Can I use S355 structural plate for a pressure vessel instead of SA516 Grade 70?

The two grades look similar on a datasheet — both land around 485 to 620 MPa tensile — but they are written for different purposes and are not interchangeable where a code applies.

SA516 Grade 70 is a carbon steel plate for moderate and lower temperature pressure vessel service. It is supplied to fine grain practice, with tight limits on carbon, sulphur and phosphorus, normalised where thickness or impact requirements demand it, and with Charpy testing at the specified design temperature. It is listed in ASME Section II Part A, which is what allows a vessel designed to Section VIII Division 1 to use it.

S355J2+N is a structural steel to EN 10025-2 with a J2 impact grade (27 J at -20 C), normalised. It is the right material for structural steelwork, skids, pipe racks, base frames and heavy fabrication. Its European pressure equipment counterpart is P355NH / P355NL1 to EN 10028-3, not S355.

Using structural plate on a pressure boundary will fail third-party inspection and voids the PED or ASME stamp, regardless of how the test figures look.

Axicor stocks both, plus SA516 Grade 60, S355J2W+N weathering plate, and the Cr-Mo pressure vessel grades (SA387) for elevated temperature and hydrogen service.