The structure

secondary phase precipitates and mechanical properties of 3 mm plates of 0.0045C-0.07Ti traditional Ti-IF steel contained 0.007P and 0.0052C-0.08Ti high strength Ti-IF steel contained 0.080P

which rolled by 4 pass in ferrite region between 800 ℃ and 680 ℃ from 24 mm plate slab

then annealed at 750℃ for 3 h

have been tested and studied. The results showed that the tensile strength of traditional Ti-IF steel was 270 MPa

the elongation 45% and the plastic strain ratio - r value 1.309

while the tensile strength of high strength Ti-IF steel was 315 MPa

the elongation 44% and the r value 1.098.The stucture of plates of both steels was recrystallized ferrite of which at center was coarser than that near surface

but there were secondary phase precipitates FeTiP in the high strength Ti-IF steel.