Abstract
The previous papers have reported that the high current AC-MIG welding process is superior to the conventional DC-MIG process in the welding efficiency as well as the welded joint performance.
The authors have employed the AC-MIG process to weld heavy steel plates of a 980 MPa tensile strength level. The weld metal with very low hydrogen content was obtained by the new process, resulting in lowering preheat temperature in high strength steel welding. Second, the AC-MIG process made welding arc climb during an electrode negative polarity. This phenomenon is preferable in narrow gap welding. Furthermore, AC-MIG weld metal contained low oxygen and thus, high toughness resulted.
As a result, a narrow gap AC-MIG process was developed to provide high efficiency in processing and metallurgically high quality welds in welding of 980 MPa high strength steels for pressure shafts in hydropower stations. The welding wire with chemical compositions satisfying the suitable strength and toughness was produced. Also, the appropriate welding parameters were determined for the narrow gap welding of pressure shafts.
