Maraging 250 Steel: Properties and Key Applications

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.

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