Forming Characteristics of Very Low Carbon High Strength Dual Phase Steels Produced through a Flex Mill Continuous Galvanizing Line 2022-01-0239

A very low carbon (<0.06 wt%), lean alloyed chemistry approach is utilized for the development of high strength dual phase (DP) steels with enhanced global and local formability though EAF-LMF-CSP route. Optimized process conditions including clean steel practices, choice of suitable casting powder, hot rolling and continuous anneal set points resulted in excellent mechanical properties and formability characteristics of the subject DP steel. The enhanced balance of strength and formability (hole expansion ratio values of 26-35% for thicknesses of 0.80-1.40mm) is attributed to the optimization of the microstructure through refinement, homogeneity, isotropy and balancing of microconstituent mechanical response. In this contribution, production strategy and formability characterization of DP steels with tensile strengths of 780 MPa and above relevant to automotive body structure applications are discussed. The steel was also subjected to global round-robin material evaluation program and results indicated the current steel to be at par with other global producers (included integrated as well as mini-CSP mills).