A Modified GMAW System for Distortion Reduction and Travel Speed Increase through Separate Heat Input and Deposition Rate Control

In traditional GMAW and modifications, the current melting the wire is the same as the current heating the base metal. To maintain a minimally acceptable productivity, the base metal heat input is typically much greater than the required to control the distortion at an acceptable or desirable level. In the modified GMAW proposed, a bypass torch is added to an existing GMAW system to bypass part of the current so that the base metal current is smaller than the wire melting current. By controlling the bypass current, the base metal current can be controlled at its desired level while the melting current can also be controlled at its own desirable level. As a result, reducing heat input thus distortion and increasing travel speed can be achieved simultaneously. While the Phase I project has proven the feasibility, this Phase II project will develop a commercial prototype system to implement the technology; establish optimal weld procedures to minimize post-weld distortion, as measured at selected representative locations, and total welding time for selected shipyard applications; adaptively control the process to assure the production of quality welds with minimized distortion and welding time; demonstrate the technology at shipyard; and generate technical data for qualifications.