Both are stabilised: 321 uses titanium, 347 uses niobium. 347 is preferred for high-temperature pressure service and where a stabilising anneal is impractical; 321 is more widely stocked in sheet.

Grades · Stainless Steel · 321

321

Data verified

321 is a titanium-stabilised 18-10 stainless developed for welded equipment operating between 425 and 900 °C, where unstabilised 304 would sensitise. It is a long-standing aircraft and exhaust-system grade.

Hardness≤217 HB (annealed)

DIN1.4541

AISI321

JISSUS321

CategoryStainless Steel

Chemical composition

Element	Content (%)
C	≤0.08
Si	≤0.75
Mn	≤2.00
P	≤0.045
S	≤0.030
Cr	17.00–19.00
Ni	9.00–12.00
Ti	5×(C+N)–0.70
N	≤0.10

Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.

Properties

Delivery condition	Annealed
Hardness	≤217 HB (annealed)
Tensile strength	515–690 MPa
Density	7.90 g/cm³

Heat treatment

Solution anneal 980–1120 °C, rapid cool; optional stabilising anneal 845–900 °C for maximum resistance to intergranular attack.

Equivalent grades

Standard	Designation
din	1.4541
aisi	321
jis	SUS321
gb	06Cr18Ni11Ti

Compare side by side: 321 vs 321H · 321 vs 347 · 321 vs 316Ti

Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.

Applications & Processing

Applications: Aircraft exhausts and collectors, expansion joints, pressure vessels, thermal oxidisers, refinery equipment.

Processing: Welds well with stabilised or low-carbon fillers; stabilisation keeps the heat-affected zone resistant without post-weld anneal.

FAQ

321 or 347?: Both are stabilised: 321 uses titanium, 347 uses niobium. 347 is preferred for high-temperature pressure service and where a stabilising anneal is impractical; 321 is more widely stocked in sheet.

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Source: ASTM A240 / EN 10088 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.