What GB angle material is equivalent to the weathering steel ASTM A588?

The GB equivalent to the weathering steel ASTM A588 is the Q355NH series (e.g., Q355GNH), as per GB/T 4171. These are high-strength, low-alloy structural steels with improved atmospheric corrosion resistance. Both A588 and Q355NH develop a protective, adherent rust patina that retards further corrosion, allowing for use in unpainted structures. Their mechanical properties are closely matched, with a minimum yield strength of 50 ksi (345 MPa). Chemically, both achieve weathering resistance through the addition of alloying elements like Copper, Chromium, Nickel, and Silicon. The specific ranges differ; for example, A588 requires a specific minimum of Chromium and Copper, while Q355NH specifies a Phosphorus-Copper or Phosphorus-Chromium-Copper system. The long-term corrosion performance is validated through different tests, but they are considered functional equivalents. For international projects specifying A588, Q355NH can be a suitable alternative, provided the chemical analysis confirms the presence of key weathering elements.