Cr 25.5, Ni 5.5, Mo 3.4 C 0.04, Mn 1.5, Si 1.0, Fe bal, N 0.175, S 0.030, Cu 2.00, P 0.040

Overview

Alloy 255 is finding many cost effective applications in the chemical, marine, metallurgical, municipal sanitation, plastics, oil and gas, petrochemical, pollution control, wet phosphoric acid, paper making and metalworking industries.

Called “super” because it is more alloyed than ordinary stainless steels and has superior corrosion resistance, alloy 255 is being used in areas where conventional stainless’ are inadequate or, at best marginal. One good example s in the paper industry which was hit with an epidemic of corrosion problems when environmental laws forced recycling of process liquids In closed systems, chemicals such as chlorides can build up to highly corrosive concentrations over time. Paper makers have found that ordinary stainless equipment, which had previously given good service, was no longer adequate for many applications.

Duplex alloy with a high strength to weight ratio, with superior abrasion and cavitation resistance. Resistance to chloride SCC, as well as crevice corrosion and pitting. Good ductility with a high fatigue strength in marine applications. Twice the yield strength of Alloy 20, and stronger than Duplex 2205. An excellent 40°C critical pitting temperature (ASTM G48-Method A), twice that of Alloy 2205.

Principal Features of Alloy 255 Compared To 300 Series Austenitic Stainless Steels

• Superior Corrosion Resistance
• Pitting
• Crevice Corrosion
• Chloride Stress Corrosion Cracking
• General Corrosion In Many Environments
• Good Ductility
• High Strength-To-Weight Ratio
• High Fatigue Strength In Marine Environments
• Superior Abrasion and Cavitation Erosion Resistance
• High Mechanical Strength – (over twice the yield strength of austenitic stainless steels)
• Good Fabricability

Characteristics

Physical Properties

• Density 0.282 lb/in
• Specific Gravity 7.81
• Thermal Expansion
• Coefficient (68° to 600°F) 6.7X10^-6 in/in/°F
• Thermal Conductivity (68°F) 105 Btu/sqr ft/hr/°F/in
• Electrical Resisitivity (68°F) 473 Ohms/cir mil ft
• Dynamic Modulus of Elasticity 30.5×10^6 psi

Applications

Alloy 255 is a cost effective alternative to materials such as the nickel alloys, 20 type alloys, brass and bronze. Marine environments have long been the domain of admiralty bronze. Alloy 255 is replacing admiralty bronze, and the nickel alloys, in offshore platforms, deck hardware, rudders and shafting.

Alloy 255 is also making inroads in “borderline” corrosion applications where the nickel alloys and high performance alloys have been used but may not have been absolutely necessary. In some instances, it has even been used to replace high performance Ni-Cr-Mo-F-Cu alloys in the phosphoric acid industry.

Valves, pumps, shafts, marine environments, Applications in down-hole, waste water, polycarbonate production, and demineralized water production.

Chemistry

The alloy’s high critical pitting temperature and high critical crevice temperature provide more resistance to pitting and crevice corrosion than lesser alloyed materials. The alloy’s very high yield strength combined with good ductility allows lower wall thicknesses in process equipment.

Tensile Data

Specifications

Machining

Other Technical Data

FERRALIUM® is a registered trademark of Langley Alloys LTD.