PURPOSE: To prevent bulging on the surface of a molded pig iron by spreading coke powder or graphite powder on the surface of the molten iron before the surface is solidified after pouring the molten iron into a mold at the time of casting the pig iron.

CONSTITUTION: In the process of pouring the molten iron, such as molten cast iron, molten pig iron, low P pig, low S pig, into the mold in a pig iron casting machine and cooling and solidifying, the coke powder or the graphite powder is spread on the surface before the molten iron surface is solidified after pouring the molten iron into the mold. By this method, the surface bulging 1 generated at the time of solidifying the molten iron is prevented.