317L Stainless Steel: Properties and Key Applications
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Table Of Content
Table Of Content
317L Stainless Steel is classified as an austenitic stainless steel, characterized by its low carbon content, which enhances its corrosion resistance and weldability. This grade is primarily alloyed with chromium (Cr), nickel (Ni), and molybdenum (Mo), with the addition of nitrogen (N) in some cases. The presence of these elements significantly influences its mechanical properties, corrosion resistance, and overall performance in various environments.
Comprehensive Overview
317L stainless steel is known for its excellent resistance to pitting and crevice corrosion, particularly in chloride environments, making it suitable for applications in chemical processing, marine environments, and food processing. Its low carbon content (≤ 0.03%) minimizes the risk of carbide precipitation during welding, which can lead to intergranular corrosion.
Advantages:
- Corrosion Resistance: Superior resistance to chlorides and acids compared to standard 304 and 316 stainless steels.
- Weldability: Low carbon content allows for easy welding without the need for post-weld heat treatment.
- Strength: Retains strength at elevated temperatures, making it suitable for high-temperature applications.
Limitations:
- Cost: Typically more expensive than 304 and 316 grades due to higher alloy content.
- Work Hardening: Can be more challenging to machine due to its work-hardening characteristics.
- Availability: Less commonly stocked than 304 and 316, which may affect lead times.
Historically, 317L has gained traction in industries requiring high corrosion resistance, such as pharmaceuticals, food processing, and petrochemicals, where its unique properties provide significant advantages over other stainless steel grades.
Alternative Names, Standards, and Equivalents
Standard Organization | Designation/Grade | Country/Region of Origin | Notes/Remarks |
---|---|---|---|
UNS | S31703 | USA | Low carbon version of 317 |
AISI/SAE | 317L | USA | Similar to 316L but with higher Mo content |
ASTM | A240 | USA | Standard specification for stainless steel plates |
EN | 1.4438 | Europe | Equivalent to 317L with minor compositional differences |
JIS | SUS317L | Japan | Closest equivalent with similar properties |
ISO | 1.4438 | International | Standard designation for austenitic stainless steel |
The differences between equivalent grades often lie in their specific alloying elements and mechanical properties. For instance, while 316L and 317L both offer excellent corrosion resistance, 317L typically has a higher molybdenum content, enhancing its performance in more aggressive environments.
Key Properties
Chemical Composition
Element (Symbol and Name) | Percentage Range (%) |
---|---|
Cr (Chromium) | 18.0 - 20.0 |
Ni (Nickel) | 11.0 - 15.0 |
Mo (Molybdenum) | 2.0 - 3.0 |
C (Carbon) | ≤ 0.03 |
N (Nitrogen) | ≤ 0.10 |
Fe (Iron) | Balance |
The primary alloying elements in 317L stainless steel play crucial roles:
- Chromium: Enhances corrosion resistance and contributes to the formation of a protective oxide layer.
- Nickel: Improves toughness and ductility, making the steel more workable.
- Molybdenum: Increases resistance to pitting and crevice corrosion, particularly in chloride environments.
Mechanical Properties
Property | Condition/Temper | Typical Value/Range (Metric) | Typical Value/Range (Imperial) | Reference Standard for Test Method |
---|---|---|---|---|
Tensile Strength | Annealed | 520 - 720 MPa | 75 - 104 ksi | ASTM E8 |
Yield Strength (0.2% offset) | Annealed | 205 - 310 MPa | 30 - 45 ksi | ASTM E8 |
Elongation | Annealed | 40 - 50% | 40 - 50% | ASTM E8 |
Hardness (Rockwell B) | Annealed | 85 - 95 HRB | 85 - 95 HRB | ASTM E18 |
Impact Strength (Charpy) | -20°C | 40 J | 29.5 ft-lbf | ASTM E23 |
The mechanical properties of 317L stainless steel make it suitable for applications requiring high strength and ductility. Its good elongation and impact strength ensure that it can withstand dynamic loads and stress without failure.
Physical Properties
Property | Condition/Temperature | Value (Metric) | Value (Imperial) |
---|---|---|---|
Density | - | 8.0 g/cm³ | 0.289 lb/in³ |
Melting Point/Range | - | 1375 - 1400 °C | 2507 - 2552 °F |
Thermal Conductivity | 20°C | 16.2 W/m·K | 112 BTU·in/h·ft²·°F |
Specific Heat Capacity | 20°C | 500 J/kg·K | 0.12 BTU/lb·°F |
Electrical Resistivity | 20°C | 0.72 µΩ·m | 0.72 µΩ·in |
Coefficient of Thermal Expansion | 20 - 100 °C | 16.0 x 10⁻⁶/K | 8.89 x 10⁻⁶/°F |
Key physical properties such as thermal conductivity and density are critical for applications involving heat exchangers and other thermal management systems. The relatively high melting point indicates good performance in high-temperature environments.
Corrosion Resistance
Corrosive Agent | Concentration (%) | Temperature (°C/°F) | Resistance Rating | Notes |
---|---|---|---|---|
Chlorides | 3-10 | 20-60 / 68-140 | Excellent | Risk of pitting |
Sulfuric Acid | 10-30 | 20-40 / 68-104 | Good | Limited resistance |
Hydrochloric Acid | 5-10 | 20-40 / 68-104 | Fair | Susceptible to SCC |
Acetic Acid | 10-50 | 20-60 / 68-140 | Good | Moderate resistance |
Sea Water | - | 20-60 / 68-140 | Excellent | Resistant to crevice corrosion |
317L stainless steel exhibits excellent resistance to a variety of corrosive agents, particularly in chloride environments, making it a preferred choice for marine applications. However, it is susceptible to stress corrosion cracking (SCC) in environments with high chloride concentrations, particularly when exposed to elevated temperatures.
When compared to 316L, 317L offers superior resistance to pitting and crevice corrosion due to its higher molybdenum content. However, 316L may be more cost-effective for less aggressive environments.
Heat Resistance
Property/Limit | Temperature (°C) | Temperature (°F) | Remarks |
---|---|---|---|
Max Continuous Service Temp | 400 | 752 | Suitable for high-temperature applications |
Max Intermittent Service Temp | 870 | 1600 | Short-term exposure only |
Scaling Temperature | 800 | 1472 | Risk of oxidation at higher temperatures |
Creep Strength considerations begin around | 600 | 1112 | Performance may degrade at elevated temperatures |
317L stainless steel maintains its strength and corrosion resistance at elevated temperatures, making it suitable for applications in heat exchangers and chemical reactors. However, prolonged exposure to temperatures above 400°C can lead to oxidation and scaling, which may compromise its integrity.
Fabrication Properties
Weldability
Welding Process | Recommended Filler Metal (AWS Classification) | Typical Shielding Gas/Flux | Notes |
---|---|---|---|
TIG | ER317L | Argon | Excellent results with minimal distortion |
MIG | ER317L | Argon/CO2 | Good for thicker sections |
SMAW | E317L | Low hydrogen flux | Requires preheat for thicker sections |
317L stainless steel is highly weldable, with minimal risk of cracking or distortion. Preheating is recommended for thicker sections to avoid thermal stress. Post-weld heat treatment is generally not required, which simplifies fabrication processes.
Machinability
Machining Parameter | [317L] | AISI 1212 | Notes/Tips |
---|---|---|---|
Relative Machinability Index | 40% | 100% | Requires slower cutting speeds |
Typical Cutting Speed (Turning) | 20 m/min | 60 m/min | Use carbide tools for best results |
317L stainless steel has a lower machinability index compared to carbon steels, necessitating slower cutting speeds and specialized tooling to achieve optimal results.
Formability
317L exhibits good formability, allowing for cold and hot working processes. However, its work-hardening characteristics can make it challenging to form complex shapes without proper techniques.
Heat Treatment
Treatment Process | Temperature Range (°C/°F) | Typical Soaking Time | Cooling Method | Primary Purpose / Expected Result |
---|---|---|---|---|
Solution Annealing | 1010 - 1120 / 1850 - 2050 | 30 minutes | Air or Water | Dissolves carbides, enhances corrosion resistance |
Stress Relief | 400 - 600 / 752 - 1112 | 1 hour | Air | Reduces residual stresses |
Heat treatment processes such as solution annealing are crucial for optimizing the microstructure of 317L stainless steel, enhancing its corrosion resistance and mechanical properties.
Typical Applications and End Uses
Industry/Sector | Specific Application Example | Key Steel Properties Utilized in this Application | Reason for Selection |
---|---|---|---|
Chemical Processing | Reactors and heat exchangers | High corrosion resistance, strength | Suitable for aggressive environments |
Marine | Shipbuilding and offshore structures | Excellent pitting resistance | Durability in saline environments |
Food Processing | Equipment and storage tanks | Corrosion resistance, ease of cleaning | Compliance with hygiene standards |
Pharmaceutical | Bioreactors and storage containers | Non-reactive, high purity | Critical for product integrity |
Other applications include:
* - Oil and gas pipelines
* - Power generation equipment
* - Pharmaceutical manufacturing equipment
The selection of 317L stainless steel in these applications is primarily due to its superior corrosion resistance and mechanical properties, which are essential for maintaining integrity and performance in challenging environments.
Important Considerations, Selection Criteria, and Further Insights
Feature/Property | 317L Stainless Steel | 316L Stainless Steel | 304 Stainless Steel | Brief Pro/Con or Trade-off Note |
---|---|---|---|---|
Key Mechanical Property | High tensile strength | Good tensile strength | Moderate tensile strength | 317L offers higher strength and corrosion resistance |
Key Corrosion Aspect | Excellent in chlorides | Good in chlorides | Fair in chlorides | 317L is superior in aggressive environments |
Weldability | Excellent | Excellent | Good | 317L requires no post-weld treatment |
Machinability | Moderate | Moderate | High | 317L is more challenging to machine |
Formability | Good | Good | Excellent | 317L may require more effort in forming |
Approx. Relative Cost | Higher | Moderate | Lower | Cost considerations may affect selection |
Typical Availability | Moderate | High | Very High | Availability can impact project timelines |
When selecting 317L stainless steel, considerations such as cost, availability, and specific application requirements are crucial. Its unique properties make it an excellent choice for demanding environments, but its higher cost and lower machinability compared to other grades may influence decisions.
In summary, 317L stainless steel is a versatile material that excels in corrosion resistance and mechanical strength, making it suitable for a wide range of applications in industries where durability and reliability are paramount.