JPS5925736B2 - Improved method for manufacturing heat-treated glass plates - Google Patents

Description

[Detailed Description of the Invention] The present invention manufactures heat-treated glass that does not cause cracks to propagate even when a glass plate cracks, has sufficient wind pressure resistance, and does not crack due to heat, and is ideal for use in windows of high-rise buildings. It is about the method.

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.

There is also a chemically strengthened glass sheet that has a high surface compressive stress and a low fragment number density as a type of tempered glass sheet, but this chemically strengthened glass sheet has a significant decrease in strength when scratched and is difficult to process during the strengthening treatment process. It is not suitable for practical use because it requires a long time.

Furthermore, since it is not possible to manufacture hand-strengthened glass with special thickness of 10 m/m or more even by allowing it to cool naturally, there has been no example of the use of the above-mentioned improved glass.

First, the applicant has discovered that, unlike conventional tempered glass plates, even when a crack occurs in the glass plate, the crack does not propagate by itself.
A heat-treated glass that has sufficient wind pressure strength and does not crack under heat and is suitable for use in window glasses or spandrels of high-rise buildings, that is, a heat-treated glass plate with a thickness of 5 to 15 mm,
The central tensile stress σt of the heat-treated glass plate is 85 kg/c
f? A heat-treated glass plate having a cross-sectional stress distribution in the range of L ~ 200 kg/i and a ratio σC/σt of the compressive stress σC on the surface and the central tensile stress σt in the range 1.5 to 3.0. provided.

The present invention was obtained as a result of repeated research aimed at providing an industrial manufacturing method for such heat-treated glass plates. After heating the glass plate to ℃, the thickness of the glass plate is h(m) and the cooling rate is k('C/
sec), by providing a cooling capacity such that hk≧45.
- Primary air cooling for 20 seconds to bring the surface temperature of the glass plate to 450 -
560°C, more preferably 500-520°C, and then the glass plate is heated to a temperature of 100-500°C,
More preferably, the glass plate is passed between opposed heating plates maintained at a temperature of 300 to 400°C and slowly cooled to 450'C or less, and then further air-cooled for a second time, so that the central tensile stress σt of the treated glass plate is The range is 85 to 200 kg/i, and the ratio of the surface compressive stress σC to the central tensile stress σt is σC/
The present invention relates to an improved method for manufacturing a heat-treated glass plate characterized in that σt is controlled to be in the range of 1.5 to 3.0.

Conventional ordinary tempered glass plates are made by heating a glass plate made of soda-lime glass to its softening point (600°C to 700°C) and then immediately blowing air onto both sides of the glass plate to quickly cool it and strengthen it. 100'Okg/cit~
A surface compressive stress of 1500 kg/ant and a tensile stress of approximately 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.

When this tempered glass plate breaks, the cracks generated in the glass plate propagate by themselves, and the fracture density is uniquely determined by the magnitude of the central tensile stress, for example, 40 to 20.
0 pieces 15C1rL It breaks into small pieces with an angle.

In addition, the semi-strengthened glass plate has a surface compressive stress of 300 to 600 kg/i and a central tensile stress σ of 250 to 400 kg/d.
t and a ratio of σC/σt of less than 1.5, and its cross-sectional stress distribution is as shown in Figure 2, so that when this semi-strengthened glass plate breaks, it does not break with small pieces. However, the cracks that occur in the glass plate at the time of destruction propagate by themselves and extend to the edges of the glass plate.

Also, chemically strengthened glass plates have a weight of 1000 kg/i to 300 kg/i
0kg/CI? Surface compressive stress of L and 10 to 60 kg/d
It has a central tensile stress of Although this is not a problem, it has poor scratch resistance and is not practical.

On the other hand, the heat-treated glass plate manufactured according to the present invention has a central tensile stress controlled to be low between 85 and 200 kg/d, and a ratio σC/σt of the surface compressive stress σC and the central tensile stress σt. The surface compressive stress is controlled within the range of 1.5 to 3.0 and is 127 to 600 k.
g/cyrt range, more preferably 250-350
kg/i 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 propagate by itself and it does not break into small pieces.

Furthermore, this heat-treated glass plate has a thickness of 5 to 151 m and a surface compressive stress of 127 kg/= to 600 kg/cyyt, more preferably 250 to 350 kg/i, so the wind pressure strength is the same. It is more than twice as thick as a raw board, has sufficient strength for use in soil, and does not crack due to heat.

For example, if the plate thickness is 6 mm, the central tensile stress σt is 250 kg.
/d, surface compressive stress σc is 500ky/i (a c/σ
In the case of the heat-treated glass plate shown in t-2), if the central tensile stress is too high and the glass plate cracks, the crack propagates on its own and the fragments become finer, resulting in a fracture pattern as shown in Figure 5. This is undesirable as there is a high risk of debris falling from the window.

In addition, the plate thickness is 8 mm and the central tensile stress σt is 300 kg/c.
r? L, surface compressive stress σc is 580 kg/cr7L (σ
Similarly, if a heat-treated glass plate with C/σt = 1.93) cracks because the central tensile stress is too high, the crack will propagate and the fragments will become finer, as shown in Figure 6. This is undesirable because it increases the risk of fragments falling out of the window.

Also, when the plate thickness is 12m7IL, the central tensile stress σt is 250
kg/ffl, surface compressive stress σc is 380 kg/ff1
Similarly, when a heat-treated glass plate with (a c/σt = 1.52) cracks because the central tensile stress is too high, the crack propagates on its own and the fragments become finer, as shown in Figure 7. This results in a fracture pattern as shown in the figure, which is undesirable as it increases the risk of the fractured pieces falling out of the window.

Also, the plate thickness is 6 mm, the central tensile stress at is 60 ky/i,
The surface compressive stress σc is 120 to 9/= (i.e. σC/σt=
The glass plate 2.0) has a low central tensile stress, so if a crack occurs in the glass plate, the crack will not propagate by itself, but the wind resistance strength is low, 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 samples of Examples 1 to 7, are as shown in Figures 8 to 14, respectively, and when a crack occurs in the glass plate, the crack does not propagate by itself. This prevents many broken lines from entering from one end of the glass plate to the other, and prevents broken pieces of the glass plate from falling from the window.

In addition, the surface compressive stress required to prevent thermal cracking and wind pressure fracture is 127 kg/cWrL or more, particularly preferably 250 kg/cWrL.
Since it has a surface compressive stress higher than kg/crtt, there is little risk of thermal cracking, and it also has sufficient wind pressure resistance.

In addition, when a glass plate breaks, the self-propagation of the 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 pieces of the glass plate falling from the window. Although it is preferable to have a small number of broken lines (cracks) extending from one side of the glass plate to the other, there is actually no danger of broken pieces falling from the window into the ground, so this type of breakage of about one line is not recommended. The presence of lines (cracks) is acceptable as a fracture pattern in the heat treated glass produced according to the present invention.

For example, a fracture pattern as shown in FIG. 13 is permitted.

Next, a specific example of the method for manufacturing a heat-treated glass plate of the present invention will be described.

FIG. 1 shows a specific example of the apparatus used for producing the heat-treated glass plate of the present invention. In the figure, 1 is the glass plate to be heat-treated, 2 is the roller berth, and 3 is the glass plate. A conveyance roll, 4 a heating device for the glass plate, 5 a first cooling nozzle provided oppositely, 6 a heating plate provided oppositely, and 7 a second cooling nozzle provided oppositely. show.

The glass plate 1 is heated to a temperature sufficient to heat-treat the glass plate while being horizontally conveyed by a conveyor roller or sliding horizontally in a roller berth, for example at 60°C.
Heated from 0 to 660°C.

The glass plate taken out from the roller berth 3 is moved between a first cooling outlet 5 provided adjacent to the outlet of the roller berth that blows out cooling air, and air is blown from the first cooling outlet 5 to the glass plate. Plate thickness/hmm, cooling rate/K0
The glass plate is cooled down to a surface temperature of 450 to 560°C, preferably 500 to 520°C by blowing for 1 to 20 seconds with a cooling power such that hK≧45 when expressed as C/sec, and then The glass plate is moved between heating plates having a temperature of 100°C to 500°C, particularly preferably 300°C to 400°C, and slowly cooled between the heating plates to 450°C or less, preferably 400°C or less. , then taken out from between the heating plates and moved between the second cooling outlets, and this second
When the glass plate is further cooled by blowing air between the cooling nozzles and the temperature of the glass plate has decreased to 100 to 300°C, it is taken out from the second cooling nozzle and the heat-treated glass is heated to have a predetermined stress value and stress distribution. Let it be a board.

In the present invention, predetermined surface compressive stress, central tensile stress,
and 600 to 660 as described above to obtain the cross-sectional stress distribution.
Heating of glass plate up to °C, cooling capacity of hK≧45 and 1~
20 seconds of primary cooling, 450-56 due to primary cooling
Cooling to 0°C, slow cooling between heating plates of 100 to 500°C until the glass plate temperature reaches 450°C or less, 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 berth, but is not limited to this method. Alternatively, the heated glass plate may be heated in a heating furnace while being suspended from a hanger while being transported, and the heated glass plate may be heat treated immediately after it comes out of the outlet of the heating furnace. It can be manufactured similarly.

In addition, when performing heat treatment according to the method of the present invention, if the second cooling port is cooled slowly in the heating plate and then returned to the first cooling port for secondary cooling, the second cooling port can be omitted and equipment costs can be reduced. 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 central tensile stress σt, surface compressive stress σC1σC/σt, and allowable load indicating wind pressure resistance of the heat-treated glass plate obtained were (Probability of breakage: 171,000 or less) and thermal cracking test results (temperature difference between the center and peripheral portions of the glass plate until thermal cracking occurs) are also shown in Table 1.

In addition, the fracture patterns when the heat-treated glass plates of Examples 1 to 7 and the heat-treated glass plates of Comparative Examples 1 to 3 were subjected to the destructive test specified in JISR3206 6-5 are shown in Figures 8 to 13. Indicated.

By the method of the present invention, the central tensile stress σt is 85 to 200.
The reason why a heat-treated glass plate can be obtained in which the surface compressive stress σC and the central tensile stress ratio σC/σt is in the range of 1.5 to 3.0 is thought 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 570
The temperature distribution (temperature difference between the surface and 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 falls below the solidification temperature (at this point, the central part is still softened), the cooling of the glass plate is stopped and the surface temperature is lowered by slowly cooling the glass plate in an atmosphere of 200 to 500°C. By delaying solidification only in the center without changing the solidification state, it is possible to relax the residual stress and reduce the central tensile stress.

In addition, for glass with a thickness of 10 to 15 m/m, it is impossible to control σt≦200 kg/d even by natural cooling due to the thick plate thickness, so it is necessary to perform an appropriate slow cooling operation as in the present invention. is necessary.

The surface compressive stress of the glass plates in the above Examples and Comparative Examples was measured using a Toshiba air-cooled tempered glass surface stress meter FS-M-30, and the central tensile stress was measured as follows.

・Measurement of central tensile stress Hold the glass plate sample 11 horizontally as shown in Figure 16,
A polarizer 13 is installed perpendicularly to the end face using a He-Ne laser 12 as a light source.
, a lens 14, and a linearly polarized light A that has passed through an aperture 15.

Let y and z be the directions parallel and perpendicular to the surface of the glass plate 11, and let X be the direction of incidence.

The direction of vibration of the incident light is set at an angle of 45° with respect to each axis in the y-z plane.

Linearly polarized light A incident from the end surface of the glass plate 11 produces a phase difference due to the principal stress difference in the y-z plane inherent in the glass, and as shown in FIG. ellipse → circle → ellipse → straight line (perpendicular to the incident light) → ellipse →
The polarization changes from circle to ellipse to straight line, and 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 within the glass and is oriented at right angles to the optical axis.
When observed from a direction of 45° with respect to the y''z axis in the -z plane, it appears as dots for each wavelength, as shown in B of FIG. 18 and FIG. 19.

Since the scattering of the float glass plate is very small, the scattered light to be observed is weak.

To this end, a night vision device with a built-in micro-channel image intensifier is used to project a dot pattern of scattered light onto a monitor television 17 through a high-sensitivity television camera 16.

In combination with the position analyzer 18, the length can be read in real time.

Since one dot corresponds to a phase difference of 360° (one wavelength), by measuring this actual length, the principal stress difference can be determined using the photoelastic constant.

From the principal stress difference Δσ found here, the central tensile stress σy is determined by the following formula.

Principal stress difference △σ σy: Component of stress in the plane direction, i.e. central tensile stress σZ: Component of stress in the thickness direction (σ2=0) λ: Laser light wavelength (632, m p, -He -N e laser) lλ : Optical path difference corresponding to 360° phase difference - Two-way elastic constant 2.63 mμ/cm/kg/cr? t (float plate) Note that the central tensile stress σt manufactured by the present invention is 85
~200kg/ml, surface compressive stress σC is 127~60
0 kg/ffl, more preferably 250-350 k
The above stress values of the heat-treated glass plate in g/ca are the 20th
As shown in the figure, 4 points P on the periphery of the heat-treated glass plate and 1 point on the center.
It is an average of the measured values at five points, including point Q, and is taken as an average value.

As described above, according to the present invention, the wind pressure strength is sufficient for practical use, there is no thermal cracking, and furthermore, even if a crack enters the glass plate, the crack will not propagate by itself and will not break into small pieces. No heat treated glass can be provided.

Even if this glass plate breaks, there is little risk that some or all of the pieces will fall off from 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 falling glass fragments, and the heat-treated glass plate produced by the method of the present invention is optimal as a glass plate for windows in high-rise buildings.

Among these, the heat-treated glass sheet manufactured by the present invention is suitable for glass sheets such as heat-absorbing glass sheets, colored coated glass sheets, and heat-reflecting glass sheets used for windows or spandrels that have a high risk of thermal cracking. be.

In addition, the glass plate manufactured according to the present invention has improved wind pressure strength and thermal cracking strength, and is also prevented from propagating cracks, so that, for example, the strength of the conventional glass plate is 10 mmN.

A 6 mm thick heat treated glass plate manufactured according to the present invention was used to replace a window glass plate for mid-to-high-rise buildings, and a 12 myrt thick conventional raw glass plate was replaced with an 8 m high glass plate according to the present invention.
It is possible to replace a heat-treated glass plate with a thickness of m or a conventional raw glass plate with a thickness of 19 mm with a heat-treated glass plate with a thickness of 12 mrIL 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, and FIG. 4 is a stress distribution diagram of a cross section in the thickness direction of a heat-treated glass plate manufactured by the method of the present invention. 5th~
Figure 7 is a diagram of the fracture pattern of the glass plate according to the comparative example, and Figures 8-
Figure 14 is a diagram of the fracture pattern of a heat-treated glass plate produced by the method of the present invention, Figure 15 is a schematic diagram of a specific example of an apparatus for carrying out the present invention, and Figure 16 is a diagram showing the central tensile stress of the glass plate. Schematic diagram of an apparatus for measuring, No. 17-1
FIG. 9 is an explanatory diagram showing the principle of measuring the central tensile stress of a glass plate, and FIG. 20 is an explanatory diagram showing stress measurement points. 1: Glass plate to be heat treated, 2: Roller hearth, 3:
Conveyance roll, 4 glass plate heating device, 5: first cooling nozzle, 6: heating plate, 7: second cooling nozzle.

Claims (1)

[Claims] 1. A glass plate with a thickness of 5 mm to 15 mm is heated at 600°C to 66°C.
After heating this glass plate to 0°C, when the thickness of the glass plate is h (im) and the cooling rate is K ('C/sec), hK≧
The surface temperature of the glass plate was lowered to 450 to 560°C by primary air cooling for 1 to 20 seconds, and the glass plate was then held at a temperature of 100 to 500°C. The treated glass plate was cooled gradually to 450°C or lower by passing it between opposing heating plates, and then further air-cooled, so that the central tensile stress σt of the treated glass plate was in the range of 85 to 200 y/=, and the surface An improved method for producing a heat-treated glass plate, characterized in that the ratio σC/σt of compressive stress σC and central tensile stress σt is controlled to be in the range of 1.5 to 3.0. 2. The method for producing a heat-treated glass plate according to claim 1, wherein the heated glass plate is subjected to primary air cooling for 4 seconds to 10 seconds. 3. The method for manufacturing a heat-treated glass plate according to claim 1, wherein the temperature of the heating plate is maintained at 300°C to 400°C. 4 A glass plate with a thickness of 5 mrn to 15 mm is transported horizontally in a roller hearth furnace at 6000 C to 660 °C.
After heating, the glass plate was taken out horizontally from the roller hearth furnace and placed between opposing primary cooling blowholes to perform primary air cooling to lower the surface temperature of the glass plate to 450 to 560°C, and then to 100°C.
Suitable between opposing heating plates at temperatures between 4°C and 500°C
2. The improved method for producing a heat-treated glass sheet according to claim 1, wherein the glass sheet is slowly cooled to 50° C. or lower, and then passed through opposing secondary cooling ports for secondary air cooling. 5. The improved method for producing a heat-treated glass plate according to claim 4, characterized in that the glass plate is heated by sliding the glass plate horizontally in a roller hearth furnace.