ASME SA588 Grade K Weathering Steel Plate
ASME SA588 Grade K Weathering Steel Plate – High Strength, Corrosion Resistant Carbon Steel for Structural Use
Explore the chemical composition, mechanical properties, and physical performance of ASME SA588 Grade K (SA588GRK) carbon steel plate. Find equivalent grades, similar materials, applications, and delivery conditions for this high-strength, low-alloy structural steel with excellent atmospheric corrosion resistance.
Hot rolling, controlled rolling, normalizing, quenching and tempering (if required), welding, cold forming, bending, machining
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ASME SA588 Grade K Weathering Steel Plate Introduction
ASME SA588 Grade K (SA588GRK) is a high-strength, low-alloy structural steel plate specified under ASME SA588/SA588M. It is designed for welded bridges, buildings, and other structures where atmospheric corrosion resistance is essential. With a minimum yield strength of 50 ksi (345 MPa) up to 4 in. thick, this weathering steel develops a protective oxide layer (patina) when exposed to the elements, reducing maintenance and eliminating the need for painting in many environments. Grade K combines moderate carbon content with carefully controlled additions of chromium, copper, vanadium, and nickel to achieve improved corrosion resistance while maintaining good weldability and toughness. It is generally supplied in the as-rolled, normalized, or controlled-rolled condition and is widely used in bridge construction, building frameworks, railcars, and transmission towers.
ASME SA588 Grade K Weathering Steel Plate Chemical Composition
The table below details the typical chemical composition limits for ASME SA588 Grade K as defined in ASME SA588/SA588M. The steel is designed to provide superior atmospheric corrosion resistance through deliberate additions of chromium, copper, vanadium, and nickel while maintaining good weldability with a low carbon equivalent. All values represent ladle analysis maximums unless a range is specified.
| Element | Standard Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | 0.17 max | Ensures strength without compromising weldability |
| Manganese (Mn) | 0.50–1.20 | Contributes to strength and hardenability |
| Phosphorus (P) | 0.04 max | Residual element; kept low for ductility and weldability |
| Sulfur (S) | 0.05 max | Residual element; kept low to avoid hot shortness |
| Silicon (Si) | 0.25–0.75 | Deoxidizer and strength enhancer |
| Nickel (Ni) | 0.40 max | Improves toughness and corrosion resistance |
| Chromium (Cr) | 0.40–0.70 | Key element for atmospheric corrosion resistance |
| Copper (Cu) | 0.30–0.50 | Promotes protective oxide layer formation |
| Vanadium (V) | 0.02–0.10 | Provides precipitation hardening and grain refinement |
| Columbium (Nb) or Niobium | Optional (usually 0.005–0.05 if added) | Grain refinement element; not always specified in Grade K but may be present |
| Molybdenum (Mo) | Not specified (may be residual) | Not a controlled element in Grade K per standard |
| Nitrogen (N) | 0.015 max (typical) | Controlled to minimize strain aging |
ASME SA588 Grade K Weathering Steel Plate Thermal and Electrical Physical Properties
These physical properties are typical values for low-alloy weathering steels similar to SA588 Grade K and are provided for design guidance. They are not guaranteed by the material standard but are commonly used in engineering calculations at room temperature unless stated otherwise. Values may vary slightly depending on final heat treatment.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20 °C |
| Modulus of Elasticity (E) | 200 ≈ 29,000 (ksi) | GPa | In tension, ambient temperature |
| Shear Modulus (G) | 77 | GPa | Calculated from E and Poisson's ratio |
| Poisson's Ratio (ν) | 0.30 | - | Elastic range, room temperature |
| Thermal Expansion Coefficient (α) | 11.7 (20-100 °C) / 12.5 (20-300 °C) | 10⁻⁶/°C | Coefficient of linear thermal expansion, typical for low-alloy steels |
| Thermal Conductivity (λ) | approx. 50 (at 100 °C) / 42 (at 300 °C) | W/(m·K) | Estimated for low-alloy steel with similar composition |
| Specific Heat Capacity | ~475 | J/(kg·K) | Between 20 and 100 °C |
| Electrical Resistivity (ρ_e) | ~0.2 | µΩ·m | At 20 °C, typical for carbon-manganese steel |
ASME SA588 Grade K Weathering Steel Plate Mechanical Properties
The mechanical properties below correspond to tensile testing requirements per ASME SA588/SA588M for Grade K steel plate. Values are guaranteed for thicknesses up to 4 in. [100 mm] unless otherwise noted. Charpy V-notch impact toughness is often specified in the purchase order using supplementary requirements (e.g., S5 for Charpy testing). Elongation is measured on a 2 in. [50 mm] gauge length for plates ≤ 3/4 in. [20 mm], and on an 8 in. [200 mm] gauge length for thinner products (tested on full-section specimens).
| Property | Standard Requirement | Unit | Test Condition / Remarks |
|---|---|---|---|
| Tensile Strength (Rm) | ≥ 485 (70 min) | MPa (ksi) | All thicknesses up to 100 mm |
| Yield Strength (ReH) | ≥ 345 (50 min) | MPa (ksi) | Thickness ≤ 100 mm |
| Elongation (A) - 2 in. gauge | ≥ 21 | % | Plate thickness ≤ 20 mm; specimen type round or flat |
| Elongation (A) - 8 in. gauge | ≥ 18 | % | Thin sheet/plate tested with 200 mm gauge length |
| Bend Test (Bend Diameter) | No cracks on outside of bent portion | - | Bend test through 180° around a diameter related to plate thickness per ASTM A6/A6M; often 1.5t for transverse specimens |
| Charpy V-Notch Impact (KV) | Typically ≥ 27 J at specified temperature (optional) | J | When ordered under Supplementary Requirement S5, test temperature agreed upon (e.g., −20°F / −30°C); not mandatory in base standard |
ASME SA588 Grade K Weathering Steel Plate Exact Equivalent Material Standards and Replaceable Grades
| Country / Region | Standard | Grade / Designation | Remarks |
|---|---|---|---|
| USA (ASME) | ASME SA588/SA588M | Grade K (SA588GRK) | Identical specification; used for pressure boundary components in ASME construction |
| USA (ASTM) | ASTM A588/A588M | Grade K | Same chemistry and mechanical requirements; commonly used for general structural applications |
| International (UNS tentative) | UNS K12232? (pending verification) | K12232 | UNS number may be assigned to ASTM A588 Grade K, but confirmation is required; not officially listed in all databases. |
ASME SA588 Grade K Weathering Steel Plate Application Introduction
ASME SA588 Grade K is widely adopted in structures where atmospheric corrosion resistance and low maintenance are priorities. Its ability to form a tightly adherent oxide layer allows it to be used unpainted in many mild environments, reducing lifecycle costs. Key application constraints include avoiding prolonged exposure to marine splash zones, de-icing salts, and chemically aggressive atmospheres. In such cases, painting or alternative protection may be required. This steel can be welded using all common methods, and preheating is rarely needed for moderate thicknesses due to its low carbon equivalent. It can be cold-formed to tight radii and machined with standard tooling.
Product Applications: Welded bridge beams and box girders, Architectonically exposed structural steel (AESS) components, Railroad car sides, floors, and underframes, Transmission tower legs and cross-arms, Painted or bare weathering steel sculptures and artwork, Shipping containers and module frames, Industrial platform grating and stair treads
Processed into products: Bolted or welded connection plates, Gusset plates and stiffeners, Flange and web sections for built-up beams, Base plates and anchor brackets, Cold-formed angles and channels for secondary framing, Welded tubular sections for light poles and masts, Shear connectors and studs (when compatible)
Application industries: Bridge construction (structural girders, bearing stiffeners, decks), Commercial and industrial building framing (exposed steel structures, facades), Railway rolling stock (wagons, hopper cars, chassis), Transmission and telecommunication towers, Highway construction (guardrails, sign supports, light poles), Container and cargo storage units, Architectural and sculptural elements
ASME SA588 Grade K Weathering Steel Plate Similar / Substitute Weathering Steel Grades
| Country / Region | Standard | Grade | Remarks / Analysis |
|---|---|---|---|
| USA | ASTM A588 | Grade B | Similar corrosion resistance; Grade B has slightly different chromium and vanadium limits, but often used interchangeably in many structural applications with careful design. |
| USA | ASTM A242 | Type 1 | Lower strength (yield 50 ksi up to 0.75 in.) but excellent corrosion resistance; typically used for lighter sections. |
| Europe | EN 10025-5 | S355J2W+N | Typical European weathering steel with yield 355 MPa; chemistry differs (higher copper, no vanadium requirement); requires assessment for substitution. |
| Europe | EN 10025-5 | S355J0WP | Phosphorus-alloyed grade (0.06–0.15% P) for enhanced corrosion resistance; higher P content may affect weldability; not a direct match for SA588 Gr.K. |
| Japan | JIS G3114 | SMA570W | High-strength weathering steel (yield 460 MPa) with 0.15–0.70% Cr and 0.30–0.50% Cu; not equivalent strength-wise but similar in corrosion concept. |
| China | GB/T 4171 | Q355NH (formerly Q345GNHL) | Chinese weathering steel with 345 MPa yield; contains Cr, Ni, Cu; close in mechanical properties but chemistry may differ; suitable for similar environments. |
Notes:
Supplementary Test Requirements: For ASME SA588 Grade K to be used in Boiler and Pressure Vessel code applications, additional testing (e.g., Charpy impact) or ultrasonic examination may be specified per purchase order using ASME SA20/SA20M supplementary requirements.
Weldability: CE(IIW) typically below 0.40% enables welding without preheat up to 50 mm thickness under most conditions, but procedure qualification is recommended. Use weathering-grade welding consumables to match color and corrosion performance.
Availability: Common thicknesses range from 3 mm to 100 mm in plate form; sheets and coils up to 12.5 mm are also stocked.
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