UNS #G43400

4340 VAC-ARC steel is a low alloy, nickel-chromium-molybdenum steel capable of being heat treated to high strength levels. The alloy has a good combination of ductility, toughness and strength along with high hardenability and better depth of hardening than chrome-moly 4140 type alloys. 4340 steel is produced by the consumable electrode vacuum arc remelting process to provide optimum cleanliness and preferred ingot structure.

Type Analysis

  • Carbon (Nominal) 0.4
  • Silicon (Nominal) 0.3
  • Nickel (Nominal) 1.8
  • Manganese (Nominal) 0.75
  • Chromium (Nominal) 0.8
  • Molybdenum (Nominal) 0.25
  • Iron (Nominal) Balance


Crank shafts, impeller shafts, support tooling, die holders, bolts, gears, flanges, collets, arbors, spindles, axles, clutch parts, forming rolls and various machine tool components.

Applicable Specifications

  • AMS 6414
  • AMS 6415 (Air Melt)
  • AMS-S-5000 (Air Melt)
  • 299-947-055 (Bell Helicopter)
  • SS 9702 (Sikrosky)




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