Steel plate (ASTM A131)

ASTM A131/A131M is the American specification for structural steel plate, shapes, and bars for ships, the US-market counterpart to IACS UR W11. It defines ordinary-strength grades A, B, D, and E (235 MPa yield) and higher-strength grades AH, DH, EH, and FH at the 32, 36, and 40 levels (315, 355, and 390 MPa yield), with the letter setting the Charpy impact temperature from 0 C down to minus 60 C. Grade A is the baseline hull plate; the H grades carry the higher yield for reduced scantlings. Classification societies recognize A131 plate as equivalent to their own grade marks for hull construction.