AASHTO M270 Vs ASTM A709 Grade Comparison

AASHTO M270 and ASTM A709 are two distinct types of steel plates commonly used in bridge construction. These materials possess mechanical and physical properties that make them suitable for withstanding harsh weather conditions and significant stresses, making them ideal choices for infrastructure projects.

AASHTO M270 and ASTM A709 are two distinct types of steel plates commonly used in bridge construction

Understanding the Standards: AASHTO and ASTM

Both M270 and A709 steel plates are produced to meet the standards set by their respective regulatory bodies. The American Association of State Highway and Transportation Officials (AASHTO) oversees the specifications for M270 steel plates, while the American Society for Testing and Materials (ASTM) governs the standards for A709 steel plates.

AASHTO Standards

AASHTO is a U.S.-based organization that sets and regulates standards for designing and constructing infrastructure across various transportation modes, including highways, railways, airways, waterways, and public transportation. AASHTO standards are typically employed by state and local government projects, ensuring materials meet the rigorous demands of public infrastructure.

AASHTO M270 Steel Plates

ASTM Standards

ASTM is an international organization that develops standards for a wide range of products across various industries, including steel, petroleum, and medical devices. ASTM standards are used in both government and private sector projects, providing a broad applicability for materials like A709 steel plates.

ASTM A709 Steel Plates

Dual Certification: AASHTO M270 and ASTM A709

Steel plates can be dual-certified to meet the specifications of both AASHTO M270 and ASTM A709. This flexibility allows buyers to ensure that their materials meet the necessary standards for specific projects. For instance, if a bridge construction project requires materials to meet AASHTO standards but prefers A709 steel, buyers can request A709 plates that are also certified to AASHTO specifications from suppliers like Steel Friend.

Considerations for Bridge Manufacturing

When sourcing steel plates for bridge construction, it’s crucial to consider the type of bridge and the environmental conditions it will face. M270 steel is primarily used for highway and transportation projects, making it suitable for road bridges. On the other hand, A709 steel can be used for various types of bridges, including railroad, road, and pedestrian bridges.

In colder climates, the steel used must withstand severe conditions without corroding or fracturing. Both M270 and A709 have weathering grades, denoted by a “W” (e.g., A709 Grade 50W), which contain additional alloys to enhance their durability in extreme weather. A709 also includes high-performance standard (HPS) grades, which provide a balance of strength, weldability, corrosion resistance, and ductility, making them ideal for challenging environments.

Specifications of M270 and A709 Grades

The chemical composition and mechanical properties of M270 and A709 steel grades are defined under ASTM specifications for A709 steel. These specifications outline the inclusion of chemical alloys that enhance the materials' properties, such as strength, hardness, and corrosion resistance.

Chemical Composition

ElementM270 Grade 50M270 Grade 50W Type AM270 Grade 50W Type BA709 Grade 50A709 Grade 50W Type AA709 Grade 50W Type BA709 HPS Grades 50W & 70W
Carbon (max)0.23%0.19%0.20%0.23%0.19%0.20%0.11%
Manganese1.35% max0.80-1.25%0.75-1.35%1.35% max0.80-1.25%0.75-1.35%1.10-1.50%
Phosphorus (max)0.030%0.030%0.030%0.030%0.030%0.030%0.020%
Sulfur (max)0.030%0.030%0.030%0.030%0.030%0.030%0.006%
NickelN/A0.40% max0.50% maxN/A0.40% max0.50% max0.25-0.40%
NitrogenN/AN/AN/AN/AN/AN/A0.015% max

The presence of these chemical elements enhances the steel’s ability to withstand the high forces and environmental conditions that bridges typically encounter.

Mechanical Properties

GradeYield Point (KSI)Tensile Strength (KSI)
M270 Grade 505065
M270 Grade 50W5070
A709 Grade 363658-80
A709 Grade 505065
A709 Grade 50W5070
A709 Grade HPS 50W5070
A709 Grade HPS 70W7085-110

Importance of Charpy Impact Test

For steel materials used in bridge construction in cold climates, a Charpy impact test is often requested. This test measures the material's ability to absorb impact at various temperatures, ensuring that the steel can withstand extremely harsh conditions without fracturing.

Sourcing M270 and A709 Steel Plates

When selecting a supplier for M270 or A709 steel plates, buyers should consider several critical factors to ensure they receive high-quality materials and services:

  • Comprehensive Documentation: Ensure that detailed paperwork, including mill test reports and invoices, is provided to
  • Quality Management System: Look for suppliers with a quality management system, such as ISO 90
  • Inventory Availability: Choose suppliers with distribution centers that stock a v

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