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INTRODUCTION

Toughened  glass is also know as Tempered glass.

Toughened or tempered glass is a type of safety glass processed by controlled thermal  or chemical treatments to increase its strength compared with normal glass.

Tempering puts the outer surfaces into compression and the inner surfaces into tension. Such stresses cause the glass, when broken, to crumble into small granular chunks instead of splintering into jagged shards. The granular chunks are less likely to cause injury.

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HISTORY

The first patent on tempered glass was held by chemist  Rudolph A. Seiden, born in 1900 in Austria.

Though the underlying mechanism was not known at the time, the effects of "tempering" glass have been known for centuries

Its popularity has increased in recent decades because of its use in the automobile and construction industries, as well as in microwaveable glassware. Among the most common current uses are for side and rear windows and windshields in automobiles, display cases, patio doors, and shower doors.

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PROPERTIES

Toughened glass is physically and thermally stronger than regular glass. The greater contraction of the inner layer during manufacturing induces compressive stresses in the surface of the glass balanced by tensile stresses in the body of the glass. For glass to be considered toughened, this compressive stress on the surface of the glass should be a minimum of 69 MPa. For it to be considered safety glass, the surface compressive stress should exceed 100 MPa. The greater the surface stress, the smaller the glass particles will be when broken

Any cutting or grinding must be done prior to tempering. Cutting, grinding, sharp impacts and sometimes even scratches after tempering will cause the glass to fracture

The strain pattern resulting from tempering can be observed with polarized light or by using a pair of polarizing sun glasses.

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STEPS INVOLVED IN MANUFACTURING OF TOUGHENED GLASS

Steps involved in making tempered glass are as follows:

1. Cut the glass into the desired shape first. 2. Inspect the glass for imperfections 3. Sand the cut edges smooth4. Wash the glass 5. Heat the glass in a tempering oven 6. Quench the glass to cool it

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Glass type Toughened glassThickness

(mm)2.8 3 4 5 6 8 10 12 15

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22

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Monolithic types

Transparent, Bodily colored, Colorfully glazed, Film plated and Toughened

glass

Combination types

Toughened insulating glass, Toughened laminated glass and Toughened

insulating laminated glass

Max size possible (mm)

5100 x 3200

Min. size possible (mm)

300 x 300

SPECIFICATIONS & SIZES OF TOUGHENED GLASS

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SAFETY  

Through the quenching process , the inside of toughened glass possesses the compressive stress , it will with stand the impact force to certain extent, even though it encountered greater load of impact and broke, its fragments seemed to lot of tiny particles with obtuse angle that hardly would do any harm to human body. While with the fragments of ordinary glass, they are similar to large size broken sharp pieces easily causing serious injuries to the people.

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APPEREANCE OF FRAGENTS

TOUGHENED GLASS

IF TOUGHENED GLASS BREAKS IF TOUGHNED GLASS BREAKS WITH HIGH PRESSURE

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ORDINARY GLASS

PLAIN ORDINARY GLASS IF ORDINARY GLASS BREAKS

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USES

Toughened glass is used when strength, thermal resistance, and safety are important considerations. The most commonly encountered tempered glass is that used for side and rear windows in automobiles

It is used for its characteristic of shattering into small cubes rather than large shards and is sometimes referred to as safety glass in this context

Toughened glass is also used in buildings for unframed assemblies (such as frameless doors), structurally loaded applications, and any other application that would become dangerous in the event of human impact.

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ADVANTAGESThe term "toughened glass" is generally used to describe

fully tempered glass but is sometimes used to describe heat-strengthened glass as both types undergo a thermal "toughening" process.

There are two main types of heat-treated glass: heat-strengthened and fully tempered. Heat-strengthened glass is twice as strong as annealed glass while fully tempered glass has typically four to six times the strength of annealed glass and withstands heating in microwave ovens. The difference is the residual stress in the edge and glass surface

It is important to note that the tempering process does not change the stiffness of the glass. Annealed glass undergoes a similar deflection compared to tempered glass under the same load,

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DISADVANTAGE

Toughened glass must be cut to size or pressed to shape before toughening and cannot be re-worked once toughened.

Polishing the edges or drilling holes in the glass is carried out before the toughening process starts.

Because of the balanced stresses in the glass, damage to the glass will eventually result in the glass shattering into thumbnail-sized pieces.

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THA

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idamakanti.jaswanth@gmail.com

NOTE:

Steps involved in the manufacturing process of TOUGHENED

GLASS can be seen in my next upload.