Taking an ideal joining technology right to where it is needed
Concurrent Technologies Corporation (CTC) is developing an innovative solution for
repair and construction of U.S. Navy ships that is not available anywhere else.
While friction stir welding (FSW) is ideally suited for repair of cracks in 5xxx
series aluminum, no commercially available FSW systems can be used shipboard or
in situ to perform weld repairs.
CTC’s patented portable friction stir welder (PFSW) and process parameters
are designed to weld inserts into ¼-inch thick sensitized 5xxx series aluminum panels.
CTC’s technology can be used for replacing sensitized and cracked material during
ship repair, avoiding costly labor and schedule delays. In addition, CTC’s PFSW
technology could be used during new construction (for example, in deck socket installation
and hull erection joints).
Uniquely Beneficial for the U.S. Navy
The use of 5xxx series aluminum is essential for reaching the design performance
required for several classes of U.S. Navy ships. However, after several years of
exposure to elevated in-service temperatures, 5xxx series aluminum can become sensitized.
Sensitized aluminum is highly susceptible to pitting and stress corrosion cracking,
and the high levels of sensitization encountered on these ships renders the material
mostly unweldable by conventional means. As a result, costly and time-consuming
repairs are required to replace the affected panels.
Why Portable Friction Stir Welding?
Large, stationary friction stir welders are used in some new ship construction applications
where the work piece must be taken to the machine. Due to their size and weight,
conventional friction stir welders cannot be utilized shipboard where many operations
would benefit from the technology. CTC’s PFSW is being developed to bring the full
advantages of the friction stir welding to the repair site:
How the Portable Friction Stir Welder Works
- Quality welds in highly sensitized material
- Less distortion/residual stress due to less heat input
- Highly repeatable weld quality
- Stronger welds due to stirring and refining of material grains
- No shielding gas required since not melting material
- No filler required since self-generated
- Does not require highly skilled welders
CTC’s PFSW consists of a weld head, track, control hardware, and data acquisition
to record and display process parameters. These components are hand carried and
assembled shipboard. Air motors are used to drive the weld head and power the spindle.
CTC’s FSW technology can be used for welding inserts of varying size and shape,
as well as welding straight erection joints. CTC’s PFSW was used to perform panel repair on a U.S. Navy Guided-Missile Cruiser (USS Vicksburg CG-69).
PFSW being used shipboard on bulkhead