JPH02267131A - Method for strengthening flat glass - Google Patents

Abstract

PURPOSE:To enable prevention of occurrence of deformation, etc., of a flat glass and sharp reduction of breakage, etc., even in thin flat glass by blowing the air generating shock wave having specific coefficient of thermal expansion and air having specific coefficient of thermal expansion in two stages into the flat glass in method for strengthening the flat glass by air cooling. CONSTITUTION:Cooling air is blown onto the surface of a flat glass heated to strain point or above from a cooling nozzle arranged in a pair of air chambers to strengthen the flat glass. In the above-mentioned method, two-stage cooling by blowing air generating shock wave having 300-1000Kcal/m<2>.h. deg.C coefficient of thermal expansion and then successively blowing air having 100-300 Kcal/m<2>.h. deg.C coefficient of thermal expansion is carried out. According to the above-mentioned method, initial heat removing effect is improved and cooling ability can be remarkably increased by breaking or thickening boundary film suppressing thermal transfer produced on the surface of heated thin plate and promoting release of heat to air.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to sheet glass, especially thin sheet glass, especially 1.5~
The present invention relates to a method for more stably and efficiently strengthening plate glass with a thickness of about 3.5 mm by air cooling. It relates to a method of strengthening thin glass that can obtain a satisfactory degree of reinforcement that can be used in automobile window glass, and is also used for railway vehicle window glass, architecture, furniture, general industry, and electronic parts. It can also be widely used in glass for industrial use and the like.

[Conventional technology]

Recently, as the weight of automobiles has been reduced, the tempered glass used has been required to be made thinner. However, when it breaks, it breaks into large, small, or long pieces, which poses a risk of injury to the driver and passengers. For example, radius 7 near the fracture starting point from the surface
, the number of glass fragments in any 5x5al area is within the range of 60 to 400, except for a 5cm circular area and a 3cm wide band near the edge, and the area of the fragments is 3ca
It is necessary to meet conditions such as not exceeding 751 mm in length and that there are no elongated pieces (called sharp edges) exceeding 751 mm in length. It can no longer be used as glass.

On the other hand, for thin glass sheets with a thickness of 3.5 mm or less, it is not possible to obtain a sufficient temperature difference in the thickness direction simply by rapidly cooling the heated thin glass sheet by blowing cooling air on it, as the sheet thickness is too thin. This is difficult, and it has been difficult to produce reinforced thin glass that satisfies the above conditions.

Conventional methods for strengthening thin glass include mist spraying, dipping, solid contact, ion exchange, and crystallization, each of which has its own problems. It is said to be increasingly difficult to strengthen glass sheets with a thickness of 2.5 to 3.5 mm, for example, by rapidly cooling the area distribution of the glass sheet at the maximum speed and simultaneously Thickness 2.5-3.5mm for use as side or rear windows of automobiles by rapidly cooling scattered areas of glass sheets at minimum speed
In manufacturing glass sheets of 2.5 to 3.5
Maximum value 62MN/mm for all glass thicknesses
Minimum value 56 for glass with a thickness of 2.5 mm from rrr
．． 5 MN/tri, further varying inversely with thickness to a minimum value of 53 MN/r in 3.5 mm thick glass
an average central tensile stress in the range of up to rr is created in the glass sheet, and a distribution of areas of unequal principal stresses acting in the plane of the glass sheet is created in the glass sheet, at least some of the areas The maximum value of the principal stress difference in the area ranges from 8 to 25 MN/rrl, most of the principal stresses in adjacent areas showing the maximum value of the principal stress difference exhibit various directions, and the center-to-center distance of such adjacent areas is 1
A method for manufacturing sheet glass, which adjusts the maximum quenching rate and the size and interval of the area of the glass sheet cooled at the maximum rate so that the quenching speed falls within the range of 5 to 30 mm (Japanese Unexamined Patent Publication No. 121620/1982). In addition, in a glass strengthening method in which a jet is blown onto at least one surface of the glass using a nozzle, a gas is supplied to the nozzle at a pressure that allows a small (or sonic) velocity at the nozzle outlet, and the jet is connected to the gas and the atomized liquid. A strengthening method and device thereof (Japanese Unexamined Patent Application Publication No. 103043/1983), further comprising:
A method and apparatus for strengthening a glass sheet in which the maximum pressure drop of the gas occurs at the free end of the nozzle in a method of strengthening a glass sheet by spraying gas onto both surfaces of the glass sheet using a nozzle (Japanese Patent Laid-Open No. 145921/1989) Public bulletin)
is known, and furthermore, the pressure of the cooling air is set to 1.5 to 8 k
0.01-0.2 suddenly from g/cm gauge pressure
A method for strengthening thin glass by reducing the pressure to a gauge pressure of kg/- to an air chamber and using the space between the inside of the air chamber and the tip of the cooling nozzle as a shock wave tube (Japanese Patent Laid-Open No. 158128/1983); In addition to the above, it is known that the present applicant has proposed a heat treatment method for glass articles (Japanese Unexamined Patent Publication No. 1983-3029) in which the peripheral portions of the glass article are cooled sequentially later than the central portion. .

[Problem that the invention seeks to solve]

In the manufacturing method described in the above-mentioned Japanese Patent Application Laid-open No. 52421620, it is difficult to obtain a sufficient degree of reinforcement for glass plates with a thickness of 2.5 mm or less to be used as side or rear window glass of automobiles. However, problems such as the occurrence of sharp edges remain, and when the plate thickness is 2.5 to 3.5
In order to obtain the target degree of hardening even in the mm range, it is necessary to adjust the maximum quenching rate and the size and spacing of the area of the glass sheet cooled at such maximum rate, and in addition, the quenching jet must be subjected to vertical rocking, etc. It requires a means to provide a
There is a tendency that the difference between the maximum number of particles and the minimum number of crushed pieces is large, and the maximum area of the crushed pieces tends to exceed 300++n2. On the other hand, in the method and apparatus described in JP-A No. 60-103043, a mixture having a specific heat larger than that of a gas jet is pulverized at approximately the speed of sound, and the mixture of the pulverized liquid and air is This method attempts to quickly remove heat from the glass surface by blowing the glass, but in the end, if the two-phase jet of the mixture is used, a sufficient degree of strengthening cannot be obtained, and the targeted strengthening cannot be achieved with an air jet. Moreover, a well-known Laval nozzle is used as the spraying means to atomize the liquid droplets very finely so that the mixture of gas and atomized liquid has time to become homogeneous between the shock wave generation point and the nozzle exit. and the nozzle must be supplied with gas at a gauge pressure of at least 10.91 bar (approximately 0.93 Kg/cnT) to permit sonic ejection of the two-phase mixture. This requires precision finishing in terms of equipment, which is expensive, and in some cases, small droplets of liquid may come into contact with the glass surface and cause damage. Furthermore, in the method and device described in JP-A-60-145921, since the tip of the nozzle is sandwiched to form an orifice, it is necessary to supply air to the nozzle at a gauge pressure of at least 0.9 bar. The thinner the glass becomes, the more easily it becomes deformed, and the arrangement of the air nozzle must also be changed. It is still not possible to say that polished sushi can be manufactured efficiently enough, and the method described in JP-A No. 64-3029 has not been able to produce glass articles with a thickness of 3 to 5 mm. This is a method that is useful for strengthening thin sheet tempered glass to a degree that is not as strong as that of ordinary tempered glass, but it is not necessarily an efficient method for strengthening thin tempered glass to an ordinary degree from the viewpoint of equipment or work. It was difficult to say.

[Means for solving problems]

The present invention has been made in view of the above-mentioned drawbacks, and involves sending high-pressure cooling air into an air chamber while rapidly releasing it, and jetting it from a cooling nozzle. The purpose of the present invention is to provide a method for strengthening thin sheet glass, which achieves a degree of strengthening that can be adopted for automobile window glass by performing two-stage cooling using air such as the above.

That is, the present invention is a method of strengthening thin glass by blowing cooling air onto the surface of the glass from cooling nozzles arranged in a pair of air chambers, in which a shock wave with a heat transfer coefficient of 300 to 1000 Kcal/+rf Hh・℃ is first applied. A method for strengthening plate glass is provided, which comprises blowing generated air and then performing two-stage cooling by blowing air having a heat transfer coefficient of 100 to 300 Kcal/m-h·°C.

Here, first, the heat transfer coefficient is 300 to 1000 Kcal/m.
The reason why we decided to blow air that generates shock waves of 2・h・℃ is because if it is less than 300Kcal/rd・h・℃%, it is difficult to obtain a high degree of reinforcement due to insufficient initial cooling capacity. , 1000Kcal/rd・h
If it exceeds 400%, various problems will occur on the equipment, such as cracking during cooling, making it difficult to stably manufacture the product, etc. ~660Kcal/%・h・℃
As a means for obtaining air generating shock waves having the above-mentioned heat transfer coefficient, for example, the pressure of the cooling air is set to 2 to 8 kg/an! 0.05~ suddenly from the gauge pressure of
0.5 kg/d, preferably 0.1-0.4 kg
This can be easily carried out by reducing the pressure to a gauge pressure of /cot and rapidly cooling the area from the air chamber to the tip of the cooling nozzle using a shock wave tube.

Next, the heat transfer coefficient is 100 to 300 Kcal/m2・h・
The reason why we decided to blow air at 100 Kc was to maintain the temperature difference within the sheet glass due to the initial cooling mentioned above and to prevent stress relaxation as much as possible.
al/m2・h ・If it is less than C, it is difficult to obtain the effect. If it exceeds 300 Kcal/m2・h ・C, it may cause cranking or deterioration of optical properties such as deformation. Furthermore, the equipment would be too large and would be uneconomical.

Note that the heat transfer coefficient is 300 to 1000 Kcal/m2.
・Various reinforcement patterns can be obtained by blowing air that generates shock waves at h°C to the center or periphery of the glass plate, or at different times, and can be implemented in a variety of ways depending on the purpose. It is something.

Furthermore, when carrying out the present invention, it goes without saying that the conditions for carrying out the present invention can be modified as necessary depending on the conditions during the heat treatment, which is the first step, or depending on the shape, thickness, curvature, etc. of the plate glass.

[For production]

As mentioned above, the heat transfer coefficient is 300 to 1000 Kcal/m''・h・
The air generating the shock wave identified as ℃ and the heat transfer coefficient 1
00 to 300Kcal/m" -h ・A film that suppresses heat transfer occurring on the heated thin glass surface by skillfully combining different specific air with "C" air to achieve two-stage cooling. By destroying or diluting the heat, it promotes the dissipation of heat into the air, enhances the initial heat removal effect, and greatly increases the cooling capacity. It maintains the temperature difference, that is, suppresses the occurrence of stress relaxation as much as possible, resulting in a tempered glass sheet with a stable quality that is superior to conventional ones.
Even with thick plate glass, there are almost no sharp edges when it is crushed, and it has a sufficient degree of reinforcement, so it can be used in a wide range of fields such as automobile window glass, vehicle window glass, architectural windows, and electronic components. In addition, it is possible to almost eliminate the wobbling or wobbling of the plate glass to be strengthened, and to drastically reduce the amount of deformation of the plate glass or the number of breakages during rapid cooling. In particular, when thin glass is made thinner, it generally becomes more susceptible to deformation, which approximates the square of the thickness of the glass, but this has the extremely large effect of preventing this along with the various effects mentioned above. It is something that plays. Furthermore, it is possible to prevent the equipment from becoming too large and to carry out the process more efficiently.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Ofune ■ An air chamber equipped with a normal cooling nozzle, a compressor, and a blower are connected by piping, and the piping in front of the air chamber is equipped with an opening and pressure adjustment mechanism to maintain a temperature of 670 to 700°C. heated to 50
0 x 300mm plate glass, plate thickness 2.9.2.3
．． Change it to 1.5mm, etc., and change the original pressure to 2.7.8kg/ci.
etc., the pressure inside the air chamber is set to 0.05.0.3.0.
The heat transfer coefficient is 300 to 1000 Kcal/m by air generating shock waves set at 5 kg/cat etc.
・h・After carrying out the cooling enhancement treatment in the range of ℃ for about 1 to 3 seconds, the heat transfer coefficient is increased to 100 by using air from a blower or mixed air from a blower and a compressor.
Cooling strengthening treatment was carried out in the range of ~300 Kcal/m2·h·°C for about 10 to 20 seconds.

Examples 1 to 5 in Table 1 are examples thereof.

Comparative Example For comparison with the present invention, when air-cooled strengthening treatment was performed using a conventional strengthening processing device consisting of a blower, etc., a case where almost no shock waves were generated, although equipped with a compressor, was performed using the plate glass described above. It was carried out.

Comparative Examples 1 to 4 in Table 1 are examples thereof.

The degree of reinforcement of plate glass in Table 1 is based on the European standard (E
It is expressed as the number of fractures at points 2 and 3 in 1.2.3 of the fracture start point (impact point) of the fracture test for reinforced plate glass described in CE R43), and the sharp edge number is the number of fractures when the length of the fractured pieces is The length was 75 mm or more, and the length to width ratio was 4 or more.

Note that the number of fractures and the number of sharp edges in the table are the numbers at arbitrary positions excluding the area 20 mm from the periphery of the plate glass and within a radius of 75 mm from the point of impact.

〔Effect of the invention〕

As is clear from the foregoing, according to the present invention, when subjected to air-cooling strengthening treatment using a blower or when carried out outside the scope of the present invention, thin glass can be used as tempered glass, particularly for automobile window glass, etc. Although it is difficult to obtain thin glass, according to the present invention, thin glass, especially 3.
By using an extremely simple method to prepare plate glass of 5mm thickness or less, especially 1.5 to 3.5+nn+ thickness, it is possible to prevent the occurrence of plate deformation, etc., and to dramatically reduce breakage, making it possible to efficiently produce thin plate tempered glass products of stable quality. It has the effect of being easily obtained.

Claims (1)

[Claims] In a method for strengthening plate glass, which strengthens the surface of plate glass heated above its strain point by blowing cooling air from cooling nozzles placed in a pair of air chambers, first, the heat transfer coefficient is 300 to 1000 Kcal/m^2・h・℃. After blowing air that generates shock waves, the heat transfer coefficient is 1.
A method for strengthening plate glass, characterized by performing two-stage cooling by blowing air at 00 to 300 Kcal/m^2・h・℃.