CO₂용접에서 FCW와 Solid Wire의 용접특성에 관한 연구

Abstract

This study on the shipbuilding and automotive industries is intended to provide the optimal welding conditions by examining the welding quality, the welding efficiency and all sorts of change in mechanical properties when Solid wire is replaced with FCW(Flux Cored wire) and used the mixed gas welding process which use the mixed gas(CO₂+ Ar). In this thesis, the yacht section in the shipbuilding and the bus section in the auto industry use commonly 4mm thick SS400(general structural steels). When welding by welding process used widely in the each industry. After welding, the change of welding heat affected zone was observed through the welded part of the macro, microscopic tissue image. This study would like to select the optimal welding conditions in automation by examining the welding quality, the welding efficiency and all sorts of change in mechanical properties. To summarize the results of this study can be summarized as follows.1. When using FCW, it will need post-treatment process because of having a large of spatter on surface. So the increase of working process will increase production speed and cost. 2. When using FCW, Welding possibility (backbead is created) minimum root gap is more than 3㎜. It is more than twice when compared with using Solid wire. As the increase of weld metal to fill will increase wire usage. Therefore it bring lower productivity by increasing the cost and time. In addition, the installation and removal of ceramic backing and end tab process is needed. 3. When using FCW, the increase of residual stress and area of geat affected zon by the increase of heat input can know to be wider. In addition, As the heat input increase, it can be enlarger than when using the crystallinity of heat affected zon Solid wire. 4. When using Sheet metal welding mixed gas(CO₂+ Ar) and solid wire, The weld zon quality improvement and productivity improvement can become possible through the decline of post-treatment process, the increase of welding speed and the lower heat input.