アルミニウム被覆鋼の合金層の組成および成因について

抄録

The composition and the structure of the alloy layer formed on steel, which was hot-dipped in molten aluminum and Al-3.3%Si alloy, were determined by some metallurgical methods including metallography, micro-hardness test, etching pits, X-ray diffraction and electron probe X-ray micro-analysis. The change in the thickness of alloy layer against immersion time at 700°∼850°C was also measured. The results obtained were as follows: (1) In the pure aluminum coating the alloy layer was composed of FeAl₃ and Fe₂Al₅ but in the Al-3.3%Si alloy coating it was sheer FeAl₃. (2) The FeAl₃ layer was constituted of fine grains and the Fe₂Al₅ layer of relatively large columnar ones almost perpendicular to the steel surface. (3) The thin layer in the Al-Si coating is due to the accelerated diffusion of iron into the molten Al-Si alloy. (4) The mechanism of the formation of the alloy layer was also discussed.