Lean Duplexes - Applications

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The duplexes have a ductile to brittle transition temperature of about -40°C or lower. These steels can also become embrittled when exposed to temperatures between 300°C and 550°C (475°C embrittlement) and 550°C and 1 000°C (sigma (σ) and chi (χ) phase formation). Thus, application temperatures are generally limited from -50°C to 300°C.

U-2001 has similar general and pitting corrosion resistance to the U-304 types. U-2304 has similar general and pitting corrosion resistance to the U-316L types. Both U-2001 and U-2304 are classified as lean duplexes.

The good strength, toughness, corrosion resistance and resistance to SCC make the lean duplexes suitable for applications such as process and storage tanks, food and beverage industry, structural applications, etc. U-2304 will be used in applications requiring better corrosion resistance, such as environments containing chlorides and polluted marine environments, desalination plants, etc.

The higher chromium, molybdenum and nitrogen contents give U-2205 significantly improved pitting and crevice corrosion resistance in the presence of chlorides. U-2205 also has better general corrosion resistance than the U- 316L types in most environments.

U-2205 is a highly suitable material for service in environments containing chlorides and hydrogen sulphide such as marine environments and the oil and gas extraction and processing industries.

Typical applications also include the chemical industry (processing, transport and storage, e.g. pressure vessels, tanks and piping), the pulp and paper industry (digesters and liquor tanks) and the mining industry.

U-2205 has thus found widespread use in production tubing and flowlines for the extraction of oil and gas from sour wells, in refineries and in process solutions contaminated with chlorides. U-2205 is also particularly suitable for heat exchangers where chloride bearing water or brackish water is used as the cooling medium.