Our previous work has demonstrated that, when welding a large diameter steel stud in the horizontal position, it is necessary to prevent molten metal from dripping from the weld pool. The formation of blowholes in the weld metal must also be suppressed to maintain the soundness of the joint. In addition, it was found that a joint can be considered suitable if its defect ratio does not exceed a threshold level of 10%, and that this can be achieved by optimizing various welding parameters, such as the arc holding time and current.
In the present study, two processes were used to further improve the soundness of joints stud-welded in the horizontal position. First, the ferrule was inverted in order to reduce the interstices between it and the stud, and to eliminate gas through-grooves. Both factors are deleterious because they can allow molten metal to hang down from the weld pool. Inversion of the ferrule was found to be effective at supporting the molten metal and ensuring a suitable degree of fusion. Second, the welding atmosphere was controlled by employing aluminum as a deoxidant in conjunction with argon gas to shield the welded region from ambient air, thus reducing the formation of blowholes in the weld metal. The formation of blowholes was significantly reduced by the combined effects of these two methods.
