Introduction to Basic Manufacturing Processes and ... - always yours

Ferrous Materials 61
carbon steel. Carbon steel has its properties mainly due to carbon content and does not
contain more than 0.5% of silicon and 1.5% of manganese.
60
Ultimate Strength
50
40
30
U ltim ate Strength
Brinell H ardn ess
D uctility
300
200
100
Brinell Hardness
20
100
Low
Pearlite %
50
Ferrite
Pearlite %
Cementite
0 0.2 0.4 0.6 0.8 1.0 1.2
Carbon %
Fig. 4.3 Effect of carbon on properties of steel
For checking microstructure of steel, its specimen is prepared by preparing a flat mirror
surface on small piece of metal through rubbing by sand papers, polishing and buffing etc.
This surface is then followed by etching with a chemical solution. The chemical solution
reacts with various constituents in varying degree to reveal crystal structure clearly. The
revealed structure is then viewed through powerful microscope. The viewed micro structures
for different steel are depicted in Fig. 4.4.
Pearlite
Pearlite
Pearlite
Ferrite
Grain
Ferrite
(0.3%C)
Ferrite
(6.6%C)
Pearlite
(0.83%C)
Cementite
(1.0%C)
(a)
(b)
(c)
(d)
(e)
Fig. 4.4 Micro structure of steel
4.3.5.1 Effect of impurities on steel
The effects of impurities like silicon, sulphur, manganese and phosphorus, on steel as
discussed under.
1. Silicon. Silicon content in the finished steel usually ranges from 0.05 to 0.30%. It
is added in low carbon steels for preventing them from becoming porous. It helps
in removing the gases and oxides. It prevents blow holes there by making steel
tougher and harder.