1. Principle of tempering
Heating the glass and then rapidly cooling it (somewhat like metal quenching) creates a large tensile stress inside the glass and a larger compressive stress on its surface. Its function is the same as that of prestressed reinforced concrete members using tensile steel bars to generate compressive stress in the part that needs to be strengthened. The difference is that prestressed reinforced concrete only produces compressive stress in some areas, while tempered glass produces compressive stress on the entire surface. The tempering and quenching process of glass is also different from the hardening process of metal surface quenching. The tempering treatment of glass does not harden the surface of the glass, so after tempering the glass, the ability of the surface to resist scratches and scratches is not significantly improved.
2. Characteristics of tempered glass
Advantages
Safety: The breaking method of tempered glass is very unique. After breaking, it becomes small fragments with relatively obtuse angles, most of which are close to small cubes. There are basically no sharp corners and will not cause major harm to the human body.
High strength: Due to the considerable compressive stress on the surface of tempered glass, it has high mechanical strength, which is 4 times and above that of annealed glass. It can meet the requirements of high-rise and super high-rise buildings.
Thermal stability: Tempered glass has good thermal stability. The temperature difference that tempered glass can withstand is 2.5 to 3 times that of annealed glass. Placing a boiling water glass directly on the ordinary annealed glass may cause the glass to break; while pouring more than 300 molten lead liquid on the tempered glass of 0, the glass will not break.
Reworkability: Generally not reworkable. Any damage to any part of the tempered glass will cause the entire piece of glass to be broken into small pieces. Therefore, the glass must be cut, edged, chamfered, drilled, etc. into the desired shape before it can be tempered.
Disadvantage
First, the tempered glass shatters on its own due to the presence of nickel sulfide impurities in very few pieces. If there is no special heat treatment after tempering, these few pieces may burst within a few months or after a few years. Secondly, the flatness of tempered glass is not as good as before tempering. Again, sometimes the stress lines on the tempered glass can be faintly or even clearly seen.
3. The role of glass tempering
Glass is a brittle material with very low tensile strength. Because the strength of brittle materials depends to a large extent on the surface structure. The surface of the glass appears to be intact and smooth, but it actually has a large number of microcracks. Under the action of tensile stress, microcracks initially expand and then break from the surface. Therefore, if the effect of these surface microcracks can be eliminated, the tensile strength can be significantly improved. Tempering is a method to eliminate the influence of surface micro-cracks, which puts the glass surface under strong compressive stress. In this way, only when the tensile stress acting on the surface of the glass exceeds the compressive stress, the glass may be broken.
The thermal insulation performance of vacuum glass is based on the principle of vacuum thermos. The thermal insulation effect of Landi V glass products exceeds that of a 1.5-meter thick brick wall, which is 4~6 times that of ordinary insulating glass, and the U value (also called heat transfer coefficient or K value) is as low as 0.4 W/m2·K (European IFT). laboratory report).
The sound insulation and noise reduction performance of vacuum glass is based on the fact that sound does not travel under vacuum conditions. The weighted sound insulation of Landi V glass reaches 39 decibels (reported by CTC National Inspection Group), and the weighted sound insulation of general insulating glass is about 28 decibels.
With Landis V glass, the interior is as quiet as a library, even at airports, viaducts or main roads.
Note: The higher the weighted sound insulation, the better the sound insulation effect. For example, the outdoor noise is 75 decibels, after using Randy V glass, the indoor sound is 36 decibels (75-39=36), and the library is generally below 40 decibels.
The life expectancy of tempered vacuum glass V glass can reach more than 25 years. It has a high vacuum inner cavity, so that the gas heat transfer can be ignored. At the same time, high-performance Low-E glass is used to greatly suppress radiation heat transfer and ensure the heat transfer coefficient of V glass (U value). ) as low as 0.4W/(m2·K). At the same time, the thermal insulation performance of V glass is 2-4 times that of insulating glass, and 6-10 times that of single glass. It can meet the requirements of international passive house for heat transfer coefficient of doors and windows when used independently.
