Effect of Prior Cold Work on Dual Phase Steel

Abstract

Dual phase steels of varying martensite fraction were produced by quenching of pre-cold worked steel sheets from the intercritical range. Up to 70% reduction of thickness was attempted for studying the effect of prior cold work. Tensile properties were measured and correlated to microstructural parameters. Prior cold work leads to increased fraction of martensite and refinement of martensite island size and ferrite grain size. It is found that hardness and tensile strength are dominated by volume fraction marten-site, with prior cold work exerting some minor influence on tensile strength. Flow stress exhibits two fold dependence on martensite fraction and extent of prior cold work. This points out the significance of martensite strength and microstructural parameters as concerns dual phase flow characteristics. The influence on ductility was also investigated.