Q345B / 16Mn
Data verifiedQ345B 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.
Chemical composition
| Element | Content (%) |
|---|---|
| C | ≤0.20 |
| Si | ≤0.50 |
| Mn | 1.00–1.70 |
| P | ≤0.035 |
| S | ≤0.035 |
| V | 0.02–0.15 (optional) |
| Nb | 0.01–0.06 (optional) |
Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.
Properties
| Yield strength | ≥345 MPa (≤16 mm) |
| Tensile strength | 470–630 MPa |
| Density | 7.85 g/cm³ |
| Impact | B grade: 20 °C, ≥34 J |
Heat treatment
Supplied hot rolled or normalized; no quench-temper needed.
Equivalent grades
| Standard | Designation |
|---|---|
| din | 1.0570 (S355J2, near) |
| aisi | A572 Gr.50 (near) |
| jis | SM490 (near) |
| gb | Q345B (GB/T 1591); 16Mn legacy |
Compare side by side: Q345B / 16Mn vs S355J2
Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.
Applications & Processing
Applications: Structural pipe, pressure vessels, bridges, machinery frames, low-pressure fluid tube.
Processing: Good weldability (CEV controlled); formable; the default upgrade from Q235 where design allows 345 MPa yield.
FAQ
- Is Q345B the same as S355?
- Near-equivalent HSLA grades with similar yield (345 vs 355 MPa). Certificates often cross-accept; impact grades and CEV limits differ slightly by standard.
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Ask for a quotationVisit NasteelSource: GB/T 1591 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.