SMA490CW Weathering Steel
SMA490CW Weathering Steel | JIS G3114 Grade Analysis & Equivalent
Comprehensive datasheet for JIS G3114 SMA490CW weather-resistant steel plate. Includes chemical composition, mechanical properties, thermal/electrical properties, international equivalents, and application industries.
Hot rolling, controlled rolling, normalizing rolling; subsequent cold forming, bending, welding, and machining are possible.
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SMA490CW Weathering Steel Introduction
JIS G3114 SMA490CW is a hot-rolled weathering steel plate designed for welded structures requiring high atmospheric corrosion resistance. It belongs to the SMA series, where "SMA" stands for Steel for Welded Structure with Atmospheric Corrosion Resistance, "490" indicates a minimum tensile strength of 490 MPa, "C" denotes enhanced corrosion resistance compared to A and B grades, and "W" confirms weather-resistant properties.
- The steel forms a protective oxide layer when exposed to the atmosphere, eliminating the need for painting in many applications.
- It offers good weldability and impact toughness at 0°C, making it suitable for bridges, architectural structures, and railway vehicles.
- Chemical composition includes copper, chromium, and nickel for corrosion resistance, with optional micro-alloying elements for strength refinement.
- Available in plate form, it is typically delivered in as-rolled or controlled-rolled condition.
SMA490CW Weathering Steel Chemical Composition
Ladle analysis according to JIS G3114:2008 for SMA490CW grade. The steel relies on copper, chromium, and nickel to develop a stable patina for atmospheric corrosion resistance. Optional micro-alloying elements (Nb, V, Ti) may be added singly or in combination, but their total content does not normally exceed 0.22%. Elements not listed in the standard are marked "—". Values are maximum unless a range is given.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.18 | max |
| Silicon (Si) | ≤ 0.75 | max |
| Manganese (Mn) | ≤ 1.40 | max |
| Phosphorus (P) | ≤ 0.035 | max |
| Sulfur (S) | ≤ 0.035 | max |
| Copper (Cu) | 0.30 – 0.50 | range |
| Chromium (Cr) | 0.45 – 0.75 | range |
| Nickel (Ni) | 0.05 – 0.30 | range |
| Niobium (Nb) | 0.015 – 0.060 | optional, if added |
| Vanadium (V) | 0.02 – 0.15 | optional, if added |
| Titanium (Ti) | 0.006 – 0.10 | optional, if added |
| Molybdenum (Mo) | ≤ 0.30 | optional, if added |
| Nitrogen (N) | ≤ 0.012 | for Al killed steel; if other elements added, might be adjusted |
SMA490CW Weathering Steel Thermal and Electrical Physical Properties
Physical properties are not part of the mandatory JIS G3114 standard but are based on published data for similar Cr-Cu-Ni weathering steels. Values are representative for room temperature unless a temperature range is specified. These properties are useful for structural design calculations.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20°C |
| Modulus of Elasticity (E) | 200 – 210 | GPa | 20°C; longitudinal |
| Shear Modulus (G) | 80 – 84 | GPa | 20°C; calculated from E and ν |
| Poisson's Ratio (ν) | 0.27 – 0.30 | — | 20°C |
| Thermal Expansion Coefficient (α) | 12.0 | ×10⁻⁶/K | 20 – 100°C |
| Thermal Expansion Coefficient (α) | 12.5 | ×10⁻⁶/K | 20 – 200°C |
| Thermal Expansion Coefficient (α) | 13.0 | ×10⁻⁶/K | 20 – 300°C |
| Thermal Conductivity (λ) | 48 | W/(m·K) | 20°C |
| Specific Heat Capacity (cp) | 460 – 480 | J/(kg·K) | 20°C |
| Electrical Resistivity (ρe) | 0.25 – 0.30 | μΩ·m | 20°C, typical for low-alloy steel |
SMA490CW Weathering Steel Mechanical Properties
Tensile and impact properties as specified in JIS G3114 for SMA490CW. Yield strength and elongation depend on plate thickness. Impact test is conducted at 0°C (C-grade) using Charpy V-notch specimens. Bending test uses a mandrel diameter expressed as a multiple of specimen thickness (t). Tests are performed on samples taken in the transverse direction unless otherwise agreed.
| Property | Standard Requirement | Unit | Test Condition / Thickness |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 365 | MPa | Plate thickness ≤ 16 mm |
| Yield Strength (ReH) | ≥ 355 | MPa | 16 < thickness ≤ 40 mm |
| Yield Strength (ReH) | ≥ 335 | MPa | 40 < thickness ≤ 75 mm |
| Yield Strength (ReH) | ≥ 325 | MPa | 75 < thickness ≤ 100 mm |
| Tensile Strength (Rm) | 490 – 610 | MPa | All thicknesses |
| Elongation (A) | ≥ 15 | % | Gauge length 50 mm (No.5 test piece), thickness ≤ 16 mm |
| Elongation (A) | ≥ 19 | % | Gauge length 200 mm (No.1A test piece), thickness ≤ 16 mm |
| Elongation (A) | ≥ 17 | % | Gauge length 200 mm (No.1A test piece), 16 < thickness ≤ 40 mm |
| Elongation (A) | ≥ 21 | % | Gauge length 200 mm (No.1A test piece), 40 < thickness ≤ 100 mm |
| Bend Test (bending angle 180°) | d = 1.5t | — | Thickness ≤ 16 mm; no cracks on outside of bent portion |
| Bend Test (bending angle 180°) | d = 2.0t | — | 16 < thickness ≤ 100 mm |
| Charpy Impact Energy (KV₂ , transverse) | ≥ 47 | J | 0°C (C-grade); average of 3 specimens (one min. 33 J) |
SMA490CW Weathering Steel Full Equivalent Material Standards & Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3114 | SMA490AW, SMA490BW | Same strength level; CW provides higher corrosion resistance; AW/BW may be accepted depending on service environment. |
| USA | ASTM A588 / A588M | Grade A, Grade B, Grade K | For structural shapes and plates; equivalent weathering properties with min 485 MPa tensile strength. |
| Europe | EN 10025-5 | S355J2W+N, S355K2W | S355J2W provides similar strength and impact toughness at -20°C (J2) or -20°C (K2); N indicates normalized or normalized rolled. |
| China | GB/T 4171 | Q355NH, Q355GNH | Q355NH is a weathering structural steel with minimum yield 355 MPa and high atmospheric corrosion resistance. |
| International | ISO 4952 | S355W | Weathering steel with comparable chemistry and mechanical properties; suitable for welded structures. |
SMA490CW Weathering Steel Application Introduction
SMA490CW is specifically developed for exposed structural applications where maintenance-free long-term performance is desired. Its corrosion-resistant patina eliminates the need for protective paint systems in many environments. Typical uses include:
- Steel bridge superstructures and decks
- Architectural facades and canopies
- Transmission line towers and poles
- Railway rolling stock and containers
- Industrial chimneys and silos
The material can be shaped, welded, and machined with standard workshop practices. Preheating for welding may be required for thicknesses above 30 mm. Cold forming (bending, rolling) is possible provided the minimum bend radius respects the bend test requirements.
Product Applications: Weathering steel plates for bridges and walkways, Hot-rolled sections (angles, channels) for lattice towers, Welded box girders and plate girders, Container frames and corner castings, Architectural curtain wall panels
Processed into products: Bridge girder web and flange plates, Railway wagon underframe and side walls, Transmission tower legs and cross arms, Pressure vessel shells (low-pressure, ambient temperature), Excavator booms and structural bodies for heavy machinery
Application industries: Civil engineering and infrastructure (bridges, overpasses), Architecture and construction (exposed structural elements), Transportation (railway cars, truck trailers, shipping containers), Power and utilities (transmission towers, wind turbine towers), Industrial equipment (hoppers, chimney shells)
SMA490CW Weathering Steel Recommendations for Similar or Alternative Materials
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3114 | SMA490BW | Lower corrosion resistance (B-grade) but similar mechanicals; use when lower corrosion class is acceptable. |
| USA | ASTM A709 / A709M | 50W (Grade 50W) | Structural steel for bridges with weathering properties; min yield 345 MPa, tensile 485 MPa. |
| Europe | EN 10025-5 | S355J0W, S355J0WP | Slightly different chemistry (P-enhanced for WP) but similar structural applications. |
| India | IS 11587 | Fe 490 W A / Fe 490 W B | Indian weathering steel with comparable strength and impact requirements. |
| Korea | KS D 3529 | SMA490AW, SMA490CW | Korean adoption of JIS standard; fully interchangeable with Japanese grades. |
Notes:
- When painting is required, special surface preparation (removal of loose patina) and compatible primers must be used to ensure adhesion over the oxide layer.
- For welded joints, low-hydrogen electrodes matching the strength level are recommended; the carbon equivalent (CE) value typically falls around 0.40–0.45, indicating good weldability but preheating may be needed for thick sections.
- The steel may be ordered with additional testing, such as ultrasonic examination, which is not mandatory in the base standard.
- If the intended service environment is extremely corrosive (marine splash zone, industrial chemicals), supplementary corrosion protection or higher alloy grades (e.g., marine grades with Ni > 1%) should be considered.
- Corrosion allowance for design should still consider the anticipated long-term thickness loss; the typical corrosion rate in rural/urban environments is in the range of 0.01–0.03 mm/year after stabilization.
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