Problem/Objective: T-beam stiffeners are used 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 of stronger materials with smaller cross-sections. These thin materials are subject to significant distortion as they are welded. Some estimates place the cost of distortion at 30% of the structural cost of the ship. To address this issue, a Navy Metalworking Center project has developed an alternative to conventional methods of manufacturing T-beams that will result in less distortion and lower fabrication cost. The specific application for this project is HSLA-80 T-beams that will be manufactured for DDG 1000 Class ships.
Accomplishments/Payoff
Process Improvement: The Integrated Project Team has developed a hybrid laser arc welding (HLAW) process to fabricate HSLA-80 T-beams. This process combines the deep penetration and high speed of laser welding with the gap tolerance of conventional gas metal arc welding (GMAW).
Process Improvement: The Integrated Project Team has developed a hybrid laser arc welding (HLAW) process to fabricate HSLA-80 T-beams. This process combines the deep penetration and high speed of laser welding with the gap tolerance of conventional gas metal arc welding (GMAW).
Implementation and Technology Transfer: The American Bureau of Shipping, the technical authority for DDG 1000, has approved the HLAW procedure for manufacturing HSLA-80 T-beams. A U.S. steel fabrication company has purchased the necessary equipment, and a U.S. shipyard is negotiating with that company to provide hybrid laser arc-welded T-Beams for DDG 1000 construction. The system is expected to be qualified and operational before the end of 2009. Other potential platforms that could benefit from this NMC project include the Littoral Combat Ship, which uses a variety of thin section materials including ASTM A710, a material very similar to HSLA-80.
Expected Benefits:
- $600K per ship reduction in structural cost due to significantly less distortion
- 45% fabrication cost reduction due to higher weld speeds, less time required to set up the weld, and less labor required to straighten beams after welding
- Better fit-up during shipyard construction, resulting in reduced assembly costs
Participants
- DDG 1000 Program Office (PMS 500)
- 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
- Navy Metalworking Center (NMC)
- Applied Thermal Sciences (ATS)
Process Improvement: The Integrated Project Team has developed a hybrid laser arc welding (HLAW) process to fabricate HSLA-80 T-beams. This process combines the deep penetration and high speed of laser welding with the gap tolerance of conventional gas metal arc welding (GMAW).