Duplex 2205 is duplex stainless steel enhanced with nitrogen that was developed to overcome typical corrosion problems with stainless steels of the 300 series. "Duplex" defines a family of stainless steels which are neither entirely austenitic, as stainless as 304, nor completely ferritic, as stainless as 430. The 2205 stainless steel duplex structure consists of austenite reservoirs, surrounded by a continuous step of ferrite. 2205 contains approximately 40-50 percent ferrite in the annealed state. Sometimes referred to as the horse grade of work, 2205 is the most commonly used grade in the stainless steel duplex band.

The 2205 duplex stainless steel is a cost-effective alternative for many applications where chloride stress corrosion cracking is susceptible to the Titanium Pipe series stainless steel. Stress corrosion cracking happens when stainless steels are exposed to tensile stress when chloride-containing solutions are in contact. Growing temperatures also make stainless steel more vulnerable to stress corrosion cracking.

The mixture of chromium, molybdenum, and nitrogen conveys the strong resistance of Duplex 2205 Tube to the pitting of chloride and corrosion of crevices. For services such as marine environments, brackish water, bleaching operations, closed-loop water systems, and some food processing applications, this resistance is extremely significant. The high content of 2205 in chromium, molybdenum, and nitrogen offers superior corrosion resistance to traditional stainless steels, such as 316L and 317L in most environments.

Characteristics

• High chloride stress resistance to cracking corrosion
• Resistance to chloride pitting and corrosion of the cracks
• Strong general résistance to corrosion
• Good resistance to corrosion under sulfide stress
• Strong Power
• Good weldability and practicality

Duplex Stainless steel provides a microstructure of both ferrite and austenite in it. As Duplex Stainless Steel is melted, it solidifies to a fully ferritic form from the liquid process. Roughly half of it transitions to an austenitic form as the material cools down. The result is an alloy with an austenite microstructure of approximately 50 percent and ferrite of 50%. Duplex alloys have greater strength and greater resistance to corrosion cracking than most austenitic alloys, and greater durability than ferritic alloys, especially at low temperatures.

A quick guide to Titanium Pipe

TITAN has the expertise and know-how to ensure that every weld is always right. Our proven track record with the reactive metals makes TITAN the perfect option for all your requirements for Duplex Stainless Steel.

Compared with the austenitic grades with equal corrosion resistance, the lower nickel and molybdenum content of the Duplex Stainless Steels gives the Duplex grades a lower cost per pound. The Duplex grades are also about twice as high, resulting in material savings due to demands on wall thickness. At a lower cost per pound, this means less scrap.

When considering Duplex Stainless Steel for heat exchangers, the advantage is sometimes even greater. The lower Duplex grade nickel content implies greater thermal conductivity as opposed to the equivalent austenitic grade. Less surface area for heat transfer is necessary to perform the same function. Welding the Duplex Stainless Steels would seem simple if the only requirements were to pass ASME code, but consideration of the all-important weld mixture and careful handling is required to ensure good corrosion resistance.