Q295GNH Weather Resistant Steel Coil per GB/T 4171
Q295GNH Weather Resistant Steel: High Durability Against Atmospheric Corrosion
Q295GNH weather resistant steel coil as per GB/T 4171 standard, offering excellent atmospheric corrosion resistance and mechanical properties for structural applications.
Hot rolling, cold forming, welding, cutting, bending
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Q295GNH Weather Resistant Steel Coil per GB/T 4171 Introduction
Q295GNH is a high atmospheric corrosion resistance structural steel specified in Chinese standard GB/T 4171. It is a low alloy steel designed to provide increased resistance to atmospheric corrosion compared to plain carbon steels, achieved by adding specific alloying elements such as copper, chromium, and nickel. The steel develops a stable, protective oxide layer under outdoor exposure, eliminating the need for painting in many applications. With a minimum yield strength of 295 MPa, it combines moderate strength with good weldability, formability, and toughness. Q295GNH is primarily supplied as hot-rolled coils, sheets, and plates. Its enhanced durability makes it ideal for use in bridge structures, railway vehicles, containers, transmission towers, and architectural facades where maintenance-free long life is required.
Q295GNH Weather Resistant Steel Coil per GB/T 4171 Chemical Composition
The chemical composition of Q295GNH is defined in GB/T 4171 to achieve the desired weathering properties. The alloy contains deliberate additions of Cu, Cr, and Ni to promote the formation of a dense, adherent rust layer. Phosphorus is also intentionally elevated to enhance atmospheric corrosion resistance. The composition limits are strictly controlled during steelmaking to ensure consistent performance.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.12 | Maximum |
| Silicon (Si) | 0.10 - 0.40 | Range |
| Manganese (Mn) | 0.20 - 0.55 | Range |
| Phosphorus (P) | 0.07 - 0.12 | Intentional addition for corrosion resistance |
| Sulfur (S) | ≤ 0.020 | Maximum |
| Copper (Cu) | 0.25 - 0.45 | Essential for weathering performance |
| Chromium (Cr) | 0.30 - 0.65 | Enhances protective rust layer |
| Nickel (Ni) | 0.12 - 0.65 | Improves toughness and weathering |
| Other elements | Residual contents as per standard | No intentional addition of microalloying elements |
Q295GNH Weather Resistant Steel Coil per GB/T 4171 Thermal and Electrical Physical Properties
Physical properties of Q295GNH steel are similar to those of low carbon structural steels. These values are typical at room temperature unless otherwise indicated. They are not part of the standard specification but are provided for design reference. Density is assumed for engineering calculations.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20 °C |
| Elastic Modulus (E) | 210 | GPa | At 20 °C |
| Shear Modulus (G) | 81 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.3 | - | Room temperature |
| Thermal Expansion Coefficient (α) | 12.0 × 10⁻⁶ (from 20 to 100 °C) | K⁻¹ | Linear expansion |
| Thermal Expansion Coefficient (α) | 13.0 × 10⁻⁶ (from 20 to 200 °C) | K⁻¹ | Linear expansion |
| Thermal Expansion Coefficient (α) | 13.5 × 10⁻⁶ (from 20 to 300 °C) | K⁻¹ | Linear expansion |
| Thermal Conductivity (λ) | 45 - 50 | W/(m·K) | At 20 °C |
| Specific Heat Capacity | 450 - 480 | J/(kg·K) | At 20 °C |
| Electrical Resistivity (ρ_e) | 0.20 - 0.25 | μΩ·m (Ω·mm²/m) | At 20 °C |
Q295GNH Weather Resistant Steel Coil per GB/T 4171 Mechanical Properties
Mechanical properties for Q295GNH are determined at room temperature in the as-delivered condition. The yield strength and tensile strength values decrease with increasing product thickness. The values below are specified in GB/T 4171 for different thickness ranges. Impact testing is typically performed at 0 °C or -20 °C as agreed.
| Property | Specified Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 295 | MPa | Thickness ≤ 16 mm |
| Yield Strength (ReH) | ≥ 285 | MPa | Thickness >16 mm ≤ 40 mm |
| Yield Strength (ReH) | ≥ 275 | MPa | Thickness >40 mm ≤ 60 mm |
| Yield Strength (ReH) | ≥ 255 | MPa | Thickness >60 mm ≤ 100 mm |
| Tensile Strength (Rm) | 430 - 560 | MPa | Thickness ≤ 100 mm |
| Elongation (A) | ≥ 24 | % | Thickness ≤ 16 mm (gauge L0=5.65√S0) |
| Elongation (A) | ≥ 23 | % | Thickness >16 mm ≤ 40 mm |
| Elongation (A) | ≥ 22 | % | Thickness >40 mm ≤ 60 mm |
| Elongation (A) | ≥ 22 | % | Thickness >60 mm ≤ 100 mm |
| Bend Test (Mandrel diameter) | d = 2a | - | Thickness ≤ 6 mm, 180° bending |
| Bend Test | d = 3a | - | Thickness >6 mm ≤ 16 mm |
| Impact Energy (KV2) | ≥ 27 | J | 0 °C, longitudinal, thickness ≥ 6 mm |
| Impact Energy (KV2) | ≥ 27 | J | -20 °C (optional, by agreement) |
Q295GNH Weather Resistant Steel Coil per GB/T 4171 Direct Equivalent Standards and Replaceable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| International | ISO 4952 | No direct equivalent | ISO 4952 includes Fe355W (S355J0W); strength higher than Q295GNH. |
| Europe | EN 10025-5 | S355J0W / S355J2W | Yield 355 MPa, higher than Q295GNH; can be considered for replacement after strength check. |
| USA | ASTM A588 / A709 | Grade A / B / C / 50W | Higher strength (345 MPa); A242 Type 1 is also higher. |
| Japan | JIS G3125 | SPA-H, SPA-C | Yield ≥355 MPa; high weathering steel, not direct equivalent. |
| Russia | GOST 27772 | 10KhSND | Chemical composition different; structural steel with enhanced corrosion resistance. |
Q295GNH Weather Resistant Steel Coil per GB/T 4171 Application Introduction
Q295GNH is specially designed for unpainted or minimally maintained steel structures exposed to the atmosphere. Its self-protecting rust layer eliminates the need for periodic painting, reducing life-cycle costs. For successful application, it should be used in an alternate wet/dry cycling environment; it is not suitable for continuous immersion or buried conditions. Design details should avoid water traps and crevices. The steel is easily formed, welded, and cut using conventional methods. Preheating is typically not required for moderate thicknesses, but welding consumables should match the weathering characteristics. The typical applications are listed below.
Product Applications: Bare weathering steel bridges, Shipping containers and corner castings, Railway passenger coaches and freight wagons, Transmission line poles and lattice towers, Architectural cladding panels and screens, Windbreak walls and noise barriers, Greenhouse structural frames, Road sign gantries and lighting columns
Processed into products: Bridge main girders, cross beams, and stiffeners, Container side panels, roof panels, and underframes, Truck chassis and trailer frames, Railway car body structures (side walls, end walls, roof), Tower mast sections and base plates, Formed C/Z-section purlins for building envelopes, Pressed panels for modular construction, Thin-walled cold-formed sections
Application industries: Bridge construction (road and railway), Rolling stock and railway vehicle manufacturing, Container and shipping industry, Electric power transmission towers, Building and architectural facades, Agricultural machinery and equipment, Industrial chimneys and ducts, Outdoor sculpture and artistic structures, Offshore topside structures (non-atmospheric submerged)
Q295GNH Weather Resistant Steel Coil per GB/T 4171 Similar or Substitute Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| China | GB/T 4171 | Q355GNH | Higher strength (≥355 MPa), similar weathering mechanism; often used when higher strength is needed. |
| China | GB/T 4171 | Q265GNH | Lower strength (≥265 MPa); can be used when strength requirement is lower. |
| Europe | EN 10025-5 | S235J0W / S235J2W | Minimum yield 235 MPa, lower than Q295GNH; suitable for less stressed weathering applications. |
| USA | ASTM A588 | Grade A (345 MPa) | Widely used weathering steel with similar corrosion resistance; requires adjustment for higher strength. |
| Japan | JIS G3125 | SPA-H | High strength weathering hot-rolled steel; yield 355 MPa, good weldability, used for similar applications. |
Notes:
- Q295GNH requires a proper weathering cycle to develop its stable patina; initial flash rusting is normal and not detrimental.
- Welding of improved atmospheric corrosion resistance can be achieved using matching weathering steel electrodes/gases (e.g., AWS E80/W or equivalent).
- For thicknesses above 20 mm, normalizing rolling may be specified to improve toughness.
- Contamination by plain carbon steel grinding dust or contact can cause visible staining, so workshop segregation is recommended.
- Actual mechanical properties may be adjusted by the manufacturer within standard limits; material certificates should be checked.
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