ASME SA588 Grade B (SA588GRB) Weathering Steel Plate
ASME SA588 Grade B (SA588GRB) Weathering Steel Plate for Structural Applications
ASME SA588 Grade B is a high-strength low-alloy structural steel with improved atmospheric corrosion resistance, ideal for unpainted bridges and buildings.
Hot rolling, controlled rolling, normalizing, welding, bending, forming
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ASME SA588 Grade B Weathering Steel Plate Introduction
ASME SA588 Grade B (SA588GRB) is a high-strength low-alloy structural steel specifically designed for enhanced atmospheric corrosion resistance. Through controlled alloying with copper, chromium, and nickel, it develops a tight, protective oxide layer (patina) when exposed to the weather, eliminating the need for painting in many applications. It offers a minimum yield strength of 345 MPa (50 ksi) and tensile strength of 485 MPa (70 ksi), with good weldability and toughness. Typical thicknesses range from 6 mm to 150 mm in plate form. The material conforms to ASME SA588/SA588M specification, primarily used in bolted, riveted, or welded structures where weight savings and durability are important, such as bridges, transmission towers, and architectural facades.
ASME SA588 Grade B Weathering Steel Plate Chemical Composition
The chemical composition of ASME SA588 Grade B is carefully balanced to provide atmospheric corrosion resistance while maintaining structural strength. Copper, chromium, and nickel are key alloying elements that promote the formation of a protective patina. The maximum phosphorus and sulfur contents are controlled to ensure weldability and toughness. Vanadium is added for grain refinement. Note that values are ladle analysis in accordance with ASME SA588/SA588M.
| Chemical Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.20 | Max |
| Manganese (Mn) | 0.75 - 1.35 | Range |
| Phosphorus (P) | ≤ 0.04 | Max |
| Sulfur (S) | ≤ 0.05 | Max |
| Silicon (Si) | 0.15 - 0.50 | Range |
| Nickel (Ni) | ≤ 0.50 | Max |
| Chromium (Cr) | 0.40 - 0.70 | Range |
| Copper (Cu) | 0.20 - 0.40 | Range |
| Vanadium (V) | 0.01 - 0.10 | Range |
ASME SA588 Grade B Weathering Steel Plate Thermal and Electrical Physical Properties
Physical properties are representative for weathering steel of similar composition at room temperature unless otherwise indicated. Density is assumed to be that of carbon steel. Thermal expansion coefficient, thermal conductivity, and specific heat are important for structural fire design and welding. Electrical resistivity may vary slightly with heat treatment. These values are not part of the mandary specification but are typical for engineering calculations.
| Property | Standard Required Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | Room temperature |
| Elastic Modulus (E) | 200 | GPa | Room temperature, tension |
| Shear Modulus (G) | 80 | GPa | Room temperature |
| Poisson's Ratio (ν) | 0.30 | Room temperature | |
| Thermal Expansion Coefficient (α) | 11.7 (0-100°C); 12.5 (0-200°C) | 10⁻⁶/K | Average linear expansion |
| Thermal Conductivity (λ) | 42 (at 20°C); 40 (at 200°C) | W/(m·K) | Estimated |
| Specific Heat | 0.46 | J/(g·K) | At 20°C |
| Electrical Resistivity (ρ_e) | 0.17 | µΩ·m | At 20°C |
ASME SA588 Grade B Weathering Steel Plate Mechanical Properties
The mechanical properties below are minimum requirements for ASME SA588 Grade B plates in the as-rolled or normalized condition. Tensile testing is performed on transverse specimens unless otherwise specified. Elongation values depend on the gauge length and plate thickness. The steel is not normally subject to Charpy impact requirements unless specified for low-temperature service; in such cases the energy values are agreed upon. Bend testing may be carried out to assess ductility.
| Property | Standard Required Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 345 | MPa | 0.2% offset, transverse, room temperature |
| Tensile Strength (Rm) | ≥ 485 | MPa | Transverse, room temperature |
| Elongation (A) in 200 mm | ≥ 21 | % | Plates ≤ 19 mm (3/4 in) thick, gauge length 200 mm |
| Elongation (A) in 50 mm | ≥ 18 | % | Plates > 19 mm thick, gauge length 50 mm |
| Bend Test (Bend Diameter) | 180° bend on diameter = 1.5t for t ≤ 25 mm; 2t for t > 25 mm | No cracks on outside of bent portion (typical supplementary requirement) |
ASME SA588 Grade B Weathering Steel Plate Completely Equivalent Standards and Substitute Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A588/A588M | Grade B | Identical chemical and mechanical requirements; structural use |
| Japan | JIS G3114 | SMA490BW (or SMA490BP) | Weather-resistant hot-rolled steel with similar corrosion resistance; slight composition differences |
| Europe | EN 10025-5 | S355J2W + N | Comparable strength (355 MPa yield) and weathering ability; close match for structural applications |
| China | GB/T 4171 | Q355NH | Equivalent Chinese weathering steel; minor adjustments in Mn, Cu, Cr contents |
ASME SA588 Grade B Weathering Steel Plate Application Introduction
ASME SA588 Grade B steel is widely used in exposed structural applications where long-term durability with minimal maintenance is desired. Its ability to form a protective rust-like patina eliminates the need for painting, reducing life-cycle costs. Typical industries, products, and components include:
Product Applications: Weathering steel plates for bridges, Structural beams and columns, Architectural cladding and sculptural elements, Container frames and chassis, Light poles and sign supports, Off-highway equipment components
Processed into products: Bridge girders, cross-frames, and stiffeners, Bolted or welded structural connections, Exposed exterior support brackets, Railway car body panels and underframes, Tower legs and antenna mounts, Fabricated box sections for artistic installations
Application industries: Civil engineering and infrastructure, Bridge construction, Architecture and building facades, Railway rolling stock and containers, Transmission and telecommunication towers, Port and marine structures (atmospheric exposure only)
ASME SA588 Grade B Weathering Steel Plate Similar / Alternative Materials Recommendation
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A242 | Type 1 | Earlier weathering steel specification; similar corrosion resistance but yield strength ~345 MPa; may have slightly different Cu-Cr content |
| USA | ASTM A709 | Grade 50W | Bridge steel with weathering option; equivalent to A588 Grade B in strength and composition |
| Europe | EN 10025-5 | S355J0W | Lower impact test temperature than J2W, but comparable strength and weathering performance |
| Japan | JIS G3125 | SPA-H | High-phosphorus weathering steel, mainly for sheet and coil; not for structural plates but used in similar corrosive environments |
| China | GB/T 4171 | Q415NH | Higher strength grade (415 MPa yield), with similar weathering alloy concept; may substitute if higher strength is needed |
Notes:
Weldability: SA588 Grade B can be welded using common processes (SMAW, SAW, GMAW, FCAW) with low-hydrogen electrodes matching the base metal strength. Preheating may be required for thick sections. Corrosion performance: The protective patina develops under cyclic wet/dry conditions; the steel should not be used in submerged or continuously wet environments. Delivery conditions: Plates may be supplied with or without impact testing as specified in the purchase order. Consult the latest edition of ASME SA588/SA588M for full requirements and optional supplementary requirements.
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