Q345B / 16Mn vs S355J2
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
Q345B / 16Mn
Pipe & Tube Steel
Q345B is China’s HSLA structural steel (successor of 16Mn) for welded structures, pressure equipment and seamless pipe — the volume grade behind much of China’s pipe and fabrication exports.
Standards: DIN 1.0570 (S355J2, near) · AISI A572 Gr.50 (near) · JIS SM490 (near) · GB Q345B (GB/T 1591); 16Mn legacy
S355J2
Pipe & Tube Steel
S355J2 is Europe’s structural HSLA steel (EN 10025-2), the benchmark for welded structures, machinery and pipe where −20 °C toughness is specified.
Standards: DIN 1.0577 (S355J2) / 1.0570 legacy St52-3 · AISI A572 Gr.50 (near) · JIS SM490B (near) · GB Q345B (near)
Chemical composition compared (%)
| Element | Q345B / 16Mn | S355J2 |
|---|---|---|
| C | ≤0.20 | ≤0.20 |
| Si | ≤0.50 | ≤0.55 |
| Mn | 1.00–1.70 | ≤1.60 |
| P | ≤0.035 | ≤0.025 |
| S | ≤0.035 | ≤0.025 |
| V | 0.02–0.15 (optional) | — |
| Nb | 0.01–0.06 (optional) | — |
Properties compared
| Property | Q345B / 16Mn | S355J2 |
|---|---|---|
| Yield strength | ≥345 MPa (≤16 mm) | ≥355 MPa (≤16 mm) |
| Tensile strength | 470–630 MPa | 470–630 MPa |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Impact | B grade: 20 °C, ≥34 J | J2: −20 °C, ≥27 J |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: Q345B / 16Mn · S355J2. Substitution decisions for certified parts stay with the design authority.