PURPOSE: To uniformize the formation of an alloy layer and to stably obtain a plated steel sheet by previously removing impurities from the surface layer part of a steel sheet at the time of producing the plated steel sheet by using a sheet of a high tensile steel with a specific composition.
CONSTITUTION: A starting sheet for plating having a composition consisting of 0.002-0.2% C, 0.1-1.4% Mn, and the balance Fe is used. In the high tensile steel containing larger amounts of elements other than iron as compared with common steel as mentioned above, finish rolling temp. is high and an oxide film formed on the surface is thick, and further, the elements other than iron are concentrated in the surface layer part of the steel sheet. Accordingly, the sufficient removal of the oxide film cannot be attained even by means of pickling treatment and the sufficient reduction of the oxide film cannot be attained even by means of treatment prior to plating, and further, the removal of the concentrated layer of the elements other than iron cannot be performed at all, and as a result, a uniform Fe-Zn alloy plated layer cannot be obtained. Therefore, the oxide film formed on the surface of the starting sheet for plating and the above concentrated layer are removed by means, e.g. of spraying an aqueous alkaline solution containing abrasive grains of the prescribed size, and then, this steel sheet is subjected to hot dip galvanizing and to heating to undergo alloying.
SUHARA MICHINORI
YAMADA MASATO
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