The choice of materials can make or break a project, especially in environments prone to corrosion or high temperatures. Hence, the reliance on stainless steel as a choice material due to its resistance to oxidation and corrosion, which makes it perfect for these conditions.
Yet, stainless steel comes in several variants, each with adjustments that makes them suitable for different projects. Among these variants are the 316 and 316L stainless steel. From the name, both have some similarities, but certain differences make them suitable for specific applications.
Understanding the differences between 316 and 316L stainless steel is crucial to a project’s success. Hence, this article thoroughly explores the two, compares their properties, and offers guidance on selecting the right one for your project.
What is 316 Stainless Steel?
316 stainless steel belongs to the 300 series of austenitic stainless steels, and has a high chromium and nickel content. The addition of molybdenum to 316 stainless steel significantly upgrades its corrosion resistance compared to the 304 standard. As a result, in chloride environments it can work optimally.
The elemental composition of the stainless steel grade includes 16-18% chromium, 10-14% nickel, and 2-3% molybdenum. Each element is highlighted in the table below with regards to their percentage composition and what they contribute to the properties of 316 stainless steel.
| Element | Composition (%) | Contribution |
| Chromium (Cr) | 16–18 | Provides corrosion resistance and forms a passive layer. |
| Nickel (Ni) | 10–14 | Enhances toughness, ductility, and resistance to oxidation. |
| Molybdenum (Mo) | 2–3 | Improves resistance to pitting and crevice corrosion. |
| Carbon (C) | ≤0.08 | Increases hardness and strength. |
| Manganese (Mn) | ≤2.00 | Improves toughness and wear resistance. |
| Silicon (Si) | ≤1.00 | Enhances oxidation resistance and strength. |
| Phosphorus (P) | ≤0.045 | Improves machinability but can reduce corrosion resistance in higher amounts. |
| Sulfur (S) | ≤0.030 | Improves machinability, though excessive amounts can weaken toughness. |
| Iron (Fe) | Balance | Base metal provides overall structural integrity. |
What sets stainless steel 316 apart is its pit resistance due to localized attack by chloride ions. As a result, it is an invaluable choice for marine applications, where contact with saltwater is inevitable.
As a result, 316 stainless steel is the choice of stainless steel grade in industries that require its robustness and resistance to chemical attacks. Common applications include the marine and chemical processing equipment, medical devices, and food processing equipment
What is 316L Stainless Steel?
316L stainless steel is the low low-carbon version of stainless steel 316. It contains less carbon, which improves its corrosion resistance after welding by preventing carbide precipitation. The elemental composition compared to 316 stainless steel is highlighted below
| Element | 316 Composition (%) | 316L Composition (%) | Contribution |
| Chromium (Cr) | 16–18 | 16–18 | Provides corrosion resistance and forms a passive layer. |
| Nickel (Ni) | 10–14 | 10–14 | Enhances toughness, ductility, and resistance to oxidation. |
| Molybdenum (Mo) | 2–3 | 2–3 | Improves resistance to pitting and crevice corrosion. |
| Carbon (C) | ≤0.08 | ≤0.03 | Lower carbon in 316L minimizes the risk of carbide precipitation during welding. |
| Manganese (Mn) | ≤2.00 | ≤2.00 | Improves toughness and wear resistance. |
| Silicon (Si) | ≤1.00 | ≤1.00 | Enhances oxidation resistance and strength. |
| Phosphorus (P) | ≤0.045 | ≤0.045 | Improves machinability but may reduce corrosion resistance if excessive. |
| Sulfur (S) | ≤0.030 | ≤0.030 | Improves machinability, though excessive amounts can weaken toughness. |
| Iron (Fe) | Balance | Balance | Base metal provides overall structural integrity. |
Furthermore, the lower carbon content significantly enhances its performance at elevated temperatures. As a result, this reduces the risk of intergranular corrosion, which is of huge concern when working at high temperatures for prolonged periods.
316L is the better choice for applications that require significant welding requirements. Common applications include high-temperature pressure vessels, oil refining and pipeline equipment, biotechnology, and pharmaceuticals.
316 vs 316L: Similarities
The elemental composition of 316 vs 316L stainless steel denotes differences, but there are also many similarities between the two stainless steel grade as summarized below:
Austenitic Structure
Both 316 and 316L stainless steels share an austenitic structure. Consequently, they have exceptional toughness and mechanical stability, even at extremely low, cryogenic temperatures.
Shared Elements
The chromium, nickel, and molybdenum bases make both steels exceptionally good for environments with high corrosion resistance.
Workability
Both are noted for their ability to be fabricated easily; they can be readily formed and welded to meet the demands of nearly any application.
316 vs 316L: Differences
Understanding the difference in the 316 vs 316L comparison will help in the quality of the final part and can be a good point to decide when looking for metal manufacturing near me. Below are the differences between the two stainless steel grades and the impending effect.
Carbon Content
Distinction between 316 and 316L stainless steel lies in their carbon content. 316 has a maximum carbon content of 0.08%, while 316L has aDue to their microstructure differences, slighted maximum of 0.03%. This lower carbon content in pitation makes 316L the preferred grade in welding applications or elevated operational temperatures.
Corrosion Resistance
316L has superior resistance in situations where the material is exposed to chlorides or other aggressive chemicals. Its reduced carbon content ensures that it resists sensitization—a type of corrosion caused by the formation of chromium carbides along grain boundaries.
Mechanical Properties
Both grades offer high tensile strength and toughness, however, 316 stainless steel is stronger and harder than 316L. Moreover, 316L has a lower carbon content hence its softness, better formability and machinability that makes it a choice of material in CNC machining operations.
Weldability
316L lower carbon content makes it more weldable than 316. In welding applications, 316 may require post-weld heat treatment to prevent carbide precipitation, while 316L does not.
High-Temperature Environments
316 can withstand slightly higher temperatures due to its higher carbon content. 316 is often chosen for applications requiring resistance to oxidation at temperatures up to 870°C, whereas 316L is better suited for continuous exposure to lower temperatures to avoid sensitization.
Durability Under Stress
316 has a slight advantage over 316L because of its higher carbon content in creep resistance hence manufacturing service providers often prefer it in heavy-duty applications where long-term strength is important.
Biocompatibility
316L is often preferred in biomedical implants and surgical instruments due to its lower carbon content, which enhances corrosion resistance and minimizes the risk of leaching into biological systems.
Magnetic Properties
Both grades are non-magnetic due to their austenitic structure. However, 316L has a lower tendency of becoming slightly magnetic after cold working which is advantageous in applications requiring non-magnetic materials, such as medical imaging equipment
Surface Finish and Aesthetic Considerations
Even though their surface finish is similar, 316L’s reduced carbon content leads to smoother and more uniform finish after polishing.
316 vs 316L: How to Select the Right One
Selecting between 316 and 316L stainless steel requires a careful assessment of the specific requirements of your project and weighing them against the distinct properties of each material.
Corrosion Resistance Needs
If the material will be exposed to chlorides, saltwater, or harsh chemicals, 316L is the better option due to its lower carbon content, which minimizes the risk of corrosion through carbide precipitation. This makes it ideal for marine environments, chemical processing plants, and areas with high humidity or salinity.
Welding Applications
Projects requiring extensive welding often benefit from 316L, as its low carbon content prevents the formation of chromium carbides during welding. This eliminates the need for post-weld heat treatment and reduces the risk of intergranular corrosion, making it more efficient and cost-effective in applications like piping, tanks, and structural components.
High-Temperature Performance
In applications with sustained exposure to elevated temperatures, 316L typically performs better. While 316 may show signs of carbide precipitation at high temperatures, 316L resists these issues, ensuring structural integrity and durability over time. This makes it suitable for use in industrial furnaces, heat exchangers, and high-temperature fluid systems.
Cost and Availability
While the cost difference between 316 and 316L is generally minimal, regional availability and supplier preferences may influence pricing. Industries with stringent material requirements, like food processing or pharmaceuticals, often stock more 316L, potentially making it easier to source. Comparing quotes from multiple suppliers can help identify the most economical choice.
Industry-Specific Standards
Certain industries have established standards that mandate the use of 316L due to its superior corrosion resistance and weldability. For example, the pharmaceutical and food industries often require 316L for its resistance to contamination and ability to withstand sterilization processes. Ensuring compliance with these standards is critical in regulated sectors.
Longevity and Maintenance
For applications where long-term performance and minimal maintenance are key priorities, 316L may offer better value. Its enhanced resistance to corrosion and wear reduces the likelihood of downtime and costly repairs, especially in demanding environments or those requiring frequent cleaning or sterilization.
Conclusion
316 and 316L stainless steels are excellent stainless steel grades but the decision between both should be based on thoroughly evaluating your project’s environmental conditions, welding needs, and specific performance requirements. Making an informed choice will ensure your project runs efficiently and effectively, minimizing maintenance and maximizing the lifespan of the equipment or structure.
