Maraging 350 Steel (UNS K93160)
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Maraging 350 (AMS 6515, MIL-S-46850)
Maraging 350 is a high-strength iron-nickel-based maraging steel capable of achieving extremely high tensile strength through precipitation hardening. Despite its strength, it retains excellent toughness, dimensional stability, and weldability. It is commonly used in aerospace structures, dies, tooling, and critical components that demand both high performance and reliability.
Chemical Composition:
| Element | Content (%) |
|---|---|
| Nickel (Ni) | 17.0 – 19.0 |
| Cobalt (Co) | 11.0 – 13.0 |
| Molybdenum (Mo) | 4.6 – 5.2 |
| Titanium (Ti) | 1.20 – 1.60 |
| Aluminum (Al) | ≤ 0.10 |
| Carbon (C) | ≤ 0.030 |
| Manganese (Mn) | ≤ 0.10 |
| Silicon (Si) | ≤ 0.10 |
| Phosphorus (P) | ≤ 0.010 |
| Sulfur (S) | ≤ 0.010 |
| Iron (Fe) | Balance |
Mechanical Properties:
| Property | Value (Aged Condition) |
|---|---|
| Tensile Strength | ≥ 2415 MPa |
| Yield Strength (0.2%) | ≥ 2280 MPa |
| Elongation (50 mm) | ≥ 5% |
| Charpy Impact Strength | ~25–35 J |
| Hardness (Rockwell C) | ~55 – 58 HRC |
Physical Properties:
| Property | Value |
|---|---|
| Density | 8.00 g/cm³ |
| Modulus of Elasticity | ~190 GPa |
| Thermal Conductivity | ~14.4 W/m·K |
| Specific Heat Capacity | ~460 J/kg·K |
| Melting Point | ~1413 °C |
| Thermal Expansion | ~10.1 µm/m·°C (20–100°C) |
| Electrical Resistivity | ~98 µΩ·cm |
Heat Treatment:
- Solution Annealing: 820 – 850°C (air cool)
- Aging: 480 – 500°C for 3–6 hours
- Achieves extremely high tensile strength and hardness with minimal distortion
Applications:
- High-performance aircraft and missile components
- Rocket motor cases
- High-strength tooling and dies
- Critical mechanical parts under extreme stress
- Shafts, fasteners, and gear parts
Corrosion Resistance
Moderate resistance better than carbon steel
Not ideal for marine or chemically aggressive environments without protective coatings
Passivation after heat treatment enhances corrosion resistance