Grade 321 Stainless Steel
Stainless steel Grade 321 is stabilized austenitic stainless steel. It is stabilized with added titanium with the presence of chromium and nickel in the composition. Titanium prevents the formation of chromium carbide precipitation from welding or exposure to high temperatures. Grade 321 is not sensitive to the carbide precipitation, which is formed after or during welding. It offers excellent corrosion resistance to intergranular corrosion after welding.
Stainless steel Grade 321 exhibits excellent forming and welding characteristics and holds good toughness at cryogenic temperature. It cannot be hardened by heat-treatment and it is non-magnetic in nature.
It is used often in applications that require intermittent heating between the temperature range of 427-899ºC, and for welding where post-weld annealing is not required. Most widely used in the aerospace industry, chemical processing, etc.
Composition
Stainless steel 321 is high chromium- high nickel stainless steel with the presence of titanium. Titanium content is at least five times the carbon content. Chromium content is in the range of 17-19% with a nickel content of 9-12%.
|
Grade |
C |
Cr |
Ni |
Si |
Mn |
P |
S |
N |
Ti |
Fe |
|
321 |
0.08 max |
17-19%
|
9-12% |
0.75 max |
2.0 max
|
0.045 max |
0.03 max |
0.10 max |
5*(C+N) 0.70 max |
balance |
Titanium bonds with carbon and forms titanium carbide precipitation as it has a stronger affinity towards carbon than chromium. Titanium carbide precipitates in the grains rather be form at grain boundaries.
Physical properties
- Stainless steel Grade 321 attains a metric density of 0.29 g/cm3.
- The modulus of elasticity is 193 Gpa.
- Electrical resistivity is 72 Microhm-cm.
- The melting point range is 1371- 1399°C
Thermal properties
- Thermal expansion coefficient is 16.6 µm/m° at 1-100°C and
- Thermal conductivity is 16.1 W/mK at 100°C and 22.2 W/mK at 500°C.
Mechanical properties
- Stainless steel 321 attains a tensile strength of 515 Mpa and yield strength of 205 Mpa. Hardness is 70B. Elongation is 40% in 50mm.
Corrosion resistance
SS 321 Grade offers excellent corrosion resistance comparable to grade 304. It offers improved corrosion resistance in the chromium carbide precipitation range of 427-816°C. It offers improved intergranular corrosion resistance due to the addition of titanium.
Grade 321 is mainly used in:
- Aircrafts exhaust
- Heat exchangers
- Spiral welded tube
- Furnace parts
- Welded equipment
- Chemical processing equipment
- Refinery equipment
- Thermal oxidizers
