Heat strengthened glass is produced by a process similar to the tempered glass but at lower quenching rate.
Its surface stress is slightly less than tempered glass. Its resistance to wind load,
impact and thermal shock is in between tempered glass and ordinary glass.
Features:
Safety: when broken, the crack extends to the edge. Its fragment can be kept in the frame
and does not fall out but it is not regarded as safety glass.
Mechanical property: its stress is 24 to 69 Mpa and its strength is 2 times of the ordinary glass.
Appearance: it has better flatness than ordinary tempered glass.