TWI Industrial Member Report Summary 828/2005
By C-M Lee and P Woollin
In the oil and gas industry, 22%Cr duplex stainless steel (DSS) is a commonly used corrosion resistant alloy and 12%Cr supermartensitic stainless steel (SMSS) is becoming an increasingly popular alternative for flowlines due to its lower cost and good corrosion resistance in deoxygenated CO2/brine environments.[1,2] In terms of girth welding, MIG welding remains the dominant high-productivity process for flowlines, although the use of power beam processes such as laser and electron beam welding are being considered as future options for high-productivity fabrication.
When new fabrication methods and new materials are introduced there is a need to develop understanding of the corrosion properties of the resulting welded joints. With this understanding, preferred welding procedures can be identified and detailed qualification testing procedures can be put in place to control the quality of manufactured components, thus reducing the likelihood of failure in service.
This project aims to identify suitable corrosion test methods for ranking of girth welded corrosion resistant alloy (CRA) pipes and to compare the corrosion resistance of welds, manufactured by arc welding and power beam welding techniques, in 12%Cr supermartensitic and 22%Cr duplex stainless steels.
- To identify test methods suitable for ranking the corrosion performance of welded joints in 12%Cr supermartensitic and 22%Cr duplex stainless steels welds.
- To compare the pitting corrosion, intergranular corrosion and sulphide stress cracking resistance of girth welds made with arc and power beam welding processes in 12%Cr supermartensitic and 22%Cr duplex stainless steels.