IACS UR W11

IACS Unified Requirement W11 sets the requirements for normal and higher-strength hull structural steels used in ship construction, the common grade system every IACS society applies. Normal-strength steel comes in grades A, B, D, and E at 235 MPa minimum yield, distinguished by Charpy V-notch impact-test temperature. Higher-strength steel uses the AH/DH/EH/FH series at strength levels 27, 32, 36, and 40 (corresponding to 265, 315, 355, and 390 MPa minimum yield), with the letter again fixing the impact temperature: A at 0 C, D at minus 20 C, E at minus 40 C, F at minus 60 C for polar service. W11 fixes chemistry, deoxidation, and impact-energy values per grade.