4330 MOD Alloy Steel - AMS 6411 VAR - UNSK23080
4330 MOD VAR AMS 6411 is AISI 4330 Steel modified with the addition of Vanadium. It is a low alloy steel capable of being heat treated to high strength levels. Vanadium is added to improve impact strength and hardenability. This is a premium aircraft quality steel usually produced as a consumable electrode remelted product (VAR). AMS 6411 also allows the 2nd melt to be ESR (Electro-Slag Remelting) when specified by the end-user.
Download DatasheetService Steel Aerospace is one of the largest distributors / suppliers of 4330 Alloy Steel available in multiple forms including round bar and block. See below for product size ranges stocked.
4330 Mod VAR Alloy Steel Applications:
Aerospace applications are those requiring high tensile strength and good ductility, coupled with high impact strength, superior transverse properties, and hardness. The carbon content lower than AISI 4340 makes this grade useful for applications that involve shock loading or stress concentration.
Common Trade Names:
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Common Specifications:
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Stocked Sizes:
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Note: Stocked as Normalized & Tempered (N&T)
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Macrostructure standards:
| Class | Condition | Severity | 1 | Freckles | A | 2 | White Spots | A | 3 | Radial Segregation | B | 4 | Ring Pattern | B |
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Longitudinal Tensile Properties:
| Property | Value | Tensile Strength | 220 ksi | Yield Strength 0.2% offset | 185 ksi | Elongation | 10% | Reduction of Area | 35% |
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After heat treating specimens per paragraph 3.4.5
Chemical Composition:
| Symbol | Element | Min % | Max % | C | Carbon | 0.28% | 0.33% | Mn | Manganese | 0.65% | 1.00% | Si | Silicon | 0.15% | 0.35% | P | Phosphorus | 0.015% | S | Sulfur | 0.015% | Cr | Chromium | 0.75% | 1.00% | Ni | Nickel | 1.65% | 2.00% | Mo | Molybdenum | 0.35% | 0.50% | V | Vanadium | 0.05% | 0.10% | Cu | Copper | 0.35% |
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Fabrication
| Forging | 1950° – 2255° F (1066° – 1235° C) |
| Machinability | Normalize & temper at 1250° F (675° C) prior to machining. Machining at max strength is usually followed by stress relieving |
| Welding | Arc or Resistance Flash weldable |
Physical Properties:
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Heat Treatment
| Type of Heat Treating | Process |
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| Normalize | 1600° - 1700° (870° - 925° C), air cool |
| Anneal | 1525° - 1575° (830° - 860° C), furnace cool |
| Harden | Austenitize 1550° - 1600° (845° - 870° C), water, oil, or polymer quench |
| Temper | 500° - 700° (260° - 240° C) for tensile 220-240 ksi |
Minimum Transverse Tensile Properties per AMS 6411:
| Cross-section Area | Tensile Strength | Yield Strength 0.2% Offset | Avg. Reduction of Area | Individual Reduction of Area |
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| Up to 144 in2, incl | 220 ksi | 185 ksi | 35% | 30% min |
| Over 144 in2 to 225 in2, incl | 220 ksi | 185 ksi | 30% | 25% min |
| Over 225 in2 | 220 ksi | 185 ksi | 25% | 20% min |
