ThePipingMart Blog Grades AISI 300M Alloy Steel (UNS K44220) – Composition, Properties, and Uses

AISI 300M Alloy Steel (UNS K44220) – Composition, Properties, and Uses


Aerospace and defence industries use high-strength steel for a variety of applications. AISI 300M is a material revered for its exceptional strength, toughness and fatigue properties. Its unique properties make it a popular choice for various industrial applications. But what is AISI 300M? Let’s explore its composition, mechanical and physical properties, as well as its uses, corrosion resistance, heat treatment, and machining techniques.

What is AISI 300M?

AISI 300M is a high-strength, low-alloy steel used in various industries, particularly those that require excellent durability and toughness. It has a carbon content range between 0.08% – 0.14%, manganese up to 1%, nickel up to 2%, chromium up to 3%, molybdenum up to 4%, phosphorus and sulfur as low as 0.03%. Its unique mechanical properties and machinability combination can be tailored for specific applications such as automotive parts, aircraft components, energy production equipment and more!

AISI 300M Composition

AISI 300M is a low-alloy steel with a chemical composition of molybdenum, nickel, and chromium. It also contains vanadium and carbon in lower concentrations. Combining these alloying elements imparts the desirable properties of toughness, fatigue resistance, and high strength to AISI 300M. The composition of AISI 300M makes it ideal for applications like high-strength fasteners, tow cables, landing gear, and drive shafts.

Element Content (%)
Iron, Fe 93.4 – 94.8
Nickel, Ni 1.65 – 2.0
Silicon, Si 1.45 – 1.80
Chromium, Cr 0.70 – 0.95
Manganese, Mn 0.65 – 0.90
Carbon, C 0.40 – 0.460
Phosphorous, P 0.035
Molybdenum, Mo 0.30 – 0.45
Vanadium, V 0.050
Sulfur, S 0.040

AISI 300M Mechanical Properties

AISI 300M is known for its excellent mechanical properties, such as high yield strength, ultimate strength, and fatigue resistance. The typical yield strength of AISI 300M is 110 ksi, and the ultimate power is up to 185 ksi. Its fatigue resistance, too, is exceptional, and it can survive over 10 million stress cycles. The material also has excellent flexibility, enabling it to withstand high loads without cracking or breaking.

Properties Metric Imperial
Shear modulus (typical for steel) 80 GPa 11600 ksi
Elastic modulus 205 GPa 29700 ksi
Poisson’s ratio 0.28 0.28

AISI 300M Physical Properties

AISI 300M has a density of 0.284 lb/in³ and a melting point between 2500 to 2750°F. The modulus of elasticity of the material is around 29×10^6 psi. The high-strength steel exhibits good impact resistance, with a Charpy impact strength of around 80-120 ft-lb.

Properties Metric Imperial
Density 7.87 g/cm3 0.284 lb/in³
Melting point 1422°C 2590°F

AISI 300M Equivalents

  • AMS 6417
  • AMS 6419
  • ASTM A579 (32)
  • ASTM A646 (300M-8)
  • MIL S-8844 (3)
  • MIL S-8844 Class 2

AISI 300M Uses

AISI 300M is a popular material for various aerospace and defence applications. The material is used in aircraft landing gear and engine components such as turbofan blades, afterburner shells, and high-pressure compressor discs. Its exceptional strength-to-weight ratio is ideal for racing car components, drive shafts, and gears for high-performance vehicles.

AISI 300M Corrosion Resistance

AISI 300M steel has good corrosion resistance compared to other low- and high-alloy steels. Its corrosion resistance enhances its service life, especially when subjected to harsh environments. However, it is essential to note that corrosion resistance can be further improved using coatings or plating techniques.

AISI 300M Heat Treatment

The heat treatment process for AISI 300M begins by preheating the steel to 1400°F, followed by quenching in oil or water. After satisfying, the material is tempered at a lower temperature of 375°F to prevent brittleness or cracking. This heat treatment process imparts good strength, toughness, and fatigue resistance properties to the material.

AISI 300M Machining

AISI 300M is a rigid hard material to machine due to its high strength and toughness. Thus, high-quality cutting tools, techniques, and best machining practices are required to ensure high-quality end products. The preferred machining technique for AISI 300M is carbide tooling due to its durability and resistance to wear and tear.


In conclusion, AISI 300M is a high-strength steel material with excellent mechanical and physical properties. Its unique combination of strength, toughness, and fatigue resistance makes it ideal for various aerospace and defence applications and high-performance vehicle industries. However, the material’s power and toughness make it harder to machine, and thus a well-designed machining process and best practices are crucial. If you are contemplating using AISI 300M steel for your next high-performance application, contact us to discuss your project needs. Our experts can help you identify suitable materials and provide machining and fabrication services to ensure you get high-quality and durable end products.

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