SAE AMS6471K-2023
Steel, Nitriding, Bars, Forgings, Mechanical Tubing, and Stock for Forging, 1.6Cr - 0.35Mo - 1.13Al (0.38 - 0.43C) (135 Mod), Premium Aircraft Quality, Consumable Electrode Vacuum Remelted

Standard No.

SAE AMS6471K-2023

Release Date

2023

Published By

Society of Automotive Engineers (SAE)  US  /  SAE

Latest

SAE AMS6471K-2023

Introduction

Standard Overview and Technological Evolution

AMS6471K is the latest revision released by SAE International in December 2023, replacing the AMS6471J version confirmed in 1999.

Performance Index	Required Values	Test Standards
Chemical Composition	0.38-0.43%C, 1.4-1.8%Cr, 0.95-1.3%Al	ASTM A751
Hardness (bar)	≤229 HBW (hot rolled) or ≤269 HBW (cold rolled)	ASTM A370
Hardenability	J12=50HRC min, J16=46HRC min	ASTM A255

Typical Application Case

This material is particularly suitable for applications requiring Nitrided parts with a surface hardness of 900 HV or higher, such as aircraft engine transmission gears, bearing seats, and other high-temperature operating components, can reduce heat treatment deformation by over 50% compared to traditional quench-hardened steel.

---

Key Process Control Points

1. Melting Process

The Vacuum Consumable Electrode Remelting (VAR) process must be used to ensure material purity meets AMS2300 aerospace-grade cleanliness requirements.

2. Decarburization Control

Differentiated control is implemented according to product type:

• Rods: ASTM E1077 microhardness method is used for testing. The decarburization depth is allowed to increase with the diameter (e.g. φ12.7mm rod ≤0.43mm)
• Mechanical pipes: inner and outer walls are controlled separately. For example, the inner wall of a 5.16mm thick pipe is ≤0.25mm and the outer wall is ≤0.51mm

---

Quality Assurance System

Test Type	Test Items	Implementation Standard
Acceptance Test	Composition, Macrostructure, Hardness, Hardenability	AMS2370/AMS2372
Periodic Inspection	Cleanliness Rating, Forging Flow Line	AMS2300

Note:All inspection reports must include the country of melting information, and abnormal materials must be marked with the "AMS6471K(EXC)" logo.

---

Implementation Recommendations

1. Product form (bar/forging/tube) and dimensional tolerance requirements (refer to AMS2251/AMS2253) should be clearly specified when ordering.
2. For hollow forgings and mechanical tubes, the macrostructure inspection method and acceptance criteria must be specified in the order.
3. Considering subsequent machining allowances, it is recommended to add 2-5mm machining allowances according to AS1182 standard.
4. Vacuum remelting process parameter recommendations: refining temperature ≥1600℃, vacuum degree ≤0.1Pa.

SAE AMS6471K-2023 Referenced Document

• AS 1182 Infant and child clothing sizing coding scheme for underwear and outerwear
• ASTM A255 Standard Test Method for Determining Hardenability of Steel
• ASTM A370 Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• ASTM A604 Standard Test Method for Macroetch Testing of Consumable Electrode Remelted Steel Bars and Billets
• ASTM A751 Standard Test Methods, Practices, and Terminology for Chemical Analysis of Steel Products
• ASTM E1077 Standard Test Methods for Estimating the Depth of Decarburization of Steel Specimens
• ASTM E112 Standard Test Methods for Determining Average Grain Size
• ASTM E140 Standard Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness, and Scleroscope Hardness

SAE AMS6471K-2023 history

• 2023 SAE AMS6471K-2023 Steel, Nitriding, Bars, Forgings, Mechanical Tubing, and Stock for Forging, 1.6Cr - 0.35Mo - 1.13Al (0.38 - 0.43C) (135 Mod), Premium Aircraft Quality, Consumable Electrode Vacuum Remelted
• 2018 SAE AMS6471J-2018 Steel@ Nitriding@ Bars@ Forgings@ and Tubing 1.6Cr - 0.35Mo - 1.13Al (0.38 - 0.43C) (135 Mod) Consumable Electrode Vacuum Melted (UNS K24065)
• 2014 SAE AMS6471H-2014 Steel, Nitriding, Bars, Forgings, and Tubing 1.6Cr - 0.35Mo - 1.13Al (0.38 - 0.43C) (135 Mod) Consumable Electrode Vacuum Melted
• 2010 SAE AMS6471G-2010 Steel, Nitriding, Bars, Forgings, and Tubing 1.6Cr 0.35Mo 1.13Al (0.38-0.43C)(135 Mod) Consumable Electrode Vacuum Melted
• 2005 SAE AMS6471F-2005 Steel, Nitriding, Bars, Forgings, and Tubing 1.6Cr 0.35Mo 1.2Al (0.38-0.43C) Consumable Electrode Vacuum Melted
• 2003 SAE AMS6471E-2003 Steel Bars, Forgings, and Tubing, Nitriding Grade 1.6Cr - 0.35Mo - 1.2Al - (0.38 - 0.43C) Consumable Electrode Vacuum Melted UNS K24065
• 1999 SAE AMS6471D-1999 Steel Bars, Forgings, and Tubing, Nitriding Grade 1.6Cr - 0.35Mo - 1.2Al (0.38 - 0.43C) Consumable Electrode Vacuum Melted
• 1992 SAE AMS6471D-1992 Steel Bars@ Forgings@ and Tubing@ Nitriding Grade 1.6Cr - 0.35Mo - 1.2Al - (0.38 - 0.43C) Consumable Electrode Vacuum Melted
• 1986 SAE AMS6471C-1986 STEEL BARS@ FORGINGS@ AND TUBING@ NITRIDING GRADE 1.6Cr - 0.35Mo - 1.2Al (0.38 - 0.43C) Consumable Electrode Vacuum Melted (UNS K24065)
• 1979 SAE AMS6471B-1979 STEEL BARS@ FORGINGS@ AND TUBING@ NITRIDING 1.6Cr - 0.35Mo - 1.2Al - (0.38 - 0.43C) Premium Quality@ Consumable Electrode Vacuum Melted (UNS K24065)
• 1972 SAE AMS6471A-1972 STEEL BARS@ FORGINGS@ AND TUBING@ NITRIDING 1.6Cr - 0.35Mo - 1.15Al (0.38 - 0.43C) Premium Quality
• 1965 SAE AMS6471-1965 STEEL BARS@ TUBING@ AND FORGINGS@ NITRIDING 1.6Cr - 0.35Mo - 1.15Al (0.38 - 0.43C) Premium Quality

Standard and Specification