What is Q355NH chemical composition

Q355NH Chemical Composition

Q355NH is a Chinese standard (GB/T 4171-2017) atmospheric corrosion-resistant structural steel, part of the Q series weathering steels. It offers enhanced resistance to atmospheric corrosion through alloying elements like copper, chromium, and phosphorus, forming a stable rust patina. It's commonly used in bridges, vehicles, and buildings, equivalent to grades like ASTM A588 or EN S355J2WP.

The chemical composition is specified as maximum values (unless noted as a range) based on ladle analysis. Values can vary slightly by producer, but must meet the standard for certification.

Additional Notes

• Total Alloying: The sum of Cr + Ni + Cu must be ≥ 0.50% to guarantee corrosion performance (4–6 times better than plain carbon steel in rural/moderate environments).
• Product Analysis Tolerances: Allow ±0.02% for C, Mn; ±0.03% for P, S; etc., per GB/T 4171.
• Mechanical Properties (for reference): Yield strength ≥ 355 MPa, tensile ≥ 470 MPa, elongation ≥ 20%, suitable for thicknesses up to 100 mm.
• Variations: Q355GNH is a variant for hot-rolled coils with similar composition but adjusted for formability.

For exact mill certificates or comparisons (e.g., to A588 Grade B), consult GB/T 4171 or suppliers like Baosteel. If you need mechanical props, equivalents, or a PDF spec sheet analysis, let me know!