what is heat soaked tempered glass

   The reason for the spontaneous breakage of normal tempered glass is that sulfur and nickel impurities are mixed in the glass manufacturing process, and nickel sulfide is generated at high temperatures. Nickel sulfide has two kinds of crystals, α phase at high temperature (t>380℃) and β phase at low temperature. Due to rapid cooling during tempering, the α phase is too late to transform into the β phase. During use, the metastable α phase at room temperature slowly transforms into a stable β phase, and the tempered glass explodes spontaneously with about 4% volume expansion. The function of the homogenizer is to completely transform the nickel sulfide α phase into the low temperature stable β phase.

   Heat soaked tempered glass is a kind tempered glass after heat soak test（HST-BSEN14179）. This process is to put the tempered glass into heat soak test furnace, keep the temperature rising rate not higher than 1.5°C/min, and continue to raise the temperature to about 300°C for several hours to promote the phase transformation of nickel sulfide (NIS) crystal inside the tempered glass or the expansion of hard silicon crystal to cause the tempered glass broken. Take out the intact tempered glass after it is gradually cooled. The function of the HST is to completely transform the nickel sulfide α phase into the low temperature stable β phase. The heat soak treatment allows the tempered glass that may spontaneous broken after use to be artificially broken in the heat soak test furnace in advance, thereby reducing the spontaneous explosion of the tempered glass in use after installation. After heat soak treatment, the spontaneous broken rate of tempered glass can be reduced to less than 0.1%. 

  Our low iron tempered glass products after HST, have no spontaneous breakage(broken) so far.

  Max size:3300*13000mm.

 GOFAI glass, customer-oriented, serves the world.