1.professional for processing thin glass with high flatness
2.simple and convenient operation
- low production cost and
4.small investment for equipment
SZ-HGL Coating Chemical Furnace is professional for tempering thin glass with perfect flatness.
I. Chemical toughened glass
as some special glass can not be physically toughened, such as thin glass thickness less than 2mm, Hyperboloid bent glass for express train, big bus,etc, or strict flatness requirement for glass, for example special glass for copier, these special glass must be chemically toughened.
The the theory of chemical toughening,
At a certain temperature, making the bigger metallic ions( such as K+ ions) exchange the smaller Na+ions in the glass surface, the stress will be formed on the glass surface when glass cools down, thereby the strength of glass is increased.
II. The traditional chemical toughening method
The traditional technics of glass chemical toughening is the potassium nitrate is put in the stainless container to be heated at temperature 450 degree Celsius to be melt as liquid, the preheated glass sheets are immersed in potassium nitrate solution for 4-8 hours at temperature 450 degree Celsius to make K+ ions on glass surface exchange Na+ ions in solution. After ions are exchanged, glass sheets are taken out from solution, annealed and cooled to room temperature, then washed. Because the size of the K+ ions is bigger than the size of Na+ ions, during period of glass surface cooling shrinkage , the stress will be formed with the internal, thereby the strength of glass surface is increased. This method is called immersing.
III. The coating method
The coating method is that some metal salt solution is mixed with some homologous chemical reagent to be evenly coated on glass surface at room temperature, glass sheet is pushed into dedicated furnace to be dried, heated, and kept warm about 2 hours after reaching a certain temperature, then annealed, cooled to room temperature, taken out and washed.
Ⅳ.Comparison of two methods
First, as the immersing method uses a stainless container which limits the size and shape of glass,
Second, because glass sheets need to be taken out from potassium nitrate solution with high temperature, a set of heat-resistance device is absolutely necessary to make the whole equipment very expensive.
Third, each time before tempering glass, the potassium nitrate in the container must be melt, the melting takes more than 48 hour, some large containers need 72 hours. This not only affects production time, but also causes energy waste, and increases production cost. The whole processing is complex and complicated.
