Maraging Steel 250/300/350: An In-Depth Guide
Introduction
Maraging steel is a unique class of ultra-high-strength, low-carbon alloys known for their exceptional toughness, ductility, and crack resistance. Unlike conventional high-strength steels, which rely on carbon for hardening, maraging steels achieve their strength through an age-hardening process that forms intermetallic compounds. This results in a material that combines superior mechanical properties with excellent weldability and minimal distortion during heat treatment. Widely used in aerospace, defense, tooling, and high-performance engineering applications, maraging steel is an essential material where strength, reliability, and durability are critical.
What is Maraging Steel?
Maraging steel is a high-strength, low-carbon steel alloy that achieves its exceptional strength and toughness through martensitic transformation and age-hardening (precipitation hardening). The term “maraging” comes from martensite + aging, referring to the way it is strengthened.
Key Features of Maraging Steel
- High Strength & Toughness – Maraging steels have very high tensile strength (up to ~2000 MPa) with excellent fracture toughness.
- Low Carbon Content – Unlike conventional high-strength steels, maraging steels contain very low carbon (<0.03%), reducing brittleness.
- Nickel-Based Composition—They primarily contain nickel (17-19%) and cobalt, molybdenum, titanium, and aluminum, which contribute to their strength.
- Precipitation Hardening – Instead of relying on carbon, these steels gain strength through the formation of nano-sized intermetallic precipitates during age-hardening heat treatment.
- Good Machinability (Before Aging) – In the annealed state, maraging steel is relatively soft, making it easy to machine before undergoing aging heat treatment.
- Excellent Weldability – Due to its low carbon content, maraging steel can be welded easily without the risk of cracking.
- High Wear & Fatigue Resistance – It is used in applications requiring high durability under stress cycles.
Composition of Maraging Steels
Maraging steels are classified based on their nickel content and strength levels, with common grades including C250, C300, and C350. Below are the compositions of each grade:
Chemical Composition (wt.%) of Maraging Steel 250 (C250)
| Grade | Ni | Co | Mn | Si | C | Al | Mo | S | P | Ti | Fe | Cr | Cu |
| C250/250 | 17.0 – 19.0 | 7.0 – 8.5 | 0.10 max | 0.10 max | 0.03 max | 0.05 – 0.15 | 4.6 – 5.2 | 0.010 max | 0.010 max | 0.3 – 0.5 | Bal | 0.5 | 0.5 |
Mechanical Properties of Maraging Steel 250 (C250)
| Grade | Condition | Ultimate Tensile Strength (Min) | Yield Strength (Min) | Elongation in 4D % (Min) | Hardness |
| C250/250 | After Maraging Heat Treatment 900°F | 1758 MPa (255 Ksi) | 1724 MPa (250 Ksi) | 6 | ≥ 48 HRC |
Maraging Steel 250 Specifications
UNS K92890, AMS 6512 Bar and Forging Stock, W.Nr. 1.6359, MIL-S-46850, BS S162, DTD 5212, MSRR 6551, MAT 102, MIA 101, Udimar 250, Vascomax C250
Chemical Composition (wt.%) of Maraging Steel 300 (C300)
| Grade | C | Si | Mn | S | P | Co | Ni | Mo | Ti | Al | Fe |
| C300/300 | 0.03 max | 0.10 max | 0.10 max | 0.010 max | 0.010 max | 8.0 – 9.5 | 18.0 – 19.0 | 4.6 – 5.2 | 0.55 – 0.80 | 0.05 – 0.15 | Bal |
Mechanical Properties of Maraging Steel 300 (C300)
| Grade | 0.2% Yield Strength (ksi) | Ultimate Tensile Strength (ksi) | Elongation in 4D (%) | Reduction of Area (%) | Hardness (Rc) |
| C300/300, Solution Annealed 1500°F (816°C), 1hr, AC | 120 | 150 | 16 | 70 | 30 |
| C300/300, Solution Annealed Plus Aged 900°F (482°C), 3 hrs AC | 280 | 290 | 8 | 40 | 52 |
Maraging Steel 300 Specifications
UNS K93120, ASTM A579, AMS 6514 – Bar, SAE AMS 6514 and AMS 6521 (UNS K93160) – Sheet, Strip, Plate, MIL S 46850, MIL S 13881, W. Nr. 1.6358 and 1.6354, Vdimor 300, Vascomax C300
Chemical Composition (wt.%) of Maraging Steel 350 (C350)
| Grade | Ni | Co | Mn | Si | C | B | P | S | Al | Mo | Ti | Zr |
| C350/300 | 18.5 | 12 | 0.10 max | 0.10 max | 0.03 max | 0.003 | 0.01 max | 0.01 max | 0.1 | 4.8 | 1.4 | 0.01 |
Mechanical Properties of Maraging Steel 350 (C350)
| Grade | 0.2% Yield Strength (ksi) | Ultimate Tensile Strength (ksi) | Elongation in 4D (%) |
| C350/350 | 330 | 350 | 8 |
Maraging Steel 350 Specifications
MIL-S-46850, AMS 6515, Maraging 350, Vascomax C350
Maraging Steel Heat Treatment Process
1. Solution Annealing (Soft State)
- Heated to ~820 – 850°C (1508 – 1562°F)
- Cooled rapidly to form a soft martensitic structure
2. Aging (Hardening Process)
- Heated to 480 – 510°C (896 – 950°F) for 3 – 6 hours
- Fine intermetallic precipitates form, significantly increasing strength
Common Applications of Maraging Steel
Due to its high strength, toughness, and wear resistance, maraging steel is widely used in:
✅ Aerospace Industry – Aircraft landing gear, rocket motor cases, and structural components
✅ Defense & Military – Missile casings, tank armor, and firearms (e.g., gun barrels)
✅ Tooling & Molds – High-performance dies, punches, and injection molding tools
✅ Automotive & Motorsports – High-performance racing car components
✅ Sports Equipment – Golf club heads, fencing swords
✅ Nuclear & Energy Industry – High-stress nuclear reactor parts
Advantages & Disadvantages
| Advantages | Disadvantages |
|---|---|
| ✅ Ultra-high strength | ❌ Expensive compared to conventional steels |
| ✅ Excellent toughness | ❌ Requires special heat treatment |
| ✅ Low carbon (good weldability) | ❌ Difficult to cold work |
| ✅ Good corrosion resistance | ❌ Limited availability in some regions |
Comparison: Maraging 250 vs. Maraging 300 vs. Maraging 350
Maraging steels (250, 300, and 350) are ultra-high-strength, low-carbon steels strengthened by precipitation hardening. They differ in strength, toughness, and composition, making them suitable for different high-performance applications.
1. Chemical Composition Comparison
| Element | Maraging 250 | Maraging 300 | Maraging 350 |
|---|---|---|---|
| Nickel (Ni) | 17.0 – 19.0 | 18.0 – 19.0 | 18.50 |
| Cobalt (Co) | 7.0 – 8.5 | 8.0 – 9.5 | 12.0 |
| Manganese (Mn) | 0.10 max | 0.10 max | 0.10 max |
| Silicon (Si) | 0.10 max | 0.10 max | 0.10 max |
| Carbon (C) | 0.03 max | 0.03 max | 0.03 max |
| Molybdenum (Mo) | 4.6 – 5.2 | 4.6 – 5.2 | 4.8 |
| Titanium (Ti) | 0.3 – 0.5 | 0.55 – 0.80 | 1.40 |
| Aluminum (Al) | 0.05 – 0.15 | 0.05 – 0.15 | 0.10 |
| Phosphorus (P) | 0.010 max | 0.010 max | 0.01 max |
| Sulfur (S) | 0.010 max | 0.010 max | 0.01 max |
| Chromium (Cr) | 0.50 | – | – |
| Copper (Cu) | 0.50 | – | – |
| Boron (B) | – | – | 0.003 |
| Zirconium (Zr) | – | – | 0.01 |
| Iron (Fe) | Balance | Balance | Balance |
🔹 Key Differences:
- Maraging 350 has the highest cobalt (12%) and titanium (1.4%) content, which increases strength but reduces toughness.
- Maraging 300 has slightly more nickel and titanium than Maraging 250, making it stronger.
- Maraging 250 has lower cobalt and titanium but retains good toughness.
2. Mechanical Properties Comparison
| Property | Maraging 250 | Maraging 300 | Maraging 350 |
|---|---|---|---|
| 0.2% Yield Strength (ksi) min. | 250 | 280 | 330 |
| Ultimate Tensile Strength (ksi) min. | 255 | 290 | 350 |
| Elongation in 4D (%) | 6 | 8 | 8 |
| Reduction of Area (%) | – | 40 | – |
| Hardness (HRC) | ≥ 48 | 52 | – |
🔹 Key Differences:
- Maraging 350 has the highest strength but slightly lower toughness.
- Maraging 300 is stronger than 250, with moderate toughness.
- Maraging 250 has better ductility but the lowest strength among the three.
3. Applications Comparison
| Application | Maraging 250 | Maraging 300 | Maraging 350 |
|---|---|---|---|
| Aerospace Components | ✅ | ✅ | ✅ |
| Missile & Rocket Casings | ✅ | ✅ | ✅ |
| Landing Gear Components | ✅ | ✅ | ✅ |
| Automotive Racing Parts | ✅ | ✅ | ✅ |
| High-Strength Tooling & Dies | ✅ | ✅ | ✅ |
| Nuclear Reactor Components | ✅ | ✅ | ✅ |
| Firearm Barrels & Components | ✅ | ✅ | ✅ |
| Ultra-High Strength Fasteners | ❌ | ✅ | ✅ |
| Heavy-Duty Structural Parts | ❌ | ✅ | ✅ |
🔹 Key Differences:
- Maraging 350 is used where maximum strength is required (e.g., ultra-high-stress components).
- Maraging 300 is a balanced choice between strength and toughness, widely used in aerospace and tooling.
- Maraging 250 is preferred for applications needing toughness and fatigue resistance, such as landing gear and firearms.
4. Summary of Differences
| Comparison Factor | Maraging 250 | Maraging 300 | Maraging 350 |
|---|---|---|---|
| Strength | ⭐⭐⭐ | ⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ |
| Toughness | ⭐⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐ |
| Hardness | ⭐⭐⭐ | ⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ |
| Ductility | ⭐⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐ |
| Cost | Lower | Moderate | Higher |
| Best For | Toughness & fatigue resistance | Balanced strength & ductility | Maximum strength applications |
Which One to Choose?
✔ Choose Maraging 250 if you need toughness & fatigue resistance (e.g., aerospace, firearms).
✔ Choose Maraging 300 if you need a balance of strength and ductility (e.g., tooling, racing).
✔ Choose Maraging 350 if you need maximum strength (e.g., missile casings, ultra-high-strength parts).
Conclusion
In conclusion, maraging steels, including grades 250, 300, and 350, represent a remarkable class of high-strength, low-carbon alloys that excel in demanding applications across aerospace, defense, tooling, and other high-performance industries. Their unique combination of exceptional strength, toughness, and ease of machinability in the annealed condition, coupled with excellent weldability and dimensional stability during aging, makes them indispensable for critical components subjected to extreme stress and environmental conditions. Understanding each grade’s specific properties, heat treatment processes, and applications is essential for leveraging their full potential. Whether you’re designing advanced tooling, aerospace components, or high-stress structural parts, maraging steels offer unparalleled performance and reliability. For more insights or to explore how these materials can meet your specific needs, visit GOLDEN SUNBIRD METALS or contact us at [email protected] to make informed decisions for your next project.
