Project Number: S2928

Project Title: Next Generation Autogenous Welding Process and Equipment Development

Period of Performance: MAY23 – OCT25

At Electric Boat (EB), to go from raw pipe material to a welded joint involves a number of steps. The process begins with the raw material selection and cutting the piece to length specified by the application. The application will call out the technical specification the joint needs to be prepared and welded in accordance with, setting the tolerances and dimensions for the bevel geometry. These pipe pieces are machined either by hand or by machine. This can be time consuming based on the design, the application, or both. Once pieces are verified to meet the specification-required dimensions, the pipe pieces are fit-up using a consumable insert ring. Consumable insert rings need to be cut and filed to accurately fit around the pipe’s inner diameters. Any spaces or gaps left between the pipe pieces or the insert and a pipe, increase the likelihood for defects to occur within the weld. Once ensuring a quality fit, the pipe moves on to welding. The amount of weld passes for a joint will increase with increasing pipe thickness. Additionally, interpass temperature and cleaning between beads will increase the number of hours spent to complete each joint.

With each step mentioned above, the potential for workmanship type defects increases. These workmanship defects are undesirable and may lead to rework of the joint. In some cases, that may require removing the joint entirely and starting from scratch. In order to maximize the amount of time saved per application, the steps to complete a pipe joint need to be made more efficient or eliminated altogether. Welding can be enhanced by potentially reducing the number of passes needed to complete the joint.

The proposed project is investigating the use of autogenous GTAW welding technology to reduce the necessary steps involved for welding thin walled, horizontally rolled pipe joints. The autogenous process can complete welds within a single pass without the use of filler material or inserts. The team is executing the research plan to investigate potentially eliminating/minimizing bevel machining of each piece for pipe applications, insert ring prep and fit up, initial tack welding (due to the square prep that is required), multiple weld passes, filler material, and additional rework based on the outcome of the weld.

By reducing the number of labor hours associated with machining, fitting and welding, EB is projecting a savings of $1.32M per VCS and $2.77M per CLB for a combined savings estimate of $27.05M delivering a five-year ROI estimate of 6.70.

Upon successful and timely completion of the CNM project, the results will be implemented at the GDEB facility. GDEB anticipates implementation in the fourth quarter of fiscal year 2026.