Maraging 250 Steel: Properties and Key Applications
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Table Of Content
Table Of Content
Maraging 250 steel is a high-strength, low-carbon alloy steel known for its exceptional mechanical properties and unique aging process. Classified as a maraging steel, it primarily consists of iron, nickel, and cobalt, with a low carbon content that enhances its ductility and toughness. The primary alloying elements include nickel (around 18%), cobalt (around 8%), and molybdenum (around 5%), which contribute significantly to its strength and hardness through a process known as aging.
Comprehensive Overview
Maraging 250 steel is renowned for its combination of high strength, toughness, and excellent weldability, making it a preferred choice in various engineering applications, particularly in aerospace, tooling, and high-performance components. The aging process, which involves heating the steel to a specific temperature and then cooling it, allows for the precipitation of intermetallic compounds that enhance its mechanical properties without compromising ductility.
Advantages and Limitations
Advantages (Pros) | Limitations (Cons) |
---|---|
Exceptional strength-to-weight ratio | Higher cost compared to conventional steels |
Excellent toughness and ductility | Limited corrosion resistance |
Good weldability and machinability | Requires careful heat treatment to achieve desired properties |
Stable mechanical properties over a wide temperature range | Not suitable for high-temperature applications |
Maraging 250 steel holds a significant position in the market due to its unique properties and applications, particularly in the aerospace and defense sectors. Its historical significance stems from its development in the mid-20th century, where it was initially used in high-performance aircraft components.
Alternative Names, Standards, and Equivalents
Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
---|---|---|---|
UNS | S25000 | USA | Closest equivalent to AISI 250 |
AISI/SAE | 250 | USA | Minor compositional differences to be aware of |
ASTM | A 203 | USA | Used for pressure vessels |
EN | 1.6350 | Europe | Equivalent to other maraging steels |
JIS | - | Japan | Not commonly specified |
The table above highlights various standards and equivalents for Maraging 250 steel. While many grades may appear similar, subtle differences in composition can significantly impact performance, particularly in applications requiring precise mechanical properties.
Key Properties
Chemical Composition
Element (Symbol and Name) | Percentage Range (%) |
---|---|
Fe (Iron) | Balance |
Ni (Nickel) | 17.0 - 19.0 |
Co (Cobalt) | 7.0 - 9.0 |
Mo (Molybdenum) | 4.5 - 5.5 |
Ti (Titanium) | 0.1 - 0.3 |
Al (Aluminum) | 0.01 - 0.1 |
Nickel is crucial for enhancing the toughness and strength of Maraging 250 steel, while cobalt contributes to its hardness and resistance to softening at elevated temperatures. Molybdenum improves hardenability and strength, making it essential for high-performance applications.
Mechanical Properties
Property | Condition/Temper | Test Temperature | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
---|---|---|---|---|---|
Tensile Strength | Quenched & Tempered | Room Temp | 1,200 - 1,300 MPa | 174 - 188 ksi | ASTM E8 |
Yield Strength (0.2% offset) | Quenched & Tempered | Room Temp | 1,050 - 1,150 MPa | 152 - 166 ksi | ASTM E8 |
Elongation | Quenched & Tempered | Room Temp | 10 - 15% | 10 - 15% | ASTM E8 |
Hardness (Rockwell C) | Quenched & Tempered | Room Temp | 40 - 45 HRC | 40 - 45 HRC | ASTM E18 |
Impact Strength (Charpy) | Quenched & Tempered | -40°C | 30 - 50 J | 22 - 37 ft-lbf | ASTM E23 |
The mechanical properties of Maraging 250 steel make it particularly suitable for applications requiring high strength and toughness, such as aerospace components and tooling. Its excellent tensile and yield strengths ensure structural integrity under significant loads.
Physical Properties
Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
---|---|---|---|
Density | - | 7.85 g/cm³ | 0.284 lb/in³ |
Melting Point | - | 1,400 - 1,500 °C | 2,552 - 2,732 °F |
Thermal Conductivity | 20°C | 25 W/m·K | 14.5 BTU·in/h·ft²·°F |
Specific Heat Capacity | 20°C | 460 J/kg·K | 0.11 BTU/lb·°F |
Electrical Resistivity | 20°C | 0.7 µΩ·m | 0.7 µΩ·in |
The density and melting point of Maraging 250 steel indicate its suitability for high-performance applications, while its thermal and electrical properties are critical in specific engineering contexts.
Corrosion Resistance
Corrosive Agent | Concentration (%) | Temperature (°C/°F) | Resistance Rating | Notes |
---|---|---|---|---|
Chlorides | 3-5 | 25°C/77°F | Fair | Risk of pitting |
Sulfuric Acid | 10 | 25°C/77°F | Poor | Not recommended |
Sea Water | - | 25°C/77°F | Fair | Moderate resistance |
Maraging 250 steel exhibits fair resistance to chlorides and seawater, but it is not recommended for environments with high concentrations of sulfuric acid due to susceptibility to corrosion. Compared to stainless steels, Maraging 250's corrosion resistance is limited, making it essential to consider protective coatings or alternative materials in highly corrosive environments.
Heat Resistance
Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
---|---|---|---|
Max Continuous Service Temp | 300°C | 572°F | Suitable for moderate temperatures |
Max Intermittent Service Temp | 400°C | 752°F | Can withstand short-term exposure |
Scaling Temperature | 500°C | 932°F | Risk of oxidation beyond this limit |
Maraging 250 steel maintains its mechanical properties at elevated temperatures, but care must be taken to avoid prolonged exposure to high temperatures, which can lead to oxidation and loss of strength.
Fabrication Properties
Weldability
Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
---|---|---|---|
TIG | ERNiCrMo-3 | Argon | Preheat recommended |
MIG | ERNiCrMo-3 | Argon/CO2 | Post-weld heat treatment needed |
Maraging 250 steel is generally weldable, but preheating and post-weld heat treatment are recommended to minimize the risk of cracking and ensure optimal mechanical properties.
Machinability
Machining Parameter | Maraging 250 Steel | Benchmark Steel (AISI 1212) | Notes/Tips |
---|---|---|---|
Relative Machinability Index | 60 | 100 | Requires specialized tooling |
Typical Cutting Speed (turning) | 30 m/min | 50 m/min | Use carbide tools for best results |
Maraging 250 steel has moderate machinability, and using appropriate cutting tools and speeds is essential to achieve desired surface finishes and tolerances.
Formability
Maraging 250 steel exhibits good formability, particularly in its annealed state. Cold forming is feasible, but care must be taken to avoid excessive work hardening, which can lead to cracking. Hot forming is also possible, but temperatures must be carefully controlled to maintain material integrity.
Heat Treatment
Treatment Process | Temperature Range (°C/°F) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
---|---|---|---|---|
Solution Annealing | 820 - 850 °C / 1,508 - 1,562 °F | 1 - 2 hours | Air | Homogenize microstructure |
Aging | 480 - 500 °C / 896 - 932 °F | 4 - 6 hours | Air | Increase hardness and strength |
The heat treatment processes for Maraging 250 steel are critical for achieving the desired mechanical properties. Solution annealing followed by aging transforms the microstructure, resulting in enhanced strength and toughness.
Typical Applications and End Uses
Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection |
---|---|---|---|
Aerospace | Aircraft landing gear | High strength, toughness | Safety and performance |
Tooling | Molds and dies | Hardness, wear resistance | Durability |
Defense | Missile components | High strength-to-weight ratio | Critical performance |
Other applications include:
* High-performance automotive components
* Sporting equipment (e.g., golf clubs, bicycle frames)
* Medical devices (e.g., surgical instruments)
Maraging 250 steel is chosen for applications requiring high strength and toughness, particularly where weight savings are critical.
Important Considerations, Selection Criteria, and Further Insights
Feature/Property | Maraging 250 Steel | AISI 4140 Steel | AISI 316 Stainless Steel | Brief Pro/Con or Trade-off Note |
---|---|---|---|---|
Key Mechanical Property | High strength | Moderate strength | Good corrosion resistance | Maraging 250 excels in strength but lacks corrosion resistance |
Key Corrosion Aspect | Fair resistance | Moderate resistance | Excellent resistance | Consider environment when selecting |
Weldability | Good | Moderate | Excellent | Maraging 250 requires careful handling |
Machinability | Moderate | Good | Moderate | Requires specialized tooling |
Approx. Relative Cost | Higher | Moderate | Higher | Cost vs. performance trade-off |
Typical Availability | Limited | Widely available | Widely available | Availability can affect project timelines |
When selecting Maraging 250 steel, considerations include cost-effectiveness, availability, and specific application requirements. Its unique properties make it suitable for high-performance applications, but its higher cost and limited corrosion resistance may necessitate careful evaluation against alternatives.
In conclusion, Maraging 250 steel stands out for its exceptional mechanical properties and versatility in demanding applications. Understanding its characteristics, fabrication properties, and performance in various environments is crucial for engineers and designers when making material selections.