Material number 1.0565: P355NH
1.0565 is the European material number (Werkstoffnummer, EN 10027-2) for P355NH, weldable fine-grain normalized steel for pressure purposes, elevated temperature specified in EN 10028-3.
What 1.0565 means
EN 10027-2 material numbers have the form 1.XXYY: the leading 1 is steel; the next two digits give the steel group (05 → steels 0.25–0.55 % C or Rm 500–700 MPa); the last two digits are a sequential number within that group. The number is unique to one composition and survives name changes, which is why 1.0565 has stayed constant while the symbolic name moved from WStE355 to P355NH.
P355NH at a glance
P355NH is the 355 MPa class of EN 10028-3, the European standard for normalized, weldable fine-grain steels for pressure purposes. Grain refinement with aluminium, niobium and vanadium (Nb + Ti + V ≤ 0.12 %) gives the toughness that plain C-Mn steel cannot reach at this strength: 27 J at −20 °C transverse for the NH and N variants, −40 °C for NL1 and −50 °C for NL2. The H suffix adds a guaranteed yield table up to 400 °C (210 MPa at 400 °C). Werkstoff number 1.0565; the DIN 17102 name WStE355 is still common.
It is the standard plate for LPG spheres and bullets, air receivers, pressure vessels in refineries and chemical plants, and — as P355NL1/NL2 — for ammonia, propane and other refrigerated-gas storage. Because carbon stays ≤ 0.20 % and CEV ≤ 0.43 %, welding is straightforward for a 355 MPa steel.
The ASME counterparts are A516-70 (lower yield, 260 MPa) and A537 Class 1 (345 MPa, normalized) — both 'near'; JIS SPV355 is identical in intent.
Full data sheet for P355NH → · Equivalent grades →