Duplex Stainless Steel Alloy

Duplex Stainless Steel Alloy: A Brief Background

Duplex stainless steel’s current microstructure is composed of different metal or non metal alloys that provide its mechanical qualities and physical appearance. Generally, such alloys enhance duplex stainless steel’s characteristics. These alloys include chromium, molybdenum, nickel, and in some cases, tungsten.

Before the 1960s, duplex stainless steel was more prone to pitting and corrosion after being welded. This problem was resolved by the introduction of argon oxygen decarburization in steel processing, which helped decrease carbon levels and stabilize nitrogen content in duplex stainless steel.

The alloying of nickel was a welcome development in the industry during those times as it helped create a stronger generation of duplex stainless steel while bringing down the cost of its production. Within two decades, new “super” grades in the family of duplex stainless steel have been introduced to answer the market’s ever-growing demand not just in Europe, but also in China and India.

Duplex Stainless Steel Alloy: Chromium and Molybdenum

Chromium and molybdenum are the two basic alloys which comprise 8% to 25% of duplex stainless steel.

Chromium is a lustrous metal that gives steel its intense, shiny, silver color. It is often used as an electroplating finish for flatware, motorcycles, and sometimes, jewelries. Chromium stabilizes steel and prevents it from corroding.

Molybdenum is a silvery free metal that makes duplex stainless steel withstand high temperatures and resist corrosion. Its lower density and affordable price makes it more favored by duplex steel fabricators over tungsten.

Duplex Stainless Steel Alloy: Nickel

Nickel is a key metal in alloying stainless steel to make it stronger even in its welded condition. It is a gray metal that gives duplex stainless steel its ductile capability as well as its resistance to heat, corrosion, and thermal expansion. Alloying nickel with duplex stainless steel during the late 60s has paved the way for the creation of sophisticated duplex grades such as the lean duplex, super duplex, and hyper duplex steel.