IntroductionWhat “L” Grades Are and Why They Are UsedWhat “H” Grades Are and Why They Are UsedWhat the Differences Are      304 and 304L      304 and 304H      316, 316L and 316H      Property Specifications      Dimensional Tolerance DifferencesPressure VesselsAlternative Grade Usage      High Temperature Strength Requirements      Tested Carbon Content – L Grades      Tested Carbon Content – H Grades      Dual Certification The common designations of austenitic grades of stainless steel, such as grades 304 and 316, include sub-grades – L and H variants used for specific applications. The low carbon “L” grades are used for applications involving welding treatments or high temperature exposure, e.g. welding of heavy or medium sections. The low carbon content of steels prevents carbide precipitation at grain boundaries, which can cause inter-granular corrosion under corrosive operation conditions. Carbide precipitation occurs at temperatures ranging from about 450 to 850°C. Based on their applications, “L” grade steels are available in the form of pipe, plate and, most commonly, in round bars. The corrosion resistances of standard austenitic and “L” grades are identi...