Ferrite Content in the Heat Affected Zone of Duplex Stainless Steels

Abstract

In as-delivery state, duplex stainless steels have between 35 to 60 % of ferrite with the rest consisting of austenite. This balance is known to be a good compromise for the maximal corrosion resistance and mechanical properties. When the duplex is heat affected by welding, the phase balance changes close to the fusion line. In this Heat Affected Zone (HAZ), the ferrite content is increased significantly, leading to a reduction in the use properties. It is also important to understand the ferrite content issues and to manage them. As a first approach, this paper will underline the main influential parameters changing the ferrite content and will show how it can be predicted. Additionally, ferrite contents achievable on duplex hot rolled plate, HAZ, and weld metal will be highlighted and discussed in relation to standards from the oil and gas industry.