AISI 316 Flat Bars

AISI 316 hot rolled, annealed and pickled flat bar is an austenitic stainless flat section rolled from a grade that carries 2 to 3 percent molybdenum beside its chromium and nickel. Molybdenum is what separates it from AISI 304: it slows pitting and crevice attack, the localised corrosion that chloride ions start in seawater, brine and process liquors. Where the medium is fresh water, food or mild chemicals, AISI 304 flat bar covers the same duty. Where chlorides are present, 316 is the usual step up. Beside it sit AISI 316L, whose lower carbon protects a welded joint from attack at the grain boundaries, and duplex 2205, which carries a higher yield strength in the same thickness.

The bar is supplied hot rolled, annealed and pickled. Annealing takes the chromium carbides back into the metal and the fast cool holds them there; pickling then removes the rolling scale and leaves a matt grey surface. In this condition the bar is non-magnetic, cannot be hardened by heat treatment, and gains strength only by cold work. ASTM A276 sets 515 MPa tensile strength and 205 MPa yield strength as the annealed minima. The grade work hardens under the tool, so drilling and milling ask for sharp edges, a firm feed and lower speeds than carbon steel. It is welded without preheat. Flat bar in this grade goes into chemical plant supports, marine deck fittings, effluent and desalination equipment, and machined clamps and flanged brackets.

Composition limits in weight percent are carbon 0.08 maximum, manganese 2.0 maximum, sulphur 0.03 maximum, phosphorus 0.045 maximum, silicon 0.75 maximum, chromium 16.0 to 18.0, nickel 10.0 to 14.0, molybdenum 2.0 to 3.0 and nitrogen 0.1 maximum.