Metsukisokakoseinosuguretagarubaniirudokohan

摘要

PURPOSE:To obtain a galvannealed steel sheet having a highly workable layer formed by galvannealing by specifying the concn. of iron in an iron-zinc alloy layer to be formed on a steel sheet by galvannealing so that the composition of the iron-zinc alloy has specified phases in order from the surface of the steel sheet to the surface of the alloy layer. CONSTITUTION:When a steel sheet is galvannealed, the concn. of iron in an iron- zinc alloy layer to be formed by galvannealing is adjusted to 15-27wt% so that the composition of the iron-zinc alloy has GAMMA-phase, mixed GAMMA+delta1 phase and delta1- phase in order from the surface of the steel sheet to the surface of the alloy layer. Thus, the workability is improved without deteriorating superior characteristics peculiar to the galvannealed steel sheet.