Q415NH Atmospheric Corrosion Resistant Weathering Steel Plate

GB/T 4171 | Patina-Forming Steel with 415 MPa Minimum Yield Strength

What is Q415NH Weathering Steel?

Q415NH 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 excellent 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 heavy-duty outdoor structures requiring high load-bearing capacity and long-term durability.

Decoding the Grade: Q415NH

The naming follows the Chinese steel grade system, where each part reveals key performance characteristics:

Q Yield Strength Designator — Structural steel where "Q" stands for "Qu" (屈), representing Yield Point.
415 Minimum Yield Strength — Guarantees a minimum yield strength of 415 MPa (for thickness ≤16mm).
NH Weathering Quality Grade — "Nai Hou" (耐候) indicates atmospheric corrosion resistance with alloying elements (Cu, Cr, Ni) enabling patina formation.

Domestic Grades Comparison

Q355NH

Yield Strength: ≥355 MPa
Strength Level: High Strength
Application: Heavy-load structures
Key Alloy Elements (GB/T 4171)
Cu: 0.25-0.55% | Cr: 0.40-0.80% | Ni: ≤0.65%

Q415NH

Yield Strength: ≥415 MPa
Strength Level: Ultra High Strength
Application: Ultra-heavy duty infrastructure
Key Alloy Elements (GB/T 4171)
Cu: 0.25-0.55% | Cr: 0.30-1.25% | Ni: ≤0.65%

Q460NH

Yield Strength: ≥460 MPa
Strength Level: Extreme High Strength
Application: Extreme heavy-load structures
Key Alloy Elements (GB/T 4171)
Cu: 0.25-0.55% | Cr: 0.40-0.80% | 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.
✔ Q415NH provides the optimal balance for most heavy-load engineering projects.

International Equivalent Grades

ISO 4952:2006
S415W
Chemical elements (typical):
C ≤0.16% | Si 0.10-0.50% | Mn 0.50-1.50%
Cu 0.25-0.55% | Cr 0.40-0.80% | Ni ≤0.65%
ASTM A871M-03
Grade 60 (415)
Chemical elements (typical):
C ≤0.15% | Si 0.15-0.50% | Mn ≤1.25%
Cu 0.20-0.40% | Cr 0.40-0.80% | Ni ≤0.40%

Chemical Composition (GB/T 4171)

Grade C Si Mn P S Cu Cr Ni Others*
Q415NH ≤0.12 ≤0.65 ≤1.10 ≤0.025 ≤0.030 0.25-0.55 0.30-1.25 ≤0.65 ①,②
📌 Notes on chemical composition:
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; total Nb+V+Ti ≤0.22%.
② Optional: Mo ≤0.30%, Zr ≤0.15% may be added by agreement. Also Ni lower limit may be waived.
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.

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
Q415NH 415 405 395 — 520 – 680 22 22 20 — a 2a 3a
415/405/395 = Yield strength by thickness (MPa) — = not applicable for >60mm 520-680 = 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.

415
Min Yield (MPa) ≤16mm
520-680
Tensile Rm (MPa)
22%
Elongation A (≤40mm)
0.25-0.55
Copper Cu %

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)
  • 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
Stock availability: Regular sizes in stock for quick delivery | Mill order: Custom sizes available with 20-35 days lead time

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

Engineering Support: Free CAD assistance, nesting optimization, technical consultation

Advantages & Typical Applications

Key Advantages

  • Ultra-high strength design, higher load capacity than Q355NH
  • Excellent weathering and corrosion resistance
  • 2-8x corrosion resistance vs carbon steel
  • Good weldability and cold forming properties
  • No painting required, reduces lifecycle costs

Typical Applications

  • Heavy-duty bridges & steel structures
  • Railway rolling stock & large containers
  • Transmission towers & high-load infrastructure
  • Engineering machinery & vehicle frames
  • Architectural structures & outdoor heavy-duty facilities

Frequently Asked Questions (FAQ)

1. What does "NH" mean in Q415NH?
2. What is the difference between Q415NH and Q355NH?
3. What is the difference between Q415NH and Q460NH?
4. What are the international equivalents of Q415NH?
5. Is Q415NH suitable for heavy structural use?

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
  • 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 Q415NH Project

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