New Process for Welding Aluminum Underwater Will Eliminate Costly,
Phoenix International and U.S. Navy Pilot Test Program with Help of Lincoln Electric
“The system runs beautifully,” Elliott says, “I attribute that to the nice finish on the wire and the speed at which the power system and wire feed can control the process."
With drydocking currently as the only option for weld repair of aluminum-hulled ships, the Navy is searching for new solutions. It may have found one with a promising new technique: underwater aluminum gas-metal-arc welding (GMAW) in a hyperbaric chamber.
In terms of chemical composition, aluminum has a high maximum solubility for hydrogen atoms in the liquid form and a low solubility at the solidification point. This means that even a small amount of hydrogen dissolved in the liquid weld metal will tend to escape as the aluminum solidifies and porosity is likely to occur – a great cause of concern during the welding process.
While welding aluminum on dry land poses a number of challenges, welding in an undersea environment vastly complicates the process. “Porosity is the major problem for aluminum,” says Pollack.
“Also, we have not experienced wire failure in terms of pushing or pulling it through a 50-foot gun cable,” Elliott continues. “A 50-foot gun cable is essential in repairing the ships in the water, and 50 feet is the extreme distance at which you can push-pull any soft material like aluminum."
Elliott reports that the team has experienced smooth wire feeding, with no wire-dross buildup on slave rolls and no undue wear on spring-loaded contact tips that represent the final element of the welding circuit. Lincoln Electric SuperGlaze aluminum wires benefit from proprietary wire surface preparation during manufacturing, resulting in an extremely smooth surface that resists common tangling issues at the feeder and wire shaving at the drive rolls or contact tips.
“The system runs beautifully,” Elliott says, “I attribute that to the nice finish on the wire and the speed at which the power system and wire feed can control the process. With this lineup, we can achieve 50-foot push-pull flawlessly. We’ve experienced no collapse of column strength and have not had feeding issues with any of the wire in the extended gun cable.”
Dependability Drives Decision-Making
As the trials head toward completion this spring, equipment and consumable dependability have been noted by Navy and Phoenix International officials.
“Aluminum can be welded in a hyperbaric chamber, but cheap, bottom-of-the-line equipment will not get us there,” Elliott reasons. “Lincoln Electric offered the best background and tech support we have seen in a long time, and the machinery is capable of taking some welding nuances out of the formula. Welders can concentrate on their bead profiles instead of thinking about what they have to do because their machines can’t. Factors such as voltage and amperage controls, and wire stickout length come into play and the Lincoln Electric machinery is well suited to handle that and perform some very technical welding.” Lincoln Electric advanced Power Wave welding power sources operate at extremely fast switching speeds, allowing fast response to changing conditions at the arc.
“We initially chose Lincoln Electric because we were looking for a company that could help support this project,” Pollack continues. “It imposed risk on that company in that they would have to let us borrow equipment before we bought. But the equipment and service allowed us to get where we are today. We have bought several machines, including both power sources and wire feeders.”
Elliott agrees with Pollack’s assessment.
“The welding equipment is a huge factor in getting repeatable, 100-percent Class 1 X-ray-quality work,” he says. “The Lincoln Electric machinery we chose for this project has offered that time and again.”