| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of Al-free hot dip galvanizing for spheroidal graphite cast iron, capable of preventing the peeling of a galvanizing layer due to graphite at the surface of a cast iron and the abnormal growth of the plating layer due to bubbles and also capable of minimizing the roughness at the surface of a casting and controlling the thickness of the plating layer. SOLUTION: A sheet or powder of pure iron, carbon steel, pure Ti or pure Mn, powder of these, or wood flour is stuck on the surface of a mold to be in contact with a casting, and a molten spheroidal graphite cast iron is poured into the mold to form a surface layer inhibiting the formation of graphite on the surface of a casting. Its sample is dipped for at least 1-3 min in a Zn bath prepared by adding Cr, Ag, Tl or misch metal independently in an additive quantity of 0.1-1.0% to a molten Zn bath. After the plating treatment, galvanizing treatment is immediately performed without cooling. The resultant galvanized sample is inserted, in a state where the prescribed space is held, into a mold where a pure Zn sheet is stuck on the mold surface to be in contact with a casting, and molten Zn is poured into the space between the mold and the sample.
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