Home > news >When people under certain lighting conditions , when a certain distance and angle of observation glass, tempered glass surface will look at some of the distribution is not very regular with colored markings , such markings with colors that we usually call " stress spot" , although the presence of plaques does not affect the stress effect of the glass reflector ( reflection without distortion ) , the effect does not affect the transmission of the glass ( not affect the resolution, optical distortion is not generated ) . It is an all optical properties of glass have quality problems or quality defects are not glass , but the toughened safety glass as more and more widely , it is the effect of the glass looks increasingly high demand , especially as large stress exists glass plaques will bring the appearance of the glass curtain wall applications adversely affected when the area , and even affect the overall aesthetic effect of the building, so people are concerned about the stress spots more intense.
Reason 1 spot stress generated
All transparent materials can be divided into isotropic and anisotropic materials materials . When light passes through an isotropic material , the speed of the light in all directions , as the change in the incident light is not emitted , good glass annealing belongs isotropic material. When light passes through the anisotropic material , the incident light into two different speeds and with different radiation from the output beam of the incident light changes, annealed glass , including glass of poor anisotropic material belongs . Anisotropic materials as glass , the phenomenon of stress can spot light bombs principle explained : When a bunch of polarized light through the glass when the glass due to the existence of a permanent internal stress ( stress steel ) , which breaks down into two beams of light beam propagation speed of different polarized light that is fast slow light , also known as birefringence . When the two light beams at a point in the beam is formed by a point of intersection of another , due to the different propagation speed of light in the beam intersection point exists a phase difference that will produce the two interference light beams when two light beams amplitude in the same direction , the light intensity enhanced bright field generated , i.e., hot spots ; amplitude in the opposite direction when the light , the light intensity decreases , resulting in a dark field , i.e., dark spots. As long as there uniform stress distribution in the plane direction of the glass will cause stress spots.
In addition reflex glass surface reflected light and transmitted occurred some polarization effect, into the interior of the glass light is actually light polarization effect with , which is why 'll see light and dark stripes or markings truth.
2 glass process factors produce stress spots
2.1 heating element
Presence on the glass front plane direction during quenching uneven heating . Uneven heating of glass during quenching , the high temperature region of compressive stress is small, the low-temperature region produces a large stress , resulting in uneven distribution of stress causes uneven heating of the glass surface . The main factors leading to uneven heating of the existence of differences in the power of the heater, heating power large area of high temperature , low temperature heating power in the region is low; heater failure can not be properly heated ; temperature sensor calibration failure or inaccurate ; temperature setting is not reasonable edge of the furnace has more heat, the temperature should be set slightly higher than the middle of absorbing more than the edge of the glass in the middle , the middle relative edge slightly higher temperatures , these factors are reflected in the settings will be applied if no resulting in uneven heating ; glass laying unreasonable , because the roller is a poor conductor of heat , such as the repeated use of a particular region will lead to lower the temperature in the region but not put the glass area , the region is relatively high temperatures , the next batch of glass when the heating temperature in this area is relatively high ; furnace seal bad , resulting in a partial cooling temperature more unequal .
2.2 Cooling factor
Toughened glass is heated during quenching , cooling and heating of the steel during the formation of the stress equally important. Deposit on the glass uneven cooling during quenching occurs before the plane direction and uneven heating , as stress can also cause uneven . Great stress surface stress , the cooling intensity of a small area formed in a large area to form the cooling intensity is small, uneven stress distribution generated on the glass surface causes uneven cooling . The main factors that have led to uneven cooling fan nozzle unreasonable distribution , nozzle gap is uneven, so uneven pressure distribution on the surface of glass , glass surface uneven cooling ; air nozzles clogged nozzle can not be part of the normal air ; roll Road thermal capacity is too large , the contact with the roller portion is rapidly cooled , the cooled first part of the formation of a large stress. The glass is uneven heating and cooling is the main spot stress generated only by the steel furnace design and pretentious use to identify the impact of uneven heating and cooling plus various factors , strengthen process control , strict adherence to rules can reduce stress generated plaques .
Other factors 3 glass plaques stress
3.1 viewing angle
The reason why we can see spot stress is due to the visible light through the glass of naturally occurring polarization light the surface of the glass ( transparent medium ) from the reflection at an angle , there occurs a portion of the light polarized by the same glass also part of the refracted light polarization occurs when the refractive index is equal to the tangent of the angle of incidence of the reflective polarizer and the glass reaches its maximum . Refractive index of glass is 1.5 , the maximum incident angle of the reflective polarizer 56 . , I.e., the incident angle of 56o to the light from the light reflected by the surface of the glass is almost all polarized light. Tempered glass , we see light reflected from each of the two 4% reflectivity of the surface reflection from the second surface of the reflective light of our distant presence of stress in the glass through which the light from the portion closer to us a first reflective surface of the light beams generated in the glass surface color pattern , so incident angle 56. Glass observed stress version of the most obvious. The same is true for steel hollow glass due to the more polarized reflective surface is greater , for the same level of stress uneven glass, we see more clearly spot stress , stress spots appear heavier .
3.2 glass thickness
As the light propagation in different thickness of glass , the thicker the longer the optical path , the more chance of light polarization occurs , so the glass for the same stress level , the greater the thickness , the more severe stress spot colors.
3.3 Glass varieties
Different varieties of glass and different stress levels on the same spot of glass stress effects, such as borosilicate glass, soda lime glass is relatively stress spot colors will appear lighter.
4 Conclusion
For tempered glass because of its enhanced specificity principle , difficult to completely eliminate a lot of stress spots , but through the use of advanced equipment, reasonable control of the production process , it can add less stress spots produced , can be achieved without affecting the level of aesthetic effects .