300M S155 Alloy Steel

Contact customer service
Heat Treatment
Cold Processing
Hot Working

300M S155 Alloy Steel

300M S155 Alloy Steel

300M S155 Alloy Steel

Supplying Size:

Rolled: Diameter 40-200mm

Forged: Diameter 80-600mm

300M/S155 is a high performance alloy steel which is a vacuum melted grade, supplied in the normalised and tempered/softened condition to enhance machinability prior to final heat treatment.

Chemical Component:

C Si Mn P S Cr Mo Ni V
0.38-0.46 1.45-1.8 0.6-0.9 0.01 0.01 0.7-0.95 0.3-0.65 1.65-2 0.05
Back to Top

Mechanical Properties:

Mechanical & Physical Properties 21 °C
Ultimate Tensile Strength /MPa 1981
0.2% Yield Strength /MPa 1672
Reduction of area % 35
Elongation % 10
Room Temperature Hardness/ Rockwell C 58

(Normalised at 927 °C for 1 hour+air cool/Austenitised at 871°C for 1 hour + oil quench/Tempered at 302°C for 1 hour+air cool)

Hardness at Various Tempering Temperature 204°C 316°C 427°C 538°C 649°C
Hardness / Rockwell C 53 52.5 50 47 35

(Austenitised at 871°C for 1 hour + oil quench/Tempered for 2+2 hour+air cool)

Back to Top


It has a combination of ultra high strength, good fatigue resistance and excellent transverse properties, and as such finds many applications in the aerospace industry, such as undercarriage components, gears and shafts.

Back to Top


AMS 6417, ASTM A579

Back to Top


300M/S155 can be used in a variety of applications, here are just a few examples:

Undercarriage components



Aircraft landing gear

High strength bolts

Back to Top



7.85 g/cm^3

Specific Heat Capacity:

448 J/kg*K

Coefficient of Thermal Expansion from -17.8-93°C:

11.34 µm/mm/°C

Back to Top