PRODUCING SPHEROIDAL GRAPHITE CAST IRON BY SUSPENSION OF GAS BUBBLES IN MELTS.

Abstract

Trials were carried out to produce spheroidal graphite cast iron by suspension of bubbles of gases such as H//2, N//2, CO//2, and Ar inside the molten cast irons. A commercial and a synthetic iron were used. Three methods were employed to suspend gas bubbles in the irons; viz, additions of Ce, La, Y, Ti, and Zr which contained large amounts of H//2, Precipitation of N//2 bubbles from supersaturated molten cast iron, and direct injection of gas bubbles into the molten cast iron through extra fine porous plugs. All three methods produced graphite nodules. Gas cavities and hollow graphite nodules were observed which seem to be the result of incomplete filling up of gas bubbles with graphite. Graphite nodules have a polycrystalline structure with the c-axis of all crystallites pointing in a radial direction. Some features of graphite nodules are explained, based on the gas bubble theory established in this work.