Influence of grain refining annealing on the low carbon steel formability limits

摘要

Sheet metal forming processes are generally limited by plastic instability phenomena and flow localizaiton.Therefore the extensive needs by industries enquire to improve parts quality and to decrease waste parts.In the present work.the effect of grain refining annealing of low carbon steel sheets on formability limits is investigated in both theoretical and experimental aspects.To fine hte grain size,the specimens are heated for 15 sec.in the salt bath furnace at 950 deg C,and then are rapidly quenched in water.Experimental results show that,larger limit strains can be achieved by fine grain size without failure.In the theoritical study,Hill's theory of orthotropic anisotropy in plane stress state and work hardening material are used to predict the instability strains.Finally,using the experimental results,the validity of the theoretical result are evaluated.