S355JR (EN 10025-2), Q355B (GB/T 1591) and A572 Gr50 (ASTM) all deliver ~345–355 MPa yield with similar chemistry — for most non-code structures they substitute freely. Code-governed projects (pressure parts, public works, seismic zones) need the specified grade with engineer sign-off; impact testing differs (JR/B = 27 J at +20 °C, A572 CVN optional).
Buyers send us drawings specifying one of these three grades — and ask whether the Chinese mill can roll the other two instead. The answer is usually yes, with three caveats. Here's the full comparison.
Chemistry and Properties Side by Side
| Property | S355JR (EN 10025-2) | Q355B (GB/T 1591) | A572 Gr50 (ASTM) |
|---|---|---|---|
| Min yield (≤16 mm) | 355 MPa | 355 MPa | 345 MPa |
| Tensile | 470–630 MPa | 470–630 MPa | 450 MPa min |
| Carbon (max, typical) | 0.24% (varies by thickness/product) | 0.20% | 0.23% |
| Manganese | ≤ 1.60% | ≤ 1.70% | ≤ 1.35% |
| Impact test | 27 J at +20 °C (JR) | 27 J at +20 °C (B quality) | CVN not mandatory unless specified |
| Weldability (CEV) | ≈ ≤ 0.45 | ≈ ≤ 0.45 | ≈ ≤ 0.47 |
| Typical forms | IPE/HEA/HEB, plate | HW/HM/HN, plate, coil | W shapes, plate |
Substitution Rules in Practice
| You Specified | Mill Offers | Verdict |
|---|---|---|
| S355JR | Q355B | Direct substitute for most structures — yield, tensile and impact match. Confirm with the design engineer for code projects. |
| A572 Gr50 | S355JR / Q355B | Commonly accepted; yield is actually 10 MPa higher. If the spec calls CVN at low temperature, order S355J2/K2 or Q355C/D instead of B/JR. |
| Q355B | S355JR | Equivalent envelope; EN-marked material often preferred for export paperwork. |
| Any of the three | "Equivalent" without MTC | Reject — every substitution must show on the mill test certificate with the actual grade and heat number. |
The Three Caveats
- Temperature service: JR and B grades are tested at +20 °C. Cold climates (−20 °C service) need S355J2/K2, Q355C/D or A572 with CVN at temperature — same family, different suffix.
- Code projects: pressure equipment, bridges and public works usually lock the grade in the design code. Substitution is an engineer's decision with documentation, not a trader's.
- Shape availability: the grade rolls in the shapes each standard supports — W shapes are natural in A572/A992, IPE/HEA/HEB in S355JR, HW/HM/HN in Q355B. Mills can roll across, but lead times differ.
Grade deep-dives: S355JR properties → · Chinese equivalents across the board: GB equivalents chart → · stainless cross-standards: stainless equivalents →
Send the spec — we quote in any of the three
Your grade and section list to [email protected] or WhatsApp +86 191 5745 8011 — we confirm rolling availability, certificates and FOB/CIF price in one working day. MOQ 5 t.
Request a Grade Quote