In the present work the textures and the microstructures of some controlled rolled low carbon steels containing Nb and B were correlated to their boron content. This varied from 5 to 21 ppm and had the effect of replacing polygonal ferrite in the lower B-content steels by bainitic ferrite in the higher B-content ones. The grain size decreased from ~3 μm in the former to 1 μm in the latter. The texture became correspondingly stronger as the transformation mechanism changed from diffusional to shear mode. Considering that the rolling schedule and cooling rate (air) were the same for all steels the textural and microstructural changes are attributed to the change in boron content.