Steels_ Metallurgy and Applications, Third Edition

146 Steels:MetaUurgyandApplications

Each of these equations illustrates very clearly the beneficial effects of a fine
ferdte grain size in increasing the yield and tensile strength and depressing the
impact transition temperature. It is also interesting to note that the pearlite content
has no significant effect on the yield strength of these low-carbon, predominantly
ferdtic steels. On the other hand, pearlite increases the tensile strength and has
a detrimental effect on toughness. The solid solution strengthening effects of
manganese, silicon and free nitrogen are also highlighted in the above equations
and it will be noted that free nitrogen is particularly detrimental to the impact
properties.

a.

or)

500

400

300

200

100

0.5 1.0 1.5

Manganese (%)

Figure 2.6 The effect of increasing manganese content on the components of the yield
stress of steels containing 0.2% carbon, 0.2% silicon, 0.15% vanadium and 0.15% nitrogen,
normalized from 900 ~ C (After Gladman et al. 6)