A Fractographical Investigation of Weld Toe Imperfections in Tandem Gas Metal Arc Welding

Abstract

Prediction and control of flaws in welds play important roles in design of complex structures against fatigue and fracture failure. Cold laps ‐ outer lack of fusion ‐ are small geometrical imperfections at weld toes, which act as fatigue crack initiation sites and reduce the life of welded structures drastically. The aim of this work is to characterize and categorize different types of such imperfections in the tandem gas metal arc welding process and find the mechanisms of their formation. Tandem welding process with different welding parameters was used to produce bead‐on‐plate coupons. These coupons were then sliced to smaller specimens for further investigations. For studying the weld toes, all the specimens were hit in an impact test machine and then the fracture surfaces of welds and base materials were analysed by scanning electron microscopy (SEM). Two types of cold laps were observed at weld toes, namely overlap and spatter. Observation and measurement showed that these imperfections are in the form of micro cracks with depth between 0.1 to 1.5mm and length between 0.1 to 4 mm.