S355K2G1W Yield Strength Explained

S355K2G1W has a minimum yield strength of 355 MPa for thicknesses up to 16mm. That's the baseline. Go thinner—say, a 5mm plate—and you still get at least 355 MPa. Go thicker, and the number steps down.

Yield strength by thickness (per EN 10025-5):

Up to 16mm: ≥355 MPa

16–40mm: ≥345 MPa

40–63mm: ≥335 MPa

63–80mm: ≥325 MPa

80–100mm: ≥315 MPa

100–150mm: ≥295 MPa

Why the drop? Thicker plates cool more slowly during manufacturing, forming larger grains. Larger grains mean slightly lower strength. That's normal. Design engineers account for this when specifying plate thickness for heavily loaded members.

What "minimum yield strength" means in practice. It's not a target—it's a floor. Actual test values usually run higher, often 370–420 MPa for thinner plates. But you never design assuming that extra margin. You design to the minimum. The steel will almost always outperform the spec, but the spec is your safety guarantee.

How it's measured. Standard tensile test using a specimen cut from the plate, tested at room temperature. The mill certificate will show the actual value for each heat. Look for the "ReH" or "upper yield strength" column.

Why yield strength matters for weathering steel. Unlike plain carbon steel, S355K2G1W carries both load and corrosion resistance. A higher yield strength means you can use thinner plates for the same structural capacity. Thinner plates weigh less, cost less, and still form that protective patina over time.

One caution. Don't confuse yield strength with impact toughness. The "K2" in the grade guarantees 27J at -20°C—that's a different property. A steel can have great yield strength but still turn brittle in the cold. S355K2G1W delivers both.