The invention discloses a
bismuth-containing inoculating agent for
cast iron and a preparation method of the inoculating agent. The inoculating agent comprises, by weight percentage, 60-70% of
silicon, 1-5% of
bismuth, 1-3% of
calcium, 1-5% of aluminum, 2-7% of a mixed
rare earth metal element, and 20-30% of iron. The
bismuth-containing inoculating agent for the
cast iron can be applied to variousgray iron
casting production processes; by adding in the bismuth element,
iron phosphide eutectic is decreased and decomposed, the reverse chill effect of a
casting is inhibited, the fracture surfacesensitivity of the
casting after inoculating is lowered, the
graphite form is changed, the rate of spheroidization is increased, and the ferrite content in a casting matrix structure is remarkably increased; by adding in the
rare earth metal element, the effects of evolving molten iron, increasing the
supercooling degree, and promoting
pearlite forming and refining crystalline grains are achieved; and by controlling the content of aluminum and
calcium, aluminum and
calcium oxide in the molten iron is within a reasonable content range, inoculating interference of the aluminum and calcium oxideon other elements is prevented, and the mechanical performance and the easy-to-
machine performance of the casting are effectively improved.