Should I specify 321 or 304L for welded elevated-temperature service?

For service between 425-815°C (800-1500°F), specify 321 or 347 (niobium-stabilized). 304L relies on low carbon (<0.03%) to prevent sensitization — but at these temperatures, chromium carbide precipitation occurs within HOURS even with ultra-low carbon, consuming grain-boundary chromium and causing intergranular attack. 321's titanium carbides are thermodynamically stable and will not release carbon to form chromium carbides. However, 321 costs 20-35% more than 304L and is harder to polish or grind (TiC particles cause 'comet tails' on polished surfaces). For service below 425°C, 304L is the cost-effective choice and does not sensitize. For service above 815°C (1500°F), consider 310S (25Cr-20Ni) for oxidation resistance — 321 oxidizes excessively and forms sigma phase (FeCr intermetallic — embrittlement).

Can 321 be used for nitric acid service?

Yes — 321 has excellent resistance to nitric acid across a wide range of concentrations and temperatures. In fact, 321 is preferred over 304L for nitric acid service in the 40-70% concentration range at temperatures up to 80°C where 304L may experience end-grain intergranular attack at sheared or machined edges (the 'end-grain corrosion' phenomenon). For hot concentrated nitric acid (>90% at >50°C), 304L may transpassively dissolve — specify silicon-containing stainless (e.g., Uranus S1, DIN 1.4361) which forms an SiO₂-rich passive film resistant to oxidizing Cr(VI) species in hot HNO₃.

Edelstahl 321 (UNS S32100): Titanium-Stabilized — Elevated Temperature & Aircraft Exhaust

ASTM A240 / ASTM A312 / AMS 5510 · Published: 2026-05-31 · Updated: July 2026

Quick Reference

Stainless Steel 321 is the titanium-stabilized version of the 18-8 (304) austenitic stainless family. Titanium addition (5× carbon content minimum, typically 0.4-0.7%) preferentially combines with carbon to form stable TiC carbides, preventing...

Edelstahl 321 is the titanium-stabilized version of the 18-8 (304) austenitic stainless family. Titanium addition (5× carbon content minimum, typically 0.4-0.7%) preferentially combines with carbon to form stable TiC carbides, preventing chromium carbide (Cr₂₃C₆) precipitation at grain boundaries. This eliminates sensitization (intergranular corrosion / 'weld decay') in the heat-affected zone of welds and during service in the 'sensitization temperature range' of 425-815°C (800-1500°F). 321 is the standard material for aircraft exhaust manifolds and collector rings (piston and early turbine engines), expansion joints and bellows in chemical/petrochemical plants, and furnace components operating continuously in the 425-815°C range where 304L and 316L would sensitize and fail from polythionic acid stress-corrosion cracking during shutdowns.

Quick Facts

Kategorie	Edelstahl
Norm	`ASTM A240 / ASTM A312 / AMS 5510`
Density	7.92 g/cm³
Yield Strength	205 MPa (30 ksi) minimum (annealed)
Tensile Strength	515 MPa (75 ksi) minimum (annealed)

Global Equivalents & Cross-Reference

Alternative Norm / Güte	Action
EN 1.4541	Compare
DIN X6CrNiTi18-10	Compare
JIS SUS321	Compare
GB 0Cr18Ni10Ti	Compare
BS 321S31	Compare

Verwandt Materials

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Frequently Asked Questions

Sollte I specify 321 oder 304L für welded elevated-temperature service?

Für service zwischen 425-815°C (800-1500°F), specify 321 oder 347 (niobium-stabilized). 304L relies ein niedrig carbon (<0.03%) zu prevent sensitization — but bei diese temperatures, chromium carbide precipitation occurs innerhalb HOURS even mit ultra-niedrig carbon, consuming grain-boundary chromium und causing intergranular attack. 321's titanium carbides sind thermodynamically stable und werden nicht release carbon zu form chromium carbides. However, 321 costs 20-35% mehr als 304L und ist harder zu polish oder grind (TiC particles cause 'comet tails' ein polished surfaces). Für service unter 425°C, 304L ist der kosten-effective choice und tut nicht sensitize. Für service über 815°C (1500°F), consider 310S (25Cr-20Ni) für oxidation widerstand — 321 oxidizes excessively und forms sigma phase (FeCr intermetallic — embrittlement).

Können 321 sein used für nitric acid service?

Ja — 321 hat excellent widerstand zu nitric acid across ein wide bereich von concentrations und temperatures. In fact, 321 ist preferred über 304L für nitric acid service in der 40-70% concentration bereich bei temperatures auf zu 80°C wo 304L kann experience end-grain intergranular attack bei sheared oder machined edges (der 'end-grain corrosion' phenomenon). Für heiß concentrated nitric acid (>90% bei >50°C), 304L kann transpassively dissolve — specify silicon-containing stainless (e.g., Uranus S1, DIN 1.4361) welche forms ein SiO₂-rich passive film resistant zu oxidizing Cr(VI) species in heiß HNO₃.

References & International Standards

ASTM International. Norm Specifications für Stahl & Metal Alloys. astm.org
International Organization für Standardization (ISO). Metallic Materials — Cross-Referenz Database. iso.org
American Iron und Stahl Institute (AISI). Stahl Güte Designations & Equivalents. steel.org
European Committee für Standardization (CEN). EN Stahl Standards & Numbering System. cencenelec.eu