Q235NH Atmospheric Corrosion Resistant Weathering Steel Plate
🛡️ Patina-Forming Steel with 235 MPa Minimum Yield Strength & Enhanced Durability
What is Q235NH Weathering Steel?
Q235NH is a Chinese-grade structural weathering steel standardized under GB/T 4171. The "NH" stands for "Nai Hou" (耐候), directly translating to "weather resistance". With a minimum yield strength of 235 MPa, Q235NH is the most widely used grade in the weathering steel family, offering an excellent balance of strength, weldability, and corrosion resistance. It forms a dense, stable, and adherent rust layer (the patina) under cyclic wet/dry conditions, providing 2 to 8 times the atmospheric corrosion resistance of standard carbon steel. This grade is the smart choice for structures where longevity and minimal maintenance are paramount, often eliminating the need for paint systems altogether.
Decoding the Grade: Q235NH
The naming follows the Chinese steel grade system, where each part reveals key performance characteristics:
Core Value Proposition
Q235NH delivers exceptional lifecycle cost savings by merging structural integrity with built-in corrosion protection. It's engineered for projects where aesthetics meet endurance, providing a robust, low-maintenance material solution for a wide range of applications.
Your Partner for Weathering Steel Supply
We are a professional Chinese supplier offering Q235NH weathering steel plates, sheets, and sections for global projects. We provide mill-direct ordering with full traceability and support the entire export process, ensuring you receive material that meets both GB/T 4171 and your specific project requirements.
Start Your Q235NH Project
We offer flexible procurement options for Q235NH, from technical consultation to reliable delivery. Benefit from competitive pricing, strict quality adherence to GB/T 4171, and dedicated support for your international project needs.
✓ Formal quotation within 8-12 hours
✓ Full technical data & mill certificates
✓ Export documentation support
Standards & International Comparisons
Q235NH is specified under the Chinese National Standard GB/T 4171 "Weathering Structural Steels". While direct, chemically identical equivalents in other standards are rare due to differing numbering systems, Q235NH is functionally comparable to several internationally recognized weathering steel grades, offering similar performance characteristics for atmospheric corrosion resistance.
Comparison with Key International Standards
| Standard | Comparable Grade | Key Similarity | Note |
|---|---|---|---|
| GB/T 4171 (China) | Q235NH | Primary reference grade. | Defines chemical composition & mechanical properties. |
| DIN EN 10025-5 (Europe) | S235J0W / S235J2W | Similar yield strength (235 MPa) and weathering principle. | J0/J2 indicates impact toughness temperature. Widely used European weathering steel. |
| ASTM A588 (USA) | Grade A (~345 MPa) | Comparable corrosion resistance profile for structural use. | A588 has higher minimum yield strength (345 MPa). Common US weathering steel spec. |
| JIS G3125 (Japan) | SMA400AW, SMA400BW | Similar weathering performance and application scope. | Japanese high-performance weathering steel for welded structures. |
Important Note: The table indicates functional comparability, not chemical identity. For any project requiring material substitution or governed by specific regional codes, engineers must verify suitability.
Chemical Composition (GB/T 4171)
The specific alloying elements (notably Copper, Chromium, and Nickel) are key to forming the protective patina. The following table details the mandatory and optional composition requirements for Q235NH.
| Grade | Chemical Composition (Quality Fraction)/% | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| C | Si | Mn | P | S | Cu | Cr | Ni | others | ||
| Q235NH | ≤0.13 | 0.1 ~ 0.4 | 0.2 ~ 0.6 | ≤0.03 | ≤0.03 | 0.25 ~ 0.55 | 0.40 ~ 0.8 | ≤0.65 | a , b | |
| Notes: ᵃ To improve properties, trace alloying elements may be added: Nb 0.015%~0.060%, V 0.02%~0.12%, Ti 0.02%~0.10%, Alt ≥0.020%. When used in combination, at least one element should meet lower limit. ᵇ The following alloying elements can be added: Mo≤0.30%, Zr≤0.15%. ᶜ Total amount of Nb+V+Ti ≤0.22%. ᵈ Through negotiation, S ≤0.008%. ᵉ Through negotiation, Ni lower limit may not be required. ᶠ Through negotiation, C may not exceed 0.15%. |
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Production & Delivery (Based on GB/T 4171)
Smelting Methods: The steel is smelted in a converter or electric furnace and is killed steel. Unless otherwise specified, the smelting method shall be selected by the supplier.
Delivery Status: Hot-rolled steel is delivered in hot-rolled, controlled-rolled, or normalized condition. Steel grades Q460NH, Q500NH, and Q550NH can be delivered in quenched and tempered condition. Cold-rolled steel is generally delivered in annealed condition.
Permissible Deviations: Shall comply with GB/T 222.
Mechanical & Processing Properties
Q235NH provides reliable structural strength combined with good formability and weldability. The mechanical properties vary slightly with plate thickness as detailed below.
| Grade | Tensile Test a | 180° Bending test mandrel diameter | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Lower yield strength ReL ≥ (MPa) | Tensile Strength Rm (MPa) |
Elongation after fracture A/% ≥ | ||||||||||||
| ≤16 | >16~40 | >40~60 | >60 | ≤16 | >16~40 | >40~60 | >60 | ≤6 | >6~16 | >16 | ||||
| Q235NH | 235 | 225 | 215 | 215 | 360 ~ 510 | 25 | 25 | 24 | 23 | a | a | 2a | ||
Note: 'a' represents the steel thickness (in mm). When a yield plateau is not evident, Rp0.2 may be used.
Advantages & Typical Applications
Key Advantages
- Superior Corrosion Resistance: Patina layer provides long-term protection, 2-8x better than carbon steel.
- Low Maintenance & Lifecycle Cost: Eliminates or reduces painting needs, saving on long-term upkeep.
- Aesthetic Appeal: Develops a unique, stable russet-brown patina that blends with natural surroundings.
- Good Weldability & Fabrication: Can be welded, cut, and formed using standard methods.
- Sustainable Choice: Long service life and reduced use of coatings contribute to greener construction.
Typical Applications
- Architectural structures (building facades, roofs, canopies).
- Bridges & highway structures (guardrails, sound barriers).
- Outdoor sculptures & art installations.
- Containers, railway cars, and transmission towers.
- Industrial & agricultural structures exposed to atmosphere.
Frequently Asked Questions (FAQ)
Find quick answers to the most common questions about Q235NH weathering steel. For more detailed inquiries, please don't hesitate to contact us.
"NH" stands for "Nai Hou" (耐候), which is the Chinese term for "weathering resistance" or "atmospheric corrosion resistance." It specifically designates the steel as a weathering steel, meaning it contains alloying elements (primarily Copper, Chromium, and Nickel) that allow it to form a protective, self-healing rust layer (patina) when exposed to the atmosphere.
One of the primary advantages of Q235NH weathering steel is that painting is generally not required for corrosion protection. The steel is designed to form a dense, adherent patina that significantly slows down further corrosion. Painting may be applied for purely aesthetic reasons or in environments with exceptional contamination, but it is not necessary for its core function.
There is no direct, chemically identical equivalent due to different national standards. However, Q235NH is most closely comparable to S235J0W or S235J2W as specified in DIN EN 10025-5. These European grades share the same minimum yield strength (235 MPa) and are designed as weathering steels ("W"). The "J0" or "J2" indicates the impact toughness testing temperature.
Yes, Q235NH has good weldability. Standard welding processes such as Shielded Metal Arc Welding (SMAW), Gas Metal Arc Welding (GMAW/MIG), and Flux-Cored Arc Welding (FCAW) can be used. It is recommended to use welding consumables that match or exceed the strength and corrosion resistance of the base metal. Standard pre-heating and post-weld heat treatment practices for low-alloy steels should be followed, especially for thicker sections.
We offer flexible MOQ options. For standard grades and sizes, typical MOQ starts from 5 metric tons, but we can discuss smaller quantities for trial orders. Lead time depends on product form and quantity. Please contact us for an accurate quotation.
Supply Information
Available Forms
- Plates & Sheets
- Hot-rolled Coils
- Sections (H-beams, I-beams, Channels, Angles)
- Bars
Delivery Condition
- Hot-rolled: As-rolled, controlled-rolled, or normalized.
- Cold-rolled: Generally annealed.
ℹ️ All technical data is based on GB/T 4171 and is for reference. Contact our sales team for a detailed technical consultation.
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