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Ferrous Materials 73
tensile strength, chemical composition. physical and surface conditions. According to this
method a particular grade designation would be applicable to certain steel only. Hence steel
may be designated by a group of symbols indicating the important characteristics.
(i) 1025. Indicates C-25 which is plain carbon steel,
(ii) 1112. It is a free cutting steel having percentage
C = 0.13 Max.
Mn = 0.7 – 1.0 %
P = 0.07 – 0.12 %
S = 0.16 – 0.23%
(iii) 4145. It is Cr-Mo – steel having percentage
C = 0.33 – 0.38%
Mn = 0.7 – 0.9%
P or S = 3.025%
Si = 0.2 – 0.35%
Cr = 0.81 – 1.1 %
Mo = 0.18 – 0.25%
(iv) 8650. It is Ni-Cr-Mo alloy steel having percentages
Ni = 0.4 – 0.7%
Cr = 0.4 – 0.6%
Mo = 0.15 – 0.25%
(v) 3145. It is a Ni-Cr steel having
Ni = 0.3 – 0.35%
Cr = 0.4 – 0.5%
(vi) 2330. It is a Ni-steel having percentages
C = 0.28 – 0.33%
S = 0.04%
Mn = 0.5%
Si = 0.02 – 0.35 %
Ni = 3.25 – 3.75%
(vii) 5150 It is a Cr-Steel
Following symbol recommended to be used to indicate heat treatment given to steel and
is to be suffixed at the end of normal symbol of steel.
(1) Annealed and softened a
(2) Case carburized c
(3) Hard, drawn, cold reduced d
(4) Hot rolled h
(5) Normalized n
(6) Spherodised 0