An Introduction To Duplex Stainless Steels

Duplex stainless steels blend the features of ferritic and austenitic families of alloys .

These give advantages of both of them, with fewer disadvantag esusually with a lower price than other alloys of steel.

But, it is just one aspect of a larger picture.

Selecting the best stainless steel also depends on what the steel can do to meet your needs.

Do you think duplex stainless steel can be used on your next design?

Let’s look at what and when duplex steel could be the best choice to your requirements.

What Is Duplex Stainless Steel?

Duplex stainless steels receive their name because of their microstructure that is two-phase.

Although exact ratios differ depending on the grade, all duplex steels are made up of a structure that is about 50-percent austenite, and 50 percent ferrrite.

This gives duplex stainless many of the perks of austenitic and ferritic families of steel while also minimizing the weaknesses.

As with other types of stainless, the precise chemical composition that is present in the stainless differs according to the grade, but typical components include:

  • Carbon
  • Manganese
  • Silicon
  • Chromium
  • Nickel
  • Phosphorous
  • Sulphur

Molybdenum, nitrogen and copper are also used to influence the characteristics that will be exhibited by the finished product.

A Brief History Of Duplex Stainless Steel


The idea of duplex stainless steel alloys was debated in the 1920s. However, the production of first duplex alloys did start until the 1930s.

These early duplex alloys were mainly restricted to casting and other specific applications since they had a significant quantity of carbon.

In the latter half in the 60s decarburization had allowed foundries that made metals to make low carbon steels with high nickel and chromium content in addition to balancing the austenite and ferrite structures.

This led to a new duplex alloy with improved performance and less disadvantages.

These stainless steels duplex share numerous similarities to the contemporary alloys currently in production -particularly, Duplex 2205 (UNS S21803/32205).

While modern standards utilize different varieties of chromium molybdenum and nickel. Industries can be grateful to the first grades developed in the 1970s to create the variety in duplex stainless steels currently in use today.

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Benefits Of Duplex Stainless Steel


Although duplex stainless steel represents a small portion of the stainless steel industry, the product comes with many advantages in comparison to the traditional austenitic stainless steels and ferritic stainless steel.

  • Improved Strength

A number of duplex grades are as strong two times more durable than ferritic or austenitic stainless steel.

  • High Toughness and Ductility

Duplex stainless is usually more flexible in the presence of pressure, than ferritic steels, and offers greater strength. While they usually have less value than austenitic steels however, the distinctive design and properties of duplex steel usually exceed any worries.

  • High Corrosion Resistance

Based on the grade of stainless steel in question, duplex steels have the same (or better) resistance to corrosion as standard austenitic grades. For alloys that have higher molybdenum, nitrogen, and chrome, the steels have superior resistance to pitting and corrosion in crevices.

  • Cost Effectiveness

Duplex stainless steel has all of these advantages and requires less molybdenum, nickel and. This means it’s an affordable alternative to traditional austenitic stainless steel. The cost of duplex alloys can be more stable than other grades of steel, making it easier to calculate the costs, both on an initial and a lifetime level. The more strength and better corrosion resistance means that parts made from duplex stainless are thinner than austenitic ones, resulting in lower prices.

Check More Information about Super Duplex Fasteners

Best Uses For Duplex Stainless Steel

Due to their superior resistance to corrosion as well as their increased strength and their low price Duplex stainless steels are in high demand across a range of industries and markets which include:

  • Near-shore and offshore operations, such as oil drilling desalination and water treatment and many other industrial activities
  • Processing of liquids and chemicals
  • Parts and components for the naval sector
  • Equipment to control pollution
  • Production of paper and pulp
  • Construction
  • Tanks for brewing and hot water

Unified Alloys offers a range of stainless steel products that are resistant to corrosion to meet the demands of various industries across Canada. Since over 40 years we’ve provided our expertise to companies of all sizes who want to use stainless steel for everything from bridge manufacturing to the processing of liquids as well as storage. Our experts are on hand to assist you in determining the most suitable alloys and products to help you achieve your objectives. Contact us now.


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