Decreasing the grain size increases the toughness
of a steel, i.e. decreases the ductile-brittle transition
temperature (DBTT), as can be seen in the diagram below for
In fact decreasing the grain size is the only
mechanism by which both the strength and the toughness of a steel is
increased. Other mechanisms of increasing strength lead to a decrease
To control the ferrite grain size two different
approaches can be used (separately or in combination)
rolling schedules, for example thermo-mechanical
alloying element additions.
Click on the above factors to find out more
about how they are used to control ferrite grain size.