Tempered Glass

Tempered glass is made by processes which create balanced internal stresses which give the glass strength. It will usually shatter into small fragments instead of sharp shards when broken, making it less likely to cause severe injury and deep lacerations. As a result of its safety and strength, tempered glass is used in a variety of demanding applications, including passenger vehicle windows, glass doors and tables, as a component of bulletproof glass, for diving masks, and various types of plates and cookware.

Tempered glass is glass that has been processed by controlled thermal or chemical treatments to increase its strengthit is physically and thermally stronger than regular glass.

Manufacturing:

Tempered glass is made from annealed glass via a thermal tempering process. The glass is placed onto a roller table, taking it through a furnace that heats it above its annealing point of about 720 °C. The glass is then rapidly cooled with forced air drafts while the inner portion remains free to flow for a short time.

An alternative chemical process involves forcing a surface layer of glass at least 0.1mm thick into compression by ion exchange of the sodium ions in the glass surface with the 30% larger potassium ions, by immersion of the glass into a bath of molten potassium nitrate. Chemical toughening results in increased toughness compared with thermal toughening, and can be applied to glass objects of complex shape.

Northglass Sunny Glass Company produces flat and bent tempered glass:

Flat Tempered Glass:

(Max. Size)：2440mm×5000mm         
(Min. Size)：300mm×300mm
(Thickness Range)： 5mm-25mm

Bent Tempered Glass:

(Max. Size)：2600mm×2440mm       
(Min. Size)：300mm×300mm
(Min.Radius)：450mm            
(Thickness Range)：4mm-25mm

Applications:

• for side and rear windows in automobiles.
• for its characteristic of shattering into small cubes.
• in buildings for unframed assemblies, such as frameless doors.
• structurally-loaded applications.
• any other application that would become dangerous in the event of human impact.

Note:

1. 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 is 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. Fully tempered glass is generally above 65 MPa while Heat Strengthened glass is between 40 and 55 MPa.

2. The 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.

3. 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.