Arc characteristics in alternating magnetic field assisted narrow gap pulsed GTAW

The exerted alternating magnetic field periodically deflects the welding arc during the pulsed current period and acts to keep a larger proportion of the arc profile attached to the sidewall for providing more arc heat in the narrow gap condition. A combined alternating magnetic field and low frequency pulsed gas tungsten arc welding (AMF-PGTAW) can enable the distribution of arc pressure and arc energy to be reasonably allocated while protecting the both sidewalls from lack-of-fusion defect. Under the same heat input, a sound weld joint without lack-of-fusion defect can be achieved by changing the arc characteristics and AMF-PGTAW features the larger sidewall penetration and smaller weld penetration due to the uniform arc heat distribution. Microstructures of both PGTAW and AMF-PGTAW reveal the significant microstructural refinement of AMF-PGTAW welds for the same heat input.