Deformation microstructure and tensile strength of cold rolled pearlitic steel sheets

The deformation microstructure produced by heavy cold rolling (from 70% to 95% reduction) of pearlitic structure with various amounts of rolling and t he tensile strength of the cold rolled sheets were studied in the plain car bon steels with various carbon contents (0.6, 0.76, and 1.0 mass%C). The de formation microstructure was classified into the following three types; 1) irregularly Bent Lameila (IBL): lamellae originally inclined with large ang les to the rolling plane and irregularly bent after deformation, 2) Coarse Lamella with Shear band (CLS) :the rhomboidal blocks of weakly deformed lam ellae bounded by shear band, 3) Fine Lamella (FL): heavily deformed lamella e aligned parallel to the rolling direction with fine interiamellar spacing s. As rolling reduction increases, the proportion of FL increases. The tensile strength of cold relied specimens increases with rolling reduct ion. Work hardening with respect to true strain by cold rolling is similar to that obtained by wire drawing. After 92% cold rolling of 1.0 mass%C stee l, the tensile strength over 2 500 MPa was achieved.