Initial grain size effect on mechanical properties and springback behavior of thin metal sheets with varying rolling reduction ratios

Abstract

The aims of this study were to investigate the effect of initial grain size on mechanical properties of thin stainless steel sheet (SUS304) with an initial thickness of 1 mm underwent varying reduction ratios by roll forming and to analyze the effect of grain refinement on springback behavior in micro V-bending process. Specimens were carried out the annealing treatment to obtain different initial grain sizes in a range of 15.1 to 30.2 mm. The annealed specimens were rolled with varying reduction ratios. All specimens were conducted the tensile test for measuring the Young’s modulus, strength coefficient and strain-hardening exponent. The rolled specimens with varying reduction ratio were carried out V-bending with an angle of 90o. Furthermore, the springback behavior was simulated using finite element method and compared the springback amount with that of the experimental result. Consequently, larger initial grain size induced higher ductility but decreased ultimate tensile strength and lower yielding strength. Although grain refinement induced brittle behavior with higher elastic modulus and smaller plasticity, high elastic modulus may contribute the higher springback amount.