316L Stainless Steel

Composition, Characteristics and Applications

To understand 316L stainless steel, one must first understand 316 stainless steel.

316 is an austenitic chromium-nickel stainless steel that possesses between two and 3% molybdenum. The molybdenum content improves corrosion resistance, increases resistance to pitting in chloride ion solutions, and improves strength at high temperatures.

What is 316L Stainless Steel?

316L is the low carbon grade of 316. This grade is immune from sensitization (grain boundary carbide precipitation). It is regularly used in heavy gauge welded components (roughly over 6mm). There is no notable price difference between 316 and 316L stainless steel.

316L stainless steel offers higher creep, stress to rupture and tensile strength at elevated temperatures than chromium-nickel austenitic stainless steels.

Alloy Designations

The “L” designation simply means “less carbon.” 316L contains less carbon than 316.

Common designations are the L, F, N, and H. The austenitic structure of these grades provide excellent toughness, even at cryogenic temperatures.

304 vs. 316 Stainless Steel

Unlike 304 steel – the most popular stainless steel – 316 possesses improved resistance to corrosion from chloride and other acids. This makes it useful for outdoor applications in marine environments or applications that risk potential exposure to chloride.

Both 316 and 316L exhibit better corrosion resistance and strength at elevated temperatures than their 304 counterpart – particularly when it comes to pitting and crevice corrosion in chloride environments.

316 vs. 316L Stainless Steel

316 stainless steel contains more carbon than 316L. 316 stainless steel possesses a mid-range level of carbon and contains between 2% and 3% molybdenum, which provides resistance to corrosion, acidic elements, and high temperatures.

To qualify as 316L stainless steel, the amount of carbon must be low – specifically, it cannot exceed 0.03%. The lower carbon levels result in 316L being softer than 316.

Despite the difference in carbon content, 316L is very similar to 316 in almost every way.

Both stainless steels are very malleable, useful when forming the shapes necessary for any project without breaking or even cracking, and possess high resistance to corrosion and high tensile strength.

Cost between the two types is comparable. Both provide good durability, corrosion-resistance, and are favorable options in high-stress applications.

316L is considered ideal for a project that requires a substantial welding. 316, on the other hand, is less corrosion-resistant within the weld (weld decay) than 316L. That said, annealing 316 is a workaround for resisting weld decay.

316L is great for high-temperature, high-corrosion uses, which attributes to its popularity in construction and marine projects.

Both 316 and 316L possess excellent malleability, performing well in bending, stretching, deep drawing, and spinning. However, 316 is a more rigid steel with higher tensile strength and ductility compared to 316L.

Applications

Here are some examples of common 316L stainless steel applications:

• • Equipment for food preparation (especially in chloride environments)
• • Pharmaceutical equipment
• • Marine applications
• • Architectural applications
• • Medical implants (pins, screws and orthopedic implants)
• • Fasteners
• • Condensers, tanks, and evaporators
• • Pollution control
• • Boat fitting, value, and pump trim
• • Laboratory equipment
• • Pharmaceutical tools and parts
• • Photographic equipment (inks, photographic chemicals, rayons)
• • Heat exchangers
• • Exhaust manifolds
• • Furnace parts
• • Heat exchangers
• • Jet engine parts
• • Valve and pump parts
• • Pulp, paper, and textile processing equipment
• • Construction encasement, doors, windows and armatures
• • Offshore modules
• • Cisterns and pipes for chemical tankers
• • Transportation of chemicals
• • Food and beverages
• • Pharmacy equipment
• • Synthetic fiber, paper and textile plants
• • Pressure vessel

• Properties of 316L

  316L stainless steel is easily identified by examining its carbon content – which should be lower than that of 316. Beyond that, here are some 316L properties that also distinguish it from other steel grades.

  Physical Properties

  316L has a density of 8000 kg/m3 and an elastic modulus of 193 GPa. At a temperature of 100°C, it has thermal connectivity of 16.3 W/m.K and 21.5 W/m.K at 500°C. The 316L also possesses an electrical resistivity of 740 nΩ.m, with a specific heat capacity of 500 J/kg.K.

  Chemical Composition

  316l SS composition features maximum carbon levels of 0.030%. The silicon levels peak at a maximum of 0.750%. Maximum manganese, phosphorus, nitrogen, and sulfur levels are set at 2.00%, 0.045%, 0.100% and 0.030%, respectively. 316L is composed of chromium at 16% min and 18% max. Nickel levels are set at 10% min and 14% max. The molybdenum content is a minimum level of 2.00% and a max of 3.00%.

  Mechanical Properties

  316L maintains a minimum tensile strength of 485 and minimum yield strength of 120 at 0.2% proof of stress. It has an elongation of 40% in 50mm/min and maximum hardness of 95kg under the Hardness Rockwell B test. 316L stainiless steel reaches a maximum hardness of 217kg under the Brinell scale test.

  Corrosion Resistance

  Grade 316L provides excellent corrosion resistance in a variety of corrosive media and atmospheric environments. It holds up well when subjected to crevice and pitting corrosion in warm chloride situations. Additionally, it proves to stay intact even under stress corrosion cracking tests at above 60 °C. 316L exhibits resistance to water with up to 1000mg/L chloride levels.

  316 grade stainless steel is particularly effective in acidic environments – especially when protecting against corrosion caused by sulfuric, hydrochloric, acetic, formic, and tartaric acids, as well as acid sulfates and alkaline chlorides.