JPH0649585B2 - Heat treatment method for thick glass articles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat treatment method for a thick glass article most suitable for a building window glass such as a high-rise building or a large area opening.
Specifically, it increases the breaking strength of thick glass articles to the extent that it does not cause fine grain shattering that does not reach the degree of strengthening of ordinary tempered glass, and various pressure resistance or heat resistance is also improved to prevent breakage. It provides thick glass products that are not dropped even if they break, and have improved safety.In addition to building window glass, various interior materials, furniture furniture, cooking utensils, glass bottles, etc. It can be widely adopted for glass articles.

[Conventional technology]

Since glass has good transparency and weather resistance, and is cheaper than other materials, it is widely used as architectural window glass, and even residential buildings can use large area window glass. However, as the number of skyscrapers continues to increase year by year, there is an urgent need to further enhance their safety. That is, it is necessary to increase the breaking strength of high-rise and large-area window glass, for example, to improve wind pressure resistance and heat resistance. Further, there is a demand for a material that does not easily protrude from the window frame so that even if it breaks, fragments do not easily drop from a high place.

However, the breaking strength increases with ordinary heat-strengthened glass, but it is a problem because it breaks finely when crushed.With chemically strengthened glass, the breaking strength is large, and even when broken, it is similar to raw glass. Although it shows a crushing pattern, it takes a lot of time for the chemical strengthening process, the production cost becomes high, and the thickness of the compressive stress layer is thin, so when it is damaged for some reason, the damaged part is a raw plate. There is a problem that it has only the same level of strength as the above.

Therefore, there is known a glass having a predetermined degree of tempering, which is obtained by using the conventional air-cooling method and lowering the degree of cooling. That is,
Instead of making the value of surface compressive stress smaller than that of conventional heat-strengthened glass, the internal tensile stress is also made smaller so that even when shattered, it does not break into pieces like conventional heat-strengthened glass. Things have been proposed. For example, JP-B-59-25734 discloses that a glass plate having a plate thickness of 10 to 15 mm is heated to 600 to 660 ° C.
~ 300 ℃ hot air is blown to cool the glass plate slower than the natural cooling in the atmosphere to cool it to the strain point temperature or less, the central tensile stress σt of this treated glass plate
Of 85 to 200 kg / cm ² and its surface compressive stress σc
The method of controlling so that the ratio σt / σc between the central tensile stress σt and the central tensile stress σt is in the range of 1.5 to 2.0 is disclosed, and Japanese Patent Publication No. 61-40608 discloses a method for strengthening a glass sheet and a strengthening made by this method. A glass sheet is described in which the quench gas stream is at least one localized gas stream, the localized gas stream interspersed in areas of tempered glass that are pulsed at a repetition rate related to the rate at which the glass sheet progresses to the quench station. It is known, for example, to provide a glass sheet with a distribution of areas of higher tempered glass.

[Problems to be solved by the invention]

As described above, in the conventional glass plate having a plate thickness of 8 mm or more, the temporary strain generated in the glass becomes too large and the degree of strengthening becomes too large, or cracks often occur. There was a problem that the cooling conditions had to be variously limited and, as a result, the time required for production was long, the productivity was poor, and the cost was high. For example, although the heat treatment method disclosed in Japanese Patent Publication No. 59-25734 mentioned above is intended to solve the problem, the treatment temperature is as high as 600 to 660 ° C., and since it is a relatively large area glass plate, the deformation and surface properties However, there is also a problem that a device for heating the cooling air to 50 to 300 ° C. is necessary.
Further, according to the method of the above Japanese Patent Publication No. 61-40608,
While cooling, pulsed air is passed through, for example, one pulsation every 0.2 seconds, and the holding time for each pulsation is set to 0.1 seconds. Even if the stress distribution in specific parts of the glass is changed, there is still a problem in obtaining a glass sheet having a predetermined degree of strengthening.

[Means for solving problems]

The present invention has been made in view of such problems in the related art, and it is intended to cool a slab glass article heated to 550 to 600 ° C intermittently in a specific cycle by combining a cooling medium having a specific heat transfer coefficient. By providing a heat treatment method for a thick glass article, a glass having a predetermined degree of strengthening can be efficiently obtained.

That is, the present invention provides a glass article having a thickness of 13 to 19 mm of 550 to
After heating to 600 ° C, air is intermittently blown at a cycle of 0.5 to 20 seconds, and the heat transfer coefficient during cooling is in the range of 5 to ²⁰ Kcal / m ² · hr · ° C during blowing.
The present invention also provides a heat treatment method for a thick glass article, which is characterized in that it is cooled to ² Kcal / m ² · hr · ° C or less when not sprayed.

Here, the heating temperature of the thick glass article is set to 550 to 600 ° C because the viscous flow almost disappears at less than 550 ° C, and it is difficult to obtain a predetermined degree of strengthening, but if it is above this temperature, the cycle of 0.5 to 20 seconds By intermittently blowing air with a heat transfer coefficient of 5 to 20 Kcal / m ² · hr · ° C, and without blowing, ² Kcal / m ² · hr · ° C or less Can be shortened,
The processing can be performed at a lower temperature than before.

Also, the intermittent spraying cycle is set to 0.5 to 20 seconds, preferably 1 to 5 seconds, because if it is shorter than 0.5 seconds, the effect of stopping the air becomes small and cracks are likely to occur. This is because it takes too much time for production because it is too long, and it becomes difficult to obtain a predetermined degree of strengthening.

Furthermore, when spraying a heat transfer coefficient, 5 to 20 Kcal / m ² · hr ・
℃, preferably 8 ~ 15Kcal / m ² · hr · ℃ was 5
If it is less than Kcal / m ² · hr · ° C, the degree of strengthening will be too small and the effect will be lost, and the time required for production will be too long. If it exceeds 20Kcal / m ² · hr · ° C, the degree of strengthening will be too large, This is because cracks are likely to occur during cooling,
² Kcal / m ² · hr · ° C or less when not spraying, preferably 1.
0Kcal / m ² · hr · ° C or less is 2Kcal / m ² · hr ・
This is because if the temperature exceeds ℃, cracking is likely to occur and sometimes the degree of strengthening becomes too large.

When cooling, for example, rather than blowing air to the entire flat surface of the glass plate at the same time, it is better to blow the air to the central portion of the glass plate first and then to spread it to the peripheral portion of the glass plate while shifting the timing. It is preferable, and the timing difference is 0.1 to 2
Sec / m is suitable, and if it is less than 0.1 sec / m, there is no great difference from simultaneous spraying, and if it exceeds 2 sec / m, unnecessary stress is applied and cracking is likely to occur.

Furthermore, as means for the heat transfer coefficient and 5~20Kcal / m ² · hr · ℃ or 2Kcal / m ² · hr · ℃ or less, varying the air pressure of the air, or the air nozzle tip of the glass plate and the blast head Needless to say, the diameter of the air nozzle and the nozzle pitch may be changed.

[Work]

As mentioned above, glass products with a thickness of 13 to 19 mm
By heating to a temperature of 550 to 600 ° C and cooling to a lower temperature, the processing time can be shortened and productivity is improved, but on the other hand, cracking is likely to occur during cooling. The cap is solved by stopping the air instead of constantly blowing the air, so that a glass article having a predetermined degree of strengthening can be obtained.

To bring about a more effective action, it is necessary to provide a timing difference so that the central portion of the glass plate starts to be cooled earlier than the peripheral portion of the glass plate as described above. It can be prevented as much as possible.

[Example] An example of the present invention will be described below.

Example 1 A glass plate having a plate thickness of 15 mm and a size of 1000 × 1000 mm ² was heated to 595 ° C., and then heated with air having a heat transfer coefficient of 20 Kcal / m ² · hr · ° C. 2
The glass is sprayed for a second and the heat transfer coefficient is 1.5 Kcal / m ² · hr · ° C for 5 seconds. When cooling was performed by blowing air, no cracks were generated during cooling.

When the breaking strengths of the five obtained samples were compared with the breaking strength, the average value of the breaking strength ratios was doubled.

Examples 2 to 5 Examples 2 to 5 are performed in the same manner as in Example 1 under the conditions shown in Table-1, and the results are also shown in Table-1.

Comparative Examples 1 to 7 The same methods as in Examples were carried out, and the conditions and results are shown in Table-1.

The heat transfer coefficient was measured using a copper plate having a size of 25 mmφ and a thickness of 3 mm.

〔The invention's effect〕

As is apparent from the above, according to the present invention,
By performing intermittent cooling for a specific period with air having a specific heat transfer coefficient, glass articles with a thickness of 13 to 19 mm are
~ 2.0 times the breaking strength, which is a glass that does not break into fine particles like ordinary tempered glass and has a predetermined degree of strengthening, making it a safer construction It can be provided as a window glass for windows and the like, and can be applied to various glass sheets such as a heat ray absorbing or reflecting glass plate and other glass articles.

Claims (1)

[Claims] 1. A glass article having a thickness of 13 to 19 mm is heated to 550 to 600 ° C., and then air is intermittently blown at a cycle of 0.5 to 20 seconds, and a heat transfer coefficient at the time of cooling is 5 to 20 Kcal / A heat treatment method for a thick glass article, characterized in that cooling is carried out within a range of m ² · hr · ° C and, when not sprayed, at ² Kcal / m ² · hr · ° C or less.