The change of structure and mechanical properties of Nb-Ti microalloying IF steel （/%: 0.006C

0. 005Si

0. 15Mn

0. 008P

0. 006S

0. 039Al

0. 01Nb

0. 048Ti

0.003 4N） during cold rolling process from 3. 98 mm hot rolled plate cold rolling to 0. 4 mm sheet （ deformation 40% to 90% ） by a four cold-rolling mill in laboratory has been tested and studied. Results show that with increasing cold-rolling reduction ratio the grains of Nb-Ti microalloying IF steel gradually decrease and flat

and the secondary phase particles are more arranged to orientate rolling direction

and the hardness

yield and tensile strength of steel increase while the elongation of steel decreases. With deformation 75% and 77% the yield strength-tensile strength ratio is lowest

and the comprehensive mechanical properties of steel could be gotten.