JPH0653585B2 - Heat treatment method for glass plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is intended for a window of a high-rise building, in which even when a glass plate is cracked, the crack does not run by itself, wind pressure strength is sufficient, and thermal cracking does not occur. The present invention relates to a method for producing an optimal heat treated glass.

[Prior Art] In high-rise buildings, glass plates with a special thickness of about 10 mm to 20 mm are used in order to improve the wind pressure resistance of window glass plates. In this way, the use of extra-thick glass plates has the drawback of significantly increasing the weight, and the use of thick heat-absorbing glass or colored coated glass plates increases the risk of thermal cracking in particular. There is a drawback that. It is possible to use air-cooled tempered glass plate as a measure for weight reduction and heat crack prevention, but since air-cooled tempered glass plate becomes many small pieces when broken, it is used for high-rise buildings. Is not preferable because there is a risk that fragments of the glass plate will fall from the windows of the skyscraper when damaged.

A glass plate made of soda lime is used in the softening temperature range 600-70
Immediately after heating up to 0 ° C., the both sides of the glass plate of the conventional reinforced quenched by blowing air ordinary tempered glass ^{plate, 1000kg / cm 2 ~1500kg / cm} 2 of surface compressive stress and its cross-sectional direction Tensile stress, which is half of the surface compressive stress, is generated at the center, and the cross-sectional stress distribution is as shown in Fig. 1. When the tempered glass plate is broken, the cracks generated in the glass plate are self-propelled, and the crushing density uniquely determined by the magnitude of the central tensile stress, for example, 40 to 200 /
It has a 5 cm square and breaks finely. In addition, the so-called semi-tempered glass plate with the degree of tempering of the glass plate adjusted is 300-600 kg / cm.
² has a ratio of the surface compressive stress σ _c to the central tensile stress σ _t of 250 to 400 kg / cm ² and the σ _c / σ _t of less than 1.5, and the sectional stress distribution is as shown in Fig. 2. When the semi-tempered glass plate is broken, fine cracks do not break, but the cracks generated in the glass plate at the time of breakage are self-propelled and extend to the end of the glass plate. Further, chemically tempered glass sheet, a surface compressive stress of ^{1000kg / cm 2 ~3000kg / cm 2} 10~60kg
It has a central tensile stress of / cm ² , and its stress distribution is as shown in Fig. 3, and there are some with a small fragment number density at the time of crushing, but this chemically strengthened glass plate has a surface compressive stress layer. Since it is thin, it has a drawback that the impact strength when scratched is remarkably lowered, and it is not suitable for practical use because it requires a long time for the strengthening treatment step.

[Problems to be Solved by the Invention] In order to solve the problems occurring when the conventional tempered glass as described above is used as a window glass for a high-rise building or the like, even when a glass plate is cracked, cracks are generated by itself. Don't run,
And heat-treated glass that is ideal for window glass or spandrel of high-rise buildings that has sufficient wind pressure resistance and does not crack by heat,
That is, the heat-treated glass having a plate thickness of 5 to 12 mm, and the center tensile stress σ _t of the heat-treated glass plate is 85 kg / cm ^{2 to} 200 kg / cm ²
A heat-treated glass plate having a cross-sectional stress distribution in which the ratio σ _c / σ _t of the compressive stress σ _{c of the} surface to the central tensile stress σ _t is in the range of 1.5 to 3.0 is proposed.

In addition, as a method for producing such a heat-treated glass plate, after heating the glass plate through a heating furnace to 600 to 660 ° C, the glass plate is taken out of the heating furnace, and immediately thereafter, air is blown to the surface of the glass plate to blow it. It is known that the cooling rate is slowed down to 1/3 to 1/4 of that of ordinary tempered glass to cool the glass sheet to a temperature below the strain point. However, in such a manufacturing method, since the cooling rate of the glass plate is small,
Since it requires a cooling time that is about 2 to 3 times that of ordinary tempered glass, it has the drawback of low productivity and unsuitable for mass production.

INDUSTRIAL APPLICABILITY The present invention is a heat treatment that is thinner than a conventional extra-thick glass plate as a window glass for a high-rise building, does not cause self-propagation of cracks, has no thermal cracks, is practically inconvenient, and can be mass-produced. It is intended to provide a glass manufacturing method.

[Means for Solving the Problem] The present invention has been made to solve the above-mentioned problems, and includes a heating step of heating a glass plate having a plate thickness of 5 mm to 12 mm to 570 ° C to 660 ° C, and The glass is taken out of the heating furnace, and immediately thereafter an air is blown to the glass surface to cool the glass plate surface to a cooling heat transfer coefficient of 40 to 60 kcal / m ² h ℃, and an initial cooling step of cooling the glass plate to a strain point temperature or less, Then, a transition step of cooling the glass sheet while gradually increasing the cooling heat transfer rate,
When the cooling heat transfer rate reaches 100 to 120 kcal / m ² h ℃, there is a secondary cooling step of cooling the glass sheet while maintaining the cooling heat transfer rate, and the central tensile stress σ of this treated glass sheet is
_t is 85~200kg / cm ^2's range, and the ratio sigma _{c /} sigma _t is from 1.5 to 3 and the surface compressive stress sigma _c and the central tensile stress sigma _t.
The present invention provides a method for heat treating a glass plate, which is controlled so as to fall within a range of 0.

The heat-treated glass sheet of the present invention has a central tensile stress σ _t of 85.
Is ～200Kg / control low during cm ^2, and the ratio σ _{c /} σ _t and the surface compressive stress sigma _c and the central tensile stress sigma _t
The surface compressive stress can be controlled by controlling the range from 1.5 to 3.0.
127 to 600 kg / cm ² , more preferably 250 to 350 kg / cm ^2.
Since it is held down to cm ^{2 and} has a cross-sectional stress distribution as shown in FIG. 4, when the heat-treated glass plate has cracks, the fracture line does not self-propagate and does not break into fine fragments.
Moreover, this heat-treated glass plate has a plate thickness of 5 mm or more and 12 mm or less, and 127 to 600 kg / cm ² , more preferably 250 to 350 k.
Since it has a surface compressive stress of g / cm ^2, the wind pressure resistance is
It is more than twice the strength of a raw plate of the same thickness and has sufficient strength for practical use.
And there is no heat crack.

For example, the plate thickness is 6 mm, the central tensile stress σ _t is 250 kg / cm ² ,
A heat-treated glass plate with a surface compressive force σ _c of 500 kg / cm ² (σ _c / σ _t = 2) has a central tensile stress that is too high. Becomes finer and becomes a crushing pattern as shown in Fig. 9,
This is not preferable because the risk of crushed pieces falling from the window increases. The same applies to a glass plate having a plate thickness of 8 mm, a central tensile stress σ _t of 300 kg / cm ² and a surface compressive stress σ _c of 580 kg / cm ² (that is, σ _c / σ _t = 1.93).

On the other hand, the crushing patterns of the heat-treated glass sheets manufactured according to the present invention, for example, the heat-treated glass sheets of the samples of Examples 1 to 3 are as shown in FIGS. 6 to 8, respectively. The running is suppressed, and the shredding lines do not enter from one end of the glass plate to the other end, and it is possible to prevent the fragments of the glass plate from falling through the window.
Further, since it has a surface compressive stress of 127 kg / cm ² or more, particularly preferably higher than 200 kg / cm ² , which is required to prevent thermal cracking and wind pressure damage, there is little risk of thermal cracking, and The wind pressure resistance is also sufficient.

When the glass plate breaks, the self-propelled cracks are suppressed so that the breaking line (crack) does not extend from one side of the glass to the other. Although it is preferable, even if there is only one breaking line (crack) extending from one side to the other side of the glass plate, the risk of falling fragments from the window is practically low, so this kind of breaking line ( The presence of cracks) is allowed as a fracture pattern in the heat treated glass produced according to the invention. For example, Figures 7 and 8 are examples of this permissibility.

FIG. 10 is used to produce the heat-treated glass sheet of the present invention-showing a specific example.
1 is a glass plate having a thickness of 5 to 10 mm to be heat-treated, 2 is a roller hearth, 3 is a glass plate transport roll, 4 is a heating device for the glass plate, 5 is a wind blower provided to face each other vertically, and 6 is up and down. 3 shows a cooling furnace surface coating surface provided so as to face each other. Only one air outlet 5 may be provided as shown in FIG. 10, and the cooling heat transfer coefficient of the glass plate surface may be controlled by controlling the intensity of the air from the air outlet 5 by a program or the like. Two or more air outlets may be provided to change the air volume. The glass plate 1 to be heat-treated is heated in the roller hearth 2 while being conveyed horizontally by the conveying rolls 3 or while being horizontally slid to a temperature sufficient to strengthen the glass plate, for example, 570 ° C to 660 ° C. To be done. (Heating step) Then, the glass plate 1 taken out from the roller hearth 2 is moved between vertically opposed air inlets, and the wind is blown from the air inlets to the glass plate surface to transfer the heat of cooling the glass plate surface. rate is the manner become 40~60kcal / m ² h ℃, the temperature of the glass plate strain point less (520 ° C. or less in the case of ordinary soda lime glass, preferably not more than 480 ° C.)
Cool until. (Initial cooling process) At this time, the optimum cooling heat transfer coefficient is about 60 kcal / m ² h ℃ for 6 mm thick glass plate, 8
mm to about 50kcal / m ² h ℃ in thick glass plate, about 40kcal / m ² h ℃ glass plate 10mm thick. At this time, if the temperature of the air to be blown is hot air of 50 ° C to 400 ° C, the pressure of the blowing air is 0.1 to 10 mmAg, and the heat transfer coefficient of the glass plate surface is 40 to 60 kca1 / m ² h ° C. Can be controlled. Furthermore, in this case, the air outlet or the cooling furnace wall was mirror-finished.
It is preferable to use SUS304 or the like to reduce the emissivity to 0.1 or less and suppress the cooling due to the emissivity, because it becomes easier to control the cooling heat transfer coefficient of the glass plate surface.

In this way, when the temperature of the glass plate falls below the strain point, cooling is then performed while gradually increasing the cooling capacity, that is, usually while gradually increasing the cooling heat transfer coefficient of the glass plate surface. (Transition step) If the ratio of this gradual increase is too large, it will cause damage to the glass plate, and if it is too small, the effect of the present invention of improving productivity will be small, and therefore, depending on the thickness of the glass plate. It is preferable to set the width within a certain range.

Specifically, a glass plate having a thickness of 6 mm is ^{2 to 4} kcal / m ² h ° Cs, a glass plate having a thickness of 8 mm is 1 to 3 kcal / m ² h ° Cs, a glass plate having a thickness of 10 mm is 0.5 to 2. It is preferably set to 5 kcal / m ² h ° C.

Cooling heat transfer coefficient of glass plate surface is 100 ~ 120kcal / m ² h ℃
After that, cooling is performed while maintaining the heat transfer coefficient. (Secondary cooling step) As can be easily understood from the above, the time required for the transition step depends on the thickness of the glass plate, but is about 20
~ 40 seconds.

FIG. 16 shows changes in the cooling heat transfer coefficient of a typical glass plate surface for each glass plate thickness. Here, the horizontal axis represents time and the vertical axis represents cooling heat transfer coefficient.

In this way, the one that is cooled by increasing the cooling heat transfer coefficient of the surface can be heat-treated for one cycle in a time of about 240 seconds to 420 seconds. This is about 1 / th compared to the conventional heat treatment method.
The time is 2 to 1/3, and it is understood that the productivity can be significantly improved by adopting the glass plate heat treatment method according to the present invention.

Then, the glass plate is taken out from the air outlet to obtain a tempered glass plate product having a predetermined stress value and stress distribution.

The manufacturing method of the heat-treated glass plate of the present invention described above uses a roller hearth, but the method is not limited to this, and the glass plate is heated while being horizontally conveyed using a gas hearth, and exited from the gas hearth outlet. Immediately after that, a method of heat-treating the heated glass plate, or a method of heat-treating the heated glass plate immediately after exiting from the outlet of the heating furnace by heating the glass plate in a heating furnace while suspending and transporting the glass plate by a hanging hand, etc. It can be manufactured similarly.

[Operation] By the method of the present invention, the central tensile stress σ _t is 85 to 200 kcal /
The reason why a heat-treated glass having a range of cm ² and a ratio of the surface compressive stress σ _c to the central tensile stress σ _t of σ _c / σ _t of 1.5 to 3.0 can be obtained is considered as follows. .

When the softened glass plate is rapidly cooled, the temperature distribution in the glass plate cross-sectional direction becomes a steady state after passing through a certain transition state. Usually, the temperature at the center of the glass plate is the solidification temperature (560-5
The temperature distribution (temperature difference between the surface and the center) when passing through 70 ° C. determines the strengthening degree of the glass plate, that is, the central tensile stress and the surface compressive stress.

The method of the present invention focuses on controlling the temperature distribution when the softened glass plate is solidified. That is, since the temperature distribution of the cross section of the glass plate is uniquely determined by the cooling condition when the plate thickness is determined, this cooling condition is controlled to control the strengthening stress generated.

Example An ordinary soda-lime glass plate (strain point 511 ° C., softening point 740 ° C.) was heat-treated under the conditions shown in Table 1 using the above-mentioned apparatus, the heat-treatment conditions, and the obtained heat-treated glass plate Central tensile stress σ _t , surface compressive stress σ _c , σ _c / σ _t , allowable load indicating wind pressure resistance (fracture probability 1/1000 or less), thermal cracking test results (central part of glass plate until thermal cracking and surroundings) Temperature difference between parts), time required for one treatment cycle, etc.
3 and Comparative Examples 1 to 4 are shown in Table 1. In addition, Example 1
The fracture patterns of the heat-treated glass sheets of Nos. 3 to 3 and the heat-treated glass sheets of Comparative Examples 1 to 3 when subjected to the destructive test specified in JIS R 3206 6-5 are shown in FIGS.

By comparing Examples 1 to 3 in Table 1 with Comparative Examples 1 to 3, according to the heat treatment method for a glass plate according to the present invention, a glass plate showing a crushing pattern substantially similar to the conventional method has a very short treatment cycle. You can see that

The surface compressive stress of the glass plate in the above Examples and Comparative Examples is measured by Toshiba wind-cooled tempered glass surface stress meter FSM-30,
The central tensile stress is measured as follows.

・ Measurement of central tensile stress As shown in Fig. 11, the glass sample 11 is held horizontally, the He-Ne laser 12 is perpendicular to the end face, the light source is the polarizer 13, and the lens.
Linearly polarized light A that has passed through 14 and the diaphragm 15 is incident. Glass plate 11
The directions parallel and perpendicular to the plane are y and z, and the incident direction is x.
And

The vibration direction of the incident light should be at an angle of 45 ° with respect to each axis in the yz plane.

The linearly polarized light A incident from the end surface of the glass plate causes a phase difference due to the principal stress difference in the yz plane existing in the glass,
An ellipse having an axis at an angle of 45 ° with the yz axis as shown in Fig. 12 →
The polarization changes from circle → ellipse → straight line (orthogonal to the incident light) → ellipse → circle → ellipse → straight line, and with the phase difference of 360 °, the original incident light and the direction of vibration return to the same linearly polarized light.

This polarized light is scattered in the glass and is perpendicular to the optical axis, y
When observed from the directions of 45 ° with the y and z axes in the −z plane, it looks like dots for each wavelength as shown in B of FIG. 13 or FIG.

Since the scattering of the float glass plate is very small, the scattered light to be observed is weak. For this reason,
Using a night-vision device with a built-in channel image intensifier, a dot pattern of scattered light is projected on the monitor TV 17 through the high-sensitivity TV camera 16. Read the length in real time in combination with the Vision Analyzer 18.

Since each dot corresponds to a phase difference of 360 ° (1 wavelength), if the actual length is measured, the principal stress difference can be calculated from the photoelastic constant.

The central tensile stress σ _y is calculated from the principal stress difference Δσ calculated here by the following formula.

Principal stress difference Δσ σ _y : component in the plane direction of stress, that is, central tensile stress σ _t σ _z : component in the thickness direction of stress (σ _z ≈0) λ: laser light wavelength (632.8 mμ-He-Ne laser) lλ: 360 ° Optical path difference (cm) corresponding to phase difference c: Photoelastic constant 2.63 mμ / cm / kg / cm ² (float plate) The central tensile stress σ _t produced by the present invention is 85 to
200 kg / cm ^2, surface compressive stress sigma _c is 127 ~600kg / cm ^2, more preferably the above stress value of the heat treatment the glass plate 200~300kg / cm ^2, the periphery of the heat treatment the glass plate as in Fig. 15 This is an average of the measured values at 5 points of 4 points P of the part and 1 point Q of the central part, which is captured as the average value.

[Advantages of the Invention] According to the present invention, the wind pressure resistance is practically sufficient, thermal cracking does not occur, and even when the crack enters the glass plate, the crack does not self-propagate and may break into fine crushes. It is possible to provide unheated glass with high productivity. Even if this glass plate is broken, there is little risk that some or all of the fragments will fall out of the window frame, and it is useful as a glass plate for buildings such as buildings and houses. In particular, while a glass plate that is free from the risk of falling fragments of the glass plate is required, the heat-treated glass plate of the present invention is most suitable as a building glass plate for windows for high-rise buildings.

Among them, for a window having a high risk of heat cracking, or a heat ray absorbing glass sheet used for a spandrel, a colored coated glass sheet, a glass sheet such as a heat ray reflecting glass sheet, the heat treated glass sheet of the present invention is suitable. .

Further, since the glass sheet according to the present invention has improved wind pressure resistance and thermal cracking strength, and crack self-propelled prevention,
For example, a glass plate having a thickness of 10 mm has been conventionally used. It is possible to replace the raw plate window glass plate for the middle and high layers with a heat-treated glass plate having a thickness of 6 mm according to the present invention, and the conventional raw plate window glass plate having a thickness of 12 mm with a heat-treated glass plate having a thickness of 8 mm according to the present invention.
The weight of the glass plate can be reduced.

[Brief description of drawings]

1 to 3 are stress distribution diagrams of a cross section in the thickness direction of a conventional tempered glass plate, and FIG. 4 is a stress distribution diagram of the cross section in the thickness direction of a heat-treated glass plate manufactured by the method of the present invention. FIG. 5 is a crushing pattern diagram of a glass plate according to a comparative example, FIGS. 6 to 8 are crushing pattern diagrams of a heat-treated glass plate manufactured by the method of the present invention, and FIG. 9 is a crushing pattern diagram of normal tempered glass, FIG. 10 is a schematic view of a specific example of an apparatus for carrying out the present invention, FIG. 11 is a schematic view of an apparatus for measuring the central tensile stress of a glass plate, and FIGS. FIG. 15 is an explanatory view showing the principle of measuring the central tensile stress, FIG. 15 is an explanatory view showing stress measurement points, and FIG. 16 is a transition of the cooling heat transfer coefficient of the glass plate surface during heat treatment of the glass plate according to the present invention. It is a graph which shows. 1: Glass plate to be heat treated, 2: Roller hearth furnace,
3: Transport rolls, 4: Glass plate heating device, 5: Air blowout port.

Claims (1)

[Claims] 1. A glass plate having a thickness of 5 mm to 12 mm is 570 ° C. to 66.
A heating step of heating to 0 ° C, taking out this glass from the heating furnace, and immediately blowing air onto this glass surface to set the cooling heat transfer coefficient of the glass plate surface to 40 ~ 60 kcal / m ² h ° C and the strain point of the glass plate. The initial cooling step of cooling to below the temperature, the transition step of cooling the glass sheet while gradually increasing the cooling heat transfer coefficient, and the cooling heat transfer coefficient when the cooling heat transfer coefficient reaches 100 to 120 kcal / m ² h ℃. It has a secondary cooling step of cooling the glass plate while holding it, and the central tensile stress σ _t of the treated glass plate is in the range of 85 to 200 kg / cm ² , and its surface compressive stress σ _c and central tensile stress. The ratio of σ _t to σ _c / σ _t is
A heat treatment method for a glass plate, which is controlled to be in the range of 1.5 to 3.0.