How to improve the annealing process of glass candle holders
Sunny GlasswareFocusing on luxury fragrance products in the latest 10 years, Sunny Glassware is the supplier of 80% fragrance brands in the United States. In terms of production is excellence, today Sunny Glassware take you to understand how to improve the annealing process of glass candlestick.
Due to the tolerance of drastic temperature changes, annealing basic rational glass is in the forming process. The inner and outer layers produce a temperature gradient, and due to the differences in the shape, thickness, and degree of cooling of the finished product, irregular thermal stresses are generated in the product. Such thermal stress can reduce the mechanical strength and thermal stability of the product, and also affect the optical uniformity of the glass. If the stress exceeds the ultimate strength of the finished product, it will break on its own. Therefore, the existence of uneven thermal stress in glass products is a serious mistake. Annealing is a heat treatment process that can eliminate or reduce the thermal stress in the glass to an allowable value as much as possible. Except for glass fibers and thin-walled small hollow products, indeed all glass products must be annealed. Thermal stress in glass products can be divided into temporary stress and permanent stress according to its characteristics.Due to its poor thermal conductivity, temporary stress. When glass is heated or cooled below the strain point temperature. Each part will form a temperature gradient, which will generate inevitable thermal stress. This kind of thermal stress, with the existence of the temperature difference, the greater the temperature difference, and the greater the stress temporarily, and disappear with the disappearance of the temperature difference. This thermal stress is called temporary stress. But before the temperature is out of adjustment, what should be paid attention to, of course, the stress can be eliminated by itself. When the stress value exceeds the ultimate strength of the glass, the glass will rupture itself abnormally, so the heating or cooling speed of the glass in the brittle temperature range should not be too fast.Thermal stress caused by temperature difference.
②Permanent stress. When the glass starts to cool from above the strain point temperature. After the glass is cooled to room temperature and the temperature of the inner and outer layers is out of adjustment, it cannot be completely dissipated. There is a certain stress in the glass imitating as before. This stress is called hydrostatic stress. The magnitude of the permanent stress depends on the cooling rate of the finished product when the temperature is above the strain point, the viscosity of the glass, the thermal shortening factor and the thickness of the product and other glass machinery.
Glass is annealed by reheating permanently stressed glass to a temperature at which particles within the glass can move. Keep mass displacement directed towards dispersed stresses (called stress relaxation) to eliminate or weaken permanent stresses. The stress relaxation rate depends on the temperature of the glass. The higher the temperature, the faster the relaxation rate. Therefore, suitable annealing temperature range is the key to good annealing quality of glass. In the actual production process, it is impossible to completely eliminate the permanent stress.
By annealing, it is hoped that the residual stress can be increased or homogenized to a minimum, so as to improve the mechanical properties of the glass.
The important characteristics of annealing are as follows: 1. The thick glass produced by this method has cold edges and thin edges, so the edge compressive stress is very large. 2. The thicker the glass, the longer heat stays in the glass. 3, in order to meet the cutting requirements, must reduce the tempering stress. 4. To prevent the edge from cooling too fast in the receding fire area, the quality of controlling the annealing of the thick glass with the edge is closely related to the thickness curve of the glass.
The values of Sunny Glassware products：Product quality is the major focus in Sunny. Sunny once demolished 80,000 pcs of glass vessel with barely visible blemish.