IRON-ZINC ALLOY ELECTRO-GALVANIZED STEEL SHEET HAVING A PLURALITY OF IRON-ZINC ALLOY COATINGS

摘要

IRON-ZINC ALLOY ELECTRO-GALVANIZEDSTEEL SHEET HAVING A PLURALITY OFIRON-ZINC ALLOY COATINGSABSTRACT OF THE DISCLOSUREAn iron-zinc alloy electro-galvanized steel sheethaving a plurality of iron-zinc alloy coatings, whichcomprises: at least one iron-zinc alloy coating as thelower layer, formed on the surface of a steel sheet, andat least two iron-zinc alloy coatings as the upper layer,formed on the at least one iron-zinc alloy coating as thelower layer. The ratio of iron content to the coatingweight of each of the at least one iron-zinc alloy coatingas the lower layer is within the range of from 1 to 15 wt.%,and the total coating weight of the at least one iron-zincalloy coating as the lower layer is within the range offrom 1 to 50 g/m2 per side of the steel sheet. The ratioof iron content to the coating weight of each of the atleast two iron-zinc alloy coatings as the upper layer isover 15 wt.%, the ratio of iron content to the coatingweight gradually increases from the innermost coatingtoward the outermost coating of the at least two iron-zincalloy coatings as the upper layer, the difference in theratio or iron content to the coating weight between twoadjacent coatings of the at least two iron-zinc alloy- 1 -coatings as the upper layer is within the range of from 1to 15 wt.%, and the total coating weight of the at leasttwo iron-zinc alloy coatings as the upper layer is withinthe range of from 1 to 40 g/m2 per side of the steel sheet.The difference in the ratio of iron content to the coatingweight between the uppermost coating of the at least oneiron-zinc alloy coating as the lower layer and the lower-most coating of the at least two iron-zinc alloy coatingsas the upper layer is within the range of from 1 to 15 wt.%.The sum of the total coating weight of the at least oneiron-zinc alloy coating as the lower layer and the totalcoating weight of the at least two iron-zinc alloy coatingsas the upper layer is within the range of from 10 to 75 wt.%per side of the steel sheet.- 2 -