Alloy Designations

Grade 1.4462/2205 is similar to:

UNS S31803
UNS S32205
BS 318S13

Supplied Forms

• Fittings & Flanges
• Pipe
• Plate
• Sheet
• Tube
• Bar

Duplex stainless steels are typically used in:

• ~ Chemical processing, transport and storage
• ~ Generally where 304 and 316L are used
• ~ Oil and gas exploration and offshore rigs
• ~ Oil and gas refining
• ~ Pressure vessels (weight savings)
• ~ Marine environments
• ~ Pollution control equipment
• ~ Pulp and paper industry (chip storage tanks, white and black liquor tanks, digestors)
• ~ Chemical process plant
• ~ Caustic solutions, organic acids (SCC resistance)
• ~ Mining (abrasion/corrosion)
• ~ Food industry

Corrosion Resistance

Duplex stainless steels are extremely corrosion resistant. They have high resistance to intergranular corrosion. Even in chloride and sulphide environments, duplex stainless steels exhibit very high resistance to stress corrosion cracking.

The super duplex grades are even more resistant to corrosion.

Heat Resistance

The high chromium content of duplex stainless steels that protects against corrosion, causes embrittlement at temperatures over about 300°C.

At low temperatures duplex stainless steels have better ductility than the ferritic and martensitic grades. Duplex grades can readily be used down to at least -50°C.

Fabrication

Fabrication of all stainless steels should be done only with tools dedicated to stainless steel materials. Tooling and work surfaces must be thoroughly cleaned before use. These precautions are necessary to avoid cross contamination of stainless steel by easily corroded metals that may discolour the surface of the fabricated product.

Machinability

Although machinable, the high strengths of duplex stainless steels makes machining difficult. As an example, machining of 2205 is around 20% slower than for 304.

Machining can be enhanced by using the following rules:

~ Cutting edges must be kept sharp. Dull edges cause excess work hardening.

~ Cuts should be light but deep enough to prevent work hardening by riding on the surface of the material.

~ Chip breakers should be employed to assist in ensuring swarf remains clear of the work

~ Low thermal conductivity of austenitic alloys results in heat concentrating at the cutting edges. This means coolants and lubricants are necessary and must be used in large quantities.

Heat Treatment

Duplex stainless steels cannot be hardened by heat treatment. They can however be work hardened.

Solution treatment or annealing can be done by rapid cooling after heating to around 1100°C.

Weldability

Duplex stainless steels have good weldability. All standard welding processes can be used. They are not quite as easily welded as the austenitic grades but low thermal expansion in duplex grades reduces distortion and residual stresses after welding. The recommended filler material for 2205 stainless steel is 2209.