| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a hot-dip galvanized steel sheet of stable quality free from an unplated spot, which does not need to construct a huge facility as in a conventional pre-plating process, but effectively prevents the formation of an oxide film of an easily oxidizable metal such as Si existing on the outermost surface of a steel sheet with a practical and comparatively easy method, and to provide a facility therefor. SOLUTION: In a process for manufacturing the hot-dip galvanized steel sheet by the steps of heating and annealing a steel sheet, and immersing the steel sheet in a hot-dip galvanizing bath to galvanize the surface of the steel sheet, the method for manufacturing the hot-dip galvanized steel sheet comprises the steps of: heating the steel sheet first in an anti-oxidation heating furnace in such a condition that an air-fuel ratio r1 satisfies 0.9≤r1<1.00, that an attainment sheet temperature (t)(°C) satisfies t≥450, and that the air-fuel ratio r1 and the attainment sheet temperature (t)(°C) satisfy t≤-1,000×r1+750; subsequently heating the steel sheet in an oxidation furnace in such a condition that an air-fuel ratio r2 satisfies r2≥1.00; and further reduction-annealing the steel sheet in a reduction furnace. COPYRIGHT: (C)2007,JPO&INPIT
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