4340 MOD Alloy Steel – AMS 6417 – AMS 6419 – UNS K44220
These 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.
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.
This grade is available as a consumable electrode vacuum remelted product. This insures a steel of the highest quality with excellent transverse ductility and toughness at high strength levels. It also insures the non-metallic cleanliness of this alloy meeting AMS 2300, thus making it most suitable for the fabrication of parts subjected to magnetic particle inspection.
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% |
Carbon Content Note: Both AMS 6257 and AMS 6419 require minimum 0.40% Carbon content
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 |
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:
- Aircraft Landing Gear
- Airframe Parts, such as Flap Tracks
- Missile Components
- Motorsport Applications
HEAT TREATMENT
Normalize-1700°F
Austenitize-1600°F
Quench-Oil,140 F maximum
Temper-500°/600° F for 270,000 psi strength level
Common Trade Names:
Lescalloy 300M Vac-Arc
4340 Modified
434M
300M CEVM
Common Specifications:
AMS 6417 (Replaces MIL-S-83135)
AMS 6419
AMS 6257 (Replaces MIL-S-8844 REV D CLASS 3)
AMS 2300 Premium Aircraft Quality Cleanliness
BMS 7-26
BE1036
CE-0896
C-05-1190
DMS 1935
GM1012
MTL 1201
S155
MAT 137
SAE 434M
IGQ 41-11
LAT 1.9042
ZFNL 9207
ASTM A646
