Alloy 317LMN and 317L are molybdenu

Alloy 317LMN and 317L are molybdenum-bearing austenitic stainless steels with greatly increased resistance to chemical attack as compared to the conventional chromium-nickel austenitic stainless steels such as Alloy 304. In addition, 317LMN and 317L alloys offer higher creep, stress-to-rupture, and tensile strengths at elevated temperatures than conventional stainless steels. All are low carbon or "L" grades to provide resistance to sensitization during welding and other thermal processes. The "M" and "N" designations indicate that the compositions contain increased levels of molybdenum and nitrogen respectively. The combination of molybdenum and nitrogen is particularly effective in enhancing resistance to pitting and crevice corrosion, especially in process streams containing acids, chlorides, and sulfur compounds at elevated temperatures. Nitrogen also serves to increase the strength of these alloys. Both alloys are intended for severe service conditions such as flue gas desulfurization (FGD) systems.
321—similar to 304 but lower risk of weld decay due to addition of titanium.
400 Series—ferritic and martensitic chromium alloys
405—a ferritic especially made for welding applications
408—heat-resistant; poor corrosion resistance; 11% chromium, 8% nickel.
409—cheapest type; used for automobile exhausts; ferritic (iron/chromium only).
410—martensitic (high-strength iron/chromium). Wear-resistant, but less corrosion-resistant.