Effect of cementite morphology in a warm-rolled low-carbon steel on its microstructure and properties after finish rolling

Different morphology of cementite distribution in a low-carbon steel was obtained by different warm-rolling processes in dual phase region of ferrite and pearlite. Microstructure with ferrite grain size of 200-500 nm was observed in the warm-rolled steel after finish rolling at relative lower temperature in austenite region. Microstructure and mechanical properties of the steel were examined by means of SEM, TEM and tensile test. The results show that both of samples have high tensile strength (>1000 MPa), lower yield ration and total elongation ≥20%. TEM results indicate that equiaxial ferrite grains and certain amount of lath and/or twin martensite are prone to be obtained in the sample with disperse cementite after finish rolling, while the proportion of equiaxial ferrite grains in the sample with concentrated cementite decreases significantly, and the dislocation density in ferrite grains is also less than that in the former.