High Strength Hot Rolled Sheet Steels for Automotive Wheel Use

Synopsis: Overall applicability of various types of high strength sheet steels to automotive wheels was investigated by means of conventional production tooling as well as laboratory forming and welding tests. Dual phase sheet steels, especially those of as hot rolled type, showed most hopeful potential in wheel discs forming because of their high workhardenability, good elongation and uniform dispersion of second phase. Special improvements in flash butt welding and roll forming conditions were necessary to make high strength sheet steels usable for the production of wheel rims and HSLA steels which contained Nb revealed comparatively stable quality in joints and HAZ of flash butt welds. Centrifugal cornering fatigue tests suggested that high strength sheet steel of 60 kgf/mm2 tensile strength could be substituted for mild sheet steel in wheels with weight saving as high as 25%. Influences of alloying elements on various properties and performances of sheet steels for wheel were summarized and utility of dual phase sheet steels was also discussed.