300M (4340 MOD) Alloy Steel - AMS 6417 - UNS K44220
300M Consumable Electrode Vacuum Remelted Steel is 4340 Alloy Steel modified with the addition of Vanadium and higher Silicon. Carbon Content in AMS 6417 Carbon content is 0.37% to 0.43”. Specifications AMS 6419 requires 0.40” – 0.45% C and AMS 6256 0.40% - 0.44%C. Service Steel Aerospace stocks material with restricted carbon content to certify chemistry to these various specifications.
Download DatasheetThese chemistry modifications provide an Alloy Steel with very good fatigue strength, ductility, impact strength and fracture toughness. 300M is widely used for Aircraft Landing Gear.
300M (4340 Mod) Alloy Steel Applications:
This grade is used high strength structural applications with sections 3.5” in and under in cross-section thickness for through-hardness requiring minimum Rockwell C hardness 52 HRC that are subject to exacting magnetic particle inspection standards. Applications include:
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Common Trade Names:
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Common Specifications:
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Physical Properties:
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Stocked Sizes:
Note: Stocked as Normalized & Tempered (N&T)
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Chemical Composition:
| Symbol | Element | Min % | Max % |
|---|---|---|---|
| C | Carbon | 0.38% | 0.43% |
| Mn | Manganese | 0.65%% | 0.90% |
| Si | Silicon | 1.45% | 1.80% |
| P | Phosphorus | 0.010% | |
| S | Sulfur | 0.008% | |
| Cr | Chromium | 0.70% | 0.95% |
| Ni | Nickel | 1.65% | 2.00% |
| Mo | Molybdenum | 0.30% | 0.50% |
| V | Vanadium | 0.05% | 0.10% |
| Cu | Copper | 0.35% |
Both AMS 6257 and AMS 6419 require minimum 0.40% Carbon content
SSA material is stocked with minimum 0.40% Carbon content to meet multiple specifications
AMS 6417 Macrostructure standards:
| Class | Condition | Severity |
|---|---|---|
| 1 | Freckles | A |
| 2 | White Spots | A |
| 3 | Radial Segregation | B |
| 4 | Ring Pattern | B |
Minimum Longitudinal Tensile Properties per AMS 6417:
| Property | Value |
|---|---|
| Tensile Strength | 270 ksi |
| Yield Strength 0.2% offset | 220 ksi |
| Elongation | 8% |
| Reduction of Area | 30% |
Minimum Transverse Tensile Properties per AMS 6417:
| Cross-section Area | Tensile Strength | Yield Strength 0.2% Offset | Avg. Reduction of Area | Individual Reduction of Area |
|---|---|---|---|---|
| Up to 100 in2, incl | 270 ksi | 220 ksi | 30% | 25% min |
| Over 100 in2 to 144 in2, incl | 270 ksi | 220 ksi | 25% | 20% min |
| Over 144 in2 to 225 in2, incl | 270 ksi | 220 ksi | 20% | 15% min |
| Over 225 in2 | 270 ksi | 220 ksi | 15% | 10% min |
AMS 6417 Heat Treatment
| Type of Heat Treating | Process |
|---|---|
| Normalize | 1700° F +/- 25° F (927° C +/- 14° C), then air cool |
| Harden | 1600° F +/- 25° F (871° C +/- 14°C), quench in oil |
| Temper | Double temper 400° – 1200° F (204° – 649° C) depending on desired strength and hardness. |
AMS 6417 Fabrication
| Forging | Forge between 1950° – 2250° F (1066° – 1232° C), min 1700° F |
| Machinability | Normalize, then temper at approx. 1200° F (649° C) for optimum condition for machining |
| Welding | Can be welded by gas or arc fusion methods. |
