Alloy 20 was designed specifically to withstand sulfuric acid. Its nickel, chromium, molybdenum and copper levels all provide excellent general corrosion resistance. Restricted carbon plus columbium stabilization permits welded fabrications to be used in corrosive environments, normally without post-weld heat treatment. At 33% nickel, Alloy 20 has practical immunity to chloride stress corrosion cracking. This alloy is often chosen to solve SCC problems, which may occur with 316L stainless.
Chemistry
| Ni | Cr | Mo | Mn | Cu | Si | C | S | P | Cb+Ta | Fe | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| MIN | 32.5 | 19.0 | 2.0 | – | 3.0 | – | – | – | – | 8.0 x C 1.0 | – |
| MAX | 35.0 | 21.0 | 3.0 | 2.0 | 4.0 | 1.0 | 0.06 | 0.035 | 0.035 | – | Balance |
Specifications
- ASME SA 240, ASME SB 366, ASME SB 463
- ASTM A 240, ASTM B 366
- ASTM B 463
- ASTM B 473
- EN 2.4660
- UNS N08020
- Werkstoff 2.4660
Inventory
- Alloy 20 Coil, Alloy 20 Plate, Alloy 20 Sheet, Alloy 20 Weld Wire
Common Trade Names
- Carpenter® 20, 20CB-3®
Features
- Excellent resistance to hot sulfuric acid
- Resistant to intergranular corrosion in the as-welded condition
- Chloride stress corrosion cracking resistance
Applications
- Sulfuric acid pickling tanks, racks and heating coils
- Phosphate coating drums and racks
- Heat exchangers
- Bubble caps
- Process piping
- Mixing tanks
- Chemical and petroleum process equipment
Physical Properties
Density: 0.278 lb/in3 annealed
Melting Point: 2525-2630°F
Electrical Resistivity: 651 Ohm-circ mil/ft
| Temperature, °F | 70 | 212 | 392 | 572 | 752 | 842 | 932 |
| Coefficient* of Thermal Expansion, in/in°F x 10-6 | – | 8.16 | 8.37 | 8.62 | 8.62 | 8.84 | 8.91 |
| Thermal Conductivity Btu • ft/ft2 • hr • °F |
6.7 | 7.57 | 8.56 | 9.53 | 10.5 | – | – |
| Modulus of Elasticity, Dynamic psi x 106 | 28 | – | – | – | – | – | – |
* 70°F to indicated temperature.
Mechanical Properties
Minimum Specified Properties, Asme Sb-688 Plate
| Ultimate tensile strength, ksi | 80 |
| 0.2% yield strength, ksi | 35 |
| Elongation, % | 30 |
| Hardness MAX, Brinell | 217 |
Typical Tensile Properties, Bar
| Temperature, °F | 70 |
| Ultimate Tensile Strength, ksi | 91 |
| 0.2% Yield Strength, ksi | 48 |
| Elongation, % | 45 |
| Charpy Impact V-notch, ft-lbs | 200 |
Carpenter® & 20CB-3® is a registered trademark of Carpenter
