EFFECT OF PHOSPHATE AMOUNT AND δ1/ζ PHASE RATIO ON FORMABILITY OF GA SHEETS FOR AUTOMOTIVE OUTER PANELS

摘要

The effect of phosphate amount and galvannealing degree on the formability behavior has been studied for side outer part of automotive applications. We prepared 6 kinds of GA specimens from automotive company which we supplied before. Phosphate adhesion amount according to the surface morphology of GA steel sheet was dependent on friction coefficient of GA surface. XRF/SEM and friction measurement were conducted to clarify the effect of surface friction coefficient. It is observed that suitable and continuous phosphate treatment according to the homogeneous morphology contributed to improve press formability of the GA steel sheets. Mechanism of improving formability will be discussed.