PURPOSE: To manufacture heat resistant spheroidal graphite cast iron with superior oxidation resistance at a low cost by spheroidizing graphite in molten cast iron having high Si content and contg. small amounts of Cr and Mo.

CONSTITUTION: Graphite in molten cast iron contg. <3.4% C, 3.5W5.5% Si, <0.6% Mn, 0.1W0.7% Cr and 0.3W0.9% Mo is spheroidized with a graphite spheroidizing agent such as Mg, Ca or Ce, and the spheroidizing agent is allowed to remain in the cast iron by ≤0.1%. Because of the high Si content the cast iron has a ferrite-base matrix with enhanced oxidation resistance, Cr and Mo strengthens the ferrite matrix, and Cr enhances the oxidation resistance. As a result, heat resistant spheroidal graphite cast iron with superior oxidation resistance as the housing material of a waste gas turbine is obtd. at a low cost without adding expensive metals such as Ni.