ASTM A572 Grade 65 High-Strength Low-Alloy Structural Steel
ASTM A572/A572M · Published: 2026-06-24 · Updated: 2026-06-25
ASTM A572 Grade 65 is a high-strength low-alloy (HSLA) structural steel offering 65 ksi minimum yield strength — 30% stronger than standard A36. It is the preferred grade for weight-sensitive structural applications where reducing steel tonnage...
ASTM A572 Grade 65 is a high-strength low-alloy (HSLA) structural steel offering 65 ksi minimum yield strength — 30% stronger than standard A36. It is the preferred grade for weight-sensitive structural applications where reducing steel tonnage directly reduces project cost. A572 Gr 65 achieves its strength through microalloying with columbium (niobium), vanadium, and nitrogen rather than through increased carbon content, maintaining excellent weldability despite the higher strength.
Common applications include long-span bridge girders, high-rise building columns where floor plate counts are reduced by using higher-strength sections, transmission towers, and heavy construction equipment booms. The grade is fully weldable using standard SMAW, GMAW, and SAW processes with low-hydrogen electrodes — no preheat required for sections under 1.5 inches.
Quick Facts
| Category | |
| Standard | ASTM A572/A572M |
| Density | 7.85 g/cm³ |
| Yield Strength | 450 MPa (65 ksi) |
| Tensile Strength | 550 MPa (80 ksi) |
Global Equivalents & Cross-Reference
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Frequently Asked Questions
What is the difference between A572 Gr 50 and Gr 65?
Grade 50 has a 50 ksi minimum yield strength while Grade 65 provides 65 ksi — a 30% increase. Grade 65 achieves higher strength through increased levels of columbium, vanadium, and nitrogen microalloying rather than higher carbon. Both grades maintain the same maximum carbon content of 0.23%, ensuring similar weldability. Grade 65 is typically 5-10% more expensive per ton but can reduce total steel weight by 20-25% in strength-governed designs.
Can A572 Gr 65 be galvanized?
Yes. The silicon content of A572 Gr 65 is controlled below 0.40%, making it suitable for hot-dip galvanizing without excessive coating thickness. Specify silicon-killed steel for critical galvanized applications. The higher yield strength is not affected by the galvanizing temperature (~840°F), which is well below the tempering temperature of HSLA steels.
References & International Standards
- ASTM International. Standard Specifications for Steel & Metal Alloys. astm.org
- International Organization for Standardization (ISO). Metallic Materials — Cross-Reference Database. iso.org
- American Iron and Steel Institute (AISI). Steel Grade Designations & Equivalents. steel.org
- European Committee for Standardization (CEN). EN Steel Standards & Numbering System. cencenelec.eu
Structural & Carbon Steel — Engineering Reference
Structural steels are the backbone of construction and heavy industry. Grades in this category are specified primarily by their yield strength, tensile strength, and weldability — the three properties that determine whether a building stands or a bridge holds.
ASTM A36/A572/A516, EN 10025, JIS G3101/G3106, GB/T 700/1591
Building frames, bridges, pressure vessels, shipbuilding, offshore platforms, pipelines
When selecting a structural grade, match the required yield strength to the design load, but also verify Charpy impact values if the structure will operate below freezing — many structural steels undergo a ductile-to-brittle transition at low temperatures.