American ASTM A36 (per ASTM A36/A36M) is the direct substitute for China's GB Q235B H-beam, with fully aligned properties for light structural applications:
Mechanical Properties:
Yield Strength: A36 has a minimum yield strength of 36 ksi (≈248 MPa) for all sections, while Q235B has 235 MPa for ≤16 mm, 225 MPa for 16–40 mm, and 215 MPa for 40–60 mm. The 13 MPa difference for thin sections is negligible for light loads (e.g., residential framing), as design codes use conservative load factors. For example, a W4x13 A36 beam and HN 100x50 Q235B beam have similar bending capacity (A36: ≈7.1 k-ft; Q235B: ≈6.8 k-ft) for a 4-meter span.
Tensile Strength: A36 ranges from 58–79 ksi (≈400–545 MPa), while Q235B ranges from 375–500 MPa-overlapping ranges, ensuring both grades withstand light to moderate loads.
Elongation: A36 requires 20% minimum elongation (over 2 inches), and Q235B requires 26% (over 50 mm)-both sufficient for bending and welding in light construction.
Impact Toughness: A36 is tested at room temperature (20–25°C) with no mandatory energy requirement, but typical values exceed 30 J-matching Q235B's 27 J at 20°C.
Chemical Composition:
Carbon: A36 (max 0.25%) vs. Q235B (max 0.22%)-minor difference, with both levels ensuring weldability.
Manganese: A36 (0.80–1.35%) vs. Q235B (0.30–0.65%)-A36's higher range boosts strength slightly but does not affect workability.
Phosphorus/Sulfur: Both capped at 0.040% (A36) and 0.045% (Q235B)-identical for practical purposes.
ASTM A36 is the most widely used structural steel in America, just as Q235B is in China, making it a seamless substitute for light-load projects like residential buildings, small warehouses, and non-critical industrial supports.