ASME SA588 Grade K
ASME SA588 Grade K - High-Strength Low-Alloy Weathering Steel Coil for Structural Applications
Comprehensive technical data for ASME SA588/SA588M Grade K carbon and low-alloy high-strength steel coil, including chemical composition, mechanical properties, and thermal-physical characteristics, with international equivalent and similar grades.
Hot rolling, control rolling, normalizing, thermo-mechanical control process (TMCP) by agreement
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ASME SA588 Grade K Introduction
ASME SA588/SA588M Grade K is a high-strength low-alloy structural steel with enhanced atmospheric corrosion resistance (weathering steel). It is designed for applications requiring weight reduction and long-term durability in unpainted conditions. The steel develops a tightly adherent protective oxide layer when exposed to the environment, eliminating the need for painting in many service environments.
- Key features: High strength, excellent corrosion resistance, good weldability and formability.
- Typical applications: Bridges, buildings, transmission towers, railway vehicles, and industrial structures.
- Availability: Supplied as hot-rolled coils, plates, and strips.
ASME SA588 Grade K Chemical Composition
The chemical composition conforms to ASME SA588/SA588M Grade K specifications. The steel is alloyed with chromium, copper, and vanadium to achieve enhanced atmospheric corrosion resistance. Maximum limits apply unless a range is shown.
| Element | Specified Value (wt%) | Remarks |
|---|---|---|
| Carbon (C) | 0.17 max | Maximum |
| Manganese (Mn) | 0.50–1.20 | Range |
| Phosphorus (P) | 0.040 max | Maximum |
| Sulfur (S) | 0.050 max | Maximum |
| Silicon (Si) | 0.25–0.50 | Range |
| Nickel (Ni) | 0.40 max | Maximum, residual element |
| Chromium (Cr) | 0.40–0.70 | Range |
| Copper (Cu) | 0.30–0.50 | Range (provides weathering resistance) |
| Vanadium (V) | 0.01–0.10 | Range |
ASME SA588 Grade K Typical Physical Properties
Physical properties are not specified in ASME SA588 standard; typical values for low-alloy steel are provided for guidance. Actual properties may vary slightly based on processing and heat treatment. These values are for general engineering calculations and not for acceptance purposes.
| Property | Typical Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Density (ρ) | 7.85 | g/cm³ | At 20 °C |
| Elastic Modulus (E) | 200 | GPa | At 20 °C, typical for steel |
| Shear Modulus (G) | 80 | GPa | At 20 °C, calculated |
| Poisson's Ratio (ν) | 0.3 | — | Typical for structural steel |
| Thermal Expansion Coefficient (α) | 11.7 × 10⁻⁶ | /K | Linear expansion, 20–100 °C range |
| Thermal Conductivity (λ) | 48 | W/(m·K) | At 20 °C |
| Specific Heat Capacity | 460 | J/(kg·K) | At 20–100 °C |
| Electrical Resistivity (ρ_e) | 0.16 | μΩ·m | At 20 °C |
ASME SA588 Grade K Tensile Properties and Bend Test
Mechanical properties are specified in ASME SA588/SA588M Table 2 and Table 3. Values apply to plates, shapes, and bars in the as-rolled condition. Yield strength (ReH), tensile strength (Rm), and elongation are mandatory. Bend test requirements depend on thickness and are usually performed for quality verification.
- Yield strength and tensile strength values are minimum unless noted.
- Elongation values refer to gauge length of 200 mm (8 in.) or 50 mm (2 in.) as indicated.
| Property | Standard Requirement | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield Strength (ReH) | 345 min | MPa | Thickness ≤ 100 mm; 50 ksi minimum |
| Tensile Strength (Rm) | 485 min | MPa | Thickness ≤ 100 mm; 70 ksi minimum |
| Elongation (A200) | 18 min | % | Gauge length 200 mm (8 in.) |
| Elongation (A50) | 21 min | % | Gauge length 50 mm (2 in.) |
| Bend Test (t = specimen thickness) | 2.0 t | — | Thickness ≤ 20 mm (≤ ¾ in.) |
| Bend Test | 2.5 t | — | Thickness >20–25 mm (>¾–1 in.) |
| Bend Test | 3.0 t | — | Thickness >25–50 mm (>1–2 in.) |
| Bend Test | 3.5 t | — | Thickness >50–100 mm (>2–4 in.) |
ASME SA588 Grade K Fully Equivalent Material Standards and Substitutable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A588/A588M | Grade K | Identical chemical and mechanical requirements; direct equivalent to ASME SA588 Grade K. |
| Europe | EN 10025-5 | S355J2W(+N) | Comparable weathering steel with similar strength and corrosion resistance; minor compositional differences. |
| Japan | JIS G3114 | SMA490CW | Atmospheric corrosion-resistant steel with comparable mechanical properties; check thickness applicability. |
| China | GB/T 4171 | Q355NH | Grade with similar weathering performance and strength class; often used for structural applications. |
ASME SA588 Grade K Application Introduction
ASME SA588 Grade K is ideal for load-bearing structures exposed to the atmosphere where corrosion resistance and reduced maintenance are priorities. The material can be welded, formed, and machined using standard practices for low-alloy steel. No protective painting is required in many environments, but attention should be paid to design details to avoid water traps and ensure free drainage.
- Welding consumables should match the base metal for weathering characteristics.
- Preheating may be needed for thick sections or low ambient temperatures.
Product Applications: Bridge girders, trusses, and deck panels, High-rise building frames and curtain walls, Transmission towers, poles, and antenna masts, Railway coaches, freight wagons, and locomotive frames, Intermodal containers and truck chassis, Corrosion-resistant structural components in chemical plants
Processed into products: Welded plates and beams for main structural members, Flanges and web plates of plate girders, Stiffeners, gusset plates, and connection angles, Cold-formed profiles (C, Z, sigma sections), Tubular sections and hollow structural sections (when produced from plate), Wind turbines and supporting structures (depending on availability)
Application industries: Bridge construction and repair, Building and civil engineering, Power transmission and telecommunication towers, Railway rolling stock and infrastructure, Container and shipping industry, Industrial and mining equipment
ASME SA588 Grade K Similar and Closely Related Weathering Steels
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| USA | ASTM A588/A588M | Grade A | Similar strength and corrosion resistance; Grade K offers tighter controls on certain alloying elements. |
| USA | ASTM A242/A242M | Type 1 | Earlier weathering steel specification; lower strength requirement, used in architectural applications. |
| Europe | EN 10025-5 | S355J0W | Lower impact energy requirement; still often interchangeable with S355J2W for static structures. |
| Japan | JIS G3114 | SMA400AW/BW/CW | Lower strength category (400 MPa class); may be considered where lower strength is acceptable. |
Notes:
ASME SA-588/SA-588M is an adoption of ASTM A588/A588M for pressure vessel applications under the ASME Boiler and Pressure Vessel Code, Section II. The material is fully suitable for structural use outside of pressure vessels. For projects requiring impact toughness beyond standard mild steel, supplementary impact testing (e.g., Charpy V-notch) may be specified by agreement. Typical Charpy V-notch absorbed energy values (for reference only, not required by base standard): approximately 34 J at 0 °C in longitudinal direction for thinner gauges; consult producer for guaranteed values.
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