Ship builders use T-beam stiffeners extensively in ship construction for decks, bulkheads, shells and other structural applications. As the need for weight and cost reduction grows, T-beams are being manufactured with stronger materials and smaller cross sections. These thin materials are subject to significant distortion as they are welded. Some estimates place the cost of distortion at 30 percent of the structural cost of the ship.
To address this issue, a Navy Metalworking Center project leveraged earlier efforts by Navy ManTech, an ONR plus-up, the National Shipbuilding Research Project and Small Business Innovative Research and developed an alternative to conventional methods of manufacturing T-beams. This alternate method will result in less distortion and lower fabrication cost. The project team determined parameters for hybrid laser arc welding HSLA-80 T-beams that will reduce production and assembly costs as well as improve T-beam quality for DDG 1000.
The American Bureau of Shipping, the technical authority for DDG 1000, has approved the hybrid laser arc welding procedure for manufacturing HSLA-80 T-beams. American Tank and Fabricating, a U.S. steel fabrication company, has purchased the necessary equipment, and Northrop Grumman Shipbuilding – Gulf Coast has contracted with the company for the procurement of fabricated T-beams for DDG 1000 construction.
Other potential platforms that could benefit from this project include the littoral combat ship, which uses a variety of thin section materials including ASTM A710, a material very similar to HSLA-80.
Project participants included: DDG 1000 Program Office; Naval Sea Systems Command; Naval Surface Warfare Center - Carderock Division; General Dynamics Bath Iron Works; Northrop Grumman Shipbuilding - Newport News; Northrop Grumman Shipbuilding - Gulf Coast; Applied Thermal Sciences; and Navy Metalworking Center.