furnace and the quench equipment to create a processing furnace system that enables continuous thermal soak processing.

FIG. 8 shows the thermal history of the improved thermal soak process obtained according to the present invention. According to this, in the cooling step after the air cooling, when held for a certain period of time in the range of 160 ° C. to 280 ° C., nickel sulfide is transformed into a stable β phase, cracks are generated, the tempered glass is broken, and soak processing is performed. I have.

Further, 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 hardly alleviated. The quality as tempered glass is not impaired.

[0056]

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.

[Brief description of the drawings]

FIG. 1 is a diagram showing a heat history of a conventional soak process.

FIG. 2 is a diagram showing temperature-time conditions under which a phase transition from an α phase to a β phase occurs in Experimental Example 1.

FIG. 3 is a diagram showing a temperature-time condition under which a phase transition from an α phase to a β phase occurs in Experimental Example 2.

FIG. 4 is a diagram showing a temperature-time condition in which a phase transition from an α phase to a β phase occurs in Experimental Example 3.

5 is a diagram showing a temperature-time condition under which a phase transition from an α phase to a β phase occurs in Experimental Example 4. FIG.

FIG. 6 is a diagram showing a temperature-time condition in which a phase transition from an α phase to a β phase occurs in Experimental Example 5.

FIG. 7 is a diagram showing a temperature-time condition under which a phase transition from an α phase to a β phase occurs when a constant temperature is maintained.

FIG. 8 is a diagram showing a heat history of a continuous soak process after improvement.

[Explanation of symbols]

 10 Curve showing the region of complete β phase

Claims (9)

[Claims] 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 a thermal residual stress and a crack generated with the thermal residual stress is removed by a predetermined method. A method for manufacturing a wind-cooled tempered glass product, wherein the tempered glass containing the foreign matter is broken and removed by volume expansion of the foreign matter by maintaining the temperature at a predetermined time. 2. When the foreign matter contains nickel sulfide,
By maintaining the air-cooled tempered glass at a predetermined temperature for a predetermined time, the nickel sulfide continuously undergoes a phase transition from a high-temperature stable α-phase to a low-temperature stable β-phase, and simultaneously undergoes volume expansion. The method for producing a tempered glass product according to claim 1, wherein the glass is broken by causing the crack to rapidly expand. 3. The method according to claim 2, wherein the predetermined temperature is 180 to 280 ° C., and the predetermined time is 1 to 20 minutes. 4. The method according to claim 2, wherein the predetermined temperature is 180 to 260 ° C., and the predetermined time is 7 to 20 minutes. 5. The method according to claim 2, wherein the predetermined temperature is 180 to 260 ° C., and the predetermined time is 12 to 30 minutes. 6. The predetermined temperature and time are 280 ° C.
(At least 20 minutes or more), 260 ° C (at least 7 minutes or more), 240 ° C (at least 6.5 minutes or more), 220 ° C (at least 9 minutes or more),
200 ° C (at least 11 minutes), 180 ° C
The method according to claim 2, wherein the temperature is (at least 13 minutes or more) or 160 ° C (at least 15 minutes or more). 7. An orthogonal coordinate system in which one axis is temperature and the other axis is time is 280 as said predetermined temperature and time.
° C (at least 20 minutes), 260 ° C (at least 7 minutes), 240 ° C (at least 6.5 minutes), 220 ° C (at least 9 minutes), 200 ° C (at least 11 minutes) Minutes or more), 18
0 ° C (hold for at least 13 minutes) or 160 ° C
(2) At least 15 minutes or more are plotted to specify regions satisfying these conditions, and any temperature and time included in these regions are included in the predetermined temperature and time. A method for producing the air-cooled tempered glass described above. 8. A tempered glass product produced by the method according to any one of claims 1 to 5, wherein the tempered glass product does not contain a foreign substance which extends a thermal residual stress and a crack generated thereby. 9. A tempering furnace for producing an air-cooled tempered glass product and a temperature control furnace or a slow cooling furnace continuously installed downstream of the quench equipment, wherein the temperature control furnace or the slow cooling furnace has a thermal residual furnace. By maintaining the wind-cooled tempered glass containing the foreign matter that extends the stress and the cracks generated with the stress at a predetermined temperature for a predetermined time, the wind-cooled tempered glass containing the foreign matter is broken and removed. Equipment for manufacturing air-cooled tempered glass products.