Professors forge onward with friction stir welding


    By Laurie Frost

    High strength steel and aluminum, as far as welders are concerned, are some downright temperamental metals. High-temperature welding twists and warps the metals, leaving companies like Boeing, Lockheed Martin and the U.S. Navy ready to tear their hair out as parts break or deteriorate.

    The Navy estimates that welding related defects cost them more than $150 million per year on their ships, and they are anxiously looking for a solution.

    That solution sits in the basement of the Crabtree Building, where professors and students have created a friction stir welding machine, nicknamed ?FSW 3,? which just may change the face of the welding industry.

    Carl Sorensen and Tracy Nelson, BYU mechanical engineering professors, are national experts on this revolutionary welding process, which uses pressure to bond the metal plates together without fumes, flames or seams.

    This is an improvement from the traditional arc welding method ? the fusing of two metals by melting them together ? which drastically distorts and weakens aluminum and steel plates.

    ?Traditional arc welding can?t recover the original properties [of the metal],? Nelson said. ?It only has 40 to 70 percent of the original strength. But friction stir welding can retain as much as 98 percent of the base metal properties.?

    Friction stir welding works by forcing together two metal plates, applying 4,000 pounds of force to the seam with a quickly rotating tool and stirring the metals together.

    However, the original tool had a few deficiencies. Its concave nature left a slight undercut in the metal, and the tool completely disintegrated when applied to steels.

    To fix the problem, Sorensen and Nelson invented a composition of synthetic materials called polycrystalline boron nitride, making it the second hardest material only to diamond, Nelson said. The new tool has a convex, slightly threaded tip to prevent furrowing and can make steel welds of 300 to 500 feet.

    ?People at The Welding Institute in Cambridge, England, used tungsten for the tool, and if their tool lasted 36 inches, they thought they were doing pretty well,? Sorensen said. ?But we?re into the hundreds of feet.?

    Another advantage to friction stir welding, Nelson said, is that it creates no fumes.

    ?There have been so many lawsuits the last decade as a result of employees affected by dangerous neurotoxins from welding,? Nelson said. ?And the welding companies are losing.?

    Sorensen said friction stir welding almost completely eliminates potentially carcinogenic fumes.

    The friction stir welding research has been progressing at BYU by leaps and bounds, thanks to funding from the Office of Naval Research.

    Maria Posada, a doctoral student, came to BYU specifically for its friction stir welding program.

    “BYU is well known for their friction stir welding advancements and for welding high-strength steels,” Posada said. “That”s where BYU has an advantage over other places, because they developed the [polycrystalline boron nitride] tool, the best tool so far for joining long lengths of steel plates with the least amount of wear.”

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