1. AHMEDABAD INSTITUTE OF TECHNOLOGY

2. PREPARED BY: SUBMITTED TO: PROF. I. J.Bhavasar NAME ENROLL. NO.
PATEL DIVYESH
13/ME/559
PATEL HARESH
13/ME/561
PANDYA VAIBHAV
13/ME/552
PATEL BHARGAV
13/ME/556
PANCHAL SUNNY
13/ME/549
KADIA POOJAN
13/ME/529
SUBMITTED TO: PROF. I. J.Bhavasar

3. The Iron-Iron Carbide Phase Diagram
Heat Treatment of Steel

5. Features Reactions Phases present L a ferrite Bcc structure
Ferromagnetic
Fairly ductile d
Bcc structure
Paramagnetic
g austenite
Fcc structure
Non-magnetic
ductile
Fe3C cementite
Orthorhombic
Hard
brittle
Reactions
Peritectic L + d = g
Max. solubility of C in ferrite=0.022%
Max. solubility of C in austenite=2.11%
Eutectic L = g + Fe3C
Eutectoid g = a + Fe3C

6. Microstructures a g

7. Steels Classification/Nomenclature
Steel is an interstitial solid solution of carbon in iron.
Theoretically steel has a maximum of 2.11% carbon.
In practice, the amount of carbon rarely exceeds 0.8%
Classification/Nomenclature
Low carbon steels up to 0.2%C
Medium carbon steels %C
High carbon steels >0.4% C
AISI 1020:
Last two numbers indicate
Amount of carbon :0.2%C
10 indicates plain carbon steel
AISI 4340: 0.4%C
43 indicates alloy steel

8. Microstructural changes in steel on cooling for different compositions

9. Eutectoid steel

10. Hypoeutectoid steel

11. Hypereutectoid steel

12. Iron-Carbon (Fe-C) Phase Diagram
Max. C solubility in  iron = 2.11 wt%
• 2 important
Fe3C (cementite)
1600
1400
1200
1000
800
600
400 1 2 3 4 5 6
6.7 L g
(austenite) +L
+Fe3C a +
L+Fe3C d
(Fe)
Co, wt% C
1148°C
T(°C)
727°C = T
eutectoid
points
-Eutectic (A): L Þ g +
Fe3C A S R
4.30
-Eutectoid (B): g Þ a +
Fe3C g
Result: Pearlite =
alternating layers of a
and Fe3C phases
120 mm
(Adapted from Fig. 9.27, Callister 7e.)
0.76 C
eutectoid B R S
Fe3C (cementite-hard) a
(ferrite-soft)

13. Eutectoid Reactions (II)
Contains an eutectic reaction
and an eutectoid reaction

14. Peritectic Reactions
Peritectic  solid phase + liquid phase will together form a second solid phase at a particular temperature and composition upon cooling
L +   
Reactions are slow as product phase will form at boundary between two reacting phases separating them
Peritectics are not as common as eutectics and eutectiods. There is one in Fe-C system

15. THANK YOU