Online Catalog

Steel 4340

4340 is a heat treatable, low alloy steel containing nickel, chromium and molybdenum. It is known for its toughness and capability of developing high strength in the heat treated condition while retaining good fatigue strength. 4340 has a favorable response to heat treatment (usually oil quenching followed by tempering) and exhibits a good combination of ductility and strength when treated thusly.

Typical applications are for structural use, such as aircraft landing gear, power transmission gears and shafts, rocket motor cases, ordnance hardware, aircraft structural components, piston pins, bearings, ordnance, dies, transmission gears, components, fasteners, and pressure vessels.

Chemical Properties

Element min max
Carbon 0.38 0.43
Manganese 0.65 0.85
Silicon 0.15 0.35
Phosphorus 0.025
Sulfur 0.025
Chromium 0.70 0.90
Nickel 1.65 2.00
Molybdenum 0.20 0.30
Copper 0.35

Mechanical Properties, Normalized (AMS 6414)

Property Value
Tensile Strength 260 ksi
Yield Strength at 0.2% Offset 217 ksi
Elongation in 4D 10%
Reduction of Area 30%

Select AMS Number:

AMS Number Alloy Type UNS Cross Ref. Spec Misc./Shape
AMS 6359 4340 Steel G43400  
AMS 6359 Plate 4340 Steel G43400 - Plate AMS 6359 Plate
AMS 6359 Sheet 4340 Steel G43400 - Sheet AMS 6359 Sheet
AMS 6359 Strip 4340 Steel G43400 - Strip AMS 6359 Strip
AMS 6409 4340 Steel G43400  
AMS 6409 Bar 4340 Steel G43400 - Bar AMS 6409 Bar
AMS 6409 Forging 4340 Steel G43400 - Forging AMS 6409 Forging
AMS 6409 Tubing 4340 Steel G43400 - Tubing AMS 6409 Tubing
AMS 6414 4340 Steel G43400  
AMS 6414 Bar 4340 Steel G43400 - Bar AMS 6414 Bar
AMS 6414 Forging 4340 Steel G43400 - Forging AMS 6414 Forging
AMS 6414 Tubing 4340 Steel G43400 - Tubing AMS 6414 Tubing
AMS 6415 4340 Steel G43406  
AMS 6415 Bar 4340 Steel G43406 MIL-S-5000 Bar AMS 6415 Bar
AMS 6415 Forging 4340 Steel G43406 MIL-S-5000 Forging AMS 6415 Forging
AMS 6415 Tubing 4340 Steel G43406 MIL-S-5000 Tubing AMS 6415 Tubing
AMS 6454 4340 Steel G43400  
AMS 6454 Plate 4340 Steel G43400 - Plate AMS 6454 Plate
AMS 6454 Sheet 4340 Steel G43400 - Sheet AMS 6454 Sheet
AMS 6454 Strip 4340 Steel G43400 - Strip AMS 6454 Strip
AMS 6456 4340 Steel - - Wire 4340
AMS 6484 4340 Steel G43400  
AMS 6484 Bar 4340 Steel G43400 AMS-S-5000 Bar AMS 6484 Bar
AMS 6484 Forging 4340 Steel G43400 AMS-S-5000 Forging AMS 6484 Forging
AMS 6484 Tubing 4340 Steel G43400 AMS-S-5000 Tubing AMS 6484 Tubing