Four low carbon bainite steels were designed to investigate the effects of Mo and Nb addition on bainitic
transformation, microstructures and properties by metallographic method and dilatometry. The results show
that single Nb addition retards bainitic transformation in low carbon bainite steels, although it can improve
strength by refining microstructures. Moreover, (Mo) addition is effective to improve the strength of low carbon
bainite steel by promoting bainitic transformation and single (Mo) addition has a better strengthening effect
than single (Nb) addition. Further, in (Mo) bearing steel, Nb addition refines bainite sheaves, butmeanwhile hinders
bainitic transformation because of smaller austenite grains. Consequently, the composite strengthening effect of
(Mo)and (Nb) addition has little improvement comparedwith individual addition of (Mo) in lowcarbon bainite steels.