To increase the use of FSW, we are developing processes applicable to steel assembles for shipbuilding and offshore structure. The welding process was optimized using a combination of operating parameters and tool geometries. In order to obtain complete penetration, two-pass welding of butt joints was carried out from both sides of 12 mm thick mild steel plates. We investigated the mechanical properties of these FSW joints. The hardened areas were observed in welded metal at the butt joint. Tensile strength tests resulted in the base material being broken when the welding was performed on both sides using optimum parameters.
Recently friction stir welding (FSW) has been applied in several areas such as railroad vehicles, airplanes and cars. While these applications have been well accepted, commercial application is limited to lower temperature materials such as aluminum alloys. Also in the area of shipbuilding and offshore structure, FSW is being applied to only the portion of the high-speed passenger ship made of aluminum alloy.
Because of this expanding application, FSW is emerging as a viable alternative to the conventional fusion welding processes because of a number of advantages. These advantages, such as low distortion, no fume, no spatter, ease of automation, etc. also can be expected for steel joints. At the same time, it should be noted that especially because of restrictions on the tool quality of the material, it is difficult to apply FSW to high temperature metals.
In this study basic welding experiments were carried out using mild steel where it is comparatively easy to apply FSW. After welding, the mechanical properties of the weld joints were investigated.
We performed a preliminary study on tool shapes and welding parameters in order to determine the process conditions for FSW of mild steel.
