Q235NH Weathering Steel
Q235NH is a Chinese standard weathering steel (GB/T 4171) offering 2–8 times better atmospheric corrosion resistance than plain carbon steel. Ideal for bridges, rolling stock, containers, and structural applications.
Chemical Composition (heat analysis, %)
| Grade | C | Si | Mn | P | S | Cu | Cr | Ni | Others* |
|---|---|---|---|---|---|---|---|---|---|
| Q235NH | ≤0.13 | 0.10–0.40 | 0.20–0.60 | ≤0.030 | ≤0.030 | 0.25–0.55 | 0.40–0.80 | ≤0.65 | ① |
📌 Notes on chemical composition:
- ① Micro-alloying: may contain Nb (0.015–0.060%), V (0.02–0.12%), Ti (0.02–0.10%). At least one element meets lower limit; total Nb+V+Ti ≤0.22%.
- ② Optional: Mo ≤0.30%, Zr ≤0.15% may be added by agreement. Also Ni lower limit can be waived, or C ≤0.15% upon request.
- ③ Permissible deviations for product analysis according to GB/T 222. Sulphur can be agreed ≤0.008%.
- ④ Smelting: converter or electric furnace, fully killed steel. Delivery states: hot-rolled / controlled-rolled / normalized (Q460NH–Q550NH may be quenched + tempered).
Mechanical Properties & Bending Test
| Grade | Lower yield strength ReL (≥ MPa) | Tensile strength Rm (MPa) | Elongation after fracture A/% ≥ | 180° Bending mandrel diameter |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ≤16 | >16-40 | >40-60 | >60 | N/mm² | ≤16 | >16-40 | >40-60 | >60 | ≤6 | >6-16 | >16 | |||
| Q235NH | 235 | 225 | 215 | 215 | 360 – 510 | 25 | 25 | 24 | 23 | a | a | 2a | ||
| 235/225/215 = Yield strength by thickness (MPa) 360-510 = Tensile strength range (MPa) a/2a = Bending mandrel diameter (a = specimen thickness) | ||||||||||||||
Note: 'a' = specimen thickness. Rp0.2 applies if no yield plateau. Bending specimen width b=35mm for arbitration.
Smelting & Delivery Conditions
- 🔹 7.1.2 – Permissible deviations for product analysis per GB/T 222.
- 🔹 7.2 – Steelmaking: converter or electric furnace, fully killed. Method at supplier's option unless specified.
- 🔹 7.3 – Delivery: hot-rolled, controlled-rolled, normalized; Q460NH–Q550NH may be quenched + tempered. Cold-rolled sheets annealed.
- 🔹 Fabrication: Excellent weldability and cold forming. Preheating (100–150°C) recommended for thickness >25 mm.
235
Min Yield (MPa) ≤16mm
360–510
Tensile Rm (MPa)
25%
Elongation A (≤40mm)
0.25–0.55
Copper Cu %
🌉 Typical Applications & Properties
Q235NH forms a dense protective patina, eliminating the need for painting in many atmospheric environments. Commonly used in:
🚆 Railway rolling stock 🌉 Bridges & girders 🏭 Industrial structures 📦 Containers ⚡ Transmission towers
Available thickness: 2mm to 50mm. Mill test certificates (EN 10204 3.1) supplied.
© Q235NH technical data sheet — Based on GB/T 4171:2008 & amendments. Always verify with mill certificate.