[China Glass Net] In the process of melting glass, if the molten glass melts unevenly, the chemical composition of the glass will be uneven. This unevenness will result in uniformity of the upper part of the glass structure and stress caused by structural unevenness. , generally referred to as structural stress, which is a relatively long-term stress. However, this stress is not eliminated during the annealing of the glass. It will always exist in the glass. Therefore, the structural stress and the longer-term stress that the annealing does not completely disappear are often collectively referred to as residual stress or Internal stress.
Different glass chemical compositions have different coefficients of thermal expansion. After the temperature reaches normal temperature, the glass is stressed due to the different shrinkage of adjacent portions of different thermal expansion coefficients. This stress due to the inherent structure of the glass is impossible to eliminate. For example, stones, streaks, and nodules present on glass articles cause stress in the interior of these defects and in the surrounding glass body, and the stress value is large at the interface. In addition, for different types of glass edging products, sometimes the thermal expansion coefficient between the glass is not matched enough, which also causes stress on the product. The greater the difference in thermal expansion coefficient, the greater the stress. When a certain degree is reached, the product will be cracked. This is the reason why the product is broken due to the difference in thermal expansion coefficient.
For a glassware product, after annealing at the annealing temperature of the glass, it is well annealed, but under the stress gauge, there is still a large stress in the glass article. This stress is generally called structural stress. The structural stress in the glass is independent of the cooling rate and annealing process during glass forming, and is primarily related to the melting process of the glass. Uneven glass batches and poor melting processes are the direct cause of structural stress on the glass. For glass with high uniformity, the method of eliminating the structural stress in the glass is to adopt mechanical agitation of the molten glass to promote mutual diffusion, so that the higher part of the glass component is to the other part of the component. Transfer, so that the degree of homogenization is achieved. In the production of the pool furnace, in order to achieve the uniformity requirement of the molten glass, in addition to mechanical agitation, measures such as bottom bubbling technology, auxiliary electrofusion heating technology and granulation technology can be adopted.
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