A588 Grade B is a type of High-Strength Low-Alloy (HSLA) weathering steel, known for its atmospheric corrosion resistance and high strength, commonly used in bridges, buildings, and heavy equipment, often called Corten steel, containing elements like Chromium, Nickel, and Copper that allow it to form a protective rust-like patina, reducing the need for painting.
Key Characteristics
Type: HSLA weathering structural steel.
Corrosion Resistance: Excellent, developing a stable rust-like layer (patina).
Strength: High strength, minimum yield point of 50 ksi (345 MPa) for plates.
Chemical Composition: Contains elements like Manganese, Chromium, Nickel, Silicon, and Copper.
Weldability: Good, using standard welding processes and appropriate filler metals (e.g., AWS A5.5 E7018).
Applications: Bridges, general construction, mining equipment, cranes, and other structural parts exposed to harsh environments.
What is the yield strength of A588 Grade B?
The minimum yield strength of ASTM A588 Grade B is 50 ksi (345 MPa) for structural shapes and plates with a maximum thickness of 4 inches (100 mm).
For thicker sections, the specified yield strength decreases according to the ASTM A588 standard:
| Product Thickness / Size | Minimum Yield Strength (0.2% Offset) |
|---|---|
| Up to 4.0 in. (100 mm) | 50 ksi (345 MPa) |
| Over 4.0 in. to 5.0 in. (100 to 125 mm) | 46 ksi (315 MPa) |
| Over 5.0 in. to 8.0 in. (125 to 200 mm) | 42 ksi (290 MPa) |
Important Context for A588 Grade B:
Material Type: Like A588 Grade A, it is a high-strength low-alloy (HSLA) weathering steel. It forms a protective patina when exposed to the atmosphere.
Tensile Strength: The minimum tensile strength is 70 ksi (485 MPa).
Key Distinction from Grade A: The primary difference is in the chemical composition limits (e.g., Grade B allows for higher Phosphorus and Silicon), not in the mechanical properties. Both Grade A and Grade B have the same yield and tensile strength profile.
Design Note: The 4-inch rule is critical. For standard structural sections (like W-shapes, angles, and plates under 4" thick), the 50 ksi yield strength applies. Always verify the exact product thickness in your design.
In summary, for the vast majority of applications using material ≤ 4 inches thick, A588 Grade B has a minimum yield strength of 50 ksi (345 MPa), combined with its signature atmospheric corrosion resistance.
1. What is A588 Grade B steel used for?
A588 Grade B is primarily used for exposed structural applications like bridges, buildings, and architectural elements where its weathering properties provide a protective rust patina, eliminating the need for painting.
2. What is the yield strength of A588 Grade B?
The minimum yield strength of A588 Grade B is 50 ksi (345 MPa) for material thicknesses up to 4 inches (100 mm).
3. How does A588 Grade B differ from Grade A?
The main difference is in chemical composition; Grade B has slightly different alloy limits (e.g., higher allowable phosphorus and silicon) to achieve similar weathering performance but allows for more flexibility in manufacturing.
4. Is A588 Grade B weldable?
Yes, it is weldable using standard processes, but it requires low-hydrogen practices and the use of weathering-type filler metals (e.g., E70xx-W series) to match the corrosion resistance of the base metal.
5. What is the corrosion resistance of A588 Grade B?
It offers atmospheric corrosion resistance approximately 4-6 times better than plain carbon steel, forming a stable, protective patina when exposed to weather cycles.
6. Can A588 Grade B be used in coastal areas?
It can be used, but performance may be reduced in severe coastal (salt-rich) environments. Grade B is not specifically optimized for high chloride exposure, and protective coatings or alternative grades are often recommended.
7. What is the European equivalent of A588 Grade B?
The closest European weathering steel equivalent is S355J0WP or S355J2WP according to EN 10025-5, which provides similar strength and atmospheric corrosion resistance.
8. Does A588 Grade B require painting?
No, it is designed to be used bare (unpainted) to form a protective patina. Painting is optional and typically only used for aesthetic reasons.
9. What is the chemical composition of A588 Grade B?
It contains alloying elements like copper, chromium, nickel, and phosphorus for weathering resistance. Key limits include carbon max 0.20%, phosphorus max 0.04%, and copper 0.20-0.40%.
10. How does A588 Grade B compare to A572 Grade 50?
Both have a 50 ksi yield strength, but A588 Grade B is a weathering steel with corrosion-resistant properties, while A572 Grade 50 is a standard high-strength low-alloy (HSLA) steel that requires painting for corrosion protection.
Full specification and details are available on request. The above information is provided for guidance purposes only. For specific design requirements please contact our technical sales staff.
