SPECIFICATION LIBRARY
ASTM A449
ASTM A449 Specification Overview
ASTM A449 is a standard specification for hex cap screws, bolts, and studs made from medium-strength, quenched, and tempered carbon or alloy steel. This specification is intended for use in general engineering applications, particularly where high strength is not required to the extent of ASTM A325 or A490 specifications.
Key Features of ASTM A449
Material: Medium-strength carbon or alloy steel.
Manufacturing Process: Components are quenched and tempered to achieve the desired mechanical properties.
Strength Level: Designed to fill the gap between low-strength ASTM A307 and high-strength ASTM A325/A490 specifications.
Chemical Composition
ASTM A449 does not specify detailed chemical composition, allowing flexibility in material selection as long as the mechanical requirements are met. However, the manufacturer must adhere to good steelmaking practices and choose materials that ensure the product's mechanical properties.
Mechanical Properties
ASTM A449 bolts have varying mechanical properties based on their diameter. Here’s a detailed breakdown:
|
Diameter Range |
Tensile Strength |
Yield Strength |
Elongation in 2" |
Reduction of Area |
Hardness |
|
≤ 1 inch (≤ 25.4 mm) |
120 ksi min |
92 ksi min |
14% min |
35% min |
25–34 HRC |
|
> 1 inch to ≤ 1-1/2 inches (25.4 mm to ≤ 38.1 mm) |
105 ksi min |
81 ksi min |
14% min |
35% min |
25–34 HRC |
|
> 1-1/2 inches (> 38.1 mm) |
90 ksi min |
58 ksi min |
14% min |
35% min |
25–34 HRC |
Key Points:
Tensile Strength: Reflects the maximum stress that the material can withstand while being stretched or pulled before necking.
Yield Strength: Indicates the stress at which a material begins to deform plastically. Below this point, the material will deform elastically and return to its original shape when the applied stress is removed.
Elongation: A measure of ductility, specifically the percentage increase in length after breaking under tensile stress.
Reduction of Area: Measures the change in cross-sectional area at the point of fracture, indicating the material’s ability to resist necking under tensile stress.
Hardness: Represents the material's resistance to indentation and wear, often correlated with tensile strength and measured on the Rockwell C scale (HRC) for ASTM A449.
Applications
ASTM A449 bolts are commonly used in construction, machinery, and other engineering applications where medium-strength fasteners are suitable. They fill a niche where higher strength than ASTM A307 is needed but the full strength of ASTM A325 or A490 is not necessary.
Quality Assurance
Products manufactured to the ASTM A449 standard must undergo rigorous testing to ensure they meet the specified mechanical properties. Tests include tensile testing, hardness testing, and proof load testing.
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