Stainless Steel 321 (UNS S32100)
SS 321 is an austenitic chromium-nickel steel stabilized with titanium (minimum 5x carbon content). Titanium has a stronger chemical affinity for carbon than chromium, precipitating as harmless titanium carbide (TiC) and keeping chromium in solid solution to maintain corrosion resistance in the 425°C to 850°C sensitization range.
Material Quick Reference
| Material Classification | Titanium-Stabilized Austenitic Stainless Steel |
|---|---|
| Pitting Resistance (PREN) | 18 - 20 |
| Temperature Limits | -196°C to +870°C |
| Governing Specifications | ASTM A312 TP321, ASTM A403 WP321, ASTM A182 F321, ASME B31.3 |
Typical Engineering Applications
- Turbine and diesel generator exhaust manifolds
- Refinery thermal cracking furnace piping
- Boiler superheater steam loops
- High-temperature chemical reactor transfer lines
Chemical Environment & Corrosion Resistance
Resistant to polythionic acid stress corrosion cracking (PASCC) in refinery units during shutdowns.
Performance in Qatar's Coastal & Industrial Climate
Essential for power generation exhaust stacks and refinery furnace piping operating in Qatar’s industrial zones.
Welding & Fabrication Guidelines
Welded with ER321 or ER347 consumables. Avoid overheating to prevent titanium burnout.
Positive Material Identification (PMI) Requirements
XRF analyzer verification of titanium content (Ti >= 5x C, max 0.70%).
Key Advantages
- Resists sensitization up to 850°C
- High creep and stress rupture properties
Engineering Limitations
- Titanium does not transfer well across welding arcs; ER347 (niobium) often used as filler
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