SMA400BW Weathering Steel Plate
SMA400BW Weathering Steel Plate: High Durability in Atmospheric Exposure per JIS G3114
Full technical data for SMA400BW weather-resistant steel plate: chemical composition, mechanical properties, physical properties, international equivalents, and recommended applications.
Hot rolling, normalizing rolling, welding, flame cutting, cold forming
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SMA400BW Weathering Steel Plate Introduction
SMA400BW is a hot-rolled atmospheric corrosion-resistant steel specified in JIS G3114, designed for welded structures exposed to weather. It contains deliberate additions of copper, chromium, and optionally nickel, forming a stable, protective rust patina that reduces further corrosion, enabling unpainted applications. This grade offers a minimum yield strength of 245 MPa and tensile strength 400–540 MPa, with good weldability and low-temperature impact toughness (27 J at 0°C). It is widely used in bridges, architectural facades, railway vehicles, and transmission towers, combining structural reliability with reduced maintenance cost.
SMA400BW Weathering Steel Plate Chemical Composition
The chemical composition of SMA400BW according to JIS G3114. It features intentional additions of copper, chromium, and optionally nickel to improve atmospheric corrosion resistance. The phosphorus and sulfur contents are controlled for good weldability and toughness.
| Element | Standard Value (%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.18 | Ladle analysis |
| Silicon (Si) | 0.15 – 0.65 | |
| Manganese (Mn) | ≤ 1.25 | |
| Phosphorus (P) | ≤ 0.035 | |
| Sulfur (S) | ≤ 0.035 | |
| Copper (Cu) | 0.30 – 0.50 | |
| Chromium (Cr) | 0.45 – 0.75 | |
| Nickel (Ni) | ≤ 0.65 | Optional, may be added for enhanced toughness |
SMA400BW Weathering Steel Plate Thermal and Electrical Physical Properties
The physical properties listed are typical values for low-alloy weathering steel at room temperature, unless otherwise noted. They are suitable for engineering calculations and may vary slightly with exact composition and heat treatment.
| Property | Reference Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20 °C |
| Modulus of Elasticity (E) | 205 | GPa | At 20 °C, typical for structural steel |
| Shear Modulus (G) | 80 | GPa | Calculated from E and ν |
| Poisson's Ratio (ν) | 0.30 | – | At 20 °C |
| Thermal Expansion Coefficient (α) | 11.7 | 10⁻⁶/K | 20 °C to 100 °C |
| Thermal Expansion Coefficient (α) | 12.5 | 10⁻⁶/K | 20 °C to 200 °C |
| Thermal Expansion Coefficient (α) | 13.2 | 10⁻⁶/K | 20 °C to 300 °C |
| Thermal Conductivity (λ) | 51.9 | W/(m·K) | At 20 °C |
| Specific Heat Capacity (cₚ) | 486 | J/(kg·K) | At 20 °C |
| Electrical Resistivity (ρₑ) | 0.22 | μΩ·m | At 20 °C, typical for low-alloy steel |
SMA400BW Weathering Steel Plate Mechanical Properties
Mechanical properties as per JIS G3114 for SMA400BW. The yield strength, tensile strength, elongation, and impact values depend on plate thickness. Bending tests are performed with a specified bend radius at 180°. Impact testing is done on longitudinal Charpy V-notch specimens.
| Property | Specified Value | Unit | Test Condition / Thickness Range |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 245 | MPa | t ≤ 16 mm |
| Yield Strength (ReH) | ≥ 235 | MPa | 16 mm < t ≤ 40 mm |
| Yield Strength (ReH) | ≥ 215 | MPa | 40 mm < t ≤ 75 mm |
| Yield Strength (ReH) | ≥ 205 | MPa | 75 mm < t ≤ 100 mm |
| Yield Strength (ReH) | ≥ 195 | MPa | 100 mm < t ≤ 160 mm |
| Tensile Strength (Rm) | 400 – 540 | MPa | t ≤ 100 mm |
| Tensile Strength (Rm) | 400 – 540 | MPa | 100 mm < t ≤ 160 mm |
| Elongation (A) | ≥ 21 | % | t ≤ 5 mm (gauge length 50 mm) |
| Elongation (A) | ≥ 17 | % | 5 mm < t ≤ 16 mm (gauge length 50 mm) |
| Elongation (A) | ≥ 21 | % | 16 mm < t ≤ 50 mm (gauge length 200 mm) |
| Elongation (A) | ≥ 23 | % | t > 40 mm (gauge length 200 mm) |
| Bend Test (180°) | d = 1.5a (t ≤ 16 mm) | – | d = diam. of mandrel, a = specimen thickness |
| Bend Test (180°) | d = 2.0a (t > 16 mm) | – | |
| Charpy Impact Absorbed Energy (KV₂) | ≥ 27 | J | 0 °C, longitudinal, standard 10×10 mm specimen |
SMA400BW Weathering Steel Plate Fully Equivalent Material Standards and Alternative Designations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3114 | SMA400BW | Original specification – weathering steel for welded structures |
| Europe | EN 10025-5 | S235J2W | Closest European grade; tensile range lower (360–510 MPa), yield ≥235 MPa |
| USA | ASTM A588/A588M | Grade B | Higher strength grade with corrosion resistance; not an exact match |
| China | GB/T 4171 | Q235NH | Similar yield and tensile level; commonly used equivalent |
| International | ISO 4952 | Fe 235W | ISO weathering steel with comparable strength; limited availability |
SMA400BW Weathering Steel Plate Application Introduction
SMA400BW is widely used in structural applications where exposure to atmosphere is continuous and painting is either undesirable or not required. Thanks to its Cu-Cr alloying, it develops a dense, adherent oxide layer that retards further corrosion, reducing life-cycle maintenance. It can be formed, welded, and cut using standard fabrication practices.
- Suitable for bare (unpainted) use in moderate atmospheres; periodic wet-dry cycling enhances patina formation.
- Welding with matching weathering steel electrodes maintains corrosion resistance at joints.
- Often delivered in normalized rolling condition for improved toughness.
Product Applications: Bridge main girders, cross beams, and stiffeners, Outdoor structural frameworks and columns, Architectural exposed steel facades and canopies, Freight wagons and intermodal containers, High-tension lattice towers, Welded piping and piling (with atmospheric exposure)
Processed into products: Bridge box girders, Railway wagon side frames and bolsters, Facade support brackets and louvers, Welded H-beams and built-up sections, Cover plates and gusset plates, Bollards and guardrail posts (unpainted)
Application industries: Civil engineering and bridge construction, Architectural and building envelopes (facades, cladding), Railway wagon and vehicle manufacturing, Container and tank construction, Transmission towers and utility poles, Offshore and coastal structures (with caution)
SMA400BW Weathering Steel Plate Similar and Alternative Weathering Steel Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3114 | SMA400AW | Without Cr/Cu, lower corrosion resistance |
| Japan | JIS G3114 | SMA490BW | Higher strength (490 MPa class), similar corrosion resistance |
| Europe | EN 10025-5 | S355J2W | Higher strength weathering steel for structural use |
| USA | ASTM A242 | Type 1 | High-strength low-alloy structural steel with atmospheric corrosion resistance |
| USA | ASTM A606 | Type 4 | Hot-rolled, improved atmospheric corrosion resistance for sheet and strip |
| China | GB/T 4171 | Q355NH | Higher strength class weathering steel |
| Korea | KS D 3529 | SMA400BW | Identical to JIS grade |
Notes:
Note on corrosion performance: The protective patina forms best under alternating wet/dry conditions and in non-marine, non-aggressive industrial atmospheres. For continuous immersion or severe marine chloride exposure, additional protective coatings are recommended. Fabrication: Preheating is typically not required for thicknesses up to 40 mm, but low-hydrogen practice and matching consumables (e.g., AWS E8018-W) are advised to preserve corrosion resistance at welds. Dimensional standards: Tolerances and flatness in accordance with JIS G3193 or agreement at time of order.
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