S355K2G2W Weathering Steel Testing Requirements

Every S355K2G2W plate comes with a mill certificate claiming EN 10025-5 compliance. Here's what tests back that claim—and what you should verify.

Chemical analysis. Every heat is tested for key alloying elements: copper (0.25–0.55%), chromium (0.40–0.80%), nickel (≤0.65%), and phosphorus (≤0.12% for G2W). Without these, you don't have weathering steel. The certificate must show both heat analysis and product analysis.

Tensile testing. Confirms yield strength (≥355 MPa for plates up to 16mm), tensile strength (470–630 MPa), and elongation (≥20%). One test per heat is standard. Results must match EN 10025-5 tables for your thickness.

Impact testing (K2 requirement). Charpy V-notch at -20°C—three specimens from the same plate. Average must be ≥27J, with no single value below 20J. For plates under 10mm, subsize specimens with proportionally lower requirements are used.

Dimensional and surface inspection. Thickness, width, and length to EN 10029 tolerances. Visual inspection for laps, cracks, or excessive scale. Heavy grinding beyond tolerance is cause for rejection.

Supplementary tests (specify when ordering). Ultrasonic testing (EN 10160) for internal defects. Bend testing for formed parts. Additional impact samples for critical applications.

What to verify on your certificate:

Impact temperature: -20°C (not 0°C)

Copper and chromium present and within spec

Yield matches thickness-dependent table

Heat number consistent across all pages

Common oversight. Assuming standard tests include UT or extra impact samples. They don't. Order supplementary tests separately.