Causes of sudden bursting of balcony window glass

1. Self-explosion rate Domestic self-explosion rate ranges from 3% to 0.3%. Generally, the self-explosion rate is calculated according to the number of photos, without considering the area and thickness of single glass, which is not accurate enough to compare with each other more scientifically. In order to calculate the self-explosion rate uniformly, a unified assumption must be determined. Set uniform conditions: every 5 ~ 8 tons of glass contains a nickel sulfide enough to cause self-explosion; The average area of each tempered glass is 1.8mm, and the nickel sulfide is evenly distributed. Then the calculated self-explosion rate of tempered glass with 6mm thickness is 0.64% ~ 0.54%, that is, the self-explosion rate of tempered glass with 6mm thickness is about 3 ‰ ~ 5 ‰. This is basically consistent with the actual value of domestic high-level processing enterprises. Even if it is completely produced according to the standard, the self-explosion of tempered glass cannot be completely avoided. Hundreds of tons of glass will be easily used in large buildings, which means that nickel sulfide and foreign impurities exist in glass at a high rate. Therefore, even if tempered glass is hot-dipped, self-explosion is inevitable. & lt/p & gt； & ltp>2. Reasons for uncontrolled spontaneous explosion of tempered glass-Nickel sulfide (nis) and heterogeneous particles are the sources of uncontrolled spontaneous explosion of tempered glass, not only NiS particles in traditional knowledge, but also many other heterogeneous particles. The initiation and propagation of cracks in glass are mainly caused by residual stress near particles. This kind of stress can be divided into two types, one is the phase change stress in the process of phase change expansion, and the other is the residual stress caused by the mismatch of thermal expansion coefficients. Nickel sulfide (nis) and heterogeneous particles. Glass contains nickel sulfide impurities in the form of small crystals. Under normal circumstances, it will not damage the glass. However, due to the reheating of tempered glass, the phase state of nickel sulfide impurities is changed. The high temperature α state of nickel sulfide is frozen when the glass cools rapidly, and it may take several years for them to return to β state. Because the impurity volume of nickel sulfide in beta state at low temperature will increase, local stress concentration will occur in the glass, and then the tempered glass will explode. However, only relatively large impurities will cause self-explosion, and only when impurities are at the core of tensile stress will tempered glass self-explode. Nis is a crystal with high temperature α-nis and low temperature β-nis, and its phase transition temperature is 379℃. When the glass is heated in the tempering furnace, nis completely transforms into α phase because the heating temperature is much higher than the phase transition temperature. However, in the subsequent quenching process, α-nis was frozen in tempered glass before being transformed into β-nis. At room temperature, α-nis is unstable and has a tendency to gradually transform into β-nis. This transformation is accompanied by about 2 ~ 4% volume expansion, which makes the glass bear huge phase transformation tensile stress, thus causing self-explosion. Scanning electron microscope photos of nis stones extracted from self-exploding glass fragments show that their surfaces are uneven and very rough. In the cross-sectional photos of glass fragments at the crack source, we can see the boundary area between the first crack trace and the second crack caused by heterogeneous particles and spherical fine particles. & lt/p & gt； & ltp>3. How to identify the self-explosion of tempered glass? First look at whether the crack point (the crack of tempered glass is radial and has a starting point) is in the middle of the glass, such as at the edge of the glass. Generally, it is because the glass is not chamfered or the edge of the glass is damaged, which leads to stress concentration and crack development. If the initiation point is in the middle of the glass, see if the initiation point has a pattern (butterfly spot) similar to two butterfly wings composed of two small polygons. If you look carefully, there should be small black particles (nickel sulfide) visible to the naked eye on the same side of two small polygons (the trunk part of the butterfly), so you can judge that it is self-explosion; Otherwise, it should be destroyed by external forces. The typical feature of glass self-explosion is butterfly spot. Glass fragments are distributed radially, and there are two pieces of glass shaped like butterfly wings in the radiation center, commonly known as "butterfly spots". Nice stone is located at the junction of two butterfly attractions. & lt/p & gt； & ltp>4. Theoretical discussion on self-explosion mechanism of tempered glass. Radial stress r≥ tangential stress r≥ stress at the interface between particles and glass. For non-uniform particles in glass matrix, the temperature during cooling is negative, so the radial stress around the particles is pressure and the tangential stress is tension. Scanning electron microscope image and edge extrusion morphology of spherical simple silicon particles in glass interlayer. The radial stress around the particle is pressure and the tangential stress is tension, so the tangential stress is the root of crack initiation. & lt/p & gt； Solution to sudden burst of<p> window