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Maraging 300 Alloy Steel AMS 6514 | UNS K93120
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Maraging 300 alloy steel offers exceptional strength and corrosion resistance, making it ideal for aerospace, defense, and precision tooling. At SteelPro Group, we provide certified AMS 6514 material in bars, plates, and sheets for critical projects. This guide covers its properties, technical specifications, and how to source it reliably.
What Is AISI Maraging 300 Steel?
Maraging 300 (AMS 6514/UNS K93120) is an 18% nickel, cobalt-strengthened steel alloy known for its ultra-high strength, toughness, and machinability. Maraging 300 is highly weldable, retains strength up to 450°C, and offers good cryogenic toughness. These properties make it ideal for aerospace fasteners, missile components, and high-stress tooling. Compared to Maraging 250, it provides higher strength but slightly reduced ductility.
Maraging 300 is produced using dual vacuum melting (VIM + VAR), which ensures minimal impurities and a uniform microstructure. The material is delivered in an annealed condition (RC 30-35), which makes it soft and easy to machine or form. A simple heat treatment at 482°C (900°F) increases its yield strength to over 1,862 MPa (270 ksi) while maintaining 11% elongation and excellent notch impact resistance.
Maraging 300 Alloy Steel Properties Overview
- Ultrahigh Tensile Strength: Achieves 2000-2400 MPa after aging, surpassing conventional tool steels.
- High Compressive Strength: Resists deformation under extreme pressure, suitable for heavy-duty tooling.
- Superior Fatigue Resistance: Withstands cyclic loading in aerospace fasteners and rotor components.
- Weldability Without Preheating: Maintains structural integrity post-welding, ideal for repair or assembly.
- Machinability & Formability: Soft annealed state enables complex shaping, cold forming, and mirror-like polishability pre-aging.
- Corrosion & Crack Resistance: Outperforms standard steels in saltwater and acidic environments.
Maraging 300 Steel Chemical Composition
| Element | Content |
| Carbon (C) | ≤ 0.03 |
| Manganese (Mn) | ≤ 0.1 |
| Silicon (Si) | ≤ 0.1 |
| Phosphorus (P) | ≤ 0.01 |
| Sulfur (S) | ≤ 0.01 |
| Nickel (Ni) | 18 ~ 19 |
| Cobalt (Co) | 8.5 ~ 9.5 |
| Molybdenum (Mo) | 4.6 ~ 5.2 |
| Titanium (Ti) | 0.5 ~ 0.8 |
| Aluminum (Al) | 0.05 ~ 0.15 |
| Chromium (Cr) | ≤ 0.5 |
| Copper (Cu) | ≤ 0.5 |
Maraging 300 Steel Mechanical Properties
| Property | Metric | Imperial |
| Yield Strength (Aged) | 1862 MPa | 270 ksi |
| Ultimate Tensile Strength | 2000–2400 MPa | 290–348 ksi |
| Elongation (Aged) | 0.11 | 0.11 |
| Hardness (Annealed) | 30–35 HRC | 30–35 HRC |
| Hardness (Aged) | 50–55 HRC | 50–55 HRC |
Maraging 300 Steel Physical Properties
| Property | Metric | Imperial |
| Density | 7.99 g/cm³ | 0.289 lb/in³ |
| Elastic Modulus | 190 GPa | 27.5 × 10⁶ psi |
| Thermal Expansion | 10.08 μm/m·°C (20–100°C) | 5.6 × 10⁻⁶ in/in/°F |
Maraging 300 Steel Bars | Plate | Sheet Specification
Our Maraging 300 steel is available in multiple product forms, including bars, plates, sheets, and tubes. Custom dimensions can be tailored to your project needs. Our engineering team ensures our products comply with AMS 6514 and AMS 6521. Below are standard stocked sizes for quick delivery:
| Product Form | Metric Dimensions | Imperial Dimensions |
| Round Bars | Diameter: 10–300 mm | Diameter: 0.4–12 in |
| Length: 1,000–6,000 mm | Length: 39–236 in | |
| Plates | Thickness: 5–150 mm | Thickness: 0.2–6 in |
| Width: 500–2,000 mm | Width: 20–79 in | |
| Sheets | Thickness: 0.5–5 mm | Thickness: 0.02–0.2 in |
| Width: 1,000–1,500 mm | Width: 39–59 in |
Maraging 300 Steel Applications
- Aerospace Components: Landing gear, rocket motor casings, and turbine shafts requiring ultra-high strength-to-weight ratios.
- Defense Systems: Missile launch tubes, armored vehicle parts, and ordnance components for blast resistance.
- Precision Tooling: Injection molds, extrusion dies, and forging tools exposed to cyclic thermal stress.
- High-Performance Shafts: Driveshafts and rotor components in power generation equipment.
- Medical Devices: Surgical instruments and implantable tools needing biocompatibility and sterilizability.
Need Maraging 300 for your project? SteelPro Group supplies certified AMS 6514 material with fast-track delivery.
Maraging 300 Steel Manufacturing & Processing
1. Melting & Casting
- Dual Vacuum Refinement: Combines Vacuum Induction Melting (VIM) and Vacuum Arc Remelting (VAR) to minimize impurities (C ≤0.03%, S/P ≤0.01%) and ensure uniform microstructure.
- Ingot Formation: Cast into billets or slabs for subsequent hot/cold working.
2. Heat Treatment
| Process | Temperature | Time | Result |
| Solution Annealing | 815–870°C (1500–1600°F) | 1 hour per inch of thickness | Prepares for machining; softens material (30–35 HRC). |
| Standard Aging | 482–496°C (900–925°F) | 6 hours | Peak strength (50–55 HRC, 2000+ MPa). |
| Specialized Aging(For Die Casting) | 527–538°C (980–1000°F) | 6 hours | Enhanced die life for casting applications. |
3. Forming Operations
- Hot/Cold Working: This process supports rolling, forging, and extrusion without intermediate annealing. Cold rolling permits up to 90% reduction without cracking.
- Near-Net Shapes: Custom forgings and preforms reduce machining waste for aerospace components.
4. Machining Techniques
- Turning: Carbide tools (C3 grade) at 475 ft/min with soluble oil cooling for Ra ≤0.4 μm finishes.
- Milling/Drilling: M2 high-speed steel cutters at 0.002–0.009 in/tooth feed rates, using sulfurized oils for chip evacuation.
- Tolerance Control: Holds ±0.002 in (±0.05 mm) for mission-critical parts like rocket casings.
5. Joining & Repair
- Welding: No preheat required; post-weld aging restores HAZ properties to 95% of base strength.
- Rework Compatibility: Damaged tools/components can be re-aged or reprocessed for secondary service life.
6. Surface Enhancement
- Electropolishing: Achieves Ra <0.2 μm for medical instruments and optical tooling.
- Stress Relief: Low-temperature annealing at 315°C (600°F) minimizes distortion in complex geometries.
Optimize Your Project with Certified Maraging 300 Steel
For mission-critical applications requiring unmatched strength and precision, SteelPro supplies Maraging 300 steel compliant with AMS 6514 and MIL-S-46850 specifications. Our inventory includes bars, plates, and tubes in standard sizes, all with ±0.002″ tolerances to match your exact blueprints.
