Q460NH Weathering Steel Pipe
Q460NH Weathering Steel Pipe: High-Strength Atmospheric Corrosion Resistant Grade (GB/T 4171)
Detailed material data and technical properties for Q460NH weathering steel pipe according to GB/T 4171, including chemistry, mechanical performance, thermal properties and international equivalents.
Hot rolling, normalizing, cold forming, welding, machining
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Q460NH Weathering Steel Pipe Introduction
GB/T 4171 Q460NH is a high-strength, weldable, atmospheric corrosion-resistant structural steel (weathering steel) with a minimum yield strength of 460 MPa. It is designed for use in load-bearing structures such as bridges, buildings, towers, and containers, where it develops a protective rust patina that significantly reduces maintenance. Its optimized Cu-Cr-Ni alloying ensures superior resistance to atmospheric corrosion compared to ordinary carbon steel, and optional micro-alloying elements (Nb, V, Ti) enhance grain refinement and toughness. The grade is typically supplied in hot-rolled or normalized condition and is suitable for welded, bolted, and riveted connections.
Q460NH Weathering Steel Pipe Chemical composition according to GB/T 4171-2008
The chemical composition of Q460NH is tightly controlled to provide a balance of strength, toughness, and atmospheric corrosion resistance. Copper, chromium, and nickel are the primary alloying elements that promote the formation of a dense, protective oxide layer. Micro-alloying elements such as niobium, vanadium, and titanium may be added singly or in combination to refine the grain structure and improve mechanical properties. The total content of these grain-refining elements shall not exceed 0.22%. Aluminum may optionally be added for deoxidation and grain refinement, with a required minimum total aluminum content of 0.020% if used.
| Element | Required value (%) | Remarks |
|---|---|---|
| C | ≤0.12 | |
| Si | ≤0.50 | |
| Mn | ≤1.50 | |
| P | ≤0.030 | |
| S | ≤0.030 | |
| Cu | 0.20~0.55 | |
| Cr | 0.30~1.25 | |
| Ni | 0.12~0.65 | |
| Nb+V+Ti | Sum ≤0.22 (at least one element ≥0.015 if added) | Optional grain-refining elements |
| Al (total) | ≥0.020 (if added) | Optional; used for deoxidation and grain refinement |
| Mo, Zr, RE, etc. | Negotiable | May be added upon agreement; RE ≤0.12% if used |
Q460NH Weathering Steel Pipe Thermal and electrical physical properties
The following physical properties are typical for Q460NH weathering steel and are not normative requirements of GB/T 4171. They are based on data for similar low-alloy structural steels and may vary slightly with exact composition, heat treatment, and manufacturing process. These values are intended for general engineering calculations at room temperature unless otherwise noted.
| Property | Typical value | Unit | Condition / Temperature |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20 °C |
| Elastic modulus (E) | 200~210 | GPa | 20 °C |
| Shear modulus (G) | ≈80 | GPa | 20 °C |
| Poisson's ratio (ν) | 0.3 | - | 20 °C |
| Thermal expansion coefficient (α) | 11×10⁻⁶ | K⁻¹ | 20~100 °C |
| Thermal conductivity (λ) | ≈45 | W/(m·K) | 20 °C |
| Specific heat capacity | ≈460 | J/(kg·K) | 20 °C |
| Electrical resistivity (ρₑ) | 0.25×10⁻⁶ | Ω·m | 20 °C |
Q460NH Weathering Steel Pipe Mechanical properties
The mechanical properties of Q460NH depend on the product thickness. The values below represent the minimum requirements for hot-rolled products. For thicknesses beyond 100 mm, properties shall be agreed upon at the time of ordering. The impact test is carried out on Charpy V-notch specimens at -20 °C in longitudinal direction. Bending test is performed over a 180° angle with the specified mandrel diameter depending on the thickness.
| Property | Required value | Unit | Test condition / Thickness range |
|---|---|---|---|
| Yield strength (ReH) | ≥460 | MPa | t ≤ 16 mm |
| Yield strength (ReH) | ≥450 | MPa | 16 < t ≤ 40 mm |
| Yield strength (ReH) | ≥430 | MPa | 40 < t ≤ 63 mm |
| Yield strength (ReH) | ≥410 | MPa | 63 < t ≤ 80 mm |
| Yield strength (ReH) | ≥400 | MPa | 80 < t ≤ 100 mm |
| Tensile strength (Rm) | 570~720 | MPa | All thicknesses (t ≤ 100 mm) |
| Elongation (A) | ≥20 | % | t ≤ 16 mm |
| Elongation (A) | ≥19 | % | 16 < t ≤ 40 mm |
| Elongation (A) | ≥18 | % | 40 < t ≤ 63 mm |
| Elongation (A) | ≥17 | % | 63 < t ≤ 80 mm |
| Elongation (A) | ≥16 | % | 80 < t ≤ 100 mm |
| Bend test (180°) | d = 2a | - | t ≤ 16 mm (a = test piece thickness) |
| Bend test (180°) | d = 3a | - | 16 < t ≤ 40 mm |
| Bend test (180°) | d = 4a | - | 40 < t ≤ 63 mm |
| Bend test (180°) | d = 5a | - | 63 < t ≤ 80 mm |
| Bend test (180°) | d = 6a | - | 80 < t ≤ 100 mm |
| Impact energy (KV₂) | ≥40 | J | Longitudinal, -20 °C (Charpy V-notch) |
Q460NH Weathering Steel Pipe Equivalent material designations – directly corresponding grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 4171-2008 | Q460NH | Original Chinese standard grade |
| Europe | EN 10025-5:2004 | S460W (1.8963) | Similar chemical basis and minimum yield strength; confirm exact composition and toughness requirements |
| Japan | JIS G3114 | SMA570W | Weathering steel with matching strength level; slight differences in Cr, Ni ranges |
Q460NH Weathering Steel Pipe Application Introduction
Q460NH weathering steel pipe is optimal for applications where long-term atmospheric exposure is expected and reduced maintenance is desired. The controlled rust patina develops after alternating wet/dry cycles and protects the underlying steel from further significant corrosion. It can be readily fabricated by welding, bolting, and cold-forming. Preheating may be required for thick sections when welding. The grade is suitable for both interior and exterior structural members.
Product Applications: Weathering steel pipes for structural columns and trusses, Welded bridge girders and box sections, Railway wagon frames and panels, Corrosion-resistant industrial piping, Architectural cladding and sculptures, High-strength bolted/riveted assemblies
Processed into products: Bridge piers, cross beams, and deck frames, Pipe trusses and space frames, Transformer tanks and capacitor enclosures, Exhaust stacks and flue ducts, Lighting poles and antenna towers, Support brackets and brackets for outdoor equipment
Application industries: Civil engineering and infrastructure, Bridge construction, Building and construction (high-rise, stadiums, facades), Railway and transportation, Energy (wind towers, transmission poles), Container and shipping, Industrial ducting and stacks
Q460NH Weathering Steel Pipe Similar / alternative weathering steel grades with comparable performance
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10025-5 | S460J0W / S460J2W | Identical strength; toughness class varies (J0: 0°C, J2: -20°C). Q460NH corresponds to -20°C rating |
| USA | ASTM A709/A709M | HPS 70W | High-performance weathering steel, 485 MPa yield; may be suitable after strength adjustment |
| International | ISO 4952 | Fe 46W | ISO weathering structural steel; 460 MPa yield category, compositional variations may apply |
| India | IS 11587 | Fe 460W | Indian weathering standard; similar strength and corrosion resistance |
Notes:
Welding: Q460NH has good weldability with low-carbon equivalent design. Preheating (typically 100-150°C) may be beneficial for sections thicker than 30 mm to avoid cold cracking. Use matching weathering steel consumables to ensure uniform corrosion behaviour.
Surface finish: The protective patina requires a clean surface free of mill scale and contaminants to develop uniformly.
Availability: Tubular products are commonly supplied as hot-finished seamless or welded pipes; dimensions and tolerances according to relevant product standards (e.g., GB/T 8162 for structural pipes).
Corrosion guidelines: Not recommended for continually wet or buried applications without additional protection. In marine atmospheres, performance may be enhanced by higher Ni content variants (consult producer).
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