Problem / Objective
The Navy is seeking solutions to reduce weight and lower the center of gravity for surface ships to improve their performance at a reasonable cost. The goal of this Navy Metalworking Center (NMC) project is to reduce top-side weight and lower the center of gravity on the CVN 21 class of ships. An initial solution using 10Ni steel did not produce the intended results. Instead of ending the project, the Integrated Project Team (IPT) pursued an alternate path--increasing the performance and strength of HSLA-100* steel through heat treatment so that it could be used at reduced thickness, and thus, reduced weight, while meeting performance requirements.
* HSLA = High-strength, low alloy
Accomplishments / Payoff
Successful vendor qualification of first article, full-size production plates of HSLA-115(named for its increased minimum yield strength of 115 ksi), weld qualification evaluations and explosion testing and completion of Material Selection Information (MSI) certification data have been achieved. NMC and the IPT successfully submitted the MSI document ahead of schedule to support key shipyard need dates.
Implementation and Technology Transfer:
The Future Aircraft Carriers Program Office recently approved the incorporation of HSLA-115 into a CVN 78 application baseline design. HSLA-115 has been incorporated into the ship specifications and fabrication document, allowing its use. The MSI document was submitted in August 2008, and in March 2009, NGSB-NN procured the first order of HSLA-115 for CVN 78. Fabrication is expected to begin later in 2009. HSLA-115 may be considered for additional future applications to improve performance and reduce weight.
Implementation of HSLA-115 into CVN 78 provides improved survivability, strength and weight reduction at an affordable price.
- HSLA-115 will reduce top side weight by 100 to 200 long tons per hull and lower the center of gravity by 0.05 ft.
- Factors of safety are improved where thickness is not reduced to improve performance for critical applications.
- The HSLA-115 implementation is projected to have an overall neutral acquisition cost impact; $1M in cost avoidance has been achieved by qualifying existing welding processes with HSLA-115.
- Reducing weight and maintaining survivability performance aid the warfigthter to carry out the mission.
- PEO Aircraft Carriers
- Naval Surface Warfare Center Carderock Division
- Naval Sea Systems Command
- Northrop Grumman Shipbuilding-Newport News
- Navy Metalworking Center
- Arcelor-Mittal Steel
- DDL Omni Engineering
- Puget Sound Naval Shipyard
- Navy Joining Center