Tempered glass is about six times more resistant to float glass, because surface defects are kept "closed" by mechanical compression tensions, while the inside remains more free from defects that can start cracks.
Tempered glass is obtained by hardening with heat treatment (tempering). The workpiece must be cut to the required dimensions and any work (such as grinding the edges or drilling and flaring) must be done before the temporing process. The glass is placed on a roller table on which it flows into a furnace, which heats it to a temperature of 640°C.
It is then quickly cooled by air jets. This process cools the superficial layers, causing it to harden, while the inside remains warm longer. The subsequent cooling of the central part produces a compression effort on the surface, balanced by tensile stresses on the inside. Tension states can be seen by observing the glass in polarized light.
Tempered safaty glass applications
- Tempered glass is very used due to the high degree of safety, resistance to mechanical and thermal stresses;
- Tempered glass is considered a "safety glass" because, as a result of breakage, it is fragmented into so many small pieces that are not dangerous to the safety of people, unlike normal glass.