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Duplex Stainless-Steel vs Super Duplex Stainless Steel

by Feb 24, 2019News

As you may know, there are hundreds of stainless-steel alloys on the market today. These alloys belong to a number of different stainless-steel classes, and possess a range of characteristics.

Two of the modern market’s most beneficial stainless-steel alloys are duplex stainless steel (S31803 or 2205) and super duplex stainless steel. While these alloys have similarities, they are not quite the same.

Wondering what their differences are? Read on! We’re going to cover them below.

Structural Composition:

Though duplex stainless steel and super duplex stainless steel possess the same metals, they possess these metals at different levels. Below, we’re going to get into the detailed structural compositions of both duplex and super duplex.

Duplex

A combination of ferritic and austenitic stainless steels, duplex stainless steel consists of 3% molybdenum, between 5% and 6% nickel, and 22% chromium.

Super Duplex

Super duplex stainless steel is essentially duplex stainless steel, but with additional characteristics. It possesses 25% chromium content, 7% nickel content, and 4% molybdenum content. Because it possesses more of each element, it has higher resistance to corrosion than does duplex stainless steel.

Comparing Characteristics:

Because they possess differing levels of specific elements, duplex and super duplex stainless steel differ from one another in terms of functionality. To illustrate these differences, we’re going to compare their characteristics against one another.

Cost

When it comes to cost, super duplex is more expensive than duplex. The reason for this is simple: super duplex stainless steel contains more nickel than does duplex stainless steel. Considering that nickel is the most expensive element used in stainless steels, it stands to reason that super duplex would be more expensive.

Strength

As far as strength goes, duplex stainless-steel ranks fairly high among other stainless steels. It can bear a great deal of weight, and can withstand a great deal of physical trauma.

However, for all the strength that duplex possesses, super duplex possesses even more. If you need a stainless steel that can be used in a high-stress, high-impact environment, you’ll be best off with choosing super duplex.

Weldability

You might have a need for welding your stainless steel. If so, you might be able to get by with duplex or super duplex stainless steel. Both of these stainless steels possess good, but not great weldability capabilities.

However, you should never choose duplex or super duplex with welding as a main priority. There are other stainless steels — ferritic stainless steels, in particular — which are better suited for welding.

Corrosion Resistance

Where both duplex and super duplex stainless steels excel is in their resistance to corrosion. Both types of stainless steel are highly resistant to stress corrosion cracking, crevice corrosion, and pitting. This is true whether or not such corrosion is brought on by high-chloride environments.

However, when compared, super duplex stainless steel comes out on top, possessing more corrosion resistance than duplex. What this means is that super duplex stainless steel can withstand corrosive environments for a longer period of time than duplex stainless steel can.

In Need of Duplex Stainless-Steel Products?

Are you interested in purchasing duplex (S31803 or 2205) stainless steel items? If so, you can find them right here at Great Plains Stainless.

We sell duplex stainless steel items of all kinds, including (but not limited to) pipes, bars, weldings, plates and fittings. Capable of shipping our products all over the world, we can get them to you regardless of where you’re located. We are master distributer of stainless steel products and one of the most trusted and experienced names in the industry.

Contact us now to discuss your duplex and super duplex stainless-steel needs!