Cast irons: element added to produce nodular (spheroidal graphite) iron Identify the element intentionally added to molten cast iron to produce nodular/spheroidal graphite (SG iron). Choose the correct element.

ConceptNodular (spheroidal graphite) cast iron is produced by magnesium treatment (sometimes rare earths like cerium are also used). Mg modifies graphite morphology from flakes to spheroids, improving ductility and toughness.

Why not othersNi, Cr, and Cu are alloying elements for strength/corrosion/wear but do not cause graphite nodularisation.

Final AnswerMagnesium