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 Flowserve Davies & Baird produce castings in a range of highly corrosion
resistant ferritic-austenitic stainless steels, known as Duplex and Super Duplex stainless steels because of their duplex metallographic structure.
The duplex and super duplex stainless steels are premium alloys combining excellent mechanical properties with
the highest levels of corrosion resistance. Using precisely controlled foundry and heat treatment processes, Flowserve Davies & Baird
produce castings with a mixed austenite and ferrite microstructure.
Mechanical Properties: The Yield and Tensile Strengths of these alloys
are approximately 200/150% greater respectively than that of comparable austenitic stainless steels.
Corrosion Resistance: The passive oxide film on stainless steels resists
attack from aggressive chloride ions found in seawater and some process fluids. In the duplex and super duplex alloys, pitting corrosion, crevice
corrosion, and stress corrosion cracking resistance is considerably higher than for conventional austenitic stainless steels.
Galvanic Compatibility: These alloys are relatively “noble” in the galvanic table, approximating titanium.
Erosion and Abrasion Resistance: Excellent resistance to erosion,
abrasion and cavitation have made these alloys a popular choice for pump and valve applications.
Fatigue Characteristics: These alloys have superior resistance to fatigue and corrosion fatigue.
Machine and Weldability: Duplex and Super Duplex alloys are readily machined. Surface work hardening can occur. These materials are also
readily weldable.
Duplex stainless steels have for years been providing excellent service in
seawater on offshore platforms and in a wide variety of other chloride containing environments.
The pitting resistance equivalent number (PREN) is an empirical guide to
the grading of materials for resistance to seawater. Duplex stainless steel has been designed to exceed the commonly specified PREN of 40 and
provide, for example, castings suitable for pumps and valves on offshore oil and gas platforms.
Standards:
- Casting specifications UNS J93404, J92205 and J93370/73
- ASTM A890 Grades 1A, 1C, 4A, and 5A
- Listed in MRO175 for sour service.
Applications:
Duplex and Super Duplex are a high-tech materials for use in many situations where safer more cost effective, high strength, corrosion resistant
materials are needed. Some of the various applications are:
- Worldwide use on offshore development.
- Marine environments.
- Seawater systems and cooling.
- Oil and gas industry.
- Process systems in Chemical plants.
- Refineries and Petrochemical plants.
- Fire water systems.
- Pump and valve castings.
Flowserve Davies & Baird would welcome the opportunity of having our experienced team of foundry engineers and metallurgists work with you to
provide the most suitable grade for your application.
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