MaterialsSteels

S355 (St 52-3) structural steel

The non-alloy structural steel S355 to EN 10025-2: the quality grades JR, J0, J2 and K2, how they relate to the old St 52-3 and St 44-2, chemical composition, yield and tensile strength by thickness, impact energy, weldability — and why "St 52" tube is a different steel.

LiveUpdated 11 October 20264 min read

S355: limits for J2 up to 40 mm, EN 10025-2

Minimum yield strength ReH, up to 16 mm: 355MPa
Tensile strength Rm, 3 to 100 mm: 470–630MPa
Impact energy of S355J2 at −20 °C: 27J
Maximum carbon equivalent CEV up to 30 mm: 0.45

S355 is a non-alloy structural steel for welded constructions, frames and machine parts, with a minimum yield strength of 355 MPa in thin sections. It is still widely known by its old German name, St 52-3.

Quality grades

The letters after S355 give the impact energy and the test temperature:

Grade	Number	Impact energy KV, min.
S355JR	1.0045	27 J at +20 °C
S355J0	1.0553	27 J at 0 °C
S355J2	1.0577	27 J at −20 °C
S355K2	1.0596	40 J at −20 °C

The four quality grades as the minimum Charpy impact energy and the temperature at which it is tested. J0 and J2 ask for the same energy as JR at a colder test; K2 asks for more at −20 °C.

“+N” after the name, as in S355J2+N, is a delivery condition (normalized or normalizing rolled), not part of the steel name; the number stays 1.0577. The current standard is EN 10025-2:2019, which replaced the 2004 edition.

Old names: St 52-3 and St 44-2

Old name (DIN 17100)	Today
St 52-3 (1.0570)	via S355J2G3 (1.0570, earlier EN 10025) to S355J2 (1.0577); ArcelorMittal maps St 52-3 N to S355J2+N and St 52-3 U to S355J0
St 44-2	S275JR (1.0044) — an S275 grade, not S355

Chemical composition

Maximum %, heat analysis, EN 10025-2, for products up to 40 mm:

Grade	C	Si	Mn	P	S	N	Cu
S355JR	0.24	0.55	1.60	0.035	0.035	0.012	0.55
S355J0	0.20	0.55	1.60	0.030	0.030	0.012	0.55
S355J2, K2	0.20	0.55	1.60	0.025	0.025	—	0.55

Above 40 mm the carbon limit of J0, J2 and K2 rises to 0.22 %; for sections, some makers’ sheets apply 0.22 % from 30 mm. The carbon equivalent CEV is limited to 0.45 up to 30 mm and 0.47 from 30 to 150 mm.

Mechanical properties

Minimum yield strength ReH falls with thickness:

Thickness t (mm)	≤ 16	16–40	40–63	63–80	80–100	100–150	150–200	200–250
ReH min (MPa)	355	345	335	325	315	295	285	275

J2 and K2 continue to 400 mm with 265 MPa. Tensile strength Rm: 510–680 MPa below 3 mm, 470–630 MPa from 3 to 100 mm, 450–600 MPa from 100 to 400 mm. Minimum elongation, longitudinal, t ≥ 3 mm: 22 % up to 40 mm, 21 % from 40 to 63 mm, 20 % from 63 to 100 mm; transverse values are 2 points lower.

Minimum yield strength ReH of S355 against nominal thickness (EN 10025-2, the values in the table above). The dashed step from 250 to 400 mm applies to J2 and K2 only.

Weldability and machining

S355 has good weldability, owing to its low carbon content and the CEV limit. For machining it behaves much like a mild steel (Murray Steel Products); Meusburger recommends a better-machining steel such as 1.1730 for parts that need no welding. In ISO 513 it belongs to group P.

Sources (14)

Every value and quotation on this page comes from the documents below.