AISI 304 Flat Bars

AISI 304 flat bar supplied hot rolled, annealed and pickled is a rectangular austenitic stainless section, rolled to size, annealed to soften the structure and pickled to strip the rolling scale. Chromium builds the thin oxide film that keeps the surface from rusting, and nickel holds the steel austenitic, which is where the older name 18/8 comes from. Against 304L, the 304 analysis allows more carbon, so it is taken where strength matters more than the welding of heavy sections, while 304L suits thick weldments that will sit in a corrosive liquid. Against 316, this grade carries no deliberate molybdenum, so it is taken where chlorides and seawater are absent and the higher price of 316 buys nothing. Laxcon Steels rolls the flat bar to order in this grade.

The bar is supplied annealed, the softening treatment that takes the carbides into solution and leaves the steel soft, non-magnetic and at its most corrosion resistant. Heat treatment cannot harden it; any added strength comes from cold work. ASTM A276 sets 515 MPa tensile strength and 205 MPa yield strength as the minima for annealed 304 bar. The grade welds by the common arc processes, but long holds at red heat cause sensitisation, in which chromium carbides gather at the grain boundaries and open a path for corrosion. Machining calls for sharp tools, a firm feed and a rigid setup, because the steel hardens under a rubbing edge. Flats in this grade go into equipment frames and skids, brackets and base plates, handrail and stair members in food and dairy plants, and blanks a customer machines or forges into fittings.

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 18.0 to 20.0, nickel 8.0 to 10.5 and nitrogen 0.1 maximum.