Iron-Carbon Equilibrium Diagram
Steel Part
ºC
Carbon content in atom percent
0
1600
2,3
3,6
1493 C
H
δ - iron
1
Liquid
o
1500
ºF
6,6
4,5
Liquid + δ - iron
A
1536
www.struers.com
B
2732
I
δ - iron + Austenite
1400
1392 N
2552
Austenite (γ - iron)
Liquid + Austenite
Body-centered
cubic
1300
2372 Yellowish white
1200
2192 Light yellow
2012 Yellow
1652 Very reddish yellow
Light red
A3
769 C
P
Reddish yellow
Austenite + Cementite
o
M
et
n
de
i
b
ar
c
f
o
on
i
t
lu
So
Full annealing
Austenite
+ Ferrite
800
1832 Light yellowish red
m
Ac
1000
911 G
900
Ferromagnetic Paramagnetic
2,05% 1146ºC
E
Homogenizing
1100
Face-centered
cubic
Annealing colours
Harde
ning +
O
Normali
zing
S
A2
723oC
A1
Light cherry red
Cherry red
(K)
Spheroidizing
Dark cherry red
1292
700
Dark red
Recrystallization annealing
Brown red
600
1112
Stress relieving
Dark brown
Body-centered
cubic
Recrystallization annealing
500
Pearlite
400
Tempering
Ferrite (α- iron)
932
Ferrite + Pearlite
300
572
200
392
Hypoeutectoid steel
Eutectoid steel
Hypoeutectoid steel
100
0
Compiled by S. Engell-Nielsen
752
Pearlite + Cementite
0
0,5
0,8
1
Carbon content in weight percent
Met. Eng. Technological Institute
Copenhagen
212
1,5
2
32
62142104 / Printed in Denmark by
Rosendahls Bogtrykkeri A/S
0
5
10
15
20
Cementite content in weight percent
25
30
Temper colours
Gray
Bluish gray
Light blue
Dark blue
Violet
Red
Yellowish brown
Straw yellow
Very pale yellow