403 Stainless Steel: Properties and Key Applications
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Table Of Content
Table Of Content
403 stainless steel is classified as a martensitic stainless steel, primarily known for its high strength and moderate corrosion resistance. The primary alloying elements in 403 stainless steel include chromium (12-14%), nickel (up to 1%), and carbon (0.15-0.40%). The presence of chromium provides corrosion resistance, while carbon contributes to hardness and strength. This steel grade is often used in applications requiring high strength and moderate corrosion resistance, making it suitable for various engineering applications.
Comprehensive Overview
403 stainless steel exhibits several significant characteristics that define its utility in engineering applications. It possesses good mechanical properties, including high tensile strength and hardness, which make it suitable for applications that require durability and wear resistance. Additionally, its moderate corrosion resistance allows it to be used in environments that may expose it to moisture and some corrosive agents.
Advantages:
- High Strength: 403 stainless steel can withstand significant mechanical loads, making it ideal for structural applications.
- Moderate Corrosion Resistance: While not as resistant as austenitic grades, it performs well in mildly corrosive environments.
- Good Fabricability: This steel can be easily machined and welded, facilitating its use in various manufacturing processes.
Limitations:
- Lower Corrosion Resistance: Compared to austenitic stainless steels, 403 has reduced resistance to pitting and crevice corrosion.
- Susceptibility to Stress Corrosion Cracking (SCC): In certain environments, it may be prone to SCC, which can compromise structural integrity.
Historically, 403 stainless steel has been utilized in applications such as turbine blades, valve components, and other high-stress environments. Its market position is stable, with a consistent demand in industries that prioritize strength and moderate corrosion resistance.
Alternative Names, Standards, and Equivalents
| Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
|---|---|---|---|
| UNS | S40300 | USA | Closest equivalent to AISI 403 |
| AISI/SAE | 403 | USA | Commonly used designation |
| ASTM | A276 | USA | Standard specification for stainless steel bars |
| EN | 1.4006 | Europe | Minor compositional differences |
| JIS | SUS403 | Japan | Similar properties, used in Japanese applications |
The differences between these equivalent grades can affect selection based on specific performance requirements. For instance, while UNS S40300 and AISI 403 are closely related, slight variations in carbon content can influence hardness and machinability.
Key Properties
Chemical Composition
| Element (Symbol and Name) | Percentage Range (%) |
|---|---|
| Cr (Chromium) | 12.0 - 14.0 |
| Ni (Nickel) | 0.5 - 1.0 |
| C (Carbon) | 0.15 - 0.40 |
| Mn (Manganese) | 1.0 max |
| Si (Silicon) | 1.0 max |
| P (Phosphorus) | 0.04 max |
| S (Sulfur) | 0.03 max |
The primary role of chromium in 403 stainless steel is to enhance corrosion resistance, while carbon contributes to the hardness and strength of the material. Manganese and silicon are added to improve the steel's toughness and ductility.
Mechanical Properties
| Property | Condition/Temper | Test Temperature | Typical Value/Range (Metric - SI Units) | Typical Value/Range (Imperial Units) | Reference Standard for Test Method |
|---|---|---|---|---|---|
| Tensile Strength | Annealed | Room Temp | 520 - 700 MPa | 75 - 102 ksi | ASTM E8 |
| Yield Strength (0.2% offset) | Annealed | Room Temp | 280 - 450 MPa | 41 - 65 ksi | ASTM E8 |
| Elongation | Annealed | Room Temp | 20 - 30% | 20 - 30% | ASTM E8 |
| Hardness (Rockwell C) | Annealed | Room Temp | 30 - 40 HRC | 30 - 40 HRC | ASTM E18 |
| Impact Strength | Annealed | -20°C | 40 J | 29.5 ft-lbf | ASTM E23 |
The combination of high tensile and yield strength makes 403 stainless steel suitable for applications that experience significant mechanical loading. Its elongation and impact strength indicate good ductility, which is essential for preventing brittle failure under stress.
Physical Properties
| Property | Condition/Temperature | Value (Metric - SI Units) | Value (Imperial Units) |
|---|---|---|---|
| Density | Room Temp | 7.75 g/cm³ | 0.28 lb/in³ |
| Melting Point | - | 1400 - 1450 °C | 2552 - 2642 °F |
| Thermal Conductivity | Room Temp | 25 W/m·K | 17.3 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 | 0.00043 Ω·in |
The density of 403 stainless steel contributes to its weight and strength, while its melting point indicates good thermal stability. The thermal conductivity and specific heat capacity are important for applications involving heat transfer.
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% | 20°C/68°F | Poor | Not recommended |
| Acetic Acid | 5% | 25°C/77°F | Good | Moderate resistance |
| Sea Water | - | 25°C/77°F | Fair | Susceptible to crevice corrosion |
403 stainless steel exhibits moderate resistance to various corrosive environments. It performs reasonably well in mild acidic conditions, such as acetic acid, but is susceptible to pitting in chloride-rich environments. Compared to austenitic grades like 304 or 316, 403 stainless steel has lower corrosion resistance, particularly in aggressive 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 | Can withstand short-term exposure |
| Scaling Temperature | 700 °C | 1292 °F | Risk of oxidation beyond this temperature |
At elevated temperatures, 403 stainless steel maintains its strength but may experience oxidation. Its performance in high-temperature applications is generally good, but care must be taken to avoid prolonged exposure to temperatures exceeding its scaling limit.
Fabrication Properties
Weldability
| Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
|---|---|---|---|
| TIG | ER403 | Argon | Preheat recommended |
| MIG | ER308 | Argon + CO2 | Post-weld heat treatment may be necessary |
403 stainless steel is generally weldable, but preheating is recommended to reduce the risk of cracking. Post-weld heat treatment can enhance the mechanical properties of the weldment.
Machinability
| Machining Parameter | [403 Stainless Steel] | AISI 1212 | Notes/Tips |
|---|---|---|---|
| Relative Machinability Index | 60% | 100% | Requires sharp tooling |
| Typical Cutting Speed (Turning) | 30 m/min | 50 m/min | Adjust for tool wear |
403 stainless steel has moderate machinability. It requires sharp tools and appropriate cutting speeds to achieve optimal results.
Formability
403 stainless steel can be cold and hot formed, but it exhibits work hardening. The minimum bend radius should be considered during forming operations to avoid cracking.
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, improved ductility |
| Hardening | 1000 - 1100 °C / 1832 - 2012 °F | 30 minutes | Oil or air | Increased hardness |
During heat treatment, 403 stainless steel undergoes metallurgical transformations that enhance its mechanical properties. Annealing softens the material, while hardening increases its strength and hardness.
Typical Applications and End Uses
| Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection (Brief) |
|---|---|---|---|
| Aerospace | Turbine components | High strength, moderate corrosion resistance | Durability under stress |
| Automotive | Exhaust valves | High temperature resistance, strength | Performance in harsh conditions |
| Oil & Gas | Pump shafts | Wear resistance, strength | Reliability in demanding environments |
Other applications include:
- Valve components
- Marine hardware
- Food processing equipment
403 stainless steel is chosen for these applications due to its combination of strength, moderate corrosion resistance, and good fabricability, making it suitable for demanding environments.
Important Considerations, Selection Criteria, and Further Insights
| Feature/Property | 403 Stainless Steel | AISI 304 Stainless Steel | AISI 316 Stainless Steel | Brief Pro/Con or Trade-off Note |
|---|---|---|---|---|
| Key Mechanical Property | High strength | Good ductility | Excellent corrosion resistance | 403 is stronger but less ductile |
| Key Corrosion Aspect | Moderate resistance | Excellent resistance | Superior resistance | 403 is less suitable for harsh environments |
| Weldability | Good | Excellent | Good | 403 requires preheating |
| Machinability | Moderate | Good | Moderate | 403 is less machinable than 304 |
| Formability | Fair | Good | Fair | 403 has limited formability |
| Approx. Relative Cost | Moderate | Higher | Higher | 403 is cost-effective for strength |
| Typical Availability | Common | Very common | Common | 403 is readily available |
When selecting 403 stainless steel, considerations include its cost-effectiveness, availability, and suitability for specific applications. While it offers high strength, its corrosion resistance is not as robust as that of austenitic grades. Therefore, it is essential to evaluate the operating environment and mechanical requirements before making a selection.