Welding with dissimilar metals

Welding Grade 91 with dissimilar metals

Joanne McIntyre - 28 January 2016

A project started in late 2013 has examined the integrity of welding Grade 91 (high chromium alloy steel) to stainless steel grades 304 and 316.

About the author

Mrs Joanne McIntyre
Joanne McIntyre is the Editor in Chief of Stainless Steel World magazine, and Conference Coordinator for the Duplex Seminar & Summit.
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Paul Murphy of Masteel UK and Dr. Sarinova Simandjuntak from the University of Portsmouth, UK recently published a paper in Stainless Steel World looking at the applications of Grade 91 and the challenges of welding it with dissimilar metals.

G91 is a commonly used material in high temperature power plants due to its high temperature creep resistance. In this study, tungsten inert gas (TIG) welding was used to ensure a high quality weld with minimal defects/inclusions.

ASTM/ASME A/SA387 Grade 91 is a modified 9Cr-1Mo steel composed of nitrogen, niobium and vanadium. Although the most common form of Grade 91 material is a plate form, the steel is incorporated into other ASME materials specifications for castings, forgings, fittings, pipes and tubes.

The most common application of ASTM/ASME A/SA387 Grade 91 material is as a high temperature structure material in the fabrication of intermediate heat exchangers, steam generators, secondary piping of a liquid metal reactor that operates at around 550°C, and boiler components used in ultrasupercritical thermal power plants that operate at around 600°C.

The School of Engineering at the University of Portsmouth along with Masteel UK Limited examined the possibility of welding ASTM/ASME A/SA387 Grade 91 material to other steels. A group of researchers and students at the school explored the possibility of a dissimilar metal weld, such as Grade 91 and Duplex/Stainless steel welds. The group studied the process control and parameters in welding that have an impact on the mechanical performances of components of a power plant.

You can read the results in the full article here.

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