SUPER DUPLEX

The original duplex stainless steel was developed in Sweden for use in the sulfite paper industry. These early alloys were developed to combat corrosion problems common in that industry as a result of chloride-bearing cooling waters. However, while these duplex stainless steels proved to be an excellent development in the field, they did not meet all needs. As a result, further innovation was needed. That innovation took the form of super duplex stainless steel. The original alloy of that range, Ferralium 255, was developed by Langley Alloys itself in the 1960s. However, the term would not be used until the 1980s, when it was used to describe highly alloyed, high-performance Duplex steel with a pitting resistance equivalent of >40 (based on Cr% + 3.3Mo% + 16N%). A number of other grades were subsequently developed. Since then, there have been a number of developments in the material, including Super Duplex F61, which was launched in 1969.