Heat Treatment Of Glass Products

Like metals, heat treatment processes are applied to glass products after the shaping processes applied on glasses. Types of heat treatment processes differs according to type of shape, thickness and other parameters of glass products defined below. In general, there are two types of heat treatment processes applied to glass products;

  • Annealing of glasses,
  • Tempering
Three types of glass products(Image Source: Pacificglass-Screen)

Why Glass Products Are Annealed?

After the shaping processes such as blowing, pressing etc. there are unwanted internal stresses which make glass products flimsy. These internal stresses take place after the solidification of molten glass. To compensate these internal stresses, annealing processes are applied to these glasswares.

Annealing is a process that the produced glassware held at elevated temperatures inside special heat treatment furnaces. These furnaces are generally in the shape of tunnels.

This heat application relieves the internal stresses in glasswares. Annealing temperatures of general glass products are around 500C degrees.

The time of heat application changes according to the shape of glass product. But in general applications, annealing time is proportional with the thickness of glass.

Cooling after the annealing must be slow. This slow coolingof glass prevents the formation of new internal stresses.

Like metals again, tempering process is also applied to glass products.

Tempering Applications To Glass Products

Tempered glass applications are very important in today’s technology. Tempered glasses are much more stronger than the conventional annealed glasses. Automobile windshields, windows of tall buildings, glass-doors are generally fabricated from tempered glasses.

When a tempered glass fractures, glass fractures are not dangerous to cut someone elses. Because, the fractures are fracturing in very small pieces because of the nature of tempered glasses.

There is an also another kind of glassware applications that conventional glasses are attached to the two sides of high strength polymer sheets to obtain high strength glass products. This type of glass applications are used in automobile windshields to prevent fragmentations which can be harmful for drivers. This application is also called as ‘laminated glass’.

Unlike annealing, the purpose of tempering heat treatment application, create internal stresses will result more strong and tough structures. Like tempering application that applied to metals, glass products are heated up to temperatures above annealing temperatures.

Again unlike annealing application, cooling is very rapid. This rapid solidification is done with quenching application of metals inside water or special oils. In the annealing of glasswares, external surfaces are rapidly cooled. And internal sections are cooled after the surface of glass product. This leads to contracting effect due to the difference between cooling of internal and external sides of glass products. This contraction leads to very good compressive strength of tempered glass.

Conclusion For Heat Treatment Applications For Glass Products

As you understand that heat treatment applications are also very important for glasswares to obtain high strength glasswares. Heat treatment applications for glasses are just like the ones that applied to metals.

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