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How much carbon can steel contain before it is classified as cast iron?
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steel
Molten steel being poured into a ladle from an electric arc furnace, 1940s.
Steel is generally classified as an alloy of iron containing less than 2 percent carbon.12
Once the carbon content exceeds this 2 percent threshold, the material is typically classified as cast iron, which generally contains between 2 and 4 percent carbon. Because of this higher carbon content, cast iron is processed at significantly lower temperatures than steel.12