It is well known that refining the grain size of metals should lead to an i
mprovement in the mechanical properties both of strength and of toughness.
Therefore, a method has to be improved for the formation of very fine ferri
te grains during hot rolling. By means of hot compression tests using an IF
-type steel and a HSLA steel the effect of chemical composition, deformatio
n temperature, strain and strain rate on the resulting ferrite grain size h
as been investigated. By optimising the different process parameters during
hot deformation, a ferrite grain of ASTM 15 can be produced. By means of t
he Hall-Petch relationship an estimation of the influence of ferrite grain
refinement on the mechanical properties can be given.