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Short note: properties of steel

Short answer

Steel is an iron–carbon alloy (≤1.5% C) with high tensile and compressive strength. Mild steel yields ~250 N/mm²; HYSD bars 415–500 N/mm². It is ductile, weldable at low carbon, elastic modulus ~2×10⁵ N/mm², density ~7850 kg/m³, and rusts unless protected.

Write a short note on properties of steel.

Steel is an alloy of iron and carbon (up to about 1.5% C) that is the most important structural material in construction. Its properties depend on the carbon content and heat treatment.

  • Strength: High strength in both tension and compression. Mild steel has yield strength about 250 N/mm²; HYSD (Fe 415/500) bars have 415–500 N/mm².
  • Ductility: Mild steel stretches a lot before failure, giving warning. Ductility falls as carbon increases.
  • Malleability and toughness: It can be rolled, forged and bent into shapes, and absorbs energy well.
  • Hardness: Increases with carbon content and by quenching.
  • Elasticity: Modulus of elasticity about 2×1052 \times 10^5 N/mm², nearly constant for all grades.
  • Weldability: Good in low-carbon steel; poor when carbon exceeds about 0.3%.
  • Density: About 7850 kg/m³.
  • Fatigue resistance and homogeneity: Uniform material with predictable behaviour.
  • Thermal and electrical conductivity: Good conductor; loses strength above about 400–500 °C.
  • Corrosion: Rusts in moist air unless protected by paint, galvanising or alloying.
  • Magnetic: Ordinary steel is magnetic (stainless austenitic grades are not).
  • Recyclable.

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