The chemical composition range of Q345 steel is shown in the following table:
| Element | Q345A | Q345B | Q345C | Q345D | Q345E |
| Carbon (C) | ≤0.20% | ≤0.20% | ≤0.20% | ≤0.18% | ≤0.18% |
| Silicon (Si) | ≤0.50% | ≤0.50% | ≤0.50% | ≤0.50% | ≤0.50% |
| Manganese (Mn) | ≤1.70% | ≤1.70% | ≤1.70% | ≤1.70% | ≤1.70% |
| Phosphorus (P) | ≤0.035% | ≤0.035% | ≤0.030% | ≤0.030% | ≤0.025% |
| Sulfur (S) | ≤0.035% | ≤0.035% | ≤0.030% | ≤0.025% | ≤0.020% |
| Vanadium (V) | ≤0.15% | ≤0.15% | ≤0.15% | ≤0.15% | ≤0.15% |
| Niobium (Nb) | ≤0.07% | ≤0.07% | ≤0.07% | ≤0.07% | ≤0.07% |
| Aluminum (Al) | – | – | ≥0.015% | ≥0.015% | ≥0.015% |
| Titanium (Ti) | ≤0.20% | ≤0.20% | ≤0.20% | ≤0.20% | ≤0.20% |
| Chromium (Cr) | ≤0.30% | ≤0.30% | ≤0.30% | ≤0.30% | ≤0.30% |
| Nickel (Ni) | ≤0.50% | ≤0.50% | ≤0.50% | ≤0.50% | ≤0.50% |
| Copper (Cu) | ≤0.30% | ≤0.30% | ≤0.30% | ≤0.30% | ≤0.3 |
