Material number 1.0425: P265GH
1.0425 is the European material number (Werkstoffnummer, EN 10027-2) for P265GH, non-alloy steel for pressure purposes with elevated-temperature properties specified in EN 10028-2.
What 1.0425 means
EN 10027-2 material numbers have the form 1.XXYY: the leading 1 is steel; the next two digits give the steel group (04 → steels 0.12–0.25 % C or Rm 400–500 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 1.0425 has stayed constant while the symbolic name moved from HII to P265GH.
P265GH at a glance
P265GH is the standard carbon-steel plate for boilers, pressure vessels and heat exchangers in Europe: P for pressure, 265 for the minimum yield in MPa, G for 'other characteristics' and H for guaranteed high-temperature properties. Werkstoff number 1.0425; the pre-1992 name HII (DIN 17155) is still in wide use, especially in Turkey, Germany and the Gulf.
What separates it from a structural steel of the same strength is the guarantee package: yield strength tabulated from 50 to 400 °C, Charpy 27 J at −20 °C transverse, sulphur held to 0.010 %, full killing with aluminium, normalized microstructure, and mandatory testing per plate under the Pressure Equipment Directive (EN 10028-2 with EN 10204 3.1/3.2 certification). Tensile is 410–530 MPa, elongation 23 %.
The usual US counterpart is ASTM/ASME A516 Grade 60 (yield 220 MPa) — a 'near' match because yield is lower and elevated-temperature values are handled differently in ASME. JIS SB410, GB Q245R and IS 2002 Grade 2 are closer. For service above ~450 °C the next step is 16Mo3.
Full data sheet for P265GH → · Equivalent grades →