| 摘要 |
An iron-zinc alloy electro-galvanized steel sheet having a plurality of iron-zinc alloy coatings, which comprises: at least one iron-zinc alloy coating as the lower layer, formed on the surface of a steel sheet, and at least two iron-zinc alloy coatings as the upper layer, formed on the at least one iron-zinc alloy coating as the lower layer. The ratio of iron content to the coating weight of each of the at least one iron-zinc alloy coating as the lower layer is within the range of from 1 to 15 wt. %, and the total coating weight of the at least one iron-zinc alloy coating as the lower layer is within the range of from 1 to 50 g/m2 per side of the steel sheet. The ratio of iron content to the coating weight of each of the at least two iron-zinc alloy coatings as the upper layer is over 15 wt. %, the ratio of iron content to the coating weight gradually increases from the innermost coating toward the outermost coating of the at least two iron-zinc alloy coatings as the upper layer, the difference in the ratio or iron content to the coating weight between two adjacent coatings of the at least two iron-zinc alloy coatings as the upper layer is within the range of from 1 to 15 wt. %, and the total coating weight of the at least two iron-zinc alloy coatings as the upper layer is within the range of from 1 to 40 g/m2 per side of the steel sheet. The difference in the ratio of iron content to the coating weight between the uppermost coating of the at least one iron-zinc alloy coating as the lower layer and the lowermost coating of the at least two iron-zinc alloy coatings as the upper layer is within the range of from 1 to 15 wt. %. The sum of the total coating weight of the at least one iron-zinc alloy coating as the lower layer and the total coating weight of the at least two iron-zinc alloy coatings as the upper layer is within the range of from 10 to 75 wt. % per side of the steel sheet. |
