Titanium-Stabilized 18/10 Austenitic Stainless for Welded High-Temp Service
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UNS NUMBER
S32100
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ALLOY FAMILY
Austenitic (Ti-stabilized)
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STRUCTURE
100% Austenite
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UTS (MIN)
≥515 MPa
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MAX TEMP
~816°C
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DENSITY
7.93 g/cm³
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Stainless Steel 321 (UNS S32100) is 304 stabilized with titanium (≥ 5× the carbon-plus-nitrogen content). The titanium ties up carbon as TiC, giving immunity to intergranular sensitization after welding and good high-temperature strength to about 816°C. It is the stabilized alternative to 304/304L where welded high-temperature service is expected.
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Cr
17–19%
Oxidation resistance
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Ni
9–12%
Austenite stabilizer
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Mo
— (none)
Not added
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Ti
5×(C+N) min
Stabilizer, ties up carbon
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UTS
≥515 MPa
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YS 0.2%
≥205 MPa
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Elong.
≥40%
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Service
up to ~816°C
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What is Stainless Steel 321?
321 is the titanium-stabilized counterpart of 304. Adding enough titanium (minimum 5×(C+N), max 0.70%) makes it preferentially form TiC, leaving chromium in solution so the steel does not sensitize during or after welding. That same stabilization lets it carry useful strength to about 816°C, higher than plain 304.
321 is chosen where a welded joint must stay corrosion-resistant and where service runs hot — intercoolers, exhaust, and high-temperature process piping. The trade-off versus 304L is that titanium can reduce creep ductility compared with niobium-stabilized 347, and titanium-stabilized welds need controlled heat input. For the highest creep duty, 347H is often preferred. For non-welded or low-temperature work, 304L is cheaper.
Chemical Composition (Weight %)
| Element |
Min (%) |
Max (%) |
Role in Alloy |
| Chromium (Cr) |
17.0 |
19.0 |
Oxidation resistance |
| Nickel (Ni) |
9.0 |
12.0 |
Austenite stabilizer |
| Titanium (Ti) |
5×(C+N) min |
0.70 max |
Stabilizer; forms TiC |
| Carbon (C) |
— |
0.08 |
At 304 level |
| Manganese (Mn) |
— |
2.00 |
Deoxidizer |
| Silicon (Si) |
— |
1.00 |
Deoxidizer |
| Phosphorus (P) |
— |
0.045 |
Impurity |
| Sulfur (S) |
— |
0.030 |
Impurity |
| Nitrogen (N) |
— |
0.10 |
Minor |
| Iron (Fe) |
Balance |
— |
Matrix former |
★ Titanium ≥ 5×(C+N), maximum 0.70%, prevents chromium-carbide sensitization after welding and supports high-temperature service to ~816°C. Carbon stays at the 304 level (up to 0.08%).
Mechanical Properties
Values are for the solution-annealed condition per ASTM A240, A182 (F321), and A312 (TP321).
| Condition / Form |
UTS (MPa) |
YS 0.2% (MPa) |
Elong. % (min) |
Hardness (max) |
| Minimum (ASTM A240 / A182 F321) |
≥515 |
≥205 |
40 |
217 HBW (95 HRB) |
| Typical mill-annealed |
515–700 |
205–350 |
45–55 |
150–195 HBW |
Modulus of Elasticity 193 GPa. Titanium stabilization avoids sensitization but gives slightly lower creep ductility than niobium-stabilized 347. Match filler ER321.
Physical Properties
| Property |
Value |
Note |
| Density |
7.93 g/cm³ |
Same as 304 |
| Melting Range |
1400–1420°C |
Solidus ~1400°C |
| Thermal Conductivity (100°C) |
16.1 W/m·K |
Comparable to austenitics |
| Thermal Expansion (20–100°C) |
17.0 ×10⁻⁶ /K |
Higher than carbon steel |
| Specific Heat |
500 J/kg·K |
At 21°C |
| Electrical Resistivity |
0.73 µΩ·m |
At 21°C |
| Magnetic Property |
Non-magnetic* |
*Slight after cold work |
| PREN (Pitting Resistance) |
~18 |
No Mo |
Corrosion Resistance
Weld Sensitization Immunity
Titanium ties up carbon as TiC, so 321 does not sensitize in the 425–815°C range after welding. It is chosen where post-weld annealing is impractical.
High-Temperature Service
321 carries useful strength and oxidation resistance to about 816°C. It was the historical high-temperature stabilized 304 before 347/321H took the extreme ends.
General & Atmospheric Corrosion
Same 18/8 resistance as 304 in fresh water, food, and mild chemicals (PREN ~18, no molybdenum). Not for chloride-heavy duty.
Pitting in Chlorides
No molybdenum means PREN ~18; 321 pits in chloride environments like 304. For chloride + heat, use 316H or 317L.
Stainless Steel 321 vs Similar Grades — Selection Guide
| If you need... |
Choose... |
Why |
| Welded high-temp to ~816°C |
321 |
Ti stabilization, no sensitization |
| Welded, low temp, cheaper |
304L |
Low-carbon route |
| Highest creep >800°C |
347H |
Nb stabilization |
| Chloride + heat |
316H / 317L |
Need molybdenum |
| General, non-welded |
304 / 304L |
Lower cost |
Applicable Standards
| Standard |
Product Form |
| ASTM A240 |
Plate, sheet, strip |
| ASTM A182 F321 |
Forged flanges & fittings |
| ASTM A312 TP321 |
Seamless & welded pipe |
| ASTM A403 WP321 |
Butt-weld fittings |
| ASTM A213 / A269 |
Tube |
| ASTM A276 / A479 |
Bar, rod, forging stock |
HT PIPE Supply — Stainless Steel 321 Product Forms
| Product Form |
Specifications |
HT PIPE Supply |
| Seamless Pipe |
ASTM A312 TP321 |
✅ Available |
| Forged Flanges |
ASTM A182 F321, ASME B16.5 |
✅ In stock |
| Butt-Weld Fittings |
ASTM A403 WP321 |
✅ Available |
| Plate / Sheet |
ASTM A240 |
✅ Available |
| Bar / Rod |
ASTM A276 / A479 |
✅ Available |
| Welded Pipe |
ASTM A312 TP321 |
✅ Available |
HT PIPE supplies 321 in pipe, flanges, fittings, plate, and bar for welded high-temperature service, with MTRs and matching ER321 welding consumables.
Project Experience — Stainless Steel 321
HT PIPE supplies 321 for welded high-temperature process, exhaust, and intercooler systems.
| Project |
Product |
Specification |
| High-Temp Process Piping (Asia) |
321 Pipe + Fittings |
A312, A403 |
| Exhaust / Manifold Hardware (Europe) |
321 Tube + Forgings |
A213, A182 |
| Welded Header (China) |
321 Flanges + Plate |
A182 F321, A240 |
We advise 321 vs 304L/321H and supply matching ER321 filler for stabilized welds.
| FREQUENTLY ASKED QUESTIONS |
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FAQ — Stainless Steel 321
| What is the difference between 321 and 304L? |
| Both avoid weld sensitization differently: 304L removes carbon (≤0.030%); 321 keeps 304-level carbon and adds titanium (≥5×(C+N)) to stabilize it. 321 also holds strength to higher temperature (~816°C). |
| What temperature can 321 withstand? |
| Oxidation resistance and useful strength extend to about 816°C. For the highest creep duty above that, niobium-stabilized 347H is preferred. |
| Is 321 good in seawater? |
| No. Like 304 it has no molybdenum (PREN ~18) and pits in chlorides. For chloride service use 316L or higher. |
| What filler is used for 321? |
| ER321 / E321 to preserve stabilization. Plain 308/316 fillers lack the titanium concept, though 347 filler is sometimes used for 321 joints. |
| When would I choose 347 over 321? |
| For the highest creep duty: niobium-stabilized 347 (NbC) stays more stable than TiC above ~1000°C and offers better creep ductility, so 347/347H is preferred for extreme high-temperature service. |
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Need Stainless Steel 321 for Welded High-Temperature Service?
HT PIPE supplies 321 (UNS S32100) pipe, flanges, fittings, plate, and bar with full MTR documentation and matching welding consumables. Contact our technical team for advice.
Request a Quote |
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