There is no shortage of stainless steel alloys for manufacturers to choose from. These alloys fit into five different classes: austenitic, ferritic, precipitation-hardening, martensitic, and duplex.
Each and every one of these classes has its high points, but perhaps the most extraordinary of them all is duplex—a class characterized by dual-phase composition and top-notch corrosion resistance.
Hoping to learn more about duplex stainless steel (S31803 or 2205)? Then read on. We’re going to grade its many characteristics below. Weldability
Though it’s not exactly the most weldable of stainless steel classes (that distinction belongs to austenitic stainless steel), duplex stainless steel does possess some weldability. It’s important to note, however, that virtually any thickness can be welded. Corrosion Resistance
As far as corrosion resistance goes, duplex stainless steel sits toward the top of the list. Not only does duplex do a terrific job of resisting corrosion due to water, but corrosion due to chloride as well. This makes it appropriate for use in both freshwater and saltwater conditions. In other words, it thrives in and around the ocean.
Now, this isn’t to say that duplex is the absolute most corrosion-resistant stainless steel. There are a few austenitic alloys with higher PREN grades. However, for its price, and considering its alternative characteristics, it’s exceedingly resistant to corrosion.
Not to mention, it handles stress corrosion cracking with more aptitude than any other class of stainless steel. This is due to its supreme combination of strength and corrosion resistance. Strength
Duplex stainless steel is one of the strongest forms of stainless steel on the market. As such, it can bear substantial amounts of weight. Because of its extreme strength, it can be stretched fairly thin, allowing manufacturers to build components that are simultaneously lightweight and strong. Toughness
A tough stainless steel, duplex can withstand a great deal of wear and tear. Terrific in cold conditions in particular, it’s perfectly suited to handle outdoor applications.
This is one of the reasons that duplex is so popular in the underwater drilling industry. Not only can it hold up against the corrosive properties of water and chloride, but it can also withstand the physical pressure of being hundreds of feet under the sea. Formability
One area where duplex stainless steel falls short is in its formability. Because of its above-average strength and hardness, it lacks malleability and ductility.
This lack of malleability and ductility limits it in terms of the applications for which it can be used. While it can be used to manufacture large, broad items, it can’t be used to manufacture small, intricate items. Magnetism
In terms of magnetism, duplex stainless steel is right in the middle of the spectrum. It ranks below ferritic and martensitic stainless steels, yet, unlike austenitic stainless steels, still possesses some magnetic attraction.
In essence, if your primary goal is to create a magnetic product, duplex is not the ideal steel to use. However, if you’re looking for a steel that is simultaneously magnetic and resistant to corrosion, it’s a very solid option.