- These days we see an increasing usage of two-phase microstructure consisting of grains of ferritic and austenitic stainless steel. This type of steel is widely know as Duplex stainless steels. UNS S31803 and UNS S32205 are commonly referred to as Duplex stainless steels, and their two-phase names consist of an arrangement of a mixture of ferrite and austenite containing approximately equal parts.
The duplex stainless steel series is typically twice as strong and offers significantly improved corrosion resistance compared to normal 304/316 austenitic stainless steels. Increasing the chromium content of the stainless steel will improve its resistance to pitting. However, the pitting resistance equivalent number (PREN), which infers the pitting resistance of an alloy, also includes many other elements in its formula. This subtlety can be used to explain how the difference between UNS S31803 and UNS S32205 is formed and whether it matters.
With the development of duplex stainless steels, the initial specification was UNS S31803. However, some leading manufacturers have been producing the grade to the upper limit of the allowed specification. This reflects their desire to maximize the corrosion performance of the alloy, which has been facilitated by the development of the AOD steelmaking process, which allows for tighter control of composition. In addition, it allows the level of nitrogen addition to be influenced, rather than just being present as a background element. As a result, the highest performance dual grades seek to maximize levels of chromium (Cr), molybdenum (Mo) and nitrogen (N). The difference between a duplex alloy whose composition meets the bottom of this specification and one that reaches the top of this specification can be based on several points of the equation PREN = %Cr + 3.3% Mo + 16% N.
Duplex stainless steel is available in various forms such as pipes, plates, fittings and flanges, widely used for wide range of engineering applications. Developed in Sweden more than 70 years ago in the sulfite paper industry, it is used to overcome corrosion problems caused by bearing cooling water and other corrosive chemicals. After that, nitrogen was deliberately used as an alloying agent, which quickly became the mainstream stainless steel alloy composition of the duplex.
The Key Products for Engineering are:
- Aluminium Blocks for Machining Applications, Aluminum Blocks Suppliers, Aluminum Block Manufacturers
- Stainless Steel Pipe Fittings, MS Flange Manufacturers, Pipe Fittings Manufacturers
- Duplex Pipes & Fittings
- Flexible Hose Pipes, Stainless Steel Flexible Hoses
- Aluminum Round Bars, Aluminium Sheets, Aluminium Plates Suppliers, HE 30/6082 T6 Plates
- Surplus Steel Buyers
- Stainless Steel Seamless Pipes, Stainless Steel Pipe Manufacturers, Stainless Steel Pipe Fittings Manufacturers
- Stainless Steel Capillary Tubes, Stainless Steel Square Pipes, SS 316L Seamless Pipes