The invention discloses high-
toughness hot-rolled medium
manganese steel with strength-
ductility balance greater than 60 GPa.% and a preparation method, and belongs to the field of high-
toughness automobile steel. The steel comprises the following chemical components of, in percentage by weight, 0.35-0.40% of C, 6.00 -6.30% of Mn, 2.20-2.35% of Al, 0-0.027% of Nb, 0.030 -0.074% of Si, 0.05% of P,0.02% of S, and the balance Fe and inevitable impurities. The preparation method comprises the steps of
raw material preparation,
smelting,
casting,
forging, hot rolling and two-phase region annealing. According to the high-
toughness hot-rolled medium
manganese steel, strength of extension is 1039-1183 MPa, after-fracture elongation rate is 43.5-64.8%, strength-
ductility balance can reach more than 60 GPa.%, but not greater than 72GPa.%. Through reasonable component proportion and optimized two-phase region annealing process, morphology and proportion of a two-phase structure are controlled, TRIP and
TWIP effects are effectively simulated to reach a high
work hardening rate, the strength and the toughness of the medium
manganese steel are greatly improved, and performance indexes of different components of an automobile are met.