Premium Quality Alloy Steel Blooms and Billets for Aircraft and Aerospace Forgings

A646/A646M- 17: Standard Specification for Premium Quality Alloy Steel Blooms and Billets for Aircraft and Aerospace Forgings

For engineers and designers working with critical aircraft and aerospace components, the integrity and reliability of raw materials are paramount. ASTM A646/A646M- 17 provides an authoritative standard that defines the stringent quality requirements for alloy steel blooms and billets destined for forging into these high-performance parts. Adhering to this specification is essential for ensuring the safety, durability, and operational success of advanced aviation and space applications.

What is A646/A646M- 17?

ASTM A646/A646M- 17 is a comprehensive industry standard developed by ASTM International. It establishes the precise criteria for producing premium quality alloy steel semic finished products, specifically blooms and billets, intended for subsequent forging into critical aircraft and aerospace components. This standard ensures that the base material possesses superior metallurgical properties and a controlled level of internal soundness, vital for applications demanding exceptional performance under extreme conditions.

Scope & Purpose

This specification governs the production and procurement of alloy steel blooms and billets that are hot rolled or forged, with cross-sectional areas of 16 in.² [103 cm²] or larger, specifically for reforging into critical aerospace parts like landing gear components. It defines three distinct classes of steel based on melting practices: Class I (vacuum-induction melted or consumable-electrode vacuum melted), Class II (air-melted vacuum degassed), and Class III (air-melted electric furnace ladle refined and vacuum degassed). The standard does not cover the final forged products themselves but focuses solely on the quality of the intermediate blooms and billets.

Who Must Comply?

• • Primary audience: Metallurgical Engineers, Materials Engineers, Quality Control Inspectors, Manufacturing Engineers, Production Managers, and Aerospace Design Engineers involved in the specification, procurement, and manufacturing of aerospace components.
• • Industries affected: Aerospace, Defense, Aviation, and Steel Manufacturing sectors.
• • Compliance nature: Voluntary, but often mandated by customer specifications and procurement requirements within the aerospace industry.
• • Enforcement: Compliance is typically verified through audits, material certifications, and testing performed by raw material suppliers, component manufacturers, and end-users (e.g., aircraft OEMs).

Key Requirements Overview

The standard requires that materials supplied under A646/A646M- 17 meet exceptionally high-quality benchmarks. Professionals must ensure that the chosen melting practice (Class I, II, or III) aligns with the application's criticality. Key provisions include stringent control over chemical composition for specified grades, demanding limitations on non-metallic inclusions, and specific requirements for macroetch and microcleanliness testing. Furthermore, the standard mandates appropriate hot-working procedures, including minimum reduction ratios from ingot to bloom for certain sizes, to ensure proper grain structure and internal soundness. Ultrasonic examination requirements are also detailed to detect internal discontinuities.

Related Standards & References

ASTM A646/A646M- 17 works in conjunction with several other ASTM and industry standards. Specification A788/A788M (Steel Forgings, General Requirements) provides overarching requirements for steel forgings and is referenced for general manufacturing, testing, and marking