Gas Metal Arc Welding (GMAW) and Distortion Mitigation for Thin Steel and Aluminum (2007-374)
- BMT Fleet Technology, Ltd.
- Marinette Marine
- Hobart Brothers
January 2007 - July 2008
NSRP ASE Investment: $243K
Industry Investment: $243K
Develop GMAW procedures using innovative machining that manipulates the wave form with a wide range of characteristics, substantially reducing weld distortion; thus mitigating re-work and increasing production.
Thin steel and aluminum alloy materials are highly sensitive to welding-induced distortion. When not controlled it can lead to costly fit-up and rework efforts throughout the build process. To increase the productivity of welding, processes with high deposition rates need to be employed; however, to reduce distortion, low heat inputs and maximizing restraint is essential. Welding processes that provide a suitable balance between productivity and distortion control, as well as those that provide a significant return on the equipment investment need to be considered. This project developed new Gas Metal Arc Welding procedures using unique technology that allows one to program the wave form for a variety of arc characteristics that can lower the effective heat input to the base plate, minimize distortion, enhance weld deposition rate for higher productivity, and allow for an increase in welding speed when welding over primed steel surfaces. In addition, mechanical tensioning was investigated to increase the restraint during welding and subsequently reduce welding induced distortion in thin panel steel and aluminum structures. The project goal was to develop processes that will reduce distortion by 30% and increase weld completion rates by 200%.
Specifically, the project team investigated the methods listed below with the following results:
Controlled Dip Transfer Welding: These welding processes have been tested on the first LCS at Marinette and have proven appropriate for a limited set of welds on distortion sensitive areas. This process provides low heat input welds with minimal spatter and excellent weld geometries; however, the process is not suited for a large range of applications. Superpulse Technology: Optimal welding procedures were developed for aluminum welding of stiffener assemblies using a new series of GMAW technologies (pulse/pulse, pulse/short, and pulse/spray). The pulse/pulse mode of transfer produced improved bead appearance and profile, as well as significantly lowered distortion (greater than 30% reduction) compared to the conventional process, but it resulted in a 40% decrease in travel speed compared to the conventional process.
Tandem Gas Metal Arc Welding (T-GMAW): The use of metal cored electrodes with the T-GMAW process (referred to as TMCAW) resulted in a 221% increase in travel speed compared to the benchmark procedures. With no clean-up operations to remove slag after welding, the actual productivity improvements are estimated at 250%. Procedures for T-MCAW were developed for welding over primers which resulted in an increase of 140% in travel speed; however, variations in the primer coating thickness can affect porosity levels.
Mechanical Tensioning: Results were inconclusive for groove weld operations joining panels together; however, success was achieved in the use of mechanical tensioning to align the fit-up of the panels to be welded. The mechanical tensioning process was successful in reducing distortion (greater than 30% reduction) in stiffener welding applications of both steel and aluminum applications.
Final Report – Approved for public release; distribution is unlimited
Point of Contact:
Darren Begg, BMT Fleet Technology, Ltd.