455 Stainless Steel: Properties and Key Applications
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Table Of Content
Table Of Content
455 Stainless Steel, also known as Custom 455, is a martensitic stainless steel that has gained recognition for its unique combination of high strength, corrosion resistance, and good fabricability. Classified primarily as a martensitic stainless steel, it is characterized by its high chromium and nickel content, which contribute to its overall properties. The primary alloying elements include chromium (Cr), nickel (Ni), and molybdenum (Mo), each playing a crucial role in defining the steel's characteristics.
Comprehensive Overview
455 Stainless Steel is designed for applications requiring high strength and moderate corrosion resistance. Its composition typically includes around 15-17% chromium, 4-6% nickel, and 0.5-1.5% molybdenum, which enhance its mechanical properties and resistance to oxidation. The martensitic structure allows for heat treatment, enabling the material to achieve high hardness and strength levels.
Key Characteristics:
- High Strength: Offers excellent tensile and yield strength, making it suitable for demanding applications.
- Corrosion Resistance: Provides good resistance to various corrosive environments, although not as high as austenitic grades.
- Fabricability: Can be easily machined and welded, although care must be taken to avoid cracking during welding.
Advantages:
- High strength-to-weight ratio.
- Good wear resistance.
- Suitable for heat treatment to enhance properties.
Limitations:
- Moderate corrosion resistance compared to austenitic stainless steels.
- Susceptible to stress corrosion cracking in certain environments.
Historically, 455 Stainless Steel has been used in aerospace, automotive, and medical applications due to its favorable properties. Its market position is strong, particularly in industries where high-performance materials are essential.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | S45500 | USA | Closest equivalent to AISI 630 |
| AISI/SAE | 455 | USA | Martensitic stainless steel |
| ASTM | A313 | USA | Standard specification for wire |
| EN | 1.4542 | Europe | Similar properties to AISI 630 |
| JIS | SUS 630 | Japan | Minor compositional differences |
The table above highlights the various standards and designations associated with 455 Stainless Steel. Notably, while grades like AISI 630 and EN 1.4542 are often considered equivalent, they may exhibit subtle differences in composition that can affect performance in specific applications. For instance, the nickel content in AISI 630 is slightly lower, which may influence its toughness and corrosion resistance.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| Cr (Chromium) | 15.0 - 17.0 |
| Ni (Nickel) | 4.0 - 6.0 |
| Mo (Molybdenum) | 0.5 - 1.5 |
| C (Carbon) | 0.05 - 0.15 |
| Mn (Manganese) | 0.5 - 1.0 |
| Si (Silicon) | 0.5 - 1.0 |
| P (Phosphorus) | ≤ 0.04 |
| S (Sulfur) | ≤ 0.03 |
The primary alloying elements in 455 Stainless Steel serve distinct roles:
- Chromium: Enhances corrosion resistance and contributes to the formation of a protective oxide layer.
- Nickel: Improves toughness and ductility, allowing for better performance under stress.
- Molybdenum: Increases resistance to pitting and crevice corrosion, particularly in chloride environments.
Mechanical Properties
| Property | Condition/Temper | Test Temperature | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
|---|---|---|---|---|---|
| Tensile Strength | Annealed | Room Temp | 860 - 1030 MPa | 125 - 150 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Annealed | Room Temp | 620 - 800 MPa | 90 - 116 ksi | ASTM E8 |
| Elongation | Annealed | Room Temp | 10 - 15% | 10 - 15% | ASTM E8 |
| Hardness (Rockwell C) | Annealed | Room Temp | 30 - 40 HRC | 30 - 40 HRC | ASTM E18 |
| Impact Strength | Annealed | -40°C | 30 J | 22 ft-lbf | ASTM E23 |
The mechanical properties of 455 Stainless Steel make it particularly suitable for applications involving high mechanical loads. Its high tensile and yield strength allow it to withstand significant stress, while its elongation and impact strength ensure that it can absorb energy without fracturing.
Physical Properties
| Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
|---|---|---|---|
| Density | Room Temp | 7.75 g/cm³ | 0.28 lb/in³ |
| Melting Point | - | 1450 - 1500 °C | 2642 - 2732 °F |
| Thermal Conductivity | Room Temp | 25 W/m·K | 14.5 BTU·in/h·ft²·°F |
| Specific Heat Capacity | Room Temp | 500 J/kg·K | 0.12 BTU/lb·°F |
| Electrical Resistivity | Room Temp | 0.72 µΩ·m | 0.72 µΩ·in |
| Coefficient of Thermal Expansion | Room Temp | 16.5 x 10⁻⁶/K | 9.2 x 10⁻⁶/°F |
The physical properties of 455 Stainless Steel, such as its density and melting point, are critical for applications that require high-temperature performance. Its thermal conductivity is moderate, making it suitable for applications where heat dissipation is necessary but not critical.
Corrosion Resistance
| Corrosive Agent | Concentration (%) | Temperature (°C) | Resistance Rating | Notes |
|---|---|---|---|---|
| Chlorides | 3-10 | 20-60 | Fair | Risk of pitting corrosion |
| Sulfuric Acid | 10-30 | 20-40 | Poor | Not recommended |
| Acetic Acid | 5-20 | 20-60 | Good | Moderate resistance |
| Sea Water | - | 20-30 | Fair | Risk of crevice corrosion |
455 Stainless Steel exhibits good resistance to various corrosive environments, particularly in moderate conditions. However, it is susceptible to pitting corrosion in chloride-rich environments, which is a critical consideration for applications in marine or coastal areas. Compared to austenitic grades like 316 stainless steel, which offers superior corrosion resistance, 455 is less favorable in highly corrosive environments.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 600 °C | 1112 °F | Suitable for high-temperature applications |
| Max Intermittent Service Temp | 650 °C | 1202 °F | Short-term exposure only |
| Scaling Temperature | 800 °C | 1472 °F | Risk of oxidation at high temps |
| Creep Strength considerations | 500 °C | 932 °F | Creep resistance decreases above this temperature |
455 Stainless Steel maintains its strength and hardness at elevated temperatures, making it suitable for applications that involve heat exposure. However, prolonged exposure to temperatures above 600 °C can lead to oxidation and scaling, which may compromise its structural integrity.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| TIG | ER455 | Argon | Preheat recommended |
| MIG | ER308L | Argon/CO2 | Post-weld heat treatment advised |
| SMAW | E308L | - | Care needed to avoid cracking |
455 Stainless Steel can be welded using various methods, including TIG and MIG welding. However, preheating is often recommended to minimize the risk of cracking. Post-weld heat treatment can further enhance the mechanical properties of the weld.
Machinability
| Machining Parameter | 455 Stainless Steel | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60% | 100% | Requires high-speed tooling |
| Typical Cutting Speed (Turning) | 30-50 m/min | 60-80 m/min | Use coolant to prevent overheating |
Machinability of 455 Stainless Steel is moderate, requiring careful selection of cutting tools and speeds. High-speed steel or carbide tools are recommended to achieve optimal results.
Formability
455 Stainless Steel exhibits moderate formability, making it suitable for cold and hot forming processes. However, due to its high strength, larger bend radii are recommended to avoid cracking during forming operations.
Heat Treatment
| Treatment Process | Temperature Range (°C/°F) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
|---|---|---|---|---|
| Annealing | 800 - 900 °C / 1472 - 1652 °F | 1-2 hours | Air or water | Softening, improving ductility |
| Hardening | 1000 - 1100 °C / 1832 - 2012 °F | 30 minutes | Oil or air | Increasing hardness and strength |
| Tempering | 500 - 600 °C / 932 - 1112 °F | 1 hour | Air | Reducing brittleness, enhancing toughness |
The heat treatment processes for 455 Stainless Steel significantly impact its microstructure and properties. Annealing softens the material, while hardening increases strength. Tempering is crucial to reduce brittleness after hardening.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection |
|---|---|---|---|
| Aerospace | Aircraft components | High strength, corrosion resistance | Lightweight and durable |
| Automotive | Engine parts | High strength, good machinability | Performance and reliability |
| Medical | Surgical instruments | Corrosion resistance, biocompatibility | Safety and durability |
Other applications include:
- Oil and gas industry components
- Marine hardware
- Fasteners and fittings
The selection of 455 Stainless Steel for aerospace and automotive applications is primarily due to its high strength-to-weight ratio, which is essential for performance and efficiency.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | 455 Stainless Steel | AISI 316 Stainless Steel | AISI 420 Stainless Steel | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | High strength | Excellent corrosion resistance | Moderate strength | 455 is stronger but less corrosion-resistant |
| Key Corrosion Aspect | Fair in chlorides | Excellent in chlorides | Poor in chlorides | 455 is suitable for moderate environments |
| Weldability | Moderate | Good | Fair | 455 requires care to avoid cracking |
| Machinability | Moderate | Good | Poor | 455 needs high-speed tooling |
| Formability | Moderate | Good | Fair | 455 has higher strength, limiting formability |
| Approx. Relative Cost | Moderate | Higher | Lower | Cost varies based on market demand |
| Typical Availability | Moderate | High | Moderate | 455 is less common than 316 |
When selecting 455 Stainless Steel, considerations include its mechanical properties, corrosion resistance, and availability. While it offers high strength, it may not be the best choice for highly corrosive environments compared to austenitic grades. Its moderate cost and availability make it a viable option for various applications, particularly where strength is prioritized over corrosion resistance.
In summary, 455 Stainless Steel is a versatile material that balances strength and corrosion resistance, making it suitable for a wide range of engineering applications. Its unique properties and fabrication characteristics provide significant advantages in demanding environments, while careful consideration of its limitations is essential for optimal performance.