SS400 압연강재의 용접방법에 따른 기계적 성질 연구

A Study on Mechanical Properties of SS400 Rolled Steel Materials according to Welding Methods

This study aims to figure out and understand mechanical properties and features of shielded metal arc welding, CO₂ gas solid wire arc welding, and CO₂ gas flux cored wire arc welding which are commonly used, in order to choose and utilize the most suitable welding method according to different structures. As a result of the study, CO₂ gas solid wire arc welding showed the largest tensile strength value, while CO₂ gas flux cored wire arc welding showed the intermediate value, and shielded metal arc welding did the lowest value. In case of CO₂ gas solid wire arc welding, it had the largest tensile strength because of weld zone hardening caused by quenching due to the absence of slag, and the lowest elongation rate. CO₂ gas flux cored wire arc welding, a semiautomatic welding method, had the intermediate value in terms of mechanical properties. Shielded metal arc welding showed the relatively low tensile strength because a weld metal zone was not quenched due to slag formed by flux melting, while its elongation rate was large. For these reasons, in case of a structure under impact loading, welding with slag which slow cooling of weld zone is available is considered to be more advantageous. Particularly when taking the mechanical properties into account, a semiautomatic welding, CO₂ gas flux cored wire arc welding, is regarded as the most ideal welding method in terms of work efficiency, tensile strength, and elongation rate.