Structural steel grade reference data for UK construction. Yield strength varies with material thickness — the values below follow BS EN 10025 (flat products and sections). Old BS 4360 equivalents are included for reference against historical drawings.
This is reference data only. Actual material properties should be confirmed from mill certificates. Design values per BS EN 1993-1-1 use the nominal yield strength fy from BS EN 10025 — not the mill certificate value.
Grade
Old BS 4360
fy ≤16mm (MPa)
fu range (MPa)
Charpy
US equivalent
Weldability
S235JR
Grade 40 / early Grade 43A (approx)
235
360–510
+20°C
ASTM A36
Excellent.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
235
16–40mm
225
40–63mm
215
63–80mm
215
80–100mm
215
100–150mm
195
Tensile strength fu by thickness
Thickness
fu (MPa)
≤3mm
360–510
3–100mm
360–510
100–150mm
350–500
UK specification notes
Weldability: Excellent. No preheat needed for typical thicknesses. Low carbon content.
Max CEV (≤30mm): 0.35
Old BS 4360: Grade 40 / early Grade 43A (approx)
S235 not commonly specified in UK practice. S275 was the standard lower-grade equivalent.
US equivalent: ASTM A36
A36 yield is 250 MPa, slightly above S235
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S235J0
Grade 40 / early Grade 43B (approx)
235
360–510
0°C
ASTM A36
Excellent.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
235
16–40mm
225
40–63mm
215
63–80mm
215
80–100mm
215
100–150mm
195
Tensile strength fu by thickness
Thickness
fu (MPa)
≤3mm
360–510
3–100mm
360–510
100–150mm
350–500
UK specification notes
Weldability: Excellent. No preheat needed for typical thicknesses. Low carbon content.
Max CEV (≤30mm): 0.35
Old BS 4360: Grade 40 / early Grade 43B (approx)
S235 not commonly specified in UK practice.
US equivalent: ASTM A36
A36 yield is 250 MPa, slightly above S235
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S235J2
Grade 40 / early Grade 43C (approx)
235
360–510
−20°C
ASTM A36
Excellent.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
235
16–40mm
225
40–63mm
215
63–80mm
215
80–100mm
215
100–150mm
195
Tensile strength fu by thickness
Thickness
fu (MPa)
≤3mm
360–510
3–100mm
360–510
100–150mm
350–500
UK specification notes
Weldability: Excellent. No preheat needed for typical thicknesses. Low carbon content.
Max CEV (≤30mm): 0.35
Old BS 4360: Grade 40 / early Grade 43C (approx)
S235 not commonly specified in UK practice.
US equivalent: ASTM A36
A36 yield is 250 MPa, slightly above S235
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S275JR
Grade 43A
275
410–560
+20°C
ASTM A36
Excellent.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
275
16–40mm
265
40–63mm
255
63–80mm
245
80–100mm
235
100–150mm
225
Tensile strength fu by thickness
Thickness
fu (MPa)
≤3mm
430–580
3–100mm
410–560
100–150mm
400–540
UK specification notes
Weldability: Excellent. Generally no preheat for t<25mm. Preheat may be needed for thick sections >40mm depending on CEV and hydrogen content.
Max CEV (≤30mm): 0.4
Old BS 4360: Grade 43A
Standard secondary steelwork grade in UK pre-2004.
US equivalent: ASTM A36
Close match on yield. No exact single ASTM equivalent.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S275J0
Grade 43B
275
410–560
0°C
ASTM A36
Excellent.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
275
16–40mm
265
40–63mm
255
63–80mm
245
80–100mm
235
100–150mm
225
Tensile strength fu by thickness
Thickness
fu (MPa)
≤3mm
430–580
3–100mm
410–560
100–150mm
400–540
UK specification notes
Weldability: Excellent. Generally no preheat for t<25mm. Preheat may be needed for thick sections >40mm depending on CEV and hydrogen content.
Max CEV (≤30mm): 0.4
Old BS 4360: Grade 43B
US equivalent: ASTM A36
Close match on yield. No exact single ASTM equivalent.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S275J2
Grade 43C/D
275
410–560
−20°C
ASTM A36
Excellent.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
275
16–40mm
265
40–63mm
255
63–80mm
245
80–100mm
235
100–150mm
225
Tensile strength fu by thickness
Thickness
fu (MPa)
≤3mm
430–580
3–100mm
410–560
100–150mm
400–540
UK specification notes
Weldability: Excellent. Generally no preheat for t<25mm. Preheat may be needed for thick sections >40mm depending on CEV and hydrogen content.
Max CEV (≤30mm): 0.4
Old BS 4360: Grade 43C/D
US equivalent: ASTM A36
Close match on yield. No exact single ASTM equivalent.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S355JR
Grade 50B
355
470–630
+20°C
ASTM A572 Grade 50
Good.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
355
16–40mm
345
40–63mm
335
63–80mm
325
80–100mm
315
100–150mm
295
Tensile strength fu by thickness
Thickness
fu (MPa)
≤3mm
510–680
3–100mm
470–630
100–150mm
450–600
UK specification notes
Weldability: Good. Preheat recommended for t>25mm depending on CEV. Higher carbon equivalent than S275, so more care needed with thick sections and high restraint joints.
Max CEV (≤30mm): 0.45
Old BS 4360: Grade 50B
S355 is now the dominant primary structure grade in the UK.
US equivalent: ASTM A572 Grade 50
Good match. Both 345-355 MPa yield.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S355J0
Grade 50C
355
470–630
0°C
ASTM A572 Grade 50
Good.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
355
16–40mm
345
40–63mm
335
63–80mm
325
80–100mm
315
100–150mm
295
Tensile strength fu by thickness
Thickness
fu (MPa)
≤3mm
510–680
3–100mm
470–630
100–150mm
450–600
UK specification notes
Weldability: Good. Preheat recommended for t>25mm depending on CEV. Higher carbon equivalent than S275, so more care needed with thick sections and high restraint joints.
Max CEV (≤30mm): 0.45
Old BS 4360: Grade 50C
US equivalent: ASTM A572 Grade 50
Good match. Both 345-355 MPa yield.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S355J2
Grade 50D
355
470–630
−20°C
ASTM A572 Grade 50
Good.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
355
16–40mm
345
40–63mm
335
63–80mm
325
80–100mm
315
100–150mm
295
Tensile strength fu by thickness
Thickness
fu (MPa)
≤3mm
510–680
3–100mm
470–630
100–150mm
450–600
UK specification notes
Weldability: Good. Preheat recommended for t>25mm depending on CEV. Higher carbon equivalent than S275, so more care needed with thick sections and high restraint joints.
Max CEV (≤30mm): 0.45
Old BS 4360: Grade 50D
Most commonly specified S355 sub-grade in UK practice.
US equivalent: ASTM A572 Grade 50
Good match. Both 345-355 MPa yield.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S355K2
Grade 50E (approx)
355
470–630
−20°C (27J)
ASTM A572 Grade 50
Good.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
355
16–40mm
345
40–63mm
335
63–80mm
325
80–100mm
315
100–150mm
295
Tensile strength fu by thickness
Thickness
fu (MPa)
≤3mm
510–680
3–100mm
470–630
100–150mm
450–600
UK specification notes
Weldability: Good. Preheat recommended for t>25mm depending on CEV. Higher carbon equivalent than S275, so more care needed with thick sections and high restraint joints.
Max CEV (≤30mm): 0.45
Old BS 4360: Grade 50E (approx)
Higher toughness requirement than 50D.
US equivalent: ASTM A572 Grade 50
Good match. K2 has higher Charpy requirement (40J vs 27J).
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S460N
Grade 55C/E (approx)
460
510–690
−20°C
ASTM A913 Grade 65
Good for its strength class.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
460
16–40mm
440
40–63mm
430
63–80mm
410
80–100mm
400
Tensile strength fu by thickness
Thickness
fu (MPa)
≤40mm
540–720
40–63mm
530–710
63–100mm
510–690
UK specification notes
Weldability: Good for its strength class. Fine grain structure improves weldability. Preheat generally needed for t>20mm. Low carbon equivalent by design.
Max CEV (≤30mm): 0.46
Old BS 4360: Grade 55C/E (approx)
US equivalent: ASTM A913 Grade 65
A913 Gr 65 yield is 450 MPa. Approximate match.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S460NL
Grade 55F (approx)
460
510–690
−50°C
ASTM A913 Grade 65
Good for its strength class.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
460
16–40mm
440
40–63mm
430
63–80mm
410
80–100mm
400
Tensile strength fu by thickness
Thickness
fu (MPa)
≤40mm
540–720
40–63mm
530–710
63–100mm
510–690
UK specification notes
Weldability: Good for its strength class. Fine grain structure improves weldability. Preheat generally needed for t>20mm.
Max CEV (≤30mm): 0.46
Old BS 4360: Grade 55F (approx)
US equivalent: ASTM A913 Grade 65
A913 Gr 65 yield is 450 MPa. NL has low-temp Charpy at -50C.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S460M
Grade 55C (thermomechanical rolling, approx)
460
510–690
−20°C
ASTM A913 Grade 65
Better weldability than S460N due to thermomechanical rolling process.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
460
16–40mm
440
40–63mm
430
63–80mm
410
80–100mm
400
Tensile strength fu by thickness
Thickness
fu (MPa)
≤40mm
540–720
40–63mm
530–710
63–100mm
510–690
UK specification notes
Weldability: Better weldability than S460N due to thermomechanical rolling process. Lower CEV than normalized equivalents. Preheat may still be needed for thick sections.
Max CEV (≤16mm): 0.43
Old BS 4360: Grade 55C (thermomechanical rolling, approx)
US equivalent: ASTM A913 Grade 65
A913 Gr 65 yield is 450 MPa. Approximate match.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S460ML
Grade 55E (thermomechanical rolling, approx)
460
510–690
−50°C
ASTM A913 Grade 65
Better weldability than S460NL due to thermomechanical rolling.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
460
16–40mm
440
40–63mm
430
63–80mm
410
80–100mm
400
Tensile strength fu by thickness
Thickness
fu (MPa)
≤40mm
540–720
40–63mm
530–710
63–100mm
510–690
UK specification notes
Weldability: Better weldability than S460NL due to thermomechanical rolling. Lower CEV. Preheat may still be needed for thick sections.
Max CEV (≤16mm): 0.43
Old BS 4360: Grade 55E (thermomechanical rolling, approx)
US equivalent: ASTM A913 Grade 65
A913 Gr 65 yield is 450 MPa. ML has low-temp Charpy at -50C.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
Weldability: Weldable, but weathering alloy additions (Cu, Cr, Ni, P) increase CEV. Use low-hydrogen electrodes. Matching weathering filler metals recommended. Preheat for t>20mm.
Max CEV (≤150mm): 0.52
Old BS 4360: Grade WR50A / Cor-Ten equivalent
Weathering steel. Most common EN weathering grade in UK practice.
US equivalent: ASTM A588 / A242
Cor-Ten equivalent family. W grade (lower phosphorus).
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S355J0WP
Grade WR50A (higher phosphorus variant)
355
—
—
ASTM A588
More difficult than W grades due to higher phosphorus content (up to 0.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
355
16–40mm
345
Tensile strength fu by thickness
Thickness
fu (MPa)
≤40mm
470–630
UK specification notes
Weldability: More difficult than W grades due to higher phosphorus content (up to 0.10%). Higher risk of hot cracking. Special welding procedures required. Low heat input, low hydrogen consumables essential.
Max CEV (≤40mm): 0.52
Old BS 4360: Grade WR50A (higher phosphorus variant)
Phosphorus-alloyed variant for enhanced weathering — less common.
US equivalent: ASTM A588
Higher phosphorus variant. Limited to max 40mm thickness.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
S355J2WP
Grade WR50A (higher phosphorus variant)
355
—
—
ASTM A588
More difficult than W grades due to higher phosphorus content (up to 0.
Yield strength fy by thickness
Thickness
fy (MPa)
≤16mm
355
16–40mm
345
Tensile strength fu by thickness
Thickness
fu (MPa)
≤40mm
470–630
UK specification notes
Weldability: More difficult than W grades due to higher phosphorus content (up to 0.10%). Higher risk of hot cracking. Special welding procedures required. Low heat input, low hydrogen consumables essential.
Max CEV (≤40mm): 0.52
Old BS 4360: Grade WR50A (higher phosphorus variant)
Phosphorus-alloyed variant for enhanced weathering — less common.
US equivalent: ASTM A588
Higher phosphorus variant. Limited to max 40mm thickness.
Source: BS EN 10025-2:2019 (carbon steel), BS EN 10025-3 (normalized S460N/NL), BS EN 10025-4 (thermomechanical S460M/ML), BS EN 10025-5 (weathering grades)
Frequently asked questions
What is the yield strength of S355 steel?
S355 has a nominal yield strength of 355 MPa for material thickness up to 16mm. For thicker material it reduces: 345 MPa at ≤40mm, 335 MPa at ≤63mm, down to 295 MPa at ≤150mm. The suffix (JR, J0, J2, K2) describes the Charpy impact test temperature, not the yield strength.
What is the difference between S275 and S355?
S275 has a yield strength of 275 MPa (≤16mm) and S355 has 355 MPa — S355 is roughly 30% stronger. In UK practice S355 is the standard primary structure grade (beams, columns, portal frames) and S275 was the standard secondary grade. S275 is still used for lighter secondary steelwork where the higher strength of S355 is not needed, and it has slightly better weldability.
What is the old BS 4360 equivalent of S355?
S355J2 is the approximate equivalent of old BS 4360 Grade 50D. S355JR corresponds to Grade 50B and S355J0 to Grade 50C. The sub-grade letters in BS 4360 and BS EN 10025 both relate to Charpy impact test temperature requirements, but the energy levels differ slightly — the mapping is approximate. BS 4360 was superseded by BS EN 10025 in 2004.
What is the US equivalent of S355?
The closest US equivalent to S355 is ASTM A572 Grade 50, which has a minimum yield of 345 MPa (50 ksi) — slightly below S355's 355 MPa. For welded structures, ASTM A992 is also commonly used in the US for wide-flange sections and has similar strength. For higher-strength grades: S460 corresponds approximately to ASTM A913 Grade 65.
What does the sub-grade letter mean on a steel grade (JR, J0, J2)?
The sub-grade letter describes the Charpy V-notch impact test requirement. JR: 27 joules at +20°C (room temperature). J0: 27 joules at 0°C. J2: 27 joules at −20°C. K2: 40 joules at −20°C. For most UK portal frame and industrial building steelwork, J2 (−20°C) is the standard sub-grade specified. JR is the minimum and is only appropriate for non-structural or lightly loaded applications.
