Steel Alloy 300M

  • Steel Alloy 300M

  • General Characteristics

    300M steel is a modified 4340 steel with added silicon allowing for use of a higher tempering temperature. The steel has high hardenability and strength with good ductility and toughness in heavy sections. It is used primarily in the 270/300 ksi (1862/2068) tensile strength range for aircraft landing gears, flap tracks and other structural applications. Vacuum arc remelting (VAR) is used to provide optimum cleanliness and preferred ingot structure.

  • Typical Chemical Composition

    Weight % C Mn P S Si Ni Cr Mo V Fe
    minimum 0.40 0.65 — — 1.45 1.65 0.70 0.30 — reminder
    maximum 0.46 0.90 0.035 0.040 1.80 2.00 0.95 0.45 0.05

  • Physical Properties

    Characteristics English Metric
    Nominal density

    (68°F/20°C)

    		 0.283 lbs/in3 7.84 g/cm3
    Specific heat

    (212 °F/100°C)

    		 0.107 BTU/lb – °F 448 J/KG- °K
    Coefficient of thermal

    expansion

    		 0°F – 200°F

    -18°C – 93°C

    		 6.30 micro in/in- °F 11.3 micro m/m- °K
    Thermal conductivity 21.7 BTU/ft- hr – °F 37.49 W/m – °K

  • Mechanical Properties

    Tensile Hardness
    Typical transverse mechanical properties with (302 °C) temper Ultimate Yield Elongation

    at break

    		 Reduction

    of area

    		 Rockwell C –

    Jomini test –

    distance from

    quenched end
    Specimen size – 0.252 KSI MPa KSI MPa % % 1” 1/2” 1/8”
    300M

    VAC-ARC

    		 660-711 mm 286 1972 240 1655 11 37 57.5 58 59
    305 mm 288 1986 242 1669 11 39
    300M-HS

    VAC-ARC

    		 660-711 mm 292 2013 246 1696 10 31 57.5 58 59
    305 mm 298 2055 251 1731 11 34

  • Specifications

    300M VAC-ARC

    • AMS – 6257, 6417, 6419
    • BMS – 7-26 (Boeing)
    • DMS – 1935 (McDonnell-Douglas)

    300M-HS VAC-ARC

    • AMS – 6419
    • MTL-1201 (Messier-Dowty)
    • LGMS 1000 (Goodrich)
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