HOT-DIP ALUMINIZED STEEL SHEET EXCELLENT IN CORROSION RESISTANCE AND PRODUCTION THEREOF

摘要

PROBLEM TO BE SOLVED: To prevent the unevenness of corrosion resistance among products of a hot-dip aluminized steel sheet and to improve the stability of quality. ;SOLUTION: This coated steel sheet has 6-12 wt.% Si content and the size S of an Al-rice phase in the coated layer having metallurgical structure in which an Si-rich phase is dispersed in the Al-rich base phase is ≤25 μm and the surface roughness Rmax on the coated layer after skin-pass with a dull roll is adjusted to ≤15 μm. In a continuous hot-dip aluminized coating line, the steel sheet is introduced into an Al-Si alloy-coating bath having 6-10 wt.% Si and the rapid cooling at ≥10°C/sec cooling speed on the coating bath is applied, and in a temper-rolling with a skin-pass mill, this aluminized steel sheet is produced through a process, in which the surface roughness of the coated layer is regulated to ≤15 μm Rmax. As the effect of the metallurgical structure of the coated layer and the adjustment of the surface roughness, the unevenness of the corrosion resistance among the products is eliminated and the stable quality and can be secured.;COPYRIGHT: (C)2000,JPO