S355K2G2W Weathering Steel -20 Degrees Celsius Impact Test

The "K2" in S355K2G2W isn't decoration. It's a tested promise: at -20°C, this steel absorbs at least 27 Joules of impact energy without fracturing.

Why -20°C matters. Ordinary steel can turn brittle in freezing weather. A sudden load—a vehicle strike, a railcar jerk, a dropped tool—can cause cracks instead of dents. The K2 rating ensures S355K2G2W bends and absorbs energy even when the thermometer drops.

What the test shows. Three Charpy V-notch specimens from the same plate are struck at -20°C. The average must be ≥27J. No single value below 20J. Actual results for S355K2G2W typically range 40–60J—well above the minimum.

Specimen size matters. For plates under 10mm, subsize specimens use proportionally lower requirements. A 7.5mm specimen needs roughly 22J average. Always check the certificate for specimen size.

Why G2W handles cold well. The nickel content (≤0.65%) improves toughness at low temperatures. Combined with controlled grain structure, the steel resists brittle fracture even in harsh winter conditions.

What to verify. Certificate must show -20°C test temperature, three individual values, and specimen size. Don't accept averages alone.

Practical tip. For welded joints in cold service, qualify your weld procedure with impact testing at -20°C. The heat-affected zone may behave differently than the base metal.