When you select structural steel for your project, choosing the right grade is very important for safety, performance, and cost-effectiveness. Two of the most commonly specified steel grades are ASTM A36 and ASTM A572.
This article presents a detailed comparison of these two standards, covering their chemical and mechanical properties, applications, cost, and selection criteria, so that you can make the best decision.
What is ASTM A36 Steel?
ASTM A36 is a standard specification for carbon structural steel, widely used in construction and manufacturing. It is classified as a mild or low-carbon steel, offering a good balance of strength, ductility, and weldability.
A36 is known for its versatility and affordability, making it a go-to material for a broad range of structural and fabricated applications.
Key Features of ASTM A36
Standard: ASTM A36/A36M
Product Forms: Plate, bar, angle, channel, H-beam, I-beam, and more
Manufacturing Process: Hot-rolled; can be normalized, annealed, or stress-relieved
Weldability: Excellent; suitable for all common welding methods
Machinability: Good; easy to cut, drill, and form.
What is ASTM A572 Steel?
ASTM A572 is a high-strength, low-alloy (HSLA) structural steel standard, designed for applications requiring greater strength and durability. It is available in several grades (42, 50, 55, 60, and 65), with Grade 50 being the most commonly used.
A572 is favored for its superior strength-to-weight ratio, toughness, and weldability, making it ideal for demanding structural applications.
Key Features of ASTM A572
Standard: ASTM A572/A572M
Product Forms: Plates, bars, structural shapes, sheet piling
Grades: 42, 50, 55, 60, 65 (increasing in strength)
Weldability: Good; requires attention to technique due to higher strength
Durability: Excellent; suitable for outdoor and high-stress environments.
Chemical Composition: A36 vs A572
Understanding the chemical makeup of each steel grade is essential for predicting performance and suitability.
1) ASTM A36 Chemical Composition
Element
Content (%)
Carbon (C)
0.25 – 0.29
Manganese (Mn)
1.03
Phosphorus (P)
0.040
Sulfur (S)
0.050
Silicon (Si)
0.280
Copper (Cu)
0.20
Iron (Fe)
Balance
2) ASTM A572 Chemical Composition (Typical for Grade 50)
Element
Content (%)
Carbon (C)
≤0.23
Manganese (Mn)
≤1.35
Phosphorus (P)
≤0.04
Sulfur (S)
≤0.05
Silicon (Si)
0.15–0.40
Iron (Fe)
Balance
Note: A572 contains slightly more alloying elements, which contribute to its higher strength and improved mechanical properties.
Common Applications and Use Cases
1) ASTM A36 Applications
Building frames (columns, beams, girders)
Bridges (beams, trusses)
Infrastructure (oil rigs, towers)
Equipment and machinery frames
Automotive and agricultural parts
Plates, bars, brackets, base plates, gussets.
2) ASTM A572 Applications
Building frames and high-rise structures
Bridges (girders, trusses)
Highway and transportation infrastructure (guardrails, sign supports)
Heavy equipment and truck frames
Poles, liners, boom sections
Energy sector power plant supports, wind turbine towers.
Selection Criteria: Which Steel Should You Choose?
Criteria
ASTM A36
ASTM A572
Strength
Moderate
High
Cost
Lower
Higher
Weldability
Excellent
Good (requires attention)
Durability
Standard
Superior (weather resistance)
Availability
Very high
High (multiple grades)
Formability
Easier
Less easy
Typical Applications
General construction, frames
Bridges, heavy structures
Selections Tips:
Choose A36 for general, cost-sensitive projects with moderate strength requirements and where ease of fabrication is important.
Choose A572 for high-stress, outdoor, or critical applications where higher strength, durability, and weather resistance are required.
Mechanical Properties: A36 vs A572
The mechanical properties of steel determine its performance under load and in various environments.
Property
ASTM A36
ASTM A572 (Grade 50)
Yield Strength (MPa)
250
345
Tensile Strength (MPa)
400–550
450–620
Elongation (%)
20
18
Modulus of Elasticity
200 GPa
200 GPa
Weldability
Excellent
Good
Machinability
Good
Moderate
Note: A572 offers significantly higher yield and tensile strength, making it suitable for heavier, more demanding applications.
Cost Comparison: A36 vs A572
A36 Steel: Generally less expensive and more widely available, making it a cost-effective choice for general applications.
A572 Steel: Higher initial cost due to enhanced strength and alloying elements, but may offer savings in material weight and long-term durability.
Note: Choose A36 for budget-sensitive projects where moderate strength is sufficient; opt for A572 when higher performance justifies the added cost.
Weldability and Fabrication</h2>
A36: Known for excellent weldability and ease of fabrication, making it ideal for projects requiring extensive welding or reshaping.
A572: Also weldable, but may require more attention to technique due to higher strength and alloy content.
Note: A36 is easier to work with for complex fabrication, while A572 may require more skilled welding practices.
Conclusion
Choosing between ASTM A36 and A572 steel depends on your project’s specific requirements. If you need a cost-effective, easy-to-fabricate material for general construction, A36 is an excellent choice.
For projects demanding higher strength, durability, and performance such as bridges, heavy equipment, or outdoor structures A572 is the superior option.
Always consider your application’s strength, cost, fabrication, and environmental needs to select the right steel grade for your project
Frequently Asked Questions (FAQs)
1. What is the main difference between ASTM A36 and A572 steel?
The main difference is strength: A572 is a high-strength, low-alloy steel, while A36 is a standard carbon steel with lower strength. A572 is better for heavy, high-stress applications, while A36 is more cost-effective for general use.
2. Can both A36 and A572 be welded?
Yes, both can be welded, but A36 is easier to weld and fabricate. A572 may require more attention to welding technique due to its higher strength.
3. Which steel is better for outdoor structures?
A572 is preferred for outdoor or exposed structures due to its superior durability and resistance to environmental stress.