SS321 Tube Sheet
Titanium-stabilized stainless that resists carbide precipitation at high temperature — the grade to reach for when service runs hot enough that standard 304/316 would sensitize over time, without moving to a nickel alloy.
Chemical Composition
| Element | Min % | Max % |
|---|---|---|
| Chromium (Cr) | 17.0 | 19.0 |
| Nickel (Ni) | 9.0 | 12.0 |
| Titanium (Ti) | 5×%C min | 0.70 |
| Carbon (C) | — | 0.08 |
Mechanical Properties
| Property | Typical Value |
|---|---|
| Tensile Strength | 515 MPa min |
| Yield Strength (0.2% offset) | 205 MPa min |
| Elongation | 40% min |
| Max. Practical Service Temp. | ~870°C (oxidation-limited) |
Equivalent Grades
| Standard | Designation |
|---|---|
| ASTM / UNS | S32100 |
| EN / DIN | 1.4541 |
| JIS | SUS321 |
Why Stabilization Matters
Available Product Forms
SS321 is most often specified as a U-Tube Tube Sheet for high-temperature boiler and process heater service, where its stabilization matters most.
Applications
High-temperature process heaters, exhaust and flue gas equipment, and any welded application cycling through the sensitization temperature range where 304/316 aren't stabilized. See also SS347 for the niobium-stabilized alternative.
Advantages & Limitations
Advantages
- Resists sensitization through the critical temperature range
- Good oxidation resistance to ~870°C
- Widely available compared to more exotic high-temp grades
Limitations
- No chloride advantage over standard 304 — still no molybdenum
- Titanium carbides can be less stable than niobium (347) in some weld conditions
- Cost premium over standard 304/316
FAQ
If a proper post-weld solution anneal is reliably part of your fabrication process, standard 304/316 can be adequate. 321 exists precisely for the many real-world cases where full post-weld heat treatment isn't practical or verifiable in the field.
321's titanium stabilization is specifically a high-temperature benefit; for cryogenic service, standard austenitic grades like 304L are generally preferred since low-temperature toughness isn't affected by the sensitization mechanism 321 addresses.
321 is more often sourced to order than 304/316L given lower demand volume — send your specification and quantity for a confirmed lead time.