ASTM A131 is a specification that covers structural steel plates, shapes, and bars intended primarily for shipbuilding. The steel plate specified under ASTM A131 is commonly used in the construction of offshore structures, including oil platforms and marine vessels.

The most common grades specified in ASTM A131 are:

1. Grade A: Has a yield strength of 34,000 psi (235 MPa) and is available in thicknesses up to 4 inches (100 mm).
   
   
2. Grade B: Has a yield strength of 34,000 psi (235 MPa) and is available in thicknesses up to 4 inches (100 mm).
   
   
3. Grade D: Has a yield strength of 46,000 psi (315 MPa) and is available in thicknesses up to 4 inches (100 mm).
   
   
4. Grade E: Has a yield strength of 57,000 psi (390 MPa) and is available in thicknesses up to 4 inches (100 mm).

ASTM A131 steel plates are typically produced through normalizing or controlled rolling processes to ensure proper mechanical properties and dimensional accuracy.