Difference between stainless steel 316 and 316L
The difference between SS316 and SS316L lies in their carbon content: 316L (low carbon) has a maximum carbon content of 0.03%, resulting in superior weldability and corrosion resistance of welded components; while 316 has a maximum carbon content of 0.08%, offering slightly higher strength, but carries the risk of "weld decay" (sensitization) if not heat-treated after welding. Both are marine-grade molybdenum-enhanced stainless steels, but for heavy-duty welding, chemical, and marine applications requiring maximum corrosion resistance, 316L is the better choice; while 316 is more suitable for applications where welding is not required or welding requirements are not stringent, as it offers better mechanical properties.
What is 316L stainless steel?
316L stainless steel is medical-grade surgical steel. It has a lower carbon content than other types of steel and boasts a perfect luster, making it suitable for various jewelry items, including bracelets, rings, pendants, earrings, necklaces, and more. In fact, the "L" in 316L (maximum carbon content of 0.03%) stands for low carbon content.
316 and 316L Stainless Steel
316 Stainless Steel
316-grade stainless steel is an austenitic stainless steel primarily composed of chromium, nickel, carbon, and molybdenum. The presence of molybdenum (typically between 2% and 3%) enhances the corrosion resistance of 316 stainless steel, making it a preferred material for most industrial applications, second only to 304 stainless steel. Molybdenum also improves the mechanical strength of the stainless steel. Therefore, 316 stainless steel is used in corrosive environments where potential problems may arise, such as in refineries or chemical plants, and in the manufacture of jet engine parts or heat exchangers.
| C | Mn | Si | P | S | Cr | Mo | Ni |
| 0-0.07 | 0-2.00 | 0-1.00 | 0-0.05 | 0-0.02 | 16.50-18.50 | 2.00-2.50 | 10.00-13.00 |
316L Stainless Steel
316L stainless steel is a "low-carbon version" of 316 stainless steel, with a carbon content of less than 0.03%. The lower carbon content reduces the precipitation of carbide deposits at grain boundaries during heat treatment. Due to the reduced risk of sensitization, 316L stainless steel exhibits higher corrosion resistance than 316 stainless steel during welding.
| C | Mn | Si | P | S | Cr | Mo | Ni |
| 0-0.03 | 0-2.00 | 0-1.00 | 0-0.05 | 0-0.02 | 16.50-18.50 | 2.00-2.50 | 10.00-13.00 |
Stainless Steel 316 Vs 316L Equivalent Grade
| Standard | 316 | 316L |
|---|---|---|
| AISI / ASTM (USA) | 316 | 316L |
| UNS (USA) | S31600 | S31603 |
| EN / DIN (Europe) | X5CrNiMo17-12-2 (1.4401) | X2CrNiMo17-12-2 (1.4404) |
| JIS (Japan) | SUS 316 | SUS 316L |
| BS (UK) | 316S31 | 316S11 |
| AFNOR (France) | Z7CND17-11-02 | Z2CND17-11-02 |
| GOST (Russia) | 03Х17Н13М2 | 03Х17Н13М2 |
| ISO | ISO 683/13-Fe 8 | ISO 683/13-Fe 8L |
Mechanical properties of AISI 316 VS 316L
| Property | Value |
|---|---|
| Tensile Strength (min) | 485 MPa (70,300 psi) |
| Yield Strength (0.2% min) | 170 MPa (24,700 psi) |
| Elongation (min) | 40% |
| Hardness (Brinell) | ≤ 217 HB |
| Hardness (Rockwell B) | ≤ 95 HRB |
| Modulus of Elasticity | ~193 GPa (28 x 10⁶ psi) |
316L vs 316 Stainless Steel: The Comparison
316L and 316 grade stainless steels are similar in terms of strength requirements and other mechanical properties. However, there are some fundamental differences between the two, as described below:
| Properties | 316L vs 316 Stainless Steel |
| Corrosion resistance | 316L stainless steel exhibits better intergranular corrosion resistance than 316 stainless steel due to its reduced carbon presence. |
| Weldability | The 316 grade is more susceptible to weld decay; thus, 316L is usually desired for projects requiring welding. The lower carbon aids in reducing the carbide precipitates along the grain boundaries during welding. |
| Temperature resistance | Both types, 316 and 316L stainless steel, are resistant to high temperatures. |
| Magnetism | 316 stainless steel is practically paramagnetic due to its austenitic crystal structure. 316L stainless steel, although similar in properties, has the capability of gaining magnetism. |
| Cost | Both 316L and 316 stainless steels are priced similarly. |
| Applications | Both stainless steels are used primarily in the chemical, pharma, food-grade, or similar industries where the resistance to heat and chemical is desired. This includes the construction of heat exchangers, jet engine parts, and exhaust manifolds. |
Welding 316 and 316L Stainless Steel
Similar to other austenitic stainless steel grades, 316 and 316L stainless steels can be welded using arc welding processes, such as TIG (Tungsten Inert Gas welding). However, they are susceptible to various problems, such as hot cracking or reduced corrosion resistance. To address these issues, the filler metal used during welding should contain sufficient molybdenum to match the composition of the base metal, thus accommodating corrosive operating environments. Additionally, high-purity argon shielding can be used to prevent oxidation at the weld root and maintain corrosion resistance.
To achieve optimal welding results with 316 and 316L stainless steels, welders need to understand their characteristics and the changes in properties that occur during processes such as welding. By understanding the differences between the 316L and 316 grades, manufacturers can ensure the strength of their application materials and achieve optimal corrosion and high-temperature resistance.
SS 316 VS 316L Difference
| Property | SS 316 | SS 316L |
|---|---|---|
| Weldability | Good | Excellent (due to low carbon) |
| Corrosion Resistance | High | Very high in welded sections |
| Mechanical Strength | Slightly higher | Slightly lower |
| Applications | Chemical processing, marine | Pharmaceutical, welded parts |
