A572 Steel: High-Strength Low-Alloy Structural Steel Grades 42, 50, 55, 60, 65
ASTM A572/A572M · Published: 2026-07-25 · Updated: July 2026
A572 steel (ASTM A572/A572M) is a high-strength low-alloy (HSLA) structural steel specification covering five grades (42, 50, 55, 60, 65) that deliver 290-450 MPa (42-65 ksi) minimum yield strength—substantially higher than the 250 MPa yield of...
A572 steel (ASTM A572/A572M) is a high-strength low-alloy (HSLA) structural steel specification covering five grades (42, 50, 55, 60, 65) that deliver 290-450 MPa (42-65 ksi) minimum yield strength—substantially higher than the 250 MPa yield of a36-steel/">A36 steel. The strength increase is achieved through micro-alloying with niobium (columbium), vanadium, or nitrogen, rather than increased carbon content—preserving good weldability, toughness, and formability while reducing the weight of structural members. Grade 50 (345 MPa yield) is by far the most common A572 grade and is now the default specification for wide-flange (W-shape) sections produced by U.S. mills, increasingly replacing A36 for new building construction. The 38% higher yield strength of Grade 50 allows 25-35% weight reduction in beams versus A36, often reducing total project cost despite a 5-10% per-pound premium. A572 is specified for buildings over 5 stories, bridge girders, transmission towers, freight railcars, heavy equipment, and offshore platforms. For fracture-critical bridge members, A572 with supplemental Charpy V-notch toughness requirements (Zone 2 or Zone 3) is specified per AASHTO. For the standard Grade 50 data sheet, see a572-gr50/">A572 Gr.50; for the higher-strength Grade 65, see a572-gr65/">A572 Gr.65.
Quick Facts
| Category | Carbon Steel |
| Standard | ASTM A572/A572M |
| Density | 7.85 g/cm³ |
| Yield Strength | 290-450 MPa (42-65 ksi) depending on grade |
| Tensile Strength | 415-550 MPa (60-80 ksi) |
Detailed Mechanical Properties
| Elongation | 18-21% (in 200mm, grade-dependent) |
| Hardness | 140-200 HB (grade-dependent) |
| Charpy V Notch | 27-34J at 0°C (Grade 50 typical) |
| Modulus Of Elasticity | 200 GPa |
Physical Properties
| Melting Point | 1420-1520 °C |
| Thermal Conductivity | 50 W/m·K at 20°C |
| Electrical Resistivity | 0.0000180 Ω·cm |
| Specific Heat | 480 J/kg·K |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| ASTM A572 | Compare |
| EN S355 (similar to Gr 50) | Compare |
| GB Q345/Q355 (similar to Gr 50) | Compare |
| CSA G40.21 350W | Compare |
Heat Treatment & Processing
| Note | A572 is supplied in as-rolled or normalized condition; heat treatment is not used to achieve strength (which comes from micro-alloying). Normalizing at 870-920°C may be specified for improved toughness in fracture-critical applications. |
Welding & Fabrication
| Preheat | Grade 50: 0-10°C for t<25mm, 10-50°C for 25-50mm, 50-100°C for >50mm. Higher grades require more preheat. |
| Filler Metal | E7018 (SMAW), ER70S-6 (GMAW) for Grade 50; match filler strength to higher grades |
| Interpass Temp | Max 315°C for Grade 50 |
| Weldability Rating | Good — low-hydrogen practice recommended; preheat required for thick sections |
Related Materials
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Frequently Asked Questions
What are the grades of A572 steel?
ASTM A572 covers five yield-strength grades: Grade 42 (290 MPa / 42 ksi), Grade 50 (345 MPa / 50 ksi), Grade 55 (380 MPa / 55 ksi), Grade 60 (415 MPa / 60 ksi), and Grade 65 (450 MPa / 65 ksi). Grade 50 is by far the most common, used for W-shapes and plate. Higher grades (60, 65) are used for high-strength plate applications like railcars and heavy equipment.
Is A572 Grade 50 replacing A36?
Yes. Most U.S. steel mills now produce W-shapes as dual-certified A36/A572 Gr 50, and A572 Gr 50 is increasingly the default specification for new construction. The 38% higher yield strength enables 25-35% weight reduction in beams, reducing foundation loads and total project cost. A36 remains specified for simple structures, repair work, and projects valuing maximum weldability.
Can A572 steel be welded?
Yes, A572 has good weldability. Grade 50 has carbon equivalent controlled to ≤0.43, requiring preheat only for thicknesses above 25 mm or for cold-weather fabrication. Use low-hydrogen electrodes (E7018, ER70S-6). For Grades 60 and 65, preheat requirements increase and low-hydrogen practice is mandatory. AWS D1.1 Table 3.2 specifies preheat based on thickness and carbon equivalent.
What is the difference between A572 and A36?
A572 Grade 50 has 345 MPa (50 ksi) minimum yield—38% higher than A36's 250 MPa (36 ksi). A572 achieves higher strength through micro-alloying (Nb, V) while keeping carbon low; A36 relies on carbon and manganese. A572 is slightly more expensive per pound but enables 25-35% lighter sections, often reducing total project cost.
What is the European equivalent of A572 Grade 50?
EN 10025 S355 (S355JR, S355J0, S355J2) is the closest European equivalent—both have 355 MPa minimum yield. The compositions differ slightly (S355 uses more Mn and Si, A572 uses micro-alloying), but for most structural design purposes they are considered equivalent. See <a href="/materials/s355-steel/">S355 steel</a> for full European grade details.
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.