Tempered glass self-explosion refers to the phenomenon of automatic cracking of tempered glass without direct mechanical external force. There are many reasons for self-explosion, and they can be summarized as follows: 1. There are stones, impurities in the glass, bubbles: Impurities in the glass are the weak points of the tempered glass, but also the stress concentration. In particular, if the stone is in the tensile stress zone of the tempered glass, it is an important factor that causes the burst. 2. The glass contains nickel sulphide crystals, and the tempered glass bleeds caused by the volume change of the nickel sulphide crystals. 3, the glass surface due to improper processing or operation caused by scratches, deep-fried mouth, deep burst and other defects, easily lead to stress concentration or lead to self-detonation of tempered glass. 4. Stress distribution in tempered glass is inhomogeneous, offset, or stress is too high.
In general, the reasons for the occurrence of self-explosion in the glass tempering process are mostly cases 3 and 4; the glass is self-exploding after leaving the factory with the majority of cases 1 and 2. After the glass is installed, the situation 1 is most typical.
Tempered glass blew how to identify?
The difference between the breakout of the tempered self-detonation and the impact of the tempered glass is mainly due to the difference in the “primary point”. Tempered glass is generally detonated in the center of the glass. The center of the detonation point has obvious debris like a butterfly, commonly known as "butterfly spot."
Tempered crushing of externally-strengthened glass generally shows impact marks at the crushing point, and there is no butterfly spot. Broken glass is radioactively distributed from the point of impact.
What is the bleed rate?
Due to the existence of an objective phenomenon of tempered glass explosion. According to statistics at home and abroad, in general, there is one case of “self-explosion” for every 4 tons of glass, and the number of glasses converted into regular glass is 3‰-5‰ in the industry. From the perspective of engineering practice, the quality of the original float film, the size of the glass layout, and the control of the deep processing technology have a great influence on the probability of self-explosion.
The influence of the quality of float film on the probability of self-explosion is decisive. 1 The sand, ore, fuel, and even nickel-iron alloy liners used in the production process of the original float film jointly determine the material basis for the formation of nickel sulphide; 2 Raw material management, melting and forming in the float process Process management, refractory erosion, etc., determine the amount of impurities such as stones, bubbles, etc. in the original glass sheet. 3 The standard and processing methods for the impurities on the cold end during the float process also determine the quality of the raw material flowing to deep processing plants.
Factors affecting the probability of self-explosion in the deep processing process are: 1 the quality of the edge treatment; micro cracks on the edge of the glass directly affect the self-detonation during the tempering process. At the same time, the rough glass is processed at the edges, and the glass is blew due to cracks in the edges during installation and use. 2 The higher the tempering stress, the higher the probability of tempered glass blew.
What is hot dip in tempered glass?
What is the principle of hot dipping to reduce the probability of tempered glass blew?
Hot dip treatment, also known as homogenization, is commonly referred to as "detonation." The hot-dip treatment is to heat the tempered glass to 290°C±10°C and hold it for a certain period of time, prompting the nickel sulfide to rapidly complete the crystal phase transformation in the tempered glass, so that the tempered glass that may be blew before use is artificially broken in advance at the factory. In a hot dip furnace, the self-explosion of the tempered glass in use after installation is reduced. This method generally uses hot air as a heating medium, and is called “Heat Soak Test” abroad, abbreviated as HST, and it is literally translated as hot-dip treatment.
Hot dip difficulties. In principle, hot-dip treatment is neither complicated nor difficult. However, it is very difficult to actually achieve this process index. Studies have shown that there are many specific chemical structural formulas for nickel sulfide in glass, such as Ni7S6, NiS, NiS1.01, etc. Not only do the proportions of various components vary but they may be doped with other elements. Its phase change speed is highly dependent on the temperature level. Studies have shown that the phase change rate at 280°C is 100 times that at 250°C, so it must be ensured that each piece of glass in the furnace experiences the same temperature regime. On the other hand, on the one hand, the temperature of the glass with low temperature is insufficient for the holding time, nickel sulfide cannot completely phase change, and the effect of hot dipping is weakened. On the other hand, when the temperature of the glass is too high, it may even cause reverse phase transition of the nickel sulfide, or the excessive stress leads to too much reduction of the tempering stress, resulting in a greater risk. Both of these conditions will lead to hot dip treatment and even counterproductive.
With foreign related statistics after a strict sense of hot-dip, the probability of bleed that can fall to tempered glass can be reduced to one case per 400 tons of glass, ie the probability of self-explosion can be reduced by 2 orders of magnitude. Because strictly speaking, it is impossible to absolutely exclude tempering and self-detonation of steel. Whether or not glass is hot-dipped cannot be detected. At the same time, the hot-dip process is time consuming and labor-consuming, and requires high equipment and processes. Therefore, many domestic non-standard production enterprises often have false heat. Dipping or incomplete hot dipping also affects the domestic acceptance of the hot dip process.
Why can ultra-white glass reduce the chance of steel explosion?
Ultra-white glass for engineering is a kind of fine float glass. Ultra-white glass can greatly reduce the probability of tempered glass bleed due to the following reasons: 1, ultra-white glass in order to ensure product quality, generally using the preferred ultra-white sand and fine ingredients, using natural gas firing, from raw materials to reduce the nickel sulfide produced possibility. 2 Ultra-white glass technology and quality control are more stringent than ordinary float glass, reducing the risk of steel explosion due to stones, bubbles and other issues.
How to evade the tempered glass blew?
1, choose the original white film;
2, hot dip treatment;
3. Appropriately control the weight of the monolithic glass to avoid oversizing and overweight of the monolithic glass.