thermal properties
High resistance of product made of the SIMAX glass to sudden change in temperature - heat stability - is done by low coefficient of linear thermal expansion, relatively low modulus of tensile elasticity, as well as relatively high thermal conductivity resulting in a lower thermal gradient in the product wall.
On cooling and heating the glass product, an undesirable internal stress arises. Breakage of the glass product due to temperature change is caused by tensile stress on the product surface arising due to action of linear dilatability of the glass on quick cooling from the product surface.
With a mechanical failure in the product surface, the heat stability can be significantly reduced.
The manufacturer may perform an exact calculation, where necessary.
cooling of SIMAX glass
Cooling represents a thermal process the purpose of which is keeping from formation of undesirable and inadmissibly high thermal stress in the glass which would reduce the product resistance, and/or removing of stress already arisen.
Cooling cycle comprises three stages:
I. Temperature increase (product heating) with heating rate from the inlet temperature to the upper cooling value.
II. Dwell (pause, tempering, stabilization) of products at upper cooling temperature for certain time when the temperature differences in the product must be equalized, including stress reduction to an admissible limit.
III. Temperature decrease (cooling and additional cooling) of the product with cooling rate from upper to the lower cooling value (this stage is important as the permanent stress can arise), and from the lower cooling temperature to the final value or ambient temperature (important for subsequent practical manipulation with the product).
Temperaturbereich