| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method for a graphite cast iron product which has strength of 900 to 1,000 N/mm<2> as-cast, and is suitable, e.g. for automobile parts, machine parts and building parts in which lightening in weight is made possible by increasing the strength. SOLUTION: The composition of molten metal is controlled to the one containing, by mass, 3.20 to 4.00% C, 2.00 to 3.20% Si, 0.3005 to 2.50% Mn, <=0.035% P, <=0.12% S, 0.30 to 3.50% Cu, 0.02 to 0.08% Mg and 0.005 to 0.30% rare earth elements, and the balance Fe. On casting, the cooling of the molten metal is accelerated by any of an inmold process, chill blocks, gas absorption from a mold the pouring of cooling gas into a mold or their combination, so that the cast iron product having a metallic structure including a petaloid structure in which ferrite or ferrite and pearlite are involved in the circumference of graphite is produced.
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