What is heat soaked glass ?

Heat soaking is a process that may expose NiS inclusions in tempered glass thereby reducing the risk of potential field cracking. The process involves placing the tempered glass inside a chamber and raising the temperature to approximately 290ºC to accelerate nickel sulfide expansion. This causes glass containing nickel sulfide inclusions to break in the heat soak chamber. 

Process editing

First Step Warming phase

The warming phase begins at the ambient temperature at which all of the glass is located, ending at the time when the last glass surface temperature reaches 280 °C. The temperature in the furnace may exceed 320 ° C, and the temperature of the glass surface is kept below 320 ° C. The glass surface temperature should be shortened as much as 300 ° C.

Second Step Insulation phase

The holding phase begins at a time when all glass surface temperatures reach 280 ° C and the holding time is at least 2 hours. During the entire incubation period, it should be ensured that the temperature of the glass surface is maintained within the range of 290 °C ± 10 °C.

Last Step Cooling stage

After the final 280 ° C glass finish 2 hours of incubation, the cooling phase begins, at which point the glass temperature drops to ambient temperature. When the furnace temperature drops to 70 ° C, the cooling phase is considered to be terminated. The cooling rate should be controlled to minimize the damage caused by the thermal stress of the glass.

The benefits of tempered glass after heat soaked 

The function of the heat soaking furnace is to completely transform the α phase of nickel sulfide into a β phase with low temperature stability, and it is impossible to self-explosion (detonation) of the glass which is discharged, which can effectively ensure that the tempered glass has no self-explosion.