Heat treatment is define as an operation involving heating and cooling of a metal in the solid state with the purpose of changing the properties of material.

1. G.H.RAISONI POLYTECHNIC ,
NAGPUR

2. YEAR:- SECOND(ME 3G )
SEC :- (A)
MADE BY =SANGHARSH.R.KAMBLE
** GUIDANCE:- BIPINWANKHEDESIR
MECHANICAL ENGINEERING
GROUP

3. TOPIC:-
HEAT TREATMENT OF STEEL
AIM :-
EXPERIMENT ON

4. HEATTREATMENT
 Heat treatment is define as an operation involving heating
and cooling of a metal in the solid state with the purpose of changing
the properties of material.
 Purpose of heat treatment :-
 1: To improve machine ability.
 2: to improve mechanical properties.

5. TYPESOFHEATTREATMENT
 1: - ANNEALING
 2:- NORMALIZING
 3:- HARDENING
 4:- TEMPERING
 5:- CARBURIZING
 6:- CYANIDING
 7:- NITRIDING

6. (1) ANNEALING

 Annealing is a softening process in which iron base alloy are heated above
the critical temp. and hold there for a proper time and then cool slowly below the
transformation range or critical temp. in the furnace itself.
 Objectives of annealing:-
 * to soften the metal so that it can be cold worked.
 *To reduce hardness and improve machine ability.

7. TYPESOFANNEALING
 (A) :- FULL ANNEALING
 1:- Full annealing removes all the structural imperfection by complete
recrystallization.
 2:-The temp. range for hypoeutectoid steels is usually between (723 to
910 degree C ).
 3:-The temp. range for hypereutectoid steels temp is ( 723 to 1130
degree C ).

8. (B) ISOTHERMALANNEALING
 1:- Isothermal is a process steel is heated to austenite state and then cooling
it down to a temp. of about (630 to 680 degree C ) at the relatively faster
rate.
 2:- After that hold it at this temp. i.e isothermally for sometime and then
cooling it down at a room temp. rapid rate .

9. (C) SPHERODIZINGANNEALING
 1:- It is another process of annealing in which high carbon steel are
heated ( 20 to 40 degree C ) below the lower critical temp.
 2:- After that held there for a considerable period of time.
 3:-Then it is cool very slowly at room temp. in furnace itself.

10. (2) NORMALIZINGPROCESS
 1:- A heat treatment process that has the object of relieving interval stress ,
refining the grain size and improving the mechanical properties.
 2:- in this process steel is heated ( 40 to 50 degree c ) above the
recrystallization temp. and held at the temp. for a short duration and
subsequently cooled in steel air at a room temp.

11. (3) HARDENINGPROCESS
1:- Hardening is defined as the heat treatment process in which steel is heated
at ( 20 degree C ) above the transformation range.
2:- soaking at this temp. for a considerable period to ensure through penetration
of the temp. inside the component.
3:- followed by the continuous cooling to room temp. by quenching in a water ,
oil or brine solution.

12. (4) TEMPERINGPROCESS
Tempering is define as reheat process in which reheating is
carried out under subcritical temp. to obtain suitable ductility and toughness.
• TYPES OF TEMPERING :-
• Low temp. tempering ( 150 to 250 degree C )
• Medium temp. tempering ( 350 to 450 degree C )
• High temp. tempering ( 500 to 650 degree C )

13. (A) MAR-TEMPERING
 1:- Mar-tempering is a type of tempering process in which iron and its base
alloy are heated above the transformation range.
 2:- Then suddenly cooled in a molten salt bath at a temp. of (180 to 300
degree C ).
 *ADVANTAGE :-
 *Less danger of cooling cracks in the work piece .

14. (B) AUS-TEMPERING
 Aus-tempering is a type of tempering
process which consist of holding the steel in a molten salt bath
having temp. (250 to 500 degree C ) above the critical temp. when
the structure consist purely austenite.

15. SURFACEHEATTREATMENT
This is also one of the methods of heat treatment in which
surface layer of a metal is harden to a certain depth while the core is maintained
relatively soft.
TYPES OF SURFACE HETAT TRAETMENT :-
1:- Surface Hardening :- (A) Flame Hardening
(B) Induction Hardening
2:- Case Hardening :- (A) Carburizing
(B) Nitriding
(C) Cyaniding

16. (A) FLAMEHARDENING
 1:- Flame hardening is the process which is use to harden the surface of the
metal parts.
 2:- When used oxyacetylene flame thin layer at the surface part is rapidly
heated to critical temp. and immediately cooled by combination of water spray
and the cold base metal.
 3:- This process produces a thin harden surface and at the same time internal
parts retain their original properties.

17. (B) INDUCTIONHARDENING
 1:-A widely use process for the a surface hardening of steel.
 2:-The components are heated by alternating magnetic field to a temp.
within or above the transformation range.
 3:-After heating metal immediately cooling is done for proper hardness.

18. NITRIDING

 1:- Nitriding is a process of producing hard surface layer on alloy steel.
 2:- Nitriding consist essentially of heating the steel in a atmosphere of
ammonia gas at temp. of (500 to 650 degree C ) without further heat
treatment.
 3:- a hard surface layer usually from 0.2 to 0.4 mm in depth produce in
50 hours.

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