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Maraging 350 Steel (C350) – AMS 6516 | UNS K92890
- John
Maraging 350 Steel isn’t just strong—it’s revolutionary. This alloy powers everything from rocket casings to precision gears. At SteelPro Group, we specialize in delivering premium Maraging 350 Steel solutions tailored to industries where failure isn’t an option.
Curious how it outperforms traditional steel? This guide cuts through the complexity: we’ll explore its unique properties, real-world uses, and product details.
What Is Maraging 350 Steel?
Maraging 350 Steel is a cobalt-enhanced nickel alloy designed for extreme strength without carbon. The alloy achieves a tensile strength of 350 ksi (2413 MPa), higher than grades 250 or 300 while maintaining toughness down to -50°C. It is widely used in aerospace and defense, including missile casings, helicopter drive shafts, and high-stress gears, where failure risks are zero.
C350 is produced through vacuum arc remelting, which ensures ultra-low impurities. Its microstructure starts as fine martensite in the annealed state, allowing for precise machining with minimal distortion (<0.05%) before aging. The alloy retains 90% of its strength up to 450°C and can be nitrided for surface hardening.
At SteelPro Group, we provide certified, precision-ready maraging 350 bars, rods, plates, and sheets stock. We also offer expert heat treatment advice to help you get the most out of it.
Maraging 350 Steel Key Features & Benefits
- Ultra-High Strength: Highest in its class for critical aerospace/defense loads.
- Carbon-Free Lightweight: Cobalt/molybdenum/titanium boost strength-to-weight ratio.
- Heat & Cold Resistant: Stable up to 450°C, tough at -50°C.
- Near-Net Machining: 0.05% aging shrinkage allows final-dimension precision.
- Workability: Easily machined in the annealed state; complex shapes achieved pre-aging.
- Surface Hardening: Nitridable for wear resistance without brittleness.
- Weld-Ready: No complex prep, minimal post-treatment.
Maraging 350 Steel Chemical Composition
| Element | Content (%) |
| Cobalt (Co) | 12 |
| Molybdenum (Mo) | 4.8 |
| Titanium (Ti) | 1.4 |
| Nickel (Ni) | Balance |
| Aluminum (Al) | 0.1 |
| Manganese (Mn) | ≤ 0.10 |
| Silicon (Si) | ≤ 0.10 |
| Carbon (C) | ≤ 0.030 |
| Sulfur (S) | ≤ 0.010 |
| Phosphorous (P) | ≤ 0.010 |
| Zirconium (Zr) | 0.01 |
| Boron (B) | 0.003 |
| Iron (Fe) | 63 |
Maraging 350 Steel Mechanical Properties
| Property | Imperial Value | Metric Value |
| Ultimate Tensile Strength | 1140 MPa | 165000 psi |
| Yield Strength @0.2% strain | 827 MPa | 120000 psi |
| Elongation at Break (4.5√A) | 0.18 | 0.18 |
| Reduction of Area | 0.7 | 0.7 |
| Modulus of Elasticity | 200 GPa | 29000 ksi |
| Bulk Modulus | 160 GPa | 23200 ksi |
| Poissons Ratio | 0.3 | 0.3 |
| Shear Modulus | 77.0 GPa | 11200 ksi |
Maraging 350 Steel Physical Properties
| Property | Imperial Value | Metric Value |
| Ultimate Tensile Strength | 1140 MPa | 165000 psi |
| Yield Strength @0.2% strain | 827 MPa | 120000 psi |
| Elongation at Break (4.5√A) | 0.18 | 0.18 |
| Reduction of Area | 0.7 | 0.7 |
| Modulus of Elasticity | 200 GPa | 29000 ksi |
| Bulk Modulus | 160 GPa | 23200 ksi |
| Poissons Ratio | 0.3 | 0.3 |
| Shear Modulus | 77.0 GPa | 11200 ksi |
Maraging 350 Steel Thermal Properties
| Property | Value | Temperature | ||
| Metric | Imperial | Metric | Imperial | |
| CTE, Linear | 11.3 µm/m-°C | 6.28 µin/in-°F | 21.0 – 480 °C | 69.8 – 896 °F |
| Thermal Conductivity | 25.3 W/m-K | 176 BTU-in/hr-ft²-°F | 20.0 °C | 68.0 °F |
| 25.8 W/m-K | 179 BTU-in/hr-ft²-°F | 50.0 °C | 122 °F | |
| 27.0 W/m-K | 187 BTU-in/hr-ft²-°F | 100 °C | 212 °F | |
Maraging 350 Steel Products Dimensions
We supply Maraging 350 Steel in versatile forms compliant with MIL-S-46850 and AMS 6515 standards, ensuring reliability for aerospace, defense, and tooling applications. Below are our stocked dimensions:
| Product Form | Metric Dimensions | Imperial Dimensions |
| Round Bars | Diameter: 10–300 mm | Diameter: 0.4–12 in |
| Rods | Diameter: 5–150 mm | Diameter: 0.2–6 in |
| Plates | Thickness: 6–100 mm | Thickness: 0.25–4 in |
| Width: 500–2500 mm | Width: 20–98 in | |
| Sheets | Thickness: 0.5–6 mm | Thickness: 0.02–0.25 in |
| Width: 1000–2000 mm | Width: 39–79 in | |
| Custom dimensions and tolerances can be provided upon inquiry. | ||
Maraging 350 Steel Applications
- Aerospace: Missile/rocket motor casings, helicopter drive shafts, landing gear components.
- Defense: Ordnance mounting blocks, armor-piercing tooling, military-grade fasteners.
- Tooling & Molds: Die-casting dies, and extrusion tooling requiring wear resistance and minimal distortion.
- High-Performance Motorsports: Lightweight drive shafts, gearbox components, turbocharger systems.
- Industrial Machinery: Load cells, precision couplings, and high-torque shafts for heavy equipment.
- Energy & Nuclear: Radiation-resistant parts, turbine components operating at elevated temperatures.
Maraging 350 Steel Heat Treatment
Unlike traditional steels that require quenching, C350 steel undergoes low-temperature aging (480–540°C / 900–1000°F) for 3–6 hours. During this process, intermetallic compounds (Ni₃Ti, Ni₃Mo) form in the martensitic matrix. This increases hardness to 55-60 HRC while maintaining ductility.
Key considerations for optimal results:
- Pre-aging: Rough machine in the annealed state, leaving minimal stock (~0.1–0.2 mm) for final aging.
- Tooling: Use carbide or coated tools for aging-hardened parts to manage increased hardness.
- Coolant: High-pressure coolant prevents work hardening during heavy cuts.
Maraging 350 Steel Machining
In its annealed state (hardness ~30 HRC), the alloy machines are like mild steel. This allows for easy cutting, drilling, or milling of intricate shapes using conventional tools. After aging, its hardness increases to 55-60 HRC. Despite this, it experiences low distortion during heat treatment (0.05% shrinkage), allowing for near-net-shape machining. This saves time and reduces material waste.
Maraging 350 Steel Welding
Maraging 350’s carbon-free composition and fine-grained structure make it easy to weld without preheating. Common welding methods include TIG, MIG, and electron beam welding (EBW). Post-weld aging restores full strength in the heat-affected zone (HAZ), ensuring uniform properties.
Trusted Maraging 350 Steel Supplier for Critical Missions
At SteelPro Group, every batch of Maraging 350 Steel is vacuum arc re-melted and fully tested. We provide complete material certifications (MIL-S-46850, AMS 6515). We stock ready-to-machine rounds, plates, and sheets, cut to your specifications.
Need help with aging cycles or nitriding?
Our metallurgy team offers free process audits to ensure your design’s success. Don’t risk working with unverified suppliers. Request a quote today and join the industry leaders who trust us!
