Experimental review of metallurgical flash weld defects in welded joints: Essence of flat spots, penetrators and oxide inclusions

Typical flash weld defects are divided into metallurgical and mechanical defects. The metallurgical defects, which also include defects known as flat spots, penetrators and oxide inclusions, are difficult problems and develop during flashing action. The appearances and differences of flat spots, penetrators and simple oxide inclusions in flash welds are determined in this study based on literature review and experimental studies with three different steel grades. It was concluded on the basis of experimental studies that the chemical compositions of flat spots and oxide inclusions are the same, and the main difference between them is their appearance: flat spots are fracture surfaces nucleated from oxide inclusions, but simple oxide containing slags can appear also in non-fractured surfaces.