Stainless steel AISI 321 (SS321), 321H, TP321
AISI 321 (SS321) stainless steel is basically type 304 with added titanium (Ti), which stabilizes carbides against sensitization to prevent intergranular precipitation of chromium carbide when the steel is heated to a temperature within the sensitization range (as during welding) . 321H is to obtain the best creep resistance and creep rupture resistance. TP321 stainless steel is for seamless, welded and heavily cold worked pipes.
Grade 321 Stainless Steel Data Sheet
The following tables and lists provide data sheets and specifications of grade 321 stainless steel, including chemical composition, physical and mechanical properties, machinability, heat treatment, welding, etc.
Chemical composition
The chemical composition of SS 321 stainless steel is listed in the following table based on casting analysis.
| Chemical composition, % | |||||||||||
| ASTM type | AISI type (UNS) | C, ≤ | Yes, ≤ | Mn, ≤ | P, ≤ | S, ≤ | Cr | No | N, ≤ | Other elements | Grades |
| ASTM A240/A240M | 321 (UNS S32100) | 0.08 | 0.75 | 2:00 | 0.045 | 0.03 | 17.0-19.0 | 9.0-12.0 | 0.10 | ≥Ti 5×(C+N), ≤ 0.70 | Plate, Sheet and Strip for Pressure Vessels |
| ASTM A276A/276M | 1.00 | – | Stainless Steel Bars and Shapes | ||||||||
| ASTM A580/A580M | – | ≥ Ti 5×C | stainless steel wire | ||||||||
| ASTM A959 | 0.10 | ≥Ti 5×(C+N), ≤ 0.70 | Forged Stainless Steels | ||||||||
| ASTM A473 | – | ≥ Ti 5×C | Stainless steel forgings | ||||||||
| ASTM A314 | – | ≥Ti 5×(C+N), ≤ 0.70 | Billets and bars for forging | ||||||||
| ASTM A240/A240M | 321H (UNS S32109) | 0.04-0.10 | 0.75 | 2:00 | 0.045 | 0.03 | 17.0-19.0 | 9.0-12.0 | 0.10 | ≥ Ti 4x(C+N), ≤ 0.70 | Plate, Sheet and Strip |
| ASTM A959 | 1.00 | 0.10 | Forged Stainless Steels | ||||||||
| ASTM A312/A312M | TP321 (UNS S32100) | 0.08 | 1.00 | 2:00 | 0.045 | 0.03 | 17.0-19.0 | 9.0-12.0 | 0.10 | ≥Ti 5×(C+N), ≤ 0.70 | Stainless Steel Tubes |
| TP321H (UNS S32109) | 0.04-0.10 | 1.00 | 2:00 | 0.045 | 0.03 | 17.0-19.0 | 9.0-12.0 | 0.10 | ≥ Ti 4x(C+N), ≤ 0.70 | ||
Properties of AISI 321 stainless steel
The tables below list the properties of AISI 321 stainless steel, including physical and mechanical properties.
Physical properties
The physical properties of AISI 321 steel are given in the following lists, including density, thermal expansion, modulus of elasticity, thermal conductivity, specific heat capacity and electrical resistance.
Grades:
- 10 -6 ·K -1 = 10 -6 /K
- 1Ω mm²/m = 1 μΩ m
- 1 g/cm3 = 1 kg/dm3 = 1000 kg/m3
- 1 GPa = 1kN/mm2
- 1 MPa = 1 N/mm2
| SS321 Physical Properties | |
| Density, g/cm3 (lb/in.3) | 7.9 (0.29) |
| Melting point, °C (°F) | 1400-1425 (2550-2600) |
| Specific heat capacity, J/kg·K (Btu/lb ·°F) | 500 (0.12) at 20°C |
| Electrical resistivity, μΩ·m | 0.72 at 20°C |
| Magnetic permeability | 1.02 (approximate) |
| Elastic modulus, GPa (10 6 psi) | 193 (28) |
| Thermal conductivity, W/m·K (Btu/ft · h ·°F) | 16.1 (9.3) at 100°C (212°F) |
| 22.2 (12.8) at 500 °C (932 °F) | |
| Coefficient of thermal expansion, 10 -6 /K (μin./in. ·°F) | 16.6 (9.2) at 0-100°C (32-212°F) |
| 17.2 (9.6) at 0-315°C (32-600°F) | |
| 18.6 (10.3) at 0-538°C (32-1000°F) | |
Mechanical properties
The mechanical properties of AISI 321 stainless steel are listed in the following tables.
| SS 321 Mechanical Properties | |||||||||
| ASTM | AISI type (UNS) | Conditions | Tensile strength, MPa (ksi), ≥ | 0.2% yield strength, MPa (ksi), ≥ | Elongation by 50 mm (2 in.), %, ≥ | Area Reduction, %, ≥ | Brinell hardness (HBW), ≤ | Rockwell hardness (HRBW), ≤ | Product Forms |
| ASTM A276/A276M | 321 (UNS S32100) | Annealed, hot finished | 515 (75) | 205 (30) | 40 | 50 | – | – | Bars and Shapes |
| Annealed, cold finished, diameter ≤ 12.7 mm (0.5 in.) | 620 (90) | 310 (45) | 30 | 40 | – | – | |||
| Annealed, cold finished, Diameter > 12.7 mm (0.5 in.) | 515 (75) | 205 (30) | 30 | 40 | – | – | |||
| ASTM A580/A580M | Annealed | 520 (75) | 210 (30) | 35 | 50 | Wire | |||
| Cold finished | 620 (90) | 310 (45) | 30 | 40 | – | – | |||
| ASTM A473/A473M | Annealed, sections ≤ 5 in. (127mm) | 515 (75) | 205 (30) | 40 | 50 | – | – | Forged | |
| Annealed, sections > 5 in. (127mm) | 70 (485) | ||||||||
| ASTM A240/A240M | 321, 321H (UNS S32109) | – | 515 (75) | 205 (30) | 40 | – | 201 | 92 | Plate, Sheet and Strip |
Young's modulus SS321: 180 GPa (26.0 x 10 6 psi), sheet, longitudinal orientation.
| TP321 Mechanical Properties | ||||
| ASTM | AISI type (UNS) | Thickness | ||
