SBIR-STTR Award

Gas Metal Arc Welding (GMAW) is the most widely used welding process. It is also the major process used in shipbuilding. In traditional GMAW and all its modifications, the current which melts the wire is the same as the current which heats the base metal. The base metal heat input is thus proportional to the heat which melts the wire. To maintain a minimally acceptable productivity as measured by the wire melting speed, the base metal heat input is typically much greater than the required to control the distortion at an acceptable level. In the modified GMAW proposed to reduce the post-weld distortion and increase the travel speed, 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. Further, by controlling the bypass current, the base metal current can be controlled at whatever the desired level is while the melting current can also be controlled at whatever the desired level is. Hence, in the modified GMAW, the productivity is decoupled from the base metal current and the base metal heat input can thus be reduced without affecting the productivity. As a result, reducing heat input thus distortion and increasing travel speed can be achieved simultaneously. The Phase I project will prove the feasibility of the modified GMAW technology for its practical use in welding a typical ship structure material DH36 at flat, horizontal and vertical (down or up) positions.

Benefit:
It is estimated that conservatively approximately 21,000 hours per DDG-1000 could be saved if this technology can be brought to fruition and implemented in shipyard due to significantly reduced accumulative heat input/distortion, increased travel speeds, and reduced fume exposure. If calculating returns at $50/hr, a minimum of $1,050,000 in savings per DDG-1000 will be generated.

Keywords:
Distortion, Distortion, Productivity, welding, GMAW, heat input

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.

Benefit:
It is estimated that conservatively approximately 21,000 hours per DDG-1000 could be saved if this technology can be brought to fruition and implemented in shipyard due to significantly reduced accumulative heat input/distortion, increased travel speeds, and reduced fume exposure. If calculating returns at $50/hr, a minimum of $1,050,000 in savings per DDG-1000 will be generated.

Keywords:
travel speed, Distortion, SAW, FCAW, Modification, Control, GMAW, Productivity