405 Stainless Steel: Properties and Key Applications
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Table Of Content
Table Of Content
405 stainless steel is classified as a martensitic stainless steel, known for its high strength and moderate corrosion resistance. This grade contains significant amounts of chromium (12-14%) and nickel (1-2%), with carbon content typically around 0.05-0.15%. The presence of chromium provides oxidation resistance, while nickel enhances toughness and ductility. The low carbon content helps in maintaining corrosion resistance while allowing for hardening through heat treatment.
Comprehensive Overview
405 stainless steel is primarily utilized in applications requiring high strength and moderate corrosion resistance. Its martensitic structure allows it to be hardened through heat treatment, making it suitable for components that endure mechanical stress. The steel exhibits good weldability and can be easily machined, which adds to its versatility in various engineering applications.
Advantages:
- High Strength: The ability to harden through heat treatment allows for enhanced mechanical properties.
- Moderate Corrosion Resistance: Suitable for environments where exposure to moisture and mild corrosive agents occurs.
- Good Fabricability: Can be welded and machined effectively, making it adaptable for various manufacturing processes.
Limitations:
- Lower Corrosion Resistance Compared to Austenitic Grades: While it performs well in certain environments, it is not as resistant to aggressive corrosive agents as austenitic stainless steels.
- Susceptibility to Stress Corrosion Cracking: In certain conditions, particularly in chloride environments, it may be prone to stress corrosion cracking.
Historically, 405 stainless steel has been used in applications such as automotive exhaust systems, heat exchangers, and various industrial components, reflecting its balance of strength and corrosion resistance.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | S40500 | USA | Closest equivalent to AISI 405 |
| AISI/SAE | 405 | USA | Commonly used designation |
| ASTM | A240/A240M | USA | Standard specification for stainless steel plates |
| EN | 1.4002 | Europe | Minor compositional differences to be aware of |
| JIS | SUS405 | Japan | Similar properties, but may vary in specific applications |
The differences between equivalent grades often lie in their specific alloying elements and mechanical properties, which can affect performance in specific applications. For instance, while both 405 and 1.4002 may offer similar corrosion resistance, the latter may have slightly different mechanical properties due to variations in nickel content.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| C (Carbon) | 0.05 - 0.15 |
| Cr (Chromium) | 12.0 - 14.0 |
| Ni (Nickel) | 1.0 - 2.0 |
| Mn (Manganese) | 0.5 - 1.0 |
| Si (Silicon) | 0.5 max |
| P (Phosphorus) | 0.04 max |
| S (Sulfur) | 0.03 max |
The primary role of chromium in 405 stainless steel is to enhance corrosion resistance and oxidation resistance. Nickel contributes to improved toughness and ductility, while manganese aids in deoxidation and improves hardenability. The low carbon content is crucial for maintaining corrosion resistance and allows for effective hardening through heat treatment.
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 | 550 - 750 MPa | 80 - 110 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Annealed | Room Temp | 300 - 450 MPa | 44 - 65 ksi | ASTM E8 |
| Elongation | Annealed | Room Temp | 20 - 30% | 20 - 30% | ASTM E8 |
| Hardness (Rockwell B) | Annealed | Room Temp | 80 - 90 | 80 - 90 | ASTM E18 |
| Impact Strength | Annealed | -20 °C | 30 - 50 J | 22 - 37 ft-lbf | ASTM E23 |
The combination of high tensile and yield strength makes 405 stainless steel suitable for applications that require structural integrity under mechanical loading. Its elongation values indicate good ductility, allowing for deformation without fracture, which is essential in dynamic applications.
Physical Properties
| Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
|---|---|---|---|
| Density | Room Temp | 7.75 g/cm³ | 0.28 lb/in³ |
| Melting Point/Range | - | 1400 - 1450 °C | 2552 - 2642 °F |
| Thermal Conductivity | Room Temp | 25 W/m·K | 14.5 BTU·in/(hr·ft²·°F) |
| Specific Heat Capacity | Room Temp | 500 J/kg·K | 0.12 BTU/lb·°F |
| Electrical Resistivity | Room Temp | 0.73 μΩ·m | 0.00000073 Ω·m |
| Coefficient of Thermal Expansion | Room Temp | 16.0 x 10⁻⁶/K | 8.9 x 10⁻⁶/°F |
The density of 405 stainless steel contributes to its weight and strength characteristics, while its melting point indicates suitability for high-temperature applications. The thermal conductivity and specific heat capacity are important for applications involving heat transfer, such as heat exchangers.
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 |
| Acetic Acid | 5 | 25 °C / 77 °F | Good | Moderate resistance |
| Sea Water | - | 25 °C / 77 °F | Fair | Susceptible to localized corrosion |
405 stainless steel exhibits moderate resistance to corrosion in various environments. It performs reasonably well in mildly corrosive conditions, such as acetic acid and sea water, but is susceptible to pitting and stress corrosion cracking in chloride-rich environments. Compared to austenitic grades like 304 or 316, 405 has lower overall corrosion resistance, particularly in aggressive environments.
Heat Resistance
| Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
|---|---|---|---|
| Max Continuous Service Temp | 650 °C | 1202 °F | Suitable for high-temperature applications |
| Max Intermittent Service Temp | 700 °C | 1292 °F | Short-term exposure only |
| Scaling Temperature | 800 °C | 1472 °F | Risk of oxidation above this temperature |
| Creep Strength considerations begin around | 500 °C | 932 °F | Creep resistance decreases significantly |
At elevated temperatures, 405 stainless steel maintains its strength but may experience oxidation. The maximum continuous service temperature indicates its suitability for high-temperature applications, while the scaling temperature highlights the risk of oxidation at extreme conditions.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| TIG | ER 405 | Argon | Good results with proper technique |
| MIG | ER 308L | Argon/CO2 | Suitable for thicker sections |
| Stick | E 308L | - | Preheat recommended |
405 stainless steel is generally considered weldable, but preheating is recommended to minimize the risk of cracking. Post-weld heat treatment can enhance the properties of the weldment, ensuring integrity and performance.
Machinability
| Machining Parameter | 405 Stainless Steel | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60 | 100 | Moderate machinability |
| Typical Cutting Speed (Turning) | 30 m/min | 50 m/min | Use carbide tools for best results |
405 stainless steel has moderate machinability, requiring appropriate tooling and cutting speeds to achieve optimal results. Carbide tools are recommended for effective machining.
Formability
405 stainless steel can be formed through both cold and hot processes. Cold forming is feasible but may require higher forces due to its strength. The material exhibits work hardening, which can affect bend radii and forming limits.
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 | Relieve stresses, improve ductility |
| Hardening | 1000 - 1100 °C / 1832 - 2012 °F | 30 minutes | Oil or air | Increase hardness and strength |
During heat treatment, 405 stainless steel undergoes metallurgical transformations that enhance its mechanical properties. Annealing relieves internal stresses and improves ductility, while hardening significantly increases strength.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection (Brief) |
|---|---|---|---|
| Automotive | Exhaust systems | High strength, moderate corrosion resistance | Durability under thermal stress |
| Oil & Gas | Valve components | High strength, weldability | Reliability in harsh environments |
| Aerospace | Engine components | High strength, heat resistance | Performance at elevated temperatures |
Other applications include:
* - Heat exchangers
* - Industrial machinery components
* - Fasteners and fittings
The selection of 405 stainless steel for these applications is primarily due to its balance of strength, corrosion resistance, and fabricability, making it suitable for components that experience mechanical stress and exposure to various environments.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | 405 Stainless Steel | AISI 304 Stainless Steel | AISI 316 Stainless Steel | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | High strength | Moderate strength | Moderate strength | 405 offers superior strength |
| Key Corrosion Aspect | Moderate resistance | Good resistance | Excellent resistance | 405 is less resistant than 304/316 |
| Weldability | Good | Excellent | Excellent | 405 requires more care in welding |
| Machinability | Moderate | Good | Moderate | 405 is less machinable than 304 |
| Formability | Moderate | Good | Good | 405 is less formable than 304 |
| Approx. Relative Cost | Moderate | Moderate | Higher | 405 is often more cost-effective |
| Typical Availability | Common | Very common | Common | 405 is widely available |
When selecting 405 stainless steel, considerations include its cost-effectiveness, availability, and suitability for specific applications. While it may not offer the same level of corrosion resistance as austenitic grades, its high strength and moderate resistance make it a viable choice for many engineering applications. Additionally, its weldability and machinability enhance its versatility in manufacturing processes.
In conclusion, 405 stainless steel is a valuable material in various industries, balancing strength, corrosion resistance, and fabricability. Understanding its properties and applications can guide engineers and designers in making informed material choices for their projects.