Alloy 20

Alloy 20

Alloy 20 (Carpenter 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

 NiCrMoMnCuSiCSPCb+TaFe
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 240ASME SB 366ASME SB 463
ASTM A 240ASTM B 366ASTM B 463ASTM B 473
EN 2.4660
UNS N08020
Werkstoff 2.4660

Inventory

Alloy 20 Plate, Alloy 20 Sheet, Alloy 20 Welding Products

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