GB/T 4171 Q500NH Weather Resistant Steel Coil
GB/T 4171 Q500NH Weather Resistant Steel Coil: Superior Atmospheric Corrosion Resistance & High Strength
Q500NH is a high-strength atmospheric corrosion-resistant structural steel under Chinese standard GB/T 4171, designed for welded, bolted, and riveted structures in unpainted or conditionally painted applications.
Hot rolling, cold forming, welding, gas cutting, machining
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GB/T 4171 Q500NH Weather Resistant Steel Coil Introduction
Q500NH is a high-strength low-alloy structural steel with improved atmospheric corrosion resistance, specified in GB/T 4171 (Weather Resistant Structural Steel). With a minimum yield strength of 500 MPa, it is widely used in bridges, buildings, railway vehicles, and containers exposed to the weather. Its enhanced corrosion resistance is achieved through the addition of alloying elements such as copper, chromium, and nickel, which form a dense, protective oxide layer under alternate wet and dry conditions.
- Excellent weldability and formability.
- Good low-temperature toughness (KV2 >= 34 J at -20°C).
- Available as hot-rolled coils, plates, and strips.
GB/T 4171 Q500NH Weather Resistant Steel Coil Chemical Composition
Chemical composition according to the ladle analysis of GB/T 4171 for Q500NH grade. All values are maximum unless a range is indicated.
- Carbon equivalent (CEV) is typically controlled to ensure weldability.
- Residual elements V, Nb, Ti, etc. may be added for grain refinement.
| Element | Specified Value (%) | Remarks |
|---|---|---|
| C (Carbon) | ≤ 0.12 | |
| Si (Silicon) | ≤ 0.50 | |
| Mn (Manganese) | ≤ 1.50 | |
| P (Phosphorus) | ≤ 0.030 | |
| S (Sulfur) | ≤ 0.030 | |
| Cu (Copper) | 0.25 – 0.55 | Key for atmospheric corrosion resistance |
| Cr (Chromium) | 0.30 – 1.25 | Enhances corrosion resistance |
| Ni (Nickel) | ≤ 0.65 | Improves toughness and weathering |
| Nb (Niobium) | 0.015 – 0.060 | Grain refiner |
| V (Vanadium) | 0.02 – 0.12 | Strengthening element |
| Ti (Titanium) | 0.02 – 0.10 | Grain refiner and strengthener |
| Mo (Molybdenum) | ≤ 0.30 | Optional |
| Al (Aluminum) | ≥ 0.020 | Deoxidizer |
| CEV (Carbon Equivalent) | Typically ≤ 0.50 | Depending on thickness and supplier |
GB/T 4171 Q500NH Weather Resistant Steel Coil Thermal and Electrical Physical Properties
Typical physical properties for Q500NH steel at ambient temperature unless otherwise indicated. These values are not mandatory by the standard but serve as engineering references. Variations may occur depending on the actual chemical composition and heat treatment.
- Density is comparable to that of plain carbon steel.
- Thermal conductivity decreases slightly with increasing alloy content.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20 °C |
| Modulus of Elasticity (E) | 207 | GPa | Room temperature |
| Shear Modulus (G) | 80 | GPa | Room temperature |
| Poisson's Ratio (ν) | 0.30 | — | Room temperature |
| Thermal Expansion Coefficient (α) | 11.5 | 10⁻⁶/K | 20 – 100 °C |
| Thermal Expansion Coefficient (α) | 12.2 | 10⁻⁶/K | 20 – 200 °C |
| Thermal Expansion Coefficient (α) | 13.0 | 10⁻⁶/K | 20 – 400 °C |
| Thermal Conductivity (λ) | 42 | W/(m·K) | 20 °C |
| Specific Heat Capacity | 460 | J/(kg·K) | 20 °C |
| Electrical Resistivity (ρ_e) | 0.25 | μΩ·m | 20 °C |
GB/T 4171 Q500NH Weather Resistant Steel Coil Mechanical Properties
Mechanical properties as required by GB/T 4171 for Q500NH. Values depend on product thickness. ReH = upper yield strength or Rp0.2 = 0.2% proof strength where applicable. Tensile test specimens are transverse. Impact test is Charpy V-notch for longitudinal specimens.
- Minimum elongation is based on a gauge length of 5.65√S0 (proportional test piece).
- Bending test (d = mandrel diameter, a = specimen thickness).
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH/Rp0.2) | ≥ 500 | MPa | Thickness ≤ 16 mm |
| Yield Strength (ReH/Rp0.2) | ≥ 470 | MPa | 16 < Thickness ≤ 40 mm |
| Yield Strength (ReH/Rp0.2) | ≥ 450 | MPa | 40 < Thickness ≤ 63 mm |
| Tensile Strength (Rm) | 600 – 760 | MPa | Thickness ≤ 63 mm |
| Elongation (A) | ≥ 15 | % | Thickness ≤ 16 mm, L0 = 5.65√S0 |
| Elongation (A) | ≥ 14 | % | 16 < Thickness ≤ 40 mm |
| Elongation (A) | ≥ 13 | % | 40 < Thickness ≤ 63 mm |
| Impact Energy (KV2) | ≥ 34 | J | Longitudinal, -20 °C |
| Bend Test | d = 3a (t ≤ 16 mm) | — | 180° bend, no cracks |
| Bend Test | d = 4a (16 < t ≤ 40 mm) | — | 180° bend, no cracks |
GB/T 4171 Q500NH Weather Resistant Steel Coil Exact Equivalent Material Standards & Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 4171 | Q500NH | Original specification and grade |
| International | ISO 4952 (Cancelled) | — | No current ISO equivalent exists |
| Europe | EN 10025-5 | — | Highest strength grade is S460J0WP/J2WP, no direct 500 MPa grade |
| USA | ASTM A709 / A588 | — | Grades such as 50W (345 MPa) are lower strength |
GB/T 4171 Q500NH Weather Resistant Steel Coil Application Introduction
Q500NH steel is engineered for load-bearing structures exposed to the atmosphere. Its combination of high strength and good weldability makes it suitable for heavy structural applications. It can be used bare (unpainted) if the environment and design details allow for the formation of a stable patina, or with conventional coating systems.
- Designers must account for the slightly reduced corrosion rate after the protective oxide layer stabilises.
- Precautions are required when welding thick sections, and low-hydrogen processes are recommended.
Product Applications: Weather-resistant bridge girders and trusses, High-strength structural frames for buildings, Railway freight car bodies and underframes, ISO shipping containers and swap bodies, Lattice transmission towers and poles, Outdoor sculptures and architectural cladding
Processed into products: Welded bridge box girders and crossbeams, Bolted structural connections and splice plates, Cold-formed stiffeners and purlins, Cut and welded brackets and supports, Flanges and webs for plate girders, Formed automotive chassis rails, Container corner posts and rails
Application industries: Bridge Construction, Construction & Civil Engineering, Railway Vehicle Manufacturing, Container & Shipbuilding Industry, Energy & Transmission Towers, Outdoor Machinery & Equipment
GB/T 4171 Q500NH Weather Resistant Steel Coil Similar / Alternative Materials Recommendation
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 4171 | Q460NH | Next lower strength class, yield 460 MPa, similar weathering characteristics |
| Europe | EN 10025-4 | S460M/ML | Thermomechanical rolled fine-grain structural steel, no explicit weathering guarantee, but similar strength |
| Europe | EN 10025-5 | S355J2W+N | Typical weathering steel (Corten B equivalent), significantly lower strength |
| Japan | JIS G 3114 | SMA570W | Superior atmospheric corrosion resisting rolled steel, min yield 460 MPa, close but not identical |
| USA | ASTM A709 | HPS 70W | High performance steel with weathering, min yield 485 MPa, close strength level |
Notes:
Welding: Q500NH can be welded by common methods (SMAW, GMAW, SAW) with low-hydrogen consumables suitable for the strength level. Preheating may be necessary for thicker sections (e.g., > 30 mm) to avoid cold cracking. Weathering performance: The atmospheric corrosion resistance is approximately 2-8 times that of plain carbon steel, depending on environment and proper alternate wetting/drying cycles. In marine or heavily industrial atmospheres, salt deposition may hinder the formation of a protective patina, and painting may be required. Availability: Typically supplied as hot-rolled coil with thicknesses from 1.5 mm to 20 mm, but plate up to 60 mm can be available. Contact your supplier for the latest datasheet and guaranteed property ranges.
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