Stainless Steel
Austenitic stainless grades cover corrosion resistance, food and chemical service, and high-temperature applications where carbon scaling fails. F316L is the workhorse. F304L follows close behind. F321 and F347 cover specialty stabilized service.
F304 / F304L
18-8 chromium-nickel austenitic. The basic stainless grade. F304 carries 0.08 percent maximum carbon. F304L caps carbon at 0.03 percent, which reduces sensitization risk in welded service. Dual-certified F304/F304L is the common product, meeting both grade specifications.
F316 / F316L
Molybdenum-bearing austenitic for chloride and acid resistance. The default stainless on chemical process, seawater-adjacent service, and food processing where chloride pitting is a concern. F316L low-carbon variant is the standard for welded fabrication. Dual-certified F316/F316L is common.
F321 / F347
Titanium-stabilized (F321) and niobium-stabilized (F347) austenitic grades. The stabilizing additions tie up carbon and resist intergranular corrosion after exposure to sensitization temperatures (800 to 1500 degrees F). Used on power plant steam piping and on high-temperature process service where regular F304 or F316 would sensitize.
Pressure-Temperature Considerations
Stainless grades carry lower pressure ratings than carbon grades at room temperature in ASME B16.5 tables, due to lower yield strength. Above 800 degrees F, stainless grades hold their pressure rating longer than carbon and chrome-moly start to lose theirs, making stainless the default for elevated-temperature continuous service.
Documentation
Stainless MTRs include PMI (positive material identification) for grade verification on critical service. Dual-certification reports show both base grade and low-carbon variant compliance. Domestic-melt availability for BABA and AIS projects is good on the major austenitic grades.