Abstract
With a view to analyzing how to suppress mottling in white cast iron, the effect of both the amount and method of bismuth addition to molten iron on graphite formation during solidification of synthetic cast iron was investigated. By directly adding bismuth to molten iron the form of graphite changes from normal flake graphite to a highly branched type. If bismuth addition is sufficient a white iron structure can be obtained. In W-type molten metal joining test material, bismuth transported from a melt with a high bismuth content accelerate the precipitation of finer graphite. It became clear in Shear Cell Joining test piece that bismuth diffusing from pure bismuth melt causes precipitation of fine graphite during solidification of cast iron. Consequently, more than critical amount of bismuth to change the graphite morphology is required to prevent the nucleation and growth of graphite in cast iron.
