| 摘要 |
PURPOSE:To obtain a hot dip galvanized steel sheet having an alloyed face with superior weldability and paintability one one side and an unalloyed face with superior adhesion and corrosion resistance on the other side by hot dip galvanizing one side of a steel sheet with a low-Al molten Zn bath and the other side with a high-Al molten Zn bath and by heat treating the hot dip galvanized steel sheet. CONSTITUTION:One side of a steel strip 2 is hot dip galvanized with molten Zn contg. 0.02-0.30% Al fed from a high-Al bath 3 to a pan 4 by means of a pickup roll 6 and a coating roll 7. The other side of the steel strip 2 is similarly hot dip galvanized with molten Zn contg. 0.05-0.10% Al fed from a low-Al bath 5. The hot dip galvanized steel strip 2 is heat treated at 500-600 deg.C in an allying furnace 8 to alloy only the side hot dip galvanized with molten Zn from the low-Al bath 5 by utilizing the difference in alloying rate caused by the different concns. of Al.
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