321/321H

ASTM StandardsBarButt Weld FittingsForgingsPipe, Welded & SeamlessTube, WeldedTube, SeamlessPlateA276, A479A403A182A312A249A213A240

Minimum Physical PropertiesTensile StrengthYield Strength75 KSI Min.30 KSI Min.

Chemical Composition (wt%)CMnPSSiNiCrFeCb&Ta0.04 – 0.082.00 Max0.04 Max0.03 Max0.75 Max9.0 – 13.017.0 – 20.0Balance0.2 – 0.6

Properties

321 and 347 are austenitic stainless steels that contain stabilizing elements. Both alloys are easily welded. Annealing is not required after welding unless stress relief is desired. Both grades have excellent resistance to oxidation and corrosion. With high creep strength, these alloys work best up to 1600 degF. The addition of titanium in 321, and columbium plus tantalum in 347 give some desired characteristics:

* Prevents harmful carbide precipitation in the heat affected zone (HAZ) of the weld area * Imparts substantial immunity to intergranular corrosion * Reduced embrittlement in the HAZ of the weld area

Applications

Both alloys are common to the petroleum refining industries: they are used to make radiant superheaters, boiler tubes, high pressure steam pipes, and general refinery piping. They are also used for heavy duty exhaust systems and manifolds.