321 / 321H
UNS S32100 / S32109
Overview
Titanium-stabilized austenitic stainless steel for elevated temperature service up to 900°C. The titanium addition (5×C minimum) prevents chromium carbide precipitation during welding and high-temperature exposure. 321H (high carbon, 0.04-0.10% C) provides enhanced creep strength above 540°C. The standard material for refinery heater tubes, boiler superheaters, and exhaust systems.
Chemical Composition (wt%)
| Element | Min | Max |
|---|---|---|
| C (Carbon) | — | 0.08 |
| Mn (Manganese) | — | 2 |
| Si (Silicon) | — | 0.75 |
| P (Phosphorus) | — | 0.045 |
| S (Sulfur) | — | 0.03 |
| Cr (Chromium) | 17 | 19 |
| Ni (Nickel) | 9 | 12 |
| Ti (Titanium) | 0.4 | 0.7 |
Mechanical Properties
| Property | Value | Condition |
|---|---|---|
| Tensile Strength | ≥ 515 MPa (75 ksi) | — |
| Yield Strength (0.2%) | ≥ 205 MPa (30 ksi) | — |
| Elongation | ≥ 40% | — |
| Hardness | ≤ 90 HRB | annealed |
| Density | 8.0 g/cm³ | — |
Physical Properties
| Property | Value |
|---|---|
| Melting Range | 1400 – 1425 °C |
| Max Service Temp | 900°C |
| Thermal Conductivity | 16.1 W/m·K (at 100°C) |
Corrosion Resistance
Comparable to 304 in general corrosion but with superior intergranular corrosion resistance after welding or high-temperature exposure. Titanium stabilization prevents chromium carbide formation at grain boundaries (sensitization). Not recommended for severe chloride environments — use 316 or duplex grades instead. Resistant to polythionic acid stress corrosion cracking in refinery service.
Typical Applications
Related Standards
Available Products in This Material
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