A Titanium Stabilized Austenitic Stainless Steel with Excellent Resistance to Intergranular Corrosion After Exposure to Temperatures in the Chromium Carbide Precipitation Range of 800–1500°F (427–816°C)
Alloy 321 (UNS S32100) is a titanium stabilized austenitic stainless steel with good general corrosion resistance. It has excellent resistance to intergranular corrosion after exposure to temperatures in the chromium carbide precipitation range of 800–1500°F (427–816°C). The alloy resists oxidation to 1500°F (816°C) and has higher creep and stress rupture properties than alloys 304 and 304L. It also possesses good low temperature toughness. Alloy 321H (UNS S32109) is the higher carbon (0.04–0.10) version of the alloy. It was developed for enhanced creep resistance and for higher strength at temperatures
above 1000°F (537°C). In most instances, the carbon content of the plate enables dual certification. Alloy 321 cannot be hardened by heat treatment, only by cold working. It can be easily welded and processed by standard shop fabrication practices.
Applications
• Aerospace—piston engine manifolds
• Chemical Processing
• Expansion Joints
• Food Processing—equipment and storage
• Petroleum Refining—polythionic acid service
• Waste Treatment—thermal oxidizers
Standard
ASTM ................. A 240
ASME ................. SA 240
AMS ................... 5510
Chemical Analysis
Weight % (all values are maximum unless a range is otherwise indicated)
| Element | 321 | 321H |
| Chromium | 17.00 min. –19.00 max | 17.00 min.–19.00 max. |
| Nickel | 9.00 min.–12.00 max. | 9.00 min.–12.00 max. |
| Carbon | 0.08 | 0.04 min.– 0.10 max. |
| Manganese | 2 | 2 |
| Phosphorus | 0.045 | 0.045 |
| Sulfur | 0.03 | 0.03 |
| Silicon | 0.75 | 0.75 |
| Titanium | 5 x (C + N) min.–0.70 max. | 4 x (C + N) min.–0.70 max. |
| Nitrogen | 0.1 | 0.1 |
| Iron | Balance | Balance |
Physical Properties
| Density |
0.286 lbs/in3
7.920 g/cm3 |
| Modulus of Elasticity |
28.0 x 106 psi
193 Gpa |
| Melting Range |
2550–2635°F
1398–1446°C |
| Specific Heat |
0.12 BTU/lb-°F (32–212°F)
500 J/kg-°K (0–100°C) |
| Thermal Conductivity 212°F (100°C) |
9.3 BTU/hr/ ft2/ft /°F
16.0 W/m-°K |
| Electrical Resistivity | 72 Microhm-cm at 20°C |
Mean Coefficient of Thermal Expansion
| Temperature Range | |||
| ℉ | ℃ | in/in ℉ | cm/cm℃ |
| 68-212 | 20-100 | 9.2 x 10-6 | 16.0 x 10-6 |
| 68-1112 | 20-600 | 10.5 x 10-6 | 18.9 x 10-6 |
| 68-1832 | 20-1000 | 11.4 x 10-6 | 20.5 x 10-6 |
Mechanical Properties
Typical Values at 68°F (20°C)
Yield Strength
0.2% Offset |
Ultimate Tensile
Strength |
Elongation
in 2 in. | Hardness | ||
| psi(min.) | (Mpa) | psi(min.) | (Mpa) | %(min.) | (max.) |
| 30,000 | 205 | 75,000 | 515 | 40 | 217 Brinell |
Corrosion Resistance
Alloy 321 exhibits good general corrosion resistance that is comparable to 304. It was developed for use in the chromium carbide precipitation range of
1800–1500°F (427–816°C) where un-stabilized alloys such as 304 are subject to intergranular attack.
The alloy can be used in most diluted organic acids at moderate temperatures and in pure phosphoric acid at lower temperatures and up to 10% diluted solutions at elevated temperatures. Alloy 321 resists polythionic acid stress corrosion cracking in hydrocarbon service. It can also be utilized in chloride or fluoride free caustic solutions at moderate temperatures. Alloy 321 does not perform well in chloride solutions, even in small concentrations, or in sulfuric acid service.
Fabrication Data
Alloy 321 can be easily welded and processed by standard shop fabrication practices.
Machining
The cold work hardening rate of 321 makes it less machinable than 410 stainless steel, but similar to 304. The table below provides relevant machining data.
| Operation | Tool | Lubrication | CONDITIONS | |||||
| Depth-mm | Depth-mm | Feed-mm/t | Feed-in/t | Speed-mm/min | Speed-ft/min | |||
| Turning |
High Speed
Steel |
Cutting
Oil | 6 | 0.23 | 0.5 | 0.019 | 12-16 | 39-52 |
| 3 | 0.11 | 0.4 | 0.016 | 28-23 | 59-75 | |||
| 1 | 0.04 | 0.2 | 0.008 | 23-28 | 75-92 | |||
| Carbide |
Dry or
Cutting Oil | 6 | 0.23 | 0.5 | 0.17 | 67-76 | 220-249 | |
| 3 | 0.11 | 0.4 | 0.16 | 81-90 | 266-295 | |||
| 1 | 0.04 | 0.2 | 0.008 | 99-108 | 325-354 | |||
| Depth of cut-m | Depth of cut-in | Feed-mm/t | Feed-in/t | Speed-mm/min | Speed-ft/min | |||
| Cutting |
High Speed
Steel |
Cutting
Oil | 1.5 | 0.06 | 0.03-0.05 | 0.012-0.002 | 16-21 | 52-69 |
| 3 | 0.11 | 0.04-0.06 | 0.016-0.024 | 17-22 | 56-72 | |||
| 6 | 0.23 | 0.05-0.07 | 0.020-0.027 | 18-23 | 59-75 | |||
| Drill Ø mm | Drill Ø in | Feed-mm/t | Feed-in/t | Speed-m/min | Speed-ft/min | |||
| Drilling |
High Speed
Steel |
Cutting
Oil | 1.5 | 0.06 | 0.02-0.03 | 0.0007-0.0012 | 9-13 | 29-42 |
| 3 | 0.11 | 0.05-0.06 | 0.0020-0.0024 | 11-15 | 36-49 | |||
| 6 | 0.23 | 0.08-0.09 | 0.0031-0.0035 | 11-15 | 36-49 | |||
| 12 | 0.48 | 0.09-0.1 | 0.0035-0.0039 | 11-15 | 36-49 | |||
| Feed-mm/t | Feed-in/t | Speed-m/min | Speed-ft/min | |||||
Milling
Profiling |
High Speed
Steel |
Cutting
Oil | 0.05-0.10 | 0.002-0.004 | 11-21 | 26-69 | ||
Hot Forming
Working temperatures of 2100–2300°F (1149–1260°C) are recommended for forging, upsetting and other hot working processes. Do not work this alloy
at temperatures below 1700°F (927°C). Material must be water quenched or fully annealed after working to re-attain maximum corrosion resistance.
Cold Forming
The alloy is quite ductile and forms easily.
Welding
Alloy 321 can be readily welded by most standard processes. A post weld heat treatment is not necessary.
