JIS G3114 SMA490AW Weather Resistant Steel Plate
JIS G3114 SMA490AW Weathering Steel Plate – High-Strength Atmospheric Corrosion Resistant Structural Steel
SMA490AW is a weather-resistant hot-rolled steel plate designed for welded structures under JIS G3114. With minimum tensile strength of 490 MPa and controlled alloying (Cu-Cr-Ni), it offers reliable atmospheric corrosion resistance for bridges, buildings, and industrial applications.
Hot rolling, welding, cold forming, machining, cutting, and bending
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JIS G3114 SMA490AW Weather Resistant Steel Plate Introduction
SMA490AW is a structural weathering steel specified in JIS G3114, developed for welded constructions exposed to outdoor environments without protective coating. It belongs to the weldable atmospheric corrosion-resistant steel group, featuring a minimum tensile strength of 490 MPa. Unlike plain carbon steels, SMA490AW forms a stable, adherent rust layer (patina) that drastically reduces further atmospheric attack, extending service life. Its balanced chemical composition includes copper, chromium, and nickel, which synergistically enhance corrosion resistance while maintaining good weldability and toughness. The material is supplied in the as-hot-rolled condition and can be fabricated into beams, columns, bridge components, containers, and rolling stock. It is widely adopted in Japan and internationally as an equivalent to EN S355J2W or ASTM A588 Grade B, offering economic benefits by eliminating the need for painting in many environments.
JIS G3114 SMA490AW Weather Resistant Steel Plate Chemical Composition
The following table lists the ladle analysis ranges according to JIS G3114:2008 for SMA490AW. Copper, chromium, and nickel are intentionally added to create a protective oxide layer. Maximum limits for phosphorus and sulfur ensure good weldability and toughness.
| Element | Standard Value (max or range) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.18 | Ladle analysis |
| Silicon (Si) | ≤ 0.55 | For killed steel |
| Manganese (Mn) | ≤ 1.40 | – |
| Phosphorus (P) | ≤ 0.035 | – |
| Sulfur (S) | ≤ 0.035 | – |
| Copper (Cu) | 0.30 – 0.50 | Key weathering element |
| Chromium (Cr) | 0.45 – 0.75 | Promotes protective rust |
| Nickel (Ni) | 0.05 – 0.30 | Improves toughness and corrosion resistance |
JIS G3114 SMA490AW Weather Resistant Steel Plate Thermal and Electrical Physical Properties
The physical property data are typical for low-alloy weathering steels similar to SMA490AW. Actual values may vary slightly depending on exact heat composition and manufacturing route.
| Property | Standard Value (Typical) | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20°C |
| Elastic modulus (E) | 207 | GPa | At 20°C |
| Shear modulus (G) | 79.3 | GPa | At 20°C |
| Poisson's ratio (ν) | 0.30 | – | At 20°C |
| Thermal expansion coefficient (α) | 11.1 | 10⁻⁶/K | 20 to 100°C |
| Thermal expansion coefficient (α) | 12.2 | 10⁻⁶/K | 20 to 200°C |
| Thermal expansion coefficient (α) | 12.8 | 10⁻⁶/K | 20 to 300°C |
| Thermal expansion coefficient (α) | 13.4 | 10⁻⁶/K | 20 to 400°C |
| Thermal expansion coefficient (α) | 13.9 | 10⁻⁶/K | 20 to 500°C |
| Thermal conductivity (λ) | 42 | W/(m·K) | At 20°C |
| Thermal conductivity (λ) | 42 | W/(m·K) | At 100°C |
| Thermal conductivity (λ) | 39 | W/(m·K) | At 200°C |
| Thermal conductivity (λ) | 36 | W/(m·K) | At 300°C |
| Thermal conductivity (λ) | 33 | W/(m·K) | At 400°C |
| Thermal conductivity (λ) | 30 | W/(m·K) | At 500°C |
| Specific heat capacity | 460 | J/(kg·K) | At 20°C |
| Specific heat capacity | 500 | J/(kg·K) | At 100°C |
| Specific heat capacity | 530 | J/(kg·K) | At 200°C |
| Specific heat capacity | 570 | J/(kg·K) | At 300°C |
| Specific heat capacity | 610 | J/(kg·K) | At 400°C |
| Specific heat capacity | 660 | J/(kg·K) | At 500°C |
| Electrical resistivity (ρₑ) | 0.15 – 0.25 | μΩ·m | At 20°C, approximate |
JIS G3114 SMA490AW Weather Resistant Steel Plate Mechanical Properties
The specified tensile properties and impact toughness are valid for the as-delivered condition according to JIS G3114. Yield strength varies with plate thickness. Charpy V-notch impact test is conducted at 0°C for the A grade, with a minimum average energy of 27 J. Transverse bend test is mandatory.
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Yield strength (ReH) | ≥ 365 | MPa | Plate thickness ≤ 16 mm |
| Yield strength (ReH) | ≥ 355 | MPa | Plate thickness >16 ≤40 mm |
| Yield strength (ReH) | ≥ 335 | MPa | Plate thickness >40 ≤75 mm |
| Yield strength (ReH) | ≥ 325 | MPa | Plate thickness >75 ≤100 mm |
| Tensile strength (Rm) | 490 – 610 | MPa | All thickness range |
| Elongation (A) | ≥ 16 | % | Thickness ≤5 mm, gauge length 5.65√S₀ (No.5 specimen), transverse |
| Elongation (A) | ≥ 17 | % | Thickness >5–16 mm, gauge length 200 mm (No.1A specimen), transverse |
| Elongation (A) | ≥ 21 | % | Thickness >16–50 mm, gauge length 200 mm (No.1A specimen), transverse |
| Elongation (A) | ≥ 23 | % | Thickness >50 mm, gauge length 50 mm (No.4 specimen), transverse |
| Charpy impact energy (KV₂) | ≥ 27 | J | At 0°C, V-notch, longitudinal, average of three specimens |
| Bend test | No cracks | – | 180° bend, d=1.5t (t ≤16 mm); d=1.5t (t >16 mm), transverse |
JIS G3114 SMA490AW Weather Resistant Steel Plate Equivalent Grades and Substitution Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10025-5:2004 | S355J2W (1.8965) | Closest equivalent weathering steel; yield 355 MPa, impact 27 J at -20°C; may need thickness adjustment. |
| Europe | EN 10025-5:2004 | S355K2W (1.8967) | Higher toughness; impact 40 J at -20°C; suitable for thicker sections. |
| USA | ASTM A588/A588M | Grade B | Minimum yield 345 MPa; atmospheric corrosion resistance comparable to SMA490AW; widely used in steel bridges. |
| China | GB/T 4171 | Q355GNH | Similar strength and corrosion resistance; yield ≥355 MPa; tensile 490–630 MPa; charpy requirement at 0°C or lower. |
| International | ISO 4952:2003 | S355W | Weathering structural steel; yield 355 MPa; suitable substitute, confirm impact test temperature. |
JIS G3114 SMA490AW Weather Resistant Steel Plate Application Introduction
SMA490AW was developed primarily for uncoated, welded structures exposed to the atmosphere. Its protective rust layer eliminates the need for painting in many environments, reducing maintenance costs. Industries utilizing this material include civil engineering, transportation, energy, and architecture.
Product Applications: Welded bridge girders and stiffeners, Transmission line pylons and telecommunication masts, Intermodal freight containers and swap bodies, Exposed architectural facades and screens, Mining dump truck bodies and heavy equipment cabins, Wind turbine tower components (inner parts, access platforms)
Processed into products: Longitudinals and crossbeams for steel bridges, Built-up box columns for high-rise buildings, Corner castings and rails for containers, Bogie frames and structural brackets for rail vehicles, Grating platforms and handrails for offshore installations, Brackets and support rings for industrial chimneys
Application industries: Bridge engineering (highway and railway girders, trusses), Building construction (exposed steel frames, facades, stadium roofs), Container and marine equipment (containers, chassis, offshore module structures), Railway and vehicles (passenger coaches, freight wagons, bogie frames), Energy and utilities (transmission towers, poles, industrial chimneys), Art and sculpture (outdoor monuments, landscape elements)
JIS G3114 SMA490AW Weather Resistant Steel Plate Similar Weathering Steel Grades for Reference
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Japan | JIS G3114 | SMA490BW | B grade; identical strength, but impact test at -5°C instead of 0°C; slightly better toughness. |
| Japan | JIS G3114 | SMA490CW | C grade; impact test at -10°C; used where low-temperature toughness is critical. |
| Japan | JIS G3114 | SMA570W | Higher strength grade (min tensile 570 MPa); similar weathering alloy concept; used for heavier-loaded structures. |
| USA | ASTM A588/A588M | Grade A | Slightly lower yield (345 MPa); similar corrosion resistance; can be used in less demanding sections. |
| China | GB/T 4171 | Q460GNH | Higher strength weathering steel with 460 MPa min yield; not a direct substitute but can be considered for strength upgrades. |
Notes:
Welding considerations: SMA490AW exhibits good weldability with standard procedures. Preheating is recommended when the carbon equivalent (Ceq) exceeds 0.42%. Matching or slightly overmatched weathering steel electrodes (e.g., JIS D5026 for manual metal arc welding) should be used to maintain corrosion resistance.
Service conditions: The protective patina develops most effectively in alternating wet/dry cycles. In continuously damp or heavily polluted (e.g., high chloride) environments, additional protection such as painting may be necessary. The material is not intended for strong acid or direct acid gas exposure without protective coating.
Delivery condition: Plates are normally supplied as-hot-rolled; stress relieving or normalizing can be agreed upon if required for dimensional stability after heavy forming. Surface grinding or descaling is optional for improved paint adhesion if coating is used later.
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