How to Read Steel Grade Designations: Q235, A36, S355, SS400 Explained
Steel grade designations look like a secret code. What does Q235 mean? How is A36 different from S355? This guide decodes the most common systems: GB, ASTM, EN, and JIS.
Chinese GB Grades
- Q235: Q = Yield strength, 235 = 235 MPa. Most common structural steel in China.
- Q355: 355 MPa yield (formerly Q345). Updated under GB/T 1591-2018.
- 20G: 0.20% carbon, G = boiler grade.
- 45#: 0.45% carbon. Medium carbon for shafts.
American ASTM Grades
- A36: 250 MPa yield. Equivalent to Q235B and S235JR.
- A572 Gr.50: 345 MPa yield. Equivalent to Q355 and S355.
- A106 Gr.B: Seamless pipe for high-temp service.
- A312 TP304: Austenitic SS pipe.
European EN Grades
- S235JR: S = Structural, 235 = yield, JR = room temp impact.
- S355JR: 355 MPa yield. Subgrades: JR, J0, J2, K2 for different temperatures.
Japanese JIS Grades
- SS400: SS = Structural Steel, 400 = tensile strength (not yield!).
- SGCC: S = Steel, G = Galvanized, C = Cold-rolled, C = Commercial.
- SUS304: SUS = Steel Use Stainless.
Cross-Reference Table
| GB | ASTM | EN | JIS |
|---|---|---|---|
| Q235B | A36 | S235JR | SS400 |
| Q355 | A572 Gr.50 | S355JR | SM490 |
| 0Cr18Ni9 | A240 304 | X5CrNi18-10 | SUS304 |
| SGCC | A653 CS-B | DX51D | SGCC |
Need help translating between standards? CoreMetal can assist.
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