Ferritic-Bainitic steel: stretch edge flangeability for cold-forming

Ferritic-Bainitic are multi-phased steels with high hole expansion ratios and good edge stretch capabilities. FB steels are suited for cold-formed and punched flanges when lightweighting automotive components such as wheels, cross members, and other structural parts.

What is the definition of FB steels?

Hot-rolled Ferrite-Bainite (FB) is comprised of very fine sized grains of ferrite and bainite. The ferrite delivers high elongation performance and the bainite contributes to FB’s good edge stretchability. 

Their minimal hardness differences between their phases adds to FB steel’s high hole expansion (HHE) performance and stretch flangeability, both key measures of local formability. Compared to high strength low alloy (HSLA) steels with similar strength levels, ferritic-bainitic steels have increased total elongation as well as a higher strain-hardening exponent (n-value).

Steel properties

  • High local formability — good for cold-forming of edge flanges with punched holes
  • High hole expansion ratios
  • Strong fatigue performance relative to its tensile strength; good for automotive parts subject to vibration
  • Good weldability, including resistance spot welding and arc welding

Chassis applications for ferritic-bainitic steels

With a combination of good fatigue performance and formability, hot-rolled SSAB Docol FB steels can be found in many chassis applications.

  • Suspension parts, including upper and lower control arms
  • Wheels
  • Beams and cross members
  • Chassis

 

Ferrite bainite steel for automotive applications