Material number S32100: 321
S32100 is the Unified Numbering System designation for 321, austenitic Cr-Ni stainless steel, titanium-stabilized specified in ASTM A240.
What S32100 means
UNS numbers (ASTM E527 / SAE J1086) use a letter for the alloy family and five digits: G = AISI/SAE carbon and alloy steels (G41400 = 4140), S = stainless and heat-resisting steels (S30400 = 304), K = miscellaneous steels (K02600 = A36), T = tool steels, N = nickel alloys. The UNS number identifies a composition, not a product form or property level, so S32100 appears in several ASTM specifications (plate, bar, pipe) with different mechanical requirements.
321 at a glance
Type 321 is 18-8 stainless stabilized with titanium (≥ 5 × carbon) so that, when the steel sits in the 425–870 °C range — in an exhaust manifold, an expansion bellows, a furnace part or a refinery heater — the carbon precipitates as harmless titanium carbide instead of chromium carbide at the grain boundaries. 304 in the same service sensitizes and corrodes intergranularly; 304L runs out of strength. 321 does neither, which makes it the standard austenitic for intermediate-temperature service and for welded equipment that cannot be annealed after welding. UNS S32100; EN 1.4541.
Room-temperature properties equal 304 (205/515 MPa minimum), corrosion resistance is a shade lower in aqueous service (Ti carbonitrides), and polishing is poorer. 321H (S32109), with 0.04–0.10 % carbon and a minimum grain size, is the creep-rated version used for ASME pressure parts above 525 °C and rated to 816 °C.
The niobium-stabilized 347 is the sister grade: Nb, unlike Ti, survives the welding arc, so 347 filler (ER347) is used for both. GOST 08Kh18N10T — the most-produced Russian stainless — and EN 1.4541 are identical.
Full data sheet for 321 → · Equivalent grades →