The structure of the spheroidal graphite cast iron part

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PROBLEM TO BE SOLVED : To provide the structure of a spheroidal graphite cast iron part which has strength of 900 to 1, 000 N/mm as-cast, and is suitable, e.g. for automobile parts, machine parts and building parts in which lightening by the increase of strength is made possible. SOLUTION : The spheroidal graphite cast iron part has a composition containing, by mass, 3.20 to 4.00% C, 2.00 to 3.20% Si, 0.30 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 0.300% rare earth elements, and the balance Fe. The spheroidal graphite cast iron part has a metallic structure including a petaloid structure in which the spacing of the layers of pearlite is narrowed, and further, ferrite or ferrite and pearlite are involved in the circumference of graphite.