Abstract: The manufacturing functional feasibility of implementing Friction Stir Welding (FSW) technology, a highly energy-efficient solid-state joining process, for field deployable, on-site fabrications of large, complex and thick-sectioned structures of high-performance and high temperature materials. The technology innovations developed herein attempted to address two fundamental shortcomings of FSW: 1) the inability for on-site welding and 2) the inability to weld thick section steels, both of which have impeded widespread use of FSW in manufacturing. Through this work, major advance has been made toward transforming FSW technology from a “specialty” process to a mainstream material joining technology to realize its pervasive energy, environmental, and economic benefits across industry. The technology development in this project primarily focused on its first targeted application: which combines the joining parts in the solid phase. Energy savings and environmental preservation are important issues for us to resolve. Since reducing the weight of vehicles is one of the efficient measures, the use of the combination of stainless steel 304 and bronz alloy has been increasing in fabricating vehicles. Under this situation, many trials to weld steel to bronz alloy have been conducted. However, sound joints have not been produced so far, because hard and brittle intermetallic compounds were formed at the weld whenever steel was welded to bronz by fusion welding. In gas welding process the metals get heated and due to the heating of the metal the strength of the metal decreases and also the microstructure of the metal changes. But in friction stir welding the metal gets less heated compared to the gas welding process. Due to the less heat absorbed by the metal the strength and microstructure changes comparatively less than the gas welding process. So comparatively friction stir welding gives accurate microstructure and tensile strength than the gas welding process. In the present work we tried to compare the micro structure, micro hardness and tensile strength of two Friction Stir welded joint with the gas welded joint.

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