Structural Bolts, Alloy Steel, Heat Treated, 150 ksi Minimum Tensile Strength

A490: Standard Specification for Structural Bolts, Alloy Steel, Heat Treated, 150 ksi Minimum Tensile Strength

For engineers and designers working with high-strength structural connections, understanding the ASTM A490 standard is absolutely essential. This authoritative document provides the foundational requirements for alloy steel, heat-treated bolts that offer superior performance in demanding construction applications. Mastering its specifications ensures the integrity and safety of critical infrastructure.

What is A490?

ASTM A490 is a comprehensive standard originating from ASTM International that defines the material properties, manufacturing processes, and performance criteria for heavy hex structural bolts. Its primary purpose is to ensure the reliability and load-carrying capacity of these fasteners, which are specifically designed for structural steel connections demanding high tensile strength.

Scope & Purpose

This standard governs the production and application of quenched and tempered alloy steel heavy hex structural bolts. It specifies requirements for bolts manufactured from specific alloy compositions, including Type 1 (medium carbon alloy steel) and Type 3 (weathering steel), in sizes ranging from 1/2 inch to 1-1/2 inches in diameter. The standard focuses on bolts intended for structural connections as defined by industry-accepted design specifications, excluding requirements for metric equivalents (covered by A490M) or non-structural applications.

Who Must Comply?

• • Primary audience: Structural Engineers, Materials Engineers, Quality Control Inspectors, Procurement Specialists, and Manufacturing Engineers.
• • Industries affected: Construction, Structural Engineering, Steel Fabrication, and Heavy Manufacturing.
• • Compliance nature: Voluntary, but essential for projects specifying A490 bolts to meet design codes and ensure performance.
• • Enforcement: Typically enforced through project specifications, quality assurance programs, and independent testing by third-party laboratories or end-users.

Key Requirements Overview

The A490 standard mandates several critical aspects for these high-strength fasteners:

• • Material Composition: Specifies precise chemical composition ranges for alloy steels to ensure desired mechanical properties.
• • Heat Treatment: Requires specific quenching and tempering processes to achieve the minimum 150 ksi tensile strength and appropriate hardness.
• • Mechanical Properties: Defines minimum tensile strength, yield strength, and hardness requirements, alongside acceptable ranges for these properties.
• • Dimensional Tolerances: Outlines acceptable dimensional variations for bolt dimensions, including thread profiles and head configurations, typically for heavy hex heads.
• • Surface Integrity: Addresses acceptable surface discontinuities and mandates testing for them to prevent premature failure.

Related Standards & References

To ensure complete and compliant structural connections, A490 is often used in conjunction with:

• • ASTM F436: This standard specifies the requirements for hardened steel washers, which are crucial for proper load distribution and preventing damage to the structural members when used with A490 bolts.
• • ASTM A563: This specification covers carbon and alloy steel nuts suitable for use with A490 bolts, ensuring compatible strength and material properties.
• • RCS Specifications (e.g., AISC's Specification for Structural Joints Using A325 or A490 Bolts): These design codes provide the framework for how A490 bolts are to be used in structural connections, dictating connection types, bolt pretensioning, and overall design considerations