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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.

Difficulty: Easy

Nickel
Chromium
Copper
Magnesium

Correct Answer: Magnesium

Explanation:

Concept
Nodular (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 others
Ni, Cr, and Cu are alloying elements for strength/corrosion/wear but do not cause graphite nodularisation.

Final Answer
Magnesium

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