Effects of Galvannealing Parameter on Structure and Powdering Resistance of Hot Galvannealed Coating on Surface of Bake-Hardening Steel

Hot galvannealing coating on surface of H220BD bake-hardening steel was prepared at different galvannealing temperatures for different times. The morphology, chemical composition and powdering resistance of the coating were studied. The results show that with the increase of galvannealing temperature or the extension of galvannealing time, the zinc and iron in the coating and steel substrate diffused fully, the iron-zinc alloy phase was formed and extended to the surface of the coating with the shape from strip columnar to fine granular, and the average iron content and powdering mass of the coating increased. When the galvannealing temperature was 480℃ and the galvannealing time was 25 s, the performance of the coating was relatively good; the iron-zinc alloy phase was in a finer-grained shape and the powdering mass of the coating was relatively small.