Grade 316 is the standard molybdenum-bearing grade, second in importance to 304 amongst the austenitic stainless steels. The molybdenum gives 316 better overall corrosion resistant properties than Grade 304, particularly higher resistance to pitting and crevice corrosion in chloride environments.
Grade 316L, the low carbon version of 316 and is immune from sensitisation (grain boundary carbide precipitation). Thus it is extensively used in heavy gauge welded components (over about 6mm). There is commonly no appreciable price difference between 316 and 316L stainless steel.
The austenitic structure also gives these grades excellent toughness, even down to cryogenic temperatures.
Compared to chromium-nickel austenitic stainless steels, 316L stainless steel offers higher creep, stress to rupture and tensile strength at elevated temperatures.
These properties are specified for flat rolled product (plate, sheet and coil) in ASTM A240/A240M. Similar but not necessarily identical properties are specified for other products such as pipe and bar in their respective specifications.
The differences between a 316L and a 316 straight grade are two-fold both in chemistry and mechanical properties. The L grade has a lower maximum carbon limit and the straight grade has increased mechanical properties. If material is certified as straight grade, the carbon content would have to be at a level of 0.030% maximum in order to be dual certified as 316L/316 grade. (presumably the mechanicals would have already been met). If the material is certified as 316L that implies the carbon is a t a maximum level of 0.030% and this can only be certified to the straight grade if the increased mechanicals are met. Below is a summary comparing the two grades for both the flat and bar product.