Formation of Retained Austenite and Effect of Retained Austenite on Elongation in Low Carbon Hot-Rolled High Strength Steels

Austenite stabilization behavior and effect of retained austenite on elongation of Fe-0.2%C-1.5%Si-1.51.7%Mn hotrolled high strength steels were investigated in the mill-scale test. The results are as follows ;(1)A large amount of retained austenite (maximum_??_15vol%) remained in steels as-hot-rolled.(2)The two metallurgical processes (ferrite transformation and bainite transformation) are important for the austenite stabilization. Especially ferrite transformation plays an important role to obtain retained austenite in 0.2%C steels. The volume fraction of retained austenite is in proportion to VPF/dPF (VPF ; volume fraction of polygonal ferrite, dPF ; grain diameter of polygonal ferrite).(3)TS×T.El value increases with the volume fraction of retained austenite. It is to be noted that the TS×T.El values of 2500030000MPa·% were obtained, which are higher than those of conventional steels.(4)TS×T.El value was improved by increasing of the plastic stability of retained austenite.