Aircraft Alloys / 9-4-30 VAC MELT N&T

9-4-30 Vac Melt Normalized & Tempered is an alloy with a high nickel and cobalt content to provide strength and toughness. This vacuum melted alloy exhibits exceptional cleanliness and comes in the normalized & tempered condition for optimal machinability before heat treat. Once heat treated and quenched this steel is designed to have high hardenability teamed with good weldability and excellent fracture toughness. Due to these qualities 9-4-30 is used to produce gears, pressure vessels, armor plate, rocket motor cases, and aircraft structural components. (UNS K91283)

Chemical Makeup

Element Min Max
Carbon, C 0.29 0.34
Manganese, Mn 0.1 0.35
Silicon, Si - 0.2
Phosphorus, P - 0.01
Sulfur, S - 0.01
Chromium, Cr 0.9 1.1
Molybdenum, Mo 0.9 1.1
Nickel, Ni 7 8
Copper, Cu - 0.35
Vanadium, V 0.06 0.12
Cobalt, Co 4.25 4.75

Common Applications

  • Aerospace Aerospace
  • Defense Defense


  • Good Strength
  • Good Hardenability
  • Excellent Fracture Toughness
  • Good Machinability
  • Good Weldability

We stock 9-4-30 VAC MELT N&T to the following specifications:

  • BMS-7-182 TYPE 2
  • MIL-STD-2154 CL A (SONIC)
  • STO-160-LBO-012

Click on a cross-section to see the sizes we stock:

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