321 stainless steel pipe seamless steel pipe (ASTM A312/213 TP321 ) is used in the manufacture of various structural low intermediate pressure boiler superheated steam pipe, water pipe and locomotive boiler superheated steam pipe, pipes, small pipe and arch brick works of high quality carbon structural steel hot rolling and cold drawing (rolling) seamless steel tube.321 Stainless Steel Plate, Sheet, Round Bar, Pipes, Tubes 321 Stainless Steel Plate, 321 Stainless Steel Sheet, 321 Stainless Steel Round Bar, 321 Pipe Tube & Fittings. Common Trade Names. 321 Stainless Steel, 321 Stainless. Features. High strength; Scaling resistance and phase stability; Excellent forming and welding characteristics; Resistant to potable water with up to 200mg/L chlorides at normal temperature.