Answer:
Q235B H-beam, a staple product listed as "Q235B Carbon Steel H-Beam for Construction" on Made-in-China.com, follows China's GB/T 11263 standard. Its chemical composition is strictly controlled to balance ductility and basic strength: Carbon (C) 0.12–0.20%, Silicon (Si) 0.17–0.37%, Manganese (Mn) 0.30–0.70%, Phosphorus (P) ≤0.045%, Sulfur (S) ≤0.045%, and trace elements (Cr ≤0.30%, Ni ≤0.30%, Cu ≤0.30%).
Carbon (0.12–0.20%) provides the base strength by forming solid solutions in the iron matrix, while silicon (0.17–0.37%) acts as a deoxidizer to reduce oxide inclusions that weaken structural integrity. Manganese (0.30–0.70%) enhances hardenability and mitigates sulfur-induced brittleness by forming MnS instead of brittle FeS. Strict P/S limits (≤0.045%) prevent cold brittleness (from P segregation) and hot shortness (from S).
Mechanically, this composition delivers a minimum yield strength of 235 MPa, tensile strength of 375–500 MPa, and elongation of ≥26% (for thickness ≤16mm)-ideal for low-load construction like residential frames. Internationally, Q235B is equivalent to ASTM A36 (USA), EN 10025-2 S235JR (EU), and JIS SS400 (Japan), ensuring compatibility in global projects.