just keep some basic in mind, its give u enough information about this topic.

1. HEAT TREATMENT
Dr. H. K. Khaira
Professor in MSME
MANIT, Bhopal

2. Introduction
• Lifting devices in their various forms are
constructed from a range of materials that
have specific properties for the function they
will perform.
• The inherent structure that provides these
necessary properties may not be capable of
meeting a range of “working demands”.
• It is then necessary to enhance these
properties by some means.

3. Introduction
• Alloying, cold working processes and heat
treatment are ways of altering the structure of a
material to improve its properties.
• These structure-altering procedures are often
employed in combination to achieve the desired
results.
• For example, iron alloyed with carbon produces
steel that is further enhanced with other metals
such as molybdenum, chromium and vanadium.
• The forging process will again change the
properties, as will heat treatment.

4. Tools for Controlling Properties of
Metals
• 1. Alloying
• 2. Cold Working
• 3. Heat treatment

5. Heat Treatment
• Heat treatment is defined as heating a metal
to a specified temperature, keeping it at that
temperature for some time followed by
cooling at a specified rate.
• It is a tool to get required microstructure and
properties in the metal.

6. Heat treatment
Heat treatment - controlled heating and cooling basically
The basic steps of heat treatment are:
Heating → Soaking → Cooling
Handouts 2
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7. Important Parameters in Heat treatment
Heating ->
Temperature
Soaking
->
Cooling
Time of soaking
Rate of cooling
Medium of cooling
-Different combinations of the above parameters
Give rise to different heat treatments
Handouts 2
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8. Cooling Rates

9. Types of Heat Treatments
•
•
•
•
•
1. Annealing
2. Normalizing
3. Hardening
4. Tempering
5. Precipitation Hardening

10. Annealing
• Annealing is a heat treatment in which the metal is heated
to a temperature above its recrystallisation
temperature, kept at that temperature some time for
homogenization of temperature followed by very slow
cooling to develop equilibrium structure in the metal or
alloy.
• The steel is heated 30 to 50oC above Ae3 temperature in
case of hypo-eutectoid steels and 30 to 50oC above A1
temperature in case of hyper-eutectoid temperature
• The cooling is done in the furnace itself.
• The aim of annealing is to increase the ductility.

11. Normalizing
• Normalizing consists of heating a suitable steel
to a temperature 50-1000 C above Ae3
temperature in case of hypoeutectoid steels
and above Acm temperature in case of hypereutectoid steel, soaking for sufficient time and
then cooling in still air.
• The aim of normalizing is to increase the
toughness.

12. Hardening
• In hardening heat treatment, the steel is heated
30 to 50oC above Ae3 temperature in case of
hypo-eutectoid steels and 30 to 50oC above A1
temperature in case of hyper-eutectoid
temperature, held at that temperature for some
time followed by cooling at a rate faster than the
critical cooling rate to produce martensite which
is a hard phase.
• The aim of hardening is to increase the hardness
and strength of the steel.

13. Critical Cooling Rate
Critical
cooling
rate

14. Tempering
• Tempering consists of heating a hardened
steel to a temperature below eutectoid
temperature and keeping it at that
temperature for a specified time to reduce
brittleness followed by air cooling.
• The aim of tempering is to decrease
brittleness of hardened steel.

15. Precipitation Hardening
• Precipitation Hardening (or Age Hardening) is
a heat treatment in which the strength
increases due to precipitation of second phase
particles in the parent phase.
• The aim of precipitation hardening is to
increase the hardness and strength .

16. Heat Treatment Temperature
←Acm
The temperature
ranges to which the
steel has to be
heated for different
heat treatments
A3 →

17. Cooling Rates for Different heat treatments

18. Tempering