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How does pearlite compare with pure iron in hardness?
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steel
Molten steel being poured into a ladle from an electric arc furnace, 1940s.
Pearlite is significantly harder than pure iron. In terms of diamond pyramid hardness (DPH), pearlite measures approximately 200 kilograms-force per square millimetre, whereas pure iron measures only 70 kilograms-force per square millimetre.1
This difference in hardness is due to the microstructure of pearlite, which consists of a fine, lamellar arrangement of alternating platelets of ferrite and cementite (iron carbide). While pure iron is soft and lacks the structural reinforcement provided by these carbides, the addition of carbon creates these harder phases, effectively strengthening the material.1