| The effect of
microstructure on toughness is linked to the effect
of composition since generally the composition alters the
microstructure, however, there are some compositional changes that
have only minor effects on the microstructure and yet affect
toughness, these are dealt with separately under compositional
effects.
For example increasing the amount of pearlite in a ferritic steel
will change the strength and toughness of the material.
 Select
a carbon level from the drop-down list to see how changing
the amount of pearlite affects the ductile-brittle transition
(DBTT) curve of a ferrite-pearlite steel.
This effect, along with other compositional changes, can be related
to the DBTT by the equation below for ferrite and pearlite steels:
- DBTT = -19 + 44 (%Si) + 700 (%Nf1/2) + 2.2
(%pearlite) - 11.5 (d-1/2)
where d is the grain
size in mm and Nf is the free nitrogen content in the
steel.
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