JFE Steel has newly developed two kinds of steel
tubes having excellent fatigue endurance for automotive suspension parts. The
tube employed to torsion beam has an excellent combination of fatigue endurance,
hydro-formability and delayed fracture resistance. These properties can be obtained
by the low C (less than 0.3%) based chemistry and the high precision controlled
rolling and cooling technique in hot rolling. Further developed steel tube for stabilizer exhibits also excellent fatigue endurance induced from
its high r-value (more than 1.5) property. This excellent crystallographic characteristics
can be obtained by the warm reducing in the “HISTORY” process and
contribute to improve the fatigue life by suppressing the wall thickness reduction
during bending applications. Moreover, JFE Steel has been promoting the application
of steel tube to automotive
suspension parts, with not only newly developed steel tubes mentioned above,
but also with the analysis of the formability of high strength tube in rotary
draw bending process and the development of the related new rotary bending method
without both mandrel and wiper.
