Q295GNH Atmospheric Corrosion Resistant Weathering Steel Plate

GB/T 4171 | High Weathering Steel with 295 MPa Minimum Yield Strength

What is Q295GNH Weathering Steel?

Q295GNH 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". Compared to standard Q295NH, Q295GNH features enhanced phosphorus content (0.07-0.12%) which significantly improves atmospheric corrosion resistance. This steel forms a dense, stable, and adherent protective patina layer when exposed to cyclic wet/dry atmospheric conditions, providing superior corrosion resistance while maintaining good weldability and formability.

Decoding the Grade: Q295GNH

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.
295 Minimum Yield Strength — Guarantees a minimum yield strength of 295 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

Q235NH

Yield Strength: ≥235 MPa
P Content: ≤0.030%
Application: General structural use
Key Alloy Elements (GB/T 4171)
Cu: 0.25-0.55% | Cr: 0.40-0.80% | Ni: ≤0.65%

Q295GNH

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

Q295NH

Yield Strength: ≥295 MPa
P Content: ≤0.030%
Application: Medium-load structures
Key Alloy Elements (GB/T 4171)
Cu: 0.25-0.55% | Cr: 0.40-0.80% | Ni: ≤0.65%

Core Characteristics:
✔ Q295GNH features 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.
✔ Q295GNH offers higher strength than Q235NH with improved weathering performance.

Chemical Composition (GB/T 4171)

Grade C Si Mn P S Cu Cr Ni Others*
Q295GNH ≤0.12 0.10-0.40 0.20-0.50 0.07-0.12 ≤0.020 0.20-0.45 0.30-0.65 0.25-0.50 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
Q295GNH 295 285 — — 430 – 560 24 24 — — a 2a 3a
295/285 = Yield strength by thickness (MPa) — = not applicable for >40mm 430-560 = 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.

295
Min Yield (MPa) ≤16mm
430-560
Tensile Rm (MPa)
24%
Elongation A (≤40mm)
0.07-0.12
Phosphorus P %

Available Supply Range

Thickness Range

  • Hot-rolled plates: 2mm - 40mm
  • 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

  • Enhanced phosphorus content for superior weathering resistance
  • Higher strength than Q235NH
  • Excellent atmospheric corrosion resistance
  • Good weldability and formability
  • No painting required, reduces lifecycle costs
  • Forms dense protective patina naturally

Typical Applications

  • Railway rolling stock & containers
  • Bridges & highway structures
  • Industrial buildings & transmission towers
  • Outdoor sculptures & architectural facades
  • Engineering machinery & vehicle frames

Frequently Asked Questions (FAQ)

1. What does "GNH" mean in Q295GNH?
2. What is the difference between Q295GNH and Q295NH?
3. What is the difference between Q295GNH and Q235NH?
4. Does Q295GNH require painting?
5. Is Q295GNH 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 Q295GNH Project

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