Material number 1.0045: S355JR
1.0045 is the European material number (Werkstoffnummer, EN 10027-2) for S355JR, non-alloy hot-rolled structural steel specified in EN 10025-2.
What 1.0045 means
EN 10027-2 material numbers have the form 1.XXYY: the leading 1 is steel; the next two digits give the steel group (00 → base steels); 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 1.0045 has stayed constant while the symbolic name moved from St52-3 U to S355JR.
S355JR at a glance
S355JR is the strength workhorse of European structural steel: 355 MPa minimum yield, 470–630 MPa tensile, 27 J Charpy at +20 °C, Werkstoff number 1.0045. It is still a non-alloy steel — strength comes from up to 0.24 % C and 1.60 % Mn rather than micro-alloying — which is why the carbon equivalent limit rises to 0.45 % and welding thick sections calls for a preheat check.
The S355 family (JR, J0, J2, K2) shares one strength table and differs only in impact temperature and cleanliness. JR is the coil and section grade for mild climates; plate for cranes, bridges and offshore is almost always ordered as J2 or K2. If a specification simply says "S355", ask which suffix — the difference decides whether the steel is accepted at −20 °C.
S355JR replaced DIN St52-3 U and BS 4360 50B; the US counterpart is ASTM A572 Grade 50, the Chinese Q355B (formerly Q345B).
Full data sheet for S355JR → · Equivalent grades →