The treatment   process   of   tempered   and   hest   strengthened   glass   is   as   when   heating   glass   close   to   molten   point,   to   carry out   even   and   rapid   cooling   treatment   on   the   surface   of   glass,   this   enhancing   the   strength   and   thermal   stability.   The   surface stress of tempered glass is above 90 Mpa, and that of hest strengthened glass is between 24 and 69 Mpa.

Feature of tempered glass:

High intensity: The anti-bending strength of tempered glass is 3-4 fold of that common glass, anti-shock strength 6-7 fold that of common glass.

Heat stability:   with high heat stability, this kind of glass can endure 300    τ   of tempera ture difference, which   is 3 fold of that common glass.

Security:   the   stress   layer   brings   it   high   anti-shock   performance, which   makes   it   not     easy   to   broke,   and   the   obtuse   angle granule after broken will have no impact on people’s health.

Characteristics of Tempered glass

Self-explosion and the causes

lmmanent cause lies in the interfusion of nickel purite in glass manufacturing process,a tiny proportion of nickel purite in about 7 tons of glass. Nickel purite has two crystal formation,smallα   crystal phase in high temperature(T ＞ 380℃ )and β   crystal phase in low temperature.

ln the stage of heating,the heating is slow,so transformation from α   crystal phase to β   crystal phase is more complete;while in the stage of cooling,there   is   no   enough time for   α   c   r y s t a   l   phase   to   transform   to   β    c   r   y   s   t   a   l   phase   because   of   rapid   cooling so that   in   room temperature,α   c r y s t a l   phase reverts to β   crystal phase gradually ,the volume will swell by about 4%,which leads to the explosion of tempered glass.

The diameter   of explosion-causing   nickel   purite   is   about   0.04-0.65mm,average   particle   diameter   is   0.2mm,nickel   purite   is   in   tensile stress area,most of which center on high tensile stress area in the core of glass plate.

Besides,defects in the original piece of glass,improper pretreatment and excessive concentration of the stress caused by uneven cooling are all the causes of self-explosion.

The way to avoid self-explosion:Heat Soak Test(hot-dipping test or igniting test)