JPH0649586B2 - Heat-treated glass plate and its manufacturing method - 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 optimum 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. For this reason, attempts have been made to prevent self-propagation of cracks by adjusting the degree of strengthening of the glass plate as so-called semi-strengthening.However, in a device that normally cools with air, natural cooling in the atmosphere where the protrusion of air was stopped Even the method with the least cooling capacity is 10 m / m
In the above glass thickness, the glass was strengthened by natural convection heat transfer, and the glass could not be manufactured under low stress where cracks did not run by itself. There is also a chemically strengthened glass plate that has a high surface compressive stress and a small fragment number density as a type of strengthened glass plate, but this chemically strengthened glass plate shows a significant decrease in strengthening when scratched and it takes a long time for the strengthening treatment process. Therefore, it is not suitable for practical use.

[Problems to be Solved by the Invention] The present invention is, as a window glass for a high-rise building or the like, thinner than or equal to or more than the thickness of a conventional extra-thickness glass sheet, and has no thermal crack and is practically inconvenient. Another object of the present invention is to provide a heat-treated glass plate that can be mass-produced and a manufacturing method thereof.

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 fracture density is uniquely determined by the magnitude of the central tensile stress, for example, 40 to 200 pieces / 5 cm square and finely cracked. Will end up. Also, the semi-tempered glass plate has a surface compression stress σ _c of 300 to 600 kg / cm ² and 250 to
Central tensile stress σ _t of 400 kg / cm ² and σ _c / σ _t less than 1.5
The cross-sectional stress distribution is as shown in Fig. 2. When this semi-tempered glass plate is broken, it does not break even with fine fragments, but the cracks generated on the glass plate at It runs and reaches the edge of the glass plate.

Further, chemically tempered glass plate has a central tensile stress of 1000kg / cm ² ~3000kg / cm ² of surface compressive stress and 10~60kg / cm ^2, as the cross-sectional stress distribution is shown in FIG. 3 Since this chemically strengthened glass plate has a thin surface compressive stress layer, the impact strength when scratched is significantly reduced.

Unlike conventional tempered glass, even when cracks occur in the glass plate, the cracks do not run on their own, and the wind pressure strength is sufficient and it is not heat cracked Optimal heat-treated glass for window glass or spandrel for high-rise buildings, that is, a heat treatment of glass plate thickness is 5 to 15 mm, the center of the heat-treated glass sheet tensile stress sigma _t is in the range of ^{85kg / cm 2 ~200kg / cm 2} , and,
Ratio σ between the compressive stress σ _{c of the} surface and the central tensile stress σ _t
It is already known in the process for producing a heat-treated glass sheet having a sectional stress distribution in which _c / σ _t is in the range of 1.5 to 3.0.

The method for producing heat-treated glass disclosed in JP-A-59-8628 is that after heating a glass plate through a heating furnace to 600 to 660 ° C.,
Remove this glass plate from the heating furnace and immediately blow hot air of 50 ° C to 300 ° C on the surface of this glass plate to cool the glass plate to a temperature below the strain point temperature of the glass plate by slowing it down from natural cooling in the atmosphere. It is to cool.

However, in such a manufacturing method, since the cooling of the glass by radiation from the glass to the cooling furnace wall is large, the temperature of the hot air is raised to a high temperature, the blowing of the hot air is weakened, and the cooling rate is slower than that of natural cooling. Must be done, especially if the thickness is 12
For ~ 19 mm glass sheets, the blowing of hot air must be uncontrollably small.

[Means for Solving the Problem] The present invention has been made to solve the above-mentioned problems, and after heating a glass plate having a plate thickness of 6 mm to 19 mm to 570 ° C to 660 ° C, the glass plate is heated. Of the glass plate is immediately placed in a cooling furnace having an inner surface with an emissivity of 0.1 to 0.3, and at the same time, the glass plate is heated to a temperature of 50
Central tensile stress σ _t characterized by cooling the glass plate by blowing hot air having a temperature of ℃ to 400 ℃ and a pressure of 0.1 mmAq to 10 mmAq to make the cooling rate of the glass plate slower than natural cooling in the atmosphere.
Of 85 to 200 kg / cm ² and the ratio σ _c / σ _{t of} the surface compressive stress σ _c to the central tensile stress σ _t is in the range of 1.5 to 3.0. Is.

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 was held down to cm ² and the cross-sectional stress distribution was as shown in Fig. 4, when the heat-treated glass plate had cracks, the fracture line did not run on its own and did not break into fine fragments. Moreover, this heat-treated glass plate has a plate thickness of 6 mm or more and 19 mm or less, and 127 to 600 kg / cm ² , more preferably 25
Since it has a surface compressive stress of 0 to 350 kg / cm ^2, the wind pressure resistance is at least twice as high as that of a green plate of the same thickness, which is a practically sufficient strength and does not cause thermal cracking.

For example, the plate thickness is 12 mm, the central tensile stress σ _t is 250 kg / cm ² ,
A heat-treated glass plate with a surface compressive stress σ _c of 380 kg / cm ² (σ _c / σ _t = 1.52) has a central tensile stress that is too high. Becomes finer and has a crushing pattern as shown in FIG. 5, and there is a high risk of the crushed pieces falling from the window, which is not preferable. The plate thickness is 15 mm and the central tensile stress σ _t is 275 kg / cm.
² , the surface compressive stress σ _c is 450 kg / cm ² (ie σ _c / σ _t = 1.6
The same applies to the glass plate of 4).

On the other hand, the crushing patterns of the heat-treated glass plates manufactured according to the present invention, for example, the heat-treated glass plates of the samples of Examples 1 to 4 are as shown in FIGS. 6 to 9, respectively. The running is suppressed, and the breaking lines do not enter from one end of the glass plate to the other end, and the fragments of the glass plate can be prevented 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 shows one specific example used for producing the heat-treated glass plate of the present invention.
1 is a glass plate to be heat-treated, 2 is a roller hearth, 3 is a glass plate conveying roll, 4 is a heating device for the glass plate, 5 is a hot air outlet provided vertically opposed, and 6 is vertically opposed. The cooling furnace surface coating surface provided is shown. The glass plate 1 to be heat-treated is transported horizontally in the roller hearth 2 by the transport rolls 3 or while being horizontally slid, to a temperature sufficient to strengthen the glass plate, for example, 570 ° C.
Heated to 660 ° C. Then, the glass plate 1 taken out from the roller hearth 1 is moved between the hot air inlets which are vertically opposed to each other, and hot air of 50 ° C to 400 ° C is blown from the hot air inlet to the glass plate surface at a wind pressure of 0.1 to 10 mmAq, and the Cool the plate to a temperature of 200-450 ° C. In this case, the hot air outlet or cooling furnace wall is made of mirror-finished SUS304 with an emissivity of 0.1.
Below, the cooling by radiation is suppressed. Then, the glass sheet is taken out from the hot air outlet to obtain a tempered glass sheet product having a predetermined stress value and stress distribution.

In the present invention, in order to obtain a predetermined surface compressive stress, central tensile stress and cross-sectional stress distribution, the above-mentioned heating temperature of the glass plate up to 570 to 660 ° C., 50 to 400 ° C., wind pressure 0.1 mmAq to 10 m
Blowing out hot air of mAq, glass plate temperature due to this blowing out hot air
It is important to cool down to 200-450 ℃, suppress radiative cooling by reducing the emissivity of the cooling furnace wall (0.1-0.3), and combine these conditions.

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, the same applies to the method of heat-treating the heated glass plate, or the method of heat-treating the heated glass immediately after exiting from the outlet of the heating furnace while the glass plate is hung by the hanging hand and conveyed and heated. Can be manufactured.

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

Generally, the residual stress generated when the softened glass plate is cooled and strengthened is calculated by the following theoretical formula.

(Heat transfer equation inside glass) Solving this gives the central tensile stress σ _t Becomes

Here, the cooling capacity of natural cooling is usually about k = 1.1 ° C / sec.

From the relation of Q = 2.5 × 10 ⁴ k kcal / m ² h Becomes

However, in the case of natural cooling, the difference in cooling ability between both surfaces of the glass plate cannot be controlled, so that the glass plate is warped. In order to adjust this, the cooling capacity of one side should be k> 1.1.
It is industrially impossible to satisfy σ _t <200 kg / cm ² for a glass plate of m / m or more.

In the present invention, it is possible to reduce the emissivity of the cooling furnace wall of k, control it by using hot air, and adjust to σ _t = 85 to 200 kg / cm ² .

[Example] A soda-lime glass plate was heat-treated under the conditions shown in Table 1 using the above-described apparatus, and the obtained heat-treated glass plate had a central tensile stress σ _t , a surface compressive stress σ _c , and σ _c / σ. Table 1 also shows _{t 1} , allowable load indicating wind pressure resistance (breaking probability 1/1000 or less), and thermal cracking test results (temperature difference between the central portion and the peripheral portion of the glass plate before thermal cracking). JIS for the heat-treated glass plates of Examples 1 to 4 and the heat-treated glass plate of Comparative Example 1
The crushing patterns when the destructive test specified in 6-5 of R 3206 is performed are shown in FIGS.

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
Parallel and perpendicular to the plane are y and z, and the incident direction is x.

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 inside the glass, and as shown in FIG. 12, an ellipse having an axis at an angle of 45 ° with the yz axis. → Circle → Ellipse → Straight line (orthogonal to incident light) → Ellipse → Circle → Ellipse → Polarization changes to a straight line and returns to linear polarization with the same oscillation direction as the original incident light with a phase difference of 360 °.

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,
A night-vision device with a built-in channel image intensifier is used to display a dot pattern of scattered light on a monitor TV 17 through a high-sensitivity TV camera 16. Read the length in real time in combination with the Vision Analyzer 18.

Since one dot corresponds to a phase difference of 360 ° (one wavelength), it is possible to know the principal stress difference by using the photoelastic constant by measuring the actual length.

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: wavelength of laser light (632.8 mμ-He-Ne laser) lλ: 360 Optical path difference (cm) C corresponding to the phase difference of ° 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 if the crack enters the glass plate, the crack does not run on its own and may break into fine pulverization. No heat treated glass can be provided. Even if this glass plate is broken, there is little risk that some or all of the fragments will fall off the window frame, and it is useful as a glass plate for construction 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 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 9 are crushing pattern diagrams of a heat-treated glass plate manufactured by the method of the present invention, and FIG. 10 is an apparatus for carrying out the present invention. Schematic diagram concerning one specific example, FIG. 11 is a schematic diagram of an apparatus for measuring the central tensile stress of a glass plate, and FIGS. 12 to 14 are explanatory diagrams showing the principle of measuring the central tensile stress of a glass plate, First
FIG. 5 is an explanatory diagram showing stress measurement points. 1: Glass plate to be heat treated, 2: Roller hearth furnace,
3: Transport roll, 4: Glass plate heating device, 5: Hot air outlet, 6: Heat exchanger.

Claims (7)

[Claims] 1. A glass plate having a thickness of 6 mm to 19 mm is 570 ° C. to 66.
After heating to 0 ℃, remove this glass plate from the heating furnace,
Immediately thereafter, the glass plate was placed in a cooling furnace having an inner surface with an emissivity of 0.1 to 0.3, and at the same time, hot air with a temperature of 50 ° C to 400 ° C and a wind pressure of 0.1 mmAq to 10 mmAq was blown onto the glass plate to cool the glass plate. Cooling the glass plate within a certain cooling capacity by slowing the cooling rate to a value lower than the natural cooling in the atmosphere, and the central tensile stress σ _t is in the range of 85 to 200 kg / cm ² and the surface thereof is Compressive stress σ _c and central tensile stress σ _t
A method for producing a heat-treated glass plate having a ratio σ _c / σ _t of 1.5 to 3.0. 2. A glass plate having a plate thickness of 6 mm to 19 mm is heated to 570 ° C. to 660 ° C. while being conveyed horizontally in a roller hearth furnace, then taken out horizontally from the roller hearth furnace and placed between opposed blow outlets. 2. The heat-treated glass according to claim 1, wherein hot glass having a temperature of 50 ° C. to 400 ° C. is blown out from the air outlet at a wind pressure of 0.1 mmAq to 10 mmAq to cool the glass plate to a strain point temperature of the glass or lower. How to make a board. 3. A hot air of 50 ° C. to 400 ° C. heated by a heat exchanger in a roller hearth furnace is blown onto both sides of a glass plate taken out horizontally from the roller hearth furnace. The method for producing a heat-treated glass plate according to item 2. 4. A heat-treated glass sheet according to claim 1, wherein a heater is inserted in the middle of a duct that allows cooling air to reach the air outlet to heat the air to 50 ° C. to 400 ° C. to produce hot air. Manufacturing method. 5. A glass plate is heated to 600 to 660 ° C., and then hot air having a temperature of 50 to 400 ° C. and a wind pressure of 0.1 mmAq to 10 mmAq is blown in a cooling furnace having a furnace wall emissivity of 0.1 to 0.3, as shown below. The central tensile stress characterized by cooling at a cooling rate K (° C / sec) is in the range of 85 to 200 kg / cm ² , and the ratio of the surface compressive stress σ _c to the central tensile stress σ _t is σ _c / σ _t is 1.5
Manufacturing method of heat-treated glass plate in the range of up to 3.0. 2.33 ≤ K ≤ 4.34 (° C / sec) when the plate thickness is 6 mm 1.79 ≤ K ≤ 3.14 (° C / sec) when the plate thickness is 8 mm 1.38 ≤ K ≤ 2.78 (° C / sec) when the plate thickness is 10 mm For 12 mm, 1.00 ≤ K ≤ 1.59 (° C / sec) For plate thickness 15 mm, 0.69 ≤ K ≤ 1.16 (° C / sec) For plate thickness 19 mm, 0.58 ≤ K ≤ 0.91 (° C / sec) 6. A cooling furnace inner surface is coated with brass, chromium, stainless steel, or metal oxides or compounds of groups 2, 3 and 4 of the periodic table (excluding Ge and Si oxides and compounds). The method for producing a heat-treated glass sheet according to claim 1 or 5, wherein the emissivity of the inner surface of the cooling furnace is set to 0.1 to 0.3 by using it as a furnace wall material. 7. After being heated to 570 ° C. to 660 ° C. and taken out from the heating furnace, immediately in a cooling furnace having an inner surface with an emissivity of 0.1 to 0.3, the surface has a temperature of 50 ° C. to 400 ° C. and a wind pressure. 0.1 m
A heat-treated glass plate having a plate thickness of 6 mm to 19 mm, which is obtained by blowing hot air of m Aq to 10 mm Aq to cool the glass at a cooling rate slower than natural cooling in the atmosphere and cooling within a certain cooling capacity,
The central tensile stress σ _t is in the range of 85 to 200 kg / cm ² , and the ratio of the surface compressive stress σ _c to the central tensile stress σ _t σ _c / σ
A heat-treated glass sheet produced by the production method according to claim 1, wherein _t is in the range of 1.5 to 3.0.