ASTM A790 S31803 Duplex Stainless Steel Seamless Pipe Chloride Corrosion Resistance

ASTM A790 S31803 Duplex Stainless Steel Seamless Pipe Chloride corrosion Resistance

Duplex stainless steels are called "duplex" because they have a two-phase microstructure consisting of ferritic and austenitic stainless steel grains. The picture shows the yellow austenite phase as "islands" surrounded by the blue ferrite phase. When duplex stainless steel melts, it solidifies from the liquid phase to a fully ferritic structure. As the material cools to room temperature, about half of the ferrite grains transform into austenite grains. The result is a microstructure of approximately 50% austenite and 50% ferrite.

While duplex stainless steels are considered resistant to stress corrosion cracking, they are not as resistant to this form of erosion as ferritic stainless steels. However, the least corrosion resistant duplex stainless steels have greater corrosion resistance than the most commonly used stainless grades, 304 and 316.

Duplex stainless steels are also magnetic, a property that can be used to easily distinguish them from common austenitic grades.

ASTM A790 UNS S31803 Duplex Stainless Steel Seamless Pipes