Q310GNH Atmospheric Corrosion Resistant Weathering Steel Plate

GB/T 4171 | High Weathering Steel with 310 MPa Minimum Yield Strength

What is Q310GNH Weathering Steel?

Q310GNH is a Chinese-grade structural weathering steel standardized under GB/T 4171. The "GNH" stands for "Gao Nai Hou" (高耐候), meaning "high weathering resistance". This grade features enhanced phosphorus content (0.07-0.12%) which significantly improves atmospheric corrosion resistance. Q310GNH forms a dense, stable, and adherent protective patina layer when exposed to cyclic wet/dry atmospheric conditions, providing superior corrosion resistance while offering higher strength than Q265GNH and maintaining good formability and weldability.

Decoding the Grade: Q310GNH

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.
310 Minimum Yield Strength — Guarantees a minimum yield strength of 310 MPa (for thickness ≤16mm).
G High Weathering — "Gao" (高) indicates enhanced weathering resistance with higher phosphorus content.
NH Weathering Quality Grade — "Nai Hou" (耐候) indicates atmospheric corrosion resistance with alloying elements (Cu, Cr, Ni, P) enabling patina formation.

Domestic Grades Comparison

Q265GNH

Yield Strength: ≥265 MPa
P Content: 0.07-0.12%
Application: Light weathering structures
Key Alloy Elements (GB/T 4171)
Cu: 0.20-0.45% | Cr: 0.30-0.65% | Ni: 0.25-0.50%

Q310GNH

Yield Strength: ≥310 MPa
P Content: 0.07-0.12% (enhanced)
Application: Medium weathering structures
Key Alloy Elements (GB/T 4171)
Cu: 0.20-0.45% | Cr: 0.30-1.25% | Ni: ≤0.65%

Q295GNH

Yield Strength: ≥295 MPa
P Content: 0.07-0.12%
Application: Medium-load weathering structures
Key Alloy Elements (GB/T 4171)
Cu: 0.20-0.45% | Cr: 0.30-0.65% | Ni: 0.25-0.50%

Core Characteristics:
✔ All three GNH grades feature enhanced phosphorus content (0.07-0.12%) for superior atmospheric corrosion resistance.
✔ The "G" designation indicates "Gao Nai Hou" (高耐候) meaning high weathering resistance.
✔ Q310GNH offers higher strength than Q265GNH while maintaining excellent weathering performance.

International Equivalent Grades

JIS G3125:2004
SPA-C
Chemical elements (typical):
C ≤0.12% | Si 0.25-0.75% | Mn ≤0.60%
P 0.07-0.12% | S ≤0.025%
Cu 0.25-0.55% | Cr 0.30-1.25% | Ni ≤0.65%
ASTM A606-04
Type 4
Chemical elements (typical):
C ≤0.12% | Si 0.25-0.75% | Mn ≤1.00%
P 0.07-0.12% | S ≤0.030%
Cu 0.20-0.55% | Cr 0.30-1.25% | Ni ≤0.65%

Chemical Composition (GB/T 4171)

Grade C Si Mn P S Cu Cr Ni Others*
Q310GNH ≤0.12 0.25-0.75 0.20-0.50 0.07-0.12 ≤0.020 0.20-0.45 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.
③ Permissible deviations for product analysis according to GB/T 222. Sulphur can be agreed ≤0.008%.
④ Through negotiation, Ni lower limit may be waived, or C ≤0.15% upon request.
⑤ 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
Q310GNH 310 — — — ≥450 26 — — — a — —
310 = Yield strength (MPa) for ≤16mm only — = not applicable for other thicknesses ≥450 = Tensile strength (min) (MPa) a = Bending mandrel diameter for ≤6mm only (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.

310
Min Yield (MPa) ≤16mm
≥450
Tensile Rm (MPa) min
26%
Elongation A (≤16mm)
0.07-0.12
Phosphorus P %

Available Supply Range

Thickness Range

  • Hot-rolled plates: 2mm - 16mm
  • Sheets / Coils: 1.5mm - 16mm
  • 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

  • Enhanced phosphorus content for superior weathering resistance
  • Higher strength than Q265GNH for demanding applications
  • High elongation (26%) for good ductility
  • Good weldability with standard processes
  • No painting required, reduces lifecycle costs
  • Forms dense protective patina naturally

Typical Applications

  • Railway rolling stock & containers
  • Bridges & highway structures
  • Industrial buildings & transmission towers
  • Architectural cladding & roofing
  • Outdoor sculptures & art installations

Frequently Asked Questions (FAQ)

1. What does "GNH" mean in Q310GNH?
2. What is the difference between Q310GNH and Q265GNH?
3. What are the international equivalents of Q310GNH?
4. Does Q310GNH require painting?
5. Is Q310GNH weldable?

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 Q310GNH Project

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