| 摘要 |
<p>PROBLEM TO BE SOLVED: To produce a hot dip Al-Zn base alloy coated steel sheet containing 4-5 wt.% Al and having excellent surface appearance. SOLUTION: After annealing the steel sheet at >=750 deg.C annealing temp., the hot dip Al-Zn base alloy coating containing 4-5 wt.% Al is applied. Otherwise, after annealing the steel sheet having <=0.5μm surface roughness Ra and/or washed with alkali, the hot dip Al-Zn base alloy coating containing 4-5 wt.% Al is applied. Uneven growth of coated alloy layer caused by rolling oil residue is prevented, and traverse wrinkle defect peculiar to the hot dip Al-Zn base alloy coated steel sheet containing 4-5 wt.% Al can be prevented.</p> |
