溶融亜鉛めっきのFe-Al金属間化合物生成挙動に及ぼす素材成分の影響

概要

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It is important to clarify fundamentally the formation mechanism of a Fe-Al interfacial layer formed on a steel sheet during hot dip galvanizing to produce galvanized steel sheets with high strength. Effect of Si, Mn, and P in a pure iron sheet on the growth of the Fe-Al layer has been investigated using baths containing 0.15 mass% Al and 0.20 mass% Al. The amount of the Fe-Al layer formed at the interface between a zinc overlayer and a base metal containing Si decreased with increasing in Si content of the base metal both in the low Al added bath and in the high Al added bath. This was explained by the decrease in the reactivity of the base metal due to surface segregation of Si occurred during recrystallization annealing. Mn in a base metal restricted the formation of the Fe-Al layer in the high Al added bath, although Mn content in a base metal did not influence the amount of the Fe-Al layer in the low Al added bath. It was considered that particles of Mn oxide dispersed on the annealed base metal surface did not affect the dissolution of iron in the low Al added bath while they impeded the diffusion of Al through the thick Fe-Al layer in the high Al added bath. The amount of the Al-rich layer formed during galvanizing did not depend on P content in base metal in both baths.