Carbon Steel Grades Chart: Q235, A36, S235, SS400 Compared
If you work with carbon steel in construction, manufacturing, or international trade, you’ve encountered different grade designations from various countries. Q235 (China), A36 (USA), S235JR (Europe), and SS400 (Japan) are all structural carbon steels — but are they interchangeable? This comprehensive chart compares their chemical composition, mechanical properties, and applications.
1. Chemical Composition Comparison
| Element | Q235B (GB) | A36 (ASTM) | S235JR (EN) | SS400 (JIS) |
|---|---|---|---|---|
| Carbon (C) | ≤0.20% | ≤0.25% | ≤0.17% | ≤0.21% |
| Manganese (Mn) | 0.30–0.70% | — | ≤1.40% | — |
| Silicon (Si) | ≤0.35% | — | — | — |
| Sulfur (S) | ≤0.045% | ≤0.050% | ≤0.035% | ≤0.050% |
| Phosphorus (P) | ≤0.045% | ≤0.040% | ≤0.035% | ≤0.050% |
Key insight: S235JR has the strictest limits on sulfur and phosphorus, making it the cleanest steel. A36 allows the highest carbon content, giving it slightly higher strength potential.
2. Mechanical Properties Comparison
| Property | Q235B | A36 | S235JR | SS400 |
|---|---|---|---|---|
| Yield Strength | ≥235 MPa | ≥250 MPa | ≥235 MPa | ≥245 MPa |
| Tensile Strength | 370–500 MPa | 400–550 MPa | 360–510 MPa | 400–510 MPa |
| Elongation | ≥26% | ≥20% | ≥22% | ≥21% |
| Test Temperature | 20°C (B grade) | Ambient | 20°C (JR grade) | Ambient |
3. Cross-Reference Table
| China (GB) | USA (ASTM) | Europe (EN) | Japan (JIS) |
|---|---|---|---|
| Q235A | A36 | S235JR | SS400 |
| Q235B | A36 | S235J0 | SS400 |
| Q345B | A572 Gr.50 | S355JR | SM490A |
4. Are They Interchangeable?
In most general structural applications, yes — these grades are considered equivalent. However, consider:
- Welding: Higher carbon content in A36 may require preheating for thick sections
- Low-temperature service: S235J0/Q235B have impact testing at 0°C/20°C; A36 and SS400 do not require it
- European projects: S235JR requires CE marking with specific documentation
5. Common Applications
- Q235B: Chinese construction, bridges, general structures — most widely used grade in China
- A36: US construction, bridges, buildings — the default structural steel in America
- S235JR: European construction, machinery, light structures
- SS400: Japanese-specification projects, shipbuilding, general structures
Conclusion
Understanding carbon steel grade equivalences helps you source materials correctly for international projects. Whether you need Q235, A36, S235JR, or SS400, CoreMetal Steel supplies all grades with full mill certificates. Contact us for competitive pricing on structural steel plates, coils, sections, and bars.