1998 Volume 16 Issue 4 Pages 453-461
In order to make factors of generation of pit and blowhole in arc fillet welding of lap joint of zinc-coated steel sheets clear, the relationship between the properties of zinc layers and the generation of pit and blowhole was investigated by carrying out CO2 arc fillet welding of lap joint of zinc coated steel sheets and Zn-Fe coated steel sheets made with base metal with different surface roughness. As the result, it was obvious that decreasing Fe content in zinc layer and decreasing surface roughness of base metal remarkably restrained generation of pit and blowhole. Decreasing Fe content of zinc layer decreased the melting point of zinc layer, so zinc layer became easy to melt fast, then liquid zinc could escape from molten pool faster. Decreasing surface roughness of base metal increased the mobility of liquid zinc on its surface near molten pool, so liquid zinc became easy to move quickly. When zinc coated steel sheets (Zn : 40 g/m2) made with smooth surface base metal (Ra : 0.1 μm) were welded at welding speed 1.0 m/min, pit and blowhole were remarkably suppressed to the same level as welding cold rolled steel sheets.
