Which ASTM grade corresponds to S355K2G2W

If you’re an engineer or buyer used to ASTM standards, staring at an EN 10025-5 grade like S355K2G2W can feel like a puzzle. You just want to know: what’s the American equivalent? The honest answer—and many suppliers won’t say it outright—is that there’s no exact one-to-one match.

Here’s why. S355K2G2W packs three specific traits: 355 MPa minimum yield strength, “K2” impact toughness at -20°C (27J), and “G2W” weathering resistance. ASTM’s closest family is A588 (standard weathering steel). Grades A588 Grade A and Grade B offer similar corrosion resistance and yield strength in the 345–350 MPa range. But their Charpy impact requirements are typically tested at 0°F (-18°C) or lower only when specified as a supplementary requirement. They don’t guarantee -20°C out of the box the way EN’s K2 marking does.

If low-temperature impact is critical for your project, don’t just substitute A588 blindly. Instead, order A588 with added impact testing at -20°C—many mills will accommodate this as a custom order. Another route: look at A709 Grade 50W (used in bridges) which often includes tougher impact options, or A871 for higher strength with atmospheric corrosion resistance.