Quenching and Tempering
Cast iron pearlite structure might be heated to lower critical temperature and after that quenched to effect extremely rapid cooling. This treatment reasons the precipitation of hard martensite phase and casting is hence capable of giving high wear resistance. The casting behind quenching treatment might be further heated to 300oC and cooled gradually to restore original toughness.
Surface Hardening
A lot of applications of cast iron demand high surface hardness. This might be attained by surface hardening treatments as like: induction and nitriding hardening.
Table: Typical Mechanical Properties and Applications of Cast Iron
|
|
Cast Iron
|
Composition wt. %
|
Condition
|
Structure
|
UTS MPa
|
YS MPa
|
Elongation
(%)
|
Typical Application
|
|
Gray Cast
Iron
|
Ferrite
|
3.4 C,
2.2 Si,
0.7 Mn
|
Annealed
|
Ferrite matrix
|
180
|
-
|
-
|
Cylinder blocks and head clutch plates
|
|
Pearlite
|
3.2 C,
2.0 Si,
0.7 Mn
|
As-cast
|
Pearlite matrix
|
250
|
-
|
-
|
Truck and tractor cylinder blocks, gear box
|
|
Pearlite
|
3.3 C,
2.2 Si,
0.7 Mn
|
As-cast
|
Pearlite matrix
|
290
|
-
|
-
|
Diesel engine castings
|
|
Melleable
Cast Iron
|
Ferrite
|
2.2 C,
1.2 Si,
0.75 Mn
|
Annealed
|
Temper carbon and ferrite
|
345
|
224
|
10
|
General engineering service machinability
|
|
Pearlite
|
2.4 C,
1.4 Si,
0.75 Mn
|
Annealed
|
Temper carbon and pearlite
|
440
|
310
|
8
|
General service with dimensional tolerance
|
|
Martensitic
|
2.4 C,
1.4 Si,
0.75 Mn
|
Quenched and Tempered
|
Tempered martenstie
|
620
|
438
|
2
|
High strength parts, connecting rods, yokes for universal joints
|
|
Ductile
Cast Iron
|
Ferrite
|
3.5 C,
2.2 Si
|
Annealed
|
Ferritic
|
415
|
275
|
10
|
Pressure casting as valve and pump bodies
|
|
Pearlite
|
3.5 C,
2.2 Si
|
As-cast
|
Ferritic pearlite
|
550
|
380
|
6
|
Crank shaft, gears and rollers
|
|
Martensitic
|
3.5 C,
2.2 Si,
|
Quenched and Tempered
|
Martensitic
|
830
|
620
|
2
|
Pinions, gears, rollers and slides
|