255

Alloy 255 is a 25% chromium super duplex stainless steel. Alloy 255 contains a copper addition which provides it with greater resistance to sulfuric acid than other super duplex grades. Because of its duplex structure alloy 255 also offers excellent strength characteristics and resistance to chloride ion stress corrosion cracking.

Chemistry

 NiCrMoMnCuSiCNSPFe
MIN 4.5 24.0 2.9 -- 1.5 -- -- 0.1 -- -- --
MAX 6.5 27.0 3.9 1.5 2.5 1.0 0.04 0.25 0.03 0.04 Balance

Specifications

ASME SA 240ASME SA 479ASME SA 789ASME SA 789 Section IV Code Case 2603ASME SA 790
ASTM A 240ASTM A 479ASTM A 480ASTM A 789ASTM A 790

Inventory

255 Pipe, 255 Plate, 255 Round Bar, 255 Sheet, 255 Tubing

Common Trade Names

Ferralium® 255, Alloy 255

Features

  • High strength
  • Chloride stress corrosion cracking resistance
  • Lower coefficient of thermal expansion than austenitic stainlesses
  • Good sulfuric acid resistance

Applications

  • Pulp and paper
  • Chemical process
  • Flue-gas desulfurization
  • Copper smelting
  • Mixers and pumps

Physical Properties

Density: 0.282 lb/in3
Melting Point: 2525-2630°F
Poisson's Ratio: 0.32 
Electrical Resistivity: 481 Ohm - circ mil/ft

Temperature, °F 70 212 392 572
Coefficient* of Thermal Expansion, in/in°F x 10-6 6.1 6.2 6.4 6.7
Thermal Conductivity Btu • ft/ft2 • hr • °F -- 8.2 9.4 10.6
Modulus of Elasticity, Dynamic psi x 106 28.9 -- -- --

* 70°F to indicated temperature.

Mechanical Properties

Minimum Specified Properties, ASTM A 240

Ultimate Tensile Strength, (ksi 110
0.2% Yield Strength, ksi 80
Elongation, % 15
Hardness MAX, Brinell 302

Ferralium® is a registered trademark of Langley Alloys Ltd.