300M high strength low alloy steel comparable to 4340 with increased alloying elements such as vanadium and silicon giving it slightly higher strength and toughness, modified version of AISI 4340 steel, It has high content of molybdenum and silicon than that of AISI 4340 steel. It has high strength, good toughness, fatigue strength and ductility. The following datasheet gives more details about the 300M low alloy steel main used in a wide array of aerospace applications including landing gear for many commercial airplanes.
Class | Condition | Severity |
---|---|---|
1 | Freckles | A |
2 | White Spots | A |
3 | Radial Segregation | B |
4 | Ring Pattern | B |
Property | Value |
---|---|
Tensile Strength | 270 ksi |
Yield Strength 0.2% offset | 220 ksi |
Elongation | 8% |
Reduction of Area | 30% |
Cross-section Area | Tensile Strength | Yield Strength 0.2% Offset | Avg. Reduction of Area | Individual Reduction of Area |
---|---|---|---|---|
Up to 100 in2, incl | 270 ksi | 220 ksi | 30% | 25% min |
Over 100 in2, incl | 270 ksi | 220 ksi | 25% | 20% min |
Over 144 in2, incl | 270 ksi | 220 ksi | 20% | 15% min |
Over 225 in2 | 270 ksi | 220 ksi | 15% | 10% min |
Grade | Chemical Composition WT % | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
C | Mn | Si | P | S | Cr | Ni | Mo | V | Fe | |
300M | 0.40-0.46 | 0.65-0.90 | 1.45-1.80 | Max 0.035 | Max 0.03 | 0.70-0.95 | 1.65-2.0 | 0.30-0.45 | Min 0.05 | 93.4-94.8 |
UNS K44220 | 0.38-0.46 | 0.60-0.90 | 1.45-1.80 | Max 0.010 | Max 0.010 | 0.70-0.95 | 1.65-2.0 | 0.30-0.65 | Min 0.05 | Bal |
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 |
Properties | Metric | Imperial |
---|---|---|
Density | 7.87 g/cm3 | 0.284 lb/in³ |
Melting point | 1422°C | 2590°F |
300M, UNS K44220 Low Alloy Steel is normalized at 927°C (1700°F). It is then heated at 872°C (1600°F) followed by oil quenching oil and tempering.
Type of Heat Treating | Process |
---|---|
Normalize | 1700° F +/- 25° F (927° C +/- 14° C), then air cool |
Harden | 1600° F +/- 25° F (871° C +/- 14°C), quench in oil |
Temper | Double temper 400° – 1200° F (204° – 649° C) depending on desired strength and hardness. |
300M, UNS K44220 Low Alloy Steel can be welded using flash resistance welding or fusion welding methods. Approved procedures such as including pre and post-heating practice are followed for performing the fusion welding method because this alloy can be air-hardened due to the heat produced by welding. This process is followed by re-normalizing, or re-normalizing and tempering before heat treatment.
300M, UNS K44220 Low Alloy Steel can be easily machined in normalized, or normalized and tempered conditions. Due to hardness of the heat treated alloy, the grinding process is performed with extreme care. After grinding, stress relief annealing is performed at 288°C (550°F).
UNS K44220, 4340MOD, Lescalloy 300M Vac-Arc, 4340 Modified, 434M, 300M CEVM
Steel grade
Special steel