Aircraft Alloy Steel AISI 4140 (AMS 6349/ AMS 6382)

Technical Data Sheet


Chemical Composition Limits
Weight% C Si Mn Cr Mo
4140 Ann 0.40 0.25 0.85 1.00 0.25
4140 Normalised 0.40 0.25 0.85 1.00 0.25

Alloy 4140 (AISI 4140) is a low alloy steel containing Chromium and Molybdenum. Alloy 4140 is the most widely used alloy for oil patch applications. Usually supplied hardened and tempered to condition T in sections up to 100mm with a tensile strength of 850 - 1000MPa and aiming for this strength range in larger sections. Alloy 4140 (AISI 4140) offers a very good balance of strength, toughness and wear resistance. Other typical applications are axles, conveyor parts, crow bars, gears, logging parts, spindles, shafts, pump shafts, sprockets, studs, pinions, rams, ring gears.

Typical Mechanical Properties


Alloy Section mm Yield Strength MPa Tensile Strength MPa Elongation % Izod J Hardness HB
Alloy 4140 50 770 930 17 90 275
Alloy 4140 100 710 920 15 70 270
Alloy 4140 200 570 850 14 60 250

Alloy 4140 (AISI 4140) is available in Bars (Rounds, Flat, Square, Hexagons).  For all stock availability contact Sales.

AMS 6349
AMS 6382
AMS S 5626
MIL S 5626
AS 1444-1996
UNS G41400

Heat Treatments
4140 Forging:
Heat to 1150°C Hold until uniform. Minimum forging temperature 850°C. Cool slowly in ashes or sand etc.

4140 Annealing:
Heat to 830°C-850°C. Cool in furnace

4140 Normalising:
Heat to 870°C-900°C
Cool in still air

4140 Stress Relieving:
Annealed: Heat to 600°C - 650°C
Hardened: Heat to 500°C - 550°C

4140 Hardening:
Heat to 830°C- 800°C
Quench in oil or polymer

4140 Tempering:
Heat to 450°C-700°C cool in still air

NB Tempering within the range 200°C - 420°C will result in temper brittleness and should be avoided
Every effort is made to ensure that technical specifications are accurate. However, technical specifications included herein should be used as a guideline only. All specifications are subject to change without notice.