Differences between 316 vs 316L – A Comparison
316 and 316L are two popular grades of stainless steel that are commonly used in a variety of applications. There are some key differences between the two that are important to understand.
What the numbers 316 and 316L represent. Both grades belong to the austenitic stainless steel family, which is known for its excellent corrosion resistance and high strength. The “L” in 316L stands for “low carbon”, indicating that it has a lower carbon content compared to 316. This difference in carbon content impacts the properties of the steel, making 316L more resistant to sensitization, or the formation of carbide precipitation during welding.
Additionally, the lower carbon content of 316L also means that it is more suitable for applications where welding or high temperatures are involved, as it reduces the risk of intergranular corrosion.
Composition and properties of 316 stainless steel
We will explore the differences between 316 and 316L, and what sets them apart from each other.
here is a simplified chart highlighting the composition and key properties of 316 and 316L stainless steel:
| Property | Composition (316) | Composition (316L) | Properties |
| Chemical Composition | |||
| Chromium (Cr) | 16-18% | 16-18% | Corrosion resistance |
| Nickel (Ni) | 10-14% | 10-14% | Improved weldability |
| Molybdenum (Mo) | 2-3% | 2-3% | Enhanced corrosion resistance |
| Iron (Fe) | Balance (approx. 66%) | Balance (approx. 68%) | Structural strength |
| Carbon (C) | ≤0.08% | ≤0.03% | Reduced risk of carbide precipitation during welding |
| Physical Properties | |||
| Density | 7.99 g/cm³ | 7.99 g/cm³ | High density |
| Melting Point | 1370-1400°C (2498-2552°F) | 1370-1400°C (2498-2552°F) | High melting point |
| Mechanical Properties | |||
| Tensile Strength | 515-620 MPa (74,700-89,900 psi) | 485 MPa (70,300 psi) | Excellent tensile strength |
| Yield Strength | 205 MPa (29,700 psi) | 170 MPa (24,600 psi) | Good yield strength |
| Elongation | 40% (in 50mm) | 40% (in 50mm) | Ductile material |
Composition and properties of 316L stainless steel
316 stainless steel is an austenitic stainless steel that contains 16-18% chromium, 10-14% nickel, 2-3% molybdenum, and small amounts of other elements such as manganese, silicon, and carbon. This composition gives 316 stainless steel its excellent corrosion resistance and high strength. It is also known for its resistance to pitting and crevice corrosion, making it suitable for use in harsh environments, such as marine and chemical processing industries.
The addition of molybdenum enhances the corrosion resistance of 316 stainless steel, particularly against chlorides and other halides. 316 stainless steel has good weldability and formability, and it can be easily fabricated into various shapes and sizes.
Corrosion resistance of 316 and 316L stainless steel
316L stainless steel is essentially the low-carbon version of 316 stainless steel. This difference in carbon content impacts the properties of the steel, making 316L more resistant to sensitization, or the formation of carbide precipitation during welding.
The lower carbon content of 316L also means that it is more suitable for applications where welding or high temperatures are involved, as it reduces the risk of intergranular corrosion. This type of corrosion occurs along the grain boundaries of the steel and can weaken the material over time. By minimizing the carbon content, 316L stainless steel exhibits better resistance to this type of corrosion, making it a preferred choice in industries such as marine, medical, and chemical processing.
| Corrosive Environment | 316 Stainless Steel | 316L Stainless Steel |
|---|---|---|
| Atmospheric Corrosion | Excellent resistance | Excellent resistance |
| Aqueous Corrosion | ||
| – Freshwater (neutral pH) | Excellent resistance | Excellent resistance |
| – Seawater | Excellent resistance | Excellent resistance |
| – Chloride Solutions | Good resistance | Excellent resistance |
| – Brine Solutions | Good resistance | Excellent resistance |
| – Sulfuric Acid (dilute) | Limited resistance | Excellent resistance |
| – Hydrochloric Acid (dilute) | Limited resistance | Excellent resistance |
| High-Temperature Corrosion | ||
| – Oxidizing Atmospheres | Good resistance | Good resistance |
| – Sulfidizing Atmospheres | Limited resistance | Limited resistance |
| Crevice and Pitting Corrosion | ||
| – Crevice Corrosion | Limited resistance | Excellent resistance |
| – Pitting Corrosion | Limited resistance | Excellent resistance |
| Intergranular Corrosion | ||
| – Sensitization | Susceptible | Reduced susceptibility |
| – Carbide Precipitation | Susceptible | Resistant |
| Hydrogen Embrittlement | Potential risk | Lower risk |
In addition to its improved corrosion resistance, 316L stainless steel retains the excellent mechanical properties of 316 stainless steel. It still offers high strength, good formability, and excellent weldability, making it a versatile choice for various applications.
Mechanical properties of 316 and 316L stainless steel
Both 316 and 316L stainless steel exhibit excellent corrosion resistance, thanks to their high chromium and molybdenum content. They are resistant to a wide range of corrosive environments, including acids, alkalis, and chloride solutions. However, the lower carbon content of 316L stainless steel provides it with better resistance to sensitization and intergranular corrosion.
| Mechanical Property | 316 Stainless Steel | 316L Stainless Steel |
| Tensile Strength (MPa) | 515-620 MPa | 485 MPa |
| Yield Strength (MPa) | 205 MPa | 170 MPa |
| Elongation (%) | 40% (in 50mm) | 40% (in 50mm) |
| Hardness (Brinell) | 149 HB | 146 HB |
| Modulus of Elasticity (GPa) | 200 GPa | 200 GPa |
| Shear Modulus (GPa) | 77 GPa | 77 GPa |
| Poisson’s Ratio | 0.29 | 0.29 |
Sensitization occurs when the high carbon content in stainless steel combines with chromium to form chromium carbides. This can deplete the chromium content in the steel, reducing its corrosion resistance. In applications where welding or high temperatures are involved, sensitization can be a concern. By using 316L stainless steel, the risk of sensitization is minimized, ensuring the long-term durability and corrosion resistance of the material.
Applications of 316 and 316L stainless steel
Both 316 and 316L stainless steel possess excellent mechanical properties, including high tensile strength, good yield strength, and excellent toughness. They exhibit good ductility and can be easily formed into various shapes and sizes. Additionally, they have excellent creep and stress rupture resistance, making them suitable for high-temperature applications.
The mechanical properties of 316 and 316L stainless steel can be further enhanced through cold working. Cold working involves subjecting the steel to mechanical stress, such as rolling or bending, to increase its strength and hardness. However, it is important to note that cold working can also reduce the corrosion resistance of the steel. Therefore, proper heat treatment and post-weld annealing are recommended to restore the material’s corrosion resistance.
Comparison of 316 and 316L stainless steel
Due to their excellent corrosion resistance, high strength, and good weldability, both 316 and 316L stainless steel find applications in a wide range of industries. Some common applications include:
1. Marine industry: 316 and 316L stainless steel are widely used in the marine industry for various components, such as boat fittings, propellers, and underwater equipment. Their resistance to saltwater corrosion makes them ideal for these demanding applications.
2. Medical industry: 316 and 316L stainless steel are also commonly used in the medical industry, particularly for surgical instruments, implants, and medical devices. Their biocompatibility, corrosion resistance, and ease of sterilization make them suitable for these critical applications.
3. Chemical processing industry: The chemical processing industry relies heavily on stainless steel for its corrosion resistance and durability. 316 and 316L stainless steel are commonly used in this industry for storage tanks, piping systems, and various equipment that come into contact with corrosive chemicals.
4. Food and beverage industry: Stainless steel is widely used in the food and beverage industry due to its hygienic properties and resistance to corrosion. 316 and 316L stainless steel are commonly used for food processing equipment, storage tanks, and brewing equipment.
| Property/Characteristic | 316 Stainless Steel | 316L Stainless Steel |
| Chemical Composition | ||
| Chromium (Cr) | 16-18% | 16-18% |
| Nickel (Ni) | 10-14% | 10-14% |
| Molybdenum (Mo) | 2-3% | 2-3% |
| Carbon (C) | ≤0.08% | ≤0.03% |
| Iron (Fe) | Balance | Balance |
| Mechanical Properties | ||
| Tensile Strength (MPa) | 515-620 | 485 |
| Yield Strength (MPa) | 205 | 170 |
| Elongation (%) | 40% (in 50mm) | 40% (in 50mm) |
| Weldability | ||
| Suitability for Welding | Excellent | Excellent |
| Corrosion Resistance | ||
| General Corrosion | Good | Good |
| Sensitization Risk | Moderate | Lower |
| Applications | ||
| Common Uses | Various industries, | Pharmaceutical, |
| including marine, | food processing, | |
| aerospace, and more | and medical devices |
Factors to consider when choosing between 316 and 316L stainless steel
The main difference between 316 and 316L stainless steel lies in their carbon content. While 316 stainless steel contains a higher carbon content, 316L stainless steel has a lower carbon content, making it more resistant to sensitization and intergranular corrosion. This difference in carbon content gives 316L stainless steel an edge in applications involving welding or high temperatures.
In terms of corrosion resistance and mechanical properties, both grades are quite similar. They exhibit excellent corrosion resistance, high strength, good formability, and excellent weldability. However, it is important to consider the specific requirements of your application and consult with a material expert to determine which grade is best suited for your needs.
Common misconceptions about 316 and 316L stainless steel
When choosing between 316 and 316L stainless steel, there are several factors to consider:
1. Weldability: If your application involves welding, particularly at high temperatures, 316L stainless steel is the preferred choice due to its lower carbon content and improved resistance to sensitization.
2. Corrosion resistance: Both 316 and 316L stainless steel offer excellent corrosion resistance. However, if your application involves exposure to corrosive environments, such as saltwater or chlorides, 316L stainless steel may provide better long-term corrosion resistance.
3. Cost: 316L stainless steel tends to be slightly more expensive than 316 stainless steel due to its lower carbon content and improved properties. Consider your budget and the specific requirements of your application when making a decision.
4. Consultation with experts: Choosing the right stainless steel grade for your application can be complex. It is always recommended to consult with material experts or engineers who can provide guidance based on your specific requirements and industry standards.
Conclusion
There are a few common misconceptions about 316 and 316L stainless steel that are worth addressing:
1. 316 and 316L stainless steel are completely interchangeable.” While they are similar in many ways, the difference in carbon content can impact their properties, particularly in terms of corrosion resistance and weldability. It is important to choose the appropriate grade based on the specific requirements of your application.
2. 316L stainless steel is always the better choice.” While 316L stainless steel offers improved resistance to sensitization and intergranular corrosion, it may not always be necessary for every application. Consider the specific requirements, budget, and consult with experts before making a decision.
3. 316 and 316L stainless steel are the only options for corrosion resistance.” While these grades are widely used for their corrosion resistance, there are other stainless steel grades available that may be better suited for certain applications. It is important to explore all available options and consult with experts to ensure the best choice for your specific needs.
UNS designations for 316 and 316L stainless steel:
- 316 Stainless Steel: UNS S31600
- 316L Stainless Steel: UNS S31603
