Glass tempering furnace use the physical or chemical methods, it will form compressive stress layer in the glass surface and tensile stress layer in the inner: the compressive stress layer may be offset by the tensile stress part to avoid glass breakage when the glass suffers the external force, so as to improve the strength of glass. Not only that, micro-cracks of the glass surface in this compressive stress becomes more subtle, at the time it will improve the strength of the glass.

 

　　Now widely used method is the physical steel namely the glass is heated to the softening point of the glass attached (650 ℃ or so), then the glass can maintain the original shape, the particles in the glass have ability to migrate and adjust the structure, in order to it can so quickly eliminate internal stress,blow the glass to let it quickly cool down, when the temperature balance, the glass surface produces compressive stress, the inner layer has a tensilestress, the glass produces a homogeneous and regular distribution of the internal stress and improve the glass as the tensile strength of brittle material, so that the bending resistance of the glass and improved impact strength.At the same time, the inner surface of the glass exists uniform stress, some part of the glass will explode for the shock beyond its bearing strength. The interior stress expload to small particles, so the safety is improved. Therefore, the tempering glass can also be called pre-stressed glass or safety glass.

 

　　Glass tempering furnace in the steel process will generally produce wind spots and stress spots, Wind spots are in the cooling process, due to the uneven cooling and uneven stress cause the glass formed, in a particular observation angle will see the glass surface of light and dark stripes. Stress spots is also caused by uneven spots, such as in the heating process, the temperature difference between the central portion and the hearth resulting uneven stress. There is no way to completely avoid stress, but well-designed steel equipment can reduce the stress spot of maximum visibility.