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The Self - Blasting Rate And The Causes Of Tempered Glass Door
Jun 09, 2017

The Self - blasting Rate and the Causes of Tempered Glass Door
    1, the rate of self-blasting rate of the country's self-blasting rate of the manufacturers are not consistent, ranging from 3% to 0.3%. The general rate of self-blasting is calculated on the basis of the number of pieces, without considering the size of single-chip glass and glass thickness, so not accurate enough, can not be more scientific comparison with each other. In order to uniformly calculate the rate of self-explosion, it is necessary to determine the uniform hypothesis. Set a uniform condition: every 5 to 8 tons of glass contains a sufficient to cause bleed nickel sulfide; each piece of tempered glass door area of an average of 1.8mm; nickel sulfide evenly distributed. Then calculate the 6mm thick tempered glass door to calculate the blasting rate of 0.64% ~ 0.54%, that is, 6mm tempered glass door blasting rate of about 3 ‰ ~ 5 ‰. This is consistent with the actual value of domestic high-level processing enterprises. Even if the production by standard, can not completely avoid the glass door blew. Large buildings will be easy to use hundreds of tons of glass, which means that the glass nickel and heterogeneous impurities in the existence of a large rate, so the glass door, although hot-dip treatment, blew is still inevitable.


    2, tempered glass door uncontrollable reasons - nickel sulfide (NiS) and heterogeneous phase grain glass door uncontrollable source is not only the traditional understanding of the nis particles, there are many other heterogeneous particles. The germination and expansion of the cracks in the glass is mainly due to the residual stresses produced in the vicinity of the particles. This type of stress can be divided into two categories, one is the phase transition during the phase transition stress, the other is the thermal expansion coefficient does not match the residual stress generated. Nickel sulfide (nis) and heterogeneous phase particles. Glass contains nickel oxide impurities, in small crystal state, in general, will not cause damage to the glass, but due to the re-heating of the glass door, changing the phase of nickel sulfide impurities, nickel sulfide high temperature α state in the glass quenching When they are frozen, they may need to be in the state of the time of the β, due to the low temperature β-state nickel sulfide impurities will produce volume increase in the glass to produce local stress concentration, then the tempered glass door blew will occur. However, only relatively large impurities will cause blew, and only when the impurity in the core of the tensile stress can occur when the tempered glass door blew. Nis is a crystal, there are two kinds of crystal phase: high temperature phase α-nis and low temperature phase β-nis, phase transition temperature of 379 ℃, glass heating furnace in the furnace, the heating temperature is much higher than the phase transition temperature, nis All into α phase. However, in the subsequent quenching process, α-nis too late to change to β-nis, which was frozen in the tempered glass door. In the room temperature environment, α-nis is unstable, there is a gradual shift to β-nis trend. This change is accompanied by about 2 to 4% of the volume of expansion, so that the glass bear a huge phase change tensile stress, resulting in blew. Scanning electron microscopy photographs of nis stones extracted from the glass fragments after blew can be seen, and the surface is undulating and very rough. Heterogeneous particles cause the tempered glass door to blew and can be broken at the source of glass fragments seen in the cross section of the photo, with a spherical tiny particle causing the first cracking traces with the secondary fragmentation of the boundary zone.


    3, how to identify the tempered glass door blew first look at the burst point (tempered glass door cracks were radial, have the starting point) whether the middle of the glass, such as the edge of the glass, generally because the glass has not been chamfered grinding or glass edge There are damage, resulting in stress concentration, the gradual development of cracks caused by; such as the starting point in the middle of the glass, look at whether there are two small pieces of polygons composed of two similar butterfly wings-like pattern (Hu Dieban), if careful observation of two small Block polygon public side (part of the trunk of the butterfly) should be visible black small particles (nickel sulfide stones), you can determine is blew; otherwise it should be external damage. The typical characteristics of the glass blew is the butterfly spot. Glass fragments were radial distribution, the radiation center has two butterfly wings like the glass block, commonly known as "butterfly spot." The stone is located on the interface of two pieces of "butterfly spot".

    4, tempered glass door blew mechanism theory of radial stress r ≥ a tangential stress r ≥ a particle and glass interface between the stress for the heterogeneous particles in the glass matrix, the cooling process temperature is negative, so the particle diameter Stress is pressure, tangential stress is tension. The radial stress at the periphery of the particles is the pressure and the tangential stress is the tensile force, so the tangential stress is the root of the crack initiation.