Discussion about heat treatment of glass, heat treated glass.

1. HeatTreatment Of Glass
PRESENTED BY
MohammadTarequl Islam
M.S.(Inorganic Chemistry)
Session: 2018-2019
Department Of Chemistry
University Of Chittagong

2. Contents
Introduction
Classification
Purpose
Methods

3. What is HeatTreatment of Glass?
Answer: HeatTreatment of Glass is a group of industrial and metalworking
processes used to alter the physical, and sometimes chemical, properties
of glass. Heat treatment techniques include annealing, case hardening,
precipitation strengthening, tempering, carburizing, normalizing and
quenching.
 What is heat treated glass?
Answer: Heat-treated glass is a term used to describe glass that has
been processed through a tempering furnace to alter its strength
characteristics, provide greater resistance to thermal and mechanical
stresses and achieve specific break patterns for safety glazing

4. CLASSIFICATION OF HEATTREATED GLASSES
 Heat-Strengthened Glass:
Heat-strengthened (HS) glass has been
subjected to a specifically controlled heating
and cooling cycle, and is generally twice as
strong as annealed glass of the same
thickness and configuration.
 FullyTempered Glass:
Tempered glass is approximately four times
stronger than regular annealed glass of the
same thickness and configuration.Tempered
glass is often referred to as ‘safety glass’ .
There are two different types of
heat treated glasses.
Heat-Strengthened(HS)
FullyTempered(FT)

5. Breakage Pattern of HS and FT Glass

6. Purpose of HeatTreatment of Glass
 Why HeatTreatment of Glass is done?
Answer: HeatTreatment of Glass is done to-
• Increase its strength to resist external stresses such as wind and snow
loads, or thermal loads caused by the sun’s energy.
• Temper glass so that it meets safety glazing requirements defined by
applicable codes or federal standards.

7. HeatTreatment Process Of Glass
ANNEALING :
• When glass cools from the forming range to room temperature , thermal
stresses develop that adversely affect strength properties.
• Annealing is done to eliminate this stress.
• Involves heating the glass to annealing range, holding it there for a period
of time, and then cooling it slowly to room temperature.
TEMPERING :
• Involves heating glass to around the softening point and then cooling it
rapidly with blasts of air or by quenching it in oil.
• Heat tempered glass is 3 to 5 times stronger than annealed glass while still
retaining its initial clarity, hardness, and expansion co-efficient.

8. ThankYou