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

Abstract

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 V_PF/d_PF (V_PF ; volume fraction of polygonal ferrite, d_PF ; 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.