Q235B, SS400 and A36 are the same structural family — mild steel around 235–250 MPa tensile-class — but they are not identical: Q235B guarantees 235 MPa yield with impact testing at +20 °C; SS400 guarantees tensile 400–510 MPa with no yield minimum and no impact test; A36 guarantees 250 MPa yield with no impact test. For most non-code structures they substitute; impact-tested projects should order Q235B.
This trio generates more equivalence questions than any other grades in the trade — "is Q235B the same as A36?" comes in from every market. The honest answer: same family, different guarantees. Here is the table that settles it.
Side by Side
| Property | Q235B (GB/T 700) | SS400 (JIS G3101) | A36 (ASTM A36) |
|---|---|---|---|
| Min yield | 235 MPa (≤16 mm) | 245 MPa min... not specified as guaranteed value* | 250 MPa |
| Tensile | 370–500 MPa | 400–510 MPa | 400–550 MPa |
| Impact test | 27 J at +20 °C (guaranteed) | Not required | Not required |
| Carbon (typ. max) | ≤ 0.22% | ≤ 0.23% (by product) | ≤ 0.26% |
| Standard system | GB/T 700 | JIS G3101 | ASTM A36 |
*SS400's "400" is the tensile number; JIS G3101 states yield 245 MPa min for thicknesses ≤16 mm but the grade is usually bought on tensile.
What That Means in Practice
- Static structures, tropical climates, private works: the three grades substitute freely — fabricators across Southeast Asia and Africa use them interchangeably every day.
- Projects that specify impact testing (cold regions, dynamic loads, some public works): Q235B wins — it is the only one of the three with a guaranteed Charpy value. A36 and SS400 ship without impact results unless specially tested.
- US-spec drawings: engineers reviewing A36 call-outs usually accept Q235B with the equivalence statement; strict compliance buys actual A36 — we supply both.
- Welding: all three weld identically with E6013/E7018-class consumables; chemistry differences are negligible for fabrication.
The Supply Reality (Why This Matters)
Chinese mills roll Q235B as their default product — best price, shortest schedule. SS400 and A36 are available as special runs. So the practical playbook:
- Drawing says SS400 or A36 → quote Q235B with the equivalence statement above attached; the engineer reviews and releases.
- Strict compliance needed → we quote the exact specified grade; mills roll it on schedule.
- Either way: EN 10204 3.1 MTC naming the actual rolled standard, heat-number traceable.
Same Family, Other Names
- EN S235JR — adds the guaranteed 27 J impact like Q235B.
- GB Q235B plate sizes and equivalents: Q235B plate page →
- Stepping up: S235 vs S275 vs S355 ladder → · Q355B (S355JR class) →
Spec says A36 or SS400? Ask for the Q235B price too.
Size list to [email protected] or WhatsApp +86 191 5745 8011 — we quote the specified grade and the Q235B equivalent side by side, with equivalence documentation. MOQ 5 t.
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