Type 321 Stainless Steelis a stabilized austenitic stainless steel
similar to Type 304 but with a titanium addition of at least five
times the carbon content. This titanium addition reduces or
prevents carbide precipitation during welding and in 800 - 1500°F
service. It also improves the elevated temperature properties of
the alloy. Type 321 provides excellent resistance to oxidation and
corrosion and possesses good creep strength. It is used primarily
in applications involving continuous and intermittent service
temperatures within the carbide precipitation range of 800 -
1500°F.
Specifications
ASTM A240
Typical Applications
annealing covers, high-temperature tempering equipment, diesel and
heavy duty automotive exhaust systems, firewalls, stack liners,
boiler casings, welded pressure vessels, jet aircraft components,
radiant super heaters, bellows and oil refinery equipment
Chemical Composition: ASTM A240
Element | Type 321 |
Carbon | 0.08 max. |
Manganese | 2.00 max. |
Sulfur | 0.030 max. |
Phosphorus | 0.045 max. |
Silicon | 1.0max. |
Chromium | 17.00 19.00 |
Nickel | 9.00 12.00 |
Titanium | 5x(C+N) min. 0.70 max. |
Nitrogen | 0.10 max. |
Mechanical Properties
Type | Yield Strength 0.2% offset (KSI) | Tensile Strength (KSI) | % Elongation (2" Gauge length) | Hardness Rockwell |
321 | 30 min. | 75 min. | 40 min. | HRB 95 max. |
Physical Properties
Density (lb./ in^2) @ RT | | 0.29 |
Modulus of Elasticity in Tension (psi x 10^6) | | 28.0 |
Specific Heat (BTU/°F/lb.) | 32 to 212 °F | 0.12 |
Thermal Conductivity (BTU/hr/ft^2/ft) | 212°F | 9.3 |
| 932°F | 12.8 |
Mean Coefficient of Thermal Expansion (in. x 10^-6 per °F) | 32 to 212°F | 9.2 |
| 32 to 600°F | 9.5 |
| 32 to 1,000°F | 10.3 |
| 32 to 1,200°F | 10.7 |
Electrical Resistivity (micro ohms - cm) | at 70°F | 28.4 |
Melting Point Range (°F) | | 2500 - 2550 |
Processing
Type 321 is non-hardenable by heat treatment. Annealing: Heat to
1750 - 2050°F, then water quench or air cool. Forming: Type 321 can
be readily formed and drawn. Like most austenitic stainless steels,
Type 321 work hardens and may require annealing after severe
forming.
Welding
This particular alloy is generally considered to have comparable
weldability to Types 304 and 304L. A major difference is the
titanium addition that reduces or prevents carbide precipitation
during welding. When a filler is needed, either AWS E/ER 347 or
E/ER 321 is most often specified.
Corrosion
Type 321 exhibits excellent resistance to organic chemicals,
dyestuffs, and a wide range of inorganic chemicals. It resists
nitric acid well and the sulfur acids moderately. Long-time
exposure in the 900 -1500F range may lower its general corrosion
resistance, but the grade still shows improved resistance to
intergranular corrosion compared to unstabilized grades.
