AMS 6415 is a sub-type specification of Steel 4340, which is low-alloy nickel-chromium-molybdenum steel with medium carbon content. The material comes in the annealed condition, but other sub-specifications come in the hardened and tempered conditions.
The quality of the alloy changes significantly after treatments, with higher strength obtained after normalizing, hardening, and tempering. For added surface hardness, an additional treatment of flame or induction hardening (Rc 50) or nitriding (Rc 60) can be carried out.
Nonetheless, AMS 6415 also becomes harder to machine and weld after normalizing, hardening, and tempering. Thus, special care should be performed. If absolutely necessary, a coarse lamellar pearlitic structure or a spheroidized structure is recommended for machining. Meanwhile, before welding, it’s best to preheat the area at 400-580 °F to (≈200-300 °C) and follow by stress relief at 1020-1200 °F (≈550-650 °F).
Tech Steel & Materials offers AMS 6415 in a bar, forging, and tubing stock. The material possesses excellent toughness, very good abrasion resistance, very good shock and impact resistance, and good atmospheric corrosion resistance. As a result, it finds use in various fields, including heavy machinery industry, commercial aircraft industry (landing gear), various automotive uses, rocket motor cases, pressure vessels, and fasteners, ordnance hardware.