I-beam steel's performance is defined by:
Mechanical Properties:
Yield Strength: Ranges from 235 MPa (Q235, China) to 450 MPa (ASTM A572 Grade 65, US). European S355 (355 MPa) suits industrial frames.
Tensile Strength: 1.2–1.5× yield strength (e.g., Q345 has ≥510 MPa), ensuring fracture resistance.
Elongation: ≥15% for structural grades (e.g., ASTM A36), critical for seismic zones (Japanese I-beams have ≥20% elongation).
Physical Properties:
Density: ~7,850 kg/m³, similar to carbon steel.
Thermal Expansion: 12 × 10⁻⁶/°C, requiring expansion joints in long spans (e.g., bridges over 50m).
Corrosion Rate: Uncoated I-beams corrode at 0.1 mm/year in cities; galvanized I-beams reduce this to 0.01 mm/year.