Study on elimination of interlayer defects in horizontal joints made by rotating arc narrow gap welding

Abstract

In this work, the characteristics of interlayer defects were studied in horizontal welds made by rotating arc narrow gap welding. The interlayer defects existed in the form of incomplete fusion and slag inclusions, occurring near the lower sidewall. In the rotating arc process, the instantaneous velocity of the arc with respect to the sample is higher when the arc is close to the lower sidewall, whereas it is lower when it is near the upper sidewall. This results in a lower effective heat input to the lower sidewall, and a corresponding reduction in the enthalpy that is transferred along with the deposited metal. Fortunately, this asymmetric nature of rotating arc welding can be exploited to minimise or eliminate interlayer defects. It is shown that, by controlling the direction of rotation for the arc, removing slag, selecting an appropriate groove size and resetting the torch position, defect free horizontal welds in heavy plates can be achieved.