The combined effect of boron addition and ausforming on the structure of low carbon low alloyed steel after the transformation of austenite has been investigated in a wide range of cooling rates. It is shown that boron hinders formation of polygonal ferrite in continuous cooling regardless of austenite predeformation and suppresses appearance of acicular ferrite. A qualitative explanation of this effect is proposed in terms of the deformation induced boron segregation on boundaries of austenite grains and subgrains. Practical significance of the obtained results is discussed in application to the thermomechanical treatment of the considered steels.