317L Stainless Steel: Properties and Key Applications

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.

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