JPH0331656B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a heat-treated glass plate that is highly safe and prevents the crack from moving on its own even if a crack occurs in the glass plate. For example, in high-rise buildings, extra-thick glass plates of about 10 to 20 mm are used to improve the wind pressure resistance of window glass plates. Using such extra-thick glass plates has the disadvantage of significantly increasing weight, and when using thick heat-absorbing glass or colored coated glass plates, there is a particular risk of thermal cracking. The disadvantage is that it is expensive. Although it is possible to use air-cooled tempered glass sheets to reduce weight and prevent heat cracking, air-cooled tempered glass sheets break into many small pieces when broken, so air-cooled tempered glass sheets are not used in high-rise buildings. It is undesirable to use glass panels because there is a risk that glass fragments may fall from the windows of high-rise buildings when they break. Also, as a type of tempered glass plate, there is a chemically strengthened glass plate that has a high surface compressive stress and a small number of fragments, but this chemically strengthened glass plate has a significant decrease in strength when scratched, and it is difficult to strengthen it. Since the process requires a long time, it is not suitable for practical use. The present invention is thinner than conventional extra-thickness glass plates for window glass plates of high-rise buildings, has the same or higher wind resistance strength, does not have thermal cracking, has no practical problems, and can be mass-produced. This was obtained as a result of repeated research with the aim of providing a manufacturing method for heat-treated glass plates that can be heated to 600°C to 660°C. , this glass plate costs 100-300Kcal/
The surface temperature of the glass plate is lowered to 450°C to 560°C by primary cooling for 1 to 20 seconds at a cooling capacity of m2^・hr・°C, and then immediately after that, it is placed in a heat treatment furnace in the range of 200°C to 500°C. The present invention relates to a method for manufacturing a heat-treated glass plate, which is characterized in that the glass plate is slowly cooled in a heat-treated glass plate to adjust the generated stress. Immediately after heating a glass plate made of soda-lime glass plate to a softening point temperature range of 600℃ to 700℃,
A conventional ordinary tempered glass plate, which is strengthened by blowing air on both sides of the glass plate and rapidly cooling it, weighs 1000 kg/
A surface pressure linear stress of cm ² to 1500 Kg/cm ² and a tensile stress of about 1/2 of the surface compressive stress are generated at the center in the cross-sectional direction, and the cross-sectional stress distribution is as shown in FIG. And when this tempered glass plate breaks,
The cracks generated in the glass plate propagate and break into small pieces with a crushing density, for example, 40 to 200 pieces/5 cm square, which is uniquely determined by the magnitude of the central tensile stress. Also, the semi-tempered glass plate is 300
Surface compressive stress σc of ~600Kg/ ^cm2 and 250~400Kg/ ^cm2
The central tensile stress σt is less than 1.5, and the cross-sectional stress distribution is as shown in Figure 2. Although the glass plate does not break, the cracks that occur in the glass plate propagate by themselves and extend to the edges of the glass plate. Also, chemically strengthened glass plate is 1000Kg/cm ² ~ 3000
It has a surface compressive stress of Kg/ ^cm2 and a central tensile stress of 10 to 60Kg/ ^cm2 , and its cross-sectional stress distribution is as shown in Figure 3.This chemically strengthened glass sheet has a surface compressive stress layer. Because it is thin, its impact strength is significantly reduced when scratched. On the other hand, in the heat-treated glass plate manufactured according to the present invention, the central tensile stress is controlled to be low between 85 and 200 Kg/ ^cm2 , and the ratio of the surface compressive stress σc to the central tensile stress σt is σc/σt. is controlled in the range of 1.5 to 3.0, and the surface compressive stress is also 127 to 3.0.
Range of 600Kg/ ^cm2 , more preferably 250-350Kg/
cm ² and has a cross-sectional stress distribution as shown in Figure 4, so when a crack occurs in this heat-treated glass plate, the fracture line does not travel on its own and it does not break into small pieces. . Moreover, this heat-treated glass plate has a thickness of 5 mm or more and less than 10 mm, and has a thickness of 127 to 600 mm.
Kg/ ^cm2 , more preferably 250 to 350Kg/ ^cm2 , which has a surface compressive stress, so the wind pressure strength is more than twice that of a raw board of the same thickness, which is sufficient for practical use, and it is also resistant to thermal cracking. do not have. For example, when the plate thickness is 6 mm, the central tensile stress σt is 250
Kg/cm ² , surface compressive stress σ is 370Kg/cm ² (σc/σt=
1.48) If the central tensile stress in the heat-treated glass plate is too high and a crack occurs in the glass plate, the broken pieces become fine even when the crack moves on its own, resulting in a fracture pattern as shown in Figure 5. This is undesirable as it increases the risk of debris falling from the window. Also, the plate thickness is 8mm and the central tensile stress σc is 580Kg/
cm ² , surface compressive stress σt is 390Kg/cm ² (σc/σt=1.49)
Similarly to the above example, in the heat-treated glass plate, if a crack occurs in the glass plate because the central tensile stress is too high, when the crack moves on its own, the broken pieces become finer and become a broken pattern as shown in Fig. 6. This is undesirable as it increases the risk of the person falling out of the window. Also, the plate thickness is 6mm and the central tensile stress σt is 60Kg/
cm ² , and the surface compressive stress σc is 120Kg/cm ² (i.e. σc/σt=
The glass plate of 2.0) has a low central tensile stress, so if a crack occurs in the glass plate, the crack will not move by itself, but the wind resistance strength is low, which is not preferable. For example, the surface compressive stress required to withstand sufficient wind pressure, e.g.
If it is lower than 250Kg/cm ² , the wind pressure resistance strength decreases, which is not preferable. On the other hand, the fracture 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 6 described later, are 7th to 1st, respectively.
As shown in Figure 2, when a crack occurs in the glass plate, the self-propulsion of the crack is suppressed and no lines of breakage extend from one end of the glass plate to the other, causing broken pieces of the glass plate to fall from the window. You can prevent it from happening. In addition, the surface compressive stress required to prevent thermal cracking and wind pressure fracture is 127Kg/cm 2 or more, preferably 250Kg/cm ² or more.
Since it has a surface compressive stress higher than cm ² , there is little risk of thermal cracking, and it also has sufficient wind pressure resistance. In addition, when a glass plate breaks, the self-propelled crack is suppressed so that the fracture line (crack) does not extend from one side of the glass to the other, so there is a risk of broken glass pieces falling from the window. Although less is preferable,
Fracture line (crack) extending from one side of the glass plate to the other
The presence of a single fracture line (crack) of this kind does not necessarily limit the fracture pattern of the heat-treated glass produced according to the present invention, since the risk of broken pieces falling from the window is practically small even if there is only one fracture line. It is allowed as. Next, a specific example of the method for manufacturing the heat-treated glass plate of the present invention will be described. FIG. 13 shows a specific example of the apparatus used for manufacturing the heat-treated glass plate of the present invention, and in the figure, 1 indicates the glass plate to be heat-treated;
2 is a roller hearth, 3 is a conveyor roll for glass plates, 4 is a heating device for glass plates, 5 is a first cooling outlet provided vertically facing each other, 6 is a heat treatment furnace provided vertically facing each other, Reference numeral 7 indicates a second cooling outlet provided vertically to face each other. The glass plate 1 is conveyed horizontally in the roller hearth by a conveyor roller, or while sliding horizontally, to a temperature sufficient to heat-treat the glass plate, for example.
Heated to 600-660℃. The glass plate taken out from the roller hearth is moved between the first blower ports provided adjacent to the outlet of the roller hearth, and air is pumped through the first blower port 5 at a rate of 100 to 300 Kcal/m ² .
Spray the glass plate for 1 to 20 seconds to achieve a cooling capacity of hr・℃ until the surface temperature reaches the solidification temperature of the glass plate,
That is, it is cooled to about 450-560℃, then heated to 200℃.
The glass plate is placed in a heat treatment furnace at a temperature of ℃ to 500℃ and slowly cooled for 2 to 5 minutes to adjust the generated stress. When the surface temperature of the glass plate has decreased to 400 to 450℃, it is taken out from the heat treatment furnace. Furthermore, the glass plate is further cooled at the second cooling outlet 7 to obtain a heat-treated glass plate having a predetermined stress value and stress distribution. In the present invention, in order to obtain predetermined surface compressive stress, central tensile stress, and cross-sectional stress distribution, the above-mentioned
Heating of glass plate to 600~660℃, 100~
Cooling capacity of 300Kcal/m ²・hr・℃, primary cooling for 1 to 20 seconds, cooling to 450 to 560℃ by primary cooling, surface temperature of glass plate in a heat treatment furnace of 200 to 500℃
Slow cooling to 400-450°C and a combination of these conditions are important. The method for manufacturing the heat-treated glass plate of the present invention described above uses a roller hearth, but the method is not limited to this method. Immediately after that, the heated glass plate is heat-treated, or the glass plate is suspended from a hanger and heated in a heating furnace while being transported, and the heated glass plate is heat-treated immediately after it comes out of the outlet of the heating furnace. It can also be manufactured in the same way. In addition, when performing heat treatment by the method of the present invention, after being slowly cooled in the heat treatment furnace 6, it is returned to the first cooling nozzle 2.
If the secondary cooling is performed, the second cooling outlet can be omitted and the equipment cost can be reduced. Example A soda-lime glass plate was heat-treated using the above-mentioned apparatus under the conditions shown in Table 1, and the resulting heat-treated glass plate had a central tensile stress σt, a surface compressive stress σc,
σc/σt, allowable load indicating wind pressure resistance (probability of failure 1/10
00 or less), and the thermal cracking test results (temperature difference between the central part and the peripheral part of the glass plate until thermal cracking occurs) are also shown in Table 1. Also, JIS R for the heat-treated glass plates of Examples 1 to 6 and the heat-treated glass plates of Comparative Examples 1 to 2.
Figures 5 to 12 show the fracture patterns obtained when the destructive test specified in 6-5 of 3206 was carried out.

[Table] By the method of the present invention, the central tensile stress σt is 85~
The reason why a heat-treated glass plate can be obtained in which the surface compressive stress σc and the central tensile stress σt are in the range σc/σt of 1.5 to 3.0 is considered ^to be as follows. When a softened glass plate is rapidly cooled, the temperature distribution in the cross section of the glass plate goes through a transition state and becomes a steady state. Normally, the temperature at the center of the glass plate is the solidification temperature (560 to 567
The temperature distribution (difference in temperature between the surface and the center) when passing through the glass plate (°C) determines the degree of reinforcement of the glass plate, that is, the central tensile stress and the surface compressive stress. The present invention obtains a preferable stress by manipulating the change in temperature before and after solidifying the glass plate by giving a history different from that of simple cooling. In other words, when only the surface temperature of the glass plate is below the solidification temperature (at this point, the central part is still softened), cooling of the glass plate is stopped and the surface is gradually cooled in an atmosphere of 200 to 500°C. By delaying solidification only in the center without changing the temperature and solidification state, it is possible to relax the residual stress and reduce the central tensile stress. The surface compressive stress of the glass plate in the above examples and comparative examples was determined by the Toshiba air-cooled tempered glass surface stress meter FSM-
30, and the central tensile stress was measured as follows. Measurement of Γ central tensile stress Hold the glass plate sample 11 horizontally as shown in Figure 14, and emit linearly polarized light A perpendicular to the end face using a He-Ne laser 12 as a light source and passing through a polarizer 13, lens 14, and aperture 15. incident. Let y and Z be the directions parallel and perpendicular to the glass plate surface, respectively, and x be the direction of incidence. The vibration direction of the incident light is on the y-z plane, and for each axis,
Make it at a 45° angle. Linearly polarized light A incident from the end surface of the glass plate is due to the principal stress difference in the yz plane inherent in the glass,
A phase difference is generated, and as shown in Figure 15, the polarization changes as an ellipse with its axis at an angle of 45 degrees with the y-z axis → circle → ellipse → straight line (perpendicular to the incident light) → ellipse → circle → ellipse → straight line,
With a phase difference of 360°, the vibration direction returns to the same linear polarization as the original incident light. This polarized light is scattered in the glass, and when observed from a direction of 45 degrees to the y and z axes in the y-z plane perpendicular to the optical axis, it has one wavelength as shown in B in Figure 16 or Figure 17. It looks like a dot shape. Since the scattering of the float glass plate is very small, the scattered light to be observed is weak. For this purpose, a night vision device with a built-in micro-channel image intensifier is used to monitor the monitor television 17 through a high-sensitivity television camera 16.
A dot pattern of scattered light is projected on top. In combination with the position analyzer 18, the length can be read in real time. One of these dots corresponds to a phase difference of 360° (one wavelength), so by measuring this actual length, the principal stress difference can be determined using the photoelastic constant. The central tensile stress σy is determined from the principal stress difference Δσ determined here using the formula below. Principal stress difference △σ △σ=σy−σz=σy=λ/c・1/lλ σy: Component of stress in the plane direction, i.e. central tensile stress σz: Component of stress in the thickness direction (σz≒0) λ: Laser Light wavelength (632.8 mμ-He-Ne laser) l〓: Optical path difference (cm) corresponding to a phase difference of 360° C: Photoelastic constant 2.63 mμ/cm/Kg/cm ² (float plate) Central tensile stress σt is 85~200Kg/
cm ² , and the surface compressive stress σc is 127 to 600 Kg/cm ² , more preferably 250 to 350 Kg/cm ² . It shows the average of the measured values at five points, point P and one point Q in the center, and is captured as an average value. As described above, according to the present invention, the wind pressure resistance strength is sufficient for practical use, the crack does not cause thermal cracking, and even if the crack enters the glass plate, the crack does not move on its own.
It is possible to provide a heat-treated glass plate that does not break into small pieces. Even if this glass plate breaks, there is little risk that some or all of the pieces will fall off the window frame, and it is useful as a glass plate for construction of buildings, houses, etc. In particular, there is a demand for a glass plate that is free from the risk of glass fragments falling, and the heat-treated glass plate of the present invention is most suitable as a glass plate for windows for high-rise hills. Among them, heat-absorbing glass sheets used for windows and spandrels with a high risk of thermal cracking,
The heat-treated glass plate produced according to the present invention is suitable for glass plates such as colored coated glass plates and heat-reflecting glass plates. In addition, the glass plate manufactured according to the present invention has improved wind pressure strength and thermal cracking strength, and also prevents cracks from running on their own. A raw window glass plate is made into a 6 mm thick heat treated glass plate according to the present invention,
Furthermore, a conventional green window glass plate having a thickness of 12 mm can be replaced with a heat-treated glass plate having a thickness of 8 mm according to the present invention, and the weight of the glass plate can be reduced.

[Brief explanation of the drawing]

1 to 3 are stress distribution diagrams of a cross section in the thickness direction of a conventional tempered glass plate, FIG. 4 is a stress distribution diagram of a cross section of a heat treated glass plate manufactured according to the present invention in the thickness direction, and FIG. , 6 is a diagram of a crushing pattern of a glass plate according to a comparative example, Figures 7 to 12 are diagrams of a crushing pattern of a heat-treated glass plate according to the present invention, and Figure 13 is a specific example of an apparatus for carrying out the present invention. Such a schematic diagram,
Figure 14 is a schematic diagram of a device for measuring the central tensile stress of a glass plate; Figures 15 to 17 are explanatory diagrams showing the principle of measuring the central tensile stress of a glass plate; Figure 18 is a stress measurement point. FIG. 1: Glass plate to be heat treated, 2: Roller hearth, 3: Conveyance roll, 4: Glass plate heating device,
5: first cooling outlet, 6: heat treatment furnace, 7: second cooling outlet.

Claims (1)

[Claims] 1 Glass plates with a thickness of 5 mm or more and less than 10 mm at 600℃
After heating to 660℃, this glass plate is heated to 100~
300Kcal/m ²・hr・℃ cooling capacity for 1 to 20 seconds 1
Next, air cooling is performed to lower the surface temperature of the glass plate to the solidification temperature of the glass plate, 450 to 560℃, and then immediately after that,
A method for producing a heat-treated glass plate, which comprises placing the glass plate in a heat treatment furnace at a temperature of 200°C to 500°C for 2 to 5 minutes to cool the glass plate and adjust the generated stress.