Q415NH Weathering Steel Plate
Q415NH Weather Resistant Steel Plate - GB/T 4171 High Strength Structural Grade
Detailed material data for Q415NH weather resistant steel plate according to China GB/T 4171 standard. Includes chemical composition, mechanical properties, thermal and electrical physical performance, equivalent grades and application guidance.
Hot rolling, normalizing, normalizing rolling, cold forming (for light gauge)
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Q415NH Weathering Steel Plate Introduction
Q415NH is a high-strength low-alloy structural steel specified in GB/T 4171-2008 "Weathering structural steel". It is designed for superior atmospheric corrosion resistance through the addition of copper, chromium, and nickel. The steel forms a dense, protective oxide layer when exposed to the atmosphere, eliminating the need for painting in many environments. With a minimum yield strength of 415 MPa for thinner sections, it offers a balance of strength, toughness, and weldability. Key features:
- Excellent corrosion resistance in atmospheric conditions
- High strength reduces structural weight
- Good weldability and cold forming capability
- Available in hot-rolled, normalized or normalizing rolled condition
Q415NH Weathering Steel Plate Chemical Composition
The chemical composition of Q415NH is designed to provide a stable protective rust layer. Copper, chromium and nickel are the key alloying elements that enhance atmospheric corrosion resistance. Low carbon content ensures good weldability, while manganese contributes to strength. Phosphorus and sulfur are kept low for toughness and cleanliness. Trace elements such as niobium, vanadium or titanium may be added for grain refinement.
| Chemical Element | Standard Value | Remarks |
|---|---|---|
| Carbon (C) | ≤0.12 | Ladle analysis |
| Silicon (Si) | 0.20-0.50 | Ladle analysis |
| Manganese (Mn) | 0.60-1.00 | Ladle analysis |
| Phosphorus (P) | ≤0.025 | Ladle analysis |
| Sulfur (S) | ≤0.020 | Ladle analysis |
| Copper (Cu) | 0.20-0.50 | Essential for corrosion resistance |
| Chromium (Cr) | 0.40-0.80 | Promotes passivation layer |
| Nickel (Ni) | 0.25-0.50 | Improves toughness and weathering |
| Others | Negotiable | Microalloying elements (Nb, V, Ti) may be added as agreed |
Q415NH Weathering Steel Plate Thermal and Electrical Physical Properties
These physical properties are typical for Q415NH steel at room temperature unless otherwise stated. They can be used for engineering calculations of heat transfer, thermal expansion, and electrical resistance. Note: Values may vary with temperature; thermal conductivity decreases and specific heat increases with rising temperature. Actual performance should be verified for critical designs.
| Property | Standard Requirement Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20°C |
| Modulus of elasticity (E) | 206 | GPa | 20°C |
| Shear modulus (G) | 79.3 | GPa | 20°C |
| Poisson's ratio (ν) | 0.3 | — | 20°C |
| Thermal expansion coefficient (α) | 12.2 | 10⁻⁶/K | 20~100°C |
| Thermal expansion coefficient (α) | 12.8 | 10⁻⁶/K | 20~200°C |
| Thermal expansion coefficient (α) | 13.5 | 10⁻⁶/K | 20~400°C |
| Thermal conductivity (λ) | 42 | W/(m·K) | 100°C |
| Specific heat capacity (cp) | 460 | J/(kg·K) | 20°C |
| Electrical resistivity (ρe) | 0.22 | μΩ·m | 20°C |
Q415NH Weathering Steel Plate Mechanical Properties
Mechanical properties are guaranteed for the delivery condition and tested in accordance with GB/T 228.1. The yield strength and tensile strength depend on product thickness. Impact energy is measured on longitudinal Charpy V-notch specimens at -20°C. Key points:
- Excellent strength-to-weight ratio
- Good ductility for forming and bending
- Guaranteed low-temperature toughness
| Property | Standard Requirement Value | Unit | Test Condition |
|---|---|---|---|
| Upper yield strength (ReH) | ≥415 | MPa | Thickness ≤16 mm |
| Upper yield strength (ReH) | ≥405 | MPa | Thickness >16 mm ≤40 mm |
| Upper yield strength (ReH) | ≥395 | MPa | Thickness >40 mm ≤60 mm |
| Upper yield strength (ReH) | ≥385 | MPa | Thickness >60 mm ≤80 mm |
| Upper yield strength (ReH) | ≥375 | MPa | Thickness >80 mm ≤100 mm |
| Upper yield strength (ReH) | ≥365 | MPa | Thickness >100 mm ≤150 mm |
| Tensile strength (Rm) | 520-680 | MPa | All thicknesses |
| Elongation after fracture (A) | ≥22 | % | Thickness ≤16 mm, L0 = 5.65√S0 |
| Elongation after fracture (A) | ≥22 | % | Thickness >16 mm ≤40 mm |
| Elongation after fracture (A) | ≥21 | % | Thickness >40 mm ≤60 mm |
| Elongation after fracture (A) | ≥20 | % | Thickness >60 mm ≤80 mm |
| Elongation after fracture (A) | ≥20 | % | Thickness >80 mm ≤100 mm |
| Elongation after fracture (A) | ≥19 | % | Thickness >100 mm ≤150 mm |
| Bend test (180°) | d = a | — | Thickness ≤16 mm |
| Bend test (180°) | d = 2a | — | Thickness >16 mm ≤100 mm |
| Bend test (180°) | d = 3a | — | Thickness >100 mm ≤150 mm |
| Charpy V-notch impact energy (KV2) | ≥34 | J | Longitudinal, -20°C |
Q415NH Weathering Steel Plate Fully Equivalent Material Standards & Recommended Substitute Grades
Q415NH has no exact duplicate in international standards, but the European grade S420W offers comparable atmospheric corrosion resistance and strength. Substitutions should consider delivery condition and impact test temperature.
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| European Union | EN 10025-5:2004 | S420W | Similar strength and weathering resistance; verify toughness for -20°C requirement |
| International | ISO 4952:2006 | S420W | Identical to EN 10025-5 version |
| Japan | JIS G 3114:2008 | SMA490AW | Lower yield strength (≥355 MPa), not fully equivalent; can be used for less demanding applications |
Q415NH Weathering Steel Plate Application Introduction
Q415NH is ideal for load-bearing structures exposed to the atmosphere without protective paint systems. Its superior corrosion resistance allows for a "rust-through" design approach, reducing maintenance costs over the lifetime. Common uses include:
Product Applications: Weathering steel bridge girders and beams, Unpainted architectural facades and sculptures, ISO shipping container panels and frames, Structural members for railway coaches and wagons, High-strength welded sections for transmission towers
Processed into products: Main girders and cross-beams, Truss chords and diagonals, Welded box columns, Brackets, stiffeners and splice plates, Bogie frames and bolster assemblies
Application industries: Bridge engineering, Architecture and building construction, Railway vehicle manufacturing, Container production, Power transmission towers and poles, Mining and earth-moving equipment
Q415NH Weathering Steel Plate Similar / Alternative Material Recommendations
These grades belong to the same high-strength weathering steel family and can be considered for applications where small adjustments in strength or chemistry are acceptable.
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 4171-2008 | Q355NH | Lower strength (≥355 MPa), widely used; easier forming |
| China | GB/T 4171-2008 | Q460NH | Higher strength (≥460 MPa), for weight-critical structures |
| USA | ASTM A588/A588M | Grade A | Yield strength 345 MPa, widely used in North America; higher Cr content |
| USA | ASTM A588/A588M | Grade B | Yield strength 345 MPa, similar weathering concept |
| India | IS 11587 | Fe 410 WA | Equivalent to S355 level, not identical strength |
Notes:
Welding: Use low-hydrogen practices and matching weathering steel filler metals (e.g., AWS E80C-Ni1 or similar) to maintain corrosion resistance. Surface preparation: For exposed applications, a uniform patina develops after 6-18 months; blasting or pickling may accelerate stabilization. Service environment: Not recommended for continuous immersion in water or exposure to high chloride concentrations without additional protection. Mechanical properties in this table refer to longitudinal specimens unless stated otherwise. All values are based on GB/T 4171-2008; for specific projects, mill certificates should be provided.
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