Honesty Steel (India) - | E-Showroom
Honesty Steel (India) - | E-Showroom
Duplex Pipe was originally developed in Sweden back in the 1940’s . DuplexPipes were originally created to combat corrosion problems caused by chloride-bearing cooling waters and other aggressive chemical process fluids. Called Duplex Pipe because of its mixed microstructure with about equal proportions of ferrite and austenite, duplex stainless steels are a family of grades, which range in corrosion performance depending on their alloy content. The chemical composition based on high contents of Cr and Mo, improves intergranular and pitting corrosion resistance, respectively. Additions of nitrogen can promote structural hardening by interstitial solid solution mechanism, which raises the yield strength and ultimate strength values without impairing toughness. Moreover, the two-phase microstructure guarantees higher resistance to pitting and stress corrosion cracking in comparison with conventional stainless steels.
The first-generation grades were alloys of chromium, nickel and molybdenum and while they provided good performance characteristics, welds had low toughness due to excessive ferrite, which limited the use of Duplex pipe steel to a few specific applications.DUPLEX 2205
ASTM A 182, A 240, A 276, A 789, A 790, A 815UNS S31803, S32205NACE MR0175Forms of Duplex 2205 AvailableDuplex 2205 is a nitrogen enhanced duplex stainless steel that was developed to combat common corrosion problems encountered with the 300 series stainless steels. “Duplex” describes a family of stainless steels that are neither fully austenitic, like 304 stainless, nor purely ferritic, like 430 stainless. The structure of 2205 duplex stainless steel consists of austenite pools surrounded by a continuous ferrite phase. In the annealed condition, 2205 contains approximately 40-50% ferrite. Often referred to as the work horse grade, 2205 is the most widely used grade in the duplex family of stainless steels.
The advantage of a duplex structure is that it combines the favorable qualities of a ferritic alloy (stress corrosion cracking resistance and high strength) with those of an austenitic alloy (ease of fabrication and corrosion resistance).
Usage of 2205 Duplex stainless steel should be limited to temperatures below 600° F. Extended elevated temperature exposure can embrittle 2205 stainless.
Corrosion Resistance
2205 duplex stainless steel is a cost effective solution for many applications where the 300 series stainless steels are susceptible to chloride stress corrosion cracking. Stress corrosion cracking occurs when stainless steels are subjected to tensile stress, while in contact with solutions containing chlorides. Increasing temperatures also increase the susceptibility of stainless steels to stress corrosion cracking.
The combination of chromium, molybdenum and nitrogen convey the good resistance of 2205 to chloride pitting and crevice corrosion. This resistance is extremely important for services such as marine environments, brackish water, bleaching operations, closed loop water systems and some food processing applications. The high chromium, molybdenum and nitrogen contents of 2205 provide corrosion resistance superior to common stainless steels, such as, 316L and 317L in most environments.