Microstructure and properties of rapidly heat treated and galvanized dual phase steel

This study aims at determining the impact of Rapid Heat Treatment on the mechanical properties and galvanisability of a Dual Phase (DP) steel. DP steel coupons were galvanized following three rapid heat treatment routes. For each thermal cycle, microstructural characteristics were related to the mechanical properties while the coating quality and reactive wetting were assessed. It was found that the thermal cycle and microsegregation of Mn in the sheet centerline influenced the mechanical properties of the Dual Phase steel through the volume fraction and distribution of non-ferritic phases, mainly martensite. In addition, the thermal treatments did not affect the reactive wetting of the Dual Phase steel nor the quality of the zinc coating, and this despite the presence of a Mn oxide layer at the steel surface during heating. Indeed, the Mn oxide layer was reduced by the Al dissolved in the zinc bath.