Q500NH Atmospheric Corrosion Resistant Weathering Steel Plate
What is Q500NH Weathering Steel?
Q500NH is a high-strength Chinese-grade structural weathering steel standardized under GB/T 4171. The "NH" stands for "Nai Hou" (耐候), directly translating to "weather resistance". As a high-strength weathering steel, it delivers exceptional mechanical performance while forming a dense, stable, and adherent protective patina layer in natural atmospheric environments. This self-protecting characteristic provides 2 to 8 times the corrosion resistance of conventional carbon steel, making it ideal for extreme heavy-duty outdoor structures requiring maximum load-bearing capacity and long-term durability.
Decoding the Grade: Q500NH
The naming follows the Chinese steel grade system, where each part reveals key performance characteristics:
Domestic Grades Comparison
Q460NH
Cu: 0.25-0.55% | Cr: 0.30-1.25% | Ni: ≤0.65%
Q500NH
Cu: 0.25-0.55% | Cr: 0.30-1.25% | Ni: ≤0.65%
Q550NH
Cu: 0.25-0.55% | Cr: 0.30-1.25% | Ni: ≤0.65%
Core Characteristics:
✔ All three grades share excellent weathering alloy composition (Cu, Cr, Ni) for superior corrosion resistance.
✔ Strength increases with grade number, while workability and cost efficiency decrease slightly.
✔ Q500NH provides the optimal balance for maximum load engineering projects.
Chemical Composition (GB/T 4171)
| Grade | C | Si | Mn | P | S | Cu | Cr | Ni | Others* |
|---|---|---|---|---|---|---|---|---|---|
| Q500NH | ≤0.12 | ≤0.65 | ≤2.00 | ≤0.025 | ≤0.030 | 0.25-0.55 | 0.30-1.25 | ≤0.65 | ①,②,③ |
① Micro-alloying: may contain Nb (0.015-0.060%), V (0.02-0.12%), Ti (0.02-0.10%), Alt ≥0.020%. At least one element meets lower limit.
② Optional: Mo ≤0.30%, Zr ≤0.15% may be added by agreement. Also Ni lower limit may be waived.
③ Total amount of Nb, V, Ti added shall not exceed 0.22%.
④ Permissible deviations for product analysis according to GB/T 222. Sulphur can be agreed ≤0.008%.
⑤ Smelting: converter or electric furnace, fully killed steel. Delivery states: hot-rolled / controlled-rolled / normalized / 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 | |||
| Q500NH | 500 | 490 | 480 | — | 600 – 760 | 18 | 16 | 15 | — | a | 2a | 3a | ||
| 500/490/480 = Yield strength by thickness (MPa) — = not applicable for >60mm 600-760 = Tensile strength range (MPa) a/2a/3a = Bending mandrel diameter (a = specimen thickness) | ||||||||||||||
Note: 'a' = specimen thickness. Rp0.2 applies if no yield plateau. Bending specimen width b=35mm for arbitration. "—" indicates the property is not specified for that thickness range. Q500NH may be delivered in quenched and tempered condition as per 7.3.
Available Supply Range
Thickness Range
- Hot-rolled plates: 3mm - 60mm
- Sheets / Coils: 1.5mm - 20mm
- Custom thickness: Available upon request
Width & Length
- Width: 900mm - 4000mm
- Length: 2000mm - 18000mm
- Custom sizes: Cut-to-length available
Product Forms
- Steel Plates (hot-rolled, normalized, Q+T)
- Steel Sheets & Coils
- Sections: H-beams, I-beams, Channels, Angles
- Flat bars & Round bars
Surface & Edge Options
- As-rolled surface / Shot blasted
- Primer coated (optional)
- Mill edge / Trimmed edge
- Beveled edge for welding
Custom Dimensions & Processing
Custom Sizes
Non-standard dimensions
Laser/Plasma Cutting
CNC precision cutting
Edge Beveling
Single/double bevel
Drilling & Punching
Custom hole patterns
Bending & Forming
Plate rolling, profiling
Surface Treatment
Shot blasting, priming
Advantages & Typical Applications
Key Advantages
- Maximum strength design, higher load capacity than Q460NH
- Excellent weathering and corrosion resistance
- 2-8x corrosion resistance vs carbon steel
- Good weldability and cold forming properties
- No painting required, reduces lifecycle costs
- Can be supplied in quenched and tempered condition
Typical Applications
- Large-span bridges & high-rise buildings
- Railway rolling stock & heavy containers
- Transmission towers & extreme high-load infrastructure
- Heavy engineering machinery & vehicle frames
- Offshore structures & outdoor heavy-duty facilities
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, or quenched + tempered (for Q460NH, Q500NH, Q550NH). Cold-rolled sheets annealed.
- 🔹 Fabrication: Excellent weldability and cold forming. Preheating (100–150°C) recommended for thickness >25 mm.
Frequently Asked Questions (FAQ)
Supply Information
Available Forms
- Plates & Sheets
- Hot-rolled Coils
- Sections (H-beams, Channels, Angles)
- Bars
Delivery Condition
- Hot-rolled: As-rolled, controlled-rolled, or normalized
- Quenched + Tempered (for high strength grades)
- Cold-rolled: Annealed condition
- Mill test certificate (EN 10204 3.1) available
MOQ & Lead Time
- Standard MOQ: 5 tons
- Stock items: 30-35 days
- Custom production: 35-45 days
Start Your Q500NH Project
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