Duplex Steel Composition

Duplex Steel Composition: What Makes Duplex Steel The Best Stainless Steel Choice

The best thing about duplex stainless steel is that you get the best of both worlds, that is, a combination of both the impressive mechanical, kinetic, and chemical qualities of austenite and ferrite in one type of steel. Austenitic steel comprise 70% of the stainless steel market and the most commonly used steel for household items for its non-corrosive quality. Moreover, this type of steel has a high resistance against corrosion and pitting. Ferritic stainless steel, meanwhile, is characterized by great machinability and are very cost-effective.

Duplex stainless steel is composed of a 50/50 ratio of austenite and ferrite except for commercial alloys in which the ratio could be 40/60. It has a substantial chromium (19-32%) but significantly low nickel and molybdenum content.

Duplex Steel Composition: Duplex Steel Production

Thousands of metric tons of duplex steel have been produced since the 80s which were most commonly used in the construction of pollution control units (e.g. flue gas desulfurisation units), storage and transportation facilities and infrastructures. The production represents only 1% of the total crude stainless steel production in the world, although studies have shown that it has grown by 100% during the past decade.

Duplex Steel Composition: The Future Of Duplex Steel

Duplex steel is ever-changing and new engineering research and technologies have made it possible. From the standard duplex (also known as 2205 grade) that has 23% to 25% chromium and 3 to 5% molybdenum content, the industry has seen the emergence of new grades that have fewer alloys yet has proven to be more resistance to corrosion. Here are the new types of duplex steel that have hit the market today:

1. Lean duplex

Lean duplex is a type of duplex steel that’s still being developed by researchers. It has a reduced amount of alloying elements than the usual duplex stainless steel grade.

2. Super duplex.

This type of duplex steel has over 25% chromium content. It has a pitting corrosion equivalent greater than 40. It is proven to be more corrosion-resistant than super-austenitic grades.

3. Hyper duplex.

Hyper duplex is a duplex grade that has a pitting corrosion equivalent that’s greater than 48. This type is fairly rare and only UNS S32707 and S33207 can be bought in the market.