AMS 6414 is a sub-type specification of Steel 4340, a high-strength steel with medium carbon content and higher concentrations of nickel, chromium, and molybdenum. Tech Steel & Materials offers AMS 6414 in a bar, forging, and tubing form.
The material comes in an annealed and vacuums art remelted condition. Meanwhile, normalizing, hardening, and stress relief can significantly increase the toughness of the parts. For increased surface hardness, additional flame hardening or nitriding can be used.
AMS 6414 can be used to manufacture high-strength parts with excellent toughness, very good fatigue resistance and wear resistance, good abrasion resistance, and very good atmospheric corrosion resistance. Moreover, the material is easy to machine in the current condition and possesses excellent ductility.
Nonetheless, additional care must be obtained when machining the material after additional heat treatments, specifically by using a spheroidized structure. Similarly, AMS 6414 can be readily welded in the annealed condition, but preheating at 400-580 °F to (≈200-300 °C), followed by after-welding stress relief at 1020-1200 °F (≈550-650 °F) is recommended for hardened and tempered parts.
Thanks to its favorable properties, AMS 6414 finds use in the heavy machinery industry, specifically for the manufacturing of transmission parts. However, the alloy also finds use in commercial aircraft (landing gear), military vehicle parts, ordnance hardware, automotive industry (fasteners), rocket motor cases.