Tandem and twin double electrode gas metal arc welding (GMAW) processes typically give two to three times the productivity of single electrode GMAW and flux cored arc welding (FCAW) processes. GMAW and FCAW employ the same equipment and apparatus to create panels, units, and ship structures in shipbuilding. The former is preferable for high-speed precision fillet welding where metal transfer must be controlled, and spatter and slag must be avoided to reduce rework. The ability to continuously deposit 3- to 4-mm precise fillets on longitudinal and transverse stiffeners reduces panel distortion and rework dramatically. As equipment, apparatus, control technology, and consumables for shipbuilding applications improve, a modern assessment of precision welding operations is required. This project aims to test next-generation double electrode technologies for 4-mm fillet welds, as this fillet size is more likely to be used in existing shipyard facilities. (The ability to deposit 3-mm fillets necessitates precision no-gap fit-up, clean bright metal surfaces, and highly accurate seam tracking, and is a future focus area.) Furthermore, double electrode methods maximize production for both small and large fillets. Tandem GMAW is already used in many shipyards for larger (5- to 7-mm) fillet welds. Newer double electrode GMAW techniques can also offer higher deposition rates, better deposit bead shape and quality, and greater robustness than traditional shipbuilding procedures.
<B>Experimental Approach: </B>
Here a multi-task experimental approach is used, and each task is defined below:
• Task 1 – Project Initiation and Kick-off Meeting
A kickoff meeting will be organized to identify the target application and procedure qualification and fabrication criteria, as well as to address shipyard implementation requirements and to establish process and procedural boundaries.
• Task 2 – Survey Suppliers for Next Generation Double Electrode (DE) GMAW Technology
This task will begin with a survey of welding equipment and consumable vendors in order to find next-generation equipment, consumables, and apparatus capable of depositing 4-mm and larger fillet welds to support panel line assembly conditions. Recommended setups and parameters for twin, hot wire tandem, tandem, adjustable configuration tandem, and advanced consumables for high-speed precision fillet welding will be discussed with equipment providers.
• Task 3 – Feasibility Testing of Next Generation DE-GMAW Processes
Feasibility experiments will be performed on candidate double electrode process variations. A set of constant deposit area (constant wire feed speed/travel speed (WFS/TS) ratio) tests will be performed at two arc lengths for each process combination utilizing the ARCWISE method. This method employs systematic tests to create operating windows, evaluate bead form, and calculate productivity for weld joint applications. All assessments for feasibility tests shall be based only on visual, dimensional, and weld surface quality data. In Task 4, up to three preferred processes will be chosen for detailed ARCWISE testing.
• Task 4 – Precision Fillet Weld Operational Windows, Bead Shape Maps, and Productivity Analysis
Systematic ARCWISE testing will be run on up to three Task 3 process combinations. A series of constant deposit area (WFS/TS ratio) experiments will be performed at two arc lengths for each process combination. The tests will be run at various speeds (for example, 0.25- to 2-m/min (10- to 80-ipm)) to determine the lowest speed required for fusion, the range of acceptable welding conditions, and the maximum speed to process failure. Each test will be assessed visually and dimensionally. Metallographic sections from each test will be extracted and utilized to characterize bead form dimensions and quality.
• Task 5 – DE-GMAW Process Benchmarking and Productivity Analysis
This task will examine all of the test results from Task 4. To assess process tolerance, operational windows will be used. The operating windows and plots that characterize the relationship between voltage, current, and wire feed speed; heat input versus deposition rate; and bead shape associations will be included in the ARCWISE data collection. The operating windows for creating precision 4-mm fillets will be used to establish the recommended welding techniques.
• Task 6 – Next Generation DE-GMAW Technology Workshop
At the end of the project, this task will give a one-day workshop to showcase the recommended techniques and discuss performance metrics.
Results and Discussion: TBD – Project to be complete before Fabtech and this data will be updated.
Conclusion: TBD – Project to be complete before Fabtech and this data will be updated.
<B>Acknowledgments:</B> Much of the content in this presentation was developed in the National Shipbuilding Research Program – Advanced Shipbuilding Enterprise (NSRP-ASE) Research Announcement (RA) Project 2019-375-009. Project participants from NASSCO, INGALLS, and NSWCCD. Additional thanks to the technology support provided by: Lincoln Electric, Miller, Fronius, Cloos, Select Arc, and D&F Specialties.
<B>Key words:</B> Welding, Fillet, DE-GMAW, double electrode, GMAW, Precision