Reducing Thin Plate Distortion Will Save Significant Labor in DDG 51 Construction

The Navy Metalworking Center (NMC) is conducting a Navy ManTech project whose goal is to reduce significant levels of distortion that Ingalls Shipbuilding is experiencing in thin plates used in DDG 51 Class ship construction.
 

Thin plate distortion results in significant rework costs associated with the required flattening and excessive weld joint gaps caused by distortion-related shapes during ship fabrication. Three main processes that may contribute to thin plate distortion during panel construction are:
• manufacturing and shipping of the plate
• thermal cutting of shapes from parent thin plates
• fitting and welding of the plate components to produce the panel.
 

To address distortion that occurs when the plates are manufactured, NMC is evaluating the current production processes at the supplying steel mills, along with their ability to produce thin plate with low residual stresses. Thermal processing data will be used to develop and analyze residual stress models and compare this information to test results. After evaluation, NMC will develop recommended plate procurement specifications to assist the supplying steel mills in reducing thermal-induced stress.
 

To address thermal-cutting distortion, NMC is investigating the shipyard’s plasma cutting equipment and practices and is establishing a set of guidelines for plate nesting, cutting, sequencing and equipment to improve the process.
Reducing thin plate distortion will improve part accuracy and will diminish weld gaps, heat input and heat straightening. Ingalls Shipbuilding estimates that labor savings resulting from this project’s recommendations will be more than $5 million over the next five years. Implementation is expected to occur by the end of 2013 at Ingalls during the construction of DDG 113.
 

In addition to Ingalls, the other contributors to this project include ArcelorMittal Burns Harbor; ESAB Cutting Systems; University of New Orleans; Naval Surface Warfare Center, Carderock Division; and NMC. The DDG 51 Program Office is monitoring the progress of the project for consideration on future DDG 51 Class ships.