Maraging 250 Alloy Steel (UNS K92890)
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Maraging 250 Steel (AMS 6512, BS S162, 1.6359)
Maraging 250 is a high-strength, low-carbon, iron-nickel alloy known for excellent toughness, weldability, and dimensional stability after heat treatment. It is part of the maraging steel family, which achieves high strength through precipitation hardening rather than carbon content. Maraging 250 is widely used in aerospace, tooling, and high-performance structural components.
Chemical Composition:
| Element | Content (%) |
|---|---|
| Nickel (Ni) | 17.0 – 19.0 |
| Cobalt (Co) | 7.0 – 8.5 |
| Molybdenum (Mo) | 4.6 – 5.2 |
| Titanium (Ti) | 0.30 – 0.50 |
| 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 | ≥ 1715 MPa |
| Yield Strength (0.2%) | ≥ 1655 MPa |
| Elongation (50 mm) | ≥ 6% |
| Charpy Impact Strength | ≥ 30 J |
| Hardness (Rockwell C) | ~52 – 55 HRC |
Physical Properties:
| Property | Value |
|---|---|
| Density | 8.00 g/cm³ |
| Modulus of Elasticity | ~190 GPa |
| Thermal Conductivity | ~16.7 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 | ~105 µΩ·cm |
Heat Treatment:
- Solution Annealing: 820 – 850°C (air cool)
- Aging (Precipitation Hardening): 480 – 500°C for 3–6 hours
- Results in high strength with minimal dimensional distortion
Applications:
- Rocket motor casings
- Missile and aircraft components
- Tooling for die casting and injection molding
- High-strength shafts, gears, and fasteners
- Structural parts requiring both high strength and toughness
Corrosion Resistance
Moderate corrosion resistance better than plain carbon steels
Not suitable for highly corrosive or marine environments without coating
Post-heat treatment surfaces may require passivation for best performance