Analysis of solidified organism in thin piece spot welding nugget

Accordinq to the research on spot welding nugget system of thin metalpieces,two kinds of solidified organism may exist in the nugget: "columnar" and "columnar+cquiaxial" structure,and the micro-structure is generally dendritie.Athird solidifled organism,the single equiaxial organism,was got for the first time byincubating the nugget.