What Is Duplex And Super Duplex Stainless Steel?

Posted by Deepak Sheth on September 30th, 2022

As a result of differences in their microstructural phases, stainless steels are categorised into various classes. While each class of stainless steel has its own microstructure, stainless steels that belong to the duplex category have a similar microstructure to two other classes, i.e. ferritic and austenitic. In the Duplex Round Bar, austenite and ferrite are mixed microstructures. 

Due to their equivalent ratio, duplex steels contain both austenite and ferrite in a 50% ratio. Duplex stainless steels can be further divided into three subcategories, one of which is super duplex stainless steel. Due to this, super duplex grades also have dual microstructures. There are very high values for PREN, or pitting resistance equivalent number, in duplex grades. The values range from 22 to 45.

It is the super duplex kind of stainless steel that offers the highest corrosion resistance out of all three duplex categories. PRENs for super duplex grades range from 38 to 45. Stainless steel grades of this type are highly alloyed, more so than conventional stainless steel alloys, such as 304 or 316. Since they are highly alloyed, they tend to offer superior corrosion resistance. 

The mechanical strength of these materials is also very high. These stainless steel metals are highly alloyed, and this is the reason for their strength and corrosion resistance, but also why super Duplex Round Bar grades are more difficult to work with. 

Moreover, due to the higher content of elements such as chromium, nickel, molybdenum, nitrogen, and even tungsten, intermetallic phases are more easily formed. These intermetallic phases reduce the impact resistance of super duplex stainless steel.

As a result, buyers need to deal with manufacturers or suppliers who are not only experienced but also deliver high-quality products. When either stainless steel grade is manufactured using faulty methods, the end product will perform very poorly.

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Deepak Sheth

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Deepak Sheth
Joined: July 29th, 2022
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