304 & 304L grades are austenitic stainless grades that cannot be hardened by heat treatment.
The “L” grade designates a low carbon expectation of .03 max which is more suited for welding. These “L” grade steels can have slightly lower yields in the order of 25ksi min.
Annealed - 30,000 psi minimum yield; cannot be hardened by heat treatment
These grades are acceptable to NACE MR-01-75/ISO 15156 at temperatures up to 140F, at Rc 22 max.