Visualization of submerged arc welding phenomena by X-ray observation and direct observation

Behaviors of flux, slag and molten metal during a submerged arc welding with a large current were observed by the X-ray observation system including a high speed video camera. Moreover, the direct observation using a high speed video camera was also carried out to observe the arc phenomena, which could not be observed by the X-ray observation. From X-ray observation results, the weld part during a submerged arc welding was classified broadly into 4 regions. Then, it was clarified that a slag was pushed backward in a welding direction when it approached to a wire which an arc plasma existed around. As a result of this series of slag behaviors, the preformed cavity was filled by the slag at the backward of the heat source. In addition, from a direct observation, it was made clear that there were bluish white plasma at beneath a molten metal droplet and orange emitting region around the plasma.