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Function of carbon in steel

Short answer

Carbon is the main element controlling steel's properties. Increasing carbon raises strength and hardness (via cementite) but reduces ductility, toughness and weldability, and enables heat treatment hardening.

What is the prime function (importance) of carbon present in steel?

Carbon is the main element that decides the strength and hardness of steel.

  • As the carbon percentage increases (up to about 1%), the strength and hardness increase, as carbon forms hard iron carbide (cementite) with iron.
  • Ductility, malleability, toughness and weldability decrease with more carbon.
  • Carbon makes steel responsive to heat treatment (hardening by quenching).

Typical range is 0.05-1.5% carbon (below 2%); above 2% it becomes cast iron.

✓ Answer checked by Claude Opus 5.5 (high effort)

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