NODULAR cast iron, so called because the graphite is present as finely dispersed, well-rounded particles, is made in two stages:
The first stage consists of the addition of magnesium or other carbide formers, which promote the formation of white iron in one normally solidifying gray. In the second stage a ferrosilicon type of inoculant overcomes the tendency toward white iron and causes the graphite to precipitate out in the form of small spherulites.
The methods of making nodular iron, the effect of composition on physical properties, economic factors involved, and potential applications are discussed in this paper.