Quality problems of glass curtain wall engineering
Because in recent years with the rapid development of building curtain wall industry, various forms of glass curtain wall become higher and higher, after installation of curtain wall glass, without external influence, toughened glass “explosion” quality problems frequently happen, leading to the ministry of construction and many provinces and cities restricted the use of glass curtain wall, seriously affected the normal development of glass curtain wall.The reasons for the self-explosion of toughened glass of curtain wall are various.
The design of curtain wall structure, glass processing, transportation, handling, installation, harsh climate, temperature and use environment all have a close impact on the glass “self-explosion”. Among them, the main reason for the tempered glass self-explosion is that the glass is brought into nickel by the main material, quartz sand or sandstone, in the production process of its original piece, bring in sulfur from fuel and accessories, Melburns from 1400 to 1500°C to form nickel sulfide (NiS) impurities. This impurity has cold expansion thermal shrinkage properties, Phase transition occurs when the nickel sulfide impurities left in the toughened glass are subject to environmental changes such as external temperature, its volume expands. The expansion of nickel sulfide in the tension stress layer of the glass plate core causes greater tension stress inside the tempered glass. When the tension stress exceeds the limit that the glass can withstand itself, it can cause the toughened glass to self-explode, the self-burst toughened glass can be found at the boom point ” butterfly spot”, “Butterfly spot” center with nickel sulfide impurities black dots.
Due to the uncertainty of nickel sulfide, the self-explosion time of toughened glass caused by nickel sulfide is also uncertain. Relevant research data show that 3 to 5 years after the general toughened glass production is the high incidence period of toughened glass self-explosion, and the current scientific and technological means can not predict when or which piece of curtain wall window will appear “self-explosion”.However, the tempered glass can be prevented, to reduce the probability of self-explosion.
1. In the production of glass raw glass sheet, it should select main materials, fuel and accessories with less sulfur and nickel elements, so as to reduce the production of nickel sulfide and reduce the content of nickel sulfide in tempered glass.
2. in the glass deep processing stage, add a homogenization processing (HST) process, the tempered glass is heated to 290°C for secondary heat treatment, and insulation for at least 2 hours before cooling to room temperature. This process makes the nickel sulfide and other impurities existing in the toughened glass to advance the crystal phase transformation, so that the active self-explosion of frameless glass curtain wall is eliminated, the probability of bursting in the process of use is very low.
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