PURPOSE: To obtain cast iron having high strength and superior heat crack resistance by regulating the amts. of C, Si, Mn, Mg, Sb, Sn, etc., in the compsn. of cast iron, the area percentage of pearlite in the matrix and the rate of spheroidizing of graphite.

CONSTITUTION: Cast iron having a compsn. consisting of, by weight, 3.2W4.2% C, 2.0W3.4% Si, 0.2W0.8% Mn, 0.005W0.03% Mg, 0.02W0.05% Sb, 0.02W0.07% Sn, ≤0.1% P, ≤0.03% S and the balance Fe, contg. ≥60% by area of pearlite in the matrix and having 30W60% rate of spheroidizing of graphite is produced. In the compsn., 0.5W0.9% Cu may be substd. for Sb. The cast iron has high strength and superior heat crack resistance and can be utilized especially for a clutch pressure plate.