Effects of arc duration and atmosphere on the strength of joints by stud welding of an AZ31B magnesium alloy

The press working of magnesium alloy sheet has been developed for the bodies of electric devices. To assemble a pressed magnesium products, studs are required to be built on them. In this study, we attempted to weld the stud 6 mm in diameter of AZ31B magnesium alloy to the AZ31B sheet 0.8 mm thick by stud welding, and compared the weldability between by using the Gap type and the Contact type method which were different in motion of the electrode and in the arc duration at welding. The following results were obtained in this study. Concerning the gap type, the joint strength decreased with decreasing accelerating distance of the stud. Under the condition that provided the sufficient joint strength of 1100 N or more, the fracture occurred in the sheet base metal. With the contact type, the joint strength increased with an increase in the thrust load of the stud. Upon lowering the thrust load to 100 N or less, the fracture occurred in the weld metal, where solidification cracks were recognized in parallel with the interface. The arc durations of 1.2 ms or less showed the high joint strength equivalent to the sheet base metal and the region of the arc duration was expanded to 1.7 ms by the use of Ar atmosphere.