Heat Strengthened Glass

Heat strengthened glass is a semi tempered glass, which has been strengthened thermally by inducing a surface compression of 6000 to 9000 psi as compared to a range of 11000 to 20000 psi in case of fully tempered glass. It is two times stronger than annealed glass. Though it is not considered to be a safety glass, it is widely used on building facades due to better optics.


Proses:
Trutuf heat strengthened glass is made on state of the art electrically heated horizontal furnace, which heats the glass to an uniform temperature of approximately 660ºC. Ceramic rolls convey the glass through these furnace at speeds regulated to ensure temperature uniformity and minimal optics distortions. The heat strengthened process parallels the traditional process of glass tempering, except that the heating temperature are lower and the cooling cycle is less rapid. During production, non-destructive verification of the range of stresses is done by using grazing angle surface polarimeter to ensure the right surface compression.


Karakteristik:

• Strength : Two times more stronger than basic float glass.
• High Thermal Shock Strength : Can withstand temperature differentials up to 130ºC.
• Safety : Will break into small, relatively harmless fragments. This substantially reduces the likelihood of injury to people as there are no jagged edges or sharp corners.
• Light and Heat transmission properties : Do not change due to tempering and remain the same as in unprocessed glass unless laminated or double glazed.
• Alterations : Tempered glass cannot be further cut, ground, drilled or worked upon. All these processes are completed prior to its tempering, in accordance with your drawings, sizes or templates.

Aplikasi:

Heat Strengthened glass is best suited for spandrel and vision panels of curtain walls and structural glazing as it safeguards against thermal breakages providing better optics than fully tempered glass provided the calculations on wind loading are within safe limits.

It is ideal for making laminated glass panels for safety combined with strength.

It is also used in complex glass combinations like – double glazed with one lite of laminated glass, pool sides, pool bottoms and aquariums etc

Precaution:

The glass cannot be cut or drilled after heat strengthening. Any field alterations including edge grinding, sand blasting or acid etching may cause premature failure.

Optics : As can be expected with any heat treated glass, bow, warp, process and roller waves distortion may be evident. This is an inherent characteristics of the manufacturing process and is within the limits set by ASTM Standard C-1048 or DIN 1249 Part 12. Optics in heat strengthened glass is generally better than fully tempered glass.

However, there are many applications where heat-strengthened glass is not sufficient, fully tempered glass is still the only option.

Availability:

Heat strengthened glass is similar to tempered glass except that after heating the glass in a furnace as in the case of tempered glass, the cooling is done at a much slower pace.
The heating temperature remains nearly the same for both processes. The residual stress on the edge and the glass surface differ in both cases with tempered glass having a
higher level of stress. Tempered Glass Breakage Pattern Heat Strengthened Glass Breakage Pattern Due to the relatively lower rate of cooling during the strengthening process, heat strengthened glass develops less stress as compared to fully tempered glass.

Characteristics of Heat Strengthened Glass:

Strength: The process increases the mechanical and thermal
strength of heat strengthened glass, making it twice as tough
as annealed glass but nearly half of fully tempered glass.
However, its breakage characteristic is similar to annealed
glass, which means that it breaks down into sharp pieces like
ordinary glass even though it has been put through the heat
strengthening process.
Optics: Heat strengthened glass has a comparatively flatter
finish than fully tempered glass. It therefore has lesser
optical distortions and so can be used in places where high
optical quality is required.
View in the Furnace
Safety: It can be used for general glazing where additional strength or resistance to mechanical/thermal
strength is desired. The glass can also be used in high wind load areas, but cannot be used in any safety glazing
applications. As Heat Strengthened glass breaks in a manner similar to that of float glass, the fragments tends to
remain in the sashes, having less probability of fallout as compared to tempered glass. In comparison with
tempered glass, heat strengthened glass is not easily broken spontaneously.
High Thermal Shock Strength : Heat Strengthened Glass will resist temperature difference of up to
approximately 130°C.