Influence of cooling rate and tempering on precipitation and hardness of vanadium microalloyed steel

In the present work precipitate distributions in a C–Mn–Al–V–N microalloyed steel and hardness were examined for as-received, heat-treated and heat-treated & tempered samples. Examination of as-received and heat-treated samples from the vanadium microalloyed steels using transmission electron microscopy revealed quite different precipitate distributions. The type and sizes of the precipitate particles and also hardness of the steel samples were markedly affected as the austenitisation time and cooling rates were changed. Tempering steel samples after air cooling produced fine matrix precipitates which are closely spaced, obstruct moving dislocations and hence make the steel harder.