Ferritic-Bainitic (FB) Steel

FB steels sometimes are utilized to meet specific customer application requirements defining Stretch Flangeable (SF) or High Hole Expansion (HHE) capabilities for improved edge stretch capability.

FB steels have a microstructure of fine ferrite and bainite. Strengthening is obtained by both grain refinement and second phase hardening with bainite. FB steels are available as hot-rolled products.

The primary advantage of FB steels over HSLA and DP steels is the improved stretchability of sheared edges as measured by the hole expansion test (λ). Compared to HSLA steels with the same level of strength, FB steels also have a higher strain hardening exponent (n) and increased total elongation.

Because of their good weldability, FB steels are considered for tailored blank applications. These steels also are characterized by both good crash performances and good fatigue properties.