Online Catalog

Steel 300M

300M is a low alloy, vacuum melted, steel of very high strength. Essentially it is a modified AISI 4340 steel with silicon, vanadium and slightly greater carbon and molybdenum content than 4340. 300M has a very good combination of strength (280 to 305 ksi), toughness, fatigue strength and good ductility. It is a through hardening alloy.

Applications for 300M steel are those that require strength in the 290 – 300 ksi range, such as aircraft landing gear, high strength bolts, flap tracks, structural applications and airframe parts.

Chemical Properties

Element min max
Carbon 0.40 0.45
Manganese 0.60 0.90
Silicon 1.45 1.80
Phosphorus 0.010
Sulfur 0.010
Chromium 0.70 0.95
Nickel 1.65 2.00
Molybdenum 0.30 0.50
Vanadium 0.05 0.10
Copper 0.35

Minimum Longitudinal Tensile Properties

Property Value
Tensile Strength 280 ksi
Yield Strength at 0.2% Offset 230 ksi
Elongation in 4D 7%
Reduction of Area 25%

Minimum Transverse Tensile Properties, Inch/Pound Units

Nominal Cross-Sectional Area Square Inches Tensile Strength ksi Yield Strength at 0.2% Offset ksi Average Reduction of Area % Individual Reduction of Area %
Up to 100, incl 280 230 30 25
Over 100 to 144, incl 280 230 25 20
Over 144 to 225, incl 280 230 20 15
Over 225 280 230 15 10

Select AMS Number:

AMS Number Alloy Type UNS Cross Ref. Spec Misc./Shape
AMS 6257 300M Steel -  
AMS 6257 Bar 300M Steel - - Bar AMS 6257 Bar
AMS 6257 Forging 300M Steel - - Forging AMS 6257 Forging
AMS 6257 Tubing 300M Steel - - Tubing AMS 6257 Tubing
AMS 6417 300M Steel -  
AMS 6417 Bar 300M Steel - - Bar AMS 6417 Bar
AMS 6417 Forging 300M Steel - - Forging AMS 6417 Forging
AMS 6417 Tubing 300M Steel - - Tubing AMS 6417 Tubing
AMS 6419 300M Steel K44220  
AMS 6419 Bar 300M Steel K44220 MIL-S-8844 Bar AMS 6419 Bar
AMS 6419 Forging 300M Steel K44220 MIL-S-8844 Forging AMS 6419 Forging
AMS 6419 Plate 300M Steel K44220 MIL-S-8844 Plate AMS 6419 Plate
AMS 6419 Tubing 300M Steel K44220 MIL-S-8844 Tubing AMS 6419 Tubing