ASTM A588 Grade K (A588GRK) Weathering Steel Plate
ASTM A588 Grade K (A588GRK) Weathering Steel Plate: Properties & Equivalents
Complete material data for ASTM A588 Grade K (A588GRK) weather resistant steel plate: chemical composition, mechanical and physical properties, international equivalents, similar grades, and application guide.
Hot-rolled, control-rolled, normalized, welding, bolting, cold forming
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ASTM A588 Grade K Weathering Steel Plate Introduction
ASTM A588 Grade K (A588GRK) is a high-strength low-alloy structural steel with improved atmospheric corrosion resistance, commonly known as weathering steel. It contains alloying elements such as copper, chromium, and nickel that promote the formation of a dense, protective oxide layer (patina) under outdoor exposure, significantly reducing the need for painting. Grade K is one of several grades within ASTM A588/A588M, designed for welded, bolted, or riveted structures in bridges, buildings, and other applications where weight savings and corrosion durability are important. Its minimum yield strength of 345 MPa (50 ksi) for sections up to 100 mm thickness, combined with excellent toughness and weldability, makes it a cost-effective alternative to conventional structural steels in corrosive environments.
ASTM A588 Grade K Weathering Steel Plate Chemical Composition
The following table lists the specified heat analysis limits for ASTM A588 Grade K as per ASTM A588/A588M. All values are in weight percent. These alloying additions, particularly Cu, Cr, and Ni, are responsible for the enhanced atmospheric corrosion resistance characteristic of this grade.
| Element | Content (wt%) | Remarks |
|---|---|---|
| Carbon (C) | 0.17 max | |
| Manganese (Mn) | 0.50 - 1.20 | |
| Phosphorus (P) | 0.04 max | |
| Sulfur (S) | 0.05 max | |
| Silicon (Si) | 0.25 - 0.50 | |
| Nickel (Ni) | 0.40 max | |
| Chromium (Cr) | 0.40 - 0.70 | |
| Copper (Cu) | 0.30 - 0.50 | |
| Vanadium (V) | 0.02 - 0.10 |
ASTM A588 Grade K Weathering Steel Plate Thermal and Electrical Physical Properties
The following physical properties are typical for ASTM A588 Grade K at room temperature unless otherwise specified. These values are general for similar low-alloy steels and can be used for engineering calculations.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | 20 °C |
| Elastic Modulus (E) | 200 | GPa | 20 °C |
| Shear Modulus (G) | 80 | GPa | 20 °C |
| Poisson's Ratio (ν) | 0.30 | - | 20 °C |
| Thermal Expansion Coefficient (α) | 12.0 x 10⁻⁶ | K⁻¹ | 20-100 °C |
| Thermal Conductivity (λ) | 50 | W/(m·K) | 20 °C |
| Specific Heat Capacity | 450 | J/(kg·K) | 20 °C |
| Electrical Resistivity (ρ_e) | 0.20 | μΩ·m | 20 °C |
ASTM A588 Grade K Weathering Steel Plate Mechanical Properties
Mechanical properties for ASTM A588 Grade K are determined in accordance with ASTM A6/A6M and ASTM A370. Requirements vary with product thickness. Values shown are the minimum specified unless a range is indicated. The steel exhibits good plastic deformation capacity and is suitable for cold bending operations.
| Property | Standard Requirement | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | 345 min | MPa | Thickness ≤ 100 mm (4 in.) |
| Tensile Strength (Rm) | 485 min | MPa | Thickness ≤ 100 mm (4 in.) |
| Elongation A (200 mm gage) | 18 min | % | Thickness ≤ 20 mm (3/4 in.) |
| Elongation A (200 mm gage) | 17 min | % | Thickness 20-40 mm (3/4-1.5 in.) |
| Elongation A (200 mm gage) | 16 min | % | Thickness >40 mm (1.5 in.) |
| Elongation A (50 mm gage) | 21 min | % | Thickness ≤ 20 mm |
| Elongation A (50 mm gage) | 20 min | % | Thickness 20-40 mm |
| Elongation A (50 mm gage) | 19 min | % | Thickness >40 mm |
| Bend Test (Bend Diameter) | 1.5t | - | Thickness ≤ 20 mm, 180° bend |
| Bend Test (Bend Diameter) | 2t | - | Thickness 20-40 mm, 180° bend |
| Bend Test (Bend Diameter) | 2.5t | - | Thickness >40 mm, 180° bend |
ASTM A588 Grade K Weathering Steel Plate Fully Equivalent Material Standards and Substitutable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| European Union | EN 10025-5 | S355K2W | Functionally equivalent; similar chemistry with slightly different Cu/Ni/Cr balance |
| Japan | JIS G3114 | SMA570W | Approximate equivalent; comparable strength and weathering resistance |
| China | GB/T 4171 | Q355NH | Closest Chinese weathering steel grade, similar mechanical properties |
ASTM A588 Grade K Weathering Steel Plate Application Introduction
ASTM A588 Grade K is widely used in unpainted applications where the natural rust-like patina provides long-term corrosion protection. Its high strength allows for weight reduction and thinner sections. The steel is readily weldable using common techniques with moderate preheat for thick sections.
Product Applications: Bridge girders and welded beam assemblies, Building columns, trusses, and frames, Architectural facades and cladding, Railway cars and truck frames, Shipping containers, Lighting poles and sign supports
Processed into products: Flange plates and web plates for welded plate girders, Corner angles and connection plates, Stiffeners and gusset plates, Cold-formed profiles (channels, Z-purlins), Bolted splice connectors, Architectural perforated panels
Application industries: Civil Engineering, Bridge Construction, Architectural Steel Structures, Transportation (Railway Wagons, Container Manufacturing), Energy (Transmission Towers, Wind Turbine Towers)
ASTM A588 Grade K Weathering Steel Plate Similar/Alternative Material Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A588 | Grade A | Same standard, different chemical composition limits but identical mechanical requirements |
| USA | ASTM A588 | Grade B | Same standard, variant with slightly higher Si and Ni limits |
| USA | ASTM A242 | Type 1 | Older weathering steel, similar strength and corrosion resistance but different chemistry |
| USA | ASTM A709 | 50W | Bridge steel with weathering capability, often dual-certified with A588 |
| International | EN 10025-5 | S355J2W | Lower toughness variant compared to K2W, otherwise similar strength and weathering |
| International | ISO 4952 | Fe355W | ISO weathering structural steel with comparable strength |
Notes:
Weathering steel performs best in alternating wet-dry environments; it is not recommended for continuously submerged or highly aggressive chemical atmospheres. When painting is desired, surface preparation must remove the existing oxide layer. Carbon equivalent (CE) values are typically below 0.44% for good weldability. Preheating and low-hydrogen welding practices are recommended for sections over 50 mm to avoid hydrogen-induced cracking. No impact test requirements are specified in ASTM A588 unless ordered with supplementary requirements.
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