How to resolve the "self-exploding" of tempered glass

How to resolve the "self-exploding" of tempered glass

Tempered Glass is a type of glass with even compressive stress on the surface which is processed by heating float glass to nearly soften point and then cooling it down rapidly by air. During the instant cooling process, the exterior of glass is solidified due to rapid cooling while the interior of glass is cooled down relatively slowly. This process will bring the glass surface compressive stress and the interior tensile stress which can improve the mechanical strength of glass by germination and result in good thermal stability.

1) Tempered glass is not easy to be broken when attacked, The broken tempered glass particle is same like honeycomb shape with obtuse angles which won’t cause severe hurt to human body.

2) The impact-resistant strength of tempered glass is 3-5 times higher than that of float glass with the same thickness.

3) Thermal stability of tempered glass is 3-4times than that of the float glass with the same thickness. Tempered glass can withstand sudden temperature shift of 220℃-250℃ while float glass can only withstand temperature shift of 70℃-100℃. When tempered glass suffers rapidly cooled of a certain extent, the internal tensile stress and compressive stress is generated on the surface can offset due to opposite stress direction. When tempered glass is heated extremely, compressive stress is generated on the surface of glass which is as double as tensile stress. Therefore, tempered glass also can withstand certain level of rapid heating up.

Although tempered glass has many advantages, it also has a congenital deficiency - self-explosion. In a broad sense, self-explosion of tempered glass is generally defined as the phenomenon that tempered glass bursts automatically without direct external force.

1) It refers to the self-explosion caused by visible defects in the glass, such as stones, sand, air bubbles, inclusions, nicks, scratches, burst edges, etc. This situation is generally visible to the naked eye and relatively easy to detect, so it is controllable in production.

2) It refers to the self-explosion of tempered glass caused by nickel sulfide (NIs) impurities and heterogeneous phase particles in the glass. Qualified tempered glass, nickel sulfide is evenly distributed, unqualified tempered glass, nickel sulfide is not evenly distributed; in the process of glass cooling, the nickel sulfide that is not evenly distributed and aggregated together hinders the normal release of energy, The energy accumulated in the nickel sulfide gathering point is more and more, and finally the energy exceeds the limit that the hardness of the tempered glass itself can bear, and an explosion will occur.

However, because the tiny nickel sulfide particles in the glass cannot be visually inspected, this self-destruction is uncontrollable and is called "the cancer of the glass."  According to industry experience generally, the self-explosion rate of ordinary tempered glass is about one thousandth to three thousandths.

Among the way to reduce the self-explosion rate of tempered glass, the top priority is to choose high-quality original flat glass.
The reason is not difficult to understand. Tempered glass is obtained by tempering the original glass sheet. The high quality of the original flat glass sheet used must be the basic factor to reduce the probability and probability of self-explosion. The reason why the self-explosion efficiency of auto glass is relatively low has a lot to do with the original film it usually uses.
In the same way, according to the classification, there will be a building-level classification, and the curtain wall safety glass must use the high-quality original flat glass.

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