GALVANNEALED LAYER AND STEEL SHEET COMPRISING THE SAME, AND METHOD FOR PRODUCING THE SAME

摘要

Provided are: a galvannealed steel sheet, reliably and sufficiently improved in the adhesiveness of a plated layer with a base steel sheet, as a galvannealed steel sheet, prepared by using a high-strength steel sheet as a base material; and a method for producing the galvannealed steel sheet. The galvannealed steel sheet wherein a galvannealed layer is formed on a base steel sheet including a high-strength steel having predetermined component composition; the average amount of Fe in the galvannealed layer is in a range of 8.0 to 12.0%; and the absolute value .DELTA.Fe of a difference between the amount of Fe in the vicinity of an interface with the base steel sheet (the amount of Fe in the vicinity of an internal side) and the amount of Fe in the vicinity of the external surface of the plated layer (the amount of Fe in the vicinity of an external side) in the plated layer is in a range of 0.0 to 3.0%. Further, in a method for producing the galvannealed steel sheet, intra-plated-layer diffusion treatment for flattening the concentration gradient of Fe in the plated layer is performed after finishing hot dip galvanizing and alloying treatment.