Study on the trip-assisted Si-Mn steel with excellent comprehensive performance obtained through direct strip casting

Two near final shape continuous casting process (direct strip casting (DSC) and compact strip production (CSP)) combined quenching & partitioning (Q&P) heat treatment routes were applied to a low carbon Si–Mn steel to create different initial microstructure before heat treatment and finally obtain a new combination of mechanical properties. The initial structure of the DSC sample is a composite structure of lath martensite and bainite. Compared with the pearlite and ferrite initial structure of CSP sample, the DSC as-cast sample shows higher comprehensive mechanical properties. After the same Q&P treatment, the DSC samples generally showed better comprehensive mechanical properties compared to the CSP samples. An optimum comprehensive mechanical property was achieved in DSC-Pt300 samples with yield strength (YS) ~ 1282 MPa, ultimate tensile strength (UTS) ~ 1501 MPa, total elongation (TE) ~ 21.5% and the production of strength and elongation (PSE) higher to 32.3 GPa%. The enhanced mechanical properties were discussed based on the distribution characteristics of each phase in the matrix, the volume fraction and carbon content of retained austenite (RA). This work has achieved the goal of obtaining excellent mechanical properties in the low-alloy trip-assisted Si-Mn steel through a simple process, demonstrating the superiority of DSC technology in manufacturing AHSSs, which has important guiding significance for the short process production of AHSSs.