1. Chemical Composition
Q450NQR1: Higher Cu (0.20–0.50%), wider Cr (0.30–1.25%) range, and controlled high P (0.07–0.15%); optional Ni for toughness.
A588 Grade B: Lower Cu (0.20–0.30%), narrower Cr (0.40–0.65%) range, and low P (≤0.035%); no Ni requirement.
2. Corrosion Resistance
Q450NQR1: Denser patina, resists harsh environments (industrial SO₂, coastal humidity, freeze-thaw cycles) better.
A588 Grade B: Suitable for mild conditions (low-pollution cities, inland areas); weaker in extreme corrosion.
3. Low-Temperature Toughness
Q450NQR1: Withstands -40°C (impact test ≥34 J), fit for cold regions.
A588 Grade B: Only resists -10°C (impact test ≥27 J), limited to temperate areas.
4. Weldability & Application Focus
Q450NQR1: Welding needs low-hydrogen electrodes/preheating; used for heavy-duty gear (railway freight cars, machinery buckets).
A588 Grade B: Easy to weld (no extra prep); for general structures (building exteriors, small bridges, sculptures).
