AMS 6484 is a sub-type specification of Steel 4340, a low-alloy steel with high strength and toughness, very good abrasion resistance, very good shock and impact resistance, and good atmospheric corrosion resistance. The material has medium carbon content and concentrations of nickel, chromium, and molybdenum.
Tech Steel & Materials offers AMS 6484 in a bar, forging, and tubing stock. All forms come in the normalized and tempered form, meaning they already provide very high strength and fatigue resistance. However, Steel 4340 in this form also has lower ductility and is harder to machine or weld.
Thus, we recommend applying special care during machining, specifically using coarse lamellar pearlitic structure or a spheroidized structure. For welding, preheating is needed to ensure that no cracking occurs.
A usual preheating treatment starts at 400-580 °F to (≈200-300 °C), followed by after-welding stress relief at 1020-1200 °F (≈550-650 °F), or 60 °F (15 °C) lower than the tempering temperature. The use of AMS 6456 welding wire is recommended for the best results.
AMS 6484 parts possess excellent wear characteristics, very good toughness and strength, good abrasion resistance, very good impact resistance, and excellent atmospheric corrosion resistance. However, since this specification already comes in the normalized and tempered form, it doesn’t possess the same ductility as the material in annealed form.