Microstructures and properties of welded joints of a duplex stainless steel

• Main Author: Ng, Chong Wei
• Other Authors: Zhou Wei
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/69430
• Institution: Nanyang Technological University

Duplex stainless steel has many uses in the oil and gas industry, chemical processing industry and basically, manufacturing industries. It has many applications in pipping system and heat exchangers. It has higher corrosion, resistance ,higher mechanical strength higher resistance ,excellent weldability than other ferrite stainless steel. In our experiments, our aim is to study about the duplex stainless steel and its properties. Secondly, our aim is to develop hand-on skill on sample preparation and material testing. Thirdly, our aim is to study the microstructure and properties of welded joints of duplex stainless steel. In my studies, sectioning should be done for the very first step. A small tensile piece should be cut out from the big piece of rolled duplex steel tubing given by my professor. Also, the welded section of the metal and parent metal are also taken to do the sample preparation. Care should also be taken when sectioning the piece. Damage to the workpiece is irreversible. The consequence will be damage to the microstructure of the duplex stainless steel. In this experiment, sample preparation of the specimens are carried out and the microstructure and properties of duplex stainless steel are studied. To study its properties, micro hardness and tensile test was carried out. Throughout our studies, We make use of the scanning electron micrograph and optical microscope microscopic to help us in our studies of its properties, chemical composition, and its microstructure. Our results was that the weld region was found to have the highest average HV at the weld region compared to the parents metal. Comparing the three tensile specimen, the highest tensile piece with the highest tensile value was found to be 847.38 Mpa. For the microscopic structure, ferrite and austenite structure can be found in parent duplex stainless steel. A stereomicropic view of the weld region has also been taken. The breaking of the tensile piece happens outside the weld.